SU1451874A1 - Method of electron beam focusing in crt - Google Patents

Abstract

The invention relates to television technology and m. used in the construction of TV film projectors, photo registration and other systems containing CRT receivers. The invention is an extension of the functionality by focusing the electron beam of the receiving CRT at any brightness of the screen. The method is to first focus the electron beam at the maximum allowable brightness of the CRT screen. In this case, at various points, the screen is illuminated with short rectangular pulses and, by changing the signal, the focusing is achieved at each illuminated point of the luminance minimum. Then stop the scan, set the working brightness of the screen and re-focus in the center of the screen. After this, the signal value; and the focusings Uc ,, for the remaining points of the screen at the operating luminance are determined from the ratio i, o, m i, (Uo macs UjHtf ,,), where cc, c is the value of the focus signal for the given raster point at max, brightness; io, „ks, U„ are the values of the focusing signal for an unbroken beam, respectively, at max and nominal luminescence of the screen. 2 Il. with (L

Description

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The invention relates to television technology and can be used in the construction of television projector, photo logging and other systems containing receiving cathode ray tubes (CRT).

The purpose of the invention is to expand the functionality by focusing the electron beam of the receiving CRT at any brightness of the screen.

Figure 1 shows a structural electrical circuit diagram of a device that realizes a method of focusing an electron beam of a receiving CRT; figure 2 - timing charts of the device.

A device that implements the method of focusing an electron beam of a receiving CRT contains a sensor 1 of a television signal on a receiving CRT, a measurer 2 digits of the derivative, a synchronization unit 3, a generator of 4 correction signals, a block 5 and 6 of memory, an adder 7, a control block 8, registers 9 and 10 of memory, blocks 11 and 12 of subtraction.

The method is as follows.

in a way.

According to the trigger signal, the generator 4 carries out by changing the voltage on the modulator of the receiving CRT, located in the sensor 1, setting the maximum permissible brightness of the screen. Using the scan generators synchronized by unit 3, the electron beam is scanned across the screen of the receiving CRT. At the same time, by feeding short rectangular pulses with a duration of one decomposition element to the modulator, those raster points are illuminated at which the focusing is done, while the amplitude of the pulses should provide the maximum permissible for a given CRT brightness of the light aperture, non-burn-through luminescent. Then, at the input of the focusing system, the CRT is given a trial value of the focus signal after converting the light flux from the CRT screen to an electrical signal the meter 2 sequentially selects the pulse signals from the highlighted points of the raster, measure the amplitudes of the impulses, check for each highlighted point

raster the minimum amplitude of the corresponding pulse at the current value of the test focus signal relative to the amplitude of the same pulse at the previous one; their values of the test focus signals are stored in block 6, the current value of the U- test focus signal, if the current pulse amplitude is minimal. Then set the next value of the focusing test signal, successively extract the pulse signals from the illuminated raster points in the electrical signal, measure their amplitudes, check them for minimality, remember the current value of the focusing test signal U 4 if the current pulse amplitude is minimal (and 2), form the next value of the focus test signal, and so on, until all the values of the focus test signals are sorted. The value of the focus signal at which a mini- mal beam cross section area in the plane of a CRT screen is ensured at a given raster point corresponds to the minimum amplitude of the corresponding selected pulse. In the absence of astigmatism, such a minimum will be one, and in the presence of astigmatism, ma - two (I. and U- in Fig. 2). Therefore, in the process of iteration of the focus signal, the number of minima for each illuminated raster point is determined, and if at least one, then the optimum value of the focus signal at this raster point is the value at which this minimum is reached, and if there are two minima, then the signal value focusings for this raster point are determined by the formula

and 0.5 (and + u).

The CRT modulator is then set to the nominal voltage, determined by the type of CRT and the conditions of its operation, the light aperture is set in the center of the CRT screen, for example, by turning off the power of the sweep, the beam is centered at the rated brightness and determined the values of the focus signal for the remaining raster points of the fsmula are

MOX

(and

with M.O. with

Thus, at time t (Fig. 2), the value U ,, is recorded in memory block 6, and at time tj (Fig. 2), the value of signal, 5 (U + Ua), formed by the adder 7 is written to memory block 5. .

If the adjusting curve has a din minimum, then after the time t. (Fig. 2) in block 5 the value of the focus signal is stored, corresponding to the minimum of the adjustment

crooked.

The focus procedure for a single raster point is considered. If it is necessary to determine focus signals, for example, for # in- (points, then this procedure is carried out in parallel at all 16x16 points. At that, one frame of the focusing test signal is set in each frame, synchronization unit 3 generates 16x16 illuminating pulses uniformly distributed over the raster , and for each of the points, the amplitude of the selected pulse is measured, compared with the previous sample for the same point, stored in memory block 5, and so on. Each of the 16M6 points in blocks 5 and 6 of memory is allocated memory cells, addressing to toryh synchronism with the scanning unit 3 is performed synchronization.

At the end of the enumeration, a pulse appears at the output of generator 4, which sets block 8 to its initial state. This signal blocks further recording of any information in memory blocks 5 and 6 and registers 9 and 10, and also connects the output of the second subtraction unit 12 to the input of generator 4. The focus adjustment mode is over. At the same time, in block 5 of the memory, the values of the focus signals for the 1X1B raster zones are stored, which is determined by the JWU

divided at maximum brightness of the CRT screen, in registers 9 and 10, respectively, the values of the focusing signals Uo and, UOHC / M D of the center of the raster, determined at maximum and nominal speeds. Since the value of U "Q, for each raster zone is read from memory block 5 synchronously with the sweep, blocks 11 and 12 of the subtraction are formed in

87A

digital fofme focus signal for each of 1b 16 raster zones, which in the generator 4 correction signals is converted into an analog signal of dynamic focusing of the electron beam of a CRT in the sensor 1.

Claims (1)

Invention Formula 0 The method of focusing the electron beam of the receiving cathode-ray tube, including the modulation of the electron beam when it is scanned at 5 raster short rectangular pulses, the selection in the electrical signal pulses corresponding. modulating rectangular pulses, changing the magnitude of the focusing signal, memorizing for each the raster point at which the Electron beam is modulated, the values of the focus signal corresponding to the minimum amplitude of the selected 25 pulses, and scattering if there are two values of the focus signal U. for any raster point, and, at which the minimum amplitude of the selected 30 pulses is reached , the required U value of the focus signal for this raster point from the ratio, 5 (Uf + U) characterized in that, in order to extend the functionality by focusing the receiving electron beam, a CRT p and any screen luminance, the beam is focused at various points of the raster at the maximum permissible brightness of the screen of the tube, then the nominal screen luminance is set and the focus of the un-tilted electron beam is reproducible, and the rest of the focus points at the rated brightness of the screen is formed equal to U nom  UMO, .C - № .. «« - and, o "), where and c is the value of the focus signal 50 for a given raster point at maximum brightness; , and about the nominal value of the focus signal for a non-deflected beam, respectively, at the maximum and nominal p55 of the screen luminescence. Output S / IOQQ. one