| 摘要 |
PURPOSE:To inhibit the arrival of an optical beam made incident upon a non- using part of a rotary mirror at a scanning position without reducing working accuracy by providing the titled device with the non-using part not to be used for light deflection and forming at least one groove on the non-using part. CONSTITUTION:An optical beam radiated from an optical beam generating means 3 is deflected by the rotary mirror 1. The rotary mirror 1 has using parts 1a, 1b to be used for light deflection and non-using parts 1c, 1d not to be used for light deflection on its periphery and at least one groove 10 is formed in each non-using part. A circular or V-shaped groove is proper and a beam arriving at the chamfer part of the V-shaped groove 10 is deflected from a scanning position, a beam arriving at a bent position on the center of the V-shaped groove is also divided into two beams and both of the divided beams are reflected to positions different from the scanning direction. Consequently, the incidence of an optical beam from the non-using parts 1c, 1d to the scanning position can be surely prevented without deteriorating the working accuracy of the using parts 1a, 1b by means of a simple constitution. |
