| 摘要 |
PURPOSE:To improve the iamge formation characteristics of an optical system scanning the suface of a plane, by utilizing simple image formation relations of lens systems to not fix positional relations of respective lens systems but make them movable in the light beam scanning optical system. CONSTITUTION:One of a collimator lines L5, an image formation lens L6, and the divergence position of the luninous flux to be collimated from a light source S is moved in the direction of the optical axis of the luminous flux in accordance with scanning of said luminous flux, thus scanning the surface of a plane. The relation between a scan angle theta and an error DELTA1 is shown by expression DELTA1=R(1/costheta-1) where R is the length from an optical deflector (scannng mirror) H to a projection plane Q (in expression, theta=omegat (omega: angular speed, t: time) is true in case of scanning at equal angles, and theta=kstnomegat (k: constant) is true in case of operation with sine wave oscillation like a galvanomirror). When the focusing lens L6 is moved to correct the error, the lens is moved by an image formation lens driving mechanism V1. When the length between the collimator lens L5 and a divergence point P (the position of a condenser lens L4) is changed to correct the error, one or both of the collimator lens L5 and the position of the divergence point P are moved by a driving mechanism V2 for the collimator lens L5 and a driving mechanism V3 for the condenser lens L4. |
