EP0372629A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Apparatus for optically scanning an information plane
Assignee: Koninklijke Philips NV
•
Filing: 1989-11-29
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Granted: —
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Expires: 2009-11-29
Abstract
Abstract An optical scanning apparatus is described, which comprises a radiation source (7) supplying a scanning beam (b₁), an objective system (8) for focusing the scanning beam (b₁) to a scanning spot (S₁) in an information plane (2) to be scanned and a first diffraction element (9) for deforming the beam reflected by the information plane (2) in such a way that a focus-error signal can be derived therefrom. The apparatus further comprises a second diffraction element (10) for forming two auxiliary beams (b₂,b₃) by means of which a tracking-error signal can be derived, which second diffraction element has such a size and is arranged at such position that the beams originating from the first diffraction element (9) do not traverse the second diffraction element.
Inventors
- 👤 Willem Gerard Opheij
- 👤 Peter Coops
- 👤 Adrianus Johannes Duijvestijn
- 👤 Dirk Cornelis Van Eck
- 👤 Peter De Zoeten
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 00:36
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/08; G11B7/09; G11B7/12; G11B7/135; G11B7/1381; G11B7/0908; G11B7/0912; G11B7/0916; G11B7/123; G11B7/13; G11B7/1353
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
205 words
An apparatus for optically scanning a radiation-reflecting information plane, which apparatus comprises a radiation source supplying a scanning beam, an objective system for focusing the scanning beam to a scanning spot in the information plane and for re-imaging the scanning spot on a composite radiation-sensitive detection system, and a first diffraction element arranged in the radiation path between the radiation source and the objective system for deflecting a part of the radiation reflected by the information plane to the radiation-sensitive detection system and for deforming the deflected scanning beam in such a way that a focus-error signal can be derived therefrom by means of the composite detection system, characterized in that a second, single diffraction element is arranged between the radiation source and the first diffraction element for splitting the beam supplied by the radiation source into a scanning beam and two auxiliary beams which form the scanning spot and the two auxiliary spots, respectively, in the information plane, in that the composite detection system comprises extra detectors for the re-imaged auxiliary spots and in that the second diffraction element is so small and is arranged at such position that the beams diffracted by the first diffraction element do not reach the second diffraction element.
Claim 2
Independent Claim
205 words
An apparatus for optically scanning a radiation-reflecting information plane, which apparatus comprises a radiation source supplying a scanning beam, an objective system for focusing the scanning beam to a scanning spot in the information plane and for re-imaging the scanning spot on a composite radiation-sensitive detection system, and a first diffraction element arranged in the radiation path between the radiation source and the objective system for deflecting a part of the radiation reflected by the information plane to the radiation-sensitive detection system and for deforming the deflected scanning beam in such a way that a focus-error signal can be derived therefrom by means of the composite detection system, characterized in that a second, single diffraction element is arranged between the radiation source and the first diffraction element for splitting the beam supplied by the radiation source into a scanning beam and two auxiliary beams which form the scanning spot and the two auxiliary spots, respectively, in the information plane, in that the composite detection system comprises extra detectors for the re-imaged auxiliary spots and in that the second diffraction element is so small and is arranged at such position that the beams diffracted by the first diffraction element do not reach the second diffraction element.
Claim 3
Dependent Claim
16 words
An apparatus as claimed in Claim 1, characterized in that the two diffraction elements are radiation-transmissive.
Claim 4
Dependent Claim
22 words
An apparatus as claimed in Claim 1, characterized in that at least one of the two diffraction elements is a reflecting element.
Claim 5
Dependent Claim
23 words
An apparatus as claimed in Claim 3, characterized in that the first diffraction element is reflecting and the second diffraction element is radiation-transmissive.
Claim 6
Dependent Claim
23 words
An apparatus as claimed in Claim 3, characterized in that the first diffraction element is radiation-transmissive and the second diffraction element is reflecting.
Claim 7
Dependent Claim
20 words
An apparatus as claimed in Claim 3, characterized in that both the first and the second diffraction element are reflecting.
Claim 8
Dependent Claim
84 words
An apparatus as claimed in Claim 6, in which the radiation source is a diode laser and the radiation-sensitive detection system comprises a composite photodiode, and in which the laser diode and the photodiode are arranged on one block at one side of a housing, which housing has a radiation window at the opposite side, characterized in that the second diffraction element is incorporated in the housing and in that the first diffraction element is fixedly connected to the radiation-transmissive side of the housing.
Claim 9
Dependent Claim
19 words
An apparatus as claimed in claim 7, characterized in that a collimator lens is fixedly connected to the housing.
Claim 10
Dependent Claim
27 words
An apparatus as claimed in Claim 7, characterized in that an objective system in the form of a single objective lens is fixedly connected to the housing.
Claim 11
Independent Claim
98 words
An apparatus as claimed in any one of Claims 1-9, characterized in that the second diffraction element is a diffraction grating having a constant grating period and whose grating strips are substantially transverse to the effective track direction, in that the first diffraction element is a diffraction grating having a varying grating period and in that the composite detection system comprises four detectors which are arranged in four different quadrants around the chief ray of the scanning beam deflected by the first diffraction grating, the shape of the re-imaged scanning spot being determined by means of said detectors.
Claim 12
Dependent Claim
23 words
An apparatus as claimed in Claim 10, characterized in that the first grating has straight grating strips and a linearly varying grating period.
Claim 13
Dependent Claim
38 words
An apparatus as claimed in Claim 10, characterized in that the grating strips of the first grating are curved and in that the separating strips of the four-quadrant detector are parallel respectively transverse to the effective track direction.
Claim 14
Independent Claim
87 words
An apparatus as claimed in any one of Claims 1-9, characterized in that the second diffraction element is a diffraction grating having a constant grating period and whose grating strips are substantially transverse to the effective track direction, in that the first diffraction element is a composite grating comprising two sub-gratings and splitting the deflected scanning beam into two sub-beams, and in that the composite detection system comprises two detector pairs, a first and a second sub-beam cooperating with a first and a second detector pair, respectively.
Claim 15
Dependent Claim
28 words
An apparatus as claimed in Claim 13, characterized in that the sub-gratings have a varying grating period and in that the grating strips of the sub-gratings are curved.
Claim 16
Dependent Claim
60 words
An apparatus as claimed in Claim 13 or 14, characterized in that the grating strips of the one sub-grating have the same main direction as those of the other sub-grating, in that the average grating periods of the sub-gratings are different, and in that the detector pairs are juxtaposed in a direction parallel to the bounding line between the sub-gratings.
Claim 17
Dependent Claim
75 words
An apparatus as claimed in Claim 13, 14, characterized in that the sub-gratings have the same average grating period, in that the main directions of the grating strips of the one sub-grating extend at a first angle and those of the other sub-grating extend at a second angle to the bounding line of the two sub-gratings, and in the detector pairs are juxtaposed in a direction transversely of the direction of the said bounding line.
Claim 18
Dependent Claim
87 words
An apparatus as claimed in Claim 13 or 14, characterized in that the main directions of the grating strips of the first sub-grating extend at a first angle and those of the grating strips of the second sub-grating extend at a second angle to the bounding line between the sub-gratings, in that the average grating periods of the two sub-gratings are different and in that the detector pairs occupy different positions both in a direction parallel to and in a direction perpendicular to the said bounding line.
Claim 19
Dependent Claim
45 words
An apparatus as claimed in Claim 11 or 12, in which one detector is provided for each deflected auxiliary beam, characterized in that the two detectors are located on either side of the four-quadrant detector, viewed in the direction transverse to the effective track direction.
Claim 20
Dependent Claim
56 words
An apparatus as claimed in Claim 16, characterized in that in the composite detection system, viewed in the direction transverse to the effective track direction, a first and a second detector for receiving the first and the second auxiliary beam are located on a first and a second side, respectively, of the two juxtaposed detector pairs.
Claim 21
Dependent Claim
88 words
An apparatus as claimed in Claim 16, characterized in that in the composite detection system a first and second, and a third and fourth detector are provided for the first and second auxiliary beams, respectively, which are each split into two sub-beams by the first diffraction grating, and in which, viewed in the direction transverse to the effective track direction, the four detectors and the two detector pairs are juxtaposed in the sequence: first detector, first detector pair, third detector, second detector, second detector pair and fourth detector.
Claim 22
Dependent Claim
78 words
An apparatus as claimed in Claim 16, characterized in that the grating strips of the first diffraction grating are substantially parallel to those of the second diffraction grating and in that, viewed in the effective track direction, a first detector for the first auxiliary beam and a second detector for the second auxiliary beam are located on different sides of the two detector pairs, which pairs are juxtaposed, viewed in the direction transverse to the effective track direction.
Claim 23
Dependent Claim
91 words
An apparatus as claimed in Claim 17, characterized in that in the composite detection system a first and second, and a third and fourth detector are provided for the first and second auxiliary beams, respectively, which are each split into two auxiliary sub-beams by the first diffraction grating, and in which, viewed in directions transverse to the effective track direction, the first and third detectors are located on either side of the first detector pair and the second and fourth detectors are located on either side of the second detector pair.
Claim 24
Dependent Claim
91 words
An apparatus as claimed in Claim 15, characterized in that in the composite detection system a first and second, and a third and fourth detector are provided for the first and second auxiliary beams, respectively, which are each split into two zuxiliary sub-beams by the first diffraction grating, and in which, viewed in directions transverse to the effective track direction, the first and third detectors are located on either side of the first detector pair and the second and fourth detectors are located on either side of the second detector pair.
Claim 25
Independent Claim
77 words
An apparatus as claimed in Claims 18 to 23, characterized in that for each detector pair the separating strip between the two detectors extends at an acute angle to the line connecting the centre of the radiation-emitting surface of the diode laser to the position occupied by the centre of the intensity distribution of the radiation spot formed on the relevant detector pair, if the scanning beam is focused on the information plane to an optimum degree.
Claim 26
Independent Claim
47 words
An apparatus as claimed in Claims 18 to 23, characterized in that the separating strips of the two detector pairs are in principle parallel to a line connecting the centre of the radiation-emitting surface of the diode laser to the centre of the composite radiation-sensitive detection system.
Claim 27
Dependent Claim
106 words
An apparatus as claimed in Claim 1, in which the radiation-sensitive detection system is a composite photo diode which is provided in a substrate, characterized in that said substrate is provided with a block having a first surface which is directed towards the composite photo diode, and a second surface opposite to the first surface, in that a diode laser is arranged on the second surface, which laser emits a radiation beam whose principal axis is directed transversely to the plane of the substrate, and in that a monitor photo diode is present in the substrate at the side of the second surface of the block.
Claim 28
Dependent Claim
78 words
An apparatus as claimed in Claim 1, in which the radiation source is a diode laser and the radiation-sensitive detection system comprises a composite photo diode, which diode laser and photo diode are accommodated at one side within a housing, characterized in that a reflector is present at the second side of the housing, which reflector reflects a portion of the diode laser radiation towards a monitor photo diode accommodated within the housing proximate to the diode laser.
Claim 29
Dependent Claim
26 words
An apparatus as claimed in Claim 27, in which the reflector is annular, characterized in that a grating is provided in the aperture of the reflector.
Claim 30
Dependent Claim
29 words
An apparatus as claimed in Claim 27 or 28, characterized in that the diode laser, the composite photo diode and the monitor photo diode are arranged on one support.
References Cited (Backward Citations)
No citation records indexed.
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