| 摘要 |
PROBLEM TO BE SOLVED: To measure the reflection luminance under the sun light accurately using an artificial light source and to measure the color tone of a metal plate by binding the positional relationship between projection and reception of light for detecting the relative ratio of reflection luminance with highest sensitivity. SOLUTION: Reflection luminance ratio between metal plates a and b is measured while varying anglesα,β,γandδvariously and the range of each angle is set by determining an arrangement for maximizing the reflection luminance ratio (uneven color tone is most prominent). More specifically, a substantially parallel light beam is projected from a projector 1 in such a direction as the inclination angleαfrom the normal N to the surface of the metal plate 5 is 25-35 deg.. In a plane defined by turning a plane including the projecting direction and the normal N by an angleβof 130-140 deg. about the normal N, reflected light from the metal plate 5 is received by a silicon diode 2a in such a direction as the angleβfrom the normal N is 40-50 deg. and converted into a luminance through a signal processor 3 (computer). According to the arrangement, reflection luminance of a metal plate can be measured with a sensitivity similar to that in case of identification under the sun light.
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