JPS594046B2 - Light pen field of view position detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting a position close to the center of the visual field of a light pen used as an interactive type in a dot-scanning type cathode ray tube display device.

The present invention also relates to a device for detecting the field of view position of a relatively minute light pen when drawing a continuous locus of points, lines, etc. on the screen of a cathode ray tube display device, that is, when writing in units of bright spots.

More specifically, the present invention relates to a field position detection method for a light pen applied to a device that enables writing to an arbitrary address in a refresh memory corresponding to each pixel at a screen display position of a cathode ray tube. It provides equipment.

As is well known, a light pen is a type of photodetector, and when placed at any position on the screen of a cathode ray tube, it can detect the display light generated by the scanning beam on the screen.

Therefore, by knowing the address of the refresh memory at the time of light detection, it is possible to detect the position on the screen where the light pen is applied. By the way, the scanning beam of the cathode ray tube screen, or raster light, detected by the light pen receiver passes through several beams within the field of view of the light pen receiver, and this is necessary to determine the exact position of the light pen. The position of the center of the visual field must be determined.

Therefore, conventionally, this type of circuit detects multiple pulse train signals generated by raster light passing through the field of view, and calculates the number of pulses to determine the position. Ta. However, the signal of this detected pulse train is detected as a pulse with a high peak value and stable as the pulse is closer to the center of the light pen field of view, but as it approaches the periphery of the field of view, it is detected as an unstable pulse with a low peak value. be done. The pulse width of this pulse also changes depending on the brightness of the raster light, and tends to widen as the brightness increases. Since the light pen is applied to the screen by the user's hand,
The angle at which it is applied is not constant and stable. Therefore, the brightness detected by the light receiving section was not constant and stable. When this type of cathode ray tube performs well-known interlaced scanning for each odd and even field, the number of detection pulses will differ when the timing for detecting raster light is determined for each field. As a result, conventional circuits of this type have the disadvantage that the number of pulses required to determine the center position of the pulse train signal detected by the light pen light receiving section is extremely unstable.

The present invention has been made in view of this point, and in order to reduce detection errors even in the case of interlaced scanning, raster light is detected for each odd or even field, and the previous one is detected for each frame period. The position of the light pen pulse train signal detected at the frame period of is detected. Further, a feature of the present invention is that the number of pulses of the pulse train signal is 2.
A first counter that counts n or 2n+1 (n is a positive integer) and outputs a count value n every frame period, and this count value n is transferred for every field.
The counted value n transferred above is counted down by the pulse train signal detected in the next frame period after the one frame period in which the pulse train signal was detected, and this counted value n
A second counter is provided which generates an output pulse when the second counter becomes zero, and the address data of the refresh memory corresponding to the address of the pixel on the screen is repeatedly output by the output pulse output from the second counter. Latch to find the center position of the light pen field of view, and the detection accuracy of the center position is 1 horizontal scanning period for the raster light that crosses the center of the field of view.
The object of the present invention is to provide a light pen position detection device that can detect the position of a light pen without a deviation of /2 or more.

The present invention will be explained below with reference to the drawings.

FIG. 1 is a wiring diagram of main parts of an apparatus according to an embodiment of the present invention, and FIG. 2 is a waveform diagram of each part in response to an input signal. In FIG. 1, 1 is a signal input terminal to which a pulse train signal detected by a light pen (not shown) is input, and 2 is a synchronization signal input terminal to which a vertical synchronization signal VD is input.

3 is an AND gate, 4 is a first counter consisting of a well-known binary up counter, and 5 is a second counter, which counts down from the count value n inputted from the first counter 4 until this count value n becomes zero. It is composed of a well-known down counter that outputs a borrow signal when the time comes.

6 is a first flip-flop; 7 is a second flip-flop consisting of a T-shaped so-called toggle flip-flop;
8 is a third flip-flop.

Further, 9 to 12 are well-known inverters, and the first and second
In order to make the output pulses of each of the flip-flops 6 and 8 into elongated pulses, a clear pulse is applied to each clear terminal CLR after an appropriate delay from the rise of each output pulse. 13 is a delay adjustment circuit,
This circuit is composed of, for example, a monostable multivibrator, and is used to adjust the timing of latching address data, which will be described later, and can be omitted as appropriate. The operation of the embodiment circuit shown in FIG. 1 will be explained below with reference to FIG. 2.

First, when the vertical synchronizing signal VD as shown in FIG. 2 is input to the first flip-flop 6, at the same time as this VD rises, the vertical synchronizing signal VD as shown in FIG. 2 is input to the load terminal LOAD of the second counter 5. A load signal like this is output from the Q terminal.

As described above, this load signal is cleared by the output from the first flip-flop 6 via the inverters 9 and 10, so it becomes a long and narrow pulse as shown in FIG. On the other hand, the output of the Q terminal having a polarity opposite to the load signal of the Q terminal is input to the clock input terminal CK of the second flip-flop 7 at the next stage. The second flip-flop 7 inverts its output every time the signal input to the clock input terminal CK falls, and outputs a field signal that is inverted every field period as shown in FIG. Therefore, this field signal is output from the second flip-flop 7 as an output of the same polarity for each odd or even field. 2nd flip-flop 7
Such a field signal at the Q terminal of is inputted to the clock input terminal CK of the third flip-flop 8 at the next stage. As shown in the second figure, the third flip-flop 8 creates a long and narrow pulse every time the above-mentioned field signal rises, and outputs it from its Q terminal. Therefore, the pulse outputted from this Q terminal is inputted to the clear terminal CLR of the first counter 4 as a frame signal outputted every frame period. As a result, the count value of the first counter 4, which will be described later, is cleared by this frame signal. Incidentally, the above-mentioned field signal is branched from the output of the Q terminal of the second flip-flop 7 and is also applied to the gate input terminal of the AND gate 3.

As a result, the gate of this AND gate 3 is opened and closed every frame period during one field period. Therefore, the pulse train signals 1 and 2 as shown in Fig. 2A, which are input from the signal input terminal 1 and detected by the light pen, are detected during one field period of the same field, either an odd number or an even number. The pulse train signal is applied to the clock input terminal CK of the first counter 4 as a pulse train signal.
As a result, the first counter 4 counts the number of pulses of such a pulse train signal, for example, a signal such as 1, every frame period. That is, if the number of pulse train signals is S5'' as shown in FIG. 2A1, the output waveform of the first counter 4 at this time will be as shown in FIG.

By the way, the output terminals QA, QB,
For QC and QD, the QA terminal is open, the QB terminal is connected to the A terminal of the input of the second counter 5, the Qc terminal is connected to the B terminal, and the QD
The terminals are each connected to a C terminal. Therefore, when the number of pulses of the above-mentioned pulse train signal is 2n or 2n+1, when inputting the count value of the first counter 4 to the second counter 5, it is always input as the count value n. The Rukoto. Here, the input D terminal of the second counter 5 is grounded so that it is always zero. As a result, in the case of the above-mentioned pulse number 5'', the count value n input to the second counter 5 becomes 2''. As already mentioned, the timing at which such a count value n is transferred to the second counter 5 is the second counter 5.
This occurs when a load signal as shown in FIG. 2 is applied to the load terminal LOAD of the counter 5. Therefore, the second counter 5 is loaded every field period and holds the count value n output from the first counter 4. On the other hand, the output of the AND gate 3, that is, the pulse train signal is branched and input to the clock input terminal CK of the second counter 5. Therefore, the second counter 5 counts down the held count value n each time one pulse of the pulse train signal is input. At this time, this second
The pulse train signal that causes the counter 5 to count down is a signal detected in the same field, either an odd number or an even number, but the pulse train signal 1 has the frame period when the second counter 5 detects the count value n already held. Unlike the pulse train signal detected in the same field period of the next frame period, for example, 2 in Fig. 2A,
becomes. Therefore, the second counter 5 counts down such a pulse train signal 2 as a clock signal input, and outputs a signal having a waveform as shown in FIG. 2 to the terminals QA, Q.
Output from B, QC, and QD. Further, the second counter 5 counts down the count value n thus held, and when the count value reaches zero, outputs a borrow signal from the terminal BORROW. Therefore, in the case of the above-mentioned count value ゞ2'', as shown in FIG. The borrow signal will be output at the same position as the second pulse.This means that it will be located at the center of the pulse train signal 1 detected in the previous frame period.In other words, the second pulse The output borrow signal is
Among the plurality of pulses of the pulse train signal detected by the light pen, the pulse train signal is output every frame period at the same timing as the pulse closest to the center of the field of view of the light pen. Therefore, such a borrow signal passes through the delay adjustment circuit 13 at the next stage and is used as a pulse signal for latching address data on a cathode ray tube screen (not shown). The delay adjustment circuit 13 is for adjusting the timing of this latch and may be omitted. FIG. 3 is a wiring diagram around a screen horizontal latch circuit for address data often used in this type of device.

In this FIG. 3, 14 is a start-stop oscillator;
15 is a monostable multi-vabrator, 17 is a fourth
18 is an inverter, 19 is an address counter, and 20 is a latch circuit. The above-mentioned borrow signal is applied to the clock input terminal CK of the latch circuit 20. Of course, this borrow signal is also used in the latch circuit for address data in the vertical direction of the screen, but an example will be described here in which it is applied to the latch circuit in the horizontal direction of the screen. First, the start-stop oscillator 14 generates clock pulses for displaying on the cathode ray tube horizontal screen data read out from a well-known refresh memory corresponding to picture elements on the screen.

This clock pulse is oscillated in synchronization with the horizontal synchronizing signal HD. The monostable multivibrator 15 (hereinafter simply referred to as monomulti) is triggered by the leading edge of the horizontal synchronizing signal, and inverts the output of the Q terminal after a predetermined time constant has elapsed. This output is input to the clock input terminal CK of the fourth flip-flop 14 at the next stage. The fourth flip-flop 14 is set by this inverted output from the monomulti 15, and releases the clear state of the address counter 19 in the next stage.

When the address counter 19 is released from the clear state, it starts counting clock pulses input from the start-stop oscillator, and when a predetermined count value is reached, it creates and outputs a carry signal. This carry signal is formed by a single pulse, and is applied to the clear terminal CLR of the fourth flip-flop 14 through the inverter 18. Therefore, the fourth flip-flop 14 is reset by the carry signal, and the address counter 19 receives its output and enters the clear state. As a result, address counter 1
9 counts the predetermined number of clock pulses in one horizontal scanning period. The count value of this address counter 19 is successively
Output to the next stage latch circuit. Latch circuit 20 holds the count value output from address counter 19 when the aforementioned borrow signal is applied to its clock input terminal CK. As described above, the count value of the output of the address counter 19, that is, the address data indicating the position on the screen at the timing when the borrow signal is applied, is held.

Therefore, as mentioned above, the timing at which the borrow signal is given is when the raster light closest to the center of the field of view of the line pen is detected. This data indicates the position closest to . As described above, the present invention
Even if the brightness of pixels on the screen changes, the most stable pulse position near the center of the field of view of the light pen is always detected, and the display data of the pixels displayed on the screen is changed for each odd and even field. Even if they are different or the same, they are always detected as a constant pulse train signal, and the detection position is updated every two frames, making it possible to detect the center position of the light pen field of view with higher accuracy. .

Although the present invention has been described above with reference to the drawings of the embodiments, the present invention is not limited to this, and as long as it is constituted by the following, the gist of the present invention will not be affected.

That is, the present invention can synchronize with a horizontal or vertical synchronization signal.
In a cathode ray tube display device equipped with an address counter that outputs address data of a refresh memory corresponding to the position of a pixel on a cathode ray tube screen by counting clock pulses that divide a scanning period into equal intervals, Means for detecting raster light passing within the field of view of the light pen by a light pen applied to an arbitrary position on the screen, and the number of pulses 2n or 2n+1 (n is a positive number) corresponding to the number of passing raster lights. means for detecting a pulse train signal (an integer) for each odd or even field; a first counting means for counting the number of pulses 2n or 2n+1 of the pulse train signal and outputting a count value n every frame period; is transferred for each field, and counts down the count n transferred by the pulse train signal detected in the next frame period after the one frame period in which the pulse train signal was detected, and when this count value n becomes zero. The present invention provides a light pen position detection device having a second counting means for generating an output pulse when the light pen position is detected, and a means for latching address data outputted from an address counter in response to the output pulse as light pen position detection data. .

[Brief explanation of drawings]

FIG. 1 is a wiring diagram of main parts of an apparatus according to an embodiment of the present invention, FIG. 2 is a waveform diagram of various parts in response to input signals, and FIG. 3 is a wiring diagram of peripheral circuits of an apparatus according to an embodiment of the invention.

Claims (1)

[Claims] 1. By counting clock pulses that are synchronized with a horizontal or vertical synchronization signal and divide one scanning period into equal intervals,
In a cathode ray tube display device equipped with an address counter that outputs address data of a refresh memory corresponding to the position of a pixel on a cathode ray tube screen, a light pen applied to an arbitrary position on the screen is used. means for detecting raster light passing within the field of view;
The number of pulses corresponding to the number of passes of this raster light is 2n or 2
means for detecting n+1 (n is a positive integer) pulse train signal for each odd or even field, and a first counter that counts the number of pulses 2n or 2n+1 of the pulse train signal and outputs a count value n every frame period. means, the counted value n is transferred field by field, and the transferred counted value n is counted down by the pulse train signal detected in one frame period following the one frame period in which the pulse train signal is detected. , a second counting means for generating an output pulse when the count value n becomes zero, and a means for latching the address data output from the address counter in response to the output pulse as light pen position detection data. Light pen position detection device.