| 摘要 |
PROBLEM TO BE SOLVED: To obtain an optical system in which the contrast and the light quantity of pattern light and the portability of a device are optimized by constituting the system so that the size of a light source, the magnification of a lens and the distance between the light source and a mask satisfy specified conditions. SOLUTION: A photographing optical system is a cylindrical lens 56 arranged in parallel with a xenon tube 52 being the light source, and the lens 56 is fixed in a light box 50 together with a diaphragm mask 58 by setting a positioning hole as reference. The mask 58 converges an optical path by its aperture 58a. A projection mask 80 is held on a mask holder 70 while securing flatness. The positions of the xenon tube 52 and the mask 80 are optimized according to the power of the lens 56 and the tube diameter of the xenon tube 52. In this case, a conditional expression 0.004<A×B/T<0.035 is satisfied. In the expression, A stands for the size of the xenon tube 52, B the magnification of the lens 56 and T the distance on the optical axis from the xenon tube 52 to the mask 80.
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