CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     The present application is a divisional of U.S. application Ser. No. 11/062,103 filed Feb. 18, 2005, now pending, the content of which is hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to a light used for curing light-activated compound materials. In particular, the present invention relates to a portable rechargeable curing light for dental applications.  
       BACKGROUND OF THE INVENTION  
       [0003]     Light-activated compounds are well known and used in a variety of commercial applications. For example, such compounds are widely used in a variety of dental procedures including restoration work and teeth filling after root canals and other procedures requiring drilling. Several well-known dental compounds have been sold, for example, under the trade names of BRILLIANT LINE, Z-100, TPH, CHARISMA and HERCULITE &amp; BRODIGY.  
         [0004]     Dental compounds typically comprise liquid and powder components mixed together to form a paste. Curing of the compound requires the liquid component to evaporate, causing the composite to harden. In the past, curing has been accomplished by air drying, which has had the disadvantage of requiring significant time. This time can greatly inconvenience the patient. More recently, use of composite materials containing light-activated accelerators has become popular in the field of dentistry as a means for decreasing curing times. According to this trend, curing lights have been developed for dental curing applications. An example of such a curing light is illustrated by U.S. Pat. No. 5,975,895, issued Nov. 2, 1999 to Sullivan.  
         [0005]     Conventional dental curing lights have employed tungsten filament halogen lamps that incorporate a filament for generating light, a reflector for directing light, and often a filter for limiting transmitted wavelengths. For example, a blue filter may be used to limit transmitted light to wavelengths in the region of 400 to 500 nanometers (nm). Light is typically directed from the filtered lamp to a light guide, which directs the light emanating from an application end of the guide to a position adjacent to the material to be cured.  
         [0006]     Filters are generally selected in accordance with the light activation properties of selected composite compound materials. For example, blue light may be found to be effective to excite composite accelerators such as camphoroquinine, which has a blue light absorption peak of approximately 470 nanometers (nm). Once excited, the camphoroquinine accelerator in turn stimulates the production of free radicals in a tertiary amine component of the composite, causing polymerization and hardening.  
         [0007]     A problem with conventional halogen-based lights is that the lamp, filter and reflector degrade over time. This degradation is particularly accelerated, for example, by the significant heat generated by the halogen lamp. For example, this heat may cause filters to blister and cause reflectors to discolor, leading to reductions in light output and curing effectiveness. While heat may be dissipated by adding a fan unit to the light, the fan may cause other undesired effects (for example, undesirably dispersing a bacterial aerosol that may have been applied by the dentist to the patient&#39;s mouth). Alternate lamp technologies using Xenon and other laser light sources have been investigated, but these technologies have tended to be costly, consumed large amounts of power and generated significant heat. Laser technologies have also required stringent safety precautions.  
         [0008]     Light Emitting Diodes (LEDs) offer a good alternative to halogen curing light sources, having excellent cost and life characteristics. Generating little heat, they also present less risk of irritation or discomfort to the patient. However, in the past, LEDs have been capable of generating only modest optical power levels. As a result, many prior art curing lights have required arrays of LEDs to generate sufficient optical power levels for curing applications (see, e.g., U.S. Pat. No. 6,331,111 to Cao).  
         [0009]     More recently, the electrical and optical power outputs for LEDs have improved substantially. For example, LEDs are currently capable of producing powers in excess of 1 watt at efficiencies in excess of 45 percent to generate more than 100 lumens per watt (see, e.g., Eric Learner, “Solid-state illumination is on the horizon, but challenges remain”, Laser Focus World, November 2002). Accordingly, it would be desirable to produce a compact, portable LED curing light for use in dental curing applications.  
       SUMMARY OF THE INVENTION  
       [0010]     A portable LED curing light is disclosed, with application to curing of dental materials and other related applications. The light includes a one-piece handle assembly including a slim probe portion with an angled light-producing end that is suitable, for example, to be positioned within a dental patient&#39;s mouth for curing a dental material positioned in a tooth of the patient. A replaceable lens for focusing light emitted by an LED light source is removably attached at the light-producing end. The handle also includes a battery and associated electronics for operating the light, including an operating switch, an audible indicator and at least one visual indicator. The handle is coupled with a base for storage and recharging of the battery. The base positions the handle at an inclined position, and provides a drain for draining moisture away from the handle.  
         [0011]     Upon operation of the switch, the light may be operated for a predetermined curing cycle, after which power is automatically removed (“sleep mode”). An audible beep is produced at predetermined intervals during the curing cycle so that a desired curing time can be determined and achieved. Circuitry in the handle monitors the status of battery voltage and handle temperature. Based on predetermined thresholds, if either battery voltage is determined to be too low or handle temperature is determined to be too high, the circuitry prevents operation of the switch from initiating a next curing cycle. If the light is currently operating in a current curing cycle at a time at which either battery voltage is determined to be too low or handle temperature is determined to be too high, the light continues to operate through completion of the duty cycle. The visual indicator indicates when either battery voltage is determined to be too low or handle temperature is determined to be too high. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0012]     A more complete understanding of the invention may be obtained by reference to the appended drawing in which:  
         [0013]     FIGS.  1 ( a )- 1 ( f ) provide orthographic and perspective views of a handle of the disclosed LED curing light;  
         [0014]      FIG. 2  provides an exploded view of the curing light handle;  
         [0015]     FIGS.  3 ( a )- 3 ( d ) provide orthographic and perspective views of a heat sink for dissipating heat in the curing light handle;  
         [0016]     FIGS.  4 ( a )- 4 ( d ) provides several views of a ball lens affixed to the curing light handle for focusing light emitted by the LED;  
         [0017]      FIG. 5  illustrated features of a left housing case of the curing light handle;  
         [0018]      FIG. 6  illustrates features of a right housing case of the curing light handle;  
         [0019]      FIG. 7  presents a schematic diagram of a circuit for operating the curing light handle;  
         [0020]      FIG. 8  presents a schematic diagram of a circuit for charging a battery in the base;  
         [0021]     FIGS.  9 ( a ),  9 ( b ) provides exploded views of components of a base for receiving the curing light handle; and  
         [0022]     FIGS.  10 ( a )- 10 ( g ) provides orthographic and perspective views of the base; 
     
    
       [0023]     In the various figures, like reference numerals wherever possible designate like or similar elements of the invention.  
       DETAILED DESCRIPTION  
       [0024]     FIGS.  1 ( a )- 1 ( f ) present several views illustrating a handle  100  of an exemplary LED curing light embodying the principles of the present invention.  FIG. 1 ( a ) presents a perspective view of the handle  100 . FIGS.  1 ( b ) and  1 ( d ) respectively present top and bottom elevation views of the handle  100 . FIGS.  1 ( c ) and  1 ( f ) respectively present right side and left side views of the handle  100 , and  FIG. 1 ( e ) presents a front view of the handle  100 .  
         [0025]     The handle  100  includes a gripping portion  10  for an operator to hold the handle  100 . The gripping portion  10  encloses, for example, electrical circuit and battery components of the handle  100  (not shown), and provides access to a switch button cover  11  for operating the curing light. The handle  100  also houses at least one visual indicator  12  (for example, comprising an LED) for indicating a current state or status of the curing light.  
         [0026]     Extending from the gripping portion of the handle  100  is a probe portion  13  of the handle  100  that has a diameter reduced from a diameter of the gripping portion  10 , and includes an angled bend  14  near a distal end  15  of the probe portion  14  in order that the distal end  15  may be conveniently positioned, for example, within a dental patient&#39;s mouth. This configuration enables a lens assembly  16  at the distal end  15  of the probe to be placed in close proximity to a patient&#39;s tooth, so that light emitted at the distal end  15  of the probe portion  13  may be used to cure a dental material that has been applied to the tooth.  
         [0027]      FIG. 2  provides an exploded view of the curing light handle  100 , including right housing case  101 , a left housing case  102 , an LED/heat sink subassembly  20 , and an optical choke  16   a  and a ball lens  16   b  positioned in proximity to an LED  21 . The ball lens  16   b  is configured to be removable and replaceable. Optical choke  16   a  and a ball lens  16   b  are selected so that the LED  21  produces a focused light output at the distal end  15  of the probe portion  13 .  FIG. 2  also illustrates a curing light circuit board assembly  30 , electrically coupled to each of the LED  21 , a battery  41 , and a battery charging terminal  42  of the handle  100 . A switch button cover  11  made of neoprene or some like material covers an operating switch  31  mounted on the circuit board  30 , and protrudes through the cases  101 ,  102  to provide external means for operating the curing light. An indicator cover  12   a  and a light pipe  12   b  are positioned over an indicator LED on the circuit board assembly  30 . Indicator cover  12   a  protrudes from the circuit board assembly  30  through the cases  101 ,  102 . Audio circuitry (not shown) for producing an audible indicator (for example, a “beep”) is also positioned on circuit board assembly  30 .  
         [0028]     FIGS.  3 ( a )- 3 ( d ) present several views illustrating a heat sink  22  of the LED/heat sink subassembly  20 , for dissipating heat primarily generated by the LED  21  of  FIG. 2 .  FIG. 3 ( a ) presents a perspective view of the heat sink  22 . FIGS.  3 ( b ) and  3 ( d ) respectively present top and bottom elevation views of the heat sink  22 , and  FIG. 3 ( c ) presents a side view of the heat sink  22 .  
         [0029]     The heat sink  22  conforms to an inner volume of the probe portion  13  of  FIG. 1 , and substantially fills this inner volume. Preferably formed in a single piece, it extends through the angled bend  14  of the probe portion  13  of  FIG. 1  in order to be directly and thermally coupled to the LED  21  of  FIG. 2 . The heat sink  22  includes, for example, lateral grooves  23  on opposing sides of heat sink  22  for directing electrical wires from the LED  21  of  FIG. 2  to the circuit board assembly  30  of  FIG. 2 . Heat sink  22  is also includes notches  24  on opposing sides of heat sink  22  at a distal end  25  of the heat sink in order to locatably couple the LED  21  at the distal end  25  The heat sink  22  preferably comprises a highly thermally conductive material such as copper  101 .  
         [0030]     FIGS.  4 ( a )- 4 ( d ) provide several views of a ball lens  16   b  affixed to the curing light handle for focusing light emitted by the LED.  FIG. 4 ( a ) presents a perspective view of the ball lens  16   b.  FIGS.  4 ( b ) and  1 ( c ) respectively present top and bottom elevation views of the ball lens  16   b,  and  FIG. 4 ( c ) presents a section view through section A-A of  FIG. 4 ( c ).  
         [0031]     The ball lens  16   b,  in conjunction with the optical choke  16   a  illustrated in  FIG. 2 , further focuses a light beam emitted by the LED  21  of  FIG. 2 . Ball lens  16   b  and optical choke  16   a  are selected so that a majority of the emitted light energy is concentrated over an area that is sufficient for curing dental composites in a patient&#39;s mouth.  
         [0032]     FIGS.  5 ( a )- 5 ( d ) and  6 ( a ),  6 ( b ) respectively illustrate features of left housing case  102  and a right housing case  101 , respectively. The right housing case  101  and left housing case  102  may be mated for example by ultrasonic welding. An energy director  102   a  of the left housing case  102  includes an outwardly extending v-shaped edge  102   b  (see, e.g., Section F-F of  FIG. 5 ( a ),  5 ( b )) that may be positively located and mated to a corresponding groove (not shown) in the right housing case (see, e.g., Section B-B of  FIG. 6 ). In addition, the v-shaped edge of the energy director is periodically relieved by an inwardly extending v-shaped groove  102   c  (see, e.g., Detail G of  FIG. 5 ( c )) that in order to receive a weld lock  101   b  of the left housing case (see, e.g., Detail H of  FIG. 6 ( b )). In this manner, the left housing case and right housing case can be easily, precisely and fixedly aligned for mating during the ultrasonic welding process. Once ultrasonically welded, the left housing case and right housing case form a rigid, one-piece housing for the handle.  
         [0033]      FIG. 7  presents a schematic diagram of a circuit  700  for operating the curing light handle. The circuit  700  is preferably powered by a conventional lithium battery (illustrated as battery  41  of  FIG. 2 ), but may alternatively be powered by a conventional nickel cadmium battery, or alternatively, by a nickel metal hydride battery.  
         [0034]     Switch  701  signals switching controller  702  via microcontroller  703  to turn on LED  21  for a predetermined curing cycle (for example, sixty seconds). Microcontroller  703  is coupled to crystal oscillator  704  to provide timed control functions. After completion of the curing cycle, microcontroller  703  removes power from LED  21  to allow the curing light to enter a sleep mode.  
         [0035]     During operation of LED  21 , microcontroller  703  periodically outputs a signal on pin  1  of microcontroller  703  (for example, every ten seconds) to cause speaker  705  to produce a regularly timed audible beep. These beeps may be used by a dentist or other operator of the handle  100  of  FIG. 1  to determine an elapsed time, and thereby to apply the curing light to cure a dental material for a desired curing time. A charging circuit  706  and fuse  707  regulate battery charging and prevent the battery from being overcharged.  
         [0036]     Microcontroller  703  is further programmed to periodically test for adequate battery voltage and excessive operating temperature (for example, every five seconds). For example, microcontroller  703  determines the adequacy of battery voltage Vdd by measuring and comparing Vdd as supplied to the circuit  700  to a fixed voltage reference measured across diodes  708 ,  709 . Microcontroller  703  further determines operating temperature by measuring a voltage drop across a resistive component of thermistor  710  relative to Vdd . As the voltage drop across the thermistor is a function of Vdd, a dimensionless ratio of these two voltages may be produced to determine a relative measure of operating temperature.  
         [0037]     If either battery voltage is determined to be inadequate and/or operating temperature is determined to be excessive, microcontroller  703  does not permit a new operating cycle to begin in response to an operation of switch  701 . If an operating cycle is in progress when battery voltage is determined to be inadequate and/or operating temperature is determined to be excessive, microcontroller  703  allows the currently operating cycle to complete before preventing initiation of subsequent operating cycles. While battery voltage and operating temperature are at proper levels for operation, microcontroller  703  controls a voltage at pin  6  to light indicating LED  711 .  
         [0038]     In order to provide for change and upgrading of its operating program, microcontroller  703  may further be coupled to programming connector  712 .  
         [0039]      FIG. 8  presents a schematic diagram of a charging circuit  800  for charging battery  41  of  FIG. 2  by means of base  200  of  FIGS. 9, 10 . As illustrated in  FIG. 8 , linear regulator  801  regulates a voltage supplied to the charging circuit  800  (for example, from a commercial power source). So long as adequate commercial power is supplied, green LED  802  lights to provide an indication that commercial power is present. As significant current is drawn at lead J 2  for recharging the battery, a voltage drop across resistors  803 ,  804  activates amplifiers  805 ,  806  to cause current flow through transistor  807  in order to light the red LED  808  to indicate that the battery is recharging.  
         [0040]     FIGS.  9 ( a ),  9 ( b ) respectively provide exploded views of components of a base  200  for receiving the curing light handle from above and below the base  200 . The components of base  200  include a main housing  201 , a lower housing  202 , a circuit board  203  including a battery charger pin assembly  203   a  and a power receptacle  203   b,  and a weight  204  for stabilizing the circuit board.  FIG. 10  provides orthographic and perspective views of the base. The components  201 - 204  may be assembled together using a variety of conventional fastening means (for example, by means of retaining pins  205  which may be ultrasonically welded, glued or thread mounted to receptacles  206 .  
         [0041]     FIGS.  10 ( a )- 10 ( g ) further illustrate the base  200 .  FIG. 10 ( a ) presents a perspective view of the base  200 . FIGS.  10 ( b ) and  10 ( c ) respectively present top and bottom elevation views of the base  200 . FIGS.  10 ( e ) and  10 ( g ) respectively present right side and left side views of the base  200 .  FIG. 10 ( f ) presents a front view of the base  200 , and  FIG. 10 ( g ) provides a rear view of the base  200 .  
         [0042]     Main housing  201  includes a conical portion  201   a  having a recess  201   b  for receiving the gripping portion of the handle for storage and re-charging of the handle. The conical portion  201   a  and recess  201   b  are co-axially oriented slightly away from a vertical angle  201   c  (for example, approximately 10 to 15 degrees). A slit  201   d  extends through the conical  201   a  portion into the recess  201   b,  and terminates at a lowest portion  201   e  of a base of the conical portion  201   a  in order to enable moisture collecting within the interior of the recess  201   b  to drain away through the slit. At least two charging pins in charging pin assembly  203   a  of  FIG. 9  extend upward from the recess near the base of the conical portion  201   a  for contact with battery charging terminal  42  of  FIG. 2  at the of handle  100 . The charging terminal  42  includes at least two, electrically isolated conductive rings (not shown). When the handle is inserted into the recess, each pin makes electrical contact with one of the conductive rings, regardless of the radial orientation of the handle in the recess.  
         [0043]     Appendix 1 provides a program listing illustrating for example the manner in which microcontroller U 2  of  FIG. 7  is operated to measure battery voltage and thermistor temperature, and therefrom to control operation of the curing cycle and lighting of the visual status indicator.  
         [0044]     The foregoing describes the invention in terms of embodiments foreseen by the inventor for which an enabling description was available, notwithstanding that insubstantial modifications of the invention, not presently foreseen, may nonetheless represent equivalents thereto.
A portable LED curing light for dental applications includes a one-piece handle assembly with an angled light-producing end for positioning within a patient's mouth for curing a dental material. A replaceable lens for focusing light emitted by an LED light source is removably attached at the light-producing end. The handle also includes a battery and associated electronics for operating the light, including an operating switch, an audible indicator and at least one visual indicator. The handle is coupled with a base for storage and recharging, which positions the handle at an inclined position for draining moisture away from the handle. Circuitry in the handle monitors the status of battery voltage and handle temperature, and prevents operation of the switch from initiating a next curing cycle when battery voltage is determined to be too low or handle temperature is determined to be too high.