| 摘要 |
PROBLEM TO BE SOLVED: To photograph a transparent pattern and to provide the video image excellent in contrast by generating transmission light at a smooth part on a surface side and scattered light at a non-smooth part where the transparent pattern is plotted by illuminating a transparent plate from a back surface side and photographing only the scattered light. SOLUTION: When the back surface 1b of the transparent plate 1 is irradiated at an incident angleθ, incident lights L1-L3 are advanced inside the transparent plate 1 and then, emitted from the surface 1a of the transparent plate 1 obliquely upwards as the transmission lights L1'-L3'. An image pickup device 3 is arranged to face each other at an appropriate distance front the transparent plate 1 and the transmission lights L1'-L3' do not reach the visual field of the image pickup device 3. The incident light L2 is irregularly reflected since a transparent pattern part 2 is turned to a slightly coarse surface and the scattered lights L41-L44 are generated. Among them, the light L42 is advanced vertically upwards and reaiches the visual field of the image pickup device 3. As a result, from the image pickup device 3, the video image of the excellent contrast (luminance difference) for which only the transparent pattern part brightly shines in a dark background is obtained.
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