Patent US3630598A successfully refreshed from Google Patents.
US3630598A
Expired / Lapsed
US
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Optical demodulation filter
Assignee: Xerox Corp
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Filing: 1970-01-02
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Granted: 1971-12-28
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Expires: 1990-01-02
Abstract
Abstract Optically screened input information is recorded as excursions on the surface of the thermoplastic film. The excursions consist of a periodic carrier wave and a modulating signal containing the input information. Highly coherent polarized light is directed incident upon the image-bearing surface whereby the light is diffracted by the signal-modulated deformations thereon. The diffracted light is then passed through a projection system including a spatial filter positioned in the focal plane of the system comprising an opaque mask having two clear apertures therein coincident with the two first diffracted order focal spots and being of a size sufficient to pass the modulated sidebands of the input signal. A device for rotating the relative planes of polarizations of the diffracted light is positioned in at least one of the diffracted beams wherein the polarization state of the two diffracted light beams are orthogonal at the scan plane of the system.
Inventors
- 👤 William S Little Jr
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 17:01
CPC Classifications
G; G02; G02B; G02B27/00; G02B27/42; G02B27/4233; G02B27/4238; G02B27/46; G03; G03G; G03G16/00
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
120 words
A spatial filter positionable in the focal plane of an optical readout system in which a phase object is illuminated by coherent polarized light, said phase object having surface deformations thereon being composed of a periodic carrier wave and an amplitude-modulating signal containing input information, the filter comprising an opaque mask having two clear apertures therein each of which is centerable about a diffracted order associated with the carrier wave frequency and being of a size sufficient to pass the diffracted order spectrum and having associated therewith means for rotating the plane of polarization of the light passing through the filter whereby the polarization planes of the two diffracted light beams are orthogonal in the scan plane of the system.
Claim 2
Dependent Claim
120 words
A spatial filter positionable in the focal plane of an optical readout system in which a phase object is illuminated by coherent polarized light, said phase object having surface deformations thereon being composed of a periodic carrier wave and an amplitude-modulating signal containing input information, the filter comprising an opaque mask having two clear apertures therein each of which is centerable about a diffracted order associated with the carrier wave frequency and being of a size sufficient to pass the diffracted order spectrum and having associated therewith means for rotating the plane of polarization of the light passing through the filter whereby the polarization planes of the two diffracted light beams are orthogonal in the scan plane of the system.
Claim 3
Dependent Claim
23 words
The filter of claim 1 wherein the two apertures are centered about the two first diffracted orders associated with the carrier wave frequency.
Claim 4
Dependent Claim
32 words
The apparatus of claim 2 wherein said means to rotate the plane of polarization of the light passing through said filter comprises a half wave plate position in one of said apertures.
Claim 5
Dependent Claim
40 words
The apparatus of claim 3 further including light-transparent means associated with the other of said apertures and being capable of retarding the light passing through said other aperture in an amount equal to the retardation of said half wave plate.
Claim 6
Dependent Claim
51 words
The apparatus of claim 1 wherein the means to rotate the plane of polarization of the light passing through the filter rotates the plane of polarization of the light passing through one of said apertures 90* in relation to the plane of polarization of the light passing through said other aperture.
Claim 7
Dependent Claim
32 words
The apparatus of claim 5 wherein said means to rotate the plane of polarization 90* comprises an optically active material positioned in the optical path of one of the diffracted light beams.
Claim 8
Dependent Claim
165 words
Apparatus for recovering input information recorded as surface deformations on a phase object, the phase object being composed of a periodic carrier wave and an amplitude-modulating signal containing the input information including means to support the phase object in a plane with the deformed surface substantially normal to said plane, means to direct a plane wave front of polarized light substantially normal to and incident upon the deformed surface of said object whereby the light is diffracted by the periodic carrier wave, a lens positioned to focus the diffracted light at points in the back focal plane of said lens, a spatial filter positionable at about the back focal plane of said lens for passing the light associated with the two diffracted orders associated with the carrier wave frequency, and means to change the polarization states of the two diffracted orders in relation to each other wherein the two diffracted light beams passed by said filter are orthogonal in the image plane of the lens.
Claim 9
Dependent Claim
165 words
Apparatus for recovering input information recorded as surface deformations on a phase object, the phase object being composed of a periodic carrier wave and an amplitude-modulating signal containing the input information including means to support the phase object in a plane with the deformed surface substantially normal to said plane, means to direct a plane wave front of polarized light substantially normal to and incident upon the deformed surface of said object whereby the light is diffracted by the periodic carrier wave, a lens positioned to focus the diffracted light at points in the back focal plane of said lens, a spatial filter positionable at about the back focal plane of said lens for passing the light associated with the two diffracted orders associated with the carrier wave frequency, and means to change the polarization states of the two diffracted orders in relation to each other wherein the two diffracted light beams passed by said filter are orthogonal in the image plane of the lens.
Claim 10
Dependent Claim
54 words
The apparatus of claim 7 wherein said means to change the polarization state of the diffracted light includes means positioned in the optical path of one of said diffracted orders for rotating the plane of polarization of the light associated with said one diffracted order about 90* in relation to said other diffracted order.
Claim 11
Dependent Claim
53 words
The apparatus of claim 7 wherein means to change the polarization state of said diffracted light includes means positioned in the optical paths of each of the two diffracted orders for rotating the polarization planes of each of the diffracted beams wherein two beams are orthogonal at the image plane of said lens.
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) | 1974-12-27 | 1975-06-28 | 1975-12-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-12-27 | 1979-06-28 | 1979-12-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-12-27 | 1983-06-28 | 1983-12-28 | $7700.00 | Window Closed / Lapsed |