Patent ID: 6473242
Filing Date: 2002-10-29
Classification: G02B

Abstract:
A projection lens having an optical axis comprising, in order from an object side of the lens to a modulator side of the lens:(a) a first lens group having a positive power including a positive lens element; (b) a second lens group including a negative meniscus element, having a concave surface toward the modulator side, wherein the second lens group fulfills the following conditions: 0.184/f<0.45 â€ƒwhere r4 is the radius of curvature of the concave surface of the negative meniscus element of the second lens group; and f is the focal length of the projection lens; (c) a third lens group having a positive refractive power including a positive lens element; (d) a fourth lens group having a negative lens element; (e) a fifth lens group including a positive lens element; and (f) a sixth lens group including a positive lens element; â€ƒwherein the maximum angle between a principal ray emerging from the projection lens and the optical axis on the modulator side of the projection lens is 2 degrees or less and the projection lens fulfills the following conditions: Nave<1.73â€ƒâ€ƒ(1) 50ave<70â€ƒâ€ƒ(2) â€ƒwhere Nave is the average value of the index of refraction of said positive lens elements, and Vave is the average value of the Abbe number of said positive lens elements.