SU617779A1 - Arrangement for reading-out coordinates from crt screen - Google Patents

Description

I

The invention relates to automation and computing, in particular to devices for retrieving coordinates from a screen of a cathode ray tube, and can be used to enter information into a computer.

Devices are known for removing coordinates from a cathode ray tube (CRT) screen.

One of the known devices contains a control unit, the inputs of which are connected to the light pen, coordinate generation units connected to the control unit and the light primer tracking unit, AND, OR 1 elements.

The disadvantage of such a device lies in its structural complexity.

Another device is known that contains a line of photocells whose inputs are optically coupled to a CRT screen, and the outputs through a gain unit are connected to threshold elements and to a pulse shaping unit, a X-coordinate shaping unit, an analog-to-digital converter, and AND, OR elements 2.

The last of the listed devices is closest to the described technical solution. Its disadvantages include constructive complexity and low reliability.

The purpose of the invention is to simplify and increase the reliability of the device.

The goal is achieved by the fact that in it the outputs of threshold elements through

the OR element is connected to one of the inputs of the first AND element, the other input of which is connected to the X coordinate formation unit, and the output is connected to the second AND elements connected to the pulse shaping unit through an analog-digital converter.

The drawing shows a block diagram of the device. The device includes a line 1 of photocells 2, an amplification block 3 with amplifiers 4, threshold elements 5, an element OR b, a block of 7 forming a coordinate X, made in the form of a potentiometer, a first element AND 8, an analog-to-digital converter 9, a block 10 of shaping pulses Formers 11 and second elements And 12.

Photo cells 2) are installed in the form of vertical to the direction of movement

(parallel to the axis Y) of the rows in which the photocells are shifted along the Y coordinate. The ruler 1 is rigidly connected to the X-coordinate formation unit 7. The device operates as follows.

When moving Liiyaki 1 along axis A, each photocell 2 forms narrow parallel lines for receiving light signals. At the same time, the ruler moves the knob of the potentiometer of the block 7. The voltage applied to the input of the element And 8 increases in proportion to the path traveled by the ruler.

When the light signal from the CRT screen hits the photocell 2, an electrical signal is generated at its output, which is amplified by amplifiers 4 of block 3. Threshold elements 5 allow choosing the moment at which the signal at the input of the element OR 6 is selected at the moment of the signal at the output of amplifier 4 corresponding to the center of the beam to accurately measure the x coordinate.

When a signal is output from the output of the threshold elements 5 to the OR 6 element, the analog current value of the X coordinate corresponding to the gray, uniform beam thickness, goes from block 7 to the input of the analog-to-digital output (through element 8). From output 1} of the converter 9 is digital. The X coordinate is fed to the inputs of elements AND 12. Due to the presence of the necessary delay in converter 9, block 10 opens only those elements 12 that correspond to illuminated photocells. The coordinate of X from the output of elements 12 goes to the output of the device. The vertical values of Y and the offset of photocells 2 in line 1 along the X axis are constant for each photocell.

Thus, the coordinates of any point can be removed from the CRT screen.

The introduction of new constructive links allowed to significantly simplify and improve the reliability of the device.

Claims (2)

1. Japanese Patent No. 48-33897, cl. G7 (7) In 41, published. 1973. 2. US patent number 3758718, cl. 178-18, onlib. 1973.