Imaging-based Methods For Photometric Measurement Of LEDs

Because Led (Light-Emitting Diode) Light source meet low carbon, green and environmental protection of social expectations,it has been widely used in the information field, lighting field, display field, and is becoming the most potential light source besides incandescent lamp, fluorescent lamp, discharge lamp. With the rapid development of photoelectric industry, people set an even higher demand on the LED performance parameters. Standards and test technologies of LED are the important factors in LED industry. Many research institutions has developed LED testing equipment with high level, but overall, equipment costs more. At present, Chinese national standards in LED and related products are nearly blank, no unified standard and requirements to regulate the industry, make that the good and bad industry products are intermingled.In this paper, according to the development and test requirement of LED, we developed a new way to measure the parameters of LED source. While designing the test system, this paper introduces the basic theory of measurement in LED. Then, according to the principle of digital imaging, we put forward two overall schemes of the measurement system. After introducing the principle of both schemes in great detail, we simulate the scheme i in a software and find scheme i wouldn’t apply.So, in this paper, the scheme ii is choosed as the main design task. Scheme ii system is mainly consists by a CCD camera and a Lambertian translucent diffuse screen. Light from an LED strikes the screen’s front surface,and then a CCD camera images the illuminated screen. We use1W LED light source as a standard and measure the intensity distribution in space with traditional gonioradiometer, from the measured data of the system we can calibration scheme ii parameters.After that,we can use this system to compute the LED space intensity distribution.This set of instrument system can measure LED space light intensity and photometric parameters in fast speed,and can be widely used in production test and LED research test.Finally, we using the development of the testing equipment and instruments to test the sample and analyses the experimental error, and puts forward improving ideas and methods of the instrument in this paper based on the work.