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Laugh track
A laugh track (or laughter track) is a separate soundtrack for a recorded comedy show containing the sound of audience laughter. In some productions the laughter is a live audience response; in the U.S., the term usually implies artificial laughter (canned laughter or fake laughter) made to be inserted into the show. This was invented by American sound engineer Charles "Charley" Douglass.
- 1 U.S. history
- 1.1 Radio
- 1.2 Early live U.S. television, film; "sweetening"
- 1.3 Filming without audience
- 1.4 1960s
- 1.5 Charley Douglass and the mysterious "laff box"
- 1.6 1970s: Carroll Pratt
- 1.7 Controversy and bucking the trend
- 1.8 Comeback of live television
- 1.9 1990 onwards
- 1.10 Cartoons and children's shows
- 1.11 Making their own
- 1.12 Children's shows: 2000s
- 2 Laugh tracks outside the U.S.
- 3 Legacy and support
- 4 See also
- 5 References
- 6 External links
U.S. history[edit]
Before television, audiences often experienced comedy, whether performed live on stage, on radio, or in a movie, in the presence of other audience members. Radio and early television producers attempted to recreate this atmosphere by introducing the sound of laughter or other crowd reactions into the soundtrack.
In 1946, Jack Mullin brought a Magnetophon magnetic tape recorder back from Radio Frankfurt, along with 50 reels of tape (it was one of the magnetic tape recorders that BASF and AEG had built in Germany starting in 1935). The 6.5mm tape could record 20 minutes per reel of high-quality analog audio sound; Alexander M. Poniatoff then ordered his Ampex company to manufacture an improved version of the Magnetophon for use in radio production.[1] Bing Crosby eventually adopted the technology to pre-record his radio show to both avoid having to do it live as well as having to perform it a second time for West Coast audiences.
With the introduction of this recording method, it became possible to add sounds during post-production. Longtime engineer and recording pioneer Jack Mullin explained how the laugh track was invented on Crosby's show:
"The hillbilly comic Bob Burns was on the show one time, and threw a few of his then-extremely racy and off-color folksy farm stories into the show. We recorded it live, and they all got enormous laughs, which just went on and on, but we couldn't use the jokes. Today those stories would seem tame by comparison, but things were different in radio then, so scriptwriter Bill Morrow asked us to save the laughs. A couple of weeks later he had a show that wasn't very funny, and he insisted that we put in the salvaged laughs. Thus the laugh-track was born."[2]
Early live U.S. television, film; "sweetening"[edit]
In early television, most shows that were not live used the single-camera filmmaking technique, where a show was created by filming each scene several times from different camera angles.[2] Live audiences could not be relied upon to laugh at correct moments; other times, audiences would laugh too loudly or for too long.[2]
CBS sound engineer Charley Douglass noticed these inconsistencies, and took it upon himself to remedy the situation.[3] If a joke did not get the desired chuckle, Douglass inserted additional laughter; if the live audience chuckled too long, Douglass gradually muted the guffaws. This editing technique became known as sweetening, in which recorded laughter is used to augment the response of the real studio audience if they did not react as strongly as desired.[3] Conversely, the process could be used to "desweeten" audience reactions, toning down unwanted loud laughter or removing inappropriate applause, thus making the laughter more in line with the producer's preferred method of telling the story.[4]
While still working for CBS, Douglass built a prototype laugh machine that consisted of a large, wooden wheel 28 inches in diameter with a reel of tape glued to the outer edge of it containing recordings of mild laughs. The machine was operated by a key that would play until it hit another detent on the wheel, thus playing a complete laugh. Because it was constructed on company time, CBS demanded possession of the machine when Douglass decided to terminate his time with them. The prototype machine fell apart within months of use.[5] Douglass developed an expansion of his technique in 1953 when he began to extract laughter and applause from live soundtracks recorded (mainly from the pantomime segments of The Red Skelton Show), and then placed the recorded sounds into a huge tape machine. This basic concept would later be reworked as the Chamberlin Music Master, which was succeeded by the Mellotron.
These recorded laughs could be added to single-camera filmed programs. The first American television show to incorporate a laugh track was the sitcom The Hank McCune Show in 1950. Other single-camera filmed shows soon followed suit,[6] though several, like The Trouble with Father (ABC, 1950–55), The Beulah Show (ABC, 1950–52), and The Goldbergs (several networks, 1949–56), did not feature an audience nor a laugh-track.
Multi-camera shows; videotape[edit]
Soon after the advent of the laugh track, Lucille Ball and Desi Arnaz devised a method of filming with a live audience using a multi-camera setup. This process was originally employed for their show I Love Lucy, which used a live television studio audience and no laugh track.[3] Multi-camera shows with live audiences sometimes used recorded laughs to supplement responses. While witnessing an early post-production editing session, comedian Milton Berle once pointed out a particular joke and said, "as long as we're here doing this, that joke didn't get the response we wanted". After Douglass inserted a hearty laugh after the failed joke, Berle reportedly commented, "See? I told you it was funny".[2]
Sketch comedy and variety shows began to migrate from live broadcasting to videotape, which allowed for greater ease in editing during post-production. Editing a prerecorded live show with quadruplex videotape caused bumps and gaps on the soundtrack,[7] Douglass was then called upon to "bridge" or "fill" these gaps; eventually, both performers and producers began to realize the power behind prerecorded laughter.[4]
Filming without audience[edit]
By the early 1960s, live television became too cost prohibitive to use on a daily or weekly basis. Filming in a studio with an audience, as I Love Lucy or The Ed Sullivan Show did, had its limitations as well, as half the audience could hardly see or hear the show from where they were sitting. Douglass was brought in to simulate the reactions from an entire live studio audience from scratch for the duration of the entire show.[8]
Producers soon realized how much simpler it was to just film a show (even variety or sketch shows that could not be done in single-camera) without any live audience at all and then create and tailor the entire audience reaction afterwards. Directors failed to allow space for inserting the laugh track, making sweetening difficult and dialogue being drowned out by a reaction. Audience response cards repeatedly came back saying that laughter seemed forced or contrived.[8] Writers gradually became more conscious of the space required for the laugh track and began timing their scripts around it. On-set directors then began leaving room for as-yet-unheard audience reactions and producers began allocating more budget money for post-production so that Douglass could edit with greater ease.[4]
Despite the success of I Love Lucy, most television comedies in the 1950s and 1960s used the single-camera technique, with a laugh track simulating the absent audience.[6] Producers became disenchanted with the multi-camera format; consensus at the time was that live audiences were tense, nervous and rarely laughed on cue anyway.[8] As a result, single-camera filming with a laugh track became the dominant mode of sitcom production throughout the 1960s.
Hogan's Heroes[edit]
Network research suggested that the laugh track was required in order to brand a single-camera show as a comedy. According to fellow sound engineer, Carroll Pratt, one early example included a network playing two different pilots to three different test audiences – the pilot which the network believed was superior contained no laugh track, while the pilot they believed to be inferior contained one – the poor pilot containing the laugh track had a far more positive response from test audiences than the better pilot without one. The experiment to see whether or not a comedy fared better with the laugh track was put to the test again in 1965, when CBS showed its new single-camera sitcom Hogan's Heroes to test audiences in two versions: one with the laugh track, the other without. Partly due to the somewhat cerebral nature of the show's humor, the version without the laugh track failed while the version with canned laughter received an excellent reaction. The show was broadcast with the laugh track, and CBS decided to utilize Douglass' services moving forward.[2]
Sitcoms had different types of laugh tracks edited onto their soundtracks, depending on style. Outlandish or fantasy shows, like Bewitched, The Munsters and The Beverly Hillbillies, are virtual showcases of Douglass' editing skill. The more outlandish the show, the more invasive the laugh track. Conversely, subdued programs, like The Andy Griffith Show, The Brady Bunch, and My Three Sons, had more modulated laughter. Certain shows, like Get Smart, featured a laugh track that became more invasive as the series progressed, while shows like M*A*S*H toned down the laughter as the series became more dramatic.[8]
By the mid-1960s, nearly every sitcom was single-camera and had canned laughter added to the soundtrack. Only a few sitcoms, such as The Jackie Gleason Show, The Dick Van Dyke Show and The Lucy Show used studio audiences and turned to Douglass only to edit or augment the real laughter via sweetening.[4][6]
Charley Douglass and the mysterious "laff box"[edit]
From the late 1950s to the early 1970s, Charley Douglass had a monopoly on the expensive and painstaking laugh business.[9] By 1960, nearly every prime time show in the U.S. was sweetened by Douglass. When it came time to "lay in the laughs", the producer would direct Douglass where and when to insert the type of laugh requested.[10] Inevitably, arguments arose between Douglass and the producer, but in the end, the producer generally won.[10] After taking his directive, Douglass would then go to work at creating the audience, out of sight from the producer or anyone else present at the studio.[10]
Critic Dick Hobson commented in a July 1966 TV Guide article that the Douglass family were "the only laugh game in town."[10] Very few in the industry ever witnessed Douglass using his invention, as he was notoriously secretive about his work,[11] and was one of the most talked about men in the television industry.[8] The Douglass family operated from their padlocked garage in the San Fernando Valley.[10] When their services were needed, they would wheel the device into the editing room, plug it in, and go to work.[10] Production studios became accustomed to seeing Douglass shuttling from studio to studio to mix in his manufactured laughs during post-production.[9]
The one-of-a-kind device — affectionately known in the industry as the "laff box" — was tightly secured with padlocks, stood more than two feet tall, and operated like an organ. Only immediate members of the family knew what the inside actually looked like[10] (at one time, the "laff box" was called "the most sought after but well-concealed box in the world").[8] Since more than one member of the Douglass family was involved in the editing process, it was natural for one member to react differently to a joke than another. Charley himself was the most conservative of all, so producers would put in bids for son Robert, who was more liberal in his choice of laughter.[10] Douglass used a keyboard to select the style, gender and age of the laugh as well as a foot pedal to time the length of the reaction. Inside the machine was a wide array of recorded chuckles, yocks, and belly laughs; exactly 320 laughs on 32 tape loops, 10 to a loop. Each loop contained 10 individual audience laughs spliced end-to-end, whirling around simultaneously waiting to be cued up.[10] Since the tapes were looped, laughs were played in the same order repeatedly. Sound engineers would watch sitcoms and knew exactly which recurrent guffaws were next, even if they were viewing an episode for the first time. Frequently, Douglass would combine different laughs, either long or short in length. Attentive viewers could spot when he decided to mix chuckles together to give the effect of a more diverse audience.[8]
Douglass also had an array of audience clapping, "oohs" and "ahhhs", as well as people moving in their seats (which many producers insisted be constantly audible).[10] There was also a 30-second "titter" track in the loop, which consisted of individual people laughing quietly. This "titter" track was used to quiet down a laugh and was always playing in the background. When Douglass inserted a hearty laugh, he increased the volume of the titter track to smooth out the final mix. This titter track was expanded to 45 seconds in 1967, later to 60 seconds in 1970, and would receive overhauls every few years (1964, 1967, 1970) Douglass also kept recordings fresh, making minor changes every few months, as he believed that the viewing audience was gradually changing.[10] A man's deep laugh would be switched for a new woman's laugh, or a high-pitched woman's giggle would be replaced with a man's snicker.[8] One producer noticed a recurrent laugh of a woman whom he called "the jungle lady" because of her high-pitched shriek. After regularly complaining to Douglass, the laugh was retired from the regular lineup.[10]
Douglass knew his material very well, as he had compiled it himself. He had dozens of reactions, and he knew where to find each one. On most occasions, he would slightly speed up the reactions to heighten the effect. Douglass's work was crisp and clean, and was considered a craft by many in the television industry.[11] He not only had an ear for inserting laughs, but he also possessed a terrific memory. Over the years, Douglass would add new recordings as well as revive old ones that had been retired and then retire the newer tracks. Laughter heard in sitcoms of the early 1960s resurfaced years later in the late 1970s.[11]
Douglass' "laff box" was unearthed in 2010. It was later discussed in detail in a June 2010 episode of Antiques Roadshow, where its historical value was appraised at $10,000.[12]
1970s: Carroll Pratt[edit]
Although Douglass had a monopoly on the laugh track, he eventually faced competition by 1977 when other sound engineers began to offer laugh tracks that differed from Douglass' distinctive laughs. Most notably, engineer and Douglass protégé Carroll Pratt started his own company, Sound One.[13] Pratt introduced an innovative laugh track that contained more realistic — though less distinctive — reactions. While Pratt's laugh track had its share of recognizable chuckles as well, they are more quiet and subtle than Douglass', which had become so familiar and ubiquitous that they sounded artificial. Several sitcoms switched to Pratt's laugh track after 1977, including M*A*S*H and The Love Boat. Several live sitcoms, such as Laverne and Shirley and Happy Days, also chose Pratt over Douglass for the sweetening process.[11][13][5] Pratt and his brother had been working under Douglass since the early 1960s, but began to notice that Douglass' technique was falling behind as advances were made in production technology. Pratt commented that after years of constant use, an audible hiss could be heard when a laugh was being cued up due to Douglass' tapes wearing out.[5] While not stubborn, Douglass was so fond of his machine and technique that he felt no urgency to advance his technology. Pratt parted ways with Douglass, and created a new "laff box," one that was simpler to use and had greater capacity than Douglass' (Pratt's recordings were on cassette tape, Douglass' on an older magnetic tape).[5] With the advent of stereo television, Pratt's stereo recordings matched the sound quality of television shows being filmed or videotaped in stereo, whereas Douglass attempted to convert previous mono analog recordings to stereo.[11]
The competition from Pratt caused Douglass to retool his library, using more extreme reactions (guffaws and belly laughs) almost exclusively, some recordings well over a decade old. The combination of classic loud guffaws, mixed with his own new, less invasive recordings, had middling results.[11]
Controversy and bucking the trend[edit]
The practice of simulating an audience reaction was controversial from the very beginning.[14] A silent minority of producers despised the idea of a prerecorded audience reaction.[8] Inventor Douglass was aware that his "laff box" was maligned by critics and actors, but also knew that the use of a laugh track became standard practice and as a result, a necessity in the industry.[14] Leading industry experts reasoned that laugh tracks were a necessary evil in prime time television: without the canned laughter, a show was doomed to fail.[8] It was believed that the absence of guffaws meant American viewers could not tell if the particular show was indeed a comedy.[4] That did not stop several from forgoing the laugh track entirely:
- Former child star Jackie Cooper believed that the laugh track was false. Cooper's comedy/drama Hennesey (CBS, 1959–62) was cancelled in 1962 after a three-season run. For its first two seasons, the show used only a mild laugh track; by the third and final season, the chuckles were eliminated completely. Cooper later commented that "we're manufacturing a reaction to our own creation, yet we'll never know if people out there are really laughing." Cooper concluded by saying, "It's a put-on all the time."[4]
- In September 1964, the comedy/drama Kentucky Jones (NBC, 1964–65), starring Dennis Weaver, tried to eliminate laughs, simulated or live. After only five episodes and slumping ratings, Douglass was recruited to add the laugh track. Kentucky Jones was cancelled the following April.[8]
- Ross Bagdasarian, Sr., creator of the Alvin and the Chipmunks franchise, outright refused to utilize a laugh track when production began on The Alvin Show (CBS, 1961–62) in 1961. Bagdasarian's reasoning was if the show was funny, the viewers would laugh without being prompted.[15] The Alvin Show was cancelled after a single season.
- Peanuts creator Charles M. Schulz refused to employ a laugh track during the production of the holiday favorite A Charlie Brown Christmas (CBS, 1965). Like Bagdasarian, Schulz maintained that the audience should be able to enjoy the show at their own pace, without being cued when to laugh. When CBS executives saw the final product, they were horrified and believed the special would be a flop. (CBS did create a version of the show with the laugh track added, just in case Schulz changed his mind. This version remains unavailable.) When the show first aired on December 9, 1965, it was a surprise critical and commercial hit.
- The musical sitcom The Monkees (NBC, 1966–68) featured a laugh track throughout its first season and several episodes of the second. Midway through Season 2, the Monkees themselves insisted the show eliminate the laugh track, believing their viewers were intelligent enough to know where the jokes were. NBC, already annoyed by the manufactured rock group wanting too much control over their show, cancelled The Monkees after Season 2 concluded, citing the missing laugh track as a major factor.[8]
- Bill Cosby's first sitcom, The Bill Cosby Show (NBC, 1969–71) was also produced without a laugh track at the insistence of Cosby. He stated that his opposition to NBC's desire to add a laugh track led to the show's cancellation after only two seasons.[8]
- The series Sledge Hammer! (ABC, 1986–88) began with laugh tracks in the soundtrack, much to creator Alan Spencer's disapproval. After months of fighting with ABC, Spencer had his wish granted when the laugh tracks were removed from the series starting with episode 14, "State of Sledge".[16]
- Larry Gelbart, co-creator of M*A*S*H (CBS, 1972–83), initially wanted the show to air without a laugh track ("Just like the actual Korean War", he remarked dryly). CBS, however, rejected the idea. Eventually a compromise was reached, and Gelbart and co-producer Gene Reynolds were permitted to omit the laugh track during scenes in the operating room if they wished. As a result, few scenes in the operating room contain canned laughter. Seasons 1–5 utilized Douglass' more invasive laugh track; Carroll Pratt's quieter laugh track was employed for Seasons 6-11 when M*A*S*H shifted from sitcom to drama upon the departure of Gelbart and Reynolds. Several episodes ("O.R.", "The Bus", ""Quo Vadis, Captain Chandler?", "The Interview", "Point of View", "Dreams") omitted the laugh track altogether; as did almost all of Season 11, including the 135-minute series finale, "Goodbye, Farewell and Amen".[8] The laugh track is also omitted from some international and syndicated airings of the show; on one occasion during an airing in the UK, the laugh track was accidentally left on, and viewers expressed their displeasure, an apology from the network for the "technical difficulty" was later released. The DVD releases, meanwhile, give the viewer a choice of laughing or non-laughing soundtracks. UK DVD critics speak poorly of the laugh track, stating "Canned laughter is intrusive at the best of times, but with a programme like M*A*S*H, it's downright unbearable."[17] "They're a lie," said Gelbart in a 1992 interview. "You're telling an engineer when to push a button to produce a laugh from people who don't exist. It`s just so dishonest. The biggest shows when we were on the air were All in the Family and The Mary Tyler Moore Show both of which were taped before a live studio audience where laughter made sense," continued Gelbart. "But our show was a film show — supposedly shot in the middle of Korea. So the question I always asked the network was, 'Who are these laughing people? Where did they come from?'" Gelbart persuaded CBS to test the show in private screenings with and without the laugh track. The results showed no measurable difference in the audience`s enjoyment. "So you know what they said?" Gelbart said. "'Since there`s no difference, let's leave it alone!'"[18]
- Sports Night (ABC, 1998–2000) premiered with a laugh track, against the wishes of show creator Aaron Sorkin, but the laugh track became more subtle as the season progressed and was completely removed at the start of the second season. In some cases, a laugh track was needed to maintain continuity, as portions of each episode were filmed in front of a live audience, while the remainder were filmed without an audience present.
Comeback of live television[edit]
Though the use of canned laughter reached its peak in the 1960s, a few shows still retained the multi-camera tradition. In 1967, Desi Arnaz produced The Mothers-in-Law (NBC, 1967–69), which was recorded in front of a live audience at Desilu Studios, with a sweetening performed in post-production.[19] A year later, The Good Guys (CBS, 1968–70) followed the same format. Production changes in location, however, caused the remainder of the first season to transition back to single-camera entirely, using only a laugh track. This continued through season two until low ratings led to its cancellation in 1970.[20]
The 1970s began with the decline of rural-based shows (The Beverly Hillbillies, Green Acres, Mayberry RFD) and the rise of socially conscious programming (All in the Family, M*A*S*H, Maude). The resulting change also spurred the return of live audiences, starting with The Mary Tyler Moore Show (CBS, 1970–77). The series' pilot episode, "Love is All Around", had been initially filmed using the single-camera method. The results were not satisfactory to Moore or the producers, who then decided to shift to multiple cameras. Since the first several episodes were taped in late summer, the pilot's first taping was not received well due to bad insulation and poor audio. The second taping, however, provided better air conditioning and a better quality sound system to the stage. Critical reception thus improved, and the show used the multi-camera format thereafter, and became a major success during its seven-year run.[21]
Creator Norman Lear's All in the Family (CBS, 1971–1979) followed suit in 1971. Videotaped live, Lear wanted the studio audience to actually like the performer, with hopes of the two developing a rapport with each other. Lear was not a fan of pretaped audiences, resulting in no laugh track being employed, not even during post-production when Lear could have had the luxury of sweetening any failed jokes (Lear relented somewhat in later seasons, and allowed Douglass to insert an occasional laugh).[8] Lear's decision resulted in the show being a huge success, and officially ushered in the return of live audiences to the U.S. sitcom mainstream. To make his point clear, an announcement proclaimed over the closing credits each week that "All in the Family was recorded on tape before a live audience" or during the show's final seasons where live audiences no longer attended tapings of the show "All in the Family was played to a studio audience for live responses."[8]
Jack Klugman and Tony Randall expressed displeasure during the first season of The Odd Couple (ABC, 1970–75), which used a laugh track without a live audience. Producers favored the laugh track-only method, as it allowed for more frequent scene changes and the ease of retakes. Theatre veteran Randall, in particular, resented the process, and disliked having to wait several seconds between punchlines in order to allot enough space for the laugh track. ABC relented and by the second season, The Odd Couple was filmed with three cameras (vs. a single camera the previous season) and performed like a stage play in front of a studio audience. The change also required a new, larger set to be constructed within a theatre.[22] With a live audience present, Randall and Klugman now enjoyed the spontaneity that came with it; any missed or blown lines went by without stopping (they could always be refilmed during post-production). In addition, it gave the show a certain edge that was lost in the first season, though actors now had to deliver lines louder, since they were on a larger sound stage as opposed to a quiet studio with only minimal crew present.[23] The sitcom Happy Days (ABC, 1974–84) mirrored The Odd Couple scenario as well. Its first two seasons used only a laugh track, and by third season, shifted over to a live audience.[8]
As a result, the resurgence of live audiences began to take hold. The shows were not entirely live, however. With the exception of All in the Family, sweetening was still a necessity during post-production in order to bridge any gaps in audience reactions. Television/laugh track historian historian Ben Glenn, II, used the sitcom Alice (CBS, 1976–85) as an example why, stating "the actors kept blowing their lines. Of course, by the third or fourth take, the joke was no longer funny. A Douglass laugh was inserted into the final broadcast version to compensate."[11]
In addition to The Odd Couple, The Mary Tyler Moore Show and Happy Days, other live sitcoms that were sweetened by Douglass were The Paul Lynde Show (ABC, 1972–73), The Bob Newhart Show (CBS, 1972–78), Maude (CBS, 1972–78), Rhoda (CBS, 1974–78), Barney Miller (ABC, 1975-82), Laverne and Shirley (ABC, 1976–83), Soap (ABC, 1977–81), Taxi (ABC, 1978–82; NBC, 1982–83), Newhart (CBS, 1982-90), Cheers (NBC, 1982–93) and its spinoff Frasier (NBC, 1993–2004).[8]
Variety shows that became prominent during the 1970s, such as The Carol Burnett Show, The Flip Wilson Show, and The Dean Martin Show (as well as The Dean Martin Celebrity Roast succeeding afterwards) also continued to use Douglass' sweetening for any less appealing jokes performed during sketches.[24]
There were still some producers who either still did not trust a live audience, produced a show that was too complex for an audience to be present, or favored the single-camera method. In these cases, Douglass orchestrated the laugh track from scratch. Sitcoms like The Brady Bunch, The Partridge Family and M*A*S*H utilized the single-camera method for their entire run.[8] Several hour-long comedy-dramas, like The Love Boat and Eight is Enough, used only a laugh track.[8]
In the intervening years beginning with live film, progressing through videotape and onto studio-filmed productions with no live audience back to live-on-tape, Douglass had gone from merely enhancing or tweaking a soundtrack, to literally customizing entire audience reactions to each performance and back again to enhancing and tweaking performances recorded with live audiences.[8]
In order to gauge the continued relevance of Douglass' laugh track, a study was published in 1974 in the Journal of Personality and Social Psychology that concluded people were still more likely to laugh at jokes that were followed by canned laughter.[25] That Girl creator Sam Denoff commented in 1978 that "laughter is social. It's easier to laugh when you're with people." Denoff added "in a movie theatre, you don't need a laugh track, but at home, watching TV, you're probably alone or with just a few others."[3]
1990 onwards[edit]
Single-camera comedy has made a comeback in the U.S. since the early 1990s, but networks have mostly abandoned the old tradition of laugh tracks for single-camera shows. A key player in this revolution was HBO, which allowed its single-camera comedies such as Dream On and The Larry Sanders Show to run without laugh tracks, and won critical praise for doing so.[26] Single-camera shows without an audience, live or laugh track, have become increasingly common on broadcast networks as well, with critical and popular hits such as Malcolm in the Middle and The Office.
Other non-laugh track sitcoms in the U.S. are as follows:
- Arrested Development
- Community
- The Crazy Ones
- Curb Your Enthusiasm
- Entourage
- Happy Endings
- It's Always Sunny in Philadelphia
- The Goldbergs
- The Wonder Years
- The Michael J. Fox Show
- The Middle
- Modern Family
- New Girl
- The Office
- Parks and Recreation
- Scrubs
- The Simpsons
- Veep
- 30 Rock
Animated shows, such as The Simpsons, Futurama, King of the Hill, South Park, American Dad!, Bob's Burgers, and Family Guy, have also gone silent, except on the rare occasion that canned laughter is used, usually as a parody of a sitcom. However, sitcoms made by It's a Laugh Productions, such as That's So Raven, use laugh tracks.[27]
Sweetening is a common practice in live awards shows such as the Emmy Awards, the Academy Awards, and the MTV Video Music Awards. The microphones onstage often do not fully pick up the audience's laughter and reaction to the monologues as audiences are not microphoned in live awards shows due to the amount of conversation that takes place during filming. Laughter and applause are often sweetened and edited prior to public viewing, or if aired live, are done on the spot via a 7-second delay. (The same crew is also used to mute swear words and controversial statements from award winners[citation needed]). The Kids Choice Awards uses laugh tracks that feature adults despite the fact that the audience is composed of mostly pre-teens.
Cartoons and children's shows[edit]
Prime time live-action shows were not the only genre to employ a laugh track, as the canned chuckles were eventually used in some prime time animated television series that would not employ a live audience. The Flintstones and The Jetsons incorporated laugh tracks.[6]
Afternoon cartoon shows employed the laugh track as well. The first episodes of Rocky and His Friends utilized one, as did The Banana Splits Adventure Hour. Eventually, the laugh track entered the world of Saturday morning cartoons, beginning with the Filmation-produced The Archie Show in 1968. Many other Filmation shows employed a laugh track, including Fat Albert and the Cosby Kids, The Brady Kids, Groovy Goolies, and The New Adventures of Gilligan.[8] Filmation continued to utilize Douglass' services until 1983, when the studio moved from producing its Saturday morning lineup into syndication, producing more heroically-themed shows such as He-Man. The last Saturday morning cartoon to utilize Douglass' laugh track for Filmation was Gilligan's Planet (CBS, 1982–83).[28]
Following Filmation were producers Sid and Marty Krofft. When production began on H.R. Pufnstuf in 1969, newly appointed executive producer Si Rose saw a funny show without a laugh track was a handicap, and convinced the Kroffts to include one on Pufnstuf. After Pufnstuf, the Kroffts employed Douglass's services on all of their shows produced for Saturday morning (except for Land of the Lost, which was more dramatic in nature), including The Bugaloos, Lidsville, Sigmund and the Sea Monsters, The Lost Saucer, and Far Out Space Nuts. When transitioning from high concept children's programming to variety shows, the Kroffts continued to employ Douglass for sweetening, since these shows were taped in small studios, with small audiences; these include Donny and Marie, The Brady Bunch Variety Hour, The Krofft Supershow, The Krofft Superstar Hour, Pink Lady and Jeff, Barbara Mandrell and the Mandrell Sisters, Pryor's Place, as well as their 1987 syndicated sitcom D.C. Follies.
In addition to Filmation and the Kroffts, by 1969, nearly all included Douglass's laugh track. Notable Saturday morning series that followed Filmation's lead include The Pink Panther Show, Scooby-Doo, Where Are You?, Harlem Globetrotters and Josie and the Pussycats.[8]
As the use of laugh tracks for Saturday Morning became more common, Douglass eventually added a number of children's laughs to his library. "Kiddie laughs", as they are known, first saw use for sweetening for the 1973 syndicated television special, The World of Sid and Marty Krofft at the Hollywood Bowl, but were soon heard on most Saturday Mornings shows by 1974, such as Uncle Croc's Block, Sigmund and the Sea Monsters, The Pink Panther Show, The Lost Saucer and Far Out Space Nuts.[2]
While appropriate, given that Saturday Morning is aimed specifically at children, critics reacted negatively to the inclusion, feeling that hearing the mix of new kiddie laughs along with Douglass' mature adult laughs seemed unnatural and unrealistic. This was especially true at the start of this new trend, when the kiddie laughs could only be heard a very small number of times throughout the program; in the following years, however, the mix became more balanced, to the point that nearly every joke, gag or punchline would be met with both a kiddie laugh and a classic Douglass chuckle.[8]
Making their own[edit]
By 1970, Douglass' laugh business was proving so lucrative that he decided to raise the rates for his services (although by then, inflation in general had also begun to rise). Unlike sitcoms, however, cartoons were produced with low budgets[29] and looked for opportunities to reduce costs. Hanna-Barbera and Rankin-Bass would distance themselves from Douglass starting in 1971, by isolating several of Douglass' chuckles. These studio-made laugh tracks were controversial: while Hanna-Barbera's laugh track maintained a balance of laugh intensity, it was extremely limited and unrealistic; Rankin-Bass' provided a better selection of laughs, was mostly updated, and somewhat kept the tradition of Douglass' methods by using mild guffaws to mute out the laughs, but it was too invasive and would often provide unnecessary placing after even a mild joke.
By 1976, the only studios who would keep Douglass' services intact for their shows were Filmation, DePatie-Freleng Enterprises (best known for the Pink Panther series), and Sid & Marty Krofft Television Productions.
Hanna-Barbera (HB) was the first cartoon production studio to cease using Douglass' services. Successful series' prior to 1971, like Scooby-Doo, Where Are You!, Harlem Globetrotters, and Josie and the Pussycats employed a full laugh track. This changed at the start of the 1971–72 season when HB employed their limited laugh track using a MacKenzie repeater machine, which cued up the same few laughs repeatedly.[30] Mixed with a tinny, metallic sound, it included three mild laughs and two uncontrollable belly-laughs (one contains a woman laughing prominently at the very end). HB used these laughs regularly over the next decade on nearly all of their Saturday morning fare.[11]
Several shows featuring the HB laugh track are listed as follows:
- Help!... It's the Hair Bear Bunch! (CBS, 1971–1972)
- The Pebbles and Bamm-Bamm Show (CBS, 1971–1972)
- The Flintstone Comedy Hour (CBS, 1972–1973)
- Josie and the Pussycats in Outer Space (CBS, 1972–1974)
- The New Scooby-Doo Movies (CBS, 1972–1974)
- The Addams Family (CBS, 1973–1974)
- Jeannie (CBS, 1973–1975)
- Hong Kong Phooey (ABC, 1974–1975)
- Partridge Family 2200 A.D. (CBS, 1974–1975)
- Jabberjaw (ABC, 1976–1978)
- The Scooby-Doo Show (ABC, 1976–1978)
- Dynomutt, Dog Wonder (ABC, 1976–1977)
- Captain Caveman and the Teen Angels (ABC, 1977–1980)
- The Super Globetrotters (NBC, 1979–1980)
- Scooby-Doo and Scrappy-Doo (ABC, 1979–1980; first installment)
The HB laugh track affected several television specials as well, including The Banana Splits in Hocus Pocus Park, The Flintstones Meet Rockula and Frankenstone, The Flintstones' New Neighbors, and Casper's First Christmas.[8] On occasion, the studio would slow down the laugh track for a greater effect; this was done in Season 2 of The New Scooby-Doo Movies.[8]
HB also used the limited laugh track when they produced Wait Till Your Father Gets Home in 1972, their first prime time animated television show since the demise of The Flintstones in 1966. This laugh track, which added an additional belly laugh to the mix, was noticeably slowed during production. (This was the only TV series produced by HB to have this added belly laugh.)[8]
The HB laugh track was discontinued after the 1979–80 television season. The final shows to receive the chuckles were Captain Caveman, Scooby-Doo and Scrappy-Doo, and Super Globetrotters. The last prime time special to feature the HB laugh track was The Flintstones: Jogging Fever, which aired on October 11, 1981.[31]
Laugh track historian/editor Paul Iverson commented "the Hanna Barbera laugh track did more to give laugh tracks a bad name than Douglass's work could ever have done. Using the same five or so laughs repeatedly for a decade does not go by unnoticed, no matter how young the viewer is." Iverson added "all it takes is watching an episode of Josie and the Pussycats alongside of Josie and the Pussycats in Outer Space and it is painfully obvious. It is a shame that a company as powerful as Hanna-Barbera — who, at its peak, practically owned Saturday mornings — thought so little of their audience by dubbing such an inferior laugh track for so long a period."[8]
Animation studio Rankin/Bass, best remembered for their holiday specials, also experimented with creating their own laugh track for The Jackson 5ive Saturday morning cartoon show. Like HB, Rankin/Bass isolated several snippets of canned chuckles from Douglass' library, and inserted them onto the soundtrack. Unlike HB, though, the chuckles were nothing but loud eruptions of laughter; mild jokes received unnatural bouts of laughter, while other times, the laughter would erupt mid-sentence. Because this laugh track was far too invasive, it only emphasized the artificial nature of canned laughter more than Hanna-Barbera's version; as a result, Rankin/Bass ceased using laugh tracks after production ceased for The Jackson 5ive.[8]
Rankin/Bass' laugh track, however, did provide a better variety of laughs when compared to the limited HB laugh track. The laugh track also was more up-to-date; most recordings were used regularly during the 1971–1972 and 1972–1973 television seasons.[8]
Jim Henson & Associates: The Muppet Show[edit]
Unlike the two "silent" pilots before it, The Muppet Show series incorporated its own laugh track onto the show, but in a completely different manner; because the variety program was modeled after vaudeville, often the viewers would be treated to glimpse of the theater audience and their reactions to The Muppets' antics on stage (though the audience was composed of Muppet characters as well).[32]
As the show was produced overseas at the ATV studios in Elstree, England, Jim Henson and his Muppet production team bypassed Douglass' familiar laughs. New laughs, chuckles, and applause were recorded for the first few episodes so they would sound fresh and new. Some of these laughs were provided by the actual cast and crew members reacting to dailies of episodes; eventually, The Muppet Show began recycling these same chuckles for later shows, establishing its own one-of-a-kind laugh track. A by-product of this convincing laugh track was the belief by viewers that The Muppet Show was indeed taped in front of a live audience, some even asking for tickets to attend tapings; Henson's son, Brian, noted how strange he thought it was that people believed the show was shot before a live audience. Henson himself knew that having a live audience would be impractical, given the production complexities (the NBC sitcom ALF was also difficult to produce and utilized only a laugh track); he also notes that because of the series' vaudeville inspiration, having sounds of laughter was a necessity, but admits that it was not an easy task – "I look at some of the early shows, I'm really embarrassed by them. The sweetening got better later on, but it's always a difficult thing to do well, and to create the reality of the audience laughing."[32] Henson also commented about the pilot episode not having a laugh track, saying "I did one special dry – without any laugh track – looked at it, and then tried it adding a laugh track to it, and it's unfortunate, but it makes the show funnier."[32]
Various Muppet characters or guest stars would break the fourth wall and acknowledge the use of the laugh track. In the fourth episode of the series, Kermit the Frog is asked by guest Ruth Buzzi if he felt a gag or routine would be funny enough for the show, to which he turns to the camera and replies, "That's up to the laugh track." A Season Two episode featuring guest Steve Martin eschewed a laugh track altogether to support the concept that the show had been canceled that night in favor of auditioning new acts; the only audible laughs are those of the Muppet performers themselves.[33]
For Muppets Tonight, the laugh track is used during the show, but is skipped at the beginning and end. Unlike the former Muppet Show however, Muppets Tonight employed mostly classic Douglass chuckles.[citation needed]
Game shows[edit]
During the 1970s through the early 1980s, some TV corporations even managed to isolate several of Douglass' guffaws and add them for sweetening on game shows (often played when a contestant or the host says something considered to be funny and only a small reaction comes from the live audience). One of the leading producers to do this was Chuck Barris, whose game shows were designed mainly to entertain the audience; the "prizes" were often rudimentary or derisive. Many of his productions, including The Gong Show and 3's a Crowd, used the isolated chuckles for sweetening.[34] Game shows produced at NBC's Burbank facilities in particular in the 1970s and 1980s used a unique library of oohs, aahs.[citation needed]
Laugh tracks were also used on Merv Griffin's Crosswords, which ran from 2007 to 2008 and, unlike most game shows, did not tape in front of a studio audience.
Children's shows: 2000s[edit]
While Disney Channel-produced sitcoms and studio-created laugh tracks are primarily recorded in front of live audiences,[35] Nickelodeon—Disney's top competitor—utilize a laugh track for shows such as iCarly and Victorious since closing the original studios fitted for live audience seating.
Glenn Martin, DDS, a claymation show produced by Nickelodeon, utilized a laugh track for the first seven episodes only before eliminating it. Series creator Eric Fogel commented, "It took too much internal thinking".[citation needed]
Laugh tracks outside the U.S.[edit]
In the 20th century, most UK sitcoms were taped before live audiences to provide natural laughter. Scenes recorded out of doors, traditionally recorded in advance of studio work, are played back to the studio audience and their laughter recorded for the broadcast show. Other comedies, such as The Royle Family and The Office, which are presented in the mode of cinéma vérité rather than in the format of a traditional sitcom, do not feature any audience laughter.
The League of Gentlemen was originally broadcast with a laughter track, but after the first two series this was dropped.[36] The pilot episode of the satirical series Spitting Image was also broadcast with a laugh track, apparently at the insistence of Central Television. This idea was dropped as it was felt by the show's producers that the show worked better without one. Some later editions, in 1992 (Election Special) and 1993 (two episodes) did use a laughter track, as these editions were performed live in front of a studio audience and included a spoof Question Time.[37]
Most episodes of Only Fools and Horses feature a studio audience, the exceptions, which featured no laughter at all, were all Christmas specials, "To Hull and Back", "A Royal Flush" and the second part of "Miami Twice". For their DVD releases, "A Royal Flush" (which was edited to remove over 20 minutes of footage) had an added laughter track, as did the second part of "Miami Twice" (which was merged with the first part to make Miami Twice: The Movie).
The 21st century, many new sitcoms inspired by mostly those of the new wave of British comedies of the late 1990s, did not feature a laugh track or studio audience. Although Green Wing does not feature audience laughter, partly due to its surreal nature, it does feature unusual lazzi techniques, where the film of the episode is slowed down immediately following a joke.
Most contemporary Canadian television comedies are laugh track-free, but some programs, such as the sitcom Maniac Mansion (1990–1993) and the children's program The Hilarious House of Frightenstein (1971) were broadcast in Canada without a laugh track, though one was added for American airings.
The children's sketch comedy series You Can't Do That on Television (1979–1990) did not utilize a laugh track during its first season as a locally televised program. However, when it entered the Canadian network realm (as Whatever Turns You On), it utilized a laugh track composed almost exclusively of children's laughter, with some peppering of adult laughter.
While unique and appropriate for the nature of the show, the use and quality of the laugh track varied from season to season. The 1981 episodes featured an excellent variety of different laughs, offering a more authentic sound. The 1982 season, which was the first season the show was produced for Nickelodeon, used less laughs, but also employed Carroll Pratt's titter track used on U.S. sitcoms such as Happy Days and What's Happening!!. The last six episodes of 1982 corrected the repetition of the kiddie track by mixing different laughs together, along with the titter track. 1983 took a noticeable downturn, with the laugh track being considerably muted and poorly edited. By 1984, the editors corrected this problem, with laughs reverting to 1982 minus the effective titter track.
In 1986, a new children's laugh track was used with decidedly younger sounding laughs to match the material, which targeting a younger demographic than earlier seasons. When the series returned in 1989, it used both 1981 and 1986 kiddie tracks.
I Love My Family, the first multi-camera sitcom in mainland China, used a live studio audience, which is a practice slowly used to today's standards.[clarification needed] Some single-camera comedies, such as iPartment, used a laugh track.
Laugh tracks are commonly used in variety shows for comic effect. Examples include Super Sunday, Kangxi Lai Le, Variety Big Brother and Home Run.
Legacy and support[edit]
Si Rose, executive producer for Sid and Marty Krofft, convinced the Kroffts to use a laugh track on their puppet shows, such as H.R. Pufnstuf, The Bugaloos and Sigmund and the Sea Monsters. Rose stated, "The laugh track was a big debate, they (the Kroffts) said they didn't want to do it, but with my experience with night-timers, night-time started using laugh tracks, and it becomes a staple, because the viewer watches the program and there's a big laugh every time because of the laugh track, and then when you see a show that's funny and there's no laugh because of no laugh track, it becomes a handicap, so I convinced them of that. Good or bad."[38] Sid Krofft commented, "We were sort of against that [the laugh track], but Si Rose — being in sitcoms — he felt that when the show was put together that the children would not know when to laugh."[39] Marty Krofft added "the bottom line — it's sad — you gotta tell them when it's funny. And the laugh track, [Si] was right. It was necessary, as much as we were always looking to have a real laugh track, a real audience. In comedies, if you don't have them, you're in big trouble, because if you don't hear a laugh track, it's not funny. And that's the way the audience [at home] was programmed to view these shows."[40]
In a 2007 interview, late Filmation producer/founder Lou Scheimer praised the laugh track for its usage on The Archie Show. "Why a laugh track?" Scheimer asked. "Because you feel that you are watching the program with a group of people instead of being alone." Scheimer confirmed that The Archie Show was the first Saturday morning cartoon to utilize a laugh track.[41]
Television and laugh track historian Ben Glenn, II commented that the laugh tracks currently used are radically different from the "carefree" quality of the laughter of past:
"Today's sitcoms are based mostly on witty reparté and no longer rely on outlandish situations or sight gags, such as you would see in an episode of Mister Ed, The Munsters or Bewitched, and today's muted laughs reflect that. Generally, laughs are now much less aggressive and more subdued; you no longer hear unbridled belly laughs or guffaws. It's 'intelligent' laughter — more genteel, more sophisticated. But definitely not as much fun. There was an optimism and carefree quality in those old laugh tracks. Today, the reactions are largely 'droll' just the way in which they sound. In the past, if the audience was really having a good time, it shone through. Audience members seemed less self-conscious and they felt free to laugh as loudly as they wanted. Maybe that's a reflection of contemporary culture. In the 1950s, the laughs were generally buoyant and uproarious, although somewhat generic, because Douglass hadn't yet refined his structured laugh technique. In the 60s, however, you could hear more individual responses — chortles, cackles from both men and women. The reactions were much more orderly and organized. I can actually tell you the exact year that a show was produced, just by listening to its laugh track."[11]
Several months after Douglass's death in 2003, his son Bob commented on the pros and cons of his father's invention:
"On some of the shows it was abused. They wanted to keep adding more and more laughs, and it would go way overboard. They thought it was going to be funnier, and it wasn't. A lot of producers would have the laughter almost louder than the dialogue, and that ruins it. It's a tool. Like music is, like sound effects, like dialogue. It's everything combined together to make a show flow along and have a nice pace to it. It's all timing. With skill, and a little luck, a well-executed laugh track can be a work of art contributing to a larger work of art. We've been around a long time, and it fills a need in the industry. We don't expect to be the main ingredient in a show. It's just part of the puzzle that puts together the shows that make for great television."[42]
Carroll Pratt confirmed Douglass's comments in a June 2002 interview with the Archive of American Television, saying that producers regularly wanted louder, longer laughs:
"In the beginning, it was terrible! It got to be a point where the more you laugh, the louder you laugh, the funnier the joke was. And that wasn't so. And that's why the press, the media, the public in general came down on laughs at all: it was just too much. And there are still shows that are required to do that, but now less is better. I think less in enthusiasm, perhaps, but not less in volume. It's been tried by some producers and some shows to lessen the volume until it was a whisper and that becomes a bigger irritation than having it too loud. A joke is a joke, but I've noticed that the public is more sophisticated now. They don't seem to be hand-fed as they were in the early days. Now, we take the light approach as far as trying to drive home a joke with audience reaction. I think that it's okay to back off a little bit especially on a live-audience show. Go with the show and let them tell you."[5]
Sound engineer John Bickelhaupt has carried on the "laff box" tradition, including the practice of secrecy. While current digital machines are not as cumbersome as Douglass's original machinery, Bickelhaupt confirmed they "are pretty anonymous, with [unlabeled] knobs and buttons. We like to remain kind of mysterious — the man-behind-the-curtain thing. We don't really like to talk about it too much.[43] Bickelhaupt added that "Most of the time, what we're doing isn't re-creating a studio audience; the audience laughter is already there. But in editing, when sections of the show are taken out, when they take out lines to make the show fit a time slot — we have to cover the bridge between one laugh and another by using the laugh machine."[18] In reference to the quiet laugh track employed on How I Met Your Mother, Bickelhaupt commented that producers are increasingly "shying away from that big, full audience — the raucous sound that was more commonplace in the 70s, 80s, and 90s. They want a more subtle track."[43]
Just Shoot Me! creator Steve Levitan commented "when used properly, the laugh guy's job is to smooth out the soundtrack — nothing more." Phil Rosenthal confirmed that he "rarely manipulated the laughs" on Everybody Loves Raymond. "I worked on shows in the past where the 'sweetener' was ladled on with a heavy hand, mainly because there were hardly any laughs from the living. The executive producers would say, 'Don't worry — you know who will love that joke? Mr. Sweet man.' " Bickelhaupt confirmed this observation, admitting there are occasions he has created all audience responses.[43]
Karal Ann Marling, professor of American studies and art history at the University of Minnesota, voiced concerns about Douglass' invention:
"Most critics think that the laugh track is the worst thing that ever happened to the medium, because it treats the audience as though they were sheep who need to be told when something is funny — even if, in fact, it's not very funny. It's probably changed comedy, particularly situation comedy. I mean, anything can be passed off as hilariously funny, at least for the first two or three go-rounds, if you've got people laughing like maniacs in the background. It's as though during a drama show, suddenly a voice in the background goes, 'Ooohh, this is scary!' or 'Oh, he looks guilty!' It seems like the next logical step if you're going to have laugh tracks. For proof of the intelligent power of a non-laugh-track show, look no further than The Simpsons. It's wonderfully written. They work for their laughs. And audiences sit there and wet their pants. That's a great example of why not to have a laugh track. Let me be the laugh track."[42]
Marling added she was concerned more about canned laughter as a symptom of a larger social willingness to accept things uncritically, which included political messages as well as commercial messages. "It's a kind of decline in American feistiness and an ability to think for yourself," she said. "It certainly is embedded, but that doesn't make it a good thing. There are a lot of things that we do every day of the week that aren't good things. And this is one of them."[42]
In 2011, critic James Parker bemoaned the absence of laugh tracks in many popular sitcoms of the time, feeling that the idea of not having an audience had become an overused gimmick:
"Silence now encases the sitcom, the lovely, corny crackle of the laugh track having vaporized into little bathetic air pockets and farts of anticlimax. Enough, I say. This burlesque of naturalism has depleted us. Give me the honest joinery of The George Lopez Show, the fat gags and the cackles on demand, over Parks and Recreation or NBC's ghastly version of The Office. Who knew irony could be so cloying?"[44]
He conceded that Modern Family was one of the few shows which benefited from not having one.[44]
A study was done as recently as 2011 to gauge the necessity of the laugh track, particularly on U.S. sitcoms. Dartmouth College Psychology professor Bill Kelley's continued study of the human brain's response to humor stated "we're much more likely to laugh at something funny in the presence of other people. Hearing others laugh — even if it's prerecorded — can encourage us to chuckle and enjoy ourselves more." Kelley's research compared student's reactions to an episode of Seinfeld, which utilizes a laugh track, to those watching The Simpsons which does not. Brain scans suggested that viewers found the same things funny and the same regions of their brain lit up whether or not they heard others laughing.[25]
Despite this, Kelley still found immense value in the laugh track. "When done well," Kelley commented, "they can give people pointers about what's funny and help them along. But when done poorly, you notice a laugh track and it seems unnatural and out of place."[25]
See also[edit]
- ^ "Audio John Mullin Man". Mixonline.com. 1999-10-01. Retrieved 2013-07-09.
- ^ a b c d e f Kitman, Marvin (August/September 1981). "Don't Make Me Laugh". Channels of Communication.
- ^ a b c d Levin, Eric (April 8, 1978). "Who does all that laughing?". TV Guide.
- ^ a b c d e f Hobson, Dick (July 9, 1966). "Help! I'm a Prisoner in a Laff Box". TV Guide.
- ^ a b c d e Carroll Pratt (June 12, 2003). Emmy TV Legends: Carroll Pratt Interview (Interview with Karen Herman). Philo, California: Archive for American Television.
- ^ a b c d "TV Party: The Laugh Track". TVparty.com. Retrieved 2010-12-27.
- ^ "The Talk of the Town: Laughs". The New Yorker. September 10, 1984.
- ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad Iverson, Paul R. (February 1994, rev. December 2012), The Advent of the Laugh Track (2nd ed.), Hempstead, New York: Hofstra University Archives
- ^ a b Washington Post Thursday, April 24, 2003; Page B06: "Charles Douglass, 93; Gave TV Its Laugh Track"
- ^ a b c d e f g h i j k l Hobson, Dick (July 2, 1966). "The Hollywood Sphinx and his Laff Box". TV Guide.
- ^ a b c d e f g h i ""Canned Laughter: A History Reconstructed. Interview with Ben Glenn II, Television Historian" at". Andheresthekicker.com. Retrieved 2013-07-09.
- ^ Antique's Roadshow: 1953 Charlie Douglass "Laff Box" (flash) (in English). Boston, USA: WGBH Boston. 2010-06-12. Retrieved 2011-02-09.
- ^ a b Thursby, Keith (November 17, 2010). "Carroll Pratt dies at 89; Emmy-winning sound engineer". Los Angeles Times. Retrieved February 27, 2012.
- ^ a b Blasina, Niki (2003-04-21). "variety.com". variety.com. Retrieved 2013-07-09.
- ^ "Chipmunk history". Chipmunks.com. Retrieved 2013-07-09.
- ^ "The Official Sledge Hammer! Website – History". Sledgehammeronline.com. Retrieved 2013-07-09.
- ^ "Myreviewer.com/Review of MASH Season 3 DVD Review". Myreviewer.com. 2004-03-20. Retrieved 2013-07-09.
- ^ a b Seibel, Deborah Starr (April 16, 1992). "Funny Business: TV Laugh Tracks Can Still Cause Frowns, But The Studios Feel A Need To Be Humored". Chicago Tribune. Retrieved 2014-01-27.
- ^ "CTVA US Comedy - "The Mothers-In-Law" (Desi Arnaz/NBC)(1967-69) Eve Arden, Kaye Ballard". Ctva.biz. 1968-11-17. Retrieved 2013-07-09.
- ^ "Television Obscurities » The Good Guys". Tvobscurities.com. Retrieved 2013-07-09.
- ^ "The Mary Tyler Moore Show: The Complete First Season." The Making of Season 1. 24 September 2002. Television.
- ^ Williams, Bob (1972). "On the Air". The New York Times.
- ^ Stark, Steven D. (January 3, 1988). "Laughs are a Serious Business". The New York Times.
- ^ "The Laugh Track / TVparty!". Tvparty.com. Retrieved 2013-07-09.
- ^ a b c Nierenberg, Cari (September 23, 2011). "We May Hate Laugh Tracks — But They Work, Studies Show". The Body Odd at MSNBC.MSN.COM/. Retrieved January 6, 2012.
- ^ Judge, Michael [1], Retrieved on May 31, 2007
- ^ That's So Raven, Retrieved on July 31, 2009
- ^ Observations. Fat Albert and the Cosby Kids was the last Filmation series to utilize a full laugh track, when these ceased the laughs for its final season.
- ^ See Limited animation
- ^ Gary Avey. "modestoradiomuseum.org". modestoradiomuseum.org. Retrieved 2013-07-09.
- ^ ON. "Jogging Fever - Video Dailymotion". Dailymotion.com. Retrieved 2013-07-09.
- ^ a b c muppetcentral.com/Jim Henson interview
- ^ "Episode 208: Steve Martin". The Muppet Show. Season 2. Episode 208.
- ^ Observations.
- ^ "TV Tickets". http://www.tvtickets.com m. Retrieved 2011-06-20.
- ^ Andrews, Scott: Review – The League of Gentlemen's Apocalypse, Retrieved on May 31, 2007
- ^ "BrokenTV: Latex Lampoonery (Spitting Image Giveaway Special, Part 1)". Broken-tv.blogspot.com. Retrieved 2013-07-09.
- ^ "The Weird World of Sid and Marty Krofft". E! True Hollywood Story. Season 4. Episode 56. December 24, 2000. 60 minutes in. E!. http://www.imdb.com/title/tt0319476/.
- ^ Sid Krofft (July 27, 2000). Emmy TV Legends: Sid and Marty Krofft Interview (Interview with Karen Herman). Sherman Oaks, California: Archive for American Television.
- ^ Marty Krofft (July 27, 2000). Emmy TV Legends: Sid and Marty Krofft Interview (Interview with Karen Herman). Sherman Oaks, California: Archive for American Television.
- ^ Lou Scheimer (2007). The Archie Show: The Complete Series, Disc 2 (DVD). Classic Media.
- ^ a b c McTavish, Brian (July 3, 2003). "Laugh track is Serious Business, But Not Everyone Gives the Invention a Standing Ovation". The Baltimore Sun. Retrieved January 6, 2012.
- ^ a b c Adalian, Josef (November 27, 2011). "Please Chuckle Here: The Return of the Sitcom Laugh Track". New York Magazine. Retrieved 2013-07-17.
- ^ a b Parker, James (November 2011). "Family Portrait". The Atlantic 308 (4): 42–44. Retrieved October 18, 2011.
External links[edit]
- TVParty.com – The Laugh Track
- Newyorktimes.com – Charles Douglass
- Canned Laughter: A History Reconstructed – An Interview with Ben Glenn II, Television Historian
- Charley Douglass Laff Box - Facebook Appreciation Page


text:
29 U.S. Code § 2002 - Prohibitions on lie detector use
Except as provided in sections
2006 and
2007 of this title, it shall be unlawful for any employer engaged in or affecting commerce or in the production of goods for commerce—
directly or indirectly, to require, request, suggest, or cause any employee or prospective employee to take or submit to any lie detector test;
to use, accept, refer to, or inquire concerning the results of any lie detector test of any employee or prospective employee;
to discharge, discipline, discriminate against in any manner, or deny employment or promotion to, or threaten to take any such action against—
to discharge, discipline, discriminate against in any manner, or deny employment or promotion to, or threaten to take any such action against, any employee or prospective employee because—
such employee or prospective employee has filed any complaint or instituted or caused to be instituted any proceeding under or related to this chapter,
(Pub. L. 100–347, § 3,June 27, 1988, 102 Stat. 646.)
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29 USC | Description of Change | Session Year | Public Law | Statutes at Large |
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subset: commoncrawl


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Review of the Arc'teryx Atom LT Hoody by Daniel Wildey for The Epicentre
[ full story ] The Jacket © Jack Geldard - Editor - UKC, Nov 2008 The Patagonia Micro Puff Jacket What is it? The Patagonia Micro Puff is a synthetic belay style jacket. It's light-weight (550g), simple, and warm when wet. It's for belaying your mate on a cold day, sticking on over your shell on a Scottish winter route, carrying on summer Alpine excursions, going to the pub in February and a host of other things. It's not water-proof, it's not quite hard-core enough for winter Alpinism, it's not for Himalayan expeditions. There are a host of insulated jackets on the market, some are thick, some are thin. The thicker they are, usually the warmer they are � but they also weigh more and take up loads of room in your sack. So the trade off, how cold are you going to get? For real winter-climbing abuse you are going to need something heavier than the Micro Puff (See UKC Review of the Mammut Jacket and also a Belay Jacket overview), but for winter rock climbing and occasional Scottish routes, a jacket of a similar weight to the Patagonia Micro Puff is a good option.
The quick answer is � yes it does. The cut of the jacket is quite large, meaning that it fits over your other clothes easily, just like it is supposed to (perfect for slinging on over your shell when belaying). The side pockets are big enough to get gloved hands in easily, but the outer skin of the pocket is only made from the shell fabric, with no insulation - so they aren't super warm. The chest pocket is large, but the opening could have been bigger, a map will squeeze past the zip, just. I couldn't get a hand in with a big glove on, but I could fit map, compass and a few twix bars in there. The large inside drop-pocket is fantastic and for winter climbing is essential. Basically it's a big pouch on the inside in which you can easily chuck your mitts, gloves or water bottle, or anything that you want to store and keep warm on a belay. Great. Also good for sticking your rock boots in when bouldering - keeping them warm whilst you rest. The drop-pocket needs to be big, easy to access and have a light elastic top. The Micro-Puff ticks all those boxes. The jacket zips are high quality YKK zips, both on the pockets and on the main zip. These are bomb-proof and have worked well. The waist draw cord works fine, but it would have been nice to have one on the neck, which brings us on to the next topic: Hoods I have the version that doesn't have a hood. For a few extra quid I would definitely plump for the hooded version. I don't know what the hood is like, not having tested it, but it has got to be better than no hood! A winter belay jacket needs to have a hood if you are braving cold weather - be it on Ben Nevis or at The Plantation Boulders. Fabrics and technical stuff The shell fabric is �Lightweight, water-resistant and windproof�. It won't repel a rainstorm, but it is very windproof and the whole jacket feels very light. The synthetic lining is warm when wet, doesn't clump together and is made from recycled polyester, great. Details from the Patagonia website:
In SummaryOne of the original and still one of the better lightweight insulated jackets. Lots of features that are handy, and a cut that actually fits. My advice is to get the hooded version. Going for a winter north face? Get something heavier and warmer! Related UKC Reviews:
UKC Articles and Gear Reviews by Jack Geldard - UKC Chief Editor:


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US 5153669 A Abstract Optical metrology method and apparatus wherein three optical wavelengths are generated and separated into a reference beam (RB) and an object beam (OB) having substantially equal optical path lengths. After reflecting from a surface being measured OB is combined with RB and provided to sensors which measure the intensity associated with each of the wavelengths. Any difference between the intensities is indicative of a difference in the optical path lengths of OB and RB and is a function of the polarization state of each of the three returned wavelengths. Differences in optical path length are shown to be indicative of a displacement of the object being measured. Preferably, two multimode laser diodes (12,14) are provided for generating the three optical wavelengths. Two synthetic wavelengths are derived from the three optical wavelengths and are employed to improve the precision of measurement while retaining a large dynamic range made possible by the use of a large synthetic wavelength.
Claims(18) 1. Optical metrology apparatus comprising:
optical source means including a plurality of laser means, at least one of which is a multi-mode laser diode means, the optical source means having an output beam that simultaneously includes at least three discrete optical wavelengths; means, coupled to an output of the optical source means, for separating the output beam into a reference beam and into a measurement beam, the measurement beam being directed to a surface of interest; means for combining into a combined beam the reference beam and a portion of the measurement beam that reflects from the surface of interest; and means, responsive to a relative interferometric phase at each of the three optical wavelengths within the combined beam, for detecting a difference between an optical path length of the reference beam and an optical path length of the measurement beam. 2. Apparatus as set forth in claim 1 and further including an optical fiber for conveying the output beam and the combined beam.
3. Apparatus as set forth in claim 2 wherein the optical fiber is a single mode optical fiber.
4. Apparatus as set forth in claim 1 wherein the detecting means includes diffraction grating means for separating the combined beam into a plurality of beams each of which corresponds to one of the three wavelengths.
5. Apparatus as set forth in claim 4 and further comprising a plurality of photodetectors individual ones of which are disposed for receiving one of the plurality of beams for measuring a beam intensity thereof.
6. Apparatus as set forth in claim 5 and further including means, coupled to an output of each of the plurality of detectors, for processing the output thereof to determine a displacement of the surface of interest.
7. Apparatus as set forth in claim 1 wherein the optical source means includes a first multi-mode laser diode means providing at least two wavelengths and a second laser diode means providing a third wavelength.
8. Apparatus as set forth in claim 7 wherein each of the laser diode means is a multi-mode laser diode.
9. Apparatus as set forth in claim 1 wherein the separating means includes a polarizing beam splitter means disposed for receiving the optical output of the source means and for orthogonally polarizing the reference beam with respect to the measurement beam.
10. Apparatus as set forth in claim 1 wherein the separating means includes means for focussing the measurement beam upon the surface of interest.
11. Apparatus as set forth in claim 1 wherein the detecting means includes means for deriving a first synthetic wavelength and a second synthetic wavelength from the three optical wavelengths.
12. Apparatus as set forth in claim 1 and further including means for phase modulating the reference beam with respect to the measurement beam.
13. A method for performing optical metrology, comprising the steps of:
operating a plurality of laser means, at least one of which is a multimode laser diode means, for generating an optical output having a plurality of optical wavelengths; modifying the optical output to provide a phase modulated reference beam and a measurement beam having a fixed polarization relationship one to another, the measurement beam being directed to and reflecting from a surface of interest; combining the phase modulated reference beam and the reflected measurement beam into a combined beam; and responsive to a relative interferometric phase at each of the three optical wavelengths within the combined beam, detecting a difference between an optical path length of the reference beam and an optical path length of the measurement beam. 14. A method as set forth in claim 13 wherein the step of modifying includes a step of phase modulating the reference beam.
15. A method as set forth in claim 13 wherein the step of detecting includes a step of deriving a first synthetic wavelength and a second synthetic wavelength from the plurality of optical wavelengths.
16. A method as set forth in claim 13 wherein the step of operating includes a step of simultaneously operating at least two multi-mode laser diodes.
17. A method as set forth in claim 13 and including a step of translating the surface of interest with respect to the measurement beam.
18. A method of performing optical metrology to determine an absolute distance (L), comprising the steps of:
operating at least one multi-mode laser diode means while generating a plurality of optical wavelengths (λ) such that λ.sub.1 <λ.sub.2 <λ.sub.3, and deriving two corresponding synthetic wavelengths Λ.sub.12 >Λ.sub.13 therefrom; for L<Λ.sub.12 /4, determining a first synthetic fringe order (M.sub.12) in accordance with M.sub.12 =f(M.sub.12)=f(m.sub.1)-f(m.sub.2), where m.sub.1 is the optical fringe order of λ.sub.1 and m.sub.2 is the optical fringe order of λ.sub.2 ; employing M.sub.12 in determining M.sub.13 in accordance with M.sub.13 =f(M.sub.13)+I((M.sub.12 Λ.sub.12 /Λ.sub.13)-f(M.sub.13)), where the function I(a) yields an integer nearest to a value of the argument (a); determining the optical fringe order m.sub.1 in accordance with m.sub.1 =f(m.sub.1)+I((M.sub.13 Λ.sub.13 /λ.sub.1)-f(m.sub.1)); and determining the absolute distance L in accordance with L=(M.sub.ij Λ.sub.ij)/2. Description This U.S. patent application is related to a copending and commonly assigned U.S. patent application Ser. No. 07/676,049, filed Mar. 27, 1991, entitled "Optical Thickness Profiler", by H. Eugene Waldenmaier, Peter J deGroot, and Guy H. Hayes. This invention relates generally to optical metrology and, in particular, to optical metrology apparatus and method that employs two synthetic wavelengths and an optical wavelength to obtain sub-nanometer measurement resolution. One known method to extend the range of optical metrology applications for interferometry is to measure the interferometric phase at two distinct wavelengths. When monochromatic light is made to interfere with itself in a two-beam interferometer, the output intensity as measured by a square-law detector is proportional to a function h: h(mx)=cos.sup.2 (πm), (1) where m is a real number, referred to herein-as the fringe order, equal to one over 2π times the relative phase of one beam to the other. The optical path difference between the two beams is related to the fringe order by L=mλ/2, (2) where L is the one-way optical path difference, including the refractive index, and λ is the vacuum wavelength. In that h is a periodic function, the integer part of m cannot be determined by inverting Eq. (1). Interferometry typically provides only the fractional part f(m) of the fringe order, with the consequence that only changes of the length L, and not its absolute value, can be measured directly. This integer fringe-order ambiguity limits the usefulness of interferometry in many applications. The purpose of multiple-color, or multiple-wavelength, interferometry is to measure the integer part of m so that the entire length L may be directly measured with great precision in terms of the vacuum wavelength. Analytical procedures for determining lengths from multiple-wavelength interferometry exist in a variety of forms. One such procedure employs the concept of synthetic wavelengths, corresponding to differences in phase measurements for pairs of wavelengths in the interferometer. By example, and considering three optical wavelengths λ.sub.1, λ.sub.2, and λ.sub.3, there are three possible synthetic wavelengths defined by 1/Λ.sub.ij =1/λ.sub.i -1/λ.sub.j,λ.sub.j >λ.sub.i. (3) It is noted that a synthetic wavelength can be made much larger than a visible wavelength by choosing appropriate pairs of wavelengths λ.sub.i, λ.sub.j. The corresponding synthetic fringe orders M.sub.ij are obtained from the differences in optical fringe orders m.sub.i and m.sub.j as: M.sub.ij =m.sub.i -m.sub.j ( 4) The length L may be calculated from a synthetic wavelength measurement as: L=(M.sub.ij Λ.sub.ij)/2. (5) The larger the synthetic wavelength the greater the range of distances L that can be accommodated without possibility of error due to an integer ambiguity in the value of M.sub.ij. Conversely, the precision in the measurement of L is optimized when using relatively small synthetic wavelengths. The following prior art discuss various aspects of conventional two-wavelength interferometry. As described in U.S. Pat. No. 4,832,489, issued May 23, 1989, to J. C. Wyant et al., a two-wavelength phase-shifting interferometer employs two laser sources for reconstructing steep surface profiles, such as aspheric surfaces. A 256 detector array is used and the technique computes an equivalent phase independently for each detector. The following articles discuss various aspects of employing a synthetic wavelength for surface profilometry. In an article entitled "Contouring Aspheric Surfaces Using Two-Wavelength Phase-Shifting Interferometry" by K. Creath, Y. Cheng, and J. Wyant, Optica Acta, 1985, Vol. 32, No. 12, 1455-1464 there is described two-wavelength holography using an argon-ion laser and a He-Ne laser. Two wavelengths from the argon-ion laser (0.4880 micrometers or 0.5145 micrometers) were employed in conjunction with a single wavelength (0.6328 micrometers) from the He-Ne laser to yield equivalent wavelengths of 2.13 micrometers and 2.75 micrometer. An uncoated test surface was placed in one arm of the interferometer and interferograms were recorded using a 100 In an article entitled "Absolute Optical Ranging with 200-nm Resolution" by C. Williams and H. Wickramasinghe, Optics Letters, Vol. 14, No. 11, Jun. 1, 1989 there is described optical ranging by wavelength-multiplexed interferometry and surface profiling said to be carried out on an integrated circuit structure. A pair of GaAlAs single-mode diode lasers are used as optical sources. In an article entitled "Two-wavelength scanning spot interferometer using single-frequency diode lasers" by A. J. de Boef, Appl. Opt., Vol. 27, No. 2, Jan. 15, 1988 (306-311) there is described the use of two single frequency laser diodes to measure the profile of a rough surface. The two wavelengths are not time-multiplexed but are instead continuously present. In an article entitled "Two-Wavelength Speckle Interferometry on Rough Surfaces Using a Mode Hopping Diode Laser" by A. Fercher, U. Vry and W. Werner, Optics and Lasers in Engineering 11, (1989) pages 271-279 there is described a time-multiplexed two-wavelength source consisting of a single mode diode that is switched between two adjacent oscillation modes. The switching is accomplished by pump-current modulation with the diode thermally tuned to a region near a so-called "mode hop", that is, near a region where the diode output readily switches from one wavelength output to another. This technique is said to have enabled the profiling of a ground lens surface. As was previously stated, the larger the synthetic wavelength, the greater the range of distances (L) that can be accommodated without possibility of error due to an integer ambiguity in the value of the synthetic wavelength fringe order (M.sub.ij). However, the precision in the measurement of L is best when small synthetic wavelengths are used. It is thus an object of the invention to provide optical metrology apparatus that employs a plurality of synthetic wavelengths of different size. It is a further object of the invention to provide optical metrology apparatus that employs a plurality of synthetic wavelengths of different size, the synthetic wavelengths being derived from three optical wavelengths emitted from two laser diodes, at least one of which is a multi-mode laser diode. It is another object of the invention to provide optical metrology apparatus that employs a plurality of synthetic wavelengths of different size, using progressively smaller synthetic wavelengths to improve the precision of measurement while retaining the dynamic range made possible by a large synthetic wavelength. The foregoing and other problems are overcome and the objects of the invention are realized by method and apparatus for performing optical metrology. In accordance with a method of the invention, and apparatus for accomplishing same, a first step generates an optical output having a plurality of optical wavelengths. A next step modifies the optical output to provide a phase modulated reference beam and a measurement beam that are orthogonally polarized with respect to one another. The measurement beam is directed to and reflects from at least one surface. A further step combines the phase modulated reference beam and the reflected measurement beam into a combined beam. A next step detects, in accordance with a polarization state of three optical wavelengths within the combined beam, a difference between an optical path length of the reference beam and an optical path length of the measurement beam. The difference in path lengths is indicative of an absolute distance L. The teaching of the invention provides an optical metrology system wherein three optical wavelengths of a fixed polarization are separated into two beams (OB and RB) having, ideally, nearly equal optical path lengths. The two beams are recombined and provided to sensors which measure the intensity associated with each of the wavelengths. The teaching of the invention furthermore provides a plurality of multimode laser diodes for generating three optical wavelengths. Two synthetic wavelengths are derived from the three optical wavelengths. The synthetic wavelengths are of different size and progressively smaller synthetic wavelengths are employed to improve the precision of measurement while retaining a large dynamic range made possible by the use of a large synthetic wavelength. The above set forth and other features of the invention are made more apparent in the ensuing detailed description of the invention when read in conjunction with the attached drawing, wherein: FIG. 1 is a simplified block diagram of a three-color interferometer for performing absolute distance measurement and surface profiling; FIG. 1a is a graph showing the combined optical spectrum of two multi-mode laser diodes; FIG. 2 is a graph depicting a high resolution displacement measurement performed by the three-wavelength interferometer of FIG. 1; and FIG. 3 is a graph of a central region of an unsilvered parabolic mirror obtained with the three-wavelength interferometer of FIG. 1. Referring first to FIG. 1 there is shown a three-wavelength, or three-color, optical metrology system 1 that is constructed and operated in accordance with an embodiment of the invention. System 1 includes a three-wavelength source 10 that includes, preferably, two multimode laser diodes 12 and 14, collimating optics 12a and 14a, mirrors 12b and 14b, and an optical isolator 15. The laser diodes 12 and 14 are simultaneously operated and thus simultaneously provide three wavelengths. The emission from each laser diode 12 and 14 is transmitted through an optical fiber 16 to phase-modulating, two-beam polarizing interferometer optics 18. A reflected object beam, also referred to as a measurement beam, and a reference beam are recombined and transmitted back through the optical fiber 16 to a diffraction grating 20. Detectors 22, 24 and 26 are positioned in space to intercept the separated wavelengths provided by the grating 20, via focussing optics 21, and to measure the intensity of the three different wavelengths. A processor 28 calculates fringe orders and determines an absolute distance (L) to the object surface. As can be seen in the graph of FIG. 1a in the three-wavelength interferometer system 1 two different wavelengths (λ.sub.1,λ.sub.2) in the 785 nm region of the spectrum are selected to derive a first synthetic wavelength Λ.sub.12 =720 micrometers, and λ.sub.1 is combined with a third wavelength λ.sub.3 from the 815 nm region for generating a significantly smaller synthetic wavelength Λ.sub.13 =20 20 micrometers. The laser wavelength separation required for a Λ.sub.13 =20 micrometer synthetic wavelength is 32 nm, which is relatively large when compared to the 0.3 nm mode separation of a typical laser diode output. Thus, two diodes are required, with different center wavelengths. In principle, since only three wavelengths are used, one laser diode may be a multimode device and the other a single-mode device. However, the use of two multimode laser diodes is preferred in that undesirable mode hopping associated with single-mode laser diodes is avoided. Two suitable multimode laser diodes are Sharp LT010MDO and LT023MDO laser diode devices. The optical fiber 16 spatially filters the emissions of the laser diodes 12 and 14 and facilitates the mechanical mounting of the interferometer optics 18 for different measurement tasks. The source light from the optical fiber 16 is focussed at the object surface by optical element 17 and is split into an object beam (OB), and into a reference beam (RB). Reference beam RB is directed, via a reflector 19, to a mirror 18a that is coupled to a piezo-electrical transducer 18b. The mirror 18a is oscillated by the transducer 18b and functions to phase modulate the reference beam RB. Suitable oscillation frequencies in the range of approximately zero to approximately 1000 Hz may be employed, although the teaching of the invention is not limited to this range. For example, an electro-optic device such as a Kerr cell may be employed to achieve significantly greater rates of oscillation. OB and RB are given fixed orthogonal polarizations by a polarizing beam splitter 18c. As a result, when the two beams are recombined into the optical fiber 16 after reflection, the resultant polarization vector rotates with the phase modulation. The light from the interferometer optics 18 is transmitted back through the fiber optic 16 to a polarizing beam splitter 30 at the source end of the optical fiber 16. The reflected light is analyzed after passing through the beam splitter 30. The light is separated into its constituent wavelengths by the diffraction grating 20 such that the individual wavelengths of the combined optical spectra appear as a series of spatially distinct points in space. The detectors 22, 24, and 26 are positioned at these spatially distinct points for detecting the intensity associated with each of the three wavelengths. The operation of the phase modulator of the interferometer optics 18 results in a wavelength-dependent and a phase-dependent amplitude modulation of the radiation. As can be seen, the teaching of the invention provides an optical metrology system wherein three wavelengths of a fixed polarization are separated into two beams (OB and RB) having substantially equal optical path lengths. The two beams are recombined and provided to sensors which measure the intensity associated with each of the wavelengths. Furthermore, the source/detector optics and the interferometer optics may be mechanically decoupled from one another by the use of the optical fiber 16. The processor 28 may actively control the phase modulation of the interferometer optics 18 while recording the intensity measured by the three detectors 22, 24 and 26. Alternately, the phase modulator may run at a fixed rate and the processor 28 may employ well known statistical methods applied over a group of samples. In either case, a suitable phase demodulation algorithm is used to determine the optical fringe orders (m) corresponding to the three wavelengths λ.sub.i. One suitable phase demodulating algorithm is known as a five point algorithm and is described by P. Harihan, B. F. Oreb and T. Eiju in Appl. Opt. 26 2504 (1987). Length calculations involving Eq.(6), Eq.(7) and Eq.(8), described below, are performed in software and the results may be displayed to an operator and/or stored on disk. The change in optical path length is measured by applying Eq. (2), (6), (7), and (8) after detection of the relative interferometric phase at each of the three wavelengths. Although not shown in FIG. 1, the system 1 further includes laser diode power supplies, thermoelectric coolers, detector amplifiers, a piezoelectric driver, and an analog input interface that couples the detector outputs to the processor 28. In accordance with an aspect of the invention there are considered three wavelengths λ.sub.1 <λ.sub.2 <λ.sub.3, and two corresponding synthetic wavelengths Λ.sub.12 >Λ.sub.13. The procedure for measuring an absolute distance L with interferometric resolution is as follows. Assuming that L is less than Λ.sub.12 /4, the integer part of the synthetic fringe order M.sub.12 is zero, and M.sub.12 =f(M.sub.12)=f(m.sub.1)-f(m.sub.2). (6) The fractional parts f(m.sub.i) of the interferometric fringe orders m.sub.i are obtained by inverting Eq. (1) or by performing some equivalent phase-detection algorithm. A next step uses the shorter synthetic wavelength Λ.sub.13 to increase the precision in the measurement. The following equation makes use of M.sub.12 in calculating M.sub.13 without an integer ambiguity: M.sub.13 =f(M.sub.13)+I((M.sub.12 Λ.sub.12 /Λ.sub.13)-f(M.sub.13)). (7) The function I(a) appearing in Eq.(7) yields the integer nearest to the argument a. The optical fringe order m.sub.1 is now calculated from m.sub.1 =f(m.sub.1)+I((M.sub.13 Λ.sub.13 /λ.sub.1)-f(m.sub.1)). (8) The final step employs Eq.(5) to determine the distance L. The measurement of L is thus accomplished as a three-step process, wherein M.sub.12 is used to remove the integer fringe order ambiguity in the calculation of M.sub.13, and M.sub.13 is used in the calculation of m.sub.1. This technique results in interferometric accuracy, but without the integer fringe-order ambiguity of conventional single-wavelength interferometry. For the illustrated embodiment the largest synthetic wavelength is 720 micrometers and the distance L is measured absolutely over a .+-.180 micrometer range about zero. When L is equal to zero there is no optical path length difference between the reference and object beams in the interferometer optics 18. For values of L outside this .+-.180 micrometer range the measurement is relative, with an ambiguity interval of 360 micrometers. However, for many metrology applications there is sufficient knowledge of the object under measurement to remove this ambiguity. The synthetic wavelengths must be chosen so as to substantially eliminate a possibility of introducing integer errors in Eq. (7) and Eq. (8). This restraint places upper limits on the size of the synthetic wavelengths used in the three-wavelength interferometer system 1. It can be shown that the following conditions must be satisfied: Λ.sub.12 <1/Δm(Λ.sub.13 /4-L/2(ΔΛ.sub.12 /Λ.sub.12 +ΔΛ.sub.13 /Λ.sub.13)) (9) and Λ.sub.13 <1/Δm(λ/4-L/2(Δλ.sub.13 /Λ.sub.13 +ΔΛ/λ))+λ. (10) where the uncertainties Δm, Δλ, ΔΛ.sub.12, and ΔΛ.sub.13 refer to the maximum absolute values of the possible errors in any one of the parameters m, λ, Λ.sub.12, and Λ.sub.13, respectively. Referring to FIG. 2 there is shown a high-resolution displacement measurement performed by the three-wavelength interferometer system 1 of FIG. 1. The object was moved slowly towards the interferometer optics 18 by a piezoelectric translator mounted behind the object mirror. The measurement repeatability was 0.5 nm. Referring to FIG. 3 there is shown a profile of a central 1 region of a 7.5 cm diameter, f/2 unsilvered parabolic mirror. Each one of the 100 independent distance measurements made for this profile was absolute. The three-color interferometer system of the invention is particularly useful for profiling unusual topographical surfaces and optical components that cannot be tested by conventional full-aperture interferometry. Since each of the 100 measurements was absolute, there was no requirement to interpret fringes or perform high-bandwidth phase tracking as the mirror was being translated from one point to the next. It should be noted that the slope of 20 micrometers of profile variation per millimeter of scan near the edge of the data grid is well beyond the capability of a conventional full-aperture figure-testing interferometer. This capability makes the three-wavelength interferometer system of the invention particularly useful for figure metrology of unusual optical components, such as off-axis aspheres and segmented optics. In general, the profilometry accuracy is determined by the flatness of travel of the XY stage, which must be characterized for high-precision measurements. Alternatively, a Fizeau-teype geometry may be used for the interferometer optics so that the measurement is less sensitive to random mechanical motion of the stage. Although the present invention has been described in the context of specific wavelengths and optical components it should be realized that other wavelengths and more or less than the number of optical components shown in the figures may be employed, while yet obtaining the same result. Also, although the various lens elements are depicted as simple lens elements it should be realized that each may include a number of optical components to achieve the desired function. Thus, while the present invention has been particularly shown and described with respect to an embodiment thereof, it will be understood by those skilled in the art that changes in form and details may be made therein without departing from the scope and spirit of the invention. Patent Citations
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Great seeing some young guys and not so young fellas getting their first bow kills in the last year or two. My first bowkill was a little 5 point whitetail back in 2000. Been a lot since then, but I'll never forget that feeling.
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