Patent ID: 6301056
Filing Date: 2001-10-09
Classification: G02B

Abstract:
A projection lens system for use in combination with a cathode ray tube, said system producing an image, having a power .PHI..sub.0, and comprising in order from its image side:(a) a negative first lens unit which comprises: (i) at least one aspheric surface and (ii) a negative lens element at the unit's image side, said negative lens element having a power .PHI..sub.E1 and an image side surface which is concave towards the image;(b) a positive second lens unit which comprises in order from its image side:(i) a positive first lens subunit which consists of a cemented color correcting doublet composed of glass and having spherical surfaces; and(ii) a positive second lens subunit which comprises at least one lens element of weak optical power having at least one aspheric surface; and(c) a third lens unit which is associated with the CRT during use of the lens system, has a strong negative power .PHI..sub.U3, and contributes to the correction of the lens system's field curvature.