US5179528A
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Signal processing system and method implementing a non-linear transfer function approximated by a piecewise linear transformation
Assignee: Raytheon Co
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Filing: 1992-02-26
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Granted: 1993-01-12
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Expires: 2012-02-26
Abstract
Abstract A programmable PLT transfer function circuit (50) uses a piecewise linear transformation (PLT) to approximate a non-linear transfer function (FIGS. 1B and 1C). The non-linear transfer function is approximated by a selected number of linear PLT segment transfer functions, each of which applies to a selected range of input data values, and is characterized by a PLT transformation (mx+b) in which output data is obtained by multiplying the input data by a gain coefficient and then adding an offset coefficient. The gain and offset coefficients that characterize the PLT segment transfer functions are updated at regular intervals, and stored in the PLT transfer function circuit (50). For each input data sample, segment selection logic (52) selects the appropriate PLT segment. The input data sample is then referenced (61) to the segment breakpoint (i.e. the initial data value) for that segment. The referenced input data sample is then multiplied (62) by the appropriate gain coefficient provided by gain selection logic (56). The gain multiplication operation is a quasi-floating point operation performed by a funnel shifter (63) and a multiplier (64 ). An offset addition operation (66) then adds to the gain-multiplied input data sample the appropriate offset coefficient provided by offset coefficient selection logic (58), to complete the PLT transformation. The PLT transfer function approximation technique is described in connection with a range compression system for thermal imaging.
Inventors
- 👤 James E. Robertson
- 👤 Jon C. Noeth
- 👤 Terry L. Zumwalt
- 👤 Glenn T. Mortland
- 👤 David O. Box
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 21:08
CPC Classifications
G; G06; G06T; G06T9/00; G06T9/001
Claims Analysis
Total Claims: 41
Claim 1
Independent Claim
140 words
A signal processing system implementing a non-linear PLT transfer function approximated by a piecewise linear transformation (PLT), comprising: a PLT processor capable of receiving input data and processing said input data in order to produce a plurality of coefficients corresponding to said processed input data, said coefficients include segment, gain, and offset coefficients; a PLT transfer function circuit coupled to said PLT processor and capable of receiving said input data and said coefficients in order to range compress said input data into a smaller output data format according to the non-linear PLT transfer function, the non-linear PLT transfer function determined from said coefficients and from a plurality of segments established by said PLT transfer function circuit from said input data according to a range of values of said input data, said coefficients corresponding to each of said plurality of segments.
Claim 2
Dependent Claim
140 words
A signal processing system implementing a non-linear PLT transfer function approximated by a piecewise linear transformation (PLT), comprising: a PLT processor capable of receiving input data and processing said input data in order to produce a plurality of coefficients corresponding to said processed input data, said coefficients include segment, gain, and offset coefficients; a PLT transfer function circuit coupled to said PLT processor and capable of receiving said input data and said coefficients in order to range compress said input data into a smaller output data format according to the non-linear PLT transfer function, the non-linear PLT transfer function determined from said coefficients and from a plurality of segments established by said PLT transfer function circuit from said input data according to a range of values of said input data, said coefficients corresponding to each of said plurality of segments.
Claim 3
Dependent Claim
32 words
The signal processing system of claim 1, wherein said PLT processor performs a histographic distribution of said input data values to produce said coefficients necessary to derive the non-linear PLT transfer function.
Claim 4
Dependent Claim
28 words
The signal processing system of claim 2, wherein said PLT processor updates said coefficients at selected intervals using said histographic distribution of said input data for such intervals.
Claim 5
Dependent Claim
24 words
The signal processing system of claim 3, wherein said input data comprises a sequence of digital samples, each with an associated input data value.
Claim 6
Dependent Claim
29 words
The signal processing system of claim 1, wherein said PLT processor is responsive to said input data to provide said segment coefficients identifying each of said plurality of segments.
Claim 7
Dependent Claim
34 words
The signal processing system of claim 5, wherein each segment coefficient comprises a segment breakpoint corresponding to an initial data value of said range of values of said input data for a corresponding segment.
Claim 8
Dependent Claim
47 words
The signal processing system of claim 6, wherein said PLT transfer function circuit comprises: reference breakpoint subtraction logic circuitry capable of subtracting from each input data value a corresponding segment breakpoint coefficient such that each of said input data values is referenced to said corresponding segment breakpoint.
Claim 9
Dependent Claim
102 words
The signal processing system of claim 1, wherein said PLT transfer function circuit further comprises: a gain multiplication logic circuit for multiplying each of said values of said input data by a corresponding gain coefficient to obtain a gain multiplication value; an offset addition logic circuit for adding to said gain multiplication value a corresponding offset coefficient; and a coefficient logic circuit capable of storing said gain and offset coefficients provided by said PLT processor, and capable of providing gain and offset coefficients respectively to said gain multiplication logic circuit and said offset addition logic circuit in synchronism with said input data.
Claim 10
Dependent Claim
61 words
A signal processing system of claim 8, wherein said coefficient logic circuit comprises: a gain coefficient logic circuit capable of storing said gain coefficients, and capable of providing said gain coefficients to said gain multiplication logic circuit; and an offset coefficient logic circuit capable of storing said offset coefficients, and capable of providing offset coefficients to said offset addition logic circuit.
Claim 11
Dependent Claim
18 words
The signal processing system of claim 9, wherein said gain and offset coefficients are stored in respective latches.
Claim 12
Dependent Claim
37 words
The signal processing system of claim 1, wherein said PLT transfer function circuit comprises: segment selection logic circuitry synchronized with said input data for sequentially generating segment codes representative of corresponding segments for said input data values.
Claim 13
Dependent Claim
65 words
The signal processing system of claim 11, wherein said segment selection logic circuitry comprises: comparison logic circuitry capable of comparing each input data value with each segment coefficient, and capable of providing comparison signals representative of which segment includes which of said input data value within its assigned range; and a segment selector responsive to said comparison signals and capable of generating said segment codes.
Claim 14
Dependent Claim
37 words
The signal processing system of claim 12, wherein said PLT transfer function circuit comprises: segment coefficient logic circuitry capable of storing said segment coefficients, and capable of providing said segment coefficients to said segment selection logic circuitry.
Claim 15
Dependent Claim
70 words
The signal processing system of claim 1, wherein said gain coefficient includes an exponent field and a mantissa field, and wherein said gain multiplication logic circuit comprises: an exponentiation logic circuit for exponentiating said input data values using said gain coefficient exponent field to obtain an exponentiated input data value; and a mantissa multiplier logic circuit for multiplying said exponentiated input data value by a corresponding gain coefficient mantissa field.
Claim 16
Dependent Claim
30 words
The signal processing system of claim 14, wherein said exponentiation logic circuit comprises a funnel shifter capable of performing the exponentiation operation and providing a selected amount of range compression.
Claim 17
Dependent Claim
277 words
A range compression system implementing a non-linear PLT transfer function approximated by a piecewise linear transformation (PLT) to range compress input digital data samples having an input range into output data samples having a compressed range, comprising: a PLT processor capable of receiving the input digital data samples and processing the input digital data samples to produce a plurality of coefficients corresponding to said processed input digital data samples, said coefficients including segment, gain, and offset coefficients; a PLT transfer function circuit coupled to said PLT processor and capable of receiving said input digital data samples and said coefficients in order to range compress said input digital data samples into a smaller output format according to the non-linear PLT transfer function, the non-linear PLT transfer function determined from said coefficients and from a plurality of segments established by said PLT transfer function circuit from said input digital data samples according to a range of values of said input digital data samples, said coefficients corresponding to each of said plurality of segments, said PLT transfer function circuit comprising: a segment selection logic circuit synchronized with the input digital data samples for sequentially generating segment codes representative of corresponding segments for the input digital data samples; a gain multiplication logic circuit responsive to each segment code for multiplying a corresponding input digital data sample by a corresponding gain coefficient to obtain a gain multiplication value; and an offset addition logic circuit responsive to each segment code for adding a corresponding offset coefficient to said gain multiplication value such that each input digital data sample is transformed into a range-compressed output data sample according to the non-linear PLT transfer function.
Claim 18
Dependent Claim
277 words
A range compression system implementing a non-linear PLT transfer function approximated by a piecewise linear transformation (PLT) to range compress input digital data samples having an input range into output data samples having a compressed range, comprising: a PLT processor capable of receiving the input digital data samples and processing the input digital data samples to produce a plurality of coefficients corresponding to said processed input digital data samples, said coefficients including segment, gain, and offset coefficients; a PLT transfer function circuit coupled to said PLT processor and capable of receiving said input digital data samples and said coefficients in order to range compress said input digital data samples into a smaller output format according to the non-linear PLT transfer function, the non-linear PLT transfer function determined from said coefficients and from a plurality of segments established by said PLT transfer function circuit from said input digital data samples according to a range of values of said input digital data samples, said coefficients corresponding to each of said plurality of segments, said PLT transfer function circuit comprising: a segment selection logic circuit synchronized with the input digital data samples for sequentially generating segment codes representative of corresponding segments for the input digital data samples; a gain multiplication logic circuit responsive to each segment code for multiplying a corresponding input digital data sample by a corresponding gain coefficient to obtain a gain multiplication value; and an offset addition logic circuit responsive to each segment code for adding a corresponding offset coefficient to said gain multiplication value such that each input digital data sample is transformed into a range-compressed output data sample according to the non-linear PLT transfer function.
Claim 19
Dependent Claim
50 words
The range compression system of claim 16, wherein said PLT processor performs a histographic distribution of the input digital data sample values, such that for each segment a magnitude of a corresponding gain coefficient is related to a proportion of input digital data sample values that are within said segment.
Claim 20
Dependent Claim
32 words
The range compression system of claim 17, wherein said segment, gain and offset coefficients are updated at selected intervals using said histographic distribution of the input digital data samples for such intervals.
Claim 21
Dependent Claim
55 words
The range compression system of claim 18, wherein the input digital data samples comprise image pixel samples that are to be range compressed into a video data format, and wherein, for each update interval, said gain coefficients are selected to achieve optimum contrast based on said histographic distribution of image pixel samples within said segments.
Claim 22
Dependent Claim
33 words
The range compression system of claim 16, wherein each segment coefficient comprises a segment breakpoint corresponding to an initial data value for said range of input digital data samples for a corresponding segment.
Claim 23
Dependent Claim
65 words
The range compression system of claim 20, wherein said PLT transfer function circuit comprises: a reference breakpoint subtraction logic circuit for subtracting from each input digital data sample a corresponding segment breakpoint coefficient prior to gain multiplication by said gain multiplication logic circuit or offset addition by said offset addition logic circuit; such that the input digital data sample is referenced to said segment breakpoint.
Claim 24
Dependent Claim
60 words
The range compression system of claim 16, wherein said PLT transfer function circuit comprises: a coefficient logic circuit capable of storing said segment, gain and offset coefficients provided by said PLT processor, and capable of providing gain and offset coefficients respectively to said gain multiplication logic circuit and offset addition logic circuit in synchronism with the input digital data samples.
Claim 25
Dependent Claim
100 words
The range compression system of claim 22, wherein said coefficient logic circuit comprises: a segment coefficient logic circuit capable of storing segment coefficients, and capable of providing segment coefficients to said segment selection logic circuit in synchronism with the input digital data samples; a gain coefficient logic circuit capable of storing gain coefficients, and capable of providing gain coefficients to said gain multiplication logic circuit in response to said segment codes; and an offset coefficient logic circuit capable of storing offset coefficients, and capable of providing offset coefficients to said offset addition logic circuit in response to said segment codes.
Claim 26
Dependent Claim
18 words
The range compression system of claim 23, wherein said segment, gain, and offset coefficients are stored in latches.
Claim 27
Dependent Claim
67 words
The range compression system of claim 16, wherein said segment selection logic circuit comprises: a comparison logic circuit capable of comparing each input digital data sample with each segment coefficient, and capable of providing comparison signals representative of which segment includes which input digital data sample value within its assigned range; and a segment selector responsive to said comparison signals and capable of generating said segment codes.
Claim 28
Dependent Claim
77 words
The range compression system of claim 16, wherein said gain coefficient includes an exponent field and a mantissa field, and said gain multiplication logic circuit comprises: an exponentiation logic circuit capable of exponentiating the input digital data sample using a corresponding gain coefficient exponent field specified by a corresponding segment code to obtain an exponentiated input sample; and a mantissa multiplier logic circuit capable of multiplying said exponentiated input sample by a corresponding gain coefficient mantissa field.
Claim 29
Dependent Claim
30 words
The range compression system of claim 26, wherein said exponentiation logic circuit comprises a funnel shifter capable of performing the exponentiation operation and providing a selected amount of range compression.
Claim 30
Independent Claim
164 words
A method of signal processing using a non-linear piecewise linear transformation (PLT) transfer function approximated by a PLT, comprising the steps of: (a) providing a PLT processor; (b) processing input data in said PLT processor to produce a plurality of coefficients corresponding to said input data and establish a plurality of segments according to a range of values of said input data, said coefficients including segment, gain and offset coefficients; (c) providing a PLT transfer function circuit coupled to said PLT processor; and (d) receiving said input data and said coefficients from said PLT processor at said transfer function circuit to range compress said input data into smaller output data format according to the non-linear PLT transfer function, the non-linear PLT transfer function determined from said coefficients and from a plurality of segments established by said PLT transfer function circuit from said input data according to a range of values of said input data, said coefficients corresponding to each of said plurality of segments.
Claim 31
Independent Claim
164 words
A method of signal processing using a non-linear piecewise linear transformation (PLT) transfer function approximated by a PLT, comprising the steps of: (a) providing a PLT processor; (b) processing input data in said PLT processor to produce a plurality of coefficients corresponding to said input data and establish a plurality of segments according to a range of values of said input data, said coefficients including segment, gain and offset coefficients; (c) providing a PLT transfer function circuit coupled to said PLT processor; and (d) receiving said input data and said coefficients from said PLT processor at said transfer function circuit to range compress said input data into smaller output data format according to the non-linear PLT transfer function, the non-linear PLT transfer function determined from said coefficients and from a plurality of segments established by said PLT transfer function circuit from said input data according to a range of values of said input data, said coefficients corresponding to each of said plurality of segments.
Claim 32
Dependent Claim
30 words
The signal processing method of claim 28 wherein said step of processing input data in said PLT processor includes performing a histographic distribution of said values of said input data.
Claim 33
Dependent Claim
30 words
The signal processing method of claim 29 and further comprising the step of updating said coefficients at selected intervals using said histographic distribution of said input data for such intervals.
Claim 34
Dependent Claim
23 words
The signal processing method of claim 28, further comprising the step of providing a segment coefficient that corresponds to each of said segments.
Claim 35
Dependent Claim
29 words
The signal processing method of claim 31, wherein said segment coefficient comprises a segment breakpoint corresponding to an initial data value of said input data for a corresponding segment.
Claim 36
Dependent Claim
20 words
The signal processing method of claim 32, further comprising the step of referencing said input data to said segment breakpoint.
Claim 37
Dependent Claim
31 words
The signal processing method of claim 31, further comprising the step of sequentially generating segment codes representative of corresponding segments for each input data value in synchronism with said input data.
Claim 38
Dependent Claim
54 words
The signal processing method of claim 34, wherein the step of generating segment codes comprises the steps of: comparing each input data value with each segment coefficient; providing comparison signals representative of which segment includes which input data value within its assigned range; and generating said segment codes in response to said comparison signals.
Claim 39
Dependent Claim
25 words
The signal processing method of claim 28, further comprising the steps of: storing said coefficients; and providing said coefficients in synchronism with said input data.
Claim 40
Dependent Claim
64 words
The signal processing method of claim 28, wherein said gain coefficient includes an exponent field and a mantissa field, and wherein the step of applying said coefficients to corresponding segments comprises the steps: exponentiating each input data value using said gain coefficient exponent field to obtain an exponentiated input data value; and multiplying said exponentiated input data value by said gain coefficient mantissa field.
Claim 41
Dependent Claim
31 words
The signal processing method of claim 37, wherein said exponentiation step is performed by a funnel shifter that both performs said exponentiation step and provides a selected amount of range compression.
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) | 1996-01-12 | 1996-07-13 | 1997-01-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-01-12 | 2000-07-13 | 2001-01-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-01-12 | 2004-07-13 | 2005-01-12 | $7700.00 | Window Closed / Lapsed |