OPTICAL UNIT, METHOD FOR CONTROLLING DRIVE, AND HOLOGRAPHIC APPARATUS

PROBLEM TO BE SOLVED: To adapt an acousto-optic deflector (AOD) to be used as a shutter such as an acousto-optic modulator (AOM). SOLUTION: The characteristics of transmittance change with respect to frequencies of applied voltages on an acoustic optical medium in an AOD are shown in Fig.6. When the element is used as a normal deflector, the frequency of the voltage applied is changed in a first frequency range (for example, a range corresponding from -V1 to V1) where the transmittance hardly changes. However, the frequency of the voltage applied is changed out of the first frequency range, but to a frequency in a second frequency range where the transmittance abruptly decreases (for example, a frequency corresponding to -V2 or V2, which minimizes the transmittance). Thus, the AOD is allowed to function as a shutter. COPYRIGHT: (C)2009,JPO&INPIT