| 摘要 |
PURPOSE:To prevent the adverse effect due to regularly reflected light from an object to be detected and to enhance detection capacity, by projecting light from a light projecting element through a polarizing filter and receiving detected light by a light receiving element through the polarizing filter. CONSTITUTION:Pulse modulated light 4 is projected from the light projecting element 2 in a case 1 through a vertical polarizing filter 3 and the detected light 4' reflected by a regression mirror 6 is received by a light receiving element 5 through a transverse polarizing filter 7. Because the regrassion mirror 6 has such a characteristic that incident light is reflected therein three times, reflected light comes to one polarized by 90 deg.. When an object 16 to be detected is present in a detection region, the object 16 to be detected has a regularly reflective surface and, therefore, the reflected light thereof has the same phase as the modulated light 4 and is blocked by the polarizing filter 7 and no light is made incident to the light receiving element 5. By this method, erroneous detection due to regularly reflected light can be prevented and detection capacity can be enhanced. |
