||The projection system in this study is divided into illumination system and imaging system. The illumination system adopts non-axisymmetic condenser including three RGB LED light sources, two dichroic mirrors, a lens array, a relay lens, a total internal reflection prism and digital mirror device system. The imaging system consists of an 1.03 million pixel DMD system, a TIR prism and a projection lens. The projection screen size is 60 inches, the projection distance is 2.1 meters, the F/# is 16.02 mm. The effective focal length of projection lens is 16.02 millimeter. The size of the projection system is 130.7 mm × 93.2 mm × 33 mm.|
The function of condenser is to project the LED light source to the entrance surface of the lens array. If the condenser adopts the axisymmetric optical system, the light source is imaged on the entrance surface of the lens array, and the numerical aperture of the image is the same in the horizontal and vertical directions, but the lens array design has different numerical apertures in the horizontal and vertical directions, so it causes energy loss and reduces efficiency. If a non-axisymmetric condenser is used, its effective focal lengths in the horizontal and vertical directions are different, and the magnifications of the horizontal and vertical directions are different, so that the numerical aperture in horizontal and vertical directions of the non-axisymmetric condenser are different. If the numerical aperture of the non-axisymmetric condenser system also matches the numerical aperture of the entrance surface of the lens array, so that light efficiency can be improved.
If the projection system is calculated by etendue, the etendue efficiency is 48.68%. The projection system in this study uses three RGB LEDs in different position, respectively, through different optical paths, and finally the light source is combined in the lens array. Under the condition that the transmittance of each optical component is 100%, the number of simulated light is 20 million. The mesh is 48×30, and the efficiency analysis on the screen, the efficiency of red light is 47.36%, the efficiency of green light is 41.66%, the efficiency of blue light is 45.03%, the efficiency of white light is 43.50%. The result is compared with the etendue efficiency of 49.58%, the energy loss is caused by two dichroic mirrors. The uniformity of white light on the screen is ANSI(+%) of 2.71%, ANSI(-%) is -3.13%, JBMA(%) is 97.80%, and the average deviation is 6.79%. Finally, the projection system has 134.46% of sRGB color gamut.
|| Texas Instruments (TI), “DLP® Discovery Optics 101 Application Note,” http://focus.ti.comlitandlpa022dlpa022.pdf|
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