| 摘要 |
PURPOSE:To irradiate always the primary diffracted light having a constant quantity of light onto a photoreceptor, by providing a feedback controlling means which controls the input for driving an optical modulator in accordance with the variance of the quantity of light of the 0-order light transmitted through a hologram to hold the quantity of light of the primary diffracted light from the hologram in a certain level. CONSTITUTION:The light from an He-Ne laser is modulated by an optical modulator 2, and a primary diffracted light L1 is incident to a hologram disc 3, and a primary diffracted light L10 is incident to a photodetector 4. The output is inputted to an amplifier 8 through a differential amplifier 5 and a gate circuit 6 to amplify the picture signal, which is inputted through a terminal 7 and the gate circuit 6, with an amplification factor proportional to the input signal. The output of the amplifier 8 is sent to the differential amplifier 5 to perform the feedback control, and simultaneously, the output is sent to an optical modulator driver 9 to drive the optical modulator 2. Since the primary diffracted light L10 is increased and decreased according as a primary diffracted light L11 of a hologram disc 3 is decreased ad increased, the light L11 is always held in a certain quantity of light by the feedback control. |
