EP0354754A2
Expired / Lapsed
EP
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Method and apparatus for adjusting target position for focusing of light beam
Assignee: Panasonic Holdings Corp
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Filing: 1989-08-07
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Granted: —
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Expires: 2009-08-07
Abstract
Abstract In an apparatus which focuses a light beam (6) on a rotating recording medium (10) in order to record and/or reproduce information, the light beam on the recording medium is controlled of its focus so that a prescribed focusing condition is accomplished. By storing a relation between a target position of focus control and the amplitude of a reproduced signal and by obtaining an optimum target position of focus control in accordance with such stored information, the target position of the focus control can be precisely and quickly adjusted, thereby properly controlling the light beam to focus on the recording medium.
Inventors
- 👤 Katsuya Watanabe
- 👤 Mitsuro Moriya
- 👤 Shinichi Yamada
- 👤 Masayuki Shibano
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 16:00
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/08; G11B7/09; G11B7/0945; G11B7/085; G11B7/0908; G11B7/094
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
101 words
An adjusting method for adjusting a target position of focus control, comprising the steps of: focusing a light beam onto a recording medium; moving the focusing point of the light beam in a direction almost perpendicular to the surface of the recording medium according to a reproduced signal which corresponds to the focusing condition of the light beam on the recording medium so that the target position of a focus control is caused to change; storing information of a relation between the target position and the amplitude of the reproduced signal; and calculating an optimum target position from the stored information.
Claim 2
Dependent Claim
101 words
An adjusting method for adjusting a target position of focus control, comprising the steps of: focusing a light beam onto a recording medium; moving the focusing point of the light beam in a direction almost perpendicular to the surface of the recording medium according to a reproduced signal which corresponds to the focusing condition of the light beam on the recording medium so that the target position of a focus control is caused to change; storing information of a relation between the target position and the amplitude of the reproduced signal; and calculating an optimum target position from the stored information.
Claim 3
Dependent Claim
28 words
A method according to claim 1, wherein the stored information is approximated by a prescribed function, and the optimum target position is calculated according to the approximated function.
Claim 4
Dependent Claim
46 words
A method according to claim 1, wherein two target positions where the amplitudes of the reproduced signal become almost equal to each other are obtained according to the stored information, and an intermediate point of the two target positions is calculated as the optimum target position.
Claim 5
Independent Claim
216 words
An apparatus for adjusting a target position of focus control comprising: focusing means for focusing a light beam on a recording medium; moving means for moving a focusing point of the light beam focused by said focusing means in a direction almost perpendicular to the surface of the recording medium; focusing condition detecting means for generating a singal corresponding to the focusing condition of the light beam on the recording medium; focus control means for driving said moving means according to the signal generated by said focusing condition detecting means so as to control the light beam irradiated on the recording medium to conform to a prescribed focusing condition; signal detecting means for detecting a signal recorded on the recording medium by a light beam transmitting through the recording medium or by a light beam reflected from the recording medium; target position changing means for changing the target position of said focus control means; memory means for storing information of a relation between said target position changed by said focus control means and the amplitude of the signal detected by said signal detecting means; and target position adjusting means for actuating said target position changing means according to the information stored in said memory means to thereby adjust the target position of said focus control system.
Claim 6
Independent Claim
216 words
An apparatus for adjusting a target position of focus control comprising: focusing means for focusing a light beam on a recording medium; moving means for moving a focusing point of the light beam focused by said focusing means in a direction almost perpendicular to the surface of the recording medium; focusing condition detecting means for generating a singal corresponding to the focusing condition of the light beam on the recording medium; focus control means for driving said moving means according to the signal generated by said focusing condition detecting means so as to control the light beam irradiated on the recording medium to conform to a prescribed focusing condition; signal detecting means for detecting a signal recorded on the recording medium by a light beam transmitting through the recording medium or by a light beam reflected from the recording medium; target position changing means for changing the target position of said focus control means; memory means for storing information of a relation between said target position changed by said focus control means and the amplitude of the signal detected by said signal detecting means; and target position adjusting means for actuating said target position changing means according to the information stored in said memory means to thereby adjust the target position of said focus control system.
Claim 7
Dependent Claim
35 words
An apparatus according to claim 4, wherein the target position adjusting means approximates the information stored in the memory means to a prescribed function so as to obtain an optimum target position from said function.
Claim 8
Dependent Claim
70 words
An apparatus according to claim 5, wherein the target position adjusting means causes the focusing condition of the light beam to change, after the amplitude of the signal detected by the signal detecting means is increased, moves the target position of the focus control means to a decreasing direction, and stores into the memory means the relation between the target position and the signal amplitude of the signal detecting means.
Claim 9
Dependent Claim
98 words
An apparatus according to claim 6, wherein if the signal amplitude of the signal detecting means in not increased, the target position adjusting means once moves the target position of the focus control means in a decreasing direction of the amplitude of the signal detected by the signal detecting means, after the signal amplitude of the signal detecting means is increased, moves the target position of the focus control means in a decreasing direction, and stores into the memory means the relation between the target position and the amplitude of the signal detected by the signal detecting means.
Claim 10
Dependent Claim
76 words
An apparatus according to claim 5, wherein the target position adjusting means causes the focusing condition of the lightbeam, after the signal amplitude of the signal detecting means is increased, moves the target position of the focus control means in a decreasing direction, changes the moving direction of the target position and moves it further, and stores into the memory means the amplitude of the signal detected by the signal detecting means at each target position.
Claim 11
Dependent Claim
52 words
An apparatus according to claim 5, wherein the target position adjusting means obtains a point where the amplitude of the signal detected by the signal detecting means becomes almost maximum by the approximated function, and adjust the target position of the focus control means using such point as an optimum target position.
Claim 12
Dependent Claim
60 words
An apparatus according to claim 5, wherein the target position adjusting means obtains two points where the amplitudes of the signal detected by the signal detecting means becomes almost equal to each other by the approximated function, uses an intermediate position of such two points as an optimum target position, and adjust the target position of the focus control means.
Claim 13
Dependent Claim
35 words
An apparatus according to claim 5, wherein the target position adjusting means approximates, using a quadratic function, the relation between the target position and the amplitude of the signal detected by the signal detecting means.
Claim 14
Dependent Claim
19 words
An apparatus according to claim 11, wherein the target position adjusting means uses three points as the measuring points.
Claim 15
Dependent Claim
62 words
An apparatus according to claim 4, wherein the target position adjusting means obtains two target positions where the amplitudes of the signal detected by the signal detecting means become almost equal to each other in accordance with the information stored in the memory means and adjust the target position of the focus control to an intermediate point of the two target positions.
Claim 16
Dependent Claim
109 words
An apparatus according to claim 13, wherein the target position adjusting means causes the focusing condition of the light beam to change, after the amplitude of the signal detected by the signal detecting means is increased, moves the target position of the focus control means in a decreasing direction, finds a first point where the amplitude of the signal detected by the signal detecting means is reduced first and a second point where the amplitude becomes almost equal to that of the first point, and adjust the target position of said focus control means to a third point which is an intermediate point of said first and second points.
Claim 17
Dependent Claim
110 words
An apparatus according to claim 13, wherein the target position adjusting means causes the focusing condition of the light beam to change, after the amplitude of the signal detected by the signal detecting means is increased, moves the target position of the focus control means in a decreasing direction, after a first point before moving the target position is found, finds a second point where the amplitude of the signal detected by said signal detecting means becomes almost equal to that of the first point, and adjust the target position of the focus control means to a third point which is an intermediate point of said first and second points.
Claim 18
Dependent Claim
102 words
An apparatus according to claim 13, wherein the target position adjusting means once moves the target position of the focus control means in a direction the amplitude of the signal detected by the signal detecting means decreases, after a first point of the target position where the amplitude of the signal detected by the signal detecting means is decreased is found, finds a second point where the amplitude becomes almost equal to that of that first point, and adjust the target position of the focus control means to a third point which is an intermediate point of said first and second points.
Claim 19
Dependent Claim
124 words
An apparatus according to claim 13, wherein the target position adjusting means adjusts the target position of the focus control means to a third point which is an intermediate point of first and second points of said two target positions where the amplitudes of the signal detected by the signal detecting means of said first and second points become almost equal to each other, after making the position of the focusing point as the first point by shifting the target position of the focus control means in a prescribed direction and after making the position of the focusing point as the second point by shifting the target position of said focus control means by a same amount in a direction opposite to said direction.
Claim 20
Dependent Claim
131 words
An apparatus according to claim 17, wherein the target position adjusting means moves the target position of the focus control system, with an increased shift amount, in a direction of the first point or the second point whichever has a greater amplitude of the signal detected by the signal detecting means when a difference of the amplitudes at the first point and the second point is greater than a prescribed difference, and moves the target position of the focus control system, with a decreased shift amount, in a direction of the first point or the second point whichever has a greater amplitude of the signal detected by the signal detecting means when the difference of the amplitudes at the first point and the second point is smaller than the prescribed difference.
Claim 21
Dependent Claim
198 words
An apparatus according to claim 17, wherein if the target position of the focus control system is moved toward the first point or the second point but the amplitude of the signal detected by the signal detecting means is not changed, the shift amount of the target position is increased in a prescribed direction the amplitude is changed to make the focusing point as a fourth point by shifting the target position, and the shift amount of the target position is increased in a direction opposite to said prescribed direction to make the focusing point as a fifth point by shifting the target position, the target position of the focus control system is moved in a direction toward a point with greater amplitude of the signal detected by the signal detecting means in accordance with a difference of the amplitudes at said fourth point and the fifth point, and adjust the target position of the focus control means to the third point which is an intermediate point between said first and second points and between said fourth and fifth points where the amplitudes of the signal detected by the signal detecting means become equal to each other, respectively.
Claim 22
Dependent Claim
32 words
An apparatus according to claim 4, wherein the target position adjusting means adjusts the target position of focus control when power of the apparatus is supplied or the recording medium is replaced.
Claim 23
Dependent Claim
23 words
An apparatus according to claim 4, wherein the target position adjusting means adjusts the target position of focus control at prescribed time intervals.
Claim 24
Dependent Claim
28 words
An apparatus according to claim 4, wherein the apparatus adjusts the target position the focus control if no signal recording or reproduction is made for a prescribed time.
Claim 25
Dependent Claim
33 words
An apparatus according to claim 4, wherein if a signal recorded on the recording medium cannot be reproduced, the apparatus reproduces said signal again after the target position of focus control is adjusted.
Claim 26
Dependent Claim
33 words
An apparatus according to claim 4, wherein if a signal cannot be recorded properly on the recording medium, the apparatus records said signal again after the target position of focus control is adjusted.
Claim 27
Dependent Claim
46 words
An apparatus according to claim 4, wherein the apparatus has an acceleration detecting means for detecting vibration or impact externally applied to the apparatus, and adjusts the target position of focus control when a acceleration signal detected by the acceleration detecting means exceeds a prescribed level.
Claim 28
Dependent Claim
43 words
An apparatus according to claim 4, wherein the apparatus has a temperature detecting means for detecting a temperature inside the apparatus, and adjusts the target position of focus control when a temperature signal detected by the temperature detecting means exceeds a prescribed level.
References Cited (Backward Citations)
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