| 摘要 |
PROBLEM TO BE SOLVED: To reproduce information with less noise at the time of using a short- wavelength laser light. SOLUTION: Laser light emitted from a laser diode 1 has the form shaped through a prism 4 and passes laser beam splitters 5 and 6 and passes an object lens 9 and irradiates an optical disk D. At the time of read, laser light reflected from the optical disk D passes the object lens 9 and is reflected by the laser beam splitter 6 and passes a beam split prism 12, an analyzer 12, a mirror 13, a lens 14 to form an image on a pin diode 15. Thus, recorded information of the optical disk D is obtained from the pin diode 15 as an optical signal. The return light from the optical disk D, which has passed the laser beam splitter 6 and has passed the laser beam splitter 5 is returned to the laser diode 1 through the prism 4. Since this return light is a serious cause of noise, a filter 3 as an optical attenuation member is inserted between a collimator 2 and the prism 4 in an optical head especially at the time of read to attenuate the return quantity to the laser diode 1. |
