Television test tables.

Television Table Table (Test table) - a special image that is played on the Kinescope screen to configure and assess the image quality of television equipment, as well as all kinds of displays (including computer monitors).

Examples

Universal Electronic Table Table (WEIT)

Designed to test color TVs operating in the standard SECAM with sides of the screen 4: 3. WEIT was developed by the candidate of Technical Sciences N. G. Dryugin and Engineer of the State Research Institute of Radio (NIIR) V. A. Minaev. The unofficial name "Color Prevention Table" (TCP). Experienced broadcasts on the ether from the Ostankino television (at the time - the Union-Union Radiotelevian Transfer Station. The 50th anniversary of October, ORPS) began in 1970. According to their results, the table was finalized, and since 1971, the second option, WEIT-2 was transferred to the ether and on the lines of communication. Main parts:

• Mesh field - table background. Allows you to adjust the reduction of the rays, and also visually breaks the table to the strings and columns. In the center of the Big Circle, additional crosshairs for centering the image as well as to adjust the static information, and in small - as the countdown points for adjusting the dynamic information;
• Table edging - reference labels to set the image size;
• Circles to control the geometric distortion of the raster. To check the accuracy of adjusting the image side relationship, you can measure the length of the sides of the square in the center;
• Colored strips of a saturation of 75% (strings 6-7) and 100% (string 14-15) to control color reproduction. In the presence of an oscilloscope, with the selection of individual lines, it is possible to configure on them instead of a separate color strip generator;
• Gray scale (8 string) - to install brightness, contrast, white balance and black level;
• Contrast colored stripes (9 string) to adjust the clarity of color transitions;
• Smooth color transition (12 string) to check the linearity of the chroma channel. In some implementations there is a full spectrum, in others - the transition from the green to purple;
• Vertical strokes on the 13th line, as well as in small circles (rows 3,4,17,18) to assess the resolution and dynamic focus. They are formed by packs of sinusoidal signals with a frequency of 2,3,4 and 5 MHz, correspond to the resolution in 220, 330, 440 and 550 lines.
• Inclined strips in 10-11 lines to control the accuracy of interlaced expandment;
• Contrast labels in the same lines to control the stretching continuations (called television contours, as well as when connecting several video output TVs through a low-quality cable) and repetitions (caused by an unsuccessful design or antenna location);
• Alternating black and white squares (16 string) - to assess the frequency response video data on all channels;

This uses a test picture with multiple test zones. With this image, you can configure the five main parameters of the image on the TV or monitor screen. The image of Ladies is in the set of test pictures, the reference to quiet will be at the bottom of the article.

Before setting, you need to turn off all the depressions and other functions on the TV affecting the image. The image can be connected via USB from a flash drive if you use another source, for example, a computer, then, see the signal parameters at the source output and at the TV input. Must match the size, and sweep and frequency of frames. You also need to install the TV to the place where it will constantly work and turn on that source of light, which will work when viewing a television.

This test has several zones that can serve as a visual standal for the image. To obtain high-quality images on your TV, you only need to make these five settings:

1. Image format, screen borders.
2. Brightness.
3. Contrast.
4. Color.
5. Clarity (focus).

Configure image boundaries (OVERSCAN)

The picture shows the tips (arrows) along the edges, so these arrows should be completely visible and tips just touch the edges of the screen. If the size is incorrectly configured, it will turn out not only the cropped image, but also the clarity will decrease. In the TV, the menu items affecting the boundaries of the picture (zoom) may be called: pixel in pixel, Full Pixel, Just Scan, Pixel-to-Pixel, Original, Overscan, etc.

The following are drawings, as incorrectly selected scaling can affect the clarity of the image:

Brightness

With the correct brightness setting, you need to look at the shades of gray at the top of the Ladies pictures. All 32 shades should be visible and have a clear border.

Below in the drawings, the red zones are encountered in which the brightness setting is visible. Or the brightness is too low, then black grades are merged into one. Or brightness large and grayscale in light areas merges.

Contrast

After adjusting the brightness, we look at the same size of the grayscale gradation. If in bright areas we see the merging of individual sections to one, then adjust the contrast on the TV. With proper configuration, we must see all 32 sections of the gray scale. As you can see incorrect adjustment of contrast affects the display of human skin. With an overwhelmed level of contrast on the skin, sections with a negative appear.

Sometimes it happens that after adjusting the contrast, you need to return to the brightness setting and then check the contrast again.

The following picture shows too low a television contrast.

Color

Very significant for properly setting the color of the human skin display. It is necessary to find a balance when and in dark areas will be all right with color and bright areas will not be dull. Sometimes it is better to put a smaller saturation of the image for the image quality, it will be natural. Of course, it should be avoided too low chroma.

When sets, you need to make sure about white. Plots of a test picture where there is white should be white. If there is any color shade, then it is incorrect.

Also pay attention to small contrast areas on the color strip. You must see them, they are regulated by the color saturation. These squares should be highlighted on the background.

Definition

Image clarity can be well checked on areas where two bands intersect. These lines should be displayed without halo and shadow. Typically, the factory definition settings are already correct and their homes need to adjust them.

Gamma

This adjustment parameter can be found far from each TV. But if it is, then you need to check it and its correct setting. To check the gamma use colored stripes and image of girls.

Conclusion

It is necessary to conduct such settings immediately after purchasing the TV. But still there are situations when the device is so bad that any settings cannot improve image quality.

With confidence, it can be argued that almost each of our readers has once been observed at the end of the TV show not entirely understandable images-screensavers. During the prevention, they can be found even during the daytime. What is this "funny pictures", and for what they are intended? ..

Fig.1 Table 0249.

Fig.2 EIA Resolution Chart

Fig.3 Table BBC.

Fig.4 Table with Philips Test Generator

Fig.5 Chess field

The problem of assessing and comparing the quality of various electronic equipment arose, possibly ahead of the appearance of this equipment itself. With regard to television technology, this problem is solved using special measuring and test tables. So, what are the most important types of test images, do we know? The first type is the so-called resolution charts or resolution tables. Their main purpose is an assessment of the allowing ability of TV or camcorders, displays, TVs, television / kinodackers and the entire transmitting and receiving path as a whole. A characteristic example is excellent to all familiar Table 0249 (Fig. 1), for a long time used domestic television as a screensaver. Another example is EIA Resolution Chart (Fig. 2), which is actually a standard for assessing the resolution developed by the Association of Radio Electronics Engineers in 1956 for the same goals.
It is this table that we use to assess the resolution in the tests of video cameras and video recorders. With the help of vertical worlds, located symmetrically from above and below from the center of the table, you can measure the resolution of the camera directly in TVL.
The quality of the work of the aperture corrector horizontally can be assessed using a horizontal wedge. For a more accurate hardware estimate of the signal level corresponding to the frequency of 200 TVL, there are a number of special zones filled with vertical and horizontal strokes, with a resolution corresponding to 200 TV. To assess the geometric distortion and resolution at the edges of the image, four combined worlds are used, inscribed in concentric circles located along the edges of the table. Evaluation of the dynamic range and operation of automatic exposure installation systems is very conveniently carried out according to the fragments of the gray wedge, inscribed in the central circumference of the table. The electronic version of the table can be downloaded at: http://www.bealecorner.com/trv900/respat/eia1956-v3.zip.
The arms at the very beginning of the television broadcasting (naturally, black and white), when in the foreground there were problems of proper focusing and geometric distortion, these tables were focused on monitoring and configuring precisely these parameters. Circle in the center and the edges of the screen filled with vertical and horizontal wedges allow you to accurately accurately appreciate and adjust the deflecting and focusing systems of the transmitting chamber and the television receiver. From other parameters of the path with their help, it is possible to estimate the transmission of the so-called gray wedge - the ability of the chamber or a telephoneial to correctly reproduce the full dynamic range of the scene and the accuracy of setting the schemes of gamma correction.
With the appearance and mass spread of color television, it turned out that the possibilities of traditional black and white tables are completely insufficient. First of all, it is due to a much more complex structure of the full color signal and the need to evaluate and adjust a much larger number of specific parameters. In addition, it became obvious that it was almost impossible to solve the task of controlling the quality of equipment and receivers of color television with a simple shot printed on paper or film film. The time of electronic test tables has come.
Explain. The test signal that creates the image of the table is not removed by the transmitting television chamber, but is synthesized by an electronic device (generator). Such test signals are not inherent in specific distortions made by transmitting television chambers. They allow not only subjectively to evaluate the image quality directly on the screen of the television receiver, but also with the help of special equipment to measure the characteristics of the video channel. Electronic test tables contain elements that allow monitoring and configuring individual assemblies of the color TV. There are a large number of variations of test tables developed by associations of radio engineers, radio-electronic firms, television broadcasting companies. Naturally, the table format is determined by the standard of the transmitted TV signal, so the appearance of the tables used for NTSC, PAL or SECAM systems will be somewhat different from each other. For example, in fig. 3 You see a test table used by BBC, and in Fig. 4 - a table obtained from the Test Generator of Philips; It is this table that is used by most broadcasting TV channels around the world. Universal Table (WEIT), shown in Fig. 6, I know the most of our readers. We see her on our screens during broadcast breaks. In addition, there are still many highly specialized measuring signals, such as, for example, a mesh field for checking ray information, a chess field (Fig. 5), etc.
And now on the example of a familiar all "our" universal table, let's see what can be seen and understand with it. For ease of designation, individual elements of the table are indicated horizontally with letters, and vertically numbers. So, what parameters of video equipment can be estimated by the measuring table, just to the eye, without any measuring instruments.

1. Image size

Fig.6 Weit.

As maybe, remember the attentive reader, a few years ago, one curious advertising quite intelligible explained that we see much less on the TV receiver screen than in fact. Really, the image on the screen is clipped by 10-15% compared to the transmitted signal. The standard frame size is installed according to the reference lines available in the table, which are combined with the edges of the frame of the kinescope. The accuracy of the image format setting can be estimated by squares and circles in the table.

2. Geometric distortion

The geometric distortions of the image are caused by the nonlinearity of the signals generated by the generators of the line and frame sweeps. Let's just say that most modern TVs for the exhaust scheme engineering problems practically do not occur with this. It is possible to estimate the nonlinearity of the scan. The amount of nonlinearity, if desired, can be estimated quantify. To do this, it is enough to measure the ratio of the parties of the square, which due to nonlinear distortion can turn into a rectangle.

3. Minor ray

The correctness of the static information of the color of the color kinescope can be checked on a white cross depicted on a gray background in the center of the table. In the presence of static rates, the white cross image does not contain color edging. Plots of the white grid in the corner zones of the table are used to control the dynamic information over the entire screen of the screen.

4. Resolving image ability

Fig.7 VHSM VHS.

Fig.8 VCR S-VHS

The resolution of the image is easily and convenient to evaluate the strip 13 (Fig. 5), in which 7 groups of strokes are formed. These barbands are created by packs of sinusoidal voltages with frequencies approximately corresponding to 200, 300, 400 and 500 lines. At the same time, the center of the highest frequency is placed in the center, and along the edges - low frequency groups. With their help, the resolution of the brightness canal is estimated. To assess the definition of the image along the edges of the raster in small circles, groups of vertical strokes corresponding to 300 and 400 lines are located. See what remains of the resolution after recording this table on the VHS video recorder (Fig. 7) and S-VHS format (Fig. 8).
In the lane 9 tables from the column F to the U column there are three groups of paired colored strokes - purple-green, yellow-blue and red-blue. With the help of these color strokes, the color clarity is estimated. We still need to notice that the strokes in the strip 13 on the color TV screen may acquire a coloring, which is called Molar.

5. Installation of brightness, contrast and assessment of white balance

Perhaps this is the most popular part of the measuring table. It is necessary that it is possible to establish the correct brightness and contrast of the received image.
In the table 8, there is a gray scale containing fragments with different brightness. This zone serves to install the contrast and the level of black. Brightness and contrast regulators should be set so that all fragments of the gray scale differ in the image. As a last resort, it is considered to be permissible to merge two adjacent fragments on the section of black and dark gray colors. The gray scale also serves to control and configure white balance. If the balance is set correctly, all gradations of the gray scale remain neutrally gray, do not acquire any color.

6. Estimation of reflected signals

7. The correctness of the color transmission

Fig.9 Color distortions when disjecting matrixing scheme

The loyalty and accuracy of color reproduction is ensured by setting the signal matrication scheme and the color synchronization system in the television receiver. Two rows of color rectangles (strip 6-7 and 14-15) are designed to control the color rectification: white, yellow, blue, purple, red, blue and black.
On the rectangles of the upper row (strip 6-7), the color saturation should be about 75%, and in the bottom row (strip 14-15) - saturation of 100%. The colors of rectangles may be distorted when the matrixation scheme is disorded (a possible option in Fig. 9). Color synchronization violation can cause color loss. The clarity of color transitions is estimated in the same area. Particularly problematic is the transition between green and purple flowers.

8. Interlacing scan

Fig.10 One of the possible types of distortion distortions of the interlaced sweep

The accuracy of the interlaced sweep can be judged by the type of inclined lines located on the sections 11, G-J and 10, Q-U table. The presence of fuses means that the rows of neighboring frames are partially superimposed. As an example in Fig. 10 shows one of the possible types of distortion of the work of the interlaced sweep.

9. Multicolution and stretching continuation

To assess this type of distortion, contrast labels are served (narrow strips; white on black and black on a white background) in the zone 10 and 11 F-U table. Interference arising from, for example, poor antenna harmonization, is clearly visible on a contrasting background of these sites, in the absence of interference labels remain clear and solitary.

10. Assessment of linearity Channel characteristics

The signal that creates in the 12 F-U table, the table wide line, smoothly changing the color from green to the purple, serves to estimate the linearity characteristic of the chroma channel. The absence of any visual distortion or additional tints speaks of a good linearity.

Of course, in one small note it is impossible to tell about the great manifold of television measurements. Today we casually touched this huge interesting world. Now, due to the rapid distribution of systems with compression, the question of the assessment again falls in full growth. And here our old good static measuring tables and signals are already bad helpers. New transmission technologies require new assessment and measurement techniques. And there is no end to this circle. But this is a completely different story.

To assist you when determining the resolution of the camcorder, as well as check other components of the video system, a special test table was developed.

We tried to make it as accurate as possible and informative, and although it can be used for testing broadcasting equipment, it should not be considered as a replacement of various test tables intended for television. This table should be applied only for security television systems and as a manual for comparing various equipment and / or transfer tools.

The table presented in this article was upgraded and has several differences from the table of the previous edition. Supplements relate mainly to white lines that will allow you to check whether a person can recognize at a certain distance. This procedure is based on VBG Recommendations (Verwaltungs-Berufsgenossenschaft): InstallationShinweise Fur Optische Raumuber-Wachungs-Anlagen (Orua) SP 9.7 / 5.

With this table, you can check many other video signal indicators, first of all, resolving the ability, as well as the width of the frequency spectrum, the linearity of the video monitor, gamma correction, color reproduction, load matching and reflection.

Before proceeding with testing

The first thing you have to do is to improve the quality of the image given by the image - it is to choose a very good lens (which resolve the ability of which is much higher than that of the CCD matrix itself). To control the optical allowing ability of lenses, the best choice will be lenses with a fixed focal length and manual adjustment of the diaphragm.

Short-focus lenses with overview angles are more than 30 degrees, since they can give spherical distortion. There will be a good choice for a CCD camcorder 1/2 ". There are 8, 12, 16 or 25 mm lenses. For CCD camcorder 1/3" it is better to use lenses 8, 12 or 16 mm.

A larger focal length will make you set the camcorder further from the test table. For this purpose, it is recommended to use a photographic tripod.

To test the resolving ability of the camcorder, it is better to choose a high-quality black and white video monitor, since its resolution reaches 1000 TVL in the center.

Colored video monitors Acceptable only if their quality corresponds or close to the quality of video monitoring of television broadcasting. To match this quality, the video monitor must have a resolution horizontal ability, at least 500 TVs. It is clear that black and white camcorders, having a horizontal resolution of more than 500 TVs, cannot be tested using such video monitor, but for testing most of the color camcorders (with a resolution of up to 480 TVL), they are quite suitable.

Installation procedure

Place the table perpendicular to the optical axis of the lens. The camcorder must "capture" the table completely, exactly to the yellow triangular arrows. To do this, you must switch the video monitor to Undescan mode, and then you will see 100% images.

If you do not have such a video monitor, the dashed line around the perimeter of the table indicates a 10% narrowing of the review - it is close to what the usual video monitor will show. However, to verify permission, this is not exactly accurate. If you have only a standard video monitor, you can resort to small tricks.

Install the camcorder on the tripod as close as possible so that the table is displayed completely. Install the frequency of the frame sweep frequency V-HOLD on the video monitor in such a position so that the personnel flushing pulse is visible (horizontal black bar between TV fields). You must install the V-HOLD in such a position to get a steady horizontal strip somewhere in the middle of the screen. Then try to adjust the position of the camcorder on a tripod and / or lens so that the upper and lower positional triangles of the test table come into contact with the border of the black strip. As soon as you adjust the vertical position of the camcorder, you can easily adjust and horizontal, since the image of the test table is in the middle of the video monitor screen. Now and now you can remove the exact data from the test table.

Light the table with two incandescent matte lamps (about 60 W) on both sides, so that the table is not glad. It would be nice that the lamps had light regulators, because in this case you could check the minimum illumination of the camcorder. Naturally, in this case, this procedure should be carried out in a room without additional light. If you need to check the operation of the camcorder at a low level of illumination, you will need to purchase an accurate luxmeter. (This method of measuring the minimum illumination will not provide high measurement accuracy, since when adjusting the brightness of incandescent lamps, their radiation spectrum changes. Note Ed.)

Install the camcorder on the tripod or on the bracket at a distance that will allow you to clearly see the entire test table. Make sure that the ends of the arrows come into contact with the edges of the full image or a black horizontal band, if you use the alternative method discussed above.

Set the lens aperture to the middle position (F / 5.6 or F / 8), since it is the best optical resolution for most lenses, and then adjust the light to obtain a complete dynamic video range. To do this, you will need an oscilloscope. Do not forget to disable all video processing schemes in a tested video camera, that is, ARU, electronic shutter, compensation of oncoming illumination (BLC).

Make sure the load is coordinated, that is, the camcorder is loaded at 75 ohms at the end of the coaxial line.

What can be tested?

To check the permitting ability of the camcorder (vertically or horizontally), you must define a point in which there are four lines inside the circle, forming a sharp triangle, merge three. This is a point that corresponds to the limiting value of the resolution; It can be read from the table. To more accurately determine the resolution horizontal, as in the case of television equipment, requires an oscilloscope with a row selection.

If you need to check the video signal frequency band, read the megahertz value next to the last clear group of lines, where black and white lines are distinguishable.

Small concentric lines in the center of the test table square can be used to adjust focus and / or adjust the rear focus. Before adjustment, check the exact distance between the camcorder and the test table. In most cases, this distance should be measured to the plane of the CCD matrix. Although some lenses indicate the distance related to the frontal part of the lens.

Playing the circle will show you the linearity of only a video monitor, since the CCD cameras do not give geometric distortion due to its design. Sometimes the linearity is easier to check by measuring the vertical and horizontal length of the squares of 6 x 6, located to the left of the focus square.

Wide white and black stripes on the left side have a double function. First, they will show you whether the wave resistance is agreed or there is a reflection of the signal, that is, swimming is white to the black area (and vice versa) is a sign of reflection of the signal from the end of the line. The same bands can be used to test the quality of a long cable, playing a video recorder and other means of transmitting or playback. Secondly, you can determine whether the combination of a video camera / lens provides a fairly detailed image to recognize activity (intrusion or attack). To do this, set the camcorder at such a distance to see the zone of 3 m wide in the plane of the test table. If you can distinguish between the bands, then the combination of the camcorder / lens you choose well ensures activity recognition. It is clear that if it is possible to distinguish between the strips next to the number 1, then it is better than in the case of bands with a number 2.

White inclined stripes on the right side are assigning, similar to the appointment of thinner stripes on the left side. If you distinguish the lines next to the green letter C, or, even better, with letters in and a, when the camcorder is at a distance, allowing to see the zone of 1 m wide in the plane of the table, then you can recognize a person at the same distance. And it is better than in, and b is better than C. With this test, it is possible to determine whether the selected combination of the camcorder / lens provides sufficient image detail. Even more valuable and informative is an assessment of the quality of playback of the recording device to the hard disk, since there are no objective methods for determining the quality of compression / decompression in the security television.

Color photo of three kids will give you a good bodily color indicator, so if you use a color camcorder, you can check the color temperature of the light source and the automatic balance of the white camcorder, if any. In this case, it is necessary to take into account the color temperature of the light source, which, if the incandescent lamp is used, is 2800 ° K.

For a more accurate color test, your camcorder use the scale located at the top of the test table. The colors of this scale correspond to color stripes formed by the usual television test generator. If you have a vector videooscope, you can check the color reproduction on one bar of the color strip scanning. As in the case of any color reproduction system, the color temperature of the source is of great importance here and in most cases it should be natural lighting.

The gray background exactly corresponds to 30% gray and together with a brightness gradation scale, located at the bottom, can be used to check the gamma correction of the video camera system / video monitor. Brightness scale - linear, unlike some logarithmic scales. The linear scale is selected because most of the modern video cameras have a linear characteristic, which makes it easier to set up different levels on an oscilloscope. The brightness gradation scale can also be used to set the optimal contrast / brightness of the video monitor.

To achieve the best settings of the video monitor, you must do the following.