JPS57205832A - Out-of-focus detecting method - Google Patents
Out-of-focus detecting methodInfo
- Publication number
- JPS57205832A JPS57205832A JP8992281A JP8992281A JPS57205832A JP S57205832 A JPS57205832 A JP S57205832A JP 8992281 A JP8992281 A JP 8992281A JP 8992281 A JP8992281 A JP 8992281A JP S57205832 A JPS57205832 A JP S57205832A
- Authority
- JP
- Japan
- Prior art keywords
- focus
- light
- optical detector
- objective lens
- forming layer
- 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 detect out-of-focus of laser light, by extracting only a light being in a position shifted from the center of an optical axis with a light shielding plate, and detecting a movement of the extracted light on an optical detector. CONSTITUTION:As shown in the figure (a), in case when a focus of laser light 11 conforms with an information forming layer 4, a reflected ray which has passed through an objective lens 17 becomes parallel with an optical axis, and a light which has passed through a light transmitting part 23a of a light shielding plate 23 is in a boundary of the first optical detector 26a and the second optical detector 23b. As shown in the figure (b), however, in case when the information forming layer 4 and the objective lens 17 are too adjacent to each other to be out of focus, or as shown in the figure (c), in case when the information forming layer 4 and the objective lens 17 are too separated to be out of focus, there is a beam spot in either the first optical detector 26a or the second optical detector 26b, and the objective lens 17 is moved in the direction being in focus, by providing output signals of the optical detectors 26a, 26b to a lens driving circuit through a differential emplifying circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8992281A JPS57205832A (en) | 1981-06-11 | 1981-06-11 | Out-of-focus detecting method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8992281A JPS57205832A (en) | 1981-06-11 | 1981-06-11 | Out-of-focus detecting method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPS57205832A true JPS57205832A (en) | 1982-12-17 |
Family
ID=13984187
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP8992281A Pending JPS57205832A (en) | 1981-06-11 | 1981-06-11 | Out-of-focus detecting method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS57205832A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5956233A (en) * | 1982-09-24 | 1984-03-31 | Ricoh Co Ltd | Focus detecting method in optical pickup optical system |
-
1981
- 1981-06-11 JP JP8992281A patent/JPS57205832A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5956233A (en) * | 1982-09-24 | 1984-03-31 | Ricoh Co Ltd | Focus detecting method in optical pickup optical system |
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