| 摘要 |
The present invention provides a light scanning apparatus including a semiconductor laser as its light source, a hologram disk having a plurality of equidistant linear gratings of hologram arranged in the form of a circle, which is driven to rotate at constant speed in a predetermined direction, a first optical system for leading the light from the laser to be incident upon one of the gratings, and a second optical system for leading the light diffracted by said one grating to a scanning surface. In one aspect, the second optical system is so structured to maintain the scanning surface to be in conjugate relation in geometric optics with the surface of said one grating thereby allowing to keep the scan line at a desired position even if the oscillation wavelength of the light varies. In another aspect, the incident angle of the light into the one grating is varied in accordance with the oscillation wavelength of the light so as to maintain a constant diffracted angle.
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