Real-time automated scene display for infrared cameras

• US 5,249,241 A
• Filed: 07/09/1991
• Issued: 09/28/1993
• Est. Priority Date: 07/09/1991
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Original Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Inventors: Sato, Darryl, Ewing, William, Silverman, Jerry, Mooney, Jonathan
• Primary Examiner(s): Mancuso, Joseph
• Application Number:
  US07/728,907
• Time in Patent Office: 812 Days
• Field of Search: 382/51, 382/6, 382/54, 382/1, 382/18, 382/56, 382/9, 382/50, 250/330
• US Class Current: 382/169
• CPC Class Codes: G06T 2207/10048 Infrared image
• CPC Class Codes: G06T 5/40 using histogram techniques
• CPC Class Codes: G06T 5/92 based on global image properties
• CPC Class Codes: H04N 23/20 for generating image signals from infrared radiation only
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20

Abstract

A histogram projection system which automatically optimizes, tracks changes in luminance and adjusts in real time the display of wide dynamic range imagery from IR cameras. It is computationally simpler than and offers markedly superior results to the standard available technique for this purpose, histogram equalization. The new technique assigns display dynamic range equally to each occupied intensity level in the raw data in contrast to the old procedure which assigns dynamic range in proportion to the number of pixels at given levels. Less shot noise and greater resolution of image detail for smaller objects or targets are the main improvements from the new algorithm. By the expedient of undersampling the image pixels in carrying out the histogram processing, one can in effect gradually increase the degree of dynamic range assigned to majority or background pixel levels, thereby enhancing the contrast in background regions when desired.

Claims

1. An IR signal processing system which provides automatic mapping of IR data signals into mapped display signals which have adjusted dynamic range, said IR signal processing system comprising:

a means for producing said IR data signals with 12 bit levels of intensity;

a means for selectively undersampling the IR data signals of the producing means by selecting a dynamic range using less that 100% of occupied pixel levels represented in the IR data signals, said undersampling means outputting thereby a set of undersampled IR data signals;

a means for mapping said undersampled IR data signals with mapped display values to output said mapped display signals with 8 bit levels of intensity; and

a means for displaying said mapped display signals with 8 bit levels of intensity, said displaying means being electrically connected with said mapping means to receive said mapped display signals therefrom.

2. An IR signal processing system, as defined in claim 1, wherein said producing means includes an infrared camera which outputs said IR display with 12 bit levels of intensity.

3. An IR signal processing system, as defined in claim 2, wherein said mapping means comprises a microprocessor which has been programmed with a histogram projection algorithm which causes said microprocessor to determine a binary histogram by counting all occupied levels in said IR data signals and determining therefrom a look-up conversion table, said microprocessor then mapping IR display signals with said mapped display values to output thereby said mapped display signals with said adjusted dynamic range.

4. An IR signal processing system, as defined in claim 3, wherein said displaying means comprises an 8 bit monitor which is electrically connected with said mapping means to receive said mapped display signals therefrom.

5. An IR signal processing system as defined in claim 4, wherein said microprocessor comprises a digital computer which has been programmed with a histogram projection algorithm which includes:

space="preserve" listing-type="tabular">______________________________________ int plot 4096 ;

int i,j, store,level,n.sub.-- occ;

n.sub.-- occ=0;

store=0;

level=0;

for (i=0;

i 4096;

i++) plot i =0;

/* develop binary version of plot*/ for(i=0;

i HEIGHT*WIDTH;

i++) .sup. j = hdata[i];

.sup. plot[i] = l;

e /*add up levels*/ for(j=0;

j 4096;

j++) store += plot[i];

n.sub.-- occ = store;

/* order from 1 to n.sub.-- occ*/ store = 1;

for(j=0;

j 4096;

j++) if(plot[i] ==

     1) .sup. plot[i] = store;

.sup. store++;

/* scale data from 0 to 255*/ for(i=0;

i WIDTH*HEIGHT;

i++) level = plot[ hdata[i] ];

output[i] = (256 * (level -

     1))/(n.sub.-- occ) ______________________________________

6. An IR signal processing system, as defined in claim 3, wherein said microprocessor comprises a digital computer which has been programmed with a histogram projection algorithm which includes:

space="preserve" listing-type="tabular">______________________________________ int plot 4096 ;

int i,j, store,level,n.sub.-- occ;

n.sub.-- occ=0;

store=0;

level=0;

for (i=0;

i 4096;

i++) plot i =0;

/* develop binary version of plot*/ for(i=0;

i HEIGHT*WIDTH;

i++) .sup. j = hdata[i];

.sup. plot[i] = l;

/*add up levels*/ for(j=0;

j 4096;

j++) store += plot[i];

n.sub.-- occ = store;

/* order from 1 to n.sub.-- occ*/ store = 1;

for(j=0;

j 4096;

j++) if(plot[i] ==

     1) .sup. plot[i] = store;

.sup. store++;

/* scale data from 0 to 255*/ for(i=0;

i WIDTH*HEIGHT;

i++) level = plot[ hdata[i] ];

output[i] = (256 * (level -

     1))/(n.sub.-- occ) ______________________________________

7. An IR signal processing system, as defined in claim 2, wherein said displaying means comprises an 8 bit monitor which is electrically connected with said mapping means to receive said mapped display signals therefrom.

8. An IR signal processing system, as defined in claim 2 wherein said mapping means comprises a computer which has been programmed. to map said IR data signals which have 12 bit levels of intensity into 8 bit levels while undersampling by various degrees to increase the dynamic range of signals of interest.

9. An IR signal processing system, as defined in claim 1, wherein said mapping means comprises a microprocessor which has been programmed with a histogram projection algorithm which causes said microprocessor to determine a binary histogram by counting all occupied levels in said IR data signals and determining therefrom a look-up conversion table, said microprocessor then mapping IR display signals with said mapped display values to output thereby said mapped display signals with said adjusted dynamic range.

10. An IR signal processing system, as defined in claim 9, wherein said displaying means comprises an 8 bit monitor which is electrically connected with said mapping means to receive said mapped display signals therefrom.

11. An IR signal processing system as defined in claim 10, wherein said microprocessor comprises a digital computer which has been programmed with a histogram projection algorithm which includes:

space="preserve" listing-type="tabular">______________________________________ int plot 4096 ;

int i,j, store,level,n.sub.-- occ;

n.sub.-- occ=0;

store=0;

level=0;

for (i=0;

i 4096;

i++) plot i =0;

/* develop binary version of plot*/ for(i=0;

i HEIGHT*WIDTH;

i++) .sup. j = hdata[i];

.sup. plot[i] = l;

/*add up levels*/ for(j=0;

j 4096;

j++) store += plot[i];

n.sub.-- occ = store;

/* order from 1 to n.sub.-- occ*/ store = 1;

for(j=0;

j 4096;

j++) if(plot[i] ==

     1) .sup. plot[i] = store;

.sup. store++;

/* scale data from 0 to 255*/ for(i=0;

i WIDTH*HEIGHT;

i++) level = plot[ hdata[i] ];

output[i] = (256 * (level -

     1))/(n.sub.-- occ) ______________________________________

12. An IR signal processing system, as defined in claim 9, wherein said microprocessor comprises a digital computer which has been programmed with a histogram projection algorithm which includes:

space="preserve" listing-type="tabular">______________________________________ int plot 4096 ;

int i,j, store,level,n.sub.-- occ;

n.sub.-- occ=0;

store=0;

level=0;

for (i=0;

i 4096;

i++) plot i =0;

/* develop binary version of plot*/ for(i=0;

i HEIGHT*WIDTH;

i++) .sup. j = hdata[i];

.sup. plot[i] = l;

/*add up levels*/ for(j=0;

j 4096;

j++) store += plot[i];

n.sub.-- occ = store;

/* order from 1 to n.sub.-- occ*/ store = 1;

for(j=0;

j 4096;

j++) if(plot[i] ==

     1) .sup. plot[i] = store;

.sup. store++;

/* scale data from 0 to 255*/ for(i=0;

i WIDTH*HEIGHT;

i++) level = plot[ hdata[i] ];

output[i] = (256 * (level -

     1))/(n.sub.-- occ) ______________________________________

13. An IR signal processing system, as defined in claim 9 wherein said mapping means comprises a computer which has been programmed to map said IR data signals which have 12 bit levels of intensity into 8 bit levels while undersampling by various degrees to increase the dynamic range of signals of interest.

14. An IR signal processing system, as defined in claim 1, wherein said displaying means comprises an 8 bit monitor which is electrically connected with said mapping means to receive said mapped display signals therefrom.

15. An IR signal processing system, as defined in claim 1 wherein said mapping means comprises a computer which has been programmed to map said IR data signals which ave 12 bit levels of intensity into 8 bit levels while undersampling by various degrees to increase the dynamic range of signals of interest.

16. An IR signal processing system, as defined in claim 1 wherein said mapping means comprises a computer which has been programmed to map said IR data signals which have 12 bit levels of intensity into 8 bit levels while assigning a common output display level to the most sparsely occupied levels while projecting the remainder into mapped level with 8 bit levels of intensity, said IR signal display system producing thereby an extended dynamic range about objects of interest in a scene.

17. An IR signal process which provides automatic mapping of IR data signals into mapped display signals which have adjusted dynamic range, said IR signal process comprising the steps of:

producing 12 bit IR data signals with an infrared camera;

determining a binary histogram from said IR data signals by counting all occupied pixel levels in said IR data signals to produce a sum N which characterizes said R data signals;

assigning said 12 bit R data signals into a set of 8 bit IR display signals by correlating each set of four 12 bit IR data signals with a single 8 bit R display signal;

writing a look-up conversion table to convert IR data signals levels into values for said IR display signal levels by assigning each the level a value of 255×

n/N where N equals said occupied pixel levels in said IR data produced by said infrared camera and n equals a level of intensity for 12 bit IR data signals, such that n is a number selected from a range which extends between 0 and 4095 ; and

displaying said mapped display signals.

18. An IR signal process which provides automatic mapping of IR data signals into mapped display signals which have adjusted dynamic range, said IR signal process comprising the steps of

producing said IR data signals;

determining a binary histogram from said IR data signals by counting all occupied pixel levels in said IR data signals to produce a sum N which characterizes said IR data signals;

assigning said 12 bit R data signals into a set of 8 bit IR display signals by correlating each set of four 12 bit IR data signals with a single 8 bit IR display signal;

writing a look-up conversion table to convert IR data signal levels into values for said IR display signal levels by assigning each the level a value of 255×

n/N where N equals said occupied pixel levels in said IR data produced by said infrared camera and n equals a level of intensity for 12 bit IR data signals, such that n is a number selected from a range which extends between 0 and 4095;

outputting said mapped display signal by performing said conversion table for each single 8 bit IR display signal; and

displaying said mapped display signals.

19. An IR signal process, as defined in claim 18, wherein said producing step comprises producing 12 bit IR data signals with an infrared camera, and wherein said mapping step is accomplished by entering said 12 bit IR data signals into said computer which has been programmed with a histogram projection algorithm.

20. An IR signal processing system which provides automatic mapping of IR data signals into mapped display signals which have adjusted dynamic range, said IR signal processing system comprising:

a means for producing said IR data signals with predetermined bit levels of intensity;

a means for selectively undersampling the IR data signals of the producing means by selecting a dynamic range using less than 100% of occupied pixel levels represented in the IR data signals, said undersampling means outputting thereby a set of undersampled IR data signals;

a means for mapping said undersampled IR data signals with mapped display values to output said mapped display signals with less than said predetermined bit levels of intensity; and

a means for displaying said mapped display signals with said less than said predetermined bit levels of intensity, said displaying means being electrically connected with said mapping means to receive said mapped display signals therefrom.

21. An IR signal processing system, as defined in claim 20, wherein said producing means includes an infrared camera which outputs said IR display signals with said predetermined bit levels of intensity.

22. An IR signal processing system, as defined in claim 21 wherein said mapping means comprises a microprocessor which has been programmed with a histogram projection algorithm which causes said microprocessor to determine a binary histogram by counting all occupied levels in said IR data signal signals and determining therefrom a look-up conversion table, said microprocessor then mapping IR display signals with said mapped display values to output thereby said mapped display signals with said adjusted dynamic range.

23. An IR signal processing system, as defined in claim 20, wherein said mapping means comprises a microprocessor which has been programmed with a histogram projection algorithm which causes said microprocessor to determine a binary histogram by counting all occupied levels in said IR data signals and determining therefrom a look-up conversion table, said microprocessor then mapping IR display signals with said mapped display values to output thereby said mapped display signals with said adjusted dynamic range.