JPH102800A - Method and system for evaluating image quantity of color display and manufacture of color display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-quality color display by inspecting an image pickup system, while correcting abnormal refraction and fluctuation in sensitivity, thereby determining and automatically evaluating the image quality of the color display with high accuracy. SOLUTION: The image of an object, e.g. the white surface of a color CRT tube 1, is picked up by means of a camera 4, comprising a lens, a color filter and a color solid-state image sensor under states of the lens being mounted and not mounted thus obtaining parameters required for correcting the sensitivity of the image pickup system at each pixel. Subsequently, a monochromatic screen of four colors or more is displayed on the CRT tube 1 and the image thereof is picked up by means of the camera 4. The R, G, B data for each pixel are converted into a colorimetric system after the difference of sensitivity has been removed through an image processor 5 and a processing unit 6, using these parameters, in order to determine and evaluate the unevenness of color and luminance over the entire screen and in the different split regions. The evaluations are combined in order to evaluate the quality of the object, thus deciding whether or not the color display is acceptable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image quality evaluation method for a color display device using a cathode ray tube, a liquid crystal display, a plasma display, an electroluminescence display and the like, and an image quality evaluation device and a method for manufacturing a color display device.

[0002]

2. Description of the Related Art In a color display device, a large number of inspections are performed during a manufacturing process and after completion. Among them, the image quality inspection is a sensory inspection that evaluates whether or not the image quality is good with the eyes of the operator. Therefore, even in a production line where most processes are automated, it is necessary to rely on the visual inspection by the operator. At present it is inevitable.

[0003] Among the items of the visual inspection, the evaluation of the uniformity of a single-color screen is an inspection with high subjectivity. In a specific inspection method, a monochrome screen is displayed on a color display device to be inspected, and the degree of color unevenness or luminance unevenness of the screen is visually determined. The monochrome screen displayed on the screen of the color display device should ideally be a completely uniform monochrome. However, for example, in a color display device using a color cathode-ray tube, even after performing necessary adjustments such as convergence and landing of an electron beam, there is a slight variation in the light emission state of the phosphor, so that the display on the screen is performed. The resulting color does not become a uniform single color, but a lightly colored portion or a portion with low or high luminance appears. This is called “color unevenness” or “luminance unevenness”.

[0004] The degree of the color unevenness and the luminance unevenness is extremely small, and the appearance thereof varies depending on the individual difference between workers and the physical condition at that time. Furthermore, the appearance state of color unevenness and luminance unevenness, such as tint, color vividness,
The shape, size, appearance position on the screen, number of appearances, and the like are extremely various. Therefore, the visual evaluation of the monochromatic uniformity has a large subjective factor as compared with other visual inspections.

[0005] The degree of the color unevenness and the luminance unevenness is evaluated by the operator while observing the screen, and expressed by numerical values called grades. For example, the larger the numerical value, the greater the color unevenness and luminance unevenness.

Therefore, there is a high demand for automation of visual inspection in order to reduce the number of inspection steps and to establish a physical and quantitative evaluation method to improve inspection accuracy and reliability.
Some attempts have been made in the past to automate the evaluation of single-color uniformity, especially in the case of white. As one of them, an uneven color inspection apparatus disclosed in Japanese Patent Application Laid-Open No. 2-243930 has been proposed.

In order to inspect the color unevenness of the color CCD chip, the color unevenness inspection apparatus uses the R, G, and B outputs from the color CCD chip when the white light-emitting surface is imaged in a coordinate system such as a Munsell color space. To color CC on the monitor
It is displayed as a chromaticity vector at each position on D.

[0008]

However, when such a color non-uniformity inspection apparatus is used for evaluating the image quality of the screen of a color display apparatus, a lens, a color filter and a color CCD constituting an image pickup system have abnormal refractive and sensitivity. Since no consideration is given to the variation in, the image quality of the screen of the color display device cannot be correctly evaluated. Therefore, the quality of the color display device may become unstable.

In view of the above-mentioned circumstances, an object of the present invention is to correct and inspect refractive errors and variations in sensitivity of a lens, a color filter, and a color CCD of an imaging system, and to improve the image quality of a screen of a color display device. It is an object of the present invention to provide an image quality evaluation method for a color display device, an image quality evaluation device, and a method for manufacturing a color display device, which can obtain a high-quality color display device by quantitatively evaluating the accuracy.

[0010]

Means for Solving the Problems In order to achieve the above object, a first invention of the present application is to provide screen information obtained by imaging a monochrome display screen displayed on a screen of a color display device.
After decomposing into R, G, B signals for each pixel constituting the screen, correcting the sensitivity difference between the light receiving elements constituting each pixel of the imaging means, and converting the R, G, B signals into a color system Calculate the chromaticity difference between any pixel in the screen and other pixels in the entire screen,
The image quality is evaluated based on the sum of the absolute values.

Further, the second invention of the present application decomposes screen information obtained by imaging a single-color display screen displayed on a screen of a color display device into R, G, and B signals for each pixel constituting the screen. After correcting the sensitivity difference for each light receiving element constituting each pixel of the imaging means and converting the R, G, B signals into a color system, the chromaticity of any pixel on the screen and other pixels on the entire screen The difference and the luminance difference are calculated, and the image quality of the color unevenness and the luminance unevenness of the entire screen is evaluated based on the sum of the absolute values.

A third invention of the present application is to decompose screen information obtained by imaging a single-color display screen displayed on a screen of a color display device into R, G, and B signals for each pixel constituting the screen. After correcting the sensitivity difference for each light receiving element constituting each pixel of the imaging means and converting the R, G, and B signals into a color system, the screen information is divided at a predetermined position and size, and the division is performed. Color unevenness and brightness unevenness having different spatial frequencies are evaluated based on the area, and the image quality is evaluated based on a combination of the evaluation results.

Further, the fourth invention of the present application decomposes screen information obtained by imaging a single-color display screen displayed on a screen of a color display device into R, G, and B signals for each pixel constituting the screen, After correcting the sensitivity difference for each light receiving element constituting each pixel of the imaging means and converting the R, G, and B signals into a color system, the screen information is repeatedly divided a plurality of times at different positions and sizes. , The luminance difference between the pixels existing in the divided area is calculated, and the image quality is evaluated using the maximum value.

According to a fifth aspect of the present invention, a screen information obtained by imaging a single-color display screen displayed on a screen of a color display device is decomposed into R, G, and B signals for each pixel constituting the screen. After correcting the sensitivity difference for each light receiving element constituting each pixel of the imaging means and converting the R, G, and B signals into a color system, the screen information is repeatedly divided a plurality of times at different positions and sizes. The average chromaticity of each divided area is obtained, and the image quality is evaluated based on the chromaticity difference or chromaticity gradient between each divided area.

Further, according to a sixth aspect of the present invention, a screen information obtained by imaging a monochromatic display screen displayed on a screen of a color display device is decomposed into R, G, and B signals for each pixel constituting the screen. After correcting the sensitivity difference for each light receiving element constituting each pixel of the imaging means and converting the R, G, B signals into a color system, the screen information is divided into different positions and sizes,
The average luminance of each divided region is obtained, and the image quality is evaluated based on the luminance difference or luminance gradient between each divided region.

Further, according to a seventh aspect of the present invention, a screen information obtained by imaging a monochromatic display screen displayed on a screen of a color display device is decomposed into R, G, and B signals for each pixel constituting the screen. After correcting the sensitivity difference of each light receiving element constituting each pixel of the imaging means and converting the R, G, and B signals into a color system, the color of an arbitrary pixel in the screen and other pixels in the entire screen is changed. Calculate the power difference, the brightness difference, evaluate the color unevenness of the entire screen and the brightness unevenness based on the sum of the absolute values, and repeatedly divide the screen information at different positions and sizes a plurality of times. Originally, color unevenness and luminance unevenness having different spatial frequencies are evaluated, and the quality of the color display device is determined based on a combination of the evaluation results.

The eighth invention of the present application is the invention according to the first to seventh inventions, wherein an arbitrary pixel on the screen when a uniform monochromatic display screen is imaged, and R, G, The ratio of the B signals is obtained, and the sensitivity difference of the imaging system is corrected based on the ratio.

In a ninth aspect of the present invention, in the first to seventh aspects of the present invention, a white screen is imaged by an image pickup means without a lens, and an arbitrary pixel in the image pickup area and other pixels are taken out. After obtaining the ratio of the R, G, and B signals and correcting the sensitivity difference for each light receiving element constituting each pixel of the imaging unit based on the ratio, a white screen is imaged with the lens attached to the imaging unit. R of any pixel in the imaging area and other pixels,
The ratio between the G and B signals is obtained, and the sensitivity difference of the imaging system is corrected based on the ratio.

Further, the tenth invention of the present application is the first invention.
In the thirteenth aspect, the chromaticity and luminance of the single-color display screen displayed on the screen of the color display device are repeatedly changed to take an image, and the R, G, and B signals output from the imaging unit and the chromaticity measurement unit are used. The relationship with the measurement result is represented by the following determinant and chromaticity conversion is performed.

[0020]

(Equation 2)

According to an eleventh aspect of the present invention, there is provided a signal generator for displaying a single-color display screen on a color display device to be evaluated, an image of the single-color display screen, and screen information of R, G, B signals. A camera that separately outputs the image, a chromaticity measuring device that measures chromaticity at an arbitrary position on the screen of the color display device, an image processing device that digitizes and stores the outputs of the camera and the chromaticity measuring device, An arithmetic processing unit for performing chromaticity conversion and quality evaluation based on a digital signal stored in the image processing apparatus, comprising a memory storing a chromaticity conversion processing table and a quality evaluation table, and an image captured by the camera And a monitor for displaying the quality evaluation result.

The twelfth invention of the present application is a method for ending at least one of the steps of a display alone, a device mounting process for displaying an image on the display alone, and an adjustment process as a display device. Thereafter, the screen information obtained by imaging the single-color display screen displayed on the screen of the color display device is decomposed into R, G, and B signals for each pixel constituting the screen, and each pixel of the imaging means is divided into light-receiving elements. After correcting the sensitivity difference and converting the R, G, and B signals into a color system, at least a chromaticity difference or a luminance difference between an arbitrary pixel in the screen and another pixel in the entire screen is obtained. A step of evaluating the image quality based on the above is performed, and the presence or absence of an abnormality in the previous step is diagnosed.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below by taking a color display device using a color CRT as an example. FIG. 1 is a configuration diagram of an image quality evaluation device according to the present invention.

In FIG. 1, reference numeral 1 denotes a color cathode ray tube;
Is a deflection yoke, which is attached to the color CRT 1. Reference numeral 3 denotes a signal generator, which causes the color CRT 1 to display a single-color screen for inspection. Reference numeral 4 denotes a camera forming an image pickup means, which is composed of a lens, a color filter, a color solid-state image pickup device (CCD) for taking in R, G, B signals, and the like. I have. An image processing device 5 is connected to the camera 4.
An arithmetic processing unit 6 is connected to the image processing device 5 and includes a memory device in which a chromaticity conversion processing method and a quality evaluation method are recorded, and performs calculation processing for chromaticity conversion and image quality evaluation. Reference numeral 7 denotes a monitor that displays an image captured by the camera 4, an evaluation result, and the like. Reference numeral 8 denotes a chromaticity measuring device which is connected to the image processing device 5 and is installed so as to face the color cathode ray tube 1.

The camera 4 itself has variations in sensitivity such as uneven refraction of the lens, unevenness in the thickness of the color filter, and variation in sensitivity between light receiving elements constituting the color solid-state imaging device. For this reason, even if a uniform single-color screen is imaged, the output of the camera has variations corresponding to color unevenness and sensitivity unevenness due to the sensitivity of the camera 4.

FIG. 2 is a flowchart showing one of the procedures for obtaining the parameters necessary for correcting the variation in the sensitivity of the camera 4 in the image quality evaluation apparatus shown in FIG.

A cap is attached to the camera 4 in advance,
An offset signal due to the Y setup level, dark current, etc. of the camera 4 is measured (204).

Next, a white surface is imaged without attaching a lens to the camera 4 (206). At this time, since the imaging surface on which the lens is not mounted is a small area, it is considered that the imaged area has an ideal white uniform screen. A coefficient for correcting the R, G, and B outputs of an arbitrary pixel on the imaging surface and other pixels is obtained (208).

Further, a lens is attached to the camera 4 and a white screen is imaged (210). At this time, since the imaging surface has a large area, the imaging surface is sampled at several points, and the chromaticity is measured by the chromaticity measuring device 8 in advance.

By obtaining a correction coefficient for multiplying the linear R, G and B terms obtained by the above (204),
Color unevenness correction by the lens at the sampled point is performed (212).

On the color cathode ray tube 1, a monochrome screen of four or more colors displayed by a combination of R, G and B is displayed, and the camera 4 captures the monochrome screen. Data on the relationship between the measurement results of the chromaticity measuring device 8 for x, y, and Y at the center of the imaging surface and the R, G, and B outputs of the camera 4 at that time is acquired (214).

The measurement results of the chromaticity measuring device 8 and R, G, B
The output relationship is approximated by a linear form, and a parameter for converting the R, G, and B outputs into chromaticity is obtained (216). The method of correcting the sensitivity of the camera 4 will be described later in detail.

FIG. 3 is a flowchart showing one of the procedures for evaluating the image quality of a color CRT in the image quality evaluation apparatus shown in FIG. In addition, FIG.
This shows an example in which a color system L * u * v * defined by (International Commission on Illumination) is used. However, CIE color system x, y, Y, L * a * b *, or RY, BY, Y, etc. extracted from a color video signal may be used.

First, using the image quality evaluation apparatus shown in FIG. 1, the light emission state of the screen of the color cathode-ray tube 1 on which a monochromatic raster screen is projected is acquired for each pixel of the camera 4.
R, G, and B data are taken into the image processing apparatus (10
2). The captured data removes a sensitivity difference caused by the imaging system for each pixel (104).

The outputs of R, G, and B from which the sensitivity difference has been removed are converted to a color system L * u * v * (106). Next, a chromaticity difference and a luminance difference between an arbitrary pixel on the screen and other pixels on the entire screen are calculated, and a quantitative evaluation of the color unevenness and the luminance unevenness of the entire screen is performed from the sum of the absolute values. (108).

Next, the captured image is divided into different sizes and different starting positions, and based on the divided areas, color unevenness and brightness unevenness having various sizes and different spatial frequencies are quantitatively evaluated. (110). The quality evaluation of color CRTs and the quality
A defective product is determined (112).

The process for obtaining the parameters required for correcting the sensitivity of the image pickup system in FIG. 2 is performed as follows. Since the output of the camera includes the Y setup level and dark current, the output (image) of R, G, and B is measured with the camera capped in advance, and the measured output is used as the offset level. Subtract from the image.

The R, G, and B signals obtained from the camera are subtracted from the offset level, and based on [Equation 3], [Equation 4], and [Equation 5], X, Y, Z, x, y,
Conversion to Y and L * u * v color system.

[0039]

(Equation 3)

[0040]

(Equation 4)

[0041]

(Equation 5)

Here, Xn, Yn, and Zn are X, Y, and Z with respect to a completely diffused surface under illumination when the color of an object is normally measured.
In the case of a display, since it is a light source color, the X, Y, and Z values at the center of the screen are adopted as Xn, Yn, and Zn.

[0043] In _{addition, a 1 1 ~a 3 3,} b 1 coefficients ~b ₃ is when capturing the previously four colors or five colors or more monochrome images R, G, B and, chromaticity meter x, The data of y and Y are acquired and calculated. In this case, for four colors,
The coefficient can be obtained uniquely, but if there are five or more colors,
A coefficient for approximating the relationship between R, G, B and x, y, Y with a minimum error is obtained by least squares approximation. Below 4 colors and 5
A method for obtaining the values for each color or more will be described.

First, in the case of four colors, the signals R, G, and B of the imaged camera and the values of x, y, and Y obtained by the chromaticity measuring device for the imaged color are used by using [Equation 4]. Calculated X,
The values of Y and Z are used. 4 colors of R taken into the camera,
The set of G and B data is (R1, G1, B1), (R
2, G2, B2), (R3, G3, B3), (R4, G
4, B4), and the corresponding values of X, Y, Z are (X1, Y1, Z1), (X2, Y2, Z2), (X
3, Y3, Z3) and (X4, Y4, Z4), the following expression is given by [Equation 3].

[0045]

(Equation 6)

The following relationship holds. One way to solve this is to subtract the equation for i = 4 from the equation for i = 1, 2, 3 and

[0047]

(Equation 7)

As follows:

[0049]

(Equation 8)

Is obtained. If Motomare is a _{1 1} ~a _{3 3,} for example from i = 1 of the formula,

[0051]

(Equation 9)

As a result, b _{1 to} b ₃ can be determined.

In the case of five or more colors, the number of colors is set to N, and the data of R, G, B, X, Y, and Z of the n-th color are represented by x _{1 n} , x _{2 n} , and x ₃ , respectively. _{n, y 1 n, y 2} n, y 3
and those obtained by substituting x _{j n (j} = 1,2,3) on the right side of [Equation 3] When the _n, i for differences of the squares of the _{y i n (i = 1,2,3)} , n Is the squared error E,

[0054]

(Equation 10)

Is as follows.

This E is _defined as a _kl , b _k (k = 1, 2, 3
By placing a 0 those obtained by partially differentiating with l = 1, 2, 3), determine the a _{i j} b _i to the square error E to a minimum.

Here, t is transposed, and

[0058]

[Equation 11]

Here,

Also,

[0061]

(Equation 12)

[0062] and if put, when the ∂E / ∂a _{k l} = 0 from [Equation 10]

[0063]

(Equation 13)

When this is changed to the form of a matrix,

[0065]

[Equation 14]

Is obtained.

When ∂E / ∂b _k = 0, (Equation 10)
Than

[0068]

(Equation 15)

Is obtained.

When this is changed to a determinant, Ax + Nb = y
Becomes

[Equation 13] By solving [Equation 14],

[0072]

(Equation 16)

Is obtained.

In this [Equation 16], x _{1 n} , x _{2 n} , x _{3
n, y 1 n, y 2} n, by substituting _{y 3 n a 1 1 ~a 3} 3,
b _{1 to} b ₃ can be obtained. This equation can be applied to the case of four colors.

FIG. 4 is an explanatory diagram showing a method for removing color unevenness of the image pickup system in the automatic image quality evaluation apparatus.

An image of a white light source having ideally uniform in-plane chromaticity and luminance is captured. The R, G, and B output values of the center pixel at this time are Rc, Gc, and Bc, the positions of the pixels other than the center are coordinates (i, j), and the outputs are R (i, j), G (i, j),
B (i, j). The unevenness caused by the camera and lens generated at this time is R, G,
The sensitivity of B is relative to the sensitivity of R, G, B of the central pixel.
At arbitrary coordinates (i, j) on the imaging surface, α (i,
j), β (i, j) and γ (i, j) times. At this time,

[0077]

[Equation 17]

Can be expressed as follows. When an arbitrary subject is imaged, the output of the camera is represented by R (i, j), G (i, j), B
If (i, j), this is 1 / α (i, j), 1 / β
Correction of camera and lens unevenness is performed by multiplying (i, j) by 1 / γ (i, j). However, since the Y setup level and dark current are on the output of the camera, R, R,
The outputs (images) of G and B are measured, and these are subtracted from the measurement target image as offset levels.

However, it is difficult to prepare an ideal uniform white light source.
The uneven refraction caused by the lens is divided and corrected in two stages.

First, in order to give a sensitivity coefficient relating to the color unevenness of the camera due to the unevenness of the film thickness of the color filter, an image of the white light source is taken by the camera with the lens removed. At this time, by making the distance between the light source and the camera as short as possible, the field of view captured by the camera is reduced, and the influence of the luminance and color unevenness of the light source is minimized.

The R, G, B output values of the center pixel of the camera are
R1c, G1c, B1c, the position of each pixel other than the center is coordinate (i, j), and the output is R1 (i, j), G
1 (i, j) and B1 (i, j). The unevenness of the camera generated at this time is such that the sensitivity of R, G, B for each pixel of the camera is α1 at the arbitrary coordinates (i, j) of the imaging surface with respect to the sensitivity of R, G, B of the center pixel. (I, j), β
1 (i, j) and γ1 (i, j), and are represented by [Equation 18].

[0082]

(Equation 18)

Then, for each pixel, α1 (i, j), β
1 (i, j) and γ1 (i, j) are obtained, and when an arbitrary subject is imaged, the camera outputs R (i, j), G
(I, j) and B (i, j) are calculated as 1 / α1 (i, j), 1
/ Β1 (i, j) and 1 / γ1 (i, j).

Therefore, at the position of the coordinates (i, j), R (i, j) / α1 (i, j) G (i, j) / β1 (i, j) B (i, j) / γ1 ( i, j) are R, which eliminates the effect of color unevenness of the camera itself,
G and B outputs can be considered.

Next, a lens is mounted on the camera, a white light source is imaged in a state of actual use, and color unevenness due to the effect of the lens in each pixel is corrected as described below.
It should be noted that the white light source that is subject to this has some uneven brightness.
Color shading may be present.

The relation shown in [Equation 3] and [Equation 4] exists between R, G, B of the central pixel and x, y, Y. Therefore, when a lens is attached to the camera, the effect of the lens is the output of each pixel after correcting the color unevenness of the camera, similarly to the color unevenness of the camera. R2 (i, j) = R (i, j) / α1 (I, j) G2 (i, j) = G (i, j) / β1 (i, j) B2 (i, j) = B (i, j) / γ1 (i, j) For outputs R2c, G2c, and B2c, respectively, α2 (i, j), β2 (i, j), γ2 (i,
j) It is assumed that the number is doubled.

At that time, at each coordinate position (i, j),
X, y, and Y are measured using a colorimeter, and the values of X, Y, and Z calculated using [Equation 4] are expressed as X (i, j), Y (i,
j) and Z (i, j), the relational expression of [Equation 19] can be described.

[0088]

[Equation 19]

[0089] However, the coefficients of _{a 1 1 ~a 3 3, b} 1 ~b 3 is assumed the same as that of the center pixel, this equation can be solved as follows.

[0090]

(Equation 20)

Therefore,

[0092]

(Equation 21)

In practice, X (i, j),
Since it is difficult to obtain Y (i, j) and Z (i, j), R is obtained by imaging the light source with a camera at a plurality of points on the screen, for example, grid points of 4 × 5 grid points. , G, and B, and X, Y, and Z at the corresponding points are measured with a colorimeter. Interpolation or function fitting is performed on the relationship between R, G, B and X, Y, Z of each point by cubic spline interpolation, quadratic function, or the like.

As a result, the values of R, G, and B at an arbitrary pixel can be converted into X, Y, and Z, with the exception of the unevenness of the imaging system. That is, α1 (i, j), β1
(I, j), γ1 (i, j), α2 (i, j), β2
R, G, B outputs of the camera obtained at each coordinate position (i, j) by (i, j) and γ2 (i, j),
X, Y, Z values X (i, j), Y (i) from R (i, j), G (i, j), B (i, j) from which color unevenness due to the influence of the camera and lens is removed , J) and Z (i, j) are obtained by the following equations.

[0095]

(Equation 22)

Next, automatic image quality evaluation is performed using the obtained chromaticity distribution data on the screen of the color CRT. Hereinafter, six examples of the automatic image quality evaluation method will be described in a case where the L * u * v * color system is used.

The first evaluation method will be described. First,
The chromaticity is measured at an arbitrary point on the screen of the color cathode ray tube, and the chromaticity vector (u * c, v * c) at the center of the screen and the chromaticity vector (u * n, v) at an arbitrary nth measurement point on the screen are measured. * N) and the chromaticity difference (Δu * n, Δv * n) between [Equation 21] are calculated.

[0098]

(Equation 23)

FIG. 5 is a diagram in which the chromaticity difference vector at each point on the screen of the color CRT is visualized and displayed.

In FIG. 5, a line segment extending from the points arranged on the chromaticity measurement surface is a vector starting from the point, and the horizontal direction represents the value of Δu * and the vertical direction represents the value of Δv *, as shown at the lower left. . The value to be evaluated is the total sum E1 of the vector lengths shown in [Equation 21] when the total number of vectors is N,

[0101]

(Equation 24)

Is defined as follows. This indicates the degree of color unevenness of the entire screen of the color cathode-ray tube.

Next, a second evaluation method will be described. As in the first method, a luminance difference between the center of the screen and a measurement point on the screen is calculated for the luminance L *, and the sum is set as a value E2 for evaluating the sum. This indicates the degree of luminance unevenness of the entire screen of the color cathode-ray tube.

Next, a third evaluation method will be described. First, after extracting a single-color raster on the screen of the color cathode ray tube in the computer, the raster image screen is divided into, for example, horizontal and vertical,
As shown in FIG. 6, area division is performed by changing the size to 4 × 3, 8 × 6, 16 × 12, or the like. Next, a u * v * color difference is calculated for a combination of all pixels in each divided region. For example, the magnitude C of the chromaticity difference between the pixel A and the pixel B in FIG.

[0105]

(Equation 25)

In each area, pixel A and pixel B in which C is maximum are searched, and C at that time is set as a value to be evaluated.

For example, as shown in FIG. 8, when a monochromatic raster of a color cathode ray tube is arranged in an xy coordinate system whose origin is at the upper left, it is assumed that the width × length is M pixels × N pixels.
At this time, the monochromatic raster of the color cathode-ray tube is divided into m1 × n1 areas each having a size of M / m1 pixels horizontally and N / n1 pixels vertically. The mth region from the left and the nth region from the top are represented by Dmn and are included in Dmn. Pixel coordinates are

[0108]

(Equation 26)

Are expressed as follows.

From the above, using [Equation 16], the area Dmn
The maximum value of C

[0111]

[Equation 27]

The following is defined. In addition, Em within all rasters
the maximum value of n

[0113]

[Equation 28]

The following is defined.

The permissible values of E3mn and E3 values in each area are determined in advance according to the size of division, and if the values are within the permissible values, the area is judged to be acceptable. This makes it possible to extract color unevenness that exists locally and has a different spatial frequency. Further, in order to prevent the unevenness from being overlooked due to the division of the raster, the same processing is performed simultaneously by moving the division start position, for example, up, down, left, and right by half the size of the divided area.

The fourth evaluation method will be described. Similar to the third evaluation method, the magnitude ΔL of the luminance difference between the pixel A and the pixel B in FIG.

[0117]

(Equation 29)

Then, similarly to the evaluation method 3, the pixels A and B having the maximum ΔL in each area are searched, and the value at that time is set as a value for evaluating ΔL.

Using [Equation 27], the maximum value of ΔL in the area Dmn is calculated as follows:

[0120]

[Equation 30]

The following is defined. In addition, Em within all rasters
The maximum value E4 of n

[0122]

(Equation 31)

The following is defined.

The allowable values of the E4mn and E4 values in each area are determined in advance according to the size of the division, and if the values are within the allowable values, the area is judged to be acceptable. As a result, it is possible to extract luminance unevenness which exists locally and has different spatial frequencies. In this case as well, in order to prevent the unevenness from being overlooked due to the division by the raster division, the same processing is performed simultaneously by moving the division start position, for example, up, down, left, and right by half the size of the divided area. .

The fifth evaluation method will be described with reference to FIG. The raster imaging plane is divided as in the evaluation methods 3 and 4, and the average chromaticity is calculated in each area. Next, a search for a combination of average chromaticities in the region where the chromaticity difference is the largest is searched for from all the combinations in each region, and each chromaticity is determined as (u * 1, v * 1), (u * 2, v *). 2) and E5
Is defined in [Equation 32].

[0126]

(Equation 32)

Here, d is the distance between the areas AB, and n is an arbitrary real number.

With the value of E5, it is possible to inspect the chromaticity change of the entire screen of the color CRT. In each divided state, if the value is smaller than a predetermined allowable value, it is determined to be acceptable.

A sixth evaluation method will be described. As in the fifth evaluation method, the raster imaging plane is divided, and the average luminance is calculated in each area. Next, a search is made for a combination of the average luminances of the regions where the luminance difference is maximum from all the combinations of the respective regions, and the respective luminances are determined as L * 1, L * 2.
And E6 is defined in [Equation 33].

[0130]

[Equation 33]

Here, d is the distance between the areas AB, and n is an arbitrary real number.

With the value of E6, it is possible to inspect the luminance change in the entire area of the screen of the color CRT. In each divided state, if the value is smaller than a predetermined allowable value, it is determined to be acceptable.

By summing up the above evaluation methods, for example, when the non-defective product limit value is E0,

[0134]

(Equation 34)

A color CRT that satisfies (where k _{1 to} k ₆ are numerical values obtained through experiments) is evaluated as good, and the image quality of a monochrome CRT monochromatic display screen is automatically evaluated.

In assembling a color display device using a color cathode ray tube, for example, a television receiver, a process of attaching a deflection coil and a converging coil of an electron beam to the color cathode ray tube, a process of assembling a printed circuit board, and a process for assembling a housing. The process of installing speakers and the like is performed in parallel, and a printed circuit board and a color cathode-ray tube are mounted on a housing to form a television receiver.

In such an assembling process, the image quality of the color cathode-ray tube is evaluated by using the color cathode-ray tube alone or with the deflection coil and the electron beam focusing coil attached to the color cathode-ray tube, or by using the television receiver. After the image quality is adjusted, a high-quality television receiver can be shipped by evaluating the image quality of the color CRT.

As described above, by quantitatively evaluating the image quality of the color display device, the reliability of the image quality evaluation can be improved, and a high-quality color display device can be obtained. Also, by using the image quality evaluation parameters, the value of [Equation 27] E3mn represents the size of color unevenness and luminance unevenness in an arbitrary area. When this value is high at the left and right ends, If the image quality is poor due to the deflection yoke attached to the color cathode ray tube, or if there are high concentric circles with high numerical values, defects in the manufacturing process can be determined from the results of the image quality evaluation parameters, such as image quality defects due to the phosphor coating process. Can be identified.

Further, by observing the transition of the evaluation value of the evaluation result, it is possible to know the change in the manufacturing process.
Defects can be prevented from occurring. Furthermore, by evaluating the image quality at a plurality of locations during the manufacturing process of the color display device, it is possible to find an abnormality more quickly, and it is possible to reduce the number of work steps and wasted material.

[0140]

As described above, according to the present invention, the quality of a color display device can be evaluated by quantitatively evaluating the color unevenness of a single-color display screen of a color display device with high accuracy within the entire screen and within a predetermined divided area. And a high quality color display device can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an image quality evaluation device.

FIG. 2 is a flowchart showing a procedure for calculating parameters for adjusting the sensitivity of a camera.

FIG. 3 is a flowchart showing a procedure for evaluating the image quality of a color CRT.

FIG. 4 is an explanatory diagram of a method of adjusting the sensitivity of an imaging system.

FIG. 5 is an explanatory diagram showing an example of a color CRT image quality visualization display;

FIG. 6 is an explanatory diagram showing an example of image capturing screen division.

FIG. 7 is an explanatory diagram of a method for evaluating a chromaticity difference between pixels in a divided area of an imaging screen.

FIG. 8 is an explanatory diagram of a method of dividing a color CRT monochromatic raster.

FIG. 9 is an explanatory diagram of a method for evaluating a difference in average chromaticity between divided regions of an imaging screen.

[Explanation of symbols]

1 ... color cathode ray tube, 2 ... deflection yoke, 3
..Signal generation devices, 4 ... Cameras, 5 ... Image processing devices, 6 ... Operation processing devices, 7 ... Monitors, 8 ...
・ Chromaticity measuring device.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Jun Mochizuki 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Hitachi, Ltd. Production Technology Research Laboratory (72) Inventor Kaoru Sakai 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa (72) Inventor Nobuo Kawai 471 Kamono-cho, Minokamo-shi, Gifu Pref.

Claims (12)

[Claims] 1. A screen display device comprising: a screen display unit configured to decompose screen information obtained by capturing an image of a single-color display screen displayed on a screen of a color display device into R, G, and B signals for each pixel constituting the screen; By correcting the sensitivity difference for each element, R, G,
After converting the B signal into a color system, a chromaticity difference between an arbitrary pixel in the screen and another pixel in the entire screen is calculated, and the image quality is evaluated based on the sum of the absolute values. An image quality evaluation method for a color display device. 2. The image processing apparatus according to claim 1, wherein the screen information obtained by imaging the single-color display screen displayed on the screen of the color display device is decomposed into R, G, and B signals for each pixel constituting the screen, and a light receiving element constituting each pixel of the imaging means. By correcting the sensitivity difference for each element, R, G,
After converting the B signal into a color system, the chromaticity difference and luminance difference between an arbitrary pixel on the screen and other pixels on the entire screen are calculated, and the color unevenness and luminance of the entire screen are calculated based on the sum of the absolute values. An image quality evaluation method for a color display device, wherein the image quality of unevenness is evaluated. 3. The image information of a single-color display screen displayed on a screen of a color display device is decomposed into R, G, and B signals for each pixel constituting the screen, and a light receiving element constituting each pixel of the image pickup means. By correcting the sensitivity difference for each element, R, G,
After converting the B signal into a color system, the screen information is divided at a predetermined position and size, and based on the divided areas, color unevenness having different spatial frequencies and luminance unevenness are evaluated. An image quality evaluation method for a color display device, wherein the image quality is evaluated by a combination. 4. The image information obtained by capturing an image of a single-color display screen displayed on a screen of a color display device is decomposed into R, G, and B signals for each pixel constituting the screen, and a light receiving element constituting each pixel of the imaging means. By correcting the sensitivity difference for each element, R, G,
After converting the B signal into a color system, the screen information is divided at different positions and sizes, the luminance difference between the pixels present in the divided area is calculated, and the image quality is evaluated using the maximum value. An image quality evaluation method for a color display device, comprising: 5. The image processing apparatus according to claim 1, wherein the screen information obtained by imaging the single-color display screen displayed on the screen of the color display device is decomposed into R, G, and B signals for each pixel constituting the screen, and a light receiving element constituting each pixel of the imaging means. By correcting the sensitivity difference for each element, R, G,
After converting the B signal into a color system, the screen information is repeatedly divided a plurality of times at different positions and sizes, an average chromaticity of each divided region is obtained, and a chromaticity difference or a chromaticity gradient between the divided regions is obtained. An image quality evaluation method for a color display device, comprising: 6. The image information obtained by imaging a single-color display screen displayed on a screen of a color display device is decomposed into R, G, and B signals for each pixel constituting the screen, and a light receiving element constituting each pixel of the imaging means. By correcting the sensitivity difference for each element, R, G,
After converting the B signal into a color system, the screen information is repeatedly divided a plurality of times at different positions and sizes, an average luminance of each divided area is obtained, and the image quality is determined by a luminance difference or a luminance gradient between the divided areas. An image quality evaluation method for a color display device, characterized by evaluating. 7. A screen information obtained by imaging a monochromatic display screen displayed on a screen of a color display device is decomposed into R, G, and B signals for each pixel constituting the screen, and a light receiving element constituting each pixel of the imaging means is received. By correcting the sensitivity difference for each element, R, G,
After converting the B signal into a color system, the chromaticity difference and luminance difference between any pixel in the screen and other pixels in the entire screen are calculated, and the color unevenness of the entire screen is calculated based on the sum of the absolute values. Evaluate the luminance unevenness, repeatedly divide the screen information at different positions and sizes a plurality of times, based on the divided area, evaluate the color unevenness with different spatial frequency, the brightness unevenness, by combining the evaluation results An image quality evaluation method for a color display device, comprising: determining whether the color display device is good. 8. A ratio between R, G, and B signals of an arbitrary pixel on the screen when a uniform monochromatic display screen is imaged and other pixels is obtained, and the sensitivity unevenness of the imaging system is corrected based on the ratio. The method for evaluating image quality of a color display device according to any one of claims 1 to 7, wherein: 9. A white screen is imaged by an imaging means without a lens, and R, R, and R of an arbitrary pixel in an imaging area and other pixels are captured.
After obtaining the ratio of the G and B signals, correcting the sensitivity difference between the light receiving elements constituting each pixel of the image pickup means based on the ratio, taking a white screen with the lens attached to the image pickup means, 8. The method according to claim 1, wherein a ratio between R, G, and B signals of an arbitrary pixel and pixels other than the pixel is obtained, and a sensitivity difference of an imaging system is corrected based on the ratio. Image quality evaluation method for a color display device. 10. A single-color display screen displayed on a screen of a color display device is repeatedly imaged by changing chromaticity and luminance.
8. The chromaticity conversion according to claim 1, wherein the relationship between the R, G, B signals output from the imaging means and the measurement result by the chromaticity measuring means is represented by the following determinant and chromaticity conversion is performed. An image quality evaluation method for a color display device. (Equation 1) 11. A signal generator for displaying a single-color display screen on a color display device to be evaluated, a camera for imaging the single-color display screen and dividing and outputting screen information into R, G, and B signals; A chromaticity measuring device for measuring chromaticity at an arbitrary position on the screen of the color display device, an image processing device for digitizing and storing the outputs of the camera and the chromaticity measuring device, a chromaticity conversion processing table and a quality evaluation table in advance A storage device, based on a digital signal stored in the image processing device, chromaticity conversion, an arithmetic processing device that performs quality evaluation, an image captured by the camera, a monitor that displays a quality evaluation result, An image quality evaluation device for a color display device, comprising: 12. A display on a screen of a color display device after completion of at least one of a display unit, a device mounting process for displaying images on the display unit, and an adjustment process as a display device. The screen information obtained by imaging the monochrome display screen is decomposed into R, G, and B signals for each pixel constituting the screen, and the sensitivity difference between the light receiving elements constituting each pixel of the imaging means is corrected. After converting the G and B signals into a color system, at least obtaining a chromaticity difference or a luminance difference between an arbitrary pixel in the screen and other pixels in the entire screen, and evaluating the image quality based on the result. A method for manufacturing a color display device, comprising: