JPS6118025A - Coordinate detector - Google Patents

Abstract

PURPOSE:To reduce an error of coordinate detection with a small amount of correction data and to improve the detecting accuracy, by storing the correction data on the detection error in response to each position of the conductors provided on a tablet in a single period. CONSTITUTION:The level of a detection error due to the distortion of a voltage waveform produced to the conductor set on a tablet 4 repeats the same change for each cycle and produces the same error at the positions corresponding to each cycle. Therefore, the correction data is also equal at the positions corresponding to each cycle. As a result, an error of the detection value can be corrected at each position as long as just the correction data of a single cycle is stored in a ROM8f. The areas shown by oblique lines show the correction data which are stored inthe ROM8f. Thus a coordinate detection error can be reduced with a small amount of correction data. Then the coordinate detecting accuracy is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coordinate detection device that detects the position of a pen, cursor, etc. on a tablet.

The coordinate detection device includes an electromagnetic device such as a pen or a cursor, and a device that supplies a sinusoidal voltage of a predetermined frequency to the electromagnetic device.
When a tablet in which Y-axis conductors, Y-axis conductors, etc. are arranged in a periodic pattern, and the electromagnetic device are placed on the tablet, the signals generated in each conductor of the tablet are processed and the electromagnetic device is activated. It consists of an arithmetic and control unit that calculates the position. An outline of such a coordinate detection device will be explained below.

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 on which necessary conductors such as X-axis circumferential conductors and Y-axis conductors are arranged in a predetermined pattern; 5 is a tablet that processes signals 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 on the tablet 4 and their output voltages will be explained.

FIGS. 7(a), (b), CC') are wiring diagrams of the X-axis circumferential conductor arranged on the tablet and waveform diagrams of generated voltages. In the figure, only the X-axis circumferential conducting wire is shown, and other conducting wires are not shown. This X-axis circumferential conducting wire is composed of a cosine line 6 and a sine line 7, as shown in FIG. 7(a). Both the cosine line 6 and the sine line 7 have the same pitch in one period (pitch p), and the sine line 7 is wired with a pitch 1/4p smaller than the cosine line 6. c.
Both ends of the os line 60 are connected to the terminal a1+at, and both ends of the sine line 7 are connected to the terminals s, , b. Now, the 6th
The voltages generated when the cursor 3 shown in the figure is placed at the position shown in the figure are shown in FIGS. 7(b) and 7(C). Figure 7(a) shows co
FIG. 7B shows the voltage waveform Vc generated between the terminals aleJ of the s line 6, and the voltage waveform Vs generated between the terminals b1 and 62 of the sine line 7. Each of these voltages is the sixth
The data is input to the arithmetic control unit 5 shown in the figure, 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.

Incidentally, in the coordinate detecting 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, a method has been adopted in which the accuracy of each position on the entire surface of the tablet 4 is measured by actual measurement, and the detected value is corrected based on the measured data. However, with such means, there is a drawback that if the 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 eliminate such conventional drawbacks and provide a coordinate detection device that can reduce errors and improve detection accuracy with a small amount of correction data.

In order to achieve this object, the present invention stores correction values for correcting errors that occur in conductors arranged in a predetermined pattern in a plurality of periods in a tablet corresponding to each position within one period in these plurality of periods. The coordinate value obtained by the calculation means is corrected using the correction value.

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 is the same tablet as shown in FIG. 6, and 8 is an arithmetic control section. The arithmetic control section 8 includes a multiplexer 8a that sequentially switches and inputs the signals generated in each conductive wire 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 ii, ) 8c, ROM (I
J-do only memory) 8d1 RAM (Random Access Memory) for temporarily storing manually generated values, calculation results, etc. 8e1 ROM (Read Only Memory) for storing correction values 8f1 and calculated values It consists of an output section 8g that outputs.

The value output from the output section 8g is displayed on the display device (CR, T),
The data will be input to a recording device, etc.

Here, the correction values stored in the ROM 8f will be explained. Generally, the error that occurs in a coordinate detection device is
By electromagnetic coupling between the cursor 3 and each conductive wire placed on the tablet 4, the output waveform of each conductor changes as shown in FIG.
) and (C), which are not ideal sine waves but include waveforms close to triangular waves or trapezoidal waves, which is considered to be the cause of distortion in many cases. 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 cursor 3 is placed at a certain position within one cycle of each conductor.
The waveform distortion that occurs when the cursor 3 is placed is the same as the waveform distortion that occurs when the cursor 3 is placed at the corresponding position in another cycle. To explain this using the layout diagram of the conducting wires shown in FIG. 7(a), now s i n 1li1
When the cursor 3 is placed at a point qt (within the first period) located at a distance r from the conductor portion 71 where the first period of sin line 7 starts, and when the second period of sin line 7 starts. A point q located at the same distance r as in the previous case from the conducting wire portion 72,
If cursor 3 is placed on CO8O2O3 child a
The voltage waveform generated between 1+am and the terminal of sin wire 7,
, b, and the voltage waveforms generated between them should be the same waveform with the same distortion. Therefore, the errors due to distortion of the voltage waveform occurring at each corresponding position within each period of the conductor (point q and point qt in the above example) are 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 represents 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 cycle.

Therefore, if the correction data for one cycle is stored in the box 0M8f shown in FIG. 1, errors in detected values at all positions can be corrected. In FIG. 2, the shaded portion is the 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 ridge is generated in the conductive wire placed on the tablet 4 according to the position, and this voltage is applied via the multiplexer 8a% A/D converter 8b. The CPU 8c performs a predetermined calculation based on the imported value and calculates the coordinate value of the cursor 3 (first step 8s).The flowchart shown in FIG. 3 only applies to the X axis. The calculated coordinate value is X. Next, from this value X, the number of cycles included in the value
(excluding the final period) multiplied by the pitch p of the period and subtracts the value np to find the position X within the final period at the value X (Step S).
(Step Sg) to extract correction data ΔX corresponding to
, this correction data ΔX is added to the value X to calculate a corrected value X' (step S4). As a result, errors caused by voltage waveform distortion can be almost eliminated, and more accurate coordinate values can be obtained. The calculated value X' is output to the external device via the output section 8g (step 5Il).
).

Note that the correction data does not need to be stored in a separately provided ROM, and can also be stored in a ROM that stores the processing procedure of the CPU.

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 output, and the previously detected coordinate value is corrected with this correction data. The correction 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 example is the first
What is different from the embodiment is that the RO stores other correction data.
It is equipped with M8h. The correction data stored in fl, 0M8h 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 errors caused by the following phenomena can also be considered. ,
Although the error shown earlier is not very large, it cannot be completely ignored. That is, 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 during use will expand or contract compared to the dimensions of the tablet during processing. This will cause 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 as curves A and B shown in FIG. ifMC is a straight line indicating 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 is created based on the obtained straight line C), and a value corresponding to the slope of this straight line is stored in the ROM 8h as correction data. To store the correction data in the ROM$h, set a predetermined coefficient k (for example, 0.1/) in advance, and use an external input device (for example, a digital switch) to input a multiplier m ( slope of straight line)
This is done by inputting digital values to create correction data.

Next, the operation of this embodiment will be explained. Tablet 4
The position of the cursor 30 placed at an arbitrary position above is calculated using a predetermined calculation, similar to step S1 shown in FIG. First, the calculated value X is corrected for the expansion/contraction error of the tablet. That is, a large amount of correction data (kXm) is output from the ROM 8h, and the CPU 8c performs calculations according to the following equation.

X'=X (1+k Thereafter, the obtained value X' is subjected to multiple processing in steps S to S4 shown in FIG. 3 to reduce errors due to expansion and contraction of the tablet 4 and periodic differences due to distortion of the voltage waveform. It is possible to output coordinate values.

In addition, the correction data (kXm) is stored in ROM8d or OM
If 8f is a storable LOM, it can be stored in these, and J)RO to 18h can be omitted.

In this way, in this embodiment, correction data for detection errors due to voltage waveform distortion and correction data for the detection side lid due to expansion and contraction of the tablet are recorded, and these correction data are used to calculate f-EJ Since the standard value is corrected, it is 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 distortion of the voltage waveform occurring in the conductive wire arranged on 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, errors in the coordinate values can be reduced by a small amount of correction data, and the accuracy of the detected values of the coordinate detection device can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the calculation 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 is the operation of the calculation side RI 141 section shown in FIG. 1. FIG. 4 is a block diagram of the arithmetic control unit 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 figure is a block diagram of the coordinate detection device, Fig. 7 (a), (b)
, (C) is a layout diagram of conductive wires arranged in the doublet and a waveform diagram of the generated voltage. 1... Sine wave generation circuit, 3... Cursor, 4... Tablet, 6... COS line, 7... Song...
Sin line, 8... Arithmetic control section, 8a...
・Multiplexer, 8b...A/D converter, 8
C...CPU, 8d, 8f. 8h...ROM, '8e...RAM,
8g...Output section.

Claims (2)

[Claims] (1) An excitation device that is excited at a predetermined oscillation frequency, a tablet that is arranged with conducting wires in a predetermined pattern having periodicity and generates an output according to the position of the excitation device, and the excitation device that is excited based on the output of the tablet. A coordinate detection device comprising: a calculation means for calculating a position of the device; A coordinate detection device comprising: a correction means for correcting the position of the excitation device calculated by the calculation means using a correction value stored in the storage section. (2) In claim (1), the correction means is a first means for determining the position within the final cycle from the coordinate origin based on the position of the excitation device calculated by the calculation means. , a second means for determining a correction value stored in the storage section corresponding to a position within the cycle determined by the first means; and a second means for calculating the correction value determined by the second means by the calculation means. A coordinate detection device comprising: an addition means for adding to the calculated position of the excitation device.