| 摘要 |
PURPOSE:To obtain a prism optical system whose geometrical property will not change with respect to a wavelength change by employing two prisms made of materials having different wavelength variances of a refraction factor at a certain interval as a prism composing the prism optical system. CONSTITUTION:A laser beam emitting from a semiconductor laser 100 is made into a parallel flux by a lens 101, converted into a flux having the width less than the effective aperture of an A/O modulator 103 by means of the 1st prism system 102 and is made incident on said modulator 103. The prism system 102 has such a feature that the flux emitting from the prism will not develop an angle change due to the wavelength change of the laser beam. The light beam emitting from the A/O modulator 103 is shaped into a circular flux by the 2nd prism system 104, and stopped down a disk 106 by a stop-down lens 105. In terms of the emitting angle change coming out of the prism, which is caused by the wavelength change of the laser beam, a change in a slopped- down spot position is effectively suppressed. Moreover, since the incident and emitting light beams are parallel, the constitution and adjustment of an optical head can be comparatively easy. |
