JP3092813B2 - Image display tube ringing inspection method and apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image quality inspection method and apparatus for an image display tube represented by a cathode ray tube as a cathode ray tube, and more particularly to an inspection method suitable for ringing inspection of an image display tube. And an inspection device.

[Conventional technology]

The ringing phenomenon of the CRT, whether black and white or color, can be confirmed by, for example, the occurrence of bright and dark stripes in the vertical direction on the left side of the screen when projecting a white screen. The ringing of the cathode ray tube causes the excitation voltage of the deflection coil to fluctuate at the rising edge and does not change linearly when the electron beam is scanned. Depending on what happens. The electron beam is normally scanned from the left end to the right end of the screen. However, ringing occurs when the excitation voltage value of the deflection coil fluctuates at the start of the scan. Therefore, the electron beam is generated only on the left side of the screen at the start of the scan.

As a conventional technique relating to this ringing inspection method,
In most cases, the judgment is made by visual inspection, and a method of making a pass / fail judgment by comparing the strength of the stripes, in fact, with a limit sample serving as an inspection standard is employed. However, in this method, there is a great difference between individuals in the evaluation, it is difficult to quantify the evaluation, and the burden on the inspector is large.

Focusing on automating ringing inspection
It is relatively late because it is more difficult to quantify the measurement result than inspection items such as convergence.

As an example of automation of image quality inspection, there is a measurement of shading characteristics (for example, see Japanese Patent Application Laid-Open No. 61-189095).
Even if a simple change in luminance can be detected, it is impossible to evaluate a ringing fringe that repeats a change in luminance value. As a method for removing ringing fringes, for example, Japanese Patent Application Laid-Open
Japanese Patent No. 6690 can be mentioned, but this is about the ringing of the video signal itself, not the ringing by the cathode ray tube itself.

[Problems to be solved by the invention]

In the above prior art, visual inspection is mostly performed, and the method has to rely on manual labor, and it is an inefficient method without consideration of automation by a ringing inspection apparatus.

Therefore, an object of the present invention is to solve the above-mentioned conventional problems, and a first object of the present invention is to quantitatively evaluate ringing by an automated inspection method that is equivalent to a visual evaluation and that is accurate and quick. It is another object of the present invention to provide an improved ringing inspection method capable of discriminating between a good product and a defective product.

A second object of the present invention is to provide an improved inspection device for specifically realizing the above inspection method.

[Means for solving the problem]

In order to achieve the above object, the present inventors have obtained the following findings as a result of various experimental studies.

In other words, the white screen projected on the CRT
Using a TV camera, an image is taken while increasing the detection sensitivity by a preamplifier, and the image is projected in the vertical direction to reduce random noise of ringing. Note that projecting the image in the vertical direction means integrating the luminance signals at the same position of each scanning line in the vertical direction.

Next, a luminance distribution that would have occurred if ringing did not exist, that is, a background luminance distribution is obtained. Then, based on the magnitude of the contrast of each ringing fringe obtained from the result of division of the projection result and the background luminance distribution, a good product or a defective product is determined. The present invention has been made based on such knowledge, and specific means for achieving the object will be described below.

The first object of the present invention is (1). A white image signal is input to an image display tube, a white image having ringing fringes is projected, the image is taken into an image pickup device, and the output signal is converted into a digital signal to obtain a vertical luminance value projection distribution of a screen. Obtaining the background luminance distribution by performing a smoothing process on the vertical luminance value projection distribution, and dividing the vertical luminance value projection distribution by the background luminance distribution, and obtaining a contrast obtained from the division result. Quantifying the magnitude of the ringing fringes projected on the image display tube.

And more preferably, (2). A white image signal is input to an image display tube, a white image having ringing fringes is projected, the image is taken into an image pickup device, and the output signal is converted into a digital signal to obtain a vertical luminance value projection distribution of a screen. Calculating the vertical luminance value projection distribution and smoothing the vertical luminance value projection distribution to obtain a background luminance distribution, dividing the vertical luminance value projection distribution by the background luminance distribution, and obtaining a contrast obtained from the division result. Comparing the preset reference contrast and determining the magnitude of the ringing fringes projected on the image display tube based on the reference contrast based on the reference contrast. Achieved by the method.

More preferably, in the ringing inspection methods of the above (1) and (2), the white image analog signal taken into the image pickup device is amplified to increase the gain and increase the sensitivity of detecting the ringing fringe, and then convert the signal to a digital signal. It is desirable to do so.

As a method for smoothing the vertical luminance value projection distribution, any known method such as a three-point moving average method, an exponential function approximation method, and a midpoint connection method may be used. Is practical and preferred.

The second object of the present invention is: (3). Means for inputting a white image signal to the image display tube;
An imaging device that captures a ringing fringe generated on a screen by the input signal; a unit that amplifies an image output signal of the imaging device and converts it into a digital signal; an image signal storage unit that captures the digitized image signal; From this image signal, a vertical luminance value projection distribution and a background luminance distribution are obtained by smoothing the vertical luminance value projection distribution, and the vertical luminance value projection distribution is divided by the background luminance distribution. An image processing device for calculating the contrast, and quantifying the magnitude of the ringing fringes projected on the image display tube from the magnitude of the contrast of the operation result. More preferably, (4). Means for inputting a white image signal to the image display tube;
An imaging device that captures a ringing fringe generated on a screen by the input signal; a unit that amplifies an image output signal of the imaging device and converts it into a digital signal; an image signal storage unit that captures the digitized image signal; An operation for obtaining a vertical luminance value projection distribution from the image signal and a background luminance distribution by further smoothing the vertical luminance value projection distribution, and further dividing the vertical luminance value projection distribution by the background luminance distribution. Processing means; contrast contrast means for comparing the contrast obtained from the division result with a preset reference contrast; ringing fringes projected on the image display tube based on the comparison result with the reference contrast A ringing inspection device for an image display tube, comprising: a determination means for determining the magnitude of It is made.

[Action]

(1) According to the present invention, a ringing fringe is photographed using an imaging device such as a TV camera while increasing the measurement sensitivity with a preamplifier, and quantitative evaluation is performed by a computer as an arithmetic processing means, whereby a rapid ringing inspection can be performed. It becomes possible.

(2) According to the present invention, the contrast of each stripe obtained from the calculation result of the vertical luminance value projection distribution and the background luminance distribution is in good agreement with human visual characteristics, and an accurate ringing test can be performed. Become.

(3) The vertical luminance value projection distribution is calculated by integrating the luminance at the same vertical position of each scanning line to obtain a distribution in the scanning direction (integrated luminance distribution). The luminance signal at the same position of the line can be easily obtained by performing an integration operation.

(4) To calculate the background luminance distribution, a luminance distribution that would have been the case if ringing did not exist is obtained. If this information is smoothed by a computer using the vertical luminance value projection distribution as a database, Can be easily obtained.

(5) The contrast may be obtained by dividing the vertical luminance value projection distribution by the background luminance distribution, which can also be easily obtained by computer processing.

Other means and operations will be supplemented in the following embodiments.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram illustrating a ringing inspection method and apparatus configuration of the present invention.

In the figure, 1 is a CRT to be inspected, 2 is a TV signal generator capable of generating a very standard test pattern, 3 is a TV camera (black and white) generally used as an industrial visual sensor, 4 Is a preamplifier for increasing image gain, 5 is an A / D converter for digitizing image signals, 6
Denotes an image memory, and 7 denotes a computer as processing means for processing image data stored in the image memory and evaluating ringing.

At the time of ringing evaluation, the cathode ray tube 1 is supplied with a video signal and a synchronization signal of a test pattern generated by the TV signal generator in a state where normal raster scanning is performed, and the pattern is projected.

A white screen is used as the inspection pattern. The image is taken by the TV camera 3 so that the entire vertical size of this screen falls within the field of view. The inspection pattern captured by the TV camera 3 enters the preamplifier 4. Here, the gain is increased while the unnecessary DC level is subtracted as an offset to improve the detection sensitivity of ringing fringes. After passing through the A / D converter 5, the image data is stored in the image memory 6 as image data. The image data is processed by the computer 7 to evaluate ringing.

Next, the arithmetic processing performed by the computer 7 will be described with reference to the schematic processing flow in FIG. 2 and the explanatory diagrams of the respective processing in FIG. 3 to FIG.

First, an image is captured as shown by 101 in FIG. At this time, about the entire screen from the left end of the CRT screen
Image up to 1/2 area. FIG. 3A shows an example of the imaging screen.

Next, the ringing fringe is an approximately uniform light and shade pattern in the vertical direction, and a random noise component added between the vertical lines is the original image, so the average of the luminance distribution in each vertical line is calculated. As a result, a random noise component for ringing can be reduced. Therefore, the brightness values of each pixel of the captured image are sequentially integrated in the vertical direction. Thereby, a one-dimensional gray-scale waveform can be obtained while reducing the influence of random noise on ringing. That is, this is the vertical projection of the luminance value (see FIG. 2).
102). FIG. 3B shows the result of the projection of the luminance values in the vertical direction.

Next, as shown in FIG. 4, the average of the projection values of a certain point and a total of three points before and after that point within the range excluding the first rise of the obtained luminance value vertical distribution is calculated as the average value of that point. , That is, a smoothing process using the three-point moving average method is performed a plurality of times on the projection distribution, and by removing small changes, a luminance distribution that would have been the case without ringing was obtained. Distribution (second
103 in the figure). FIG. 3 (c) shows an example of the result.

As a method of obtaining the background luminance distribution, in addition to the three-point moving average method used this time, an exponential function approximation method in which a projection value shown in FIG. 5 is applied to an exponential function, or a projection value peak shown in FIG. Any method such as the midpoint connection method of connecting the midpoints of the valley and the valley can be used. However, the three-point moving average method is particularly preferable in practical use, and is employed in this embodiment.

Next, a division process of dividing the luminance value projection distribution by the background luminance distribution is performed (104 in FIG. 2). Thereby, the contrast is calculated.

Hereinafter, the basis of the method of calculating the contrast and the quantitative evaluation of the ringing will be described.

In the first place, it is considered that the projection waveform is generated by two of ringing and CRT luminance shading in which the luminance value is lower at the end of the screen than at the center. Therefore, the following simple model was assumed.

Line rate in the absence of ringing is constant at v _0,
The luminance distribution in that case is defined as L ₀ (x). Here, x represents coordinates taken in the horizontal direction (scanning line direction). This L
₀ (x) shows the form of luminance shading. Further, the scanning linear velocity in the presence of ringing is represented by v (x) = k (x) × v ₀ (1). Here, k (x) represents a transient component of the scanning linear velocity. The actual luminance distribution observed at this time is considered to be L (x) = L ₀ (x) × F (k (x)) (2). However, F is a kind of luminous efficiency determined by the speed, and is a function such that F increases as k (x) increases. In other words, the closer the speed is to 0, the longer the irradiation time per unit area of the phosphor by the electron beam becomes, so that the luminous luminance increases, and the luminous luminance decreases as the speed increases. Therefore, it is conceivable to determine the shape of F as F (k) = 1 / k (3), but it is unlikely that the shape can be expressed in such a simple form in practice. But,
It can be considered that at least L (x) / L ₀ (x) is an amount reflecting the physical state of the luminance distribution caused by ringing.

That is, the ringing waveform can be reproduced by calculating L (x) / L ₀ (x). Here, the CRT luminance shading L ₀ (x) is referred to as a background luminance distribution.

Further, since the ringing test is a sensory test, it is necessary to associate the ringing test with visual characteristics. Therefore, by applying Weber's law, which is an experimental psychological rule regarding stimulus intensity, good agreement with visual characteristics can be obtained. Equation (2) shows Weber's law.

ΔI / I = const. (4) where I is the background luminance, and ΔI is the minimum luminance difference at which a change is perceived. Now, when Weber's law is expanded and interpreted and the vertical projection distribution is A and the background luminance distribution is B,
(AB) corresponds to ΔI, B corresponds to I, and the contrast に よ る (AB) / B = A / B−1 (5)

Considering that the vertical luminance distribution / background luminance distribution is represented as A / B, subtracting 1 from this is contrast due to visual perception (the minimum luminance difference at which a change is perceived). The division process is a process of obtaining a ringing waveform component and simultaneously obtaining a contrast of the light and dark pattern of the ringing by visual perception.

Next, the difference (intensity) between the valley of the profile of luminous contrast (division result) and the peak on the right side thereof as shown in FIG.
Obtained from the length (width) between two points crossing zero (second
105 in the figure). Ringing is quantified from the contrast difference (intensity) and the width of one peak crossing 0,
A quantitative evaluation of the ringing, that is, a quality judgment of the cathode ray tube, is performed based on the magnitude relationship with the set value of the ringing of the limit sample which is allowable even if the ringing obtained in advance is determined (No. 2).
Figure 106). That is, as shown in FIG. 8, by simultaneously performing visual judgment and quantitative evaluation according to the present invention using a large number of cathode ray tubes including non-defective to defective products as samples, the non-defective product limit can be experimentally obtained. A ringing inspection is performed using the non-defective product limit.

FIG. 9 shows the results of this test, in which 12 sample cathode ray tubes (sample No. 1) selected by a skilled inspector were selected.
1 passing product, 11 ringing defective samples 2 to 12
2) shows the results of actual measurement using an apparatus employing the inspection method of the present embodiment. As shown in the figure, the evaluation result according to the present embodiment is in good agreement with the inspection result of a skilled inspector.

From the results of the evaluation experiment, the contrast is 0 in this method.
Detection of fringes up to about 01 (1%) is possible. 1% of the contrast substantially matches the visual recognition limit, which means that the detection sensitivity is practically sufficient. According to the inspection results by a skilled inspector, it is impossible to accurately determine the magnitude of the quantitative ringing even if defective ringing products can be selected. Quantification is possible.

〔The invention's effect〕

As described above, according to the present invention, it is possible to quantify and measure ringing without relying on the human eye for ringing while maintaining good agreement with visual evaluation, and quickly distinguish non-defective / defective products. Can be performed.

The present invention is expected to make a great contribution to the industry, which can contribute to automation of an inspection process at the time of manufacturing a high-quality color cathode-ray tube, which is expected to increase in demand in the future, and to quality inspection at the time of new product development. Is done.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a ringing inspection method and an inspection apparatus according to an embodiment of the present invention, FIG. 2 is a schematic flowchart of an arithmetic operation performed by a computer according to the embodiment, and FIG. ) Is a diagram showing a ringing phenomenon occurring on a CRT, FIG. 3 (b) is a curve diagram showing a vertical projection distribution of luminance values, and FIG. 3 (c) is a characteristic curve diagram showing a calculation result of a background luminance distribution. FIG. 4 shows the 3rd smoothing process.
Explanatory diagram showing the point moving average method, FIG. 5 is an explanatory diagram showing the exponential function approximation method, FIG. 6 is an explanatory diagram showing the midpoint connection method, and FIG. 7 shows definitions of ringing intensity and width. FIG. 8 is an explanatory diagram showing the criteria for judging whether ringing is good or not and the result of selection, and FIG. 9 is a sample distribution diagram showing the actual measurement results of quantification of ringing according to the embodiment of the present invention. <Description of Codes> 1 ... CRT, 1 ... TV signal generator, 3 ... TV camera, 4 ... Preamplifier, 5 ... A / D converter, 6 ... Image memory, 7 ... Calculator.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A 1-314074 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 17/00-17/06

Claims (6)

(57) [Claims] 1. A white image signal is input to an image display tube, a white image having ringing fringes is projected, the image is taken into an image pickup device, and an output signal is converted into a digital signal to convert the image into a vertical signal. Obtaining a luminance value projection distribution; and obtaining a background luminance distribution by performing a smoothing process on the vertical luminance value projection distribution. Dividing the vertical luminance value projection distribution by the background luminance distribution; Quantifying the extent of the ringing fringes projected on the image display tube by the construct obtained from the method. 2. A white image signal is input to an image display tube, a white image having ringing fringes is projected, the image is taken into an image pickup device, and an output signal is converted into a digital signal to convert the image into a vertical signal. Obtaining a luminance value projection distribution; and obtaining a background luminance distribution by performing a smoothing process on the vertical luminance value projection distribution. Dividing the vertical luminance value projection distribution by the background luminance distribution; Comparing the contrast determined from the above with a preset reference contrast, and determining the magnitude of the ringing fringes projected on the image display tube based on the reference contrast. Ringing inspection method for image display tubes. 3. The image display according to claim 1, wherein the white image analog signal taken into the image pickup device is amplified to increase the gain and increase the sensitivity of detecting the ringing fringes before converting the signal into a digital signal. Tube ringing inspection method. 4. A ringing inspection method for an image display tube according to claim 1, wherein the method of smoothing the vertical luminance value projection distribution is performed by a three-point moving average method. 5. A means for inputting a white image signal to an image display tube; an image pickup device for picking up ringing fringes generated on a screen by the input signal; and an image output signal of the image pickup device is amplified and converted into a digital signal. Means; an image signal storing means for taking in the digitized image signal; and a vertical luminance value projection distribution from the image signal, and a background luminance distribution by smoothing the vertical luminance value projection distribution. Calculation processing means for obtaining the contrast by dividing the vertical luminance value projection distribution by the background luminance distribution, and from the magnitude of the contrast of the calculation processing result, the image is displayed on the image display tube. A ringing inspection device for an image display tube, which quantifies the extent of the ringing fringes. 6. A means for inputting a white image signal to an image display tube; an image pickup device for picking up ringing fringes generated on a screen by the input signal; and an image output signal of the image pickup device is amplified and converted into a digital signal. Means; an image signal storing means for taking in the digitized image signal; and a vertical luminance value projection distribution from the image signal, and a background luminance distribution by smoothing the vertical luminance value projection distribution. Calculation processing means for obtaining and further dividing the vertical luminance value projection distribution by the background luminance distribution; and contrast comparing means for comparing the contrast obtained from the result of the division with a preset reference contrast;
A ringing inspection device for an image display tube, comprising: determination means for determining the magnitude of the ringing fringe projected on the image display tube based on the comparison result with the reference contrast.