Optical head device using cross-polarized from a light source for use in optical disk system

• US 5,151,889 A
• Filed: 01/19/1990
• Issued: 09/29/1992
• Est. Priority Date: 01/20/1989
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited 1006 OAZA Kadoma-Shi Osaka Japan
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Momoo, Kazuo, Saimi, Tetsuo
• Primary Examiner(s): Richardson, Robert L.
• Application Number:
  US07/467,119
• Time in Patent Office: 984 Days
• Field of Search: 369/44.14, 369/44.37, 369/44.38, 369/44.41, 369/110, 369/112
• US Class Current: 369/44.37
• CPC Class Codes: G11B 7/12 Heads, e.g. forming of the optical beam spot or modulation of the optical beam disposition or mounting of head elements within housing or with provision for moving of light source, optical beam or detector, irrelevant to the transducing method G11B7/08 ; modulating lasers H01S3/10; controlling the intensity, colour, phase, polarisation or direction of light beams arriving from an independent light source, e.g. switching gating or modulating G02F1/00
• CPC Class Codes: G11B 7/13 Optical detectors therefor

Abstract

An optical head system for optically recording and reproducing information on and from an optical recording medium. The optical head system comprises a light source for emitting a light beam, a collimator lens for causing the light beam from the light source means to become a parallel light beam, and an objective lens for converging the parallel light beam from the collimator lens on the optical recording medium. Between said collimator lens and the objective lens is provided a first optical device for reflecting the light beam returning from the optical recording medium. Also included is a second optical device for separating the light beam from the first optical device to generate two light beams, the two separated light beams directing in the substantially same direction and being separated by a predetermined distance from each other. The two separated light beams from said second optical device are separately incident on a photodetector assembly. The photodetector assembly comprises first and second light-receiving portions which are placed on a common substrate. One of the two separated light beam is incident on the first light-receiving portion so as to obtain a focus error signal and the other separated light beam is incident on the second light-receiving portion so as to obtain a tracking error signal.

Claims

1. An optical head device for optically recording and reproducing information on and from an optical recording medium, comprising:

light source means for emitting a light beam;

collimator means for causing said light beam from said light source means to become a parallel light beam;

objective lens means for converging said parallel light beam from said collimator means on said optical recording medium;

first optical means provided between said collimator means and said objective lens means for reflecting the light beam returned from said optical recording medium;

converging means for converging the light beam reflected by said first optical means;

second optical means for separating the light beam from said converging means to generate two light beams which are optically cross-polarized, said two separated light beams directing in the substantially same direction and being separated by a predetermined distance from each other, said second optical means being arranged to cause the optical path length of one of said two separated light beams to be longer than that of the other separated light beam; and

photodetector means for respectively receiving the two separated light beams from said second optical means.

2. An optical head device for optically recording and reproducing information on and from an optical recording medium, comprising:

light source means for emitting a light beam;

collimator means for causing said light beam from said light source means to become a parallel light beam;

objective lens means for converging said parallel light beam from said collimator means on said optical recording medium;

first optical means provided between said collimator means and said objective lens means for reflecting the light beam returned from said optical recording medium;

converging means for converging the light beam reflected by said first optical means;

second optical means for separating the light beam from said converging means to generate two light beams which are optically cross-polarized, said two separated light beams directing in the substantially same direction and being separated by a predetermined distance from each other;

photodetector means for respectively receiving the two separated light beams from said second optical means;

third optical means provided between said second optical means and said photodetector means for dividing one of the two separated light beams from said second optical means into two light beams which are separately incident on said photodetector means and for transmitting the other separated light beam which is directly incident thereon.

4. An optical head device as claimed in claim 2, wherein said photodetector means is composed of a substrate and first and second light-receiving portions placed on said substrate, said first light-receiving portion being divided along a line into two portions and said second light-receiving portion comprises two sections each of which is divided along two parallel lines into three portions, said first and light-receiving portions are provided such that the division line of said first light-receiving portion is perpendicular to the two parallel division lines of said second light-receiving portion.

5. An optical head device as claimed in claim 4, wherein said first light-receiving portion receives the other separated light beam emerged from said second optical means and passing through said thrid optical means, and said second light-receiving portion receives the two divided light beams obtained by dividing the one separated light beam from said second optical means by means of said third optical means into two.

3. An optical head device as claimed in calim 2, wherein said third optical means is arranged so that the optical path length of one of the two divided light beams is longer than that of the other divided light beam.

6. An optical head device for optically recording and reproducing information on and from an optical recording medium, comprising:

light source means for emitting a light beam;

collimator means for causing said light beam from said light source means to become a parallel light beam;

objective lens means for converging said parallel light beam from said collimator means on said optical recording medium;

first optical means provided between said collimator means and said objective lens means for reflecting the light beam returned from said optical recording medium;

converging means for converging the light beam reflected by said first optical means;

second optical means for separating the light beam from said converging means to generate two light beams which are optically cross-polarized, said two separated light beams directing in the substantially same direction and being separated by a predetermined distance from each other;

photodetector means for respectively receiving the two separated light beams from said second optical means;

third optical means provided between said second optical means and said photodetector means for causing one of the two separated light beams from said second optical means to generate astigmatism.

7. An optical head device for optically recording and reproducing information on and from an optical recording medium, comprising:

light source means for emitting a light beam;

collimator means for causing said light beam from said light source means to become a parallel light beam;

objective lens means for converging said parallel light beam from said collimator means on said optical recording medium;

first optical means provided between said collimator means and said objective lens means for reflecting the light beam returned from said optical recording medium;

second optical means for separating the light beam from said first optical means to generate two light beams which are optically cross-polarized to each other;

third optical means for reflecting the two separated light beams so as to direct in the substantially same direction after reflected, said third optical means being arranged such that one of the two separated light beams assumes a critical angle with respect to a reflection surface thereof; and

photodetector means for respectively receiving the two separated light beams from said third optical means.

8. An optical head device as claimed in claim 7, wherein said photodetector means comprises first and second light-receiving portions each of which is divided into two portions or more, the division line of said first light-receiving portion being arranged to be perpendicular to that of said second light-receiving portion, said first light-receiving portion receiving one of the two separated light beams from said third optical means and said second light-receiving portion receiving the other separated light beam therefrom.