JPH0319000Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to an image display device that can draw images on a cathode ray tube using a light pen.

(B) Prior Art A video display device that displays graphics on a cathode ray tube using a light pen has already been put into practical use, and is generally constructed as shown in FIG.

The clock φc from the reference signal generator 1 is input to the synchronization signal generation circuit 2.
outputs a horizontal synchronizing signal H and a vertical synchronizing signal V, respectively, and these signals H and V are connected to a cathode ray tube (hereinafter referred to as
(CRT) 3.

The clock φc is input to the address counter 4 and outputs an address signal AD to the image memory 5. This address signal AD is also input to a latch circuit 7 for detecting the address corresponding to the coordinates on the CRT screen indicated by the light pen 6.

The data output from the image memory 5 is input to the D/A conversion circuit 8, where it is converted into an analog signal.
Displayed on the CRT3 screen. light pen 6
A light pen signal including a switching signal SW1 indicating whether the light pen is applied to the CRT 3 and a bright line detection signal M detecting a bright line on the CRT is output. The switching signal SW1 is turned on (high level as a signal) when the light pen 6 is pressed against the CRT 3.

The latch circuit 7 latches the output of the address counter 4 using this light pen signal, and the latched address counter 4 output is determined by the light pen 6.
This corresponds to the coordinate position of the CRT 3, and this, ie, the coordinate signal, is input to the write data control circuit 9, and the image data in the image memory 5 at that address position is rewritten.

The bright line detection signal M is output every frame period of the CRT screen, and if the contents of the image memory 5 are to be rewritten only for addresses determined by this bright line detection signal M, for example, the light pen 6 can be rewritten.
If you slide it while pressing it against the CRT3 tube surface,
Only the address points obtained for each frame are displayed on the CRT3 screen, and as a result, a dotted line is drawn along the light pen sliding trajectory. Therefore, by performing interpolation processing between these points in the write data control circuit 9, it is possible to draw a free curve using a light pen. However, as a result, the user can only draw solid lines; to draw broken lines, chain lines, etc., press the light pen 6 against the CRT 3 screen and draw a solid line of a certain length, then write pen 6
It is difficult to operate because the operator has to repeat the process of separating the line from the CRT surface, leaving a blank space between the broken and chain lines, and then drawing a solid line again.

(c) Purpose of the invention The present invention aims to provide a video display device that can easily draw lines with partially blank areas, such as broken lines.

(d) Structure of the invention The present invention aims to provide the above-mentioned blank space in the light pen signal for drawing a display corresponding to the trajectory of the light pen running on the CRT on the CRT. gate signal generating means for generating a gate signal in a predetermined time-series pattern to a display position determining circuit that supplies a coordinate signal to a write data control circuit in order to provide modulation corresponding to intermittently lifting the display position from the write data control circuit; The video display device is characterized by comprising a gate means for gating the light pen signal with a gate signal generated from the gate signal generating means to form the light pen signal into a predetermined time-series pattern.

(E) Embodiment FIG. 1 is a block diagram of an embodiment of the device of the present invention, and FIG. 2 is a waveform diagram for explaining the operation of the device.

Functional elements in FIG. 1 that are the same as those in FIG. 3 are given the same reference numerals to avoid redundant explanation.

10 is a display position determining circuit which receives a light pen signal from the light pen 6 and sends the output of the image memory 5 to the write data control circuit 9.
A coordinate signal is supplied to the CRT 3 so that a display corresponding to the trajectory of the light pen 6 traveling on the CRT 3 is displayed.

The display position determining circuit 10 is a gate signal generating means 1
1, gate means 12, and a latch circuit 7 which receives the output of the gate means 12 and the bright line detection signal in the light pen signal and latches the output of the address counter 4.

The gate signal generating means 11 includes a gate signal generating circuit 13 that generates a plurality of types of gate signals, for example, the gate signals shown in FIGS. a selection circuit 14 that outputs the selection gate signal, a command circuit 15 that controls the validity of the selection gate signal, and a command circuit 15 that controls the application of the selection gate signal to the gate means 12.
It also includes a gate circuit 16 that performs control based on the output. The selection circuit 14 is controlled by a selection switch 17 that selects the size of one blank area such as a broken line or a dashed-dot line, and the output of the selection switch to select a plurality of gate signals from the gate signal generation circuit 13. A multiplexer 18 is provided. Further, the command circuit 15 includes a line designation switch 19 that is turned on when designating a special line larger than a solid line, and an inverter 20. A special line is designated when the inverter 20 output is in a high state, and a solid line is designated when the inverter 20 output is in a low state. The output of the gate circuit 16, which is a NAND gate, is input to the gate means (AND gate) 12, and the other input of this gate means 12 is a switch signal in the light pen signal (this switch signal is used when the light pen runs on the CRT). It is in a high state and becomes a low state when it is separated from the CRT) is input. Then, a new switching signal SW2 gated by this gate means 12 is input to the write data control circuit 9.

Next, the operation for drawing special lines such as broken lines and chain lines will be explained. For convenience of explanation, it is assumed that the gate pulse for the broken line (FIG. 2A) is selectively outputted to the multiplexer 18 output.

When the line designation switch 19 is open, the output of the inverter 20 is in a low state, so the output of the gate means 16 is in a high state, and the light pen switch signal SW1 is input to the write data control circuit 9 without being gated. Section C in Figure 2
PQ).

When the line designation switch 19 is closed, the inverter 20 output is high (FIG. 2D), and the output of the gate circuit 12 depends on the output of the multiplexer 18 (FIG. 2E). And gate circuit 1
When the output 6 (FIG. 2F) is in a low state, the light pen switch signal is gated by this low signal S, and as seen from the write data control circuit 9, the state is the same as when the light pen 6 is separated from the surface of the CRT 3. Therefore, while the output of this gate circuit 16 is in a low state, drawing is prohibited. Conversely, when the gate circuit 16 output is high, the light pen 6
It is pressed against the CRT 3, and the above-described drawing operation is performed (section QR in FIG. 2C).

Therefore, the line drawing result by the above operation becomes as shown in FIG. 2H on the CRT 3 according to the output of the gate means 12 shown in FIG. 2G, and the line designation switch 19
The solid line is in section PQ where line designation switch 19 is open, and the broken line is in section QR where line designation switch 19 is closed.
Displayed on CRT3.

(F) Effect of the invention The device of the invention can draw arbitrary special lines such as broken lines and chain lines on the CRT tube surface by selecting the gate signal from the gate signal generating means in advance. It is possible to draw without touching or separating the light pen from the line, which simplifies the drawing operation of special lines, which is practical.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an embodiment of the device of the present invention, FIGS. 2A to 2H are waveform diagrams for explaining the operation of the device, and FIG. 3 is a schematic diagram of a conventional device. Explanation of main symbols, 3...Cathode ray tube (CRT), 5
...Image memory, 9...Write data control circuit, 6...Light pen, 10...Display position determining circuit, 11...Gate signal generation means, 12...Gate means.

Claims (1)

[Claims for Utility Model Registration] (1) A cathode ray tube, an image memory storing a video signal applied to the cathode ray tube, a write data control circuit for updating the stored contents of the image memory, and a cathode ray tube; a light pen that outputs a light pen signal indicating whether or not the light pen is applied to the cathode ray tube; and a light pen that receives the light pen signal from the light pen and sends the output of the image memory to the write data control circuit. a display position determining circuit that supplies a coordinate signal to the cathode ray tube so as to provide a display corresponding to a travel locus of the light pen traveling on the cathode ray tube; a gate signal generating means for generating a gate signal in a time-series pattern; and a gate for gating the light pen signal with the gate signal generated from the gate signal generating means to form the light pen signal into a predetermined time-series pattern. A video display device comprising: means. (2) The gate signal generation means includes a gate signal generation circuit that generates gate signals of a plurality of types of time-series patterns, and a selection that selects the gate signals of the gate signal generation circuit and outputs one selected gate signal. a command circuit that controls the validity of the selection gate signal; and a gate circuit that controls application of the selection gate signal to the gate means based on the output of the command circuit. A video display device according to claim (1) of patent registration.