Object imaging system

• US 5,631,976 A
• Filed: 04/29/1994
• Issued: 05/20/1997
• Est. Priority Date: 04/29/1994
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Haas, Norman, Connell, Jonathan H., Mohan, Rakesh, Bolle, Rudolf M., Taubin, Gabriel
• Primary Examiner(s): Boudreau, Leo
• Assistant Examiner(s): KELLEY, CHRISTOPHER S
• Application Number:
  US08/235,064
• Time in Patent Office: 1,117 Days
• Field of Search: 382/8, 382/9, 382/171, 382/173, 382/174, 382/274, 235/460, 348/135, 348/92, 348/370, 348/227, 358/464
• US Class Current: 382/174
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction
• CPC Class Codes: G06T 7/11 Region-based segmentation
• CPC Class Codes: G06T 7/194 involving foreground-background segmentation
• CPC Class Codes: H04N 23/74 by influencing the scene brightness using illuminating means
• CPC Class Codes: H04N 5/275 Generation of keying signals

Abstract

An image processing system segments an object from the background of a scene by controlling a light source to illuminate the object more in one scene image than in another scene image. The two scene images are captured by an image input device and are then compared. The part of the image that experienced an increase in intensity is segmented as corresponding to the object. The image input device and the light source can also be placed in an opaque enclosure with an opening through which the input device can view and the light can illuminate the object. By placing the enclosure the correct distance away from the object, the effects of ambient light on the image are removed. Object glare is removed by a polarizing filter system.

Claims

1. An image processing system for separating one or more objects in a scene from a background of the scene, comprising:

a controllable light source for illuminating the scene, the controllable light source having an on illumination level and a reduced illumination level, the controllable light source positioned at an object distance from the object and a background distance from the background, a reflectance of light from the object divided by the square of the object distance being greater than a reflectance of light from the background divided by the square of the background distance when the controllable light source is at the on illumination level and the reduced illumination level;

an image input device taking two or more images of the the scene, a first scene image taken with the controllable light source on and a second scene image taken with the controllable light source at the reduced illumination level, the first scene image having an object image brighter than the object image in the second scene;

a comparator comparing the first and second scene images, one or more pixels being object pixels that are brighter in the first scene image than in the second scene image; and

a comparator designator designating the object pixels as an object image separate from a background image of the background of the scene.

2. A system, as in claim 1, where one or more pixels are background pixels, the background pixels having the same brightness, within a tolerance, in the first and second scene images, and the comparator designator designating the background pixels as a background image of the background of the scene instead of designating the object image.

3. A system, as in claim 1, where one or more pixels are background pixels, the background pixels having the same brightness, within a tolerance, in the first and second scene images and the comparator designator designating the background pixels as a background image of the background of the scene in addition to the object image.

4. A system, as in claim 1, where the comparator designator is a digital circuit for selecting the pixels that were brighter in the first scene image than the second scene image.

5. A system, as in claim 4, where the digital circuit is a computer and one or both of the scene images is stored on a memory storage device before being compared.

6. A system, as in claim 1, where the comparator designator is an analog circuit which subtracts and tolerances two synchronized video signals.

7. A system, as in claim 1, where the object is closer to the light source than the background and the illumination of the scene by the light source makes the object brighter, by more than a tolerance, than a brightness of the background.

8. A system, as in claim 1, where the reduced illumination level of the light source is off.

9. A system, as in claim 1 where the angle formed by the image input device, the object, and the light source is between 0 and 15 degrees.

10. A system, as in claim 1, where the image input device is a camera.

11. A system, as in claim 1, further comprising an output device.

12. A system, as in claim 1, where a part of the object image is further separated into a dark part that was dark in the first scene image and a light part that was light in the first scene image, the dark part being an image of one or more opaque parts of the object and the light part being an image of one or more translucent parts of the object.

19. A system, as in claim 1, where more than two images are taken, each image being taken at a different light intensity of the controllable light source.

13. An image processing system for separating one or more objects in a scene from a background of the scene, comprising:

a controllable light source for illuminating the scene, the controllable light source having an on illumination level and a reduced illumination level, the controllable light source positioned at an object distance from the object and a background distance from the background, a reflector of light from the object divided by the square of the object distance being greater than a reflectance of light from the background divided by the square of the background distance when the controllable light source is at the on illumination level and the reduced illumination level;

an image input device taking two or more images of the scene, a first scene image taken with the controllable light source on and a second scene image taken with the controllable light source at the reduced illumination level, the first scene image having an object image of each of the objects brighter than the object image in the second scene;

an opaque enclosure that encloses the image input device and the light source, the enclosure having an opening facing the object so that the light can illuminate the object and the image input device can image the object, the enclosure opening being placed a first distance from the object so that there is a reduction in the ambient light reflected from the object to the imaging input device;

a comparator for comparing the first and second scene images, one or more pixels being object pixels that are brighter in the first scene image than in the second scene image; and

a comparator designator designating the object pixels as the object image separate from a background image of the background of the scene.

14. A system, as in claim 13, where there is a transparent cover over the enclosure opening.

15. A system, as in claim 14, where the transparent cover supports the object.

16. A system, as in claim 13, where the light source is a polarized light used to reduce glare from the objects and from the supporting surface.

17. A system, as in claim 16, where a linear polarizer is placed over the light source and another linear polarizer is placed over the image input device such that the polarization axes of the two polarizers are perpendicular.

18. A system, as in claim 13, where there is a mesh covering the opening in the enclosure for supporting the object.