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The Barrow County Sheriff's Office reported the following incidents:
An alleged drunken driver was arrested on a felony eluding charge early Thursday after he tried to flee from an officer, Athens-Clarke police said.
A thief stole a 1996 Ford Ranger valued at $5,000 from a home on Prince Avenue between 11 p.m. Wednesday and 1 a.m. Thursday, Athens-Clarke police said.
A man reported a handgun and two rifles altogether worth $1,350 were stolen from his home in the 500 block of Rustwood Drive between July and Wednesday, Athens-Clarke police said.
A 23-year-old man faces possible theft and bad check charges after he was found living in squalid conditions in an apartment on Barnett Shoals Road from which he was being evicted, Athens-Clarke police said.
Members of the Northeast Georgia Regional Drug Task Force searched a home on Waddell Street Tuesday, making one arrest and seizing crack and powder cocaine, digital scales, cash, and a rifle, Athens-Clarke police said.
South Carolina coach Steve Spurrier stirred up some mild controversy this spring when he called out Georgia for consistently having players suspended during their annual match-up.
Many factors will determine the outcome of Saturday night's showdown between Georgia and South Carolina, but one thing that will almost assuredly play a role is the turnover battle.
Heading into this weekend's pivotal showdown, there is little debate that the Georgia-South Carolina rivalry is as monumental as it's ever been.
JERUSALEM — If the Messiah descends from the Mount of Olives as foretold in the Bible, America's two biggest Christian broadcasters are well-positioned to cover it live thanks to recent acquisitions of adjacent Jerusalem studios on a hill overlooking the Old City.
Texas-based Daystar Television Network already beams a 24-hour-a-day live webcam from its terrace. Not to be outdone, Costa Mesa, Calif.-based Trinity Broadcasting Network last month bought the building next door.
The Jackson County Sheriff's Office reported the following incidents:
The MacDonalds have a farm. And on this farm, they have ZOMBIES!!! Cynthia and Patrick MacDonald co-created Zombie Farms, which opens today in Athens.
The following events are going on around Athens on Friday, October 5, 2012:
GAINESVILLE, Ga. — Gainesville's fire chief will retire after two decades with the department in northeast Georgia.
ATLANTA — Georgia health officials are helping to notify more than 150 people who may have received steroids produced by a firm tied to a meningitis outbreak.
Athens-Clarke police arrested a 36-year-old man Wednesday morning after he beat his girlfriend to "exorcise" her of demons that made her cheat on him.
MACON, Ga. — Authorities in a central Georgia county say they're investigating the deaths of several dogs they believe were poisoned.
ATLANTA — Authorities say a former Verizon Wireless employee has been sentenced to prison after federal officials say he ordered nearly $2.8 million in equipment for the firm and then sold it out of his Georgia home.
DALLAS, Ga. — A Georgia couple accused of confining their teenage son to a bedroom for years with little food are scheduled to appear in court.
MACON, Ga. — Officials from the Bibb County Sheriff's Office will discuss the findings of an internal probe into a traffic stop involving a local judge.
The Madison County Sheriff's Office reported the following incidents:
FORT LAUDERDALE, Fla.— Florida can begin removing about 200 potentially ineligible voters from state rolls because they might not be U.S. citizens, a federal judge ruled Thursday.
FORT WORTH, Texas — American Airlines is cancelling dozens of flights as it scrambles to fix seats that could pop loose during flight.
NEW YORK (AP) — Ann Romney is guest-hosting "Good Morning America" next Wednesday.
NEW YORK — The Nielsen ratings company says an estimated 67.2 million people watched the first debate between President Barack Obama and challenger Mitt Romney, the largest TV audience for a presidential debate since 1992.
STATE COLLEGE, Pa. — A judge on Thursday granted a request by former Penn State assistant football coach Jerry Sandusky that the court return to his wife the $50,000 she put up for his bail before he was convicted this summer of sexually abusing nearly a dozen boys.
HOUSTON — Actress Daryl Hannah of "Splash" fame was arrested in northeast Texas on Thursday, along with a 78-year-old landowner as the pair protested an oil pipeline designed to bring crude from Canada to the Gulf Coast.
MADISON, Wis.— His performance panned, President Barack Obama is changing his debate strategy against Republican Mitt Romney, aides conceding the president must find a crisper way to sell his agenda and counter his opponent without getting lost in the weeds.
LOS ANGELES — A former Charles Manson follower imprisoned for 40 years in a double murder engineered by Manson won a recommendation of parole Thursday in his 27th appearance before a parole board panel.
NEW YORK — Is this "Idol" threat an idle threat?
NEW YORK - Former PBS anchor Jim Lehrer says a debate moderator should be like a baseball umpire - get out of the way and let the candidates play.
BOSTON — A career criminal whose bail was reduced after a chemist was accused of mishandling drug samples at a state lab failed to show up for a court date and is now a fugitive, authorities said Thursday.
DENVER — A federal appeals court in Denver is refusing to block extradition of a gay illegal immigrant who sought protection in the U.S. claiming Mexican authorities persecute gay people.
LOS ANGELES — Randy Newman, Public Enemy, N.W.A, Donna Summer and — to the delight of progressive rock fans around the world — Rush are among the names on the final nominees list for 2013 induction into the Rock and Roll Hall of Fame, which for the first time will be announced at a ceremony to be held next year in Los Angeles.
MADISON, Wis. — President Barack Obama will fire-up his Democratic base during a rally Thursday at the University of Wisconsin-Madison, where he's expected to urge his supporters to vote early.
NEW YORK — Facebook has topped 1 billion users, but the past few months have not been easy.
NASHVILLE, Tenn. — An outbreak of a rare form of meningitis is likely to grow after sickening 26 people in five states, including four who died, health officials warned.
Like so many other Americans, David Becker knew long before Wednesday night's debate whom he'd be supporting in the presidential election. And, like so many other Americans, he tuned in anyway.
DENVER — Little more than a month from Election Day, Republican Mitt Romney is barreling out of the first presidential debate energized by a solid performance that telegraphed his determination to take it to President Barack Obama with gusto. The president, intent on keeping his momentum from stalling, is warning Americans that his GOP rival's policy prescriptions for a fragile economy are more fantasy than reality.
Social networks lit up Wednesday as users argued over who emerged as the key character from Wednesday's first president debate. The candidates? Forget it — most attention focused on moderator Jim Lehrer, or the cherished children's TV character Big Bird. Here are some of key online trends from the night:
DENVER — President Barack Obama says Republican rival Mitt Romney would turn Medicare into a private system and put seniors at the mercy of insurance companies. Romney counters that the incumbent Democrat already has raided the Medicare fund and weakened the system.
DENVER — Political buffs and young people looking for free T-shirts crowded the University of Denver campus Wednesday to watch the first debate between President Barack Obama and Republican Mitt Romney on large outdoor screens.
Some notable moments from the first presidential debate Wednesday night between Democratic President Barack Obama and Republican Mitt Romney, just 34 days before the Nov. 6 election.
WASHINGTON — Mitt Romney's idea to impose a $17,000 limit on taxpayer deductions would hit hardest on wealthy Americans, who make the most use of deductions to reduce their tax burden. But that adjustment alone would not be enough to make up for the revenue lost in Romney's plan to reduce income tax rates for everyone by 20 percent.
DENVER — Americans demanded details and, boy, did they get them.
The Oconee County Sheriff's Office reported the following incidents:
This cartoon appears in the Athens Banner-Herald on October 5, 2012.
WHO CAN SAY?: As of presstime Thursday, it was unclear whether the Clarke County Board of Education might join a number of other school boards around the state in pursuing a resolution opposing a proposed constitutional amendment that will appear on Georgia ballots next month regarding the state's ability to approve charter schools for local school districts. Among other things, opponents of the measure worry that it could further erode state funding for public schools.
Georgia's offensive line has gone into stealth mode for its monster challenge.
Josh Brewer is getting a double dose of competition and history in his first home tournament as the Georgia women's golf coach.
Athens, GA • Athens Banner-Herald ©2016. All Rights Reserved.


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Solar photovoltaics for lighting projects
A presentation at LightFair International focused on solar photovoltaics, providing the attendee with information on how to select the right PV option.
At "The Technology of Solar Photovoltaics in the Lighted Environment" session at LightFair International on June 5, 2014, Jeff Shields of WFLI-JAX and Stephanie Holloran of Solar Electric Power Co. focused on how clients can incorporate solar photovoltaic (PV) systems into projects. They focused on the four types of solar PV:
- Stand-alone
- Grid-tied solar
- Battery back-up
- Hybrid solar
Depending on the type of project, they said, one of the above options may be appropriate. They provided project samples, and discussed PV system controls.
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Consulting-Specifying Engineer's Product of the Year (POY) contest is the premier award for new products in the HVAC, fire, electrical, and...
Consulting-Specifying Engineer magazine is dedicated to encouraging and recognizing the most talented young individuals...
The MEP Giants program lists the top mechanical, electrical, plumbing, and fire protection engineering firms in the United States.
40 Under 40; Stand-alone medical buildings; NFPA 92; Specialty fire suppression; Applying 90.1 in lighting design
2016 Product of the Year Finalists: Vote now; Data center Q&A; LED codes; Smart buildings
Fire pump power system design: How to design safe, reliable fire pump power service; Water management in commercial buildings; Emergency egress, illumination
Designing generator systems; Using online commissioning tools; Selective coordination best practices
Understanding transfer switch operation; Coordinating protective devices; Analyzing NEC 2014 changes; Cooling data centers
As brand protection manager for Eaton's Electrical Sector, Tom Grace oversees counterfeit awareness...
Amara Rozgus is chief editor and content manager of Consulting-Specifier Engineer magazine.
IEEE power industry experts bring their combined experience in the electrical power industry...
Michael Heinsdorf, P.E., LEED AP, CDT is an Engineering Specification Writer at ARCOM MasterSpec.

subset: commoncrawl


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am the network administrator of a country wide net. with 5 branches. I
have 2 windows 2003 servers in each branch.
In the last june, one of my remote DC Server started to show the event
2019, and then stoped servinng all the network services. We restarted the
server every 6 hours until reformated.
Now I start having the same problem in another DC server in other
branch. I will format it the next weekend.
I was looking for information about this in the newsgroups and in the
microsoft support site and I only found something related with macaffe
Antivirus. We don´t use any macaffe product.
Do you have any suggestion about that ? Do you know another case like
this ?
I am very happy with Windows 2003 & Exchange 2003 BUT I really don´t
want to reformat the servers every 6 months
Thanks in advance


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A rundown on former Auburn players during Week 12 of the NFL season. Full story »
On the day after Alabama defeated Auburn 29-13 in the Iron Bowl at Jordan-Hare Stadium, the NFL is staging the closest thing it can have to the Iron Bowl in the 2015 season at Paul Brown Stadium. Full story »
St. Louis Rams left offensive tackle Greg Robinson realized the transition from college to the NFL wouldn't be entirely smooth, but he didn't think it would be this difficult. Full story »
Since coming back from a knee injury suffered at Georgia last season, Todd Gurley of the St. Louis Rams has run the ball as no rookie in NFL history has. Full story »
The St. Louis Rams' rallying cry during the 2014 NFL season could have been "War Ram Eagle." Running back Tre Mason and offensive lineman Greg Robinson emerged as starters during their rookie seasons out of Auburn, and St. Louis had former Tigers Daren Bates and Will Herring in its linebacking corps and leading the special teams. Former Auburn receiver Emory Blake was on the Rams' practice squad. Full story »
Neither Greg Robinson nor Tre Mason was in the starting lineup for the St. Louis Rams' first four games of the 2014 season, even though Robinson was the second player picked in last year's NFL Draft and Mason joined the team in the third round. When the Rams kick off the 2015 season on Sept. 13, St. Louis general manager Les Snead expects both of the former Auburn stars to be in the lineup. Full story »
Auburn did not enjoy its finest season at the NFL level in 2014. The conference championship games were played without a former Auburn player on any of the four teams. Several of Auburn's most established NFL players, such as Karlos Dansby, Nick Fairley and Cam Newton, had their seasons derailed to various degrees by injuries. Full story »
Auburn's 2011 class finished No. 5 in the nation according to the 247 Composite Rankings, which take the average of every major recruiting service, and to a large degree, served as a good foundation for the Tigers. For starters, 17 of the 24 signees finished their careers with the Tigers, and the class has already produced two NFL draft picks -- including the No. 2 pick in the 2013 draft -- a Heisman Trophy finalist, four participants in this year's Senior Bowl (meaning more draft picks are to come) and 11 regular starters. Full story »
. This year, with three players involved in the Iron Bowl rivalry on the St. Louis Rams roster, former Alabama center Barrett Jones and former Auburn running back Tre Mason and left tackle Greg Robinson made a bet: if your team loses, you have to wear your rivals' T-shirt. Full story »
St. Louis running back Tre Mason couldn't wait to get to San Diego, where the Rams will play the Chargers on Sunday - and not just because he's coming off his first 100-yard rushing game in the NFL. Mason was looking forward to seeing former Auburn teammate and Iron Bowl hero Chris Davis, who is a cornerback for the Chargers. Full story »
Auburn bought a policy last season for former left tackle Greg Robinson, who ended up being selected by the St. Louis Rams with the No. 2 pick. Full story »
In his first start at left offensive tackle in the NFL, Greg Robinson earned a game ball. St. Louis coach Jeff Fisher gave game balls to the entire Rams' offensive line last week after the linemen overcame uncertainty, injuries and the San Francisco 49ers defense for a 13-10 victory. Full story »
Two members of Auburn's 2013 SEC championship team made their first NFL starts on Sunday, with cornerback Chris Davis on the San Diego Chargers' first-team defense and running back Tre Mason on the St. Louis Rams' first-team offense. Full story »
The St. Louis Rams selected Auburn's Greg Robinson with the second pick of the 2014 NFL Draft to be their left offensive tackle of the future. The future arrives on Sunday when the Rams visit the San Francisco 49ers. Robinson will make his first NFL start at the position he played for the Tigers. Full story »
St. Louis Rams running back Tre Mason hadn't carried the ball in a meaningful game since he'd run 37 yards for a touchdown to put Auburn ahead of Florida State in the fourth quarter of the BCS national championship game on Jan. 6. After being inactive for his first four games in the NFL, Mason broke a 24-yard run in his first official pro rushing attempt on Monday night against the San Francisco 49ers. Full story »
Greg Robinson had played 10 snaps for the St. Louis Rams offense in the 2014 season heading into Monday night's game against the San Francisco 49ers. The game turned into the coming-out party for the second selection in the 2014 NFL Draft. The former Auburn star started at left guard, played all 74 offensive snaps and earned another start on Sunday against the Seattle Seahawks. Full story »
Former Auburn running back Tre Mason's first NFL rushing attempt went right up the middle and gained 24 yards for the St. Louis Rams on Monday night. Mason made his NFL debut in St. Louis' fifth game of the season. Full story »
When the St. Louis Rams selected Auburn offensive tackle Greg Robinson with the second selection in the NFL Draft in May, they penciled him in as their starting left guard. On Monday night, that's finally going to happen. Full story »
Whenever St. Louis Rams coach Jeff Fisher has been asked about the second player picked in the 2014 NFL Draft, former Auburn offensive tackle Greg Robinson, he's said about the same thing throughout the 2014 season. Full story »


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Have your child star in an adventure book!
Created by Rebekah knight at slow down mummy creations.
Available to buy at slow down mummy on facebook.
Other story adventures available.
'Adventures in Wonderland'
I am a Creative, spiritual, Wife, Mother, woman & friend. I enjoy writing poetry, I have some published, I recently created slow down mummy creations off the back of success of the poem. Life is a journey and each day brings a challenge, but I am here with arms wide open!
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Giorgia-Evie and the Owl Published March 15, 2013
The adventures of Jessie & SlackJack Published August 11, 2012


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6th Annual
Green Bay Film Festival
March 03, 2016 to March 06, 2016
Select a Category of Entry to View
Wisconsin's Own
Native American Films
In Focus
Film Market
Submit Online
211 N. Broadway Street, Ste 218
Green Bay WI 54303
Phone: 920-265-0333
CLOSED FOR THE SEASON • Information may be outdated. Add this event to your Watch List and set a Remind-Me if you want to be notified when the next Call For Entries is posted.
A "creative treatment of actuality". A nonfictional film intended to document some aspect of reality, primarily for the purposes of instruction or maintaining a historical record.
We are accepting films for consideration with a running time of less than 45 minutes. Shorts will be playing throughout the festival. If your short fits another category such as our "IN FOCUS: ( social issue/social justice, woman's issues), is a family PG orientated film or Animation, Wisconsin made, Documentary or Native American film please be sure to enter in those appropriate categories.
We are also have a Saturday night screening selection of horror or cult films!
We are accepting films in all genres for consideration with a running time of 45 minutes or longer. We will be playing a variety of features and hope to give our audiences a well-rounded selection!
Features will be playing throughout the festival with one selection opening the festival. If your feature focus is a family PG orientated film, Wisconsin made, Documentary, Native American, Animation or fits this year's "In Focus" (Social Justice or Women's Issues) please be sure to enter in those appropriate categories.
We are also have a Saturday night screening selection of horror or cult films!
We offer a special opportunity for families to introduce their children to independent films. If your story is directed to entertain Children then this category is perfect for you. Please be sure that the material is PG appropriate. Films can be any length but should engage the attention span of children. IF your film is an animation, please use the NEW Animation Category. Your film still may play with Children and Family films.
Wisconsin's Own
As part of our mission to encourage & support local filmmakers, we are looking for films made in Wisconsin and/or films made by Wisconsin filmmakers. These can be features or shorts of any genre. Please be sure to include your submission in the Wisconsin category!
Native American Films
GBFF supports and encourages Native American Filmmakers and films about Native Americans to enter into this category.
In Focus
"IN FOCUS" is a category created to expand our community awareness. This year we are considering films about Social Justice Issues and Women's Issues. Talkbacks, Seminars and other programs with St. Norbert College may be formed around these films.
We are excited to add Animation as a NEW category this year! All Animated or Anime films will be considered.
The mission of the Green Bay Film Festival is to provide a rich cultural and educational experience for our community and visitors while promoting Green Bay as a hub for film making and film appreciation.
You are cordially invited to attend the 6th Annual Green Bay Film Festival.
This year the festival is partnering with St. Norbert College with all new venues! The festival weekend takes place March 4-6, 2016 and expands with the new "Festival Around Town" showing Festival selections once a week for six weeks starting mid January and Festival Film Favorites will have the added prestige to be shown at special event showings later in March and April. These specially selected films will screen at both the "Festival Around Town' & the festival weekend.
Now in it's 6th year this Festival not only expands screening opportunities it also is adding a new category, ANIMATION. The partnership with St. Norbert College highlights SOCIAL JUSTICE & WOMEN'S FILMS in this year's IN FOCUS category. We continue to encourage NATIVE AMERICAN FILMS, and encourage filmmakers to submit THRILLER & HORROR films for our Saturday night evening of Terror.
For all our filmmakers we are focused to present a variety of experiences to connecting filmmakers in a community setting! Showing many genre's of films, this festival also includes talk backs, seminars, awards, parties, networking all In typical Midwest fashion! You are our guest extraordinaire!
You have the opportunity to make your name and film known to a community thirsty for talent with a thriving knowledgeable film base.
As one filmmaker said last year, "Green Bay is the perfect place to host a film festival. The talent is real and everyone's doors are open." We couldn't agree more.
See you there!
Alex Zacarias (Chairperson); Cyndee Sweetland (Festival Registrar, Director)
Additional rules not already specified are as follows:
Competition Rules
Submissions in all categories must be received by the end of the day on October 4, 2015. Absolutely no late submissions will be considered after this date. All submissions must be received through Withoutabox, Submittable and FilmFreeway. You may submit a vimeo link & password thru WAB by including it on your cover letter.
For specific contest rules for The Future Filmmakers competition for high school, middle and primary school students in Wisconsin (not college students), please go to our website.
CAN YOU BE PRESENT AT THE FESTIVAL? Please do! We have set up the festival to be filmmaker friendly with plenty of press, interfacing with other filmmakers, seminars, and audience interaction. We offer seminars specific to our filmmakers to learn about what is going on in the industry today, to connect, network and learn. We would like to provide our audience with the opportunity to learn more about a variety of film types and filmmaking. We are including question and answer periods after the showings as well as opportunities for our viewers and sponsors to interact with filmmakers. We will be looking for films that can also provide a representative at the festival. This can be the writer, producer, director, and/or cast members from the production.
The GBFF reserves the right to determine eligibility of any work submitted. All films submitted must have a completion date after March 1, 2014.
Preferred format for screening copies are: WAB-upload file to secure screener or you can provide a vimeo link & password on WAB in your cover letter. Our jury screens online films only. Please make sure your uploaded file works correctly. If you have any problems with WAB secure online screener, please contact WAB, the festival cannot help you with this. If you have any questions in regards to this, contact the festival director.
We ask that if your film includes non-English dialogue that you provide either English subtitles or an English dubbed version. Please make sure your subtitles are big, easy to read, and don't fly of the screen so fast you can't read them.
We must receive your entry fee prior to accepting your film for submission. Please make your payment online. You may send a check to the address below. Your fee is non-refundable.
Green Bay Film Festival
Attention: Submissions
211 N. Broadway St. Ste 218
Green Bay, WI 54303
You may submit as many films as you like. Each film can only be submitted into one category. We do not offer reduced rates for multiple submissions. Please upload each film separately, or put each film on a separate DVD.
Films selected for screening at the Festival will be notified approximately November 18, 2015. All attending filmmakers will be provided with two all-access pass to the 2015 GBFF, good from March 4-6, 2016 which includes the "Festival Around Town" screenings, all seminars and festival weekend events. Awards will be presented on Sunday, March 6.
Terms and Conditions:
1. I have read, understood and complied with all eligibility requirements of the categories for which I would like this film to be considered.
2.To the best of my knowledge, all of the statements in this document are true.
3.This film is not subject to litigation nor is threatened by any litigation.
4.I am duly authorized to submit this film to the Festival and its Competition and understand if accepted, that the Festival holds the right to screen my film for Festival screenings the year of the festival I have submitted to.
5.I understand that the Green Bay Film Festival and Film Green Bay are not responsible for any type of damage to or loss of the print during screenings, at any other time during the course of the Festival, while the film is in the Festival's possession or while en route to or from the Festival, and I release Green Bay Film Festival and Film Green Bay from any and all liabilities regarding damage to or loss of the print while en route to/from the Festival or while it is in their possession.
6.Should this film win an award at the Green Bay Film Festival, I am authorized and/or empowered by all parties legally representing this film to name the individual(s) listed on the Award Designation List (to be received upon notice of selection to Festival) to receive any and all award(s). If a film is eligible for an award and no one was designated to accept the award, the award will be deemed forfeit and another award winner will be chosen. In the event the designated party is unable to attend the awards ceremony, I understand that the director and/or producer of the film as listed in the credits of the film shall accept any and all awards in their stead.
7.You must clear all copyrighted material included in your film before you can publicly screen it. The Green Bay Film Festival does not check to make sure that you have cleared these materials at any point during the application process, nor will we be held responsible for any inclusion of un-cleared materials in your film. It is the sole responsibility of the entity submitting the project to secure permission from the copyright holder of the material in question, whether it is music, stock footage, or any other elements that could violate an existing copyright. Quite often, rights holders offer reduced rates for festival films, so you should contact them directly to avoid any possible rights infringements.
8.If selected as a participant in the Festival, promotional materials, television ready media clips (trailers and/or posters) of the film must be provided by the date provided on notice of selection. Should these not be provided within the festivals timeline, the festival can extract clips from this film for promotional purposes.
9.I am aware Festival may provide critics an opportunity to review films prior to the Festival.
10.I understand that Film Green Bay is a not for profit and does not have additional resources to return films. Should I send a DVD or Blu-ray copy of my film to the Festival, it will not be returned via mail unless I provide the necessary shipping envelope and postage or appropriate shipping account #. You may also pick it up at the festival.


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- Artists Van Did, Karl M
- Release Date 2013-10-21
- Labels Visionary Mind Records
- Catalog VMR13081EP
Life is a rhythm that must be comprehended. Everything that lives is related to a deep and wonderful relationship: man and the stars, amoebas and the sun, the heart and the circulation of an infinite number of worlds. These ties are unbreakable." Nikola Tesla
Visionary Mind Records proudly releases the result of first meeting between the inspired producers Karl M and Van Did. The celebration of the detailed net of connections in the sensible world is one of the keys to transform sadness into happiness.


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Those who know our community remark on its numerous strengths. We have excellent schools, outstanding community centers and libraries, top-notch hospitals and beautiful parks. We have wonderful people and organizations doing excellent work to create an enviable quality of life. However, our most valuable asset isn't included on this list.
This most valuable asset is our philanthropy. And we have exceptional individuals like Ed and Dollie Lynch, recent recipients of the Vollum Award for Lifetime Achievement, to thank for their tireless efforts. They have added immensely to what so many in our community build every day.
While Ed accomplished many engineering feats at Kiewit Pacific Co., his most significant project was constructing a legacy of philanthropy with his late wife, Dollie.
In preparing the Lynches' nomination for the Vollum Award, this legacy became even more evident. The numerous endorsements told of the countless causes and organizations the Lynches have contributed to during their 54 years in Vancouver. Each story was reinforced by the couple's undeniable commitment, integrity and compassion for our community. Their boundless generosity built much of the philanthropic infrastructure for which our community is regarded. In effect, they built a bridge for the rest of us to cross, and inspired other leaders and philanthropists to build bridges of their own.
Through a deep desire to improve humanity and devotion to their community, Ed and Dollie have supported every significant civic endeavor they found — both personally and financially. But their enterprising spirit and belief that many hands make for light work made more of an impact than any dollar amount ever could.
This is a philosophy Ed applied to his professional leadership as well, inspiring a lineage of Kiewit executives to follow in his philanthropic footsteps. In recent years, these engineering executives have invested tens of millions of dollars in local projects and programs.
People like Ed and Dollie Lynch build more than infrastructure; their leadership inspires action and investment in our community. They help build culture — a culture that places our region's per capita civic involvement and charitable giving in the top three within every category reported on the Civic Life in America website.
'Duty' to community
It's an honor that many large cities would envy, and we owe it all to the good people who represent our communities, whether Ed and Dollie, the many who came before them or the many who are now following in their path. We owe a lot to those who regard giving as a "duty." That sense of duty is what makes our communities stronger, as well as humanity as a whole.
Although Ed recently turned 91, he hasn't slowed down his civic involvement, and he is not done giving. Ed understands there are many more projects ahead and announced that he'll dedicate 98 percent of his estate to charity. His gift is also a signal to our community: our work isn't finished.
After accepting the Vollum Award for Lifetime Philanthropic Achievement, Ed gave credit to all those who had helped him throughout his 91 years. He said the support he received from people like his family, teachers, ministers, friends and even strangers allowed him to accomplish many things. "Without all of that, I would not be here today, and I'm well aware of that. So, thank you," he said.
On that note, let's show our appreciation for generous role models like Ed and Dollie by helping others this holiday season, and throughout our lives. Please donate to the charity of your choice and help make our community even better. Let's all contribute to building bridges for the many who will follow in our paths.
There's nothing greater to be thankful for than a strong culture of giving in our community. Thanks, Ed and Dollie, for continuing to build bridges and showing us all how it's done.
Richard Melching is president of Community Foundation for Southwest Washington.


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The popular Marcel Toulouse Aachen Dressage Saddle has a medium twist for a close contact feel, a deep seat and fully covered leather flaps. The Adjusta-Bloc system allows riders to custom configure the position of the blocks to best suit their needs. This dressage saddle has flocked panels and the Genesis ™ Adjustable tree.
The Marcel Toulouse Genesis Annice Saddle features a Genesis adjustable tree so it perfectly fits multiple horses. Doubled leather panels provide extra grip yet break in quickly. There is a reinforced strip at the bottom of panes to help protect against wear.
For a custom feel in the saddle, this Marcel Toulouse Premia with Genesis adjustable tree is a great choice. Its nicely padded seat is slightly flatter with a narrow twist. Combination foam and wool panels, movable knee blocks for a custom feel. Anatomic knee rolls and a leather reinforcement at flap bottom. The Genesis tree is backed by a 10-year guarantee.
The Marcel Toulouse Annice saddle features a close-contact feel and a traditional show ring-ready look. Featuring a slightly wider, medium-deep seat and a moderate twist helping hold the rider in the correct position. Genesis™ adjustable gullet system allows for a single saddle to custom fit multiple horses.
Ideal for eventing, show jumping or for anyone who wants a more forward flap and a bit more security, this Marcel Toulouse Platinum Marielle with Genesis adjustable tree is a great choice. Fully covered flap with full grain leather reinforcement at the bottom to help guard against wear. Shaped knee pads and large external rear block. Features Marcel Toulouse Soft Touch wool flocked panels. The Genesis adjustable tree is backed by a 10-year guarantee. Requires a short girth.
The Marcel Toulouse Aachen Pro Dressage Saddle is designed to meet the demands of the serious dressage rider. In durable pull-up leather with a soft, broken-in feel, this saddle features the Genesis™ adjustable gullet system and Soft Touch wool flocked panels.


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Regulations for F-1 Students
New Regulations for International Students in F-1 Status
As a service to our international students, we are providing this information to update you on the new regulations that went into effect on January 1, 2003 regarding F-1 students. We understand that this information may appear complicated and very lengthy; however, we need to stress the importance of reading this information thoroughly and making sure you understand how it affects you, your dependent family members and your stay in the U.S. If you have any questions, please do not hesitate to call the International Students Counselor at 292-2254 or stop by the office, located in Building 1, Room 231 in the Counseling and Advising Center.
What is SEVIS?
Every F and J visa holder must understand the Student and Exchange Visitor Information System (SEVIS), the new mechanism employed by the U.S. government to track the arrival, enrollment and departures of international students and their dependents. As of January 30, 2003, Monroe Community College, and every other college and university in the United States, is now required to use SEVIS.
SEVIS is an internet-based system that requires schools and the Bureau of Citizenship and Immigration Services (BCIS) to exchange data on the immigration and academic status of international students and their dependents. Information pertaining to an F-1 or J-1 student or dependent's stay in the United States is available to U.S. embassies and consulates as well as to the INS.
Data schools must report
- Name, date of birth, country of birth, country of citizenship, source and amount of financial resources, academic program, level of study, program start and end dates
- Arrival and enrollment or failure to enroll
- A change of the student or dependent's legal name or address
- Graduation prior to the end date listed on the I-20
- Academic or disciplinary actions taken due to criminal conviction
- Registration for less than a full course of study without PRIOR authorization from the International Students Counselor.
- Termination date and reason for termination
- Other data generated by standard procedures such as program extension, school transfer, change in level of study, employment authorization, and reinstatement
- Failure to complete the academic program or program objective
How does this affect you as an international student?
You MUST maintain your legal immigration status at all times in order to remain legally in the United States. Here are some rules you MUST follow:
Checking in with the International Counselor: If you have NEVER reported to the International Students Counselor with your immigration documents, you MUST do so immediately. These documents include: Form I-20, passport, visa, and I-94 card.
Enrolling full time: Undergraduate students MUST be enrolled for at least 12 credit hours per semester.
Dropping below full time: If for some reason, you don't intend to enroll full time during a semester (taking a leave of absence, medical problem, or initial difficulties) you MUST talk to the International Students Counselor before you drop below full time. We must approve this action prior to it happening or you will fall out of status.
Changing your degree program: If you change your degree program, talk to the ISC first. This information must be updated in the SEVIS system as soon as you know about the change.
Transferring to another school: If you plan to transfer to another school, you must first come to the ISC. The ISC will need to complete an immigration transfer procedure, BEFORE the new school will be permitted to issue you a new I-20.
Updating your address: You MUST update your address with the immigration service within 10 days whenever you move within the U.S.
Those subject to Special Registration (NSEERS) requirements must use the Special Registration form AR-11SR: Special Registration AR-11
The address you enter on the AR-11 should be the place you actually live, rather than a P.O. Box. If you cannot receive mail at your residence, you may indicate a P.O. Box, but must separately notify the ISSO of your actual physical location. No office addresses may be utilized. Privacy can be maintained by checking the appropriate box in "Just the Facts". Failure to complete the address change could result in fines, imprisonment or deportation.
Outside of the U.S.: If you are planning on traveling outside of the U.S., please come into the ISO before you depart. We will need to check your documents and possibly produce a new I-20 or prior to your departing the U.S.
Within the U.S.: For travel in the U.S., we recommend that you carry your immigration documents (I-20, passport, I-94 card), or minimally, copies of these documents.
Graduating and Applying for Practical Training for F-1 students
Timing your application: Regulations have changed regarding the time period that you are eligible to apply for practical training. In the past you could apply for practical training within in 60 days of graduating. Now you MUST complete the application and it must be at the BCIS by graduation day. We will no longer complete practical training recommendations once you have graduated. If you do not complete your application in time, you will forfeit your ability to apply. Those who have completed at least one full academic year of study (fall and spring semesters) may begin the application process up to 120 days before graduation. Those who have not yet completed one full academic year of study (i.e. those in 9-month programs), may apply up to 90 days before graduation.
Get a second degree at a higher level, get another 12 months: Another amendment to the regulations state that you are eligible for an additional 12 months of practical training if you have completed a second degree at a higher level. If you got your bachelors degree, applied for and received 12 months of OPT, and then complete a masters or PhD, you are now eligible to apply for another 12 months of OPT.
Full-time study: Dependents of F students (those holding F-2 status) are no longer able to study full time at the college level. If your spouse is planning on studying full time they will need to be a matriculated student and apply for their own F-1 student visa. F-2's who were, prior to January 1, 2003, pursuing full time study, must apply for a change of status to F-1 by March 11, 2003. Dependents of J visitors (those holding J-2 status) are currently able to be full-time students. This may change in the very near future, so look for further updates on this issue.
Immigration documents for dependents: All F-2 and J-2 dependents will now have to have their own I-20/DS-2019. The ISC will provide further information on this issue in the near future.
Contact Information
Brighton Campus
Building 3, Room 103
M-F 8:45 a.m. - 4:45 p.m.
(585) 292-2030


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A 2-year-old boy was rushed to PeaceHealth Southwest Medical Center after he fell from a second-floor window of a mall-area hotel Friday night.
At 7:12 p.m., firefighters, police and AMR Northwest ambulance paramedics rushed to the Rodeway Vancouver Inn, 9201 N.E. Vancouver Mall Drive, said Capt. Kevin Murray with the Vancouver Fire Department.
Murray said he was told the boy landed on landscaping.
Sergeant Kevin Hatley with the Vancouver Police Department said the fall is believed to have been accidental. He said police don't know whether the window was open before the child approached it.
Hatley said the boy's injuries were believed signifcant, but it did not appear they were life-threatening.
John Branton: 360-735-4513 or firstname.lastname@example.com.


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|Numéro de publication
|Type de publication
|Numéro de demande
|Date de publication
|28 mars 1989
|Date de dépôt
|19 mai 1986
|Date de priorité
|19 mai 1986
|État de paiement des frais
|Numéro de publication
|Kie L. Soohoo
|Cessionnaire d'origine
|Rockwell International Corporation
|Exporter la citation
|BiBTeX, EndNote, RefMan
|Citations de brevets (3), Référencé par (21), Classifications (5), Événements juridiques (8)
|Liens externes: USPTO, Cession USPTO, Espacenet
1. Field of the Invention
The present invention relates to optical gyroscopes and more particularly to passive ring resonator gyroscopes which have bias and frequency errors resulting from mechanically or thermally induced dimensional changes.
2. Description of Prior Art
This application relates to three previously submitted applications, Ser. No. 676,322, "PASSIVE RING RESONATOR GYROSCOPE", filed 11/29/84, inventor Sanders et al; Ser. No. 701,891, "TWO SERVO LOOP PASSIVE RING LASER GYROSCOPE", filed 2/13/85, inventors SooHoo and Valle; and Ser. No., 839,292, "TWO SOURCE LASER PASSIVE RING LASER GYROSCOPE", filed 3/13/86, inverter SooHoo, and all having common assignee.
The first previous application described a laser gyro having a single piece body incorporating a linear laser light source, a passive resonant cavity and which relies on three active servo loops for operation.
The second previous application described a passive laser gyroscope having a single piece body and having a single linear laser light source and a passive resonant cavity. This gyro uses first and second active servo loops for operation.
The third application describes a single body passive ring laser gyroscope having a first laser source to produce a clockwise beam and a second laser source to produce a counterclockwise beam, both beams circulating in a sealed, evacuated passive cavity within the same body.
In a passive ring resonator gyroscope, a pair of monochromatic light beams counterpropagate about a closed-loop optical path, which forms a high Q resonant optical circuit. The stability of the path length between reflective surfaces forming the closed path is critical in maintaining resonance in the passive ring resonator cavity since dimensional changes contribute to bias frequency errors. The relationship between a linear laser and a ring resonator to form a prior art passive ring resonator gyro is depicted in an article by S. EZEKIEL and S. R. BALSAMO titled "A Passive Ring Laser Gyroscope", Applied Physics Letters, Vol. 30, No. 9, May 1, 1977, pg. 478-480. (NOTE: Usually a resonator is conceived as a linear or standing wave resonator in which the light completes an optical round trip by reflecting off a mirror and retracing its path. These forward and backward waves create a standing wave in the cavity. In a ring resonator, the light completes an optical round trip without retracing its path and hence the path encloses an area as shown in Ezekiel's paper.) For a description of lasers and resonators refer to: Yariv, A., QUANTUM ELECTRONICS (John Wiley & Sons, 1975) or Sargent, M., et.al., LASER PHYSICS (Addison-Wesley Pub., 1974).
In the passive ring resonator, such as that described in the EZEKIEL reference, the two beams, traveling in opposite directions around the closed-loop optical path, are injected into the passive ring resonator from a single frequency light source. As the ring resonator gyroscope cavity rotates in inertial space, the two counterpropagating beams travel unequal path lengths. This path difference, due to rotation in inertial space, gives rise to a relative frequency difference (Sagnac effect) between the two counterpropagating beams. (NOTE: A ring resonator, as opposed to a linear resonator, can exhibit the Sagnac effect and detect inertial rotation.) E. J. Post, "Sagnac Effect", Review of Modern Physics, Vol. 39, No. 2, April 1967, p. 475-493.
The relative frequency difference is detected as a changing interference fringe pattern which is then electronically interpreted to indicate the direction and inertial rate of rotation of the passive gyro about the gyro's sensitive axis. The sensitive axis of the gyro is along the direction normal to the plane of the passive resonator.
The single frequency light source for the passive resonator is typically an external linear laser. Spectra Physics Inc. of Sunnyvale, CA. produces stabilized lasers with the required characteristics.
It is known that bias errors in the detected signal of a ring resonator gyro result from dimensional changes in the laser and in the passive ring resonator. Bias errors also result from Fresnel Drag; these errors arise from the presence of gases (e.g. air) in the path of the counterpropagating beams in the resonator. Bias errors are typically characterized as a frequency difference between the two beams which is not related to the rotation rate. Bias errors are sometimes detected as a frequency difference in the absence of rotation or as post calibration changes in the frequency difference for a specific absolute inertial rotation rate.
The Passive Ring Resonator Gyroscope of the type described in the EZEKIEL reference is typically constructed by placing optical elements, such as mirrors, beamsplitters, etc. on an optical bench. The location, spacing and geometrical relationships between the elements of the gyro function to enhance the passive ring resonator gyroscope's sensitivity and stability. Experimental passive ring resonator gyroscopes typically have path lengths of a few meters making them unsuitable for use as a navigational instrument. The large size of prior art passive ring resonator gyroscopes, such as that characterized in the EZEKIEL reference, also contributes to the likelihood of bias errors due to mechanical coupling and mechanical drift of the optical elements in response to physical and thermal forces acting on the laser and on the optical table or bench.
The objective of this invention is to provide a phase locked passive ring resonator gyro suitable for use as a navigational instrument having reduced bias errors and bias error sensitivity while having substantially enhanced stability and sensitivity. This is accomplished by constructing a gyro having a single source laser and a ring resonator within a single housing or one piece body in which the total resonator path length is substantially below a half meter.
Another objective of this invention is to provide a single source passive ring laser gyroscope using two phase locked tracking servos for peaking the intensity of the CW (clockwise) and CCW (counterclockwise) propagating light beams in the passive cavity.
Another objective of the invention is to change the passive cavity's path length with a control signal to achieve resonance locking of the cavity to the center frequency of the linear laser without the need for periodic AC modulation of the passive cavity's path length.
A particular embodiment of this innovative passive ring resonator gyroscope has a single piece body, typically fabricated from a block of glass ceramic material such as ZERODUR®, (a trademark of the JENAER GLASSWERK SCHOTT & GEN. of MAINZ, GERMANY), which forms a fixed reference frame for all required optical elements, including first and second resonator cavities. A laser means is composed of a linear or "L" shaped laser that uses the first cavity. This laser, when operated with suitable excitation, functions as a linear laser providing a source of single mode TEMoo, single frequency light for the third resonator cavity.
In a more particular alternative embodiment, the laser means first resonator cavity has a transmitting optical port for transmitting stabilized single frequency light to the second resonator cavity. The internal body-mounted reflective surfaces are coupled to and mechanically spaced by the single piece body. A gain medium, such as a Helium Neon gas mixture is contained in the first resonator cavity but the second cavity is evacuated.
A means for exciting the gain medium, including a power source, to induce lasing in the first resonator cavity is provided. The output of the single frequency light sources is directed through at least one transmitting optical port of each of the first and second resonators.
The second resonator cavity and its reflective elements form a passive high Q cavity having a closed optical path tuned to resonate at substantially the same frequency as the first resonator cavity. Means are provided for modulating the frequency of the light source and means are provided for splitting this source into first and second rays and coupling the first and second rays into the second passive resonator cavity, thereby forming CW and CCW light beams in the second resonator. These means are implemented using conventional beamsplitters, mirrors, and lenses.
The second resonator cavity is oriented and dimensioned in relation to the first and second resonator cavities to have substantially equivalent optical path length changes in response to any induced body dimensional changes.
Bias errors are diminished since the passive ring resonator is a passive device and has no internal excitation to frequency shift the cavity resonances. Bias errors due to axial gas flow or Fresnel drag is eliminated since the second resonator is evacuated. Taken together, these features form a gyroscope with increased stability and reduced bias errors.
A cavity servo means controls the resonant frequency of the laser light source. The cavity servo means has a servo loop that locks the first laser's single frequency light source relative to the FCW resonance. The cavity servo loop is synchronized with a first oscillator that frequency modulates light leaving the laser via an electro-optic modulator at a frequency Fm (typically 10 MHz). The first oscillator also provides a reference signal to a first and second phase-sensitive detector to obtain a demodulated error signal for integration. The integrated error signal from an integrator provides a second cavity path length control signal for the resonator. The first servo means enables the first cavity to track the resonant frequency of the second resonator's FCW beam.
The first cavity linear laser has a first cavity path length adjusting means such as a piezoelectric transducer responsive to the first cavity path length control signal for shifting the resonant frequency of the first cavity. The first cavity path length adjusting means shifts the frequency of the single frequency light source in response to the integrated phase locked error signal applied to the PZT to maximize the intensity of the second resonator CW beam. The frequency of the CW beam is upshifted by an acousto-optic modulator (AO1) driven by a reference oscillator before it is injected into the second resonator.
A second servo is provided for frequency shifting the FCCW beam in the second cavity as it enters the second resonator to form the CCW beam. The second servo means is also referenced to the first oscillator. A (Fm) frequency modulated light source is up shifted in frequency by an acousto-optic coupler (AO2) driven by a voltage controlled oscillator (VCO). The VCO adjusts its output frequency in response to a second servo control signal and adds enough of a frequency increase to the Fm modulated laser light source to shift the center frequency of the FCCW beam entering the second cavity to the second cavity (passive resonator) line width resonant point. A portion of the CCW beam is extracted from the resonator and a photodetector responds to the beat signal at the frequency of the Fm signal. The Fm signal thus extracted is coupled to a second phase sensitive detector, also referenced to the first oscillator. If the upshifted frequency modulated light source, FCCW, is above or below the line center of the CCW cavity resonance, the second phase sensitive detector develops an error signal having a magnitude related to the CCW frequency error and a polarity related to the position of the error above or below the cavity's CCW peak resonance.
In this embodiment, a means for detecting the frequency difference between a clockwise upshift oscillator and a counterclockwise VCO upshift oscillator provides a signal representing a measure of the input body rate.
FIG. 1 is a prospective view of the phase locked passive ring resonator gyroscope.
FIG. 2 is a top planar view of the two source passive ring resonator gyroscope 10 of FIG. 1 showing the first and second resonator cavities in phantom. Left and right partially transmissive mirrors 43, 41 represent first and second partially transmissive and receiving ports.
FIG. 3 is a front view of the phase locked passive ring resonator gyroscope body.
FIG. 4 is a rear view of the phase locked passive ring resonator gyroscope body.
FIG. 5 is a cross sectional view of the phase locked passive ring resonator gyroscope body taken along line 5--5 of FIG. 3.
FIG. 6 is a cross sectional view of the phase locked passive ring resonator gyroscope body taken along sectional line 6--6 of FIG. 3 and viewed from the bottom.
FIG. 7 is a combination schematic and block diagram of the associated electronics and optical elements of the phase locked passive ring resonator gyroscope using two servo control loops.
FIG. 8 is a schematic of a phase sensitive detector.
FIG. 9 shows a waveform depicting the response characteristic and center frequency of a passive resonator and depicting the center frequency of a HeNe laser.
FIG. 10a shows the relative position of two detector diodes in relation to a laser source on the left and a passive cavity on the right.
FIG. 10b shows the response characteristic of the rightmost detector.
FIG. 10c shows the response characteristic of the lower detector.
FIG. 11a shows a wave form that represents the spectral amplitude characteristic or intensity of a laser source that is frequency-modulated over a range of from (Fo-Fm) to (Of+Fm), where Fo is the laser center frequency.
FIG. 11b shows a wave form represents the output voltage response from a phase sensitive detector as the laser source is tuned over a range extending from (Fo-Fm) to (Fo+Fm) while the passive resonator is tuned to resonate at a relatively fixed frequency Fo.
Referring now to FIG. 1, an embodiment of the invention phase detector passive ring resonator gyroscope 10 is depicted having a single piece body 12 having integral first, and second resonator cavities 15, 16. The term "integral" is meant to convey the idea that the body 12 is formed from one homogeneous piece of material such as ZERODUR. The top layer has a first cavity that serves as a linear laser. The output of the linear laser is not influenced by inertial rate inputs to the gyroscope.
The first laser means (cavity 15) is shown sourcing single frequency light at frequency Fo through the first resonator partially transmissive mirror 20 to E0 (electro-optic modulator) 17. The beam is frequency modulated by E0 17 and at frequency +/-Fm and passes to beamsplitter 21 to form first and second frequency modulated rays 22, 14, respectively.
A first oscillator, OSC1, 33 provides a sinusoidal reference signal at a frequency Fm (typically 50 MHz) to E0 17 and as a reference signal to PSD1 27 and PSD2 61 (Phase Sensitive Detector).
The E0 device is typically a phase modulator device obtained from a company such as LASERMETRICS, Electro-Optics Div. at 196 Coolidge Ave., Englewood, NJ 07631, or one such as Model 10-P-22-3-2-2.5 obtained from QUANTUM TECHNOLOGY, INC. of 2620 Iroquois Ave., Sanford, Fla. 32771.
The E0 17 frequency modulates light from laser 15 to add frequency side bands at (Fo-Fm) and (Fo+Fm) where Fo is the laser center frequency and where Fm is the frequency output of OSC1 33.
Beamsteering optics, such as first prism 18 couples the first frequency modulated ray as beam 22 through AO1 (acousto-optic modulator) 29. AO1 is a frequency shifter driven by OSC2, 45, a sinusoidal oscillator typically operating at a second reference frequency in the range of from 50 MHz to 80 MHz. The AO1 device is structured to upshift the frequency of the first frequency modulated ray 22 to a frequency F1 higher than that of the first frequency modulated ray.
FIG. 8 is a schematic of a PSD (phase sensitive detector) such as PSD1 27 and PSD2 61. FIG. 8 shows the structure of a PSD to be a passive device. The circuit of FIG. 8 is a type referred to as a double balanced mixer. The PSD1 and PSD2 mixers 27, 61 of FIG. 7, respectively, operate as phase-sensitive detectors in applications where the frequency of signal applied to the L0 terminal 810 is the same as the frequency of the signal applied to the RF terminal 820. The PSD1 and PSD2 mixers 27, 61 are typically commercial components such as the OAD-6 from the MINI-CIRCUITS COMPANY at P.O. Box 166, Brooklyn, NY 11235. A further discussion of the operation of balanced mixers is found in an article entitled "Mixers As Phase Detectors", RF SIGNAL PROCESSING COMPONENTS, by the Watkins-Johnson Company, 1983/84, p. 605-631.
The L0 (local oscillator) terminal 810 is driven by a reference signal such as Fm from OSC1, 33 as shown in FIG. 7. The RF (radio frequency) terminal 820 typically receives a signal for detection such as the output signals from DET 1 (detector 1) 31 on signal path 34 or from DET2 63 via signal output 64. The output signal from a phase sensitive detector is fed from the IF terminal 830 to load R1. The signal at IF terminal 830 is filtered and typically has a zero volt value where the frequency of the signal at the L0 terminal 810 is the same as the frequency of the signal at the RF terminal 820 and where the phase difference is zero degrees. With a fixed frequency signal, such as Fm, present at terminal 810 and with a fixed frequency input signal of the same frequency present at the RF input terminal 820 the IF port will output a DC signal related to the phase of the L0 and RF signals. A DC output signal develops at terminal 830 of one polarity for an input RF signal having the same phase relationship as that of the L0 signal; an opposite polarity signal will result at the IF terminal 830 for an input RF signal having an opposite phase relationship with that of the L0 signal.
The waveform in FIG. 11a represents the spectral content of light 32 and 40 incident on DET1 31 and DET2 63 with the detectors being located as shown in FIG. 7. The upper waveform of FIG. 11 is obtainable by monitoring the input beams 32 and 40 with a spectrum analyzer. The waveform of FIG. 11b depicts the signal response of PSD1 and PSD2 at their respective IF terminals 830 in FIG. 8 or such as 28, 56 in FIG. 7, as the center frequency of the laser is gradually tuned over a frequency range extending from below (Fo-Fm) to a high frequency of (Fo+Fm) and while leaving the spectral feature, in this case, the resonator cavity 16 having a fixed center frequency at F0.
Referring again to FIG. 1 and to FIG. 7, BS1 21 splits the frequency modulated light source into first and second frequency modulated rays 22, 14 respectively. The first frequency modulated ray 22 passes to AO1, 29. AO1 aperture 68 acts as a propagating beam source to provide a propagating beam 67. Beam 22 is upshifted in frequency by AO1, 29 to form the propagating beam 67. Propagating beam 67 is directed to partially transmissive mirror MIR1, 43. The portion of the propagating beam 43 that passes through MIR1 into the second resonator cavity forms the propagating light beam (FWC) within the second resonator cavity.
The second frequency modulated ray 14 is first reflected by MIR5, 47 to A02, 49. Ray 14 is upshifted in frequency by A02. Aperture 70 of A02 serves as a counterpropagating beam source to provide a counterpropagating beam 69. FCCW within the second resonator cavity counterpropagating light beam. directed to partially transmissive mirror MIR4, 41. The portion of the counter propagating beam 69 that passes through MIR4 forms the counterpropagating light beam FCCW within the second resonator cavity. Counterpropagating beam 69 is a source for the counterclockwise light beam, FCCW as it passes through MIR4, a partially transmissive mirror 41. The. A02 device 49 upshifts the frequency of ray 14 by F2 Hertz to form the couterpropagating beam 69 that enters cavity 16 via MIR4, at 41.
Acousto-optic device A02 49 and VCO 51 in combination represent a means responsive to a second frequency modulated ray for frequency shifting the second frequency modulated ray in response to a second control signal from the output of AMP3, 53.
The second resonator cavity 16 is a passive high Q evacuated cavity having a closed optical path with first, second, third, and fourth segments, 44, 46, 48, 50 tuned in combination to resonate at a frequency derived from the first resonator cavity. The sensitive axis, characterized by Vector 54, and shown in FIG. 3 and FIG. 4, is essentially normal to the plane of the closed second optical path established by the plane of segments 44, 46, 48, 50.
Part of the propagating beam is reflected off the cavity 16 at MIR1 43 and is focused on output detector 31 at DET1 receiving aperture 32. Detector DET1 31 and DET2 63 are typically silicon photodiode amplifier assemblies.
First detector 31 provides a detected FCW signal on signal line 34 to the RF input of PSD1 27. PSD1 provides a positive or negative phase error signal on signal line 28 to INTEG1 23 for integration. INTEG1 provides a first phase control signal on signal line 38 to the inputs of AMP1 19 and AMP2 25. AMP1 conditions the phase control signal and provides drive signal to PZT1 13 to shift the frequency of linear laser 15 in a direction that will drive the phase error signal on signal line 28 to zero volts.
Second detector 63 provides a detected FCCW signal on signal line 64 to the RF input of PSD2 61. PSD2 provides a positive or negative phase error signal on signal line 56 to INTEG2 65 for integration. INTEG2 65 provides a second phase control signal on signal line 59 to the inputs of AMP3 53. AMP3 53 conditions the phase control signal and provides drive signal to VCO 51 which changes the frequency that the A02, 49 shifts the FCCW beam in a direction that will drive the phase error signal on signal line 56 to zero volts.
These elements represent in combination, a cavity servo means responsive to the first phase error signal. They provide control signals to the first laser transducer PZT1 to control the resonant frequency of the first single frequency light sources F0. The first single frequency light source is tuned to control and maintain the clockwise propagating (FCW) light beam in the second resonator at peak resonance.
The second single frequency light source is tuned to control and maintain the counterpropagating light beam (FCCW) at peak resonance.
OSC2 45, represents a second reference oscillator that operates in combination with AO1, 29 as shown within phantom block 60 to form a means for shifting the center frequency of the first frequency modulated ray 22 by a fixed offset frequency F1. VCO 51 is the oscillator that operates in combination with A02, 49, as shown in phantom block 75, to shift a ray 69 into peak resonance of the CCW modulated beam.
Output counter means 71 is provided for measuring and outputting the frequency difference between said fixed offset frequency and said variable offset frequency. The measured frequency difference representing the difference in frequency due to an input gyro body rate about said sensitive axis increased by the fixed frequency of the fixed offset frequency. Output counter means 71 is typically a counter such as a HP3335 by Hewlett Packard for use in a laboratory, but in alternative product designs, the counter would be fabricated from conventional high speed logic circuit elements such as MECL or ECL logic by MOTOROLA suitable for use at frequencies at and above F1, the frequency of the reference signal generator (to the AO).
The first partially transmissive and receiving port 43 is characterized to receive and pass a portion of the propagating beam 67 into the second resonator cavity 16 to form the propagating light beam (FCW).
The second partially transmissive and receiving optical port 41 is characterized to receive and pass the counterclockwise beam 69 into the second resonator cavity 16 to form a counterpropagating light beam (FCCW).
PZT2 and PZT3 35, 57 shown in FIG. 7 represent piezoelectric transducers. PZT2 and PZT3 each function as an electromechanical transducer, attached to reflective surfaces 37, 39 so as to modulate the second resonator's optical path length to maintain the propagating light FCW at peak resonance within cavity 16. PZT2, 35 is a piezo-electric transducer attached to a mirrored surface, that represents a dynamic path length adjusting means for adjusting the optical path length of the second resonator cavity and has an input terminal coupled via a signal line 26 to the output of AMP2. PZT2 is adjusted, by the first control signal from first integrator INTEG1, 23 via the output 26 of AMP2, 25 for adjusting the optical path length of the second resonator cavity 16 to maintain the propagating beam FWC at peak resonance
PZT3, 57 is a static optical path length adjusting means that provides an initial coarse adjustment for the cavity 16. PZT3, 57 is adjusted by adjusting the output voltage of DC TUNING SOURCE 58.
The first detector 31 receives a large portion of the FCW light beam reflected off the first partially transmissive and receiving port MIR1, 43.
The second cavity detector 63 receives a large portion of the counterpropagating light beam FCCW reflected off the second partially transmissive and receiving port MIR4, 41.
Mirrors 43 and 41 have reflective surfaces positioned to direct the reflected incident beams to their respective detectors 31 and 63. The intensity of the light striking detector 31 or 63 has a high background level that dips as the resonant cavity 16 achieves resonance in response to a shift in frequency of the respective laser source. FIG. 10a characterizes a laser source directing a beam at a representative port with a portion of the beam being reflected to a detector such as detector 63. FIG. 10b depicts a peak response to incident light from detector 1009. FIG. 10c shows a dip in the background of the light intensity 1013 striking the detector such as 1005 as the laser source at 1001 is tuned to the resonance point of the passive cavity 1007.
Conversely, detector 63 senses light sourced from resonator cavity 16 via second partially transmissive port MIR4, mirror 41, to detector receiving aperture 40. The background light including signal information incident at aperture 40 dips to a minimum as the cavity is tuned to resonance.
FIG. 9 depicts the pass band of a typical passive cavity having a resonance peak at 1002. The approximate frequency spread between reference 1004 and 1006 represents a typical frequency range between the half-power points and is included in FIG. 9 along with the indicated laser center frequency, to provide the reader with a visual appreciation of the "Q" of the second resonator. The phrase "frequency stabilization" is understood to mean phase sensitive detecting and is also meant to include the principle of servo locking the laser output to the intensity peak of the passive cavity.
A HeNe laser typically has an instantaneous line width of less than one Hz but the operating frequency is subject to considerable jitter.
The dip represented by FIG. 10c would also typically have half-power points separated by 100 kHz. Typically, a HeNe input laser would have its output at 4.74×1014 Hz injected along path 1003 into the passive cavity 1007.
FIG. 6 shows the second resonator cavity in section as viewed from the bottom surface to the top of the gyro. The second cavity 16 has first, second, third and fourth evacuated hollow segments, 44, 46, 48, 50. In the case of a triangular cavity (not shown) only three segments would be used. The segments of cavity 16 are coupled at their ends to form a closed planar evacuated path. For example, one end of segment 44 is joined with one end of segment 46 at an intersection where mirror surface 37 is attached to PZT2 35.
In another alternative embodiment of the phase locked passive ring laser gyro 10, the first resonator cavity 15 is positioned and dimensioned in relation to the second resonator cavity 16 to provide partial dimensional change compensation for optical path length changes in response to induced body dimension changes by temperature or external force. Bias errors relating to temperature induced body dimension changes or to changes from external forces applied to said body are cancelled providing a passive ring resonator gyroscope having enhanced stability using only two servos.
FIG. 5 shows the first resonator cavity 15 in section. The first resonator cavity has a transmitting optical port means at first cavity port 20 for transmitting stabilized single frequency light F0 and at least two internal body-mounted reflective surfaces such as partially transmissive mirror 20 and mirror surface 9 on piezoelectric transducer PZT1, 13.
An appropriate gain medium, such as a mixture of Helium and Neon, is contained in the first resonator cavity 15 at a pressure in the range of 4 to 10 torr when sealed.
Referring to FIG. 7, block 80 represents a means for exciting the gain medium within said first cavity 15 to induce lasing. This element is also shown in the embodiment of FIG. 1. This element is typically a controllable current source capable of an output voltages determined by the ionization potential of the gas mixture and an output current in the range of one to ten milliamperes.
Although FIGS. 1 and 7 each depict use of straight cavities for the first laser means, the use of an L-shaped laser as the first resonator cavity above, below or in the same plane as the second resonator are anticipated to be alternative embodiments that can offer the promise for dimensional compensation. Additional alternative embodiments include an arrangement in which the first laser means has segments orientated to be transverse to the plane of the second resonator cavity 16.
Optical detector DET1 units (such as first detector 31 and second detector DET2 63 typically contain a reversed biased PIN diode and a low noise preamplifier. A detector such as the SD-00-12-12-231 manufactured by the Silicon Detector Corp. of Newbury Park, CA. or the model FND-100 by EG&G Corp. of Wakefield, Mass. is suitable for use with a Helium Neon laser light source.
The first and second detectors 31 and 63 of FIG. 7 are positioned to receive reflected light as detector 1005 does from laser 1001 in FIG. 10a. FIG. 10c shows a response curve having a dip at resonance 1013. This response characteristic corresponds to that for diode 1005 receiving the reflected input beam. The response curves for detectors 31 and 63 dips at resonance because, in the embodiment depicted by FIG. 1 and FIG. 7, these diodes receive reflected light from mirrored surfaces 43 and 41, respectively. At resonance, second cavity 16 absorbs light entering from ports 43 and 41, thereby leaving less light for reflection from the respective mirrored surface. Detector 1009 of FIG. 10b is positioned to receive light from resonator 1007 in accordance with the response characteristic 1011 of FIG. 10b. The relative position of detector 1009 to measure the transmitted light is not used in the embodiment of FIG. 7.
The respective DC AMP (19, 25) is driven by the integrator to apply a signal to the PZT to move the frequency of the respective laser in a direction to increase the response of the signal from the second resonator cavity. As the signal from the DC AMP (19, 25) reaches a value sufficient to peak the tuning of the resonator, the signal out of the low-pass filter goes to zero and the output of the integrator stops changing, leaving the frequency of the affected laser unchanged. A change in the body rate or a change due to induced drift moves the laser off resonance; however the servo responds by shifting the timing voltage to the PZT to re-establish resonance.
Due to the Sagnac effect, the path lengths of the clockwise (CW) and counterclockwise (CCW) beams in ring resonator differ as a function of body rotation rates. Consequently, the resonant frequencies for CW and CCW light in the passive cavity have a corresponding different dependence. The goal of the optics and electronics of the Passive Ring Resonator Gyroscope (PRRG) is to detect the frequency difference that arises between the CW and CCW beams due to inertial rotations. The intent of the single body small source linear phase locked laser/passive cavity design is to eliminate bias errors caused by the resonant frequencies of the linear laser and passive cavity changing with respect to one another. In this integral, single block, or single piece body these bias errors will also be independent of input rotation rates. The two cavities are arranged mechanically and geometrically to insure that shifts in laser frequency arising from body dimensional changes are experienced by both the passive resonator cavity and the linear laser cavity and therefore reduce the effect of such bias errors.
To obtain such bias compensation, the Free Spectral Range of the first resonant cavity 15 is made equal to the Free Spectral Range of the second resonant cavity 16. The Free Spectral Range (F.S.R.)=c/p where c is the speed of light and p is the optical round trip pathlength of a resonator. Thus, the F.S.R. of a square passive ring resonator with sides of length L is c/4L. To meet the F.S.R. requirement, two cases arise contingent upon the linear resonator design. The first resonator forming the laser means is comprised of a mirror with no curvature, i.e. a flat mirror, and a mirror with a predetermined radius of curvature, i.e. a curved mirror, the required resonator length between mirrors is L. The F.S.R. of this flat mirror, curved mirror resonator equals c/4L. However, a resonator using two curved mirrors requires a resonator length between mirrors equal to 2L. This configuration also has a F.S.R. equaling c/4L. With the criteria (F.S.R.)Laser=(F.S.R.)Passive Resonator=c/4L, it is apparent that any change in the F.S.R. of the laser resonator will equal any change in the F.S.R. of the passive ring resonator which may arise from thermal or mechanical changes.
Mirrors with piezoelectric (PZT) backings supply a path length adjusting means to the passive resonator cavity. This adjustment effects both the CW and CCW beams.
Light reflected off the passive second cavity from the CW direction is detected and phase sensitive demodulated by employing a mixer. The error signal drives a piezoelectric backed mirror in the first linear laser to bring it into the CW beam's resonance. In the preferred embodiment, the DC error signal is applied to PZT1 and PZT2. Light reflected off the passive second cavity from the CCW direction is detected and phase sensitive demodulated by employing a mixer amplifier. The error signal drives a VCO which shifts the frequency of the injected CCW beam to bring it into the passive cavity's resonance. In the preferred embodiment, a DC tuning source signal from DC TUNING SOURCE 80 is applied to PZT3 to provide for initial coarse frequency alignment.
The two AO devices are each typically made up of a piezoelectric transducer attached to a crystal. The AO device is fabricated from a piezoelectric crystal material such as quartz, TeO2 (Telurium Dioxide) or PbMoO4 (Lead Molybdate). In the preferred embodiment, the AO1 transducer driven at F1, establishes an acoustic wave at frequency F1 in the crystal. Associated with the acoustic wave is a varying index of refraction due to the compressions and rarefactions of atomic density in the crystal. Incoming light diffracts off this induced grating giving rise to many orders of diffracted beams. The 0th order beam is at the frequency of the single frequency light, (Fo.+Fm). The first order beam has the frequency (Fo+/-Fm)+F1 where F1 is the frequency of the acoustic wave.
The output from the A02 device has the discrete frequencies (Fo+/-Fm)+nF2 where n=0,1,2 . . . each separated in space by an angle proportioned to n. Thus, we see that by shifting the AO F2 wave frequency by 1 Hz, we can add 1 Hz to the frequency of the first order beam exiting the A02 device. Therefore, the AO's operate as frequency shifters in our application. (See e.g., Optical Waves in Crystals, A. Yariv & P. Yeh (John Wiley & Sons)
The Phased Locked ring laser gyroscope shown in FIG. 1 has a first servo control loop and a second servo control loop, each being referenced to OSC1 (oscillator 1) 33. Each servo loop uses light originating from linear laser 15 and modulated by E0 (electro-optic modulator) 17.
Laser 15 provides a relatively coherent light source at frequency F0 to E0 (electro-optic modulator) 17. E0 17 is driven by OSC1, 33 at Fm. Therefore, E0 17 frequency modulates the F0 source at frequency Fm (typically 50 MHz). For small modulation amplitudes, the light source from E0 17, ray 72, has side bands at F0+Fm and at F0-Fm. The modulated laser light source is split by beamsplitter 21 to source a first beam, ray 22, to AO1 (acousto-optic modulator 1) 29 and a second beam, ray 14, to MIR5 (mirror 5) and thence to A02, 49 (acousto-optic modulator 2).
OSC2, (oscillator 2) 45 typically operates at a frequency of 80 MHz and drives A01 29 at frequency F1. The light source having frequency components F0, F0+Fm and F0-Fm passes through A01 29 and is frequency shifted to contain frequency components F0+F1+Fm, F0+F1-Fm and Fo+F1.
The light source from A01 output port 24, is directed to and predominately reflects off of partially transmissive reflector 43. That portion of ray 24 that enters passive cavity 16 circulates as ray 44, ray 46, ray 48 and ray 50 to form the FCW (clockwise) beam in the cavity.
Referring to FIG. 7, the input path to the first servo loop consists of the path of ray 20, through BS1 21, to A01 29, to MIR1 43, to reflected ray 32, and to DET1 31. DET1 31 provides an electrical signal via signal line 34 to the RF input of PSD1 (phase sensitive detector 1) 27. PSD1 27 also receives a signal at frequency Fm at its L0 input. PSD1 provides a phase related error signal at its IF output to INTEG (integrator 1) 23.
Each error signal is produced as the instantaneous frequency of the laser is swept past the line bandwidth of the cavity. At that moment, the cavity absorbs the FCW light on MIR1 to produce a dip in the signal to the DET1 31 and subsequently to PSD1 27. PSD1 is a phase sensitive detector referenced to the OSC1 source 33 at frequency Fm and is sensitive only to the Fm signal component within ray 32 to DET1.
VCO 51 typically operates at a variable offset frequency and drives A02 49 at frequency F2. The light source having frequency components F0, F0+Fm and F0-Fm passes through A02 49 and is frequency shifted to contain frequency components F0+F2+Fm, F0+F2-Fm and Fo+F2.
The light source from A02 is directed to and predominately reflects off of partially transmissive reflector 41. That portion of the CCW ray that enters passive cavity 16 circulates as ray 48, ray 46, ray 44 and ray 50 to form the FCCW (counterclockwise) beam in the cavity.
Referring to FIG. 7, the input path to the second servo loop consists of the path of ray 20, through BS1 21, to A02 49, to MIR4 41, to ray 40, and to DET2 63. DET2 63 provides an electrical signal via signal line 64 to the RF input of PSD2 (phase sensitive detector 2) 61. PSD2 61 also receives a signal at frequency Fm at its L0 input. PSD2 provides a phase related error signal at its IF output to INTEG2 (integrator 2) 65.
Each error signal is produced as the instantaneous frequency of the laser is swept past the line bandwidth of the cavity. At that moment, the cavity absorbs the FCCW light on MIR4 to produce a dip in the signal to the DET2 3 and subsequently to PSD2 61. PSD2 is a phase sensitive detector referenced to the OSC1 source at frequency Fm and is sensitive only to the Fm signal component within ray 40 to DET2. PSD2 provides a polarized error signal via signal line 56 to the input of integrator INTEG2 65.
Frequency modulation spectroscopic techniques have been recently developed as a means to enhance the signal to noise ratio and obtain finer resolution of weak absorbing lines. In normal phase sensitive detection schemes, the frequency of the input source is dithered or frequency modulated about a small portion (less than the Full Width Half Max, (FWHM) point) of the cavity absorption resonance of interest. Therefore, for a resonance centered at Fo, and a frequency modulation Fm with amplitude "a", the source frequency can be represented as
F=A*COS(2πFo*t+a*COS 2πFm*t)
where "a" is the modulation depth (less than the FWHM of the resonance) and "A" is the amplitude of the source. Normally, "a" is small and therefore a Taylor expansion or the equivalent Bessel function expansion for small arguments will give a system response of a DC term and harmonics at 1Fm, 2Fm, 3Fm, etc. For a small "a", the 1Fm term will dominate and phase sensitive detection at Fm will result in a derivative response of the resonance (centered at Fo with FWHM greater than a). This derivative signal has the correct + or - error signal that is readily tractable to a zero seeking servo loop such that at zero signal, the servo is at the peak of the resonance. This frequency stabilization technique works well for most applications but for the utmost in resolution and phase stability, an expanded approach is utilized. Instead of modulating (Fm at depth a) within the FWHM of the resonance, a larger frequency swing (depth) is used to drive the source frequency outside the absorption resonance's FWHM and therefore into the frequency domain where there is little background noise from the resonance signal (large depth a). With higher modulation frequencies Fm (>1 MHz), the system operates out of the 1/f noise and low frequency noise spectrum of the frequency source and in the regime of shot noise limited frequency output of the laser. Accordingly, the source frequency will be
F=A*COS (2πTFo*t+a*COS 2πTFm*t)
where "a" is large ("a" at least 10 times greater FWHM), Fo is the center absorption resonance frequency, and Fm is the modulation frequency (Fm>1 MHz). A complete Bessel function expansion of F results in frequencies centered at Fo, Fo+/-nFm where "n" is an integer with amplitudes related to the Bessel functions Jn. For Phase Locked Passive Ring Laser Gyro (PRLG) applications, the modulation depth "a" is picked such that the dominant response is limited to Fo and Fo+/-Fm and all subsequent sidebands are negligible. This frequency modulation process is accomplished by injection of the source Fo into an E0 17 which frequency modulates the light at Fm. In the passive cavity approach Fm is about 10 MHz for a passive cavity having an FWHM of 100 KHz.
As signals Fo, Fo+/-Fm pass through A01 or A02, the three frequencies are upshifted in frequency by F1 or F2, respectively to Fo+F1, Fo+/-Fm+F1, or Fo+F2, Fo+/-Fm+F2. Each of these sets of frequencies are injected into the passive cavity 16 as either the CW or CCW beam. The Phase Locked PRLG of FIG. 1 through FIG. 7 shows an embodiment in which the reflected beam 32 is detected as opposed to the transmitted beam in alternative passive cavity configurations. A dip in the detector signals via signal lines 34, 64 will appear instead of a resonance peak. The fast response detectors 31 or 63 function as beat frequency detectors and also provide signal information with a DC intensity level. The three frequency components (Fo+F1), (Fo+F1+/-Fm) mix with each other to produce a beat frequency at Fm (all other frequencies Fo, Fo+/-F1, etc. are too high in frequency≈(1014 Hz), to be detected by the rest of the detector servo system). Normally, if there is no background or resonance signal, the photocurrents from the beat signals resulting from the two sidebands + Fm and -Fm are opposite in phase and will cancel out at the photodetector. However, where there is a resonance, after phase sensitive demodulation, a quasi-derivative signal as shown in FIG. 11b will result which provides an error signal having a + or - polarity, herein referred to as a DC error signal, utilized in a zero seeking servo loop. By phase sensitive detecting the resulting +Fm and -Fm signals from detectors 31 and 63 using mixer PSD1 or PSD2, the demodulated DC level signals as shown in FIG. 11b are obtained and utilized in the servo loop via the integrators and amplifiers to maintain CW and CCW resonance.
Note that FIG. 11b represents the resulting PSD DC level output amplitude as the source laser Fo is scanned from at least Fo-Fm to F-+Fm. As the source laser is exactly at Fo, the DC level is zero and there is no error correcting signal to the servo loop.
The acousto-optic device is an essential element in the output servo loop. Clockwise light is detected and phase sensitive demodulated to produce a DC error signal comparable to that in FIG. 11b resulting from the frequency modulation stabilization technique. This DC signal is the servo error signal which is integrated and then amplified using a high voltage amplifier to the appropriate levels needed to drive the PZT elements of the input source laser and the passive cavity. In this way, the input CW beam is locked to the CW passive cavity's resonance.
The CCW light is detected and phase sensitive demodulated in its corresponding servo loop. PSD2 provides the demodulated CCW error signal on signal line 56 to the input of INTEG2 65 where it is integrated and amplified and fed into a voltage controlled oscillator (VCO) 51. The VCO output frequency is used to change the frequency that A02 shifts the CCW beam such that the frequency of the CCW beam is brought into the cavity's resonance. The input rotation rate to the Phase Locked PRLG sensitive axis is related to the VCO's frequency and is the frequency difference of the frequencies supplied to A01 and A02. This frequency difference is counted using counter 71 to form a digital output signal which is scaled to provide a digital representation of the rotation rate about the sensitive axis.
Two acousto-optic devices are used so each beam encounters similar phase shifts. A02 is driven by the voltage controlled oscillator VCO 51 and shifts the CCW light up in frequency by F2 plus or minus a frequency related to the input rotation rates A01 in the CW beam path is driven by oscillator OSC2 and shifts the CW beam up in frequency by F1. By passing the CW light through an acousto-optic device, common mode bias errors are eliminated with respect to the CCW beam.
Although the invention has been disclosed and illustrated in detail, it is to be clearly understood that the same is by way of illustration as an example only and is not to be taken by way of limitation. The spirit and scope of this invention is to be limited only by the terms of the appended claims.
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|28 juil. 1986
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