JPH05312873A - Surface potential and shape measuring apparatus - Google Patents

Abstract

PURPOSE:To enable the measurement of surface potential and shape with high accuracy and high responsiveness by controlling the amplitude of alternating voltage in such a way that electrostatic force at the time of alternating voltage superimposed on d.c. voltage being deflected to the positive side or the negative side or the sum of the electrostatic force is constant. CONSTITUTION:Alternating voltage V8 is applied to an exciting device PZT7 so as to detect (12) electrostatic force Fs acting between a probe 3 and the surface potential Vs of a measured object 2. The output V obtained by adding (31) the electrostatic force Fs is compared (32) with the reference value V13, and a high band component signal WM is separated (34) from the output V15 obtained by integrating the output V obtained by comparison and fed back as a control signal to the voltage source 17 for generating alternating voltage V4. The amplitude of the voltage V4 is controlled in such a way that the electrostatic force Fs at the time of the voltage V4 being deflected to the positive side or the negative side or the sum of two electrostatic force Fs is constant, and in this state, the voltage V4 is added (18) to d.c. voltage V9 and amplified (19) to output voltage V6. Accordingly, the tip voltage of the probe 3 also becomes the corresponding potential so as to enable simultaneous and independent measurement even if the fluctuation of the surface potential Vs and the fluctuation of distance caused by the irregular surface are generated simultaneously.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface potential and shape measuring instrument used for measuring the potential distribution on the surface of a photosensitive drum in an electrophotographic apparatus, measuring the toner shape or toner charge distribution, or picking up an electrostatic memory. Regarding

[0002]

2. Description of the Related Art Generally, a printed image in an electrophotographic process is based on an electrostatic latent image formed on a photoconductor. Therefore, in the electrophotographic method, it is important to know the state of the electrostatic latent image in order to evaluate and analyze the printing process such as charging, exposure, and development, and the photoconductor.

Since static electricity has a high voltage but a small amount of charge, static electricity leaks through the voltmeter when the electrostatic potential is measured by a general contact electrometer. Causes measurement problems. Therefore, it is said that a non-contact type electrometer, that is, a surface electrometer is suitable for measuring the electrostatic potential.

In consideration of these points, an electrostatic latent image measuring device capable of directly measuring an electrostatic latent image formed on a photoconductor is an electrophotographic society journal, Vol. 30, No. 2 (1991). ), "High-resolution measurement of electrostatic latent image on photoconductor" (p.
123-130) (referred to as the first conventional example). This is a so-called DC amplification type, in which the measuring electrode is brought close to the object to be measured (photoreceptor), the electric charges induced in the measuring electrode at that time are converted into a voltage by the measuring capacitor, and an amplifier with a high input impedance is used. It is designed to be amplified by.

Here, the probe for measuring the sample surface potential is determined by the distance between the tip of the probe and the sample surface.
It causes a large error in the measurement result. Therefore, in such a surface potential measuring device, the one in which the distance between the sample surface and the probe is kept constant is disclosed in, for example, the document “TECHNICAL DIGEST OF THE 9TH SENSORSYMPOS”.
IUM, 1990, pp, 129-132 ', "Image Charge Se"
nsing by Scanning Electrometer ”(referred to as a second conventional example), in which a pair of laser diode and PSD (semiconductor position detector) are provided on both sides of the probe to irradiate the sample surface with laser light. The distance between the probe tip and the sample surface is measured according to the position where the reflected light returns to the PSD, and feedback control is applied to the actuator that moves the entire probe from this measurement result, and the distance between the probe tip and the sample surface is kept constant. It is intended to be.

However, in the case of the first conventional example, a shield case is required in order to prevent the current from flowing into the measuring capacitor through the stray capacitance, and the probe itself cannot be miniaturized. A device for keeping the distance between the measurement electrode and the photoconductor constant in order to keep the stray capacitance constant (that is, the second conventional method). A gap sensor or a gap controller as in the example is required, and there is a problem that the device becomes large and complicated.

Therefore, a surface electrometer which facilitates miniaturization and arraying of probes has been proposed by the present applicant as Japanese Patent Application No. 3-316872 (first proposal example). This has means for detecting an electrostatic force generated between the electric charge existing on the surface of the object to be measured and the probe, and the potential of the probe is adjusted so that the electrostatic force becomes zero or almost zero. The surface potential is controlled to be equal, and the potential of the probe at this time is converted to obtain the surface potential measurement result.

An example of the structure is shown in FIG. First, the substrate 1a
An electric charge Q is present on the surface of the sample 2 which is a measurement object by laminating the photoconductor 1b on the top, and a potential difference (surface potential) V _S is generated between the sample 2 and the ground GND. Such a photoreceptor 1b
A conductive probe 3 is provided in close proximity to the surface. The probe 3 is provided with a pair of electrodes 5, 6 with respect to the fixed base 4.
A piezoelectric cantilever having an edge, a PZT 7 in this case, and an electrically conductive cantilever 9 whose one end is fixedly supported via an insulating film 8 is attached to the lower end of the tip. That is, the probe 3 is displaceably supported at the tip end side thereof in a shape of the cantilever 9 as a leaf spring, and the probe 3 and the cantilever 9 are electrically connected. There is. The PZT7 has electrodes 5,
An AC voltage V ₈ is applied from the driving power supply 10 via 6, and the PZT 7 is configured to vibrate at the frequency of the AC voltage V ₈ . This frequency is assumed to vibrate at the natural vibration frequency f ₀ of the mechanical vibration of the cantilever 9.

On the other hand, a mirror 11 is fixed to the rear surface of the probe 3 of the cantilever 9, and the probe 3 and the photosensitive member 1b are moved through the displacement of the tip of the cantilever 9 using this mirror 11. An optical lever displacement detector 12 is provided as an electrostatic force detecting means for detecting an electrostatic force acting between the surface potential V _s and the surface potential V s.
This optical lever displacement detector 12, together with this mirror 11,
A laser diode 13 for irradiating the mirror 11 portion with laser light, and a position detection photodiode (PSD) 1 for receiving reflected light at a position angularly displaced according to the displacement of the mirror 11 portion.
4 and. The output of the PSD 14 is output by the preamplifier 15 as an electric signal V ₀ representing vibration.

Therefore, when an electrostatic force (electrostatic attraction) acts between the tip of the probe 3 and the surface potential V _S of the photoconductor 1b, the spring constant of the cantilever 9 is equivalently changed by the force. It has been done. As a result, the resonance point of the cantilever beam 9 is displaced, but since the cantilever beam 9 is forcibly vibrated by the PZT 7 at the natural frequency f ₀ of the cantilever beam 9, its vibration amplitude becomes small. Such a decrease in the vibration amplitude is regarded as a decrease in the amount of displacement of the tip of the cantilever 9 and the optical lever method displacement detector 12
Captured by. That is, the displacement detection by the optical lever displacement detector 12 corresponds to the detection of the electrostatic attractive force applied to the probe 3.

Further, a potential control means 16 for variably controlling the potential of the probe 3 based on the output V ₀ of the optical lever displacement detector 12 is provided. This potential control means 16
Is a DC voltage V ₉ = V _S / G ₁ set in advance
The adder 18 with a gain of 0 that superimposes the trapezoidal waveform AC voltage V ₄ and the output voltage V ₅ of the adder 18 are amplified and the output voltage V ₆ is applied to the probe 3 (cantilever 9). Power amplifier 19 with gain G ₁ and the preamplifier 15
AM demodulator 2 for converting the amplitude of the output V ₀ of the DC voltage into the DC voltage V ₁
0, sample hold circuits 21 and 22 that sample and hold this DC voltage V ₁ at a predetermined timing, and a differential amplifier that takes the difference between the voltages V ₂₁ and V ₂₂ obtained from these sample hold circuits 21 and _22. 23 and an integrator 24 having an inverting integrator configuration for integrating the output voltage V ₃ of the differential amplifier 23 and increasing / decreasing the DC voltage V ₉ are connected in a loop. Here, the sync signal V ₇₂ from the power source 17 to the sample and hold circuit 22
Is taken out in synchronism with the AC voltage V ₄ , and the synchro signal V ₇₁ inverted by the inverter 25 is given to the sample hold circuit 22. Further, a voltmeter 26 serving as a potential measuring means for measuring the value of the DC voltage V ₉ is provided.

However, in the case of the surface electrometer according to the configuration of the first proposed example, the electrostatic force acting between the probe 3 and the surface of the photosensitive member 1b has a high potential difference between the surface potential and the probe 3. When the distance between the probe 3 and the surface of the photoconductor 1b becomes shorter, the surface potential and the surface shape cannot be measured simultaneously and independently. There is inconvenience.

That is, when measuring the surface potential distribution of a drum-shaped photoconductor for an actual plain paper copying machine (PPC),
While the photoconductor is rotated, the probe is fixed and supported on the apparatus main body side, but the photoconductor generally has a drum center eccentric on the order of 100 μm, or the photoconductor surface shape is not always a mirror surface. No organic photoconductor (O
In the case of (PC), there are pigment particles and unevenness due to scratches caused by cleaning and the like. Therefore,
The distance between the surface of the photoconductor and the probe changes depending on the rotation of the photoconductor. In the case of the first proposed example method, the distance changes even if the surface potential of the photoconductor is uniform. It will be measured as a change in potential. Also,
When the charge distribution on the toner particles is examined, as described above, since the toner usually has an uneven shape, it is necessary to measure the charge distribution and the surface shape at the same time.

Further, in the case of the second conventional example, if the unevenness of the sample surface is large, the laser beam is scattered and the beam spot diameter incident on the PSD becomes large, which deteriorates the distance measurement accuracy.

Further, when the sample is a photoconductor for PPC, there is a possibility that the photoconductor senses a laser beam and the charge on the surface of the photoconductor is discharged and disappears. Therefore, from this aspect, even when using a photoconductor or the like as the measurement target,
The surface potential and surface shape (distance) of the surface are controlled accurately without affecting the electric charge on the surface.
It is desired to be able to measure and.

A surface potential and shape measuring instrument considering such a point has been proposed by the present applicant as Japanese Patent Application No. 4-66871 (second proposal example). In order to measure the potential distribution and shape distribution of the sample surface of the measurement object, a DC bias voltage and an AC voltage superimposed on the DC bias voltage are applied to the conductive probe. The electrostatic attractive force acting between the probe and the sample surface when the AC voltage swings to the positive side with respect to the DC bias voltage and the static attraction acting between the probe and the sample surface when swinging to the negative side. The DC bias is controlled so that it becomes equal to the electromotive force, and the surface potential is measured from this DC bias voltage. On the other hand, the distance between the tip of the probe and the sample surface is controlled so that the sum of these electrostatic attractive forces becomes equal to the reference value. The distance control is performed by an actuator that moves the sample or the probe, and the sample surface shape is measured by measuring the distance at which this actuator operates.

[0017]

Here, in the case of the second proposed example, the actuator in the Z-axis direction is installed on the sample side, but when the sample to be measured is heavy, the Z-axis is mounted on the cantilever side. A shaft actuator will be provided. That is, the Z-axis actuator is provided between the fixed base and the cantilever beam vibrating piezoelectric element.

This method has the following drawbacks.

A. First, the method of measuring the vibration of the cantilever beam by an optical method has high accuracy, so it can be said that it is the best method when importance is attached to accuracy. However, when measuring the vibration of the cantilever beam by an optical method, if the cantilever beam is moved up and down according to the unevenness of the sample surface, the laser beam for vibration measurement will not hit the mirror of the beam or the position where it hits. Will be deviated, and the measurement accuracy will decrease. Also, moving the entire optical system by the Z-axis actuator is
Considering the weight, it is extremely difficult.

B. As a method to avoid this, instead of an optical method, a cantilever with a piezoresistive element,
By measuring the vibration of the cantilever beam by changing the resistance value of the piezoresistive element, there is a device in which an optical system is unnecessary and a Z-axis actuator is attached to the root portion of the cantilever beam.

However, the piezoresistive element method also has the following drawbacks.

A. The Z-axis actuator usually uses a combination of two actuators, one for coarse movement and one for fine movement,
For fine movement, a piezoelectric element such as PZT is generally used. However, although PZT is relatively excellent in the linearity between the applied voltage and the distance displacement, it has a hysteresis characteristic and has a problem in measurement accuracy.

B. Further, the PZT for fine movement is required to have a displacement of about 10 μm. Therefore, the laminated PZT is used. However, since the actuator having such a structure is heavier than the vibration PZT, the actuator is mounted on the fixed base, and the vibration PZT and the cantilever are arranged in this order. In other words, the PZT for fine movement is the P for vibration
It will move the ZT and the cantilever. Also, for fine movement P
ZT is displaced following the unevenness on the sample surface. Therefore,
If there are sharp protrusions or depressions on the surface, the fine-movement PZT will abruptly displace / move the cantilever. here,
The frequency component of such displacement often includes the resonance frequency component of the cantilever. Accordingly, this causes ringing (a phenomenon in which the cantilever resonates while being attenuated) vibration. At this time, since the cantilever is originally vibrated by the vibrating PZT in the vicinity of the resonance point, such ringing vibration is mixed into the cantilever vibration and the measurement accuracy is deteriorated.

C. Since PZT is an electrically capacitive load, it has poor responsiveness at a frequency of more than 10 kHz due to charge and discharge of the capacity. Further, in driving at a frequency higher than this, the current or the PZT itself is damaged due to the loss due to the capacitive current. Therefore, when measuring the surface shape of the sample, it is not possible to keep the distance between the sample surface and the probe at the tip of the cantilever constant by following the unevenness of the surface that may appear at a frequency higher than this. As a result, the measurement accuracy in this frequency band deteriorates.

Therefore, there is a demand for a surface potential and shape measuring instrument which solves such a problem and has both high measurement accuracy and high response speed.

By the way, in some samples for measuring the surface potential or shape, there is a waviness of about 100 μm on the sample surface. In this case, during measurement, the sample surface fluctuates with an amplitude of about 100 μm at a repetition period of about several Hz. On the other hand, the height and width of the sample surface are several to several tens of μ.
There is a concave and convex shape of about m, which causes an up and down with an amplitude of several to several tens of μm at a repetition frequency of several kHz or more.

In this respect, according to the second proposed example, the feedback signal to the actuator is separated by the frequency band with respect to such two types of distance variation between the sample surface and the probe, and each frequency component is divided into frequency components. I am trying to control a suitable actuator. More specifically, a voice coil is used for large low frequency displacement, and PZT is used for small high frequency displacement. However, in this system, since the PZT fine movement actuator is used, there are some drawbacks as described above.

Therefore, it is desired that the surface potential or shape of a measuring object having a large undulation can be measured during measurement without lowering the measurement accuracy and resolution.

[0029]

According to a first aspect of the present invention, a conductive probe is provided to face an object to be measured, and a static force acting between the probe and the surface potential of the object is measured. An electrostatic force detecting means for detecting electric power is provided, and an electrostatic force when the alternating voltage is swung to the positive side and an electrostatic force when the alternating voltage is swung to the negative side by superposing the alternating voltage on the direct current voltage with respect to the probe. A potential control unit that varies the DC voltage so as to be equal is provided, and a DC potential measurement unit that measures the potential of the DC voltage of the probe and an electrostatic force when the AC voltage swings to the positive side are constant. Or, the electrostatic force when swinging to the negative side becomes constant,
Alternatively, an amplitude control means for controlling the amplitude of the AC voltage is provided so that the sum of the electrostatic force when swung to the positive side and the electrostatic force when swung to the negative side is constant, and the potential of the AC voltage is set. An AC potential measuring means for measuring was provided.

According to the second aspect of the present invention, a probe held at the tip of the cantilever vibrated by the vibrating device is provided, and the displacement for detecting the vibration amplitude of the probe which changes according to the electrostatic force is provided. An electrostatic force detecting means by a detector is provided, and the electrostatic force when the AC voltage is swung to the positive side and the electrostatic force when the AC voltage is swung to the negative side are equal to each other by superposing the AC voltage on the DC voltage with respect to the probe. To provide a potential control means for varying the DC voltage,
A DC potential measuring means for measuring the potential of the DC voltage of the probe is provided, and the AC voltage has a constant amplitude of the probe when swung to the positive side, or the above when swung to the negative side. Vibration by the vibrating device such that the amplitude of the probe becomes constant, or the sum of the amplitude of the probe when swung to the positive side and the amplitude of the probe when swung to the negative side becomes constant. An amplitude control means for controlling the amplitude is provided, and a vibration amplitude measuring means for measuring the vibration amplitude is provided.

According to a third aspect of the present invention, instead of the amplitude control means and the vibration amplitude measuring means in the second aspect of the invention, frequency control means for controlling the vibration frequency by the vibrating device and this vibration frequency are measured. A vibration frequency measuring means is provided.

In the invention described in claim 4, as in the invention described in claim 1, the probe, the electrostatic force detection means, the potential control means and the DC potential measurement means are provided, and the AC voltage is swung to the positive side. Static force is constant, or the electrostatic force when it swings to the negative side is constant, or the sum of the electrostatic force when it swings to the positive side and the electrostatic force when it swings to the negative side is constant. And a separating means for separating the feedback signal for controlling so that the amplitude of the AC voltage is controlled by the feedback signal of a part of the separated frequency band. A distance control means having an actuator for controlling the distance between the object to be measured and the probe by a feedback signal excluding the signal in the part of the frequency band for controlling the amplitude of the AC voltage separated by Of the actuator It provided a displacement measuring means for measuring a position quantity.

According to the fifth aspect of the invention, similarly to the second aspect of the invention, the probe, the electrostatic force detecting means, the potential control means and the direct current potential measuring means are provided, and the alternating voltage is swung to the positive side. When the amplitude of the probe becomes constant, or when it swings to the negative side, the amplitude of the probe becomes constant, or when it swings to the positive side and when it swings to the negative side Of the vibrating device by a feedback signal of a partial frequency band separated by a separating means for separating a feedback signal by a frequency band for controlling so that the sum with the amplitude of the probe becomes constant. An amplitude control means for controlling the vibration amplitude is provided, a vibration amplitude measuring means for measuring the vibration amplitude is provided, and a signal in the partial frequency band for controlling the vibration amplitude by the vibrating device separated by the separating means is provided. Except for the return signal, the measurement object The distance control means having an actuator for controlling the distance between the probe provided, provided with displacement measuring means for measuring the displacement amount of the actuator.

According to the sixth aspect of the invention, similarly to the third aspect of the invention, a probe, an electrostatic force detecting means, a potential control means and a DC potential measuring means are provided, and the AC voltage swings to the positive side. When the amplitude of the probe becomes constant, or when it swings to the negative side, the amplitude of the probe becomes constant, or when it swings to the positive side and when it swings to the negative side Of the vibrating device by a feedback signal of a partial frequency band separated by a separating means for separating a feedback signal by a frequency band for controlling so that the sum with the amplitude of the probe becomes constant. Provided with frequency control means for controlling the vibration frequency,
Provided with a vibration frequency measuring means for measuring this vibration frequency,
Distance having an actuator for controlling the distance between the object to be measured and the probe by a feedback signal excluding the signal in the part of the frequency band for controlling the vibration frequency by the vibrating device separated by the separating means Provided with control means,
Displacement measuring means for measuring the amount of displacement of the actuator is provided.

[0035]

According to the first, second and third aspects of the invention, since the vibration of the probe support member forming a part of the electrostatic force detecting means is measured, it is possible to perform measurement using an optical measuring method with high measurement accuracy. Becomes In addition, since it is not necessary to use a Z-axis actuator such as PZT, the measurement accuracy does not deteriorate due to its hysteresis characteristics and ringing of the probe support member due to the displacement of PZT. Furthermore, PZT, which is a capacitive load
Since it is not used, the measurement of the surface shape in the high frequency band can be sufficiently followed.

In addition, according to the present invention as defined in claims 4, 5 and 6, the potential of the AC voltage applied to the probe and the cantilever are used even in the measurement of the surface potential or the shape of the measuring object having a large undulation. It is possible to measure the surface shape using a simple proportional expression from the change in the vibration amplitude or the vibration frequency of the cantilever. That is, according to the first, second and third aspects of the present invention, since the amplitude variation value is not in a linear relationship with the distance between the surface of the object to be measured and the tip of the probe, the change in the parameter of the feedback signal for feedback is changed. It is not possible to obtain the distance variation in a linear form from the minutes, and when applying it to the measurement of the potential and shape of the surface of the measurement object with a large undulation of about 100 μm, it is necessary to obtain the distance variation using a complicated conversion formula. , This process becomes easy. Further, the measurement resolution decreases as the distance between the tip of the probe and the surface of the measuring object decreases, but regarding this point as well, the tip of the probe and the surface of the measuring object are brought close to each other by actuator control, and a substantially constant distance is obtained. Can be maintained and the measurement resolution does not decrease.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the invention described in claims 1 and 4 is shown in FIG.
Or, it demonstrates based on FIG. The same parts as those shown in FIG. 9 are designated by the same reference numerals. That is, basically, the probe 3 for the sample 2, the optical lever displacement detector 12 serving as the electrostatic force detecting means, the potential control means 16, and the electrometer 26 serving as the DC potential measuring means are used as they are in this embodiment. There is. However, the natural vibration frequency f ₀ of mechanical vibration related to the PZT 7 is a resonance point when the cantilever 9 receives no force other than the force excited by the PZT 7. Further, the probe 3 is held at the tip of a cantilever 9 supported by a voice coil 27 as a coarse actuator and a PZT 28 as a fine actuator with respect to the fixed base 4. The sample 2 side is held on the X and Y axis actuators 29.

Surface potential V _S of the tip of the probe 3 and the photosensitive member 1b
When the electrostatic force (electrostatic attractive force) due to the potential difference V between and acts, the spring constant of the cantilever 9 changes equivalently. As a result, the mechanical resonance point of the cantilever beam 9 is displaced, so that the vibration amplitude of the forced vibration due to the frequency of the AC voltage V ₈ is reduced.

Now, the resonance frequency f ₀ (resonance angular frequency ω
The vibration amplitude of the tip of the cantilever 9 when the cantilever 9 is vibrated in ₀ ) and no external force such as electrostatic attraction acts on the cantilever 9 is A ₀ . If x is the average distance between the tip of the probe 3 and the surface of the sample 2 (distance between the vibration center of the tip of the probe 3 and the surface of the sample 2), some physical force (electrostatic force, magnetic force or van der The change ΔA of the vibration amplitude of the cantilever beam 9 when F is applied to the tip of the probe 3 is approximately ΔA = a · A ₀ · ∂F / ∂x ……………… ……………………… It is represented by (1). However, a is a proportional constant.

In order to simplify the explanation, as schematically shown in FIG. 2, the tip of the probe 3 is considered to be a flat plate having an area S and faces the surface of the sample 2 in parallel. And In addition, the distance between the tip of the probe 3 and the surface of the sample 2 is x,
The potential difference between the two is V. Then, the force F acting between them
Is expressed by F = (b / 2) · V ² / x ² ………………………… (2). However, b is a proportional constant.

From the equation (2), ∂F / ∂x = −b · V ² / x ³ ………………………… (3) is obtained. Therefore, the change ΔA caused by the electrostatic force F
From equations (1) and (3), ΔA = −a · b · V ² / x ³ ………………………… (4). The vibration amplitude A at this time is A = A ₀ + ΔA = A ₀ −a · b · V ² / x ³ ……………… (5).

Such a decrease in vibration amplitude is caused by the cantilever beam 9.
It is captured by the optical lever displacement detector 12 as a decrease in the displacement of the tip. That is, the detection of the change in the displacement amount by the optical lever displacement detector 12 corresponds to the detection of the electrostatic attractive force applied to the probe 3.

Here, the output V ₀ of the optical lever displacement detector 12, and thus the preamplifier 15, becomes a voltage representing the vibration of the cantilever 9. Further, since the voltage V ₁ is obtained by converting the amplitude of the voltage V ₀ into a DC voltage, the voltage value is V ₁ = c · A = c · A ₀ −d · V ² / x ³ ... …………… It is expressed as (6). However, both c and d are proportional constants, and d = a · b.

Now, c · A ₀ = v ₀ ………………………………………… (7) dV ² / x ³ = Δv ………………………… …………………… (8), the voltage V ₁ is expressed by V ₁ = v ₀ −Δv ………………………………………… (9) ..

In addition, in the present embodiment, in addition to the configuration similar to the first and second proposed examples, an adder 31 for adding outputs V ₂₁ and V ₂₂ from the sample hold circuits 21 and ₂₂ is provided,
A differential amplifier 32 for comparing the output V ₁₀ from the adder 31 with a preset reference voltage (reference value) V ₁₃ is provided. An integrator 33 that integrates the output V ₁₄ of the differential amplifier 32 is provided. A bandpass filter 34 is provided as a separating means for separating the output V ₁₅ of the integrator 33 according to the frequency band. The bandpass filter 34 serves to separate the output V ₁₅ higher-band component signal V _H, the middle band component signal V _M, the third signal of the low-band component signal V _L. Of these separated signals, the high band component signal V _H is the voltage source 1 for generating the alternating voltage V _4.
7 is fed back as an amplitude control signal, the middle band component signal V _M is fed back as a control signal to the PZT 28 through the power amplifier 35, and the low band component signal V _L is fed through the power amplifier 36 to the coarse actuator. That is, it is fed back to the voice coil 27. Therefore, the feedback system of the high band component signal V _H constitutes the amplitude control means 37 for controlling the amplitude of the AC voltage V ₄ , and this output line serves as an AC potential measuring means for measuring the AC potential. A voltmeter 38 is connected. Further, the feedback system of the middle band component signal V _M and the low band component signal V _L constitutes the distance control means 39, and voltmeters 40 and 41 serving as displacement measuring means are connected to the respective output lines. ing.

In such a structure, as shown in FIGS.
The measurement operation of the surface potential V _S and the surface shape will be described with reference to the timing waveform diagram shown in FIG. First, for PZT7, see FIG.
An alternating voltage V ₈ is applied as shown in FIG.
The trapezoidal waveform AC voltage V ₄ shown in (b) is set to a frequency (preferably 1/10 or less) lower than the cycle of the AC voltage V ₈ and input to one input terminal of the adder 18. In addition, as shown in FIG. 7C, the voltage Vb becomes V _b / G _1.
It is assumed that ₉ is input to the other input terminal of the adder 18. Then, the output voltage V ₅ of the adder 18 is shown in FIG.
Further, the output voltage V ₆ amplified by the power amplifier 19 having the gain G ₁ is as shown in FIG. That is, mainly the DC voltage V _b V _b -V _p from V _b +
Voltage swings between V _p, i.e., the voltage waveform of the AC voltage V ₄ obtained by superimposing an AC voltage ₁ times G into a DC voltage V _b. Therefore, the tip potential of the probe 3 also becomes a potential corresponding to this output voltage V ₆ .

Now, the surface potential V _{S of the} photosensitive member 1b
Is V _S = V _Sa and the voltage V _b is V _b = V _Sa. Further, the amplitude of the AC voltage V ₄ of the voltage source 17 is also controlled by the high band component signal V _H , and it is assumed that V _p = V _pa . Then, at time t ₁ , the voltage V _{6 changes to the} voltage V _Sa.
It becomes larger by V _pa and becomes smaller by V _{pa at} time t ₂ . Therefore, the tip of the probe 3 in the times t _1, t _2, since there is a potential difference of V _pa between the surface potential V _Sa, as shown in FIG. (F), each F _1a, F _2a becomes static Receive power F _S. This is equivalent to the change in the spring constant of the cantilever 9 as described above, and the vibration amplitude of the cantilever 9, and thus the probe 3, is reduced. Therefore, the amplitude signal V ₀ obtained through the optical lever displacement detector 12 becomes small as shown in FIG. Note that time t
_{At 3} , V ₆ = V _Sa, which is the same potential,
The probe 3 does not receive the electrostatic attractive force F _S , and the amplitude of the amplitude signal V ₀ also increases.

Such an amplitude signal V ₀ is sent to the AM demodulator 20.
Is demodulated and converted into a DC voltage V ₁ as shown in FIG. Here, the voltage V _{11a at} time t ₁ is equal to the voltage V _{12a at} time t ₂ . This is time t
_{This is because} the respective absolute values of the difference between the voltage V ₆ at ₁ and t ₂ and the voltage V _Sa are equal, and the values of the electrostatic attractive forces F ₁ and F ₂ acting at the times t ₁ and t ₂ are equal. ..

That is, when x = x _a , the potential difference between the probe 3 and the surface of the sample 2 with reference to the surface potential of the sample 2 at time t ₁ is V _pa , and the potential difference at time t ₂ is −V.
_pa . Therefore, the force F acting at the times t ₁ and t _2
1a and F _2a are respectively F _1a = (b / 2) · V _pa ² / x _a ² …………………… (10) F _2a = (b / 2) (− V _pa ) ² / x _a ² ……………………… (11).

[0050] Therefore, the voltage V _11a, V _12a is (6) from each _{V 11a = c · A 0 -d} · V pa 2 / x a 3 = v 0 -Δv 11a ............... (12 ) becomes _{V 12a = c · a 0 -d} · (-V pa) 2 / x a 3 = v 0 -Δv 12a ...... (13). However, Δv _11a = d · V _pa ² / x _a ³ ………………………… (14) Δv _12a = d (−V _pa ) ² / x _a ³ …………………… ……… (15)

Here, since Δv _11a = Δv _12a …………………………………… (16), V _11a = V _12a …………………………………… …………… It becomes (17).

From the power source 17, the AC voltage V ₄
The synchronized signal V ₇₂ as shown in FIG. 7 (j) synchronized with the above is taken out, and the sampling time of the sample hold circuit 22 is determined. Similarly, as shown in (i) of the same figure, a synchro signal V ₇₁ is generated by inverting this synchro signal V _72, and the sampling time of the sample hold circuit 21 is determined. In this example, since the sample-hold circuits 21 and 22 are configured to sample at the rising edges of the sync signals V ₇₁ and V ₇₂ , the sample-hold circuit 21 changes the value of the DC voltage V ₁ at time t _{1 to} V _{1. When 21} = V _11a , the sample hold circuit 22 samples and holds the value of the DC voltage V ₁ at time t ₂ as V ₂₂ = V _12a (see (k) (l) in the same figure).

These voltages V ₂₁ and V ₂₂ are applied to the differential amplifier 23.
Is input to, the difference is taken, and output as V ₃ . Since V _21a = V _{12a and} V ₂₁ = V ₂₂ as described above, V ₃ = V ₂₂ −V ₂₁ = 0 as shown in FIG.
Becomes The output V ₃ of the differential amplifier 23 is input to the integrator 24, but since V ₃ = 0, the value of the DC voltage V ₉ that is the output of the integrator 24 changes at the original V _Sa / G ₁ . No, therefore, the DC voltage V ₆ of the voltage V ₆ applied to the probe 3
The value of _b also does not change.

Thus, the surface potential V _S of the photosensitive member 1b is
Unless change from V _S = V _Sa, the DC voltage V _b of the voltage V ₆ tip potential of the probe 3 is also shown in FIG. 3 (e) also maintains the voltage V _Sa. Therefore, the surface potential V _S is obtained as V _S = V _Sa by reading the DC voltage V ₉ with the voltmeter 26 and multiplying the gain G ₁ of the power amplifier 19.

On the other hand, these voltages V ₂₁ and V ₂₂ are added to the adder 3
The voltage V ₁₀ added by 1 is compared with the reference voltage V ₁₃ in the differential amplifier 32. The value of this reference voltage V ₁₃ is determined by the probe 3
Is preset to a value equal to the output of the voltage V ₁₀ when the average distance x between the tip of the and the surface of the photoconductor 1b becomes the desired distance x _a . Further, the voltage V _p at this time is set as V _p = V _pa .

That is, the voltage V ₁₀ at this time is V ₁₀ = V ₂₁ + V ₂₂ = V _11a + V _12a = 2 (c · A ₀ −d · V _pa ² / x _a ³ ) ... 18)

Therefore, the reference voltage V ₁₃ is also set as V ₁₃ = V ₁₀ = 2 (c · A ₀ −d · V _pa ² / x _a ³ ) ... (19).

[0058] Now, the tentatively average distance x is a desired value (x = x _a), equal value V _10a is the reference voltage V ₁₃ of the voltage V ₁₀ at this time, i.e., V _10a = V _11a + V _12a =
Suppose it was V ₁₃ . Then, the voltage V ₁₄ at this time is V ₁₄ = 0, and the integrated output V ₁₅ does not change. Therefore, the signals V _L , V _H , and V _{M obtained} by separating the output V ₁₅ by the bandpass filter 34 in the frequency band do not change. Therefore, the signals V _L and V _M remain the voltages V _La and V _Ma required to maintain the distance x at the desired value x _a , respectively, and the signal V _H is the amplitude of the AC signal of the voltage source 17 that is V a.
_The voltage V _Ha required to maintain the voltage at _4a is maintained. Therefore, the voice coil 27 for coarse and fine movements, the PZT
28 shows no displacement, and the amplitude of the alternating voltage by the voltage source 17 also shows no change.

Next, consider a case where the sample 2 is moved in the X-axis or Y-axis direction by the X, Y-axis actuator 29 and the position of the sample surface immediately below the probe 3 is moved. Here, due to such movement, the surface potential V _S of the photoconductor 1b does not change from the state shown in FIG. 3 and remains V _S = V _Sa , and the surface of the photoconductor 1b has the height Δx. only the distance x between the probe 3, the photosensitive member 1b by the presence of the projections is decreased only Δx minute (approach), and shall become _{x = x b = x a -Δx} , with reference to FIG. 4 and the measurement sequence Explain.

However, in order to facilitate the explanation of the operation, Δx
The change in distance is included only in the high frequency component in the frequency band. Therefore, it is assumed that the signal V _H changes but the signals V _M and V _L do not change.

First, when the surface of the photosensitive member 1b and the tip of the probe 3 come close to each other, the value of x in the equation (2) becomes small, so that the force F
Grows. That is, F _1b = (b / 2) · V _pa ² / x _b ² = (b / 2) · V _pa ² / (x _a −Δx) ² > (b / 2) · V _pa ² / x _a ² = F _1a …………………… (20) F _2b = (b / 2) (− V _pa ) ² / x _b ² = (b / 2) (− V _pa ) ² / (x _a −Δx ) ² > (b / 2) (− V _pa ) ² / x _a ² = F _2a …………………… (21).

As a result, the vibration amplitude A also becomes small, and the voltages V _11b and V _12b representing this amplitude are respectively V _11b = cA ₀ -dV _p ² / x ³ = cA ₀ -d V _pa ² / x _b ³ = c · A ₀ −d · V _pa ² / (x _a −Δx) ³ <c · A ₀ −d · V _pa ² / x _a ³ = V _{11 a} ……………… _{(22) V 12b = c ·} A 0 -d (-V p) 2 / x 3 = c · A 0 -d (-V pa) 2 / x b 3 = c · A 0 -d (-V pa) ² / (x _a −Δx) ³ <c · A ₀ −d (−V _pa ) ² / x _a ³ = V _{12 a} ………… (23).

Further, since V _pa ² = (-V _pa ) ² …………………………………… (24), from the equations (22) and (23), V _11b = V _12b …………………………………………………… (25).

Here, V ₂₁ is the voltage V _{1 at} time t ₁ .
, V _11b and V ₂₂ holds the voltage V _12b at time t _2, so V ₂₁ = V _11b , V ₂₂ =
It becomes V _12b . Therefore, from the equation (25), V ₃ = V ₂₂ −V ₂₁
= 0.

That is, V _11b and V _12b are V _11b <V _11a ………………………………………… (26) V _12b <V _12a …………………… Although it is (27), since V _11b = V _12b as shown in the equation (25), V ₃ = 0. Therefore, the voltage V ₉ obtained by integrating the voltage V ₃ does not change, and the DC bias voltage V ₆ of the voltage V ₆ does not change.
_b does not change from the state shown in FIG. Therefore, the voltage V
Reference numeral ₉ represents the surface potential of the photoconductor 1b.

According to this, the surface potential V _{S of the} photosensitive member 1b is
_Does not change as V _S = V _Sa , even if the distance d between the surface of the photoconductor 1b and the probe 3 becomes small due to the protrusion on the surface, such a variation is not observed in the measurement result of the surface potential. It has no effect, and the correct result with the surface potential of V _Sa is obtained. That is, the measurement result of the surface potential becomes insensitive to the variation of the distance d.

On the other hand, assuming that the value of the voltage V ₁₀ which is the sum of the voltages V ₂₁ and V ₂₂ at this time is V _10b , from the equations (26) and (27), V _10b = V _11b + V _12b <V _11a + V _12a = V ₁₃ (28) and V ₁₄ =-(V _11b + V _12b -V ₁₃ )> 0 (29).

Here, the integrator 33 is an inverting integrator,
When the voltage V ₁₄ becomes positive, the value of the voltage V ₁₅ becomes smaller. As described above, since it is assumed that this change has a high frequency band, only the value of the signal V _H becomes smaller. At this time, the voltage source 17 has its amplitude V _p.
There are controlled by the signal V _H, it becomes smaller the amplitude V _p the signal V _H is reduced. As the amplitude V _p becomes smaller, the values of V _11b and V _12b become larger from the expressions (22) and (23). Such an operation is continued until V _11b + V _12b = V ₁₃ (30). Therefore, from the change of the signal V _H , it is possible to measure the protrusion Δx on the surface of the sample 2, that is, the surface shape. Even when Δx is not a projection but a depression, the polarities are opposite in the above operation, and the same measurement can be performed.

In particular, as described in the fourth aspect of the invention, the voice coil 27 for coarse and fine movements and the PZT 28 are used to eliminate the distance variation between the surface of the sample 2 and the probe 3 which has a large amplitude at a low frequency. Therefore, when measuring a distance variation of small amplitude at high frequency by the amplitude of the AC component of the voltage applied to the probe 3, a proportional relationship is established between the amplitude variation of the AC component and the distance, which is easy. The surface shape can be measured. here,
Since the amplitude V _p of the AC component of the voltage V ₆ is controlled by the signal V _H , if there is a proportional relationship between V _H and V _p ,
The value of the protrusion height Δx on the surface can be linearly measured from the measurement result of the voltmeter 38.

As described above, the X, Y axis actuator 2
By the operation of 9, the surface portion of the sample 2 immediately below the probe 3 moves,
As a result, the potential of the surface of the sample 2 directly below the probe 3 does not change,
Even when the protrusion with the height Δx appears just below the probe 3, the measured value of the surface potential (the measured value of the voltmeter 26) is Δx.
Become insensitive to. At the same time, it is possible to measure only Δx from the value of the signal V _H measured by the voltmeter 38.

Next, the sample 2 is moved in the X-axis or Y-axis direction by the X- and Y-axis actuators 29, and the surface of the sample 2 immediately below the probe 3 is moved, whereby the state shown in FIG. 3 is exposed. Only the surface potential V _S of the body 1b changes and V _S = V _Sc
= V _Sa −ΔV _S , but the distance x between the surface of the photoconductor 1b and the tip of the probe 3 does not change (x = x _a remains, and there is no unevenness on the surface). The measurement sequence will be described with reference to FIG.

Now, the surface potential V _S changes from V _Sa to V _Sc = V _Sa
It is assumed that the temperature has changed to −ΔV _S. Also, the tip potential V of the probe 3
_It is assumed that ₆ is the same as the value shown in FIG. Then,
As shown in FIG. 5A, the potential difference between the surface of the photoconductor 1b and the tip of the probe 3 is V _pa + ΔV _{S at} time t ₁ and time t.
_{At 2} , V _pa −ΔV _S. That is, the potential difference at time t ₁ becomes larger than the potential difference at time t ₂ . Therefore, the electrostatic attractive force F _{S received} by the tip of the probe 3 is also shown in FIG.
As shown in (b), the time t _{1 is} greater than the value F _2c at the time t _2.
The value F _1c at that time becomes larger.

That is, F _1c = (b / 2) (V _pa + ΔV _S ) ² / x _a ² > F _1a = F _2a (31) F _2c = (b / 2) (V _pa −ΔV _S ). ^{Since 2} / x _a ² <F _1a = F _2a (32) and F _1c > F _2c , the values V _11c and V _12c of the voltage V ₁ at the times t ₁ and t ₂ are respectively V _11c. = C · A ₀ −d (V _p + ΔV _S ) ² / x _a ³ <V _11a = V _12a ……………………………… (33) V _12c = c · A ₀ -d ( ^{_{V p -ΔV S) 2 / x}} a 3> V 12a = V 11a ....................................... becomes (34). Therefore, the result of V _11c <V _12c ……………………………… (35) is obtained.

As a result, as described above, the sample hold voltage V _{11c at} time t ₁ becomes smaller than the sample hold voltage V _12c at time t ₂ (see FIG.
(See (d) to (f)). Therefore, the sample hold circuit 2
Between each of the output voltages V _21, V ₂₂ of 1, 22, V ₂₁ <
The relationship of V ₂₂ is established. Therefore, the output V ₃ of the differential amplifier 23 becomes a positive voltage as shown in FIG. The voltage V ₃ is represented by _{V 3 = V 3c = V 12c} -V 11c = (4d / x a 3) · V p · ΔV S ........................ (36). Here, since the integrator 24 is an inverting integrator,
By integrating this voltage V ₃ , the potential of the DC voltage V ₉ is reduced from the initial value V _Sa / G ₁ .

As the DC voltage V ₉ decreases, the bias voltage V _b (center voltage of amplitude) of the AC amplitude of the voltage V ₆ with respect to the probe 3 (cantilever 9) also decreases as shown in FIG. When this bias voltage V _b becomes V _Sa −ΔV _S ,
That is, when V _b = V _Sc , the fluctuation of V _b stops.
Then, as in the case of FIG. 3, the voltage V ₆ is V _b = V _Sa −
The voltage has an amplitude V _pa centered on a direct current voltage ΔV _S = V _Sc . Since the surface potential of the photoconductor 1b at this time is V _Sa −ΔV _S , the electrostatic attractive forces F _1d and F _2d received at the times t ₁ and t ₂ are F _1d = F ₁ as shown in FIG. 5 (i). It becomes _2d . As a result, the voltage V ₃ becomes V ₃ = 0, and the DC voltage V ₉ becomes (V _Sa
Maintain a voltage of −ΔV _S ) / G ₁ . At this time, the surface potential of the photoconductor 1b is the value indicated by the voltmeter 26 (V _Sa −Δ
It is obtained by multiplying V _S ) / G ₁ by a known value G ₁ .

When the surface potential of the photoconductor 1b is changed to V _Sa + ΔV _S , the voltage increase / decrease relationship in the above processing is simply reversed, and the voltage V ₉ is similarly changed to the final value. Specifically, V _b = V _Sa + ΔV _S.

On the other hand, the measurement of the distance between the surface of the photosensitive member 1b and the tip of the probe 3 will be described. In the equations (33) and (34) described above, in the actual measurement, if feedback control to the voltage of the probe 3 is always applied, V _pa >> ΔV _S ………………………………………… Since (37), V _pa ² >> ΔV _S ² ……………………………… (38) 2V _pa · ΔV _S >> ΔV _S ² ……………………… …………… (39).

Therefore, from the equations (33) and (34), V _11c = c · A ₀ −d (V _pa + ΔV _S ) ² / x _a ³ = c · A ₀ −d (V _pa ² + 2V _pa · ΔV _S + ΔV _S ² ) / x _a ³ ≈c · A ₀ −d (V _pa ² + 2V _pa · ΔV _S ) / x _a ³ ………… (40) V _12c = c · A ₀ −d (V _pa −ΔV _S ) ² / x _a ³ = c · A ₀ −d (V _pa ² −2V _pa · ΔV _S + ΔV _S ² ) / x _a ³ ≈c · A ₀ −d (V _pa ² −2V _pa · ΔV _S ) / x _a ³ ………… (41)

[0079] At this time, the voltage V ₂₁ at time t ₁ the voltage V _21, V ₂₂ is (= V _11c), the voltage at time t ₂ V
_Since it holds ₂₂ (= V _12c ), FIG.
As shown in (f), V ₂₁ = V _11c and V ₂₂ = V _12c .

Further, the voltage V ₁₀ is these voltages V ₂₁ and V _22.
V ₁₀ = V ₂₁ + V ₂₂ = V _11c + V _12c = c · A ₀ −d (V _pa ² + 2V _pa · ΔV _S ) / x _a ³ + c · A ₀ −d (V _pa ² − 2V _pa · ΔV _S ) / x _a ³ = 2c · A ₀ -2d · V _pa ² / x _a ³ = 2 (c · A ₀ −d · V _pa ² / x _a ³ ) ……………… ( 42)

Further, since the reference voltage V ₁₃ is set in advance to the value obtained by the equation (19), the equation (19) and the equation (42) are used.
Even in the state shown in, V ₁₃ = V ₁₀ . Therefore, V ₁₄ is also V
₁₄ = 0. This means that V ₁₅ does not change,
The indicated value of the voltmeter 38, which is the measurement result of the surface unevenness of the sample 2, is not affected by the change in the surface potential V _S and does not change. That is, V _p = V _pa remains unchanged.

From the above, even when there is no unevenness on the surface of the photoreceptor 1b and only the surface potential changes,
Only the change in the surface potential V _S can be measured.

Further, the surface potential V _S changes from V _Sa to V _Sd = V
_A description will be given of the measurement sequence when _Sa- ΔV _S and the distance x simultaneously changes from x _a to x _d = x _a −Δx due to the protrusion having the height Δx. In this case, although the timing chart is not shown, only the sequences shown in FIGS. 4 and 5 occur at the same time. Therefore, according to the above description, the surface potential V _S and the change in the distance x are independent. It can be measured at the same time.

In this case, the values of the voltages V ₂₁ and V ₂₂ are V _11d and V _12d , respectively. In addition, x _d = x _a −Δx,
It is assumed that V _Sd = V _Sa −ΔV _S and that V _p = V _pa remains. Then, as in the case of the equations (12) and (13), V _11d = c · A ₀ −d (V _pa + ΔV _S ) ² / (x _a −Δx) ³ ……… (43) V _12d = c · A ₀ −d {− (V _pa −ΔV _S )} ² / (x _a −Δx) ³ (44)

The potential difference V ₃ between these voltages V ₂₁ and V ₂₂ is V ₃ = V ₂₂ −V ₂₁ = V _12d −V _11d = {d / (x _a −Δx) ³ } {(V _pa + ΔV _S ). ²⁻ (V _pa −ΔV _S ) ² } = {4d / (x _a −Δx) ³ } · V _pa · ΔV _S …………………… (4
5) becomes. Here, since x _a >> Δx, (x _a −Δ
x) ³ > 0 and V ₃ > 0.

Therefore, as in the case shown in FIG. 5, the voltage V ₉ decreases, V _b = V _Sd , and V ₆ decreases until V ₂₂ = V _21, and finally V _6. V _b = V _Sd and stabilize. Therefore, from the value of the voltage V ₉ to the surface potential V _Sd
Can be measured.

On the other hand, regarding the measurement of the distance, V _10d = V _12d + V _11d = 2c · A ₀ -d {(V _pa −ΔV _S ) ² + (V _pa + ΔV _S ) ² } / (x _a −Δx) ³ = 2c · A ₀ −d (V _pa ² −2V _pa · ΔV _S + ΔV _S ² + V _pa ² + 2V _pa · ΔV _S + ΔV _S ² ) / (x _a −Δx) ³ = 2c · A ₀ −2d (V _pa ² + ΔV _S ² ) / (x _a −Δx) ³ …………………………………… (46). Here, since V _pa ² >> ΔV _S ² , the formula (46) is V _10d = 2c · A ₀ -2d · V _pa ² / (x _a −Δx) ³ …………………… (47) Becomes

From the equation (19), since V _10d <V ₁₃ ………………………… (48), the voltage V ₁₄ becomes positive and the voltage V ₁₅ becomes small. Become. As a result, the signal V _H becomes smaller and the amplitude V _p also becomes smaller. This operation is continued until V ₁₀ = V ₁₃ . As for the distance at this time, the protrusion height Δx can be measured from the measurement result of the voltmeter 38, as in the case described with reference to FIG.

As described above, even if the fluctuation of the surface potential V _{S and} the distance fluctuation due to the surface unevenness occur at the same time, the surface potential and the distance (protrusion height) can be measured separately.

As a result, the sample 2 is two-dimensionally moved by the X and Y axis actuators 29 and the surface of the sample 2 is raster-scanned by the probe 3 in accordance with the above-described operation. The surface shape distribution can be measured simultaneously and independently.

Next, one embodiment of the invention described in claims 2 and 5 will be described with reference to FIG. The same parts as those shown in the above-mentioned embodiments are designated by the same reference numerals (the same applies to the following embodiments). In this embodiment, the bandpass filter 34
The signal V _H in the highest frequency band separated by
Instead of No. 7, the drive power source 10 for the PZT 7 is fed back and the voltage amplitude (vibration amplitude) of the drive power source 10 is controlled by the signal V _H. Specifically, the amplitude of the AC voltage V ₈ increases as the signal V _H decreases.
A voltmeter 42 serving as a vibration amplitude measuring means for measuring the voltage amplitude is connected to the output line of the signal V _H. Other configurations are the same as those in the above-mentioned embodiment.

Now, assuming that the amplitude of the AC voltage V ₈ is represented by V _z , the operation of this embodiment will be described. Also in the case of this embodiment, the equation (1) is established and the vibration amplitude A ₀ of the cantilever 9 is P.
It is proportional to the vibration amplitude of ZT7, and the vibration amplitude of PZT7 is proportional to the amplitude V _{z of the} applied voltage thereto. That is, A ₀ ∝V _z …………………………………………………… (49) is established. Therefore, if e ′ and e ″ are proportional constants,
According to the equations (1), (3) and (49), ΔA = -e ″ · V _z · V ² / x ³ A ₀ = e ′ · V _z ………………………………………… ( 50).

Therefore, the amplitude at this time is A = A ₀ + ΔA = e ′ · V _z −e ″ · V _z · V ² / x ³ (51) where the voltage V ₁ is Since it is proportional to the amplitude A, e
_{If 1} and e ₂ are proportionality constants, then V ₁ = V _z (e ₁ −e ₂ · V ² / x ³ ) ... (52)

Here, the surface potentials V _S = V _Sa , V _b =
If V _Sa , V = V _p = V _pa , x = x _a , and V _z = V _za , then V _11a = V _12a = c · A ₀ −e · V _za · V _pa ² / x _a ³ ……… …………… (53). Therefore, since it is V ₃ = 0, the value of the voltage V ₉ unchanged, V _S is also not changed to keep the V _b = V _Sa.

By the way, V ₁₃ is set as the value of the voltage V ₁₀ when x = x _a . That is, V ₁₃ = 2V _za (e ₁ −e ₂ · V _pa ² / x _a ³ ) = 2c · A ₀ −2e · V _za · V _pa ² / x _a ³ …………………… (54 ). Then, as long as x = x _a , V ₁₃ = V ₁₀ and V ₁₄ = 0, so that the signal V _H does not change as in the case described with reference to FIG.

[0096] Then, the value of miso changes in the distance _{x, x = x b = x} a -Δx , and the surface potential V _S and shall not change. Further, it is assumed that V _z = V _za is still _maintained . Then, V _11b = V _12b = V _za {e ₁ −e ₂ · V _pa ² / (x _a −Δx) ³ } (55), so V ₃ = 0 and the surface potential V _S is measured. The resulting voltage V ₉ does not change.

On the other hand, V ₁₀ at this time, that is, V _10b is V _10b = V _11b + V _12b = 2V _za {e ₁ −e ₂ · V _pa ² / (x _a −Δx) ³ } <V ₁₃ ... Since (56), the voltage V ₁₅ becomes smaller.

As a result, the signal V _H becomes smaller and the amplitude V _z of the driving power supply 10 becomes larger. From equation (56),
As the amplitude _Vza increases, the value of _V10b also increases. This operation is continued until V _10b = V _11b + V _12b = V ₁₃ . Therefore, from the change of the signal V _H , it is possible to measure the protrusion Δx on the surface of the sample 2, that is, the surface shape. Even when Δx is not a projection but a depression, the polarities are opposite in the above operation, and the same measurement can be performed.

In particular, as described in the fifth aspect of the invention, the voice coil 27 for coarse and fine movements and the PZT 28 are used to eliminate the variation in the distance between the surface of the sample 2 and the probe 3 which has a large amplitude at a low frequency. Therefore, when measuring the distance variation of small amplitude at high frequency by the amplitude variation of the excitation voltage for exciting the probe 3, a proportional relationship is established between the amplitude variation of the excitation voltage and the distance. , The surface shape can be easily measured. Here, since the amplitude V _Z of the voltage V ₈ is controlled by the signal V _H , if there is a proportional relationship between V _H and V _Z , the height Δx of the protrusion on the surface is determined from the measurement result of the voltmeter 42. The value of can be measured linearly.

Next, only the surface potential V _S is V _S = V _Sc = V
Consider a case where _Sa −ΔV _S and x does not change. When V ₂₁ and V ₂₂ at this time are V _11c and V _12c , V _11c = c · A ₀ −e (V _pa + ΔV _S ) ² · V _za / x _a ³ ………… (57) V _12c = c · A ₀ −e (V _pa −ΔV _S ) ² · V _za / x _a ³ (58) At this time, V ₃ is V ₃ = V _3c = V _12c −V _11c = 4e (V _za / x _a ³ ) · V _pa · ΔV _S > 0 ……………………………………………… It is represented by (59).

As a result, the value of V ₉ decreases, and V ₉
It becomes stable when ₉ = V _Sc / G ₁ . Therefore, the surface potential V _Sc can be measured by the value of V ₉ .

On the other hand, regarding the measurement of the distance, V _11c ≈c · A ₀ −e (V _pa ² + 2V _pa · ΔV _S ) · V _za / x _a ^{3 in the same} manner as in the case of the equations (40) and (41). … (60) V _12c ≈ c · A ₀ −e (V _pa ² −2V _pa · ΔV _S ) · V _za / x _a ³ … (61) V ₁₀ = V _11c + V _12c = 2 (c · A ₀ − e · V _pa ² · V _za / x _a ³ ) …………………………………… (62). Here, since V ₁₀ = V ₁₃ from the equation (54) and the signal V _{H of the} high frequency component does not change, the distance measurement result does not change.

Then, the surface potential V _S changes from V _Sa to V _Sd = V
The measurement will be described when the distance x changes from _{Sa to} ΔV _S and the distance x changes from x _a to x _d = x _a −Δx at the same time due to the protrusion having the height Δx. Here, the values of V ₂₁ and V ₂₂ are V _11d and V _12d , respectively. Also, x _d = x _a −Δx, V _Sd
= V _Sa −ΔV _S , and V _z = V _za is still _maintained .

Then, V _11d = c · A ₀ −e (V _pa + ΔV _S ) ² · V _za / (x _a −Δx) ³ (63) V _12d = c · A ₀ −e {-(V _pa −ΔV _S )} ² · V _za / (x _a −Δx) ³ …………………………………… (64), and V ₃ = V ₂₂ −V ₁₁ = V _12d −V _11d = {E · V _za / (x _a −Δx) ³ } {(V _pa + ΔV _S ) ² − (V _pa −ΔV _s ) ² } = {4 e · V _za / (x _a −Δx) ³ } · V _pa · ΔV _S …………… (65)

Here, since x _a >> Δx, (x _a −Δ
x) ^3> 0 becomes, V _3> 0 the ......................................................... (66). Therefore, as in the case described with reference to FIG.
The value of ₉ is decreasing to V _b = V _Sd and V ₂₂ = V ₂₁
The value of V ₆ decreases until it becomes V _b = V _Sd
Stabilizes at. Therefore, the surface potential V _Sd can be measured from the value of the voltage V ₉ .

On the other hand, regarding the distance measurement, when the voltage V ₁₀ at this time is V _10d , V ₁₀ = V _10d = V _12d + V _11d = 2c · A ₀ − {e · V _za / (x _a −Δx ) ³ } {(V _pa + ΔV _S ) ² + (V _pa −ΔV _S ) ² } = 2c · A ₀ − {2e · V _za / (x _a −Δx) ³ } (V _pa ² + ΔV _S ² ) ... (67)

From the equations (38) and (67), V _10d = 2c · A ₀ − {2e · V _za / (x _a −Δx) ³ } · V _pa ² (68) From equation (54), V _10d <V ₁₃ ………………………………………………………… (69). Therefore, the value of the voltage V ₁₄ becomes positive and the value of the voltage V ₁₅ becomes smaller. As a result, the high frequency component signal V _H becomes smaller and the amplitude V _z becomes larger. This operation continues until V ₁₀ = V ₁₃ .

As described above, the surface potential V _S and the sample 2
Even if the surface irregularities change at the same time, each can be measured independently.

As a result, the above-described operation is performed by moving the sample 2 two-dimensionally by the X and Y axis actuators 29 and raster-scanning the surface of the sample 2 with the probe 3, whereby the surface potential distribution on the surface of the sample 2 and The surface shape distribution can be measured simultaneously and independently.

Further, an embodiment of the invention described in claims 3 and 6 will be described with reference to FIGS. 7 and 8. The configuration is the same as that of the above-described embodiment, but in the above-described embodiment, the signal V _H of the high frequency component frequency-separated by the bandpass filter 34 is set to P
While this is used for controlling the vibration amplitude of the drive power supply 10 for ZT7, in this embodiment, the vibration frequency by the drive power supply 10 is controlled by this signal V _H. The frequency of the driving voltage V ₈ decreases due to the decrease of the signal V _H. Further, a voltmeter 43 serving as a vibration frequency measuring means for measuring the frequency is connected to the output line of the signal V _H.

In this structure, in order to make the operation of this embodiment easy to understand, the frequency of the amplitude V _z and the cantilever beam 9 are used.
The relationship with the vibration amplitude of Now, in FIG. 8, the vibration amplitude A and the vibration frequency f (V _{z in} FIG. 7) of the cantilever beam 9 in a state where no force acts between the probe 3 and the surface of the sample 2.
It is assumed that the characteristics of and are shown by. Next, it is assumed that the tip of the probe 3 comes close to the surface of the sample 2 and an electrostatic attractive force acts between the two, and the amplitude A-excitation frequency f characteristic becomes as shown by.

During this period, if the excitation frequency f is kept fixed at f ₀ , the amplitude A shifts from A _{0 in} the state (0) to the state in (b) and becomes A ₀ -ΔA _b . ΔA _b at this time is represented by ΔA _b = −g · V ² / x ³ ………………………………………… (70), where g is a proportional constant.

Next, from the state of (b), the frequency is changed from f ₀ to Δ.
When f is decreased, the amplitude A is increased by ΔA _f from the state of (b). Here, if Δf << _{f 0} , then ΔA _f = h · Δf …………………………………… (71). Therefore, the difference ΔA from A ₀ at this time is ΔA = ΔA _b + ΔA _f = −g · V ² / x ³ + h · Δf (72)

Therefore, the amplitude A at this time is A = A ₀ + ΔA = A ₀ −gV ² / x ³ + hΔf (73) Here, since the voltage V ₁ is proportional to the amplitude A,
If i and j are proportionality constants, then V ₁ = c · A ₀ −i · V ² / x ³ + j · Δf (74)

Now, the surface potentials V _S = V _Sa , V _b = V _Sa , V
= V _p = V _pa , x = x _a , and Δf = 0, V _11a = V _12a = c · A ₀ −i · V _pa ² / x _a ³ ………… (75) , V ₃ = 0, the value of V ₉ does not change, and V _b = V _Sa is maintained as long as the surface potential V _S does not change.

By the way, when x = x _a , the reference voltage V ₁₃ is set to the same value as V ₁₀ when Δf = 0, that is, f = f ₀ and V = V _p = V _pa . That is, V ₁₃ = 2 (c · A ₀ −i · V _pa ² / x _a ³ ) ……………………………… (76). Also, V _S = V _Sa = V _b , and V ₁₀ = V
_If it is ₁₃ , similar to the case described in FIG. 3,
Neither V _H nor V ₉ changes.

The value of the reference voltage V ₁₃ is set to the value of V ₁₀ when x = x _a . That is, if set as in the expression (76), V ₁₃ = V ₁₀ as long as x = x _a , and V _H does not change as in the case described with reference to FIG.

Next, it is assumed that the value changes only for the distance x, x = x _b = x _a −Δx, and the surface potential V _S does not change. Further, the excitation frequency f = f ₀ (that is, Δf =
It is assumed that it remains 0). Then, V _11b = V _12b = c · A ₀ −i · V _pa ² / (x _a −Δx) ³ (77), so V ₃ = 0 and the measurement result of the surface potential V _S. V ₉ does not change.

On the other hand, V ₁₀ at this time, that is, V _10b is V _10b = V _11b + V _12b = 2 {c · A ₀ −i · V _pa ² / (x _a −Δx) ³ } <V ₁₃ ... Since it becomes (78), the value of V ₁₅ becomes smaller. As a result, the signal V _H of the high frequency component becomes small, and the drive power source 10
The frequency f of the voltage V ₈ becomes smaller. From Figure 8 (7
In the expression (3), h is h <0. Therefore, when the frequency f decreases, that is, when Δf <0, the amplitude A increases. This operation continues until V _10b = V _11b + V _12b = V ₁₃ .

In particular, as described in the sixth aspect of the invention, the coarse / fine voice coil 27 and the PZT 28 are used to remove the variation in the distance between the surface of the sample 2 and the probe 3 which has a large amplitude at a low frequency. Therefore, in the case of measuring the distance variation of high amplitude and small amplitude by the frequency variation of the AC component of the voltage applied to the probe 3, a proportional relationship is established between the frequency variation of the excitation voltage and the distance. , The surface shape can be easily measured.

Δx at this time can be easily known from the change Δf of the frequency f by a proportional expression. That is, if the frequency change Δf is made to be proportional to the signal V _{H of the} high frequency component, the value of Δx can be obtained from the value of this signal V _H by the proportional expression.

Next, only the surface potential V _S is V _S = V _Sc = V
_Sa −ΔV _S (where ΔV _S > 0) and the distance x does not change. V ₂₁ and V ₂₂ at this time are V
_11c and V _12c , and the frequency f is equal to the frequency before the surface potential V _S changes, that is, Δf = 0. Then, V _11c = c · A ₀ −i (V _pa + ΔV _S ) ² / x _a ³ ……………… (79) V _12c = c · A ₀ −i (V _pa −ΔV _S ) ² / X _a ³ …………………… (80) is established. Therefore, V ₃ at this time becomes _{V 3 = V 3c = V 12c} -V 11c = 4i · V pa · ΔV S / x a 3> 0 ........................ (81). As a result, the value of V ₉ decreases and V ₉ =
It stabilizes at V _Sc / G ₁ . Therefore, the surface potential V _Sc can be measured based on this V ₉ .

On the other hand, the distance is measured in the same manner as the equations (40) and (41) by V _11c ≉cA ₀ -i (V _pa ² + 2V _{paΔV S} ) / x _a ³ ...... (82 ) V _12c ≈ c · A ₀ −i (V _pa ² −2V _pa · ΔV _S ) / x _a ³ ………… (83) V ₁₀ = V _11c + V _12c = 2 {c · A ₀ −i · V _pa ² / x _a ³ } ………………………… (84). At this time, from the expression (76), V ₁₀ = V ₁₃ , and the high-frequency component signal V _H does not change. Therefore, the distance measurement result does not change.

Next, the surface potential V _S changes from V _Sa to V _Sd = V
The measurement will be described when _Sa −ΔV _S and the distance x simultaneously changes from x _a to x _d = x _a −Δx due to the protrusion having the height Δx. In this case, the values of V ₂₁ and V ₂₂ are respectively V _11d ,
V _12d . In addition, x _d = x _a −Δx, V _Sd = V _Sa −Δ
It becomes V _S , and Δf remains 0. Then x _a
>> By Δx V _11d = c · A ₀ −i (V _pa + ΔV _S ) ² / (x _a −Δx) ³ ………… (85) V _12d = c · A ₀ −i {− (V _pa −ΔV _S )} ² / (x _a −Δx) ³ (86) V ₃ = V ₂₂ −V ₂₁ = V _12d −V _11d = {i / (x _a −Δx) ³ } {(V _pa + ΔV _S ) ²⁻ (V _pa −ΔV _S ) ² } = {4i / (x _a −Δx) ³ } · V _pa · ΔV _S > 0 ………… (87).

Therefore, as in the case described with reference to FIG. 5, the voltage V ₉ decreases, V _b = V _Sd , and V ₂₂ = V _21.
V ₆ decreases until it becomes, and stabilizes at V _b = V _Sd . Therefore, the surface potential V _Sd can be measured from the value of the voltage V ₉ .

On the other hand, regarding the measurement of the distance, V ₁₀ = V _10d = V _12d + V _11d = 2c · A ₀ − {i / (x _a −Δx) ³ } {(V _pa −ΔV _S ) ² + (V _pa + ΔV _S ) ² } = 2c · A ₀ -2 {i / (x _a −Δx) ³ } (V _pa ² + ΔV _S ² ) ... (88). From equations (88) and (38), V _10d = 2c · A ₀ -2i · V _pa ² / (x _a −Δx) ³ ………… (89), and from equation (75), V _10d <V ₁₃ ………………………………………………………… (90). Therefore, V ₁₄ becomes positive and V ₁₅ becomes smaller. As a result, the signal V _H of the high frequency component becomes small,
The amplitude V _p also becomes smaller. This operation continues until V ₁₀ = V ₁₃ .

As described above, the surface potential V _S and the sample 2
Even if the surface irregularities change at the same time, each can be measured independently.

As a result, the above-described operation is performed by moving the sample 2 two-dimensionally by the X and Y axis actuators 29 and raster-scanning the surface of the sample 2 with the probe 3. The surface shape distribution can be measured simultaneously and independently.

Although the X and Y axis actuators 29 are provided on the sample 2 side in these embodiments, they may be provided on the base side of the cantilever beam 9 to move the probe 3 side. .. Also, give priority to a feedback control for the surface potential measurement distance control, voltage V ₂₂ (= V ₁₂₎ in the voltage V ₂₁ (= V ₁₁₎ and the time t ₂ at time t ₁ and is, V ₁₁ = V ₁₂ After that, the value of V ₁₁ or V ₁₂ may be sampled and _held to generate the signal V ₁₀ that captures the change in the distance x.

[0130]

According to the first, second and third aspects of the present invention, the vibration of the probe support member forming a part of the electrostatic force detecting means is measured by measuring the potential of the amplitude-controlled AC voltage. Since the measurement is performed by measuring the vibration amplitude of the vibration control device with amplitude controlled for the needle, or by measuring the vibration frequency of the vibration control device with frequency controlled for the probe, the optical response is high and the measurement accuracy is high. Can be measured using a dynamic measurement method,
Further, since it is not necessary to use a Z-axis actuator such as PZT, there is no decrease in measurement accuracy due to its hysteresis characteristics, ringing of the probe support member due to displacement of PZT, and the capacitive load. Is PZT
Since it is not used, it is possible to sufficiently follow the measurement of the surface shape in the high frequency band.

In addition, according to the invention described in claims 4, 5 and 6, the feedback signal is separated by the frequency band and the amplitude, the vibration amplitude or the vibration frequency is controlled by the signal of a part of the frequency band. Since the actuator for controlling the distance is controlled by the signal of the remaining frequency band component, the measurement of the surface potential or the shape of the measuring object having a large undulation at the time of measurement is also preferable.
The surface shape can be measured from a change in the potential of the AC voltage using a simple proportional expression without obtaining the distance fluctuation using a complicated calculation expression as in the described invention. The tip of the needle and the surface of the object to be measured can be brought close to each other and can be maintained at a substantially constant distance, and the measurement resolution does not deteriorate.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the invention described in claims 1 and 4.

FIG. 2 is an enlarged schematic view showing the vicinity of a probe.

FIG. 3 is a timing waveform chart showing a measurement operation when there is no fluctuation in surface potential and fluctuation in distance.

FIG. 4 is a timing waveform chart showing the measurement operation when the distance changes.

FIG. 5 is a timing waveform chart showing the measurement operation when the surface potential changes.

FIG. 6 is a circuit configuration diagram showing an embodiment of the invention described in claims 2 and 5.

FIG. 7 is a circuit configuration diagram showing an embodiment of the invention described in claims 3 and 6.

FIG. 8 is a vibration frequency-vibration amplitude characteristic diagram.

FIG. 9 is a circuit configuration diagram showing an already proposed example.

[Explanation of symbols]

 2 object to be measured 3 probe 7 vibrating device 9 cantilever 12 electrostatic force detection means 16 potential control means 26 DC potential measurement means 27, 28 actuator 34 separation means 37 amplitude control means 38 AC potential measurement means 39 distance control means 40 , 41 displacement measuring means 42 vibration amplitude measuring means 43 vibration frequency measuring means

Claims (6)

[Claims] 1. A conductive probe facing a measurement target, electrostatic force detection means for detecting an electrostatic force acting between the probe and the surface potential of the measurement target, and the probe. And a potential control means for varying the DC voltage so that the AC voltage is superimposed on the DC voltage and the electrostatic force when the AC voltage swings to the positive side becomes equal to the electrostatic force when the AC voltage swings to the negative side. , A DC potential measuring means for measuring the potential of the DC voltage of the probe, and an electrostatic force when the AC voltage swings to the positive side becomes constant, or an electrostatic force when the AC voltage swings to the negative side becomes constant. Next to
Alternatively, an amplitude control unit that controls the amplitude of the AC voltage so that the sum of the electrostatic force when swung to the positive side and the electrostatic force when swung to the negative side is constant, and the potential of the AC voltage is measured. And a surface potential and shape measuring instrument. 2. A probe held at the tip of a cantilever vibrated by a vibrating device, and an electrostatic force detecting means by a displacement detector for detecting a vibration amplitude of the probe which changes in accordance with an electrostatic force. And by varying the DC voltage so that the electrostatic force when the AC voltage is swung to the positive side and the electrostatic force when the AC voltage is swung to the negative side are equalized by superposing the AC voltage on the probe. Potential control means, a DC potential measuring means for measuring the potential of the DC voltage of the probe, and the AC voltage, the amplitude of the probe becomes constant when it swings to the positive side, or to the negative side The amplitude of the probe when shaken is constant, or the sum of the amplitude of the probe when shaken to the positive side and the amplitude of the probe when shaken to the negative side is constant. Amplitude control means for controlling the vibration amplitude by the vibrating device, and vibration amplitude measuring means for measuring the vibration amplitude A surface potential and shape measuring instrument comprising: 3. A probe held at the tip of a cantilever vibrated by a vibrating device, and an electrostatic force detecting means by a displacement detector for detecting a vibration amplitude of the probe which changes according to an electrostatic force. And by varying the DC voltage so that the electrostatic force when the AC voltage is swung to the positive side and the electrostatic force when the AC voltage is swung to the negative side are equalized by superposing the AC voltage on the probe. Potential control means, a DC potential measuring means for measuring the potential of the DC voltage of the probe, and the AC voltage, the amplitude of the probe becomes constant when it swings to the positive side, or to the negative side The amplitude of the probe when shaken is constant, or the sum of the amplitude of the probe when shaken to the positive side and the amplitude of the probe when shaken to the negative side is constant. A frequency control means for controlling the vibration frequency by the vibrating device and a vibration frequency measurement for measuring this vibration frequency. A surface potential and shape measuring instrument, characterized in that it comprises a measuring means. 4. A conductive probe facing the object to be measured, electrostatic force detection means for detecting electrostatic force acting between the probe and the surface potential of the object to be measured, and the probe. And a potential control means for varying the DC voltage so that the AC voltage is superimposed on the DC voltage and the electrostatic force when the AC voltage swings to the positive side becomes equal to the electrostatic force when the AC voltage swings to the negative side. , A DC potential measuring means for measuring the potential of the DC voltage of the probe, and an electrostatic force when the AC voltage swings to the positive side becomes constant, or an electrostatic force when the AC voltage swings to the negative side becomes constant. Next to
Alternatively, the feedback signal for controlling so that the sum of the electrostatic force when swung to the positive side and the electrostatic force when swung to the negative side is constant is separated by using a separating means for separating the feedback signal by the frequency band. Amplitude control means for controlling the amplitude of the AC voltage by the feedback signal of the partial frequency band, and a feedback signal excluding the signal of the partial frequency band for controlling the amplitude of the AC voltage separated by the separating means A surface potential and shape measuring instrument comprising: a distance control means having an actuator for controlling a distance between the measuring object and the probe; and a displacement measuring means for measuring a displacement amount of the actuator. .. 5. An electrostatic force detecting means using a probe held at the tip of a cantilever vibrated by a vibrating device and a displacement detector for detecting a vibration amplitude of the probe which changes according to electrostatic force. And by varying the DC voltage so that the electrostatic force when the AC voltage is swung to the positive side and the electrostatic force when the AC voltage is swung to the negative side are equalized by superposing the AC voltage on the probe. Potential control means, a DC potential measuring means for measuring the potential of the DC voltage of the probe, and the AC voltage, the amplitude of the probe becomes constant when it swings to the positive side, or to the negative side Control so that the amplitude of the probe when shaken becomes constant, or the sum of the amplitude of the probe when shaken to the positive side and the amplitude of the probe when shaken to the negative side becomes constant. Of a part of the frequency band separated by separating means for separating the feedback signal by the frequency band Amplitude control means for controlling the vibration amplitude of the vibration device by a feedback signal, vibration amplitude measuring means for measuring the vibration amplitude, and the part for controlling the vibration amplitude of the vibration device separated by the separating means. A distance control means having an actuator for controlling the distance between the object to be measured and the probe by a feedback signal excluding a signal in the frequency band, and a displacement measuring means for measuring the displacement amount of the actuator. Characteristic surface potential and shape measuring instrument. 6. A probe held at the tip of a cantilever vibrated by a vibrating device, and an electrostatic force detecting means by a displacement detector for detecting a vibration amplitude of the probe which changes according to an electrostatic force. And by varying the DC voltage so that the electrostatic force when the AC voltage is swung to the positive side and the electrostatic force when the AC voltage is swung to the negative side are equalized by superposing the AC voltage on the probe. Potential control means, a DC potential measuring means for measuring the potential of the DC voltage of the probe, and the AC voltage, the amplitude of the probe becomes constant when it swings to the positive side, or to the negative side Control so that the amplitude of the probe when shaken becomes constant, or the sum of the amplitude of the probe when shaken to the positive side and the amplitude of the probe when shaken to the negative side becomes constant. Of a part of the frequency band separated by separating means for separating the feedback signal by the frequency band Frequency control means for controlling the vibration frequency of the vibration device by a feedback signal, vibration frequency measuring means for measuring the vibration frequency, and the part for controlling the vibration frequency of the vibration device separated by the separating means. A distance control means having an actuator for controlling the distance between the object to be measured and the probe by a feedback signal excluding a signal in the frequency band, and a displacement measuring means for measuring the displacement amount of the actuator. Characteristic surface potential and shape measuring instrument.