| 摘要 |
PROBLEM TO BE SOLVED: To stably maintain the light condensing state of a laser beam on an image surface against the temperature change in a wide range even in the case of the wavelength change of a laser light source in the small range at a laser beam optical device. SOLUTION: This optical device is provided with a light source unit 11 incorporating a variable wavelength laser diode and a Fresnel lens as a condensing element, a cylindrical lens 13, a polygon mirror 15 and an fθlens 16. In this case, the light emission wavelength of the laser diode is controlled by a CPU 60 through a wavelength control driver 61. The change of ambient temperature is detected by a sensor 65 and a detected value is fed back for wavelength control.
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