JP7256989B2 - To-be-charged body surface layer thickness detection device, image forming apparatus, and to-be-charged body surface layer thickness detection method - Google Patents

Description

The present invention relates to a device for detecting surface layer thickness of a charged body, an image forming apparatus, and a method for detecting the surface layer thickness of a charged body.

processing means for charging or discharging the object to be charged; characteristic detection means for detecting characteristics of the surface layer of the object to be charged that has been processed by the processing means; 2. Description of the Related Art A device for detecting the thickness of a surface layer of a member to be charged is known.
For example, Patent Literature 1 discloses a device that has means for detecting the thickness of a member to be charged based on an electrode member in contact with the member to be charged, a voltage applied to the electrode member, and a current flowing through the electrode member. A device for detecting the thickness of a member to be charged is described. Examples of electrode members include charging rollers, transfer rollers, and dedicated electrodes. Further, the thickness detection of the object to be charged is performed by comparing the current flowing through the electrode member due to the voltage applied to the electrode member and the slope data of the preset VI characteristics (voltage/current characteristics) regarding the thickness of the object to be charged. It is also described that

However, in the conventional method, there remains a possibility that the thickness cannot be detected accurately when the thickness of the surface layer deviates in the main direction of the member to be charged.

In order to solve the above-mentioned problems, the device for detecting surface layer thickness of a member to be charged according to the present invention electrically controls the processing position for charging or discharging in the direction of the member to be charged and the processing position for charging or discharging in the sub direction of the member to be charged. a position-variable processing means that can be changed by the position-variable processing means, a characteristic detecting means for detecting the characteristics of the surface layer of the charged body for a plurality of areas that have been processed at different positions in the main direction and the sub-direction by the position-variable processing means ; The plurality of regions are formed so that there is no overlapping range in both the main direction and the sub direction, and the thickness of the surface layer is detected based on the detection result of the characteristic detection means.

According to the present invention, it is possible to detect the thickness relatively accurately even when there is a deviation in the thickness of the surface layer in the main direction of the member to be charged.

1 is a schematic configuration diagram showing a printer according to an embodiment; FIG. FIG. 2 is a block diagram of an electric circuit of the same printer; FIG. 4 is an image of a destaticized area X of the same printer, and an explanatory diagram of applied voltage during recharging. FIG. 5 is an explanatory diagram of a relational expression between Vc and Iout obtained by measurement of the same printer; 4 is a flowchart of film thickness detection control of the same printer;

An embodiment of a printer that forms an image by electrophotography will be described below as an image forming apparatus equipped with a surface layer thickness detection device for an image carrier as a member to be charged to which the present invention is applied. An image carrier is an example of a member to be charged, and a printer according to an embodiment described below is just an example of an image forming apparatus to which the present invention is applied. The present invention is not limited to these.

FIG. 1 is a schematic configuration diagram showing a printer according to an embodiment. The printer according to the embodiment includes a drum-shaped photoreceptor 1 as an image carrier, a charging device 2 as uniform charging means, a surface potential sensor 3, a developing device 4, a transfer device 5, a cleaning device 6a, and a static elimination means. It includes a static eliminator 6b as a static eliminator, a registration roller pair 7, an optical writing device 8 as optical writing means, and the like. It also has a paper feed cassette 20, a paper feed roller 21, a fixing device 22, a paper discharge path 23, a paper discharge roller pair 24, a paper discharge tray 25, and the like.

A drum-shaped photosensitive member 1 has an organic photosensitive layer on the surface of a drum substrate, and is rotationally driven clockwise in the figure by a driving means. Around the photoreceptor 1, a charging device 2, a surface potential sensor 3, a developing device 4, a transfer device 5, a cleaning device 6a, and a neutralizing device 6b as uniform neutralizing means are arranged.

The charging device 2 uniformly charges the surface of the rotationally driven photoreceptor 1 at a position facing the photoreceptor 1 . In this printer, as the charging device 2, a charging bias is applied to a brush charging roller that rotates while being in contact with the photoreceptor 1, thereby uniformly charging the photoreceptor 1. FIG. Instead of such a system, a scorotron charger arranged facing the surface of the photoreceptor 1 with a predetermined gap therebetween may be used. In addition, by applying a charging bias in a state in which the photoreceptor 1 is arranged in contact with or close to the surface of the photoreceptor 1, a discharge is generated between itself and the photoreceptor 1, and the surface of the photoreceptor 1 is made uniform. A charging roller that charges in a similar manner may be used.

The surface of the photosensitive member 1 uniformly charged by the charging device 2 is optically scanned by the writing light L emitted from the optical writing device 8 . Of the entire area of the photoreceptor 1, the area irradiated with the writing light L by optical scanning attenuates the potential and carries an electrostatic latent image. As the optical writing device 8, a scanning type one is used. Alternatively, a line head system may be used. The optical writing device 8 corresponds to position variable processing means capable of changing, by electrical control, the processing position of static elimination by light irradiation in the main scanning direction or the main direction, which is the longitudinal direction of the line head.

The surface potential sensor 3 as a surface potential detecting means detects a surface potential Vd which is the potential of the background after the photoreceptor 1 is uniformly charged, and a latent image potential Vl which is the potential of the electrostatic latent image. etc., and outputs the result as a signal to the control unit.

The surface of the photoreceptor 1 that has passed the position facing the surface potential sensor 3 as it is driven to rotate enters the position facing the developing device 4 . The developing device 4 consists of a well-known one-component developing device or two-component developing device, and attaches toner to the electrostatic latent image on the photoreceptor 1 in the area facing the photoreceptor 1, thereby electrostatically developing the image. A toner image is obtained by developing the latent image. As the photoreceptor 1 is driven to rotate, the toner image thus developed enters a transfer portion where the photoreceptor 1 and the transfer device 5 face each other.

On the other hand, a paper feed cassette 20 is attached to the main body of the printer. A paper feed roller 21 is in contact with the recording sheet P as the uppermost transfer member in the sheet bundle accommodated in the paper feed cassette 20 . A registration roller pair 7 is arranged near the end of the paper feed path. The registration roller pair 7 feeds out the recording sheet P toward the transfer portion, which is the portion where the photoreceptor 1 and the transfer device 5 face each other.

The transfer device 5 forms a transfer electric field between the recording sheet P sent to the transfer portion and the electrostatic latent image on the photoreceptor 1 to electrostatically move the toner from the photoreceptor 1 side to the recording sheet P side. . The toner image on the photoreceptor 1 is transferred onto the surface of the recording sheet P sent to the transfer section by the action of the transfer electric field. In this printer, as the transfer device 5 , a transfer bias is applied to a transfer roller that forms a transfer nip in contact with the photoreceptor 1 , and the recording sheet P sandwiched in the transfer nip is transferred onto the photoreceptor 1 . A system of transferring a toner image is used. A well-known corona charger may be used instead of the transfer device 5 of such a system. Alternatively, a transfer bias may be applied to the transfer voltage applying member, which is different from the transfer roller, while the transfer voltage applying member is brought into contact with the photoreceptor 1 .

The recording sheet P that has passed through the transfer section is sent to the fixing device 22 . The recording sheet P fed into the fixing device 22 is heated and pressed in the fixing nip, thereby fixing the toner image on the surface.

On the other hand, the surface of the photoreceptor 1 that has passed the transfer section enters a position facing the cleaning device 6a. The cleaning device 6a comprises a cleaning member. Transfer residual toner adhering to the surface of the photoreceptor 1 is scraped off from the surface of the photoreceptor 1 by a cleaning member. After that, the surface of the photoreceptor 1 is uniformly destaticized by irradiating the surface of the photoreceptor 1 with destaticizing light from the destaticizing lamp of the uniform destaticizing device 6b. The surface of the photoreceptor 1 that has been neutralized is uniformly charged again by the charging device 2 to prepare for the next latent image formation.

After passing through the fixing device 22 , the recording sheet P is discharged out of the apparatus via the paper discharge path 23 and the paper discharge nip of the paper discharge roller pair 24 . Then, the sheets are stacked on the discharge tray 25 provided outside the machine.

FIG. 2 is a block diagram showing part of an electric circuit in the printer according to the embodiment; In the figure, a main control unit 100 controls the driving of each device in the printer, and includes a CPU (Central Processing Unit), a RAM (Random Access Memory) as data storage means, and a ROM (Read Only Memory) as data storage means. Memory), etc. Based on the programs stored in the ROM, it controls the driving of various devices and executes predetermined arithmetic processing.

The surface potential sensor 3, the process motor 10, the development bias power supply 11, the transfer bias power supply 12, the registration clutch 13, etc. are connected to the main control unit 100. FIG. An operation display unit 15, a power supply 16 for the charging device 2, a power supply 17 for the static elimination device 6b, an optical writing control unit 18, an image information receiving unit 19, and the like are also connected.

The image information receiving section 19 receives image information sent from a personal computer or scanner operated by a user, and sends the information to the main control section 100 and the optical writing control section 18 . The optical writing control unit 18 optically scans the surface of the photoreceptor 1 by controlling the driving of the optical writing device 8 based on the image information sent from the image information receiving unit 19 . Examples of the optical writing device 8 that optically scans the photoreceptor 1 with the writing light L include a well-known laser writing optical system and an LED array.

A process motor 10 is a motor that serves as a drive source for the photosensitive member 1, the developing device 4, various rollers, and the like. The rotational driving force of the process motor 10 is transmitted to the registration roller pair 7 via the registration clutch 13 . The rotation drive force of the process motor 10 is connected to the registration roller pair 7 by turning on the registration clutch 13 at an arbitrary timing by the main control unit 100 .

The developing device 4 causes the toner carried on the surface of the developing roller to adhere to the electrostatic latent image on the photoreceptor 1 . In order to selectively adhere the toner only to the electrostatic latent image in the entire surface area of the photoreceptor 1, the developing roller has the same polarity as the toner, and the absolute value thereof is the absolute value of the latent image potential _VL . , and less than the charged potential _VD of the background portion of the photoreceptor 1 is applied. For example, a developing bias of -550 [V] is applied to the developing roller under the conditions of photoreceptor background potential=-800 [V] and electrostatic latent image potential=-130 [V]. The development bias power supply 11 outputs such development bias. The main control unit 100 sends an output command signal to the developing bias power supply 11 to cause the developing bias power supply 11 to output the developing bias at an arbitrary timing.

Further, the main control unit 100 causes the transfer bias power supply 12 to output the transfer bias by sending an output command signal to the transfer bias power supply 12 at arbitrary timing. The transfer bias is a transfer electric field between the recording sheet P and the electrostatic latent image on the photoreceptor 1 at the transfer unit where the photoreceptor 1 faces the transfer device composed of the transfer roller 27, the conveying belt unit, and the like. is the voltage for forming

The operation display unit 15 has a touch panel, numeric keys, etc., and displays images on the touch panel, and sends information input by the touch panel, numeric keys, etc. to the main control unit 100 .

The result of detection of the surface potential of the photoreceptor 1 by the surface potential sensor 3 is sent to the main controller 100 as a digital signal.

A charging device power source 16 is provided with a charging current measuring circuit 16a for detecting the photoreceptor film thickness, which will be described later, and its output is sent to the main controller 100. FIG. Alternatively or additionally, a current measuring circuit 1a for detecting the current flowing through the base of the photoreceptor 1 may be provided and its output sent to the main controller 100. FIG.

In the device described in Patent Document 1, an example is described in which a charging roller or a transfer roller is also used as a contact electrode for the photoreceptor to detect the film thickness of the photoreceptor. By applying a voltage to the contact electrode, the film thickness of the photoreceptor is obtained from the current flowing between the photoreceptor and the photoreceptor due to discharge and the DC component of the applied voltage. Specifically, different voltages are applied and the corresponding currents are measured. Gradient data of the VI characteristic line is obtained from these, and the film thickness of the photoreceptor is obtained by comparing with the gradient data obtained and stored in advance. The slope data of the VI characteristic line is used because the intercept of the graph of the VI characteristic line changes depending on the environment such as temperature and humidity, but the slope is constant, so the slope is used. there is A photoreceptor whose VI characteristic does not easily change depending on the environment such as temperature and humidity is used, and the environmental dependency of the VI characteristic is corrected by environmental countermeasure control using the output of another temperature and humidity environment sensor. In this case, the film thickness can be obtained from one voltage value and the current value at that time instead of the slope.

If the film thickness of the photoreceptor can be detected, as described in Patent Document 1, the end of the life of the photoreceptor, which causes image fogging due to excessive thinning due to scraping, can be detected. It is possible to issue a warning to prompt replacement of the battery. Further, it is also possible to control the image quality by feeding back the film thickness of the photoreceptor to the image forming conditions (image forming bias, amount of light for writing, amount of light for charge elimination).

However, in Patent Document 1, since the current flowing through the electrode member is the integrated value of the entire region in the longitudinal direction of the electrode member, only the average thickness of the photosensitive member in the longitudinal direction can be predicted. Therefore, when used for life prediction or feedback to image forming conditions, uneven wear of the photoreceptor cannot be considered as an error factor. When the photoreceptor is unevenly worn, problems such as image density unevenness in the longitudinal direction of the photoreceptor and carrier adhesion may occur. Assuming that the error due to uneven wear is accumulated and controlled, if the error is accumulated too much, even when there is actually no uneven wear, the life may be judged by considering the uneven wear, and conversely, the error If a small number of toner cartridges are piled up, an abnormal image such as uneven density may occur due to uneven wear, although the life has not yet been reached. Since uneven wear cannot be detected in this way, uneven wear becomes an error factor, making accurate life prediction impossible.

Therefore, in the present embodiment, the optical writing device 8, which serves as a light source for drawing an electrostatic latent image of the image forming apparatus, is used to generate discharge only at selective positions in the longitudinal direction. It is possible to detect the photoreceptor film thickness corresponding to different positions of A specific method is as follows. Detection of the photoreceptor film thickness by this method is performed during a period in which an image forming operation is not performed, for example, during an operation preparation period after power-on of the apparatus, or during a period during which printing operations are gathered.

After the photosensitive member is uniformly charged by the charging device 2, writing is performed by the optical writing device 8 to form a neutralized area near 0V. If there is an inflow of charge from the transfer device 5, the potential before discharge is not stabilized, so the transfer current is turned off. The static eliminator 6b for normal printing operation is also turned off.

FIG. 3 is an explanatory diagram of the image of the area X that has been destaticized by the electrostatic latent image and the corresponding waveform of the applied voltage during recharging. The lower half of the drawing schematically shows the positions of the regions on the surface of the photoreceptor. Two or more regions subjected to processing at different positions in the main scanning direction, in the illustrated example, three regions X at the center and both ends are formed. When the positions in the main scanning direction are different from each other, it is desirable that no overlapping range occurs, but they may partially overlap. This is because the degree of influence of overlapping ranges can be calculated as a ratio. It is desirable that the regions to be processed do not overlap in the sub-scanning direction, but they may partially overlap. This is because the degree of influence of overlapping ranges can be calculated as a ratio. It is preferable that there is no overlapping range in both the main direction and the sub-direction and that both the main direction and the sub-direction are areas of the same size, because this simplifies the calculation. In the example shown in the drawing, a region having no overlapping range is formed in this way.

The direct-current component Vc of the charging voltage is changed (switched) at the timing when the charge-eliminated area X on the photoreceptor comes to a position facing the charging device 2 again. The upper half of FIG. 3 shows changes in the DC component of the voltage applied during recharging by the charging device 2 with respect to the static elimination area, which will be described later, according to the position of the surface of the photosensitive member in the sub-scanning direction. The current is measured to obtain the relational expression between the current Iout and the DC component Vc of the voltage at this time. For this current measurement, the charging current measuring circuit 16a provided in the charging device power supply 16 in FIG. 2 can be used, or the current measuring circuit 1a for detecting the current flowing through the base of the photosensitive member 1 can be used. In the illustrated example, the DC component Vc is changed to four values.

Since the surface of the photoreceptor is already charged in areas other than the areas where the charges have been removed, no discharge occurs from the charging device 2 . Therefore, the obtained relational expression between Vc and Iout is for the area X where the charge has been removed. By taking the relational expression between Vc and Iout while changing the position of the portion to be neutralized in the longitudinal direction, it is possible to estimate the photoreceptor film pressure associated with the position in the longitudinal direction. After obtaining the relational expression between Vc and Iout at one point in the longitudinal direction, before starting the measurement at the next position, the photoreceptor is uniformly recharged so that discharge does not occur at positions other than the neutralized position. It is desirable to

The film thickness of the photosensitive member and the current Iout flowing through the charging member of the charging device can be approximated as follows.
Iout=C×(Vc-Vth- _Vd0 )×λ×α (Formula 1)
C: electrostatic capacity of photoreceptor, Vc: voltage applied to charging member, Vth: discharge start voltage, _Vdo : surface potential of photoreceptor before charging, λ: process linear velocity, α: coefficient where electrostatic capacity of photoreceptor C can be represented by Equation 2 below.
C=(εS)/d (Formula 2)
ε: dielectric constant of the photoreceptor, S: electrode plate area when the photoreceptor is viewed as a capacitor, and d: film thickness of the photoreceptor.
Iout=((εS)/d)×(Vc-Vth- _Vd0 )×λ×α (Formula 3)

Summarizing the terms whose change over time is negligible and assuming a coefficient α1, Iout=(1/d)×(Vc−Vth−V _d0 )×α1 (Formula 4)
Since Vc-Vth is the photoreceptor surface potential after discharging,
Iout is represented by two relational expressions of "surface potential difference before and after discharge" and "photoconductor film thickness".
That is, if the slope of Iout (the denominator of the fraction on the right side below) with respect to the surface potential difference before and after discharge (the numerator of the fraction on the right side below) is known, the photoreceptor film thickness d can be predicted.
d=((Vc−Vth−V _d0 )/Iout)×α1 (Formula 5)

Then, in the present embodiment, as in the invention described in Patent Document 1, Vc is set to obtain the slope of the VI characteristic so that the film thickness can be obtained in a manner that is independent of the environment such as temperature and humidity. Iout is measured while switching so that it becomes 2 or more, the slope is obtained, and the film thickness is obtained by comparing this slope with the slope data previously obtained by experiment and stored in the storage unit as reference data. ing. By switching Vc, the charging intensity is switched.

FIG. 4 is an explanatory diagram of an output image of the relational expression between Vc and Iout obtained by the above measurement. It is an example of the relationship between Vc and Iout when there is a deviation in the film thickness of the photosensitive member in the longitudinal direction. This is an example in which the film thickness is relatively thick on the device front side (front side) and the film thickness is relatively thin on the device rear side (rear side). The solid line a is the characteristic line of the average value in the entire longitudinal direction, the one-dot chain line b is the rear side of the device, and the two-dot chain line c is the front side of the device. As will be described later, the thinner the film, the larger the charging current.

FIG. 5 is a flow chart of the film thickness detection control described above. In step 1, each region X is formed and the current Iout when recharging the region is measured. In step 2, the film thickness is obtained by referring to the reference data based on the measurement result, and it is judged whether or not the photoreceptor has reached the end of its service life by comparing it with the criterion obtained in advance by experiment. If it is determined that the life of the photoreceptor has expired (Y in step 2), in step 3, a message to replace the photoreceptor is displayed on the operation display unit 15 (see FIG. 2). If it is determined that the life of the photoreceptor has not expired (N in step 2), it is determined in step 4 whether or not it is necessary to change the image forming conditions according to the film thickness. If it is determined that the change is necessary (Y in step 4), the image forming conditions are changed to appropriate ones according to the film thickness, and are set for the subsequent normal image forming operation. If it is determined that no change is necessary (N in step 4), this control is terminated.

The "characteristic detection means" is realized by the process of "measure the current Iout. In step 2, refer to the reference data based on the measurement result to obtain the film thickness" in steps 1 and 2 above.

The change of the image forming conditions includes a countermeasure against changes in the film thickness as a whole and a countermeasure against the deviation of the film thickness in the main scanning direction. The latter is addressed by image forming conditions that can change the image formation in the main scanning direction, for example, by correcting the amount of writing light of the optical writing device 8 in the main scanning direction. The former can be dealt with by correcting the uniform charging potential and developing bias instead of or in addition to this. These correction values correspond to positions on the surface of the photoreceptor. Therefore, even during film thickness detection, the correction values can be set together with information on the rotational position of the photoreceptor and the position in the main scanning direction. Along with these positional information, measurements are obtained. It should be noted that when there is a deviation in the main scanning direction, it is desirable to determine the necessity of determining the lifespan and the necessity of changing the image forming conditions based on the thinner film thickness.

In this embodiment, since the predicted value of uneven wear of the actual photoreceptor can be used for control, there is no need to add an error due to uneven wear more than necessary, and the life of the photoreceptor can be used to the limit. , the cost can be reduced. In addition, it is possible to prevent the occurrence of abnormal images before the life of the photoreceptor.

Unlike the above embodiment, the charging device 2 is configured as a position-variable processing means, and after uniformly discharging the photosensitive member, which is the member to be charged, by the discharging device 6b or the optical writing device 8, the main directions are different from each other. The thickness may be detected by forming an electrified area X at a position and measuring the current during the formation of this area X. FIG. The charging means can be configured as a position variable processing means by using two or more charging members having mutually different processing ranges in the main direction.

In addition, the static eliminator 6b is configured as a position variable processing means, and after the photosensitive member, which is the member to be charged, is uniformly charged by the charging device 2, different positions in the main direction are statically eliminated by the static eliminator 6b, and the region X is formed. The thickness may be detected by measuring the current when forming and recharging this region X. An optical static eliminator using an LED array can be given as the static eliminator as the position variable processing means. Two or more static elimination lamps having different processing ranges in the main direction may also be used.

Reference Signs List 1: Photoreceptor 1a: Current measuring circuit 2: Charging device 4: Developing device 5: Transfer device 6a: Cleaning device 6b: Eliminating device 7: Registration roller pair 8: Optical writing device 10: Process motor 11: Development bias power supply 12 : Transfer bias power supply 15 : Operation display unit 16 : Charging device power supply 16a : Charging current measuring circuit 18 : Optical writing control unit 100 : Main control unit

JP-A-5-223513

Claims (11)

position variable processing means capable of changing, by electrical control , a processing position for charging or discharging in the main direction of the object to be charged and a position for processing charging or discharging in the secondary direction of the object to be charged ;
a characteristic detecting means for detecting characteristics of the surface layer of the member to be charged with respect to the plurality of areas processed at different positions in the main direction and the sub-direction by the variable position processing means .
forming the plurality of regions so that there is no overlapping range in either the main direction or the sub direction;
A device for detecting the surface layer thickness of a member to be charged, wherein the thickness of the surface layer is detected based on the detection result of the characteristic detecting means. After the characteristics of the surface layer of the charged body are detected in one area by the characteristic detecting means, and before detection is performed in the next area by the characteristic detecting means, the body to be charged is uniformly charged. 2. The device for detecting surface layer thickness of a member to be charged according to claim 1. Equipped with electrification processing means and static elimination processing means,
3. The apparatus for detecting surface layer thickness of a member to be charged according to claim 1, wherein said static elimination processing means is said position variable processing means. 4. The device for detecting the surface layer thickness of a member to be charged according to claim 3, wherein the charge removing means performs charge removal by irradiating light onto the member to be charged after being charged by the charge processing means. 5. The method according to claim 4, wherein the characteristic of the surface layer detected by the characteristic detecting means is a voltage-current characteristic during recharging by the electrifying means of a region that has been electrified after being electrified by the electrifying means. A device for detecting the surface layer thickness of a member to be charged as described. 6. The device for detecting surface layer thickness of a member to be charged according to claim 5, wherein during said recharging, the charging strength by said charging processing means is switched, and the slope of a voltage/current characteristic line is detected as said voltage/current characteristic. . 7. An image forming apparatus comprising the device for detecting surface layer thickness of a member to be charged according to claim 1 , wherein the thickness of the surface layer of an image carrier as a member to be charged is detected. 8. The device for detecting the surface layer thickness of a member to be charged according to claim 4 , wherein the static elimination processing means for performing static elimination by light irradiation is an optical writing means for drawing a latent image. image forming device. a member for applying a transfer voltage for transferring the image from the image carrier to the transfer member;
9. The image forming apparatus according to claim 8, wherein the charging, discharging, and recharging for detecting the thickness of the surface layer are performed by stopping voltage application by the transfer voltage applying member. A uniform charge removing means for uniformly removing charges from the surface prior to charging by the charge processing means,
10. The image forming apparatus according to claim 8, wherein during charging, discharging and recharging for detecting the thickness of the surface layer, processing of the uniform discharging means is stopped. A position variable processing means capable of changing a processing position of charging or discharging in the main direction of the charged body and a processing position of charging or discharging in the sub direction of the charged body by electric control at different positions in the main direction and the sub direction. forming a plurality of treated regions;
a step of detecting the characteristics of the surface layer of the member to be charged for the plurality of regions;
detecting the thickness of the surface layer based on the detection result of the detecting step ;
A method for detecting the surface layer thickness of a member to be charged, wherein the plurality of regions are formed so that there is no overlapping range in either the main direction or the sub direction .

Images