JPH11231005A - Surface charge measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To favorably measure surface charge by coexisting resolution, sensitivity, and accuracy with each other, based on the surface charge measuring device in which an optical element having electro-optical effect is utilized. SOLUTION: The potential of surface charge 13 corresponding to the part to be detected of a measured object 12 is caused on an optical element 3 having horizontal electro-optical effect such as an optical crystal, and by measuring change of the polarized state and the like of a light beam emitted from the optical element 3, the surface potential of the measured object 12 is measured. By utilizing the optical element 3 having the horizontal electro-optical effect, it is equivalent to detect an electric field 10H spreading in the horizontal direction in the crystal, but because in the crystal of large dielectric constant, the incident electric field is faced to the direction along the face, the surface charge can be measured in high resolution, high sensitivity, and high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface charge measuring device capable of measuring a surface charge with high resolution and sensitivity with high accuracy.

[0002]

2. Description of the Related Art Generally, in various image recording applications such as a plate making apparatus, a copying apparatus, a laser plotter, etc., image recording is performed by using an electrophotographic process. Image recording by an electrophotographic process uses, for example, an electrophotographic photosensitive member having an optical semiconductor layer and a conductive support layer, and after uniformly charging the optical semiconductor layer of the electrophotographic photosensitive member by corona discharge or the like, the light By performing image exposure by beam scanning or irradiation of reflected light from the original, the charged charges on the exposed portion on the optical semiconductor layer are released to form an electrostatic latent image, and the toner is charged to the opposite polarity to the electrostatic latent image. To develop the electrostatic latent image into a visible image.

In the image recording of such an electrophotographic process, the basis of the image formation is an electrostatic latent image, and knowing the state of the electrostatic latent image = surface charge is an electrophotographic photosensitive member or a mark. This is important in performing individual evaluation and analysis of the copying process (charging, exposure, development), and further in evaluating and analyzing the entire recording system. In particular, in recent years, image quality has been improved even in image recording in an electrophotographic process, and the need to measure an electrostatic latent image with high definition (high resolution) has increased.

The same applies to the measurement of not only the electrostatic latent image on the electrophotographic photosensitive member but also the polymer spacer of the gas-insulated cable in which the creeping discharge has occurred, the measurement of the surface charge of the charged member, and the like.

Conventionally, such surface charge distribution of an electrostatic latent image or the like has been measured by using a surface electrometer using an induced current. However, in the case of using such a surface voltmeter, the resolution is low, and only the potential of the entire surface in a range of 1 to 2 mm square can be measured. In particular, in image recording by light beam scanning, one scanning line (one raster) is usually one.
Since the thickness is about 0 to 100 μm, it is necessary to measure the surface potential distribution in such a minute portion, but such a surface potential meter cannot perform such a measurement, and a sufficient measurement result is obtained. Can not.

[0006] A method using an electron beam is also known as a method of measuring the surface charge distribution with higher definition. However, this method has a drawback that it cannot be measured in the air and that it is a destructive inspection of the electrostatic latent image. In addition, it takes a long time from charging of the electrophotographic photosensitive member to measurement, and it can be said that measurement is difficult with an electrophotographic photosensitive member having relatively large dark decay using zinc oxide or an organic photosensitive material.

To solve such problems, a surface charge measuring device using an optical element having an electro-optical effect has been developed as a device capable of measuring a surface potential with high resolution and high accuracy. Has been reported by For example,
"Study on measurement of dielectric surface charge distribution using electro-optic effect", Musashi Institute of Technology paper (1994) and "ac surface" in the document "J. Appl. Phys. 76 (6), 15 September 1994". dischargeon dielectric material obs
erved by advanced Pockels effect technique ", which indicates the Pockels effect (first-order electro-optic effect).
_{Using a 12} SiO ₂₀ (BSO) single crystal, the time change of the residual charge distribution generated on the dielectric film due to the creeping discharge between the needle and the plate electrode is measured.

[0008] Further, the document "J. Phys. D: Appl.
s. 27 (1994) 1646-1652. “Highly sensitive measurement of surface charge” in “Printedin the UK”
distribution using the Pockels effect and an imag
According to the “e lock-in amplifier”, a two-dimensional optical phase modulator is constructed using BSO single crystal, and the optical phase of the entire measurement surface is modulated in synchronization with the frame period of the photodetection camera, and the detected image is converted. The phase charge is measured to improve the S / N of the measured charge diagram, thereby measuring the surface charge distribution.

These surface charge measuring devices introduce an electric field generated from a surface charge on an object to be measured into a crystal having an electro-optic effect, and induces a potential corresponding to the surface charge distribution in the electro-optic crystal. The polarization, phase, and refractive index of the light beam passing through the crystal are changed, and the change is detected to measure the surface charge distribution of the measured object. In such a surface charge measuring device utilizing the electro-optic effect, the resolution of the surface potential measurement can be adjusted by the thickness of the crystal exhibiting the electro-optic effect and the thickness of the object to be measured, and the resolution is about 100 μm square. Of the surface potential can be measured.

[0010]

However, in the case of such a surface charge measuring device utilizing the electro-optical effect, the resolution can be increased by making the crystal thinner, but the mechanical strength is correspondingly increased. As a result, the effective area that can be measured becomes small, and the sensitivity of the surface charge measurement also decreases. In other words, it is difficult to realize high-resolution and high-sensitivity surface charge measurement by making all of them compatible.

In the case of such a surface charge measuring device utilizing the electro-optical effect, in order to measure the surface charge with high resolution, the electric flux lines generated from the charge on the object to be measured are applied to the lower electrode. It is desirable to move vertically. However, in actual surface charge measurement using an electro-optic crystal, a certain thickness of the crystal is required, and the lines of electric force spread before reaching the lower electrode. The result is a bad charge latent image. Furthermore, since the dielectric constant of the electro-optic crystal is large, the incident lines of electric force are refracted in the direction along the plane at the crystal interface, causing the electric field distribution detected by the crystal to spread, resulting in errors in the measurement results of the surface charge distribution. And the spatial resolution is reduced.

Accordingly, the present invention utilizes an optical element having an electro-optic effect in addition to being capable of extremely high resolution, high sensitivity and high precision measurement as compared with a conventional surface charge measuring device utilizing an induced current or the like. It is an object of the present invention to provide a surface charge measuring device capable of realizing good surface charge measurement while satisfying both resolution, sensitivity and accuracy based on the improved surface charge measuring device.

[0013]

According to the first aspect of the present invention,
An optical element having a horizontal electro-optic effect, at least one electrode electrically contacting the optical element, a light source emitting light incident on the optical element, and a polarization state of light emitted from the optical element And measuring means for measuring.

Accordingly, an electric potential corresponding to the detected portion of the charged body as the object to be measured is induced in an optical element such as an optical crystal having a horizontal electro-optical effect, and the polarization of the light beam emitted from the optical element is changed. The surface potential of the charged body is measured by measuring changes in phase, refractive index, and the like. Here, by using an optical element having a horizontal electro-optic effect, an electric field spreading in the lateral direction in the crystal is detected.In a crystal having a large dielectric constant, the incident electric field is directed in a direction along the plane.
Surface charge can be measured with extremely high resolution, high sensitivity and high precision.

According to a second aspect of the present invention, in addition to the surface charge measuring device of the first aspect, the surface charge distribution of the object to be measured obtained from the polarization state measured by the measuring means is subjected to Fourier transform and Fourier transform. After the result is corrected by the spread function of the measurement area of the measurement system, an operation unit is provided which performs an inverse Fourier transform to obtain a measurement result of the surface charge distribution.

Although the signal measured by the measuring means has a high sensitivity and a high resolution, it represents a horizontal electric field. Therefore, it takes time to imagine the charge distribution from the measurement result. Since the crystal exhibiting the optical effect has a thickness, the distribution of the electric field to be detected is widened, and the measurement result of the surface charge distribution is blurred, and there is a concern that the resolution and sensitivity may be reduced. In this regard, in the present invention, the spread of the electric field is converted into a function, and the measurement result is corrected using this function and the Fourier transform. Therefore, the surface is not blurred due to the spread of the electric field, and has high resolution, high sensitivity, and high accuracy. The charge distribution can be measured.

According to a third aspect of the present invention, there is provided an optical element having a horizontal electro-optical effect, at least one electrode electrically contacting the optical element, and a light source for emitting light incident on the optical element. An optical system for two-dimensionally expanding light emitted from the light source and incident on the optical element, and measuring means for two-dimensionally measuring a polarization state of light emitted from the optical element are provided.

Therefore, it is the same as the first aspect of the present invention, but in particular, since the detection signal by the measuring means is an image having a two-dimensional spread, measurement for each point is performed in order to observe the charge distribution. There is no need to repeat, and the distribution state can be grasped at a glance. Moreover, since there is no need to sweep the beam, the time required to obtain one screen is short, and continuous observation can be performed. It is also possible to observe a change over time in the surface charge distribution, such as the holding state.

According to a fourth aspect of the present invention, in addition to the surface charge measuring device according to the second aspect, the second aspect of the present invention is a device for measuring a surface charge measured by a measuring means.
A two-dimensional Fourier transform is performed on the surface charge distribution of the measured object obtained from the two-dimensional polarization state, and the result of the Fourier transform is corrected by a spread function of a measurement area of the measurement system, and then a two-dimensional inverse Fourier transform is performed. And calculating means for obtaining the measurement result of the surface charge distribution.

Therefore, as in the second aspect of the present invention, the spread of the electric field is converted into a function, and the measurement result is corrected using this function and the two-dimensional Fourier transform.
It is possible to measure the surface charge distribution with high resolution, high sensitivity and high accuracy without blurring due to the spread of the electric field.

The fifth aspect of the present invention provides the first, second, and third aspects.
Alternatively, LiNbO ₃ was used as an optical element having a horizontal electro-optical effect in the surface charge measuring device described in 4.

Therefore, LiNbO ₃ has a very large electro-optic effect, especially of the horizontal type, and is most suitable for achieving higher resolution, higher sensitivity and higher precision.

The invention according to claim 6 is the invention according to claims 1, 2, and
The light emitted from the surface charge measuring device optical element described in 3, 4 or 5 is light reflected from the interface between the optical element and the object to be measured.

Accordingly, the detection light is light that has transmitted twice through the optical element having the electro-optical effect in a reciprocating manner, so that the sensitivity is twice as high as that of the transmitted light, and the surface charge can be obtained with high sensitivity and high precision. Since the measurement can be performed and the optical element having the electro-optic effect can be made thinner by the high sensitivity, it is convenient to measure the surface charge with high resolution. In addition, since the DUT itself does not need to transmit light, the surface charge distribution of the optically opaque DUT can also be measured.

[0025]

FIG. 1 shows a first embodiment of the present invention.
A description will be given based on FIG. FIG. 1 shows a schematic configuration example of a surface charge measuring device 1 of the present embodiment. Basically, a light source 2 that emits a light beam L0 as measurement light, a measurement head 4 formed using an optical element 3 having a horizontal electro-optic effect, and a transmission (or reflection) through the measurement head 4 )
The photoelectric conversion element 5 as a measuring means for measuring the amount of optical information such as the light amount of the light beam L1 obtained, and the surface charge information is calculated by performing predetermined arithmetic processing based on the measurement information measured by the photoelectric conversion element 5. And a signal processing device 6 having a function of an arithmetic unit.

Here, as the light source 2, a laser light source such as a gas laser or a semiconductor laser is used. However, the light source 2 is not limited to a light source that emits coherent light such as laser light.
For example, a light source that emits light having a relatively uniform wavelength, such as an LED, may be used. The distribution of surface charges may be obtained by directly irradiating the measurement head 4 with the light beam L0 emitted from the light source 2 and sweeping the same. On an optical path between the light source 2 and the measuring head 4, a polarizer 7 and a λ / 4 plate 8 are interposed. The polarizer 7 is for converting the light beam L0 into linearly polarized light, and the λ / 4 plate 8 is for applying an optical offset to the polarization phase difference.

As shown in FIG. 2, the measuring head 4 is based on an optical element 3 having a horizontal electro-optical effect showing a characteristic that an electric flux is refracted in an in-plane direction of the element. is there. That is, since the permittivity of the optical element 3 is generally several tens times larger than the permittivity of air,
2 is refracted greatly in a direction (lateral direction) parallel to the element surface as shown in FIG. 2, and at this time, the horizontal electric field 10 _H indicated by the vector is compared with the vertical electric field 10 _V. It shows characteristics that become extremely large. Here, as such an optical element 3, a horizontal type having a large electro-optical effect is preferable, for example, γ of LiNbO ₃ (lithium niobate).
22 are used. In addition, although the sensitivity is poor, NH ₄ H ₂
PO ₄ and γ63 of KH ₂ PO _4, of the α crystal γ11, Bi ₁₂
Γ41, ZnS, ZnT of SiO ₂₀ or Bi ₁₂ GeO ₂₀
Most electro-optic crystals can be used, such as e, γ41 of Bi ₄ GeO ₁₂ and the like. On one surface of the optical element 3, a conductive film 11 serving as an electrode is formed. In the present embodiment, since the transmitted light is used as the detection light, a film exhibiting light transmittance with respect to the wavelength of the light source 2, for example, an ITO film is used. Further, in the present embodiment, the conductive film 11 is grounded, but a bias voltage may be applied depending on the measurement purpose. Such an optical element 3 of the measuring head 4
On the other hand, for example, an insulating film 12 is attached as an object to be measured for the surface charge, and a horizontal electro-optical effect is induced inside the optical element 3 by an electric field of the surface charge 13 distributed on the insulating film 12. Provided for measurement.

An analyzer 14 is provided on the optical path between the measuring head 4 and the photoelectric conversion element 5.

In such a configuration, basically, by attaching an insulating film 12 which is an object to be measured and has a surface charge 13 to the optical element 3 having an electro-optical effect,
The electro-optical effect is induced inside the optical element 3 by the electric field of the surface charges 13 distributed on the insulating film 12, and the density and distribution of the surface charges 13 are measured.
First, after the light beam L0 emitted from the light source 2 is converted into linearly polarized light by the polarizer 7, the optical element 3 of the measuring head 4
Incident on At this time, if an optical offset is applied to the polarization phase difference by transmitting the linearly polarized light transmitted through the polarizer 7 through the λ / 4 plate 8, the polarity of the surface charge 13 can be determined. Here, in the optical element 3, since exhibits spread laterally as the electric field is an electric field 10 _H based on the surface charge 13 as shown in the enlarged view of FIG. 2, light incident on such an optical element 3 The beam L0 is emitted with high sensitivity under the influence of the electric flux 9 with or without the polarization state. Light beam L1 emitted from optical element 3
The light intensity distribution is measured by transmitting the light through the analyzer 14 for detecting the polarization state, then entering the photoelectric conversion element 5 and receiving the light. Through the arithmetic processing in the signal processing device 6 based on the light intensity distribution, the charge amount and the charge distribution are calculated and displayed.

As described above, according to the surface charge measuring device 1 of the present embodiment, the optical element 3 having the horizontal electro-optic effect is applied to the surface charge 13 of the detected portion of the insulating film 12 which is the measured object. The electric potential of the insulating film 12 is measured by inducing the electric potential and measuring changes in the polarization, phase, refractive index, and the like of the light beam L1 emitted from the optical element 3. By using the optical element 3 having an effect, the electric field 10 _H spreading in the lateral direction in the crystal is detected. However, in the case of a crystal having a large dielectric constant, the incident electric field 10 _H is directed in the direction along the plane. The surface charge 13 can be measured with high resolution, high sensitivity, and high accuracy. In particular, by using a horizontal LiNbO ₃ having an extremely large electro-optical effect as the optical element 3, extremely high resolution, high sensitivity and high precision surface charge 1 can be obtained.
3 can be measured.

Now, the signal processing in the signal processing device 6 will be described. The measurement result by the photoelectric conversion element 5 is transferred to the signal processing device 6 and used for calculating the surface charge distribution. Here, the output as the measurement result of the photoelectric conversion element 5 does not represent the surface charge distribution as it is, but merely indicates the polarization state. Therefore, the correction function and the Fourier transform are applied to the measured signal. By performing correction using the calculation, an arithmetic process is performed so as to output the surface charge distribution of the device under test (insulating film 12).

That is, in the measurement system for measuring the surface charge 13 of the insulating film 12 in a non-contact manner as in this embodiment, the electric field spreads inside the optical element 3 and a complete line is measured. However, since the line width slightly spreads, a correction function is created based on the spread function of the line image in the measurement system, and the measurement result is corrected using the correction function. However, a known charge distribution or voltage may be applied to the optical element 3, a correction function may be created from the measurement signal at that time and the known charge distribution, and this correction function may be used. The spread function of such a measurement system is based on the MTF (Modulation Trans
The correction function can be obtained in the same manner as in the case of fer Function, and the correction function can be created by performing the Fourier transform on the spread function and obtaining the reciprocal thereof by the inverse Fourier transform. As described above, in the arithmetic processing in the signal processing device 6, the spread of the electric field is converted into a function, and the measurement result is corrected using the function and the Fourier transform. Sensitivity and highly accurate measurement of the surface charge distribution can be performed.

Next, a second embodiment of the present invention will be described. The surface charge measuring device of the present embodiment also basically conforms to the configuration of the surface charge measuring device 1 as shown in FIG. An expanding beam expander is interposed as an expanding optical system. As a result, the light beam L0 whose diameter has been expanded by the beam expander is applied to the entire or a part of the measuring head 4. Correspondingly, in the present embodiment, a two-dimensional photoelectric conversion element is used instead of the photoelectric conversion element 5, and the light transmitted through the optical element 3 of the measuring head 4 can be detected as an image. Have been. As such a two-dimensional photoelectric conversion element, for example, C
Semiconductor photodetectors such as CD cameras and MOS type image sensors,
An imaging tube such as a vidicon or a carnicon, a PD array, a phototransistor array, a still camera, a digital camera, or the like can be used. In particular, if a photodetector such as a CCD camera or an image pickup tube capable of outputting and recording moving images is used, dynamic observation of the charge distribution can be performed with high resolution and high sensitivity.

Therefore, when the information of the surface charge distribution in the measurement plane is captured as an image, the measurement can be performed by sweeping the light beam L0. However, according to the present embodiment, the two-dimensional photoelectric conversion can be performed. Since the detection signal from the element is an image having a two-dimensional spread, it is not necessary to repeat the measurement for each point in order to observe the charge distribution, and the distribution state can be grasped at a glance. Since there is no need to sweep the beam, the time required to obtain one screen is short, and continuous observation can be performed.
A change with time of the surface charge distribution can also be observed.

Here, the processing in the signal processing device in the present embodiment will be described. Basically, it is the same as the processing in the signal processing device 6 in the first embodiment. An image showing a charge diagram captured by a camera that digitally records and outputs an image is obtained by using a detected image signal, a two-dimensional correction function, and a two-dimensional Fourier transform in a signal processing device. The output is corrected and output as the surface charge distribution of the insulating film 12, which is the object to be measured.

The optical element 3 used in the present embodiment is preferably the same as that of the first embodiment and has a large area. Specifically, LiNbO ₃ is preferable. Regarding other electro-optic crystals, for example, Bi ₁₂
In the case of SiO ₂₀ or Bi ₁₂ GeO ₂₀ or the like, when a crystal ingot is sliced, it becomes a vertical optical element having an electro-optical effect. It is not suitable because it has to be cut out from.

A third embodiment of the present invention will be described with reference to FIG. 1 and 2 are denoted by the same reference numerals, and description thereof will be omitted. The surface charge measurement device 21 of the present embodiment is configured to use a reflection type optical system. That is, the light beam L emitted from the light source 2
0 is incident on the measurement head 4 and is reflected at the interface 22 between the optical element 3 and the insulating film (object to be measured) 12. The conductive film 11 is configured to have transparency to allow light to enter and exit. In the present embodiment, a beam expander 23 is provided as an optical system for expanding the light beam L0 emitted from the light source 2, and a photoelectric conversion element 24 serving as a measuring unit is a CCD camera or the like.
A dimensional element is used. Further, a λ / 8 plate 25 through which the light beam L1 incident on and reflected by the optical element 3 reciprocates is also provided. Further, in the case of the present embodiment,
Although the incident angle of the light beam L0 can be set arbitrarily, as shown in the figure, in the case of a configuration in which the light beam L0 is perpendicularly incident on the measuring head 4, as shown in the figure, the beam splitter 26 is interposed on the optical path. It is configured to separate the path between the incident light and the output light. Further, a condensing optical system (not shown) may be interposed between the beam splitter 26 and the photoelectric conversion element 24, and the reflected light from a desired surface may be selectively detected by an aperture. The optical element 3 is the same as that of the second embodiment, and has a large electro-optic effect and a large area of LiNbO 3.
₃ is preferred.

Therefore, according to the present embodiment, the detection light is light that has transmitted through the optical element 3 having the electro-optical effect twice in a reciprocating manner, and thus the detection light is not transmitted light as in the first embodiment. The double sensitivity is obtained, and the measurement of the surface charge 13 can be performed with high sensitivity and high accuracy. Also, because the sensitivity is high,
Since the optical element 3 having the electro-optic effect can be made thin, it is convenient to measure the surface charge 13 with high resolution. Further, since the object itself does not need to transmit light, the surface charge distribution of the optically opaque object can be measured.

The signal processing in the signal processing device 27 having the function of the calculating means in the present embodiment is the same as that in the second embodiment described above. The image showing the charge diagram captured by the CCD camera is corrected in the signal processing device 27 using the detected image signal, the two-dimensional correction function, and the two-dimensional Fourier transform, and the measurement target object is measured. Is output as the surface charge distribution of the insulating film 12, and image processing such as left-right inversion is performed as necessary in consideration of reflected light.

[0040]

According to the first aspect of the present invention, a potential corresponding to the surface charge of the portion to be detected of the charged body which is the object to be measured is induced in an optical element such as an optical crystal having a horizontal electro-optic effect. Since the surface potential of the charged body is measured by measuring changes in the polarization, phase, refractive index, etc. of the light beam emitted from this optical element, an electric field spreading in the lateral direction in the crystal is detected. In a crystal with a large dielectric constant, the incident electric field is directed along the plane.
Surface charge can be measured with extremely high resolution, high sensitivity, and high accuracy.

According to the second aspect of the present invention, in addition to the surface charge measuring device of the first aspect, the spread of the electric field is converted into a function, and the measurement result is corrected using this function and Fourier transform. Therefore, high-resolution, high-sensitivity, and high-accuracy measurement of the surface charge distribution can be performed without blurring due to the spread of the electric field.

According to the third aspect of the invention, the same effects as those of the first aspect of the invention can be obtained. However, in particular, since the detection signal by the measuring means is an image having a two-dimensional spread, the charge distribution It is not necessary to repeat the measurement for each point in order to observe, and it is possible to grasp the distribution state at a glance. Moreover, since it is not necessary to sweep the beam, the time for obtaining one screen is short, and Since the observation can be performed continuously, it is also possible to observe a change over time in the surface charge distribution such as the state of retaining electric charges.

According to the fourth aspect of the present invention, similar to the second aspect of the invention, the spread of the electric field is converted into a function, and the correction of the measurement result is performed using this function and two-dimensional Fourier transform. Since this is performed, it is possible to measure the surface charge distribution with high resolution, high sensitivity and high accuracy without blurring due to the spread of the electric field.

According to the invention described in claim 5, according to claim 1,
The use of a horizontal LiNbO ₃ having a very large electro-optical effect as the optical element having a horizontal electro-optical effect in the surface charge measuring device described in 2, 3, or 4, further improving the resolution, sensitivity and precision. In particular, there is obtained an advantage that a large area can be easily obtained even in achieving a two-dimensional structure as in the third and fourth aspects of the present invention.

According to the invention described in claim 6, according to claim 1,
Light emitted from the surface charge measuring device optical element described in 2, 3, 4 or 5 is reflected light from the interface between the optical element and the object to be measured, and the detection light travels back and forth through the optical element having the electro-optical effect. Is transmitted twice, so that it is possible to obtain twice the sensitivity to the transmitted light, and to measure the surface charge with high sensitivity and high accuracy. Since the thickness of the optical element can be reduced, it is convenient to measure the surface charge with high resolution.Furthermore, since the measured object itself does not need to transmit light, the optically opaque measured object can be measured. The surface charge distribution can also be measured.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram showing the measuring head portion in an enlarged manner.

FIG. 3 is a schematic configuration diagram illustrating a surface charge measuring device according to a third embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 2 light source 3 optical element 5 measuring means 6 calculating means 11 electrode 12 DUT 22 interface 24 measuring means 27 calculating means

Claims (6)

[Claims] 1. An optical element having a horizontal electro-optic effect, at least one electrode electrically contacting the optical element, a light source for emitting light incident on the optical element, and an optical element emitted from the optical element. A surface charge measuring device comprising: a measuring unit for measuring a polarization state of light. 2. A Fourier transform of a surface charge distribution of an object to be measured obtained from a polarization state measured by a measuring means, and a result of the Fourier transform is corrected by a spread function of a measurement area of the measurement system, and then an inverse Fourier transform is performed. 2. The surface charge measuring device according to claim 1, further comprising a calculation unit that calculates a surface charge distribution measurement result. 3. An optical element having a horizontal electro-optical effect, at least one electrode electrically contacting the optical element, a light source for emitting light incident on the optical element, and a light source emitted from the light source. The light incident on the optical element is 2
A surface charge measurement device comprising: an optical system that expands two-dimensionally; and measurement means that two-dimensionally measures the polarization state of light emitted from the optical element. 4. A two-dimensional Fourier transform of a surface charge distribution of an object to be measured obtained from a two-dimensional polarization state measured by a measuring means, and a result of the Fourier transform is used as a spread function of a measurement area of a measuring system. 3. The surface charge measuring device according to claim 2, further comprising: an arithmetic unit that performs a two-dimensional inverse Fourier transform after the correction by the above and performs a measurement result of the surface charge distribution. 5. The surface charge measuring device according to claim 1, wherein LiNbO ₃ is used as an optical element having a horizontal electro-optic effect. 6. The light emitted from the optical element is light reflected from an interface between the optical element and an object to be measured.
The surface charge measuring device according to 3, 4, or 5.