EP0093582A1
Expired / Lapsed
EP
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Scanning servo system for optical-disc information reproducing apparatus
Assignee: Toshiba Corp
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Filing: 1983-04-28
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Granted: —
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Expires: 2003-04-28
Abstract
Abstract A scanning servo system for an optical-disc information reproducing apparatus includes; (a) a light source (12) for generating a light beam (10) to scan a selected track location on an optical-disc (16) wherein the information is stored as a series of pits or recesses arranged in the form of a track (24); (b) an objective lens (20) for applying a scanning spot (18) of the light beam to the selected track location; (c) a transducer (26) for converting an optical signal of an image (28) of a pit or recess into an electrical signal; (d) an actuator (58 or 72) for driving the objective lens in response to the electric signal in a direction vertically or radially relative to the optical-disc, thereby causing the scanning spot to scan the selected track location accurately, the actuator being variable as regards its response characteristics in response to the electrical signal; (e) a circuit (44) for detecting a dropout of the information on the selected track location and generating a signal responsive to the dropout of information; (f) a circuit (78) for delaying the signal responsive to the dropout of information for one rotation period of the optical-disc; and (g) a circuit (32, 36) for lowering the response characteristics of the actuator in response to the signal responsive to the dropout of information through the delaying circuit.
Inventors
- 👤 Daiki C/O Patent Division Nabeshima
- 👤 Hiroshi C/O Patent Division Nakane
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-01 12:17
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/08; G11B7/09; G11B7/0948; G11B7/0941
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
209 words
A scanning servo system for an optical-disc information reproducing apparatus in which information stored on an optical-disc as a series of recesses or pits arranged in concentric tracks or in a single spiral track is read out during rotation of the optical-disc by a scanning spot of a light beam, the system comprising: a light source for generating the light beam used for reading out the information as an optical signal; means for applying the scanning spot of the light beam to a selected track location; a transducer for converting the optical signal into an electric signal; means for controlling said scanning spot applying means in response to the electric signal, thereby causing the scanning spot to scan the selected track location accurately, said controlling means being variable in its response characteristics in response to the electric signal; and means for detecting a dropout of the information on the selected track location and generating a signal responsive to said dropout of information, characterised in that the system includes: means for delaying said signal responsive to said dropout of information for one rotation period of the optical-disc; and means for lowering the response characteristics of said controlling means in response to the delayed signal responsive to said dropout of information.
Claim 2
Dependent Claim
209 words
A scanning servo system for an optical-disc information reproducing apparatus in which information stored on an optical-disc as a series of recesses or pits arranged in concentric tracks or in a single spiral track is read out during rotation of the optical-disc by a scanning spot of a light beam, the system comprising: a light source for generating the light beam used for reading out the information as an optical signal; means for applying the scanning spot of the light beam to a selected track location; a transducer for converting the optical signal into an electric signal; means for controlling said scanning spot applying means in response to the electric signal, thereby causing the scanning spot to scan the selected track location accurately, said controlling means being variable in its response characteristics in response to the electric signal; and means for detecting a dropout of the information on the selected track location and generating a signal responsive to said dropout of information, characterised in that the system includes: means for delaying said signal responsive to said dropout of information for one rotation period of the optical-disc; and means for lowering the response characteristics of said controlling means in response to the delayed signal responsive to said dropout of information.
Claim 3
Dependent Claim
60 words
A scanning servo system according to claim 1, characterised in that said delaying means includes a register for storing said signal responsive to said dropout of information and means for detecting one rotation period of the optical-disc and for triggering said register to output the stored signal responsive to said dropout of information after one rotation period of the optical-disc.
Claim 4
Dependent Claim
25 words
A scanning servo system according to claim 2, characterised in that said register and said one rotation period detecting means are formed by a microcomputer.
Claim 5
Dependent Claim
31 words
A scanning servo system according to claim 2 or 3, characterised in that it further comprises means for increasing the signal width of the signal responsive to said dropout of information.
Claim 6
Dependent Claim
78 words
A scanning servo system according to claim 4, characterised in that said increasing means includes means connected to said one rotation period detecting means for generating an integral number of pulses each of the same width divided equally in the one rotation period of the optical-disc by the same integral number for each rotation of the optical-disc, and a flip-flop having its set input connected to said transducer and its reset input connected to said pulse generating means.
Claim 7
Dependent Claim
24 words
A scanning servo sy stem according to claim 5, characterised in that said register is a shift register having shift-steps of the integral number.
Claim 8
Dependent Claim
49 words
A scanning servo system according to claim 6, characterised in that further includes means for changing the integral number between a small number for a relatively short period of one rotation of the optical-disc and a large number for a relatively long period of one rotation of the optical-disc.
Claim 9
Dependent Claim
49 words
A scanning servo system according to claim 7, characterised in that said one rotation period detecting means is adapted for detecting one rotation period of the optical-disc by a time signal related to a reproduction time elapsed, the time signal being extracted from a signal recorded on the optical-disc.
Claim 10
Dependent Claim
35 words
A scanning servo system according to claim 7, characterised in that said one rotation period detecting means is adapted for detecting one rotation period of the optical-disc by detecting a rotation speed of the optical-disc.
Claim 11
Dependent Claim
73 words
A scanning servo system according to claim 7, 8 or 9, characterised in that said controlling means includes an amplifier for amplifying the electric signal and an actuator for driving said scanning spot applying means by the amplified electric signal, and wherein the gain of said amplifier responsive to the response characteristics of said controlling means is lowered in response to the signal responsive to said dropout of information through said delaying means.
Claim 12
Dependent Claim
36 words
A scanning servo system according to claim 10, characterised in that said controlling means are further provided with a phase compensating circuit for changing the frequency-to-phase characteristics thereof in response to the gain of said amplifier.
Claim 13
Dependent Claim
29 words
A scanning servo system according to any preceding claim, characterised in that said scanning spot applying means is means for focusing the scanning spot to the selected track location.
Claim 14
Dependent Claim
18 words
A scanning servo system according to claim 12, characterised in that said focusing means is an objective lens.
Claim 15
Dependent Claim
46 words
A scanning servo system according to claim 13, characterised in that said scanning spot controlling means includes an actuator for driving said objective lens in a direction vertical to the optical-disc so as to focus the scanning spot at the surface of the selected track location.
Claim 16
Dependent Claim
48 words
A scanning servo system according to claim 13 or 14, characterised in that said scanning spot controlling means includes an actuator for driving said objective lens in a direction radial to the optical-disc so as to move the position of the scanning spot to the selected track location.
References Cited (Backward Citations)
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