JPWO2005108912A1 - Visualization sensor - Google Patents

Abstract

Provided is a visualization sensor that does not require a vacuum state and can realize visualization of an object with a small and simple configuration. The oscillator 2 regards the distance between the antenna electrode 8 that is one point of the probe array 1 and the object as the capacitance of the capacitor, and oscillates a signal having a frequency f2 corresponding to the capacitance. The oscillator 3 always oscillates a signal having a fixed frequency f1. The mixer 4 inputs the signal of the frequency f2 and the signal of the fixed frequency f1, and performs a multiplication process. The filter 5 removes signal components of frequencies f1, f2, f1 + f2, 2f1, and 2f2 from the signal input from the mixer 4, and outputs only a signal of frequency f1-f2. The counter 6 counts the frequency of the signal having the frequency f1-f2. The PC 7 calculates the distance between the object and the antenna electrode 8 in the probe array 1 based on the count value.

Description

  The present invention relates to a sensor that detects a spatial change in impedance of an object, and more particularly to a sensor that realizes visualization of an object by detecting a frequency change using an antenna connected to a high-frequency transmission circuit.

  Conventionally, a scanning electron microscope, a scanning probe microscope, or the like has been used as a device for detecting a spatial change in impedance at a submicron resolution and realizing object visualization. A scanning electron microscope realizes visualization of an object by irradiating an object with an electron beam to generate secondary electrons and detecting the secondary electrons. In addition, the scanning probe microscope realizes visualization of an object by detecting a phenomenon that occurs between the object and the probe (for example, detecting a tunnel current and an atomic force). At present, development and improvement focusing on the size and resolution of a microscope have been made, and further studies for dealing with objects having various shapes and properties have been made (see, for example, JP-A-2001-108596). ).

  An example of a scanning capacitance microscope is described in JP-A-9-282579. This scanning capacitance microscope is a device for measuring a capacitance between an electrode and a surface of a measurement object using a capacitance sensor and obtaining a capacitance distribution on the surface of the measurement object. Specifically, a capacitor configured by an oscillation circuit that oscillates a signal having a fixed frequency, a resonance circuit in which a measured capacitor Cm is connected in parallel to an LC parallel resonance circuit, and an output circuit that outputs a change in the resonance frequency as a voltage. The capacitance distribution is obtained by utilizing the fact that the resonance frequency is changed by the sensor under the influence of the measured capacitance Cm. The capacitance sensor converts the change in the resonance frequency into the change in the voltage of the output circuit, whereby the capacitance distribution is obtained. Japanese Patent Application Laid-Open No. 11-30622 also describes a scanning capacitance microscope using the same measurement principle.

  An example of a capacitive displacement sensor is described in Japanese Patent Application Laid-Open No. 2004-170163. This capacitance type displacement sensor is a sensor that measures the capacitance by measuring the capacitance between the electrode and the surface of the object to be measured and utilizing the fact that this capacitance is inversely proportional to the distance between the two. Specifically, the capacitance type displacement sensor includes a circuit in which a measured capacitor Cm and a reference capacitor Cr are connected in series, a circuit for detecting a partial voltage of an alternating voltage in the measured capacitor Cm, and a measured capacitor Cm. The circuit includes a circuit that generates and amplifies the dependent AC voltage, a circuit that converts the amplitude of the AC voltage into a frequency, and a circuit that detects the frequency. Under such a configuration, the capacitance type displacement sensor uses the V / F converter to convert the alternating voltage in the capacitance Cm to be measured into a frequency, thereby obtaining frequency information and specifying the oscillation frequency and measuring the distance. To do.

  A fingerprint sensor is known as a sensor for detecting a change in capacitance. This fingerprint sensor is a sensor that detects a change in time required for charging as a change in capacitance when a DC voltage source charges the capacitor Cm to be measured via a resistor having a constant value. That is, by converting the change in capacitance into a change in voltage value, the capacitance is obtained from the voltage value after a certain time.

  Japanese Patent Application Laid-Open No. 2001-17412 discloses a sensor that captures unevenness on the finger surface as a change in impedance and reads out the change in impedance using a high-frequency signal. Specifically, the sensor includes a plurality of output electrodes, a single input electrode, a drive circuit that selects one of the plurality of output electrodes and supplies a high-frequency carrier signal, and the input electrode It is constituted by a detection circuit that inputs a carrier signal and extracts impedance information from the amplitude of the carrier signal. That is, since the amplitude of the carrier signal varies depending on the impedance (unevenness on the finger surface), the unevenness information on the finger surface can be obtained by converting the impedance information into a digital signal. As described above, development and research for realizing visualization of an object are performed using various technologies.

  However, in the above-mentioned scanning electron microscope, it is necessary to prepare a vacuum state and to irradiate an object with an electron beam. For this reason, when the observation object is a living thing, the living thing cannot be observed as it is, and it cannot be adapted to visualization of a biological substance. On the other hand, since the scanning probe microscope requires advanced noise countermeasures and precise machine control, the entire apparatus becomes a large-scale and complicated configuration.

  In the scanning capacitance microscope described above, in order to measure the capacitance using the resonance frequency, it is necessary to provide a resonance circuit in which the capacitance Cm to be measured and the LC parallel resonance circuit are connected in parallel. For this reason, miniaturization cannot be realized and integration is difficult.

  In the above-described capacitance type displacement sensor, since the change in capacitance is converted into the change in AC voltage, the sensitivity is limited by the SN ratio of the electronic circuit, and high accuracy cannot be realized. Furthermore, this electrostatic capacitance type displacement sensor requires many circuits such as a partial pressure detection circuit, an amplification circuit, and a voltage frequency conversion circuit, so that the circuit scale becomes large. Further, in the above-described fingerprint sensor, the sensitivity is limited by the S / N ratio of the electronic circuit as in the capacitance type displacement sensor, and high accuracy cannot be realized.

  Therefore, the present invention has been made to solve such problems. The first object of the present invention is to make it possible to visualize an object with a small and simple configuration without having to prepare a vacuum state. Is to provide a simple visualization sensor. A second object of the present invention is to provide a visualization sensor that achieves high sensitivity and high accuracy. Furthermore, a third object of the present invention is to provide a visualization sensor that realizes high resolution.

[Principle of the present invention]
Visualization of an object according to the present invention is based on the operating principle of a musical instrument called “Theremin”. This “termin” is to change the pitch and volume of the generated musical sound by changing the capacitance between the antenna and the hand by blocking the two antennas provided on the musical instrument with the hand. Specifically, since the capacitance is inversely proportional to the distance between the antenna and the hand, a signal having a frequency corresponding to the capacitance is oscillated, and the oscillation frequency is converted into a pitch and sound.

  First, the observation principle of an object according to the present invention based on the above-described “thermin” operation principle will be described in detail with reference to FIG. In FIG. 1, the system includes a probe array 1, oscillators 2 and 3, a mixer 4, a filter 5, a counter 6, and a PC (personal computer) 7. The probe array 1 is composed of a plurality of antenna electrodes 8 arranged in a lattice shape, and an object to be observed (not shown) is placed on the probe array 1. The antenna electrode 8 is an electrode of a capacitor having a capacitance with an object.

Oscillator 2, captures the distance between the antenna electrode 8 is one point of the object and the probe array 1 as an electrostatic capacitance of the capacitor oscillates a signal of frequency f ₂ in accordance with the capacitance. In this case, relationship of the distance between the object and the antenna electrode 8 is the capacitance is changed when changing the capacitance is the oscillation frequency f ₂ also changes vary. The oscillator 2 is a circuit that oscillates a signal having a frequency f ₂ corresponding to the capacitance. For example, when an LC oscillation circuit is used, the capacitance C and the oscillation frequency f have the following relationship. .
Formula: f = 1 / 2π√ (L × C)
Furthermore, the oscillator 3 is always oscillates a signal of fixed frequency f _1. The object is when not placed on the probe array 1, a signal of frequency f ₂ and oscillator 3 oscillator 2 oscillates is assumed to be the same as the fixed frequency f ₁ to oscillate.

The mixer 4 receives the signal oscillated from the oscillator 2 at the frequency f ₂ and the signal oscillated from the oscillator 3 at the fixed frequency f ₁ , and performs multiplication processing. As a result, the frequencies f ₁ , f ₂ , f ₁ −f ₂ , f ₁ + f ₂ , 2f ₁ , 2f ₂ signals are output. The filter 5 is an LPF (Low Pass Filter) that removes a high-frequency signal component. The filter 5 removes signal components of frequencies f ₁ , f ₂ , f ₁ + f ₂ , 2f ₁ , 2f _{2 from} the signal input from the mixer 4 and outputs only a signal of frequency f ₁ −f ₂ .

The counter 6 counts the frequency of the signal having the frequency f ₁ -f ₂ input from the filter 5 and calculates a count value per unit time, that is, the frequency f ₁ -f ₂ . The PC 7 inputs the count value from the counter 6 and calculates the distance between the object and the antenna electrode 8 in the probe array 1 based on the count value. In this case, the capacitance between the object and the antenna electrode 8 is the surface of the object in the direction perpendicular to the array surface of the probe array 1, and is perpendicular to the electrode surface of the antenna electrode 8 of the probe array 1. Since the electrostatic capacity is between the vicinity of the object surface in the existing object surface and the electrode surface of the antenna electrode 8, the distance calculated from the electrostatic capacitance is between the electrode surface of the antenna electrode 8 and the vicinity of the object surface. The average distance. And the shape (object image) of the object seen from the probe array 1 can be imaged by calculating the distance between the object and the antenna electrode in the probe array 1 for each antenna electrode.

  In this way, an oscillator is used to oscillate at a frequency corresponding to the capacitance between the object and the antenna electrode in the probe array 1, and the distance is calculated based on the frequency, thereby imaging the shape of the object. can do.

  FIG. 2 shows the relationship between the distance calculated based on the oscillation frequency and the rate of frequency change when LC oscillators are used for the oscillators 2 and 3. FIG. 2 shows that the frequency change rate decreases as the distance increases, and the frequency change rate increases as the distance decreases. It can also be seen that the higher the frequency, the better the distance sensitivity. Experiments have shown that oscillation does not occur when the frequency is increased to around 5 GHz. By using a frequency close to 5 GHz and oscillating, a highly sensitive distance can be calculated.

  Based on the above-described principle, the visualization sensor according to the present invention has an antenna electrode provided opposite to an object, connected to the antenna electrode, and having an oscillation frequency corresponding to the capacitance between the object and the antenna electrode. A first oscillator that outputs a signal, a second oscillator that outputs a signal having a reference oscillation frequency, an oscillation frequency of the signal output by the first oscillator, and a signal output by the second oscillator Output means for generating and outputting a signal having a frequency corresponding to the difference from the reference oscillation frequency. Since the electrostatic capacitance depends on the distance between the object and the antenna electrode, the distance between the object and the antenna electrode can be calculated based on the signal output from the output means.

  Instead of the output means, for the signal output from the first oscillator, a frequency obtained by dividing the oscillation frequency by a frequency ratio of 1 is generated, and the signal of the frequency coincides with the input reference frequency signal. A first synchronizing circuit that generates and outputs a control frequency signal for the first oscillator, and a reference oscillation frequency signal output by the second oscillator, and inputs the reference oscillation frequency to a predetermined value. It is preferable to include a second synchronization circuit that generates a frequency divided into a frequency ratio of the frequency and outputs a signal of the divided frequency as the reference frequency signal. As a result, the distance between the object and the antenna electrode can be calculated based on the signal output from the first synchronization circuit and the signal output from the second synchronization circuit. In this case, the control frequency signal can be output using a higher frequency, and the distance between the object and the antenna electrode can be calculated with high sensitivity.

  In addition to the configuration of the visualization sensor, it is preferable to provide a ground electrode provided facing the object and held in a grounded state. This eliminates the need to consider the capacitance that varies depending on the object other than the capacitance between the object and the antenna electrode. It is possible to calculate the distance between them with high accuracy. The visualization sensor preferably includes a plurality of antenna electrodes, and the first oscillator, the second oscillator, and the output means are provided for each of the plurality of antenna electrodes.

  In addition, the visualization sensor according to the present invention outputs a signal having an oscillation frequency corresponding to an electrostatic capacity between an antenna electrode provided opposite to an object and the antenna electrode connected to the antenna electrode. 1 oscillator, a second oscillator that outputs a signal having a reference oscillation frequency, an oscillation frequency of a signal output by the first oscillator, and a reference oscillation frequency of a signal output by the second oscillator Output means for generating and outputting a signal having a frequency corresponding to the difference between the two. This makes it possible to calculate the distance between the object and the antenna electrode based on the signal output from the output means. The visualization sensor preferably includes a plurality of antenna electrodes, and the first oscillator, the second oscillator, and the output means are provided for each of the plurality of antenna electrodes.

  In addition to the visualization sensor, it is preferable that a switch for selecting one of the output means provided for each antenna electrode is provided. Further, it is preferable that the first oscillator, the second oscillator, and the output means are provided on the opposite side to the object when viewed from the plurality of antenna electrodes. In addition, it is preferable that the first oscillator and the second oscillator are configured in a common centroid arrangement in which an odd number of inverters are respectively connected in series.

  In addition, the visualization sensor according to the present invention includes a single antenna electrode provided to face an object, a signal having an oscillation frequency that is connected to the antenna electrode and that corresponds to the capacitance between the object and the antenna electrode. A first oscillator that outputs a signal having a reference oscillation frequency, an oscillation frequency of the signal output by the first oscillator, and a reference oscillation of the signal output by the second oscillator Output means for generating and outputting a signal having a frequency corresponding to the difference between the frequency and a member provided on the side where the object is present as viewed from the antenna electrode, wherein the member constitutes a plurality of intersections When one intersection of the plurality of intersections is selected, a plurality of linear members in which the two members constituting the intersection are held open and the other members are held grounded With the features That. Thereby, based on the signal output from the output means, it is possible to calculate the distance between the object and the antenna electrode at the intersection of the linear members.

  The plurality of linear members include a plurality of linear members in the vertical direction and a plurality of linear members in the horizontal direction with respect to the surface of the antenna electrode. It is preferable that a plurality of antenna electrodes respectively opposed to the plurality of linear members in the direction are provided. In addition, it is preferable that the visualization sensor or the antenna electrode is provided with a means for moving the visualization sensor or the antenna electrode.

  According to the present invention, when calculating the distance to the object and realizing the visualization of the object, it is not necessary to prepare a vacuum state and it is not necessary to irradiate the object with an electron beam. It can be observed. In addition, since advanced noise countermeasures and precise machine control are not required, and an optical system such as light or an electron beam is not required, visualization of an object can be realized with a small and simple configuration. Further, an object in the micron to submicron region can be visualized, and a resolution equivalent to that of a scanning electron microscope or a scanning probe microscope can be obtained. In this way, the first object can be achieved.

  Further, according to the present invention, the antenna electrode and the first oscillator are connected, and the first oscillator and the output means are connected, so that the antenna electrode is provided between the antenna electrode and the output means. There are no transistors or the like for selection. Thereby, there is little influence of wiring capacity and it does not receive influence of capacity, such as a transistor. Therefore, when calculating the distance between the object and the antenna electrode, it is possible to achieve the second object of high sensitivity and high accuracy.

  Further, according to the present invention, a plurality of linear members are provided for the antenna electrode, and the distance is determined based on the frequency according to the capacitance between the object and the antenna electrode at the intersection of the linear members. Calculated. Thereby, it is not necessary to provide an antenna electrode for each pixel. Therefore, it is possible to realize the third object, high resolution.

FIG. 1 is a block diagram for explaining the observation principle of an object according to the present invention based on the operation principle of “Theremin”. FIG. 2 is a diagram showing the relationship between the distance and the rate of frequency change when the LC oscillation circuit is used. FIG. 3 is a block diagram showing the configuration of the visualization sensor according to the first embodiment of the present invention. FIG. 4 is a block diagram showing a configuration of a modification of the first embodiment shown in FIG. FIG. 5 is a block diagram showing a configuration of the PLL circuit shown in FIG. FIG. 6 is a top view of the probe array when the ground electrode is arranged. FIG. 7 is a cross-sectional view for explaining the capacitance between the object (conductor) and the probe array. FIG. 8 is an equivalent circuit diagram of an object (conductor), a probe array, and an oscillator. FIG. 9 is a diagram showing the relationship between the capacitances C1 and Cpr that determine the oscillation frequency. FIG. 10 is a diagram illustrating the relationship between the error rate ε due to the influence of Cgnd and P (= Cgrd / Cpr). FIG. 11 is a block diagram showing a configuration of a visualization sensor according to a second embodiment of the present invention. 12 is a logic circuit diagram showing a configuration of the oscillator shown in FIG. FIG. 13 is a block diagram showing a configuration of a visualization sensor according to a third embodiment of the present invention. FIG. 14 is a cross-sectional side view of an antenna electrode and wiring for explaining a measurement mechanism according to the third embodiment shown in FIG. FIG. 15 is a diagram for illustrating the capacitance of the sensor electrode. FIG. 16 is a diagram showing an outline of a modification of the third embodiment shown in FIG. FIG. 17 is a diagram for explaining a capacitance and an equivalent circuit between an object (insulator) and a probe array. FIG. 18 is a schematic configuration diagram for explaining an example of moving a sensor or an antenna electrode. FIG. 19 is a graph showing the number of pixels when antenna electrodes are arranged in an area of 1 cm square. FIG. 20 is a schematic diagram for explaining the circuit arrangement of the visualization sensor shown in FIG. 11. FIG. 21 is a numerical value conversion graph when a CMOS of 0.09 μm is used. FIG. 22 is a graph showing the relationship between the sensor position and the frequency of the oscillator. FIG. 23 is a graph showing an estimate of the dimensions of the antenna electrode.

Hereinafter, embodiments of the visualization sensor according to the present invention will be described in detail with reference to the drawings.
[Example 1]
FIG. 3 is a block diagram showing the configuration of the visualization sensor according to the first embodiment of the present invention. The system 10 captures the distance between the object as the capacitance of the capacitor, outputs a signal having a frequency corresponding to the capacitance (visualization sensor) 30, and the probe array 11 provided in the sensor 30. Output an address signal for specifying an antenna electrode, and an interface 40 for calculating a count value of the frequency, and a PC 17 for calculating a distance between the object and the sensor 30 and imaging the shape of the object. ing. The sensor 30 includes a probe array 11, oscillators 12 and 13, a mixer 14, a filter 15, and a decoder 31. The interface 40 includes a counter 16 and an input / output unit 41.

  Similar to the probe array 1 shown in FIG. 1, the probe array 11 provided in the sensor 30 includes a plurality of antenna electrodes, and an object to be observed (not shown) is placed on the probe array 11. In the decoder 31, a transistor for selecting an antenna electrode is provided for each antenna electrode, and an address signal for specifying one antenna electrode of the plurality of antenna electrodes in the probe array 11 is input from the interface 40. One transistor is operated based on the address signal, and one antenna electrode is specified and selected.

Oscillator 12 has the same function as that of the oscillator 2 shown in FIG. 1 oscillates a signal of frequency f ₂ corresponding to the electrostatic capacitance between the one antenna electrode, which is specified by the object decoder 31 . Further, the oscillator 13 has the same function as the oscillator 3 shown in FIG. 1, always oscillates a signal of fixed frequency f _1. The object is when not placed on the probe array 11, the frequency f ₂ and the oscillator 13 of the signal oscillator 12 oscillates is assumed to be the same as the fixed frequency f ₁ to oscillate.

The mixer 4 has the same function as the mixer 4 shown in FIG. 1, and outputs signals of frequencies f ₁ , f ₂ , f ₁ −f ₂ , f ₁ + f ₂ , 2f ₁ and 2f ₂ . The filter 5 has the same function as the filter 5 shown in FIG. 1, and outputs only a signal having a frequency f ₁ -f ₂ .

Counter 16 with the interface 40 has the same function as that of the counter 6 shown in FIG. 1, counts the frequency for the signal of the frequency _f 1 -f _2, the count value or frequency _f 1 -f ₂ calculate. The input / output unit 41 inputs an address signal for specifying one antenna electrode for calculating the distance to the object from the PC 17, and outputs the address signal to the decoder 31 of the sensor 30. The input / output unit 41 inputs a frequency count value at one antenna electrode specified by the address signal from the counter 16, and outputs the address signal and the frequency count value to the PC 17.

  The PC 17 outputs an address signal for specifying the antenna electrode to the input / output unit 41 of the interface 40, and inputs the address signal and the frequency count value from the input / output unit 41. Then, the PC 17 calculates the distance between the object and the antenna electrode in the probe array 11 based on the count value. In this case, the capacitance between the object and the antenna electrode is, as described above, between the vicinity of the object surface in the direction perpendicular to the array surface of the probe array 11 and the antenna electrode as viewed from the specified antenna electrode. Capacitance between. Therefore, the address signal information corresponds to the object surface in the direction perpendicular to the array surface of the probe array 11 as viewed from the antenna electrode. The PC 17 sequentially outputs an address signal for specifying one of the antenna electrodes in the probe array 11, inputs a frequency count value, and calculates the distance between the object and the antenna electrode, respectively. By doing so, the shape of the object viewed from the probe array 11 can be imaged.

As described above, according to the visualization sensor 30 of Example 1, the oscillator 12 oscillates a signal of frequency f ₂ corresponding to the capacitance between the antenna electrode of the object and the probe array 11, the mixer 14 is The difference between the frequency f ₂ and the reference frequency f ₁ is output. Thus, based on the difference between f ₁ -f ₂ frequency, it is possible to calculate the distance between the object and the antenna electrode, and imaging the shape of the object as viewed from the probe array 11 (the object image) it can.

  In the visualization sensor 30 according to the first embodiment, LC oscillators such as a Corbitz oscillation circuit can be used as the oscillators 12 and 13. In this case, an oscillation circuit that oscillates at a lower gain than the Corbitz oscillation circuit can be used. However, since the Corbitz oscillation circuit has a simple circuit configuration, the sensor 30 as a whole can have a small and simple configuration.

[Modification 1]
Next, a modification of the first embodiment will be described in detail with reference to FIGS. Modification 1 shown in FIG. 4 has a configuration different from the block configuration shown in the operation principle of “Theremin” in FIG. 1, but paying attention to the capacitance between the object and the antenna electrode, Common in calculation. In the first embodiment based on the operation principle of “Theremin” shown in FIG. 3, the oscillation frequency f2 of the oscillator 12 and the oscillation frequency f1 of the oscillator 13 are made the same with no object placed on the probe array 11. There is a need to. In this case, since the oscillator 12 and the oscillator 13 are separate circuits, it is extremely difficult to design with high accuracy so as to be the same. Therefore, the first modification is made to solve such a design problem.

  Referring to FIG. 4, this system 100 includes a sensor 130 that captures a distance between an object as a capacitance of a capacitor and outputs a frequency control voltage corresponding to the capacitance, and the sensor 130. The PC 117 outputs an address signal for specifying an antenna electrode in the probe array 111, calculates a distance between the interface 140 that inputs a frequency control voltage signal from the sensor 130, and the object, and images the shape of the object. And an oscillator 150 that outputs a signal of a reference oscillation frequency with high accuracy to the sensor 130. The sensor 130 includes a probe array 111, a decoder 131, and PLL (Phase Locked Loop / phase-locked loop) circuits 132 and 133. The interface 140 includes an input / output unit 141 and a comparison unit 142.

  The probe array 111 provided in the sensor 130 is the same as the probe array 1 shown in FIG. 1 and the probe array 11 shown in FIG. The decoder 131 has the same function as that of the decoder 31 shown in FIG. 3, and receives an address signal for specifying one antenna electrode of the plurality of antenna electrodes in the probe array 111 from the interface 140. One antenna electrode is specified and selected based on the above.

  The PLL circuit 132 inputs a signal A1 having a highly accurate reference oscillation frequency fr from the oscillator 150. The PLL circuit 132 has a frequency fo (fo = N × fr (N = 1, 2, 4, 8,...)) Obtained by dividing the reference frequency fr of the signal A1 input from the oscillator 150 into a predetermined frequency ratio. The signal B1 is output and the reference frequency control voltage signal C1 for generating the signal B2 is output. Here, the PLL circuit is generally a circuit that generates an output signal having no frequency or phase shift with respect to an input signal. Specifically, the external input signal and the output signal from the built-in oscillator are compared, and the frequency and phase error are detected and fed back to the oscillator to match the two signals. This is a circuit that obtains an output signal without misalignment.

  The PLL circuit 133 receives the signal B1 having the frequency fo, that is, the signal A2 from the PLL circuit 132, and outputs the signal B2 having the frequency fo divided by a frequency ratio of 1 times. When the object does not exist on the probe array 111 (when the object exists at an infinite position from the probe array 111), the frequency control voltage signal C2 (= α) for generating the signal B2 is output. In this case, the frequency control voltage signal C2 (= α) is the same signal as the signal C1 output from the PLL circuit 132. On the other hand, when an object exists on the probe array 111, the signal B2 changes due to the presence of a capacitor load whose capacitance is the distance between the object and the antenna electrode of the probe array 111. Then, in the PLL circuit 133, the frequency control voltage signal C2 for generating the signal B2 changes so that the signal B2 and the signal A2 are the same. That is, the change in the distance between the object and the antenna electrode of the probe array 111 appears in the change in the frequency control voltage signal C2 (C2 = β).

  A block diagram showing a specific configuration of the PLL circuits 132 and 133 is shown in FIG. The PLL circuit 132 is a reference circuit, and includes an oscillator 132-1, a frequency divider 132-2, a phase comparator 132-3, and a filter 132-4. The PLL circuit 133 is a circuit for measurement, and includes an oscillator 133-1, a frequency divider 133-2, a phase comparator 133-3, and a filter 133-4. The frequency divider 132-2 of the PLL circuit 132 changes the frequency of the input signal to a constant multiple (N times). The phase comparator 132-3 receives the signal A1 of the reference frequency fr input from the external oscillator 150 and the signal input from the frequency divider 132-2, and outputs the difference between the frequencies. The filter 132-4 converts the input frequency difference into a voltage (frequency control voltage) and outputs the voltage. The oscillator 132-1 receives a frequency control voltage (reference frequency voltage), and outputs a signal B1 (a signal obtained by dividing the reference frequency fr by a predetermined constant multiple) having a frequency fo corresponding to the voltage. That is, the PLL circuit 132 receives the signal A1 having the reference frequency fr from the oscillator 150, outputs the signal B1 having the frequency fo that is a high-frequency signal divided by N times, and generates a signal having the frequency fo. The frequency voltage signal C1 (= α) is output.

  The oscillator 133-1, the frequency divider 133-2, the phase comparator 133-3, and the filter 133-4 of the PLL circuit 133 are the oscillator 132-1, the frequency divider 132-2, and the phase comparator 132- of the PLL circuit 132, respectively. 3 and the filter 132-4 have the same functions. The frequency divider 133-2 of the PLL circuit 133 outputs a signal B2 having a frequency ratio of 1 with respect to the frequency fo of the input signal A2. In this way, the PLL circuit 133 receives the signal A2 having the frequency fo from the PLL circuit 132, outputs the signal B2 having a frequency ratio that is one time the frequency fo, and generates the signal B2. The voltage C2 is output. In this case, as described above, since the frequency of the signal B2 changes according to the distance between the object and the antenna electrode of the probe array 111, the oscillator 133-1 keeps the frequency fo of the signal B2 constant. The frequency control voltage signal C2 (= β) corresponding to the distance is input.

  That is, the PLL circuit 132 outputs the reference frequency control voltage signal C1 (= α) to the interface 140, and the PLL circuit 133 has a frequency signal corresponding to the capacitance between the object and the antenna electrode of the probe array 111. The frequency control voltage signal C2 (= β) with the signal C1 as a reference is output to the interface 140.

  Returning to FIG. 4, the comparison unit 142 included in the interface 140 inputs the reference frequency control voltage signal C <b> 1 from the PLL circuit 132 and the frequency control voltage signal C <b> 2 from the PLL circuit 133, compares both signals, Calculate the signal difference. Then, the comparison unit 142 outputs the difference signal to the input / output unit 141. The input / output unit 141 inputs an address signal for specifying one antenna electrode for calculating the distance to the object from the PC 117, and outputs the address signal to the decoder 131 of the sensor 130. In addition, the input / output unit 141 inputs a frequency control voltage difference value at one antenna electrode specified by the address signal from the comparison unit 142, and outputs the address signal and the difference value to the PC 117.

  The PC 117 outputs an address signal for specifying the antenna electrode to the input / output unit 141 of the interface 140, and inputs the value of the difference between the address signal and the frequency control voltage from the input / output unit 141. Then, the PC 117 calculates the distance between the object and the antenna electrode in the probe array 111 based on the difference value. In this case, as described in the first embodiment, the address signal information is the position information on the observation plane of the object observed by the one antenna electrode, that is, the array of the probe array 111 as viewed from the antenna electrode. It corresponds to the object plane in the direction perpendicular to the plane. Therefore, the PC 117 sequentially outputs an address signal for specifying one antenna electrode among all the antenna electrodes in the probe array 111, inputs a value of the difference in frequency control voltage, and determines between the object and the antenna electrode. , The shape of the object viewed from the probe array 111 can be imaged.

  As described above, according to the visualization sensor 130 of the first modification, the PLL circuit 133 generates the signal B1 having the frequency fo higher than the reference frequency fr, and the PLL circuit 133 uses the frequency fo and the signal B2 of the signal A2. The frequency control voltage signal C2 is output so that the frequencies of the antennas are the same, and the PC 117 calculates the distance between the antenna electrode and the object by the frequency control voltage C2. As shown in FIG. 2, the higher the frequency, the better the sensitivity of the distance. Therefore, by using the signal B1 having the frequency fo higher than the reference frequency fr using the two PLL circuits 132 and 133, the object The distance between the antenna electrode and the antenna electrode can be calculated with high sensitivity.

[Modification 2]
Next, an embodiment in which ground electrodes are arranged in the probe arrays 11 and 111 of the first embodiment and the first modification thereof will be described in detail with reference to FIGS. FIG. 6 is a top view when the ground electrode is arranged on the probe array. FIG. 6A is an example in which the dotted ground electrodes 150 are arranged between the antenna electrodes 151, and FIG. 6B is an example in which the grid-like ground electrodes 152 are arranged between the antenna electrodes 153. FIG. 7 is a cross-sectional view for explaining the capacitance between the objects 160 and 170 and the antenna electrodes of the probe arrays 164 and 173. In FIG. 7A, when the ground electrode is arranged, the electrostatic capacity Cpr between the object 160 and the antenna electrode 163, and the electrostatic capacity Cgnd1 between the object 160 and the ground electrode 162-1, the object 160 and the ground. The capacitance Cgnd2 between the electrode 162-2, the capacitance Cd between the antenna electrode 163 and the ground electrodes 162-1 and 160-2, the stray capacitance of the entire object (the surrounding metal other than the ground electrode, etc. The total unintended capacitance between Ct) and the wiring capacitance Cs due to the oscillator 161 and the like. In FIG. 7B, when the ground electrode is not disposed, the capacitance Cpr, the floating capacitance Ct of the entire object, and the wiring capacitance Cs due to the oscillator 171 and the like exist between the object 170 and the antenna electrode 172.

Here, assuming that Cgnd = ΣCgndi + Ct (i = 1, 2,...), The equivalent circuit of the cross-sectional views shown in FIGS. 7A and 7B is the circuit shown in FIG. Cpr and Cgnd (including Ct) are capacitances that vary depending on the object, and Cd and Cs are fixed capacitances that do not vary depending on the object and are inherent to the probe arrays 164 and 173. Therefore, the overall capacitance is as shown in FIG.
Formula: C = Cpr × Cgnd / (Cpr + Cgnd) + Cd + Cs
Thus, when the Cpr × Cgnd / (Cpr + Cgnd) portion of the entire capacitance C changes, the oscillation frequency of the signal oscillated by the oscillator 161 changes. That is, the distance between the objects 160 and 170 is calculated using an oscillation frequency corresponding to Cpr × Cgnd / (Cpr + Cgnd). When the ground electrode shown in FIG. 7B is not arranged, Cgnd = Ct.

  As described above, in both cases where the ground electrode shown in FIG. 7 (1) is arranged and in the case where the ground electrode shown in FIG. 7 (2) is not arranged, Cgnd differs for each object. As long as Cgnd is included in the converted capacitance Cpr × Cgnd / (Cpr + Cgnd), the principle of calculating the distance between the object and the antenna electrode based on Cpr cannot be applied. However, when Cgnd> Cpr (see FIGS. 9 and 10, details will be described later), the capacitance that determines the oscillation frequency can ignore Cgnd and is almost equal to Cpr. Can be solved. That is, when Cgnd> Cpr, the distance between the object and the antenna electrode can be calculated with high accuracy. Details will be described below.

Assuming that the capacitance for determining the oscillation frequency for calculating the distance between the object and the antenna electrode is C1, as described above,
Formula: C1 = Cpr × Cgnd / (Cpr + Cgnd)
It becomes. In this case, when C1 and Cpr are substantially equal, Cgnd can be ignored, and the distance between the object and the antenna electrode can be calculated with high accuracy. FIG. 9 is a diagram illustrating the relationship between C1 and Cpr. In the drawing, curve a is C1 = Cpr (when Cgnd is not affected at all), curve b is Cgnd = 10 × Cpr, curve c is Cgnd = Cpr, curve d is Cgnd = 0.1. The case of × Cpr is shown. From FIG. 9, the difference between C1 and Cpr is large when Cgnd <Cpr and small when Cgnd> Cpr. In the capacitance scale shown in FIG. 9, when Cgnd is about 10 times Cpr, C1 is hardly influenced by Cgnd, but only by Cpr. In this case, when the ground electrode shown in FIG. 7 (2) is not arranged, Cgnd = Ct, and since the stray capacitance Ct is generally smaller than Cpr, the ground electrode shown in FIG. 7 (1) is arranged. In the case, the error is smaller than in (2), and the distance can be calculated with high accuracy.

Further, the error rate ε due to the influence of Cgnd is expressed by the following equation.
Formula: ε = (C1-Cpr) / Cpr = −1 / (1 + P), P = Cgnd / Cpr
FIG. 10 is a diagram illustrating a relationship between the error rate ε due to the influence of Cgnd and P (= Cgnd / Cpr) in the above equation. From FIG. 10, the error rate ε due to the influence of Cgnd becomes closer to zero as Cgnd is larger than Cpr. From the above formula, when N-bit accuracy is required, the following formula must be satisfied.
Formula: P = Cgnd / Cpr ≧ | 2 ^N −1 |

  In reality, when the object is sufficiently larger than between the antenna electrodes, the influence of Cgnd can be ignored, but in the same case, if the value of Cgnd is different, the distance between the object and the antenna electrode is unique. Cannot be determined automatically, resulting in noise. In this case, noise can be removed by image processing such as a low-pass filter. In other words, if the object is as large as the distance between the antenna electrodes, the distance to the object cannot be calculated, so the object cannot be visualized, and the resolution is the number of distances between the antenna electrodes. It will go down to about twice.

  As described above, according to the visualization sensor of Modification Example 2, since the ground electrode is arranged in the probe array, the static electricity that changes depending on the object other than the electrostatic capacitance between the object and the antenna electrode can be obtained. Compared to an example in which the capacitance is not considered and the ground electrode is not disposed, the capacitance C1 that determines the oscillation frequency when Cgnd> Cpr is not affected by Cgnd. Can be calculated with high accuracy.

[Example 2]
FIG. 11 is a block diagram showing a configuration of a visualization sensor according to a second embodiment of the present invention. Comparing Example 1 and Example 2 shown in FIG. 3, in Example 1, any one of a plurality of antenna electrodes constituting a probe array is selected by a decoder 31 including a transistor. Example 2 is different in that any one of a plurality of antenna electrodes 237, oscillators 232 and 233, and a mixer 234 is selected by the decoder 231 and the transistor 236. In the first embodiment shown in FIG. 3, the wiring capacitance from the oscillator 12 to the antenna electrode of the probe array 11 via the decoder 31 and the electrostatic capacitance of the transistor in the decoder 31 provided for the antenna electrode, respectively. the capacitance is present, the change in capacitance between the antenna electrode and the object becomes small when the total capacitance becomes smaller changes in the frequency f ₂ by the oscillator 12. That is, in Example 1, it is not possible to sufficiently achieve high sensitivity and high accuracy. Therefore, in order to solve such a problem, the second embodiment is configured to include the oscillators 232 and 233 and the mixer 234 for each antenna electrode 237.

  Referring to FIG. 11, this system 200 includes a sensor 230 that outputs a signal having a frequency corresponding to the capacitance between the object and the antenna electrode 237, a plurality of antenna electrodes 237 provided in the sensor 230, and an oscillator. An address signal for selecting one of the pair 232, 233 and the mixer 234, the distance between the object 240 and the antenna electrode 237, and the interface 240 for calculating the frequency count value; And a PC 217 for imaging the shape. The sensor 230 includes a decoder 231, a filter 235, a plurality of antenna electrodes 237, oscillators 232 and 233 corresponding to the antenna electrodes 237, a mixer 234 corresponding to the antenna electrodes 237, and a transistor 236 corresponding to the antenna electrodes 237. . The interface 240 includes an input / output unit 241 and a comparison unit 242.

In the sensor 230, the antenna electrode 237 for oscillating an object and a signal of oscillator 232, a fixed frequency _{f 1} for oscillating a signal of a frequency _{f 2} corresponding to the capacitance between the antenna electrode 237, a mixer 234, a filter 235, an interface 240, the input / output unit 241, the input / output unit 242, and the PC 217 are equivalent to the oscillators 12 and 13, the mixer 14, the filter 15, the input / output unit 41 of the interface 40, the counter 16, and the PC 17 shown in FIG. It has the function of. The antenna electrode 237 of the sensor 230 is configured in the same manner as the antenna electrode of the probe array 11 shown in FIG. 3, and an object to be observed is placed thereon. The decoder 231 receives an address signal from the input / output unit 241 of the interface 240 and operates one of the plurality of transistors 236. Accordingly, one set of the plurality of antenna electrodes 237, the oscillators 232 and 233, and the mixer 234 is selected.

  The PC 217 sequentially outputs an address signal for specifying a set of the antenna electrode 237, the oscillators 232 and 233, and the mixer 234, inputs the count value of the frequency, and calculates the distance between the object and the antenna electrode, respectively. . Thereby, the shape of the object seen from the antenna electrode can be imaged.

As described above, according to the visualization sensor 230 of the second embodiment, each antenna electrode 237 includes the oscillators 232 and 233 and the mixer 234, and the decoder 231 and the transistor 236 include the plurality of antenna electrodes 237, the oscillators 232 and 233, and One set of the mixers 234 is selected. Thus, because the decoder 231 and the transistor 236 during the period from the oscillator 232 to the antenna electrode 237 is not present, frequency f ₂ corresponding to the capacitance between the object and the antenna electrode 237, less affected by the wiring capacitance And the capacitance of the transistor 236 is not affected. Therefore, the change in capacitance between the antenna electrode 237 and the object is larger than that in the first embodiment shown in FIG. That is, it is possible to increase the change of the frequency f ₂ by the oscillator 232, it is possible to realize high sensitivity and a high accuracy.

Here, FIG. 20 shows a schematic diagram of a circuit arrangement of the oscillators 232 and 233, the mixer 234, and the transistor 236 in the visualization sensor 230 of the second embodiment shown in FIG. The oscillators 232-1 and 233-1, the mixer 234-1, and the transistor 236-1 are disposed below the antenna electrode 237-1. The oscillators 232-2, 233-2, the mixer 234-2, and the transistor 236-2 are disposed at the antenna electrode 237. -2 are respectively arranged via a row selection line and a column selection line. With this arrangement, since it is possible to further suppress the influence of the wiring capacity, further, it is possible to increase the change of the frequency f _2, it is possible to realize high sensitivity and a high accuracy.

The comparison of the change in the oscillation frequency f ₂ between the second embodiment shown in Example 1 and 11 shown in FIG. 3 are shown in Table 1. Table 1 shows the oscillation frequency f ₂ when the object is placed and when not placed on the antenna electrode (capacitance 0F) (46.5F). Change in frequency _{f 2} of Example 1 is 4 MHz, the change of the frequency _{f 2} of the second embodiment because it is 52 MHz, it can be seen that better in Example 2 is large variation. The conditions of Example 1 are that the area of the sensor plate as the antenna electrode is 38.5 μm × 38.5 μm, the wiring length between the antenna electrode and the oscillators 12 and 13 is 4 mm, and the condition of Example 2 is In this case, the area of the sensor plate which is the antenna electrode 237 is 38.5 μm × 38.5 μm, and the oscillators 232 and 233 and the mixer 234 are disposed below the antenna electrode 237. Both have one antenna electrode.
Table 1:

また、図２２に、図３に示した実施例１と同じ条件の下で、４ｍｍ角に８０個のアンテナ電極を配置して行ったシミュレーションの結果を示す。図２２において、各位置における周波数の差は時間変化しないため、雑音が混入しても後に取り除くことが可能であるが、周波数の測定精度が十分に高くない場合は大きな誤差になる。尚、図１１に示した実施例２の場合は、アンテナ電極の数（画素数）の影響は全くない。また、図２３に、アンテナ電極の寸法の見積りを示す。図２３には、表１に示した実施例２から予想されるアンテナ電極の寸法、発振器を内蔵した場合のアンテナ電極の最小寸法、及び、発振器を外部に設けた場合のアンテナ電極の最小寸法が示されている。The sensor detection capacity shown in Table 1 is a value when an object larger than the antenna electrode is placed at a distance of 1 μm, and is also an ability to detect an object near 1 μm. The numerical values in Table 1 are calculated based on the manufacturing technology parameters of CMOS 0.35 μm, and this numerical value depends on the manufacturing technology. In the case of CMOS, in general, the transistor size and the maximum frequency of the oscillator are in an inversely proportional relationship. When CMOS of 0.09 μm at the current mass production level is used, it is converted to the numerical values shown in Table 1. FIG. 21 shows the relationship with the technology node (technical generation of manufacturing technology).
Table 2:

FIG. 22 shows the result of a simulation performed by arranging 80 antenna electrodes on a 4 mm square under the same conditions as in Example 1 shown in FIG. In FIG. 22, since the frequency difference at each position does not change with time, even if noise is mixed in, it can be removed later. However, if the frequency measurement accuracy is not sufficiently high, a large error occurs. In the case of the second embodiment shown in FIG. 11, there is no influence of the number of antenna electrodes (number of pixels). FIG. 23 shows an estimate of the dimensions of the antenna electrode. FIG. 23 shows the dimensions of the antenna electrode expected from Example 2 shown in Table 1, the minimum dimension of the antenna electrode when the oscillator is built in, and the minimum dimension of the antenna electrode when the oscillator is provided outside. It is shown.

FIG. 12 is a logic circuit diagram showing the configuration of the oscillators 232-1 and 233-1 of the second embodiment shown in FIG. The other oscillators 232-2, 233-2 and the like have the same configuration. Oscillator 232-1 for oscillating a signal of a frequency _{f 2} corresponding to the distance between the object and the antenna electrode 237 is composed of three inverters 232-1-1,232-1-2,232-1-3 The Similarly, oscillator 233-1 for oscillating a signal of a fixed frequency _{f 1} to be a reference is also composed of three inverters 233-1-1,233-1-2,233-1-3. Such a configuration is called a common centroid arrangement (common central arrangement), and the oscillators 232-1 and 233-1 are arranged close to each other, and the inverter 232-1-2 of the oscillator 232-1 and the inverter 233 of the oscillator 233-1 are arranged. The arrangement of -1-2 is changed.

  Thus, by arranging the oscillator 232-1 and the oscillator 233 close to each other, the frequencies of the two oscillators vary in the same manner. In the first and second embodiments, the mixers 14 and 234 output a frequency difference signal, so that the frequency variation can be absorbed. Further, by configuring in a common centroid arrangement, it is possible to further absorb frequency variations and reduce frequency errors. FIG. 12 is a logic circuit diagram showing an example of the configuration of the oscillators 232-1 and 233-1, and the present invention is not limited to the oscillator having such a configuration.

Example 3
FIG. 13 is a block diagram showing a configuration of a visualization sensor according to a third embodiment of the present invention. When the second embodiment and the third embodiment shown in FIG. 11 are compared, in the second embodiment, the sensor 230 includes a plurality of antenna electrodes 237, the decoder 231 and the transistor 236 include a plurality of antenna electrodes 237, oscillators 232 and 233, and a mixer. In the third embodiment, the sensor 330 includes a single antenna electrode 337, oscillators 332 and 333, and a mixer 334, and an upper portion (object direction) of the antenna electrode 337 is selected. Are arranged on the lattice, and the decoder 331 and the transistor 336 select one of the wirings 338-L in the column (vertical) direction and the wiring 338- in the row (horizontal) direction. The difference is that one of C is selected. In the second embodiment shown in FIG. 11, high sensitivity and high accuracy are realized by disposing the oscillators 232 and 233 and the mixer 234 below the antenna electrode 237. However, an antenna corresponding to one pixel is used. The plate area of the electrode 237 becomes large and it becomes difficult to achieve high resolution. Therefore, in the third embodiment, in order to solve such a problem, the fine wiring 338 for position detection is arranged on the single antenna electrode 337 in the vertical direction and the horizontal direction, and the distance of the object at each intersection point. Is calculated.

  Referring to FIG. 13, this system 300 outputs a sensor 330 that outputs a signal having a frequency corresponding to the capacitance between the object and the antenna electrode 337, and an address signal for selecting the intersection position of the wiring 338. An interface 340 for calculating the frequency count value and a PC 317 for calculating the distance between the object and the antenna electrode 237 and imaging the shape of the object are provided. The sensor 330 includes a decoder 331, a filter 335, a single antenna electrode 337, M wirings 338-L1 to LM arranged in the vertical direction on the upper surface of the antenna electrode 237, and N pieces of wiring arranged in the horizontal direction. Wirings 338-C1 to CN, transistors 336-L1 to LM and C1 to CN for selecting these wirings 338, a mixer 234, and oscillators 332 and 333 are provided. The interface 340 includes an input / output unit 341 and a comparison unit 342.

In the sensor 330, the antenna electrode 333 for oscillating the object and the oscillator 332, the signal of the fixed frequency _{f 1} that oscillates a signal of frequency _{f 2} based on the capacitance between the antenna electrode 337, a mixer 334, a filter 335, an interface The input / output unit 341, the input / output unit 342, and the PC 317 of the 340 include the oscillators 232 and 233, the mixer 234, the filter 235, the input / output unit 241, the input / output unit 242, and the PC 217 of the interface 240 shown in FIG. Have the same functions. The antenna electrode 337 of the sensor 330 has an object to be observed placed thereon. The decoder 331 receives an address signal from the input / output unit 341 of the interface 340, and the L decoder uses one of the transistors 336-L1 to LM corresponding to the vertical wirings 338-L1 to LM as the C decoder. Operates one of the transistors 336-C1 to CN corresponding to the horizontal wirings 338-C1 to CN, respectively. As a result, one of the vertical wirings 338-L1 to LM and one of the horizontal wirings 338-C1 to CN are selected, and the selected wiring is released, and the other wirings are selected. Is held in the ground state. That is, the position of the antenna electrode 337 in the plate plane with respect to the observed object is selected.

  The PC 317 sequentially outputs an address signal for specifying the position of the antenna electrode 337 in the plate surface (intersection of the wiring 338), inputs the count value of the frequency at the intersection, and the object and antenna electrode at the intersection Each of the distances to 337 is calculated. By calculating the distances at all the intersection positions, the shape of the object viewed from the antenna electrode 337 can be imaged.

FIG. 14 is a sectional side view of the antenna electrode 337 and the wiring 338 for explaining the measurement mechanism according to the third embodiment shown in FIG. Hereinafter, a description is given of a principle of oscillating a frequency f ₂ corresponding to the distance between the antenna electrode 337 and the wiring 338 is placed on these objects. 14, the capacitance between the antenna electrode 337 and the wiring 338-C1 is C _p1 , the capacitance between the wiring 338-C1 and the wiring 338-L1 is C _g1 , and the wiring 338-C1 is The capacitance between the wiring 338-L2 is C _g2 , the capacitance between the wiring 338-L1 and the object at the position where the wiring 338-L1, C1 overlaps is C _o1 , and the wiring 338-L2, C1 is overlapping. The capacitance between the wiring 338-L2 at the position and the object is C _o2 , and the capacitance between the object and the ground is C _s .

Here, in order for the PC 317 to calculate the distance between the object and the antenna electrode 337 at the intersection of the wirings 338 -L 1 and C 1, an address signal for specifying the intersection is decoded via the input / output unit 341. To 331. The decoder 331 inputs the address signal, the L decoder operates the transistor 336-L1 to open the wiring 338-L1, and the C decoder operates the transistor 336-C1 to open the wiring 338-C1. . Accordingly, the wiring 338-L2~LM, since C2-CN is connected to the _{ground, C o2,} C g2 _{~C gM} is shielded between the object and the wiring 338-C1. Therefore, the capacitance (for example, C _o2 ) at the intersection other than the wirings 338-L1, C1 does not affect the antenna electrode 337, and the capacitances C _o1 , C _{g1 at} the intersections of the wirings 338-L1, C1 and Only C _s and C _p1 will affect the oscillator 332. Thus, the oscillator 332 oscillates a signal of frequency _{f 2} corresponding to the capacitance _{C o1} on the intersection of lines 338-L1, C1. The PC 317 inputs a frequency count value via the mixer 334, the filter 335, the counter 342, and the input / output unit 341, and based on the count value, the object and the antenna electrode 337 at the intersection of the wirings 338-L1 and C1. (The distance between the object located in the vertical upper part and the surface of the antenna electrode 337 located in the vertical lower part at the intersection).

Similarly, the PC 317 outputs an address signal at the intersection in order to calculate the distance between the object and the antenna electrode 337 at the intersection of the wirings 338-L2 and C1, and only the capacitance C _{o2 at the} intersection. enter the count value corresponding to the frequency f ₂ of the signal corresponding to calculate the distance. In this way, the address signal at the intersection of the wiring 338 is sequentially output, the frequency count value is input, and the distance between the object and the antenna electrode 337 at the intersection is calculated from the antenna electrode 337. The shape of the object can be imaged.

  FIG. 15 is a diagram for illustrating the capacitance of the sensor electrode 337 in FIG. Here, the electrostatic capacitance (sensor electrode capacitance) of the antenna electrode 337 is the electrostatic capacitance between the object and the antenna electrode 337 at the intersection of the wirings 338. The sensor electrode capacitance between the object and the antenna electrode 337 at the intersection of the wirings 338-Li and Cj is expressed by the equation shown in FIG. Here, Cs is the stray capacitance of the object on the sensor electrode 337, Coij is the capacitance generated between the object and the i-row wiring (wiring 338-Li), and Cgij is the i-row wiring (wiring 338-Li). , Cpj is a capacitance generated between the j-row wiring (wiring 338-Cj) and the antenna electrode 337, and Cpk is a k-row wiring (wiring 338-Cj). 338−Ck) and the antenna electrode 337, and Cpj = Cpk = Cp and Cgij = Cg hold for all (i, j). Note that the coordinates of the object to be detected are the sum of the coordinates of the antenna electrode 337 and the relative coordinates of the wiring 338 with respect to the antenna electrode 337.

  As described above, according to the visualization sensor 330 of the third embodiment, the fine wiring 338 for position detection is arranged on the single antenna electrode 337 in the vertical direction and the horizontal direction, and the object and antenna at each intersection point are arranged. A frequency corresponding to the capacitance between the electrode 337 and the electrode 337 was detected. Thereby, since it is not necessary to provide an antenna electrode for each pixel, high resolution can be realized.

[Modification 3]
Next, a modification of the third embodiment will be described with reference to FIG. In the third embodiment shown in FIG. 13, a single antenna electrode 337 is provided, but in this example, as shown in FIG. 16, the elongated antenna electrodes 337-1 to 337 -M are longitudinal wirings 338. -L1 to LM are provided to face each other. Under such a configuration, the decoder 331 and the transistor 336 select the wiring 338 and the antenna electrode 337 and switch them, so that the oscillator 332 is connected between the object at each intersection of the wiring 338 and the antenna electrode 337. A signal having a frequency corresponding to the capacitance is oscillated. The sensor electrode capacitance between the object and the antenna electrode 337 at the intersection of the wirings 338-Li and Cj is expressed by the equation shown in FIG.

  As described above, according to the visualization sensor of the modification example 3, by providing the elongated antenna electrodes 337-1 to 337 -M, the sensor electrode capacitance becomes the equation shown in FIG. 16, and the antenna electrode 337- i is the vertical wiring other than the intersection of the wirings 338-Li and Cj among the vertical wirings 338-L1 to LM, and prevents the generation of capacitance not related to the presence or absence of an object. Therefore, the object detection sensitivity is increased.

  Next, FIG. 19 shows a graph of the number of pixels (number of antenna electrodes) when the antenna electrodes are arranged in an area of 1 cm square. In the figure, the expected limit of the example in the conditions of Table 1 shown in the description of Example 1 shown in FIG. 3, Example 2 shown in FIG. 11, and Example 2 is shown. In addition, the prediction limit of Example 2 shown in FIG. 11 is a calculation result based on the optimum value designed in the CMOS 0.35 μm technology.

  The present invention has been described with reference to the examples and the modifications. However, the present invention is not limited to the above examples, and various modifications can be made without departing from the spirit and the intention of the present invention. For example, in the first modification, the two PLL circuits 132 and 133 are provided, and the distance between the object and the antenna electrode is calculated based on the difference C1-C2 between the two frequency control voltage signals. May receive a reference frequency signal from the external oscillator 150, calculate a change in distance only by the frequency control voltage signal C2 output from the PLL circuit 133, and image the shape of the object.

  In the first embodiment, the LC oscillation circuit is exemplified as the oscillators 12 and 13; however, the present invention is not limited to this and can be applied to various oscillation circuits. For example, you may use the oscillator comprised from the some inverter of common centroid arrangement | positioning shown in FIG. Further, an LC oscillation circuit may be used for the oscillators of the above-described embodiments 2 and 3 and modifications 1 to 3, and the oscillator shown in FIG. 12 may be used.

  In the first modification, the PLL circuit 132 divides the frequency to a predetermined frequency ratio and outputs the high-frequency signal B1, but the frequency ratio of the frequency divider 132-2 in the PLL circuit 132 can be set. A frequency ratio setting unit may be provided outside, and the frequency ratio may be set from the outside with respect to the frequency ratio setting unit. In this case, the distance detection sensitivity can be changed or adjusted by changing the frequency ratio setting. Thereby, the detection sensitivity according to the shape of the object can be set, and more accurate distance calculation and shape imaging can be realized.

  In the first modification, in the sensor 130, the PLL circuit 132 outputs the reference frequency control voltage signal C1 and the PLL circuit 133 outputs the frequency control voltage signal C2. However, the sensor 130 outputs these signals. Means for inputting and outputting the difference may be provided.

  In FIG. 12, the oscillators 232-1 and 233-1 are configured by three stages of inverters, but are not limited to three stages, and are configured by odd-numbered inverters such as 1, 5, and 7 stages. You may do it. In this case, the greater the number of stages, the more stable the frequency and the more the variation is absorbed, but the sensitivity is lowered. Therefore, as shown in FIG. 12, it is suitable to be constituted by three stages of inverters.

  Further, the ground electrode shown in FIG. 6 may be configured to be applied to the second or third embodiment or the third modification, and instead of the elongated antenna electrodes 337-1 to 33-M shown in FIG. You may comprise so that the elongate antenna electrode facing the wiring 338-C1-CN of the horizontal direction may be provided, respectively.

  Moreover, although the said Example and modification demonstrated the case where an observation object was a conductor, an insulator may be sufficient. With reference to FIG. 17 corresponding to FIG. 7 and FIG. 8, the capacitance between the object which is an insulator and the probe array and its equivalent circuit will be described. FIG. 17A is a cross-sectional view illustrating the capacitance between the object 160 and the antenna electrode of the probe array 164. A capacitance Cpr between the object 160 and the antenna electrode 163, a capacitance Cgnd between the object 160 and the ground electrode 162-2, and a static between the antenna electrode 163 and the ground electrodes 162-1 and 160-2. There are a capacitance Cd, a floating capacitance Ct of the entire object, a wiring capacitance Cs by the oscillator 161, and electrostatic capacitances Cb and Cc inside the object 160.

Here, since the capacitance Ct is a small stray capacitance, and the capacitance Cc is connected in series with the capacitance Ct, the capacitances Ct and Cc can be ignored. Accordingly, the equivalent circuit of the cross-sectional view shown in FIG. 17A is the circuit shown in FIG. Cpr, Cb, and Cgnd are capacitances that vary depending on the object, and Cd and Cs are fixed capacitances that do not vary depending on the object, and are inherent to the probe array 164. Therefore, the total capacitance is as shown in FIG.
Formula: C = Cpr * Cb * Cgnd / (Cpr * Cb + Cb * Cgnd + Cgnd * Cpr) + 2Cd + Cs
Thus, when the Cpr × Cb × Cgnd / (Cpr × Cb + Cb × Cgnd + Cgnd × Cpr) portion of the entire capacitance C changes, the oscillation frequency of the signal oscillated by the oscillator 161 changes. That is, the distance to the object 160 is calculated using the oscillation frequency corresponding to the part.

  Moreover, in the said Example and modification, although comprised, the sensor and the antenna electrode were fixed, you may comprise so that the relative position between these and an observation object may be changed. FIG. 18A is a schematic configuration diagram for explaining a case where the sensor is moved. In this example, a simple instruction film for placing an observation object is provided, and a member capable of vibrating in the lateral direction such as a piezoelectric element is provided below the sensor. By vibrating the piezoelectric element or the like in the lateral direction, the sensor can be moved in the lateral direction while the observation object is stationary. FIG. 18B is a schematic configuration diagram for explaining a case where the antenna electrode is moved. In the figure, a protective film covering the antenna electrode is provided on the upper part of the sensor, a space is provided around the antenna electrode so that the antenna electrode can be moved, and a contact electrode for moving the antenna electrode is further provided. Yes. Under such a configuration, the antenna electrode can be moved by using MEMS (micromachine) technology or the like. In this way, the relative position between the sensor or antenna electrode and the observation object is changed, the distance between the observation object at each position is calculated, and image data is generated. Then, by superimposing these images, it is possible to achieve higher resolution.

  In the visualization sensor, a plurality of antenna electrodes are arranged in the vertical direction such as the wiring 338-L in the example (vertical) direction and the wiring 388-C in the row (horizontal) direction shown in the third embodiment. You may comprise so that it may provide as a direction antenna electrode. When one antenna electrode is selected from each of the plurality of antenna electrodes provided in the vertical direction and the horizontal direction, one of the antenna electrodes at the selected intersection is connected to the oscillator, and the object and its intersection The distance between is calculated.

Claims (11)

A sensor that converts capacitance between an object to an oscillation frequency and realizes visualization of the object,
An antenna electrode provided facing the object,
A first oscillator connected to the antenna electrode and outputting a signal having an oscillation frequency corresponding to a capacitance between the object and the antenna electrode;
A second oscillator that outputs a signal having a reference oscillation frequency; and
Output means for generating and outputting a signal having a frequency corresponding to a difference between an oscillation frequency of the signal output from the first oscillator and a reference oscillation frequency of the signal output from the second oscillator; Visualization sensor characterized by that. The visualization sensor according to claim 1,
For the signal output from the first oscillator, a frequency obtained by dividing the oscillation frequency by a frequency ratio of 1 is generated, and the first oscillator is set so that the signal of the frequency matches the input reference frequency signal. A first synchronization circuit for generating and outputting a control frequency signal for
The reference oscillation frequency signal output from the second oscillator is input, a frequency obtained by dividing the reference oscillation frequency into a predetermined frequency ratio is generated, and the divided frequency signal is output as the reference frequency signal. A second synchronization circuit that
A visualization sensor comprising a first synchronization circuit and a second synchronization circuit in place of the output means. The visualization sensor according to claim 1 or 2,
Furthermore, the visualization sensor characterized by including the ground electrode provided facing the object and held in a grounded state. The visualization sensor according to any one of claims 1 to 3,
A visualization sensor comprising a plurality of the antenna electrodes, wherein the first oscillator is sequentially connected to one of the plurality of antenna electrodes. The visualization sensor according to claim 1,
A visualization sensor comprising a plurality of the antenna electrodes, wherein the first oscillator, the second oscillator, and the output means are provided for each of the plurality of antenna electrodes. The visualization sensor according to claim 5,
The visualization sensor further comprises a switch for selecting one of the output means provided for each antenna electrode. The visualization sensor according to claim 5 or 6,
A visualization sensor characterized in that the first oscillator, the second oscillator, and the output means are provided on the opposite side to an object when viewed from a plurality of antenna electrodes. The visualization sensor according to any one of claims 5 to 7,
The visualization sensor, wherein the first oscillator and the second oscillator are configured in a common centroid arrangement in which an odd number of inverters are respectively connected in series. A sensor that converts capacitance between an object to an oscillation frequency and realizes visualization of the object,
A single antenna electrode provided opposite the object,
A first oscillator connected to the antenna electrode and outputting a signal having an oscillation frequency corresponding to the capacitance between the object and the antenna electrode;
A second oscillator that outputs a signal having a reference oscillation frequency;
Output means for generating and outputting a signal having a frequency corresponding to the difference between the oscillation frequency of the signal output by the first oscillator and the reference oscillation frequency of the signal output by the second oscillator; and
A member provided on the side where the object is present when viewed from the antenna electrode, wherein a plurality of intersections are formed by the members, and the intersection is formed when one of the plurality of intersections is selected. A visualization sensor comprising a plurality of linear members in which two members are held in an open state and the other members are held in a grounded state. The visualization sensor according to claim 9.
The plurality of linear members include a plurality of linear members in the vertical direction and a plurality of linear members in the lateral direction with respect to the surface of the antenna electrode,
A visualization sensor comprising a plurality of antenna electrodes opposed to a plurality of linear members in a vertical direction or a horizontal direction instead of the single antenna electrode. In the visualization sensor according to any one of claims 1 to 10,
A visualization sensor comprising means for moving the visualization sensor or antenna electrode relative to an object.

Images