JPH03201018A - Position detector and its sense part - Google Patents

Abstract

PURPOSE:To reduce the invalid area of a sense part by increasing the arrangement density of loop coils at the points near both ends of the sense part in its position detecting direction. CONSTITUTION:At a sense part of a position detector, the loop coils (c), (d)... having the width D are arranged in a pitch P in the position detecting direction (X direction). The loop coils (a') and (b') having the widths D1 and D2 (D1<D2<D) are arranged so that a space P is obtained between the right lines of both coils (b') and (c) together with a space P is obtained between the right lines of both coils (a') and (b') respectively. Thus an area where a position can be specified is set at the right of a position x1' where the signals Ea' and Ec produced at the loop coils cross to each other. Meanwhile an area where no position is specified, i.e., an invalid area is set between a position x0 at one of both ends of the sense part and the position x1'. As a result, the invalid area of the sense part is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a position detection device using electromagnetic action and a sensing section thereof.

(Prior Art) Conventionally, based on the electromagnetic interaction between a sensing unit including a large number of loop coils arranged in parallel in the position detection direction and a position indicator having at least a coil, a position specified by the position indicator is detected. 2. Description of the Related Art Position detection devices that obtain coordinate values are known. Position detection in this type of device involves selecting one loop coil from among a large number of loop coils in the sense section, and when an AC signal is supplied to the second loop coil (or the coil of the position indicator), the coil of the position indicator (or the above-mentioned - loop coil), or an alternating current generated in the - loop coil by radio waves emitted from the tuned circuit of the position indicator excited by radio waves generated from the - loop coil or other loop coils. This is achieved by detecting the signal level, sequentially switching the selected loop coils, and performing a predetermined calculation using the signal level that depends on the distance between the position indicator and each loop coil. was.

FIG. 2 shows the main part of the sensing section of a conventional position detecting device of this type and the signals generated in each loop coil thereof. In the figure, a, b, c, d, . . . are loop coils each having a width, and are arranged in parallel at a pitch P in the position detection direction, here the X direction. Also, Ea, E
b, Ec, Ed, ...... each loop coil a, b, c when the position indicator (not shown) is moved in the X direction
, d, . . .

By the way, there are various methods of calculating the coordinate values mentioned above,
Typically, there are three signal levels consisting of the maximum signal level, i.e. the signal level when the loop coil closest to the position indicator is selected, and the signal level when the loop coils on either side of it are selected, or further on both sides. Calculations are made based on four signal levels, including the signal level when the closest loop coil is selected by the position indicator among the loop coils.

(Problem to be Solved by the Invention) However, near both ends of the sensing section of the device in the position detection direction, there are areas (hereinafter referred to as invalid areas) where the three or four signal levels described above cannot be obtained. However, there is a drawback that position detection cannot be performed within the invalid area.

Furthermore, the size of the ineffective area is determined by the width of the loop coil and the calculation method of the coordinate values, and the size of the entire sensing section, in other words, the size of the area where the position can be detected (hereinafter referred to as effective area). Therefore, there is a problem in that the proportion of the ineffective area in the sensing section becomes large, especially in small devices such as those that are integrally combined with a liquid crystal display panel or used in electronic notebooks.

In FIG. 2, position X of one end of the sense section. and signal Ea
The area between position X1 where and Ec intersect is an invalid area when using the coordinate value calculation method based on the four signal levels described above. There are invalid areas.

An object of the present invention is to reduce or completely eliminate the ineffective area in the sensing section of a position detection device.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention provides an electromagnetic interaction between a sensing section having a large number of loop coils arranged in parallel in the position detection direction and a position indicator having at least a coil. In the position detecting device that determines the coordinate values of a specified position by the position indicator based on
Means is provided for determining the coordinate values for at least part of the vicinity of both ends using a method different from that for other parts.

(Function) According to the present invention, a larger number of signals are obtained near both ends of the sensing section in the position detection direction compared to other parts, thereby expanding the area in which the position of the position indicator can be specified (
(or an unspecified area is caught), and its coordinate values are determined using a different method from that of other parts, and as a result,
The invalid area occupied by the sense section becomes smaller or disappears altogether.

(Embodiment) FIG. 1 shows the main parts of the first embodiment of the sensing section of the position detection device of the present invention and the signals generated in each loop coil thereof. In the figure, the same components as in FIG. are represented by the same symbols. i.e. c, d.

Loop coils e, f, . . . each have a width, and are arranged in parallel at a pitch P in the position detection direction, here the X direction. Further, a' and b' are loop coils having widths D1 and D2 (Dl<D2<D), respectively, and the distance between the lines on the right side of the loop coil b' is P with respect to the loop coil C, and Loop coil a' is arranged such that the distance between the lines on the right side of loop coil b' is P. Also, Ea-, Eb
-, Ec.

Ed, Ee, Ef, . . . are each loop coil a when the position indicator (not shown) is moved in the X direction.

Signals occurring at b=, c, d, e, f, . . . are shown.

In the sense section, the area whose position can be specified by the coordinate value calculation method based on the four signal levels described above is the area to the right of the position x, - where the signals Ea- and Ec intersect, and the area which cannot be specified, i.e. The invalid area is at position X at one end of the sense section. and the position X, -. Here, as described above, since the widths of the loop coils a' and b' are narrower than the loop coils a and b of the conventional example, the ineffective area of this embodiment is smaller than that of the conventional example.

However, even if it is to the right of the position x, -, the position where four signals can be obtained from the loop coil having the original width,
That is, on the left side of the position x2 where the signals Ec and Ee intersect, accurate coordinate values cannot be obtained even if the calculation is performed as is.

Therefore, for the area between positions xl - and x2 (hereinafter referred to as the interpolation area), the correspondence between the predetermined calculated values based on each signal and the actual coordinate values (interpolated values) is investigated in advance and compiled into a table. The interpolated value may be read out during position detection.

Although not shown, the loop coil at the other end of the sensing section has a similar configuration, and its ineffective area is smaller than that of the conventional example, and there is also an interpolation area similar to the above, but it can be Correct coordinate values can be determined.

FIG. 3 shows details of the interpolation area, which is further divided into a plurality of areas depending on the magnitude of the signal of each loop coil. That is, the position Xll where the signals Ea- and Ec intersect
, the position x1□ where the signals Eb- and Ed intersect, and the signal E
c and Ed intersect at position X13, here, between position x, - and Xll, between Xll and x1□, and x
The areas between 1□ and X13 and between X13 and x2 are designated as areas I, II, ■, and ■, respectively. Also, Fig. 4(a)
(b) (c) (d) are each area I, II, ■
The correspondence between the actual coordinate values and the calculated values in and ■ is shown.

During actual position detection, the area where the position indicator exists is detected from the signal level of each loop coil, and a table of the corresponding area is prepared in advance with interpolated values corresponding to the calculated values obtained by performing predetermined calculations. This is done by reading from

Fig. 5 shows an example of a position detection device using the aforementioned sense section, and here is an example applied to a device that determines the coordinate values of a specified position by reciprocating radio waves between the sense section and a position indicator. shows. In the figure, 1 is a sense section, 2 is a selection circuit, and 3
4 is an oscillator, 5 is a signal detection circuit, 6 is a processing device, and 7 is a position indicator.

The sense unit 1 includes the aforementioned large number of loop coils ab-, c,
It consists of d,... The selection circuit 2 selects one loop coil from a large number of loop coils in the sensing section 1, and operates based on selection information from the processing device 6. The transmission/reception switching circuit 3 connects the selected loop coil to the oscillator 4 and the signal detection circuit 5 alternately, and operates based on a switching signal from the processing device 6.

The oscillator 4 has a predetermined frequency f. generates a reference clock for
This is supplied to the transmission/reception switching circuit 3 via the processing device 6 and a low-pass filter and drive circuit (not shown). The signal detection circuit 5 includes an amplifier, a bandpass filter whose passband is the frequency f, a detector, and a low-pass filter, and the signal detection circuit 5 includes an amplifier, a bandpass filter whose passband is the frequency f, a detector, and a low-pass filter.

Outputs a DC signal with a level corresponding to the energy of the component.

The processing device 6 is composed of a well-known microprocessor or the like, and has the frequency f. A transmission/reception switching signal is created from the reference clock of the transmission/reception switching circuit 3, and the selection circuit 2
is controlled to switch the loop coil of sense unit 1, and
The output level of the signal detection circuit 5 is set to analog/digital (
A/D) conversion is performed, and the arithmetic processing described later is executed to obtain the coordinate values of the position designated by the position indicator 7.

The position indicator 7 has a built-in tuning circuit 8 consisting of passive elements such as a coil and a capacitor, and the tuning frequency of the tuning circuit 8 is the frequency f of the reference clock mentioned above. is set to .

FIG. 6 is a flowchart of the processing in the processing device 6, and the operation will be explained below according to this flowchart.

First, the processing device 6 causes the selection circuit 2 to select - of the sense section 1.
At the same time, a signal for selecting the transmitting side is sent to the transmitting/receiving switching circuit 3, and the above-mentioned -
frequency f based on the reference clock of the oscillator 4 in the loop coil of. by supplying a sinusoidal signal of frequency f. generate radio waves. At this time, when the position indicator 7 is placed on the sensing section 1, the radio wave excites the tuning circuit 8, which receives the frequency f. generates an induced voltage.

When the processing device 6 sends out a signal to select the sending side to the transmission/reception switching circuit 3 for a certain period of time, it sends out a signal to select the receiving side.
Eliminates radio waves generated by the loop coil. On this occasion,
The induced voltage generated in the tuning circuit 8 of the position indicator 7 gradually attenuates in accordance with its loss and reaches a frequency f. A radio wave is transmitted, which in turn excites the loop coil mentioned above, generating an induced voltage.

After the processing device 6 sends a signal for selecting the receiving side to the transmission/reception switching circuit 3 for a certain period of time, it sends out a signal again for selecting the sending side, and thereafter transmits and receives the same radio waves as described above multiple times for the loop coil of -, for example. Repeat a total of 4 times. Next, the processing device 6 changes the information sent to the selection circuit 2 to switch the loop coil to be selected, and thereafter transmits and receives radio waves in the same manner as described above for all the loop coils of the sensing section 1 (
Step 81).

The induced voltage generated in the loop coil of the sensing unit 1 during the above-mentioned four reception periods is averaged by the bandpass filter of the signal detection circuit 5, further detected, converted into a DC signal, and sent to the processing device 6. Since the level of the DC signal is a value that depends on the distance between the position indicator 7 and the loop coil, the processing device 6 determines whether the maximum value is greater than or equal to a predetermined threshold (step 82 ), it is determined whether the position indicator 7 is within the effective reading height of the sensing section 1. If it is determined that the position indicator 7 is within the above height, four signals are extracted in descending order of the level from the obtained signals for each loop coil, and these are Eo.
, El, E2. E3 (Eo > El > E2 > E3)
(Step S3). Note that if it is determined that there is no position indicator 7 within the height, the process of step S1 is repeated.

Next, the processing device 6 processes the obtained signal E. - The area where the position indicator 7 exists is determined based on E3 (step 84). FIG. 7 is a detailed flowchart of the area determination process.
(2) It is determined whether the object exists in the normal area or in the normal area.

As a result of the determination, if the position indicator 7 is within the invalid area, the processing device 6 repeats the process of step S1 described above (
Step S5). Further, if the position indicator 7 is in the normal area within the effective area (step S6), the signal E, -
Step S7 to perform well-known coordinate calculation based on E3.
), the coordinate values of the position designated by the position indicator 7 are determined. On the other hand, if the position indicator 7 is in any of the areas I to (3), the signal E is received. -E3 is used to calculate the following formula to obtain a calculated value F (step S8), and the coordinate values corresponding to the calculated value F are read out from a pre-stored table of the corresponding area (step S9).

F= (Eo El 1 E2 E3) / (Eo
-E2+E, -E3) The coordinate values obtained in this way are transferred to a host computer (not shown) and processed as appropriate (step 51).
0).

FIG. 8 shows the main part of the second embodiment of the sensing section of the present invention and the signals generated in each loop coil thereof.
Components that are the same as those in FIG. 2 are represented by the same reference numerals. That is, a, b, c, d, . . . are loop coils each having a width, and are arranged in parallel at a pitch P in the position detection direction, here the X direction. Further, p and q are loop coils having widths D3 and D4 (D3 x D4 <D), respectively, and the left side of loop coil p is very close to the left side of loop coil a, and the line on the right side of loop coil p is very close to the left side of loop coil a, and so that the wire is located on the dirt floor between the wires to the left of loop coils C and d.
Also, the line on the left side of loop coil q is loop coil p.
The loop coils are arranged so that they are very close to the line on the left and the line on the right is located between the lines on the left of loop coils d and e. Also, Ep.

Eq, Ea, Eb, Ec, Ed, ・------ is each loop coil p when the position indicator is moved in the X direction.

Signals occurring at q, a, b, c, d,... are shown.

According to the sensing section, four signal levels can be detected in most parts of the invalid area in the conventional example, and the position can be specified. can do. Note that the interpolation method is basically the same as in the first embodiment.

Although not shown, the loop coil at the other end of the sense section has a similar configuration, and its invalid area is also O.
Interpolation for the interpolation area can also be performed in the same manner as described above.

FIG. 9 shows details of the interpolation area, where the signal Ep
and Eq intersect at position X21, signal Ep and Eb intersect at position X22, and signal Eq and Eb intersect at position X
23 and signals Ea, l! :Position X24 where Eb intersects
It is divided into multiple areas ■, ■, ■, ■, and ■. Further, FIGS. 10(a), (b), (c), (d), and (e) show the correspondence between the actual coordinate values and calculated values in each of the areas (2), (2), (2), (2), and (2). Further, FIG. 11 shows a detailed flow of area determination processing in a processing device when the sensing section of this embodiment is used in the position detection device of FIG. 5.

In addition, although the above embodiment detects the coordinate value of a specified position in only one direction of the X direction, another sense part similar to the sense part 1, that is, a sense part in the Y direction, is arranged so that they are orthogonal to each other. are placed close to each other, and a selection circuit and a transmission/reception switching circuit similar to the selection circuit 2 and transmission/reception switching circuit 3 are connected thereto;
Furthermore, by providing an XY switching circuit between these two selection circuits and transmission/reception switching circuits, and the oscillator and signal detection circuit, and by slightly changing the program of the processing device 6, it is possible to set specified positions in two directions, the X direction and the Y direction. It goes without saying that the coordinate values of can be detected.

(Effects of the Invention) As explained above, according to the present invention, since the arrangement density of the loop coils is increased near both ends of the sensing section in the position detection direction, a larger number of signals can be obtained compared to other parts. As a result, the area where the position of the position indicator can be specified is expanded (or the area where the position cannot be specified is narrowed), and
Since the coordinate values for at least part of the vicinity of both ends are determined using a different method from that for other parts, correct coordinate values can be obtained, thereby reducing or eliminating the invalid area in the sense section. A more useful position detection device and its sensing section can be provided.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the main parts of the first embodiment of the sensing section of the position detecting device of the present invention and the signals generated in each loop coil thereof, and FIG. 2 is the main part of the sensing section of the conventional position detecting device. An explanatory diagram showing signals generated in the section and each loop coil thereof,
FIG. 3 is an explanatory diagram showing details of the interpolation area in the first embodiment of the present invention, and FIG. 4 (a) (b) (c) (d
) is an explanatory diagram showing the correspondence between the actual coordinate values and calculated values in the interpolation area of FIG. is a flowchart of processing in the processing device of the position detection device in FIG. 5,
FIG. 7 is a detailed flowchart of the area determination process in the processing device of the position detection device using the sense section of the first embodiment, and FIG. FIG. 9 is an explanatory diagram showing the main part and signals generated in each loop coil thereof. FIG. 9 is an explanatory diagram showing details of the interpolation area in the second embodiment of the present invention. FIGS. 10 (a) (b) (c
) (d) (e) is an explanatory diagram showing the correspondence between the actual coordinate values and calculated values in the interpolation area in Figure 9, and Figure 11 is an illustration of the position detection device using the sense unit of the second embodiment. It is a detailed flowchart of area determination processing in a processing device. 1: Sense section, 2: Selection circuit, 3: Transmission/reception switching circuit, 4:
Oscillator, 5: Signal detection circuit, 6: Processing device, 7: Position indicator, a, a-, b, b-c, d, ... p, q, ...
...: Loop coil.

Claims (8)

[Claims] (1) A position where the coordinate values of a specified position by the position indicator are determined based on the electromagnetic interaction between a sensing unit made up of a large number of loop coils arranged in parallel in the position detection direction and a position indicator having at least a coil. In the detection device, the arrangement density of the loop coils is increased near both ends of the sensing section in the position detection direction, and means is provided for determining coordinate values for at least a portion of the vicinity of the both ends using a method different from that for other parts. A position detection device characterized by: (2) The position detection device according to claim 1, wherein the loop coils near both ends of the sense section in the position detection direction are narrower than the loop coils therebetween. (3) Claim (1) characterized in that the width of the loop coils near both ends of the sensing section in the position detection direction is narrower than the loop coils between them, and becomes narrower as it approaches the ends.
) position detection device. (4) The position detection device according to claim (1), characterized in that loop coils each having a width narrower than the other loop coils are added near both ends of the sense section in the position detection direction. (5) At least two types of loop coils, each narrower than the other loop coils and having different widths, are added near both ends of the sensing section in the position detection direction, with the narrower loop coil being closer to the end. Claims (
1) The position detection device described above. (6) A table showing the correspondence between the values for specifying the coordinate values of the specified position by the position indicators existing near both ends and the actual coordinate values, and means for determining whether the position indicators exist near both ends. and means for calculating values for specifying the coordinate values of the positions specified by the position indicators located near both ends, and means for reading out actual coordinate values corresponding to the calculated values from the table. Claims (1) to (5)
) The position detection device described in any of the above. (7) A position detection device characterized in that a large number of loop coils having a predetermined width are arranged in parallel in the position detection direction, and loop coils each having a width narrower than the loop coils are added near both ends of the position detection direction. sense department. (8) A large number of loop coils with a predetermined width are arranged in parallel in the position detection direction, and at least two types of loop coils each having a narrower width and different width than the loop coil are arranged near both ends of the position detection direction. A sensing section of a position detecting device, characterized in that a loop coil is added closer to an end.