JPH0353649B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a light pen input device for a raster scan type CRT display device, and in particular, to accurately detect and correct the position of a light pen and to prevent changes over time. The present invention relates to a light pen input device that can be used without using a light pen.

[Background of the invention]

As a conventional light pen input device, as shown in Japanese Patent Application Laid-Open No. 58-192135, etc.,
A configuration as shown in the figure is known.

In FIG. 2, the screen memory 7 sequentially outputs display data according to a signal (address) supplied from the display control circuit 1. The display data is once latched by the latch 6A and then inputted to the pattern generator 8 as an address.

The pattern read out from the pattern generator 8 is
After being latched by latch 6B, it is converted into serial data by PIS converter 9. The serial data is supplied to the CRT display device 10 via an OR circuit O1 and an AND circuit A1.

The AND circuit A1 includes latches 6C and 6
D inputs a display timing signal which is latched in the same way as the image data and whose timing has been synchronized, so that the serial data is actually displayed on the CRT only during the timing determined by this signal.
The voltage is applied to the display device 10 and displayed on the display surface.

On the other hand, when the light pen 4 is brought into contact with the CRT screen and a switch (not shown) is operated, the light pen control circuit 2 outputs a switch signal sw.
In response, the grid display circuit 3 is prompted to display the grid.

The grid display circuit 3 sequentially displays a grid starting from the first row of the display screen according to the raster address given from the display control circuit 1. When the light pen 4 detects this grid, the light pen control circuit 2 stores the display address at that time in response to the detection signal ld, and sends this to the correction calculation circuit 5 as the detection address.

The correction calculation circuit 5 corrects the detection delay based on the display address and the time until the detection signal ld rises or falls, and can know the position on the CRT screen where the light pen 4 is in contact. .

By the way, if the relationship between the detection range of the light pen and the unit size of the display screen is almost equal, as shown in Figure 3a, there is no problem with the conventional method, but as shown in Figure 3b, , Due to the high density display,
If the size of the detection unit (for example, one character) is considerably smaller than the detection range of the light pen,
There is a risk of detection errors.

That is, for example, in b of FIG. 3, although the letter "B" is specified, the light pen control circuit 2 detects the position of xo, which is the rising edge of the detection signal, so it appears as if the letter "A" ”, resulting in detection errors.

Therefore, in addition to correcting the detection time delay, the correction calculation circuit 5 shown in FIG. 2 is also required to perform correction such as shifting the detection position to the right by dx as shown in FIG. 3b.

However, in this case, for the character at the left edge of the screen (i.e., the scanning start edge), in the conventional method, the third
As shown in Figure c, the display start points of the grid and screen coincide, so the detection point of the light pen is also the display start point of the grid and screen xo
I end up in the position of

For this reason, if only dx is corrected, as in FIG. 3b, a problem arises in that the designated position and the detected position differ at the left end.

Also, the size of the detection range of the light pen varies depending on the individual light pens, or changes due to changes in the brightness (luminance) of the screen of the CRT display device, so the correction value dx is There is also the problem of having to make adjustments each time.

In addition, although the case where the position detection is performed at the front end (rising end) of the detection signal from the light pen 4 has been described above, the case where the position detection is performed at the rear end (falling end) of the detection signal from the light pen 4 is described. It is easy to understand that the same problem as described above occurs at the right edge of the screen.

[Purpose of the invention]

SUMMARY OF THE INVENTION The present invention is aimed at eliminating the above-mentioned problems, and by extending the grid display timing signal on at least one side of the front and rear sides of the scan direction, It is an object of the present invention to provide a light pen input device that can prevent position detection errors at the ends and, if necessary, detect the midpoint of the detection signal generation timing.

[Summary of the invention]

The present invention extends the grid generation time so that the relative relationship between the detection range of the light pen and the detection light of the grid etc. is the same at any position on the actual display screen, and at the edge of the screen. It is also characterized in that it is configured to ensure detection position accuracy.

In addition to the above, the present invention is configured to ensure detection position accuracy even with changes in light pen sensitivity and CRT brightness by using the temporal midpoint of the light pen detection signal. It has characteristics.

[Embodiments of the invention]

A block diagram of one embodiment of the present invention is shown in FIG. In this figure, the same reference numerals as in FIG. 2 represent the same or equivalent parts.

As is clear from the comparison with FIG. 2, this embodiment adds display timing signal latches 6E, 6F and OR circuit O2 to the conventional example of FIG.
The display timing signal for the grid is separated from the display timing signal for the actual display (CRT image), and a counter circuit 11 is further added to measure the time width of the light pen detection signal.

First, a circuit for generating a grid display timing signal will be explained. FIG. 4 is the timing chart.

The display timing signal b output from the display control circuit 1 is applied to a two-stage latch 6 to which a display unit clock (generally a character clock, not shown) is applied.
After passing through C and 6D, it becomes a display timing signal a for actual display, and is supplied to an AND circuit A1.

On the other hand, the grid display timing signal d is a signal c after the actual display display timing signal a has further passed through two stages of latches 6E and 6F, and the display timing signal b which has not passed through any stage of latches. It is created by logical sum.

As shown at d in FIG. 4, the grid display timing signal d obtained by ORing the display timing signals b and c is longer than the actual display timing signal a by two display units before and after.

The actual display timing signal a is a timing signal that defines the area in which an image can be displayed, so if you look at it at the left end of the CRT screen, you will see that the grid is aligned with the image as shown in Figure 3d. Since the display will protrude by one character to the left side (scanning start edge side) of the displayable area, the same correction value is applied to the left edge of the screen as for other parts.
It is possible to correct it correctly with DX.

FIG. 5 is a block diagram showing a specific circuit example of the newly added counter circuit 11 (FIG. 1) in one embodiment of the present invention.

Since the AND gate A2 is open while the light pen 4 outputs the detection signal ld, the clock ck is applied to the counter 12. The value counted by this counter 12 - that is, the detection range width of the light pen 4 indicated by the symbol D in Fig. 3b -
is taken into the correction calculation circuit 5, and half the count value is used as a correction value for the detected address.

With such correction, even if the detection range of the light pen changes, it is possible to always perform correct correction and accurately detect the center position of the detection range.

That is, for example, as shown in FIG. 6, when the detection range or count value of the light pen 4 is A, the correction value is dx(A), which corresponds to A/2; When the detection range or count value of is B, the correction value is dx(B), which corresponds to B/2. The center of the range will be found.

At this time, the clock applied to the counter 12
It is preferable that ck is a clock (such as a dot clock) with a frequency that is an integral multiple of the clock frequency with a period of one display unit, and by setting the frequency of this clock higher, the center position can be adjusted. It is also possible to increase the detection accuracy.

Further, the counter 12 can be reset using a light pen operation start signal, for example, a switch signal sw.

In the above, a case has been described in which the position of the light pen 4 is detected while monitoring its detection range, but it is easily understood that monitoring of the detection range is not necessarily necessary.

As is clear, if the detection range is not monitored, the counter circuit 11 can be omitted in the embodiment shown in FIG. When the counter circuit 11 is omitted as described above, depending on whether the position detection of the light pen 4 is performed at the front end or the rear end of the detection signal ld, (1) If it is performed at the front end, , the signal shown in waveform b in FIG. 4 may be used as the grid display timing signal, so in FIG.
(2) If the operation is performed at the rear end, the signal shown in waveform c in Fig. 4 can be used as the grid display timing signal. Therefore, in Fig. 1, the display control circuit Signal line from 1 to OR circuit O2 and OR circuit O
2 can be omitted.

〔Effect of the invention〕

As is clear from the above explanation, the present invention makes it possible to significantly improve the detection resolution of light pens, which has relatively decreased as conventional CRTs have become high-density displays. It has also become possible to significantly improve the detection accuracy at the edges of the screen, which tends to occur.

Furthermore, replacing the light pen or aging,
It is now possible to ensure detection accuracy even when the detection range changes due to changes in CRT brightness.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG.
Figure 3 is a block diagram of a conventional light pen input device, Figure 3 is a diagram showing an example of the relationship between the actual display on a CRT and the detection range of the grid and light pen, and Figure 4 is a grid display timing signal suitable for the present invention. Figure 5 is a specific circuit diagram showing an example of the counter circuit in Figure 1. Figure 6 is the actual display on the CRT and grid and light pen detection when the light pen detection range changes. It is a figure which shows the example of the relationship of ranges. 1...Display control circuit, 2...Light pen control circuit,
3...Grid display circuit, 4...Light pen, 5...Correction calculation circuit, 6...Timing latch, 7...Screen memory, 8...Pattern generator, 9...Parallel-serial converter, 10...CRT display device, 11...Counter circuit,
12...Counter.

Claims (1)

[Claims] 1 Image display using raster scan method
a CRT display device; a grid display circuit that generates a signal for displaying a light pen detection grid on the CRT display device; a light pen for generating a detection signal in response to the presence or absence of a light pen; means for activating the grid display circuit in response to contact with the screen of the CRT display device; means for detecting the display address of the grid;
and a correction calculation circuit for correcting the contact position of the light pen based on the display address detected as described above.
A light pen input device further comprising means for extending the display area of the detection grid in each scanning line direction of the CRT display beyond the image displayable area on at least one side thereof. 2. The means for extending the display area of the detection grid in each scanning line direction of the CRT display device, at least on one side, beyond the image display area sends a signal that is ahead of the image display timing signal by a scheduled time. The light pen input device according to claim 1, further comprising means for supplying a grid display timing signal to a grid display circuit. 3. The means for extending the display area of the detection grid in each scanning line direction of the CRT display device, at least on one side, beyond the image display area sends a signal delayed by a scheduled time from the image display timing signal. The light pen input device according to claim 1, further comprising means for supplying a grid display timing signal to a grid display circuit. 4 Display images using raster scan method
a CRT display device; a grid display circuit that generates a signal for displaying a light pen detection grid on the CRT display device; a light pen for generating a detection signal in response to presence or absence; means for activating the grid display circuit in response to contact with the screen of the CRT display device; and means for activating the grid display circuit in response to the detection signal; and a means for detecting a display address of a CRT.
means for extending the display area of the detection grid in each scanning line direction of the display device beyond the image displayable area on both sides; a counter circuit for counting the duration of the detection signal; A light pen input device further comprising: a correction calculation circuit that corrects and calculates a contact position of the light pen based on the display address and the duration of the detection signal.