JP4851786B2 - Measuring method of micro area potential of photoconductor - Google Patents

Description

  The present invention relates to a method for measuring a micro area potential of a photoconductor and a measurement apparatus for a micro area potential of a photoconductor capable of measuring a micro area potential of a photoconductor charged to a high potential with high spatial resolution.

Electrophotographic image formation in a copying machine, a laser printer, etc., is usually a charging process that uniformly charges the surface of the photoreceptor, an exposure process that forms an electrostatic latent image by exposing the charged photoreceptor surface, A developing process for developing the formed electrostatic latent image with a developer (toner), a transferring process for transferring the obtained toner image to a recording medium or an intermediate transfer belt, and a fixing process for fixing the transferred toner image And a cleaning process for removing residual toner on the photoconductor after transfer, and a charge eliminating process for removing an electrostatic latent image on the photoconductor.
Thus, since each process is involved in the output quality of the final image in electrophotographic image formation, it is not easy to know the latent image quality in the exposure process from the final image. For this reason, the charging potential for a certain charging condition and the post-exposure potential for a certain exposure condition are measured, how these characteristic values change under a constant temperature and humidity environment, or charging and exposure. The only way to estimate the quality of the latent image formed was to see how it would change after repeated cycles.
However, with such an evaluation means, the latent image is deteriorated, so-called background dirt, so-called background dirt, and abnormal images such as image blurring (or image blur) are evaluated by a surface electrometer in a wide area on the photoconductor. Since the charged potential in a region (a region having a diameter of 10 to 15 mm with respect to a distance of 2 mm between the surface of the photoreceptor and the surface electrometer probe) was measured macroscopically, it was impossible to know the abnormality of the latent image. Therefore, in recent years, it has been desired to provide a method for directly measuring the electrostatic latent image in a minute region and accurately evaluating the state of the latent image in the course of improving the image quality.

Recently, for example, (1) cantilever method, (2) electrometer method, and (3) displacement current method (induced current method) by light attenuation have been proposed as methods for directly evaluating the electrostatic latent image of a minute region. ing.
In the cantilever method (1), the mechanical displacement of the cantilever beam due to the force F (for example, electrostatic attraction) acting between the surface of the photosensitive member and the probe is measured, or the change in the vibration state is measured. In this method, the back surface is irradiated with laser light, the reflected light is detected, and the surface potential is measured from the displacement value (see Patent Document 1 and Patent Document 2).
However, in the cantilever method (1), the cantilever and the photosensitive member come into contact with each other with electrostatic force at a charging potential of several hundred volts as in the photosensitive member. Further, if the distance is set so that the photoconductor and the cantilever do not come into contact with each other, the spatial resolution is lowered. Further, there is a problem that deterioration in sensitivity is inevitable if a material having a bending force that does not contact the photosensitive member and the cantilever is used for the cantilever.

The (2) electrometer method is a method in which an electrode having a certain area is arranged in the vicinity of the surface of the photosensitive member, and the electric potential induced by the electrode is measured with respect to the ground (Patent Document 3). reference).
In the electrometer method (2), a charge amount corresponding to a charge amount in a predetermined region on the surface of the photoreceptor is induced in the electrode, and it is necessary to narrow a distance (gap) between the photoreceptor and the electrode. In this method, generally, when A (μm) is required as the spatial resolution of measurement, the gap is within A (μm) and the electrode size is within A (μm) × A (μm). There is a need. Therefore, it is necessary to reduce the gap with a small electrode in order to realize a small spatial resolution. In this method, a method of measuring a displacement current induced when a charged photoreceptor moves and a surface charge crosses an electrode is often used, but a narrow gap is kept constant during measurement. A special mechanism is required. Moreover, since the electrode size is reduced and the detection signal is reduced, measurement becomes extremely difficult.

The induced current method (3) is an electrode installed in the vicinity of the surface of the photoconductor, and the charged surface of the photoconductor is irradiated with a minimal spot light and is induced to the electrode by the disappearance of the surface charge due to light attenuation. This is a method of measuring the amount of charge (induced current) and measuring the surface potential (see Non-Patent Document 1). In the induction current method (3), an electrode in which a transparent conductive film is formed on a transparent glass is used, and light irradiation is performed from the back surface. In principle, the spatial resolution is limited to the size of the spot light to be irradiated. Therefore, the electrode size is arbitrary, and in this method, the distance (gap) between the surface of the photoreceptor and the probe is also arbitrary up to about 2 mm (however, of course, if the gap becomes larger, The detection signal is small).
In the induced current method (3), a 10 μm-sized beam spot is irradiated from the back surface of the transparent glass electrode, and an induced current (displacement current) due to a light attenuation potential change occurring in the 10 μm region is detected, and the magnitude of the signal is detected. Then, the potential before spot light irradiation is obtained, and the measurement position is sequentially changed to obtain a latent image profile (one-dimensional profile in the sub-scanning direction). However, the width of the latent image of one line that was written and formed with a beam of 80 μm width (sub-scanning direction) was measured to be a width (μm) that is about twice as large as the beam size. This is the current situation.

Thus, in the direct measurement of the latent image, there is a problem that the signal is small and is easily buried in noise. For example, in order to ensure that a profile of a latent image having a width of 80 μm is measured at a pitch of 10 μm (a spatial resolution of measurement is 10 μm), the beam size needs to be 10 μm or less. As a result, there is a problem that the exposure area on the photoconductor is small, the area where the potential decay occurs is small, and the current signal induced in the electrode is small.
Also, in order to obtain a larger signal intensity, when the electrode is brought closer to the surface of the photoconductor, the light incident on the photoconductor is reflected and returns to the electrode, where it is incident on the front when reflected and incident on the photoconductor. The angle is different. As a result, there is a problem that the exposure area is expanded beyond the size of the incident spot light, and the spatial resolution of the measurement is deteriorated.

Japanese Patent Application Laid-Open No. 5-119093 Japanese Patent Laid-Open No. 5-149988 JP-A-11-184188 Japan Hard Copy 2001 Proceedings P281

  An object of the present invention is to solve various problems in the prior art and achieve the following objects. That is, the present invention exposes a minute laser spot light to a photosensitive member charged to a high potential, causes a surface potential change in a minute region, measures a change in the amount of charge induced to the electrode due to the potential change, and It is an object of the present invention to provide a method for measuring a micro area potential of a photoconductor and an apparatus for measuring a micro area potential of the photoconductor, which can know the level of the surface charge potential before exposure from the signal magnitude.

  As a result of intensive studies by the present inventors in order to solve the above-mentioned problems, in particular, the conventional problem of degrading the spatial resolution of the measurement can be effectively solved, and the photoconductor before exposure is unknown. The present inventors have discovered a method for measuring a micro area potential of a photoconductor and an apparatus for measuring a micro area potential of a photoconductor capable of accurately and efficiently measuring the level of the charging potential of the photoconductor.

This invention is based on the said knowledge by this inventor, and the means for solving the said subject are as follows. That is,
<1> The charged photosensitive member is exposed to a short pulse with a spot light having a predetermined beam size, and a potential change at this time is detected as a signal intensity by an electrode that is in close proximity to the photosensitive member. Apply to the calibration curve data created from the relationship with the signal intensity when the spot light is applied to a known charged potential, and obtain the unknown charged potential level of the photoreceptor to be measured to obtain the micro-region potential of the photoreceptor. Measuring method,
The calibration curve data is moved a plurality of times so that the signal intensity with respect to a predetermined charging potential satisfies the following formula, pitch S ≧ “beam size in the measurement direction”, where the position of the surface of the photoreceptor is pitch S, This is a method for measuring the micro-region potential of a photoreceptor, characterized in that it is data obtained by irradiating spot light each time.
<2> When the signal intensity is a constant value and the number of measurements when the signal intensity is stable is N (where N ≧ 1), calibration curve data is created using the signal intensity for the Nth and subsequent times as the signal intensity for the charged potential. In addition, spot light irradiation is started from a position (N−1) × pitch S away from the position at which measurement is to be started on the photoconductor to be measured, and the measurement at pitch S is repeated N times or more. 1> is a method for measuring a microregion potential of a photoconductor.
In the method for measuring the microregion potential of the photoconductor of the present invention according to any one of the above <1> and <2>, the reflected light from the photoconductor is reflected and reincident by the electrode, and the exposure region is larger than the measurement pitch. Measurement can be performed without degrading the spatial resolution defined by the measurement pitch even if the spread is increased.

<3> A device for measuring a micro area potential of a photoconductor used in the method for measuring a micro area potential of the photo conductor according to any one of <1> to <2>,
A photosensitive member, a rotating means for holding and rotating the photosensitive member, a charger for uniformly charging the surface of the photosensitive member, and a laser for exposing the charged photosensitive member to spot light having a predetermined beam size for a short pulse exposure. An apparatus for measuring a micro area potential of a photoconductor, comprising an exposure device, an electrode for detecting a potential change in a micro area of the photoconductor, and a static eliminator in this order in the rotation direction of the photoconductor.
In the measurement device for the micro area potential of the photoconductor of the present invention, even if the reflected light from the photoconductor is reflected and re-entered by the electrode, and the exposure area spreads beyond the measurement pitch, the spatial resolution specified by the measurement pitch is obtained. Measurement is possible without dropping.

  According to the present invention, a conventional problem can be solved, and a fine laser spot light is exposed to a photosensitive member charged to a high potential, a potential change is generated in a minute region of the photosensitive member, and the potential change induces the electrode. By measuring the change in the amount of charge generated, that is, the induced current (displacement current), it is possible to know the level of the unknown charging potential in the minute area of the photoreceptor before exposure from the magnitude of the signal. It is possible to provide a method for measuring a micro-region potential and an apparatus for measuring a micro-region potential of a photoreceptor.

(Measuring method of micro area potential of photoconductor and measuring apparatus of micro area potential of photoconductor)
According to the method of measuring the microregion potential of the photoconductor of the present invention, the charged photoconductor is exposed to a short pulse with a spot beam having a predetermined beam size, and the change in potential at this time is detected by an electrode in close proximity to the photoconductor. And the signal intensity is applied to calibration curve data created from the relationship with the signal intensity when the spot light is irradiated to a plurality of known charged potentials, and the photoconductor to be measured is unknown. A method for measuring a micro-region potential of a photoconductor for obtaining a charge potential level, wherein the calibration curve data has a signal intensity with respect to a predetermined charge potential, where the position on the surface of the photoconductor is a pitch S, the following formula: pitch S ≧ This is data obtained by moving a plurality of times so as to satisfy the “beam size in the measurement direction” and irradiating the spot light each time.
In this case, when the signal strength is a constant value and the number of measurements when the signal strength is stable is N (where N ≧ 1), the calibration curve data is created using the signal strength for the Nth and subsequent times as the signal strength for the charged potential. In addition, it is possible to start spot light irradiation at a position separated by (N−1) × pitch S from the position at which measurement is to be started on the photoconductor to be measured, and repeat measurement at pitch S N times or more. preferable.

The measurement device for the microregion potential of the photoconductor of the present invention is used in the method for measuring the microregion potential of the photoconductor of the present invention,
A photosensitive member, a rotating means for holding and rotating the photosensitive member, a charger for uniformly charging the surface of the photosensitive member, and a laser for exposing the charged photosensitive member to spot light having a predetermined beam size for a short pulse exposure. An exposure unit, an electrode for detecting a change in potential of a micro area of the photoconductor, and a static eliminator are provided in this order in the rotation direction of the photoconductor, and further include other members as necessary. .
Hereinafter, the details of the measuring device for the micro area potential of the photoconductor of the present invention will be clarified through the description of the method for measuring the micro area potential of the photoconductor of the present invention.

  The method of measuring the microregion potential of the photoconductor of the present invention is to subject the photoconductor charged to a potential from a high potential to a low potential one-shot exposure of a microlaser, intentionally causing a change in the surface potential of the microregion, A change in the amount of charge induced in an electrode placed close to the photoreceptor due to the potential change, that is, an induced current (displacement current) is measured, and the level of the surface potential before exposure is obtained from the magnitude of the signal. It is an improvement of the method.

In the conventional measuring method described in “Japan Hard Copy 2001 Proceedings P281” (Non-Patent Document 1) and the like, the measurement position is changed at a minute pitch in the photosensitive drum rotation direction, the above measurement is repeated, and finally a latent image is obtained. In order to secure a spatial resolution of measurement, it is necessary to reduce the beam used for potential detection (use a beam size of 10 μm). As a result, there is a problem that the region where the potential change occurs is small and the signal obtained is small.
Examples of a solution to the problem include (1) improvement of a signal processing circuit (amplifying circuit) and (2) bringing the electrode closer to the photoreceptor. In (1), it is difficult to amplify a one-shot signal (meaning single-shot signal) while ensuring an S / N ratio. On the other hand, if possible, it is conceivable to use means such as repeatedly capturing the same signal and amplifying by superposition, but this is not possible due to the principle of measurement. The above (2) is effective, and if the distance 1 mm between the electrode and the photosensitive member is 0.1 mm, it is increased about 10 times.

  Since the method for measuring a micro area of the photoconductor of the present invention measures a one-dimensional profile of a latent image in the sub-scanning direction, the exposure size in the main scanning direction is increased. That is, by increasing the area where the potential change occurs, it is possible to reduce the exposure size in the sub-scanning direction, ensure the spatial resolution of the measurement, bring the electrode closer to the photoconductor, and the signal S / N ratio. After making improvements, the effect of approaching the electrode is not negligible. Specifically, the light incident on the photoreceptor reflects, returns to the electrode, and then reflects and re-enters. This solves the problem that the exposure area expands beyond the pitch and degrades the spatial resolution.

  First, spot light (hereinafter sometimes referred to as “detection light”) having a predetermined beam size is exposed to a charged photosensitive member for a short pulse, and a potential change on the photosensitive member at this time is detected by electrodes that are closely opposed to each other. With respect to the method, a relationship with signal intensity when the detection light is irradiated to a plurality of known charged potentials in advance (hereinafter also referred to as “calibration curve data”) is obtained. In the evaluation method for irradiating the detection light to the unknown charged potential of the measurement object based on the calibration curve data and knowing the charged potential level of the irradiated portion from the obtained signal intensity, the calibration curve data is a predetermined value. The signal intensity with respect to the charging potential is data obtained by moving the position on the photoconductor a plurality of times at a pitch S (where pitch S ≧ “beam size in the measurement direction”) and irradiating the detection light each time. When the number of measurements when the signal intensity is stabilized at a constant value is N (where N ≧ 1), calibration curve data is created with the signal intensity for the Nth and subsequent times as the signal intensity for the charged potential at this time, and When irradiating an unknown charged potential region, irradiation is started from a position separated by (N−1) × pitch S from a position where measurement is desired to be started, and measurement is repeated N times or more at pitch S.

Here, the larger the beam size of the detection light, the larger the signal intensity. However, in order to ensure the spatial resolution of the measurement, it is better that the signal intensity is small, and there is a trade-off relationship. As one method for solving this, there is a method using a linear laser beam as detection light. In the present invention, the linear laser beam uses 18000 μm in the main scanning direction × 24 μm (655 nm) in the sub-scanning direction. Thereby, a signal intensity sufficient to enable measurement is obtained, and a spatial resolution of measurement in the sub-scanning direction is ensured. A size of 5000 μm in the main scanning direction (gap: 0.2 mm, charging potential lower limit: 500 V) is also possible, and conditions are determined according to the purpose of measurement.
In the laser exposure optical system of the present invention, the size in the sub-scanning direction is determined by the distance between the photoreceptor surface and the optical system, and the size changes as this distance changes. The distance at this time is a unique value of the manufactured optical system unit, and there is a tolerance in the distance. The optical unit to be manufactured, and hence the beam size, is determined in consideration of how closely the distance can be set and maintained in relation to the tolerance.

  The signal intensity also depends on the gap between the surface of the photoreceptor and the electrode, and the signal intensity increases as the signal intensity becomes narrower. Also from the ease of gap control, 0.1 to 0.5 mm is preferable.

Here, FIG. 1 is a schematic view showing an example of a measuring device for the micro-region potential of the photoreceptor of the present invention. The measuring apparatus shown in FIG. 1 includes a photosensitive member 1, a rotating unit 9 that holds and rotates the photosensitive member 1, a charger 13 that uniformly charges the surface of the photosensitive member, and the charged photosensitive member 1. A laser exposure device 10 that performs short pulse exposure of a spot beam 5 having a predetermined beam size, an electrode 4 that detects a potential change in a minute region of the photoreceptor 1, and a static eliminator 14 are arranged in this order in the rotation direction of the photoreceptor. Have.
In FIG. 1, 2 is a latent image writing device, 3 is a surface potential meter probe, 6 is a laser beam optical system, 7 is a PC controller, 8 is a current amplifier, 10 is a pulse generator, 11 is an oscilloscope, and 12 is an LD driver. Respectively.

The electrode 4 is formed by forming a transparent conductive thin film on a transparent glass, and this can be irradiated with light through the electrode when the glass electrode is opposed to the photoreceptor sample. Ease of use improves. The transparent glass may be general glass, but BK-7, quartz glass, and the like have a wide pass wavelength range and are preferable for measurement.
There is no restriction | limiting in particular as said transparent conductive thin film, According to the objective, it can select suitably, For example, ITO etc. are suitable. The transparent conductive film may be formed on the entire surface of one side of the glass, or may be formed in a mesh shape with a thin line (≦ 1 mm) using a pattern mask. In this case, if the area ratio of [area of the ITO film forming portion / area of the ITO non-film forming portion] is about 0.2, when the light passing through the electrode includes a wavelength of 800 nm or more, this wavelength Light can pass through without significant loss. This can be appropriately selected according to the purpose of measurement.

When the light to be transmitted is a laser, it is preferable to provide an antireflection film on the glass on the laser incident side. This is to prevent so-called return light noise, in which the laser beam reflected from the glass surface on the laser incident side returns to the light emitting portion, forms a composite resonator, and the laser beam fluctuates.
In the case where the electrode 4 is placed facing the photoconductor, the closer the distance to the photoconductor, the greater the signal, which is preferable. In the photoconductor used in the embodiment, it is predicted from the calculation that a gap of about 10 to 15 μm gives the maximum signal intensity. On the contrary, the signal intensity decreases as the distance further approaches. In this invention, it is preferable to install an electrode so that a gap may be 0.1-0.5 mm from the ease of gap control.

  The exposure energy given to the photosensitive member is set to a predetermined potential, for example, the optical power and time so that the exposure energy (= light power × lighting time) required to change 800 (−V) to 100 (−V). Decide. The optical power is determined by adjusting the laser driving current, and the laser lighting time is preferably set to be shorter than this with reference to the carrier transit time of the photoreceptor. This is because the measured signal intensity is the flow of charge density induced in the electrode, and the shorter the time, the greater the signal.

The laser beam is assumed to be a beam having a normal Gaussian distribution, and the position (diameter) at which the intensity becomes 1 / e ² (about 13.5%) of the maximum intensity is set as the beam diameter. On the other hand, the size of the potential attenuation region on the photoreceptor where the beam is irradiated and the potential is attenuated depends on the intensity of the exposure energy. If the exposure energy is extremely weak, the region may be smaller than 1 / e ^2. If the exposure energy is extremely strong, potential attenuation occurs even in a region wider than 1 / e ² . This can be understood from the fact that the size determined by 1 / e ² contains about 94.5% of the total energy and the remaining 5.5% of the energy is outside 1 / e ² .
In this case, the potential attenuation occurs in a region wider than 1 / e ² when the exposure energy is several tens, several hundreds times or more of the exposure energy required to attenuate the photosensitive member from the predetermined potential to near 0V. If it is less than or equal to the required exposure energy, the potential attenuation outside 1 / e ² is small and almost negligible, so for convenience, “beam size = exposure area size = potential attenuation area size”.

Hereinafter, the procedure in the method for measuring the microregion potential of the photoconductor of the present invention will be specifically described.
(1) Calibration Curve Data Acquisition Procedure As shown in FIGS. 1 and 2, the photosensitive drum 1 is rotated and the surface of the photosensitive member is charged by a charger (not shown). Next, there is a step of writing one line by the latent image writer 2, but here the writing is OFF. Charging and rotation are stopped when the part on the photoreceptor corresponding to the latent image of one line comes immediately before the signal detection unit.
Next, 655 nm detection light (linear laser beam: main scanning direction 18000 μm × sub-scanning direction 24 μm) is irradiated. At this time, an induced current (displacement current) due to potential decay (= charge change) is measured. The surface of the photosensitive drum is moved by a measurement pitch S (where S is a beam size of 24 μm or more in the sub-scanning direction, 50 μm here), and a detection light is irradiated to obtain a signal. This is repeated a predetermined number of times. An example of the resulting signal is shown in FIG.
In FIG. 8, “signal intensity” is the height (width) from the rising start point of the signal to the maximum peak. In FIG. 8, the signal rises downward because of the (−) polarity. The signal intensity obtained from the beginning gradually decreases, because the light reflected by the electrode returns as described above, widens the exposure area, and extends beyond the measurement pitch S. Next, this is because when the irradiation is performed by moving by the measurement pitch S, the potential is already slightly affected by the previous irradiation. The reason why this signal can be obtained stably through repeated measurement is that the influence of the previous and previous irradiations is the same. Assuming that the number of measurements when the signal intensity starts to be obtained stably is the Nth and the total number of repetitions is n, the Nth data or the data from the Nth to n (number: (n−N + 1) The average value of)) is the signal intensity obtained with respect to the charging potential at this time.
Next, the charge potential is changed and the same measurement is repeated to obtain calibration curve data of “charge potential” versus “signal intensity”.

(2) Procedure for Measuring Charging Potential As shown in FIGS. 1 and 2, the photosensitive drum 1 is rotated and the surface of the photosensitive member is charged by a charger (not shown). Next, one line writing is performed by the latent image writer 2. However, the size of one line in the sub-scanning direction is about 85 μm. Charging and rotation are stopped when the part on the photoreceptor corresponding to the latent image of one line comes immediately before the signal detection unit.
At this time, the operation stops before the pitch S × (N−1). Detecting light of 655 nm (linear laser beam: main scanning direction 18000 μm × sub-scanning direction 24 μm) is irradiated. Next, an induced current (displacement current) due to potential decay (= charge change) is measured. Next, the surface of the photosensitive drum is moved by the measurement pitch S, and a signal is obtained by irradiating detection light. This is repeated a predetermined number of times. When moving at the measurement pitch S (here, S is 50 μm), the measurement level after the Nth time has the same degree of influence due to the irradiation of the previous time, the last time, etc., so that it is up to (N−1) times. The signal strength data is discarded and the signal strength data from the Nth time is read. This data is applied to calibration curve data prepared in advance to determine the charging potential. Further, by plotting the obtained charging potential data against the measurement position, it is possible to obtain a one-line-written latent image profile (sub-scanning direction) with a spatial resolution of pitch S (= 50 μm).

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

The apparatus for measuring the microregion potential of the photoreceptor shown in FIG. The following equipment configuration and conditions are common to all the following embodiments unless otherwise specified.
As a photosensitive drum, a laminated OPC (organic optical semiconductor) drum (outer diameter 60 mm × length 334 mm) manufactured by Ricoh Co., Ltd., exposure necessary for potential attenuation from a charged potential 800 (−V) to 100 (−V) The energy is 0.3 μJ / cm ² at 655 nm. The transit time at 800 (−V) is approximately 300 μs.
Laser optical system for detection light (stationary beam exposure): main scanning direction 18000 μm × sub-scanning direction 24 μm, wavelength 655 nm (manufactured by Ricoh Optical Co., Ltd.), distance to the photoreceptor surface 74 mm (value unique to this optical system) The beam size was defined by keeping the beam area, and the beam area was 0.43 mm ² . The exposure energy to be applied is determined by the laser drive current and the optical power is determined. Here, the exposure energy required to change 800 (−V) to 100 (−V) was used. The beam profile of the used linear beam is shown in FIG.
Rotation of photosensitive drum: A precision rotary stage KS432-75 (manufactured by Suruga Seiki Co., Ltd.) + Controller D223 (manufactured by Suruga Seiki Co., Ltd.) was used. One measurement cycle: rotation-stop-pulse exposure-rotation period was about 0.8 s.
Electrode: An ITO film formed on one side of quartz glass having a size of 30 mm × 10 mm and a thickness of 1 mm was used. This electrode has an antireflection film formed on the laser incident side. The average film thickness of ITO was 169 μm, and the surface resistance was 54Ω / □.
-The gap between the photoconductor and the electrode was 0.1 mm.
Laser trigger: An arbitrary waveform generator (manufactured by Agilent Technologies, HP33120A) was used to generate One shot pulse, which was used as a trigger. The pulse width was 2 μs.
-Image writer: The laser writing device of the laser printer manufactured by Ricoh Co., Ltd. was removed, and this was modified and incorporated.
Signal processing system: current amplifier (KEITHLEY428) + oscilloscope (Yokogawa Electric Corporation, DL708)
Drum holding and rotating device: A drum evaluation device manufactured by Ricoh Co., Ltd. having the configuration and functions shown in FIG. 1 was used.
Charger: The scorotron charger was charged by applying the output of a high-voltage power supply (TREK 609A-3), and the charged potential used when preparing the calibration curve data was confirmed with a surface potentiometer (TREK Model 344). The charging potential was in the range of 800 (-V) to 200 (-V).
・ All measurements are automated and are based on self-made software.

Example 1
-Measurement of micro-region potential-
The micro area potential of the photoconductor was measured on the photoconductor based on the procedure (1) using the measuring apparatus. There were three measurement pitches S, 30 μm, 50 μm, and 100 μm. The charging potential was one of 800 (-V). The results are shown in Table 1 and FIG. Also. FIG. 5 shows the result of converting the data for each measurement count to the measurement position.

（＊）「安定する位置」は、測定開始位置からの距離を表す。

(*) “Stable position” represents the distance from the measurement start position.

From the results of Table 1, FIG. 4 and FIG. 5, it can be seen that the signal intensity changes (becomes smaller) from the beginning of the measurement by repeated measurement with the measurement position changed. It can also be seen that the data is stable at a position about 100 μm away from the first measurement.
From these facts, it was found that the influence of the spread of the exposure region due to reflection at the electrode is about 100 μm on one side.

(Example 2)
-Measurement of micro-region potential-
Using the above measuring apparatus, the gap between the photoconductor and the electrode was 0.2 mm, the measurement pitch S was 100 μm, 150 μm, and 200 μm, and the microregion potential was measured. The results are shown in Table 2 and FIG.

（＊）「安定する位置」は、測定開始位置からの距離を表す。

(*) “Stable position” represents the distance from the measurement start position.

From the results of Table 2 and FIG. 6, it can be seen from the beginning of the measurement that when the measurement pitch S is 100 μm, the signal intensity changes by repeated measurement with the measurement position changed. When the measurement pitch S was 150 μm and 200 μm, data having no change was obtained between the first time and the second time.
From these results, it was found that the influence of the spread of the exposure region due to reflection at the electrode was about 100 μm on one side.

(Example 3)
−Creation of calibration curve data−
In the same manner as in Example 1, the charging potential was measured at intervals of 100 V at 800 (−V) to 200 (−V) for each measurement pitch S. In the data of each measurement pitch, the data after the number of times that the signal intensity is stabilized was averaged, and the calibration curve data was created according to the above procedure with the average value as the signal intensity corresponding to the charged potential at that time. The results are shown in FIG.
From the results of FIG. 7, the shorter the measurement pitch with respect to the same charged potential, the smaller the signal intensity is because the number of times of measurement until the signal intensity becomes stable is much, and the number of times affected by reflection and re-incidence by the electrode. This is probably due to the large decrease in the charging potential.

Example 4
-Measurement of charging potential based on calibration curve data-
In Example 3, the photoconductor was charged to a charging potential that was not used when the calibration curve data was created, and measurement was performed at 30 μm pitch, 50 μm pitch, and 100 μm pitch, and the fifth measurement, the third measurement, and the measurement, respectively. A third signal strength was acquired. This data was applied to the calibration curve data of Example 3, and the charged potential was read. The obtained charging potential value was compared with the charging potential value monitored by a surface potential meter. The results are shown in Table 3.

表３の結果から、測定ピッチ５０μｍ、及び測定ピッチ１００μｍであれば検量線データから読み出されるデータには問題はないことがわかった。

From the results of Table 3, it was found that there is no problem in the data read from the calibration curve data if the measurement pitch is 50 μm and the measurement pitch is 100 μm.

  According to the method for measuring the micro area potential of the photoconductor and the apparatus for measuring the micro area potential of the photoconductor of the present invention, the charged potential of the micro area of the photoconductor can be directly measured to evaluate the state of the latent image. This makes it possible to accurately evaluate abnormal images such as background stains and image blurring (or image blur), which are so-called background stains, which are deterioration of latent images in image forming apparatuses that have been difficult.

FIG. 1 is an overall schematic diagram showing an example of a measuring device for a micro area potential of a photoconductor of the present invention. FIG. 2 is a diagram illustrating a sequence example of measurement data. FIG. 3 is a diagram illustrating a profile of a linear beam used for detection light in the example. FIG. 4 is a graph showing measurement data of Example 1 (X-axis is the number of measurements). FIG. 5 is a graph showing measurement data of Example 1 (X axis is a distance from the start of measurement). FIG. 6 is a graph showing measurement data of Example 2 (X-axis is the number of times of measurement). FIG. 7 is a graph showing measurement data (calibration curve data) of Example 3. FIG. 8 is a graph showing measurement data of Example 4 (example of signals obtained, description of signal strength).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Latent image writing device 3 Surface potential meter probe 4 Electrode 5 Incident laser 6 Laser beam optical system 7 PC controller 8 Current amplifier 9 Rotating means 10 Pulse generator 11 Oscilloscope 12 LD driver 13 Exposure unit 14 Charger 14

Claims (1)

The charged photoconductor is exposed to a short pulse with a spot beam having a predetermined beam size, and the potential change at this time is detected as a signal intensity by an electrode in close proximity to the photoconductor, and the signal intensity is detected by a plurality of known charging charges. A method for measuring a micro area potential of a photoconductor to obtain an unknown charged potential level of a photoconductor to be measured by applying it to a calibration curve data created from a relationship with a signal intensity when the spot light is applied to the potential. Because
The calibration curve data is obtained by measuring the surface of the photoconductor a plurality of times so that the signal intensity with respect to a predetermined charging potential satisfies the following formula, pitch S ≧ “beam size in the measurement direction”, where the position of the photoconductor surface is pitch S. Data obtained by irradiating a spot light each time it is moved and stopped, and the number of signal intensity measurements when the signal intensity is constant and stable is N (where N ≧ 1), the calibration curve data is created with the signal intensity for the Nth and subsequent times as the signal intensity with respect to the charging potential, and when the unknown charging potential level of the photosensitive member is obtained, measurements started like the position (N-1) to start the irradiation of the spot light from a position spaced × pitch S, a signal strength measurement at the pitch S to repeat N times or more, up to (N-1) times discard the signal strength data Measurement method for a micro region potential of the photosensitive member, wherein the door.

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