Patent EP0272873A2 successfully refreshed from Google Patents.
EP0272873A2
Expired / Lapsed
EP
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Tracking servo systems for optical disc players
Assignee: Sony Corp
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Filing: 1987-12-15
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Granted: —
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Expires: 2007-12-15
Abstract
Abstract A track servo system in a recordable optical disc player utilizes clock signals produced by irradiating a laser beam (P) on clock pits (3) in servo areas as a reference signal for on-track adjustment. Based on the clock signal, the polarity of a tracking error signal is detected (20) for selectively opening and closing a servo loop (50) of the tracking servo system. CLOSED LOOP on-track adjustment is performed while a laser beam spot is in a range where the tracking error indicating value decreases as the distance of the laser beam spot from the track centre decreases. On the other hand, OPEN LOOP on-track adjustment is performed while the laser beam spot is in a range where the tracking error indicating value increases as Since the polarity of the tracking error signal indicates the range of the laser beam spot position, selection of the CLOSED LOOP and OPEN LOOP can be made without requiring the signal to be reproduced from the data area.
Inventors
- 👤 Naoya Eguchi
- 👤 Norio Nishida
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-06 13:27
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/08; G11B7/09; G11B7/0938; G11B7/085; G11B7/08505; G11B7/08517; G11B7/0901; G11B7/094
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
374 words
A tracking servo system for an optical disc player for reproducing and/or recording data on a plurality of coaxially formed recording tracks on an optical disc (D) which has a pair of servo pits (2A, 2B) and a clock pit (3) on each of said recording tracks, said pair of servo pits (2A, 2B) being circumferentially spaced by a known distance and radially offset by a known distance in respective opposite directions from the track centre, the system comprising: a laser beam generator means (10) for irradiating a laser beam (P) onto said disc (D) for scanning the recording tracks; a laser beam driving means (55) for causing shift of the irradiating point of said laser beam (P) in the radial direction; a tracking servo circuit (50) for controlling said laser beam driving means (55), said tracking servo circuit (50) being operable for operating said laser beam driving (55) means to cause radial shifting of said laser beam irradiating point and operable in feedback manner for adjusting said laser beam irradiating point relative to the centre of the recording track; a light receiving means (11) for receiving the light beam reflected from the laser beam irradiating point and producing a light intensity indicating signal; a first signal processing means (20) for receiving said light intensity indicating signals respectively representative of the light intensity of the light beam reflected from respective servo pits (2A, 2B) for deriving a tracing error signal based on the light intensity indicating signal values; and a second signal processing means (39) for receiving said light intensity indicating signal representative of the light intensity of the light beam reflected from said clock pit (3), detecting the shifting direction of the laser beam irradiating point in the radial direction, and producing a state indicating signal indicative of the shifting direction of said laser beam irradiating point relative to said track centre; characterized by: third signal processing means (40) for receiving said tracking error signal to detect zero-crossing of the tracking error signal value for producing a zero-crossing indicating signal, and deriving a servo control signal for enabling and disabling said feedback mode tracking servo control of said tracking servo circuit (50) based on said state indicating signal and said zero-crossing indicating signal.
Claim 2
Dependent Claim
374 words
A tracking servo system for an optical disc player for reproducing and/or recording data on a plurality of coaxially formed recording tracks on an optical disc (D) which has a pair of servo pits (2A, 2B) and a clock pit (3) on each of said recording tracks, said pair of servo pits (2A, 2B) being circumferentially spaced by a known distance and radially offset by a known distance in respective opposite directions from the track centre, the system comprising: a laser beam generator means (10) for irradiating a laser beam (P) onto said disc (D) for scanning the recording tracks; a laser beam driving means (55) for causing shift of the irradiating point of said laser beam (P) in the radial direction; a tracking servo circuit (50) for controlling said laser beam driving means (55), said tracking servo circuit (50) being operable for operating said laser beam driving (55) means to cause radial shifting of said laser beam irradiating point and operable in feedback manner for adjusting said laser beam irradiating point relative to the centre of the recording track; a light receiving means (11) for receiving the light beam reflected from the laser beam irradiating point and producing a light intensity indicating signal; a first signal processing means (20) for receiving said light intensity indicating signals respectively representative of the light intensity of the light beam reflected from respective servo pits (2A, 2B) for deriving a tracing error signal based on the light intensity indicating signal values; and a second signal processing means (39) for receiving said light intensity indicating signal representative of the light intensity of the light beam reflected from said clock pit (3), detecting the shifting direction of the laser beam irradiating point in the radial direction, and producing a state indicating signal indicative of the shifting direction of said laser beam irradiating point relative to said track centre; characterized by: third signal processing means (40) for receiving said tracking error signal to detect zero-crossing of the tracking error signal value for producing a zero-crossing indicating signal, and deriving a servo control signal for enabling and disabling said feedback mode tracking servo control of said tracking servo circuit (50) based on said state indicating signal and said zero-crossing indicating signal.
Claim 3
Dependent Claim
42 words
A system according to claim 1 wherein said third signal processing means (40) includes a D flip-flop (18) having a D-terminal for receiving said state indicating signal and a clear-terminal for receiving said zero-crossing indicating signal, and supplying said servo control signal.
Claim 4
Dependent Claim
368 words
A tracking servo system for an optical disc player for reproducing and/or recording data on a plurality of coaxially formed recording tracks on an optical disc (D) which has first and second servo pits (2A, 2B) and a clock pit (3) in each servo area of each of said recording tracks, said first and second servo pits (2A, 2B) being circumferentially spaced by a known distance and radially offset by a known distance in respective opposite directions from the track centre, the system comprising: a laser beam generator means (10) for irradiating a laser beam (P) onto said disc (D) for scanning the recording tracks; a laser beam driving beam (55) for causing shift of the irradiating point of said laser beam (P) in the radial direction; a tracking error signal generating means (20) for deriving a tracking error signal on the basis of a difference of light intensity of reflected light beam reflected from said first and second servo pits (2A, 2B); and a shifting state detector means (30) monitoring the relative position between the recording tracks and the laser beam irradiating point for discriminating a shifting between a first state in which said laser beam irradiating point shifts away from said track centre, and a second state in which said laser beam irradiating point approaches said track centre, and producing a state indicating signal; characterized by: a tracking servo circuit (50), operable in CLOSED LOOP mode and OPEN LOOP mode, for controlling said laser beam driving means (55), said tracking servo circuit means (50) being operable for operating said laser beam driving means (55) to cause radial shifting of said laser beam irradiating point and to adjust said laser beam irradiating point to the centre of said recording track in said CLOSED LOOP mode; a mode selector means (40) for receiving said tracking error signal to detect zero-crossing of said tracking error signal to detect zero-crossing of said tracking error signal value for producing a zero-crossing indicating signal and deriving a mode selector signal for selectively operating said tracking servo circuit means (50) in one of said CLOSED LOOP mode and said OPEN LOOP mode, based on said state indicating signal and said zero-crossing indicating signal.
Claim 5
Dependent Claim
368 words
A tracking servo system for an optical disc player for reproducing and/or recording data on a plurality of coaxially formed recording tracks on an optical disc (D) which has first and second servo pits (2A, 2B) and a clock pit (3) in each servo area of each of said recording tracks, said first and second servo pits (2A, 2B) being circumferentially spaced by a known distance and radially offset by a known distance in respective opposite directions from the track centre, the system comprising: a laser beam generator means (10) for irradiating a laser beam (P) onto said disc (D) for scanning the recording tracks; a laser beam driving beam (55) for causing shift of the irradiating point of said laser beam (P) in the radial direction; a tracking error signal generating means (20) for deriving a tracking error signal on the basis of a difference of light intensity of reflected light beam reflected from said first and second servo pits (2A, 2B); and a shifting state detector means (30) monitoring the relative position between the recording tracks and the laser beam irradiating point for discriminating a shifting between a first state in which said laser beam irradiating point shifts away from said track centre, and a second state in which said laser beam irradiating point approaches said track centre, and producing a state indicating signal; characterized by: a tracking servo circuit (50), operable in CLOSED LOOP mode and OPEN LOOP mode, for controlling said laser beam driving means (55), said tracking servo circuit means (50) being operable for operating said laser beam driving means (55) to cause radial shifting of said laser beam irradiating point and to adjust said laser beam irradiating point to the centre of said recording track in said CLOSED LOOP mode; a mode selector means (40) for receiving said tracking error signal to detect zero-crossing of said tracking error signal to detect zero-crossing of said tracking error signal value for producing a zero-crossing indicating signal and deriving a mode selector signal for selectively operating said tracking servo circuit means (50) in one of said CLOSED LOOP mode and said OPEN LOOP mode, based on said state indicating signal and said zero-crossing indicating signal.
Claim 6
Dependent Claim
43 words
A system according to claim 3 wherein said shifting state detector means (30) detects the light intensity of the reflected light beam reflected from said clock pit (3) and discriminates said first and second states based on variation of the detected light intensity.
Claim 7
Dependent Claim
44 words
A system according to claim 4 wherein said state indicating signal produced by said shifting state detector means (30) is variable between HIGH and LOW level and is held at HIGH level in said first state and at LOW level in said second state.
Claim 8
Dependent Claim
36 words
A system according to claim 5 wherein said mode selector means (40) is responsive to said zero-crossing indicating signal to be reset and set at the level corresponding to the level of said state indicating signal.
Claim 9
Independent Claim
43 words
A system according to any one of claims 3 to 6 further comprising a light receiving means (11) for continuously receiving said reflected light beam and producing a light intensity indicating signal indicative of the light intensity of said reflected light beam (P).
Claim 10
Dependent Claim
104 words
A system according to claim 7 wherein said tracking error signal generator means (20) includes first means (12A) for sampling said light intensity indicating signal at a first known timing at which said laser beam (P) is irradiated onto said first servo pit (2A), a second means (12B) for sampling said light intensity indicating signal at a second known timing at which said laser beam (P) is irradiated onto said second servo pit (2B), and third means (13, 14) for deriving a difference between said light intensity indicating signals sampled by said first and second means (12A, 12B) for deriving said tracking error signal.
Claim 11
Dependent Claim
58 words
A system according to claim 8 wherein said shifting state detector means (30) includes fourth means (15) for sampling said light intensity indicating signal at a third known timing at which said laser beam is irradiated onto said clock pit (3) to produce a signal having a phase shift of known magnitude relative to said tracking error signal.
Claim 12
Dependent Claim
12 words
A system according to claim 9 wherein said phase shift is π/2.
Claim 13
Independent Claim
27 words
A system according to any one of the preceding claims applicable for an optical disc (D) having a writable and readable data area on said recording track.
Claim 14
Dependent Claim
15 words
A system according to claim 11 wherein said disc (D) is an optomagnetic disc (D).
References Cited (Backward Citations)
No citation records indexed.
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