PURPOSE: To efficiently reflect light even in an angular direction other than a retroreflecting direction by changing a simple optical condition.
CONSTITUTION: When the light emitted from a light source is made incident on the light reflecting plane of an optical reflector on an optical path 8, incident light is reflected on the light reflecting planes 6, 7, and is reflected on an optical path 9 shifted slightly from the incident light. Also, when the light in parallel with the optical path 8 is made incident on the light reflecting plane 7 of light reflection on an optical path 10. the incident light is reflected on the light reflecting planes 7. 6, and it is reflected on an optical path 12 shifted in a direction opposite to that of the optical path 9 for the incident light. In other words, the light made incident on the optical reflector is reflected in a direction shifted slightly at an angle in an opposite direction with respect to the optical axis of the incident light. In such a case, reflecting light quantity of observation angle 5° exceeds 15% of that of observation angle 2° at an incident angle -5°. Therefore, it is possible to extremely reduce the loss of light due to irregular reflection, etc., at an observing position at an angle shifted slightly from the light source, which enables high light quantity to be obtained.
TANAKA OSAMU
UCHIDA MINORU
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