JPS6010327B2 - Scanning method of electronic whiteboard system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a scanning method for an electronic blackboard system, and more particularly, the present invention relates to a scanning method for an electronic blackboard system, and in particular, the coordinates of characters written with a writing instrument such as chalk on a blackboard on which matrix electrodes are arranged are displayed on a cathode ray tube via a telephone line. The present invention relates to a scanning method for an electronic blackboard system that reproduces images of characters and the like corresponding to handwritten content by transmitting them to a display device such as a display device.

The blackboard used in the electronic blackboard system uses an elastic conductor sheet that deforms near the point where pressure is applied and changes its resistance value when pressure is applied due to the smell of writing such as chalk, and this change in resistance value is extracted to the outside. This is used as the detection signal.

However, due to the nature of the elastic conductor sheet, not only the point at which writing pressure is applied but also the resistance around the point change.

Therefore, if all portions corresponding to changes in resistance value were reproduced as pen pressure point coordinates, there would be a drawback that a thicker line would be reproduced than the line actually written on the blackboard. Therefore, an object of the present invention is to provide a scanning method for an electronic whiteboard system that can remove pen pressure point coordinates that occur secondarily around a true pen pressure application point.

In order to achieve such an object, the present invention detects only the coordinates of a writing pressure point corresponding to a point where a writing pressure equal to or higher than a predetermined writing pressure is applied among the writing pressure application points.

The present invention will be explained in detail below using the drawings. FIG. 1 is a top view of a blackboard used in an embodiment of the present invention, and FIG. 2 is a cross-sectional view. In the figure, 1 and 2 are a horizontal electrode group and a vertical electrode group arranged in a matrix, and an elastic conductor sheet 3 is inserted between these electrode groups. This elastic conductor sheet 3 is a composite material in which homogeneous conductive fibers (acicular carbon fibers) 3b are embedded in a sheet-like silicon rubber 3a, which is an insulator, as shown in a cross-sectional view in FIG. When pressure is applied as shown by the arrow, the silicone rubber 3a deforms and the carbon fibers protrude and are pressed against both sides of the sheet, changing the resistance value. In FIG. 2, when the choke 4 is pressed down, the resistance value of the elastic conductor sheet 3 changes and this change is extracted from the horizontal electrode group 1 and the vertical electrode group 2.
In this case, the distance d between adjacent electrodes is the resolution limit.

FIG. 4 is a block diagram showing one embodiment of the present invention, which is a pressure sensor type blackboard having the structure shown in FIGS. 1 and 2. FIG.

The vertical electrode group 2 of this blackboard 10 is an x-coordinate switch circuit 11
The horizontal electrode group 1 is connected to a y-coordinate switch circuit 12. And these x coordinate switch circuits 1
1 and the y-coordinate switch circuit 12 perform scanning according to a control signal from the scan control circuit 13, and when the point to which pen pressure is applied is scanned, the x-coordinate switch circuit 11 outputs a detection signal. The output of the x-coordinate switch circuit 11 is converted into an analog/digital converter (hereinafter referred to as A/D converter) 14.
The output of the maximum pen pressure point detection circuit 15 is supplied to the microcomputer 6 via the maximum pen pressure point detection circuit 15.
supplied to A control logic circuit 17 decodes signals from the microcomputer 6 to control the scanning control circuit 13 or the storage circuit control section.
On the other hand, the memory circuits 19 and 20' are the scanning control circuit 13.
, various information is supplied from the microcomputer 16, and reading and outputting of the information is performed under the control of the storage circuit control section 18.

Note that 21 is a transmitter that converts the signal sent from the microcomputer 6 into a signal suitable for transmission over the telephone line L, and 22 is a display unit 23 that converts the signal sent from the microcomputer 6 into a signal suitable for transmission over the telephone line L.
This is a receiving section that converts the signal into a signal that is compatible with the standard. The operation of the electronic whiteboard system according to the present invention configured as described above is as follows.

Before entering into a detailed explanation, first, in order to facilitate understanding of the present invention, the general operation will be explained using the circuit diagrams shown in FIG. 5 and FIG. When no pressure is applied on the blackboard 10, the fifth
As shown in the figure, scanning is performed in which all the y-coordinate switch circuits 12 are turned on, and the x-coordinate switch circuits 11 are sequentially turned on one by one.

At a certain point the coordinates (fu, Y.

), the x-coordinate switch circuit 1
A detection signal is obtained from the x-coordinate switch circuit 11 at the time when 1 scans the sentence=fu. Once this detection signal is obtained, x
The coordinate switch circuit is fixed at x=F, and the y-coordinate switch circuit 12 is sequentially scanned as shown in FIG.
Then, when the y-coordinate switch circuit 12 scans y=Yo, a detection signal is again obtained from the x-coordinate switch circuit 11. Since the first pen pressure point coordinates x=F, y:Yo have been detected, next, based on this point, only the electrodes in a predetermined range are scanned one pixel at a time in the horizontal and vertical directions.

This allows detailed partial scanning around x=~, y=Yo. In this case, for example, a range of 8 pixels is scanned around x = Fu, y = Yo, and the scanning speed of 1 pixel is 8 h.
s, the scanning frequency is as follows.

7=57-8KHZ This value is the scanning frequency of 56.8kHz when scanning one pixel at a time. Approximately 1'100 of wound MH2
0, and it is easy with current transmission technology to transmit the signal corresponding to the coordinates of the pen pressure point taken by this scanning frequency through a telephone line whose bandwidth is limited by the bandwidth of pine HZ. In this specification, the state until the coordinates of the first pen pressure point is detected (that is, the scanning state in which the length of one side of the blackboard 10 is performed as a unit is a line scan, and the coordinates of the first pen pressure point are detected. The state after scanning, that is, the scanning state in which only a predetermined range is scanned pixel by pixel, is defined as partial scanning.Once the initial pen pressure point coordinates are detected and the predetermined scan range is set, the predetermined scan range will be set. By performing partial scanning while moving the pen in the direction in which the coordinate signal changes, it is possible to track the pen pressure points.

Then, when the pen pressure point cannot be detected, the partial scanning returns to the line scanning and the entire blackboard 10 is scanned. In this case, when writing a broken line, etc., the writing pressure is temporarily removed from the blackboard 10. Therefore, if there is no pen pressure, you can reduce the number of line scans by checking that there is no pen pressure in that range even after scanning several frames of the last partial scan, and then proceeding to line scan. It is possible to reduce the amount of noise and detect minute ranges with high accuracy. Note that the blackboard 10, which has pixels of 490 x spots 1, is scanned at 57. It takes 5.5 seconds to sequentially scan all the pixels in 2-day departure, but it takes the same 57.
If line scanning is performed even at the Fox HZ frequency, the time to scan one frame will be as follows. 5.5×Kihi = 2 plates S Therefore, the coordinates of the pen pressure point applied on the blackboard 10 can be detected within 2 plates S, and a practically sufficient performance can be obtained.

Next, the block diagram of FIG. 4 will be explained in detail.

The scanning of the blackboard 10 is carried out according to the flowchart shown in FIG. A signal is supplied to turn on one switch among the switch circuits 11. Therefore, the control logic 17 decodes this signal and controls the scanning control circuit 13 to the state shown in FIG. 7B, which is the state according to the signal from the microcomputer 16. At this time, unless pressure is applied to the blackboard 1, no coordinate signal is output from the x-coordinate switch circuit 11, so the microcomputer 16 switches the adjacent new x-coordinate switch in place of the currently on x-coordinate switch. The control logic 17 sends a signal that turns on the
Send to. By this, control logic 1
Step 7 turns on the adjacent switch of the x-coordinate switch circuit 11, which has been on until now, while keeping all the y-coordinate switch circuits on. Also at this time, the x-coordinate switch circuit 11
If the detection signal is not output from the Repeat the action. Here, when a pen pressure is applied to the blackboard 1, a detection signal is output from the x-coordinate switch circuit 11, and this signal is passed through the A/D converter 14 and the maximum pen pressure point detection circuit 15 to the microcontroller. The state shown in FIG. 5 is reached when the computer 16 is integrated.

Then, the microcomputer 16 fixes the x-coordinate switch circuit 11 to the switch that outputs the detection signal, and supplies the control logic 17 with a signal that turns on one switch among the y-coordinate switch circuits 12. Therefore, the control logic 17 decodes this signal and controls the scanning control circuit 13 in accordance with the signal from the microcomputer 16, resulting in the state shown in FIG. In this case, if no detection signal is obtained from the x-coordinate switch circuit 11, the microcomputer 16
In the same way as when scanning 1, the scanning points are sequentially transferred to adjacent squares. As the y-coordinate switch circuit 12 is sequentially scanned, the pen pressure point on the blackboard 10 is reached and a detection signal is output from the x-coordinate switch circuit 11, resulting in the state shown in FIG. 7E.

At this time, the memory circuits 19 and 20 also have the scan control circuit 13
From x coordinate switch circuit 11 and y coordinate switch circuit 12
A control signal is supplied, and this control signal is the coordinates of the pen pressure point. For this reason, the microcomputer 1
6 supplies a signal to the control logic 17 to store the control signal as the pen pressure point coordinates, so the control logic 17 decodes this signal and controls the storage circuit control section 18. Therefore, storage circuits 19 and 2
0, the one designated by the storage circuit control unit 18 stores the control signal. The two memory circuits 13 and 20 are provided because this electronic whiteboard system operates in real time, and even when coordinate signals are being stored, the microcomputer 16 is not performing processing for transmission. Is going. For this reason, two circuits are used so that while writing is being performed in one memory circuit, data can be output in the other memory circuit. When the storage of the control signal as a coordinate signal is completed, the microcomputer 16 sets a predetermined range frame for partial scanning based on the location where the detection signal is generated, and controls the scanning of the x-coordinate switch circuit 11 and the y-coordinate switch circuit 12. Start 7th
It will be in the state shown in Figure F.

Therefore, the pen pressure point on the blackboard 10 can be scanned in detail, and this coordinate data is supplied to the microcomputer 16 via the A/D converter 14 and the maximum pen pressure point detection circuit 15. The microcomputer 16 transmits the input data to the transmitter 21.
It is transmitted to the receiving section 22 via the. By the way, the coordinates of the pen pressure point applied on the blackboard generally change over time, so it is necessary to constantly track this pen pressure point and move the range in which the frame is set as necessary. .

For this reason, when scanning the frame, if the first pressure point coordinates detected are different from those one frame ago, a new frame is set again based on the new pressure point coordinates. Then, as shown in FIG. 8, the frame moves in the order of A→B→C→D along with the movement of the pen pressure point, allowing the pen pressure to be tracked. In this case, each time a new pen pressure point coordinate was detected within the scanning range, the frame was moved based on the new pen pressure point coordinate, but if the limit point of the frame was scanned, the "pen pressure point coordinate You can also move it in the direction estimated by the vector of the pen pressure point coordinates.

Further, as described above, after the coordinates of the pen pressure point are no longer detected within the frame, a small range can be detected with high accuracy by performing useless scanning for several frames. The frame is set based on the pen pressure point coordinates, and in the present invention, the frame is set based on the coordinates corresponding to the maximum pen pressure point among the pen pressure point coordinates.

This means that when pressure is applied to blackboard 1, blackboard 10'
Since the elastic conductor sheet used here has elasticity, even if the tip of the chalk, etc. that comes into contact with the blackboard 101 is sufficiently smaller than the resolution range, the brush will not touch the area around the contact area between the blackboard 10 and the chalk. Pressure is applied. For this reason, the setting range of the frame changes depending on how the pen pressure point is selected, so to prevent this, the frame is set based on the maximum pen pressure point. Furthermore, if all pen pressure point coordinates are transmitted to the receiving side, the lines on the display screen will become thicker, and a large amount of information must be sent.

For this reason, the present invention uses the pen pressure point coordinates of the maximum pen pressure point, but it is also possible to use other pen pressure points with a predetermined pen pressure or higher as the pen pressure point coordinates within a range that does not interfere with display. For example, the degree of redundancy increases, so there is an advantage that coordinate loss due to noise is less likely to occur. This maximum writing pressure point detection is performed, for example, with a configuration as shown in FIG.

In the figure, 24 is an input terminal, which is connected to the x-coordinate switch circuit 11 of FIG. and input terminal 24
The detection signal supplied to the analog comparator 25 is input to one input terminal of the analog comparator 25. Since the other input terminal of this analog comparator 25 is supplied with a voltage that determines the threshold level of pen pressure sensitivity, only when the value of the detection signal is greater than this threshold level, the analog comparator 25 2
5 supplies the output signal to the control end of an analog-to-digital converter (hereinafter referred to as A/D converter) 26. Since the input terminal 24 is also connected to the input terminal of the A/D converter 26, the A/D converter 26 converts the analog signal into a digital signal when the output signal of the analog comparator 25 is supplied, and converts the analog signal into a digital signal. Generates a completion pulse when the conversion is completed.

Then, this completion pulse and digital signal are supplied to the writing pressure maximum point detection circuit 15. The maximum pen pressure point detection circuit 15 is composed of a digital comparator, which temporarily holds the input digital signal, compares it with the next input digital signal, stores the larger value, and outputs it. It is something to do. By comparing the coordinate signals in this way, the maximum pen pressure point where the applied pen pressure is maximum can be detected, so this output signal is sent from the output terminal 27 to the fourth point.
The data is supplied to the microcomputer 16 shown in the figure.

The analog comparator 25 is provided in order to reduce the processing time of the microcomputer 16 by not operating the A/D converter 26 when the writing pressure is less than a predetermined value. In addition to this, there is a method called coordinate midpoint detection as a method for detecting the maximum pen pressure point.

This is because the surrounding points of the maximum pen pressure point are symmetrical with respect to the maximum pen pressure point, so the maximum and minimum coordinate values are determined separately in the vertical and horizontal directions, and (maximum coordinate value + minimum coordinate value) value)/2
The average coordinate value of is set as the point of maximum pen pressure. Furthermore, in the present invention, white characters or figures are displayed on the display screen based on the detected pen pressure point coordinates, so when erasing, black is set and the displayed white part is erased.

In this embodiment, the scanning frequency is set to 57. Although the frequency is set to Gobi 2, it is not limited to this frequency, and although the frame is set in a rectangular shape, other shapes such as a circle may also be used.

As explained above, the scanning method of the electronic whiteboard system according to the present invention detects only the pen pressure point coordinates corresponding to the point where a pen pressure equal to or higher than a predetermined pen pressure is applied among the pen pressure application points. , it has an excellent effect of being able to remove the coordinates of the pen pressure points that occur secondarily around the true pen pressure application point.

[Brief explanation of the drawing]

1 and 2 are a top view and a sectional view of a blackboard used in an embodiment of the present invention, FIG. 3 is a sectional view showing the structure of an elastic conductor sheet used in the blackboard, and FIG. A block diagram showing an embodiment of the invention, FIGS. 5 and 6 are circuit diagrams of the blackboard and the x-coordinate and y-coordinate switch circuits,
FIG. 7 is a flowchart, FIG. 8 is a front view of the blackboard showing the frame moving on the blackboard, and FIG. 9 is a block diagram showing the A/D converter and the maximum pen pressure point detection circuit. 1...Horizontal electrode group, 2...Vertical electrode group, 3
......Elastic conductor sheet, 4...Choke, 10...Sato board, 11...x coordinate switch circuit, 12...y coordinate Switch circuit, 13...
...・Scanning control circuit, 15... Maximum writing pressure point detection circuit,
16...Microcomputer, 19,20...
...Memory circuit. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9

Claims (1)

[Claims] 1. The coordinates of a writing pressure point are detected by horizontally and vertically scanning an image transmission screen consisting of a group of electrodes arranged in a matrix, and the writing image is created based on a signal corresponding to the coordinates of the writing pressure point. In the scanning method of the electronic whiteboard system for reproducing the information, the pen pressure point coordinates are characterized in that only the pen pressure point coordinates corresponding to points to which a writing pressure equal to or higher than a predetermined writing pressure is applied among the writing pressure application points are transmitted. Scanning method for electronic whiteboard system. 2. The scanning method for the electronic whiteboard system according to claim 1, wherein the pen pressure point coordinates transmit only the pen pressure point coordinates corresponding to the maximum pen pressure point among the pen pressure application points.