Patent ID: 7562825

Claim:
An apparatus for optically reading out, through an imaging optics, information by a photodetector, the information being attached to a target, the apparatus comprising: a collimated-beam irradiating unit configured to irradiate on the target a substantially collimated beam with a size thereon; a first pickup unit configured to cause the photodetector to pick up through the imaging optics a first image of the target while the substantially collimated beam is being irradiated on the target by the collimated-beam irradiating unit; a measuring unit configured to measure size information indicative of the size of the collimated beam being irradiated on the target based on the picked-up first image; and a distance determining unit configured to determine a distance between the apparatus and the target based on the measured size information of the collimated beam, wherein the imaging optics has a predetermined field angle, and the collimated-beam irradiating unit is configured to irradiate on the target the substantially collimated beam along one edge of a field defined by the field angle of the imaging optics.