| 摘要 |
PURPOSE:To avert the uneven scanning lines on a scanning plate owing to the deviation in a hologram rotating body at a low cost and with ease, by providing a means for correcting eccentricity which changes the course of light by a required quantity in the direction of compensating the deviation of the hologram rotating body. CONSTITUTION:Tapered plates PL1-PL8 having light transmittability are disposed on the holograms formed on a hologram rotating body 10. These plates are tapered to the degrees of the tendency at which the deviations of the holograms corresponding to said plates are compensated. The plates PLs function as a kind of prism, wherein the relation epsilon=(theta1+theta'2)-sigma holds if the vertical angle thereof is designated as sigma, the angle of deviation as epsilon, the indicent angle as theta1, and the exit angle theta'2. When the width of the prism changes from l to l', the difference DELTAl thereof and the shift DELTAx in the course of the light have the relation DELTAx=DELTAltanepsilon. Therefore, the deviation in the optical path of the scanning light owing to the eccentricity of the hologram rotating body is corrected by adjusting and setting the width of the prism. |
