| 摘要 |
PURPOSE: A light-scanning optical system is provided to adapt to realize high definition printing by effectively avoiding any printing slippage in the main scanning direction. CONSTITUTION: A light-scanning optical system comprises a light source, a first optical system, a light deflector having a deflection surface, a second optical system, a photodetector and a luminous flux delimiting member. A luminous flux emitted from the light source is trimmed and imaged as a linear luminous flux extending in the main scanning direction by the first optical system. The deflection surface of the deflector is arranged near the imaging position of the first optical system so that it reflects and deflects the linear luminous flux for scanning operation. The deflected luminous flux is then imaged on the plane to be scanned by the second optical system that establishes a substantially conjugate relationship between the deflection surface and the plane to be scanned. Part of the deflected luminous flux, in the meantime, is reflecte by a bending mirror arranged on the light path between the second optical system and the plane to be scanned, and detected by the photodetector that generates a write-start position synchronizing signal for controlling the timing of spotting the scanning start point on the plane to be scanned. The bending mirror thus operates as the luminous flux delimiting member for the incident luminous flux entering the photodetector. The light source may have a plurality of light emitting sections and in that case, the quantity of light detected by the photodetector is equalized for all the plurality of luminous fluxes emitted from the photodetector.
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