Study On Quality Measuring System For DLP Projection Display System

Digital Light Processing technology is one of the advanced projection display technologies at present, but the quality measuring system for DLP projection display screen is still on the research way.The dissertation introduces the working principle of the DLP projection display system which is based on the characteristic of the persistence of human vision, the DMDs are used as the modulator that flip frequently to modulate the red, green and blue light, diversified colors are produced by the modulation method with the three colors accumulating respectively in extremely short duration. The above characteristic makes it different from the traditional way to measure quality of the display device with the special principle and method described as following points. Firstly, measuring the imaging quality takes the CCD to shoot the imaging unit (DMD pixel unit) on the DLP projection display screen and acquires the data of the image to calculate its point spread function. High intensity of the light from the DLP optical projector needs tiny time of exposure to be less than 1/10000 second. Secondly, the time of exposure of CCD must be synchronized with the image signal from the screen, which makes the system need nine CCDs altogether to measure the whole screen quickly and the CCDs must synchronize each other.The dissertation proposes a design which works with external trigger, in pulse width control mode to drive the CCDs. The imaging quality measuring system is composed of six components: green sensor module, synchronization unit, signal generation subsystem, photoelectric conversion subsystem, image acquisition subsystem and the computer.The green sensor module and synchronization unit are designed and made. The imaging quality measuring system is set up on the basis of studying on the working property of signal generation, exposure of CCD to read and write image data, image acquisition, and time order between eachcomponent.According to the user requirement and functional needs, three modules make up the software of the measuring system. They are main control module, photo-measuring module and imaging quality measuring module. The photo-measuring module includes color measurement and lightness measurement. The imaging quality measuring module includes three sub modules: initial configuration sub module, image data acquisition sub module, fourier transform sub module. The initial configuration sub module configures the hardware of the imaging quality measuring system via software and transfers the parameters from the main control module to software configuration. The image data acquisition sub module controls the signal generation part and imaging acquisition part to get the image data from CCDs. Fourier transform sub module realizes data transformation to get the point spread function results. The finished software can realize the full control to measure in the mode of auto or manual.After multiple debuggings and modifications, the measuring system has experienced long time test run which indicates that, on one hand, the photo-measuring results are less than 5% error with the results of the existent well-rounded measuring system; on the other hand, the imaging measuring results are in accordance with the theory analysis, the stability is with the variation coefficient less than 3.5%, the reproducibility is with the variation coefficient less than 4.5%. Both the results of photo-measurement and imaging quality measurement achieve the aim of the planned design and it can provide strong technical specification with this measuring system for the study and manufacture of DLP optical projector and DLP projection display device.