Infrared face detection and recognition system

1. A detection system comprising:

a first array of detector pixels having a first field of view;

a second array of detector pixels having the first field of view;

a subtractor connectable to each pixel pair of the first and second arrays; and

a comparator connected to the subtractor; and

wherein:

the first sensing array has a sensitivity to light in a lower portion of a reflective infrared spectrum;

the second sensing array has a sensitivity to light in an upper portion of a reflective infrared spectrum;

a pixel pair includes a first pixel at a location of the first array of detector pixels of the first array which a one-to-one correlation with a second pixel of the pixel pair at a corresponding location of the second array of detector pixels;

the subtractor detects the differences of magnitudes of output signals from the first and second pixels of each pixel pair and output a magnitude difference signal for each pixel pair; and

a comparator compares the magnitude difference signals to a certain threshold value and select the pixel pairs having magnitude difference values on one side of the threshold value.

2. The system of claim 1 , wherein:

the second pixels at each at the pixel pairs having a magnitude difference value on one side of the threshold value exhibit detected low reflectance areas in the field of view; and the low reflectance areas indicate skin of a person.

3. The system of claim 2 , further comprising:

a face feature selector;

a framer; and

an extractor; and

wherein:

an image from of the second array of detector pixels reveals the skin of a person in the field of view;

the feature selector locates features of a face in the shin;

the framer places a frame around the face in the image;

pixels of the frame around the face are matched with pixels at corresponding locations in an image from the first array of detector pixels; and

the extractor extracts a sub-image containing the face within the frame in the image from the first array of detector pixels.

4. The system of claim 3 , further comprising:

a face recognition system; and

wherein:

the face recognition system matches the sub-image of the face with another sub-image of an identified face.

5. The system of claim 4 , further comprising:

an evaluator; and

wherein the evaluator indicates a confidence level of recognition of the face within the frame.

6. The system of claim 5 , further comprising a database of sub-images of identified faces, connected to the face recognition system.

7. A human detection system comprising:

a multi-band camera having first and second outputs;

a subtractor connected to the first and second outputs;

a thresholder connected to the subtractor;

a feature selector connected to the thresholder;

a framer connected to the thresholder;

a pixel integrator connected to the framer and the first output;

an extractor connected to the integrator;

a recognition system connected to the extractor.

8. The system of claim 7 , further comprising an evaluator connected to the recognition system.

9. The system of claim 8 , wherein:

the first output of the multi-band camera has a bandwidth in the lower reflective region of the infrared spectrum; and

the second output of the multi-band camera has a bandwidth in the upper reflective region of the infrared spectrum.

10. The system of claim 9 , wherein

the subtractor removes pixels from an image which are not representative of skin.

11. The system of claim 10 , wherein:

the feature selector seeks out features of a face in the image;

the feature selector retains only the face in the image; and

the framer outputs a framed image of the face.

12. The system of claim 11 , wherein:

the pixel integrator matches the pixels of the framed image with an image from the first output of the multi-band camera; and

the integrator superimposes the frame on the image from the first output of the multi-band camera.

13. The system of claim 12 , wherein the extractor extracts a portion of the image within the frame.

14. The system of claim 13 , wherein:

the portion of the image is sent to a recognition system; and

the recognition system performs a match of the portion of the image with a similar image from a data system.

15. The system of claim 14 , wherein the evaluator provides a confidence level of recognition of the match.

16. The system of claim 15 , further comprising a light source for providing infrared lighting as needed.

17. A method for detecting a face in a scene, comprising:

capturing a first image of the scene with a first sensing array sensitive to a first band of reflective infrared light;

capturing a second image of the scene with a second sensing array sensitive to a second band of reflective infrared light; and

wherein:

the first image comprises m×n pixels;

the second image comprises m×n pixels;

the first and second images have the same field of view of the scene;

each pixel P (i,j)1 of the first image is located at an i th row and a jth column;

each pixel P (i,j)2 of the second image is located at an i th row and a jth column;

1≦i≦m;

1≦j≦m;

each pixel P (i,j)1 of the first image has a counterpart pixel P (i,j)2 in the second image in a one-to-one mapping of the first image to the second image;

a difference intensity pixel ΔI P(i,j) may be determined from an intensity of each pixel I P(i,j)1 of the first image and each counterpart pixel I P(i,j) of the second image, for all of the pixels of the first and second images;

each difference intensity pixel ΔI P(i,j) has an intensity value that is measured against an intensity threshold value and has its value nullified if it does not meet a certain range of intensity values relative to the intensity threshold value, and becomes a thresholded difference intensity pixel TΔI P(i,j) ;

each thresholded difference intensity pixel together with each other thresholded difference intensity pixel forms a third image having a one-to-one mapping of pixels to the first and second images; and

features of a face are sought, and if found, a face is detected in the third image and a frame is scribed as frame pixels in the third image around the face.

18. The method of claim 17 , further comprising:

transferring the frame pixels from the third image to the first image on a one-to-one mapping basis; and

extracting the pixels within the frame in the first image to form a fourth image having the face extracted from the first image.

19. The method of claim 18 , further comprising:

comparing the face in the fourth image with faces from a database; and

matching the face in the fourth image with a face from the data base.

20. The method of claim 19 , further comprising:

evaluating the matching of the face in the fourth image with the face from the database; and

determining a confidence level of recognition of the face in the fourth image relative to the face from the database.

21. The method of claim 20 , wherein:

the first band of reflective infrared light is approximately between 800 and 1400 nanometers; and

the second band of reflective infrared light is approximately between 1400 and 2200 nanometers.

22. The method of claim 21 , further comprising shining infrared light on the scene as needed for obtaining adequate first and second images of the scene.

23. Means for detecting faces, comprising:

means for obtaining a first image with a first field of view of a scene at a lower reflective infrared band of light;

means for obtaining a second image with the first field of view of the scene at an upper reflective infrared band of light;

means for subtractively combining the first and second images into a third image;

means for thresholding the pixels of the third image to result in a fourth image having only the pixels meeting a set threshold value;

means for finding features of a face in the fourth image;

means for inserting a frame around the face based on the features; and

means for transferring the frame to be around the face in the first image.

24. The means of claim 23 , further comprising:

means for extracting a sub-image of the face within the frame; and

means for possibly at least approximately matching the face with at least one other face in a database.

25. The means of claim 24 , further comprising:

means for evaluating the matching the face with the at least one other face in the database; and

means for determining a confidence level of recognition of the face within the frame.

26. The means of claim 25 , further comprising means for providing infrared lighting on the scene as needed for obtaining the first and second images.

27. The means of claim 26 , wherein:

the lower reflective infrared band of light is approximately between 800 and 1400 nanometers; and

the upper reflective infrared band of light approximately between 1400 and 2200 nanometers.