JP3481147B2 - Coordinate detection device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate detecting device for detecting the coordinates of a digitizer.

[0002]

2. Description of the Related Art In recent years, many lightweight and portable small portable information processing devices have been commercialized, and products for handwriting input and icon operation using a pen have been increasing. In this product, a resistance film pressure-sensitive digitizer is widely used because it can be realized with a cheap and simple structure regardless of the type of pen used.

The structure of the resistance film pressure-sensitive digitizer will now be described. As shown in FIG. 7, the resistance film pressure-sensitive digitizer is composed of two upper and lower panels 30 made of a resin film or the like.
1 are arranged face to face, and a resistance film 302 as a conductive sheet is formed inside the panel 301 by vapor deposition or the like to form a sandwich structure. Here, an insulating spacer 303 is provided so as to prevent the two conductive sheets 302 from coming into contact with each other when not pressed, and electrodes are provided at both ends of each resistance film. Lead wires are connected to each electrode and are used as terminals for voltage application and voltage detection. The installation directions of the electrodes of each resistance film are arranged so that the two resistance films are orthogonal to each other. One of the two resistive films is used for detecting the X coordinate and the other is used for detecting the Y coordinate. That is, in the resistance film for X-coordinate detection, electrodes are provided at both left and right ends, while in the resistance film for Y-coordinate detection, electrodes are provided at both upper and lower ends.

Here, in the conventional digitizer, 4
There is a linear type. That is, as shown in FIG. 8, the coordinate detection device using the 4-wire type digitizer has a digitizer 10 and switches SW0 to SW4.
And an A / D converter 14 and an arithmetic control unit 16 '. Then, as shown in FIG. 9, the digitizer 10 has an X coordinate detecting resistance film Xt and a Y coordinate detecting resistance film Yt.
And a pair of electrodes are provided in parallel to the X-coordinate detection resistance film Xt and the Y-coordinate detection resistance film Yt, respectively, and an electrode is provided on the X-coordinate detection resistance film Xt.
The electrodes are provided so as to be orthogonal to the electrodes provided on the Y coordinate detection resistance film Yt. Further, a lead wire is wired to each of the electrodes. That is, in the case of the 4-wire type, one electrode is provided at the end of each resistance film, and the digitizer 10
A total of four electrodes are provided on each of the electrodes, and wiring is provided from each of the electrodes.

Here, the basic principle of coordinate detection will be described. When the digitizer surface is pressed with a pen or the like, the electric potential Vp at the pressing point is detected, and the electric potential Vp can be detected by comparing it with the constant voltage Vcc. Is. That is, in FIG. 8, when detecting the X coordinate, the switch SW0 is set to b.
, The switch SW1 is connected to the a side, the switch SW2 is connected to the b side, the switch SW3 is connected to the b side, and the switch SW4 is connected to the a side, the X coordinate detection resistance film Xt is energized between Vcc and the ground. Alternatively, the potential Vp at the pressing point is detected from the switch SW4. Then, the X coordinate can be detected by calculating Vp / Vcc. Note that the same applies to the Y coordinate.

However, the coordinate detection method in the above ideal circuit does not take into consideration the resistance component of the lead wire other than the resistance film of the digitizer and the contact resistance of the connector, so that there is a problem that the coordinate detection accuracy decreases. It was So 4
In a linear digitizer, correction is performed by setting a reference value. That is, a method for detecting coordinates when setting the reference value will be described with reference to FIGS.

That is, after the idle state (S10
0), it is determined whether or not the reference value setting control is performed (S1).
01). For this, the time when the reference value is set is determined in advance, and it is determined whether or not it has come. For example, if the reference value is set when the power of the coordinate detection device is turned on, it is determined that the reference value setting control is performed when the power is turned on. If the reference value is set, the process proceeds to step S102. If not, step S10 is performed.
Move to 7.

In step S102, the potential at the first point is detected (S102). That is, the digitizer 10
Two predetermined points are displayed on the display surface of and the user is made to press the two points with a pen or the like. Then, when the first point is pressed, the potential at that time is detected. That is, both the potential on the resistance film Xt for detecting the X coordinate and the potential on the resistance film Yt for detecting the Y coordinate are detected. Then, the data of the detected potential for the first point is stored (S103). next,
The potential at the second point is detected (S104). That is, when the user presses the second point, the potential at that time is detected. Also in this case, both the potential on the X-coordinate detection resistance film Xt and the potential on the Y-coordinate detection resistance film Yt are detected. Then, the data of the detected potential for this second point is stored (S105).

Next, a coefficient relating to the potential gradient is calculated based on the coordinates of the two points (S106). That is, with respect to the X coordinate and the Y coordinate, two data of the pressed point and its potential as shown in FIG. 11 are obtained, and based on these, the formula of X = C * V + D (X is the position, V is the potential) Show)
The values of the coefficients C and D in are calculated. These coefficients are X
It is calculated for each of the coordinate calculation and the Y coordinate calculation. As a result, the position coordinates can be calculated from the detected potential. For example, X when pressing a certain position
If the potential of the coordinate detection resistance film Xt is Vp, this V
The position of the X coordinate is calculated by substituting the value of p into the above equation.

Next, it is determined whether or not there is pen down (S107). The detection of the pen down is performed depending on whether or not the pen down signal is detected. That is, for each switch in the configuration of FIG.
1 is switched to the b side, SW2 is switched to the b side, SW3 is switched to the a side, and SW4 is switched to the b side. Then, if there is a pen down, the output potential of the pen down signal drops. Therefore, it is determined whether or not there is a pen down by looking at this.

Next, when it is determined that there is pen down, the potential is detected in the resistance film for detecting the X coordinate (S108). In that case, for each switch in FIG. 8, SW0 is on the b side, SW1 is on the a side, and SW2 is on the b side.
Side, SW3 is switched to the b side, and SW4 is switched to the a side. Then, in the X coordinate detection resistance film Xt, the current is changed from Vcc to G.
Since it flows toward ND, the potential of the pressing point is set to SW2 or S
Detect via W4. Then, next, the potential is detected in the resistance film for detecting the Y coordinate (S109). In that case, for each switch in FIG. 8, SW0 is on the b side, SW1 is on the b side, SW2 is on the a side, SW3 is on the a side, and S is on the S side.
Switch W4 to side b. Then, a current flows from Vcc to GND in the Y resistance film detecting resistance film Yt, so that the potential at the pressing point is detected via SW1 or SW3. Then, the X coordinate and the Y coordinate are calculated based on the detected potential (S110). That is, the detected potential is substituted into the above equation to obtain the position. In addition,
If it is not determined in step S107 that pen down has occurred, the process returns to step S100.

In the conventional digitizer, there is also an 8-wire type digitizer. In other words, in the 4-wire digitizer, there is a problem that the resistance component of the lead wire other than the resistance film of the digitizer and the contact resistance of the connector are not taken into consideration. The coordinate position of the digitizer can be accurately detected by obtaining the voltage at the end of the. That is, in the 8-wire type digitizer, two lead wires are provided for each electrode, and the potential at the end of the digitizer can be accurately detected. When the potentials at the ends of the two digitizers are detected, the potential gradient is detected from them. The circuit configuration of the 8-wire digitizer is as shown in FIG.

The operation of detecting coordinates in the 8-wire digitizer will now be described with reference to FIGS. 12 and 13. First,
After the idle state (S200), it is determined whether or not the end voltage detection control is performed (S201). For this, the time for performing the end voltage detection control is determined in advance, and it is determined whether or not it has come. For example, if the end voltage detection control is performed when the power of the coordinate detection device is turned on, it is determined that the end voltage detection control is performed when the power is turned on.
When the end voltage detection control is performed, the process proceeds to step S202, and when not performed, the process proceeds to step S205.

Then, in step S202, the end voltage in the X coordinate detecting resistance film Xt is detected (S20).
2). That is, the potentials of the two electrodes when the constant voltage Vcc is applied to the X coordinate detection resistance film Xt are detected. Then Y
The end voltage on the coordinate detection resistance film Yt is detected (S2).
03). That is, the constant voltage Vcc is applied to the Y coordinate detection resistance film Yt.
The potentials of the two electrodes when the voltage is applied are detected.

Then, the coefficient relating to the potential gradient straight line is calculated based on the detected potential (S204). That is,
As shown in FIG. 13, since the terminal voltages Vmax and Vmin are calculated, the potential gradient straight line based on these values is V = A * X.
+ Vmin (X indicates a position and V indicates a potential) is modified, and the values of the coefficients P and Q at X = P * V + Q are calculated. These coefficients are the X coordinate detection resistance films Xt and Y.
It is calculated for each of the coordinate detection resistance films Yt.
As a result, the position coordinates can be calculated from the detected potential. For example, when the electric potential of the X coordinate detecting resistance film Xt when a certain position is pressed is Vp, the value of this Vp is substituted into the formula for the X coordinate detecting resistance film Xt calculated above. The position of the X coordinate is calculated.

Next, it is determined whether or not there is pen down (S205). The detection of the pen down is performed depending on whether or not the pen down signal is detected. That is, for each switch in the configuration of FIG.
1 is switched to the b side, SW2 is switched to the b side, SW3 is switched to the a side, and SW4 is switched to the b side. Then, if there is a pen down, the output potential of the pen down signal drops. Therefore, it is determined whether or not there is a pen down by looking at this.

Next, when it is determined that pen down has occurred, the potential is detected in the resistance film for detecting the X coordinate (S206). In that case, for each switch in FIG. 3, SW0 is on the b side, SW1 is on the a side, and SW2 is on the b side.
Side, SW3 is switched to the b side, and SW4 is switched to the a side. Then, in the X coordinate detection resistance film Xt, the current is changed from Vcc to G.
Since it flows toward ND, the potential at the pressing point is detected via the lead wire provided on the Y coordinate detection resistance film Yt. Then, next, the potential is detected in the resistance film for Y coordinate detection (S208). In that case, for each switch in FIG. 3, SW0 is on the b side, SW1 is on the b side, and SW is
2 is switched to the a side, SW3 is switched to the a side, and SW4 is switched to the b side.
Then, in the Y resistance film detecting resistance film Yt, the current is Vcc.
Flow toward the GND from the contact point, the potential at the pressing point is detected via the lead wire provided on the X coordinate detection resistance film Xt. Then, the X coordinate and the Y coordinate are calculated based on the detected potential (S208). That is, the detected potential is substituted into the above equation to obtain the position. In addition,
If it is not determined in step S205 that the pen is down, the process returns to step S200.

Thus, according to the 8-wire digitizer,
Since the electric potential at the end of the digitizer can be known, there is an advantage that no alignment work is required and that even if the electrical resistance of the digitizer, the wiring resistance, or the contact resistance of the connector is changed, it is not easily affected.

[0019]

However, in the above-described 4-wire coordinate detection method, an operation of pressing a predetermined position must be performed in order to set the reference value. On the other hand, in the 8-wire digitizer, since only the voltage at the end position is detected, it is not possible to cope with the change in the linearity of the digitizer, and as a result, accurate coordinate detection cannot be performed. Therefore, in the present invention, even with an 8-wire digitizer, a method of setting a reference value is introduced to enable more appropriate coordinate detection, and the user does not have to perform an operation of pressing a predetermined position one by one. Another object of the present invention is to provide a coordinate detection device capable of performing coordinate detection based on a reference value setting method.

[0020]

Coordinate detection according to claim 1
The device includes a resistance film for X-coordinate detection and a resistance film for Y-coordinate detection.
Coordinate detection to detect the coordinates pressed by the digitizer
The device does not push the preset display point to the user.
Then, the potential gradient is detected by detecting the potential of the pressing point.
For calculating a coefficient related to
The number calculation / holding means and the electric power of the end position of the resistance film for X-coordinate detection.
Position and the end position of the Y coordinate detection resistance film.
An end potential detecting means for detecting the potential and the end potential detecting means
Change to at least one of the detected potentials
If there is, it is held in the coefficient calculation / holding means
Coefficient correction means for correcting the coefficient, and the coefficient calculation / holding means
Uncorrected reference value potential gradient straight line based on the coefficient held in the stage
Difference between two end potentials (Vwmin, Vwmax) at (Lk)
Is set to ΔVw and obtained before correction based on the detection of the end potential.
A correction front end potential gradient straight line which is a potential gradient straight line,
Uncorrected reference potential corresponding to the uncorrected reference potential line (Lk)
Two end potentials (Vmin, Vma) on the gradient straight line (Lh)
x) difference is ΔVm, and the fluctuation amount of the end potential is ΔVa, ΔV
In case of b, the potential gradient straight line based on the corrected coefficient
Terminal voltage on a certain corrected reference value potential gradient straight line (Lk ')
Position (Vwmin ', Vwmax') and the pre-correction reference value potential gradient straight line
Two corresponding end potentials (Vwmin, Vwm) in (Lk)
ax) is ΔVc and ΔVd, respectively,
ΔVc and ΔVd are given by ΔVc = ΔVa · ΔVw / ΔVm
Based on the formula and the formula of ΔVd = ΔVb · ΔVw / ΔVm
It is characterized by being calculated.

A coordinate detecting device according to a second aspect is the first aspect.
In the invention according to claim 1, the digitizer is an 8-wire type digitizer.
It is characterized by having a tyzer.

A coordinate detecting device according to a third aspect is the first aspect.
Or the invention according to 2, wherein the coefficient correcting means is
The feature is that the correction amount is calculated according to the fluctuation amount of the position.
It

A coordinate detecting device according to a fourth aspect of the present invention is as follows.
In the invention according to 1, 2, or 3, the above-mentioned end potential detection means
Detection of the end potential by the
Correction is performed each time the coordinate detection device is powered on.
It is characterized by

The coordinate detecting device according to claim 5 is
In the invention according to 1, 2, or 3, the above-mentioned end potential detection means
Detection of the end potential by the
Correction is the detection of pen down to the digitizer.
It is characterized by performing to and.

The coordinate detecting device according to claim 6 is
In the invention according to 1, 2, or 3, the above-mentioned end potential detection means
Detection of the end potential by the
Correction is to be performed each time a prescribed command is given.
Is characterized by. Further, the coordinate detection device according to claim 7,
In the invention according to claim 1, 2 or 3, the coordinate detection
The device further determines the coordinates of the pressed point according to the corrected coefficient.
It is characterized by having a coordinate calculation means for calculating.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. As shown in FIGS. 1 to 3, the coordinate detecting device S according to the present invention includes a digitizer 1 as shown in FIG.
0, a switch circuit 12, an A / D converter 14, an arithmetic control unit 16, a pen-down detection unit 18, a sampling period counter 20, and a host CPU 22.

Here, the digitizer 10 is a pressure-sensitive coordinate detection sensor having a resistance film Xt for detecting X-coordinates and a resistance film Yt for detecting Y-coordinates. When the digitizer 10 is pressed by a pen or a finger, An electric signal corresponding to the pressed position is output. Further, as shown in FIG. 3, the switch circuit 12 has switches SW0, SW1, SW2, SW3, and SW4. That is, the switch SW0 switches the connection between the resistance film Xt for detecting the X coordinate and the constant voltage Vcc for detecting the pen down, and the switch SW1 switches the constant voltage Vcc for one electrode of the resistance film Xt for detecting the X coordinate. The connection is switched, and the switch SW2 is used for the Y coordinate detection resistance film Yt.
The connection of one electrode to the constant voltage Vcc is switched, and the switch SW3 is used for the X coordinate detection resistance film Xt.
The other electrode is switched to the ground (Gnd) connection, and the switch SW4 switches the Y coordinate detection resistance film Y.
The connection of the other electrode of t to the ground (Gnd) is switched. The switching control of each switch is performed by the arithmetic control unit 16.

Next, the A / D converter 14 converts the voltage value as an electric signal detected from the digitizer 10 from analog data into digital data. The arithmetic control unit 16 performs various controls in detecting coordinates, and controls the sampling period counter 20, the switch circuit 12, and the A / A by software processing.
Control of the D converter 14, calculation processing for coordinate calculation, correction processing, noise processing, and the like are performed. Further, in particular, in this embodiment, the reference value is set at a predetermined timing, and further, the end position potential of each resistance film is detected at a predetermined timing to calculate the fluctuation component of the end position potential as the reference value. Control is performed to reflect the coefficient in the coefficient and correct the reference value calculation coefficient. That is, as shown in FIG. 2, the arithmetic control unit 16 includes the coefficient calculating unit 16a, the end potential detecting unit 16b, and the coefficient correcting unit 16.
c, the coordinate calculation unit 16d, and the like. Here, the coefficient calculation unit 16a calculates the coefficient in the potential gradient straight line based on the reference value setting control, and the end potential detection unit 16b calculates the resistances in the X coordinate detection resistance film Xt and the Y coordinate detection resistance film Yt. The membrane end potential is detected. Also, the coefficient correction unit 16c
When the end potential fluctuates, the coefficient is corrected according to the fluctuation amount. The coordinate calculator 16d is for calculating the coordinates of the pressed point. The coefficient calculator 16
a functions as the coefficient calculating / holding means and computing means, the end potential detecting section 16b functions as the end potential detecting means, and the coefficient correcting section 16c functions as the coefficient correcting means and correcting means. To do. In addition, the coordinate calculation unit 16
d functions as the coordinate calculating means. Details of the correction of the reference value calculation coefficient will be described later.

The pen-down detector 18 detects whether or not there is a pen-down, and detects the pen-down signal when the switch circuit 12 is switched to the switch state for pen-down detection. The sampling period counter 20 also generates a periodic sampling time. Further, the host CPU 22 interprets the coordinate data generated by the arithmetic control unit 16 and performs processing such as drawing on the display device and character recognition processing.

The operation of the coordinate detecting device A having the above structure will be described with reference to FIGS. 4, 5 and 6. First, after the idle state (S10), it is determined whether or not the end potential detection control is performed (S11). In this determination, the timing and timing for performing the end potential detection control are set in advance,
It is determined whether or not the time or timing has come. For example, if the end voltage detection control is performed when the power of the coordinate detection device A is turned on, it is determined that the end voltage detection control is performed when the power is turned on. When the end voltage detection control is performed, the process proceeds to step S12, and when not performed, the process proceeds to step S18.

Then, the end voltage at the X coordinate detecting resistance film Xt is detected (S12). That is, the potentials of the two electrodes when the constant voltage Vcc is applied to the X coordinate detection resistance film Xt are detected. These potentials are detected by the lead wire f for potential detection provided on the electrode of the resistance film Xt for X coordinate detection.
1, f2 (see FIG. 3). Next, the end voltage in the Y coordinate detection resistance film Yt is detected (S1).
3). That is, the potentials of the two electrodes when the constant voltage Vcc is applied to the Y coordinate detection resistance film Yt are detected. Detection of these potentials is performed via potential detection lead wires g1 and g2 (see FIG. 3) provided on the electrodes of the Y coordinate detection resistance film Yt. Then, the data of the detected end potential is stored (S14). That is, two end potential data for the X-coordinate detection resistance film Xt and the Y-coordinate detection resistance film Yt.
And two potential data of The end potential detection unit 16b detects and holds the end potential.

When the potential data is stored, it is compared with the previously stored end potential data (S15), and it is determined whether there is a change in the end potential (S16). Here, if there is a change in any one of the two detected end potentials in a certain resistance film, it is determined that there is a change. Then, if there is a change, processing for correcting the coefficient is performed (S17). That is, the value of the coefficient stored in the reference value setting control is corrected. Detailed processing will be described later. It is also possible to set a threshold value for the variation amount of the end potential and correct the coefficient when the threshold value is exceeded. When the end potential is first detected, there is naturally no comparison target, so step S
In step 15, no comparison is made, and the process proceeds from step S16 to step S10. Alternatively, it may be determined whether or not there is a comparison target, and if there is, a comparison may be performed.

On the other hand, in step S18, it is determined whether or not the reference value setting control is performed (S18). In this determination, the timing and timing for performing the reference value setting control are set in advance, and it is determined whether or not the timing and timing have been reached. For example, the reference value setting may be performed only once, and when the reference value setting has already been performed, the reference value setting may not be performed. In that case, it is determined whether or not the reference value has already been set. Then, this one-time reference value setting is performed, for example, before shipping the product. If the reference value setting control is not performed, the process proceeds to step S25.

When the reference value is set, the digitizer 1
Two predetermined points are displayed on the display unit such as an LCD provided at 0, and the user is made to press the two points with a pen or the like. Then, the potential at the first point is detected (S19). This potential is the X coordinate detection resistance film Xt.
Both the electric potential at and the electric potential at the Y coordinate detection resistance film Yt are detected. That is, when detecting the potential on the resistance film Xt for detecting the X coordinate, in FIG. 3, the switch SW0 is on the b side, the switch SW1 is on the a side, and the switch SW is
2 is the b side, switch SW3 is the b side, and switch SW4 is the a side.
Switch to the side. Then, in the X-coordinate detection resistance film Xt, current is applied between the constant voltage Vcc and the ground (Gnd), so that the potential of the pressing point in the X-coordinate detection resistance film Xt is detected via the lead wire g1 or g2. In addition, in the case of detecting the potential on the resistance film Yt for Y coordinate detection, FIG.
, Switch SW0 is on the b side and switch SW1 is on the b side.
Side, switch SW2 to side a, switch SW3 to side a, and switch SW4 to side b. Then, in the Y coordinate detection resistance film Yt, the constant voltage Vcc and the ground (Gn
Since electricity is applied during d), the potential of the pressing point on the Y coordinate detection resistance film Yt is detected via the lead wire f1 or f2. The detected potential is converted into digital data by the A / D converter 14 and sent to the arithmetic control unit 16. Then, the data of the detected potential for the first point is stored (S20).

Next, the potential at the second point is detected (S21). That is, when the user presses the second point, the potential at that time is detected. In this case as well, the potential on the resistance film Xt for detecting the X coordinate and the resistance film Yt for detecting the Y coordinate are indicated.
Both potentials at are detected. Then, the data of the detected potential for this second point is stored (S
22).

Next, a coefficient relating to the potential gradient is calculated based on the coordinates of the above two points (S23). That is, with respect to the coordinates of the two pressed points, the data of the pressed points and their potentials as shown in FIG. 5 are obtained, so that the coefficient of the potential gradient straight line Lk passing through the two points is calculated. The coefficient is obtained, for example, in the form of the slope of the straight line and one end potential. that time,
The coefficient is obtained for each of the X coordinate and the Y coordinate. For example, regarding the X coordinate, if the detected potential at the first point is V1 and the detected potential at the second point is V2, as shown in FIG. 5, two points of data are obtained. Is obtained. The formula of this straight line is V =
Assuming A * X + Vwmin (Equation (1)) (X indicates position and V indicates potential), A and Vwmin in this Equation (1) are calculated as coefficients. These coefficients are reference value calculation coefficients. These coefficients correspond to the relationship between the potential and the coordinate position. Then, the calculated coefficient is stored (S2
4). Note that a pair of end potential data may be calculated as a coefficient. The coefficient calculation unit 16a performs the processes in steps S19 to S24. Then, when the process of step S24 ends, step S1
Return to 0.

On the other hand, when the reference value is not set in step S18, the process proceeds to step S25 and it is determined whether or not there is pen down (S25). The detection of the pen down is performed depending on whether or not the pen down signal is detected. That is, for each switch in the configuration of FIG. 3, SW0 is the a side, SW1 is the b side, SW2 is the b side, and S is the S side.
W3 is switched to a side and SW4 is switched to b side. Then, if there is a pen down, the output potential of the pen down signal drops. Therefore, it is determined whether or not there is a pen down by looking at this.

Next, when it is determined that there is pen down, the potential is detected in the resistance film for detecting the X coordinate (S26). In that case, for each switch in FIG. 3, SW0 is on the b side, SW1 is on the a side, and SW2 is on the b side.
Side, SW3 is switched to the b side, and SW4 is switched to the a side. Then, in the X coordinate detection resistance film Xt, the current is changed from Vcc to G.
Since it flows toward ND, the potential at the pressing point is set to the lead wire g1.
Alternatively, it is detected via g2.

Then, the potential is detected in the resistance film for detecting the Y coordinate (S27). In that case, for each switch in FIG. 3, SW0 is on the b side and SW1 is
Is switched to the b side, SW2 is switched to the a side, SW3 is switched to the a side, and SW4 is switched to the b side. Then, in the Y resistance film detecting resistance film Yt, a current flows from Vcc to GND, so that the potential at the pressing point is detected via the lead wire f1 or f2.

Then, the X coordinate and the Y coordinate are calculated based on the detected potential (S28). That is, the position coordinates corresponding to the detected potential are calculated according to the potential gradient straight line obtained in step S20. That is, the detected electric potential is substituted into the equation of the straight line having the coefficient obtained in step S23. This S26
The coordinate calculation unit 16d performs the coordinate calculation process from S28 to S28. If it is not determined in step S25 that the pen is down, the process returns to step S10.

Here, the method of correcting the coefficient in step S17 will be described more specifically. That is, it is assumed that the potential gradient by the end potential detection and the potential gradient by the reference value setting control detected at the same time are as shown in FIG. That is, it is assumed that the potentials detected in the end potential detection are Vmin and Vmax as shown in FIG. 5, and the potential gradient straight line based on the detected end potentials is the potential gradient straight line Lh. The potential gradient straight line obtained by the reference value setting control performed at the same time as the end potential detection is assumed to be the potential gradient straight line Lk. That is, the potential gradient straight line Lh and the potential gradient straight line Lk correspond to each other.

Then, as shown in FIG. 6, the end potentials obtained by the end potential detection performed thereafter are Vmin 'and Vmin.
It is assumed that max becomes 'and the potential gradient straight line changes from Lh to Lh'. That is, as shown in FIG. 6, the end potential is Δ
It is assumed that only Va and ΔVb have changed. Further, the potential gradient straight line based on the corrected coefficient in the reference value setting control is defined as a potential gradient straight line Lk '.

Then, the fluctuation of the end potential is reflected on the potential gradient straight line in the reference value setting control, which is performed as follows. That is, as shown in FIG. 6, the difference between the end potentials Vmin and Vmax on the potential gradient straight line (pre-correction end potential gradient straight line) Lh is ΔVm, and the end potential Vwm on the potential gradient straight line (pre-correction reference value potential gradient straight line) Lk.
The difference between in and Vwmax is ΔVw, and the potential gradient straight line after correction in the reference value setting control (corrected reference value potential gradient straight line) L
The difference between the end potential Vwmin ′ at k ′ and the above Vwmin is ΔV
c, the other end potential Vwm on the potential gradient line Lk '
Assuming that the difference between ax ′ and Vwmax is ΔVd, the following equation (2) holds for the fluctuation of one end potential. [Delta] Va / [Delta] Vm = [Delta] Vc / [Delta] Vw (Equation (2)) When this Equation (1) is modified, it becomes the following Equation (3). ΔVc = ΔVa · ΔVw / ΔVm (Equation (3)) Therefore, the value of the one end potential of the potential gradient straight line Lk ′ is represented by the following Equation (4). Vwmin '= Vwmin + [Delta] Vc = Vwmin + [Delta] Va. [Delta] Vw / [Delta] Vm (4) Similarly, the value of the other end potential is expressed by the following equation (5). Vwmax ′ = Vwmax + ΔVd = Vwmin + ΔVb · ΔVw / ΔVm (5) Then, based on the calculated end potential data, the above equation (1), that is, the slope A of V = A * X + Vwmin is obtained. Although the above is the case where Vmin'-Vmin and Vmax'-Vmax are positive, naturally when ΔVc in equation (4) and ΔVd in (5) are opposite. That is, when Vmin'-Vmin becomes negative, the above formula (4) becomes Vwmin '= Vwmin-ΔVc, and when Vmax'-Vmax becomes negative, the above formula (5) becomes Vwmax ′ = Vwmax−ΔVd.

As described above, the previous coefficient is updated with the newly obtained coefficient A and Vwmin to correct the coefficient. That is, the potential gradient straight line in the reference value setting control is corrected. Therefore, after the coefficient correction, the X-coordinate and the Y-coordinate are detected in steps S26 to S28 by the newly obtained coefficient.
That is, to explain with reference to FIG. 6, the coordinates are detected based on the potential gradient straight line Lk ′ obtained by the correction. It should be noted that the above correction of the coefficient is, of course, when the end potentials of both the X-coordinate detection resistance film Xt and the Y-coordinate detection resistance film Yt are changed, the X-coordinate detection resistance films Xt and Yt.
The coefficient is corrected for both of the coordinate detection resistance films Yt. The correction of the coefficient is performed by the coefficient correction unit 1
6c.

When the coefficient is corrected, the held coefficient and the end potential data are updated and held as the corrected coefficient and the end potential data at that time. The held coefficient and the end potential are used as a reference. That is, when there is a change in the updated end potential, the updated coefficient is corrected according to the amount of change. However, the coefficient calculated first and the data of the end potential at that time may always be used as a reference.

As described above, according to the coordinate detecting apparatus of this embodiment, the fluctuation component of the end position potential can be reflected in the calculation coefficient obtained by setting the reference value. It can be said that even a digital digitizer can set a reference value like a 4-wire system. That is,
The conventional reference value setting method and the 8-wire method obtained from the end potential are associated with each other. Therefore, by detecting the end potential, it is possible to appropriately detect a change in the detected coordinates due to aging, and it is possible to perform accurate coordinate detection. Also,
The first detection of the end potential, that is, the processing of steps S12 to S14 performed first in the coordinate detection device A, and the reference value setting control performed at the same time as the detection of the first end potential (S19).
The steps S24 to S24) are performed once before the product is shipped, and thereafter, the end potential is detected at the timing when the power of the coordinate detection device A is turned on, and the coefficient is corrected. There is no need to perform value setting operations.

In the above description, the processing for detecting the end potential and the processing for correcting the coefficient, that is, step S1.
Although the processing of 2 to S17 is described as being performed at the timing when the power of the coordinate detecting device A is turned on, the processing is not limited to this, and the processing may be performed when a command is instructed. That is, when a predetermined command for performing the process is received from the host CPU 22, the process, that is, the process of detecting the end potential and the process of correcting the coefficient may be performed. Further, the processing may be performed when the pen down is detected. When there is a pen down, the flowchart shown in FIG.
It looks like this: That is, if the processing of steps S12 to S17 is located between steps S25 and S26 and there is pen down in step S25, step S1
Move to 2. When there is no change in the end potential in step S16, the process proceeds to step S26. Note that step S
After 17 as well, the process proceeds to step S26. Further, step S11 is deleted, and the process proceeds from step S10 to step S18.

[0048]

According to the coordinate detecting device of the present invention,
It is possible to reflect the fluctuation component of the end position potential in the calculation coefficient obtained by so-called reference value setting, that is,
Even with an 8-wire digitizer, the reference value can be set. Further, the initial detection of the end potential and the reference value setting control are performed, for example, once before the shipment of the product, and thereafter, the end potential is detected at a predetermined timing such as when the coordinate detection device is powered on. If the coefficient is corrected by performing the above procedure, the user does not need to perform the reference value setting operation one by one.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a coordinate detection device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an arithmetic control unit.

FIG. 3 is a circuit diagram showing a configuration of a digitizer and a switch circuit connected to the digitizer in the coordinate detecting device according to the embodiment of the present invention.

FIG. 4 is a flowchart illustrating an operation of the coordinate detecting device according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram illustrating an operation of the coordinate detecting device according to the embodiment of the present invention.

FIG. 6 is an explanatory diagram illustrating an operation of the coordinate detecting device according to the embodiment of the present invention.

FIG. 7 is a basic configuration diagram of a resistive film pressure-sensitive digitizer.

FIG. 8 is a circuit diagram showing a configuration of a conventional 4-wire digitizer and a switch circuit connected thereto.

FIG. 9 is a plan view showing the outline of a conventional 4-wire digitizer.

FIG. 10 is a flowchart illustrating the operation of a conventional 4-wire digitizer.

FIG. 11 is an explanatory diagram illustrating an operation of a conventional 4-wire digitizer.

FIG. 12 is a flowchart illustrating the operation of a conventional 8-wire digitizer.

FIG. 13 is an explanatory diagram illustrating an operation of a conventional 8-wire digitizer.

[Explanation of symbols]

S coordinate detector 10 digitizer 12 switch circuits 14 A / D converter 16 Arithmetic control unit 16a coefficient calculator 16b End potential detector 16c coefficient correction unit 16d Coordinate calculation unit 18 Pen-down detector

Continuation of the front page (56) References JP-A-9-146681 (JP, A) JP-A-8-314613 (JP, A) JP-A-7-182093 (JP, A) JP-A-2-273822 (JP , A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G06F 3/03-3/033

Claims (7)

(57) [Claims] 1. A resistance film for X-coordinate detection and a resistance for Y-coordinate detection
A seat for detecting the pressed coordinates in a digitizer having a membrane
A target detection device, which allows a user to press a preset display point to
By detecting the potential of the
A coefficient calculation / holding unit that calculates and holds the coefficient
And the potential at the end position of the X-coordinate detection resistance film is detected.
In addition, the edge voltage for detecting the potential at the edge position of the Y coordinate detection resistance film
Position detection means and at least the potential detected by the end potential detection means
Also, if one potential fluctuates, the above coefficient calculation and
Coefficient correction means for correcting the coefficient held in the holding means, and correction based on the coefficient held in the coefficient calculation / holding means
Two end potentials on the previous reference value potential gradient line (Lk)
The difference between (Vwmin, Vwmax) is set to ΔVw, and based on the end potential detection.
The uncorrected terminal voltage which is the straight line of the potential gradient before correction
Of the reference gradient line (Lk) before correction
On the corrected front potential gradient line (Lh) corresponding to
The difference between the end potentials (Vmin, Vmax) of ΔVm is defined as
When the fluctuation amount of ΔVa and ΔVb is set, the corrected coefficient
Corrected reference value potential gradient straight line which is a potential gradient straight line based on
The end potentials (Vwmin ', Vwmax') at (Lk ') and the
Corresponding two in the straight forward reference value potential gradient straight line (Lk)
And the end potentials (Vwmin, Vwmax) of ΔVc,
When ΔVd, ΔVc and ΔVd are ΔVc = Δ
Formula of Va · ΔVw / ΔVm and ΔVd = ΔVb · ΔVw
/ ΔVm formula
Target detection device. 2. The digitizer is an 8-wire digitizer.
The coordinate detection device according to claim 1, wherein the coordinate detection device is provided. 3. The coefficient correcting means adjusts the fluctuation amount of the end potential.
The correction amount is calculated in accordance with the above items.
The coordinate detection device according to 2. 4. Detection of an end potential by the end potential detection means.
And the correction of the coefficient by the above-mentioned coefficient correction means is the coordinate detection.
A contract that is performed every time the device is powered on
The coordinate detection device according to claim 1, 2, or 3. 5. An end potential detection by the end potential detection means.
And the correction of the coefficient by the coefficient correction means is
Characterized by performing a pen down to Isa every time it is detected
The coordinate detection device according to claim 1, 2, or 3. 6. An end potential detection by the end potential detection means.
And the correction of the coefficient by the coefficient correction means is
The method is performed every time a command is issued
The coordinate detection device according to 1, 2, or 3. 7. The coordinate detection device is further corrected.
The coordinate calculation means that calculates the coordinates of the pressed point according to the coefficient
The seat according to claim 1, 2 or 3, characterized in that
Target detection device.