| 摘要 |
PURPOSE:To easily vary a scanning range by using a hologram disk as an optical deflector and providing an optical path switching device on the optical path of a laser beam from a light source. CONSTITUTION:The beam which is incident on the hologram disk HD through a mirror M1 is switched to strike a track A or B of a hologram array on the hologram disk HD, thereby switching the scanning range on a scanning surface S to A4 size or B4 size. This switching device P shifts the optical path y prism length by a 45 deg. parallel prism 1, which is held by a holder 2 rotated by a step ping motor M through a gear 3. When the beam is made incident on the track B on the hologram disk HD, the 45 deg. parallel prism is held horizontally and when the beam is incident on the track A, the stepping motor M is driven to hold the prism slantingly as shown by a dotted line.
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