JP6291077B2 - Input device - Google Patents

Description

  The present invention relates to an input device that inputs information according to a change in capacitance due to the proximity of an object, and more particularly to an input device that includes a sensor that detects a change in capacitance between a detection electrode and a ground. Is.

  Sensors that detect changes in capacitance can detect the proximity of an object (finger, pen, etc.) with a simple configuration, so user interface devices for various electronic devices such as touchpads for notebook computers and touch panels for smartphones Widely used in

  Capacitive sensors mainly include a mutual capacitance sensor that detects a change in capacitance between the drive electrode and the detection electrode, and a self-capacitance type that detects a change in capacitance of the detection electrode with respect to the ground. There is a sensor. The mutual capacitance type sensor can detect a change in capacitance at a plurality of positions on the detection electrode, and therefore is suitable for multipoint detection as compared with the self-capacitance type sensor. On the other hand, the self-capacitance type sensor has an advantage that the detection sensitivity is higher than that of the mutual capacitance type sensor because it directly detects the capacitance change between the adjacent object and the detection electrode. Therefore, a high-sensitivity self-capacitance type sensor is advantageous when realizing a hovering function that detects the operation of a finger at a position away from the operation surface.

  However, even with a relatively high-sensitivity self-capacitance type sensor, the change in capacitance due to the proximity of the finger is extremely small, so if you receive large noises through electronic components or the human body placed around the sensor It becomes difficult to accurately detect the change in capacitance.

  The following Patent Document 1 describes a liquid crystal device in which a noise electrode is provided between a capacitive touch panel and a liquid crystal panel. The noise electrode functions as a shield for preventing noise propagating from the liquid crystal panel to the touch panel, and also functions as an electrode for detecting noise from the liquid crystal panel. A plurality of capacitance values detected at the noise electrode are averaged and multiplied by a predetermined coefficient to obtain a noise correction value. This noise correction value is subtracted from the capacitance value (detection value) detected by each detection electrode of the touch panel.

JP 2011-198208 A

  However, in the invention described in Patent Document 1, noise from the liquid crystal panel is detected because the noise electrode is located away from the surface on the front side of the touch panel (the surface on which an object such as a finger or a pen is close). However, noise from nearby objects is not detected. Therefore, there is a problem that noise transmitted from an adjacent object cannot be removed.

  In order to avoid this problem, it is conceivable that a noise electrode is arranged on the front side of the touch panel so that noise from an adjacent object can be detected by the noise electrode. However, when correction similar to the above (correction by subtracting the noise correction value from the detection value) is performed using the capacitance value detected by the noise electrode, only the noise component from the adjacent object is obtained. In addition, the electrostatic capacitance component between the object to be detected and the detection electrode is also removed. Therefore, the function as a sensor for detecting the proximity of an object cannot be performed.

  In addition, if a capacitance detection circuit is provided for each of the plurality of detection electrodes in the touch panel, the circuit scale becomes very large. Usually, a plurality of detection electrodes are switched and connected to one capacitance detection circuit. Configuration is adopted. In this case, since the electrostatic capacitances of the plurality of detection electrodes are sequentially detected one by one, if the noise level changes every moment, each detected value includes a different noise component. Therefore, the method of uniformly correcting the detection values of all the detection electrodes with a common noise correction value has a problem that noise that changes every moment cannot be effectively removed.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an input device that can effectively remove noise transmitted from an object to be detected and accurately detect a change in capacitance due to the proximity of the object. There is.

  An input device according to the present invention includes a detection electrode provided so that an object electrically or electrostatically coupled to a ground can be brought close to the ground, and the ground and the detection electrode formed by the proximity of the object to the detection electrode. An input device for inputting information according to the change in the capacitance between the reference electrode and the reference electrode provided to detect noise from at least one noise source causing noise to the detection electrode, and the detection A first capacitance detection unit that detects a capacitance between an electrode and the ground and obtains a detection value indicating the detection result; and detects a capacitance between the reference electrode and the ground. The second capacitance detection unit that obtains a reference value indicating the detection result and the detection of the second capacitance detection unit while repeating the detection of the first capacitance detection unit, the second capacitance detection unit repeats the detection of the second capacitance detection unit. Detection of the capacitance detector The simultaneous detection reference that is the reference value acquired by the detection control unit and the detection value acquired by the first capacitance detection unit by the detection simultaneously with the detection value by the second capacitance detection unit A correction unit that corrects the value based on an average reference value obtained by averaging the plurality of reference values acquired by repetition of detection in the second capacitance detection unit.

According to said structure, the electrostatic capacitance between the said detected value and a ground changes, when objects, such as a human body, adjoin. The reference electrode detects noise from a noise source that causes noise to the detection electrode. The first capacitance detection unit detects a capacitance between the detection electrode and the ground, and acquires the detection value as a detection result. The second capacitance detection unit detects a capacitance between the reference electrode and the ground, and acquires the reference value as a detection result. When the capacitance is detected in the first capacitance detector, the capacitance is also detected in the second capacitance detector, and the detection result corresponds to the detection value. The simultaneous detection reference value is acquired. In the second capacitance detection unit, the detection of capacitance is repeated, and a plurality of reference values are acquired as detection results. The detection value of the first capacitance detection unit includes the simultaneous detection reference value acquired by simultaneous detection in the second capacitance detection unit and a plurality of detection values acquired in the second capacitance detection unit. Is corrected based on the average reference value obtained by averaging the reference values.
Accordingly, when noise caused by a noise source of an object such as a human body is detected at the reference electrode, the first reference capacitance between the reference electrode and the object can be estimated from an average reference value. Then, from the difference between the first reference capacitance estimated by the average reference value and the simultaneous detection reference value, it is possible to estimate the intensity of noise caused by the noise source of the object at the time of detection of the detection value It becomes.
Further, even when noise caused by a noise source other than an object such as a human body is detected by the reference electrode, the first reference capacitance between the reference electrode and the object can be estimated from the average reference value, From the difference between the first reference capacitance estimated by the average reference value and the simultaneous detection reference value, it is possible to estimate the intensity of noise caused by a noise source other than the object at the time of detection of the detection value.

Preferably, the input device may include a plurality of detection electrodes and a first selection unit that selects one detection electrode from the plurality of detection electrodes and connects the detection electrode to the first capacitance detection unit. . The first capacitance detection unit may detect the capacitance of the detection electrodes connected via the first selection unit. The detection control unit sequentially selects each of the plurality of detection electrodes in the first selection unit, and each time one detection electrode is selected in the first selection unit, the detection of the first capacitance detection unit. At the same time, the second capacitance detection unit may perform detection. The correction unit may correct the detection value using the average reference value obtained by averaging a series of the plurality of simultaneously detected reference values acquired in accordance with the sequential selection operation of the first selection unit. .
According to the above configuration, the capacitances of the plurality of detection electrodes are sequentially detected by the first capacitance detection unit, and in parallel with this, the capacitances of the reference electrode are changed to the second electrostatic capacitance. It is repeatedly detected by the capacitance detection unit. The average reference value used for correcting the detection value of each detection electrode is obtained by averaging the simultaneous detection reference values used for correcting the detection value of each detection electrode. That is, the reference value that is not used for correcting the detection value of each detection electrode may not be acquired separately for calculating the average reference value.

  Preferably, the correction unit decreases the detection value as the simultaneous detection reference value increases with respect to the average reference value, and increases the detection value as the simultaneous detection reference value decreases with respect to the average reference value. The detected value may be corrected so that

Preferably, the correction unit may stop correcting the detection value when a difference between the simultaneous detection reference value and the average reference value is smaller than a predetermined threshold value.
As a result, it is possible to avoid generation of useless errors caused by performing correction in a state where noise is small.

Preferably, the correction unit may stop correcting the detection value when the simultaneous detection reference value is smaller than a predetermined threshold value.
As a result, correction is not performed in a state where excessive noise is added.

Preferably, the correction unit may acquire a correction detection value corresponding to a multiplication result obtained by multiplying the correction value obtained by dividing the average reference value by the simultaneous detection reference value and the detection value. As a result, the noise caused by the noise source of an object such as a human body is corrected.
In this case, when the average reference value is smaller than a predetermined threshold, the correction unit stops correcting the detection value, or predetermined value is obtained by subtracting the average reference value from the simultaneous detection reference value. A correction detection value corresponding to a subtraction result obtained by subtracting a correction value obtained by multiplying the coefficient by the above detection value may be acquired. Thereby, when the noise caused by the noise source of the object such as the human body is small, the correction of the detection value is stopped or the noise caused by the noise source other than the object such as the human body is removed.

  Preferably, the correction unit obtains a correction detection value corresponding to a subtraction result obtained by subtracting a correction value obtained by subtracting the average reference value from the simultaneous detection reference value by a predetermined coefficient from the detection value. Good. Thereby, noise caused by noise sources other than an object such as a human body is removed.

Preferably, the input device may include a second selection unit that selects at least one detection electrode of the plurality of detection electrodes as the reference electrode and connects the selection electrode to the second capacitance detection unit. The second capacitance detection unit may detect the capacitance using the detection electrode connected via the second selection unit as the reference electrode.
With the above configuration, since a part of the plurality of detection electrodes is used as the reference electrode, an area required for the arrangement of the reference electrode can be saved as compared with the case where the reference electrode is provided independently of the detection electrode. .

Preferably, when the first selection unit selects one detection electrode included in the group of detection electrodes selected as the reference electrode in the second selection unit, the detection control unit The selection of one detection electrode may be canceled.
Thereby, the detection electrode used as the reference electrode is not simultaneously connected to the first capacitance detection unit and the second capacitance detection unit.

Preferably, the detection control unit specifies a detection electrode close to the object based on the detection values of the plurality of detection electrodes acquired most recently or the correction result of the correction unit with respect to the detection value, and specifies A detection electrode may be selected as the reference electrode in the second selection unit.
As a result, since the detection electrode close to the object is selected as the reference electrode, noise from the object is detected with high sensitivity at the reference electrode.

  Preferably, the detection control unit determines that the correction result of the correction unit is greater than a predetermined threshold value and / or the order in which the magnitudes of the correction results of the correction unit are relatively compared is predetermined from the top. At least one detection electrode satisfying that it is within the order may be specified as a detection electrode close to the object.

Preferably, the input device includes two reference electrodes having different intensity of noise from the noise source and two second capacitance detection units corresponding to the two reference electrodes. Good. The two second capacitance detection units may detect capacitances between the corresponding reference electrodes and the ground, respectively. The detection control unit may detect the two second capacitance detection units simultaneously with the detection of the first capacitance detection unit every time one detection electrode is selected by the first selection unit. . The correction unit refers to the two simultaneous detection references acquired by the two second capacitance detection units by detecting the detection value acquired by the first capacitance detection unit at the same time as the detection value. You may correct | amend based on a value and two said average reference values which are the average of a series of said simultaneous detection reference values acquired simultaneously in the said 2nd 2nd electrostatic capacitance detection part.
According to the above configuration, when the capacitance of the detection electrode is detected in the first capacitance detector, the capacitance of the reference electrode is simultaneously detected in the two second capacitance detectors. Detection is performed, and the reference value is acquired as the two simultaneous detection reference values corresponding to the detection value. Further, the detection of capacitance is repeated in the two second capacitance detection units, and a series of the plurality of reference values are acquired as the detection results. The detection value of the first capacitance detection unit includes two simultaneous detection reference values acquired by simultaneous detection in the two second capacitance detection units, and the two second capacitance detections. The correction is performed based on two average reference values obtained by averaging a series of the reference values respectively acquired in the unit.
The first reference capacitances of the two reference electrodes and the object can be estimated from the two average reference values, respectively. In addition, the relationship between one of the first reference capacitances estimated by one of the average reference values and the corresponding simultaneously detected reference value, and the other of the first reference capacitances estimated by the other average reference value From the relationship between the 1 reference capacitance and the corresponding simultaneous detection reference value, the noise intensity caused by the noise source of the adjacent object and the noise intensity caused by the noise source other than the adjacent object are Either can be estimated.

The detection value of the first capacitance detection unit is a first noise component from a first noise source that causes noise to the detection electrode via an adjacent object, and is between the object and the detection electrode. A first noise component corresponding to a product of the first capacitance of the first noise source and a first noise coefficient indicating a noise intensity of the first noise source, and a second noise source that causes noise to the detection electrode without passing through the object A second noise component corresponding to a product of a second capacitance between the second noise source and the detection electrode and a second noise coefficient indicating a noise intensity of the second noise source. It may be estimated that the noise component is equal to the sum of the first capacitance.
The simultaneous detection reference value of the second capacitance detection unit is a first reference noise component from the first noise source that causes noise to the reference electrode through the object, and the object and the A first reference noise component according to a product of a first reference capacitance between the reference electrode and the first noise coefficient; and a second noise source that causes noise to the reference electrode without passing through the object. A second reference noise component corresponding to a product of a second reference capacitance between the second noise source and the reference electrode and the second noise coefficient; It may be estimated that it is equal to the sum of the reference capacitance.
Further, the reference component may be estimated to be equal to the average reference value.
In this case, the correction unit includes the detection value, the two simultaneous detection reference values, the two average reference values, and the two second reference capacitances acquired in advance for the two reference electrodes. And a corrected detection value approximated to the first capacitance may be calculated based on the second capacitance acquired in advance for the detection electrode.

Preferably, the correction unit is configured such that a difference between two simultaneous detection reference values acquired by simultaneous detection with the detection value in the two second capacitance detection units is smaller than a predetermined threshold value, and / Or when the difference between two average reference values, which is an average of a series of the simultaneous detection reference values acquired simultaneously in the two second capacitance detection units, is smaller than a predetermined threshold value, You may cancel the correction.
Thereby, when the noise from an object such as a human body is small, the correction of the detection value is stopped.

Preferably, the correction unit is configured such that a difference between two simultaneous detection reference values acquired by simultaneous detection with the detection value in the two second capacitance detection units is smaller than a predetermined threshold value, and / Or one reference when a difference between two average reference values, which is an average of a series of the simultaneous detection reference values acquired simultaneously in the two second capacitance detection units, is smaller than a predetermined threshold value A corrected detection value corresponding to a subtraction result obtained by subtracting, from the detection value, a correction value obtained by subtracting a value obtained by subtracting the average reference value from the simultaneous detection reference value at the electrode from the detection coefficient may be acquired.
Thereby, when noise from an object such as a human body is small, noise caused by a noise source other than the object such as a human body is removed.

Preferably, the input device may include at least one second selection unit that selects at least one detection electrode of the plurality of detection electrodes as the reference electrode and connects to the second capacitance detection unit. . The at least one second capacitance detection unit may detect the capacitance using the detection electrode connected via the second selection unit as the reference electrode.
With the above configuration, since a part of the plurality of detection electrodes is used as the reference electrode, an area required for the arrangement of the reference electrode can be saved as compared with the case where the reference electrode is provided independently of the detection electrode. .

Preferably, when the first selection unit selects one detection electrode included in the group of detection electrodes selected as the reference electrode in the second selection unit, the detection control unit The selection of one detection electrode may be canceled.
Thereby, the detection electrode used as the reference electrode is not simultaneously connected to the first capacitance detection unit and the second capacitance detection unit.

Preferably, the detection control unit specifies a detection electrode close to the object based on the detection values of the plurality of detection electrodes acquired most recently or the correction result of the correction unit with respect to the detection value, and specifies A detection electrode may be selected as the reference electrode in the second selection unit.
As a result, since the detection electrode close to the object is selected as the reference electrode, noise from the object is detected with high sensitivity at the reference electrode.

  Preferably, the correction unit may calculate the average reference value by averaging a series of a predetermined number of simultaneously detected reference values including the recently acquired simultaneously detected reference values, and the second selecting unit. When the detection electrode selected as the reference electrode is changed based on the corrected value of the detection value most recently acquired in the first capacitance detection unit for the changed detection electrode, A series of a predetermined number of simultaneous detection reference values may be initialized.

  According to the present invention, it is possible to effectively remove noise transmitted from an object to be detected and accurately detect a change in capacitance due to the proximity of the object.

It is a figure which shows an example of a structure of the input device which concerns on the 1st Embodiment of this invention. It is a figure which shows an example of a structure of a 1st electrostatic capacitance detection part. It is a figure for demonstrating the noise source which brings about noise to a detection electrode through an electrostatic capacitance. It is a figure for demonstrating the influence which the noise source of a human body has on the detected value of an electrostatic capacitance. It is a figure for demonstrating the influence which the noise source of a non-human body has on the detected value of an electrostatic capacitance. It is a flowchart for demonstrating the process which acquires the electrostatic capacitance value of a detection electrode in the input device which concerns on 1st Embodiment. It is a flowchart for demonstrating the correction process of the detected value in the input device which concerns on 1st Embodiment. It is a figure for demonstrating that the influence of a human body noise is estimated from a simultaneous detection reference value and an average reference value. It is a figure for demonstrating that the influence of a non-human body noise is estimated from a simultaneous detection reference value and an average reference value. It is a figure which shows the structure of the modification of the input device which concerns on 1st Embodiment, and shows the 1st example which has a reference electrode only for noise detection. It is a figure which shows the structure of the modification of the input device which concerns on 1st Embodiment, and shows the 2nd example which has a reference electrode only for noise detection. It is a flowchart for demonstrating the 1st modification of the correction process in the input device which concerns on 1st Embodiment. It is a flowchart for demonstrating the 2nd modification of the correction process in the input device which concerns on 1st Embodiment. It is a flowchart for demonstrating the 3rd modification of the correction process in the input device which concerns on 1st Embodiment. It is a flowchart for demonstrating the 4th modification of the correction process in the input device which concerns on 1st Embodiment. It is a figure which shows an example of the circuit structure for averaging a series of predetermined number of simultaneous detection reference values in a correction | amendment part. It is a flowchart for demonstrating the 5th modification of the correction process in the input device which concerns on 1st Embodiment. It is a flowchart for demonstrating the 6th modification of the correction process in the input device which concerns on 1st Embodiment. It is a flowchart for demonstrating the 7th modification of the correction process in the input device which concerns on 1st Embodiment. It is a figure which shows an example of a structure of the input device which concerns on the 2nd Embodiment of this invention. It is a figure for demonstrating that the influence of two types of noise (human body noise, non-human body noise) is estimated from two simultaneous detection reference values and two average reference values. It is a flowchart for demonstrating the process which acquires the electrostatic capacitance value of a detection electrode in the input device which concerns on 2nd Embodiment. It is a flowchart for demonstrating the correction process of the detected value in the input device which concerns on 2nd Embodiment. It is a figure which shows the structure of the modification of the input device which concerns on 2nd Embodiment, and shows the example which has a reference electrode only for noise detection. It is a flowchart for demonstrating the 1st modification of the correction process in the input device which concerns on 2nd Embodiment. It is a flowchart for demonstrating the 2nd modification of the correction process in the input device which concerns on 2nd Embodiment. It is a flowchart for demonstrating the 3rd modification of the correction process in the input device which concerns on 2nd Embodiment.

<First Embodiment>
FIG. 1 is a diagram showing an example of the configuration of an input device according to the first embodiment of the present invention.
The input device shown in FIG. 1 includes an electrode unit 10, a first selection unit 20, a second selection unit 30, a first capacitance detection unit 40, a second capacitance detection unit 50, and a signal generation unit. 60, a processing unit 70, a storage unit 80, and an interface unit 90.

When an object such as a finger or a pen comes close to the detection electrodes (ES _{1 to} ES _n ) of the electrode unit 10, the capacitance formed between the detection electrode and the ground changes. The input device according to the present embodiment is a device that inputs information according to a change in capacitance of detection electrodes (ES _{1 to} ES _n ) caused by the proximity of an object. For example, the proximity of the object to the electrode unit 10 This is applied to a user interface device (touch pad, touch panel, etc.) that acquires information such as the presence / absence of the object, the proximity position of the object, the distance between the electrode unit 10 and the object, and the size of the object. Note that “proximity” in the present specification includes both being close in a contact state and being close in a non-contact state.

[Electrode part 10]
Electrode portion 10 includes a n number of detection electrodes ES ₁ ~ES _n for detecting the proximity of an object such as a finger or a pen. The detection electrodes ES _{1 to} ES _n are arranged in a lattice shape along the surface of the detection region of the object, for example. The position of the object in the vertical direction of the detection area is specified from the capacitance values of the detection electrodes arranged in the vertical direction of the detection area. Further, the position of the object in the lateral direction of the detection region is specified from the capacitance value of the detection electrodes arranged in the lateral direction of the detection region.

[First selection unit 20]
The first selection unit 20 selects one detection electrode from the _n detection electrodes ES _{1 to} ES _n (hereinafter, an arbitrary one detection electrode may be referred to as “ES _i ”) to select the first electrostatic This circuit is connected to the capacity detection unit 40 and switches the connection according to the control of the processing unit 70.

[Second selection unit 30]
The second selection unit 30 is a circuit that selects one or a plurality of detection electrodes from the _n detection electrodes ES _{1 to} ES _n and connects to the second capacitance detection unit 50 as a reference electrode for noise detection. The connection is switched according to the control of the processing unit 70. When selecting a plurality of detection electrodes, the second selection unit 30 connects to the second capacitance detection unit 50 in a state where the plurality of detection electrodes are electrically connected.

[First Capacitance Detection Unit 40]
The first capacitance detection unit 40 detects the capacitance between the detection electrode ES _i connected via the first selection unit 20 and the ground, and acquires a detection value S _i indicating the detection result. . The first capacitance detection unit 40 detects the capacitance at a timing controlled by the processing unit 70.

FIG. 2 is a diagram illustrating an example of the configuration of the first capacitance detection unit 40. The first capacitance detection unit 40 shown in FIG. 2, an operational amplifier 41, a capacitor _{C f,} a subtractor 42, a multiplier 43, an integrator 44, an analog - digital converter (AD converter) 45 Have.

The operational amplifier 41 and the capacitor C _f constitute a charge amplifier that outputs a signal corresponding to the charge transmitted through the detection electrode ES _i . Inverting input of the operational amplifier 41 is connected to the output of the operational amplifier 41 via a capacitor C _f, is connected to the detection electrode ES _i. The drive wave of the signal generator 60 is input to the non-inverting input of the operational amplifier 41.

Since the output of the operational amplifier 41 is negatively fed back to the inverting input via the capacitor _Cf , the voltage is almost the same as the inverting input and the non-inverting input of the operational amplifier 41. Therefore, the capacitance C formed between the detection electrode ES _i and ground, substantially the same AC voltage as the drive wave is applied. When the capacitance C is charged / discharged according to the AC voltage, the capacitor _Cf is also charged / discharged by the same charge. Thus, the operational amplifier 41 outputs a voltage corresponding to the sum of the voltage and drive waves generated in the capacitor C _f. When the drive wave voltage is “V _drv ”, the output voltage of the operational amplifier 41 is “V _drv * (C / C _f ) + V _drv ”.

The subtractor 42 outputs a detection wave obtained by subtracting the drive wave voltage from the output voltage of the operational amplifier 41. The detected wave is expressed by “V _drv * (C / C _f )” and has an amplitude proportional to the capacitance C. The multiplier 43 multiplies the detection wave output from the subtractor 42 and the demodulated wave of the signal generator 60, and the integrator 44 integrates the multiplication result. Since the demodulated wave and the drive wave are the same signal generated in the signal generator 60, the detected wave and the demodulated wave have the same frequency component. By multiplying and integrating the detected wave and the demodulated wave, a DC component proportional to the amplitude of the same frequency component as the demodulated wave included in the detected wave is obtained. This operation corresponds to _obtaining a Fourier coefficient having the same frequency component as that of the drive wave ( _Vdrv ) included in the detection wave, and can be regarded as a narrow-band bandpass filter. Since the drive wave and the demodulated wave are supplied from the same signal generator 60 and the frequency error between the two is substantially negligible, an output proportional to the capacitance C can be stably obtained from the integrator 44. The AD converter 45 AD-converts the output and outputs it as a detection value S _i of the digital signal.

If the capacitance C is what applied other parasitic capacitance to the capacitance of the detection target object (such as a human body), the influence of the parasitic capacitance, the later the detection value S _i when there is no detected object Correction can be performed by subtraction by the processing unit 70 (calibration). In this way, the detection value S _i indicates the capacitance value between the detection electrode ES _i and the ground, which is generally the capacitance value between the detection electrode ES _i and the detection target (such as a human body). .

The circuit composed of the multiplier 43 and the integrator 44 in the first capacitance detector 40 operates as a narrow-band bandpass filter and has a high noise removal capability. If the drive wave is set to 100 kHz, all noise components other than the vicinity of 100 kHz can be removed. In this case, for example, noise having a frequency in the range of DC to several tens of kHz has no effect. However, even in this circuit, noise having a frequency the same as or close to the drive wave is passed. The noise component that could not be filtered remains as a frequency component of about zero to several kHz in the detection value S _i . This residual component has a plurality of frequency components and phases, and the noise influence is the sum of the amount determined by the intensity and phase of each frequency component. Therefore, when the detection value S _i is sampled at a frequency of about 100 Hz, the noise component is measured as a random fluctuation that changes at every sampling.

[Second capacitance detecting unit 50]
The second capacitance detection unit 50 detects the capacitance between the noise detection reference electrode (one or a plurality of detection electrodes) connected via the second selection unit 30 and the ground, and A reference value indicating the detection result is acquired. The second capacitance detection unit 50 detects the capacitance of the reference electrode simultaneously with the detection of the capacitance of the detection electrode in the first capacitance detection unit 40 according to the control of the processing unit 70. The reference value acquired in the second capacitance detection unit 50 by the detection at the same time as the detection value S _{i of} the first capacitance detection unit 40 is referred to as “simultaneous detection reference value Q _i ” in the following description.

The second capacitance detection unit 50 has, for example, the same circuit configuration as the first capacitance detection unit 40 shown in FIG. 2, and has the same drive wave (demodulation wave) as the first capacitance detection unit 40. Operates synchronously. Since the simultaneous detection reference value Q _i is simultaneously detected in synchronization with the same drive wave (demodulated wave) as the detection value S _i , the simultaneous detection reference value Q _i has a correlation with the detection value S _i with respect to noise influence.

[Signal Generator 60]
The signal generator 60 supplies a common drive wave (demodulated wave) to the first capacitance detector 40 and the second capacitance detector 50. For example, the signal generator 60 may change the frequency of the drive wave (demodulated wave) according to the control of the processing unit 70. As a result, the frequency of the drive wave (demodulated wave) can be changed according to the noise frequency, and noise interference to the detection value S _i can be made difficult to occur.

[Processing unit 70]
The processing unit 70 is a circuit that controls the overall operation of the input device, and includes, for example, a computer that performs processing according to the instruction code of a program stored in the storage unit 80 and a logic circuit that implements a specific function. Composed. All of the processing of the processing unit 70 may be realized based on a program in a computer, or part or all of the processing may be realized by a dedicated logic circuit.
In the example of FIG. 1, the processing unit 70 includes a detection control unit 71, a correction unit 72, and a coordinate calculation unit 73.

The detection control unit 71 performs selection of detection electrodes in the first selection unit 20 and the second selection unit 30 and control of detection operations in the first capacitance detection unit 40 and the second capacitance detection unit 50.
Specifically, the detection control unit 71 repeats the detection of the capacitance in the first capacitance detection unit 40 while switching the selection of the detection electrode in the first selection unit 20, and the first capacitance detection unit. Simultaneously with the detection of 40, the detection of the second capacitance detection unit 50 is repeated. That is, the detection control unit 71 selects each of the detection electrodes ES _{1 to} ES _n one by one in order in the first selection unit 20, and each time one detection electrode is selected in the first selection unit 20, the first electrostatic unit The detection of the capacitance detection unit 40 and the detection of the second capacitance detection unit 50 are performed simultaneously.

  Further, the detection control unit 71 changes the selection of the reference electrode (one or a plurality of detection electrodes) for noise detection in the second selection unit 30 according to the correction result of the correction unit 72 described later. That is, the detection control unit 71 detects the object to be detected (based on the detection values of the plurality of detection electrodes most recently acquired by the first capacitance detection unit 40 and the correction result of the correction unit 72 for the detection values). A detection electrode close to a finger or the like is specified, and the specified detection electrode is selected as a reference electrode by the second selection unit 30. Specifically, the detection control unit 71 determines that the condition in which the correction result of the correction unit 72 is greater than a predetermined threshold or the order in which the magnitudes of the correction results of the correction unit 72 are relatively compared from a higher order in a predetermined order. One or a plurality of detection electrodes satisfying certain conditions are specified as detection electrodes close to the object. As a result, the detection electrode that is susceptible to noise from the object is selected as the reference electrode, so that the noise from the object can be effectively corrected by the correction unit 72 described later.

When the second selection unit 30 selects a group of detection electrodes as reference electrodes, the first selection unit 20 selects one detection electrode ES _i included in the group of detection electrodes. The unit 71 cancels the selection of the one detection electrode ES _i in the second selection unit 30 (separates the detection electrode ES _i from the second capacitance detection unit 50). That is, the detection control unit 71 prevents the same detection electrode from being connected to both the first capacitance detection unit 40 and the second capacitance detection unit 50 at the same time.
Further, in this case, the detection control unit 71 calculates the sum of the detection value S _i acquired by the first capacitance detection unit 40 and the reference value Q _i acquired by the second capacitance detection unit 50, This is acquired as a simultaneous detection reference value (S _i + Q _i ) corresponding to the detection value S _i . This is because the sum of the capacitance of the detection electrode ES _i selected in the first selection unit 20 and the capacitance of the reference electrode (excluding the detection electrode ES _i ) selected in the second selection unit 30 is: This is because it corresponds to the capacitance of the entire reference electrode including the detection value S _i .

In addition, when only one detection electrode ES _i is selected as the reference electrode in the second selection unit 30, the detection control unit 71 does not select the detection electrode ES _i in the first selection unit 20, and the detection electrode It omitted to obtain the detection value _{S i} for ES _i. That is, also in this case, the detection control unit 71 prevents the same detection electrode from being connected to both the first capacitance detection unit 40 and the second capacitance detection unit 50 at the same time.

Correcting unit 72, the detection value of the detection electrode obtained (detection electrodes _ES 1 _{~ES n)} in the first capacitance detection portion 40 _(S 1 to S _n), in the second capacitance detection unit 50 corrected based on the reference value of the reference electrode is obtained _(Q 1 ~Q _n). Specifically, the correction unit 72 uses the detection value S _i of the detection electrode ES _i as a reference value acquired by simultaneous detection with the detection value S _i , the simultaneous detection reference value Q _i , and the second capacitance. The detection unit 50 corrects a series of a plurality of reference values (simultaneous detection reference values) acquired by repeated detection based on an averaged reference value _Qavr .

The correction unit 72 _decreases the detection value (correction detection value SA _i ) of the correction result as the simultaneous detection reference value Q _i becomes larger than the average reference value Q _avr , and the simultaneous detection reference value Q _i becomes the average reference value Q _avr. The detected value S _i is corrected so that the corrected detected value SA _i increases as the value decreases.
For example, the correction unit 72 acquires a correction detection value SA _i corresponding to a multiplication result obtained by multiplying the correction value obtained by dividing the average reference value Q _avr by the simultaneous detection reference value Q _i and the detection value S _i (formula described later). (3)).
Alternatively, the correction unit 72 corrects the detection value SA _i which corresponds to the subtraction result obtained by subtracting the correction value obtained by multiplying a predetermined coefficient to a value obtained by subtracting the average reference value Q _avr from simultaneous detection reference value Q _i from the detected value S _i (Equation (7) described later) may be acquired.

When only one detection electrode ES _i is selected as the reference electrode in the second selection unit 30, the correction unit 72 uses the average reference value Q _avr as the corrected detection value SA _i of the detection electrode ES _i . In this case, since the capacitance of the detection electrode ES _i is repeatedly detected by the second capacitance detection unit 50, the average reference value Q _avr obtained by averaging the detection results of the second capacitance detection unit 50 is detected. It can be regarded as a corrected detection value SA _i obtained by correcting the noise of the detection value S _i of the electrode ES _i .

Based on the corrected detection values (SA _{1 to} SA _n ) of the respective detection electrodes (ES _{1 to} ES _n ) corrected by the correction unit 72, the coordinate calculation unit 73 has an object (such as a finger) in the detection region of the electrode unit 10. Calculate the coordinates that are close to each other. For example, the coordinate calculation unit 73 calculates the vertical coordinates of the object proximity position based on the plurality of correction detection values acquired for the plurality of detection electrodes arranged in the vertical direction, and also uses the plurality of detection electrodes arranged in the horizontal direction. Based on the plurality of corrected detection values acquired for, the horizontal coordinate of the object proximity position is calculated. In addition, the coordinate calculation unit 73 may calculate the size of the object, the distance from the electrode, and the like based on the corrected detection values (SA _{1 to} SA _n ).

[Storage unit 80]
The storage unit 80 stores constant data and variable data used for processing in the processing unit 70. When the processing unit 70 includes a computer, the storage unit 80 may store a program executed on the computer. The storage unit 80 includes, for example, a volatile memory such as DRAM or SRAM, a non-volatile memory such as flash memory, a hard disk, and the like.

[Interface unit 90]
The interface unit 90 is a circuit for exchanging data between the input device and another device (such as a control IC for an information device equipped with the input device). The processing unit 70 outputs information such as the coordinates of the proximity position of the object calculated by the coordinate calculation unit 73, the size of the object, and the distance from the detection electrode from the interface unit 90 to a host device (not shown). In the host device, a user interface such as a pointing operation and a gesture operation recognition is constructed using these pieces of information.

  Further, the interface unit 90 acquires a program executed in the computer of the processing unit 70 from a disk drive device (not shown) (device that reads a program recorded on a non-temporary recording medium), a server, or the like, and stores the program in the storage unit 80. You may load it.

  Here, noise that affects the detected capacitance value in the input device having the above-described configuration will be described.

Figure 3 is a view for explaining the capacitance _(C x, C _s) noise source resulting in noise in the detection electrode ES _i through the (N1, N2).
“C _x ” in FIG. 3 is a capacitance between the human body (object) adjacent to the electrode unit 10 and the detection electrode ES _i and changes according to the proximity of the human body (hereinafter referred to as “first capacitance C”). _x "). Although the human body has a relatively large capacitance (about 100 pF) with respect to the ground, the change in the first capacitance C _x between the human body and the detection electrode ES _i is sufficiently small. Therefore, as shown in FIG. 3, the capacitance between the human body and the ground is generally negligible. However, the human body is induced by noise from various peripheral devices, and becomes a voltage-type noise source N1. Human noise source N1 (hereinafter may be referred to as "first noise source N1") of causes a change in charge of the detection electrodes ES _i through the first capacitance C _x. For this reason, the first noise source N1 generates “a fluctuation proportional to the first capacitance C _x between the human body and the detection electrode ES _i ” in the detection value S _i .

On the other hand, “C _s ” in FIG. 3 is a capacitance involved in noise propagation from the noise source N2 other than the human body (hereinafter, may be referred to as “second capacitance C _s ”). This second capacitance C _s exists regardless of the presence or absence of a human body, and does not depend on the self-capacitance (first capacitance C _x ) of the detection electrode ES indicating the proximity state of the human body. The second capacitance C _s is corrected by calibration or the like including other parasitic capacitances not involved in noise propagation, and ideally does not appear in the detected value. The value of the second capacitance C _s can be measured in advance for each detection electrode and used for the correction process. When there is not much change for each detection electrode, the second capacitance C _s may be a fixed value common to all the detection electrodes. A noise source N2 in FIG. 3 represents a source of noise existing other than the human body, such as a liquid crystal panel or a power line. This non-human body noise source N2 (hereinafter sometimes referred to as “second noise source N2”) changes the charge of the detection electrode ES _i through the second capacitance C _s , and the detection value S _i becomes “constant”. ”Fluctuation”.

As is apparent from the equivalent circuit model shown in FIG. 3, these noise sources N1 and N2 have an additive effect on the detection waves of the capacitance detection units (40, 50) (superposition theory). The detection target in the input device is a first capacitance C _x (self-capacitance) between the human body and the detection electrode ES _i . The first noise source of the human body N1 generates a proportional fluctuation in the first capacitance C _x. The second noise source N2 in non-human body, generates extraneous fluctuations to the first capacitance C _x. The detection value S _i includes noise obtained by adding both fluctuations. Therefore, the detection value S _i of the capacitance C _x can be expressed by the following equation.

In Expression (1), “A _i * C _x ” represents a noise component (first noise component) caused by the first noise source N1 of the human body, and “B _i * C _s ” represents the second noise source of the non-human body. The noise component (2nd noise component) resulting from N2 is shown. Further, “A _i ” is a coefficient (first noise coefficient) indicating the intensity of the first noise source N1, and “B _i ” is a coefficient (second noise coefficient) indicating the intensity of the second noise source N2. The first noise coefficient A _i and the second noise coefficient B _i are random values having a certain fluctuation width, and become different values every time the capacitance is detected.

FIG. 4 is a diagram for explaining the influence of the first noise source N1 on the human body on the detection value S _i and the simultaneous detection reference value Q _i . The function of the detection value S _i with respect to the first capacitance C _x is a linear function as shown in Expression (1). The same applies to the function of the simultaneous detection reference value Q _i for the first capacitance C _x . When there is no noise from the human body, the slope of the linear function is constant, but when there is noise from the human body, this slope changes every time capacitance is detected.

On the other hand, FIG. 5 is a diagram for explaining the influence of the non-human second noise source N2 on the detection value S _i and the simultaneous detection reference value Q _i . When there is no noise from the human body, the intercept of the linear function shown in Equation (1) is constant (zero), but due to the presence of noise from the non-human body, the intercept of the linear function is Change.

In the input device according to the present embodiment, the unknown coefficient (A _i , coefficient B in Equation (1) is used by using the simultaneous detection reference value Q _i and the average reference value Q _avr acquired by the second capacitance detection unit 50. By estimating _i ), a corrected detection value SA _i corresponding to the first capacitance C _x in equation (1) is calculated.

  Next, processing relating to capacitance detection and correction of the detection result in the input device according to the present embodiment will be described.

  FIG. 6 is a flowchart for explaining processing for acquiring the capacitance value of the detection electrode in the input device according to the first embodiment. In the process shown in FIG. 6, the capacitance of each detection electrode included in the electrode unit 10 is detected and corrected. By periodically repeating this process, the change in the capacitance of each detection electrode in accordance with the movement of an object (such as a finger) close to the electrode unit 10 is periodically measured.

In the process shown in FIG. 6, first, a reference electrode for noise detection is determined from the detection electrodes of the electrode unit 10 (ST100). Next, a detection electrode to be selected by the first selection unit 20 and a detection electrode to be selected as a reference electrode by the second selection unit 30 are set, and the electrodes according to the setting are the first capacitance detection unit 40 and the second detection electrode. Each is connected to the capacitance detector 50 (ST130). The first capacitance detection unit 40 and the second capacitance detection unit 50 detect the capacitance of the detection electrode and the capacitance of the reference electrode at the same time, and the detection value S _i and the simultaneous detection reference value Q _i are obtained. Obtained (ST140). Steps ST130 and ST140 are repeated until the capacitances of all the detection electrodes are detected (ST230). When the capacitances of all the detection electrodes are detected, an average reference value Q _avr that is an average value of the simultaneous detection reference values Q _{1 to} Q _n is calculated (ST240). Each detection value S _i is corrected based on the simultaneous detection reference value Q _i and the average reference value Q _avr, and a correction detection value SA _i is obtained as a correction result (ST250).
Hereinafter, each step of the flowchart will be described in detail.

ST100:
The detection control unit 71 of the processing unit 70 determines a reference electrode for noise detection to be selected by the second selection unit 30 from the detection electrodes ES _{1 to} ES _n of the electrode unit 10. The reference electrode is desirably an electrode that is induced with a large amount of noise to be corrected. Therefore, when correcting noise from the human body, the detection control unit 71 determines a detection electrode that is close to the human body as a reference electrode.

Since the capacitance (C _x ) of the detection electrode increases as the human body approaches, the detection value of the first capacitance detection unit 40 increases or the detection value after correction in the correction unit 72 increases. There is a high possibility that the human body is close to the detection electrode. Therefore, for example, the detection control unit 71 detects an object (such as a finger) based on the detection values of the plurality of detection electrodes most recently acquired by the first capacitance detection unit 40 or the correction result of the correction unit 72 for the detection values. Identifies one or more detection electrodes close to each other and determines them as reference electrodes.
Specifically, the detection control unit 71 uses, as a reference electrode, one or a plurality of detection electrodes that satisfy the condition that the correction result (or the detection value before correction) of the correction unit 72 is greater than a predetermined threshold value. decide. Alternatively, the detection control unit 71 may satisfy one or a plurality of conditions in which the order of comparison of the magnitudes of the correction results (or detection values before correction) of the correction unit 72 is within a predetermined order from the top. These detection electrodes may be determined as reference electrodes. In still another embodiment, the detection control unit 71 may determine, as a reference electrode, a detection electrode that satisfies at least one of these conditions, or may determine only a detection electrode that satisfies both conditions as a reference electrode. Good.

  Note that when all the detection electrodes (except those selected by the first selection unit 20) are used as reference electrodes, the processing unit 70 may omit the process of step ST100.

ST130:
The detection control unit 71 sets detection electrodes to be selected by the first selection unit 20 and the second selection unit 30, respectively. That is, the detection control unit 71 selects the detection electrodes in the order of “ES ₁ , ES ₂ ,..., ES _n ” in the first selection unit 20, and the reference electrodes determined in step ST 100 in the second selection unit 30. select.

When the first selection unit 20 selects one detection electrode ES _i included in the group of detection electrodes determined as reference electrodes in step ST100, the detection control unit 71 uses the detection electrode in the second selection unit 30. Deselect ES _i .
When only one detection electrode ES _i is determined as the reference electrode in step ST100, the detection control unit 71 does not select the detection electrode ES _i in the first selection unit 20 (the detection electrode ES _i Skip selection).
Thereby, the detection control part 71 prevents that both the 1st electrostatic capacitance detection part 40 and the 2nd electrostatic capacitance detection part 50 are simultaneously connected to the same detection electrode.

ST140:
The detection control unit 71 simultaneously detects the capacitance in the first capacitance detection unit 40 and the second capacitance detection unit 50, and acquires the detection value S _i and the simultaneous detection reference value Q _i . The detection control unit 71 stores the acquired data in a predetermined storage area of the storage unit 80.

The simultaneous detection reference value Q _i detects a capacitance Q (capacitance between the reference electrode and the object) that shows a substantially constant value when there is no noise. Here, the meaning of “substantially constant” indicates that the change in the capacitance Q due to the movement of the object (human body) can be ignored. For example, when detecting the position of the finger, even while the detection of step ST140 in order to acquire a detection value S _i of the respective detection electrodes of the electrode portions 10 are repeated, the change in capacitance Q may occur by the movement of the finger. The detection time of step ST140 performed for each detection electrode is determined to be a length such that the change in the capacitance Q is sufficiently small and can be ignored.

As described above, the first selection is performed to prevent the detection electrode ES _i included in the reference electrode from being connected to both the first capacitance detection unit 40 and the second capacitance detection unit 50. When the detection electrode ES _i is selected in the unit 20, the selection of the detection electrode ES _i is canceled in the second selection unit 30. In this case, the detection control unit 71 adds the detection value S _i acquired by the first capacitance detection unit 40 and the reference value Q _i acquired by the second capacitance detection unit 50 (S _i + Q _i ) As a simultaneous detection reference value. The correction unit 72 uses the simultaneous detection reference value (S _i + Q _i ) for calculating the average reference value Q _avr and for correcting the detection value S _i .
The simultaneous detection reference value (S _i + Q _i ) includes the capacitance of the detection electrode ES _i connected to the first capacitance detection unit 40 and a part of the reference electrode connected to the second capacitance detection unit 50 ( It represents the sum of the capacitance of excluding the detection electrode ES _i remaining part), which is equivalent to the capacitance of the entire reference electrode comprising a sensing electrode ES _i.

ST230:
If the detection of the capacitance has not been completed for all the detection electrodes, the detection control unit 71 returns to step ST130, selects the next detection electrode, and detects the capacitance (ST140). Thereby, the detection value S _i and the simultaneous detection reference value Q _i are acquired for each detection electrode of the electrode unit 10.

ST240:
The correcting unit 72 calculates the average reference value Q _avr based on the simultaneous detection reference value Q _i acquired by repeating Step ST140.

The simultaneous detection reference value Q _i indicates a substantially constant capacitance Q when there is no noise. However, when there is a noise source as shown in FIG. 3, the detection value is affected by the constantly changing noise. Different values each time. Therefore, the difference between the true capacitance Q and the simultaneous detection reference value Q _i indicates the influence of noise. The true capacitance Q cannot be detected directly, but can be estimated by an average reference value Q _{avr obtained} by averaging a series of a plurality of simultaneously detected reference values Q _i .

Since the average reference value Q _avr is an average value of the plurality of simultaneously detected reference values Q _i that are repeatedly detected, the capacitance Q approaches as much as possible when the number of repetitions is increased. That is, when the simultaneous detection reference value Q _i has a distribution of “σ ² ” due to the influence of noise, the variance of a value obtained by simply averaging the N simultaneous detection reference values Q _i is “σ by the central limit theorem. ² / N ". For this reason, the error between the average reference value Q _avr and the true capacitance Q decreases with a ratio of “1 / √N” as N increases.

For example, the correction unit 72 calculates the average reference value Q _avr by averaging _n simultaneous detection reference values Q _{1 to} Q _n acquired by repeating Step ST140. Alternatively, the correction unit 72 may calculate the average reference value Q _avr as a moving average value of the simultaneously detected reference values greater than or less than n. The number of simultaneous detection reference values to be averaged may be set in a range in which the change in the capacitance Q due to the movement of an object (human body or the like) can be ignored.
In addition to the method of obtaining a simple average of a plurality of simultaneous detection reference values, the correction unit 72 may be, for example, an average of the maximum value and the minimum value of the simultaneous detection reference values detected in a certain period, You may acquire the median of the simultaneous detection reference value acquired in a period as average reference value _Qavr . Or the correction _| amendment part 72 may acquire average reference value _Qavr using the other various algorithms which estimate a true value from the some data varied by noise.

ST250:
Average correction unit 72, the detected value _S 1 to S _n of the respective detection electrodes obtained by repetition of steps ST140, the simultaneous detection reference value _Q 1 to Q _n acquired in step ST140, obtained in step ST240 Correction is performed based on the reference value _Qavr .

FIG. 7 is a flowchart for explaining the detection value correction process (ST250) in the flowchart shown in FIG.
The correction unit 72 selects one detection value S _i in order from the detection values S _{1 to} S _n (ST300), and the selected detection value S _i is based on the simultaneous detection reference value Q _i and the average reference value Q _avr. The correction detection value SA _i is acquired as the correction result (ST350). Correcting unit 72 repeats step ST350 until correct all of the detected value _S 1 ~S _n (ST380).

In the present embodiment, the correction unit 72 corrects the detection value S _{i on} the assumption that only one of the two types of noise sources (N1, N2) shown in FIG. 3 exists. Which noise is to be corrected may be appropriately selected by the user, or the correction unit 72 switches according to a signal (such as a signal indicating the operating state of the electronic device) from the electronic device on which the input device is mounted. You may do it. Or the correction | amendment part 72 each acquires the correction | amendment detection value assumed that only one of two types of noise sources (N1, N2) exists, and the correction | amendment detection value assumed that only the other exists, The said two An average value or a weighted average value of correction detection values may be used as a final correction result.
Hereinafter, each noise correction method will be described.

[When correcting noise (human body noise) from the first noise source N1]
In this case, the second noise source N2 of the non-human body in FIG. 3 is ignored, and the second capacitance C _s that propagates noise from the second noise source N2 to the detection electrode ES _i is assumed to be zero. That is, in the above equation (1), it is assumed that the noise component (second noise component) represented by the product “B _i * C _s ” of the second noise coefficient B _i and the second capacitance C _s is zero. To do. Then, the detection value S _i is expressed as the sum of the first noise component (A _i * C _x ) caused by the first noise source N1 of the human body and the first capacitance C _x . This is equal to a value obtained by multiplying the first capacitance C _x by the coefficient “1 + A _i ”.

When the capacitance between the reference electrode (one or more detection electrodes selected by the second selection unit 30) and the human body is “first reference capacitance Q”, the simultaneous detection reference value Q _i is expressed by the equation ( It can be considered that “C _x ” in 1) is replaced with “Q”. Since the second capacitance C _s between the detection electrode ES _i and the second noise source N2 is assumed to be zero, the reference electrode composed of one or more detection electrodes ES _i is also connected to the second noise source N2. The capacitance between is zero. Accordingly, the noise component caused by the non-human second noise source N2 is also zero for the simultaneous detection reference value Q _i . Noise component caused by the first noise source N1 of the human body are the noise component propagated through the first reference capacitance Q from the detection value S _i and the same first noise source at the same time N1, the detected value S _i The same first noise coefficient A _i is used to express “A _i * Q”. Therefore, the simultaneous detection reference value Q _i is expressed as the sum of the human body noise component (A _i * Q) and the first reference capacitance Q. This is equal to a value obtained by multiplying the first reference capacitance Q by the coefficient “1 + A _i ”.
In summary, the detection value S _i and the simultaneous detection reference value Q _i are respectively expressed by the following equations.

Since the value to be obtained by correcting the detection value S _i is the “first capacitance C _x ”, “C _x ” in the equation (2-1) is replaced with the correction detection value SA _i to obtain the equation (2-1). When the equation (2-2) is arranged, the corrected detection value SA _i is expressed by the following equation.

From equation (3), the corrected detection value SA _i is obtained as a result of multiplying the correction value “Q _avr / Q _i ” obtained by dividing the average reference value Q _avr by the simultaneous detection reference value Q _i and the detection value S _i .

  Substituting Equations (2-1) and (2-2) into Equation (3) yields the following equation.

“Q _avr / Q” in Expression (4) indicates an error of the corrected detection value SA _{i with} respect to the first capacitance C _x . Accordingly, the error correction detection value SA _i is determined by the error of the mean reference value Q _avr for the first reference capacitance Q, the average reference value Q _avr decreases closer to the first reference capacitance Q.

FIG. 8 is a diagram for explaining that the influence of human body noise is estimated from the simultaneous detection reference value Q _i and the average reference value Q _avr . As shown in FIG. 4, the noise from the human body changes the slope of the linear function of the detection value S _i with respect to the first capacitance C _x . This slope is the same as a linear function of the simultaneous detection reference value Q _{i for} the first capacitance C _x , and when noise from other than the human body is ignored, as shown in FIG. 8, the simultaneous detection reference value Q _i And the average reference value Q _avr can be estimated. Therefore, by _{applying the} slope (1 + A _i ) estimated from the simultaneous detection reference value Q _i and the average reference value Q _avr to the linear function of the detection value S _{i for} the first capacitance C _x , the detection value S _i is obtained. The corrected detection value SA _i can be calculated as the estimated value of the corresponding first capacitance C _x .

If the simultaneous detection reference value Q _i does not vary so much and the difference ΔQ _i (ΔQ _i = Q _i −Q _avr ) between the simultaneous detection reference value Q _i and the average reference value Q _avr is small, It is also possible to approximate the corrected detection value SA _i shown in (3) as follows.

Further, the correction detection value SA _i may be obtained by a calculation process, or may be acquired by using a conversion table including a numerical value of the calculation result.

[When correcting noise (non-human body noise) from the second noise source N2]
In this case, in Equation (1), it is assumed that the first noise component (A _i * C _x ) resulting from the first noise source N1 of the human body is zero. Therefore, the detection value S _i is represented as the sum of the second noise component (B _i * C _s ) caused by the non-human second noise source N2 and the first capacitance C _x .

Further, when the capacitance between the non-human body second noise source N2 and the reference electrode is “second reference capacitance C _q ”, the simultaneous detection reference value Q _i is “C _s ” in the equation (1). It can be considered that it is replaced with “C _q ”. Also in the simultaneous detection reference value Q _i , the noise component caused by the first noise source N1 of the human body is regarded as zero, similarly to the detection value S _i . Since the noise component caused by the second noise source N2 in non-human body, a noise component propagated through the second reference capacitance C _q from the detection value S _i and the same second noise source at the same time N2, the detection value S _It is expressed as “B _i * C _q ” using the same second noise coefficient B _i as _i . Therefore, the simultaneous detection reference value Q _i is expressed as the sum of the non-human body noise component (B _i * C _q ) and the first reference capacitance Q.
In summary, the detection value S _i and the simultaneous detection reference value Q _i are represented by the following equations, respectively.

When “C _x ” in equation (6-1) is replaced with correction detection value SA _i and equations (6-1) and (6-2) are rearranged, correction detection value SA _i is expressed as the following equation. .

From Expression (7), the corrected detection value SA _i is obtained by multiplying a value _obtained by subtracting the average reference value Q _avr from the simultaneous detection reference value Q _i by a predetermined coefficient (C _s / C _q ) “(Q _i − Q _avr ) * (C _s / C _q ) ”is obtained as a result of subtraction from the detection value S _i .

The second capacitance C _s and the second reference capacitance C _q are constant regardless of the proximity of the human body and can be measured in advance for each electrode. For example, each measured value is stored in the storage unit 80. Place, may be used those measurements when correcting unit 72 calculates the correction detection value SA _i.

  Substituting Equations (6-1) and (6-2) into Equation (7) yields the following equation.

“(Q−Q _avr ) * (C _s / C _q )” in Expression (8) indicates an error of the corrected detection value SA _{i with} respect to the first capacitance C _x . The coefficient “C _s / C _q ” in Equation (8) is set to 1 by selecting the reference electrode so that the same noise as the noise induced from the second noise source N2 to each detection electrode is also induced in the reference electrode. It is possible to make it close to a suitable value. Accordingly, the error correction detection value SA _i is generally determined by the error of the mean reference value Q _avr for the first reference capacitance Q, the average reference value Q _avr decreases closer to the first reference capacitance Q.

FIG. 9 is a diagram for explaining that the influence of non-human body noise is estimated from the simultaneous detection reference value Q _i and the average reference value Q _avr . As shown in FIG. 5, the noise from the non-human body changes the intercept of the linear function of the detected value S _i with respect to the first capacitance C _x , and the intercept is the second capacitance C _s and the second noise. It is represented by the product (B _i * C _s ) with the coefficient B _i . The noise from the non-human body also changes the intercept of the linear function of the simultaneous detection reference value Q _{i for} the first capacitance C _x , and the intercept is the second reference capacitance C _q and the second noise coefficient B _i. (B _i * C _q ). When noise from the human body is ignored, as shown in FIG. 9, the intercept (B _i * C _q ) can be estimated from the simultaneous detection reference value Q _i and the average reference value Q _avr . Accordingly, the second noise coefficient B _i is obtained based on the intercept (B _i * C _q ) estimated from the simultaneous detection reference value Q _i and the average reference value Q _avr , and this is the detected value for the first capacitance C _x . by applying a linear function of S _i, it can be calculated corresponding to the detected value S _i corrected detection value SA _i.

In the above two types of noise correction methods, as can be seen from the equations (3) and (7), the detection value S _i decreases as the simultaneous detection reference value Q _i increases with respect to the average reference value Q _avr . becomes, simultaneous detection reference value Q _i is the correction of the detected value S _i such becomes smaller as the detected value S _i to the average reference value Q _avr increases performed. Conversely, becomes smaller as the detected value S _i mean reference value Q _avr is against simultaneous detection reference value Q _i becomes smaller, as the average reference value Q _avr increases relative simultaneous detection reference value Q _i detected value S _The detection value S _i is corrected so that _i increases. That, in the two correction methods, is corrected to the detected value S _i is opposite to the direction of change of the simultaneous detection reference value Q _i, the detection value S _i with respect to the direction of change in the average reference value Q _avr is It is corrected in the same direction. This is because the average reference value Q _avr is regarded as the true value of the first capacitance C _x and the difference between the true value and the detected value S _i is corrected as a noise amount. Therefore, if the detection value S _i is corrected in the reverse direction or the same direction as described above according to the change direction of the simultaneous detection reference value Q _i and the average reference value Q _avr , the expression is limited to Expression (3) and Expression (7). It is possible to obtain a correction effect that reduces the error from the true value.

As described above, according to the input device according to the present embodiment, the capacitance between the detection value _Si and the ground changes when an object such as a human body approaches. The reference electrode, noise from the noise source to provide a noise detection electrodes ES _i (N1, N2) are detected. In the first capacitance detection unit 40, the capacitance between the detection electrode ES _i and the ground is detected, and the detection value S _i is acquired as the detection result. Further, the second capacitance detection unit 50 detects the capacitance between the reference electrode and the ground, and acquires a reference value as the detection result. When the first capacitance detection unit 40 detects the capacitance, the second capacitance detection unit 50 simultaneously detects the capacitance, and the reference value of the detection result becomes the detection value S _i . Acquired as the corresponding simultaneous detection reference value Q _i . Further, the second capacitance detection unit 50 repeats the detection of the capacitance, and a plurality of reference values are acquired as the detection result. The detection value S _i of the first capacitance detection unit 40 is acquired by the second capacitance detection unit 50 and the simultaneous detection reference value Q _i acquired by simultaneous detection in the second capacitance detection unit 50. Further, correction is performed based on an average reference value Q _avr obtained by averaging a plurality of reference values.

Therefore, when the noise caused by the noise source (N1) of a nearby object (such as a human body) is detected at the reference electrode, the first reference capacitance Q between the reference electrode and the object is estimated by the average reference value _Qavr . It becomes possible. From the difference between the first reference capacitance Q estimated by the average reference value Q _avr and the simultaneous detection reference value Q _i , the intensity of noise from the noise source (N1) at the time of detection of the detection value S _i is determined. It can be estimated. Thereby, the noise resulting from the noise source (N1) of the adjacent object can be effectively removed from the detection value S _i . Therefore, it accurately detects changes in capacitance of the detection electrode ES _i by proximity of an object.

In addition, even when noise caused by a noise source (N2) other than an adjacent object is detected at the reference electrode, the first reference capacitance Q between the reference electrode and the object can be estimated by the average reference value Q _avr . From the difference between the estimated first reference capacitance Q and the simultaneous detection reference value Q _i , the strength of noise from the noise source (N2) at the time of detection of the detection value S _i can be estimated. Thereby, the noise caused by the noise source (N2) other than the adjacent object can also be effectively removed from the detection value S _i . Therefore, it accurately detects changes in capacitance of the detection electrode ES _i by proximity of an object.

A method is generally known in which all detection electrodes are each provided with a circuit for detecting capacitance, and the capacitances of all the detection electrodes are simultaneously detected. According to this method, even when noise is induced from a nearby object to each detection electrode, by comparing the capacitance detected at each detection electrode relatively, which detection electrode is close to which detection electrode. Can be identified. However, in this method, in addition to the fundamental problem that the number of capacitance detection circuits increases, there is a problem that noise components and capacitance components in detection results of individual detection electrodes cannot be distinguished. To do. For example, if an object is in close proximity to multiple detection electrodes (such as when the palm is in contact with a wide area), even if the capacitances of the detection electrodes are compared relatively, whether the difference is due to noise components or static It cannot be distinguished whether it is due to the capacitance component. Therefore, when a large measurement value is accidentally obtained at a certain detection electrode due to noise, it may be erroneously determined that an object is close to the detection electrode.
In contrast, in the input device according to this embodiment, since the capacitance change of the individual detection electrodes (change of the first capacitance C _x of the object and the detection electrode) can be detected accurately, a plurality of detection electrodes Even when a palm or the like is in contact at the same time, it is possible to make it difficult to make an erroneous determination of the proximity position of the object as described above. That is, according to the input device according to the present embodiment, it is possible to achieve performance equivalent to or better than the method of simultaneously detecting the capacitance in all the detection electrodes with only two capacitance detection units.

In the input device according to the present embodiment, the first reference capacitance Q between the reference electrode and the object is estimated by the average reference value Q _avr , and the estimated first reference capacitance Q and the simultaneously detected reference value are estimated. From the difference from Q _i , the relationship of the detection value S _i with respect to the first capacitance C _x between the detection electrode ES _i and the object (human body, etc.) is estimated, and approaches the true value of the first capacitance C _x. The detected value S _i is corrected. Therefore, the correction accuracy of the detection value S _i (accuracy with respect to the true value of the first capacitance C _x ) depends on the estimation accuracy of the first reference capacitance Q based on the average reference value Q _avr . The average reference value Q _avr can be easily approximated to the true value of the first reference capacitance Q by increasing the number of reference values to be averaged. The first reference capacitance based on the average reference value Q _avr Q estimation accuracy can be easily improved. Therefore, since the accuracy of correcting the detection value S _i can be easily improved, a change in the capacitance of the detection electrode ES _i due to the proximity of an object can be detected accurately.

  Furthermore, in the input device according to the present embodiment, one or more detection electrodes are selected from the plurality of detection electrodes as reference electrodes in the second selection unit 30 and connected to the second capacitance detection unit 50. Therefore, it is not necessary to provide a reference electrode dedicated for noise detection. Thereby, the apparatus size can be reduced and the number of parts can be suppressed.

Moreover, in the input device according to the present embodiment, the detection electrodes close to the object are identified based on the detection values of the plurality of detection electrodes acquired most recently or the correction result of the correction unit 72 for the detection values, and the identification The detection electrode thus selected is selected as a reference electrode in the second selection unit 30 and connected to the second capacitance detection unit 50. Thus, since the reference electrode as large noises from an object close is detected is selected, it is possible to improve the accuracy of the correction of the detected value S _i.

  Next, several modifications of the input device according to the first embodiment will be described.

(Modification 1)
FIG. 10 is a diagram illustrating a configuration of a modification of the input device according to the first embodiment, and illustrates a first example having a reference electrode ER dedicated to noise detection.
The input device shown in FIG. 10 deletes the second selection unit 30 from the input device shown in FIG. 1 and newly provides a reference electrode ER dedicated to noise detection. The reference electrode ER is provided as the second capacitance detection unit 50. Is connected directly to. When noise induced in the detection electrodes ES _{1 to} ES _n can be stably detected at the reference electrode ER with high sensitivity, the second selection is performed by directly connecting the reference electrode ER to the second capacitance detection unit 50. The part 30 can be deleted, and the configuration can be simplified. For example, human body noise can be guided to the reference electrode ER without depending on the proximity position of the detection target object by extending the mesh-like reference electrode ER around the entire operation surface where the detection target object (human body or the like) is close.

(Modification 2)
FIG. 11 is a diagram showing a configuration of a modification of the input device according to the first embodiment, and shows a second example having a reference electrode ER dedicated to noise detection.
The input device shown in FIG. 11 is obtained by adding a reference electrode ER dedicated to noise detection to the input device shown in FIG. The reference electrode ER is directly connected to the second capacitance detection unit 50 without going through the second selection unit 30. By providing the reference electrode ER so that noise from a noise source that causes noise to the detection electrodes ES _{1 to} ES _n can be detected with higher sensitivity than these detection electrodes, the correction accuracy of the detection value S _i can be increased. .

(Modification 3)
FIG. 12 is a flowchart for explaining a first modification of the correction process in the input device according to the first embodiment. The flowchart shown in FIG. 12 is obtained by adding steps ST310 and ST320 to the flowchart shown in FIG.

When the correction unit 72 selects one detection value S _i in order from the detection values S _{1 to} S _n (ST300), first, the simultaneous detection reference value Q _i and the average reference value Q corresponding to the selected detection value S _i are firstly selected. A difference from _avr (absolute value _obtained by subtracting average reference value Q _avr from simultaneous detection reference value Q _i ) is compared with predetermined threshold value TH1 (ST310). If the difference is the threshold value TH1 is smaller than the correction unit 72 stops the correction of the detected value _{S i} (ST320). When the correction is stopped, the correction unit 72 treats the detection value S _i as the correction detection value SA _i as it is. On the other hand, when the difference is larger than the threshold value TH1, the correction unit 72 corrects the detection value S _{i based} on the simultaneous detection reference value Q _i and the average reference value Q _avr, and a correction detection value SA as a correction result thereof. _i is acquired (ST350). Correcting unit 72, until the correct all of the detected values _S 1 to S _n, and repeats the processing of steps ST300~ST350 (ST380).

The elements constituting the circuit are a slight noise source. These are known by names such as thermal noise, shot noise, and flicker noise. Since the first capacitance detection unit 40 and the second capacitance detection unit 50 are configured by separate circuit elements, such element noise causes individual fluctuations in the detection value S _i and the simultaneous detection reference value Q _i. Is generated. Also, quantization noise always occurs in the digital circuit, and this also causes individual fluctuations in the detection value S _i and the simultaneous detection reference value Q _i . Such fluctuations in individual measurement values that do not have a correlation between the two capacitance detection units (40, 50) cannot be corrected by the method of the correction unit 72 described above. If the difference (| Q _i −Q _avr |) between the simultaneous detection reference value Q _i and the average reference value Q _avr is a value close to the fluctuation of such individual measurement values, the value is not reliable, Conversely, an error may be added by performing correction by the correction unit 72. _Further , the difference between the simultaneous detection reference value Q _i and the average reference value Q _avr being a value close to zero indicates that the error due to noise is low in the first place, and the necessity for the correction unit 72 to perform correction is low. . Therefore, when the difference between the simultaneous detection reference value Q _i and the average reference value Q _avr is lower than the predetermined threshold value TH1, it is possible to prevent unnecessary correction from being performed by stopping the correction process of the correction unit 72. In addition, an increase in error due to correction can be prevented.

(Modification 4)
FIG. 13 is a flowchart for explaining a second modification of the correction process in the input device according to the first embodiment. The flowchart shown in FIG. 13 is obtained by adding step ST330 to the flowchart of Modification 3 shown in FIG.

In addition to the case where the difference between the simultaneous detection reference value Q _i and the average reference value Q _avr is smaller than the predetermined threshold value TH1, the correction unit 72 has a case where the simultaneous detection reference value Q _i is smaller than the predetermined threshold value TH2. In addition, the correction of the detection value S _i is stopped (ST330). When the difference between the simultaneous detection reference value Q _i and the average reference value Q _avr is larger than the threshold value TH1, and the simultaneous detection reference value Q _i is larger than the threshold value TH2, the correction unit 72 corrects the detection value S _i . To obtain the corrected detection value SA _i (ST350).

When correcting noise from the human body, when the simultaneous detection reference value Q _i approaches zero, the denominator of the correction equation shown in Equation (3) is close to zero, so that the calculation error increases. This occurs when excessive noise is added and exceeds the correction capability of the correction unit 72. In such a case, it is desirable to stop the correction of the correction unit 72 or change the frequency of the drive wave (demodulation wave) of the signal generation unit 60 and perform the capacitance detection again.

(Modification 5)
FIG. 14 is a flowchart for explaining a third modification of the correction process in the input device according to the first embodiment. The flowchart shown in FIG. 14 is obtained by adding steps ST340 and ST370 to the flowchart of the modification 4 shown in FIG. 13 and replacing step ST350 with step ST360.

The correction unit 72 _determines that the difference between the simultaneous detection reference value Q _i and the average reference value Q _avr is larger than the predetermined threshold value TH1 (ST310), and the simultaneous detection reference value Q _i is larger than the predetermined threshold value TH2. In the case (ST330), it is determined whether or not the average reference value _Qavr is larger than a predetermined threshold value TH3 (ST340). If the average reference value _{Q avr} threshold TH3 smaller, the correction unit 72 calculates the correction value detected SA _i for non human noise shown in Equation (7) (ST370). On the other hand, if the average reference value _{Q avr} is greater than the threshold TH3, the correction unit 72 calculates the correction value detected SA _i for human noise shown in equation (3) (ST360).

The average reference value Q _avr indicates an estimated value of the first reference capacitance Q between the adjacent human body and the reference electrode. _{That the} average reference value _Qavr is small indicates that the human body is not close to the reference electrode, and the reference value detected by the reference electrode has less human body noise. Since the human body noise correction error is expressed by “Q _avr / Q” as shown in Equation (4), the smaller the first reference capacitance Q, the greater the correction _{due to} the slight measurement error of the average reference value Q _avr. An error occurs. Therefore, when the average reference value Q _avr is extremely small, it is not preferable to calculate the correction detection value SA _i for human body noise expressed by the equation (3) in the correction unit 72.
On the other hand, the fact that the human body noise is small in the reference value means that most of the noise included in the reference value is non-human body noise. Therefore, when the average reference value Q _avr is smaller than the threshold value TH3, the non-human body noise included in the detection value S _i is calculated by calculating the corrected detection value SA _i (formula (7)) for non-human body noise. It can be corrected with high accuracy.

Even if the human body is not close to the reference electrode, there is a possibility that the human body is close to another detection electrode. _Therefore , if the average reference value Q _avr is extremely small, the second selection unit 30 appropriately It is also possible that no reference electrode has been selected. Therefore, in still another modification of the present embodiment, when it is determined in step ST340 that the average reference value _Qavr is smaller than the threshold value TH3, the process may move to step ST320 and the correction process may be stopped. Alternatively, returning to step ST100 (FIG. 6), the selection of the reference electrode may be performed again.

(Modification 6)
FIG. 15 is a flowchart for explaining a fourth modification of the correction process in the input device according to the first embodiment. The flowchart shown in FIG. 15 is obtained by adding steps ST110, ST120, ST150, and ST200 and deleting steps ST240 and ST250 in the flowchart shown in FIG.

In the process of the flowchart shown in FIG. 6, after all the detection values S _{1 to} S _n and all the simultaneous detection reference values Q _{1 to} Q _n are acquired, the average reference value Q _avr is calculated and the detection value S _i is corrected. (ST240, ST250). On the other hand, in the process of the flowchart shown in FIG. 15, the average reference value Q _avr is calculated (ST150) in the loop process (ST130 to ST230) that repeats the acquisition of the detection value S _i and the simultaneous detection reference value Q _i. The detection value S _i is corrected (ST200).

When calculating the average reference value Q _avr in step ST150, 1 single in the loop obtained simultaneous detection reference value Q _i method of using only in at the beginning of the loop process, acquired the simultaneous detection reference value Q _Since the number of _i is small, the error of the average reference value Q _{avr with} respect to the true value of the first reference capacitance Q becomes large. Accordingly, the correction unit 72 performs a series of a predetermined number of simultaneous detections including not only the simultaneous detection reference value Q _i acquired in the loop processing being executed but also the simultaneous detection reference value Q _i obtained in the past loop processing. The average reference value Q _avr is calculated by averaging the reference value Q _i .

FIG. 16 is a diagram illustrating an example of a circuit configuration for averaging a series of a predetermined number of simultaneously detected reference values Q _i in the correction unit 72. In the example of FIG. 16, the correction unit 72 includes a m flip-flops _FF 1 to ff _m cascaded, and a mean value calculating section 74 for calculating an average value of the output of the flip-flop _FF 1 to ff _m . The flip-flops FF _{1 to} FF _{m form} a FIFO (first in first out), and the simultaneous detection reference values (Q ₁ , Q ₂ ,...) Input to the _first flip-flop FF ₁ are the first flip-flops FF. _The shift is sequentially performed from ₁ to the final flip-flop FF _m . The average value calculation unit 74 calculates an average reference value Q _avr by averaging a series of m simultaneous detection reference values (Q _{1 to} Q _m ) held in the flip-flops FF _{1 to} FF _m . In the example of FIG. 16, the average value is calculated by a logic circuit (hardware), but the average value can also be calculated by software using a computer.

Note that, when the average value is calculated by storing a predetermined number of simultaneous detection reference values in the FIFO as described above and the reference electrode is changed in step ST100, the simultaneous detection reference detected in the past reference electrode The value remains in the FIFO. If the average reference value Q _avr is calculated in a state where the old simultaneous detection reference value remains in the FIFO, a large error may occur with respect to the value to be obtained with the current reference electrode. Accordingly, the correction unit 72 monitors whether or not the reference electrode is changed in step ST100 (ST110), and the reference electrode is changed (the detection electrode selected as the reference electrode by the second selection unit 30 is changed). ), A series of a predetermined number of simultaneous detection reference values held in the FIFO are initialized (ST120). “Q _ini ” in FIG. 6 indicates an initial value given to initialize the flip-flops FF _{1 to} FF _m . The correction unit 72 sets the initial value Qini based on the corrected detection value acquired for the changed reference electrode (one or more detection electrodes). For example, when the changed reference electrode is one detection electrode, the correction unit 72 initializes the FIFO using the correction detection value acquired for the detection electrode as the initial value Qini. When the changed reference electrode is a plurality of detection electrodes, the correction unit 72 initializes the FIFO using the sum of the correction detection values acquired for the plurality of detection electrodes as an initial value Qini.

(Modification 7)
FIG. 17 is a flowchart for explaining a fifth modification of the correction process in the input device according to the first embodiment. The flowchart shown in FIG. 17 is obtained by adding steps ST160 and ST170 to the flowchart of the modification 6 shown in FIG. The contents of the processing in steps ST160 and ST170 are the same as those in steps ST310 and ST320 in the flowchart (modification 3) already described in FIG. According to the modified example 7, as in the modified example 3, when the difference between the simultaneous detection reference value Q _i and the average reference value Q _avr is smaller than the predetermined threshold value TH1 (ST160), the detection value S _i is corrected. Canceled (ST170).

(Modification 8)
FIG. 18 is a flowchart for explaining a sixth modification of the correction process in the input device according to the first embodiment. The flowchart shown in FIG. 18 is obtained by adding step ST180 to the flowchart of the modified example 7 shown in FIG. The contents of the process in step ST180 are the same as those in step ST330 in the flowchart (Modification 4) of FIG. 13 already described. According to the modified example 8, as in the modified example 4, when the simultaneous detection reference value Q _i is smaller than the predetermined threshold value TH2 (ST180), the correction of the detected value S _i is stopped (ST170).

(Modification 9)
FIG. 19 is a flowchart for explaining a seventh modification of the correction process in the input device according to the first embodiment. The flowchart shown in FIG. 19 is obtained by adding steps ST190 and ST220 to the flowchart of the modification 8 shown in FIG. 18 and replacing step ST200 with step ST210. The processing contents of steps ST190, ST210, and ST220 are the same as steps ST340, ST360, and ST370 in the flowchart (Modification 5) described above with reference to FIG. According to the modified example 9, as in the modified example 5, when the average reference value Q _avr is smaller than the threshold value TH3 (ST190), the correction detection for the non-human body noise shown in the equation (7) in the correcting unit 72 is performed. When the value SA _i is calculated (ST220), and the average reference value Q _avr is larger than the threshold value TH3 (ST190), the correction detection value SA _i for human body noise shown in Expression (3) is calculated by the correction unit 72. (ST210).

In yet another modification of the present embodiment, when it is determined in step ST190 that the average reference value _Qavr is smaller than the threshold value TH3, the process may move to step ST170 and the correction process may be stopped. Alternatively, in this case, the process may return to step ST100 (FIG. 6) and redo the selection of the reference electrode.

<Second Embodiment>
Next, a second embodiment of the present invention will be described.
In the input device according to the first embodiment, correction is possible if only one of the noise of the human body or the noise other than the human body, but both of these two types of noise are added at the same time in a magnitude that cannot be ignored. The noise cannot be corrected effectively. The input device according to the present embodiment detects capacitance at the same time in the detection electrode and the two reference electrodes, and estimates the magnitudes of the two types of noise using the detection results of the two reference electrodes. Both noises can be corrected effectively.

FIG. 20 is a diagram illustrating an example of the configuration of the input device according to the second embodiment of the present invention.
The input device shown in FIG. 20 has the same configuration as that of the input device shown in FIG. 1, and includes a second selection unit 30A and a second capacitance detection unit 50A. The configurations of the second selection unit 30A and the second capacitance detection unit 50A are the same as those of the second selection unit 30 and the second capacitance detection unit 50 in FIG. The second selection unit 30A connects one or more detection electrodes selected from the detection electrodes ES _{1 to} ES _n as reference electrodes to the second capacitance detection unit 50A.

  The detection control unit 71 controls the second selection unit 30A and the second capacitance detection unit 50A in the same manner as the second selection unit 30 and the second capacitance detection unit 50 described above. That is, the detection control unit 71 repeats the detection of the second capacitance detection unit 50A simultaneously with the detection of the first capacitance detection unit 40.

  However, the detection control unit 71 selects a detection electrode different from the second selection unit 30 as a reference electrode in the second selection unit 30A. For example, the detection control unit 71 selects a detection electrode close to an object to be detected (such as a finger) as a reference electrode in the second selection unit 30, while the second selection unit 30 </ b> A selects in the second selection unit 30. At least a part of the remaining detection electrodes not selected is selected as a reference electrode. That is, the detection control unit 71 uses the second selection unit 30 to select a detection electrode that easily receives noise from the object, and selects a detection electrode that hardly receives noise from the object in the second selection unit 30A. In this way, by making the detection sensitivity of noise from the object different between the two reference electrodes, the noise from the object can be effectively corrected in the correction unit 72 described later.

The correction unit 72 detects the detection value S _i acquired by the first capacitance detection unit 40 by simultaneously detecting the detection value S _i with the second capacitance detection unit 50 and the second capacitance detection unit 50A. It is the average of two acquired simultaneous detection reference values (Q _i , P _i ) and a series of simultaneous detection reference values acquired simultaneously in the second capacitance detection unit 50 and the second capacitance detection unit 50A. Correction is performed based on the two average reference values (Q _avr , P _avr ). However, the simultaneous detection reference value “P _i ” indicates a reference value acquired by the second capacitance detection unit 50A by detection at the same time as the detection value S _i . The average reference value “Q _avr ” indicates a value obtained by averaging a series of reference values acquired by the second capacitance detection unit 50A.

Assuming that the noise estimation model of the detection electrode ES _i shown in FIG. 3 also applies to the reference electrode of the second capacitance detection unit 50 and the reference electrode of the second capacitance detection unit 50A, the detection values S _i , The simultaneous detection reference value Q _i and the simultaneous detection reference value P _i are each expressed by the following equations.

Expression (9-1) is the same as Expression (1) already described. The first capacitance C _x indicates the capacitance between the detection electrode ES _i and the human body. The second capacitance C _s indicates the capacitance between the detection electrode ES _i and the non-human second noise source N2. The first noise coefficient A _i indicates the intensity of noise propagating from the first noise source N1. The second noise coefficient B _i indicates the intensity of noise propagating from the second noise source N2. The detection value S _i includes the first capacitance C _x , the first noise component “A _i * C _x ” attributed to the first noise source N1, and the second noise component “B” attributed to the second noise source N2. _i * is expressed as the sum of the _{C s} ".

In Expression (9-2), the first reference capacitance Q indicates the capacitance between the reference electrode selected by the second selection unit 30 and the human body. The second reference capacitance C _q indicates the capacitance between the reference electrode and the second noise source N2. The simultaneous detection reference value Q _i includes the first reference capacitance Q, the first reference noise component “A _i * Q” caused by the first noise source N1, and the second reference noise caused by the second noise source N2. It is expressed as the sum with the component “B _i * C _q ”.

In Formula (9-3), the first reference capacitance P indicates the capacitance between the reference electrode selected by the second selection unit 30A and the human body. The second reference capacitance C _p indicates the capacitance between the reference electrode and the second noise source N2. The simultaneous detection reference value P _i includes the first reference capacitance P, the first reference noise component “A _i * P” caused by the first noise source N1, and the second reference noise caused by the second noise source N2. Expressed as the sum with the component “B _i * C _p ”.

The first reference capacitance Q in equation (9-2) is approximated by the average reference value Q _avr , the first reference capacitance P in equation (9-3) is approximated by the average reference value P _avr , and the equation (9) a first capacitance C _x of 9-1) replaced with the correction detection value SA _i, and rearranging these equations, the correction detection value SA _i is expressed by the following equation.

  Equation (10) can also be expressed as:

Accordingly, the correction unit 72 detects the detection value S _i , the simultaneous detection reference values Q _i and P _i , the average reference values Q _avr and P _avr , the second reference capacitances C _q and C _p , and the second static capacitance Based on the capacitance C _s , the corrected detection value SA _i is calculated by the equations (10) and (11).

  By substituting the formulas (9-1), (9-2), and (9-3) into the formula (10) or the formula (11), the following formula is obtained.

From the equation (12), when the average reference value Q _avr is equal to the first reference capacitance Q (Q = Q _avr ) and the average reference value P _avr is equal to the first reference capacitance P (P = P _avr ) It can be seen that the error of the correction detection value SA _{i with} respect to the first capacitance C _x becomes zero. This error does not include noise (A _i , B _i ) in each measurement, and is _{only in} the approximation accuracy of the average reference values Q _avr and P _avr (error with respect to the first reference capacitances Q and P). Dependent. This approximation accuracy can be easily increased by increasing the number of reference values used for calculating the average reference value. Therefore, also in this embodiment, it is possible to easily increase the accuracy of the correction detection value SA _i .

FIG. 21 shows that the influence of two types of noise (human body noise and non-human body noise) is estimated from two simultaneous detection reference values (Q _i , P _i ) and two average reference values (Q _avr , P _avr ). It is a figure for demonstrating.
The function of the simultaneous detection reference value Q _i with respect to the average reference value Q _avr is a linear function as shown in Expression (9-2). Further, the function of the simultaneous detection reference value P _i with respect to the average reference value P _{avr is} also a linear function as shown in Expression (9-3). If the second reference capacitances C _q and C _p are equal, the simultaneous detection reference value Q _i and the linear function of the average reference value P _avr coincide with each other, and this linear function is a single straight line shown in FIG. Represented. Accordingly, the slope and intercept of the linear function are determined from the two simultaneous detection reference values (Q _i , P _i ) and the two average reference values (Q _avr , P _avr ), and the first noise coefficient A _i that is an unknown parameter is determined. Since the second noise coefficient B _i is determined, the corrected detection value SA _i represented by the equations (10) and (11) can be calculated.

The average reference value Q _avr , the average reference value P _avr , the simultaneous detection reference value Q _i and the simultaneous detection reference value P _i work in a complementary manner depending on the magnitude relationship of each other, thereby separating and correcting two types of noise components Is done. As shown in FIG. 21, in the case of “Q _avr > P _avr ” and “Q _i > P _i ”, when the average reference value Q _avr increases or the simultaneous detection reference value P _i increases, the slope of the linear function decreases. Since the intercept increases, the detection value S _i is corrected in the increasing direction. If the average reference value P _avr increases or the simultaneous detection reference value Q _i increases, the slope of the linear function increases and the intercept decreases, so that the detection value S _i is corrected in the decreasing direction.

In addition, the correction unit 72 determines the difference between the two simultaneous detection reference values (| Q _i −) acquired by the second capacitance detection unit 50 and the second capacitance detection unit 50A by the detection at the same time as the detection value S _i. P _i |) is smaller than a predetermined threshold TH5, or two averages of a series of simultaneously detected reference values acquired simultaneously in the second capacitance detection unit 50 and the second capacitance detection unit 50A. When the difference between the average reference values (| Q _avr −P _avr |) is smaller than the predetermined threshold value TH4, the correction of the detection value S _i is stopped.
As described above, in the correction process of the correction unit 72, two types of noise components are estimated based on the difference in noise detection sensitivity between the two reference electrodes. Therefore, when the detection results of the electrostatic capacitances at the two reference electrodes have close values, the error due to correction may increase. Therefore, when the difference between the two simultaneous detection reference values (| Q _i −P _i |) or the difference between the two average reference values (| Q _avr −P _avr |) becomes smaller than a certain value, the detection value S _i By stopping the correction, an increase in error due to the correction can be prevented.

Note that the correction unit 72 has a value that the first reference capacitances Q and P have close values (i.e., the human body is in contact with the transition of a series of correction detection values SA _i (or detection values S _i ) at each detection electrode). When it is predicted that the detected value S _i is not in the vicinity, the correction of the detection value S _i may be stopped.

  Here, processing relating to detection of capacitance and correction of the detection result in the input device having the above-described configuration will be described.

  FIG. 22 is a flowchart for explaining a process of acquiring the capacitance value of the detection electrode in the input device according to the first embodiment. The process shown in FIG. 22 is periodically repeated similarly to the process shown in FIG.

First, the detection control unit 71 determines a reference electrode for noise detection for each of the second selection unit 30 and the second selection unit 30A from the detection electrodes of the electrode unit 10 (ST500).
Next, the detection control unit 71 selects a detection electrode selected by the first selection unit 20, a detection electrode selected as a reference electrode by the second selection unit 30, and a detection electrode selected by the second selection unit 30A as a reference electrode. Each is set, and electrodes corresponding to the settings are connected to the first capacitance detection unit 40, the second capacitance detection unit 50, and the second capacitance detection unit 50A, respectively (ST530).
Then, the detection control unit 71 simultaneously detects the capacitance in the first capacitance detection unit 40, the second capacitance detection unit 50, and the second capacitance detection unit 50A, and detects the detection value S _i simultaneously. The detection reference value Q _i and the simultaneous detection reference value P _i are acquired (ST540).
The detection control unit 71 repeats the processes of steps ST530 and ST540 until the capacitances of all the detection electrodes are detected (ST620).

When the capacitances of all the detection electrodes are detected, the correction unit 72 determines the average reference value Q _avr that is an average value of the simultaneous detection reference values Q _{1 to} Q _n and the simultaneous detection reference values P _{1 to} P _n. An average reference value P _avr that is an average value of the values is calculated (ST630). Then, the correction unit 72 corrects the detection value S _i of each detection electrode based on the two simultaneous detection reference values Q _i and P _i and the two average reference values Q _avr and P _avr, and the correction result is as follows. The correction detection value SA _i of each detection electrode is acquired (ST640).

FIG. 23 is a flowchart for explaining the detection value correction process (ST640) in the flowchart shown in FIG.
First, the correction unit 72 compares the difference (| Q _avr −P _avr |) between the two average reference values calculated in step ST630 with a predetermined threshold value TH4 (ST700). If the difference between the two average reference values (| Q _avr −P _avr |) is smaller than the threshold value TH4 as a result of the comparison, the correction unit 72 stops correcting the detection value S _i and corrects the detection value S _{i as it} is. Obtained as detection value SA _i .

The difference between the two average reference value _(| Q _{avr -P} avr _|) is greater than the threshold value TH4, the correction unit 72 selects one of the detected values _{S i} in order from the detection value _S 1 to S _n ( ST720), the difference (| Q _i −P _i |) between the two simultaneous detection reference values corresponding to the selected detection value S _i is compared with a predetermined threshold value TH5 (ST 740). The difference between the two simultaneous detection reference value _(| Q i _-P i |) if the threshold value TH5 smaller, the correction unit 72 stops correction of the detected value _{S i,} the detection value _{S i} is directly corrected detection value SA Obtained as _i (ST760). On the other hand, when the difference (| Q _i −P _i |) between the two simultaneous detection reference values is larger than the threshold value TH5, the correction unit 72 corrects the correction detection value SA _i . That is, the correction unit 72 includes the detection value S _i , the simultaneous detection reference values Q _i and P _i , the average reference values Q _avr and P _avr , the second reference capacitances C _q and C _p , and the second static capacitance Based on the electric capacity C _s , the corrected detection value SA _i is calculated by equations (10) and (11) (ST750). The second reference capacitances C _q and C _p and the second capacitance C _s use capacitance value data measured in advance for each detection electrode and stored in the storage unit 80. Correcting unit 72 repeats step ST720~ST760 until correct all of the detected value _S 1 ~S _n (ST780).

As described above, according to the input device according to the present embodiment, when the capacitance of the detection electrode is detected in the first capacitance detection unit 40, the second capacitance detection unit 50 and the first capacitance detection unit 40 simultaneously. Also in the two capacitance detection unit 50A, the capacitance of the reference electrode is detected, and the reference value is acquired as two simultaneous detection reference values (Q _i , P _i ) corresponding to the detection value S _i . In addition, the second capacitance detection unit 50 and the second capacitance detection unit 50A repeat the detection of capacitance, and a series of reference values are acquired as the detection results. The detection value S _i of the first capacitance detection unit 40 is obtained from two simultaneous detection reference values (Q _i , Q _i ,) acquired by simultaneous detection in the second capacitance detection unit 50 and the second capacitance detection unit 50A. P _i ) and two average reference values (Q _avr , P _avr ) obtained by averaging a series of reference values acquired in the second capacitance detection unit 50 and the second capacitance detection unit 50A, respectively. Corrected.

Therefore, the first reference capacitances Q and P between the two reference electrodes and the object can be estimated from the average reference values Q _avr and P _avr . Further, the relationship between the first reference capacitance Q estimated by the average reference value Q _avr and the simultaneous detection reference value Q _i, and the first reference capacitance P estimated by the average reference value P _avr are detected simultaneously. From the relationship with the reference value P _i , the noise intensity (A _i ) caused by the noise source (N 1) of the adjacent object (human body, etc.) and the noise caused by the noise source (N 2) other than the adjacent object Any of the strengths (B _i ) can be estimated. Therefore, it is possible to effectively remove two types of noise components included in the detection value S _i , and it is possible to more accurately detect a change in the capacitance of the detection electrode ES _i due to the proximity of an object.

Further, according to the input device according to the present embodiment, the correction accuracy of the detection value S _i (accuracy with respect to the true value of the first capacitance C _x ) is the first reference capacitance Q based on the average reference value Q _avr . It depends on the estimation accuracy and the estimation accuracy of the first reference capacitance P by the average reference value P _avr . The average reference values Q _avr and P _avr can be easily brought close to the true values of the first reference capacitances Q and P by increasing the number of reference values to be averaged. Therefore, since the accuracy of correcting the detection value S _i can be easily improved, a change in the capacitance of the detection electrode ES _i due to the proximity of an object can be detected accurately.

  Next, some modifications of the input device according to the second embodiment will be described.

(Modification 1)
FIG. 24 is a diagram showing a configuration of a modification of the input device according to the second embodiment, and shows an example having a reference electrode ER dedicated to noise detection.
In the input device shown in FIG. 24, the second selection unit 30A is deleted from the input device shown in FIG. 20, and a reference electrode ER dedicated to noise detection is newly provided. The reference electrode ER is used as the second capacitance detection unit 50A. Is connected to. If the noise is induced in the detection electrode ES ₁ to S _n it can be detected in stably high sensitivity in the reference electrode ER, by directly coupling the reference electrode ER to the second capacitance detection unit 50, the second selection The part 30A can be deleted, and the configuration can be simplified.

For example, the reference electrode ER is a place where noise induction from a detection target (such as a human body) is hardly received, and noise from a noise source other than the detection target (such as parts inside the electronic device) is highly sensitive. It is installed in a place where it can be detected. In this case, since the average reference value P _avr can be regarded as zero, Equation (10) can be simplified as follows.

When a noise source other than the object to be detected is close to the electrode unit in a planar shape like a liquid crystal display panel, the capacitance coupling value between each detection electrode of the electrode unit and the noise source is set to each detection electrode. It is also possible to make it almost uniform without depending on. If the second capacitance C _s , the second reference capacitance C _q, and the second reference capacitance C _p are the same value, Equation (13) can be further simplified as follows.

(Modification 2)
FIG. 25 is a flowchart for explaining a first modification of the correction process in the input device according to the second embodiment.
In this modification, the correction unit 72 selects one detection value S _i in order from the detection values S _{1 to} S _n (ST720), and the difference between two average reference values corresponding to the selected detection value S _i ( | Q _avr −P _avr |) is compared with a predetermined threshold value TH4 (ST730). If the difference between the two average reference values (| Q _avr −P _avr |) is larger than the threshold value TH4 as a result of the comparison, the correction unit 72 determines the difference between the two simultaneous detection reference values corresponding to the detection value S _i ( | Q _i −P _i |) is compared with a predetermined threshold value TH5 (ST740). When the difference between the two simultaneous detection reference values (| Q _i −P _i |) is larger than the threshold value TH5, the correction unit 72 calculates the corrected detection value SA _i using the equations (10) and (11) (ST750). ). On the other hand, when it is determined in step ST700 that the difference between the two average reference values (| Q _avr −P _avr |) is smaller than the threshold value TH4, or in step ST740, the difference between the two simultaneous detection reference values (| Q _i − If it is determined that P _i |) is smaller than threshold value TH5, correction unit 72 calculates correction detection value SA _i for non-human body noise shown in equation (7) (ST770). For example, the correction detection value SA _i for non-human body noise shown in Expression (7) is calculated for each of the two reference electrodes, and the average value is obtained as the correction detection value SA _i .

When the difference between the two average reference values (| Q _avr −P _avr |) or the difference between the two simultaneous detection reference values (| Q _i −P _i |) becomes smaller than a certain value, an object is applied to the detection electrode of the electrode unit 10. (Human body) may not be in close proximity. In this case, since the noise from the object (human body) is small, it is included in the detection value S _i by calculating the corrected detection value SA _i of Equation (7) for correcting noise from other than the object (human body). You may try to remove noise.

(Modification 3)
FIG. 26 is a flowchart for explaining a second modification of the correction process in the input device according to the second embodiment. The flowchart shown in FIG. 26 is obtained by adding steps ST510, ST520, ST550 to ST590 and deleting steps ST630 and ST640 in the flowchart shown in FIG.

In the process of the flowchart shown in FIG. 22, after all of the detected values _S 1 to S _n and all simultaneous detection reference value _Q 1 _{to Q n,} the P 1 to P _n is acquired, the average reference value _{Q avr, P avr} And correction of the detected value S _i are performed (ST630, ST640). On the other hand, in the process of the flowchart shown in FIG. 26, the average reference value Q in the loop process (ST530 to ST620) that repeats the acquisition of the detection value S _i , the simultaneous detection reference value Q _i, and the simultaneous detection reference value P _{i. avr,} calculation of _{P avr} (ST550) and the correction of the detected value _{S i} (ST580) is performed. In this case, the correction unit 72 calculates average reference values Q _avr and P _avr as moving average values using the FIFO shown in FIG. 16 already described.

Correcting unit 72 obtains the simultaneous detection reference value _{Q i} and simultaneous detection reference value _{P i} in step ST540, and supplies the reference value new simultaneous detection _{Q i} and simultaneous detection reference value _{P i} in the FIFO illustrated in FIG. 16 The values of the average reference values Q _avr and P _avr are updated (ST550). Next, the correction unit 72 _compares the difference between the two average reference values (| Q _avr −P _avr |) with the threshold value TH4 (ST560), and when this is smaller than the threshold value TH4, the detection value S _i The correction is stopped (ST590). Further, the correction unit 72 compares the difference (| Q _i −P _i |) between the two simultaneous detection reference values with the threshold value TH5, and corrects the detection value S _i even when the difference is smaller than the threshold value TH5. Stop (ST590). The difference between the two average reference values (| Q _avr −P _avr |) is larger than the threshold value TH4, and the difference between the two simultaneous detection reference values (| Q _i −P _i |) is larger than the threshold value TH5. In this case, the correction unit 72 calculates the correction detection value SA _i using the equations (10) and (11) (ST580). The correcting unit 72 repeats the processes of steps ST530 to ST590 until the capacitances of all the detection electrodes are detected (ST620).

  Further, the correction unit 72 monitors whether or not the reference electrode is changed in step ST500 (ST510), and the reference electrode is changed (detection selected as the reference electrode by the second selection unit 30 or the second selection unit 30A). If it is determined that the electrode has been changed, a series of a predetermined number of simultaneous detection reference values held in the FIFO are initialized (ST520). For example, the correction unit 72 sets an initial value to be held in the FIFO based on the corrected detection value acquired for the changed reference electrode (one or a plurality of detection electrodes).

(Modification 4)
FIG. 27 is a flowchart for explaining a third modification of the correction process in the input device according to the second embodiment. The flowchart shown in FIG. 27 is obtained by replacing step ST590 in the flowchart of the third modification shown in FIG. 26 with step ST600. In this modification, the correction unit 72 determines that the difference between the two average reference values (| Q _avr −P _avr |) is smaller than the threshold value TH4 in step ST560, or two simultaneous detection references in step ST570. When it is determined that the value difference (| Q _i −P _i |) is smaller than the threshold value TH5, a correction detection value SA _i for non-human body noise shown in Expression (7) is calculated (ST770). In this case, since the noise from the object (human body) is expected to be small, the detection value S _i is calculated by calculating the correction detection value SA _i of equation (7) for correcting noise from other than the object (human body). You may try removing the noise contained in _i .

  Although various embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and includes various variations.

In the second embodiment described above, an example of correcting noise caused by two types of noise sources has been described. However, in another embodiment of the present invention, noise caused by three or more types of noise sources is corrected. Is also possible. For example, when there are N unknown parameters related to multiple types of noise, the detected value S can be obtained by using N or more simultaneously detected reference values and N or more average reference values detected by N or more reference electrodes. _The N parameters related to the noise included in _i can be estimated, and the noise of the detected value can be corrected using the estimated N parameters. In this case, the relationship between the true first capacitance C _x and the detected value S _i does not have to be a linear function such as a linear function, and a solution can be obtained by assuming an appropriate function. . If the assumed function cannot be solved analytically, an approximate solution can be obtained by using an analytical method such as Newton's method.

In the first embodiment described above, an example is given in which one of the corrected detection value SA _i shown in Expression (3) or the corrected detection value SA _i shown in Expression (7) is calculated. In this embodiment, these two types of corrections may be performed twice.
For example, in the input device having the configuration shown in FIG. 20, when the first reference capacitance Q is larger than the first reference capacitance P (P <Q), the detection value S _i and the simultaneous detection reference are first performed. The correction for non-human body noise shown in Formula (7) using the simultaneous detection reference value P _i and the average reference value P _avr is _performed on the value Q _i . Then, the correction for the human body shown in Expression (3) using the corrected simultaneous detection reference value Q _i and its average value (average reference value) is performed on the corrected detection value S _i . . As described above, even when the two types of correction are performed twice, there is an effect of reducing two types of noise included in the detection value.
Note that the above example may be modified so that the correction for non-human body noise shown in Expression (7) is performed after the correction for human body shown in Expression (3) is performed.

  In the correction equations shown in equations (10), (11), etc., the calculation error increases as the denominator approaches zero. Therefore, when the denominator value approaches zero, the correction equation is switched to another correction equation. You may make it cancel.

  The plurality of capacitance detection units used in the input device of the present embodiment may have the same circuit configuration. In that case, the capacitance detection unit for the detection electrode and the capacitance detection unit for the reference electrode may be appropriately replaced as necessary. Moreover, you may replace | exchange the electrostatic capacitance detection part suitably between several reference electrodes.

In the above-described embodiment, the example in which the correction process is performed every time when the detection value S _i is acquired has been described. However, the correction process may be skipped depending on conditions. In the period when the correction process is not performed, the capacitance detection unit for the reference electrode may also be used, and the capacitance detection of the detection electrode may be simultaneously performed in the plurality of capacitance detection units. For example, in the case where there are 40 detection electrodes for detecting electrostatic capacity, if the electrostatic capacity is detected simultaneously by two electrostatic capacity detection units, the detection sequence of 40 times is usually repeated 20 times. Detection of the capacitance values of all the detection electrodes is completed in the detection sequence.

  In the above-described embodiment, an example in which there is one first capacitance detection unit for the detection electrode is given. However, in another embodiment of the present invention, a plurality of first capacitance detection units are provided. Thus, detection operations may be performed in parallel. Capacitance values of all the detection electrodes can be obtained in a short time by detecting the capacitance in parallel in the plurality of first capacitance detection units. In this case, each correction value obtained in the plurality of first capacitance detection units may be subjected to noise correction using the simultaneous detection reference value and the average reference value.

  The input device of the present invention is not limited to a user interface device that inputs information by operating a finger or the like. That is, the input device of the present invention is widely applicable to devices that input information according to changes in the capacitance of the detection electrode caused by the proximity of various objects that are not limited to the human body.

DESCRIPTION OF SYMBOLS 10 ... Electrode part, 20 ... 1st selection part, 30 ... 2nd selection part, 40 ... 1st electrostatic capacitance detection part, 41 ... Operational amplifier, 42 ... Subtractor, 43 ... Multiplier, 44 ... Integrator, 45 ... AD converter 50 ... second capacitance detection unit 60 ... signal generation unit 70 ... processing unit 80 ... storage unit 90 ... interface unit 71 ... detection control unit 72 ... correction unit 73 ... coordinate calculation Part, ES _{1 to} ES _n ... detection electrode, ER ... reference electrode, S _i ... detection value, SA _i ... correction detection value, Q _i , P _i ... simultaneous detection reference value, Q _avr , P _avr ... average reference value, C x _... first capacitance, Q, P ... first reference capacitance, C s _... second capacitance, _{C q,} C p _... second reference capacitance, A i _... first noise factor, B _{i is} the second noise coefficient.

Claims (20)

A detection electrode provided in such a manner that an object electrically or electrostatically coupled to the ground can be brought close to the ground, and the capacitance between the ground and the detection electrode caused by the proximity of the object to the detection electrode; An input device for inputting information according to changes,
A reference electrode provided to detect noise from at least one noise source causing noise to the detection electrode;
A first capacitance detection unit that detects a capacitance between the detection electrode and the ground, and acquires a detection value indicating the detection result;
A second capacitance detection unit that detects a capacitance between the reference electrode and the ground, and acquires a reference value indicating the detection result;
A detection control unit that detects the second capacitance detection unit simultaneously with the detection of the first capacitance detection unit while repeating the detection of the second capacitance detection unit;
The detection value acquired by the first capacitance detection unit is used as the simultaneous detection reference value that is the reference value acquired by the second capacitance detection unit by detection at the same time as the detection value; 2. An input device comprising: a correction unit configured to correct based on an average reference value obtained by averaging a plurality of the reference values acquired by repeated detection in the capacitance detection unit. A plurality of the detection electrodes;
A first selection unit that selects one detection electrode from the plurality of detection electrodes and connects to the first capacitance detection unit;
The first capacitance detection unit detects the capacitance of the detection electrode connected via the first selection unit,
The detection control unit sequentially selects each of the plurality of detection electrodes in the first selection unit, and each time one detection electrode is selected in the first selection unit, the detection of the first capacitance detection unit. At the same time, the second capacitance detector is detected,
The correction unit corrects the detection value by using the average reference value obtained by averaging a series of the plurality of simultaneously detected reference values acquired in accordance with the sequential selection operation of the first selection unit. The input device according to claim 1. The correction unit decreases the detected value as the simultaneous detection reference value increases with respect to the average reference value, and increases the detected value as the simultaneous detection reference value decreases with respect to the average reference value. The input device according to claim 2, wherein the detection value is corrected. The input device according to claim 3, wherein the correction unit stops correcting the detection value when a difference between the simultaneous detection reference value and the average reference value is smaller than a predetermined threshold value. The input device according to claim 3 or 4, wherein the correction unit stops correcting the detection value when the simultaneous detection reference value is smaller than a predetermined threshold value. 6. The correction unit according to claim 3, wherein the correction unit acquires a correction detection value corresponding to a multiplication result obtained by multiplying the correction value obtained by dividing the average reference value by the simultaneous detection reference value and the detection value. The input device according to any one of the above. The correction unit stops correction of the detection value when the average reference value is smaller than a predetermined threshold value, or multiplies a value obtained by subtracting the average reference value from the simultaneous detection reference value by a predetermined coefficient. The input detection device according to claim 6, wherein a correction detection value corresponding to a subtraction result obtained by subtracting the correction value from the detection value is acquired. The correction unit acquires a correction detection value corresponding to a subtraction result obtained by subtracting a correction value obtained by subtracting the average reference value from the simultaneous detection reference value by a predetermined coefficient from the detection value. The input device according to any one of claims 3 to 5. A second selection unit that selects at least one detection electrode of the plurality of detection electrodes as the reference electrode and connects to the second capacitance detection unit;
The said 2nd electrostatic capacitance detection part detects the said electrostatic capacitance by making the detection electrode connected via the said 2nd selection part into the said reference electrode. The any one of Claims 2 thru | or 8 characterized by the above-mentioned. The input device according to item. When the first selection unit selects one detection electrode included in the group of detection electrodes selected as the reference electrode in the second selection unit, the one detection unit in the second selection unit The input device according to claim 9, wherein the selection of the electrode is canceled. The detection control unit identifies a detection electrode close to an object based on a detection value of the plurality of detection electrodes acquired most recently or a correction result of the correction unit with respect to the detection value, and determines the identified detection electrode. The input device according to claim 9 or 10, wherein the second selection unit selects the reference electrode. In the detection control unit, the correction result of the correction unit is larger than a predetermined threshold value, and / or the order in which the magnitudes of the correction results of the correction unit are relatively compared is within a predetermined order from the top. The input device according to claim 11, wherein at least one detection electrode satisfying a certain condition is specified as a detection electrode close to an object. Two reference electrodes with different intensity of noise from the noise source;
Two second capacitance detectors corresponding to the two reference electrodes, and
The two second capacitance detection units detect capacitances between the corresponding reference electrodes and the ground, respectively.
The detection control unit performs detection of the two second capacitance detection units simultaneously with the detection of the first capacitance detection unit each time one detection electrode is selected in the first selection unit,
The correction unit refers to the two simultaneous detection references acquired by the two second capacitance detection units by detecting the detection value acquired by the first capacitance detection unit at the same time as the detection value. The correction is performed based on a value and two average reference values that are averages of a series of the simultaneous detection reference values acquired simultaneously in the two second capacitance detection units. The input device described. The detection value of the first capacitance detection unit is
A first noise component from a first noise source that causes noise to the detection electrode via an adjacent object, the first capacitance between the object and the detection electrode and the noise of the first noise source A first noise component corresponding to a product of a first noise coefficient indicating intensity;
A second noise component from a second noise source that causes noise to the detection electrode without passing through the object, the second capacitance between the second noise source and the detection electrode, and the second noise source A second noise component corresponding to a product of a second noise coefficient indicating the noise intensity of
Estimated to be equal to the sum of the first capacitance and
The simultaneous detection reference value of the second capacitance detection unit is
A first reference noise component from the first noise source that causes noise to the reference electrode through the object, the first reference capacitance between the object and the reference electrode and the first noise coefficient; A first reference noise component corresponding to the product of
A second reference noise component from the second noise source that causes noise to the reference electrode without passing through the object, the second reference capacitance between the second noise source and the reference electrode, and the second A second reference noise component corresponding to the product of the two noise coefficients;
Estimated to be equal to the sum of the first reference capacitance and
When estimating that the reference component is equal to the average reference value,
The correction unit includes the detection value, the two simultaneous detection reference values, the two average reference values, the two second reference capacitances acquired in advance for the two reference electrodes, and the detection The input detection device according to claim 13, wherein a correction detection value approximated to the first capacitance is calculated based on the second capacitance acquired in advance for the electrode. When the difference between the two simultaneous detection reference values acquired by the detection simultaneously with the detection value in the two second capacitance detection units is smaller than a predetermined threshold, and / or When a difference between two average reference values, which is an average of a series of the simultaneous detection reference values acquired simultaneously in the two second capacitance detection units, is smaller than a predetermined threshold value, the detection value is corrected. The input device according to claim 13 or 14, wherein the input device is stopped. When the difference between the two simultaneous detection reference values acquired by the detection simultaneously with the detection value in the two second capacitance detection units is smaller than a predetermined threshold, and / or When a difference between two average reference values, which is an average of a series of the simultaneous detection reference values acquired simultaneously in the two second capacitance detection units, is smaller than a predetermined threshold value, the reference electrode in the one reference electrode The correction detection value corresponding to the subtraction result obtained by subtracting from the detection value a correction value obtained by subtracting a predetermined coefficient from a value obtained by subtracting the average reference value from the simultaneous detection reference value is obtained. The input device described in 1. Having at least one second selection unit that selects at least one detection electrode of the plurality of detection electrodes as the reference electrode and connects to the second capacitance detection unit;
The at least one second capacitance detection unit detects the capacitance using the detection electrode connected via the second selection unit as the reference electrode. The input device according to any one of the above. When the first selection unit selects one detection electrode included in the group of detection electrodes selected as the reference electrode in the second selection unit, the one detection unit in the second selection unit The input device according to claim 17, wherein the selection of the electrode is canceled. The detection control unit identifies a detection electrode close to an object based on a detection value of the plurality of detection electrodes acquired most recently or a correction result of the correction unit with respect to the detection value, and determines the identified detection electrode. The input device according to claim 17 or 18, wherein the second selection unit selects the reference electrode. The correction unit is
Calculating the average reference value by averaging a series of a predetermined number of simultaneously detected reference values including the recently acquired simultaneously detected reference values;
When the detection electrode selected as the reference electrode in the second selection unit is changed, a value after correction of the detection value most recently acquired in the first capacitance detection unit for the changed detection electrode The input device according to any one of claims 9 to 12 and 17 to 19, wherein the series of the predetermined number of simultaneous detection reference values is initialized.

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