| 摘要 |
PURPOSE:To make the speed of optical scanning uniform by arranging plural pieces of linear gratings consisting of holograms to a toric shape and specifying an inter- grating spacing dtheta in such a manner that the angle thetaR of rotation of the gratings and the angle thetaS of the optical deflection attain thetaS=alphathetaR with a proportional constant as alpha. CONSTITUTION:The linear gratings 12 consisting of the holograms are arranged to the toric shape on a substrate 10 for a hologram disk. The inter-grating spacing dtheta is so determined as to satisfy dtheta=lambdasinthetaR/sin(alpha.thetaR) with lambda as the wavelength of the incident light in such a manner that the angle thetaR of rotation of the gratings 12 and the angle thetaS of the optical deflection attain thetaS=alphathetaR with the proportional constant as alpha. The spacings between the linear gratings 12 are dense in the central part and are coarser toward the right and left. The gratings 12 are formed by coating a hologram recording material on the bottom surface of the substrate 10, providing laser light sources A, B having the equal wavelength to the positions symmetrical with the z-axis and irradiating the laser beams through cylindrical lenses 14, 16 extending in a direction y and convergent rays p, q in such a manner that the beams are made incident on the substrate at the equal angle thetaO of the main optical plane relative with the z-axis. The uniform speed characteristic of the optical scanning is thereby improved effectively.
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