| 摘要 |
PROBLEM TO BE SOLVED: To restrain the deviation of a write start position in a main scanning direction caused by the fluctuation of the oscillating wavelength of a light source so as to be small by providing a means for decreasing the dispersion of the light of a scanning image-forming optical system between the scanning image-forming optical system and a light beam detector. SOLUTION: The optical scanner is composed of at least the light source to emit a light beam, a coupling lens to guide the light beam emitted from the light source to a deflector, the deflector to deflect the light beam from the coupling lens so as to perform scanning, an Fθlens 4 to condense the light beam L deflected by the deflector on a medium to be scanned 6, the scanning image-forming optical system 5, and the light beam detector 7 to detect the write start position in main scanning by the light beam L. In the scanner, a member for decreasing the dispersion of the light, for example, a prism 41 is provided between the optical system 5 and the detector 7, thereby reducing the deviation of the write start position in the main scanning direction caused by the fluctuation of the oscillating wavelength of the light source. COPYRIGHT: (C)2004,JPO
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