| 摘要 |
<p>PURPOSE:To surely detect a substrate regardless of the transparency and surface state of the substrate by setting the incidence angle to the substrate so that the reflection factor of the detection light from a reflection type photoelectric switch on the surface of the substrate is made a specific value. CONSTITUTION:A reflection type photoelectric switch 3 is arranged so that the incidence angle theta1 of the detection light 6 of a light projection section 1 to a substrate 4 to be detected is made 70 deg. or above, and a reflecting plate 5 is arranged on the axis of the light 6 across the substrate 4 so that the light 6 reflected on the plate 5 is fed to a light reception section 2 when no substrate 4 exists. The light quantity of the light 6 transmitting the substrate 4 is the remainder of the light 6 at least reflected twice on the surface or the back face of the substrate 4, it is extremely smaller than the light quantity of the light 6, and the presence of the transparent substrate 4 can be detected when the threshold value of the switch 3 is set to a value larger than the light reception quantity when the transparent substrate 4 exists. The relation between the incidence angle and the reflection factor of the substrate 4 is changed according to the material and surface state of the substrate 4, and the incidence angle is preferably set to make the reflection factor about 0.2 or above.</p> |
