| 摘要 |
PURPOSE:To make a device smaller in terms of size and weight and to reduce the number of parts by providing a semiconductor laser, a photodetector, a birefringence body and a 1/4 wavelength plate. CONSTITUTION:Linearly polarized beams coming out of the semiconductor laser are made parallel to each other by a collimate lens 10, passes through the birefringence body 9 and the 1/4 wavelength plate 11 and form a focus on the surface of an optical disk 13 by an objective lens 12. The reflected light from the surface of the optical disk 13 reversely passes through the objective lens 12, while an initially linear polarization laser beam passes through the 1/4 wavelength plate twice, and rotates perpendicularly to its polarization direc tion. Accordingly, the returning beam reversely passes through the birefringence body 9, however it takes an optical path different from a going route because refraction angles are different. With respect to the collimate lens 10, the returning beam returns back by tilting against the coming out light beam of the semiconductor laser, and accordingly returns to the longitudinal side of the semiconductor laser. Thus, the device can be made smaller in terms of its size and weight. |
