Fixed-focus lens

Abstract

A fixed-focus lens adapted to be disposed between a magnified side and a reduced side is provided. The fixed-focus lens includes a first lens group, a second lens group, and a third lens group. The first lens group disposed between the magnified side and the reduced side includes three lenses and has a negative refractive power. The second lens group disposed between the first lens group and the reduced side includes five lenses and has a positive refractive power. The third lens group disposed between the second lens group and the reduced side includes five lenses and has a positive refractive power. The fixed-focus lens satisfies |F1 / F|<1.35, 3.5<|F2 / F|<4.5, and 4<|F3 / F|<5, wherein F1 is the effective focal length (EFL) of the first lens group, F2 is the EFL of the second lens group, F3 is the EFL of the third lens group, and F is the EFL of the fixed-focus lens.

Description

technical field [0001] The present invention relates to a lens (lens), and in particular to a fixed-focus lens (fixed-focus lens) Background technique [0002] Generally, if a projector is to project onto a larger screen, it usually needs a longer projection distance; relatively, if it wants to project a large-sized image at a shorter projection distance, it usually needs to use a special wide-angle lens. [0003] In the design process of wide-angle lenses, aberration is a difficult problem faced by designers. Therefore, designers often use various methods to improve this problem, such as US Patent No. 6,621,645, No. 6,560,041, No. 6,999,247, No. 6,542,316, No. 6,885,506, No. 7,184,219, No. and No. 7,173,777. [0004] In Patent No. 6,621,645 and Patent No. 6,560,041, the designer uses aspherical lenses for part of the lens of the wide-angle lens. However, in Patent No. 6,621,645, the designer uses at least one piece of molding glass, and in Patent No. 6,560,041 Using at l...

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Problems solved by technology

[0004] In Patent No. 6,621,645 and Patent No. 6,560,041, the designer uses aspherical lenses for part of the lens of the wide-angle lens. However, in Patent No. 6,621,645, the designer uses at least one piece of molding glass, and in Patent No. 6,560,041 Using at least three aspherical lenses will not only increase the manufacturing cost, but also cause difficulties in assembly

Conversely, if fewer aspherical lenses are used and aberrations can be effectively improved, the total length of the lens will be increased, and the volume of the projection system will become larger. mm

[0005] On the other hand, designers also use more lenses to correct aberrations. For example, in patents No. 6,885,506 and No. 7,184,219, more than fourteen lenses are used, but this is likely to cause difficulties in assembly and increase in manufacturing costs

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