JP3914910B2 - Display inspection method and apparatus - Google Patents

Description

  The present invention relates to an inspection method for an LCD display or the like, and more particularly to an inspection method and apparatus for display quality of a display.

  As a method of evaluating luminance unevenness and color unevenness in a conventional color display or the like, the display screen is imaged, and the luminance difference and chromaticity difference between an arbitrary point in the captured image and other points are calculated, and at multiple points. A method for evaluating luminance unevenness and color unevenness of the entire screen based on the sum of absolute values of the calculated luminance difference and chromaticity difference (Patent Document 1), or an arbitrary image on an image obtained by imaging a display screen of a color display device The evaluation point chromaticity of the evaluation point that is the point and the surrounding average chromaticity in a limited range around the evaluation point are obtained, and the difference between the evaluation point chromaticity and the surrounding average chromaticity is preset. When the threshold value is exceeded, a numerical value corresponding to the amount exceeding the threshold value is used as the evaluation value of the evaluation point, and the total value of the plurality of evaluation values on the display screen is evaluated as the color unevenness value of the entire display screen of the color display 2) etc. are known.

JP-A-10-2800 JP 2003-57146 A

  In the conventional color display evaluation method in which the inspection screen displayed on the display to be inspected is imaged with a CCD camera, and the captured image data is input to a personal computer and processed, thereby automatically inspecting the display quality of the display. Although it is possible to evaluate luminance unevenness and color unevenness over the entire screen, it is difficult to perform accurate evaluation when the luminance unevenness is locally generated in an island shape.

  For example, uneven brightness that changes throughout the screen, such as uneven brightness of the backlight of an LCD display, is considered to be a good product, but uneven brightness that is locally island-like is conspicuous even with a similar brightness difference, and is considered a defective product. In such a case, it is difficult to distinguish between the luminance change of the entire screen and the local luminance change with the conventional evaluation method. There is a problem that non-defective product brightness is determined to be defective.

  SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a display inspection method capable of ignoring luminance unevenness that changes locally on the entire screen and NG determination only on luminance unevenness that is locally island-like. Is to provide.

In the display inspection method of the present invention, a rectangular minute area is set by equally dividing the screen in the vertical direction and the horizontal direction, respectively, and the three minute areas continuously touching in the horizontal or vertical direction are spread over the entire screen. It is calculated by scanning at a predetermined pitch and substituting the average luminance values L1, L2, L3 and the average chromaticity values x1, y1, x2, y2, x3, y3 in the three minute areas into the following equation. Brightness non-uniformity determination value LD and chromaticity non-uniformity determination values XD and YD are calculated for each scanning position, and the quality determination of luminance non-uniformity and chromaticity non-uniformity is performed based on the calculated determination values of all scanning positions. .
LD = ABS (D / SQR ((L1-L3) ^ 2 + D ^ 2) * ((L1 + L3) / 2-L2))
XD = ABS (D / SQR ((x1-x3) ^ 2 + D ^ 2) * ((x1 + x3) / 2-x2))
YD = ABS (D / SQR ((y1-y3) ^ 2 + D ^ 2) * ((y1 + y3) / 2-y2))
Where D is the distance between the minute areas on both sides, ABS (x) is the absolute value of x, SQR (x) is the square root of x, x ^ y is x to the power of y, and x * y is x and y Is the product.

  According to another display inspection method of the present invention, a rectangular minute area is set by equally dividing the screen in the vertical and horizontal directions, and the three minute areas that are continuously in contact with each other in the horizontal or vertical direction are set on the entire screen. The image is scanned at a predetermined pitch, and the average luminance values L1, L2, L3 and the average chromaticity values x1, y1, x2, y2, x3, y3 in the three minute areas are obtained, and the average of the areas on both sides is obtained. Average value of luminance values L1, L3 and average chromaticity values x1, y1, x3, y3 (L1 + L3) / 2 and (x1 + x3) / 2, (y1 + y3) / 2, average of the middle area The difference between the luminance value L2 and the average chromaticity values x2 and y2 is obtained for each scanning position, thereby determining whether or not the luminance unevenness and the chromaticity unevenness are acceptable.

Further, the display inspection apparatus of the present invention includes an image acquisition means for acquiring a display screen image obtained by imaging a display screen of a color display device, and a rectangular shape by equally dividing the acquired display screen image in the vertical direction and the horizontal direction, respectively. Are scanned at a predetermined pitch over the entire screen, and the average luminance values L1, L2, Means for determining L3 and average chromaticity values x1, y1, x2, y2, x3, y3, and average luminance values L1, L2, L3 and average chromaticity values x1, y1, means for calculating the luminance unevenness determination value LD and the chromaticity unevenness determination values XD and YD for each scanning position by substituting x2, y2, x3, and y3 into the following equation; Characterized in that it comprises a means for performing the quality determination of the brightness unevenness and chromaticity unevenness by decision values for all scan positions.
LD = ABS (D / SQR ((L1-L3) ^ 2 + D ^ 2) * ((L1 + L3) / 2-L2))
XD = ABS (D / SQR ((x1-x3) ^ 2 + D ^ 2) * ((x1 + x3) / 2-x2))
YD = ABS (D / SQR ((y1-y3) ^ 2 + D ^ 2) * ((y1 + y3) / 2-y2))
Where D is the distance between the minute areas on both sides, ABS (x) is the absolute value of x, SQR (x) is the square root of x, x ^ y is x to the power of y, and x * y is x and y Is the product.

  Another display inspection apparatus according to the present invention includes an image acquisition unit that acquires a display screen image obtained by imaging a display screen of a color display device, and a rectangular shape by equally dividing the acquired display screen image in the vertical direction and the horizontal direction, respectively. Are scanned at a predetermined pitch over the entire screen, and the average luminance values L1, L2, Means for determining L3 and average chromaticity values x1, y1, x2, y2, x3, y3, and average luminance values L1, L2, L3 and average chromaticity values x1, y1, x2 of the three micro areas thus determined , Y2, x3, y3, average luminance values L1, L3 and average chromaticity values x1, y1, x3, y3 of both sides (L1 + L3) / 2 and (x1 + x3) / 2, (y1 + y3) / 2 and the middle bro Means for calculating the luminance unevenness determination value and the chromaticity unevenness determination value for each scanning position based on the difference between the average luminance value L2 and the average chromaticity values x2 and y2, and the calculated determination values for all the scanning positions. Means for determining whether or not luminance unevenness and chromaticity unevenness are acceptable.

  According to the present invention, it is possible to extract only luminance unevenness that is locally island-like while ignoring changes in luminance on the entire screen. If the brightness variation that changes on the entire screen is a non-defective product, but the brightness variation that is locally island-like is conspicuous even with the same brightness difference, it will be a defective product. The brightness unevenness is ignored, and only the brightness unevenness that is locally island-shaped can be determined as NG.

  FIG. 1 is a conceptual diagram showing an embodiment of a display inspection apparatus of the present invention in which a display of a mobile phone is an inspection object.

  The display inspection apparatus according to the present embodiment captures a mobile phone 1 having displays 1-1 and 1-2 to be inspected, a CCD camera 2 that images the screen of the display 1-1, and a screen of the display 1-2. A CCD camera 3, an image input board 4 for A / D converting video signals output from the CCD cameras 2, 3, a DC power supply 5 for generating power to be supplied to the mobile phone 1, and a DC power supply 5 A circuit for connecting the power source to the mobile phone 1, a power source circuit for the CCD cameras 2 and 3, a circuit for connecting the video signals output from the CCD cameras 2 and 3 to the image input board 4, and a communication for controlling the mobile phone 1 I / F box 6 provided with a circuit for use, and the mobile phone 1 is controlled via the I / F box 6 to display an inspection screen on the displays 1-1 and 1-2 and to display the I / F box And an automatic inspection control apparatus (hereinafter referred to as a personal computer) comprising a personal computer or the like that automatically inspects the display quality of the displays 2 and 3 by processing the image data of the CCD cameras 2 and 3 input via the image box 6 and the image input board 4. 7) and a display 8 for displaying the inspection result by the output from the personal computer 7.

  FIG. 2 shows an operation flowchart of the display inspection apparatus of the present embodiment. 3 to 7 are diagrams for explaining the processing of the image data in the present embodiment, and FIG. 8 is a diagram for explaining a method for calculating the local luminance unevenness determination value of the image data in the present embodiment. FIG. Hereinafter, the operation of the present embodiment will be described with reference to FIGS.

  First, the personal computer 7 controls the mobile phone 1 via the I / F box 6 to display an all white screen on the display 1-1. Next, the personal computer 7 inputs captured image data of the CCD camera 2 via the I / F box 6 and the image input board 4. Since the CCD camera 2 is installed so that the entire screen of the display 1-1 is in the field of view, the input image data 9 is data as shown in FIG.

  Next, the personal computer 7 detects the screen position in the input image data 9 according to the screen position detection method shown in FIG.

  First, the personal computer 7 calculates a linear expression indicating the screen upper contour line 10-1 by detecting the contour line downward from the upper end of the image data 9. Next, by performing contour detection upward from the lower end of the image data 9, a linear expression indicating the screen lower contour 10-2 is calculated. Next, by performing contour detection in the right direction from the left end of the image data 9, a linear expression indicating the screen left contour 10-3 is calculated. Next, by performing contour detection in the left direction from the right end of the image data 9, a linear expression indicating the screen right contour 10-4 is calculated. By performing the above processing, it can be recognized that the range surrounded by the contour lines 10-1 to 10-4 is the screen position.

  Next, the personal computer 7 calculates the screen center luminance and chromaticity of the input image data 9 according to the screen center luminance and chromaticity calculation method shown in FIG.

First, the personal computer 7 calculates average values Rc, Gc, and Bc of pixel values R (red component), G (green component), and B (blue component) in a rectangular area 11 having a center of 10 mm on the screen. Then, Rc, Gc, and Bc are converted into tristimulus values Xc, Yc, and Zc of the XYZ color system by [Formula 1-1], [Formula 1-2], and [Formula 1-3]. 1] [Expression 2-2] Xc, Yc, Zc are converted into color coordinates xc, yc and luminance value Lc by [Expression 2-3].
X = 0.607R + 0.174G + 0.201B (Equation 1-1)
Y = 0.299R + 0.587G + 0.114B (Equation 1-2)
Z = 0.066G + 1.117B (Formula 1-3)
x = X / (X + Y + Z) ... (Formula 2-1)
y = Y / (X + Y + Z) (Equation 2-2)
L = Y (Equation 2-1)
X, Y, Z: Tristimulus values in the XYZ color system
R, G, B: 3 primary color stimulus values
x, y: Color coordinates
L: Luminance

  Next, the personal computer 7 determines whether or not the luminance value Lc and the color coordinates xc and yc are within a preset allowable range. Display on the display 8 to end the inspection.

  When the luminance value Lc and the color coordinates xc and yc are within the allowable range, the personal computer 7 uses the peripheral luminance unevenness and peripheral chromaticity unevenness determination values as the peripheral luminance unevenness and peripheral chromaticity unevenness determination values shown in FIG. The calculation is performed according to the calculation method method.

  First, the personal computer 7 calculates the position of a minute area that equally divides the screen into 6 parts in the vertical direction and 8 parts in the horizontal direction. Average luminance and average chromaticity are calculated using [Formula 1-1] to [Formula 1-3] and [Formula 2-1] to [Formula 2-3].

  Then, difference values between the average luminance and average chromaticity in the 24 minute areas in the screen peripheral area 12 and the average luminance and average chromaticity of the rectangular area 11 of the screen center 10 mm are calculated, respectively. The maximum value of the difference chromaticity is set as the peripheral luminance unevenness determination value and the peripheral chromaticity unevenness determination value.

  Next, the personal computer 7 determines whether or not the peripheral luminance unevenness determination value and the peripheral chromaticity unevenness determination value are within a preset allowable range, and if they are not within the allowable range, the inspection result NG is determined. It is displayed on the display 8 and the inspection is finished.

  When the peripheral luminance unevenness determination value and the peripheral chromaticity unevenness determination value are within the allowable range, the personal computer 7 converts the local luminance unevenness and local chromaticity unevenness determination values into the local luminance unevenness shown in FIGS. It calculates according to the calculation method of a local chromaticity nonuniformity determination value.

  When the horizontal direction local luminance unevenness determination value and the horizontal direction local chromaticity unevenness determination value are calculated, as shown in FIG. 6, the personal computer 7 has a vertical width V / 6 (V is the screen) that touches the upper left end of the screen. Vertical area), horizontal area H / 8 (H is the horizontal width of the screen) area A1, area A2 of the same shape in contact with the right of A1, and area A3 of the same shape in contact with the right of A2 are calculated. Average luminances L1 to L3 and average chromaticities x1 to x3 and y1 to y3 are calculated.

  Then, Diff_L_H, Diff_x_H, and Diff_y_H are calculated by substituting L1 to L3, x1 to x3, and y1 to y3 into [Expression 3-1] to [Expression 3-3]. Subsequently, Diff_L_H, Diff_x_H, and Diff_y_H at positions where the blocks A1, A2, and A3 are shifted to the right by H / 16 are calculated. Further, Diff_L_H, Diff_x_H, and Diff_y_H at each position are calculated until A3 touches the right edge of the screen while shifting rightward by H / 16.

When A3 touches the right edge of the screen, next, the blocks A1, A2, and A3 are shifted downward by V / 12, and Diff_L_H, Diff_x_H, and Diff_y_H are calculated while shifting again from the left edge to the right edge at an H / 16 pitch. Then, Diff_L_H, Diff_x_H, and Diff_y_H are calculated while shifting at the same pitch until the blocks A1, A2, and A3 reach the lower right end. When the blocks A1, A2, and A3 reach the lower right corner, the maximum values of Diff_L_H, Diff_x_H, and Diff_y_H calculated so far are obtained, and the maximum values are determined as horizontal local luminance unevenness determination values and horizontal local chromaticity unevenness determination values. And
Diff_L_H = ABS ((H / 4) / SQR ((L1-L3) ^ 2 + (H / 4) ^ 2) * ((L1 + L3) / 2-L2)) ... (Equation 3-1)
Diff_x_H = ABS ((H / 4) / SQR ((x1-x3) ^ 2 + (H / 4) ^ 2) * ((x1 + x3) / 2-x2)) (Equation 3-2)
Diff_y_H = ABS ((H / 4) / SQR ((y1-y3) ^ 2 + (H / 4) ^ 2) * ((y1 + y3) / 2-y2)) ... (Equation 3-3)
Here, ABS (x) means the absolute value of x, SQR (x) means the square root of x, x ^ y means x to the power of y, and x * y is the product of x and y. means. H / 4 corresponds to the distance between the minute areas A1 and A3 on both sides.

  Next, when calculating the vertical direction local luminance unevenness determination value and the vertical direction local chromaticity unevenness determination value, as shown in FIG. 7, the personal computer 7 has a vertical width V / 6 in contact with the upper left end of the screen, The position of the area A1 having a width H / 8, the area A2 having the same shape in contact with A1 and the area A3 having the same shape in contact with A2 is calculated, and the average luminances L1 to L3 and the average chromaticity in each area are calculated. x1 to x3 and y1 to y3 are calculated.

  Then, Diff_L_V, Diff_x_V, and Diff_y_V are calculated by substituting L1 to L3, x1 to x3, and y1 to y3 into [Expression 3-4] to [Expression 3-6]. Subsequently, Diff_L_V, Diff_x_V, and Diff_y_V at positions where the blocks A1, A2, and A3 are shifted to the right by H / 16 are calculated. Further, Diff_L_V, Diff_x_V, and Diff_y_V at each position are calculated until A3 touches the right edge of the screen while shifting rightward by H / 16.

When A3 touches the right edge of the screen, next, the blocks A1, A2, and A3 are shifted downward by V / 12, and Diff_L_V, Diff_x_V, and Diff_y_V are calculated while shifting again from the left edge to the right edge at H / 16 pitch. Then, Diff_L_V, Diff_x_V, and Diff_y_V are calculated while shifting at the same pitch until the blocks A1, A2, and A3 reach the lower right end. When the blocks A1, A2, and A3 reach the lower right corner, the maximum values of Diff_L_V, Diff_x_V, and Diff_y_V calculated so far are obtained, and the maximum values are determined as the vertical direction local luminance unevenness determination value and the vertical direction local chromaticity unevenness determination value. And
Diff_L_V = ABS ((V / 3) / SQR ((L1-L3) ^ 2 + (V / 3) ^ 2) * ((L1 + L3) / 2-L2)) ... (Equation 3-4)
Diff_x_V = ABS ((V / 3) / SQR ((x1-x3) ^ 2 + (V / 3) ^ 2) * ((x1 + x3) / 2-x2)) ... (Equation 3-5)
Diff_y_V = ABS ((V / 3) / SQR ((y1-y3) ^ 2 + (V / 3) ^ 2) * ((y1 + y3) / 2-y2)) ... (Equation 3-6)

  The graph shown in FIG. 8 shows the relationship between the luminance values L1, L2, and L3 with respect to the horizontal positions A1, A2, and A3 when calculating the horizontal direction local luminance unevenness determination value. As is apparent from the equation shown in FIG. 8, the horizontal local luminance unevenness determination value Diff_L_H expressed by [Equation 3-1] is the amount of protrusion of the middle luminance L2 with respect to the change from the luminance L1 to L3 on both sides. (Distance between bd) is shown. Therefore, by using Diff_L_H for the horizontal direction local luminance unevenness determination value, it is possible to extract only the luminance unevenness that is locally in an island state while ignoring the change in luminance in the entire screen.

  Therefore, for example, uneven brightness that changes throughout the screen, such as uneven brightness of the backlight of an LCD display, is considered to be a good product, but uneven brightness that is locally island-like is conspicuous even with a similar brightness difference. However, if this determination value is used, it is possible to ignore the luminance unevenness that changes on the entire screen and to perform NG determination only on the local luminance unevenness.

  Although FIG. 8 shows only the case of the horizontal direction local luminance unevenness determination value, the horizontal direction local chromaticity unevenness determination value, the vertical direction local luminance unevenness determination value, and the local chromaticity unevenness determination value are expressed [Formula 3-2. ] To [Expression 3-6] mean the same principle.

  Next, the personal computer 7 determines that the horizontal direction local luminance unevenness determination value, the horizontal direction local chromaticity unevenness determination value, the vertical direction local luminance unevenness determination value, and the vertical direction local chromaticity unevenness determination value fall within the preset allowable ranges. If it is not within the allowable range, the test result NG is displayed on the display 8 and the test is terminated.

  When the horizontal direction local luminance unevenness determination value, the horizontal direction local chromaticity unevenness determination value, the vertical direction local luminance unevenness determination value, and the vertical direction local chromaticity unevenness determination value are within the allowable ranges, the personal computer 7 The mobile phone 1 is controlled via the F box 6 and an all white screen is displayed on the display 1-2. And the inspection similar to the display 1-1 is performed by performing the same process as the display 1-1.

  When all the inspection items on the display 1-1 and the display 1-2 are OK, the personal computer 7 displays the inspection result OK on the display and ends the inspection.

  In the above embodiment, the local luminance unevenness determination and the local chromaticity unevenness determination in the horizontal direction and the vertical direction are performed by [Expression 3-1] to [Expression 3-6]. Instead of the protruding amount bd of the middle luminance L2 with respect to the change from the side luminance L1 to L3, the average value (L1 +) of the average luminance values L1, L3 and average chromaticity values x1, y1, x3, y3 of both side blocks L3) / 2 and (x1 + x3) / 2, (y1 + y3) / 2 and the difference bet between the average luminance value L2 and the average chromaticity values x2, y2 of the middle block, the horizontal direction and the vertical direction It is also possible to perform local luminance unevenness determination and local chromaticity unevenness determination. However, the determination accuracy is lower than in the above embodiment.

  In the embodiments of the present invention, the case where a display mounted on a cellular phone is inspected is shown. However, the present invention is not limited to other types of displays such as a display for a personal computer and a display for a television. It can be carried out for inspection.

It is a conceptual diagram which shows embodiment of the display test | inspection apparatus of this invention. It is an operation | movement flowchart of the display test | inspection apparatus of this embodiment. It is a figure for demonstrating the process of the image data in this embodiment. It is a figure for demonstrating the process of the image data in this embodiment. It is a figure for demonstrating the process of the image data in this embodiment. It is a figure for demonstrating the process of the image data in this embodiment. It is a figure for demonstrating the process of the image data in this embodiment. It is a figure for demonstrating the calculation method of the local brightness nonuniformity determination value of the image data in this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cellular phone provided with display 1-1 and 1-2 1-1, 1-2 Display 2 CCD camera which images the screen of display 1-1 3 CCD camera which images the screen of display 1-2 4 CCD camera 2 3 Image input board for A / D converting video signals output from 5 DC power supply 6 I / F box 7 Automatic inspection control device (personal computer)
8 Display for displaying inspection results 9 Image data 10-1 to 10-4 Screen outline 11 Rectangular area at the center of the screen 12 Screen peripheral area A1, A2, A3 Three minute areas that touch continuously in the horizontal or vertical direction

Claims (4)

A rectangular minute area is set by equally dividing the screen in the vertical direction and the horizontal direction, and the three minute areas continuously touching in the horizontal or vertical direction are scanned at a predetermined pitch over the entire screen, Luminance unevenness determination value LD and color calculated by substituting the respective average luminance values L1, L2, L3 and average chromaticity values x1, y1, x2, y2, x3, y3 in the three minute areas into the following equations: A display inspection method characterized in that the degree unevenness determination values XD and YD are calculated for each scanning position, and the quality unevenness and chromaticity unevenness are determined based on the respective determination values for all the calculated scanning positions.
LD =
ABS (D / SQR ((L1-L3) ^ 2 + D ^ 2) * ((L1 + L3) / 2-L2))
XD =
ABS (D / SQR ((x1-x3) ^ 2 + D ^ 2) * ((x1 + x3) / 2-x2))
YD =
ABS (D / SQR ((y1-y3) ^ 2 + D ^ 2) * ((y1 + y3) / 2-y2))
Where D is the distance between the minute areas on both sides, ABS (x) is the absolute value of x, SQR (x) is the square root of x, x ^ y is x to the power of y, x * y is x and y Is the product of A predetermined rectangular area is set at the center of the screen, the luminance value Lc and the chromaticity values xc and yc in the rectangular area are calculated, and the calculated luminance and chromaticity at the center of the screen are within a preset allowable range. It is determined whether or not, and then the difference between the average luminance and average chromaticity in the minute area located around the screen and the luminance and chromaticity at the center of the screen is calculated, respectively, and the maximum value The display inspection method according to claim 1, further comprising: determining whether or not is within a preset allowable range, and performing the pass / fail determination according to claim 1 for those that have cleared these determinations . Image acquisition means for acquiring a display screen image obtained by imaging the display screen of the color display device;
A rectangular minute area is set by equally dividing the acquired display screen image in the vertical direction and the horizontal direction, and the three minute areas that are in continuous contact in the horizontal or vertical direction have a predetermined pitch over the entire screen. Means for obtaining the average luminance values L1, L2, L3 and the average chromaticity values x1, y1, x2, y2, x3, y3 in the three minute areas;
By substituting the obtained average luminance values L1, L2, L3 and average chromaticity values x1, y1, x2, y2, x3, y3 in the three minute areas into the following expressions, luminance unevenness determination values LD and Means for calculating chromaticity unevenness determination values XD and YD for each scanning position;
A display inspection apparatus comprising: means for determining whether or not luminance unevenness and chromaticity unevenness are good based on the calculated determination values of all the scanning positions.
LD =
ABS (D / SQR ((L1-L3) ^ 2 + D ^ 2) * ((L1 + L3) / 2-L2))
XD =
ABS (D / SQR ((x1-x3) ^ 2 + D ^ 2) * ((x1 + x3) / 2-x2))
YD = ABS (D / SQR ((y1-y3) ^ 2 + D ^ 2) * ((y1 + y3) / 2-y2))
Where D is the distance between the minute areas on both sides, ABS (x) is the absolute value of x, SQR (x) is the square root of x, x ^ y is x to the power of y, x * y is x and y Is the product of Means for setting a predetermined rectangular area at the center of the acquired display screen and calculating the luminance value Lc and chromaticity values xc, yc in the rectangular area; and the calculated luminance and chromaticity at the center of the screen in advance A means for determining whether or not the set allowable range is satisfied, and a difference value between each average luminance and average chromaticity in the minute area located around the screen and the luminance and chromaticity at the center of the screen, respectively. 4. The display inspection apparatus according to claim 3, further comprising means for determining whether or not the maximum value is within a preset allowable range.

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