Photocopying – Projection printing and copying cameras – Illumination systems or details
Patent
1998-12-29
2000-10-31
Adams, Russell
Photocopying
Projection printing and copying cameras
Illumination systems or details
359654, 359789, 359785, 359784, G03B 2754, G02B 300, G02B 914, G02B 912
Patent
active
061410845
ABSTRACT:
In a three-lens configuration, the first lens is formed into a biconvex lens, the third lens is formed into a positive meniscus lens having a concave surface directed onto the object side, and the refractive index distribution of the refractive index distribution type second lens is defined by a predetermined conditional expression, whereby various kinds of aberration are made favorable even when used for reading out images at a magnification near 1:1, while achieving wider angle of view, higher performances, and compactness. An imaging lens for copying to be used at a magnification near 1:1 comprises the first lens L.sub.1 having a biconvex form, the second lens L.sub.2 having a biconcave form with a refractive index distribution along the optical axis direction, and the third lens L.sub.3 made of a positive meniscus lens having a concave surface directed onto the object side, whereas a stop i is disposed between the second lens L.sub.2 and the third lens L.sub.3. The refractive index of the second lens L.sub.2 gradually decreases from the object side to the image side. The difference .DELTA.n between the respective refractive index values at the object-side surface apex and image-side apex of the second lens L.sub.2 is made smaller than 0.1, and the refractive index distribution in the second lens L.sub.2 is represented by a predetermined conditional expression.
REFERENCES:
patent: 5172272 (1992-12-01), Aoki
patent: 5268791 (1993-12-01), Tsuchida
patent: 5680254 (1997-10-01), Ueda et al.
patent: 5861987 (1999-01-01), Nakamura et al.
patent: 5973850 (1999-10-01), Nagaoka
Adams Russell
Brown Khaled
Fuji Photo Optical Co., Ltd.
Snider Ronald R.
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