US 5,687,008 AGranted

Image reading apparatus

AssigneeDainippon Screen Mfg. Co., Ltd.

InventorsHideki Morikawa, Junichi Masuo, Norizo Takao, Masahide Okazaki

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Abstract

A drum scanning type image reading apparatus includes an illumination optical system and an imaging optical system. The illumination optical system is an optical system for irradiating light upon an original. A variable aperture stop is disposed at a conjugate position with the original. In the imaging optical system, a pick-up lens focuses an image of an image reading region of the original on an image focusing surface, and photomultiplier tubes read light passing through one of holes which are formed in a main aperture plate which is disposed on the image focusing surface. To change an image reading resolution in the image reading apparatus, the image reading region and an illumination region are changed by changing the aperture size of the main aperture plate and the size of the variable aperture stop.

Claims16

Dependent claims

A scanning image reading apparatus which reads an original, said apparatus comprising:

an illuminating optical system which generates light;
a scanner for scanning the light from the illumination optical system against an illumination region on the original;
an imaging optical system for forming an image on said original positioned in a reading region on an image focusing surface;
photoelectric conversion means for reading an image formed on said image focusing surface and outputting an image signal;
designating means for designating a change in image reading resolution;
image reading region changing means for changing the size of said reading region in accordance with an image reading resolution which is designated through said designating means;
and
illumination region changing means for changing said image illumination region in accordance with said image reading resolution which is designated through said designating means.

5 more elements

Dependencies are inferred from the claim text.