OPTICAL DEVICE AND DOCUMENT READER USING THE SAME

摘要

In an optical device, small lenses are arranged in two or more rows to constitute a lens array, a plurality of such lens arrays are superimposed with each other between first and second planes, the distance between the optical axes of the rows of small lenses in at least one lens array is set to be different from that in the remaining lens arrays, and a multiple image of an optical image on the first plane is formed on an imaging surface. The distance between the optical axes can be changed by shifting the optical axis of one lens array among a plurality of small lenses forming one imaging system in the lens arrays from those of remaining lenses. The direction and amount of such lens offset are properly selected to suppress moiré. Another important invention concerns a document reader having a lens system of such an optical device, a line image sensor having tricolor separation filters arranged in the imaging surface in the horizontal scanning direction in correspondence with picture elements, and filters arranged in the optical paths of corresponding rows of small lenses of the lens arrays and capable of transmitting light of corresponding colors. A multiple image is a double image or a triple image. Moiré and color misregistration are prevented, and an image quality substantially equivalent to a color system having a plurality of color separation imaging surfaces is obtained.