| 摘要 |
<p>PURPOSE:To detect an insensitive area between a projector and a receptor by a method wherein a plural number of projectors and receptors are placed on both sides of a sensor area and while a projector is operating, a receptor is periodically changed over. CONSTITUTION:Projectors P1-P4 and corresponding receptors R1-R4 are placed at specific intervals on both sides of a sensor area 10. Projectors P1-P4 project rays, which are pulse-modulated by a pulse signal supplied from a projection oscillation frequency circuit 12 via a projector changeover switch 14, to the sensor area 10 via a lens 16. The projected rays are received by receptors R1-R4 via a lens 18. When the projector changeover switch 14 is switched and one projector is operating, receptors are periodically switched by a receptor changeover switch 20. This allows not all receptors to receive a ray at the same time but allows receptors to sequentially receive it one by one. Therefore a ray from one projector can be projected to not only a facing receptor but also other receptors.</p> |
