Arbitrary Uniform Waveform Optical Source Based On White LED

In recent years,the energy crisis is increasing seriously.The national strategic that emerging LED industry has developed rapidly and the market has great potential.Due to the lack of standards and the imbalance of their own existing facilities and equipment,working basis and technology development,there are numerous kind of LED products with different performance in the market.Therefore,the relative LED standards system is urgently needed.This paper mainly focus on high-power white LED and the goal is to develop an arbitrary uniform waveform optical source based on white LED which is used to calibrate testing equipment LED photoelectric characteristics.The technology of secondary optical design for LED dimming and drive is studied.For the current problem that LED light is uneven and nonlinear,substantial researches are conducted and list as follows:1)The development,application and trends of LED is introduced briefly.The review of advantages of LED secondary optics design is followed by the international development and application status about nonlinear optical design method.2)The concept of photometric and radiometric and their internal relations are explained.Then the basic structure of the LED is also described.The packaging form,light-emitting principle of LED electrical and optical characteristics are all analyzed additionally.To lay the foundation of further research,LED performance characteristics are summarized,either.3)It exists for the LED light uniformity,using non-imaging optics for high-power white LED for secondary optical design.Based on the principle of marginal rays and Etendue conservation thinking,combined with a compound parabolic concentrator and symmetrical free curved lens axis.Designed and developed high-power light emitting diode extended source of reflection / refraction collimator.Using Tracepro software system for beam tracing simulation and experimental guidance.The LED light output expansion divergence angle ± 12°,measured from the outgoing face mask at the spot at 50 cm in size 14 cm × 14 cm lighting range within the measured spot horizontal center line of the non-uniformity of brightness is better than 4.1%,the non-uniformity of brightness vertical center line of better than 3.8%,LED light source light at the excellent overall optical efficiency target spot at the screen 40%.4)For the nonlinear problems of LED light signal,relative drive is designed and corresponding calibrated method is also proposed.According to the electrical characteristics of the LED,based on the analysis and comparison of common LED drive mode,constant current drive linear control method is employed to amplify the linear signal.In this way,the distortion effect in signal amplification process is reduced.Selecting OPA541 operational amplifier as a high-power linear regulator simplify LED drive circuit which has a signal power amplifier and drive LED light function.Calculating circuit parameters accurately,the software of Altium Designer is employed to design circuit schematic and PCB board.According to the LED voltage characteristic curve,analyzing the relationship between the electric power and the peak irradiance,the algorithm of software look-up table is adopted to moderate the nonlinear phenomena of light signal waveform.Therefore,the irradiance value changing with time has a good linear relationship.Meanwhile,the optical source has output characteristics of arbitrary waveform and it can be regarded as arbitrary waveform optical source.