A television test table (test table) is a special image that is displayed on the kinescope screen for adjusting and evaluating the image quality of television equipment, as well as all kinds of displays (including computer monitors ). It is transmitted by television stations before and after broadcasting .
It is a complex color signal that allows you to visually assess the image quality, and measure the characteristics of the television's electrical circuits using instruments. Previously, tables printed in a printing house were used, which were transmitted using special cameras (so-called monoscopes ). Today, standard signal generators (for television equipment) are commonly used. For computers, there are programs and DVDs with recording test images.
The adjustment tables are mainly used for visual evaluation of the signal on the TV screen. Setting up a TV with a simple table oscilloscope is difficult because the table is a mixture of different signals. Usually, more complex instruments are used for tuning according to tables, for example, an oscilloscope with a row highlighting unit that allows you to select lines from the tuning table in which the color bar signal is transmitted. More often, a simple oscilloscope in combination with simpler test signals is used to tune analog TVs for instruments.
Content
Examples
Universal Electronic Test Chart (UEIT)
Designed for testing color televisions operating in the SECAM standard with a 4: 3 aspect ratio. UEIT was developed by Candidate of Technical Sciences N. G. Deryugin and engineer V. A. Minaev, State Radio Research Institute (NIIR). The unofficial name is “color prophylaxis table” (TCP). [1] [2] The pilot broadcasts from the Ostankino television tower (at that time - the All-Union Radio and Television Broadcasting Station named after the 50th anniversary of the October Revolution, ORPS) began in 1970. According to their results, the table was finalized, and since 1971, the second option, UEIT-2, was broadcast and via communication lines. [3] Main parts:
- Mesh field - table background. Allows you to customize the mixing of rays , and also visually breaks the table into rows and columns. In the center of the big circle there is an additional crosshair for centering the image as well as for adjusting the static information, and in small - as the reference point for adjusting the dynamic information
- Table edging - reference marks for setting the image size;
- Circles to control the geometric distortion of the raster. To check the accuracy of adjusting the aspect ratio of the image, you can measure the lengths of the sides of the square in the center;
- Color bars with 75% saturation (lines 6-7) and 100% (lines 14-15) to control color reproduction . If there is an oscilloscope with highlighting of individual lines, it is possible to configure them instead of a separate generator of color bars;
- Gray scale (line 8) - to set the brightness , contrast , white balance and black level;
- Contrast color stripes (line 9) to adjust the clarity of color transitions;
- Smooth color transition (12 lines) to check the linearity of the color channel. In some implementations, there is a full range, in others, a transition from green to purple;
- Vertical strokes on line 13 and in small circles (lines 3,4,17,18) to evaluate resolution and dynamic focus. They are formed by packs of sinusoidal signals with a frequency of 2, 3, 4 and 5 MHz, corresponding to a resolution of 220, 330, 440 and 550 lines.
- Inclined stripes in 10-11 lines to control the accuracy of interlaced scanning ;
- Contrast marks in the same lines for monitoring stretching continuations (caused by a malfunction of the TV circuits, as well as when connecting several TVs via video output via a low-quality cable) and repetitions (caused by an unsuccessful antenna design or location);
- Alternating black and white squares (line 16) - to estimate the frequency response of the video path across all channels;
TIT-0249 Television Test Chart
A black and white test chart developed in 1949. There were two ways of transmitting TIT-0249: shooting with a camera from a graphic original or reproduction using a monoscope . Currently, television channels are practically not used, but sometimes it is used to assess the resolution of video cameras.
TIT-0154 Test Table
This table was created in 1954 specifically for the then developed experimental color television system with sequential color rendering. It is described in [4] and [5] . The use of this table, as well as the experimental system itself, was soon discontinued.
EIA Resolution Chart
Developed in 1956 and has become a kind of standard test pattern.
Notes
- ↑ Deryugin N.G., Minaev V.A., Universal Electric Test Table, Technique of Cinema and Television, 1970, No. 10.
- ↑ Deryugin N.G., Minaev V.A. New universal electric test table [for monitoring television images]. - Telecommunications, 1972, No. 2, p. 1-5.
- ↑ Messenger of Communications , 1973 [1] .
- ↑ V. Semenov, L. Baldin. TV "Rainbow". Radio, No. 11, 1954.
- ↑ B. Semenov, L. Baldin, Setting up the Rainbow TV. Radio, No. 12, 1954.
Links
See also
- TV Tuning Signal