| 摘要 |
PURPOSE:To obtain a light variable attenuator which is stable to the mechanical impact, the temperature variation, etc. by controlling a voltage current control type light attenuator so that a constant ratio is secured between the input light volume and the output light volume of the light attenuator. CONSTITUTION:An incident light 2 is attenuated by a voltage control type attenuator 6 through a half-mirror 4 and then radiated through a half-mirror 8. The light (an extremely small part of light) branched by the mirror 8 is put into a photodiode 14, and the output of the diode 14 gives an input of Vo to a divider 18 via an amplifier 16. The light (an extremely small amount) branched by the mirror 4 is put into a photodiode 10, and this output gives an input of Vi to the devider 18 via an amplifier 12. The specific output Vd to the Vi and Vo given from the divider 18 is compared with the set value Vs through a differential amplifier 20, and an attenuation amount control disk 22 of the attenuator 6 is turned by the output signal Vc to control the volume of transmitted light. In such a way, a light attenuator is obtained with high stability to the mechanical impact, the temperature variation, etc. |
