US5202741A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Active imaging system with Faraday filter
Assignee: United States Department of Energy
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Filing: 1992-06-29
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Granted: 1993-04-13
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Expires: 2012-06-29
Abstract
Abstract An active imaging system has a low to medium powered laser transmitter and receiver wherein the receiver includes a Faraday filter with an ultranarrow optical bandpass and a bare (nonintensified) CCD camera. The laser is locked in the vicinity of the passband of the Faraday filter. The system has high sensitivity to the laser illumination while eliminating solar background.
Inventors
- 👤 James J. Snyder
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 06:08
CPC Classifications
G; G01; G01S; G01S17/00; G01S17/88; G01S17/89
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
56 words
An active imaging system comprising: a Faraday filter having a center wavelength in the visible to near infrared; means for receiving laser light reflected from a distant target and transmitting said light to said filter; and a non-intensified CCD camera for receiving a filtered version of the laser light from the distant target from the filter.
Claim 2
Dependent Claim
56 words
An active imaging system comprising: a Faraday filter having a center wavelength in the visible to near infrared; means for receiving laser light reflected from a distant target and transmitting said light to said filter; and a non-intensified CCD camera for receiving a filtered version of the laser light from the distant target from the filter.
Claim 3
Dependent Claim
20 words
An active imaging system according to claim 1 wherein said Faraday filter has a center wavelength of approximately 852 nanometers.
Claim 4
Dependent Claim
26 words
An active imaging system according to claim 1 wherein said means for receiving and transmitting laser light reflected from a distant target comprises a telescope means.
Claim 5
Dependent Claim
25 words
An active imaging system according to claim 3 wherein said telescope means comprises a steering mirror for steering laser light received from the distant target.
Claim 6
Dependent Claim
27 words
An active imaging system according to claim 1 comprising means for providing laser light having a wavelength locked to approximately the center wavelength of the Faraday filter.
Claim 7
Dependent Claim
37 words
An active imaging system according to claim 5 wherein said means for providing laser light having a wavelength in the visible to near infrared comprises means for providing laser light having a wavelength of approximately 852 nanometers.
Claim 8
Dependent Claim
35 words
An active imaging system according to claim 5 comprising means responsive to laser light from said laser light providing means for controlling the wavelength of the laser light provided by said laser light providing means.
Claim 9
Dependent Claim
36 words
An active imaging system according to claim 7 wherein said means for controlling the wavelength of the laser light provided by said laser light providing means comprises a second Faraday filter having a predetermined center wavelength.
Claim 10
Dependent Claim
36 words
An active imaging system according to claim 7 wherein said means for controlling the wavelength of the laser light provided by said laser light providing means comprises a cesium absorption filter having a predetermined center wavelength.
Claim 11
Dependent Claim
38 words
An active imaging system according to claim 1 comprising means for transmitting a portion of the laser light received from a distant target by said laser light receiving and transmitting means to sensors other than the CCD camera.
Claim 12
Dependent Claim
44 words
An active imaging system according to claim 10 wherein said means for transmitting a portion of the laser light received from a distant target by said laser light receiving and transmitting means to sensors other than the CCD camera comprises a dichroic beam splitter.
Claim 13
Dependent Claim
29 words
An active imaging system according to claim 1 comprising means for filtering the laser light being transmitted to the Faraday filter from said laser light receiving and transmitting means.
Claim 14
Dependent Claim
35 words
An active imaging system according to claim 12 wherein said means for filtering the laser light being transmitted to the Faraday filter from said laser light receiving and transmitting means comprises a dielectric bandpass filter.
Claim 15
Dependent Claim
27 words
An active imaging system according to claim 13 wherein said dielectric bandpass filter has a center wavelength substantially equal to the center wavelength of the Faraday filter.
Claim 16
Dependent Claim
60 words
An active imaging system according to claim 5 wherein said means for providing laser light having a wavelength in the visible to near infrared comprises: a source of laser light; and means for transmitting laser light from said source to the distant target through said means for receiving and transmitting laser light reflected from the distant target to said filter.
Claim 17
Dependent Claim
55 words
An active imaging system according to claim 15 wherein said means for transmitting laser light from said source to the distant target through said means for receiving and transmitting laser light reflected from the distant target to said filter comprises a beam splitter located between said laser light receiving and transmitting means and said filter.
Claim 18
Dependent Claim
17 words
An active imaging system according to claim 16 wherein said beam splitter comprises a 50--50 beam splitter.
Claim 19
Dependent Claim
78 words
An active imaging system according to claim 16 wherein the source produces linearly polarized light and the beam splitter is highly reflective to the linearly polarized light from the source and highly transmissive to light with an orthogonal linear polarization, and further comprising a polarizer between the beam splitter and said means for receiving and transmitting laser light which changes the polarization of light reflected from the target to an orthogonal linear polarization of light from the source.
Claim 20
Dependent Claim
16 words
An active imaging system according to claim 18 wherein the polarizer is a quarter wave plate.
Claim 21
Dependent Claim
22 words
An active imaging system according to claim 1 wherein the imaging system is positioned at least about one kilometer from the target.
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) | 1996-04-12 | 1996-10-12 | 1997-04-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-04-12 | 2000-10-12 | 2001-04-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-04-12 | 2004-10-12 | 2005-04-13 | $7700.00 | Window Closed / Lapsed |