| 摘要 |
An optical scanner comprises a laser diode which scans laser beam of definite wavelength; first optical element which patterns the beam scanned from the laser diode to an almost parallel beam; a slit where long hole has been formed in main scan direction parallel to optical axis which slit is located in front of the first optical element; second optical element located in front of the slit, having refractivity in direction perpendicular to optical axis; an optical deflector where reflection plane has been provided which reflects with designated angle the laser beam that has been scanned from the laser diode and has passed the first optical element, slit and second optical element; and third optical element whose main scan direction is nonspherical shape and subscan direction is made spherical surface which optical element spots to scanned surface the laser beam reflected from the optical deflector. So it makes effect that the birefringence influence is decreased and the metal mold machining and the injection molding are made easier by making both surfaces of third optical element to have slow curvature shapes having relatively few inflection points. And it achieves effect that performance deterioration according to errors in assembling and environmental variation of temperature and humidity etc. by way of making refractivity of both surfaces of lens in main scan direction to be similar.
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