JPS62110167A - Apparatus for detecting surface potential - Google Patents

Abstract

PURPOSE:To reduce output variation based on the variation in the distance between a detection electrode and an electrode to be measured by simple constitution, by a method wherein the output of a detection means is separated corresponding to a phase to obtain a first and a second phase outputs and the ratio of said phase outputs is taken to correct the phase outputs. CONSTITUTION:A vibration electrode 2 is vibrated by the piezoelectric tuning fork vibrated by a piezoelectric tuning fork oscillation circuit 11 and charge based on the change in the capacity between an electrode 2 and a surface to be measured is induced on the electrode 2. This charge is converted to voltage by the integrating circuit constituting a detection means and said voltage is amplified by an amplifying circuit 13 to be applied to half wave separators 14, 15. The separators 14, 15 respectively separate the output of the circuit 12 to apply first and second phase outputs. The first phase output from the separator 14 is smoothed and amplified by a smoothing/ amplifying circuit 16 and a detection signal before correction is applied to a multiplier circuit 18. The second phase output from the other separator 15 is applied to a dividing circuit 19 to operate the ratio of the first and the second phase outputs. This calculated ratio is applied to the circuit 18 to be multiplied by the first phase output while the corrected output is amplified by an amplifying circuit 20 to be applied to an output terminal 21.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides an electric field fG having a structure that reduces output fluctuations due to fluctuations in the distance between the surface to be measured and the vibrating electrode.
Regarding detection H''PI.

[Prior art 1] As a device for non-contact detection of the upper surface of the surface to be measured,
There are some well-known types such as the ``boo'' brim type or the ``vJ shape'' type. However, in both types of detection devices, due to variations in the distance between the surface to be measured and the sensing electrode,
It was inevitable that the output would change. This is because the surface potential is detected based on the change in charge induced on the sensing electrode due to the seedling coupling between the surface to be measured and the seedling.

Therefore, attempts have been made to reduce the distance dependence by attaching a correction electrode near the sensing electrode and feeding back the output from the upper electrode, or to reduce the distance dependence. As disclosed in ヂ] Tsuba ni ken9JI 'jF+tIN'! A method has been proposed that feeds back the output of , and reduces distance dependence.

[Problems to be Solved by the Invention] However, in the configuration for reducing the distance dependence described above, the configuration of the correction circuit is complicated, and there are also problems in that insulation is difficult because high voltage signals are fed back. was there. In addition, the surface potential detection device itself is large in size, and therefore, it is difficult to mount the surface potential detection device in cases where there is not much space for installation in the device into which it is installed, for example, when it is mounted around the photosensitive drum of a copying machine.

Therefore, an object of the present invention is to provide a surface potential detection Vt having a relatively simple structure and having a structure that effectively reduces output fluctuations caused by fluctuations in the distance between a sensing electrode and a surface to be measured.
The aim is to provide a

[Means for Solving the Problems] The surface potential detection device of the present invention has the above-mentioned vibration chamber. This is an improved type of surface potential detection device, and has the following configuration.

In other words, there is a oscillating VJ electrode in which a charge is induced based on a capacitance change between it and the surface to be measured, and an electric charge induced on this oscillating voltage. a detecting means for extracting the voltage as a voltage change, a separating means for separating the output of the detecting means into first and second phase outputs according to the phase, and a first and second phase output provided from the separating means. and a correction means for calculating the ratio and correcting the first and second phase outputs based on the ratio.

[Operation] This invention provides that when the outputs taken out from the vibrating electrodes are separated by phase, the ratio of the first and second phase outputs is Using the fact that the distance between the measurement surface and the vibrating electrode is inversely proportional to the amplitude of the vibrating electrode, the detection signal obtained from the vibrating electrode, which is the first or second phase output, is multiplied by this ratio. By combining these, it is possible to correct output fluctuations of the surface potential detection device caused by fluctuations in the set distance between the surface to be measured and the vibrating electrode and fluctuations in amplitude.

That is, as shown in FIG. 2, the distance from the surface to be measured 1 to the l1li71 electrode 2 is now d
, the amplitude of the grazing C electrode 2 is 2Δd.

In this case, if the potential of the surface to be measured 1 is V and the capacitance between the surface to be measured 1 and the vibrating electrode 2 in a resting state is Cn, then the electric charge Q induced in the vibrating electrode 2 is calculated by the following formula ( 1)
It is expressed as

Δd1 Q = V(VCo/(1+2;Slnωt)
A change in charge Q can be converted into a change in voltage by, for example, an integrating circuit shown in FIG. 3. If the converted output is V, then ■ is expressed by the following equation (2).

Now, if we consider the case where sinω is 1 ± 1, then sinω is -
When 1, V becomes the minimum value, and when sinω℃−1, V
takes the maximum value. Therefore, the minimum and maximum values are V iiz and Vl, respectively. A and taking the ratio γ of its absolute value, it is expressed by the following equation (3).

The ratio γ represented by the above formula (3) 'C- is d, and Δ
d, and therefore the amplitude 2Δ of the vibrating electrode 2
Assuming that d is constant, the change in γ due to a change in do and the change in γ due to a change in Δd are expressed by the following equations (4) and (5), respectively. It can be seen that the vibration is inversely proportional to the distance between the electrode 2 and the amplitude 2Δd of the vibration electrode 2. Therefore, by adjusting the value of this ratio γ to an appropriate value and multiplying it by the output of the surface potential detection device, it is possible to compensate for fluctuations in the distance wi between the surface to be measured and the vibrating electrode and the amplitude of the vibrating electrode. It can be seen that the upper detection device is configured to provide a surface that is not easily affected. The surface potential detecting device of the present invention separates the output of the vibrating seperator according to the phase, calculates the ratio of each separated output, and converts the output of the surface potential detecting device into the It is something to do.

[Description of Embodiment 1] FIG. 1 is a block diagram of a surface potential detection device according to an embodiment of the present invention. Referring to FIG. 1, the vibrating electrode 2 is at a distance of 1! from the surface to be measured. It is placed across the Irdo, for example a vibration type... 2 is pressure? It is attached to one arm of the H tuning fork, and the amplitude is 2Δd'' by the piezoelectric tuning fork oscillation circuit 11.
c It is configured to vibrate. On the basis of this vibration, a charge corresponding to the potential of the surface to be measured 1 is induced on the vibrating separator 2 due to a change in capacitance with the surface to be measured 1.

The output of Kando'ichigoku 2 is given to an integrating circuit 12.

The integrating circuit 12 constitutes a detection means for extracting the charge induced on the vibration vJ electric current 2 as a voltage change. In other words, the integrating circuit 12 is constituted by, for example, a circuit as illustrated in FIG. 3, and converts the charge induced on the @i1J electrode 2 into a voltage. The output converted into this voltage is given to the amplifier circuit 13 and amplified. The output of the amplifier circuit 13 is sent to a half-wave separator 14.15. 14 and 15 constitute separation means that separates the output of the amplifier circuit 13 according to the phase and provides first and second phase outputs, respectively. One half-wave separator 14
The output, that is, the first phase output, is fed to a smoothing 1j4 width circuit 16 for smoothing and amplifying the waveform of the first phase output, and the other half wave component # is also fed to the device 15. The first phase output smoothed and amplified by the smoothing amplification circuit 16 increases the corrected detection output by 4.
The multiplier is applied to the arithmetic circuit 18 and also to the division circuit 19 in order to calculate the ratio γ mentioned above.

The other half wave I! Similarly, the second phase output of the III unit 15 is smoothed and amplified by the other smoothing amplifier circuit 17, and is provided to the divider circuit 19. ! The IJ i circuit 19 calculates the ratio of the first phase output and the second phase output, that is, calculates the value of γ, and supplies this to the multiplication circuit 18.

In the multiplication circuit 18, the detection output obtained by multiplying the first phase output by V is multiplied by the above-mentioned γ, and the corrected output is given to the amplifier circuit 20.
An output is provided to the output terminal 21 that is not affected by the distance between the electrodes and the layer width of the moving electrode.

Next, the operation will be explained. In the embodiment shown in FIG. 1, the vibrating electrode 2 is vibrated by a piezoelectric tuning fork driven by a piezoelectric tuning fork oscillation circuit 11, and as a result, charges are induced on the vibrating electrode 2 based on the capacitance change between it and the surface to be measured. Ru. This charge is
The integrator circuit 12 converts it into a voltage. The output waveform of the integrating circuit 12 is shown in FIG. Next, the output of the integrating circuit 12 is amplified by the amplifier 13, and the output of the integrating circuit 12 is amplified by the wave separator 14.
I'll be back on the 15th. The half-wave components 11fll and 1/1.15 are connected to the integrator circuit 12 shown in FIG. 4 depending on the phase, respectively.
The output of 9 is inputted to give the first and second phase outputs.

In this embodiment, the half-wave M dividers 14 and 15 separate the outputs, which are changed by the integrating circuit 12 depending on the positive and negative phases. The output of one half-wave separator 14 is shown in FIG. 5, and the output of the other half-wave divider 15 is shown in FIG. In addition, integrating circuit 1
In the case of a valve section with an output of 2, it is not necessary to separate by positive phase (1), but it is also possible to add an arbitrary reference voltage by 5 and separate by IJ to the reference voltage.

The output of the half-wave separator 14, i.e., the first phase output, is smoothed and amplified by the smoothing amplifier circuit 16, and the output signal before correction is sent to the arithmetic circuit 18.

At the same time, the output of the V-slip amplifier circuit 1G is also given to one υ1 circuit in order to calculate T.

The output of the other half-wave separator 11Ts15, that is, the second phase output, is given to the vj calculation circuit 19, which separates the first phase output and the second phase output.
The ratio to the phase output is calculated using only one circuit. This obtained ratio γ is given to the multiplication circuit 18, and the first phase output and one trigram are combined. By the way, the outputs of each smoothing amplifier circuit 16 and 17 are as shown in FIG.

As is clear from equations (4) and (5) above, the second phase output V cuff shown in FIG.
The phase output Vmlγ is the potential to be measured V1. Even when x changes, the relationship shown in FIG. 23 is expressed. Therefore, even if V,x changes, γ-V,. Me/Vvai%
remains almost constant. Therefore, the phase output ki- has T
By combining these values, it becomes possible to obtain an output that is not affected by the distance between the surface to be measured and the vibrating electrode and that corresponds to the potential of the surface to be measured. Moreover, at the same time, it is possible to obtain a detection output that is not easily affected by fluctuations in the amplitude of the vibrating electrode.

[Effects of the Invention] In this invention, the ratio of the separation means for separating the output of the detection means into a first phase output and a second phase output according to the phase and each phase output given from this separation means is calculated, and the ratio is calculated by analogy. Accordingly, even if the mounting accuracy of the vibrating electrode, that is, the set distance between the surface to be measured and the vibrating electrode changes, there is no change in the set distance. It is possible to accurately detect the surface potential of the surface to be measured without being affected by the Furthermore, as is clear from equations (4) and (5) above, the influence due to amplitude fluctuations of the vibrating electrode can also be significantly reduced.

Therefore, in the surface potential detection device of the present invention, it is possible to realize a surface potential detection device that does not require complicated work for attaching and adjusting the position of the vibrating electrode, and is characterized by stable output.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram of one embodiment of the present invention. FIG. 2 is a side view showing the relationship between the vibrating electrode and the surface to be measured. FIG. 3 is a circuit diagram showing an example of an integrating circuit. FIG. 4 is a diagram showing the output waveform of the integrating circuit, FIG. 5 is a diagram showing the output waveform of one half-wave separator, and FIG. 6 is a diagram showing the output waveform of the other half-wave separator. It is a diagram. Figure 7 is. It is a figure which shows the output waveform of both smoothing amplifier circuits. FIG. 8 is a diagram showing the relationship between the first phase output, the second phase output, and the potential of the surface to be measured. In the figure, 1 is the surface to be measured, 2 is a vibrating electrode, 12 is an integrating circuit constituting the detection means, 14.15 is a half-wave separator constituting the separating means, 19 is a dividing circuit constituting the correcting means, 18 The symbol composing the correction means indicates an arithmetic circuit. @4koku

Claims (2)

[Claims] (1) A vibrating electrode in which an electric charge is induced based on a capacitance change between the vibrating electrode and the surface to be measured, a detection means for extracting the electric charge induced on the vibrating electrode as a voltage change, and an output of the detection means according to the phase. a separating means for separating into first and second phase outputs; and calculating a ratio of the first and second phase outputs given from the separating means, and correcting the first or second phase output based on the ratio. A surface potential detection device comprising: a correction means for detecting a surface potential; (2) The correction means includes a division circuit that calculates the ratio of the first and second phase outputs, and a correction output based on the ratio given by the division circuit, to the first or second phase output. 2. The surface potential detection device according to claim 1, further comprising a multiplication circuit for multiplying .