Patent EP0583036A2 successfully refreshed from Google Patents.
EP0583036A2
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Device for optically scanning a surface
Assignee: Koninklijke Philips NV
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Filing: 1993-08-09
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Granted: —
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Expires: 2013-08-09
Abstract
Abstract A device for optically scanning an information plane (2) having tracks (5) is described. The radiation supplied by a radiation source (7) is focused on the information plane by an objective system (8). The beam reflected by the information plane is incident on a dividing element, for example a grating (12) which divides the beam into two halves along a dividing line (17). Two sub-gratings (15, 16) at both sides of the dividing line each form a sub-beam from one half of the beam, which sub-beams are detected by a detection system (10). A focus error signal is generated from the detector signals. According to the invention, the modulation of the focus error signal by the track structure will be minimal if the dividing line (17) is located at an angle between 15° and 80° to the direction of the tracks.
Inventors
- 👤 Willem Gerard c/o Int. Octrooibureau B.V. Opheij
- 👤 Jozef P.H. c/o Int. Octrooibureau B.V. Benshop
- 👤 Heidrun c/o Int. Octrooibureau B.V. Steinhauser
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 05:53
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/12; G11B7/13; G11B7/131; G11B7/135; G11B7/1353
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
119 words
A device for optically scanning tracks (4) in a radiation-reflecting information plane (2), which device comprises a radiation source (7) for supplying a scanning beam (6), an objective system (8) for focusing the scanning beam to a scanning spot (S a ) on the information plane, a dividing element (12, 55) comprising two sub-areas (15, 16) located symmetrically at both sides of a dividing line (17) and arranged in the optical path of the radiation from the information plane for splitting at least a part of said radiation into two scanning sub-beams (13, 14), and a radiation-sensitive detection system (10), characterized in that the angle between the dividing line and the effective track direction is between 15° and 80°.
Claim 2
Dependent Claim
17 words
A device as claimed in Claim 1, characterized in that the angle is between 30° and 60°.
Claim 3
Dependent Claim
32 words
A device as claimed in Claim 1 or 2, characterized in that the dividing element is a prismatic dividing plate (55) in which each sub-area consists of a prism face (56, 57).
Claim 4
Dependent Claim
30 words
A device as claimed in Claim 1 or 2, characterized in that the dividing element is a diffraction element (12), in which each sub-area consists of a sub-grating (15, 16).
Claim 5
Independent Claim
116 words
A device as claimed in any one of Claims 1 to 4, characterized in that a further diffraction element (30) having substantially straight grating lines is arranged in the optical path of the scanning beam (6) between the radiation source (7) and the objective system (8) for splitting the beam emitted by the radiation source into the scanning beam and two auxiliary beams (31, 32), which auxiliary beams are focused by the objective system to two further radiation spots (S b , S c ) on the information plane (2), and in that the device comprises two further detection systems (35, 40) each being associated with one of the auxiliary beams reflected by the information plane.
Claim 6
Dependent Claim
68 words
A device as claimed in Claim 5, characterized in that the detection systems (35, 40) for the auxiliary beams (31, 32) are located at both sides of the detection system (10) for the scanning beam (6) in a direction transverse to the perpendicular from the centre of the detection system (10) for the scanning beam to the optical axis of the zero-order beam of the diffraction element (12).
Claim 7
Dependent Claim
101 words
A device as claimed in Claim 5, characterized in that the detection systems (10, 35, 40) for the scanning beam (6), the first auxiliary beam (31) and the second auxiliary beam (32) comprise a first and second (43, 44), a third and fourth (36, 37), and a fifth and sixth detector (41, 42), respectively, the six detectors being juxtaposed in the sequence: three, one, five, four, two, six, viewed in a direction transverse to the perpendicular from the centre of the detection system (10) for the scanning beam to the optical axis of the zero-order beam of the diffraction element (12'').
Claim 8
Independent Claim
53 words
A device as claimed in any one of Claims 1 to 7, characterized in that the detection system (10) for the scanning beam (6) comprises two detectors, at least one of which is divided by means of a bounding line (22) into two detection elements (20, 21) for detecting a scanning sub-beam (13).
Claim 9
Dependent Claim
36 words
A device as claimed in Claim 8, characterized in that the bounding line (22) between the detection elements (20, 21) is substantially directed towards the optical axis of the zero-order beam of the diffraction element (12).
Claim 10
Independent Claim
25 words
A device as claimed in any one of Claims 1 to 9, characterized in that the sub-areas (56, 57; 71, 72) have different optical strengths.
Claim 11
Independent Claim
32 words
A device as claimed in any one of Claims 1 to 10, characterized in that the dividing element (12, 12', 12'', 45, 55, 70) and/or the further diffraction element (30) are reflecting.
References Cited (Backward Citations)
No citation records indexed.
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