| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To simplify, relatively miniaturize and reduce the power consumption of a structure for varying a focal length in an image forming optical part. <P>SOLUTION: A light receiving sensor 2, an image forming lens 3, an illumination part and the like for reading a two-dimensional code C recorded on a reading target are disposed in a tip part of a body case, and an optical member 6 is disposed between the image forming lens 3 and the light receiving sensor 2. The optical member 6 is substantially a hexagonal prism formed from a transparent material of a high refractive index, and has three sets of opposite parallel faces 6a to 6c on the periphery. The optical member 6 is stopped in three predetermined rotational positions that determine the thickness over which a reading optical axis R penetrates the optical member 6 to change the focal length of the image forming optical part 4 and thus a reading distance. Distance measuring means measure a distance to the reading target, and a drive mechanism rotates the optical member 6 to a given rotational stop position depending on the measurement result. <P>COPYRIGHT: (C)2005,JPO&NCIPI</p> |
