Abstract:
Applicant&#39;s invention relates to a photo-curing light assembly having calibration circuitry determinative of the intensity level of the light source and the generation of an analogue control voltage from a digital control voltage during use which automatically adjusts light intensity to achieve proper energy levels during programmed curing times.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of provisional application 60/177,367 filed Jan. 24, 2000. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates to a photo-curing light assembly for photosensitive compounds and more particularly to a photo-curing light assembly having calibration circuitry permitting lamp intensity control throughout time frame illumination. 
     2. Description of the Prior Art 
     Numerous substances are sensitive to light energy. One class of such substances undergo polymerization in response to applied light energy. Such class of substances includes composites and adhesives that have found uses in the dental arts for dental repair and the fabrication of dental prosthetics. 
     The time to cure a photosensitive composite or adhesive is a function of several factors, including the type of composite or adhesive, the amount of composite or adhesive required for the application, intensity of the light energy delivered, and the time duration of exposure. The intensity level of the light source decreases over the life of the source thereby affecting the intensity level and amount of light energy delivered to cure the composite or adhesive. In such situation, longer exposure times are required. 
     Adjustment of the exposure time includes the varying of the intensity of the light source, e.g. utilizing low intensity light over greater exposure times or high intensity light over shorter exposure times. Depending upon the type and amount of composite or adhesive being utilized, it may be beneficial to vary the intensity of the light during the actual photo-curing operation by either steadily increasing the intensity or stepping the intensity of the light over the exposure time. Pre-programmed photo-curing systems allow the user to select from two or more pre-programmed intensity modes. Since the intensity level of the curing lamp decreases over time there is a need to provide for a photo-curing assembly which provides for proper curing control notwithstanding any such diminished capacity of the curing lamp. 
     OBJECTS OF THE INVENTION 
     An object of the present invention is to provide for a novel photo-curing light assembly permitting the calibration of the intensity level of the light source prior to use. 
     A further object of the present invention is to provide a novel photo-curing light assembly permitting calibration of the intensity level of the light source in a fast and efficient manner. 
     A further object of the present invention is to provide for a novel photo-curing light assembly permitting calibration of the intensity level of the light source constantly permitting automatic readjustment of the light output during use to achieve proper curing energy level for the programmed curing time, not withstanding the diminished intensity of the curing lamp during its usable life. 
     A still further object of the present invention is to provide a novel photo-curing light assembly permitting the user to program a desired light intensity level over the duration time, to maintain a constant intensity, to increase intensity or to step intensity. 
     A still further object of the present invention is to provide a novel light curing assembly automatically increasing the duration time when the intensity level has reached its maximum output, but is unable to provide the required energy level for curing. 
     SUMMARY OF THE INVENTION 
     Applicant&#39;s invention relates to a photo-curing light assembly having calibration circuitry determinative of the intensity level of the light source and the generation of an analogue control voltage from a digital control voltage during use which automatically adjusts light intensity to achieve proper energy levels during programmed curing times. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects of the present invention will become apparent particularly when considering the following detailed description and the accompanying drawings wherein: 
     FIG. 1 is a block diagram of the photo-curing light system; 
     FIG. 2 is a detailed illustration of the calibration assembly; 
     FIGS. 3,  4 , and  5  illustrate curing, wave shaping attainable by the photo-curing light system and the calibration method; and 
     FIG. 6 illustrates the standard wave shape achieved by the prior art. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, and particularly FIG. 1, there is provided a photo-curing light assembly of the present invention, generally indicated as  10 , comprised of an electronic module  12 , a curing lamp  16 , power supply module  14 , and an optics module  18 . Such modules are mounted within a housing positioned proximate a dentist chair. Illumination from the lamp  16  is spectrally modified by the optic light guide  18  and transmitted to a tooth structure on which dental work is being performed. Transmission of such light is accomplished by a fiber optic or liquid core light guide  20  terminating in a curing tip  22  positioned in a dental hand piece (not shown). 
     The electronic module  12  of the photo-curing light assembly  10  is comprised of a microprocessor  28  provided with a nonvolatile RAM NVRAM  29 , a user interface  24  comprised of an input pad device  26  and a display unit  30  and an intensity control  32 . The microprocessor is connected to the input pad device  26  and display unit  30  of the user interface  24 , to the intensity control unit  32  and the light sensor  34  within the electronic module  12 . There is also included an amplifier  46  connected to a photodiode  44  having an external calibration post  40  provided with a diffuser glass  42 . (See FIG.  2 ). In operation, the dentist or dental technician enters light intensity data and/or time duration data onto the input pad  26 . Such data is communicated to the microprocessor  28 (and displayed by the display device  30 ) and thence to the intensity control module  32  controlling curing lamp power supply  14  and the amount of current transmitting to curing lamp  16  to achieve the intensity selectively inputted via the input pad  26 . 
     Over the course of time, the curing lamp  16  deteriorates in the amount of intensity which can be transmitted. Therefore, it is desirable to continuously know the maximum intensity of the curing lamp  16  at any time during use to adjust time duration needed to achieve proper curing. The light sensor  34  of the electronic module  12  senses light intensity emitted by the curing tip  22  to permit continuous calibration of the curing lamp  16 , as herein more fully described. 
     The light sensor  34 , referring to FIG. 2, includes an amplifier  46  connected to a photodiode  44  having an extended calibration port  40  provided with a diffuser glass  42 . In operation, the curing tip  22  is inserted into the external radiometer calibration port  40  with light from the curing tip  22  illuminating the diffuser glass  42  to provide a uniform light beam. Such uniform light beam is viewed by the photodiode  44  having spectral response wave length is in the range of from 400 nm to 500 nm. The photodiode  44  in turn is in communication with the gain operational amplifier integrated circuit  46  generates a signal of the spectral response intensity from photodiode  44 , and is thence transmitted to the microprocessor  28 . Once the microprocessor  28  detects light, the calibration process is commenced. 
     Curing lamp  16  is caused to be automatically turned to its maximum light level and remain at such light level for a period of time to stabilize the light output. Such period of time is in the range of about 7 seconds. Once stabilized, the microprocessor  28  automatically reduces the light intensity of the curing lamp  16  to 50 percent of such maximum. Lamp current to the curing lamp  16  is adjusted until the signal level from the photodiode  44  circuit to the microprocessor  28  is nominally 50 percent. Such signal is stored in the non-volatile RAM (NVRAM) integrated circuit  29 . The microprocessor  28  then changes the control signal in five percent, increasing increments until 100 percent intensity is achieved. The signal level for each of these increments is stored in NVRAM  29 . 
     Once 100 percent intensity is achieved, the process is reversed with the microprocessor  28  reducing the control signal by five percent increments from 100 percent to 50 percent. Each of these signals at the five percent increment levels is stored and replaces the stored signals of the ascending increments. The signals now stored in the NVRAM  29  are utilized in controlling the light intensity level during actual use. It is understood by one of ordinary skill in the art that calibration of the light output of the curing lamp is effected on a daily basis during the life of the curing lamp. 
     The entire calibration process takes approximately 10 seconds. At conclusion, the light output goes to the programmed level in the selected mode of operation as inputted by the user via the input pad  26 . It can therefore be understood that the speed and accuracy of this calibration permits the dentist or dental technician to calibrate the instrument before each and every patient use, thereby assuring a more accurate cure and also permitting a greater variety of selected modes of cure. 
     The calibration method and scheme as described herein, assures the dentist and the dental technician that light intensity and duration are sufficient for the curing process being programmed. It allows the user to get the maximum life and benefit from the curing lamp  16  without premature replacement and serves as a warning to the user when lamp light guide or curing tip may have reached its life expectancy. 
     In operation, when light output from the curing tip  22  decreases, as measured by the external radiometer calibration port  40 , the microprocessor controlled electronics automatically adjusts the light output to achieve proper curing energy or intensity for the programmed curing time as inputted on the input pad  26 . When light output has been increased to its maximum output (and cannot produce the required curing energy for the programmed time), curing time is automatically increased by the microprocessor and is displayed in second increments. The maximum increase time which the microprocessor is automatically programmed is twice the program time inputted by user on the input pad  26 . At such time, the display unit will flash indicating that the light output is reduced to one half of the maximum achievable output and the user can take appropriate action with respect to the curing lamp  16 , light guide or curing tip. 
     Similarly, when the light output has been increased to its maximum output and the time has automatically increased to produce the proper curing energy, reducing the programmed intensity will automatically shorten the duration time. 
     Once the curing lamp  16  has been calibrated using the calibration method as set forth above, the light output can be controlled via settings selected in the programming mode by the dentist or dentist technician. The microprocessor  28  will automatically generate the proper signal levels based on the stored memory and the programmed inputs to control the lamp current such that the light output is set at the desired level which is a percentage of the maximum light output as defined by factory setting. The ability of the calibration method of the present invention to control the lamp current and hence lamp intensity is provided by an analog control voltage to the control line input of the high voltage power supply. 
     As illustrated in FIG. 2, an analog lamp control voltage signal  50  is digitally generated by microprocessor  28 , and applied to the lamp current control line  52  controlling lamp intensity. Such analog control voltage  50  is digitally generated by the microprocessor  28  and converted to an analog signal  54  by means of a digital to analog converter circuit  56  which in turn is connected to a constant current circuit  58  utilizing an operational amplifier integrated circuit  60  and transistor  62 . Thus, the microprocessor  28  utilizes the stored signal levels generated during the calibration process to generate the lamp current control signal  52  so as to generate a constant current to the lamp power supply  14  and thence to lamp  16 . The microprocessor as a result of the calibration method will automatically adjust the time duration based upon the intensity of light available as a result of the age or use of the curing lamp  16  and condition of the light guide and curing tip. 
     The ability to calibrate the curing lamp  16  to ascertain its maximum intensity during life time allows the dentist or dentist technician the ability to accurately control light intensity and/or time duration in the programming of inputs to the microprocessor which permits accurate light output wave shaping. 
     FIG. 3 is illustrative of a step mode curing. Duration time is measured on the horizontal axis and light intensity measured on the vertical axis. The input pad  26  of the photo-curing light system  10  assembly permits the user to input multiple intensity and time levels resulting in a step mode curing wave shape where curing is initiated at an initial intensity  70  for an initial duration  72  and then increased to a second intensity  74  for a second duration  76 . 
     FIG. 4 illustrates a partial ramp mode in which curing is begun at an initial intensity  80  and continually increased to a second intensity  82  over a time duration  84  and it is maintained at such second intensity  82  for a time duration  86 . 
     FIG. 5 illustrates a full ramp mode with respect to the photo-curing light assembly  10  in which curing commences at an initial intensity  90  and continuously increases to a maximum intensity  92  over a time duration  94 . 
     The wave shaping capabilities available to the user at the discretion of the user thereby permits the user to compensate for different types of photo-curable composites, adhesives, sealants, etc., and different thicknesses of photo-curable composites as applied to the tooth structure. The calibration scheme heretofore discussed provides the user with confidence that the desired intensity and desired time duration will be accurately provided by the photo-curing light system in order to insure adequate and total curing of the composite, adhesive or sealant. 
     If the light intensity of the curing lamp has been increased to its maximum and cannot produce the required curing energy, the programmed time is automatically increased to achieve the desired curing and the user can program the photo-curing light assembly to include curing at a fixed intensity, a continuously increasing intensity from one level of light output intensity to another level of light output intensity or in a step mode having a fixed level of initial light intensity for a fixed duration and an increase to a second level of fixed light intensity for a second fixed duration. 
     While the invention has been described in connection with an exemplary embodiment thereof, it will be understood that many modifications will be apparent to those of ordinary skill in the art; and that this application is intended to cover any adaptations or variations thereof. Therefore, it is manifestly intended that this invention be only limited by the claims and the equivalents thereof.