Automatic Image Correction Techniques For CF-LCoS Pico-Projection Optical Engine

With the rapid development of high-power LED light source and micro-display chip industry, pico-projection applied on mobile devices has stepped into people’s lives. Pico-projection optical engine can be embedded into smart phones, laptops, video game players, digital cameras and other portable electronic devices. Higher resolutions and larger images make these devices realize the exchange and sharing of information more effectively.The CF-LCoS and the CS-LCoS have different requirements to the driving characteristics of the LED. For these requirements, a driver circuit to white LED working continuously and a high power RGB three-color LED driver circuit controlled by a PWM signal are designed for LCoS pico-projection. The projection displays of the CF-LCoS and the CS-LCoS are achieved.Then a driver circuit for pico-projection is designed. As a video signal conversion chip RTD2662is produced by the Realtek corporation. It converts the analog signals such as the input AV signal, HDMI signal and VGA signal into digital signals. The HX7809-type chip produced by the Himax corporation raises the frame rate of the digital signals to120Hz. The mission to drive the HX7015-type CF-LCoS is completed.The output image of the pico-projection optical engine shows that the change of the brightness level is irregular and the distortion of color is serious. Especially for the CF-LCoS pico-projection optical engine, the problems of poor image contrast and dim color can be often seen. In order to enhance the image quality of the projection display, a set of automatic correction system for embedded pico-projection optical engine display images is built. It succeeds in correcting the brightness and color of pico-projection display images by adjusting the CF-LCoS Gamma curve. First, it collects feedback signals on the screen through the photoelectric conversion system. Then it evaluates the feedback signals obtained and adjusts the gamma curve characteristics according to the results of the assessment. Finally the brightness of the display images is adjusted by changing the relationship between the input information and the output voltage.The automatic correction system changes the gamma curve characteristic of the three colors respectively by separately adjusting the RGB three Gamma curves of the CF-LCoS. When different gradation test images are input, the chromaticity coordinates of the main gradation display images are adjusted close to the target color so as to achieve the purpose of the color correction. The color distortion of the display images reaches a minimum and the differences in color between the projection picture and the original image are fixed. Not only product quality is improved, but also the projection products will be more popular and the projection industry will be vigorously promoted.