JP2006079005A - Image forming apparatus and photoreceptor unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate an LUT setting procedure in the case of exchanging a photoreceptor unit. <P>SOLUTION: The photoreceptor unit 20 comprises a photoreceptor drum 9, an electrifying device 21, a developing device 22 and a cleaning device 23, and also comprises an ID chip 24 functioning as a non-volatile storage means capable of realizing radio data transmission and reception. The photoreceptor unit 20 completed in a photoreceptor unit manufacturing stage is attached to a printer equipped with a data conversion processing function for converting binary input data of main M×sub M pixels (meaning main scanning direction M pixels×subscanning direction M pixels, and so forth on) into multi-valued data of main N×sub N pixels (M and N are integers, M<N, and N/M is a non-integral number) and outputting the data, and an LUT is set by the conventional method, and the set value is stored in the ID chip 24 provided in the photoreceptor unit. The processing is performed by using software incorporated in a printer main body control part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a digital copying machine and a printer, and a photosensitive unit detachably attached to the image forming apparatus.

  2. Description of the Related Art In an electrophotographic image forming apparatus using a so-called negative / positive process method in which an image portion on a photosensitive member is irradiated with laser light and toner is attached to the irradiated portion to form an image, 2 × 2 = 4 pixels By converting binary input data into multi-value data of N × N = N square pixels and outputting them, for example, 400 dpi binary input data can be output with a 600 dpi multi-value engine using a pixel clock or polygon scanner rotation speed. There is a non-integer double-dense processing method that can output without changing (see, for example, Patent Document 1).

An image forming apparatus using the 3/2 double density processing method will be described with reference to FIG. Here, a case will be described in which input image data having a pixel density of 400 dpi is received in both the main / sub scanning directions and an image is output using an image forming apparatus having a recording density of 600 dpi in both the main / sub scanning directions.
In FIG. 4, 400 dpi binary image data is input to the pattern detection processing circuit 2 via the line memory 1. The pattern detection processing circuit 2 refers to the on / off information of 2 dots continuous in the main scanning direction and 2 dots above and below them in the 400 dpi binary image data, and 4 dots, and according to the pattern. The received code is sent to the LUT (lookup table) 3. The LUT 3 sends a preset output pulse width and output pulse position signal to the PWM circuit 4 corresponding to the code sent from the pattern detection processing circuit 2. The PWM circuit 4 sends a PWM signal to the LD driver 5 based on the received output pulse width and output pulse position signal. The PWM signal is output in synchronization with the pixel clock signal (frequency of 600 dpi). The LD driver 5 supplies a drive current to an LD (laser diode) 6 when receiving an “ON” signal and an offset current when receiving an “OFF” signal. The subsequent processing will be described in the embodiment of the present invention.

In this way, it is possible to output an input image of 400 dpi without changing the pixel clock frequency, the polygon scanner rotation speed, and the feed speed in the sub-scanning direction by using an image forming apparatus having a recording density of 600 dpi. If this method is applied to a multi-beam writing engine, it is not necessary to switch the beam sub-scanning pitch, which was conventionally necessary when changing the dpi.
Japanese Patent Laid-Open No. 5-68162

As described above, it is necessary to set the output pulse width and the output pulse position corresponding to the code sent from the pattern detection processing circuit 2 to the LUT 3. In that case, an appropriate LUT setting value changes according to the photoreceptor characteristics. On the other hand, there is known a photoconductor unit that is detachable from a printer or a copying machine main body, and is integrated with a photoconductor, a charging device, a developing device, and a cleaning device. When the photoconductor unit is replaced due to out of toner or the like, it is necessary to re-set the LUT according to the photoconductor characteristics of the newly installed photoconductor unit.
An object of the present invention is to eliminate the LUT setting procedure when the photosensitive unit is replaced.

  In the image forming apparatus according to the first aspect of the present invention, binary input data of main M × sub M pixels is main N × sub N pixels (M, N are integers, M <N, N / M is non-integer). An image forming apparatus provided with data conversion processing means for converting to multi-value data and outputting, and a lookup table used for the data conversion processing, and storing at least photosensitive member means and values to be set in the lookup table A photosensitive unit having a non-volatile storage means is detachably mounted.

  The image forming apparatus according to a second aspect of the present invention is the image forming apparatus according to the first aspect of the present invention, wherein the value of the look-up table stored in the non-volatile storage means is converted in a state where the photosensitive unit in the recycling process is mounted. When a plurality of test patterns having the same on-pixel density and different on-pixel positions in the main M × sub-M pixels are output onto the medium, the multi-value data pulse is set so that their densities are equal. The width and the pulse position are set.

  An image forming apparatus according to a third aspect of the invention is characterized in that, in the first or second aspect of the invention, the nonvolatile storage means is an IC chip.

  According to a fourth aspect of the present invention, there is provided a photoconductor unit including at least a photoconductor means and detachable from an image forming apparatus, comprising a non-volatile storage means, wherein the non-volatile storage means includes: Data conversion function for converting binary M input data of main M × sub M pixels into multi-value data of main N × sub N pixels (M, N are integers, M <N, N / M is non-integer) and output. When the photoconductor unit is attached to the image forming apparatus having the above, a value set in a look-up table used for data conversion processing is stored.

  According to a fifth aspect of the present invention, there is provided a photoconductor unit according to the fourth aspect of the present invention, wherein the value of the look-up table stored in the non-volatile storage means is the data stored in the photoconductor unit in the recycling process of the photoconductor unit. When data conversion processing is performed in a state of being attached to an image forming apparatus having a conversion function, and a plurality of test patterns having the same on-pixel density and different on-pixel positions in the main M × sub-M pixels are output onto the medium. The pulse width and pulse position of the multi-value data are set so that their concentrations are equal.

  According to a sixth aspect of the present invention, there is provided the photosensitive unit according to the fourth or fifth aspect, wherein the nonvolatile memory means is an IC chip.

According to the first, third, fourth, and sixth aspects of the invention, since the LUT set value stored in the non-volatile storage means such as an ID chip provided in the photosensitive unit is downloaded and used, the photosensitive unit is replaced when the photosensitive unit is replaced. It is not necessary to perform LUT setting according to body characteristics, and the time required for replacement can be shortened.
According to the second and fifth aspects of the present invention, even when the photoconductor characteristics change with time, the LUT setting value corresponding to the photoconductor characteristics is stored in the non-volatile storage means. Therefore, the LUT setting is performed when the photoconductor unit is replaced. There is no need to do.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a conceptual configuration of the photosensitive unit according to the first embodiment of the present invention.
The photoconductor unit 20 includes a photoconductor drum 9, a charging device 21, a developing device 22, a cleaning device 23, and the like, and an ID chip 24 as a non-volatile storage means capable of wireless data transmission / reception. The ID chip 24 includes an antenna and an IC chip. The IC chip includes a power supply rectification unit, a transmission unit, a reception unit, and a storage unit. An image forming apparatus main body such as a printer main body is provided with an antenna and a control unit for transmitting and receiving data to and from the ID chip 24.

Next, the operation will be described.
The photoconductor unit 20 completed in the photoconductor unit manufacturing process is converted into binary input data of main M × sub-M pixels (main scanning direction M pixels × sub-scanning direction M pixels, the same shall apply hereinafter) as main N × sub-M pixels. Installed in a printer with a data conversion function that converts and outputs multi-value data of N pixels (M, N are integers, M <N, N / M is non-integer), and sets the LUT by the conventional method described above Then, the value is stored in the ID chip 24 provided in the photoconductor unit 20. This processing is performed using software built in the printer main body control unit. The processing flow is shown in FIG.

  In FIG. 2, in the manufacturing process of the photoconductor unit 20, the printer main body is set in the process setting mode, and the process is started. When the mounting of the photoconductor unit 20 is detected by the main body side mechanical switch (S1, YES), in the process setting mode (S2, YES), the LUT setting procedure is executed (S3), and the set LUT data is stored in the main body. The data is transmitted to the ID chip 24 through the antenna and stored (S4). An example of the data format stored in the ID chip 24 is shown in FIG.

  When the printer main body is not in the process setting mode (during normal use), if the mounting of the photoconductor unit 20 is detected by the main body side mechanical switch in S1, (S2, NO) is obtained and data is received from the ID chip 24 by the main body antenna. (S5) The photoconductor unit identification code of the received data is compared with the stored value. If it is the same, the process ends. If not (S6, NO), it is determined that the photoconductor unit 20 is new and has already been obtained. The LUT value is set from the received data, and a new photoconductor unit identification code is held as a stored value (S7).

  According to the present embodiment, since the LUT setting value read from the ID chip 24 of the photoconductor unit 20 is downloaded and used, it is not necessary to perform the LUT setting procedure when replacing the photoconductor unit, and the time required for the replacement is shortened. can do.

Next, a second embodiment of the present invention will be described.
In the process of recycling the photoconductor unit 20 collected due to running out of toner or the like, the binary input data of main M × sub-M pixels, main N × sub-N pixels of the photoconductor unit 20 that has been filled with toner and has undergone parts replacement work. (M, N are integers, M <N, N / M is a non-integer) Attached to a printer having a data conversion processing function that converts and outputs multi-value data, sets the LUT by the conventional method described above, The value is stored in the ID chip 24 provided in the photoconductor unit 20. This processing was performed by software built in the printer main body control unit. The processing flow is shown in FIG.

  In FIG. 2, in the recycling process of the photoconductor unit 20, the printer main body is set in the process setting mode, and the process is started. Thereafter, the same processing as in the first embodiment is performed, and when the mounting of the photoconductor unit 20 is detected by the main body side mechanical switch, in the process setting mode, the LUT setting procedure is executed and set. The LUT data is transmitted to the ID chip 24 by the main body antenna and stored.

  According to the present embodiment, even when the photoconductor characteristics change with time, the LUT setting value corresponding to the photoconductor characteristics is stored in the ID chip 24. Therefore, it is necessary to perform LUT setting when the photoconductor unit 20 is replaced. The time required for replacement can be shortened.

  Next, several embodiments of the image forming apparatus to which the above-described photoreceptor unit 20 according to the present invention can be applied will be described. Here, binary input data of main M × sub M pixels is converted into multi-value data of main N × sub N pixels (M, N are integers, M <N, N / M is non-integer) and output. An image forming apparatus as a printer having a data conversion processing function will be described.

FIG. 4 shows the configuration of an image forming apparatus according to the third embodiment of the present invention.
In FIG. 4, as described above in the background art, an on / off signal is supplied from the LD driver 5 to the LD 6. The beam emitted from the LD 6 is scanned in the main scanning direction by the polygon mirror 7 that rotates at a constant speed, and forms an image on the surface of the photosensitive drum 9 via the lens 8. Thereafter, a transfer material on which the image is transferred is output through a known image forming process. The sub-scanning pitch of the beam from the LD 6 on the surface of the photosensitive drum 9 is 600 dpi (42 μm). The synchronization detector 10 includes a photoelectric conversion element and a signal waveform shaping circuit, detects the beam of the LD 6, and sends a synchronization detection signal to the memory control circuit 11. The memory control circuit 11 controls the output of image data from the line memory 1 to the pattern detection processing circuit 2 based on the synchronization detection signal.

  The pattern detection processing circuit 2 refers to the ON / OFF information of 4 dots in the image data of 600 dpi, 2 dots continuous in the main scanning direction to be recorded by the LD 6 and 2 dots below the 2 dots. The reference 2 × 2 matrix is referred to as a reference matrix), and a code corresponding to the pattern is sent to the LUT 3. An example of a reference matrix used in the pattern detection processing circuit 2 is shown in FIG. FIG. 5 is a reference matrix at the time of 3/2 double density processing.

  The LUT 3 sends a preset pulse width and pulse position signal to the PWM circuit 4 corresponding to the code sent from the pattern detection processing circuit 2. The PWM circuit 4 sends a PWM signal to the LD driver 5 based on the received pulse width and pulse position signal. The PWM signal is output in synchronization with the video clock signal (frequency of 600 dpi). The PWM circuit 4 can output a pulse signal in which the pulse width and the pulse start position are set with 1/256 resolution of the write cycle within the write cycle of 600 dpi. The LD driver 5 supplies a drive current to the LD 6 when receiving the “ON” signal and an offset current when receiving the “OFF” signal.

  Table 1 shows codes generated by the pattern detection processing circuit 2 according to the on / off information of the image data.

  Table 2 shows the set values of LUT3.

  The output code arithmetic expression is as follows.

In Table 1,
The width code is determined by the output code arithmetic expressions (1) to (9) from the detection result of 4 dots in the reference matrix. The output pulse width corresponding to the width code is set in the LUT (Table 2).
The position code is determined from equations (10) to (14) from the detection result of 4 dots in the reference matrix. The output pulse position corresponding to the position code is set in the LUT (Table 2).
FIG. 6 shows a test pattern output for setting the output pulse width corresponding to the width code. Each test pattern has the same on-pixel density but has a different relative position with respect to the reference matrix, so that the width code generated by the pattern detection processing circuit 2 is different (selected so). The pattern shown in FIG. 6 is a part of the test pattern, and the size of the actually output pattern is 20 mm × 20 mm. An example in which the on-pixel density is the same and the relative position with respect to the reference matrix is different is shown in FIG.

The setting procedure of the output pulse width is shown in the flowchart of FIG.
The width code 0 corresponds to a case where all the dots in the reference matrix are off. However, if a light pulse is output at this time, an undesired image may be drawn on a white background of the image, so-called background contamination may occur. The output pulse width was fixed at 0.

In FIG. 8, after setting the default values of the width and position and outputting the test pattern (S11, S12), the adjustment of the pulse width is as follows:
Is the density of the 2 dot width vertical line (1) and the 2 dot width horizontal line (1) appropriate? If (S13) is No,
A predetermined appropriate density range <pattern density → W4C is reduced.
Predetermined appropriate density range> pattern density → W4C is increased (S14).
Increasing the pulse width results in an increase in toner adhesion density and an increase in pattern density.

And after outputting a test pattern (S15),
Are the concentrations of the 1 dot width horizontal line (1) and the 1 dot width horizontal line (2) equal? And the density of the 2 dot width horizontal line (1) and the 2 dot width horizontal line (2) are equal? If (S16) is No,
1 dot width horizontal line (1) is a combination of 4C and 2C, 1 dot width horizontal line (2) is also a combination of 4C and 2C, 2 dot width horizontal line (1) is only 4C, and 2 dot width horizontal line (2) is a combination of 4C and 2C. So
2 dot width horizontal line (1) concentration> 2 dot width horizontal line (2) concentration → W2C is increased.
2 dot width horizontal line (1) concentration <2 dot width horizontal line (2) concentration → W2C is reduced (S17).

After outputting the test pattern (S18),
Are the densities of the 1 dot width vertical line (1) and the 1 dot width vertical line (2) equal? And 2 dot width vertical line (1) and 2 dot width vertical line (2) are equal in density? If (S19) is No,
1dot wide vertical line (1) is a combination of 4C and 2L, 1dot wide vertical line (2) is a combination of 4C and 2R, 2dot wide vertical line (1) is only 4C, 2dot wide vertical line (2) is 4C Since it consists of a combination of 2R and 2L,
1 dot width vertical line (1) density> 1 dot width vertical line (2) density → W2R is increased or W2L is decreased.
1 dot width vertical line (1) density <1 dot width vertical line (2) density → W2R is decreased or W2R is increased.
2 dot width vertical line (1) density> 2 dot width vertical line (2) density → W2R and W2L are increased.
2 dot width vertical line (1) density <2 dot width vertical line (2) density → W2R and W2L are reduced (S20).

After outputting the test pattern (S21),
Are the concentrations of 1 dot independent (1) and 1 dot independent (2) equal? If (S22) is No,
1 dot independent (1) is a combination of 4C, 2L, 2C, 1L, and 1 dot independent (2) is a combination of 4C, 2R, 2C, 1R.
1 dot independent (1) concentration> 1 dot independent (2) concentration → W1R is increased or W1L is decreased.
1 dot independent (1) concentration <1 dot independent (2) concentration → W1R is decreased or W1L is increased (S23).

After outputting the test pattern (S24),
Are the concentrations of 3dot independent (1) and 3dot independent (2) equal? If (S25) is No,
3dot independent (1) is a combination of 4C, 3L, 2C, 2L, and 3dot independent (2) is a combination of 4C, 3R, 2C, 2R.
3 dots independent (1) Concentration> 3 dots independent (2) Concentration → W3R is increased or W3L is decreased.
3 dots independent (1) concentration <3 dots independent (2) concentration → decrease W3R or increase W3L (S26)
Like that.

The pulse position is
L (phase code <0): extending from the left end of the pixel period to the right side C (phase code = 0): extending from the center of the pixel period to the left and right sides R (phase code> 0): from the right end of the pixel period Adjust to extend to the left.

Using the LUT in which the output pulse width corresponding to the width code is set according to this procedure, an image including all the test patterns in FIG. 6 is output to the transfer material, and as a result of visual evaluation,
The density of the 2-dot width vertical line (1) and 2-dot width horizontal line (1) is appropriate.
The density of the 1-dot width horizontal line (1) and the 1-dot width horizontal line (2) is the same.
The density of the 2-dot width horizontal line (1) and the 2-dot width horizontal line (2) is the same.
The densities of the 1-dot width vertical line (1) and the 1-dot width vertical line (2) are the same.
The densities of the 2-dot width vertical line (1) and the 2-dot width vertical line (2) are the same.
The density of 1-dot independent (1) and 1-dot independent (2) is the same.
The density of 3 dots independent (1) and 3 dots independent (2) is the same.
Met. If the LUT setting is not appropriate, a density difference occurs when images having the same halftone dot pattern and different relative positions to the reference matrix are output.

FIG. 9 shows a configuration of an image forming apparatus according to the fourth embodiment.
In this embodiment, two density detectors 12 for measuring the light reflectance of the surface of the photosensitive drum 9 are provided. Reference numeral 14 denotes a transfer portion. An electrostatic latent image of a pair of test patterns that should have the same density is formed in the measurement area of the density detection unit 12, toner is adhered, and the light reflectance of the toner adhesion part is measured by the density detection unit 12 and measured. The results are sequentially compared, and the comparison results are sent to the image forming apparatus main body control unit (the measurement result comparison unit and the main body control unit are not shown).
In this way, the density comparison / determination portion of the flowchart of FIG. 8 can be implemented as hardware. The LUT setting procedure according to the flowchart can be automated by the control software of the image forming apparatus main body.

FIG. 10 shows a configuration of an image forming apparatus according to the fifth embodiment.
In this embodiment, two density detectors 15 for measuring the light reflectance of the surface of the intermediate transfer belt 14 are provided. A pair of test patterns that should have the same density is transferred and formed in the measurement area of the density detector 15, the light reflectance of the toner adhesion part is measured by the density detector, the measurement results are sequentially compared, and the comparison results are imaged. The data is sent to the forming apparatus main body control section (the measurement result comparison section and the main body control section are not shown).

In this way, the density comparison / determination portion of the flowchart of FIG. 8 can be implemented as hardware. The LUT setting procedure according to the flowchart can be automated by the control software of the image forming apparatus main body.
In this method, since the density of the test pattern transferred onto the intermediate transfer body 14 is detected and compared, the final output medium (paper or the like) is compared with the case where the density of the test pattern formed on the photosensitive drum 9 is detected and compared. ) Adjustment in a state closer to the above image density is possible.

FIG. 10 shows a configuration of an image forming apparatus according to the sixth embodiment.
In this embodiment, two potential detectors 16 for measuring the surface potential of the photosensitive drum 9 are provided. An electrostatic latent image of a pair of test patterns that should have the same density is formed in the measurement region of the density detection unit 12, the surface potential of the pattern formation unit is measured by the potential detection unit, and the measurement results are sequentially compared and compared. The result is sent to the image forming apparatus main body control section (the measurement result comparison section and the main body control section are not shown).

In this way, the density comparison / determination portion of the flowchart of FIG. 8 can be implemented as hardware. The LUT setting procedure according to the flowchart can be automated by the control software of the image forming apparatus main body.
With this method, the potential detection unit 16 necessary for setting the image forming process conditions can be used as the density detection unit, and it is not necessary to provide a light detection unit for density detection. Further, since no toner image is formed in the LUT setting procedure, there is an advantage that toner is not consumed.

FIG. 12 is a process flowchart of the image forming apparatus according to the seventh embodiment.
If the LUT (output pulse width corresponding to the code) that has been defined is used continuously, the same halftone dot pattern and the reference matrix may be used due to changes in the characteristics of the photosensitive drum over time or a decrease in the amount of light due to deterioration over time of the LD. Although the densities of images having different relative positions differ, setting the LUT every time the image forming apparatus is turned on does not cause a difference in density.

FIG. 13 is a process flowchart of the image forming apparatus according to the eighth embodiment.
When the LUT setting is performed for the second time or later, the previous setting result is used as a default value (initial value) for LUT adjustment. The previous setting result is held by a non-volatile storage means such as an ID chip provided in the main body control unit (not shown).
This method reduces the number of adjustments of the output pulse width and the output pulse position based on the density comparison result compared to the case where the initial value of LUT adjustment is a fixed value, and can shorten the time required for LUT setting.

Summarizing the effects and actions of the third to eighth embodiments,
Third Embodiment: LUT setting can be performed according to the relationship between the exposure amount of the photosensitive member and the image density to be formed.
Fourth Embodiment: The LUT setting procedure can be automated.
Fifth Embodiment: LUT setting can be performed under conditions close to the image density on the final output medium.
Sixth Embodiment: Since the potential detection unit necessary for setting the image forming process conditions is used as the density detection unit, it is not necessary to provide a light detection unit for density detection.
Seventh Embodiment: An image output that is the same as the initial output can be obtained even if the photoreceptor characteristics change due to deterioration over time.
Eighth Embodiment: The time required for LUT setting can be shortened compared to the case where the initial value of LUT adjustment is a fixed value.

1 is a configuration diagram conceptually showing a photoreceptor unit according to an embodiment of the present invention. FIG. It is a flowchart which shows the process regarding LUT by the 1st, 2nd embodiment of this invention. It is a block diagram which shows the data format of LUT. It is a block diagram of the image forming apparatus by the 3rd Embodiment of this invention. It is a block diagram which shows the reference matrix at the time of 3/2 times dense process. It is a block diagram which shows the test pattern output in order to set the output pulse width corresponding to a width code. It is a block diagram which shows the example of binary input data and an output code in case on-pixel density is the same and the relative position differs with a reference matrix. It is a flowchart which shows the setting procedure of an output pulse width. It is a block diagram of the image forming apparatus by the 4th Embodiment of this invention. It is a block diagram of the image forming apparatus by the 5th Embodiment of this invention. It is a block diagram of the image forming apparatus by the 6th Embodiment of this invention. 16 is a process flowchart of an image forming apparatus according to a seventh embodiment of the present invention. It is a process flowchart of the image forming apparatus by the 8th Embodiment of this invention.

Explanation of symbols

1 line memory 2 pattern detection processing circuit 3 LUT (Look Up Table)
4 PWM circuit 5 LD driver 6 LD
9 Photosensitive drum 11 Memory control circuit 20 Photosensitive unit 24 ID chip

Claims (6)

Data conversion processing for converting binary input data of main M × sub M pixels into multi-value data of main N × sub N pixels (M, N are integers, M <N, N / M is non-integer) and output. And an image forming apparatus comprising a lookup table used for the data conversion process,
An image forming apparatus, comprising: a photosensitive member unit including at least a photosensitive member unit and a non-volatile storage unit that stores a value set in the lookup table.   The value of the lookup table stored in the non-volatile storage means is obtained by performing the data conversion process in a state where the photoconductor unit in the recycling process is mounted, the on-pixel density is the same, and main M × sub M The multi-value data pulse width and pulse position are set so that the densities are equal when a plurality of test patterns having different on-pixel positions in a pixel are output onto the medium. Item 2. The image forming apparatus according to Item 1.   The image forming apparatus according to claim 1, wherein the nonvolatile storage unit is an IC chip. A photoconductor unit including at least photoconductor means and detachable from the image forming apparatus,
Non-volatile storage means includes binary input data of main M × sub-M pixels, main N × sub-N pixels (M and N are integers, M <N and N / M are non- When the photoconductor unit is attached to an image forming apparatus having a data conversion function of converting to (multiple) multi-value data and outputting the value, a value to be set in a lookup table used for the data conversion process is stored. A photoreceptor unit.   The value of the lookup table stored in the non-volatile storage means is subjected to the data conversion processing in a state where the photoconductor unit is attached to the image forming apparatus having the data conversion function in the recycling process of the photoconductor unit. When a plurality of test patterns having the same on-pixel density and different on-pixel positions in the main M × sub-M pixels are output onto the medium, the pulse width and the pulse of the multi-value data are set so that their densities are equal. 5. The photosensitive unit according to claim 4, wherein the position is set.   6. The photosensitive unit according to claim 4, wherein the nonvolatile storage means is an IC chip.

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