US3781547A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Optical receiver with extended source discrimination
Assignee: United States Department of the Air Force
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Filing: 1972-11-22
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Granted: 1973-12-25
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Expires: 1992-11-22
Abstract
Abstract An optical receiver comprising a lens system for forming an image of a distant light source at its focal plane. The light on either side of the focal plane is intercepted by a reticle of alternate opaque and transparent strips of equal widths which move at constant speed and always in the same direction across the light while the reticle continuously oscillates back and forth along the optical axis between extreme positions one of which is in the focal plane of the lens. A photodetector converts the light transmitted by the reticle into a proportionate electrical signal. An inhibit gate located between the output of the photodetector and the receiver output circuit is made to respond to the presence of an amplitude modulation of the AC component of the photodetector output at either the oscillating frequency of the reticle or twice this frequency to prevent an output from the receiver when either of these modulations is present.
Inventors
- 👤 C Thomas
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 11:14
CPC Classifications
G; G01; G01S; G01S3/00; G01S3/78; G01S3/781
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
205 words
An optical receiver comprising a lens system for forming an image of a distant light source at its focal plane; a chopping reticle of alternate opaque and transparent strips of equal widths; means for imparting two simultaneous motions to said reticle, one motion constituting a continuous oscillation of the reticle back and forth along the optical axis of the lens between two extreme positions one of which is in the focal plane of the lens, and the other motion constituting a continuous constant speed movement of said strips in a direction normal to the strips and to the optical axis of the lens; a photodetector receiving the light transmitted by the reticle and converting said light into a proportionate electrical signal in its output circuit, said signal having an alternating component due to the light chopping effect of the reticle; a receiver output circuit; a signal transmission circuit including a normally transmitting gate circuit coupled between the photodetector output circuit and the receiver output circuit; and means responsive to amplitude modulation of the alternating component of the photodetector output signal at either the oscillation frequency of said article or twice this frequency to inhibit signal transmission through said gate during the presence of said modulation.
Claim 2
Dependent Claim
205 words
An optical receiver comprising a lens system for forming an image of a distant light source at its focal plane; a chopping reticle of alternate opaque and transparent strips of equal widths; means for imparting two simultaneous motions to said reticle, one motion constituting a continuous oscillation of the reticle back and forth along the optical axis of the lens between two extreme positions one of which is in the focal plane of the lens, and the other motion constituting a continuous constant speed movement of said strips in a direction normal to the strips and to the optical axis of the lens; a photodetector receiving the light transmitted by the reticle and converting said light into a proportionate electrical signal in its output circuit, said signal having an alternating component due to the light chopping effect of the reticle; a receiver output circuit; a signal transmission circuit including a normally transmitting gate circuit coupled between the photodetector output circuit and the receiver output circuit; and means responsive to amplitude modulation of the alternating component of the photodetector output signal at either the oscillation frequency of said article or twice this frequency to inhibit signal transmission through said gate during the presence of said modulation.
Claim 3
Dependent Claim
114 words
Apparatus as claimed in claim 1 in which said reticle and said means for imparting two simultaneous motions thereto comprise: a disc having said alternate opaque and transparent strips in the form of a band of sectorial strips at its periphery, said disc being mounted at its center on a shaft with the angle between the disc and the shaft slightly less than 90* in order to impart a wobble to the disc when the shaft is rotated, said shaft being parallel to the optical axis of the lens and spaced therefrom as required for the optical axis to pass through said band of strips, and means for rotating said shaft at constant speed.
Claim 4
Dependent Claim
98 words
Apparatus as claimed in claim 2 in which the last named means of said claim comprises: a demodulator situated in said signal transmission circuit between the photodetector output circuit and said gate circuit for deriving the amplitude modulation of the alternating component of the photodetector output signal; a filter passing only the said oscillation frequency of said reticle and twice that frequency; means for rectifying the output of said filter to produce a direct inhibit voltage; and means for applying said inhibit voltage to said gate for preventing signal transmission therethrough in the presence of the inhibit voltage.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-12-24 | 1977-06-25 | 1977-12-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-12-24 | 1981-06-25 | 1981-12-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-12-24 | 1985-06-25 | 1985-12-25 | $7700.00 | Window Closed / Lapsed |