SU1580411A1 - Device for reading coordinates from screen of cathode-ray tube - Google Patents

Abstract

The invention relates to automation, in particular to a device for reading coordinates from a CRT screen, and can be used to enter data into a computer. The purpose of the invention is to improve the accuracy of the device. The goal is achieved by selecting the center line of the raster from several adjacent lines that fall within the field of view of the coordinate remover, which is ensured by the introduction of the fifth and sixth counters and the pulse reject selector. 1 il.

Description

The invention relates to automation and computing, in particular to a device for reading coordinates from a screen of a cathode ray tube (CRT).

The purpose of the invention is to improve the accuracy of the device by selecting the center line from the raster lines in the field of view of the coordinate remover.

-The drawing shows the block diagram of the device.

The device contains the first 1, second 2, third 3 and fourth 4 counters, first 5 and second 6 registers, element AND 7, element OR 8, cathode-ray tube 9, puller 10 coordinates, made in the form of a light pen, pulse selector 11 , made in the form of a pulse edge separation circuit, the fifth 12th and sixth 13 counters. The drawing also shows the inputs-outputs 14-21 of the device.s

The device works as follows.

In the initial state, for example, the light pen 10 is retracted from the screen of the CRT 9, therefore there are no signals at its output, therefore, there are no signals at the input of the register 5 and the inputs of counters 12 and 13. At the outputs of the registers 5 and 6, the code corresponding to the previous state.

On code inputs 15 of counter 1, a correction code is set, which is defined as the difference between code 111 ... 111 and the binary code of a number equal to the ratio of the delay time of the signal at the output of the light pen 10 to the period of clock pulses (TI). CRT enters 21

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the beam disconnect signal that forms the rectangular raster on the screen. Synchronously with the deviation signal, TIs enter the device 14, the frequency of which determines the number of coordinates read by X, 16 horizontal sync pulses (FID) to the 16 input, and vertical sync pulses (XI) to the 18 input. The luminance control signal from input 20 through the element OR 8 to the control input of a CRT forms an image to be processed on the e-screen.

When a pulse arrives at the inputs of writing the codes of counters 1 and 3, the code is recorded in the register of counter 1, and the code from the output of register 5 in the register of counter 3. After the pulse expires, counter 1 adds to the written code TI arriving at its summing input. , at the same time, at the output of counter 1, a code is generated corresponding to the number of TIs that have passed since the end of the FID, minus the number Corresponding to the correction code. Counter 3 subtracts from the 5 TI recorded from the register, and at the moment of going through Zero, the output of the counter Po appears at the pulse arriving at the input of the And 7 element.

During the XI, the counter 2 is set to the zero state, the code from the output of register 6 is written to the register of counter 4, and the code of the higher bits (except the younger one) is written to the register of counter 13 From the output of counter 12. The offset of the code bits ensures division into two times the number of pulses counted by counter 12,

Under the action of the CSI, which arrives at the selector 11, the pulse is formed last, which arrives at the counter 12 and sets it to the zero state.

At the end of the XSI, the counter 2 summarizes the FID received at its input, and the counter 4 subtracts the FID from the recorded code. At the output of counter 2, a code of the current coordinates along Y is formed, and from the output of the overflow of counter 4, an impulse of a duration corresponding to the duration of the forward stroke of the line is removed. At the moment of coincidence of the pulses arriving at the first and second inputs of AND 7, a pulse appears at its output, which, having passed through the element OR 8 to the input of the control

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The brightness of the CRT 9 causes the illumination of the raster element on its screen corresponding to the codes recorded in registers 5 and 6.

When the electron beam crosses the field of view at the output of the puller 10 coordinates, pulses are formed, the number of which during the frame sweep period is equal to the number of raster lines that fall into its field of view. From its output, the pulses are fed to the input of the register 5, to the summing input of the counter 12 and to the subtracting input of the counter 13.

When a batch of pulses arrives at the input of register 5, each pulse records the code of the current X coordinate coming from the output of counter 1 to the output register register 5, which is fed to the input register of counter 3. Before the next line begins to pass by the electron beam, this code is written to counter 3 register. At the end of the FID and the beginning of the direct code, the TI is subtracted from this code, and at the output of the overflow of the counter 3, an impulse appears that at the permitting potential at the second input of the element And 7 would pass through him and the element OR 8 and would cause the highlight of a point on the CRT screen with the coordinate corresponding to the coordinate of the point of the previous line that caused the formation of a signal at the output of the coordinate remover. Thus, signals from the output of counter 3 would provide illumination of a vertical line with the coordinate X points located in the field of view of the light pen.

When a batch of pulses arrives at the summing input of the counter 12, they are counted during the frame time and at the output of the counter 12 there appears a code corresponding to the number of these pulses. The code output of the counter 12 is connected to the code input of the counter 13 with a shift by one bit, while the output of the n-th bit of the counter 12 is connected to the input of the (n-1) -th bit of the counter 13, and the high-level input of the counter 13 is connected with zero bus. This ensures that a number in the input register of the counter is two times smaller than the number of 12 pulses that have arrived at the input of the counter. The leading edge of the XI rewrites this number into the internal register of the 13S counter and during the next frame at the output, ne 51

the replenishment of counter 13 appears a pulse arriving at the input of register 6 at time. corresponding to the intersection of the CRT by the central part of the field of view of the coordinate remover, but with a time shift by one scanning frame. At the output of register 6 and at the input of the counter, the code of this line appears. During the next frame, a pulse arrives at the output of counter 4, arriving at the second input of element And 7, enabling the point to be illuminated exactly on the line passing through the central part of the field of view.

Thus, the device reads the coordinates of the image element from the screen of the cathode-ray tube located on the central line intersecting the field of view of the light pen, regardless of the number of lines of the raster that are in the field of view of the light pen, and the backlight of this element .

Claims (1)

Invention Formula A device for reading coordinates from a cathode ray tube screen, containing the first counter, whose information input is the information input of the device, the counting input is the clock input of the device, the clock input is the first synchronizing input of the device, and the output is connected to the information input the input of the first register, the synchronization input of which is connected to the output of the coordinate remover, the input of which is optically connected with the screen of the cathode ray tube, the second counter, the counting input of which It is connected to the first clock input, and the setup input is the second clock input of the device, and the output is connected to the information $. 0 five 0 5 0 Q s five I6 the second register, the third counter, the information input of which is connected to the output of the first register, which is the first information output of the device, the subtractive input of the third counter is connected to the clock input of the device, the synchronization input is connected to the first synchronization input of the device, and the output is connected to one input of the first element And, the fourth counter, the subtracting input of which is connected to the first synchronizing input of the device, the information input is connected to the output of the second register, The second information output of the device, the setup input of the fourth counter is connected to the second synchronization input of the device, and the output is connected to another input of the AND element, the output of which is connected to one input of the OR element, the other input of which is the first control input of the device connected to the control input of the cathode ray tube, the beam deflection input of which is the second control input of the device, characterized in that, in order to increase the accuracy of the device, Selection of the central line from the raster lines in the field of view of the coordinate remover, it contains the fifth counter, the summing input of which is connected to the output of the coordinate remover, the sixth counter, whose information input is connected to the output of the fifth counter, the subtractive input is connected to the output of the coordinate remover, synchronizing input connected to the second clock input of the device, and the output is connected to the clock input of the second register, and the pulse decay selector, the input of which is connected to the second clock input of the device output is connected to the setup input of the fifth counter.