Optical recording/reproducing apparatus for optical disks with various disk substrate thicknesses

a technology of optical discs and substrates, applied in the field of optical disc apparatuses, can solve the problems of a thin substrate optical head not being able to be used for a thick substrate optical disc, affecting the quality of the optical disc,

Inactive Publication Date: 2006-12-26
PANASONIC CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

"The invention is an optical disc apparatus that can record, play, or erase information on multiple optical discs that have different thicknesses. The apparatus includes N converging means that have corrected aberrations for the N disc substrates. The apparatus also has discriminating means that can identify the thickness of the disc substrate and select the converging means with the least aberration based on the discriminated information. This allows for more precise and accurate recording, playback, and erasure of information on the optical discs."

Problems solved by technology

When NA of the lens increases, however, an aberration of the converged beam due to an inclination error of the disc called a tilt increases.
However, the optical head which has been designed for a thin substrate cannot be used for an optical disc of a thick substrate.
Since such an aberration is corrected in accordance with the thickness of the disc substrate, the aberration correction is not accurately performed for the converged beam which passes through the disc substrate having a thickness different from the design value.
Therefore, in the case of using the objective lens whose aberration has been corrected for a thin disc substrate, an information signal cannot be recorded, reproduced, or erased onto / from an optical disc having a thick disc substrate.
Similarly, in the case of using the objective lens whose aberration has been corrected for a thick disc substrate, an information signal cannot be recorded, reproduced, or erased onto / from an optical disc having a thin disc substrate.

Method used

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  • Optical recording/reproducing apparatus for optical disks with various disk substrate thicknesses
  • Optical recording/reproducing apparatus for optical disks with various disk substrate thicknesses
  • Optical recording/reproducing apparatus for optical disks with various disk substrate thicknesses

Examples

Experimental program
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first embodiment

[0034]FIG. 1 is a constructional diagram of an optical disc apparatus in the invention. FIG. 2 is a plan view showing an arrangement of a main section of the embodiment. FIGS. 3A and 3B are perspective views of cartridges of optical discs in the embodiment.

[0035]In FIGS. 1 to 3A and 3B, reference numeral 1 denotes a first or second optical disc. Thicknesses of disc substrates of both of the first and second optical discs are different. Reference numeral 2 denotes a cartridge which encloses the optical disc 1 and protects. The cartridge 1 is made of plastics or the like. Reference numeral 3 denotes a first optical head and 5 indicates a second optical head. Each of the optical heads is constructed by a converging optical systemunit comprising: an objective lens; a semiconductor laser; a photo detector; a beam splitter; and the like (all of the above components are not shown). Each of the optical head detects an information signal, a focusing error signal, and a tracking error signal ...

second embodiment

[0049]Further, FIG. 6 shows a detailed constructional diagram of the third optical head 30 in the invention. In the diagram, reference numeral 1 denotes the first or second optical disc; 32 a first semiconductor laser as a light source; 33 a first collimating lens for converting a laser beam from the first semiconductor laser 32 into a parallel beam; 34 first beam splitter to divide the beam into two beams; 35 a first mirror to change the direction of the beam; 36 a first objective lens to converge the beam onto the optical disc 1; 37 a first detecting lens to converge the reflected lights which have been divided by the beam splitter 34; and 38 a first photo detector to obtain an information reproduction signal, a focusing error signal, and a tracking error signal from the converged reflected lights. The above components 32 to 38 constructs a first converging optical system 31.

[0050]Reference numeral 39 denotes a lens holder to hold the first objective lens 36 and a second objective...

fourth embodiment

[0065]FIGS. 9A and 9B show a detailed constructional diagram of an optical head of an optical disc apparatus in the invention. In FIG. 9A, since the optical disc 1, first semiconductor laser 32, first collimating lens 33, first beam splitter 34, second objective lens 46, first detecting lens 37, and first photo detector 38 are constructed in a manner similar to those in the foregoing fourth optical head 50, their descriptions are omitted here. Reference numeral 56 denotes a lens holder to hold the second objective lens 46; 57 an actuator to which the lens holder 56 is attached; 54 a wave front correcting lens attached to a slider 55, which will be explained hereinlater, so that the optical axis is in parallel with the optical axis of the second objective lens 46; and 55 the slider which supports the wave front correcting lens 54 and is arranged so as to transverse in the plane which is perpendicular to the light flux between the first beam splitter 34 and the second objective lens 4...

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Abstract

An optical disc apparatus for recording, reproducing or erasing an information signal by converging a light flux onto a recording layer through a transparent substrate. The apparatus includes one or a plurality of optical heads having a plurality of objective lenses whose aberrations have respectively been corrected for a plurality of disc substrates of different thicknesses, a cartridge for enclosing the optical disc, a discrimination hole which is formed on the cartridge, and a sensor for detecting the opening / closing state of the discrimination hole and for generating a discrimination signal. In accordance with the result of the discrimination as to the thickness of the loaded optical disc, the objective lens, in which the occurrence of the aberration is smallest, is used, so that the information signal can preferably be recorded, reproduced or erased onto / from the optical discs having different substrate thicknesses. Instead of an optical head having objective lenses, an optical head having a waveguide and a plurality of converging grating couplers whose aberrations have respectively been corrected for a plurality of disc substrates of different thicknesses is provided to achieve the same object.An optical recording / reproducing apparatus for recording, reproducing or erasing an information signal onto / from an optical disc having at least a transparent substrate and an information layer by converging a light flux on the information layer through the transparent substrate. The apparatus includes optical converging devices, with different numerical apertures, focal distances or working distances, such as objective lenses or grating lenses, for performing aberration correction over a plurality of transparent substrates of different thicknesses of optical discs and a device for discriminating the type of optical disc based on the thicknesses of the transparent substrates. One of the optical converging devices that generates the least aberration is used according to a result of the discrimination of the thickness of the optical disk loaded in the apparatus to cause the information signal to be suitably recorded, reproduced or erased onto / from the optical discs having the different substrate thicknesses.

Description

[0001]This is a reissue continuation application of reissue application Ser. No. 08 / 396,981 which issued as RE 36,445 on Dec. 14, 1999, which was a reissue of U.S. Pat. No. 5,235,581 issued Aug. 10, 1993. The following are related continuation reissue applications: application Ser. No. 09 / 420,603 filed Oct. 19, 1999, application Ser. No. 09 / 609,829 filed Nov. 22, 1999, application Ser. No. 09 / 460,222 filed Dec. 13, 1999, application Ser. No. 09 / 460,223 filed Dec. 13, 1999, application Ser. No. 09 / 460,221 filed Dec. 13, 1999, application Ser. No. 10 / 677,167 filed Oct. 2, 2003, which is a continuation of application Ser. No. 09 / 460,221, application Ser. No. 10 / 677,168 filed Oct. 2, 2003, which is a continuation of application Ser. No. 09 / 420,603, and application Ser. No. 10 / 693,810 filed Oct. 23, 2003, which is a continuation of application Ser. No. 09 / 460,223.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The invention relates to an optical disc apparatus which can r...

Claims

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Application Information

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Patent Type & AuthorityPatents(United States)
IPC IPC(8): G11B7/00G11B7/0037G11B7/085G11B7/12G11B7/135G11B19/12G11B23/03G11B23/30
CPCG11B7/0037G11B7/085G11B7/08505G11B7/12G11B7/124G11B7/1245G11B7/1353G11B7/1374G11B7/1378G11B7/13925G11B19/12G11B23/0302G11B23/30G11B2007/0006
InventorMIYAGAWA, NAOYASUGOTOH, YASUHIRO
OwnerPANASONIC CORP