JPS5611629A - Focus detector for optical information reproducing unit - Google Patents

Focus detector for optical information reproducing unit

Info

Publication number
JPS5611629A
JPS5611629A JP8531579A JP8531579A JPS5611629A JP S5611629 A JPS5611629 A JP S5611629A JP 8531579 A JP8531579 A JP 8531579A JP 8531579 A JP8531579 A JP 8531579A JP S5611629 A JPS5611629 A JP S5611629A
Authority
JP
Japan
Prior art keywords
lens
photodetector
point
convex
focus
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP8531579A
Other languages
Japanese (ja)
Inventor
Yoshiharu Tanaka
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mansei Kogyo KK
Original Assignee
Mansei Kogyo KK
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mansei Kogyo KK filed Critical Mansei Kogyo KK
Priority to JP8531579A priority Critical patent/JPS5611629A/en
Publication of JPS5611629A publication Critical patent/JPS5611629A/en
Pending legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
    • G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B7/0908—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for focusing only

Landscapes

  • Automatic Focus Adjustment (AREA)
  • Optical Recording Or Reproduction (AREA)

Abstract

PURPOSE:To make small the unit in size, by forming imagewise on the photodetector and decreasing the distance between the photodetector and the converging lens, through the provision of optical element consisting of the combination of convex or concave lenses in the optical path of reflection beam. CONSTITUTION:The incident beam 2 through the converging lens 4 forms the focus on a point on the recording disc outside the optical axis (m) and the reflection beam 5 passes through the coverging lens 4 and the convex lens 8 inserted in the optical path. The image point P1 without the convex lens 8a moves to P2. To extend the diameter of the spot of the point P2, when the light beam passes through the convex lens 8b, the image point moves to P3 and spot is produced on the photodetector 6. Although the sensitivity of focus is kept constant with the insertion of the lens systems 8a, 8b, since the distance l1 is reduced, the unit is made small in size.
JP8531579A 1979-07-05 1979-07-05 Focus detector for optical information reproducing unit Pending JPS5611629A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP8531579A JPS5611629A (en) 1979-07-05 1979-07-05 Focus detector for optical information reproducing unit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP8531579A JPS5611629A (en) 1979-07-05 1979-07-05 Focus detector for optical information reproducing unit

Publications (1)

Publication Number Publication Date
JPS5611629A true JPS5611629A (en) 1981-02-05

Family

ID=13855164

Family Applications (1)

Application Number Title Priority Date Filing Date
JP8531579A Pending JPS5611629A (en) 1979-07-05 1979-07-05 Focus detector for optical information reproducing unit

Country Status (1)

Country Link
JP (1) JPS5611629A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63104015A (en) * 1986-10-22 1988-05-09 Asuka Denshi:Kk Observing device for minute area magnetic domain structure
EP0390116A2 (en) * 1989-03-31 1990-10-03 Kabushiki Kaisha Toshiba Optical information processing system

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63104015A (en) * 1986-10-22 1988-05-09 Asuka Denshi:Kk Observing device for minute area magnetic domain structure
EP0390116A2 (en) * 1989-03-31 1990-10-03 Kabushiki Kaisha Toshiba Optical information processing system

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