| 摘要 |
PURPOSE:To apply large amplitude to a shield plate by a small-sized chopper mechanism, by providing a shield plate for shielding the infrared red rays incident to a pyroelectric element to the leading end of a support arm elastically supporting a base part. CONSTITUTION:When an AC power supply is connected to the coil connection terminals 35, 35 led out from a stem 20 to supply a current to an exciting coil 33, a yoke 31 is excited. Electromagnetic force acts between the end part of the yoke 32 and permanent magnets 30, 30 opposed thereto to vibrate a support arm 28 between the dampers 32, 32 fixed to the end part of the yoke 31 in the direction crossing the length direction of the support arm 28 at a right angle. Since this vibration vibrates the support arm 28, the amplitude of the armature 28 at the leading end thereof becomes large according to the principles of the lever. Therefore, the infrared rays incident to a pyroelectric element 26 through the opening part 36a of a cap can be made stably intermittent by a shield plate 29 vibrating within a plane and continuously detected. As mentioned above, large amplitude can be given to the shield plate 29 by a chopper mechanism B. |
