| 摘要 |
PURPOSE:To attain stable optical beam scanning also at the time of rapid rotation by adding optical members having density almost equivalent to that of a halving optical member and different optical properties to the halving optical member. CONSTITUTION:The optical (glass) members 30, 32 for rotation balance are arranged in the rotational shaft direction of the halving optical member 10 and these optical members 30, 32 are formed by a material having density equal to that of the optical member 10 and having optical properties, especially a refractive index, different from that of the optical member 10. Thereby, the whole constitution is a cylindrical shape symmetrically about the shaft and is dynamically balanced. Even if the optical member 10 is rotated in the arrow FA direction together with the optical members 30, 32, the optical member 10 can be prevented from vibration due to the optical members 30, 32. Thus, stable optical beam scanning can be attained in spite of the increase of rotational frequency.
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