US3687535A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Optical demodulation system
Assignee: Xerox Corp
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Filing: 1970-02-13
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Granted: 1972-08-29
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Expires: 1990-02-13
Abstract
Abstract Optically screened input information is recorded as excursions on the surface of a thermoplastic film. The excursions basically consist of a periodic carrier wave and a modulating signal containing the input information. Highly coherent light is directed incident upon the image bearing surface whereby the signal modulated deformations thereon cause the light to become diffracted. The diffracted light is then passed through a projection system including a spatial filter which is positionable in the focal plane of the system. The filter comprises a thin opaque mask having two clear apertures therein, which, when the mask is positioned in the systems focal plane, are coincident with the two first diffracted order focal spots, the two apertures being of a size capable of passing the modulated side bands of the input signal. The mask also has a third aperture centered about the optical center line of the system and being of a size such that the Airy disc of the zero diffracted order just fills, or preferably, slightly more than fills the central aperture when the two first diffracted order focal spots are centered in the other two apertures. The optical path length of one of the light beams passing through the filter is retarded in relation to the other beams whereby interference between the light beams is produced at the scan plane of the system.
Inventors
- 👤 John C Heurtley
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 15:37
CPC Classifications
G; G02; G02B; G02B27/00; G02B27/42; G02B27/4233; G02B27/4238; G02B27/46; G03; G03G; G03G16/00
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
188 words
In an optical read-out system of the type for recovering information stored on the surface of a receptor in the form of surface deformations which comprise a periodic carrier wave and a modulating signal containing the input scene information having a source of light to illuminate the receptor surface with coherent light whereby the light is diffracted in accordance with the carrier wave frequency and a projection lens for presenting the diffracted light beams at focal spots in the focal plane of the lens, the improvement apparatus comprising a spatial filter positionable in the focal plane of the lens comprising a thin opaque mask having at least three apertures therein including a central aperture located about the focal spot of the zero diffracted order being of a size smaller than the Airy disc of illumination associated with the zero diffracted order and side apertures located about the focal spots of non-zero diffracted orders and being of a size capable of passing the modulated side bands containing the input scene information and phase shift means for changing the phase relation between the light passed by central and side apertures.
Claim 2
Dependent Claim
188 words
In an optical read-out system of the type for recovering information stored on the surface of a receptor in the form of surface deformations which comprise a periodic carrier wave and a modulating signal containing the input scene information having a source of light to illuminate the receptor surface with coherent light whereby the light is diffracted in accordance with the carrier wave frequency and a projection lens for presenting the diffracted light beams at focal spots in the focal plane of the lens, the improvement apparatus comprising a spatial filter positionable in the focal plane of the lens comprising a thin opaque mask having at least three apertures therein including a central aperture located about the focal spot of the zero diffracted order being of a size smaller than the Airy disc of illumination associated with the zero diffracted order and side apertures located about the focal spots of non-zero diffracted orders and being of a size capable of passing the modulated side bands containing the input scene information and phase shift means for changing the phase relation between the light passed by central and side apertures.
Claim 3
Dependent Claim
28 words
The spatial filter of claim 1 wherein said side apertures are centered about the focal spots of the two first diffracted orders associated with the carrier wave frequency.
Claim 4
Dependent Claim
30 words
The apparatus of claim 1 wherein said phase shift means includes light retarding means for changing the optical path length of one of the diffracted orders passing through the mask.
Claim 5
Dependent Claim
44 words
The apparatus of claim 1 wherein said phase shift means includes a light retarding means mounted in the central aperture of the mask which is arranged to change the optical path length of the zero diffracted order in relation to the side diffracted orders.
Claim 6
Dependent Claim
37 words
The apparatus of claim 4 wherein said side apertures comprise two clear apertures positioned equally distant from said centrally located aperture such that all three apertures lie along a common line in the plane of said mask.
Claim 7
Dependent Claim
191 words
Apparatus for recovering data stored on the surface of a receptor in the nature of deformations having a periodic carrier wave and a carrier modulating signal containing the input scene information including means to support the deformed surface of the receptor in a plane, means to direct a plane wave front of light incident upon the deformed surface of said receptor whereby the light is diffracted in accordance with the carrier wave frequency, a lens positioned to focus the diffracted light beams at a point in the focal plane of said lens, a spatial filter positionable in and about the focal plane of said lens for passing substantially the entire Airy disc of the zero diffracted order and at least one side diffracted order, a viewing screen located at an image plane of said lens, and a carriage rigidly coupling said lens and filter relative to each other and supported for movement relative to said receptor and viewing screen to alter the optical path of light passed by the filter to change the phase relation of the light passed by the central aperture relative to the light passed by side apertures.
Claim 8
Dependent Claim
191 words
Apparatus for recovering data stored on the surface of a receptor in the nature of deformations having a periodic carrier wave and a carrier modulating signal containing the input scene information including means to support the deformed surface of the receptor in a plane, means to direct a plane wave front of light incident upon the deformed surface of said receptor whereby the light is diffracted in accordance with the carrier wave frequency, a lens positioned to focus the diffracted light beams at a point in the focal plane of said lens, a spatial filter positionable in and about the focal plane of said lens for passing substantially the entire Airy disc of the zero diffracted order and at least one side diffracted order, a viewing screen located at an image plane of said lens, and a carriage rigidly coupling said lens and filter relative to each other and supported for movement relative to said receptor and viewing screen to alter the optical path of light passed by the filter to change the phase relation of the light passed by the central aperture relative to the light passed by side apertures.
Claim 9
Dependent Claim
73 words
The apparatus of claim 6 wherein said spatial filter comprises a relatively thin opaque mask having a central aperture located about the focal spot of the zero diffracted order of a size to pass less than all the entire Airy disc and at least two side apertures therein located about the focal spots of some non-zero diffracted order and of a size to pass the side diffracted orders containing the input scene information.
Claim 10
Dependent Claim
26 words
The apparatus of claim 7 wherein said spatial filter has side apertures arranged to pass the two first diffracted orders associated with the carrier wave frequency.
Claim 11
Dependent Claim
48 words
The apparatus of claim 6 wherein said opaque mask includes two side apertures located equal distance from the central aperture such that all the apertures lie along a common line in the plane of the mask and the line extending perpendicular in relation to the periodic carrier waves.
Claim 12
Dependent Claim
28 words
The apparatus of claim 6 further including detecting means to sense the image passed by the spatial filter which is presented in the read-out plane of the system.
Claim 13
Dependent Claim
80 words
The apparatus of claim 10 wherein said detecting means to sense the image in the read-out plane of the system includes scanning means having a response capable of recording a signal voltage proportional to the intensity of the image in the read-out plane of the lens, and electrical means to demodulate the carrier frequency component of the signal voltage corresponding with the interference frequency of the zero diffracted order and the transmitted diffracted orders associated with the carrier wave frequency.
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) | 1975-08-29 | 1976-02-28 | 1976-08-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-08-29 | 1980-02-28 | 1980-08-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-08-29 | 1984-02-28 | 1984-08-29 | $7700.00 | Window Closed / Lapsed |