| 摘要 |
PURPOSE:To make it possible to sufficiently secure difference of intensities between light from a background and light from a mark by supplying illuminating light to the mark and adjusting reflectance ratio of a variably reflective reflecting member opposed to an object lens forming a picture of the mark to a value in accordance with reflecting information of the mark. CONSTITUTION:A mirror member 8 is an article that electrochromic elements (EC element) 8b are stuck on a mirror surface 8a, and reflectance ratio of the whole is adjusted by inputting electric signal to change transparency of the EC element 8b. Namely, when reflectance ratio of a mark 7 is high, reflectance ratio of the mirror member 8 is set to low, reflecting light of the mark 7 is formed on a CCD1 as a clear picture, and when reflectance ratio of the mark 7 is low, reflectance ratio of the mirror member 8 is raised, reflecting light from the mirror member 8 is made so as to transmit the mark 7 to light the same, and intensity difference of light on the background is secured, besides a position judging electric circuit is changed over so as to invert output of the CCD1 to judge. Intensity difference between light from the background and light from the mark is sufficiently secured. |
