| 摘要 |
PURPOSE:To deal with a great change of a detection area by forming an opening in the front surface of a main body case where a detecting circuit including a heat ray sensor is put, and mounting a lens block in the opening detachably. CONSTITUTION:The opening 3 is bored in the front surface of the main body case 1 where the detecting circuit which includes the heat ray sensor 1 is put. Lens blocks 6 and 6' formed by uniting condenser lenses 4 made of Fresnel lenses for converging heat rays from plural detection areas on the sensor 1 and frames 5 and 5' for holding them are inserted into the opening 3 and the blocks 6 and 6' are mounted detachably in the opening 3 by plural engagement claws 8 and collar parts 7. Then, the block 6 whose detection area is set over, for example, a wide range is detached and the block 6' whose detection area is set newly is mounted to easily change the detection areas. Further, the lenses 4 and 4' with which desired detection areas are designed including even the frame 5, so even a large change in detection area is easily dealt with. |
