JPH0449834B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a white unevenness inspection device suitable for use in image quality inspection in quality control of television receivers.

[Background of the invention]

Conventionally, when manufacturing television receivers, a quality control step is provided as the final step of the production line, and the performance of the television receiver is inspected in this step. For this performance test, methods are adopted depending on the target to be tested. One method is to project a test pattern, which is a still image, on the screen of the television projector to be tested. There is a method of inspecting the image quality of such a test pattern to evaluate the quality of the performance of the television receiver to be inspected.

Incidentally, in recent years, automation and labor saving have been promoted in the manufacturing process of television receivers, but in the quality control process, which is one of the processes, human labor is required for image quality inspection, with some exceptions. Ori,
In reality, sensory tests are conducted based on visual evaluation of test patterns by experienced inspectors.

However, this image quality inspection method based on visual evaluation has problems such as individual differences in evaluation, poor reproducibility of evaluation, low inspection efficiency, and required skill for inspection. It was extremely difficult to obtain objective test results, and it was not possible to perform sufficient quality control.

In particular, one important factor that affects the image quality of color television receivers is the white uniformity of color cathode ray tubes, and among the many inspection items, the white unevenness inspection of color cathode ray tubes is one of the important inspection items. There is.

One of the causes of white unevenness in color cathode ray tubes, that is, nonuniform white color across the entire screen, is the landing error of the electron beam, that is, the electron beam that passes through the hole in the shadow mask does not accurately hit the corresponding phosphor. The white unevenness in conventional color cathode ray tubes was mainly caused by this landing error.

Conventionally, the conventional method for inspecting such white unevenness has been a visual method, in which a monochromatic screen of red, green, and blue is sequentially projected as a test pattern on a color television receiver to be inspected, and the color of the monochromatic screen is checked. The white unevenness was inspected by visually evaluating the unevenness. However, this method has the problems mentioned above.

In response to this, a method has been proposed in which white unevenness is inspected by making the landing error visible (Japanese Patent Laid-Open No. 49-40426). In this method, for example, 15 points on the screen of the color cathode ray tube to be inspected are picked up, each point is sequentially imaged at high magnification using an industrial television camera, and the enlarged screen is projected.
The dot pattern position is visually measured.
Although this method allows for some improvement in terms of individual differences in evaluation and reproducibility,
Inspection requires manpower and a certain level of technical skill.

In addition, in recent years, black matrix tubes have become the mainstream color cathode ray tube, but in such black matrix tubes, in addition to landing errors, irregularities in the shape and size of graphite holes are the main cause of white unevenness. This reduces uniformity. For this reason, more and more sophisticated techniques are required to inspect white unevenness, and it is necessary to inspect the entire screen without corners, taking into account irregularities in graphite holes. Therefore, the method described in JP-A No. 49-40426 requires a very long time to inspect a single color cathode ray tube for white unevenness, and is rarely implemented in reality. It is not possible.

[Purpose of the invention]

The present invention eliminates the drawbacks of the prior art described above, and provides a white unevenness inspection device that can objectively and automatically evaluate the white uniformity of a color cathode ray tube to be inspected in real time and has a simple circuit configuration. .

[Summary of the invention]

In order to achieve this object, the present invention sequentially projects two screens corresponding to two different monochromatic video signals on a color cathode ray tube to be inspected, images the screens through the same color optical filter, and displays the respective screens. The present invention is characterized in that the white unevenness of the color cathode ray tube to be inspected can be quantitatively evaluated by obtaining image data for each color and subtracting or dividing these image data from each other.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a white unevenness inspection apparatus according to the present invention, in which 1 is a color television receiver to be inspected, 2 is a monochromatic optical filter,
3 is a television camera, 4 is a test pattern signal generation circuit, 5 is a synchronization signal generation circuit, 6 is an analog-to-digital conversion circuit, 7 and 8 are frame memories, 9 is a screen switching circuit, 10 is an arithmetic circuit, and 11 is a frame Memory, 12 is a computer.

In the figure, a color television receiver 1 to be inspected is supplied with a monochrome video signal from a test pattern signal generation circuit 4 and displays a monochrome screen, and this monochrome image is passed through a monochrome optical filter 2 and then sent to a television camera 3. Imaged. A synchronizing signal is supplied from the same synchronizing signal generating circuit 5 to the television camera 3 and the test pattern signal generating circuit that generates the monochromatic test pattern signal. and TV Camera 3 are synchronized.

The screen switching circuit 9 operates based on commands from the computer 12, controls the test pattern signal generating circuit 4 to switch the monochrome screen displayed on the color television receiver 1 to be tested, and also controls the frame memories 7 and 8. Alternately write state.
Therefore, the color television receiver 1 to be inspected
1 obtained by imaging a certain monochromatic screen projected on
The image data of the frame period is written to the frame memory 7, and the image data obtained by imaging another monochrome screen is 1
Image data for the frame period is written into the frame memory 8.

The arithmetic circuit 10 subtracts or divides the image data stored in the frame memories 7 and 8 from each other at each sampling point, and supplies the obtained arithmetic results to the frame memory 11. When the calculation results for all sampling points are written into the frame memory 11, the computer 12 evaluates color unevenness based on these calculation results.

Next, the operation of this embodiment will be explained.

First, the landing error, which is one of the causes of white unevenness on the projection screen of a color television receiver, will be explained with reference to FIG.

FIG. 2 is an enlarged view showing a part of the phosphor screen of a black matrix color cathode ray tube, and shows a red phosphor section R, a green phosphor section G, and a blue phosphor section that are vertically band-shaped on the phosphor screen. The portions B are arranged in the order of R, G, and B in the horizontal direction, and a non-light emitting portion N is provided between these phosphor portions R, G, and B.

Therefore, when a white screen is projected on a color cathode ray tube, an electron beam modulated by a red signal (hereinafter referred to as "red electron beam") passes through a predetermined hole provided in a shadow mask (not shown) and emits red fluorescent light. An electron beam (hereinafter referred to as
The green phosphor section G is irradiated with a green electron beam, and the blue phosphor section B is irradiated with an electron beam modulated by a blue signal (hereinafter referred to as a blue electron beam). The red phosphor portion R emits red light, the green phosphor portion G emits green light, and the blue phosphor portion B emits blue light, and these primary color lights are additively mixed to produce white light.

In this case, the red electron beam is irradiated only on the red phosphor part R, and the green electron beam is irradiated on the green phosphor part G.
In addition, the blue electron beam is irradiated only on the blue phosphor section B, which is the part where there is no uneven white on the projection screen of the color CRT, but it is the part where there is a landing error on the projection screen. In this case, the electron beam not only hits a certain phosphor part, but also
Part of the adjacent phosphor section will also be irradiated.
That is, as shown in FIG. 2, the red electron beam is irradiated to a range S _R that spans the red phosphor section R and a part of the green phosphor section G, and the green electron beam is irradiated to the range S R that spans the red phosphor section R and a part of the green phosphor section G. A range S _G spanning part of the body part B is irradiated with the blue electron beam, and a range S _B spanning part of the blue phosphor part B and the red phosphor part R is irradiated with the blue electron beam. As a result, each phosphor portion R,
The ratio of red light, green light, and blue light generated in G and B changes, resulting in white unevenness on the screen of a color cathode ray tube.

Therefore, the operation of this embodiment when white unevenness occurs due to the cause shown in FIG. 2 will be explained.

In FIG. 1, a green filter is installed as the monochromatic optical filter 2, and under the command of the computer 12, the screen switching circuit 9 causes the test pattern signal generation circuit 4 to generate a green test pattern signal and transmit it to the color television to be inspected. A green screen is displayed on the television receiver 1, and at the same time, the frame memory 7 is set to a writing state and the frame memory 8 is set to a non-writing state.

In this case, the color television receiver to be inspected 1
As shown in Figure 3a, in the part of the screen projected on the screen where white unevenness does not occur, the range S _G where the green electron beam is irradiated onto the phosphor screen overlaps only the green phosphor part G, but the white unevenness does not occur. As shown in FIG. 3b, in the area where this occurs, not only the green phosphor section G but also a part of the blue phosphor section B are affected. Therefore, in this portion, the blue phosphor portion B also generates blue light, albeit slightly, and becomes green with less blue.

Therefore, if the monochromatic optical filter 2 is a green filter and this screen is imaged by the television camera 3 through the green filter 2, the green filter 2 will only transmit green light and block other primary color lights. Therefore, only the green light emitted from the green phosphor section G is received by the television camera 3. Therefore, in areas where the color television receiver 1 to be inspected does not have white unevenness, it emits green light over the entire width (hatched area) of the green phosphor section G, as shown in Figure 4a. Although the amount of light emitted is large, in the part where white unevenness occurs, as shown in FIG. 4b, green light is emitted from the part of the green phosphor part G excluding a part (shaded part). The amount of light emitted decreases.

By receiving such green light, a video signal for a green screen from the television camera 3 is transmitted to an analog-to-digital conversion circuit (hereinafter referred to as A/D).
For example, the signal is supplied to a conversion circuit (referred to as a conversion circuit) 6, and is converted into image data of digital values representing 256 gradations of amplitude from 0 to 255 at each sampling point, for example. This image data is supplied to the frame memory 7, and 1
The image data of the frame is written into the frame memory 7.

Next, the computer 12 sends a command signal to the screen switching circuit 9, and the screen switching circuit 9 causes the test pattern signal generating circuit 4 to generate a red test pattern signal, so that the color television receiver 1 to be inspected receives a red screen. is displayed, and at the same time, the frame memory 7 is set to a non-writing state, and the frame memory 8 is set to a writing state.

In this case, the color television receiver to be inspected 1
As shown in FIG. 5a, in the area of the screen where white unevenness does not occur, the red electron beam is irradiated only to the red phosphor portion R, so the other phosphor portions G and B do not emit light. However, in areas where white unevenness occurs, as shown in FIG.
Green light is generated from this part, and the projected screen becomes a red screen with a green tint.

Therefore, when the projected screen is captured by the television camera 3 through the green filter 2, the green filter 2 blocks the red light and transmits only the green light. In areas where white unevenness does not occur, Figure 6a
As shown in FIG. 3, the red light is blocked, the amount of light received by the television camera 3 becomes zero, and an image signal with zero amplitude is obtained. On the other hand, in the part where white unevenness occurs on the projected screen of the color television receiver to be inspected, as shown in FIG. Since green light is generated, this green light passes through the green filter 3 and is received by the television camera 3, from which an image signal having an amplitude corresponding to the amount of received light is obtained.

An image signal obtained from the television camera 3 is converted into a digital signal by an A/D conversion circuit 6 to become image data, and one frame of the image data is written into a frame memory 8.

When one frame of image data is written into each of the frame memories 7 and 8, the image data is then simultaneously read out from each of the frame memories 7 and 8 and supplied to the arithmetic circuit 10. That is, the image data consists of digital values at a series of sampling points of the image signal sampled by the A/D conversion circuit 6, and the frame memories 7 and 8 each have a digital value of 1 at this sampling point.
The image data that is read out one after another, and that is read out simultaneously from the frame memory 7 and the frame memory 8, is at sampling points that correspond to each other, that is, at the same position on the projection screen of the color television receiver 1 to be inspected. The digital values of are read out at the same time.

The arithmetic circuit 10 performs subtraction processing or division processing on the supplied image data, and supplies the result of this calculation to the frame memory 11. That is, when performing a subtraction process, the image data supplied from the frame memory 8 is subtracted from the image data supplied from the frame memory 7, and when performing a division process, the image data from the frame memory 7 is subtracted from the image data supplied from the frame memory 7. Divide by the image data from 8. In all of these calculation results, the larger the white unevenness, the smaller the value.

When the calculation results of all the image data of one frame are written into the frame memory 11, the computer 12 reads these calculation results and performs predetermined processing to determine the degree of white unevenness.

Next, determination of the degree of white unevenness in this example will be explained.

FIG. 7 is an explanatory diagram showing an example of the light emitting state of the fluorescent surface of a color cathode ray tube when the projection screen is a green screen, and parts corresponding to those in FIG. 2 are given the same reference numerals.

Now, regarding the part of the projected screen of the color television receiver 1 to be inspected (FIG. 1) where white unevenness does not occur, the brightness when the projected screen is a red screen is V _R , and the brightness when the projected screen is a green screen is V R . Assuming that the brightness is V _G and the brightness when the screen is blue is V _B , the output level of the television camera 3 (Fig. 1) in the area where white unevenness does not occur when the projection screen is green is v _G is v _G =k・V ^r _G ……(1). However, k is a proportionality constant, and r is a constant representing the comma characteristic of the television camera 3.

On the other hand, in the part of the projection screen where white unevenness occurs, when this projection screen is made into a white screen, the seventh
As shown in the figure, the irradiation width of the green electron beam is equal to the width W of each phosphor section R, G, and B, and the green electron beam is shifted from the green phosphor section G to the adjacent blue phosphor section B. If the green electron beam is irradiated over _a width A _R , and the green phosphor part G is covered by the width X.

Therefore, the output level v _G ′ of the television camera 3 for green light in the area where such white unevenness occurs is expressed as v _G ′=k・(W−X− a/W・V _G +X/W・V _R )
^r ...(2).

In this way, the output level of the television camera 3 is affected by its comma characteristic, and when r=1, it is proportional to the input brightness and the gradation of the input image and the output image are equal, but when r>1 When r>1, the output changes rapidly with respect to the input, the gradation of the output image narrows, and the contrast becomes strong, and when r>1, the contrast becomes weak.

Incidentally, in recent years, solid-state image sensors have been used in television cameras, and the comma characteristic of the solid-state image sensors is r=1. Therefore, in this example,
It is assumed that the television camera 3 also uses a solid-state image sensor as an image sensor, and in order to simplify calculations, the description will be made assuming that r=1 in the above equations (1) and (2).

Therefore, the luminance change Δv _G (=v _G ′−v _G ) due to the occurrence of white unevenness due to the degree X of other colors is given by the following equation.

△v _{G =} -X + _a / WV _G + It is expressed as the formula.

△v _R =X/WV _G -X+a/WV _R ...(4) Figure 8 a shows the degree of other color printing X from equations (3) and (4).
FIG. As is clear from the figure, △v _G and △v _R monotonically decrease and monotonically increase, respectively, with respect to the degree of other color printing X. Therefore, if the arithmetic circuit 10 (FIG. 1) subtracts the difference between the green screen and the red screen, for example, the value of the corresponding point of the red screen data from the green screen data, it can be determined that no white unevenness has occurred. A difference of △v _G − △v _R can be obtained between the normal part and the part where white unevenness has occurred. From this difference in luminance, the degree X of other color printing can be determined. Furthermore, at the same time, it is also possible to determine the extent of the portion where the white unevenness occurs, that is, the area.

Next, from the above equations (3) and (4), the ratio of the brightness of the green screen and the red screen with respect to the degree of other color printing is determined as shown in FIG. 8b. Therefore, in the arithmetic circuit (Fig. 1), if one of the screen data of the green screen and the red screen is used as a divisor, for example,
By using the red screen data as a divisor and performing a division operation on the values of the corresponding points on each screen, Figure 8b is obtained.
The degree X of other color printing can be determined by . Furthermore, the area of the portion where white unevenness occurs can also be determined at the same time.

As described above, according to this embodiment, for example, a color television receiver to be inspected is imaged by a television camera through the same green optical filter, and a green screen is displayed on the color television receiver to be inspected. By determining the difference or ratio between the brightness and the brightness of the brightness, the white unevenness can be quantified, and the white unevenness can be quantitatively inspected. Furthermore, this embodiment can be constructed using existing technology and has a simple circuit configuration, and is also based on data obtained by measurements using the same optical filter and the same television camera. Because it performs calculations, there is no need to replace optical filters or television cameras, and therefore there is no need to make corrections due to differences in the characteristics of each.
In addition, inspection work is also simplified.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to evaluate white uniformity automatically and in real time without requiring human intervention, and it can also be done quantitatively, ensuring objectivity. The reproducibility of test results is also improved, increasing reliability.
The circuit configuration is not complicated, and it is possible to provide a white unevenness inspection device with excellent functions without the drawbacks of the above-mentioned conventional technology.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a white unevenness inspection device according to the present invention, FIG. 2 is an enlarged front view showing a part of the fluorescent surface of a color cathode ray tube, and FIGS.
Fig. 4b is an enlarged front view illustrating the state of normal parts and white unevenness parts of the fluorescent surface of a color cathode ray tube when the screen is set to green; Figs. 4a and b are Figs.
Fig. 5a and b are enlarged front views showing the light emitting state of the color cathode ray tube when the green screen in b is viewed through a green optical filter, and Figs. An enlarged front view illustrating the light emitting state, Fig. 6 a, b is an enlarged front view showing the light emitting state of the color cathode ray tube when the red screen of Fig. 5 a, b is seen through a green optical filter, and Fig. 7 is a green screen. FIGS. 8a and 8b are enlarged front views for explaining the light emitting state of a portion where white unevenness occurs on the fluorescent surface of a color cathode ray tube. FIGS. 1...Color television receiver to be inspected, 2...
... Monochromatic optical filter, 3... Television camera, 4... Test pattern signal generation circuit, 5...
Synchronous signal generation circuit, 6... Analog-digital conversion circuit, 7, 8... Frame memory, 9... Screen switching circuit, 10... Arithmetic circuit, 11... Frame memory, 12... Computer.

Claims (1)

[Claims] 1 In a white unevenness inspection device that sequentially projects different first and second monochrome screens by applying different first and second monochrome video signals to a color television receiver to be inspected, the first an optical filter that transmits monochromatic light; an imaging device that images the monochromatic screen displayed on the color television receiver to be inspected through the optical filter; and a video signal obtained by the imaging device. At least first and second frame memories for storing image data and an arithmetic circuit for subtracting or dividing the image data stored in the first and second frame memories are provided, and the first frame The memory stores the image data obtained by applying the first monochromatic video signal to the color television receiver to be inspected to display the first monochromatic screen of the first monochromatic light; The frame memory is obtained by applying the second monochromatic video signal to the color television receiver to be tested to display the second monochromatic screen of a second monochromatic light different from the first monochromatic light. A white unevenness inspection device, characterized in that the image data is stored and the white unevenness inspection device is configured to inspect white unevenness based on the calculation result by the arithmetic circuit.