Method and device for compensating for shadows in digital images

• US 20050236555A1
• Filed: 05/02/2005
• Published: 10/27/2005
• Est. Priority Date: 10/31/2002
• Status: Active Grant

• Current Assignee: Bayerische Motoren Werke AG
• Original Assignee: Bayerische Motoren Werke AG
• Inventors: Eisenmann, Lutz, Koch, Carsten, Yoon, Jason Jeong-Suk
• Granted Patent: US 7,362,882 B2
• Time in Patent Office: Days
• US Class Current: 250/208.100
• CPC Class Codes: G01S 17/04 Systems determining the presence of a target
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction
• CPC Class Codes: G06T 7/0002 Inspection of images, e.g. flaw detection

Abstract

The invention relates to a method for generating a computed digital image of a scene, which can be illuminated with different luminous intensities at a first illumination angle by a first light source. An image sensor records a number of individual images of the scene under different lighting conditions, and these images are set against one another in a pixel-by-pixel manner in a data processing device in order to generate a resulting image. The invention is characterized in that at least one additional light source is provided by means of which the scene can be illuminated at an illumination angle that is different from the illumination angle of the first light source. The different lighting conditions when recording the individual images are obtained by various combinations of luminous intensities of the first and of the at least one other additional light source. The invention also relates to a device for carrying out the inventive method.

Claims

1. A method of producing a computed digital image of a scene which can be illuminated with different luminous intensities at a first illumination angle by a first light source, a plurality of individual images of the scene under different lighting conditions being taken by an image sensor and being offset against one another in a pixel-by-pixel manner in a data processing device for generating a result image, the method comprising the acts of:

illuminating the scene with at least one other light source at an illumination angle with different luminous intensities which differ from the illumination angle of the first light source; and

achieving the different illumination conditions during the taking of individual images by different combinations of the luminous intensities of the first and of the at least one other light source.

2. The method according to claim 1, wherein offsetting of the individual images with one another takes place such that two pixels respectively of the result image on which scene points are imaged which are illuminated by at least one light source and which are directly illuminated by different light sources or different numbers of light sources, with the exception of a factor representing the reflectance of the respective scene point, have essentially the same pixel value.

3. The method according to claim 1, wherein for computing a result image, three individual images are taken, two light sources being controlled such that:

during the taking of a first individual image, the first light source illuminates the scene with a first luminous intensity and the second light source illuminates the scene with a second luminous intensity which differs from the first;

during the taking of a second individual image, the first light source illuminates the scene with the second luminous intensity and the second light source illuminates the scene with the first luminous intensity; and

during the taking of a third individual image, both light sources each illuminate the scene with the second luminous intensity.

4. The method according to claim 2, wherein for computing a result image, three individual images are taken, two light sources being controlled such that:

during the taking of a first individual image, the first light source illuminates the scene with a first luminous intensity and the second light source illuminates the scene with a second luminous intensity which differs from the first;

during the taking of a second individual image, the first light source illuminates the scene with the second luminous intensity and the second light source illuminates the scene with the first luminous intensity; and

during the taking of a third individual image, both light sources each illuminate the scene with the second luminous intensity.

5. The method according to claim 3, wherein the offsetting of the individual images with one another comprises the computing of the pixel-by-pixel difference of the first and of the second individual image.

6. The method according to claim 3, wherein the offsetting of the individual images with one another comprises the computing of the pixel-by-pixel sum of the first and of the second individual image.

7. The method according to claim 5, wherein the offsetting of the individual images with one another further comprises the computing of the pixel-by-pixel sum of the first and of the second individual image.

8. The method according to claim 3, wherein the offsetting of the individual images with one another comprises the computing of the pixel-by-pixel sum from the amount of the difference and of the sum of the first and of the second individual image.

9. The method according to claim 5, wherein the offsetting of the individual images with one another comprises the computing of the pixel-by-pixel sum from the amount of the difference and of the sum of the first and of the second individual image.

10. The method according to claim 7, wherein the offsetting of the individual images with one another comprises the computing of the pixel-by-pixel sum from the amount of the difference and of the sum of the first and of the second individual image.

11. The method according to claim 3, wherein the offsetting of the individual images with one another comprises the pixel-by-pixel subtraction of the third individual image.

12. The method according to claim 3, wherein the pixel values of the result image can essentially be represented as follows

I_out=|I₁−

I₂|+(I₁+I₂)−

2·

I₃,

wherein I_out is the value of a pixel of the result image, I₁ is the value of the corresponding pixel of the first individual image, I₂ is the value of the corresponding pixel of the second individual image, and I₃ is the value of the corresponding pixel of the third individual image.

13. The method according to claim 1, wherein the result image is subjected to another image processing whose result is used for an automated decision finding within the scope of the monitoring of an interior of a motor vehicle.

15. A device for producing a computed digital image, comprising:

a first light source by which a scene to be taken can be illuminated at a first illumination angle with different luminous intensities;

an image sensor for the imaging detection of the illuminated scene and the output of digital images of the scene comprising a plurality of pixels;

control devices for the coordinated controlling of the light source and of the image sensor, so that individual images of the scene can be taken under different illumination conditions;

a data processing device for the pixel-by-pixel offsetting of at least some of the individual images with one another; and

at least one other light source by which the scene can be illuminated at a second illumination angle which differs from the first with different luminous intensities,

wherein the light sources are controllable by the control devices such that the different illumination conditions during the taking of the individual images can be achieved by different combinations of the luminous intensities of the first and of the at least one other light source, wherein the control devices and the data processing system are structured to implement a method according to claim 2.

14. A device for producing a computed digital image, comprising a first light source by which a scene to be taken can be illuminated at a first illumination angle with different luminous intensities, an image sensor for the imaging detection of the illuminated scene and the output of digital images of the scene comprising a plurality of pixels, control devices for the coordinated controlling of the light source and of the image sensor, so that individual images of the scene can be taken under different illumination conditions, a data processing device for the pixel-by-pixel offsetting of at least some of the individual images with one another and

at least one other light source by which the scene can be illuminated at a second illumination angle which differs from the first with different luminous intensities,

wherein the light sources are controllable by the control devices such that the different illumination conditions during the taking of the individual images can be achieved by different combinations of the luminous intensities of the first and of the at least one other light source.

16. The device according to claim 14, wherein the device is integrated as part of a monitoring system in an interior of a motor vehicle.

17. The device according to claim 14, wherein the light sources emit light in the close infrared region.

18. The device according to claim 14, wherein the light sources are arranged relative to one another and relative to the scene detected by the image sensor such that no distance between a scene point and a light source is small in comparison to a distance between two scene points.

19. A method for generating a computed digital image of scene, the method comprising the acts of:

controlling a first and a second light source operable to illuminate the scene with different luminous intensities at different illumination angles;

taking a first individual image, wherein the first light source illuminates the scene with a first luminous intensity and the second light source illuminates the scene with a second luminous intensity differing from the first;

taking a second individual image wherein the first light source illuminates the scene with the second luminous intensity and the second light source illuminates the scene with the first luminous intensity, and

taking a third individual image wherein both light sources each illuminate the scene with the second luminous intensity; and

computing a result image based on the three individual images taken.