Patent ID: 6571025
Filing Date: 2003-05-27
Classification: G06K

Abstract:
A code reader adapted to optically read a code pattern recorded on a recording medium while being manually moved over the code pattern in contact with the recording medium, comprising:a photosensor; and an optical system which forms an optical image of the code pattern onto the photosensor; wherein said photosensor converts the optical image formed by said optical system into an electrical signal, wherein a modulation transfer function (MTF) best position on a subject-side of said optical system at a spatial frequency corresponding to the code pattern is set to be present at a given distance from a surface of the code reader which is brought into contact with the recording medium, in a direction away from said code reader, thereby widening a readable range of the code reader in a forward/backward direction on an optical axis with respect to the modulation transfer function (MTF) best position, the readable range being a range in which a contrast value of the optical image of the code pattern formed onto the photosensor is equal to or higher than a predetermined value; and wherein the code reader is enabled to accurately read the code pattern even if the surface of the code reader is inclined with respect to the recording medium or separated from the recording medium while the code pattern is being manually moved over an entire length of the recording medium, and a distance between the code reader and the recording medium is changed.