JPH0326845B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coordinate detection device for detecting the position of a marker, cursor, etc. on a tablet.

The coordinate detection device consists of an electromagnetic device such as a cursor, a device that supplies a sine wave voltage of a predetermined frequency to the electromagnetic device, and a tablet in which X-axis conductors, Y-axis conductors, etc. are arranged in a periodic pattern. The device is comprised of an arithmetic and control unit that processes signals generated in each conductor of the tablet to calculate the position of the electromagnetic device when the electromagnetic device is placed on the tablet. An outline of such a coordinate detection device will be explained with reference to the drawings.

FIG. 6 is a block diagram of the coordinate detection device. In the figure, 1 is a sine wave generating circuit that generates a sine wave of a predetermined frequency, 2 is an amplifier that amplifies the sine wave voltage of the sine wave generating circuit 1, and 3 is a cursor having a resistor 3R and a coil 3L. 4 is a tablet in which required conductors such as X-axis conductors and Y-axis conductors are arranged in a predetermined pattern; 5 is a tablet that performs arithmetic processing on the signal output from the tablet 4 when the cursor 3 is placed on the tablet 4; This is an arithmetic control section. Here, the conductive wires arranged in the tablet 4 and their output voltages will be explained.

Figure 7 a, b, c are Xs placed on the tablet.
FIG. 2 is a wiring diagram of a shaft conductor and a waveform diagram of a generated voltage. In the figure, only the X-axis conducting wire is shown, and other conducting wires are not shown. This X-axis conductor is the 7th
As shown in Figure a, it is composed of a cosine line 6 and a sine line 7. Both the cosine line 6 and the sine line 7 have the same pitch per period (pitch p), and the sine line 7 has the same pitch (pitch p).
The wiring is shifted from the cos line 6 by a pitch of 1/4p. Both ends of the cosine wire 6 are connected to terminals a ₁ and a ₂ , and both ends of the sine wire 7 are connected to terminals b ₁ and b ₂ . Now, when the cursor 3 shown in Fig. 6 is placed at the position shown in Fig. 7 a, the voltage generated is shown in Fig. 7 b, c.
Shown below. 7b shows the voltage waveform Vc generated between terminals a ₁ and a ₂ of the cosine wire 6, and FIG. 7c shows the voltage waveform Vs generated between the terminals b ₁ and b ₂ of the sine wire 7. It is a diagram. Each of these voltages is calculated by the arithmetic control section 5 shown in FIG.
is input, and the X coordinate of the cursor 3 is calculated through predetermined arithmetic processing. Note that since the calculations and controls for this calculation are well known, their explanation will be omitted.

By the way, in the coordinate detection device described above, even if correct arithmetic processing is performed in the arithmetic control section 5, errors cannot be avoided in the detected values. For this reason, conventionally, tablet 4
A method was adopted in which the accuracy of each position was measured by actual measurements over the entire surface, and the detected values were corrected based on the measured data. However, such a method has the disadvantage that if the precision measurement positions are made dense, the amount of correction data becomes enormous, and if the measurement positions are made coarse, the detection accuracy decreases.

SUMMARY OF THE INVENTION An object of the present invention is to provide a coordinate detection device that eliminates such conventional drawbacks and can reduce errors and improve detection accuracy with a small amount of correction data.

To achieve this objective, the present invention provides an excitation device that is excited at a predetermined oscillation frequency, a sin wire and
A tablet in which cosine wires are arranged in a meandering manner at a predetermined period and outputs are generated from the output ends of the sinusoidal wire and the cosine wire according to the position of the excitation device, and the excitation device A coordinate detection device comprising a calculation means for calculating a position of the sine line or the cosine line, the coordinate detection device comprising: a correction value for correcting an output error specific to each position within any one of the periods of the sine line or the cosine line; The present invention is characterized in that it includes a storage unit for storing information, and a correction unit for correcting the position of the excitation device calculated by the calculation unit using a correction value corresponding to the position stored in the storage unit.

In the above coordinate detection device, accurate positions of multiple points within an arbitrary period of each period of the sine line or the cosine line are measured in advance with respect to the tablet. Next, the positions of the multiple points are detected using a coordinate detection device. Next, a correction value is determined based on the error between the measurement result and the detection result for each point, and is stored in the storage section. When the coordinates of the position specified by the excitation device are calculated by the coordinate detection device, a correction value corresponding to the position within the cycle where the position exists is retrieved from the storage unit, and the detected coordinates are calculated using the correction value. to correct.

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 1 is a block diagram of an arithmetic control section of a coordinate detection device according to a first embodiment of the present invention. In the figure, 4
8 is the same tablet as shown in FIG. 6, and 8 is an arithmetic control unit. The arithmetic control unit 8 includes a multiplexer 8a that sequentially switches and inputs the signals generated in each conductor of the tablet 4, an A/D converter 8b that converts the input signals into digital values, and a CPU (central CPU) that performs necessary arithmetic and control operations. Processing device) 8c, this CPU8
A ROM (read-only memory) 8d stores the processing procedure of step c, a RAM (random access memory) 8e temporarily stores input values, calculation results, etc., and correction values are stored.
It consists of a ROM (read only memory) 8f and an output section 8g that outputs the calculated value. The value output from the output section 8g is input to a display device (CRT), a recording device, etc.

Here, the correction values stored in the ROM 8f will be explained. Generally, errors occurring in coordinate detection devices are caused by electromagnetic coupling between the cursor 3 and each conductor placed on the tablet 4, which causes the output waveform of each conductor to have an ideal shape as shown in Figures 7b and c. It is thought that this is often caused by distortion caused by the inclusion of a waveform close to a triangular wave or trapezoidal wave rather than a sine wave. The form of such waveform distortion is expected to vary depending on the manner of electromagnetic coupling between the cursor 3 and each conducting wire, in other words, the positional relationship between the cursor 3 and each conducting wire. However, since the form of waveform distortion is determined by the positional relationship between the cursor 3 and each conductor, the waveform distortion that occurs when the cursor 3 is placed at a certain position within one cycle of each conductor, and the waveform distortion that occurs in other cycles The waveform distortion that occurs when the cursor 3 is placed at the corresponding position should be the same. To explain this using the layout diagram of the conducting wire shown in _{FIG .}
(within the first period), and a point at the same distance r as in the previous case from the conductor section 7 ₂ where the second period of the sin line 7 begins.
When cursor 3 is placed on q ₂ , the voltage waveform generated between terminals a ₁ and a ₂ of cos wire 6 and the voltage waveform generated between terminals b ₁ and b ₂ of sine wire 7 have the same distortion. It should be the same waveform. Therefore, each corresponding position in each period of the conductor (in the above example, point q ₁ and point
The error due to voltage waveform distortion occurring in q ₂ ) is also the same. The above was confirmed not only theoretically but also experimentally.

FIG. 2 is a waveform diagram of detection error. In the figure, the horizontal axis shows the position on the same axis on the tablet, and
The vertical axis represents the magnitude of the error in the detected value.
In the figure, a curve A shows the error at each position, and a dotted curve B shows correction data that is symmetrical about the horizontal axis with respect to the curve A. By performing correction according to curve B for each position, errors due to voltage waveform distortion can be almost eliminated. As is clear from the figure, the magnitude of the error repeats the same change in each cycle, and the same error occurs at the corresponding position in each cycle. Therefore, the correction data also becomes the same data at corresponding positions in each period.

Therefore, by storing correction data for only one period in the ROM 8f shown in FIG. 1, errors in detected values at all positions can be corrected. In Figure 2, the shaded area is
This is correction data stored in the ROM 8f.

Next, the operation of this embodiment will be explained with reference to the flowchart shown in FIG. When the cursor 3 is placed at an arbitrary position on the tablet 4, a voltage is generated in the conductor arranged on the tablet 4 according to the position, and this voltage is applied to the multiplexer 8a, A/
The CPU 8c performs a predetermined calculation based on the imported value.
Calculate the coordinates of cursor 3 (first step
_S1 ). Note that the flowchart shown in FIG. 3 shows only the X axis, and the calculated coordinate value is X. Next, from this value
The multiplied value np is subtracted to find the position x within the final period at the value X (step S ₂ ). Then,
The correction data Δx corresponding to the determined position x is taken out from the ROM 8f (step S ₃ ), and the corrected value is obtained by adding this correction data Δx to the above-mentioned value X.
Calculate X' (step _S4 ). As a result, errors caused by voltage waveform distortion can be almost eliminated, and more accurate coordinate values can be obtained. Calculated value
X' is output to an external device via the output section 8g (step _S5 ).

Note that the correction data does not need to be stored in a separate ROM, and the processing procedures of the CPU are stored.
It can also be stored in ROM.

In this way, in this embodiment, the correction data for detection errors due to voltage waveform distortion is stored in correspondence with each position during one period of the conductor placed on the tablet, and the coordinate values are determined by a predetermined calculation. After being detected, the position within the final cycle of the coordinate value is determined, the correction data corresponding to this position is extracted, and the previously detected coordinate value is corrected using this correction data, so the correction is extremely small. The data can reduce errors in coordinate values and improve detection accuracy.

FIG. 4 is a block diagram of an arithmetic control section of a coordinate detection device according to a second embodiment of the present invention. In the figure, the same parts as those shown in FIG. 1 are given the same reference numerals. This embodiment differs from the first embodiment in that it includes a ROM 8h that stores other correction data. The correction data stored in the ROM 8h will be explained below.

In the previous example, only the error caused by distortion of the voltage waveform due to electromagnetic coupling between the cursor and the conductor was considered, but this is not the only error that occurs in the coordinate detection device, and the following phenomena can also occur. Although the resulting error is not as large as the error shown earlier, it cannot be completely ignored. In other words, if the tablet 4 is processed at a low temperature and the coordinate detection device is used at a high temperature, or vice versa, the dimensions of the tablet 4 during use will expand and contract compared to the dimensions of the tablet during processing. This causes an error in the detected value. The occurrence of such errors is affected not only by the temperature difference between processing and use but also by humidity. Naturally, such an error increases almost proportionally as the detection position moves away from the origin of the tablet 4.

FIG. 5 is a waveform diagram of detection errors including errors due to expansion and contraction of the tablet. In the figure, the horizontal axis represents the position on the same axis on the tablet, and the vertical axis represents the magnitude of the error in the detected value. Curves A and B are the same curves as curves A and B shown in FIG. Straight line C is a straight line that shows the error due to expansion and contraction of the tablet, and its slope is exaggerated to aid understanding. The periodic error due to distortion of the voltage waveform described in the previous embodiment appears exactly in the form centered on this curve C. In order to eliminate this error, correction can be performed using correction data that follows a straight line D (indicated by a broken line) that is symmetrical about the horizontal axis with respect to the straight line C.

The straight line C is obtained by actually measuring at regular intervals under the same conditions as when the coordinate detection device is used or where it is used. Then, a straight line D is created based on the obtained straight line C, and a value corresponding to the slope of this straight line D is stored in the ROM 8h as correction data. To store the correction data in the ROM 8h, set a predetermined coefficient k (for example, 0.1 mm/m) in advance, and use an external input device (for example, a digital switch) to input the multiplier m (the slope of the straight line D) to the coefficient k. ) is input as a digital value to create correction data.

Next, the operation of this embodiment will be explained. The position of the cursor 3 placed at an arbitrary position on the tablet 4 is calculated by a predetermined calculation as in step _S1 shown in FIG. First, the calculated value X is corrected for the expansion/contraction error of the tablet. That is, the correction data (k×m) is taken out from the ROM 8h, and the CPU 8c performs calculations according to the following equation.

X' =
There is also no difference in the pitch of the cycle. Thereafter, the obtained value X' is processed according to steps _S2 to _S4 shown in FIG. 3 to output coordinate values that reduce errors caused by expansion and contraction of the tablet 4 and periodic errors caused by distortion of the voltage waveform. be able to.

Note that the correction data (k×m) can be stored in ROM8d or ROM8f if they are writable ROMs.
h can be omitted.

In this way, in this embodiment, correction data for detection errors due to voltage waveform distortion and correction data for detection errors due to expansion and contraction of the tablet are stored, and the coordinate values obtained by predetermined calculations are corrected using these correction data. This makes it possible to further reduce errors in coordinate values and further improve detection accuracy using extremely small amount of correction data.

As described above, in the present invention, correction data for errors caused by voltage waveform distortion occurring in the conductive wire arranged in the tablet is stored in correspondence with each position during one period of the conductive wire, and a predetermined calculation is performed. Since the coordinate values obtained are corrected according to the correction data, it is possible to reduce errors in the coordinate values with a small amount of correction data and improve the accuracy of the detected values of the coordinate detection device.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the arithmetic control section of the coordinate detection device according to the first embodiment of the present invention, FIG. 2 is a waveform diagram of detection error, and FIG. 3 shows the operation of the arithmetic control section shown in FIG. 4 is a block diagram of the arithmetic control section of the coordinate detection device according to the second embodiment of the present invention, FIG. 5 is a waveform diagram of detection errors including errors due to expansion and contraction of the tablet, and FIG. The block diagram of the coordinate detection device, FIGS. 7a, 7b, and 7c, shows the arrangement of conductive wires arranged in the tablet and the waveform diagram of the generated voltage. 1...Sine wave generation circuit, 3...Cursor, 4...
...tablet, 6...cos line, 7...sin line, 8...
...Arithmetic control unit, 8a...Multiplexer, 8b...
...A/D converter, 8c...CPU, 8d, 8f,
8h...ROM, 8e...RAM, 8g...output section.

Claims (1)

[Claims] 1. An excitation device that is excited at a predetermined oscillation frequency;
A tablet in which a sine line and a cosine line are arranged in a meandering manner at a predetermined period, and outputs are generated from the output ends of the sine line and the cosine line according to the position of the excitation device, and based on each output from this tablet. and a calculation means for calculating the position of the excitation device, wherein the sine line or the cosine
a storage unit that stores a correction value for correcting an output error specific to each position within any one of the periods of the line; and a storage unit that stores the position of the excitation device calculated by the calculation means. A coordinate detection device comprising a correction means for correcting the position using a correction value corresponding to the position stored in the coordinate detection device. 2. In claim 1, the correction means includes a position detection means for determining a position within the cycle in which the position exists based on the coordinates of the position of the excitation device calculated by the calculation means;
reading means for reading out a correction value stored in the storage unit corresponding to the position determined by the position detection means; and addition means for adding the correction value read by the reading means to the coordinates of the position of the excitation device. A coordinate detection device comprising: