JPH0250218A - On-screen position storage device - Google Patents

Abstract

PURPOSE:To simplify constitution and to reduce cost by storing a position on the screen of a CRT display as an analog signal with an analog circuit. CONSTITUTION:A circuit 5 to separate a synchronizing signal from a video signal and circuits 6 and 7 to generate a saw tooth wave signal, which is synchronized to the separated synchronizing signal, are provided. Then, circuits 8 and 9 to sample and hold the saw tooth wave signal in responding to the output pulse of a write pen 3, and comparators 10 and 11 to compare the output level of the sample and hold circuits 8 and 9 with the level of the saw tooth wave signal are provided. Accordingly, the position on the screen is stored as the analog signal by the analog circuit such as the saw tooth wave signal generating circuit, sample and hold circuit and comparator, etc. Thus, a counter or a memory, etc., is not needed and the constitution is simplified. Then, the cost can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an apparatus for storing positions on the screen of a CRT display.

<Prior Art> Conventionally, for example, a plurality of positions on the screen of a CRT display are memorized, and another screen is fitted into a predetermined area on the screen surrounded by the plurality of memorized positions, or, Various types of image processing are performed, such as changing the hue of the screen in a predetermined area.

There is a device shown in FIG. 3 that stores such a position on the screen.

In FIG. 3, a VTR1 as a video signal source
The video signal from the CRT display 2 is supplied to the CRT display 2 for image display, and is supplied to the synchronization separation circuit 5 to separate the horizontal synchronization signal Hs and the vertical synchronization signal Vs. The synchronization signals Hs and Vs from the synchronization separation circuit 5 are respectively given to the counters 15 and 16 as reset signals, thereby resetting the counters ts and te.

The output of each counter 15, 16 is the output of each latch circuit 17.1.
8 are given respectively.

To memorize the position on the screen, press Lipen 3 in CR.
By pressing against the screen of the T-display 2, a pulse signal is output from the light pen 3, and at the output timing of this pulse signal, the output of each counter I5, 16 is latched and stored in each memory 19, 20, respectively. Ru.

FIG. 4 is a timing chart of the above-mentioned conventional example,
(A) is the output of the Lipen 3, (B) is the horizontal synchronization signal Hs, (C) is the output of the counter 15 reset by the horizontal synchronization signal Hs, and (D) is the output of the memory 19.
shows the input data. In FIG. 4, only the timing chart corresponding to the horizontal synchronizing signal Hs is shown, but the vertical synchronizing signal Vs is basically the same.

As shown in FIG. 4, by pressing the pen 3 against the screen of the CRT display 2, the pen 3
A pulse signal is output from , and at that timing, the output of the counter 15 corresponding to the position on the screen, a digital signal indicating 4 in this example, is latched and stored in the memory 19 .

However, such a conventional on-screen position storage device requires counters 15, 16, memories 19, 20, etc., and therefore has a problem of being complicated and expensive.

<Objective of the Invention> The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide an on-screen position storage device that has a relatively simple configuration and is inexpensive.

<Configuration of the Invention> In order to achieve the above-mentioned object, the present invention provides an on-screen position storage device that stores the position on the screen of a CRT display to which a video signal is applied in response to an output pulse of a light pen. a synchronization separation circuit that separates a horizontal synchronization signal and a vertical synchronization signal from the video signal; and a first sawtooth wave signal having a sawtooth voltage waveform synchronized with the horizontal synchronization signal separated by the synchronization separation circuit. a first sawtooth wave generation circuit; and a second sawtooth wave signal that generates a second sawtooth wave signal having a sawtooth voltage waveform synchronized with the vertical synchronization signal separated by the synchronization separation circuit.
a sawtooth wave generating circuit; the second sawtooth signal,
first and second sampling and holding circuits that respectively sample and hold in response to output pulses of the light pen; and a first comparator that compares the output level of the first sampling and holding circuit with the level of the first sawtooth signal. and a second comparator that compares the output level of the second sampling and holding circuit with the level of the second sawtooth signal.

According to the above configuration, the position on the screen is stored as an analog signal by analog circuits such as the sawtooth wave generation circuit, the sampling hold circuit, and the comparator.
The configuration is simpler than conventional examples that require counters, memories, etc., and costs can be reduced.

<Examples> Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention;
Portions corresponding to the conventional example in the figures are given the same reference numerals.

In the same figure, ■ is a VTR as a video signal source, 2
is a C that displays an image using the video signal from this VTR1.
The RT display 3 is a light pen that specifies the position on the screen of the CRT display 2.

The on-screen position storage device 4 of this embodiment is synchronized with the synchronization separation circuit 5 that separates the horizontal synchronization signal Hs and the vertical synchronization signal Vs from the video signal of the VTR 1, and the horizontal synchronization signal Hs separated by the synchronization separation circuit 5. A first sawtooth wave generation circuit 6 generates a first sawtooth wave signal whose voltage waveform is sawtooth, and a second sawtooth waveform whose voltage waveform synchronized with the vertical synchronization signal Vs separated by the synchronization separation circuit 5 is sawtooth. a second sawtooth wave generation circuit 7 that generates a wave signal; the second sawtooth signal,
The first one samples and holds each sample in response to the output pulse from the light pen 3. a second sampling and holding circuit 8.9, a first comparator lO that compares the output level of the first sampling and holding circuit 8 and the level of the first sawtooth signal; A second comparator 11 is provided to compare the level of the second sawtooth wave signal.

Next, the operation of the on-screen position storage device 4 having the above configuration will be explained based on the signal waveform diagram of FIG.

In this Figure 2, (A) is the output of the light pen 3, (B) is the horizontal synchronizing signal Hs, (C) is the first sawtooth wave signal, and (D) is the first The output of the sampling hold circuit 8 and (E) in the figure show the output of the first comparator 10, respectively.

Although FIG. 2 shows only the waveform corresponding to the horizontal synchronizing signal Hs, the same applies to the vertical synchronizing signal.

The first sawtooth wave generation circuit 6 generates a first sawtooth wave signal having a sawtooth voltage waveform synchronized with the horizontal synchronization signal Hs shown in FIG.

By pressing the light pen 3 against the screen of the CRT display 2, the light pen 3 outputs a pulse signal at a timing shifted by a time t from the rising edge of the horizontal synchronization signal Hs, as shown in FIG. 2(A). Then,
The first sampling and holding circuit 8 samples and holds the first sawtooth wave signal at that timing, as shown in FIG. 2(D), and holds it until a new output pulse is given from the light pen 3.

The output level of this first sampling and hold circuit 8 and the level of the first sawtooth wave signal are compared by a first comparator 10, and as shown in FIG. An output that becomes high level with a time t lag from the rising edge of Hs and becomes low level in synchronization with the falling edge of horizontal synchronizing signal Hs is obtained. That is, for every l line, an output that becomes high level corresponding to the horizontal position on the screen is obtained.

Regarding the vertical synchronization signal, in the same way, ■ the second comparator 11 corresponding to the vertical position on the screen for each field;
The output will be obtained, which will determine the position on the screen.

In this way, the output of each comparator 10, 11 is
This corresponds to the position on the screen of the display 2, so based on these outputs, for example, by switching the video signal given to the CRT display 2 to another video signal, a predetermined area on the screen can be It is possible to fit the screen in the same way as before.

<Effects of the Invention> As described above, according to the present invention, C
Since the position on the screen of the RT display is stored as an analog signal, the configuration is simplified and the cost is reduced compared to the conventional example in which the position is stored as a digital signal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a block diagram of an embodiment of the present invention.
Signal waveform diagrams of each part in the figure, Figure 3 is a block diagram of the conventional example,
FIG. 4 is a timing chart of a conventional example. 2...CRT display, 3...Light pen, 4
...On-screen position storage device, 5...Synchronization separation circuit, 6
゜7... 1st. Second sawtooth wave generation circuit, 8.9...
1st゜Second sampling and hold circuit, 10.2...
First and second comparators.

Claims (1)

[Claims] (1) An on-screen position storage device that stores the position on the screen of a CRT display to which a video signal is applied in response to an output pulse from a light pen, and separates a horizontal synchronization signal and a vertical synchronization signal from the video signal. a first sawtooth wave generation circuit that generates a first sawtooth wave signal in which a voltage waveform synchronized with the horizontal synchronization signal separated by the synchronization separation circuit is separated by the synchronization separation circuit; a second sawtooth wave generation circuit that generates a second sawtooth wave signal having a sawtooth voltage waveform synchronized with the vertical synchronization signal; first and second sampling and holding circuits that respectively sample and hold in response; a first comparator that compares the output level of the first sampling and holding circuit with the level of the first sawtooth signal; and the second sampling and holding circuit. An on-screen position storage device comprising: a second comparator that compares the output level of the circuit and the level of the second sawtooth wave signal.