US3787668A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Adaptive threshold unit
Assignee: United States Department of the Army
•
Filing: 1973-02-22
•
Granted: 1974-01-22
•
Expires: 1993-02-22
Abstract
Abstract In conjunction with an infrared detection device, the adaptive threshold unit eliminates much of the clutter or false targets in the field of view of the detection device. This is accomplished by converting received analog intensities which represent the true target and clutter into digital form and processing them in a special purpose digital processor. The digital processor passes target or possible target pulses only from those field of view segments which have a higher intensity than the average intensity of the eight surrounding segments. Each segment of space subtends a one milliradian by one milliradian angle and each segment of the sector being viewed is periodically compared with the surrounding segments.
Inventors
- 👤 R Currie
- 👤 T Peacher
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 21:26
CPC Classifications
G; G01; G01S; G01S3/00; G01S3/78; G01S3/782; G01S3/783; G01S3/784; G01S3/781
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
200 words
An adaptive threshold system for converting selected analog signals into digital form and comparing respective digital signals with the average signal level of subsequent and preceeding digital signals, and comprising: an analog to digital converter having an input for receiving periodic input signals and converting said signals to digital words, and having a plurality of outputs for coupling out said words; a plurality of parallel shift register delay lines having respective inputs coupled to said converter outputs for simultaneously receiving sequential bits of digital words coupled thereto and having selected tapped output positions for coupling out preselected digital word bits, a digital adding network having plural inputs coupled to selected of said tapped outputs for receiving, summing, and averaging said bits, and an output for coupling out the summed average of said plural inputs; and a comparator circuit having a first input coupled to sequentially receive a single word from a first of said tapped outputs, a second input coupled to said adding network output to sequentially receive said average sum output, and an output for coupling out an output signal when the word coupled to said first input is greater than the average word received by said second input.
Claim 2
Dependent Claim
200 words
An adaptive threshold system for converting selected analog signals into digital form and comparing respective digital signals with the average signal level of subsequent and preceeding digital signals, and comprising: an analog to digital converter having an input for receiving periodic input signals and converting said signals to digital words, and having a plurality of outputs for coupling out said words; a plurality of parallel shift register delay lines having respective inputs coupled to said converter outputs for simultaneously receiving sequential bits of digital words coupled thereto and having selected tapped output positions for coupling out preselected digital word bits, a digital adding network having plural inputs coupled to selected of said tapped outputs for receiving, summing, and averaging said bits, and an output for coupling out the summed average of said plural inputs; and a comparator circuit having a first input coupled to sequentially receive a single word from a first of said tapped outputs, a second input coupled to said adding network output to sequentially receive said average sum output, and an output for coupling out an output signal when the word coupled to said first input is greater than the average word received by said second input.
Claim 3
Dependent Claim
94 words
An adaptive threshold system as set forth in claim 1 and further comprising a multiplexer having a plurality of inputs for sequentially receiving adjacent segments of an analog signal level, a first output coupled as an input to said analog to digital converter, and a second output; a gate circuit having first and second inputs and an output, said first input being coupled to the output of said comparator for gating the output signal therefrom and said second input being coupled to the second output of said multiplexer for receiving preselected inhibiting input signals.
Claim 4
Dependent Claim
44 words
An adaptive threshold system as set forth in claim 2 and further comprising a plurality of infrared detectors arranged in a column for detecting impinging energy, said detectors having outputs coupled as inputs to said multiplexer for sequential and continuous scanning by said multiplexer.
Claim 5
Dependent Claim
82 words
An adaptive threshold system as set forth in claim 3 wherein said parallel shift register delay lines are 67 bits long, sequentially from 0 through 66, with respective bit positions 0, 1, 2, 32, 33, 34, 64, 65, and 66 being tapped, tapped output 33 being the central storage position of the delay line and being coupled to said first comparator input, and said tapped bit positions forming adjacent positions of digital words corresponding to adjacent infrared detector outputs of signal intensity.
Claim 6
Dependent Claim
132 words
In a spatial tracking system wherein adjacent sectors of space are periodically scanned for aircraft and infrared optical energy is detected sequentially from adjacent sectors, the method of discerning targets within sectors of space comprising the steps of: converting analog infrared intensities into digital words for respective segments of a spatial sector, simultaneously coupling the bits of each digital word to respective shift registers, advancing respective bits of each word simultaneously through respective shift registers, sequentially and continuously coupling respective bits of incoming digital words into said shift registers while advancing previously received word bits, sequentially and continuously monitoring selected shift register positions for comparing adjacent intensity levels, indicating a target when a selected one of said shift register positions has a signal level greater than the average signal of adjacent positions.
Claim 7
Dependent Claim
132 words
In a spatial tracking system wherein adjacent sectors of space are periodically scanned for aircraft and infrared optical energy is detected sequentially from adjacent sectors, the method of discerning targets within sectors of space comprising the steps of: converting analog infrared intensities into digital words for respective segments of a spatial sector, simultaneously coupling the bits of each digital word to respective shift registers, advancing respective bits of each word simultaneously through respective shift registers, sequentially and continuously coupling respective bits of incoming digital words into said shift registers while advancing previously received word bits, sequentially and continuously monitoring selected shift register positions for comparing adjacent intensity levels, indicating a target when a selected one of said shift register positions has a signal level greater than the average signal of adjacent positions.
Claim 8
Dependent Claim
108 words
The method of discerning targets as set forth in claim 5 and further comprising monitoring selected shift register positions by the steps of: summing the instantaneous input digital word with the first previously received word, summing the second previously received digital word with the 32nd previously received word, summing the 34th previously received word with the 64th previously received word, summing the 65th previously received digital word with the 66th previously received word, adding and averaging these summed words for providing a single average digital word, and comparing the 33rd previously received digital word with said average digital word for obtaining an output signal indicative of target presence.
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) | 1977-01-21 | 1977-07-23 | 1978-01-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-01-21 | 1981-07-23 | 1982-01-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-01-21 | 1985-07-23 | 1986-01-22 | $7700.00 | Window Closed / Lapsed |