Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Patent
1995-07-18
1997-09-02
Young, W. R.
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
369 4437, 369112, 369110, G11B 7095
Patent
active
056639406
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/JP94/01968 filed Nov. 21, 1994.
TECHNICAL FIELD
This invention relates to an optical pick-up device suitable when used as an optical system of an optical disc recording apparatus, an optical disc reproducing apparatus, or an optical disc recording/reproducing apparatus, etc. for carrying out recording/reproduction of desired record information onto an optical disc, e.g., a magneto-optical disc, a compact disc (CD) or a video disc, etc.
BACKGROUND ART
A conventional optical pick-up device for magneto-optical disc has a configuration as shown in FIG. 22. At the time of reproduction (or at the time of recording), laser beams of so called P polarization component are emitted from a laser diode 201. These laser beams are changed into rays of parallel light by a collimator lens 201a, and are caused to undergo shaping by a shaping prism 202. The rays of light thus shaped are incident to a S polarization beam splitter 203.
A polarization beam splitter film 203a provided at the S polarization beam splitter 203 has the characteristic that it allows 100% of rays of light of S polarization component having polarization direction perpendicular to the P polarization component to be reflected, and allows 50% of rays of light of P polarization component to be reflected and allows the remaining 50% thereof to be transmitted therethrough. For this reason, one half of the laser beams of the P polarization component incident to the S polarization beam splitter 203 are reflected and the remaining half thereof are transmitted therethrough. The laser beams transmitted through the S polarization beam splitter 203 are reflected by a 45 degree mirror 204A, and are irradiated onto a magneto-optical disc 206 through an object lens (objective) 205.
In this example, at the time of recording, data is delivered to a magnetic head 208 through an input terminal 207. Thus, the magnetic head 208 is driven in accordance with the data, so a magnetic field corresponding to the data is produced. This magnetic field is applied to the portion where laser beams are irradiated of the magneto-optical disc 206. Thus, recording of data is carried out.
When laser beams are irradiated onto the magneto-optical disc 206 as described above, a reflected light is produced. Rays of this reflected light are reflected by the 45 degree mirror 204A through the object lens 205, and are incident to the S polarization beam splitter 203.
The rays of reflected light are reflected in a manner deviating with respect to the S polarization component in accordance with data recorded on the magneto-optical disc 206. However, such deviation quantity is very small, and most of such rays of light are reflected as the P polarization component. The S polarization beam splitter 203 allows 100% of rays of the S polarization component to be reflected, and allows 50% of rays of the P polarization component to be reflected and allows the remaining 50% to be transmitted therethrough as described above. For this reason, rays of reflected light of the S polarization component of the rays of the reflected light are all reflected by the S polarization beam splitter 203 and are incident to a polarization beam splitter 204. On the other hand, one half of rays of reflected light of the P polarization component are reflected and the remaining half are transmitted therethrough by the S polarization beam splitter 203.
A polarization beam splitter film 204a of the polarization beam splitter 204 has the characteristic that it allows all of rays of light of the P polarization component to be transmitted therethrough and allows all of rays of light of the S polarization component to be reflected. For this reason, rays of the reflected light of the P polarization component of the rays of reflected light incident to the polarization beam splitter 204 are transmitted through the polarization beam splitter film 204a and are incident to a servo signal detection system 213. Moreover, rays of the light of the S polarization component are reflected by the polarization
REFERENCES:
patent: 5231620 (1993-07-01), Ohuchida
patent: 5297125 (1994-03-01), Yamagami et al.
patent: 5483509 (1996-01-01), Yang et al.
Horimai Hideyoshi
Maruo Tsunehiro
Sony Corporation
Young W. R.
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