Patent ID: 6141154
Filing Date: 2000-10-31
Classification: G02B

Abstract:
A projection lens system for use with a cathode ray tube, said lens system having an overall optical power .PHI..sub.0 consisting in order from its long conjugate to its short conjugate of:(a) a first lens unit having an optical power .PHI..sub.1 and consisting in order from the lens system's long conjugate to its short conjugate of:a first lens subunit having an optical power .PHI..sub.S1 ; anda second lens subunit having an optical power .PHI..sub.S2 ;(b) a second lens unit having an optical power .PHI..sub.2 ; and(c) a third lens unit which has an optical power .PHI..sub.3, is associated with the cathode ray tube during use of the lens system, and provides correction to the field curvature of the lens system;wherein each of the first, second, and third lens units has at least one aspherical surface and wherein .PHI..sub.1, .PHI..sub.S1, .PHI..sub.S2, .PHI..sub.2, and .PHI..sub.3 satisfy the following conditions:(i) .PHI..sub.1 >0;(ii) .PHI..sub.1 /.PHI..sub.0 <0.3;(iii) .PHI..sub.S1 <0;(iv) .vertline..PHI..sub.S1 .vertline./.PHI..sub.0 >0.4;(v) .PHI..sub.S2 >0;(vi) .PHI..sub.S2 /.PHI..sub.0 >0.3;(vii) .PHI..sub.2 >0;(viii) .PHI..sub.2 /.PHI..sub.0 >0.4; and(ix) .PHI..sub.3 <0.