| 摘要 |
PURPOSE:To prolong the service life of an acoustooptical modulation element by providing said element between a light source and a convergence lens as a deflecting means of light. CONSTITUTION:When a modulation signal is inputted to the acoustooptical modulation element 4, by a deflecting means 18 being an acoustooptical modulation element, the light from the light source 19 is incident on the convergence lens 2. When an optical modulation element driving part 3 transmits no modulation signal to the element 4, the means 18 polarizes the light from the light source 19 and the light is not incident on the lens 2. Hence the element 4 is radiated by laser beams converged by the lens 2 only when the modulation signal based on a video signal is transmitted from the driving part 3. When the video signal is not transmitted, no light is projected to the element 4 because the means 18 does not project light to the lens 2. Thus the service life of the element can be prolonged by reducing the irradiation time of laser beams projected on the element 4.
|
