| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a device of simple configuration which easily discriminates original spot light for reflection light, when a plurality of spot light is emitted and presence of an object in a region which is to be measured is detected, based on direction of its reflection light. SOLUTION: A light source 14 is a light-emitting diode which selectively emits light of two kinds of wavelengths (250 and 850 nm). A long-wavelength transmission filter 30 allows light of 950 nm to path while blocks light of 850 nm. Meanwhile, a short-wavelength transmission 32 blocks light of 950 nm and allows light of 850 nm to path. So, when the light of 950 nm is emitted, a lens 24a forms a first spot light 26 while a second spot light 28 is not formed. Therefore, a reflection light 36 photodetected by a light receiving part 16 is known as the reflection light of the spot light 26. Inversely, when the light of 980 nm is emitted, it is judged as the reflection light of the spot light 28.</p> |
