Image reading apparatus having aberration correction function

Abstract

The invention relates to an image reading apparatus having an aberration correction function, which can correct color migration generated by a chromatic aberration and distortion aberration caused by an optical element through a digital filter in only one direction in a condition without using a switch for switching. An aberration correction unit has a digital filter group, a delay control unit, and a memory. The digital filter group take one of multiple colored lights controlled through a delay time caused of the aberration of the optical element of each read image of a line image sensor as a benchmark colored light and the rest colored lights are treated as other colored lights, and are disposed on the rest colored lights. The delay control unit, based on a calculation value of each delay amount between formed images of the benchmark colored light and other colored lights, controls a filter coefficient of the digital filter group. The delay control unit, when a picture transverse width of other colored lights gets wider with respect to a picture transverse width of the benchmark colored light, in a state of reading image positions of scanning finishing ends of the bench colored light and other colored lights, begins to read, from scanning beginning end formed images of the other colored lights, the calculation value of each delay amount which takes a scanning beginning end formed image of the benchmark colored light as a benchmark, controls the filter coefficient of the digital filter group, and thus the color migration generated by the aberration of the optical element can be corrected.

Description

technical field [0001] The present invention relates to an image reading device having an aberration correction function that corrects aberrations caused by an optical element that forms a read image of a document or the like. Background technique [0002] There are aberrations in a lens that is an optical element that forms a read image of a document or the like, and one of the chromatic aberrations is caused by a slightly different refractive index of glass (dispersion) depending on the wavelength. [0003] This appears as axial chromatic aberration and lateral chromatic aberration, and when three line image sensors are used for color, they need to be arranged at imaging point positions matching the respective wavelengths of RGB. [0004] In addition, the above-mentioned aberrations are all aberrations related to smudges, imaging positions, and image size of the imaged image, but there are also distortion aberrations as aberrations related to distortion of the overall imag...

AI Technical Summary

Problems solved by technology

This distortion aberration has a characteristic that although there is almost no distortion near the center of the imaged image, the distortion changes and gradually becomes larger as it approaches the periphery.

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