Patent ID: 8693112

Claim:
A projection lens unit for a pico-projector which comprises a lens array, a field lens, a cover glass and an image panel, the lens array comprising: a 1 st lens with negative (−) refractive power, a 2 nd lens with positive (+) refractive power, a 3 rd lens with negative (−) refractive power, and a 4 th lens with positive (+) refractive power, wherein the 1 st to 4 th lenses are arranged in order from a screen upon which an image is projected, the 1 st to 3 rd lenses are plastic lenses and the 4 th lens is a biconvex glass lens, and wherein a BFL between the 4 th lens and the field lens has a change rate of 1.63 μm/° C. in relation to a temperature.