| 摘要 |
PURPOSE:To form a stable, high-fidelity image even for a system which has an unstable threshold level by forming both end parts of an image forming part steeply through the deflecting operation of scanning beams. CONSTITUTION:Beams 11-13 and 17-19 are moved as shown by arrows E and F to obtain beams 11'-13' and 17'-19'. An ultrasonic optical modulator 20 for shifting a scanning beam in position deflects and leads out the incident light beam 10 in proportion to the frequency (f) of an applied ultrasonic wave to shift the beam in position. Then, a modulator 20 is so set that its scanning direction and deflection direction are coincident with each other; and the extent of deflection is made large at a leading edge part beta1, standard at a picture element formation part alpha, and decreased gradually at a leading edge part beta2. The incident light beam 10 wavelength lambda is deflected by a deflection angle thetabeta with the ultrasonic wave of frequency (f) inputted to the modulator to form an image at a position 10b on an image plane 4 while displaced from an original projection position 10a. Then, thetaS=lambda/2LAMBDA=lambdaf/2V, where LAMBDA is the ultrasonic wavelength and V is the speed.
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