JPH0155636B2 - - Google Patents

Description

[Detailed Description of the Invention] (1) Technical Field of the Invention The present invention relates to a display device using a CRT (cathode ray display tube), in which brightness decreases due to poor adjustment or circuit failure of the CRT's deflection circuit system. This invention relates to an inspection method for CRT display screens that uses an observation device to automatically inspect abnormal display phenomena due to non-uniformity.

(2) Background and problems of the technology In display devices using CRTs, if abnormal display phenomena such as tilt, distortion, misalignment, or non-uniform brightness occur on the screen displayed on the CRT, the quality of the screen will deteriorate significantly.

Non-uniformity in brightness is problematic because it is particularly noticeable due to reflection. Reflection can occur when one end of the scanning line (mainly the right end) is folded back due to improper adjustment of the deflection circuit system or circuit failure, causing the brightness of that part to become high and uneven (folded reflection), and when a horizontal straight line There are cases where the quality defect is extremely shifted to one end, and the brightness at one end of the left or right becomes high and becomes non-uniform (non-linear distortion reflection).

FIG. 1 shows an example of poor CRT screen display quality caused by an abnormal display phenomenon using a grid-frame test pattern. P indicated by a dotted line in the display frame F is the display screen of a normal test pattern, Q is the display screen of an abnormal test pattern, and SH
is the horizontal line of the test pattern, SV is the vertical line of the test pattern, BR is the high brightness area caused by folded reflection, BD is caused by non-linear distortion reflection,
In other words, it shows a high-brightness region created by increasing the density of straight lines.

a is when the vertical amplitude is insufficient, b is when the screen is tilted, c is when pincushion distortion occurs, d is when the center position of the screen is shifted, e is when vertical linearity is poor, f is when folding When reflection occurs, g is the case when nonlinear distortion reflection occurs.

When such an abnormal display phenomenon occurs, displayed figures, graphs, characters, symbols, etc. are deformed in a display device for information processing, which causes a significant drop in screen quality, which is particularly problematic.

Conventionally, the main method for inspecting CRT display screens to detect this abnormal display phenomenon has been manual inspection by visual inspection by inspectors. However, in this case, there were problems such as eye fatigue for the inspector, difficulty in maintaining constant inspection quality due to visual inspection, and difficulty in speeding up the inspection.

Therefore, in order to solve these problems, TV
The same applicant has proposed a method for automatically inspecting the display screen of a CRT using an observation device such as a camera (Japanese Patent Application No. 113566/1983
-4383 Publication)).

This method uses a test pattern in the form of a grid frame, and measures the display frame F and test pattern Q displayed on the CRT using an observation means such as a TV camera.
Based on the relative dimensional relationship between the display frame F and the test pattern Q, the display dimensions, positional deviation, tilt, and various distortion values of the display screen are determined, and it is determined whether or not these are within predetermined reference values. By doing so, the quality of the CRT display screen can be automatically inspected.

This method can detect the presence or absence of dimensional changes, positional deviations, inclinations, and distortions of the display screen illustrated in a to e of FIG. 1, and therefore can inspect most of the abnormal display phenomena. However, in the case of reflection, since there is little change in the relative dimensions of the display frame and the test pattern, it is difficult to detect the presence or absence of reflection, particularly the presence or absence of folded reflection, with the above method.

(3) Purpose of the Invention The purpose of the present invention is to provide a CRT display screen inspection method that reliably detects the presence or absence of abnormal display phenomena due to reflection and automatically and quickly tests the quality of the CRT display screen. It's about doing.

(4) Structure of the invention In order to achieve this object, the CRT display screen inspection method of the present invention uses a CRT display device and this CRT display screen inspection method.
A test pattern generating means for generating a test pattern having a pattern area of a constant width at the left and right ends of the display screen of the display device, an observation means for observing the test pattern, and a left and right pattern area of the test pattern observed by the observation means. pattern position/width detection means for detecting the edge pattern position and area width; left edge maximum luminance detection means for detecting the maximum luminance value of the left edge pattern area; and right edge luminance detection means for detecting the maximum luminance value of the right edge pattern area. a maximum value detection means; a brightness comparison means for comparing the outputs of the left end brightness maximum value detection means and the right end brightness maximum value detection means to determine a ratio thereof; A CRT is provided with a width comparison means for determining and a determination means for determining whether the quality of the screen is good or bad from the output information of the brightness comparison means and the width comparison means.
It is characterized by inspecting the display screen for abnormal conditions.

(5) Embodiments of the Invention In the present invention, when a test pattern having a pattern area of a constant width at the left and right ends is displayed on a CRT, this is observed using a TV camera, etc., and the pattern area at the left and right ends is The quality of the display screen is determined based on whether the maximum brightness value or the area width ratio is within a predetermined reference value.

An embodiment of the present invention will be described below with reference to FIGS. 2 to 7.

Figures 2 and 3 explain in more detail the abnormal display phenomenon due to reflection shown in f and g in Figure 1. Figure 2 shows the case of folded reflection, and Figure 3 shows the case of non-linear distortion reflection. The case is shown below.

Folded reflections occur due to a mismatch between the retrace start point of the scanning line and the blanking start point, so they usually occur at the right edge of the display screen or in a folded state, as shown in Figure 2a, and the portion BR is The brightness becomes even higher.

FIG. 2b shows the output data of the horizontal scanning line of a normal display screen without aliasing, and a video output with a height HA is generated at the vertical scanning line SV of the test pattern Q.

Figure 2c shows the horizontal scanning line output data when aliasing occurs, and the video output HB at the right end where aliasing occurs is one level higher than the video output HA of the normal part. Become something.

However, since it has almost no effect on the relative dimensions of the display frame F and the test pattern Q, it is difficult to detect the presence or absence of folded reflection using a method that detects abnormal display phenomena from changes in the relative dimensions of the two. It is.

Next, Figure 3 shows nonlinear distortion reflection,
If the nonlinear distortion is extremely shifted to one end (usually to the right),
As shown in FIG. 3a, the vertical line density of the right end portion BD becomes high. FIG. 3b shows the output data of the horizontal scanning line when non-linear distortion reflection occurs, and the vertical line density of the right end portion BD is high. Therefore, as shown in FIG. 3c, the average luminance of the portion BD where non-linear distortion reflection occurs has a level MB higher than MA in the area of width W compared to the level MA of the normal portion.

However, in the case of non-linear distortion reflection, the display frame F
Since there is almost no change in the relative dimensions of the test pattern Q and the test pattern Q, the presence or absence of non-linear distortion reflection cannot be detected from the change in the relative dimensions of the two. In addition, in the method proposed by the same applicant, non-linear distortion may be detected using a change in the relative dimension of the interval between the vertical lines SV of the test pattern Q as a type of relative dimension. If there is an extreme deviation, linearity is good in the middle, but the area near one end of the test pattern becomes non-linear and reflections occur, so it is difficult to detect the presence or absence of reflections unless the number of vertical lines SV is increased. It is difficult.

The present invention is based on the discovery that if a test pattern in which pattern areas of a constant width are provided at both left and right ends is used, both folded reflections and non-linear distorted reflections can be reliably detected.

FIG. 4 shows the test pattern R used in the present invention. As shown in FIG.
W ₀ pattern areas A and B are provided. Of course, vertical and horizontal lattice patterns may be provided in the intermediate region as in the conventional method. Figure 4b shows the output data of the horizontal scanning line in a normal case.
W ₀ , produces a high H ₀ video output.

FIG. 5 shows the case where there is folded reflection. When the folded part is as small as W _BR1 , as shown in Figure 5b, there is a part on the right end with a narrow width of W _BR1 but a very high brightness of H _BR1 , and a part with a width of W _BR2 and a brightness of H on the left end. Generates a video output consisting of a portion with _HBR2 approximately equal to _AR .

Therefore, if the maximum brightness value H _AR of the left end area A and the maximum brightness value H _BR1 of the right end area B are detected, and the ratio of the two is close to 2, for example, it is determined that there is an aliasing reflection. In fact, if the ratio H _BR1 /H _AR of the two is about 2, it is safe to conclude that folded reflection has occurred.

The width of the brightness area at the right end changes depending on the folding width, but the value of the maximum brightness value H _BR1 does not change much depending on the folding width as long as there is an overlapping part between the folding part and the normal display part. Judging from the ratio of the maximum brightness values at both ends, the presence or absence of folded reflection can be reliably detected.

Next, when the aliasing becomes extreme and there is no overlap between the aliasing part and the normal display part, the video output at the right end is lower than the brightness H _AR at the left end, as shown in Figure 5c. It has a brightness H _BR3 and a width W _BR3 that is much wider than the left end width W _AR . W _AR <W _BR3 because the blanking period is much shorter than the scanning period.

The reason why the folding becomes extreme here is as follows.

In a CRT display device, an electron beam carrying information to be written on the screen is scanned horizontally line by line from left to right, hitting the phosphor on the CRT's glass surface and emitting light. By performing several hundred scans in the horizontal direction while shifting them slightly in the vertical direction (downward), it is possible to write characters and figures on the entire screen.

By the way, when scanning an electron beam in this manner, it is necessary for the electron beam to temporarily return to the left end after scanning to the right end. During this period of return (return section), the electron beam exits and enters, so it is necessary to control this point correctly. This section where the electron beam returns is also called a blanking section because no signal is output.

If this blanking starts later,
The display also appears during the return time of the electron beam, resulting in a phenomenon called reflection.

The extreme turning means that the blanking starts late, and the pattern that I want to display for inspection on the right end completely falls into the retrace section from the point where it should be displayed. This is what is meant here, and for that reason, the display will be performed and entered at the time of return. Therefore, during retrace, the return speed of the electron beam is several times faster than during display, so the width of the display pattern appears wider (W _AR < W _BR3 ).

Therefore, in this case, find the ratio of the region widths at both ends, and make sure that the ratio of both W _BR3 /W _AR is greater than a predetermined value (for example, 2
degree), it can be determined that folded reflection has occurred.

FIG. 6 shows a case where there is non-linear distortion reflection. In the case of non-linear distortion reflection, the line density at the right end is high as shown in Figure 6a, so the area width is
W _BD becomes narrower. However, the maximum brightness is _HBD, which is higher than the leftmost brightness _HAD , as shown in FIG. 6b.

Therefore, as in the case of folded reflection, the maximum brightness value at both ends is determined, and if the ratio H _BD /H _AD of both is equal to or greater than a predetermined value (for example, about 2), it is determined that there is non-linear distorted reflection.

In this case as well, non-linear distorted reflection can be detected more reliably by determining from the ratio of the maximum luminance value than from the change in the region width at both ends.

In addition, when non-linear distortion reflections occur, the intervals between vertical lines SV are often uneven, so in many cases non-linear distortion reflections are caused by the display frame and test pattern proposed by the same applicant. Non-linear distortion is detected by a method that detects non-linear distortion from the relative dimensions of. The present invention can effectively detect cases where there is significant non-linear distortion near one end of the display screen, causing reflection.

From the previous explanations regarding both folded reflection and nonlinear distortion reflection, first, the maximum brightness values at both ends of the test pattern are compared, and if the ratio is greater than or equal to a predetermined value, it is determined that reflection exists, and the width of both areas is When the ratio is greater than or equal to a predetermined value, it is determined that extreme folded reflection exists, and when both ratios are less than or equal to a predetermined value, it is determined that the display screen is normal.

Note that the explanation so far has been about the case where reflection occurs at the right end, but depending on the deflection circuit system, it may occur at the left end (but not at both ends), but in that case, the explanation so far does not apply. It is clear that it can be applied as is, just by reversing the left and right sides.

FIG. 7 is a block diagram of a specific apparatus for implementing the CRT display screen inspection method of the present invention.

In the figure, 11 is a CRT display device to be observed;
2 is a test pattern generator, 13 is an observation device such as a TV camera, 14 is a line buffer, 15 is a pattern signal detection circuit, and 16 detects the pattern positions of areas A and B at the left and right ends of the test pattern and their area widths. Pattern position and width detection circuit, 17 is a left end brightness maximum value detection circuit for detecting the maximum brightness value at the left end (area A), 18 is a right end brightness maximum value detection circuit for detecting the maximum brightness value at the right end (area B), 19 20 is a brightness comparison circuit that compares the outputs of the left and right end brightness maximum value detection circuits 17 and 18 and calculates the ratio between the two;
21 is a width comparison circuit that compares the area widths of the patterns of areas A and B at both left and right ends and calculates the ratio; 21 detects the presence or absence of reflection from the outputs of the brightness comparison circuit 19 and the width comparison circuit 20, and determines the display screen quality. This is a judgment circuit that judges pass/fail.

In this configuration, the observed CRT display device 11
receives the output of the test pattern generator 12 and generates the fourth
The test pattern R shown in Figure a is displayed on the CRT.
The observation device 13 observes the test pattern R,
The data is amplified by a line buffer 14 and supplied to a pattern signal detector 15 and left and right end brightness maximum value detection circuits 17 and 18.

The pattern signal detection circuit 15 detects the presence or absence of a pattern signal in areas A and B at both left and right ends by setting a certain threshold level. The pattern position and width detection circuit 16 detects the position and width of the pattern signals in areas A and B, and outputs the output terminal a.
, a gate signal GA having a width W _A is placed at a position corresponding to the pattern signal of the leftmost area A, and a gate signal GA having the width W B is placed at a position corresponding to the pattern signal of the rightmost area B at the output end _b . A gate signal GB is generated, an area width signal W _AC indicating the area width _WA is generated at the output terminal c, and an area width signal W _BD indicating the width W _B is generated at the output terminal d.

The left end brightness maximum value detection circuit 17 receives a gate signal
The maximum value of the test pattern signal during the GA application time, that is, the maximum brightness value H _A of the left end area A is determined. The right end brightness maximum value detection circuit 18 receives a gate signal
The highest value of the test pattern signal during the application time of GB, that is, the highest brightness value H _B of the right end region B is determined.

The brightness comparison circuit 19 detects the maximum brightness value H _A at the left and right ends.
and H _B are compared to determine the ratio (H _B /H _A ) between the two.

The width comparison circuit 20 receives the left and right area width signals W _A and W _B from the pattern position and width detection circuit 16, compares them, and determines the ratio (W _B /W _A ).

The determination circuit 21 receives the outputs of the brightness comparison circuit 19 and the width comparison circuit 20, determines the presence or absence of reflection based on whether or not these values are above a predetermined level, and determines the presence or absence of reflection and the quality of the display screen. Outputs the signal shown.

If H _B /H _A is greater than a predetermined value (for example, about 2), it is determined that reflection exists, and if H _B /H _A does not reach the predetermined value, and W _B /W _A is a predetermined value (for example, about 2).
If it is more than that, it is judged that there is an extreme folded reflection,
If neither H _B /H _A nor W _B /W _A reaches a predetermined value, it is determined that the display screen is normal.

It is clear that even if the reflection occurs at the left end, it can be determined in the same way by reversing the left and right sides in the above description.

(6) Effects of the Invention According to the present invention, it is possible to automatically determine whether or not an abnormal display phenomenon due to reflection is occurring on a CRT display screen. Since this is done automatically without manual intervention, there is no problem of fatigue caused by visual inspection, and CRT
The quality of the display screen can be determined quantitatively, reliably, and quickly.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of an example of an abnormal display screen, Fig. 2 is an explanatory diagram of folded reflection, Fig. 3 is an explanatory diagram of nonlinear distortion reflection, and Fig. 4 is an explanatory diagram of the test pattern of the present invention and its output data. , FIG. 5 is an explanatory diagram of folded reflection when using the test pattern of the present invention, FIG. 6 is an explanatory diagram of nonlinear distortion reflection when using the test pattern of the present invention, and FIG. FIG. 1 is a configuration diagram of an embodiment. In the figure, 11 is a CRT display device to be observed, 12 is a test pattern generator, 13 is an observation device, 14 is a line buffer, 15 is a pattern signal detection circuit, 1
6 is a pattern position and width detection circuit, 17 is a left end brightness maximum value detection circuit, 18 is a right end brightness maximum value detection circuit, 19 is a brightness comparison circuit, 20 is a width comparison circuit, 2
1 is a determination circuit.

Claims (1)

[Claims] 1. A CRT display device, a test pattern generating means for generating a test pattern having a pattern area of a constant width at the left and right ends of the display screen of the CRT display device, an observation means for observing the test pattern, and an observation means for observing the test pattern. A pattern position/width detection means for detecting the pattern position and area width at the left and right ends of the observed test pattern, a left end maximum brightness value detection means for detecting the maximum brightness value of the left end pattern region, and a brightness of the right end pattern region. a right end brightness maximum value detection means for detecting the maximum value; a brightness comparison means for comparing the outputs of the left end brightness maximum value detection means and the right end brightness maximum value detection means to obtain a ratio thereof; and a width of the pattern area at both left and right ends. and determining means for determining the quality of the screen from the output information of the brightness comparing means and the width comparing means, and for inspecting abnormal conditions of the CRT display screen. Characteristic CRT display screen inspection method.