Patent EP0545133A2 successfully refreshed from Google Patents.
EP0545133A2
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EP
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Optical pickup device and focusing servo device employed therein
Assignee: Sony Corp
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Filing: 1992-11-16
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Granted: —
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Expires: 2012-11-16
Abstract
Abstract An optical pickup is adapted for recording and/or reproducing signals by radiating a light beam from a light source (11) on an optical recording medium (16) via an object lens (15) and includes a light receiving device (46,47) for receiving a return light from the optical recording medium (16) , a focusing error detecting unit (48, 25) for detecting an amount of deviation of the focal point along the optical axis, as a measure of a focusing error, based on signals from the light receiving device (46, 47), and an electrostriction device (20) arranged on a path of light outgoing from the light source (11) to the optical recording medium (16) and having a central section (23) and a peripheral section (24) exhibiting a phase difference from each other depending on an applied voltage. Focusing errors may be detected with high accuracy with the optical pickup. On the other hand, a focusing servo device is adapted for controlling the focal point along the optical axis of the optical pickup and includes an object lens driving unit (17) for moving the object lens (15) along the optical axis, a focusing error detecting unit (48, 25) for detecting an amount of deviation of the focal point along the optical axis, as a measure of a focusing error, based on signals from the light receiving device (46, 47), and an electrostriction device (20) arranged on a path of light outgoing from the light source (11) to the optical recording medium (16) and having a central section (23) and a peripheral section (24) exhibiting a phase difference from each other depending on an applied voltage. Depending on error detection signals from the focusing error detection unit (48, 25), rough servo is carried out by the object lens driving unit (17) up to the vicinity of the depth of focus, and fine servo is carried out by the electrostriction device (20) within the range of the depth of focus.
Inventors
- 👤 Ohsato Kiyoshi
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-02 13:19
CPC Classifications
B; B82; B82Y; B82Y10/00; G; G11; G11B; G11B7/00; G11B7/08; G11B7/09; G11B7/0908; G11B7/0912; G11B7/095; G11B7/0956; G11B7/12; G11B7/135; G11B7/1365; G11B7/1369; G11B7/1381; G11B7/1392; G11B7/13925; G11B7/13927; G11B11/00; G11B11/10; G11B11/105; G11B11/10532; G11B11/10541; G11B11/10543; G11B11/1055; G11B11/10576; G11B7/1372; G11B2007/13727
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
143 words
An optical pickup for recording/reproducing signals on or from an optical recording medium by radiating a light beam from a light source (11) to the optical recording medium (16) via an object lens (15), comprising co-focal point detecting optical means (13,41,42,43) for receiving a return light from the optical recording medium (16), focusing error detection means (46,47,48) for detecting a focusing error by signals from said co-focal point detecting optical means(13,41,42,43), said focusing error signal being a amount of deviation of the focal point of said object lens (15) along the optical axis, and an electrostriction device (20) arranged in an outgoing light path from said light source (11) to said recording medium (16), said electrostriction device (20) having a central region (23) and a peripheral region (24) exhibiting a phase difference from each other in an amount corresponding to an applied voltage.
Claim 2
Dependent Claim
45 words
The optical pickup as defined in claim 1 wherein said electrostriction device comprises a piezoelectric plate and electrodes arranged on both sides of said piezoelectric plate (21), one of the electrodes of said piezoelectric plate having a central electrode (23) and a peripheral electrode (24).
Claim 3
Dependent Claim
205 words
A focusing servo device for controlling the focal point along the optical axis of an optical pickup adapted for recording/reproducing signals on or from an optical recording medium (16) by radiating a light beam from a light source (11) to the optical recording medium (16) via an object lens (15), comprising object lens driving means (17) for moving said object lens (15) along the optical axis, focusing error detection means (46,47,48) for detecting a focusing error by signals from a light receiving element (46,47) adapted for receiving the return light from the optical recording medium, said focusing error signal being a amount of deviation of the focal point along the optical axis, an electrostriction device (20) arranged in an outgoing light path from said light source to said recording medium (16), said electrostriction device (20) having a central region (23) and a peripheral region (24) exhibiting a phase difference corresponding to an applied voltage, and control means (25) for effecting, responsive to error detection signals from said focusing error detecting means (46,47,48), a rough servo up to the vicinity of the depth of focus by said object lens driving means (17) and a fine servo within the depth of focus by said electrostriction device (20).
Claim 4
Dependent Claim
77 words
The focusing servo device as defined in claim 3 further comprising a beam splitter (13) for separating a light beam from the light source (11) from a return beam from the optical recording medium (16) for directing the return light beam to said light receiving device (46,47) and pinholes (44,45) provided between said beam splitter (13) and said light receiving device (46,47) and ahead and at the back of a focal point of said return light beam.
Claim 5
Dependent Claim
95 words
The focusing servo device as defined in claim 3 further comprising a beam splitter (13) for separating a light beam from the light source (11) from a return beam from the optical recording medium (16) for directing the return light beam to said light receiving device (46,47), said light receiving device (46,47) receiving said return light beam separated by said beam splitter (13) having a light receiving surface made up of a circular central light receiving section (46C, 47F) and a peripheral light receiving section (46D, 47E) around said central light receiving section (46C, 47F).
Claim 6
Dependent Claim
199 words
An optical pickup for recording and/or reproducing desired information on an information recording surface (106) of an optical disc (102) using a light beam incident on said optical disc (102) via a transparent member (104) formed on a surface of said optical disc (102) so as to be converged on said information recording surface (106), comprising a light source (110) radiating said light beam, an object lens (114) converging said light beam outgoing from said light source (110) to said information recording surface (106), and a transparent electrostriction device (120) arranged on a path of the outgoing light from said light source to said object lens (114) or a light path between said object lens (114) and the optical disc (102) and adapted for dividing a region transmitted through by said light beam into plural regions, said electrostriction device (120) having the thicknesses of said regions changed depending on voltages (V1, V2, V3) applied across transparent electrodes arranged on upper and lower surfaces thereof, said voltage (V1, V2, V3) applied across said regions being changed depending on the tilt of said optical recording medium for correcting the coma aberrations of said light beam on said information recording surface (106).
Claim 7
Dependent Claim
91 words
The optical pickup as defined in claim 6 further comprising a beam splitter (122) for separating a light beam outgoing from said light source (110) and a return light beam from said optical disc (102), light detection means (126) for detecting the light beam separated from said beam splitter (122), and detection means (128, 134) for detecting the tilt of said optical disc (102) based on a detection output of said light detecting means (126), a detection output of said detection means (128, 134) being supplied to said electrostriction device (120).
Claim 8
Dependent Claim
55 words
The optical pickup as defined in claim 6 wherein said electrostriction device (120) comprises a piezoelectric plate (120A) and electrodes (120B, 120B1, 120B2, 120B3) arranged on both sides thereof, one of said electrodes being made up of a central electrode (120B2) and peripheral electrodes (120B1, 120B3) arranged on both sides of said central electrode (120B2).
Claim 9
Dependent Claim
34 words
The optical pickup as defined in claim 6 wherein said electrostriction device (120) comprises a piezoelectric plate and electrodes arranged on both sides thereof, one of said electrodes being formed by four divided electrodes.
Claim 10
Dependent Claim
206 words
An optical pickup comprising a light source (11), an object lens (15) for converging a light beam outgoing from said light source on an optical recording medium (16), a beam splitter (13) for separating a light beam incident thereto via said object lens (15) from a light beam outgoing from said light source (11), light detecting means (46,47) for detecting the light beam separated by said beam splitter (13), control signal generating means (48) for detecting a signal generated on the basis a detection output from said optical detection means (46,47), said signal indicating a deviation from a regular radiation state on said optical recording medium (16), object lens driving means (17) for driving said object lens (15) on the basis of an error signal generated on the basis of the detection output from said light detecting means (46,47), and an electrostriction element (20) arranged on a path of an outgoing light from said light source (11) to said optical recording medium (16) and having a central section (23) and a peripheral section (24) , said central section receiving the light beam from said light source (11) having a phase difference from the light beam received from said light source (11) by said peripheral section (24).
Claim 11
Dependent Claim
82 words
The optical pickup as defined in claim 10 wherein said electrostriction device (20) comprises a piezoelectric plate (21) and electrodes arranged on both sides thereof, one of said electrodes being made up of a central electrode (23) and peripheral electrodes (24), said central electrode being transmitted through by a central portion of a light beam outgoing from said light source (11) and said peripheral electrode being transmitted through by a peripheral portion of said light beam outgoing from said light source (11).
References Cited (Backward Citations)
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