| 摘要 |
<p>PROBLEM TO BE SOLVED: To set a sensitivity accurately and easily. SOLUTION: A screw 15 secures a body case 11 to an installation face 17 and a throttle plate 23 is fixed to the body case 11 rotatably about the axis of one screw 15. When one screw 15 is loosened and the throttle plate 23 is operated rotationally, a throttle hole 31-33 faces a window 21 selectively thus throttling light emitted through the window 21. In this regard, even if one screw 15 is loosened at the time of adjusting sensitivity, the body case 11 is held in optical axis adjusted state by the other screw 15. Since the light receiving quantity is prevented from being deviated from a value corresponding to the size of the throttle hole 31-33 at the time of adjusting sensitivity, the sensitivity is set accurately according to the size of the throttle hole 31-33. Furthermore, sensitivity adjusting work is facilitated because a troublesome work of loosening both screws 15 while fixing the body case 11 with hand is not required.</p> |
