JPS57183639A - Focus detector - Google Patents
Focus detectorInfo
- Publication number
- JPS57183639A JPS57183639A JP6832181A JP6832181A JPS57183639A JP S57183639 A JPS57183639 A JP S57183639A JP 6832181 A JP6832181 A JP 6832181A JP 6832181 A JP6832181 A JP 6832181A JP S57183639 A JPS57183639 A JP S57183639A
- Authority
- JP
- Japan
- Prior art keywords
- wedge
- split
- luminous flux
- error signal
- parts
- 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
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 extract an accurate focus error signal without using the position controlling mechanism of an optical element which splits the luminous flux into two parts, by vibrating the optical element that slipts the luminous flux to be made incident to a photodetector into two parts, within a face vertical to the optical axis in order to detect the focus. CONSTITUTION:The luminous flux given from a light source 1 is condensed on the information surface 3 of an optical disk, and this reflected light is reflected by a beam splitter 4 to be made incident to a wedge 5. The wedge 5 is vibrated by a vibrating device 11 in the direction (toward an arrow 12) which is vertical to the optical axis and with an amplitude larger than the expected shift of position of the wedge 5. The light incident to the wedge 5 is split into two parts and made incident to a 4-split photodetector 6. The output of the detector 6 is fed to a differential amplifier 8, and the output focus error signal is always turned positive or 0 with a frequency which is twice the vibrating frequency of the wedge 5 according to the change of the output signals 6a'-6d' of the split photodetetors 6a-6d, respectively. Then the focus error signal is smoothed by an LPF13 to be turned into a focus detection signal 14. Thus the position controlling mechanism is eliminated for the wedge 5.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6832181A JPS57183639A (en) | 1981-05-08 | 1981-05-08 | Focus detector |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6832181A JPS57183639A (en) | 1981-05-08 | 1981-05-08 | Focus detector |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPS57183639A true JPS57183639A (en) | 1982-11-12 |
Family
ID=13370435
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP6832181A Pending JPS57183639A (en) | 1981-05-08 | 1981-05-08 | Focus detector |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS57183639A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0317224A2 (en) * | 1987-11-17 | 1989-05-24 | Matsushita Electric Industrial Co., Ltd. | Focus detection system for an optical disk drive using photo sensor elements in the far field of information pits |
| US5146445A (en) * | 1989-08-04 | 1992-09-08 | Matsushita Electric Industrial Co., Ltd. | Optical head with tracking error detecting system |
-
1981
- 1981-05-08 JP JP6832181A patent/JPS57183639A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0317224A2 (en) * | 1987-11-17 | 1989-05-24 | Matsushita Electric Industrial Co., Ltd. | Focus detection system for an optical disk drive using photo sensor elements in the far field of information pits |
| US5146445A (en) * | 1989-08-04 | 1992-09-08 | Matsushita Electric Industrial Co., Ltd. | Optical head with tracking error detecting system |
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