title: High efficiency pocket-size projector with a compact projection lens and a light emitting diode-based light source system.
abstract: We present a light emitting diode (LED)-based ultramini digital micromirror device projector with a size of 75 mm x 67 mm x 42 mm and a weight of 338 g. The LED illuminator inside this projector makes it possible to achieve a volume of 18 cm(3) by using a dichroic filter and a collimating lens. The illumination system consists of high uniformity of 93% through a microlens array as a homogenizer. A total internal reflection prism is also used to reduce the size of both the illumination system and the telecentric projection lens. A projection lens system with an ultrasmall track of 42 mm, including a high modulation transfer function value of 0.4 at 46.2 line pairs/mm, an optical distortion of only 0.25 %, and a television distortion of 0.01%, is designed. Through the above superior specification, we can produce a 20 in. (51 cm) color display comparable in brightness to a laptop with a contrast of 3700:1. The device is compact and suitable for personal use.
authors.affiliation: Department of Optics and Photonics, National Central University, Jhongli, Taiwan. rwpan@ios.ncu.edu.tw
authors.forename: Jui-Wen
authors.initials: JW
authors.lastname: Pan
authors.forename: Sheng-Han
authors.initials: SH
authors.lastname: Tu
authors.forename: Chih-Ming
authors.initials: CM
authors.lastname: Wang
authors.forename: Jenq-Yang
authors.initials: JY
authors.lastname: Chang