US3913076A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Reading out and tracking a recorded diffractive trace with an elongated read out spot
Assignee: Thomson-Brandt SA
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Filing: 1974-02-27
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Granted: 1975-10-14
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Expires: 1994-02-27
Abstract
Abstract The present invention relates to the optical read-out of a diffractive track carried by a record. The read-out system in accordance with the invention comprises means for projecting onto the surface of the record, a read-out spot of oblong form whose major axis intersects the longitudinal axis of the read-out track. Photodetector means receive separately the diffracted radiation components corresponding to the zero order and to higher orders.
Inventors
- 👤 Jean Claude Lehureau
- 👤 Claude Bricot
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 01:18
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/08; G11B7/09; G11B7/0908; G11B7/0917; G11B7/004; G11B7/005; G11B7/12; G11B7/24; G11B7/2407; G11B7/24085
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
166 words
Optical system for reading-out a diffractive track of predetermined width forming at the surface of a record an embossed pattern constituted by successive diffracting elements, said optical system comprising: a source of radiant energy, illuminating means associated with said source for projecting onto said surface an elongated read-out spot, and photo-electric means arranged for receiving selected portions of the radiant energy emerging from the illuminated portion of said surface; said elongated read-out spot having a major axis at an angle with the longitudinal axis of said track for exploring said surface along a strip having a width greater than said predetermined width; said photo-electric means comprising a main photodetector, further photodetectors and electrical transmission means coupled to said photodetectors; said main photodetector receiving at least one portion of the zero order diffracted component contained in the radiation emerging from the illuminated portion of said surface; said further photodetectors being arranged outside the beam containing said zero order diffracted component for picking-up diffracted components of higher orders.
Claim 2
Dependent Claim
166 words
Optical system for reading-out a diffractive track of predetermined width forming at the surface of a record an embossed pattern constituted by successive diffracting elements, said optical system comprising: a source of radiant energy, illuminating means associated with said source for projecting onto said surface an elongated read-out spot, and photo-electric means arranged for receiving selected portions of the radiant energy emerging from the illuminated portion of said surface; said elongated read-out spot having a major axis at an angle with the longitudinal axis of said track for exploring said surface along a strip having a width greater than said predetermined width; said photo-electric means comprising a main photodetector, further photodetectors and electrical transmission means coupled to said photodetectors; said main photodetector receiving at least one portion of the zero order diffracted component contained in the radiation emerging from the illuminated portion of said surface; said further photodetectors being arranged outside the beam containing said zero order diffracted component for picking-up diffracted components of higher orders.
Claim 3
Dependent Claim
48 words
Optical read-out system as claimed in claim 1, wherein said illuminating means comprise a projection objective lens associated with optical filter means of non-uniform transparency effecting apodization of the diffraction pattern projected onto said surface; the body of said projected diffraction pattern corresponding substantially to said read-out spot.
Claim 4
Dependent Claim
25 words
Optical read-out system as claimed in claim 1, wherein said illuminating means comprise at least one holographic lens; said source being a coherent radiation source.
Claim 5
Dependent Claim
81 words
Optical read-out system as claimed in claim 1, wherein said further photodetectors comprise two lateral photodetectors located respectively to either side of the plane containing said longitudinal axis and the optical axis of said illuminating means; said electrical transmission means comprising a first differential amplifier having two inputs respectively supplied by said lateral photodetectors, and a second differential amplifier having two inputs respectively supplied from said main photodetector and with the mean value of the voltages produced by said lateral photodetectors.
Claim 6
Dependent Claim
99 words
Optical read-out system as claimed in claim 4, wherein said illuminating means comprise a projection objective lens causing the radiation issuing from said source to converge at a geometric point located, considering the ideal read-out position, in said surface; said lateral photodetectors being arranged apart from one another between said source and the entry face of said projection objective lens for delimiting a pupil of elongated from; said main photodetector receiving through the medium of a semi-transparent plate arranged between said lateral photodetectors and said source, a fraction of the zero order diffracted component reflected by said read-out surface.
Claim 7
Dependent Claim
81 words
Optical read-out system as claimed in claim 1, wherein said illuminating means comprise a projection objective lens associatEd with an opaque mask containing an elongated aperture; the geometric centre of convergence of the radiation issuing from said objective lens, in the ideal read-out position, being located in said surface and at the centre of said read-out elongated spot; said main contour in relation to said geometric centre of the perimeter of said aperture; said further photodetectors being located outside said contour.
Claim 8
Dependent Claim
31 words
Optical read-out system as claimed in claim 6, wherein said aperture is a rectangular aperture having a major axis; said major axis forming with the optical longitudinal axis of said track.
Claim 9
Dependent Claim
27 words
Optical read-out system as claimed in claim 6, wherein anamorphotic optical transmission means are arranged between said source and the entry face of said projection objective lens.
Claim 10
Dependent Claim
40 words
Optical read-out system as claimed in claim 8, wherein said anamorphotic optical transmission means comprise a divergent cylindrical lens and a convergent cylindrical lens, having a common focal line disposed normally in relation to the longitudinal axis of said track.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-10-13 | 1979-04-14 | 1979-10-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-10-13 | 1983-04-14 | 1983-10-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-10-13 | 1987-04-14 | 1987-10-14 | $7700.00 | Window Closed / Lapsed |