Patent ID: 7626764
Filing Date: 2009-12-01
Classification: G02B

Abstract:
1. A projecting lens system comprising, in this order from the screen-side thereof: a first lens positive in power, a second lens negative in power, a third lens positive in power, and a fourth lens positive in power; the projecting lens system meeting a criteria of 1.4<TT/f<1.7; where TT denotes a total length of the projecting lens system and f denotes an effective focal length of the projecting lens system, wherein the specifications of the projecting lens are listed in the following table: wherein TT=135 mm, f=82.91 mm, BFL3=66.83 mm, f4=124.74 mm, AVE (Vb 1 - 3 )=55.5322, FNo=3.41, and 2ω=33.72°, where TT denotes a total length of the projecting lens system, f represents a focal length of the projecting lens system, BFL 3 denotes a back focal length of the projecting lens system, AVE (Vb 1 - 3 ) denotes an average value of Abbe numbers of the first lens and the third lens, FNo represents the aperture F-number, and 2ω represents a field angle of the projecting lens system.