High dynamic range sensor system and method

• US 20090268192A1
• Filed: 04/25/2008
• Published: 10/29/2009
• Est. Priority Date: 04/25/2008
• Status: Active Grant

• Current Assignee: Rockwell Collins, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Rockwell Collins, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Koenck, Steven E., Jensen, David W.
• Granted Patent: US 7,843,554 B2
• Time in Patent Office: Days
• US Class Current: 356/3
• CPC Class Codes: G01C 3/06 Use of electric means to obtain final indication

Abstract

A high dynamic range sensor assembly includes a plurality of sensing sets that are organized into a sensing array. Each of the sensing sets includes a set of sensing elements for sensing physical phenomena. Each set of sensing elements has a locally selectable integration time. An analog-to-digital (A/D) converter operatively connected to the set of sensing elements acquires and converts an analog signal from each of the sensing elements into a digital signal. A processor operatively connected to the A/D converter and to the set of sensing elements manages the selectable integration time for the set of sensing elements and analyzes the digital signals from each of the sensing elements in the set of sensing elements. The digital signals from each of the sensing elements are measured by the processor and an integration scaling factor for the set of sensing elements is computed and controlled by the processor to adjust the integration time. The integration scaling factor for the set of sensing elements is mathematically combined with a value of the digital signal from the A/D converter to form a larger data word than what is generated by the A/D converter. The larger data word is utilized to represent a magnitude of each of the sensing elements. If a substantial number of A/D values have saturated, the integration time is decreased; and, if a substantial number of A/D values are below a predetermined threshold, the integration time is increased.

Claims

1. A high dynamic range sensor assembly, comprising:

a plurality of sensing sets, said sensing sets being organized into a sensing array, each of said sensing sets comprising;

a) a set of sensing elements for sensing physical phenomena, said set of sensing elements having a locally selectable integration time;

b) an analog-to-digital (A/D) converter operatively connected to said set of sensing elements for acquisition and conversion of an analog signal from each of said sensing elements into a digital signal; and

,

c) a processor operatively connected to said A/D converter and to said set of sensing elements for managing said selectable integration time for said set of sensing elements and for analyzing said digital signals from each of said sensing elements in said set of sensing elements, wherein said digital signals from each of said sensing elements are measured by said processor and an integration scaling factor for said set of sensing elements is computed and controlled by said processor to adjust said integration time.

2. The high dynamic range sensor assembly of claim 1, wherein said integration scaling factor for said set of sensing elements is mathematically combined with a value of said digital signal from said A/D converter to form a larger data word than what is generated by said A/D converter, said larger data word being utilized to represent a magnitude of each of said sensing elements.

3. The high dynamic range sensor assembly of claim 2, wherein said integration scaling factor for said set of sensing elements is a mathematical function of form J/I.

4. The high dynamic range sensor assembly of claim 2, wherein said integration scaling factor for said set of sensing elements is the reciprocal of a nonlinear mathematical function.

5. The high dynamic range sensor assembly of claim 2, wherein said integration scaling factor for said set of sensing elements is selected from a data set {½

<sup>(N−

1)</sup>, . . . ⅛

, ¼

, ½

, 1}, said data set containing N items, where N is an integer and N>

=1.

6. The high dynamic range sensor assembly of claim 5, wherein the magnitude of said digital signals from each of said sensing elements has a resolution of K bits, where K=N+M, N is the total number of different integration scaling factors and M is the number of bits of resolution of said A/D converter, and initially said magnitude being set by an estimated integration scaling factor with the trailing L bits and the leading (N−

L) bits of said magnitude being set to zero, said estimated integration scaling factor being ½

^L, where L is an integer and L is not more than N.

7. The high dynamic range sensor assembly of claim 6, wherein K is at least 20 bits.

8. The high dynamic range sensor of claim 1, wherein said integration scaling factor for said set of sensing elements is computed by said processor by analyzing said digital signal from said A/D converter, wherein if a substantial number of A/D values have saturated, said integration time is decreased;

and, wherein if a substantial number of A/D values are below a predetermined threshold, said integration time is increased.

9. The high dynamic range sensor of claim 8, wherein, as said processor reads out said digital signal of said A/D converter for each pixel in said set of sensing elements, if the number of said digital signals that is at the full scale range (FSR) exceeds a predefined threshold, said processor decreases said selectable integration time and effectively doubles said output value of said A/D converter by shifting said (N+M) bits magnitude value to left by one bit and rightmost bit will be filled with zero.

10. The high dynamic range sensor of claim 8, wherein, as said processor reads out said digital signal of said A/D converter for each pixel in said set of sensing elements, if the number of said digital signals that is well below a predefined value exceeds a predefined threshold, said processor increases said selectable integration time and effectively decreases said output value of said A/D converter by half by shifting said (N+M) bits magnitude value to right by one bit and leftmost bit will be filled with zero.

11. The high dynamic range sensor of claim 8, wherein said predetermined threshold is one half of the full scale range (FSR) of said A/D converter.

12. The high dynamic range sensor of claim 1, wherein said sensing array is an optical focal plane array image sensor.

13. The high dynamic range sensor of claim 12, wherein said optical focal plane array image sensor is capable of night vision sensing.

14. The high dynamic range sensor assembly of claim 1, wherein each of said sensing elements, comprises:

a) a sensor sensing physical phenomena and generating an electrical signal;

b) a storage element storing said electrical signal;

c) a reset switch resetting said storage element to an initial state having no signal;

d) a sample switch moving said electrical signal from said sensor to said storage element; and

,

e) an analog interface operatively connected to said sample switch, said storage element, and said A/D converter, said A/D converter being shared with each of said sensing elements in said sensing sets,

wherein, said reset switch, said sample switch and said analog interface are controlled by said processor.

15. The high dynamic range sensor assembly of claim 1, wherein said processor comprises a dedicated processor executing a sequence of stored program instructions.

16. The high dynamic range sensor assembly of claim 15, wherein said processors of said sensing sets are interconnected to communicate image information with each other.

17. The high dynamic range sensor assembly of claim 16, wherein said interconnected processors perform image processing functions.

18. A high dynamic range night vision sensor assembly, comprising:

a plurality of pixel sets, said pixel sets being organized into an array, each of said pixel sets comprising;

a) a focal plane array comprising a set of pixel elements having a locally selectable integration time;

b) an analog-to-digital (A/D) converter operatively connected to said focal plane array for acquisition and conversion of an analog signal from each of said pixel elements into a digital signal; and

,

c) a dedicated processor operatively connected to said A/D converter and to said focal plane array for managing said selectable integration time for said set of sensing elements and for analyzing said digital signals from each of said pixel elements in said focal plane array, wherein said digital signals from each of said pixel elements is measured by said processor and an integration scaling factor for said focal plane array is computed and controlled by said processor to adjust said integration time.

19. The high dynamic range night vision sensor assembly of claim 18, wherein a light intensity value for each of sensing pixel in said focal plane array is represented by a data word mathematically combining said integration scaling factor for said set of sensing elements and a value of said digital signal from said A/D converter, the resolution of said light intensity value for each pixel in said focal plane array being (N+M) bits, where N is the total number of integration scaling factors and M is the bits of resolution of said A/D converter.

20. The high dynamic range night vision sensor assembly of claim 18, wherein as said processor reads out said output of A/D converter for each pixel element in said focal panel array, if the number of said output that is at FSR exceeds a predefined threshold, said processor decreases said selectable integration time by approximately one-half and effectively doubles said output value of said A/D converter by shifting said (N+M) bits light intensity value to left by one bit and rightmost bit will be filled with zero decreasing said integration scaling factor by approximately one-half.

21. The high dynamic range night vision sensor assembly of claim 18, wherein as said processor reads out said output of A/D converter for each pixel element in said focal panel array, if the number of said output that is well below a predefined value exceeds a predefined threshold, said processor increases said selectable integration time and effectively decreases said output value of said A/D converter by half by shifting said (N+M) bits light intensity value to right by one bit and leftmost bit will be filled with zero, said integration scaling factor being approximately doubled.

22. A method for providing high dynamic range sensing, comprising the steps of:

providing a plurality of sensing sets, said sensing sets being organized into a sensing array, each of said sensing sets operating by utilizing the following steps;

a) sensing a selected physical phenomena using a set of sensing elements having a locally selectable integration time;

b) acquiring and converting an analog signal from each of said sensing elements into a digital signal using an analog-to-digital (A/D) converter operatively connected to said set of sensing elements; and

,

c) managing said selectable integration time for said set of sensing elements and analyzing said digital signals from each of said sensing elements in said set of sensing elements, utilizing a processor operatively connected to said A/D converter and to said set of sensing elements, wherein said digital signals from each of said sensing elements are measured by said processor and an integration scaling factor for said set of sensing elements is computed and controlled by said processor to adjust said integration time.

23. The method of claim 22, wherein said step of managing said selectable integration time for said set of sensing elements and analyzing said digital signals from each of said sensing elements in said set of sensing elements, comprises the step of mathematically combining said integration scaling factor for said set of sensing elements with a value of said digital signal from said A/D converter and forming a larger data word than what is generated by said A/D converter, said larger data word being utilized to represent a magnitude of each of said sensing elements.

24. The method of claim 22, wherein said step of managing said selectable integration time for said set of sensing elements and analyzing said digital signals from each of said sensing elements in said set of sensing elements, comprises the step of decreasing said integration time if a substantial number of A/D values have saturated, and increasing said integration time if a substantial number of A/D values are below a predetermined threshold.

25. The method of claim 22, wherein said step.of managing said selectable integration time for said set of sensing elements and analyzing said digital signals from each of said sensing elements in said set of sensing elements, comprises the step of reading out said digital signal of said A/D converter for each pixel in said set of sensing elements utilizing said processor, if the number of said digital signals that is at the full scale range (FSR) exceeds a predefined threshold, said processor decreases said selectable integration time and effectively doubles said output value of said A/D converter by shifting said (N+M) bits magnitude value to left by one bit and rightmost bit will be filled with zero.

26. The method of claim 22, wherein said step of managing said selectable integration time for said set of sensing elements and analyzing said digital signals from each of said sensing elements in said set of sensing elements, comprises the step of reading out said digital signal of said A/D converter for each pixel in said set of sensing elements utilizing said processor, if the number of said digital signals that is well below a predefined value (i.e. FSR/2) exceeds a predefined threshold, said processor increases said selectable integration time and effectively decreases said output value of said A/D converter by half by shifting said (N+M) bits magnitude value to right by one bit and leftmost bit will be filled with zero.

27. The method of claim 22, wherein said step of sensing a selected physical phenomena using a set of sensing elements having a locally selectable integration time, comprises the following steps:

a) sensing physical phenomena and generating an electrical signal utilizing a sensor;

b) storing said electrical signal utilizing a storage element;

c) resetting said storage element to an initial state having no signal utilizing a reset switch;

d) moving said electrical signal from said sensor to said storage element utilizing a sample switch; and

,

e) acquiring and converting said electrical signal into a digital signal utilizing an analog interface operatively connected to said sample switch, said storage element, and said A/D converter, said A/D converter being shared with each of said sensing elements in said sensing sets,

wherein, said reset switch, said sample switch and said analog interface are controlled by said processor.