Patent US5321676A successfully refreshed from Google Patents.
US5321676A
Expired / Lapsed
US
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Record carrier scanning apparatus wherein the scanning head is positioned without feedback and a predetermined range of fine positioning of the scanning point is maintained
Assignee: US Philips Corp
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Filing: 1992-09-28
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Granted: 1994-06-14
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Expires: 2012-09-28
Abstract
Abstract Scanning apparatus for a disc-shaped record carrier having a spiral track, the apparatus including a scanning head arranged on a slide which is radially displaceable with respect to the record carrier. The scanning point produced by the scanning head is maintained on the track by a tracking control system which includes a fine positioning device secured to the slide and which radially displaces the scanning point within a predetermined limited range of displacement determined by the positioning of the fine-positioning device with respect to the slide. A position-indication signal (PS) indicative of such position is generated, and a control unit detects when such signal exceeds a predetermined limit value. In that event, the control unit energizes a driving motor of the radial displacement device by supplying an energizing pulse pattern thereto which causes displacement of the slide to a position at which the position-indication signal returns to a value below the limit value. The energizing pulse pattern is adjusted by the control unit so that the displacement of the fine-positioning device in response thereto remains within predetermined limits and/or is symmetrical about a central position of such device relative to the slide.
Inventors
- 👤 Johannes L. van Velthoven
- 👤 Antonius H. M. Akkermans
- 👤 Theodorus A. Koopmanschap
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 05:56
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/08; G11B7/09; G11B7/0901; G11B7/085; G11B7/08505; G11B7/08517
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
288 words
Apparatus for scanning a disc-shaped record carrier having a track in the form of spiral turns around a center of rotation of the record carrier, said apparatus comprising: a scanning head for producing a scanning point on the record carrier and detection signals indicative of the position of the scanning point relative to said track; support means for supporting the scanning head and which is radially displaceable with respect to the record carrier; drive means for radially displacing the support means and thereby also radially displace the scanning point; a fine-positioning device on said support means for further radially displacing said scanning point within a predetermined limited range in accordance with variation of the position of said fine-positioning device relative to said support means; a tracking control circuit for receiving the detection signals from the scanning head and deriving therefrom a position-indication signal indicative of the position of said fine-positioning device relative to said support means; and control means coupled to the tracking control circuit to receive the position-indication signal, detecting when said signal exceeds a predetermined limit value, and in that event temporarily energizing said drive means so as to displace said support means towards a position at which said signal resumes a value below said limit value; the energizing of said drive means by said control means being in accordance with an energizing pattern which is independent of the instantaneous value of the position-information signal and which is determined by said control means by (i) detecting the effect on the position-information signal of energizing said drive means in accordance with a selected energizing pattern, and (ii) modifying the selected energizing pattern so that the modified pattern effects the position-information signal in accordance with a predetermined criterion.
Claim 2
Dependent Claim
288 words
Apparatus for scanning a disc-shaped record carrier having a track in the form of spiral turns around a center of rotation of the record carrier, said apparatus comprising: a scanning head for producing a scanning point on the record carrier and detection signals indicative of the position of the scanning point relative to said track; support means for supporting the scanning head and which is radially displaceable with respect to the record carrier; drive means for radially displacing the support means and thereby also radially displace the scanning point; a fine-positioning device on said support means for further radially displacing said scanning point within a predetermined limited range in accordance with variation of the position of said fine-positioning device relative to said support means; a tracking control circuit for receiving the detection signals from the scanning head and deriving therefrom a position-indication signal indicative of the position of said fine-positioning device relative to said support means; and control means coupled to the tracking control circuit to receive the position-indication signal, detecting when said signal exceeds a predetermined limit value, and in that event temporarily energizing said drive means so as to displace said support means towards a position at which said signal resumes a value below said limit value; the energizing of said drive means by said control means being in accordance with an energizing pattern which is independent of the instantaneous value of the position-information signal and which is determined by said control means by (i) detecting the effect on the position-information signal of energizing said drive means in accordance with a selected energizing pattern, and (ii) modifying the selected energizing pattern so that the modified pattern effects the position-information signal in accordance with a predetermined criterion.
Claim 3
Dependent Claim
35 words
Scanning apparatus as claimed in claim 1, wherein said control means determines the energizing pattern for energizing said drive means during a predetermined time interval following termination of a previous energization of said drive means.
Claim 4
Dependent Claim
60 words
Apparatus as claimed in either of claims 1 or 2, wherein said control means is adapted to detect from the position-information signal whether the displacement of said support means caused by energizing of said drive means falls within a predetermined range, and to modify the energizing pattern supplied to said drive means if said displacement extends beyond said predetermined range.
Claim 5
Dependent Claim
105 words
Scanning apparatus as claimed in either of claims 1 or 2, wherein after energizing said drive means in accordance with a first energization pattern said control means is adapted to detect whether the resulting position-information signal reaches an absolute value which exceeds a second predetermined limit value by an amount which is greater than first-named limit value, said second limit value being opposite in sign to said first-named limit value, and in that event to energize said drive means in accordance with a second energization pattern which displaces said support means in an opposite direction to the displacement thereof produced by said first energization pattern.
Claim 6
Dependent Claim
15 words
Scanning apparatus as claimed in claim 1, wherein said drive means is a self-braking motor.
References Cited (Backward Citations)
GB1429882A
Cited
US4899325A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1997-06-13 | 1997-12-13 | 1998-06-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-06-13 | 2001-12-13 | 2002-06-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-06-13 | 2005-12-13 | 2006-06-14 | $7700.00 | Window Closed / Lapsed |