SU1023639A1 - Device for step-wise scanning of crt beams - Google Patents

Abstract

A DEVICE FOR ACCESSIBLE BEAM EXPLOSION ELECTRON-BEAM PIPE containing a shaper-sawtooth driver, the first and second outputs of which are connected respectively to the line and frame deflection coils, the third output through the first one-oscillator to the first input of the element, and the fourth output through the second device, the second output device through the second deflection coils, the third output through the first single-oscillator the second input of the element K, and the generator of step pulses, the output of which is connected to the third input of the element I, the output of which is connected to the input of the former of the step-sawtooth current, o t It is necessary that, in order to expand the range of operation, an input shaper of impulses, a frequency divider, a trigger and a switch, the first and second fixed contacts of which are connected respectively to the outputs of the first and second one-vibrators, are entered into it the contact is connected to the first input of the trigger, the output of which is connected to the fourth input of the element I, the second input to the output of the frequency divider, the input of which is f / J pogo connected to the output of the input —wi pulse generator.1, tsd 00 and 00 co ggl

Description

The invention relates to a pulse technique and can be used to scan images with a wide range of frame durations.

A device for stepwise scanning of a beam of a cathode ray tube is known, which contains a m-bit digital-analog converter, a beam deflection unit, an amplifier, a pulse generator, and triggers 1 ..

The drawback of the device is the lack of synchronization of the sweep with the frequency of the mains voltage.

The closest technical solution to the proposed is a device for stepped scanning of a beam of a cathode ray tube containing a shaper-saw current driver, the first and second outputs of which are connected respectively to the horizontal and vertical deflection coils, and the third output through the first single vibrator. , the fourth you-: move - through the second one-shot -. / to the second input of the element I, a step pulse generator whose output is connected to the third input of the element I, the output of which is connected to the input of the former of the step-shaped current G2.

The disadvantage of the device is that it does not provide for the synchronization of the sweep with the frequency of the network voltage in a wide range of variation of the frame duration,

The purpose of the invention is to expand the range of operation of the device. This goal is achieved by the fact that in a device for a stepped sweep of a beam of a cathode ray tube containing a former step-sawtooth current former, the first and second outputs of which are connected respectively to the horizontal and vertical deflection coils, the third output, through the first one-shot, to the first the input element And, the fourth output through the second one-shot - to the second input of the element And and the generator of step pulses, the output of which is connected to the third input of the element And, the output of which is connected to the input of the forms bodies stepwise sawtooth current generator administered input pulses, a frequency divider and a trigger. a switch, the first and second fixed contacts of which are connected respectively to the outputs of the first and second one-shot, the movable contact is connected to the first input of the trigger, the output of which is connected to the fourth input of the element I, the second input to the output of the divider hour, the totah which input is connected to the output of the input pulse shaper;

Figure 1 shows the block diagram of the device; Fig. 2 is a time diagram of currents and voltages, explaining the operation of the device.

The device contains a former 1 step-sawtooth current, made, for example, on counters 2.3 steps in line and frame, digital to analogue converters 4.5 output amplifiers 6.7, horizontal and frame deflecting coils 8.9, single vibrators 10, Element 11 And 12, the inverter 13 stepping pulses, shaper 14 input pulses, frequency divider 15, trigger 16, switch 17.

The device works as follows.

In the initial position of the switch 17 (Fig. 1), each scan frame is synchronized with the grid voltage frequency. In this case, the clock pulses are removed from the output of the frequency divider 15, the period of which corresponds to the selected duration of one scan frame. From the voltage of Fig. 2a, rectangular pulses are formed (shaper 14), the fronts of which (Fig. 26) coincide in time, with: the moment when the network voltage passes through a zero value.

For simplicity, the case is considered when the frame duration is swept by, twice as long as the mains voltage period (frequency divider division factor - DEA. Synchronizing pulses at the divider 15 output (at the counting input of the trigger 16) are shown in Fig. 2). switching on trigger 16, as well as triggers of step counters in row and frame will be in an arbitrary position. For definiteness, we assume that the output of trigger 16 will have a logic zero signal, in this case, the step pulses from generator 13: do not come through circuit 12 at input The line has two steps in a row. In the line and frame coil, currents are proportional to the numbers corresponding to the positions of the flip-flops in both counters. At time t, trigger 16 switches the negative front of the divider 15 to its counting input and its output a logical unit signal is generated (fig. -2d). In this case, through the circuit 12, pulses from the generator 13 will start to flow to counter 2, ensuring the formation of a step-sawtooth current in the lowercase coil After the end of the forward stroke of the horizontal sweep of the pulse with overflow of counter 2, it will arrive at counter 3, providing pe. passing the beam to the next line - and will start the one-shot 10, - at the output of which a logical zero signal with a duration slightly longer than the return stroke of the line will be output (Fig. will prohibit through the AND entry for this time), stepping pulses to counter 2 ,.

After the end of the forward stroke of the frame sweep (Fig. 2), the overflow pulse of counter 3 will trigger a one-shot 11 at the output of which a logical zero signal will appear and switch trigger 16 on the setup input, the logic zero output of which (fig. T. And the arrival of pulses at counter 2. At time tj, trigger 16 switches the negative edge of the synchronization pulse (Fig. 22-) received at its counting input and step impulses again arrive at counter 2 input - sweep begins A new frame, the start of the sweep of which is synchronized with the mains voltage {.the moment of its zero crossing. This synchronization is also performed for each subsequent frame, but for it to be stable, it is necessary that the total duration of the forward and reverse run of the frame sweep is slightly less synchronization pulses. When changing the frame duration, the division factor of divider 15 changes, but the total frame duration must be a multiple of the network period duration. If at the moment of switching on the output of the flip-flop 16 there is a signal of a logical unit, then the operation of the device is illustrated by the diagrams of FIG. 2 hp is the voltage at the output of the trigger 16, fig. 2ux is the voltage at its installation input and Fig. 2, trk in the frame coil. The operation of the device is carried out in a similar way, but the synchronization of the beginning of the frame sweep with the network frequency will begin later, from the moment t (Fig. 2e).

When switching the switch 17, the setup input of the trigger 16. is connected to the output of the one-shot 10. In this case, the device synchronizes each row with the network frequency. This kind of synchronization is convenient for very slow sweeps so that the division factor of divider 15 is not required too much; The principle of operation of the device is similar to that indicated, but from the output of the divider 15, the synchronizing pulses are removed, the period of which corresponds to the duration of one scanning line. In order for the time diagrams (Fig. 2) to illustrate the operation of the device in this mode, consider the case when the length of the scanning line is twice the period of the network voltage; The diagrams in FIG. 2 and 2 J now correspond to the currents in the line coil. Features of work in this mode are as follows. If at the moment of switching on at the output of the trigger-16 there appears a logical zero (Fig. 21-, then the sweep will begin at the moment. Time t

when the trigger 16 is switched by the incoming to its counting input from the divider 15, the synchronization impulse (Fig. 2) .- After the end of the forward hog

A 5 line horizontal sweep at time t a pulse of overflow of counter 2 arrives at counter 3 / ensuring the transition of the beam to the next line, and starts a one-shot 10 / at its output a logical or longer signal slightly longer than the return time along the line of FIG. 2e, and, by the installation input, trigger 16, the signal logic i zero zero at the output of which

5 moment tj. prohibits the input of pulses through counter 2 through element -I. 12 At time t, trigger 16 switches on the counting input with a negative edge of a synchronizing pulse (Fig. 2d-Li to counter 2 input again begins stepwise impulses — a new line will be developed, t i.e. from this moment the beginning of the sweep of each line is synchronized with the mains voltage. The period of the step pulses for reliable synchronization is chosen so that the duration

The forward and reverse horizontal sweeps were slightly less than the period of the sync pulses. At the moment when the vertical sweep ends, the counter overflow pulse 3 starts one 5 vibrator 11, which through element 12 prohibits the arrival of pulses to counter 2 for the reverse progress on the frame. If at the moment of switching on the output of the trigger 16 is a logical unit, then the operation of the device is illustrated by the diagrams of fig. 2g, where the voltage at the output of the trigger i6 and its installation input are shown respectively. On figs in

5 In this case, the law is shown kzmen & No current in the line coil. The device operation is similar, but forced synchronization of the sweep with the network frequency will begin

0 carried out later, since t (fig.2d).

It should be noted that the use in television of synchronization of the sweep with the frequency of the network by

5 phase voltage phase comparison

frames (lines) with the frequency of the network or a multiple of it, followed by adjustment of the frequency of the master oscillator is unsuitable in the device of the stepwise sweep. Indeed, if, in accordance with the phase of the mains voltage, the frequency of the step pulse generator changes, then an equal stepwise increase in the current —a coils occurs at different times, and this leads to nonlinear distortions of the deflecting current, which is unacceptable. especially with a large number of frame decomposition elements. To avoid this, the step pulse generator is made frequency stable.

In the proposed sweep device, the sweep is synchronized with the mains frequency in a wide range of frame durations, which makes it possible to reduce the visibility in the image of interference from the mains (alternating current background), since in this case the noise is fixed on the screen of the electron-beam tube.

The application of the proposed scanning device in raster electron microscopes and X-ray microanalyzers allows improving the quality of the obtained images and resolution. However, it is possible to reduce the complexity of setting up these complex devices, since the general requirements for the permissible background of alternating current in these devices can be significantly reduced.

Claims (1)

DEVICE FOR STEP-BY-STEP REVERSION OF THE ELECTRON BEAM TUBE BEAM, comprising a step-sawtooth current shaper, the first and second outputs of which are connected respectively to the line and frame deflecting coils, the third output through the first one-shot to the first input of the element And, the fourth output through the second one element And * and a step pulse generator, the output of which is connected to the third input of the element And, the output of which is connected to the input of the step-sawtooth current former, In order to expand the range of operation, an input pulse former, a frequency divider, a trigger and a switch are introduced into it, the first and second fixed contacts of which are connected respectively to the outputs of the first and second single-vibrators, the movable contact is connected to the first input of the trigger the output of which is connected to the fourth input of the And element, the second input to the output of the frequency divider, the input of which is connected to the output of the input Pulse former. that—