| 摘要 |
PURPOSE:To simplify the control and at the same time realize a miniaturization with a light weight for a projecting device using a semiconductor laser beam source which is used to an optical information reproducing device, by correcting the beam section form of the semiconductor laser beam source to a circular shape by means of a diffractive element which causes a deflection of light. CONSTITUTION:The beams emitted from a semiconductor laser beam source 1 are turned parallel by a collimator lens 2 and then incident to a diffraction grating 3 for correction. The beams passed through the grating 3 are diffracted and go toward the direction which is deflected by an angle theta from the course (toward dotted lines) of beam in case no grating 3 is provided to be made incident to an objective lens 5 after passing through a beam splitter 4. A laser beam is turned into a light spot having a circular section of a diameter of about 1mum by the lens 5 and then converged so that the focus matches with the surface of a disk 6 having a spiral information track. The reflected light modulated by the information of the disk 6 is condensed by the lens 5, separated from the original optical path by the splitter 4 and enters a photodetector 8 to be turned into an electric signal. |
