Road surface reflection detecting apparatus

• US 7,676,094 B2
• Filed: 01/11/2005
• Issued: 03/09/2010
• Est. Priority Date: 01/14/2004
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Kobayashi, Kenji, Hoki, Kenta, Tamatsu, Yukimasa
• Primary Examiner(s): Bali; Vikkram
• Assistant Examiner(s): ENTEZARI, MICHELLE M
• Application Number:
  US11/032,893
• Publication Number:
  US 20050152581A1
• Time in Patent Office: 1,883 Days
• Field of Search: None
• US Class Current: 382/199
• 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 1/143 combined with another condition, e.g. using vehicle recognition from camera images or activation of wipers
• CPC Class Codes: B60Q 2300/054 Variable non-standard intensity, i.e. emission of various beam intensities different from standard intensities, e.g. continuous or stepped transitions of intensity
• CPC Class Codes: B60Q 2300/112 Vehicle speed
• CPC Class Codes: B60Q 2300/122 Steering angle
• CPC Class Codes: B60Q 2300/134 Yaw
• CPC Class Codes: B60Q 2300/142 Turn signal actuation
• CPC Class Codes: B60Q 2300/312 Adverse weather
• CPC Class Codes: B60Q 2300/41 preceding vehicle
• CPC Class Codes: G06V 10/44 Local feature extraction by analysis of parts of the pattern, e.g. by detecting edges, contours, loops, corners, strokes or intersections; Connectivity analysis, e.g. of connected components
• CPC Class Codes: G06V 20/56 exterior to a vehicle by using sensors mounted on the vehicle
• CPC Class Codes: G06V 2201/08 Detecting or categorising vehicles
• CPC Class Codes: G08G 1/161 Decentralised systems, e.g. inter-vehicle communication

Abstract

A road surface reflection detecting apparatus includes a road recognition unit for recognizing a road in a picture taken by a camera of a road existing in front of a vehicle. A road surface reflection detection unit extracts a picture from the road recognized by the road recognition unit and determines the degree of reflection of light from the surface of the road based on the picture extracted from the road. The picture includes the reflection of light beam radiated from vehicle headlights. If the reflection is determined to be high, the direction or intensity of the light beam from the vehicle headlights is regulated.

Claims

1. A road surface reflection detecting apparatus comprising:

a picture-taking means for taking a first picture including a road in front of a vehicle;

a road recognition means for recognizing a road in the first picture taken by the picture-taking means by identifying horizontal pixel numbers representing a location of pixels serving as horizontal line boundaries of the road and identifying vertical pixel numbers representing a location of pixels serving as vertical line boundaries of the road;

a picture extraction means for extracting from the first picture taken by the picture-taking means a second picture based on the identified horizontal and vertical pixel numbers, the second picture being only a picture in the road recognized by the road recognition means; and

a road surface reflection detection means for detecting a degree of reflection from the surface of a road in the road from the second picture extracted by the picture extraction means.

2. The road surface reflection detecting apparatus according to claim 1, wherein the road surface reflection detection means includes:

a road surface reflection computation means for computing an average luminance value in the road from luminance value of pixels in the second picture extracted by the picture extraction means; and

a determination means for determining whether the average luminance value computed by the road surface reflection computation means is more than a threshold value for the average luminance value, wherein the road surface reflection detection means outputs a determination result indicating that the degree of reflection from the surface of the road is high, when the determination means determines that the average luminance value is more than the threshold value.

3. The road surface reflection detecting apparatus according to claim 1, wherein the road surface reflection detection means includes:

a road surface reflection computation means for computing a luminance gradient representing a rate of change in luminance value of each pixel in the direction of a horizontal line in the second picture extracted by the picture extraction means and computing an average luminance gradient for the entire picture from the computed luminance gradients; and

a determination means for determining whether the average luminance gradient computed by the road surface reflection computation means is more than a threshold value for the average luminance gradient, wherein the road surface reflection detection means outputs a determination result indicating that the degree of reflection from the surface of the road is high, when the determination means determines that the average luminance gradient is more than the threshold value.

4. The road surface reflection detecting apparatus according to claim 1, wherein the road surface reflection detection means includes:

a road surface reflection computation means for computing a luminance gradient representing a rate of change in luminance value of each pixel in the direction of a horizontal line in the second picture extracted by the picture extraction means and computing a luminance gradient count representing the number of aforementioned computed luminance gradients; and

a determination means for determining whether the luminance gradient count computed by the road surface reflection computation means is more than a threshold value for the luminance gradient count, wherein the road surface reflection detection means outputs a determination result indicating that the degree of reflection from the surface of the road is high, when the determination means determines that the luminance gradient count is more than a threshold value for the luminance gradient count.

5. The road surface reflection detecting apparatus according to claim 1, wherein the road surface reflection detection means includes:

a road surface reflection computation means for locating, based on luminance value of pixels in the second picture extracted by the picture extraction means, pixel positions each having a high luminance of more than a threshold value and computing a size of a high luminance area comprising the located pixel positions; and

a determination means for determining whether the area size of the high luminance area computed by the road surface reflection computation means is more than a threshold value for the size of the high luminance area, wherein the road surface reflection detection means determines the degree of reflection from the surface of the road based on a determination result output by the determination means.

6. The road surface reflection detecting apparatus according to claim 5, wherein:

the road surface reflection computation means computes the number of pixels included in the high luminance area as the size of the high luminance area;

the determination means determines whether the number of pixels included in the high luminance area is more than a pixel count threshold value; and

the road surface reflection detection means outputs a determination result indicating that the degree of reflection from the surface of the road is high, when the determination means determines that the number of pixels included in the high luminance area is more than the pixel count threshold value.

7. The road surface reflection detecting apparatus according to claim 5, wherein:

the road surface reflection computation means computes an aspect ratio of the high luminance area as the size of the high luminance area;

the determination means determines whether the aspect ratio of the high luminance area is more than a threshold value for the aspect ratio; and

the road surface reflection detection means outputs a determination result indicating that the degree of reflection from the surface of the road is high, when the determination means determines that the aspect ratio of the high luminance area is more than threshold value for the aspect ratio.

8. The road surface reflection detecting apparatus according to claim 1, wherein the road surface reflection detection means includes:

a road surface reflection computation means for locating, based on luminance value of pixels in the second picture extracted by the picture extraction means, pixel positions each having a high luminance at least equal to a threshold value and computing a fluctuation quantity representing the degree of smoothness of the boundary line enclosing a high luminance area comprising the located pixel positions; and

a determination means for determining whether the fluctuation quantity representing the degree of smoothness of the boundary line enclosing the high luminance area is more than a threshold value for the fluctuation quantity, wherein the road surface reflection detection means outputs a determination result indicating that the degree of reflection from the surface of the road is high, when the determination means determines that the fluctuation quantity representing the degree of smoothness of the boundary line enclosing the high luminance area is more than the threshold value for the fluctuation quantity.

9. The road surface reflection detecting apparatus according to any one of claims 2 to 8, wherein the road surface reflection computation means locates at least one of the positions of pixels in one of driving lane marks including a traffic lane inside the road and the positions of pixels in road paint based on luminance value of pixels in the second picture extracted by the picture extraction means, and excludes at least one of the luminance value of the located positions of pixels, luminance gradients existing at the located positions of pixels, and the high luminance area from computation.

10. The road surface reflection detecting apparatus according to any one of claims 5 to 8, wherein, in case a plurality of the high luminance areas exists, the road surface reflection computation means computes degrees of separation between the high luminance areas, and determines the degree of reflection from the surface of a road by treating a plurality of high luminance areas each having a degree of separation not exceeding a threshold value for the degree of separation as one high luminance area.

11. The road surface reflection detecting apparatus according to any one of claims 5 to 8, wherein, in case a plurality of high luminance areas exists, the road surface reflection computation means locates the positions of driving lanes in the road based on luminance value of pixels in the picture extracted by the picture extraction means, and computes the size of a high luminance area existing between the located positions of the traffic lanes or a fluctuation quantity representing the degree of smoothness of a boundary line enclosing the high luminance area.

12. The road surface reflection detecting apparatus according to claim 11, wherein, in case a plurality of high luminance areas exists between the located traffic lanes, the road surface reflection computation means computes the size of a high luminance area closest to the center line of the traffic lanes or a fluctuation quantity representing the degree of smoothness of a boundary line enclosing the high luminance area.

13. The road surface reflection detecting apparatus according to any one of claims 5 to 8, wherein the road surface reflection computation means finds the direction of the long axis of the high luminance area and, when the direction of the long axis of the high luminance area is different from a direction toward a light source of the vehicle or a direction toward the picture-taking means, excludes the high luminance area from computation.

14. The road surface reflection detecting apparatus according to claim 1, further comprising:

a body detection means for detecting a body existing in front of the vehicle, wherein the picture extraction means extracts the second picture in a road located between the vehicle and the body existing in front of the vehicle in case the body detection means detects the body.

15. The road surface reflection detecting apparatus according to claim 1, further comprising:

a body detection means for detecting a body, which exists in front of the vehicle and includes a vehicle running immediately ahead of the vehicle, wherein the picture extraction means extracts the second picture in a road located between the vehicle and the body, which exists in front of the vehicle and is the vehicle running immediately ahead of the vehicle in case the body detection means detects the body;

wherein the road surface reflection detection means includes;

a road surface reflection computation means for computing luminance derivative value between pixels in a horizontal direction of the second picture from luminance value of pixels in the second picture extracted by the picture extraction means and computing a sum of the computed luminance derivative value for the entire picture from the luminance derivative value, and

a determination means for determining whether the sum of the luminance derivative value computed by the road surface reflection computation means is more than a threshold value for the sum of the luminance derivative value, and wherein the road surface reflection detection means outputs a determination result indicating that the degree of reflection from the surface of the road is high, when the determination means determines that the sum of the luminance derivative value is more than a threshold value for the sum of the luminance derivative value.

16. The road surface reflection detecting apparatus according to claim 14 or 15, wherein the body detection means detects the body, which exists in front of the vehicle and includes a vehicle running immediately ahead of the vehicle, by using at least the picture taken by the picture-taking means of a picture output by a radar.

17. The road surface reflection detecting apparatus according to claim 1, wherein:

the road surface reflection detection means includes a plurality of road surface reflection computation means which computes respective degrees of reflection from the surface of the road in a different manner from one another; and

wherein the road surface reflection detection means determines a final degree of reflection from the surface of the road based on at least two of computed degrees of reflection from the surface of the road.

18. The road surface reflection detecting apparatus, according to claim 17, wherein the determination means includes a plurality of threshold value, as a criterion threshold value, and outputs a result of determination based on the criterion threshold value, and wherein the road surface reflection detection means determines the degree of reflection from the surface of the road based on a determination result by using the criterion threshold value.

19. The road surface reflection detecting apparatus according to claim 17, wherein the road surface reflection detection means determines a final degree of reflection from the surface of a road by at least considering changes observed with the lapse of time by detecting a degree of reflection from the road or considering detection results obtained at different times by detecting a degree of reflection from the surface of the road.

20. The road surface reflection detecting apparatus according to claim 1, further comprising:

a speed detection means for detecting a speed of the vehicle, wherein the picture extraction means has an extracted-range determination means for determining a range of a picture to be extracted based on a detection result produced by the speed detection means.

21. The road surface reflection detecting apparatus according to claim 1, further comprising:

a turn signal detection means for detecting a turn signal of the vehicle, wherein the picture extraction means has an extracted-range determination means for determining a range of the picture to be extracted based on a detection result by the turn signal detection means.

22. The road surface reflection detecting apparatus according to claim 1, further comprising:

a vehicle condition detection means for detecting one of vehicle conditions, which are a steering angle of a steering wheel in the vehicle and an angular speed around the vertical direction of the vehicle, wherein the picture extraction means has an extracted-range determination means for determining a range of the picture to be extracted based on a detection result produced by the vehicle condition detection means.

23. The road surface reflection detecting apparatus according to any one of claims 20 to 22, wherein the extracted-range determination means determines a range of the picture to be extracted based on at least two of the detection results by the speed detection means, the turn signal detection means and the vehicle condition detection means.

24. The road surface reflection detecting apparatus according to claim 1, further comprising:

a headlight control means for executing control of at least either directions of light beams radiated by headlights of the vehicle or light intensities of the light beams in accordance with a detection result by the road surface reflection detection means.

25. The road surface reflection detecting apparatus according to claim 1, further comprising:

an inter-vehicle distance control means for executing control of a distance between the vehicle and a vehicle running immediately ahead of the vehicle in accordance with a detection result by the road surface reflection detection means.

26. The road surface reflection detecting apparatus according to claim 1, wherein the road surface reflection detection means determines a plurality of high luminance areas based on the degree of reflection and computes one high luminance area, each of the plurality of the high luminance areas being separated from one another by less than a threshold value.

27. The road surface reflection detecting apparatus according to claim 1, wherein the road surface reflection detection means computes positions of driving lanes in the road based on the second picture extracted by the picture extraction means, and computes a size of a high luminance area existing within the computed position of the driving lane or a fluctuation quantity representing a degree of smoothness of a boundary line enclosing the high luminance area.

28. The road surface reflection detecting apparatus according to claim 1, wherein the road surface reflection detection means determines a high luminance area of higher luminance than a predetermined luminance, finds a direction of a longitudinal axis of the high luminance area, and excludes the high luminance area from being used in computation when the direction of the longitudinal axis of the high luminance area is different from a direction toward a light source of the vehicle or a direction toward the picture-taking means.

29. A road surface reflection detecting apparatus comprising:

a camera provided on a vehicle for taking a picture of a front area including a road in front of the vehicle and generating a picture signal of the front area;

a road recognition unit connected to the camera for recognizing only a road in the picture signal by identifying horizontal pixel numbers representing a location of pixels serving as horizontal line boundaries of the road and identifying vertical pixel numbers representing a location of pixels serving as vertical line boundaries of the road, wherein the road information is based on the identified horizontal and vertical pixel numbers and defines the road in the first picture signal;

a picture extraction unit connected to the camera for extracting a second picture, the second picture being only a picture in the road based on the road information produced by the road recognition unit; and

a road surface reflection detection unit for detecting a degree of reflection of light from a surface of the road from the second picture extracted by the picture extraction unit.

30. A road surface reflection detecting apparatus comprising

a picture-taking means for taking a first picture including a road in front of a vehicle;

a road recognition means for recognizing a road in the first picture taken by the picture-taking means by identifying horizontal pixel numbers representing a location of pixels serving as horizontal line boundaries of the road and identifying vertical pixel numbers representing a location of pixels serving as vertical line boundaries of the road;

a picture extraction means for extracting a second picture of only the road recognized by the road recognition means based on the identified horizontal and vertical pixel numbers; and

a road surface reflection detection means for detecting a degree of reflection from the surface of a road in the road from the second picture extracted by the picture extraction means.

31. A road surface reflection detecting apparatus comprising:

a picture-taking means for taking a first picture including a road in front of a vehicle;

a road recognition means for recognizing a road in the first picture taken by the picture-taking means by identifying horizontal pixel numbers representing a location of pixels serving as horizontal line boundaries of the road and identifying vertical pixel numbers representing a location of pixels serving as vertical line boundaries of the road;

a picture extraction means for extracting a second picture based on the identified horizontal and vertical pixel numbers, the second picture being only a picture in the road recognized by the road recognition means; and

a road surface reflection detection means for detecting a degree of reflection from the surface of a road from the second picture extracted by the picture extraction means, wherein the road surface reflection detection means includes;

a road surface reflection computations means for (1) locating pixel positions each having a high luminance of more than a first threshold value indicative of a predetermined luminance of a pixel based on luminance values of pixels in the second picture extracted by the picture extraction means and (2) computing a size of a high luminance area including the located pixel positions, the high luminance area including a plurality of high luminance areas each having a degree of separation not exceeding a second threshold value indicative of a predetermined degree of separation between the high luminance areas in case the high luminance areas exist at a plurality of positions; and

a determination means for determining whether an area size of the high luminance area is more than a third threshold value indicative of a predetermined size of the high luminance area, wherein the road surface reflection detection means determines the degree of reflection from the surface of the road based on a determination result output by the determination means.

32. A road surface reflection detecting apparatus comprising:

a picture-taking means for taking a first picture including a road in front of a vehicle;

a road recognition means for recognizing a road in the first picture taken by the picture-taking means by identifying horizontal pixel numbers representing a location of pixels serving as horizontal line boundaries of the road and identifying vertical pixel numbers representing a location of pixels serving as vertical line boundaries of the road;

a picture extraction means for extracting a second picture based on the identified horizontal and vertical pixel numbers, the second picture being only a picture in the road recognized by the road recognition means; and

a road surface reflection detection means for detecting a degree of reflection from the surface of a road in the road from the second picture extracted by the picture extraction means,

wherein the road surface reflection detection means includes;

a road surface reflection computation means for (1) locating, based on luminance value of pixels in the second picture extracted by the picture extraction means, pixel positions each having a high luminance of more than a first threshold value indicative of a predetermined luminance of a pixel, (2) computing a size of a high luminance area including the located pixel positions, (3) computing degrees of separation between the high luminance areas in case a plurality of the high luminance areas exist, (4) treating a plurality of the high luminance areas each having a degree of separation not exceeding a second threshold value indicative of a predetermined degree of separation as one high luminance area, (5) computing a fluctuation quantity representing a degree of smoothness of a boundary line enclosing the one high luminance area in case the one luminance area exists at a plurality of positions; and

a determination means for determining whether the fluctuation quantity representing the degree of smoothness of the boundary line is more than a third threshold value indicative of a predetermined fluctuation quantity,

wherein the road surface reflection detection means outputs a determination result indicating that the degree of reflection from the surface of the road is high, when the determination means determines that the fluctuation quantity representing the degree of smoothness of the boundary line enclosing the high luminance area is more than the third threshold value.

33. A road surface reflection detecting apparatus comprising:

a picture-taking means for taking a first picture including a road in front of a vehicle;

a road recognition means for recognizing a road in the first picture taken by the picture-taking means by identifying horizontal pixel numbers representing a location of pixels serving as horizontal line boundaries of the road and identifying vertical pixel numbers representing a location of pixels serving as vertical line boundaries of the road;

a picture extraction means for extracting a second picture based on the identified horizontal and vertical pixel numbers, the second picture being only a picture in the road recognized by the road recognition means; and

a road surface reflection detection means for detecting a degree of reflection from the surface of a road in the road from the second picture extracted by the picture extraction means,

wherein the road surface reflection detection means includes;

a road surface reflection computation means for (1) locating, based on luminance value of pixels in the second picture extracted by the picture extraction means, pixel positions each having a high luminance of more than a first threshold value indicative of a predetermined luminance of a pixel, (2) computing a size of a high luminance area including the located pixel positions, the high luminance area existing in a traffic lane in the road, which is determined based on the luminance value of each pixel in the second picture extracted by the picture extraction means, in case the high luminance areas exists at a plurality of positions in the road; and

a determination means for determining whether an area size of the high luminance area is more than a second threshold value indicative of a predetermined size of high luminance area, and

wherein the road surface reflection detection means determines the degree of reflection from the surface of the road based on a determination result output by the determination means.

34. A road surface reflection detecting apparatus comprising:

a picture-taking means for taking a first picture including a road in front of a vehicle;

a road recognition means for recognizing a road in the first picture taken by the picture-taking means by identifying horizontal pixel numbers representing a location of pixels serving as horizontal line boundaries of the road and identifying vertical pixel numbers representing a location of pixels serving as vertical line boundaries of the road;

a picture extraction means for extracting a second picture based on the identified horizontal and vertical pixel numbers, the second picture being only a picture in the road recognized by the road recognition means; and

a road surface reflection detection means for detecting a degree of reflection from the surface of a road in the road from the second picture extracted by the picture extraction means,

wherein the road surface reflection detection means includes;

a road surface reflection computation means for (1) locating, based on luminance value of pixels in the second picture extracted by the picture extraction means, pixel positions each having a high luminance of more than a first threshold value indicative of a predetermined luminance of a pixel, (2) computing a fluctuation quantity representing a degree of smoothness of a boundary line enclosing a high luminance area including the located pixel positions in case the one luminance area exists at a plurality of locations, the fluctuation quantity being with respect to one of a plurality of high luminance areas existing at a position closest to a center position of a traffic lane in the road in case the high luminance area exists at a plurality of positions inside the traffic lane, and

a determination means for determining whether the fluctuation quantity representing the degree of smoothness of the boundary line is more than a second threshold value indicative of a predetermined fluctuation quantity,

wherein the road surface reflection detection means outputs a determination result indicating that the degree of reflection from the surface of the road is high, when the determination means determines that the fluctuation quantity is more than the second threshold value.

35. A road surface reflection detecting apparatus comprising:

a picture-taking means for taking a first picture including a road in front of a vehicle;

a road recognition means for recognizing a road in the first picture taken by the picture-taking means;

a picture extraction means for extracting from the first picture taken by the picture-taking means a second picture, the second picture being only a picture in the road recognized by the road recognition means; and

a road surface reflection detection means for detecting a degree of reflection from the surface of a road in the road from the second picture extracted by the picture extraction means, wherein the road surface reflection detection means includes;

a road surface reflection computation means for locating, based on luminance value of pixels in the second picture extracted by the picture extraction means, pixel positions each having a high luminance at least equal to a threshold value and computing a fluctuation quantity representing the degree of smoothness of the boundary line enclosing a high luminance area comprising the located pixel positions, the fluctuation quantity being a summation of deviation magnitudes of positions of pixels at a horizontal-direction center of corresponding horizontal lines; and

a determination means for determining whether the fluctuation quantity representing the degree of smoothness of the boundary line enclosing the high luminance area is more than a threshold value for the fluctuation quantity, wherein the road surface reflection detection means outputs a determination result indicating that the degree of reflection from the surface of the road is high, when the determination means determines that the fluctuation quantity representing the degree of smoothness of the boundary line enclosing the high luminance area is more than the threshold value for the fluctuation quantity.

36. A road surface reflection detecting apparatus comprising:

a picture-taking means for taking a first picture including a road in front of a vehicle;

a road recognition means for recognizing a road in the first picture taken by the picture-taking means;

a picture extraction means for extracting from the first picture taken by the picture-taking means a second picture, the second picture being only a picture in the road recognized by the road recognition means; and

a road surface reflection detection means for detecting a degree of reflection from the surface of a road in the road from the second picture extracted by the picture extraction means, wherein the road surface reflection detection means includes;

a road surface reflection computation means for locating, based on luminance value of pixels in the second picture extracted by the picture extraction means, pixel positions each having a high luminance of more than a threshold value and computing a size of a high luminance area comprising the located pixel positions; and

a determination means for determining whether the area size of the high luminance area computed by the road surface reflection computation means is more than a threshold value for the size of the high luminance area, wherein the road surface reflection detection means determines the degree of reflection from the surface of the road based on a determination result output by the determination means,

wherein, in case a plurality of the high luminance areas exists, the road surface reflection computation means computes degrees of separation between the high luminance areas, and determines the degree of reflection from the surface of a road by treating a plurality of high luminance areas each having a degree of separation not exceeding a threshold value for the degree of separation as one high luminance area.

37. A road surface reflection detecting apparatus comprising:

a picture-taking means for taking a first picture including a road in front of a vehicle;

a road recognition means for recognizing a road in the first picture taken by the picture-taking means;

a picture extraction means for extracting from the first picture taken by the picture-taking means a second picture, the second picture being only a picture in the road recognized by the road recognition means; and

a road surface reflection detection means for detecting a degree of reflection from the surface of a road in the road from the second picture extracted by the picture extraction means, wherein the road surface reflection detection means includes;

a road surface reflection computation means for locating, based on luminance value of pixels in the second picture extracted by the picture extraction means, pixel positions each having a high luminance of more than a threshold value and computing a size of a high luminance area comprising the located pixel positions; and

a determination means for determining whether the area size of the high luminance area computed by the road surface reflection computation means is more than a threshold value for the size of the high luminance area, wherein the road surface reflection detection means determines the degree of reflection from the surface of the road based on a determination result output by the determination means,

wherein in case a plurality of high luminance areas exists, the road surface reflection computation means locates the positions of driving lanes in the road based on luminance value of pixels in the second picture extracted by the picture extraction means, and computes the size of a high luminance area existing between the located positions of the traffic lanes or a fluctuation quantity representing the degree of smoothness of a boundary line enclosing the high luminance area,

wherein in case a plurality of high luminance areas exists between the located traffic lanes, the road surface reflection computation means computes the size of a high luminance area closest to the center line of the traffic lanes or a fluctuation quantity representing the degree of smoothness of a boundary line enclosing the high luminance area, the fluctuation quantity being a summation of deviation magnitudes of positions of pixels at a horizontal-direction center of corresponding horizontal lines.