Method for adjusting an image sensor

• US 20060228024A1
• Filed: 11/12/2003
• Published: 10/12/2006
• Est. Priority Date: 01/17/2003
• Status: Abandoned Application

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Koninklijke Philips N.V.
• Inventors: Fritz, Steffen, Haug, Karsten, Franz, Matthias
• Application Number:
  US10/542,672
• Publication Number:
  US 20060228024A1
• Time in Patent Office: Days
• US Class Current: 382/169
• CPC Class Codes: G06V 10/147 Details of sensors, e.g. sensor lenses fingerprint or palmprint sensors G06V40/13; vascular sensors G06V40/145; eye sensors G06V40/19
• CPC Class Codes: G06V 20/56 exterior to a vehicle by using sensors mounted on the vehicle
• CPC Class Codes: H04N 23/70 Circuitry for compensating brightness variation in the scene

Abstract

A method and a processing unit for adjusting the characteristic curve of the exposure sensitivity of at least one pixel of at least one image sensor in a motor vehicle are described. The optimal characteristic curve of the exposure sensitivity is determined from the histogram of the gray values of at least one image as a function of image signals from at least one image sensor. The freely definable characteristic curve of the image sensor having linear segments is chosen so that it agrees at least approximately with the optimal characteristic curve. Along with the size and/or the position of the characteristic curve of the exposure sensitivity, alternatively or in addition the shape of the characteristic curve is adjusted.

Claims

1-14. -14. (canceled)

15. A method for adjusting a characteristic curve of an exposure sensitivity of at least one pixel of at least one image sensor, in a motor vehicle, the characteristic curve being formed in segments of functions, the method comprising:

adjusting the characteristic curve of the exposure sensitivity as a function of image signals from at least a part of the scene registered by the at least one image sensor so that at least one of the following is satisfied;

a frequency of the gray values of at least a part of the histogram of image signals from the at least one image sensor of the at least one part of the registered scene is approximately constant; and

the gray value density of at least a part of the histogram of image signals from the at least one image sensor of the at least one part of the registered scene is approximately constant.

16. The method of claim 15, wherein the characteristic curve of the exposure sensitivity is adjusted as a function of image signals from at least a part of the scene registered by the at least one image sensor, so that, when a gray value wedge having two segments with different gradients of the gray values is registered as the scene, the at least one image sensor generates an image nearly free of apparent contours.

17. The method of claim 15, wherein the characteristic curve of the exposure sensitivity is adjusted as a function of a determined optimal characteristic curve of the exposure sensitivity, including a determined characteristic curve of the exposure sensitivity which is optimal according to information theory, at least one of the optimal characteristic curve of the exposure sensitivity and the characteristic curve of the exposure sensitivity which is optimal according to information theory being determined as a function of image signals from the at least one image sensor.

18. The method of claim 17, further comprising:

determining the optimal characteristic curve of the exposure sensitivity as a function of a histogram of the gray values of at least one image and/or of at least one image detail;

approximating the characteristic curve of the exposure sensitivity to the determined optimal characteristic curve of the exposure sensitivity, including approximation of the characteristic curve of the exposure sensitivity to the determined optional characteristic curve of the exposure sensitivity through at least one numerical approximation method and/or at least one segmenting method.

19. The method of claim 15, wherein at least one of the gain, the offset, the integration time and at least one additional parameter for adjusting the characteristic curve of the exposure sensitivity of the at least one pixel of the at least one image sensor is adjusted, the at least one additional parameter for adjusting the characteristic curve of the exposure sensitivity being at least one of (i) at least one parameter for adjusting the number of segments of the characteristic curve of the exposure sensitivity, (ii) at least one parameter for adjusting the position of the segments of the characteristic curve of the exposure sensitivity, (iii) at least one parameter for adjusting the size of the segments of the characteristic curve of the exposure sensitivity, and (iv) at least one parameter for adjusting the at least one function.

20. The method of claim 15, wherein at least one of the functions is a linear function.

21. The method of claim 15, wherein the characteristic curve of the exposure sensitivity of the at least one pixel of the at least one image sensor is adjusted as a function of image signals from at least two image sensors, including at least one stereo camera.

22. A processing unit for generating at least one adjustment signal for adjusting the characteristic curve of the exposure sensitivity of at least one pixel of at least one image sensor, including in a motor vehicle, the characteristic curve being formed in segments of functions, including of linear functions, comprising:

an arrangement to generate the at least one adjustment signal to adjust the characteristic curve of the exposure sensitivity as a function of image signals from at least a part of the scene registered by the at least one image sensor so that at least one of a frequency of the gray values of at least a part of the histogram of image signals from the at least one image sensor of the at least one part of the registered scene is approximately constant, and a gray value density of at least a part of the histogram of image signals from the at least one part of the registered scene is approximately constant.

23. The processing unit of claim 22, wherein the processing unit generates the at least one adjustment signal to adjust the characteristic curve of the exposure sensitivity as a function of image signals from at least a part of the scene registered by the at least one image sensor, so that, when a gray value wedge having two segments with different gradients of the gray values is registered as the scene, the at least one image sensor generates an image nearly free of apparent contours.

24. The processing unit of claim 22, wherein the processing unit adjusts the characteristic curve of the exposure sensitivity as a function of a determined optimal characteristic curve of the exposure sensitivity, including a determined characteristic curve of the exposure sensitivity which is optimal according to information theory, the processing unit determining at least one of the optimal characteristic curve of the exposure sensitivity and the characteristic curve of the exposure sensitivity which is optimal according to information theory as a function of image signals from the at least one image sensor.

25. The processing unit of claim 24, wherein the processing unit performs at least one of the following:

determines the optimal characteristic curve of the exposure sensitivity as a function of a histogram of the gray values of at least one image and/or of at least one image detail; and

approximates the characteristic curve of the exposure sensitivity to the determined optimal characteristic curve of the exposure sensitivity, including that the processing unit approximates the characteristic curve of the exposure sensitivity to the determined optimal characteristic curve of the exposure sensitivity by at least one of numerical approximation methods and segmenting methods.

26. The processing unit of claim 22, wherein the processing unit generates at least one adjustment signal for adjusting at least one of the gain, the offset, the integration time and at least one additional adjustment signal for adjusting the characteristic curve of the exposure sensitivity of the at least one pixel of the at least one image sensor, and wherein the at least one additional adjustment signal for adjusting the characteristic curve of the exposure sensitivity is at least one of (i) at least one adjustment signal for adjusting the number of segments of the characteristic curve of the exposure sensitivity, (ii) at least one adjustment signal for adjusting the position of the segments of the characteristic curve of the exposure sensitivity, (iii) at least one adjustment signal for adjusting the size of the segments of the characteristic curve of the exposure sensitivity, and (iv) at least one adjustment signal for adjusting the at least one function.

27. The processing unit of claim 22, wherein the processing unit generates the at least one adjustment signal for adjusting the characteristic curve of the exposure sensitivity of the at least one pixel of the at least one image sensor as a function of image signals from at least two image sensors, including at least one stereo camera.

28. A computer program executable on a computer, comprising:

a program code arrangement for adjusting a characteristic curve of an exposure sensitivity of at least one pixel of at least one image sensor, in a motor vehicle, the characteristic curve being formed in segments of functions, by performing the following;

adjusting the characteristic curve of the exposure sensitivity as a function of image signals from at least a part of the scene registered by the at least one image sensor so that at least one of the following is satisfied;

a frequency of the gray values of at least a part of the histogram of image signals from the at least one image sensor of the at least one part of the registered scene is approximately constant; and

the gray value density of at least a part of the histogram of image signals from the at least one image sensor of the at least one part of the registered scene is approximately constant.

29. The computer program of claim 28, wherein the characteristic curve of the exposure sensitivity is adjusted as a function of image signals from at least a part of the scene registered by the at least one image sensor, so that, when a gray value wedge having two segments with different gradients of the gray values is registered as the scene, the at least one image sensor generates an image nearly free of apparent contours.

30. The computer program of claim 28, wherein the characteristic curve of the exposure sensitivity is adjusted as a function of a determined optimal characteristic curve of the exposure sensitivity, including a determined characteristic curve of the exposure sensitivity which is optimal according to information theory, at least one of the optimal characteristic curve of the exposure sensitivity and the characteristic curve of the exposure sensitivity which is optimal according to information theory being determined as a function of image signals from the at least one image sensor.

31. The computer program of claim 30, further comprising:

determining the optimal characteristic curve of the exposure sensitivity as a function of a histogram of the gray values of at least one image and/or of at least one image detail;

approximating the characteristic curve of the exposure sensitivity to the determined optimal characteristic curve of the exposure sensitivity, including approximation of the characteristic curve of the exposure sensitivity to the determined optional characteristic curve of the exposure sensitivity through at least one numerical approximation method and/or at least one segmenting method.

32. The computer program of claim 28, wherein at least one of the gain, the offset, the integration time and at least one additional parameter for adjusting the characteristic curve of the exposure sensitivity of the at least one pixel of the at least one image sensor is adjusted, the at least one additional parameter for adjusting the characteristic curve of the exposure sensitivity being at least one of (i) at least one parameter for adjusting the number of segments of the characteristic curve of the exposure sensitivity, (ii) at least one parameter for adjusting the position of the segments of the characteristic curve of the exposure sensitivity, (iii) at least one parameter for adjusting the size of the segments of the characteristic curve of the exposure sensitivity, and (iv) at least one parameter for adjusting the at least one function.

33. The computer program of claim 28, wherein at least one of the functions is a linear function.

34. The computer program of claim 28, wherein the characteristic curve of the exposure sensitivity of the at least one pixel of the at least one image sensor is adjusted as a function of image signals from at least two image sensors, including at least one stereo camera.