| 摘要 |
PROBLEM TO BE SOLVED: To provide a scanning optical device capable of making the plotting speed higher than that in a conventional single-beam device without increasing the revolving speed of a polygon mirror, making the arranging space smaller than that in a multibeam device and making the set cost low. SOLUTION: A laser beam emitted from a light source part 10 is deflected in a main scanning direction by the polygon mirror 20 and formed into an image on a surface to be scanned 40 through a diffraction grating 25 and an fθlens 30 so as to form a scanning line. The emitting direction of the diffracted light from the grating 25 has wavelength dependency. By switching the wavelength of the incident laser beam between 1st wavelength and 2nd wavelength, luminous flux L1 going to the upside and luminous flux L2 going to the downside are switched. By applying modulation in accordance with the plotting data of the 1st scanning line in the 1st wavelength and the plotting data of the 2nd scanning line in the 2nd wavelength while switching the emitted light wavelength of a semiconductor laser with high frequency, plural scanning lines can be formed by one scanning.
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