| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a dot mark reader that ensures visibility for infinitesimal dot marks, even the influence of which has not been predicted because of their conventional visibility. SOLUTION: A mark-formed surface, on which infinitesimal dot marks protruding upward are formed, is irradiated with light, the irradiating angleαbetween the central optical axis of the illuminating light and the optical axis of the image pickup device being adjusted to approximately 20 to 45 degrees. The image pickup device is arranged on a normal line of the mark-formed surface and receives light reflected by the mark-formed surface. As long as the irradiating angle is within the range, it is possible to ensure optically sufficient visibility even for infinitesimal dot marks of different height or size by adjusting the amount of illuminating light because the contrast value, that is, the dif ference in brightness, is high and the value of recognition score, that is, the correlation coefficient used for recognizing characters is also high.</p> |
