JPH0727808A - Noncontact type surface potentiometer - Google Patents

Abstract

PURPOSE:To make a surface potentiometer which measures the surface potential of a photoreceptor, etc., in a non contact state not to be affected even when the position of the potentiometer is mechanically shifted and, at the same time, to reduce the size of a sensor probe so that the probe can be easily approached a sample to be detected. CONSTITUTION:A sensor element 11 is constituted of a Pockels crystal, polarizer, wave plate, and analyzer. A detection electrode 13 which is counterposed to a sample 1 to be detected is provided and connected to one 12a of the electrodes 12a and 12b attached to both side faces of the element 11. A signal processing section 15 finds the surface potential of the sample 1 from the intensity of the light passed through the Pockels crystal of the element 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to PPC (plain paper).
The present invention relates to a non-contact type surface electrometer for measuring the surface potential of a photoconductor used for copier), FAX (facsimile), etc. in a non-contact manner.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram showing the measurement principle of a conventional surface potential meter which measures the surface potential in a non-contact manner. In the figure, 1 is a sample to be detected such as a photoconductor of a copying machine, which is charged to + (positive) by a power source 2.

Reference numeral 3 is a case of the sensor section, which is a small window 4 for measurement.
Is provided, and a pair of tuning fork type vibrators 5 are arranged inside the small window 4. Reference numeral 6 is a detection electrode arranged inside the small window 4.

FIG. 8 schematically shows the structure of the sensor section. The pair of vibrators 5 are integrally formed with a tuning fork 8 to which a piezoelectric element (piezoelectric ceramics) 7 is adhered, and an alternating voltage is applied to the piezoelectric element 7 from a drive circuit 9. The output of the detection electrode 6 is amplified by the preamplifier 10 and input to a signal processing circuit (not shown).

In the case of measuring the surface potential of the sample 1 to be detected in the surface electrometer as described above, Case 3 is used.
The small window 4 is set toward the surface of the sample to be detected 1. At this time, if there is electric charge on the surface of the sample 1 to be detected due to corona discharge or the like, electric lines of force A as shown by the broken line in FIG. This line of electric force A is
Although it reaches the detection electrode 6 through the small window 4 of the case 3,
Here, the distance between the sample to be detected 1 and the detection electrode 6 is fixed to a constant value, the electric force line A is choppered by some method, and the time of the electric force line A reaching the detection electrode 6 having the area S is determined. The surface potential of the sample to be detected 1 can be known by inputting the amount of dynamic change into the gate of the FET incorporated in the signal processing circuit and detecting the amount.

That is, as one method of the chopper of the electric flux line A, the AC method is used in the example of FIG.
Attach the piezoelectric element 7 to the tuning fork 8 with stable frequency,
AC voltage is applied to the piezoelectric element 7 to move the vibrator 5 to the arrow B
In this way, the lines of electric force A are chopped. At this time, when the sample 1 to be detected and the detection electrode 6 in the electrostatic field are regarded as a flat plate capacitor with an electrode space r containing an air layer having _a dielectric constant ε _a , the electrostatic capacitance C and the charge Q of this capacitor are When the applied voltage (potential of the sample to be detected 1) is V, C = ε _a S / r and Q = CV.

From the relation of the above equation, the change in the leakage current I of the capacitor due to the chopping of the electric force line A is obtained, and this is detected as the AC signal voltage. This current I is

[0008]

[Equation 1]

It is represented by At this time, if C = constant,

[0010]

[Equation 2]

[0011] Then, this is amplified as an AC signal voltage by the preamplifier 10 to relatively determine the surface potential of the sample 1 to be detected.

[0012]

However, in the above-mentioned conventional non-contact type surface electrometer, when the position of the detection electrode or the position of the chopper deviates from the small window through which the lines of electric force pass, the output is generated. There is a problem in that the level changes from a predetermined value and the surface potential cannot be measured accurately.

Further, since it has a small window, when it is actually incorporated into a machine for use, for example, toner or the like enters the case and adversely affects the piezoelectric tuning fork, resulting in leakage or deterioration of sensitivity. There were problems such as.

The present invention has been made by paying attention to the above-mentioned problems. It is possible to accurately measure the surface potential, a dustproof structure is possible, and it is possible to prevent the occurrence of leakage due to toner or the like. In addition, it is an object of the present invention to provide a non-contact type surface electrometer which can reduce the size of the sensor probe and can easily clean the sensor probe.

[0015]

The non-contact surface electrometer of the present invention comprises a sensor element using a Pockels crystal in which the refractive index of light changes according to an applied voltage, and a sensor element facing the surface of a sample to be detected. A detection electrode that is arranged and electrically connected to one of the electrodes on both sides of the sensor element, and a signal processing unit that detects the surface potential of the sample to be detected from the intensity of light that has passed through the Pockels crystal of the sensor element. It is composed of.

Further, the area of the sensing electrode is larger than the area of the electrode connected to the sensing electrode of the above-mentioned sensor element, and has a proportional relationship.

[0017]

In the non-contact type surface electrometer of the present invention, since the optical sensor is used, the measurement can be performed without being affected by the mechanical positional relationship, and the dustproof structure can be obtained.

Further, since the sensor probe having only the detection electrode and the other portion can be separated, the sensor probe can be downsized and the sensor probe can be easily cleaned.

[0019]

1 is a diagram showing a schematic configuration of a non-contact type surface electrometer according to an embodiment of the present invention. In the figure, 1 is a sample to be measured whose surface potential is to be measured, 11 is a sensor element using a Pockels crystal in which the bending ratio of light changes according to an applied voltage, and electrodes 12a and 12b are arranged in parallel on both sides. It is provided.

Reference numeral 13 denotes a detection electrode which is arranged so as to face the surface of the sample to be detected 1 and which is located on both sides of the sensor element 11.
a and 12b, which are electrically connected to one electrode 12a of the sensor element 11 by the lead wire 14, and the other electrode 1 of the sensor element 11
2b is grounded. A signal processing unit 15 detects the surface potential of the sample 1 to be detected from the intensity of light that has passed through the Pockels crystal in the sensor element 11.

The detection electrode 13 is formed of, for example, a metal plate of copper, brass, aluminum or the like, and the lead wire 14 is connected to the end portion thereof. And this detection electrode 13
Are arranged in parallel with the sample to be detected 1 with a distance r1, and a voltage corresponding to the surface potential of the sample to be detected 1 is detected by the detection electrode 13.
The intensity of the emitted light that has been applied to the sensor element 11 through the sensor element 11 and has passed through the sensor element 11 changes according to the applied voltage. Therefore, the signal processing unit 15 can obtain the surface potential of the sample to be detected 1 from the intensity of the emitted light.

FIG. 2 is a block diagram showing the measuring principle of the above-mentioned non-contact type surface electrometer. The sample 1 to be detected is charged positively or negatively (here, positive) by the power supply 2. Further, in the sensor element 11, the bending ratio (transmittance) of light changes according to the applied voltage (surface potential of the sample 1 to be detected) as described above. This sensor element 11 is composed of isotropic photoelastic crystal, especially uniaxial crystal system LiTaO ₃ , LiNbO ₃ or other Pockels (P
ockels) It consists of a crystal, a polarizer, a wave plate, and an analyzer. When a voltage is applied, the bending ratio of the light changes linearly according to the applied voltage, and the intensity of the emitted light that passes through it. Has the property of depending on the applied voltage.

Further, in FIG. 2, 16 is a light receiving portion having a photodiode (PD) for receiving the light passing through the inside of the sensor element 11, and 17 is an amplifier for amplifying the output of the light receiving portion 16. Signals are signal processing circuits (including arithmetic unit)
The signal is input to 18, and the signal processing circuit 18 detects the surface potential of the sample 1 to be detected from the intensity of light from the sensor element 11.

FIG. 3 is a diagram showing a measuring operation by the surface electrometer of FIG. The positional relationship between the sensor element 11 and the sample to be detected 1 is as shown in FIG. 3 (a). The sensor element 11 is placed in an electric field, light is made incident through the polarizer from its end face, and the emitted light Measure the strength.

At this time, the incident light is first converted into linearly polarized light through the polarizer, passes through the inside of the crystal having the length L in the sensor element 11, and is converted into elliptically polarized light. FIG. 3B shows such a state. When linearly polarized light having a wavelength of 45 ° is incident on the XZ plane, the linearly polarized light is bent in the X-direction and the Y-direction at a bending ratio n. When passing through the inside of the crystal due to the difference between _X and _ny , it is converted into elliptically polarized light.

Here, when the sensor element 11 is directly placed in an electric field as shown in FIG. 3A, when the surface of the sample 1 to be detected is charged, a potential difference is generated across the sensor element 11 due to electrostatic capacitance. Occurs. The equivalent circuit at this time is shown in FIG. If the capacitor capacity of the air layer between the sample to be detected 1 and the sensor element 11 is C1 and the capacitor capacity of the sensor element 11 is C2, these can be regarded as a series connection, and FIG. The relationship between the respective potential differences V1 and V2 shown in FIG. 3 is that when the distance between the sample to be detected 1 and the electrode surface on the opposite side of the sensor element 11 is r and the thickness of the crystal is d,

[0027]

[Equation 3]

Can be represented by

That is, the sample to be detected 1 and the electrode 12b
When the surface potential of the sample 1 to be detected changes while the distance r between the electrodes is constant, the potential between the electrodes 12a and 12b also changes,
According to the magnitude of this potential, the sensor element 1 whose light has an optical path length L
The intensity of the emitted light when passing through the inside of 1 changes. Therefore, by detecting the intensity of the light emitted from the sensor element 11,
If the detected voltage is obtained, the values of r and L are known, so that the surface potential of the sample 1 to be detected can be known.

The measurement principle of the optical surface electrometer has been described above. However, in this embodiment, as shown in FIG. 1, a detection electrode 13 is newly provided, and in addition to the case of FIG. The potential difference has the same effect.

That is, when the detection electrode 13 is arranged so as to face the sample 1 to be detected, a potential difference is generated across the sensor element 11 due to the surface potential of the sample 1 to be detected. This potential difference depends on the surface area of the detection electrode 13 and is determined by the amount of electric force lines emitted from the sample 1 to be detected.

There is a correlation between the surface area S1 of the electrode 12a of the sensor element 11 connected to the detection electrode 13 and the area S2 of the detection electrode 13, and the area S1 is larger than the area S1.
2 is larger and has a proportional relationship.

For example, a crystal of LiTaO _{3 has} a thickness t =
Area S1 = 1 of the electrode 12a of the sensor element 11 of 0.5 mm
12 mm ² , inter-electrode distance r1 = 0.5 mm, applied voltage V = 3
Table 1 shows the relationship between the area S2 of the detection electrode 13 and the applied voltage V2 of the sensor element 11 under the condition of 00V.

[0034]

[Table 1]

With this structure, as shown in FIG. 5, the sensor probe 19 having only the detection electrode 13 is provided.
It is possible to realize an optical surface electrometer which is separated into a main body 20 including an optical system (sensor element 11) and a signal processing unit 15 and connected by a lead wire 14.

Therefore, there is no influence of mechanical displacement as in the conventional case, the surface potential can be easily and accurately measured, a dustproof structure is possible, and leakage due to toner or the like can be prevented. it can.

Since the sensor probe 19 having only the detection electrode 13 and the main body 20 including other optical system and signal processing system can be separated as described above, the sensor probe 19 should be brought close to the surface of the sample 1 to be detected. It is possible to reduce the size of the sensor probe 19, and
Cleaning of the sensor probe 19 is easy.

FIG. 6 is an external view showing an example of the sensor probe 19. This sensor probe 19 has a resin frame 2
1 has a configuration in which the detection electrode 13 is fitted, and one end of the detection electrode 13 and the lead wire 14 are connected.
Further, the resin frame 21 is provided with a screw fixing hole 22 for fixing at the time of mounting.

[0039]

As described above, according to the present invention, the optical sensor element is used, and the detection electrode is provided and the sensor element is connected to the detection electrode. There is no effect, and the surface potential can be measured easily and accurately, and a dustproof structure can be obtained.

Further, since the sensor probe having only the detection electrode and the main body including the other optical system and the signal processing system can be separated, the sensor probe can be downsized and the sensor probe can be easily cleaned. effective.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing the measurement principle of the electrometer of FIG.

FIG. 3 is an explanatory diagram showing a measurement operation of the electrometer of FIG.

FIG. 4 is an equivalent circuit diagram of the sensor element of FIG.

5 is a block diagram showing the overall configuration of the electrometer of FIG.

6 is an external view showing an example of the sensor probe of FIG.

FIG. 7 is a configuration diagram showing a conventional example.

8 is a perspective view showing the structure of the sensor unit of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Detected sample 11 Sensor element 12a, 12b Electrode 13 Detection electrode 14 Lead wire 15 Signal processing part 19 Sensor probe 20 Main body

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[Procedure amendment]

[Submission date] April 7, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 2

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

Furthermore, it is large area of area than the detection electrode of the electrodes of the sensor element, which is constituted and to have a proportional relationship.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

[0019]

1 is a diagram showing a schematic configuration of a non-contact type surface electrometer according to an embodiment of the present invention. In the figure, 1 is the detected sample to be measured the surface potential, 11 refraction index of the light changes depending on the voltage applied Pockels (Pockel
s) A sensor element using a crystal, electrodes 12a, 1 on both sides
2b are provided in parallel.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0022

[Correction method] Change

[Correction content]

FIG. 2 is a block diagram showing the measuring principle of the above-mentioned non-contact type surface electrometer. The sample 1 to be detected is charged positively or negatively (here, positive) by the power supply 2. The sensor element 11, refraction of the light (transmittance) changes depending on the voltage applied as described above (the surface potential of the detection sample 1). The sensor element 11 is a trigonal uniaxial crystal Li.
Pockels such as TaO ₃ and LiNbO ₃
s) It consists of a crystal, a polarizer, a wave plate, and an analyzer.
When a voltage is applied, it has a property of light refraction index of the in accordance with the applied voltage linearly changes, the intensity of outgoing light that has passed through it depends on the applied voltage.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Name of item to be corrected] 0025

[Correction method] Change

[Correction content]

At this time, the incident light is first converted into linearly polarized light through the polarizer, passes through the inside of the crystal having the length L in the sensor element 11, and is converted into elliptically polarized light. Figure. 3 (b) is limited to showing its state, when the incident linearly polarized light of wavelength incident in the X-Z plane for example 45 °, refraction index the linearly polarized light in the X direction and the Z-direction When passing through the inside of the crystal due to the difference between n _X and n _Z , it is converted into elliptically polarized light.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction content]

Here, when the sensor element 11 is directly placed in an electric field as shown in FIG. 3A, when the surface of the sample 1 to be detected is charged, electrostatic induction induces a potential difference across the sensor element 11. Occurs. The equivalent circuit at this time is shown in FIG. If the capacitor capacity of the air layer between the sample to be detected 1 and the sensor element 11 is C1 and the capacitor capacity of the sensor element 11 is C2, these can be regarded as a series connection, and FIG. The relationship between the potential differences V1 and V2 shown in Fig. 4 is that the distance between the sample to be detected 1 and the electrode surface on the opposite side of the sensor element 11 is r, the thickness of the crystal is d 2 , and the Pockel
If the relative permittivity of the element is ε ,

[Procedure Amendment 7]

[Document name to be amended] Statement

[Name of item to be corrected] 0027

[Correction method] Change

[Correction content]

[0027]

[Equation 3]

[Procedure Amendment 8]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

Claims (2)

[Claims] 1. A sensor element using a Pockels crystal in which the refractive index of light changes according to an applied voltage, and one of electrodes on both sides of the sensor element, which is arranged so as to face the surface of a sample to be detected, is electrically connected to the sensor element. A non-contact type surface electrometer comprising a detection electrode connected to the sensor element and a signal processing unit for detecting the surface potential of the sample to be detected from the intensity of light passing through the Pockels crystal of the sensor element. 2. The non-contact type surface potential according to claim 1, wherein the area of the sensing electrode is larger than the area of the electrode connected to the sensing electrode of the sensor element and has a proportional relationship. Total.