Patent DE1126073B successfully refreshed from Google Patents.
US3721500A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Instrument for measuring the depolarization of backscattered light
Assignee: United States Department of the Navy
•
Filing: 1971-08-06
•
Granted: 1973-03-20
•
Expires: 1991-08-06
Abstract
Abstract An instrument capable of obtaining information on the polarization properties of ocean waters. Operation of the instrument is as follows: Light from a He-Ne laser passes through a rotating beam chopper, a rotating linear polarizer, and a light guide and an aperture (to block spurious reflections) into the scattering medium, generally seawater. A portion of the backscattered light is intercepted by an analyzer-detector module, and after amplification the detector output is displayed on an oscilloscope. The beam is chopped at 20 times the rotational frequency of the polarizer. This provides an a-c backscatter signal which is independent of detector drift and changes in background illumination, if detector saturation is avoided. The rotating polarizer produces a modulation of the signal at twice the rotational frequency. The maximum signal Pmax occurs when the polarizer and analyzer are in the ''''aligned'''' position, and the minimum signal Pmin occurs when they are ''''crossed.'''' The degree of polarization is given by
Inventors
- 👤 R Fugitt
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 00:38
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/17; G01N21/21; G01N21/47; G01N2021/4792
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
301 words
An instrument for measuring the depolarization of backscattered light, from a target located in a target area, comprising: a housing, also serving as a support for the various components of the instrument; means, disposed within the housing, for producing a beam of collimated, polarized light, the beam traversing a path; means, disposed within the housing, for chopping, or periodically interrupting, the beam of light; a polarizing plate, disposed within the housing, which is inserted in the path of the beam of polarized light when the light is not interrupted; means for rotating the polarizing plate, to cause the polarization of the beam of polarized light which has traversed the polarizing plate to vary; a light guide having two ends disposed within the housing, for channeling the beam of varying polarized light from one end and permitting it to exit through the other end; a window, disposed at one end of the housing, which permits light leaving the light guide to illuminate the target area and be reflected back into the instrument; a quarter-wave plate, disposed within the housing in a manner to be alternately interposed in and out of the light path between the window and the light guide; and an analyzer-detector assembly, disposed within the housing, comprising; a linear polarization analyzer so disposed as to intercept the light reflected off the target and back through the window; a light collector, including a narrow-bandpass filter, collecting lens, and diaphragm, for filtering and focusing the analyzed reflected light; and a photodetector, whose output comprises a detected voltage, for measuring the intensity of the focused reflected light, thereby enabling a comparison to be made of the intensity of the reflected or back-scattered light, and therefore of the detected voltage, when the quarter-wave plate is in the beam path and when it is not.
Claim 2
Dependent Claim
301 words
An instrument for measuring the depolarization of backscattered light, from a target located in a target area, comprising: a housing, also serving as a support for the various components of the instrument; means, disposed within the housing, for producing a beam of collimated, polarized light, the beam traversing a path; means, disposed within the housing, for chopping, or periodically interrupting, the beam of light; a polarizing plate, disposed within the housing, which is inserted in the path of the beam of polarized light when the light is not interrupted; means for rotating the polarizing plate, to cause the polarization of the beam of polarized light which has traversed the polarizing plate to vary; a light guide having two ends disposed within the housing, for channeling the beam of varying polarized light from one end and permitting it to exit through the other end; a window, disposed at one end of the housing, which permits light leaving the light guide to illuminate the target area and be reflected back into the instrument; a quarter-wave plate, disposed within the housing in a manner to be alternately interposed in and out of the light path between the window and the light guide; and an analyzer-detector assembly, disposed within the housing, comprising; a linear polarization analyzer so disposed as to intercept the light reflected off the target and back through the window; a light collector, including a narrow-bandpass filter, collecting lens, and diaphragm, for filtering and focusing the analyzed reflected light; and a photodetector, whose output comprises a detected voltage, for measuring the intensity of the focused reflected light, thereby enabling a comparison to be made of the intensity of the reflected or back-scattered light, and therefore of the detected voltage, when the quarter-wave plate is in the beam path and when it is not.
Claim 3
Dependent Claim
22 words
The instrument according to claim 1, wherein the means for producing a beam of collimated polarized light comprises a laser light source.
Claim 4
Dependent Claim
59 words
The instrument according to claim 2, wherein the means for interrupting the beam of light and the polarizing plate comprise an opaque toothed wheel, or rotator, with openings between the teeth, and with a polarizing material at the openings between the teeth, the plane of polarization of the material being oriented with respect to a diameter of the wheel.
Claim 5
Dependent Claim
52 words
The instrument according to claim 3, wherein the plane of polarization of the polarizing material at openings between the teeth of one half of the wheel is oriented at right angles to the plane of polarization of the material at the openings between the teeth of the other half of the wheel.
Claim 6
Dependent Claim
22 words
The instrument according to claim 4, further comprising: electronic circuitry connected to the output of the photodetector, for amplifying the detected 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) | 1976-03-19 | 1976-09-18 | 1977-03-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-03-19 | 1980-09-18 | 1981-03-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-03-19 | 1984-09-18 | 1985-03-20 | $7700.00 | Window Closed / Lapsed |