Method for determining the luminance of traffic signs and device for implementing same

• US 9,171,362 B2
• Filed: 04/30/2014
• Issued: 10/27/2015
• Est. Priority Date: 02/12/2008
• Status: Active Grant

• Current Assignee: AMAC NORTH AMERICA, LLC
• Original Assignee: Dbi/cidaut Technologies, LLC
• Inventors: Burgoa Roman, Francisco Javier, Gutierrez Mendez, Jose Antonio, Mansilla Gallo, Alberto, Ortiz de Lejarazu Machin, Diego, Perales Garcia, Alberto Senen
• Primary Examiner(s): VANCHY JR, MICHAEL J
• Application Number:
  US14/265,747
• Publication Number:
  US 20140233850A1
• Time in Patent Office: 545 Days
• Field of Search: 382/100, 382/103, 382/104, 382/190, 382/274, 382/275, 348/148
• US Class Current: 1/1
• CPC Class Codes: B60Q 1/085 due to special conditions, e.g. adverse weather, type of road, badly illuminated road signs or potential dangers B60Q1/10, B60Q1/12, B60Q1/1423 take precedence
• CPC Class Codes: B60Q 1/18 being additional front lights bracket mounted headlights B60Q1/0483
• CPC Class Codes: B60Q 2300/314 Ambient light
• CPC Class Codes: B60Q 2300/45 Special conditions, e.g. pedestrians, road signs or potential dangers
• CPC Class Codes: G01N 2021/551 Retroreflectance
• CPC Class Codes: G01N 21/55 Specular reflectivity
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction
• CPC Class Codes: G06V 20/582 of traffic signs
• CPC Class Codes: H04N 13/279 the virtual viewpoint locations being selected by the viewers or determined by tracking

Abstract

The method of the invention comprises: obtaining a sequence of at least two images, with different levels of illumination; extracting the region containing the sign in the image; calculating the luminance values of the signs; and obtaining the difference in luminance of the sign corresponding to the two levels of illumination. The value obtained is the luminance of the sign (11) corresponding to an illumination equal to the difference between the illuminations, or additional illumination. This result is based on the additive property of luminance, according to which the luminance of a sign is the sum of the luminance produced by each source of illumination. A basic illumination device (5), an additional illumination device (7), at least one camera for taking images, and image recording, positioning and synchronism systems are required to implement the method.

Claims

1. A computer-implemented method for determining luminance of a traffic sign, comprising the steps of:

a) obtaining a first image using a first illumination level at a first point in time, the first illumination level being based on a first base illumination and a first ambient illumination;

b) obtaining a second image using a second illumination level at a second point in time, the second illumination level being based on a second base illumination, a second ambient illumination and an additional illumination, the second illumination level being different from the first illumination level, a difference between the first point in time and the second point in time being an interval of time corresponding to a frequency of an electric grid such that the first image and the second image are obtained at a same point of a sine wave of a supply voltage from the electric grid;

c) extracting a first array of pixels in the first image, the first array of pixels being representative of the traffic sign;

d) extracting a second array of pixels in the second image, the second array of pixels being representative of the traffic sign;

e) calculating a first luminance value of the traffic sign using the first array of pixels, the first luminance value being based on the first base illumination and the first ambient illumination;

f) calculating a second luminance value of the traffic sign using the second array of pixels, the second luminance value being based on the second base illumination, the second ambient illumination and the additional illumination; and

g) calculating a luminance difference value of the traffic sign corresponding to a difference between the first luminance value and the second luminance value.

2. The computer-implemented method of claim 1, wherein a camera is used to perform steps a) and b).

3. The computer-implemented method of claim 2, wherein the camera is coupled to a vehicle.

4. The computer-implemented method of claim 1, wherein a processor is used to perform steps c) through g).

5. The computer-implemented method of claim 4, wherein the processor is coupled to a vehicle.

6. The computer-implemented method of claim 1, wherein the first image includes a third array of pixels and wherein the second image includes a fourth array of pixels, the third array of pixels and the fourth array of pixels each corresponding to a second traffic sign.

7. The computer-implemented method of claim 1, further comprising:

emitting, via a stabilized base illumination light source, light corresponding to the first base illumination and the second base illumination.

8. The computer-implemented method of claim 7, further comprising:

stabilizing light to be emitted by the stabilized base illumination light source to compensate for oscillations in power supplied to the stabilized base illumination light source.

9. The computer-implemented method of claim 8, wherein the stabilized base illumination light source is coupled to a vehicle.

10. The computer-implemented method of claim 1, further comprising:

emitting, via an additional illumination light source, light corresponding to the additional illumination; and

stabilizing light to be emitted from the additional illumination light source to compensate for oscillations in power supplied to the additional illumination light source.

11. The computer-implemented method of claim 1, further comprising:

establishing the first point in time when the first image is obtained and establishing the second point in time when the second image is obtained.

12. The computer-implemented method of claim 1, wherein calculating a luminance difference value further comprises:

cancelling out the first base illumination with the second base illumination; and

cancelling out the first ambient illumination with the second ambient illumination.

13. The computer-implemented method of claim 1, wherein the luminance difference value is a function of the additional illumination.

14. The computer-implemented method of claim 13, wherein the first base illumination is equal to the second base illumination and the first ambient illumination is substantially equal to the second ambient illumination.

15. A system for determining luminance of a traffic sign, comprising:

a camera configured to;

a) obtain a first image using a first illumination level at a first point in time, the first illumination level being based on a first base illumination and a first ambient illumination;

b) obtain a second image using a second illumination level at a second point in time, the second illumination level being based on a second base illumination, a second ambient illumination and an additional illumination, the second illumination level being different from the first illumination level, a difference between the first point in time and the second point in time being an interval of time corresponding to a frequency of an electric grid such that the first image and the second image are obtained at a same point of a sine wave of a supply voltage from the electric grid; and

a processor configured to;

c) extract a first array of pixels in the first image, the first array of pixels being representative of the traffic sign;

d) extract a second array of pixels in the second image, the second array of pixels being representative of the traffic sign;

e) calculate a first luminance value of the traffic sign using the first array of pixels, the first luminance value being based on the first base illumination and the first ambient illumination;

f) calculate a second luminance value of the traffic sign using the second array of pixels, the second luminance value being based on the second base illumination, the second ambient illumination and the additional illumination; and

g) calculate a luminance difference value of the traffic sign corresponding to a difference between the first luminance value and the second luminance value.

16. The system of claim 15, wherein the camera is coupled to a vehicle.

17. The system of claim 15, wherein the processor is coupled to a vehicle.

18. The system of claim 15, wherein the first image includes a third array of pixels and wherein the second image includes a fourth array of pixels, the third array of pixels and the fourth array of pixels each corresponding to a second traffic sign.

19. The system of claim 15, further comprising:

a stabilized base illumination light source configured to emit light i) corresponding to the first base illumination included in the first illumination level and ii) corresponding to the second base illumination included in the second illumination level, wherein the first base illumination is equal to the second base illumination.

20. The system of claim 19, further comprising:

a stabilizer device configured to stabilize light to be emitted from the stabilized base illumination light source to compensate for oscillations in power supplied to the stabilized base illumination light source.

21. The system of claim 20, wherein the stabilized base illumination light source is coupled to a vehicle.

22. The system of claim 15, further comprising:

an additional illumination light source configured to emit light corresponding to the additional illumination; and

a stabilizer device configured to stabilize light to be emitted from the additional illumination light source to compensate for oscillations in power supplied to the additional illumination light source.

23. The system of claim 15, further comprising:

a synchronization system coupled to the camera, the synchronization system being configured to establish the first point in time when the first image is obtained and the second point of time when the second image is obtained.

24. The system of claim 15, wherein the first ambient illumination is substantially equal to the second ambient illumination.

25. A system for calculating a luminance of a traffic sign, comprising:

a camera configured to;

(i) obtain a first image of the traffic sign at a first point in time and

(ii) obtain a second image of the traffic sign at a second point in time, a difference between the first point in time and the second point in time being an interval of time, the interval of time corresponding to a frequency of an electric grid such that the first image and the second image are obtained at a same point of a sine wave of a supply voltage from the electric grid;

a processor configured to;

i) extract a first array of pixels in the first image, the first array of pixels being representative of the traffic sign;

ii) extract a second array of pixels in the second image, the second array of pixels being representative of the traffic sign;

(iii) calculate a first luminance value of the traffic sign represented by a first array of pixels in the first image;

(iv) calculate a second luminance value of the traffic sign represented by a second array of pixels in the second image, the second luminance value being different from the first luminance value; and

(v) calculate a luminance difference value corresponding to a difference between the first luminance value and the second luminance value.

26. The system according to claim 25, wherein the first image includes a first illumination level based on a first ambient illumination and the second image includes a second illumination level based on a second ambient illumination and an additional illumination, the first ambient illumination being substantially equal to the second ambient illumination.

27. The system of claim 26, wherein the first illumination level is based on a first base illumination and the second illumination level is based on a second base illumination, the first base illumination being equal to the second base illumination.

28. The system of claim 27, further comprising:

a stabilized base illumination light source configured to emit light corresponding to i) the first base illumination and ii) the second base illumination.

29. The system of claim 28, wherein the stabilized base illumination light source is coupled to a vehicle.

30. The system of claim 28, further comprising:

a stabilizer device configured to stabilize light to be emitted from the stabilized base illumination light source to compensate for oscillations in power supplied to the stabilized base illumination light source.

31. The system of claim 26, further comprising:

an additional illumination light source configured to emit light corresponding to the additional illumination; and

a stabilizer device configured to stabilize light to be emitted from the additional illumination light source to compensate for oscillations in power supplied to the additional illumination light source.

32. The system of claim 25, wherein a synchronization system is coupled to the camera, the synchronization system being configured to establish the first point in time when the first image is obtained and the second point of time when the second image is obtained.

33. The system of claim 25, wherein the camera is coupled to a vehicle.

34. The system of claim 25, wherein the processor is coupled to a vehicle.

35. The system of claim 25, wherein the first image includes a third array of pixels and wherein the second image includes a fourth array of pixels, the third array of pixels and the fourth array of pixels each corresponding to a second traffic sign.

36. A computer-implemented method for calculating a luminance of a traffic sign, comprising:

a) obtaining a first image of the traffic sign at a first point in time;

b) obtaining a second image of the traffic sign at a second point in time, a difference between the first point in time and the second point in time being an interval of time, the interval of time corresponding to a frequency of an electric grid such that the first image and the second image are obtained at a same point of a sine wave of a supply voltage from the electric grid;

c) extracting a first array of pixels in the first image, the first array of pixels being representative of the traffic sign;

d) extracting a second array of pixels in the second image, the second array of pixels being representative of the traffic sign;

e) calculating a first luminance value of the traffic sign represented by a first array of pixels in the first image;

f) calculating a second luminance value of the traffic sign represented by a second array of pixels in the second image, the second luminance value being different from the first luminance value; and

g) calculating a luminance difference value of the traffic sign corresponding to a difference between the first luminance value and the second luminance value.

37. The computer-implemented method of claim 36, wherein a camera is used to perform steps a) and b).

38. The computer-implemented method of claim 37, wherein the camera is coupled to a vehicle.

39. The computer-implemented method of claim 36, wherein a processor is used to perform steps c) through e).

40. The computer-implemented method of claim 39, wherein the processor is coupled to a vehicle.

41. The computer-implemented method of claim 36, wherein the first image includes a third array of pixels and wherein the second image includes a fourth array of pixels, the third array of pixels and the fourth array of pixels each corresponding to a second traffic sign.

42. The computer-implemented method of claim 36, wherein the first image includes a first illumination level based on a first ambient illumination and the second image includes a second illumination level based on a second ambient illumination and an additional illumination, the first ambient illumination being substantially equal to the second ambient illumination.

43. The computer-implemented method of claim 42, wherein the first illumination level is based on a first base illumination and wherein the second illumination level is based on a second base illumination, the first base illumination being equal to the second base illumination.

44. The computer-implemented method of claim 43, further comprising:

emitting, via a stabilized base illumination light source, light corresponding to the first base illumination and the second base illumination; and

stabilizing light to be emitted from the stabilized base illumination light source to compensate for oscillations in power supplied to the stabilized base illumination light source.

45. The computer-implemented method of claim 44, wherein the stabilized base illumination light source is coupled to a vehicle.

46. The computer-implemented method of claim 42, further comprising:

emitting, via an additional illumination light source, light corresponding to the additional illumination; and

stabilizing light to be emitted from the additional illumination light source to compensate for oscillations in power supplied to the additional illumination light source.

47. The computer-implemented method of claim 36, further comprising:

establishing the first point in time when the first image is obtained and establishing the second point in time when the second image is obtained.