| 摘要 |
PURPOSE:To shorten the length of an optical path and make the device compact by covering the inner peripheral side of the regular polygon of a rotary polygon mirror with a light-reflecting material and varying the refractive index of an integrated lens member stepwise or graduary. CONSTITUTION:The rotary polygon mirror 1 consists of the integrated lens member 11 and a material 12 which covers the whole or part of the inner peripheral side regular prism part of the integrated lens member 11 and reflects light. In this case, the integrated lens member 11 is formed of glass, plastic, etc., for an optical lens which transmits a used light beam well and the light reflecting material 12 only needs to have a high reflection factor; and the inner peripheral prism part of the hollow integrated lens member 11 is covered by using the above material. The refractive index of the integrated lens member 11 varies concentrically, stepwise, or graduary. For example, the refractive index varies in two stages at lens members 11a and 11b and the refractive index of the lens member 11b is large. In this case, the angle theta2 between directions M3 and N3 as the projection directions of the light beam is obtained as a scanning angle. |
