Abstract
We provide a novel achromatic design in the illumination system for a mini projector with an LED light source. The lateral color aberration at the corners of the DMD active area can be reduced to 0.48 μm by our compact ATIR prism. The total prism size is 4091 mm(3). The spot sizes at the corner and the edge are also controlled under 198 μm. Moreover, we use a light pipe for color uniformity at the center of the DMD active area. Under the two components for color uniformity, the Δu' v' is well controlled under 0.016 by a 20 mm length of light pipe. The illuminance uniformity at the active area of the DMD chip is higher than 92.8%. The optical efficiency of the light pipe is 94.1%.
Highlights
Light-emitting diodes (LEDs) are the new generation of light sources
An LED light source has been widely used for digital light processing (DLP) and liquid crystal on silicon (LCoS) projectors [2,3]
We introduce novel achromatic prisms in the illumination system of a projector in order to solve the lateral color aberration at the corner of the digital micromirror device (DMD) active area and to control color uniformity at the center of the DMD active area with a light pipe
Summary
Light-emitting diodes (LEDs) are the new generation of light sources. LEDs are power-saving and environmentally friendly [1]. According to our research, “Homogenized LED-illumination using microlens arrays for a pocket-sized projector [10],” we used an LED light source in our mini projector where there are serious color uniformity issues at the center and corner of the projection screen. We introduce novel achromatic prisms in the illumination system of a projector in order to solve the lateral color aberration at the corner of the digital micromirror device (DMD) active area and to control color uniformity at the center of the DMD active area with a light pipe. For color uniformity we use a light pipe to control the color uniformity at the center of the DMD active area. We can get illuminance uniformity at the DMD active area by choosing a suitable length of a hollow-mirrored light pipe with low-loss efficiency [11,12]. The illuminance uniformity at the DMD active area is higher than 92.8%
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