| 摘要 |
PROBLEM TO BE SOLVED: To solve a reflection problem of incident light by offsetting a light receiving element by a prescribed distance in a plane vertical to a normal at point of incidence with respect to the normal of the light to be detected prescribed in a refraction layer, refracting the light to be detected made incident on the refraction layer in the refraction layer with respect to its offset amount and receiving the light on the light receiving surface of the light receiving element. SOLUTION: The offset amount of a photodiode 14 against the normal X at point of incidence is made so that the main light made incident on the refraction layers 18, 20 is refracted by the refraction layers 18, 20 and received on the light receiving surface of the photodiode 14. This offset amount ΔS is defined by the equation: ΔS=t.tan(θ') [θ'=sin<-1> (n/n.sin(θ))] wherein (θ is the incident angle of the main light, (n) is the refractive index of the refraction layers 18, 20, (t) is the distance from the incident point of the main light to the refraction layers 18, 20 to the surface containing the light receiving surface of the photodiode 14 along the incident normal X). Thus, the reflection light isn't returned to a main light direction, and a stray light problem doesn't occur without adding a cost. |
