JPH0269815A - Coordinate position detector - Google Patents

Abstract

PURPOSE:To improve an S/N and detection precision, to eliminate a trouble on mounting space and to reduce cost by separately providing loop coils for oscillation and for reception and switch-using them. CONSTITUTION:The oscillation loop coil 1 and the reception loop coil 2 are separately arranged on a coordinate input detection board, and an X-axis board and a Y-axis board are crossly arranged on both sides of the detection board. Since the oscillation (transmission) loop coil 1 and the reception loop coil 2 are separate, a field effect transistor in which a large current can be caused to flow can be used as a switch element, and a miniature and conventional switch element can be used for reception. Consequently, the number of using times of the field effect transistor can be restricted to small. Furthermore, there is no influence on resolution when the pattern pitch of the reception loop coil 2 is made narrow even if the pattern pitch of the oscillation loop coil 1 is enlarged. Thus, the S/N and detection precision can be improved at low cost.

Description

[Detailed Description of the Invention] (a) Industrial Application Field The present invention relates to a coordinate position detection device used when inputting information such as handwritten characters or figures into an electronic device such as a computer using an input ben. More specifically, the present invention relates to an electromagnetic induction type coordinate position detection device for detecting an input ben contact position on a coordinate input detection plate.

(b) Conventional technology The electromagnetic induction type coordinate position detection device uses a detection board for coordinate input in which loop coils are arranged at regular intervals. An induced voltage is generated by electromagnetic induction in the induction coil of the input pen that is in contact with the board to charge the capacitor connected to the induction coil, and then the loop coil is switched to the receiving circuit and connected as the capacitor discharges. By detecting the signal flowing through the loop coil, the contact position of the input pen was determined.

(c) Problems to be solved by the invention By the way, in the above coordinate position detection device, the S/N
In order to improve the detection accuracy, it is necessary to flow a large oscillation current, but since the above loop coil is shared for transmission and reception, there are restrictions on the type of switching element that can be used, which may cause an increase in the oscillation current. It was difficult.

This is because a large number of switching elements are required to sequentially switch the large number of loop coils placed on the coordinate input detection board one by one during transmission or reception.
Using the switch element in a field-effect transistor (FET) that can flow a large current poses a mounting space problem because the transistor is relatively large. Due to the characteristics of the switching element (MPX) used, an oscillation current of only up to 20 mA can flow.

In addition, as a method to enable the use of field-effect transistors without causing mounting space problems, it was considered to expand the pattern pitch of the loop coil to limit the number of transistors used, but this method has obvious problems. However, this resulted in another problem in that the resolution and detection accuracy levels were below the practical level.

The object of the present invention is to provide a coordinate position detection device that solves these problems.

(d) Means for Solving the Problems The present invention is characterized by a coordinate position detection device in which loop coils are provided separately for oscillation and reception, and are configured to be used selectively.

(E) Effect According to the present invention, since the oscillation (transmission) loop coil and the reception loop coil are separate, a field effect transistor that can flow a large current can be used as the switching element of the oscillation loop coil. , small conventional switching elements can be used for reception, thus limiting the number of field effect transistors used.

Moreover, even if the pattern pitch of the oscillation loop coil is widened, as long as the pattern pitch of the receiving loop coil is narrowed, resolution etc. will not be affected. can limit the number of uses.

(F) Effects of the Invention Therefore, according to the present invention, the oscillation current can be increased by using field effect transistors to improve the S/N ratio and detection accuracy, and implementation can be achieved by limiting the number of field effect transistors used. Space problems can be eliminated and costs can be reduced.

(I.) Examples An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a conceptual diagram of a coordinate position detection device according to the present invention.
The plate surface constituting each of the shafts is the oscillation loop coil 1.
and the receiving loop coil 2 are separately arranged on the coordinate input detection plate 3 shown in FIG.

The oscillating loop coil 1 is connected to the transmitting circuit 4, and the receiving loop coil 2 is connected to the receiving circuit 5, and the oscillating current is passed through the oscillating loop coil 1 for the time width shown in Fig. 2 A and as shown in Fig. 2. , input pen or cursor induction coil I-
An induced voltage is generated by electromagnetic induction to fill the capacitor C connected to the induction coil, and then the charge in the capacitor C is discharged to the induction coil L by switching to reception for the time period shown in Fig. 2 (2). 2C), thereby extracting the reception signal shown in FIG.
The contact coordinate position of the input pen (hereinafter abbreviated as input pen) is determined.

To explain further, since the X-axis and Y-axis are the same, one example is that as shown in Figure 3, one loop coil 1 for transmitting is provided for every eight loop coils 2 for receiving. . In other words, while the pattern pitch of the oscillating loop coil 1 is widened, the receiving loop coil 2 is patterned at a narrow pitch, for example, four circles. MPX is a switching element for switching reception, and FET is a switching element (field effect transistor) for switching transmission.

Furthermore, 7 is a common line for oscillation and reception.

As described above, the receiving loop coils 2 are arranged at 4-circle intervals, and each eight of them is grouped into a block, and a required number of such blocks 8 are provided. As shown in FIG. 3, the receiving loose coils are always used to pick up received signals in a loop formed by three coils of the same order in each of three adjacent blocks. For example, each of the three blocks 8
The second receiving loop coil 2 of each block 8 is used to pick up the received signal, and the second receiving loop coil 2 of each block 8 is then used to pick up the first received signal. .

If the received signal is picked up with three loops in this way, the received guidance signal can be received to a greater extent (three times) than in the case of one loop, leading to improvements in the S/N ratio and detection accuracy.

Further, by using a three-loop configuration, the induced voltage generated in the common line 7 can be canceled and distortion of the received signal can be eliminated.

That is, if the induction coil L is touched in a state as shown in FIG. 4, a current flows in the opposite direction to the common line 7, so that the induced voltage on the common line 7 side is canceled out. Without such a configuration, the contact position of the input pen would be on the common line 7.
The induced 'jt pressure of the common line varies depending on whether it is close to or far from , which affects the received signal picked up from the receiving loop coil and causes a detection error.

The input pen does not necessarily rest directly on any of the receiving loop lines 2, but is touched between the receiving loop lines as shown in FIG.

In this case, the coordinates cannot be specified unless the CPU 6 determines where the input pen is located relative to the receiving loop line. Now, in Fig. 5, the receiving loop line 2a
, 2b, 2c, the left fl of the receiving loop line! II
Assuming that it is at position A, current flows from line 2a to line 2b in the direction of the solid arrow.

However, if it is on the right side B with respect to the line 2b, the current flows from the line 2b to the line 2c in the direction of the broken arrow, and the direction of the current on the receiving loop line 2b is reversed. As a result, the phase of the received signal is inverted as shown in the signal 41 in FIG. Therefore, the CPU 6 can detect the input pen using this transfer/reversal data and determine the position of the input pen using the reception loop line 2b as the reversal line.

This phase reversal detection is performed as shown in FIG.

Using the comparator 27 of the circuit in FIG. 10, create a received clock pulse signal from the reception signal port or signal E in FIG. Compare signal A and the rising edge of the pulse. Since the received signal is generated in the receiving loose line 2 by the discharge of the capacitor C, a certain deviation occurs between the received signal and the transmitted clock pulse signal A, as shown in signal 2. However, at the receiving signal port before inversion, only the signal 2 with this deviation is extracted, whereas in the receiving signal E after the inversion, the width of the deviation increases like the signal G with the deviation by the amount of inversion. This fact is used to detect reversal.

The actual detection of the deviation width signals 2 and 7 is performed in the circuit shown in FIG.
The waveform is shaped into a rectangular wave by the phase detection circuit 28, and by comparing it with the oscillation clock pulse signal A, the deviation of the signal 2 and 2 is detected.

Furthermore, the phase detection circuit #128 has a clock pulse (16M
The counter has a counter driven at a frequency of Hz), and the counter measures and outputs the width of each deviation signal as a count value.

When the amount of this shift is larger than the set value for detecting phase inversion, the CPU 6 determines that there is a phase inversion.

In this way, the inversion line of the received signal is determined by phase inversion, and it can be determined which side of the inversion line the input pen is touching.

Furthermore, unless it is possible to measure the distance from the reversal line, the center position of the human-powered pen, that is, the coordinates, cannot be determined. Therefore, the CPU 6 performs the following processing.

In other words, if the center P of the input pen is located at the position shown in Figure 7 A or Figure 8 A (the vertical line in each figure A is 4 r
(referring to a receiving loop coil with an interval of alI), a guided signal having a peak value as shown in each figure or figure C is collected in a time-sharing manner. The CPU 6 sequentially stores the output of the receiving loop line (line 2b explained in Fig. 5) in the built-in RAM.
Therefore, pick up the count value corresponding to the induced voltage (peak value) at specific points a and b at the two front and rear ports that sandwich the phase inversion line, and set the center value using the value obtained by a - b p5 calculation. Calculate how far P is from the reversal line. The opening in Figure 7 shows the case where the center P of the input pen is in the center, and the count values of specific points a and b are equivalent.
Figure A shows a positive value on the side close to the reversal line, and Figure 8 shows a negative value on the side far from the reversal line.

The above processing is performed by the clock count circuit 9 in FIG. 10, and the output signal obtained by slicing the output of the integrating circuit 26 at a predetermined level is counted by the clock count circuit 9 based on the clock pulse (8M) [2]. , is input to the CPU 6.

The CPU 6 sequentially stores this count value, and when a phase inversion line is specified as described above, the second grain a before this line is
Then, the count value of the second to last row is read out, this is subtracted, and the coordinate value is calculated from the difference value.

Next, the operation of the implementation circuit shown in FIG. 10 will be explained.

The synchronous timing circuit 10 uses the output of the oscillation circuit 11 to send a synchronous signal to the sine converter 12.

This synchronization signal is sent to the switch element FE' for oscillation and reception.
r', controls the MPX switching (2MHz) timing, and also uses an input pen (500KHz) as an input means.
) and a cursor (250 KHz).

The sine converter 12 outputs an oscillation signal converted into a positive magnetic wave using the synchronization signal, and sends this to the current boost circuit 1.
After changing the current to a large current in step 3, the oscillation decoder 14 causes a large current to flow through the oscillation loop coil while switching the switching element FET.

As a result, the capacitor C of the input pen that touched the coordinate input detection plate 3 is charged.

The coordinate input detection plate 3 described above forms, for example, an X-axis oscillation/reception loop on the top side and a Y-axis oscillation/reception loop on the back side, and these loops are constructed by crossing the configuration shown in FIG. 3 above. It is set up.

In the receiving operation, as described above, three same-order coils in three adjacent blocks constitute the receiving loop coil 2, and these three
It is performed in a scanning motion in which the ranking is shifted one by one in real leather position. The reception decoder 15 successively picks up the reception signals on the reception loop line 2 .

A reception amplifier circuit 16 amplifies the X-axis and Y-axis separately with corresponding amplification factors, and then passes through an amplification factor switching circuit (described later) 17 to a waveform shaping circuit 18. send.

A specific circuit diagram of this waveform shaping circuit 18 is shown in FIG. 11, and includes a differential amplifier 19, a bandpass filter 2
0, the received signal A in FIG. 12 which has passed through the gain switcher 21 and the amplifier 22 is rectified by the full-wave rectifier 23 to produce the signal B in FIG.
The peak hold circuit 25 converts the signal into the signal shown in FIG.

The comparator 27 converts the integral signal E into the signal A shown in FIG.
/D conversion is performed, and the output width of this signal is counted by a tally counter circuit 9 to calculate the output value of the received signal.

This clock count process is the calculation of the count value of the received signal explained in FIG.

This clock count circuit 9 is supplied with a tarock signal (<16 MHz) from an oscillation circuit 11, and as shown in FIG.
During the signal width from the time when the comparator output is input,
The clock signals are counted and the count value is input to the CPU 6.

The CPU 6 sequentially stores the input count values as the magnitude of the received guidance signal.

On the other hand, the signal shown in FIG.
The received pulse is shaped into a received pulse as shown in Figure E and sent to the phase detection circuit 28, where it is compared with the oscillation clock pulse (output of the sine converter 12) in Figure 9A, as described in Figure 5. At the same time as finding the phase inversion line, the amount of deviation (current value) is calculated using the signal (16MJ-Iz) from the oscillation path 1.

In addition, the CPU 6 picks up the peak value (count value) of the guidance signal of the reception loop line at specific points a and b (see Figures 7 and 8) on the two days before and after this reversal line, and The coordinate specifying process described in FIGS. 7 and 8 is performed.

Note that the processing of the CPU 6 for specifying the coordinates described in FIGS. 7 and 8 only needs to be performed on the reception loop coil portion where the input pen is located, and processing on other portions is unnecessary.

For this purpose, from the peak hold circuit 25 to the comparator 2
When the signal outputted via 7 is at a set level, it is assumed that the input pen exists, and the signal is input to the CPU 6 as a tight detection signal. Process only the part of the receiving loop coil that is present.

Based on the above-mentioned processing data, the CP tJ 6 uses the expansion ROM circuit 29 to output the coordinate values of the input pen.

Incidentally, since the NB large input can be performed with a cursor in addition to the above-mentioned input pen, it is necessary to distinguish between the input pen and the cursor. Therefore, in the example circuit of FIG. 10, the resonance frequency of the input pen's induction coil is set to 500 KH.
z, the resonant frequency of that of the input cursor is 250 K
Hz, and sends synchronization signals of respective frequencies from the synchronization timing generation circuit 10 to the sine converter 12, while the CPU 6 identifies from the received signal whether the input pen or input cursor is being used, and converts the sine converter. It functions to switch the resonant frequency of the oscillation signal sent from 12.

In this case, the CPU 6 detects a touch using 250 KHz oscillation as shown in the flowchart of FIG. 13, and if it is detected, the cursor is being used, so coordinate values are created based on it.Steps nl, n2. n3. n4
).

Also, if no touch is detected, the touch is detected by 500KHz oscillation, and if it is detected, the input pen is being used, so coordinate values are created based on that (step n5.n
6. n7. n8).

In this way, the CPU 6 automatically determines whether it is an input pen or a cursor and changes the resonance frequency of the oscillation signal, so there is no need for the operator to set the switching between the input pen and the cursor, and the operation system is improved accordingly.

The input pen or cursor is provided with multiple selection functions, such as selection of various processing modes. Specifically, this selection function includes an input pen 30 and a cursor 31 as shown in FIG.
Capacitors CI, C2... with different capacities connected in parallel to capacitor C, and selection switches SWI, SW2...
Select the required mode by turning on the switch,
And input.

On the receiving side, the CPU 6 operates as follows to detect the selected function.

As described above, the phase detection circuit 28 detects the phase inversion line as a phase difference count value, so this process is utilized.

That is, the phase detection circuit 28 receives the received signal from the amplification factor switching circuit 17, and which switch S
If the received signal is A in Fig. 16 when WI, SW2, etc. are not turned on, then if the switch is turned on and the capacitor C1 is used in parallel with the capacitor C1, C2, etc., then the capacitors used in parallel are Depending on the capacity of , in other words, depending on the switch turned ON, the received signal leads or lags in phase with respect to the received signal in A as shown in FIG.

For example, when the switch SWI is turned on as shown in Fig. 15, the received signal at that time shifts in the direction in which the phase advances.
The phase detection circuit 28 detects the width of this phase shift using the received clock pulse (Fig. 15 C) and the transmitted clock pulse (Fig. 15 E), and detects the clock pulse between this width (Fig. 15 E). The number of signals is counted and input to the CPU 6.

Then, the CPU 6 detects the phase difference based on the count value, and
Refer to the switch identification table for that value, and
1 to determine the selected function mode.

Note that the phase difference shift due to each switch SWI to SW4 (
count value) is determined by the above-mentioned phase inversion line detection process (9th count value).
Since the deviation is much smaller than that of the process shown in the figure, the two can be clearly distinguished.

This has the advantage that coordinate value detection and switch identification can be performed simultaneously using the same guidance signal (received signal).

By the way, when performing switch identification as described above, if the phase of the received signal shifts due to the characteristics of the components of the receiving circuit due to temperature change, the switch will be erroneously detected. Therefore, in the circuit shown in FIG. 10, a switch discrimination temperature compensation circuit 32 is provided, and when detecting coordinates, the sequential oscillation circuit and the receiving circuit are short-circuited to send the oscillation signal to the receiving side, and the phase shift is determined by the phase detection circuit 28. In this case, the amount of deviation is output as a phase count value, and the switch identification count value is corrected using this phase count value. This prevents false detection even if there is a temperature change and improves reliability.

Also, when switches SWI, SW2... are set to ONI,
The signal level decreases because the resonance frequency shifts.

Therefore, in the circuit of FIG. 10, the amplification factor switching circuit 17 is turned ON.
A command is given according to the switched switch, and the received signal and amplification factor of the circuit are changed, so that a nearly constant signal level is always maintained at the circuit output.6 In Fig. 17, the main cursor 31 is It shows a combination of coil L1 and subcoil L2. The main coil L1 is for coordinate input with a resonance frequency of 250 KHz, and the sub-coil L2 is for angle input with a resonance frequency of 500 KHz.

When input using these two induction coils Ll and L2, the CPU 6 operates as shown in the flowchart of FIG.

That is, 250 K 1 (when there is contact with the main coil due to z oscillation, coordinate values by this main coil are created (steps nil, n12.n13).

Next, when the subcoil comes in contact with the 500KHz oscillation, coordinate values are created by this subcoil and both coordinate values are sent out (steps n14.n15.n16 n17.n
18).

This invention has been described in detail above, but the oscillation loop coil 1 and the reception loop coil 2 are separate,
Each of them is switched and used by a switch element FETMPX. Therefore, even if a large field-effect transistor is used as a switching element in the oscillation loop coil 1 due to the need to flow a large current, a small, small-current switching element can be used for reception, so a field-effect transistor can be used as a switching element for reception. The number of transistors used can be reduced. Moreover, the oscillation loop:
By widening the pattern pitch of one tile compared to that for reception, the number of patterns used can be further reduced. Therefore, all the switch elements can be arranged compactly in terms of space, and at the same time, by passing a large current through the oscillation loop coil 1 during oscillation, it is possible to improve the S/N ratio and detection accuracy.

In addition, in the correspondence between the configuration of the present invention and the above-described embodiment, the oscillation loop line of the present invention corresponds to the oscillation loop line 1 of the embodiment, and similarly, the reception loop line is as follows. Receiving loop line 2 2a
, 2b, and 2c, the coordinate input detection board corresponds to the coordinate input detection board 3, the input means corresponds to the input ben 30 or the cursor 31, and the induction coils correspond to the induction coils L, Ll, and L2. Correspondingly, the capacitors are capacitors C, CI, C2, C3, and C4.
Although the means for switching the loop coil corresponds to the switching elements FET and MPX, the present invention is not limited to the configuration of the above-described embodiment.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a conceptual diagram of a coordinate position detection device; FIG. 2 is a timing chart of oscillation and reception in FIG. 1; FIG. 3 is a configuration diagram of an oscillation and reception loop pattern; Fig. 71 is an explanatory diagram of the operation of the receiving loop coil, Fig. 5 is an explanatory diagram of the phase inversion line detection operation, Fig. 6 is a reception signal waveform diagram of Fig. 5, and Figs. 7 and 8 are the input pen and the guided signal. 9 is a timing chart of phase inversion detection processing operation, 10 is an oscillation/reception control circuit diagram, 11 is a specific circuit diagram of a waveform shaping circuit, 12 is a 11th
Figure 13 is a flow chart of input pen and cursor switching operation; Figure 14 is a circuit diagram of the cursor and input pen; Figure 15 is an explanatory diagram of switch identification operation; Figure 16 is switch ON. FIG. 17 is a circuit diagram of a cursor with an angle input function, and FIG. 18 is an operation flowchart when the cursor shown in FIG. 17 is used. 1...Oscillating loop line 2.2a, 2b, 2c...Receiving loop line 3...
・Detection board for coordinate input 30...Input ben 31...Cursor L, Ll, L2...Induction coil C, C1, C2, C3, C4...Capacitor FET・
...Switch element MPX...Switch element 1st prisoner 1σ signal 10 and Fig. 6 IN signal M3 in Fig. 5
- The crane's support is heavy D - ÷ 7 - To (E) ☆ Cancer signal 30 ... Input 31 ... D - Crane L ... Exclusive] Ile C, C1 to C4・Container No. 14 Prisoner - Crane Pen circuit diagram W1 W2 Figure 15 Switch 9-m9-m5l1 Explanation Figure 16 Zuin ÷ ON eel

Claims (1)

[Claims] (1) An input means comprising an induction coil and a capacitor connected to the induction coil is brought into contact with a coordinate input detection board on which loop coils are arranged at regular intervals, and the capacitor is charged by an oscillation signal flowing through the loop coil. A coordinate position detecting device that receives the discharge with the loop coil, wherein the loop coil is provided separately for oscillation and reception, and is configured to switch between the two.