Focus fixing lens

Abstract

The invention relates to a fixed-focus lens comprising a first lens group and a second lens group the dioptre of which are all positive, wherein, the first lens group consists of a first lens, a second lens, a third lens, a fourth lens and a fifth lens which are arranged in order from an object side to an image side, wherein, the dioptre from the first lens to the fifth lens is orderly negative, negative, negative, positive and positive, and the first lens is an aspheric lens; the second lens group consists of two balsaming lenses and a positive lens positioned between the two balsaming lenses; the fixed-focus lens meets the following conditions: (1) FL45 is more than 5.0 and less than 7.5; (2) FG2 / F is more than 3.5 and less than 4.8; (3) FG2 / H is more than 3.755, wherein, FL45 refers tothe effective focal length between the fourth lens and the fifth lens of the first lens group; the FG2 is the effective focal length of the second lens group; F refers to the effective focal length ofthe fixed-focus lens; and H refers to the maximum image height on the image side.

Description

technical field [0001] The present invention relates to a lens, and in particular to a fixed-focus lens. Background technique [0002] Please refer to figure 1 The fixed-focus lens 100 disclosed in the U.S. No. 6,542,316 patent that is traditionally applied to a rear projection TV includes a first lens group 110, a second lens group 110, and a second lens group 110 arranged in sequence from an object side to a light valve (light valve) 50. The lens group 120 and a third lens group 130 . The first lens group 110 includes six lenses 112 , 114 , 116 , 117 , 118 , 119 , the second lens group 120 includes one lens 122 , and the third lens group 130 includes four lenses 132 , 134 , 136 , 138 . [0003] Due to the large number of lenses in the conventional fixed-focus lens 100 , the production cost is relatively high. In addition, the larger number of lenses also results in a longer length of the fixed-focus lens 100 , resulting in a thicker rear projection television (RPTV) usi...

AI Technical Summary

Problems solved by technology

[0003] Due to the large number of lenses in the traditional fixed-focus lens 100, the production cost is relatively high

In addition, the larger number of lenses also results in a longer length of the fixed-focus lens 100, resulting in a thicker rear projection television (RPTV) using the fixed-focus lens 100.

If the thickness of the rear projection TV is reduced, the optical imaging aberration will increase, and even ghost images and other phenomena will affect the image quality.

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