| 摘要 |
PROBLEM TO BE SOLVED: To regulate an incident state of a light to a site of a light transmitting portion of a scale board without regulating a thickness of an incident plate by forming a transparent portion and a diffusing portion of the incident plate integrally with by a transparent material and a diffusing material. SOLUTION: In an incident plate 50 of light, a transparent portion 50a for introducing light from a light source 70 and a diffusing portion 50b for diffusing an incident light are respectively formed integrally with a transparent material and a diffusing material. The light from the source 70 is incident from its inner peripheral end face 51a in the portion 50a of the plate 50. Then, the incident light is radially propagated toward the portion 50b in the portion 50a. In this case, since the portion 50a is formed of a transparent resin material, the incident light is incident in the portion 50b without almost attenuating. Then, the light is diffused in the portion 50b and incident to a pattern display of a scale plate 20a as a planarly diffused light. In this case, since the portion 50b is formed of a diffusing resin material, the light is uniformly diffused to become a planarly diffused light.
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