JPH09281167A - Apparatus for measuring surface potential - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the SN ratio and reliability and detect a surface potential stably with high sensitivity by using as a measuring electrode a vibrating member electrically independent of a body to be measured and spaced a predetermined distance from the body to be measured. SOLUTION: A moving coil method of a voice coil 12 is utilized for fitting A hollow solenoid coil 16 to a vibrating member 7 as an elastic body. When an alternating current signal is applied to the coil 16, the coil 16 is changed because of a mutual action of a magnetic field generated by the current impressed to the coil 16 and a permanent magnetic field of a permanent magnet 17. The cantilever member 7 is vibrated in an A direction. While a potential- sensing surface 9 is vibrated, a surface potential signal of a body 2 to be measured from a direction B of an electric field is received at the surface 9 via a potential measurement window 15 of a shield case 14. As a result, a change of induced charges generated at the surface 9 is detected as a surface potential signal at a potential signal-detecting part 4 connected to a fixed end 11 of the member 7 and taken outside as a detection signal from the case 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitance type surface potential measuring device for measuring the surface potential of an object to be measured, such as a conductor or an insulator, by vibrating members and measuring electrodes provided in a non-contact manner. More specifically, the present invention relates to a surface potential measuring device used for controlling a charging potential of a photoconductor or a developing roller of a copying machine, a fax machine, a printing machine, a printer and a plotter.

[0002]

2. Description of the Related Art In various fields, it is often necessary to detect and measure the surface potentials of conductors and insulators. Particularly in the field of electrophotographic copying machines and the like, it is important to accurately detect the surface potential on the photoconductor and control the surface potential in order to improve image quality. As a means for detecting the surface potential, a non-contact type surface potential measuring device has been used so far so as to prevent the leakage of charges from the object to be measured. The non-contact type surface potential measuring device can be roughly classified into an electric device and a mechanical device.

Electrical surface potential measuring devices are expensive because they require special functional materials. There is also a problem that the surface of the measuring electrode is contaminated by electrostatic attraction and the sensitivity is lowered due to polarization of the insulator used.

On the other hand, the mechanical surface potential measuring device has an advantage in that the sensitivity change due to contamination of the measuring electrode is small and the mechanical surface potential measuring device can be manufactured at a relatively low cost. Therefore,
Most of the surface potential measuring devices currently used are mechanical.

A mechanical surface potential measuring device comprises a vibrating member and a measuring electrode, and the vibrating member periodically changes the electrostatic capacitance between the object to be measured and the measuring electrode. The surface potential of is detected as an AC signal. There are two types of mechanical surface potential measuring devices, a chopper type and a vibration capacitance type. The chopper-type surface potential measuring device obtains an AC signal by periodically interrupting the lines of electric force incident on the measuring electrode to change the amount of electric charge induced on the measuring electrode. Further, the vibration capacitance type surface potential measuring device periodically changes the capacitance between the measured object and the measuring electrode by cyclically changing the measuring electrode in the electric field direction from the measured object. , The AC signal generated according to the change is taken out.

An example of a mechanical surface potential measuring device is shown below.

For example, in (a) Japanese Patent Publication No. 63-1547, in order to extract the surface potential of the object to be measured as an AC signal, a tuning fork vibrator is vibrated and used as a chopper means. A surface electrometer for measuring the surface potential with a fixed measuring electrode is disclosed.
According to this surface electrometer, an inexpensive surface electrometer can be obtained with a relatively simple structure.

(B) In Japanese Unexamined Patent Publication No. 60-120267, a tuning fork type vibrator is used to extract the surface potential of the object to be measured as an AC signal, as disclosed in the above publication. A contact type surface potential detecting device is disclosed. That is, in this device, the measurement electrode is installed on the tuning fork vibrator, and the measurement electrode is vibrated in a direction substantially parallel to the electric field formed between the measured object and the measurement electrode. And
The vibration between the measurement electrodes changes the capacitance between the measurement object and the measurement electrode, and the surface potential of the measurement object can be detected. According to this non-contact type surface potential detecting device, the SN ratio of the surface potential detecting device can be improved.

(C) Japanese Utility Model Publication No. 4-30545 discloses that
The above-mentioned Japanese Patent Application Laid-Open No. 60-120267 discloses a surface potential detecting device in which the structure of the measuring electrode installed on the tuning fork vibrator is improved. That is, in this device, a flexible printed circuit board is used for the measurement electrodes,
The measurement electrode pattern and the extraction electrode pattern are formed on the printed circuit board. According to this surface potential detecting device, an inexpensive surface potential detecting device can be obtained with a relatively simple structure.

(D) Japanese Unexamined Patent Publication No. 60-55273 discloses a surface potential sensor having a structure in which a measuring electrode is installed on a tuning fork-shaped vibrating piece in order to extract the surface potential of the object to be measured as an AC signal. There is. With this device, the tuning fork-shaped vibrating piece is vibrated like a chopper type to directly vibrate the measurement electrode, and the area of the measurement electrode facing the measured object is changed to change the capacitance between the measured object and the measured electrode. Change. Then, the surface potential of the object to be measured can be detected from the change in the capacitance. According to this surface potential sensor, an inexpensive surface potential sensor can be obtained with a relatively simple structure.

(E) Japanese Patent Application No. 6-244339 employs a voice coil as a means for changing the electrostatic capacitance between the object to be measured and the measuring electrode, and drives the voice coil to measure the object to be measured. There is disclosed a surface potential measuring device adapted to detect an accurate surface potential. This surface potential measuring device
The present invention relates to a capacitance-type surface potential measuring device that measures the surface potential of an object to be measured with a vibrating member and a measuring electrode that are provided in a non-contact manner. Further, according to this surface potential measuring device, it is possible to obtain the electrostatic capacitance changing means capable of improving the SN ratio with a simple structure which is small in size and inexpensive and capable of highly sensitive measurement, and the surface potential measuring device using the same. .

[0012]

However, the above-mentioned conventional surface potential measuring device has the following problems.

(A) According to Japanese Patent Publication No. 63-1547, the tuning fork vibrator is vibrated and used as a chopper means to extract the surface potential of the object to be measured as an AC signal, and is fixed to the tuning fork vibrator. With the measuring electrode, a surface electrometer can be obtained at a low cost with a relatively simple structure.

However, the surface electrometer disclosed in Japanese Examined Patent Publication No. 63-1547 requires the measurement electrode to be provided separately from the tuning fork type vibrator, which increases the number of parts and increases the cost. Further, when the tuning fork type vibrator is used as the chopper means, it is necessary to make a space between the tuning fork vibrator and the measuring electrode, which limits the miniaturization of the probe shape of the measuring device. Furthermore, it is necessary to give sufficient consideration to the positional relationship between the tuning fork vibrator and the measurement electrode so that the potential detection signal becomes maximum. That is, in the case of the chopper type, the measurement electrode is usually arranged behind the tuning fork type vibrator with respect to the object to be measured, so that the measurement sensitivity to the surface potential deteriorates.

(B) According to Japanese Patent Laid-Open No. 60-120267, a measuring electrode is installed on a tuning-fork type vibrator in order to extract the surface potential of the measured object as an AC signal. It is possible to measure the surface potential by vibrating the measurement electrode in a direction substantially parallel to the electric field formed between and, and improving the SN ratio from the change in the capacitance between the measured object and the measurement electrode. .

However, JP-A-60-120267
Similarly, in the non-contact type surface potential detecting device disclosed in the publication, the measuring electrode needs to be provided separately from the tuning fork vibrator, resulting in an increase in the number of parts and an increase in cost. Further, when the measurement electrode is installed on the tuning fork vibrator, the signal line for extracting the signal from the measurement electrode vibrates following the vibration of the tuning fork. As a result, the vibration of the signal line adversely affects the vibration characteristics of the tuning fork, making the vibration characteristics of the tuning fork unstable.
Also, a thin wire is usually used for the signal line so that it does not affect the vibration characteristics of the tuning fork.
In the worst case, vibration causes a problem that the signal line is broken. Therefore, it is necessary not only to connect the signal lines, but also to attach them with care so as not to break them when connecting the signal lines. Further, since it is necessary to use an expensive material having excellent flexibility and fatigue strength for the signal line, the cost becomes higher. Furthermore, when the measuring electrode is installed on the tuning fork vibrator, the driving unit of the tuning fork vibrator needs to vibrate not only the tuning fork vibrator but also the measuring electrode and its signal line. Large drive power is required.

(C) The surface potential detecting device disclosed in Japanese Utility Model Publication No. 4-305545 is for solving the above-mentioned problems, and is a tuning fork disclosed in Japanese Patent Laid-Open No. 60-120267. The structure of the measurement electrode installed on the vibrator is improved, and the measurement electrode pattern and the extraction electrode (signal line) pattern are formed on the printed circuit board by using the flexible printed circuit board for the measurement electrode, and the structure is relatively simple. Therefore, the surface potential can be measured with excellent reliability and at low cost.

However, also in the surface potential detecting device disclosed in Japanese Utility Model Publication No. 4-305545, it is necessary to provide the measuring electrode separately from the tuning fork vibrator, as described above, so that the number of parts is increased and the cost is increased. Get higher In addition, the measurement electrode and the extraction electrode (signal line) pattern are formed on the flexible printed circuit board by etching or the like, which increases the cost. Furthermore, since it is necessary to use the flexible printed circuit board by bonding and fixing it to the tuning fork vibrator,
Adhesive work is required. In addition, depending on the bonding method, there is a problem that the vibration characteristics of the tuning fork vibrator become unstable, and in the worst case, the printed board is peeled off due to vibration. As described above, the present invention has not achieved the fundamental solution to the above-mentioned problems of the prior art.

(D) According to Japanese Patent Laid-Open No. 60-55273, a tuning fork-shaped vibrating piece is used to extract the surface potential of the object to be measured as an AC signal, and a measuring electrode is placed on the tuning fork-shaped vibrating piece. Then, by vibrating the tuning-fork vibrating piece like a chopper type and directly vibrating the measuring electrode to change the area of the measuring electrode facing the measured object, the static between the measured object and the measured electrode is changed. It is possible to measure the surface potential in a small size and at a low cost with a relatively simple structure from the change in the capacitance.

However, in the surface potential sensor disclosed in Japanese Patent Laid-Open No. 60-55273, it is necessary to provide the measuring electrode separately from the tuning fork vibrator, similarly to the above, so that the number of parts is increased and the cost is increased. Becomes higher. Further, when the measuring electrode is installed on the tuning fork-shaped vibrating piece, it is disclosed in JP-A-60-1.
As described in the invention disclosed in Japanese Patent No. 20267, there is a problem regarding the signal line of the measuring electrode and the driving means of the tuning-fork vibrating piece.

Further, in any of the above-mentioned devices, the tuning fork is used as a vibrator to extract the surface potential of the object to be measured as an AC signal. Therefore, SN with higher sensitivity
In order to improve the ratio and detect the surface potential,
It is necessary to further increase the vibration amplitude of the tuning fork. Possible methods include using the mechanical resonance vibration of the tuning fork and increasing the length of the tuning fork in the longitudinal direction. However, when using the mechanical resonance vibration, the resonance point (resonance frequency) is extremely low. It is stable. Therefore, since the surface potential detection signal obtained according to the amplitude value of the vibration is also obtained as a very unstable signal value, it becomes relatively difficult to detect an accurate surface potential. Further, when the longitudinal direction of the tuning fork is lengthened, there is a problem that the shape of the sensor probe becomes large.

Further, a piezoelectric material is adopted as a means for vibrating the tuning fork and is attached to the tuning fork, which is disclosed in the above publication. However, since the piezoelectric material is weak against mechanical stress, the material may be cracked or broken. Moreover, when an overvoltage is applied to the piezoelectric material, the polarization of the material is broken, and the measurement electrode does not fluctuate. In addition, since the piezoelectric material is generally a special material, it is relatively expensive, and the fluctuation range of the material is easily affected by the surrounding environment (especially temperature), and the measured value tends to be unstable. .

Furthermore, in any of the above-mentioned devices,
Since the capacitance between the object to be measured and the measuring electrode is proportional to the reciprocal of the measuring distance between the object to be measured and the measuring distance, the output value obtained changes greatly depending on the measuring distance. Therefore, for example, when measuring the surface potential of a moving ratio measuring body such as a photoconductor drum of a copying machine or the like, whether the fluctuation of the output value depends on the measuring distance or the surface potential distribution of the measured object. There is a problem that it cannot be determined. Therefore, it is difficult to accurately obtain the surface potential of the measured object.

In order to solve the above problems, in Japanese Patent Application No. 6-244339, a voice coil is used as a means for changing the electrostatic capacitance between the object to be measured and the measuring electrode. A surface potential measuring device has been proposed which is capable of being driven to detect two or more output signals different from the potential of the measurement electrode and obtaining an accurate surface potential from the output signals.

However, also in the surface potential measuring device of Japanese Patent Application No. 6-244339, since the measuring electrode is required separately from the vibrator of the voice coil as in the above-mentioned invention, the number of parts is increased and the cost is increased. Becomes higher. Further, when the measurement electrode is installed on the voice coil oscillator, as described in the invention disclosed in the above-mentioned Japanese Patent Laid-Open No. 60-120267, it relates to the signal line of the measurement electrode and the driving means of the voice coil oscillator. There is a problem. Further, when the voice coil is used, there are problems such as influence on the vibration characteristic of the vibrator and disconnection, which are given by the drive signal line for driving the solenoid coil similarly to the signal line of the measurement electrode.

Therefore, the present invention has been made in view of the above, and provides a small and inexpensive surface potential measuring device with a simple structure capable of improving the SN ratio and reliability and performing stable and highly sensitive measurement. The purpose is to do.

[0027]

In order to achieve the above object, the surface potential measuring device according to claim 1 of the present invention is electrically independent of the object to be measured at a position spaced apart from the object by a predetermined distance. And a capacitance changing unit that vibrates the measurement electrode and changes a capacitance formed between the object to be measured and the measurement electrode that is the vibration member. A potential detection unit that detects a potential of the measurement electrode that changes according to a change in the electrostatic capacitance induced corresponding to a surface potential of the measurement target, and the measurement target based on a detection signal of the potential detection unit. And a surface potential deriving means for deriving the surface potential of.

The surface potential measuring device according to a second aspect of the present invention is the surface potential measuring device according to the first aspect, wherein the potential signal of the measuring electrode is taken out from the node portion or the fixed portion of the vibrating member. .

A surface potential measuring device according to a third aspect of the present invention is the surface potential measuring device according to the first aspect, in which the measuring electrode is vibrated and is formed between the object to be measured and the measuring electrode. The electromagnetic coil is used as the capacitance changing means for changing the electrostatic capacitance.

A surface potential measuring device according to a fourth aspect of the present invention is the surface potential measuring device according to the first aspect, in which the measuring electrode is vibrated and formed between the object to be measured and the measuring electrode. A voice coil is used as the capacitance changing means for changing the electrostatic capacitance.

The surface potential measuring device according to claim 5 of the present invention is the surface potential measuring device according to claim 1, wherein at least two output signals are detected from the detection signals of the potential detecting means. It is equipped with means.

A surface potential measuring device according to a sixth aspect of the present invention is the surface potential measuring device according to the first aspect, wherein the vibrating member is constituted by a plurality of conductive layers with an insulating layer interposed therebetween.

A surface potential measuring device according to a seventh aspect of the present invention is the surface potential measuring device according to the first aspect, wherein a plurality of conductor regions are provided on the surface of an insulator to constitute the vibrating member. Is.

The surface potential measuring device according to claim 8 of the present invention is the surface potential measuring device according to claim 4, wherein the vibrating member is constituted by a plurality of conductive layers with an insulating layer interposed therebetween. A drive signal for the voice coil is applied from a node or a fixed portion.

The surface potential measuring device according to claim 9 of the present invention is the surface potential measuring device according to claim 4, wherein a plurality of conductor regions are provided on the surface of an insulator to constitute the vibrating member. A drive signal for the voice coil is applied from a node or a fixed portion of the vibrating member.

A surface potential measuring device according to a tenth aspect of the present invention is the surface potential measuring device according to the first aspect, in which one end of the vibrating member is fixed and the vibrating member is located close to the object to be measured. To form the other end of.

Further, the surface potential measuring device according to claim 11 of the present invention is the surface potential measuring device according to claim 4, wherein a high magnetic permeability member is arranged around a permanent magnet used for the voice coil, A magnetic circuit is formed with a permanent magnet to drive the vibrating member.

[0038]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, prior to the description of the embodiments of the present invention, the principle of measurement of a conventional surface potential measuring device using non-contact type mechanical means will be described. FIG. 37 is a block diagram showing a configuration of a conventional surface potential measuring device.
(A) is a chopper type surface potential measuring device, FIG. 37 (b)
Shows a vibration capacitance type surface potential measuring device.

As shown in FIG. 37 (a), in the chopper type surface potential measuring device, the measuring electrode 1 is arranged so as to face the object to be measured 2, and the chopper is provided between the object to be measured 2 and the measuring electrode 1. The electrode 3 is provided. Then, the chopper electrode 3 is vibrated in the direction of the arrow in the figure to periodically interrupt the line of electric force that is incident on the measurement electrode 1 from the DUT 2 and is generated between the DUT 2 and the measurement electrode 1. The capacitance C ₀ is changed.

Further, as shown in FIG. 37 (b), in the vibration capacitance type surface potential measuring device, the measuring electrode 1 is arranged to face the object to be measured 2 similarly to the chopper type surface potential measuring device. . Then, the measurement electrode 1 is periodically vibrated in a direction facing the object to be measured 2 to change the capacitance C ₀ generated between the object to be measured 2 and the measurement electrode 1.

As described above, in any of the devices, the electrostatic capacitance C ₀ generated between the device under test 2 and the measuring electrode 1 is mechanically and periodically changed. The amount of minute charge induced on the measurement electrode 1 changes according to the change of the electrostatic capacitance.
The potential signal detector 4 detects this change in the amount of electric charge as an AC signal, and the signal amplifier 5 amplifies the AC signal to obtain an output signal corresponding to the surface potential of the DUT 2.

Here, the capacitance C ₀ is measured by the measuring electrode 1
Where S is an effective area, L is a measurement distance between the object to be measured 2 and the measurement electrode 1, and ε _air is a permittivity of _air .

C ₀ = ε _air (S / L) (1)

The mechanical surface potential measuring device changes the value of C ₀ by changing S or L in the equation (1). A device that changes S is a chopper type, and a device that changes L is a vibration capacitance type surface potential measuring device. Assuming that the change amount C _{C of} C ₀ caused by the periodic mechanical vibration is approximately given by the equation (2), the charge Q _C induced on the measurement electrode by the surface potential V _S of the measured object is ( It is given by the equation 3). C _C = α ₀ · C ₀ · sin ωt (2) Q _C = C _C · V _S (3)

Here, t is the change time, ω is the angular frequency of vibration, and α ₀ is the rate of change of the electrostatic capacitance C ₀ . Therefore, the current I _C generated in the measurement electrode is calculated by the equations (2) and (3).
Is expressed as I _C = dQ _C / dt = α ₀ · ω · C ₀ · V _S · cos ωt (4) Therefore, the output signal V ₀ obtained from the measurement electrode is approximately V ₀ = A _{0 · α 0 · ω · C 0} · V S · cosωt ... is expressed as (5). However, A ₀ represents a constant relating to the amplification degree.

Next, an embodiment of the surface potential measuring device according to the present invention will be described in detail with reference to the drawings.

[First Embodiment] FIG. 1 is a block diagram showing a schematic configuration of a surface potential measuring device according to a first embodiment. The surface potential measuring device shown in FIG. 1 uses a principle similar to that of the chopper type surface potential measuring device described with reference to FIG.

In the surface potential measuring device 6, a cantilever-shaped vibrating member 7 is used as the measuring electrode 1 in FIG. The surface potential measuring device 6 receives the surface potential signal of the object to be measured from the direction of the electric field (arrow symbol B) on the potential sensing surface 9 of the vibrating member 7, while the vibration driving section 8 indicates the arrow A in FIG. By vibrating the vibrating member 7 in the direction, the line of electric force that is incident on the potential sensing surface 9 like the chopper electrode is periodically interrupted and the capacitance generated between the DUT 2 and the vibrating member 1 is changed. Then, the change in electrostatic capacitance is extracted as a potential detection signal from the fixed end 11 of the vibrating member 7 fixed by the fixing member 10 through the potential signal detection unit 4.

A specific configuration example of the surface potential measuring device according to the first embodiment will be described below as an example.

(Embodiment 1) FIG. 2 shows a constitutional example of a surface potential measuring device using a voice coil 12 for a vibration driving unit 8 of a vibrating member 7, and FIG. 2 (a) is a side view of the surface potential measuring device. 2 (b) is a top view.

In the present invention, the voice coil is
It is composed of an electromagnetic coil and an elastic body, and the fluctuation of the electromagnetic coil is used as a fluctuation source, and the fluctuation range is limited by the elastic body. In the case of the present invention, the voice coil particularly refers to a moving coil system, and the vibrating member is its elastic member. Although metal, resin, rubber material, etc. can be used as the elastic body, in the case of the present invention, it is the cheapest and simplest configuration to use the elastic body made of a metallic beam-shaped leaf spring as the vibrating member 7. Therefore, it is preferable. Hereinafter, in the embodiments of the present invention, an example using a vibrating member of a beam-shaped leaf spring will be mainly described.

In the surface potential measuring device shown in FIGS. 2A and 2B, the vibrating member as a leaf spring having the potential sensing surface 9 in the shield case 14 for shielding the electric field having the potential measuring window 15. One end of 7 is fixed by an insulating fixing member 10, and the vibration member 7 is installed in a cantilever shape. Using the moving coil system of the voice coil 12, the vibrating member (leaf spring) 7 is used as an elastic body and the air-core solenoid coil 16 is attached to this, and by applying an AC signal to the solenoid coil 16, a current flows through the solenoid coil 16. The solenoid coil 16 fluctuates due to the interaction between the magnetic field generated by the current and the permanent magnetic field of the permanent magnet 17, and the cantilever-shaped vibrating member 7 (leaf spring) vibrates in the direction of arrow A. While vibrating the potential sensing surface 9 by the vibration of the vibrating member 7, the potential sensing surface 9 receives the surface potential signal of the DUT 2 from the electric field direction (arrow B) through the potential measuring window 15 of the shield case 14. As a result, it is possible to detect a change in the induced charge generated on the potential sensing surface 9 as a surface potential signal by the potential signal detection unit 4 connected to the fixed end 11 of the vibrating member 7 and take it out as a detection signal to the outside of the shield case 14. .

In FIGS. 2 (a) and 2 (b), 1
Reference numeral 9 is a detection signal line which is used to connect the vibrating member and the signal detection unit 18, 20 is a drive signal line which is for supplying drive power to the voice coil, and 21 is a potential The signal line is used for transmitting the potential signal detected by the signal detection unit 18.

In the first embodiment, the effective area S of the vibrating member 7 used as the measuring electrode is a relative relationship between the area of the potential sensing surface 9 of the vibrating member 7 and the area of the potential measuring window 15 provided in the shield case 14. Is determined by the area where the potential sensing surface 9 is exposed to the surface of the DUT 2. Further, it is necessary to vibrate the vibrating member 7 so that the amount of induced charge on the potential sensing surface 9 received from the device under test 2 changes. Further, in order to detect the potential signal from the vibrating member 7, it is desirable to lead out the detection signal line 19 from the fixed end 11 of the vibrating member 7 and connect it to the potential signal detecting section 4 as shown in FIG.

As is clear from Example 1, the surface potential measuring device of the first embodiment is separate from the chopper electrode 3 as in the conventional chopper type surface potential measuring device shown in FIG. 37 (a). Since it is not necessary to provide the measuring electrode 1 on the surface, a more compact and low-cost surface potential measuring device can be obtained.

(Example 2) In Example 1, a cantilever beam was used as the vibrating member 7, but as Example 2 shown in FIG. 3, a tuning fork-shaped vibrating member 22 was used as the vibrating member 7. can do. That is, in the surface potential measuring device of the second embodiment, the tuning fork-shaped vibrating member 2 is externally driven by the vibration driving unit 8.
2 is vibrated in the direction of arrow A, and the potential sensing surface 9 of the tuning fork-shaped vibrating member 22 receives a surface potential signal from the electric field direction (direction B) of the DUT 2 (not shown in FIG. 3). are doing. Also in the second embodiment, the voice coil described above can be used as the vibration drive unit 8.

The shape of the vibrating member 7 is the same as in the first and second embodiments.
It is not limited to those shown in. However, when the tuning fork-shaped vibrating member 22 is used as the vibrating member 7, the detection signal line 19 for extracting the potential signal from the vibrating member 7 is
As shown in FIG. 3, it is preferable that the tuning fork-shaped vibrating member 22 is led out from a node 23 that serves as a node of vibration.

Further, in the surface potential detecting devices of Examples 1 and 2, the voice coil 12 was used as the vibration driving unit 8 for vibrating the vibrating member 7, but FIG. 4A or FIG.
As shown in (b), the cantilever or tuning-fork vibrating member 7 can be vibrated by the plunger vibrating electromagnetic coil 25.

Next, the characteristics of the surface potential measuring devices of Examples 1 and 2 will be compared. In the case of the chopper type surface potential detecting device, the rate of change α ₀ of the electrostatic capacitance C ₀ is expressed as α ₀ = ΔS / S (6) However, ΔS represents a change in the effective area of the potential sensing surface.

Here, in order to improve the SN ratio, ΔS may be increased. The use of the voice coil 12 is effective as a means for increasing ΔS. That is, Example 1
2 and 2, the vibrating member 7 is attached to the electromagnetic coil portion (solenoid coil 16) of the voice coil 12, and the vibrating member 7 fluctuates as the electromagnetic coil fluctuates.

As the vibrating member 7, the variation range of the fluctuation of the vibrating member 7 in the surface potential detecting device using the beam-like vibrating member and the surface potential detecting device using the tuning fork-shaped vibrating member 22 shown in FIGS. In comparison, the device using the beam-shaped vibrating member can obtain a fluctuation range 10 times or more larger than that of the device using the tuning-fork-shaped vibrating member 22. Therefore, the surface potential detection signal obtained according to the magnitude of the change width is 10 times or more larger when the beam-shaped vibrating member is used than when the tuning fork-shaped vibrating member 22 is used. The SN ratio can be improved according to the magnitude of the signal.

As the voltage or current for driving the voice coil 12, a direct current or a cyclically changing voltage or current can be used.

(Third Embodiment) As a third embodiment, a configuration example of the voice coil 12 will be described. 5A to 5F are top views of the surface potential measuring device showing an example in which the voice coil 12 is used for the vibration driving unit 8 of the chopper type surface potential measuring device. Note that FIG. 5A shows the same configuration as the surface potential measuring device shown in FIG.

The electromagnetic coil portion 24 of the voice coil is composed of the solenoid coil 16 and the permanent magnet 17, and there are some shown in FIGS.
In the electromagnetic coil unit 24, by applying a direct current or a time-varying voltage or current to the solenoid coil 16, a magnetic field corresponding to the applied voltage or the applied current is generated around the solenoid coil 16, and the magnetic field and the permanent magnet 17 are generated.
The solenoid coil 16 side or the permanent magnet 17 side fluctuates due to the interaction with the permanent magnetic field generated from. The magnitude of the fluctuation is limited by the vibrating member 7 which is a leaf spring attached to the electromagnetic coil portion 24.

In the third embodiment, a case where the permanent magnet 17 is mainly used as the structure of the electromagnetic coil portion 24 will be described. However, a solenoid coil is used instead of the permanent magnet 17, a direct current or a time-varying voltage or current is applied to the solenoid coil, and the interaction of the magnetic fields generated by the two solenoid coils is used to It is also possible to change one solenoid coil.

In FIGS. 5A to 5F, the solenoid coil 16 and the permanent magnet 17 of the voice coil 12 are shown.
Although a cylinder or a cylinder is assumed as the shape of, the solenoid coil 16 or the permanent magnet 1 can be used as a prism or a prism without any problem.
Either one of 7 can be changed. Further, the number of vibrating members 7, which are leaf springs, can be changed even if the number is two. With respect to the support of the vibrating member 7, it is not always necessary to support the vibrating member only at one end, and the vibrating member 7 may be configured to be supported at both ends. .
The vibrating member 7 can be changed whether the magnetic pole direction of the permanent magnet 17 is substantially parallel or perpendicular to the axial direction of the solenoid coil 16.

As a method of changing the voice coil,
As shown in FIGS. 5A to 5F, a method of fixing the permanent magnet 17 and varying the solenoid coil 16 to vary the vibrating member 7 (FIGS. 5A, 5C, and 5E) and the solenoid. There is a method of fixing the coil 16 and varying the permanent magnet 17 to vary the vibrating member 7 (FIGS. 5B, 5D, and 5F). In either case, the vibration member 7 can be easily changed. However, in order to increase the fluctuation speed with a small amount of power and increase the response speed of surface potential detection, it is preferable to fix the permanent magnet 17 and change the solenoid coil 16 to change the vibrating member 7. This is because, in general, a solenoid coil can be made relatively lighter than a permanent magnet. The lighter the weight, the weaker the magnetic field needs to be to obtain the same fluctuation range, and the fluctuation speed is higher. Can be fast.

A coil bobbin may be used to maintain the shape of the solenoid coil 16, or the coil bobbin may be eliminated and the coil may be changed to an air-core coil having only conductive wires. As shown in FIGS. 5 (c) and 5 (e), by arranging the permanent magnet 17 outside the solenoid coil 16, a small and lightweight voice coil can be obtained, and the assembling thereof is easy. You can

(Fourth Embodiment) As a fourth embodiment, a configuration for preventing the signal line from affecting the vibration characteristics of the vibrating member and preventing disconnection will be described.

FIG. 6 shows essential parts of the solenoid coil 16 and the drive signal line 20 when a voice coil is used for the vibration drive unit 8. When the moving coil method (method in which the solenoid coil is changed) is adopted for the voice coil, there are advantages that the device configuration is small and inexpensive, and the response speed is high with small driving power. Normally, the solenoid coil 16 used in the voice coil and the drive signal line 20 for driving the voice coil are the same and an integral wire rod is used. In this case, it is desirable that the spring constant of the drive signal line 20 be sufficiently smaller than the spring constant of the vibrating member 7. Because the drive signal line 20 of the solenoid coil 16 is the vibration member 7 as shown in FIG.
This is because it is a separate body and is not synchronized with the vibration of the vibrating member 7. For example, when vibrating the vibrating member 7 in the direction of the arrow A, the drive signal line 20 affects the vibration characteristic of the vibrating member 7, gives unstable vibration, and in the worst case, the drive signal line 20 is disconnected. Cause problems.

Therefore, when the drive signal line 20 influences the vibration characteristics of the vibrating member 7, the signal member 7 is composed of a plurality of conductive layers 27 with the insulating layer 26 interposed therebetween as shown in FIG. Can be used as one vibration member. For example, using one conductive layer 27 as a measurement electrode,
The remaining conductive layer 27 is used to apply a drive signal to the solenoid coil 16. In this case, since the drive signal line 20 is integrated, even if the vibrating member 7 is vibrated in the direction of arrow A, the drive signal line 20 does not affect the vibrating member 7 at all and obtains stable vibration. be able to.

It should be noted that it is effective to use a metallic substance for the conductive layer 27 and the insulating layer 26 is made of a resin material.
A rubber material or the like can be used.

(Fifth Embodiment) As a fifth embodiment, another structure for preventing the signal line from affecting the vibration characteristics of the vibrating member and preventing disconnection will be described.

As shown in FIG. 8, the vibrating member 7 is made of an insulator, and a plurality of conductor regions 28 are provided on the surface of the vibrating member 7, which is used as one vibrating member. Accordingly, if, for example, one conductor area 28 is used as a measurement electrode and a drive signal is applied to the solenoid coil 16 using the remaining conductor area, the drive signal line 20 is integrated with the vibration member 7. Therefore, even when vibrating the vibrating member 7 in the direction of the arrow A, the drive signal line 20 does not affect the vibration characteristic of the vibrating member 7 and stable vibration can be obtained.

It is effective to use a metallic substance for the conductor region 28, and a resin material, a rubber material or the like can be used for the insulator.

In the fourth and fifth embodiments shown in FIGS. 7 and 8 described above, the plurality of conductive layers 27 or the plurality of conductor regions 28 are used as the measurement electrodes and the drive signal lines. All of the plurality of conductive layers 27 or the plurality of conductor regions 28 can be used as measurement electrodes. As for the drive signal line 20, as in the case of the detection signal line 19, as shown in FIGS. 7 and 8, the drive signal line 20 is derived from the fixed end 11 of the vibrating member 7 and a drive voltage is applied thereto. Is desirable.

(Embodiment 6) As Embodiment 6, a specific structure for improving the detection sensitivity of the surface potential measuring device will be described.

In order to improve the detection sensitivity of the surface potential of the object to be measured 2, as shown in FIG. 9A or 9B, the free end side of the vibrating member 7 is moved toward the object to be measured 2. Configure to change the height. As a result, as is apparent from the equation (1), the measurement distance L with the device under test 2 decreases (S /
The value of L) can be increased, and the value of the capacitance C ₀ can be increased. Further, as can be derived from the equation (5), the potential detection signal V ₀ can also be increased according to C ₀ , so that the surface potential signal of the DUT 2 can be detected by improving the SN ratio and improving the detection sensitivity. can do.

(Embodiment 7) As Embodiment 7, a structure for efficiently vibrating the vibrating member of the surface potential measuring apparatus will be described.

As shown in FIG. 10, when a moving coil system of a voice coil is adopted for the vibrating member 7 and the vibrating member 7 is vibrated in the direction of arrow A, normally the solenoid coil 1 is used.
A permanent magnet 17 is arranged around 6 such that the magnetic field of the solenoid coil 16 and the permanent magnetic field of the permanent magnet 17 interact with each other. If an AC signal is applied to the solenoid coil 16 in this state, the solenoid coil 16 fluctuates and the vibrating member 7
Can be vibrated.

The vibrating member 7 is efficient with less driving power.
11 to 13, the vibrating member 7 can be efficiently vibrated with a driving power of 1/10 or less compared with the conventional one. Specifically, a high-permeability member 29 is arranged around the permanent magnet 17 to form a permanent magnet 17 and a magnetic circuit 31, and a void 30 is provided in a part of the magnetic circuit 31 to pass through the void 30. The current of the solenoid coil 16 may be made to flow in a direction that intersects with the direction of the permanent magnetic field.

For example, the surface potential measuring device shown in FIG.
A permanent magnet 17 is arranged in the solenoid coil 16, and a magnetic circuit 31 having a void 30 in a part is formed around the permanent magnet 17 or in a part thereof by a high magnetic permeability member 29, and a magnetic circuit 31 is provided in the void 30. Solenoid coil 16 in the interlinking direction
Is arranged. In FIG. 11, by applying an AC drive signal to the solenoid coil 16,
The vibrating member 7 can be vibrated in the arrow A direction. The shorter the length of the void 30, the better the efficiency, and the shape of the high magnetic permeability member 29 is preferably such that the permanent magnetic field from the permanent magnet 17 has a magnetic flux density just saturated.

The high magnetic permeability member 29 may be made of pure iron, an alloy containing iron, ferrite or the like.

In the surface potential measuring device shown in FIG. 12, a high magnetic permeability member 29 is arranged in the solenoid coil 16, and the high magnetic permeability member 29 and the permanent magnet 17 are partially provided on the outer circumference of the solenoid coil 16 or a part thereof. A magnetic circuit 31 having an air gap 30 is formed in the air gap 30, and the solenoid coil 16 is arranged in the air gap 30 in a direction interlinking with the magnetic circuit 31.
This surface potential measuring device can also be driven by a method similar to that shown in FIG. 11, and it is desirable that the high magnetic permeability member 29 as the magnetic circuit 31 has a shape similar to that shown in FIG.

In the surface potential measuring device shown in FIG. 13, a high magnetic permeability member 29 is arranged in the solenoid coil 16, and the high magnetic permeability member 29 and the permanent magnet 17 are partially provided on the outer circumference of the solenoid coil 16 or a part thereof. A magnetic circuit 31 having an air gap 30 is formed in the air gap 30, and the solenoid coil 16 is arranged in the air gap 30 in a direction interlinking with the magnetic circuit 31.
This surface potential measuring device can also be driven by a method similar to that shown in FIGS. 11 and 12, and the shape of the high magnetic permeability member 29 as the magnetic circuit 31 is also the same as that of FIGS. 11 and 12. Is desirable.

[Second Embodiment] FIG. 14 is a diagram showing a surface potential measuring device according to a second embodiment of the present invention. This surface potential measuring device 6 uses the same principle as that of the vibration capacitance type surface potential measuring device described with reference to FIG.

In FIG. 14, the surface potential measuring device 6 is
The cantilever-shaped vibrating member 7 is used like the measuring electrode 1 shown in FIG. 37 (b), and is vibrated in the direction of arrow A by the vibration driving unit 8 to measure the object 2 (not shown in FIG. 14). ) Surface potential signal from the electric field direction (arrow B) on the potential sensing surface 9 of the vibrating member 7, and periodically vibrates the potential sensing surface 9 in the direction facing the measured object 2 to measure the measured object. The capacitance generated between the vibration member 2 and the vibrating member 7 is changed, and the change is taken out from the fixed end 11 of the vibrating member 7 via the potential detecting unit 4 as a potential detection signal. The potential detection signal obtained by the surface potential measuring device 6 is the same as that of the output formula shown in the formula (5).

(Embodiment 1) FIG. 15 shows Embodiment 1 of the surface potential measuring device 6 shown in FIG. 14, and FIG.
Shows a side view and FIG. 15 (b) shows a top view. The surface potential measuring apparatus according to the first embodiment uses the voice coil 12 in the vibration driving unit 8 of the vibrating member 7 so that the surface potential of the DUT 2 can be measured.

In the surface potential measuring device of Example 1,
Shield case 1 for shielding an electric field having a potential measurement window 15
One end of the vibrating member 7 having the above-mentioned potential sensing surface 9 is fixed in the inside 4 by the insulating fixing member 10, and the vibrating member 7 is installed in a cantilever shape. The moving coil system of the voice coil 12 is used to attach the air-core solenoid coil 16 using the vibrating member 7 as an elastic body.
A rod-shaped permanent magnet 17 is installed inside. Voice coil 12
When an AC signal is applied to the solenoid coil 16 as a drive signal for the electric current, a current flows through the solenoid coil 16, and the interaction between the magnetic field generated by the current and the permanent magnetic field of the permanent magnet 17 causes vibration of the cantilever beam. 7 vibrates in the direction of arrow A (arrow symbol A). The potential sensing surface 9 vibrates due to the vibration of the vibrating member 7, and the shield case 14
The surface potential signal of the DUT 2 is received from the potential measurement window 15 from the electric field direction (arrow B and arrow symbol B) on the potential sensing surface 9, and the change in induced charge generated on the potential sensing surface 9 is used as the surface potential signal. This is to take out from the fixed end 11 of the vibrating member 7 to the outside of the shield case 14 as a detection signal via the potential signal detecting section 4.

In the case of the first embodiment, the effective area S of the measuring electrode composed of the vibrating member 7 is the relative relationship between the area of the potential sensing surface 9 of the vibrating member 7 and the area of the potential measuring window 15 provided in the shield case 14. Is determined by the area where the potential sensing surface 9 is exposed to the surface of the DUT 2. The vibrating member 7 needs to be vibrated so that the amount of induced charges on the potential sensing surface 9 received from the object to be measured changes. Further, in order to detect the potential signal from the vibrating member 7, the detection signal line 19 is led out from the fixed end 11 of the vibrating member 7 as shown in FIG. 15, and the potential signal detecting section 4 detects the potential signal. Is desirable.

In the surface potential measuring device of Example 1,
Since it is not necessary to provide the measuring electrode separately from the vibrating member as in the conventional vibration capacitance type surface potential measuring device, the surface potential measuring device can be further downsized and at low cost.

(Example 2) In Example 1, a cantilever beam was used as the vibrating member 7, but a tuning-fork vibrating member 22 as shown in FIG. 16 can be used as the vibrating member 7. That is, the tuning fork-shaped vibrating member 22 is vibrated in the direction of arrow A by the vibration driving unit 8 from the outside, and the measured object 2 is vibrated.
Electric field direction (not shown in FIG. 16) (arrow symbol B)
Is received by the potential sensing surface 9 of the tuning-fork vibration member 22. In addition, this vibrating member 7
As in the first embodiment, the voice coil 12 can be used as the vibration driving unit 8 for vibrating the tuning fork-shaped vibrating member 22.

In the second embodiment, the shape of the vibrating member 7 shown in FIG. 14 is not limited to that of the first and second embodiments described above. However, the second embodiment shown in FIG.
When the tuning fork-shaped vibrating member 22 is used as the vibrating member 7 as described above, the detection signal line 19 for extracting the potential signal from the tuning-fork-shaped vibrating member 22 is led out from the nodal portion 23 which is a node of the tuning fork-shaped vibrating member 22 Is desirable.

In addition, Example 1 (FIG. 15) and Example 2
In FIG. 16, the voice coil 12 is used as the vibration driving unit 8 for vibrating the vibrating member 7, but as shown in FIGS. 4A and 4B described in the first embodiment, the cantilever beam shape is used. Alternatively, the tuning fork-shaped vibrating member 7 can be vibrated using the plunger vibrating electromagnetic coil 25.

Next, the characteristics of the surface potential measuring devices of Examples 1 and 2 described above will be compared. In the case of the vibration capacitance type surface potential detecting device described as the second embodiment, the rate of change α ₀ of the electrostatic capacitance C ₀ is expressed as α ₀ = ΔL / L (7) However, ΔL is the potential sensing surface 9 of the vibration member 7.
Represents the fluctuation range of the fluctuation.

Here, in order to improve the SN ratio, ΔL may be increased. The use of the voice coil 12 is effective as a method of increasing ΔL. The vibrating member 7 is attached to the electromagnetic coil portion, and the vibrating member 7 fluctuates as the electromagnetic coil fluctuates.

In the case of the vibration capacitance type surface potential measuring device, as in the case of the chopper type described in the first embodiment, there are a vibrating member 7 of a tuning fork type and a beam type. When the variation width of the fluctuation of the vibrating member 7 is compared, the vibrating member 7 using the beam-shaped one is 10 times larger than that using the tuning-fork-shaped one.
The fluctuation range of can be obtained. Therefore, as for the surface potential detection signal obtained according to the magnitude of the change width, a beam-shaped device can obtain a detection signal that is 10 times or more larger than that of a tuning-fork-shaped device. Therefore, the SN ratio can be improved according to the magnitude of the detection signal.

Example 3 FIGS. 17 (a) to 17 (f) are top views showing a schematic configuration of Example 3 of the surface potential measuring apparatus according to the second embodiment. An example is shown in which the voice coil 12 is used for the vibration driving unit 8 that vibrates the vibration member 7 of the apparatus. Note that FIG.
15A shows the same configuration as that of the first embodiment shown in FIG.

In FIGS. 17A to 17F, the solenoid coil 16 and the permanent magnet 17 of the voice coil 12 are assumed to have a cylindrical shape or a cylindrical shape, but a rectangular cylinder or a prism may be used without any problem. The permanent magnet 17 can be changed. Further, the vibrating member 7 acting as a leaf spring can be changed even if it is two. Further, with respect to the support of the vibrating member 7, it is not always necessary to support one end side of each leaf spring, and both end sides of each leaf spring may be supported.
Furthermore, the magnetic pole direction of the permanent magnet 17 is
It may be substantially parallel or perpendicular to the axial direction of 6.

As a method of varying the voice coil 12, a method of varying the vibrating member 7 by fixing the permanent magnet 17 and varying the solenoid coil 16 (FIG. 17A,
(C), (e)) and a method of fixing the solenoid coil 16 and varying the permanent magnet 17 to vary the vibrating member 7 (FIGS. 17 (b), (d), (f)). Both are methods that can be easily changed, but the change speed can be increased with a small amount of power,
To increase the response speed of surface potential detection, use a permanent magnet 1
It is preferable to fix 7 and change the solenoid coil 16 to change the vibrating member 7. This is because, in general, the solenoid coil 16 can be made relatively lighter than the permanent magnet 17. Therefore, the lighter the weight, the weaker the magnetic field needs to be generated to obtain the same fluctuation range, and the fluctuation speed can be increased.

The solenoid coil 16 may use a coil bobbin to maintain its shape, or may be changed to an air-core coil having only a conductive wire without the coil bobbin.

By arranging the permanent magnet 17 outside the solenoid coil 16 as shown in FIGS. 17C and 17E, the size of the voice coil 12 can be made small and lightweight, and the assembling can be facilitated. be able to.

Also in the second embodiment, when the drive signal line 20 influences the vibration characteristics of the vibrating member 7, the vibrating member having the configuration described in the first embodiment with reference to FIGS. 7 and 8 is used. By using, it is possible to stably vibrate the vibrating member without affecting the vibration characteristics of the vibrating member. Further, in order to enhance stable reliability, it is possible to provide a plurality of conductive layers or a plurality of conductor regions and use all of them as measurement electrodes.

Also in the second embodiment, it is desirable that the drive signal line 20 is connected to the fixed end 11 of the vibrating member 7 to apply the drive signal. Further, when it is desired to improve the detection sensitivity of the surface potential of the object to be measured 2, the free end side of the vibrating member 7 should be positioned close to the object to be measured as shown in FIGS. 9 (a) and 9 (b). By deforming the shape, the SN ratio and the detection sensitivity can be improved and the surface potential signal of the measured object can be measured. Furthermore, when it is desired to vibrate the vibrating member 7 efficiently with a small amount of driving power, the configuration shown in FIGS. 11 to 13 described in the first embodiment can be used to efficiently drive the vibrating member 7 with a smaller amount of driving power. Can be vibrated.

(Embodiment 3) When the measurement distance between the object to be measured and the measurement electrode is changed, a configuration for correcting the output signal which changes according to the change of the measurement distance is used in the embodiment 3.
It will be described as.

In the second embodiment, as described above, the surface potential V _S and the capacitance C _{0 of the} object 2 to be measured are calculated from the equation (5).
Also, the output signal V ₀ can be obtained in proportion to the magnitude of the rate of change α ₀ of the capacitance C ₀ . However, as is clear from the equation (1), since the electrostatic capacitance C ₀ is proportional to the reciprocal of the facing distance (measurement distance) L between the object to be measured and the measuring electrode, it is proportional to the electrostatic capacitance C _0. The output signal V ₀ obtained as a result also greatly changes depending on the facing distance L. Therefore, when the measurement distance changes, there arises a problem that it is difficult to obtain an accurate surface potential of the device under test 2. Therefore, as a means for correcting the output fluctuation due to the fluctuation of the measurement distance, as shown in FIG. 18, a plurality of different output signals (V ₁ , V ₁ ) that vary depending on the measurement distance L from one measurement electrode (vibrating member 7). ₂ ,
V ₃ , ...) is obtained by the first output signal detector 32, the second output signal detector 33, the third output signal detector 34, ... And each output signal is measured by the output corrector 35. Correcting according to the distance makes it possible to measure the accurate surface potential independent of the measuring distance.

Therefore, as a means for obtaining a plurality of different output signals that change depending on the measurement distance from one measuring electrode (vibrating member 7), the vibration capacitance type surface potential measuring device described in the second embodiment. Is preferred. In the surface potential measuring device using the chopper-type vibrating member described in the first embodiment, it is possible to obtain a plurality of different output signals that change depending on the measuring distance from one measuring electrode (vibrating member 7). Have difficulty.

A method of detecting an accurate surface potential without depending on the measurement distance by using the vibration capacitance type surface potential measuring device will be described below.

FIG. 19 is an explanatory diagram relating to a method of detecting a plurality of output signals having different frequencies from one measuring electrode and correcting the output fluctuation of the potential detection signal. 19 is shown in FIG.
In the device for detecting a plurality of output signals described in 8,
By periodically vibrating in a sinusoidal manner with the measurement electrodes summed with different frequency components of ω ₁ and ω ₂ , each frequency component is detected as a different output signal from the potential detection signal of the measurement electrode. 2 shows a method of correcting the output of the.

In FIG. 19, the amplitude of the vibration of ω ₁ of the measuring electrode is ΔL ₁ , the amplitude of the vibration of ω ₂ is ΔL ₂ , and the measuring electrode temporally changes ΔL ₁ · sinω ₁ t + ΔL ₂ · sin ω.
Considering the case of vibrating at ₂ t, the electrostatic capacitance C _t which changes with time due to the periodic mechanical vibration is

[Equation 1] And further transforming Eq. (8),

[Equation 2] It is expressed as

Here, (ΔL ₁ · sin) on the right side of the equation (9)
ω ₁ t + ΔL ₂ · sin ω ₂ t) / L is physically

(Equation 3) Therefore, the right side of equation (9) can be mathematically expanded by Tiller.

Therefore, if the Tiller expansion of the right side of the equation (9) is performed,

(Equation 4) And C _t is the 0th order in time (measurement electrode is stationary)
Can be expressed as a plurality of frequency components including a higher-order term in addition to the first term (measurement electrode changes sin ω ₁ t and sin ω ₂ t with time).

Therefore, the charge Q _t induced on the measurement electrode by the C _t and the surface potential V _S of the object to be measured is

(Equation 5) It is expressed as

From the equation (11), the current I _t generated at the measuring electrode is

(Equation 6) Becomes

Potential detection signal V obtained from the measuring electrode
_t is

(Equation 7) It is expressed as However, A ₀ represents a constant relating to the amplification degree.

As can be seen from the equation (14), a plurality of different frequency components that change depending on the measurement distance L appear from the potential detection signal obtained from the measurement electrode. Therefore,
By detecting the plurality of different frequency components as different output signals, a plurality of output signals that change depending on the measurement distance L can be obtained from one measurement electrode, and the measurement distance fluctuations can be obtained by using the respective output signals. It is possible to correct the output fluctuation of the potential detection signal due to.

Here, as the output signals having different frequencies from the potential detection signal of the equation (14), since the signal output level of the third and subsequent frequency components is relatively small, the third and subsequent frequency components are ignored and the first and second order frequency components are ignored. By using only the secondary frequency component as the output signal, the output signal can be efficiently detected with a sufficient SN ratio. Therefore, a sufficiently accurate surface potential output can be obtained.

Therefore, from the potential detection signal of the equation (14), 1
If only the second and second order frequency components are detected, approximately

(Equation 8) Therefore, in equation (15), ω ₁ , ω ₂ , 2ω ₁ , 2
By detecting each frequency component of ω ₂ , ω ₂ + ω ₁ , and ω ₂ −ω ₁ , six output signals having different frequencies can be obtained.

In the case of the second embodiment, assuming that ω ₁ << ω ₂ , and considering (ΔL ₂ / L) ² << 1, the equation (15) is considered again and further simplified,

[Equation 9] Ω ₂ , ω ₂ + ω ₁ (or ω ₂ −
If only each frequency component of ω ₁ ) is selectively detected, two output signals V ₁ and V ₂ having different frequencies can be efficiently obtained with a sufficient SN ratio.

A method for obtaining an accurate surface potential by correcting the output variation of the potential detection signal due to the variation of the measurement distance by using the output signals V ₁ and V ₂ having different frequencies thus obtained will be described below. To do.

First, as a first method, the measurement distance L is uniquely obtained from the output signals V ₁ and V ₂ independently of the surface potential V _{S of the} object to be measured, and the obtained measurement distance is calculated. A method of obtaining an accurate surface potential will be described.

The magnitudes (output values) | V ₁ | and | V ₂ | of the output signals V ₁ and V ₂ detected by the equation (16) are

(Equation 10) In order to uniquely obtain the measurement distance L without depending on the surface potential VS, the output ratio of | V ₁ | and | V ₂ | may be obtained.

For example, when the output ratio is | V ₂ | / | V ₁ |, | V ₂ | / | V ₁ | is given by equations (17) and (18).

[Equation 11] And is represented as a temporary function F (L) with respect to L. At this time, the relationship between L and | V ₂ | / | V ₁ | is represented by a relationship curve as shown in FIG. 20 (a), and the output ratio | V ₂ |
By obtaining / | V ₁ |, L can be uniquely obtained without depending on the surface potential V _S.

When the output ratio is | V ₁ | / | V ₂ |, | V ₁ | / | V ₂ |

(Equation 12)And similarly expressed by a temporary function F (L) with respect to L
You. At this time, L and | V ₁｜ / ｜ V_TwoFig. 2 shows the relationship with |
It is represented by a relational curve such as 0 (b), which is also output
Ratio | V₁｜ / ｜ V_TwoIf | is obtained, the surface potential V_Sdependent upon
It is possible to uniquely obtain L without doing so.

[0125] In this way, by using the L determined uniquely by a known | V ₁ | or | V ₂ | output value from the relationship between the measured distance L | V ₁ | or | V ₂ The output value of | is corrected and the known surface potential V _S and output value | V ₁ |
Or | V ₁ | or | V corrected from the relationship with | V ₂ |
By obtaining the surface potential V _S corresponding to the output value of ₂ |, the accurate surface potential of the measured object can be obtained.

The obtained L is │V ₁ │ or │V ₂ │
It is also possible to uniquely determine the surface potential of the object to be measured by substituting it in the output equation (Equation (17) or (18)) and determining V _S.

Next, as a second method, since the output signals V ₁ and V ₂ change depending on the measurement distance L, | V
_A correction method will be described in which an output value of ₁ |, | V ₂ | is used to perform an operation process of canceling the variable of L so as not to depend on the measurement distance L, and an accurate surface potential is obtained from the operation result.

For example, (1
(7) | V ₁ | is cubed and the result is |
By dividing V ₂ | by the squared value,

(Equation 13) The output result is as follows. Since the output value corresponding to the surface potential V _S of the measured object that does not depend on the measurement distance L is obtained from the equation (21), from the relationship between the output value of the equation (21) and the surface potential V _S of the measured object, It is possible to obtain an accurate surface potential.

Also, | V ₂ | of the equation (18) is squared,
By dividing | V ₁ | in the equation (17) by the cubed value,

[Equation 14] An output result such as the above can be obtained, and an accurate surface potential can be obtained from the relationship between the output value of the equation (22) and the surface potential V _{S of the} object to be measured as described above.

When the equation (19) is used, | V ₁ | of the equation (17) is divided by the value obtained by squaring the output value of the equation (19) or the output value of the equation (19) is squared. The divided value is divided by | V ₁ | in equation (17) to obtain equation (21) or (2
An output result as shown in equation (2) is obtained, and similarly, an accurate surface potential can be obtained.

Further, | V ₂ | of the equation (18) is divided by the value obtained by cubed the output value of the equation (19), or the value obtained by squaring the output value of the equation (19) is obtained by the equation (18). Also by dividing by | V ₂ |, the output result as in the equation (21) or the equation (22) can be obtained, and an accurate surface potential can be similarly obtained.

Further, when the expression (20) is used, (1
7) | V ₁ | multiplied by the value obtained by squaring the output value of equation (20), or | V ₂ | of equation (18) multiplied by the value obtained by squaring the output value of equation (20) By combining, (2
The output result as shown in the equation (1) is obtained, and similarly, the accurate surface potential can be obtained.

FIG. 21 shows that an accurate output signal corresponding to the surface potential of the object to be measured is obtained by correcting the output fluctuation of the potential detection signal due to the fluctuation of the measurement distance by utilizing the plurality of output vibrations having different frequencies as described above. FIG. 6 shows a device configuration diagram for explaining specific means for obtaining the above. That is, FIG.
Is a measurement distance L which is uniquely obtained from the output signals V ₁ and V ₂ by the measurement distance detection unit 36 without depending on the surface potential V _{S of the} object to be measured, and an accurate surface is obtained from the obtained measurement distance. A means for obtaining an electric potential is shown.

The apparatus shown in FIG. 21 detects a minute change in the amount of electric charge induced on the measurement electrode (vibrating member 7) as an AC signal by the potential signal detection unit 4, and detects a difference in frequency from the detected signal. The two output signals V ₁ and V ₂ are detected by the first and second output signal detectors 32 and 33, and the measurement distance is obtained and obtained by the measurement distance detector 36 using the output ratio of the respective output signals. The output value of each output signal is corrected by the output correction unit 35 from the measured distance, and an accurate surface potential output signal is obtained.

As means for detecting a minute AC signal generated at the measuring electrode in the potential signal detecting section 4, FET, O
An AC signal amplification circuit using a P amplifier or the like can be used. Further, as means for detecting the output signals having different frequencies in the output signal detection sections 32 and 33, a synchronous detection circuit, a demodulation circuit, a narrow band pass filter circuit that passes only necessary frequency components, etc. should be used. You can As means for obtaining the measurement distance from the output ratio of each output signal in the measurement distance detection unit 36, an analog arithmetic circuit for multiplication or division, an analog-digital conversion circuit, a computer or the like can be used, and arithmetic processing is performed by these. By doing so, the measurement distance can be obtained. Further, as the means for correcting the output value of each output signal from the measured distance in the output correction section 35 to obtain the surface potential output signal, a computer, a digital-analog conversion circuit or the like can be used.

The output values of each output signal | V ₁ |, | V
22 (a) to (e) are available as means for performing calculation processing using ₂ | so as not to depend on the measurement distance L and obtaining an accurate surface potential from the calculation result.

The surface potential measuring device shown in FIG.
The potential signal detector 4 detects a minute change in the amount of charge induced on the measurement electrode 7 as an AC signal, and outputs two output signals V ₁ and V ₂ having different frequencies from the detected signal as first and _second signals. _First , the output signal detection units 32 and 33 detect | V ₁ | to the third power to obtain | V ₁ | ³ in order to perform arithmetic processing using output values of each output signal so as not to depend on the measurement distance. a second arithmetic unit 38 to obtain a ^2, | | calculation unit 37 and | V ₂ | square to | V ₂ a ³ | | V ₁ V ₂ |, and a third calculation unit 39 divided by ² is provided, From this calculation result, an accurate surface potential output signal that does not depend on the measured distance is obtained. The apparatus shown in FIG. 21 can be applied to the potential signal detecting section and the output signal detecting sections having different frequencies.

The first calculation unit 37, the second calculation unit 38 and the third calculation unit
In the arithmetic unit 39, as means for arithmetically processing each output value to obtain a surface potential output signal, an analog arithmetic circuit such as multiplication or division, an analog-digital circuit, a computer or a digital-analog conversion circuit may be used. it can.

The surface potential measuring device shown in FIG.
The potential signal detector 4 detects a minute change in the amount of charge induced on the measurement electrode 7 as an AC signal, and outputs two output signals V ₁ and V ₂ having different frequencies from the detected signal as first and _second signals. The output signals are detected by the output signal detectors 32 and 33, and the output value of each output signal is used to perform arithmetic processing so as not to depend on the measurement distance. Therefore, | V ₂ | is divided by | V ₁ | a fourth arithmetic unit 40 for multiplication, | V ₂ | a | V ₁ |
Divide by and square the value (| V ₂ | / | V ₁ |)
5 shows a device configuration in which a fifth division unit 41 for dividing ² by | V ₁ | is provided and an accurate surface potential output signal independent of the measurement distance is obtained from the calculation result.

The same means as in FIG. 21 can be applied to the potential signal detector 4 and the output signal detectors 32 and 33 having different frequencies. As the means for arithmetically processing the output values in the fourth arithmetic unit 40 and the fifth arithmetic unit 41 to obtain the surface power output signal, the same means as shown in FIG. 22A can be used.

The surface potential measuring device shown in FIG.
The potential signal detector 4 detects a minute change in the amount of electric charge induced on the measurement electrode 7 as an AC signal, and outputs two outputs V ₁ and V ₂ having different frequencies from the detected signal as first and second signals.
The output signals of the output signals are detected by the output signal detectors 32 and 33, and | V ₂ | is divided by | V ₁ | in order to perform arithmetic processing using output values of the respective output signals so as not to depend on the measured distance.
The sixth computing unit 42 to be multiplied and | V ₂ | are divided by | V ₁ |, and the value is cubed (| V ₂ | / | V ₁ |) ³ to | V
7 shows a device configuration in which a seventh operation unit 43 for dividing by ₂ | is provided and an accurate surface potential output signal independent of the measurement distance is obtained from the operation result.

The same means as in FIG. 21 can be applied to the potential signal detector 4 and the output signal detectors 32 and 33 having different frequencies. As the means for arithmetically processing the output values in the sixth arithmetic section 42 and the seventh arithmetic section 43 to obtain the surface power output signal, the same means as shown in FIG. 22A can be used.

The surface potential measuring device shown in FIG.
A slight change in the amount of charge induced on the measurement electrode is detected as an AC signal by the potential signal detection unit 4, and two output signals V ₁ and V ₂ having different frequencies are detected from the detection signal as output signal detection units 32. , 33, and the output value of each output signal is used to perform arithmetic processing independent of the measurement distance. Therefore, | V ₁ | is divided by | V ₂ | and the value is squared. The operation unit 44 and | V ₁ | are divided by | V ₂ |, and the value is squared (| V ₁ | / | V ₂ |) ² and |
9 shows a device configuration in which a ninth calculation unit 45 for multiplying V ₁ | and a ninth calculation unit 45 is provided, and an accurate surface potential output signal independent of the measurement distance is obtained from the calculation result.

The same means as that shown in FIG. 21 can be applied to the potential signal detector 4 and the output signal detectors 32 and 33 having different frequencies. As the means for arithmetically processing the output values in the eighth arithmetic unit 44 and the ninth arithmetic unit 45 to obtain the surface power output signal, the same means as shown in FIG. 22A can be used.

The surface potential measuring device shown in FIG.
The potential signal detector 4 detects a minute change in the amount of charge induced on the measurement electrode 7 as an AC signal, and outputs two output signals V ₁ and V ₂ having different frequencies from the detected signal. In order to perform calculation processing that does not depend on the measurement distance by using the output value of each output signal detected by 32 and 33, | V ₁ | is divided by | V ₂ | and the value is raised to the third power. The operation unit 46 and | V ₁ | are divided by | V ₂ |, and the value is cubed (| V ₁ | / | V ₂ |) ³ and |
11 shows an apparatus configuration in which an eleventh calculation unit 47 for multiplying by V ₂ | is provided and an accurate surface potential output signal that does not depend on the measurement distance is obtained from the calculation result.

The same means as that shown in FIG. 21 can be applied to the potential signal detector 4 and the output signal detectors 32 and 33 having different frequencies. Tenth calculation unit 46 and eleventh
As the means for arithmetically processing the output values and obtaining the surface electric power output signal in the arithmetic unit 47, the same means as shown in FIG. 22A can be used.

When the electrode vibrating means for vibrating the measuring electrode (vibrating member 7) is used in the second embodiment, for example, the frequency ω ₁ as shown in FIG.
(Ω ₁ + ω ₂ ) voltage (current) waveform in a state in which the drive voltage (drive current) waveform of ( ₁ ) and the drive voltage (drive current) waveform of frequency ω ₂ as shown in FIG. By applying a voltage (current) having the same figure (c)) to each electrode vibrating means, it is possible to vibrate the measuring electrode at a plurality of different frequencies by one electrode vibrating means.

As in the third embodiment, by using only the primary and secondary frequency components as output signals having different frequencies, a sufficiently accurate surface potential can be efficiently obtained. If you want to further improve the measurement accuracy, use the third and subsequent frequency components in addition to the primary and secondary frequency components, obtain two or more output signals from one measurement electrode, and use each output signal. Then, the surface potential of the measured object may be obtained. Further, in order to improve reliability, two or more measurement electrodes may be provided, and the surface potential of the object to be measured may be obtained by using the same measurement method and measurement means as described above for each measurement electrode.

As another example, FIG. 24 is an explanatory diagram relating to a method of detecting a plurality of output signals having different frequencies from one measurement electrode and correcting the output fluctuation of the potential detection signal. This is a method of detecting a plurality of output signals described above. As shown in FIG. 24, the potential of the measurement electrode (vibration member 7) is periodically vibrated largely at a single frequency ω in a sinusoidal manner. A plurality of frequency components are generated from the detection signal, each frequency component is detected as a different output signal, and the output of the potential detection signal is corrected.

In FIG. 24, assuming that the amplitude of the vibration of the measuring electrode is d and the measuring electrode is vibrating with d · sin ωt in time, the electrostatic which changes with time due to the periodic mechanical vibration. The capacitance C _t is

(Equation 15) Given by and transforming equation (23),

(Equation 16) It is expressed as

Here, (d / L) ·
sin ωt is physically

[Equation 17] Therefore, the right side of equation (24) can be mathematically expanded by Tiller.

Therefore, if the right side of the equation (24) is subjected to Tiller expansion,

(Equation 18) And C _t is the 0th order in time (measurement electrode is stopped)
In addition to the first term (measurement electrode sin ωt with time), a plurality of frequency components including higher-order terms appear.

Therefore, the electric charge Q _t induced on the measurement electrode by the C _t and the surface potential V _S of the object to be measured is

[Equation 19] And the current I _t generated in the measurement electrode is

(Equation 20) And the potential detection signal V _t obtained from the measurement electrode is

(Equation 21) It is expressed as However, A ₀ represents a constant relating to the amplification degree.

As can be seen from the equation (29), a plurality of different frequency components that vary depending on the measurement distance L appear from the potential detection signal obtained from the measurement electrode. Therefore,
By detecting the plurality of different frequency components as different output signals, a plurality of output signals that change depending on the measurement distance L can be obtained from one measurement electrode. Then, by using each output signal, it is possible to correct the output fluctuation of the potential detection signal due to the measurement distance fluctuation.

Since the signal output level of the third and subsequent frequency components is relatively small, the third and subsequent frequency components are ignored and (2
By using only the primary and secondary frequency components as the output signals having different frequencies from the potential detection signal of the expression (9), the output signals can be efficiently detected with a sufficient SN ratio. Therefore, a sufficiently accurate surface potential output can be obtained.

Therefore, from the potential detection signal of the equation (29), 1
If only the second and second frequency components are detected, approximately,

(Equation 22) Therefore, by selectively detecting each frequency component of ω and 2ω in the equation (30), two output signals V ₁ and V ₂ having different frequencies can be obtained.

A method of obtaining an accurate surface potential by using the output signals V ₁ and V ₂ having different frequencies thus obtained and correcting the output variation of the potential detection signal due to the variation of the measuring distance will be described below. .

First, as a first method, the measurement distance L is uniquely obtained from each of the output signals V ₁ and V ₂ independently of the surface potential V _{S of the} object to be measured, and the obtained measurement distance is calculated. A method of obtaining an accurate surface potential will be described.

The magnitudes (output values) | V ₁ | and | V ₂ | of the output signals V ₁ and V ₂ detected by the equation (30) are

(Equation 23) In order to uniquely obtain the measurement distance L without depending on the surface potential V _S , the output ratio of | V ₁ | and | V ₂ | may be obtained.

For example, when the output ratio is | V ₂ | / | V ₁ |, | V ₂ | / | V ₁ | is (31) and (32)
From the formula,

(Equation 24) And is expressed as a linear function F (L) with respect to L.

At this time, the relationship between L and | V ₂ | / | V ₁ | is represented by a relationship curve as shown in FIG.
By obtaining V ₂ | / | V ₁ |, L can be uniquely obtained without depending on the surface potential V _S.

When the output ratio is | V ₁ | / | V ₂ |, | V ₁ | / | V ₂ |

(Equation 25) Similarly, it is expressed by a linear function F (L) with respect to L. At this time, the relationship between L and | V ₁ | / | V ₂ |
It is represented by a relational curve as shown in (b). Similarly, if the output ratio | V ₁ | / | V ₂ | is obtained, L can be obtained without depending on the surface potential V _S.

[0163] In this way, by using the L determined uniquely by a known | V ₁ | or | V ₂ | output value from the relationship between the measured distance L | V ₁ | or | V ₂ The output value of | is corrected and the known surface potential V _S and output value | V ₁ |
Or | V ₂ | the corrected from the relationship between | V ₁ | or | V ₂ | of by obtaining the corresponding surface potential V _S to the output value, it is possible to obtain an accurate surface potential of the object to be measured Becomes The surface potential of the object to be measured is uniquely obtained by substituting the obtained L into the output formula ((31) or (32)) of | V ₁ | or | V ₂ | and obtaining V _S. be able to.

Next, as the second method, since the output signals V ₁ and V ₂ change depending on the measurement distance L, | V
_A method will be described in which the output values of ₁ | and | V ₂ | are used to perform an operation process of canceling the variable of L so as not to depend on the measurement distance L, and an accurate surface potential is obtained from the operation result.

For example, (3
1 | Equation | V ₁ | raised to the power of 3 and the result is |
By dividing V ₂ | by the squared value,

(Equation 26) The output result is as follows. Since the output value corresponding to the surface potential V _S of the measured object that does not depend on the measurement distance L is obtained from the equation (35), it is accurate from the relationship between the output value of the equation (35) and the surface potential V _S of the measured object. It is possible to obtain a high surface potential.

Also, | V ₂ | of the equation (32) is squared,
By dividing | V ₁ | in the equation (31) by the cubed value,

[Equation 27] The output result is as follows. Similarly to the above, it is possible to obtain an accurate surface potential from the relationship between the output value of the equation (36) and the surface potential V _S of the measured object.

When the expression (33) is used, | V ₁ | of the expression (31) is divided by the value obtained by squaring the output value of the expression (33), or the output value of the expression (33) is squared. The divided value is divided by | V ₁ | of equation (31) to obtain equation (35) or (3
An output result as shown by the equation (6) is obtained, and an accurate surface potential can be obtained as described above.

Further, | V ₂ | of the equation (32) is divided by the value obtained by cubed the output value of the equation (33), or the value obtained by cubed the output value of the equation (33) is obtained by the equation (32). Also by dividing by | V ₂ |, the output result as in the equation (35) or the equation (36) can be obtained, and an accurate surface potential can be obtained in the same manner as described above.

Further, when the expression (34) is used, (3
1) | V ₁ | multiplied by the value obtained by squaring the output value of equation (34), or | V ₂ | of the equation (32) multiplied by the value obtained by squaring the output value of equation (34) By combining, (3
An output result as shown by the equation (5) is obtained, and an accurate surface potential can be obtained in the same manner as described above.

Also in this example, a plurality of output signals having different frequencies are used to correct the output fluctuation of the potential detection signal due to the fluctuation of the measurement distance to obtain an accurate output signal corresponding to the surface potential of the object to be measured. As a means, a measuring distance L is uniquely obtained from the output signals V ₁ and V ₂ without depending on the surface potential V _{S of the} object to be measured, and an accurate surface potential is obtained from the obtained measuring distance. For this, the device described in FIG. 21 can be applied. Further, as means for performing an arithmetic process using the output values | V ₁ |, | V ₂ | of each output signal so as not to depend on the measurement distance L and obtaining an accurate surface potential from the arithmetic result, FIG. The devices described in a) to (e) can be applied.

Further, by using only the primary and secondary frequency components as the output signals as the output signals having different frequencies as in this example, it is possible to efficiently obtain a sufficiently accurate surface potential. In order to further improve the measurement accuracy, in addition to the primary and secondary frequency components, the third and subsequent frequency components are used to obtain two or more output signals from one measuring electrode and to output each output signal. The surface potential of the object to be measured may be obtained by utilizing this. Further, in order to improve reliability, two or more measurement electrodes may be provided, and the surface potential of the object to be measured may be obtained by using the same measurement method and measurement means as described above for each measurement electrode.

As another example, FIG. 25 is an explanatory diagram regarding a method of detecting a plurality of output signals having different output values from one measurement electrode and correcting the output fluctuation of the potential detection signal. This is a method of obtaining two or more output signals as described above, by changing the detection position of the measurement electrode while periodically changing the measurement electrode in the direction of the measurement object to detect the surface potential. The surface potential of the object to be measured is obtained from each output signal by varying the distance between the body and the measurement electrode. The principle of detecting the surface potential of the object to be measured is the same as that shown in FIG. As the method of changing the measurement electrode, the surface potential can be detected by using a periodic or aperiodic change such as a sine wave shape shown in FIG. 25, a rectangular wave shape, a trapezoidal wave shape, a triangular wave shape, a sawtooth wave shape, or a pulse wave shape. Is possible.

In FIG. 25, it is assumed that the output signal when the measuring electrode is at the distance L ₁ from the object to be measured is V ₁ , and the output signal when the distance away from L ₁ by d is L ₂ is V _2. , The output value fluctuates depending on the measurement distance.
Signals with different output values are obtained. In this case, the detection position of the measuring electrode is between L ₁ and L ₂ (distance d)
By changing the frequency periodically or aperiodically, the sine wave (Fig. 27), rectangular wave (Fig. 28), triangular wave (Fig. 2)
9), sawtooth waveform (FIG. 30), trapezoidal waveform (FIG. 31), and other signals having different output values can be obtained.

Next, using the different output values V ₁ and V ₂ obtained as described above, the measurement distance L ₁ is inversely uniquely obtained without depending on the surface potential V _{S of the} object to be measured. First, in the case of the vibration capacitance type, the capacitance C between the object to be measured and the measurement electrode is
Change rate alpha _{0 0,} The measurement distance _{L 1, L 2, α 1} = ΔL / a _{(L 1 -ΔL) ... (37} ) α 2 = ΔL / (L 2 -ΔL) ... (38) Table To be done. However, ΔL represents the change width of the fluctuation of the measurement electrode.

Here, assuming that the capacitance when the measurement electrode is at a distance of L ₁ from the object to be measured is C ₁ and the capacitance when it is at a distance of L ₂ is C ₂ , each output signal V ₁ , V _{2 using} the output formulas (1), (5), (37), (38), V ₁ = A ₀ · α ₁ · ω · C ₁ · V _S · cosωt = A ₀ · ΔL / (L ₁ −ΔL) · ω · ε _air · (S / L ₁ ) · V _S · cos ωt (39) V ₂ = A ₀ · α ₂ · ω · C ₂ · V _S · cos ωt = A ₀ · ΔL / (L ₂ -ΔL) is expressed as _{· ω · ε air · (S} / L 2) · V S · cosωt ... (40).

Since L ₂ is L ₂ = L ₁ + d, (3
9) and (40), the measurement distance L ₁ can be obtained in reverse, and in order to uniquely obtain L ₁ without depending on the surface potential V _S , V can be obtained from equations (39) and (40). ₁ , V ₂
The output ratio of

For example, when the output ratio is V ₂ / V ₁ ,
V ₂ / V ₁ is V ₂ / V ₁ = L ₁ · (L ₁ −ΔL) / [L ₂ · (L ₂ −ΔL)] = L ₁ · (L ₁ −ΔL) / [(L ₁ + d ) · (L ₁ + d−ΔL)] = F (L ₁ ² ) ... (41), which is represented by a quadratic function F (L ₁ ² ) with respect to L ₁ . At this time, the relationship between L ₁ and V ₂ / V ₁ is shown in FIG.
If the output ratio V ₂ / V ₁ is represented by the relational curve as shown in (a), L ₁ can be uniquely determined without depending on the surface potential V _S.

If the output ratio is V ₁ / V ₂ , then V ₁
/ V ₂ is V ₁ / V ₂ = L ₂ · (L ₂ −ΔL) / [L ₁ · (L ₁ −ΔL)] = (L ₁ + d) · (L ₁ + d−ΔL) / [L 1 · (L ₁ −ΔL)] = F (L ₁ ² ) (42), which is similarly expressed by a quadratic function F (L ₁ ² ) with respect to L ₁ , where L ₁ and V ₁ / V ₂ The relationship with
It is expressed by a relational curve such as 2 (b), and similarly, if the output ratio V ₁ / V ₂ is obtained, L is independent of the surface potential V _S.
It is possible to uniquely determine ₁ .

By using L ₁ thus uniquely obtained, the output value of V ₁ or V ₂ is corrected from the relationship between the known output value of V ₁ or V ₂ and the measurement distance L, further is known the surface potential V _S and the output value V ₁ or a surface potential corresponding to the output value of V ₁ or V ₂ which has been corrected from the relationship between V ₂ V _S
By obtaining, it becomes possible to accurately obtain the surface potential of the object to be measured. In addition, the obtained L ₁ is V ₁ or V ₂
By substituting it into the output formula (formula (39) or (40)) and calculating V _S , the surface potential of the measured object can be accurately obtained.

Also in the case of this example, the measurement distance correction unit 49 corrects the measurement distance from the two or more output signals obtained by the first and second output signal detection units 32 and 33 by using the configuration shown in FIG. By doing so, it becomes possible to obtain an accurate output signal corresponding to the surface potential of the DUT.

Further, as shown in FIG. 25, in order to detect the surface potential, the detection position of the measurement electrode is changed while periodically changing the measurement electrode in the direction of the measurement object so that the distance between the measurement electrode and the measurement electrode is changed. As means for making the distance different, a drive voltage (drive current) waveform as shown in FIG. 23 (a) and a drive voltage (drive current) waveform as shown in FIG. 23 (b) are superimposed on the electrode vibrating part described above. Voltage waveform in open state (Fig. 23 (c))
Is possible by applying to each variation means. The waveform of the applied voltage (applied current) is shown in FIG.
Not limited to the sinusoidal waveform shown in (c), the waveform for varying the measuring electrode (rectangular waveform, trapezoidal waveform, triangular waveform,
Waveforms that fluctuate cyclically or aperiodically, such as sawtooth and pulse waves, and waveforms (sine wave (FIG. 27), rectangular wave (FIG. 28), triangle wave (FIG. 29) for changing the detection position of the measurement electrode. ), A sawtooth waveform (FIG. 30), a trapezoidal waveform (FIG. 31), or other waveforms that fluctuate periodically or aperiodically) can be used.

Furthermore, as another example, FIG. 34 is an explanatory diagram relating to a method of detecting a plurality of output signals having different output values from one measurement electrode and correcting the output fluctuation of the potential detection signal. This is a method of obtaining two or more output signals described above, in which the measuring electrode is periodically changed in the direction of the object to be measured in order to detect the surface potential, and at that time, the change width of the change is made different and each change is made. It shows a method of obtaining the surface potential of the measured object from the output signal corresponding to the width. The principle of detecting the surface potential of the object to be measured is the same as that shown in FIG.

As a method of changing the measuring electrodes, the method shown in FIG.
The surface potential can be detected by using a periodic or aperiodic variation such as a sine wave, a rectangular wave, a trapezoidal wave, a triangular wave, a sawtooth wave, or a pulse wave as shown in FIG.

In FIG. 34, the output signal when the measuring electrode is arranged at a distance L apart from the object to be measured and the measuring electrode is varied in the direction of the object to be measured with a change width of ΔL ₁ is V ₁ ,
Letting V _{2 be} the output signal when changing with the change width of ΔL ₂ , the output signal is almost proportional to the change width of the change of the measuring electrode, and therefore the output values corresponding to V ₁ and V ₂ in FIG. Are obtained. In this case, by varying the fluctuation range of the measurement electrode periodically or aperiodically, a sine wave (FIG. 27), a rectangular wave (FIG. 28), a triangular wave (FIG. 29), a sawtooth wave (FIG. 30) , Trapezoidal wavy (Fig. 31)
It is possible to obtain signals having different output values that fluctuate in the same manner.

Next, by using the different output values V ₁ and V ₂ obtained as described above, the measurement distance L is uniquely determined on the contrary without depending on the surface potential V _{S of the} object to be measured. First, in the case of the vibration capacitance type, the rate of change α ₀ of the capacitance C ₀ between the object to be measured and the measurement electrode is determined by the change width Δ of the variation of the measurement electrode.
With respect to L ₁ and ΔL ₂ , β ₁ = ΔL ₁ / (L−ΔL ₁ ) ... (43) β ₂ = ΔL ₂ / (L−ΔL ₂ ) ... (44)

Therefore, the output equations of the output signals V ₁ and V ₂ are: V ₁ = A ₀ · β ₁ · ω · C using the equations (1), (5), (43) and (44) ₀ · V _S · cos ωt = A ₀ · ΔL ₁ / (L−ΔL ₁ ) · ω · ε _air · (S / L) · V _S · cos ωt (45) V ₂ = A ₀ · β ₂ · ω · denoted as _{C 0 · V S · cosωt =} a 0 · ΔL 2 / (L-ΔL 2) · ω · ε air · (S / L) · V S · cosωt ... (46). In order to find L unconditionally without depending on the surface potential V _S , V ₁ and V can be obtained from the equations (45) and (46).
The output ratio with ₂ should be obtained.

For example, when the output ratio is V ₂ / V ₁ ,
V ₂ / V ₁ is V ₂ / V ₁ = ΔL ₂ · (L-ΔL ₁ ) / [ΔL ₁ · (L-ΔL ₂ )] = F (L) (47), which is a linear function of L It is represented by F (L). At this time, the relationship between L and V ₂ / V ₁ is represented by a relationship curve as shown in FIG. 35 (a), and if the output ratio V ₂ / V ₁ is obtained, L is not dependent on the surface potential V _S. It is possible to ask uniquely.

When the output ratio is V ₁ / V ₂ , V
₁ / V _2, the primary with respect to _{V 1 / V 2 = ΔL 1} · (L-ΔL 2) / _{[ΔL 2 · (L-ΔL 1} ) ] = F (L) ... (48 ) , and the likewise L It is represented by a function F (L), and the relationship between L and V ₁ / V ₂ is represented by a relationship curve as shown in FIG. Therefore, similarly, the output ratio V ₁ / V
_{If 2} is obtained, L can be uniquely obtained without depending on the surface potential V _S.

By using L uniquely obtained in this way, the output value of V ₁ or V ₂ is corrected from the relationship between the known output value of V ₁ or V ₂ and the measurement distance L, and the known value is further calculated. V ₁ where the surface potential V _S is corrected from the relation between the output value V ₁ or V ₂
Alternatively, by obtaining the surface potential V _S corresponding to the output value of V ₂ , the surface potential of the measured object can be accurately obtained. In addition, the obtained L is output formula of V ₁ or V ₂ ((4
It is also possible to uniquely determine the surface potential of the object to be measured by substituting it into Eq. 5) or (46) and obtaining V _S. In the case of this example as well, with the configuration shown in FIG. 33, it is possible to correct the measurement distance from two or more output signals and obtain an accurate output signal corresponding to the surface potential of the measured object.

Furthermore, as shown in FIG. 34, the means for periodically varying the measuring electrode in the direction of the object to be measured in order to detect the surface potential and varying the variation range is as shown in FIG.
This is possible by applying a voltage (current) having a voltage (current) waveform in a state in which the magnitude of the drive voltage (driving current) is different as shown in 6 (a).

As shown in FIG. 36B, the voltage (current) of the voltage waveform with the frequency of the drive voltage (driving current) varied while the magnitude of the driving voltage (driving current) is constant. It is also possible to apply it.

Further, in each of the driving voltage (driving current) waveforms shown in FIGS. 36A and 36B, the voltage (current) in a state in which the magnitude of the driving voltage (driving current) and its frequency are made different at the same time It is also possible to apply a waveform voltage (current) to each varying means.

The applied voltage (applied current) waveform is not limited to the sinusoidal waveform shown in FIGS. 36 (a) and 36 (b), but a waveform for changing the measuring electrode (rectangular wave, trapezoidal wave). , A waveform that fluctuates periodically or aperiodically such as a triangular waveform, a sawtooth waveform, and a pulse waveform) and a waveform for varying the variation width of the measurement electrode variation (sine waveform (FIG. 27),
An applied voltage waveform that follows a periodic or aperiodic waveform such as a rectangular wave (FIG. 28), a triangular wave (FIG. 29), a sawtooth wave (FIG. 30), a trapezoidal wave (FIG. 31) can be used. .

[0194]

As described above, according to the surface potential measuring device (Claim 1) of the present invention, the vibration which is electrically independent of the non-measuring body at a position spaced from the non-measuring body by a predetermined distance. Since the member is used as a measurement electrode, the SN ratio and reliability can be improved, and stable and highly sensitive surface potential can be detected, and a compact and inexpensive surface potential measuring device with a simple configuration can be obtained. You can

Further, according to the surface potential measuring device (Claim 2) of the present invention, since the potential signal of the measuring electrode by the vibrating member is taken out from the node portion or the fixed portion of the vibrating member, it is possible to stably output from the measuring electrode. The potential signal can be taken out, the surface potential can be detected with high reliability, and a compact and inexpensive surface potential measuring device can be obtained with a simple configuration.

According to the surface potential measuring device (claim 3) of the present invention, the vibrating member is vibrated to change the electrostatic capacitance formed between the object to be measured and the measuring electrode of the vibrating member. Since the electromagnetic coil is used as the capacity changing means, S
The N ratio and reliability can be improved, and stable and highly sensitive surface potential can be detected, and a compact and inexpensive surface potential measuring device can be obtained with a simple configuration.

According to the surface potential measuring device of the present invention (claim 4), the vibrating member is vibrated to change the electrostatic capacitance formed between the object to be measured and the measuring electrode of the vibrating member. Since the voice coil is used as the capacity changing means,
The SN ratio and reliability can be improved, stable and highly sensitive surface potential detection can be performed, and a compact and inexpensive surface potential measuring device can be obtained with a simple configuration.

According to the surface potential measuring device of the present invention (Claim 5), the vibrating member is vibrated in the direction opposite to the object to be measured and is formed between the object to be measured and the measuring electrode of the vibrating member. The electrostatic potential of the measuring electrode of the vibrating member, which is induced in response to the surface potential of the object to be measured and changes with the change of the electrostatic capacitance, is detected, and at least two of the detected signals are detected. Since the output detection means for detecting the above output signal and the surface potential deriving means for deriving the surface potential of the object to be measured from the output signal are provided, a highly accurate surface without the potential output signal depending on the measurement distance. An inexpensive surface potential measuring device capable of detecting the potential and having a simple structure can be obtained.

Further, according to the surface potential measuring device of the present invention (claim 6), since the vibrating member is composed of a plurality of conductive layers with the insulating layer interposed therebetween and is used as one vibrating member, it is stable. The surface potential can be detected with high reliability, and an inexpensive surface potential measuring device can be obtained with a simple structure.

According to the surface potential measuring device of the present invention (Claim 7), since the vibrating member is an insulator, and one vibrating member having a plurality of conductor regions provided on the surface is used. Thus, it is possible to stably and reliably detect the surface potential, and an inexpensive surface potential measuring device can be obtained with a simple configuration.

According to the surface potential measuring device of the present invention (claim 8), the vibrating member is composed of a plurality of conductive layers with the insulating layer interposed therebetween, and the voice coil is driven by the node or the fixed portion of the vibrating member. Since a signal is applied, stable and highly reliable detection of the surface potential can be achieved, and an inexpensive surface potential measuring device can be obtained with a simple configuration.

Further, according to the surface potential measuring device of the present invention (claim 9), a vibrating member is provided in which a plurality of conductor regions are provided on the surface of an insulator, and the vibrating member includes a node or a fixed portion. Since the drive signal of the voice coil is applied, stable and highly reliable detection of the surface potential can be achieved, and an inexpensive surface potential measuring device can be obtained with a simple configuration.

Further, according to the surface potential measuring device of the present invention (claim 10), the height of the free end of the vibrating member is made different in the direction close to the direction of the object to be measured. It is possible to obtain a stable and highly reliable detection of the surface potential and to obtain an inexpensive surface potential measuring device with a simple configuration.

Further, according to the surface potential measuring device of the present invention (claim 11), a high magnetic permeability member is arranged around a permanent magnet used for a voice coil to form a permanent magnet and a magnetic circuit. Since the driving member is driven by the drive member, the vibrating member can be efficiently driven with a small electric power, and a surface potential measuring device capable of detecting the surface potential with high accuracy can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a surface potential measuring device according to a first embodiment of the present invention.

2A and 2B are explanatory views showing a schematic configuration in the case where a voice coil is used for a vibration driving unit of the surface potential measuring device shown in FIG. 1, in which FIG. 2A is a side view and FIG. 2B is a top view.

FIG. 3 is an explanatory diagram showing a schematic configuration in the case where a tuning fork-shaped vibrating member is used as the vibrating member of the surface potential measuring device shown in FIG.

4A and 4B are explanatory views showing a schematic configuration in the case where a plunger vibration type electromagnetic coil is used for a vibration driving unit of the surface potential measuring device shown in FIG. 1, and FIG. , (B) show the state of being applied to a tuning fork-shaped vibrating member.

5A and 5B are explanatory views showing a schematic configuration in the case where a voice coil is used for the vibration driving unit of the surface potential measuring device shown in FIG. 1, and FIGS. 5A to 5F show configuration examples of the voice coil. .

6 is an explanatory diagram showing a configuration in the case where a voice coil is used in a vibration driving unit of the surface potential measuring device shown in FIG.

FIG. 7 is an explanatory diagram showing a configuration of a vibrating member of the surface potential measuring device shown in FIG.

8 is an explanatory diagram showing a configuration of a vibrating member of the surface potential measuring device shown in FIG.

9 (a) and 9 (b) are explanatory views showing a configuration of a vibrating member of the surface potential measuring device shown in FIG. 1, and FIGS. 9 (a) and 9 (b) show vibrating members having different shapes.

10 is an explanatory diagram showing a configuration in the case where a voice coil is used in a vibration driving unit of the surface potential measuring device shown in FIG.

11 is an explanatory diagram showing a configuration of a voice coil when the voice coil is used in the vibration driving unit of the surface potential measuring device shown in FIG.

12 is an explanatory diagram showing a configuration of a voice coil when the voice coil is used in the vibration driving unit of the surface potential measuring device shown in FIG.

13 is an explanatory diagram showing a configuration of a voice coil in the case where a voice coil is used in a vibration driving unit of the surface potential measuring device shown in FIG.

FIG. 14 is an explanatory diagram showing a schematic configuration of a surface potential measuring device according to a second embodiment of the present invention.

15A and 15B are explanatory views showing a schematic configuration in the case where a voice coil is used for a vibration driving unit of the surface potential measuring device shown in FIG. 14, FIG. 15A being a side view and FIG.

16 is an explanatory diagram showing a schematic configuration when a tuning fork-shaped vibrating member is used as the vibrating member of the surface potential measuring device shown in FIG.

FIG. 17 is an explanatory diagram showing a schematic configuration in the case where a voice coil is used in the vibration driving unit of the surface potential measuring device shown in FIG. 14, and FIGS. 17 (a) to 17 (f) show configuration examples of the voice coil. .

FIG. 18 is a block diagram showing a schematic configuration of a surface potential measuring device according to a second embodiment of the present invention.

FIG. 19 is a waveform diagram showing how the vibrating member vibrates in the surface potential measuring device shown in FIG. 18.

20 is a graph showing an output signal of the surface potential measuring device shown in FIG.

FIG. 21 is a block diagram showing a schematic configuration of a surface potential measuring device according to a second embodiment of the present invention.

FIG. 22 is a block diagram showing a schematic configuration of a surface potential measuring device according to a second embodiment of the present invention, including (a) to (f).
Shows a plurality of configuration examples.

23 is a diagram for explaining an example of a method of creating a voltage for driving a measurement electrode (vibrating member) in the surface potential measuring device shown in FIG.

FIG. 24 is an explanatory diagram regarding a method of detecting a plurality of output signals having different frequencies from one measurement electrode and correcting the output fluctuation of the potential detection signal in the second embodiment.

FIG. 25 is an explanatory diagram regarding a method of correcting a plurality of output signals having different output values from one measurement electrode and correcting the output fluctuation of the potential detection signal in the second embodiment.

FIG. 26 is a diagram showing an output signal when the measuring electrode (vibrating member) is displaced in the method shown in FIG. 25.

27 is a diagram showing an output signal when the measuring electrode (vibrating member) is periodically changed in the method shown in FIG.

28 is a diagram showing an output signal when the measuring electrode (vibrating member) is periodically changed in the method shown in FIG.

29 is a diagram showing an output signal when the measuring electrode (vibrating member) is periodically changed in the method shown in FIG. 25.

30 is a diagram showing an output signal when the measuring electrode (vibrating member) is periodically changed in the method shown in FIG. 25.

FIG. 31 is a diagram showing an output signal when the measuring electrode (vibrating member) is periodically changed in the method shown in FIG. 25.

32A and 32B show the relationship between the ratio of the output signal and the distance when the distance between the measuring electrode (vibrating member) and the object to be measured is changed in the method shown in FIG. 25. It is a figure.

FIG. 33 is a block diagram showing an example of a suitable signal detection circuit of the surface potential measuring device according to the second embodiment of the present invention.

FIG. 34 is an explanatory diagram related to a method of detecting a plurality of output signals having different output values from one measurement electrode and correcting the output fluctuation of the potential detection signal.

35 (a) and (b) show the relationship between the ratio of the output signal and the distance when the distance between the measuring electrode (vibrating member) and the ratio measuring body is changed in the method shown in FIG. It is a figure.

FIG. 36 is a diagram showing a waveform of a voltage (current) applied to a vibration drive unit that periodically displaces a measurement electrode (vibration member).

FIG. 37 is a block diagram showing a configuration of a conventional surface potential measuring device, FIG. 37 (a) shows a chopper type surface potential measuring device, and FIG. 37 (b) shows a vibration capacitance type surface potential measuring device. There is.

[Explanation of symbols]

 1 Measurement Electrode 2 Object to be Measured 3 Chopper Electrode 4 Potential Signal Detection Section 5 Signal Amplification Section 6 Surface Potential Measuring Device 7 Cantilevered Vibration Member 8 Vibration Drive Section 9 Potential Sensing Surface 10 Fixed Section 11 Fixed End 12 Voice Coil 13 Vibration member (leaf spring) 14 Shield case 15 Potential measurement window 16 Solenoid coil 17 Permanent magnet 18 Signal detection part 19 Detection signal line 20 Drive signal line 21 Potential signal line 22 Tuning fork vibrating member 23 Node part 24 Electromagnetic coil part 25 Plunger Type electromagnetic coil 26 Insulating layer 27 Conductive layer 28 Conductor region 29 High permeability member 30 Air gap 31 Magnetic circuit 32 First output signal detector 33 Second output signal detector 34 Third output signal detector 35 Output corrector 36 Measuring distance detection unit 37 First calculation unit 38 Second calculation unit 39 Third calculation unit 40 Fourth calculation unit 41 Fifth calculation 42 sixth arithmetic unit 43 seventh arithmetic unit 44 the eighth arithmetic unit 45 a ninth arithmetic unit 46 tenth arithmetic unit 47 first 11 computation unit 48 signal amplifier 49 measuring distance correcting unit

Claims (11)

[Claims] 1. A measurement electrode comprising a vibrating member provided at a position spaced apart from the measurement object by a predetermined distance and electrically independent of the measurement object, and the measurement electrode is vibrated to produce the measurement object. And a capacitance changing means for changing the electrostatic capacitance formed between the measuring electrode composed of a vibrating member and the measuring electrode, and changing with the change of the electrostatic capacitance induced corresponding to the surface potential of the measured object. 2. A surface potential measuring device comprising: a potential detecting unit that detects a potential of the measuring electrode; and a surface potential deriving unit that derives a surface potential of the measured object from a detection signal of the potential detecting unit. 2. The surface potential measuring device according to claim 1, wherein a potential signal of the measuring electrode is taken out from a node portion or a fixed portion of the vibrating member. 3. The surface potential measuring device according to claim 1, wherein the measuring electrode is vibrated, and an electromagnetic coil is used as a capacitance changing means for changing a capacitance formed between the object to be measured and the measuring electrode. A surface potential measuring device characterized by using. 4. The surface potential measuring device according to claim 1, wherein the voice coil is used as a capacitance changing unit that vibrates the measuring electrode and changes a capacitance formed between the object to be measured and the measuring electrode. A surface potential measuring device characterized by using. 5. The surface potential measuring device according to claim 1, wherein at least 2 is detected from the detection signal of the potential detecting means.
A surface potential measuring device comprising an output detecting means for detecting one or more output signals. 6. The surface potential measuring device according to claim 1, wherein the vibrating member is composed of a plurality of conductive layers with an insulating layer interposed therebetween. 7. The surface potential measuring device according to claim 1, wherein the vibrating member is constituted by providing a plurality of conductor regions on a surface of an insulator. 8. The surface potential measuring device according to claim 4, wherein the vibrating member is composed of a plurality of conductive layers with an insulating layer interposed, and a drive signal of the voice coil is applied from a node or a fixed portion of the vibrating member. A surface potential measuring device characterized by: 9. The surface potential measuring device according to claim 4, wherein a plurality of conductor regions are provided on a surface of an insulator to configure the vibrating member, and a node or a fixed portion of the vibrating member is used to form the voice coil. A surface potential measuring device characterized by applying a drive signal. 10. The surface potential measuring device according to claim 1, wherein one end of the vibrating member is fixed and the other end of the vibrating member is formed so as to be close to the object to be measured. measuring device. 11. The surface potential measuring device according to claim 4, wherein a high magnetic permeability member is arranged around a permanent magnet used for the voice coil, and a magnetic circuit is formed with the permanent magnet to form the vibrating member. A surface potential measuring device characterized by being driven.