| 摘要 |
PURPOSE:To obtain an optical device which has >=0.4 numerical aperture and has a collimating lens whose optical coupling efficiency with a semiconductor laser is large, by constituting a lens system of lenses having refractive power of positive, positive and negative, respectively, from a light emitting source. CONSTITUTION:A collimate optical system 6 is formed by the first lens 8 having positive refractive power, the second lens 9 having positive refractive power, and the third lens 10 having negative refractive power, whose concave face has been faced to a light emitting source side, from a semiconductor laser side. According to such a lens system, light having a large spreading angle, which has been emitted from the semiconductor laser can be collimated efficiently, and it can be widely utilized for a device for which a laser scanning technique is used, such as a laser printer, a laser reader, an optical disk device, etc. |
