JPH0746239B2 - Copying device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying apparatus capable of controlling image recording conditions for forming an image corresponding to an original image according to the original image.

(Prior Art) USP29564 is a technology for making the reproduced image clear by detecting light, charging potential, etc. corresponding to the document density information.
No. 87. Also, many proposals have been permitted or published since this US patent.

For example, in a copying machine, when forming an image on a photosensitive drum by moving a document and an optical system including a light source lamp relatively, an image is formed while automatically changing image conditions.

Specifically, it is known that the amount of light reflected from the document surface is sampled by an optical sensor, the result is calculated, and the developing bias or the document exposure light amount is controlled in real time.

However, when an image is formed on the basis of the proper image condition, unclear fog occurs in the image in the area corresponding to the edge of the document.

None of the conventional proposals solve such problems, and even the cause has not been clarified.

(Object of the Invention) An object of the present invention is to provide an image recording apparatus capable of investigating the cause of such a problem and solving the problem.

Another object of the present invention is to provide an image recording apparatus capable of providing an image corresponding to a document with excellent reliability without fog.

In order to achieve the above object, the present invention provides an image forming means for forming an image on a photoconductor based on an original, a detecting means for scanning the original to detect the density of the original for each predetermined width, and the detecting means. In a copying apparatus having a density control unit that controls the image forming condition of the image forming unit based on the detected density of the document, the density control unit is configured to detect a region other than a document end region in the scanning direction of the document. Controls the image forming condition on the basis of the area corresponding to each of the predetermined widths of the document, and sets the image forming condition on the basis of an area adjacent to the edge area of the original for the edge area of the original in the scanning direction of the original. It is characterized by controlling.

(Description of Embodiments) FIG. 1 shows a schematic configuration of an electrophotographic copying machine in which the present invention is implemented.

The image of the original 1 is illuminated by the original exposure lamp 3,
The reflected light is guided to the photosensitive drum 6 having a photosensitive layer by the optical system members (mirrors 141 to 144, lens 4, diaphragm slit 21). The photosensitive drum 6 is preliminarily uniformly charged by the charger 13 so that an electrostatic latent image of the original image is formed according to the amount of the reflected light.

This latent image is visualized by the developing device 7 using the developing powder (toner). This toner image is transferred to the recording sheet 9 by the transfer charger 18, and then fixed to the sheet 9 by a fixing device (not shown). The rotation speed of the photosensitive drum 6 in the arrow direction and the rotation speed of the sheet 9 in the arrow direction are the same, and the sheet 9 is conveyed at a predetermined timing so that the toner image is transferred onto the sheet 9 without any inconvenience. . The surface of the photosensitive drum after the transfer is the front static eliminator 10, the cleaner 11, the pre-exposure 12
Then, it is charged again by the charger 13 to prepare for the next image exposure.

When the AE mode for optimizing the image density of the original is selected in the above image formation, the proper image formation for the image density for each predetermined width W of the original is detected by the semiconductor image sensor behind the lens 4. The density detecting optical sensor 5 as described above, the microcomputer 20 as the central control means, and the developing bias control means 19 which influences the developing conditions are performed.

The problem at the trailing edge of the original when the present invention is not applied will be described with reference to FIGS. 2 and 3.

The predetermined width W of this document is a time width that keeps it constant even if the document size changes variously, for example, a half-wave of the power supply frequency, and at a power supply frequency of 50 Hz, sampling of 8 points is performed in the predetermined width (process). The speed is set to 8 mm at 100 mm / S. The average value Sx (X: 1 to n) obtained by averaging the image densities for each predetermined width from the leading edge of the document is corrected according to various image forming conditions (magnification, etc.). It is assumed that the calculated developing bias value Vx (X: 1 to n) is determined, but as shown in the enlarged view of FIG. A problem arises when the white surface of the base plate 2 is included.

That is, when the detection width is set so that the original 1 has 4 points and the pressure plate 2 has 4 points, the value Sn (1) of the original portion is 8 points Sn.
8 points Sn between (1) 'and original platen pressure plate Sn (2)
The relationship between (2) ′ and the actual sampling value Sn is when the original is a dark original such as a newspaper and the original platen is white (1)
Expression, and the relationship of the developing bias value with it becomes Expression (2).

Sn (1) '<Sn <Sn (2)' ... (1) Vn (1) '>Vn> Vn (2)' ... (2) Vn (1) 'is the appropriate development bias value for the original. However, since Vn is actually output due to sampling, it was found that the trailing edge of the formed image is unclear and has fog.

This cause is a problem commonly occurring at the edge of the document, but the flowchart of FIG. 4 solves the problem only at the trailing edge of the document.

That is, a real-time method is adopted in which a proper image is obtained while exposing the original by using the time difference between the exposure of the original and its reflected light reaching the exposure section Ep, and then the developing section Dp. The flowchart in FIG. 4 was executed.

When the print signal is input to the microcomputer 20, the photosensitive drum 6 is rotated, and the microcomputer 20 controls the movement of each member according to the pulse signal at constant intervals from this rotation.

The leading edge 15 of the document is positioned by the positioning plate 17 of the document glass 18, and the periphery of the leading edge 15 (the area including the leading edge of the document)
The image is whitened by the white plate 16 that is in close contact with the lower surface of the glass 18 below it. This is to form a white non-image portion on the leading edge of the sheet 9 to assist separation from the photosensitive drum and the fixing roller. This tip also has a problem caused by the above-mentioned cause. When the lamp 3 moves at a constant speed from the leading edge 15 to the trailing edge 1A of the document in the document image exposure area, the amount of reflected light is sequentially input to the optical sensor 5. When 0 (X + 1) is input to X in order to determine the value of the predetermined interval, the output of the optical sensor 5 is output to the second and fourth microcomputers as shown in FIG.
As shown in the figure, sampling is performed at regular intervals, digitization, averaging, and magnification correction are performed to digitize the image density of that area as Sx (STEP 1), then the appropriate developing bias amount corresponding to this is determined and analogized. The developing bias value (Vx) is determined, and the image forming conditions for optimizing the area X are stored (step 2).

Next, in step 3, the Sx value Vx value is determined until the trailing edge 1A of the document is detected, and the area X is controlled by the developing bias value Vx to form a proper image.

As shown in FIG. 5, if the trailing edge 1A of the original is detected at X = n and the inverted signal A is input, it means that the conditions for determining the Sn and Vn values and the boundary information of the trailing edge of the original are input. Therefore, as shown in STEP 5, Sn, Vn obtained corresponding to the edge area n of the document is cleared (or not detected or calculated), and the area (n-1) of the document, that is, the area The data before n is stored as the image condition of the n area. Then, for the region n, the bias value Vn _-1 of the region (n-1) is input as a new Vn value and executed as an image condition (STEP
6).

After that, if there are continuous copies for the same original, image formation is similarly performed with the development bias value stored in each area, and this flow ends when the continuous copies are completed.

This flow may be performed when a new document is copied.

To detect the trailing edge of a document, it is sufficient to detect it by the number of pulses of a pulse signal or a micro switch provided in advance for the end of each document size, for example, 129 pulses for Japanese Industrial Standard B5 and 148 pulses for A4. , B4 may be set as a reference value of the microcomputer 20 such as 182 pulses. Further, if the original table is such that the rear end of the original can be manually specified even if the original size is random, it is sufficient to store the specified position as the rear end position of the original.

Note that 1B in FIG. 1 indicates the trailing edge of the original when the original size becomes large, and in this size, the inversion signal B becomes the determination signal in STEP3.

When the trailing edge of the document is detected in STEP5 in the flowchart of FIG. 4, this does not cause a large error in the Sx value when the trailing edge of the document is detected as the boundary of each vertex region. Therefore, the case where Vx corresponding to the Sx value may be determined and executed is included. This may be done as needed.

In the above example, the rear end portion of the original is described. However, when the original is not accurately placed at the front end of the original and the white (or stain) of the original platen pressure plate 2 is read as the original even at the front end, the glass 18 is used. When the reflected light from both the white liquid 16 and the original 1 below is used as an information source, the above-mentioned problem occurs when the shadow due to the white plate is read by two parts of the end portion of the white plate 16 of the original. Occur.

Even in such a case, it is inconvenient to determine the image forming condition according to the image information of the area 1.

Therefore, the bias value V ₂ of the next area ₂ is used for the bias value of the image forming condition for the area 1 at the front end of the document to form an image (solid line in FIG. 5) or the white plate 16 is developed. The bias value (V ₀ + V ¹ ) obtained by adding the bias correction value V ¹ in consideration of the reduction amount of the reflected light amount due to the platen glass 18 to the bias value V ₀ that can be obtained as a white image without setting the image condition, etc. By doing so, the inconvenience can be solved.

As the bias correction value V ¹ , 10V to 50V corresponds to the light amount reduction of 5% to 15%, for example.

1 in FIG. 1 is a white plate 16 corresponding to the leading edge of the original.
The length is shown in FIG. 2 and is generally about 2 mm to 5 mm, and is 4 mm in this example. Since the white plate 16 is fixed in advance to the position where the front end 15 of the document is placed, the length 1 is also constant. Therefore, only the length 1 in the area 1 is stored as a white plate, and the bias value is set to V ₀ during the sampling period for the length 1 of the white plate from the start of the document exposure, and the remaining sampling period in the area 1 is set. Different controls may be used as the predetermined value (V ₀ + V ¹ ). Of course, only the image forming condition for the remaining sampling period of the area 1 may be the bias value V ₂ .

Although the flow chart for this embodiment is not shown, it may be, for example, a flow chart in which the value V ₂ is stored and the control of the value V ₂ is applied to the areas 1 and ₂ as understood in the chart of FIG. Good. Also, for region 1,
Control may be performed with the bias value V ₀ or (V ₀ + V ¹ ) of a predetermined value only for the period of the desired number of pulses after the leading edge image reaches the developing unit Dp.

The image forming conditions for the end area of the original including the trailing edge or the leading edge of the original do not correspond to the image conditions from the end area of the original, and different image forming conditions are set for the original. An image that is always clear and does not have the above-described fog at the trailing edge is possible regardless of the type (especially, a document with a dark background color).

The image forming condition may be any one of the average density of a part or the whole of the original area not including the original end area, the average bias value of a plurality of image areas, or the bias value of non-adjacent areas other than the above example. Although it is good, it is preferable to meet the conditions of the adjacent regions as described above in the sense of stabilizing the density change.

The predetermined width W in the above embodiment is 8 mm width (process speed 100 mm
/ s50Zz zero cross signal 8 point sample)
It may be any fixed value.

The same applies to the system in which the above-mentioned optical sensor is used for measurement, and the control value is fed back to the exposure amount control of the document exposure lamp, or the latent image on the photosensitive drum is measured by the surface potential sensor and fed back to the developing bias. It is needless to say that the above effect can be obtained and is included as an embodiment of the present invention.

With the above configuration, when the original is a dark-colored original such as a newspaper and there is a density difference from the original pressure plate (white), or the sampling value of the reflected light amount extends across the boundary between the original edge and the pressure plate. In either case, there is an effect that a clear and clean image free from fog at the edge of the copy image can be obtained.

In the present embodiment, the optical system moving type copying machine has been described as an example, but the present invention is also applicable to a document table moving type copying machine.
It can also be applied to an apparatus for copying while flowing a document.

According to the present embodiment, the optimum image reproduction corresponding to the density of the original can be performed, and since the sequential control is performed within the same original, it is possible to perform the image control that follows the density change within the same original. Therefore, the waste of transfer paper due to miscopy is eliminated and an efficient copying function is realized.

As described above, according to the present invention, the same operation condition as the operation condition of the image forming means other than the edge region of the document is set for the edge region of the document, so that even in the case of a halftone chart or the like. The operating conditions can be set accurately and reliably, and stable image formation can be performed.

In FIG. 6, 101 is a main body, 102 is a document table cover, and 103.
Is an operation unit and a document table, 104 is a document exposure lamp, 105a
~ 105d is a reflection mirror, 106 is a zoom lens for zooming, 107 is a fan for exhausting heat, 108 is a photosensitive drum, 109 is a photosensitive drum 10
A cleaner for removing the toner remaining on 8 is a charger 110 for uniformly charging the photosensitive drum 108 positively or negatively, 111
Is a blank exposure lamp for removing charges in the non-image area on the photosensitive drum 108, 112 is a developing device for developing the electrostatic latent image on the photosensitive drum 108, 113 is a paper feed cassette containing transfer paper, and 114 is A transfer charging device for transferring the toner image on the photosensitive drum 108 to the transfer paper, 115 a transfer roller, 116 a conveying roller, 117 a fixing device for fixing the toner image on the transfer paper, 118
Is a copy tray, 119 is an image sensor that outputs a signal indicating the leading edge of the original, 120 is a registration roller, 121 is a light receiving sensor that detects the intensity of light reflected from the original to detect the density of the original, 122 is a power switch, 123 is a home position sensor. Since the copying process of this copying machine is not so different from that shown in FIG. 1, its details are omitted.

FIG. 7 shows a circuit for detecting the document density. The photodetection current by the photodiode 31 corresponding to the light receiving sensor 121 is converted into a current-voltage by the operational amplifier 32, and the operational amplifier
At 33, the gain of the input voltage to the microcomputer 37 is adjusted. Microcomputer 37 has a built-in AD converter
It is a chip microcomputer. The microcomputer 37 outputs a PWM (pulse width modulation) pulse from the output boat 1 in order to output the developing bias DC value of the developing device 112 calculated by the input level of AD1 and the inputs from the volumes 35 and 36, This is level-converted through an integrator and used as a developing bias control signal input to the high voltage transformer 38. Here, the volume 35 is for determining the developing bias DC value to be applied with respect to a predetermined reference density determined for the original according to the sensitivity change of the photosensitive drum 108, in this embodiment the PC drum, and the volume 36 Is for determining the variable width of the developing bias DC value corresponding to the second reference density separately determined from the first reference density described above.
Further, 39 is a transformer, which performs full-wave rectification on the secondary side and performs zero-cross detection by an operational amplifier 41. The zero-cross pulse is input to the ▲ ▼ interrupt terminal of the microcomputer 37, and the interrupt processing by it causes AD as shown in FIG.
Sample 1 As shown in FIG. 9, the waveform of AD1 is cycled with the lighting voltage waveform of the halogen lamp LA1 which is the original exposure lamp 104, and half of the power supply frequency changes synchronously as shown in the figure, so sample at the zero cross point. Is effective in picking up accurate data. Switches 44 and 45 select the amount of light from the halogen lamp (4 levels) and use the D / A converter to adjust the lamp regulator LR1.
A lighting voltage control signal is sent to. Output boat 2
Outputs a lamp lighting signal.

FIG. 10 shows a timing chart of the automatic proper density adjusting function (hereinafter abbreviated as AE function) according to the present invention. A copying machine embodying the present invention uses a zoom lens 106 as shown in FIG. 6 and has a continuous variable magnification function having an enlargement / reduction function for each 1% with respect to an original, and a sensor output for an original having the same density. The relationship between (AD1) and the magnification is expressed by a linear expression as shown in FIG. Therefore, it is necessary to correct the sampled sensor output value (AD1) according to the copy magnification by the linear equation shown in FIG. Explaining FIG. 10, the AE function according to the present embodiment uses a real-time method, detects the amount of light reflected from the document surface by the optical sensor 31 while scanning the document, samples the output at the zero cross point, and samples it. The developing bias is controlled by an appropriate developing bias value calculated based on the data. First, according to the optical sensor output sampled at the zero-cross point after the document edge signal is input from the image edge sensor 119 while the platen is moving forward, the first development bias value V1 is calculated by sampling 8 points when the power supply frequency is 50 Hz. To do. At 60Hz
Calculate with 10 points. In the middle of the first sampling section, that is, as shown in Figs. 11 and 12, the next sampling section starts in parallel from the 5th point at 50Hz and the 6th point at 60Hz.
At the point, the next bias DC value V2 is calculated. Hereinafter, the same control is repeated to calculate V3, V4 ...

The developing bias DC value Vn thus obtained is sequentially output from V1 at the bias switching timing, as shown in FIGS. These include examples of special settings around the edges of the document.

Of these, FIG. 11 has the same concept as the example shown in FIG. 5, and the bias switching timing is divided by the exposure position A on the photosensitive drum and the distance 32 mm between the developing sleeve and the process speed 100 mm / S. This is the timing when the time 320 mS has elapsed after the image destination signal was input.

However, the data V ₁ cannot be handled as proper data because it includes the image leading edge margin of about 2 mm. Therefore, as shown in FIG. 7 and FIG.
V ₁ is substituted by data V ₂ immediately after the image tip. As a result, even if the leading edge of the image is a halftone chart or the like, it is possible to form an image without toner fog.

As is apparent from the above, regarding the sequential control AE according to the present embodiment, the latent image area developed by the developing bias value Vn refers to the original portion corresponding to the bias value and the original document density of the original area. It is decided by.
This is because the AE control has a specific time width (40 mS at 50 Hz, 60
Since the developing bias is controlled in units of 41.5 mS at Hz, the result is taken into consideration so as not to cause an extreme density change in the image at the boundary where the developing bias value is switched from Vn to Vn + 1. Further, in FIG. 12, the bias switching timing is slightly before the timing when 320 mS, which is the distance between the exposure position A on the photosensitive drum and the developing sleeve 32 mm divided by the process speed 100 mm / S, elapses after the image destination signal is input. In this embodiment, the timing is 40 mS before, that is, the timing when 280 mS has elapsed after the image destination signal was input.

This is because the input error and the rise time of the developing bias are taken into consideration.

As is apparent from the above, regarding the sequential control AE according to the present embodiment, the latent image area developed by the developing bias value Vn refers to the original portion corresponding to the bias value and the original document density of the original area. It is decided by.
This is because the AE control has a specific time width (40 mS at 50 Hz, 60
Since the developing bias is controlled in units of 41.5 mS at Hz, the result is taken into consideration so as not to cause an extreme density change in the image at the boundary where the developing bias value is switched from Vn to Vn + 1. According to these methods, the operating conditions of the image forming means with respect to the leading edge of the document are set from a region slightly before the leading edge of the document, so that the operating conditions are systematic and reliable regardless of input errors and the rise time of the developing bias. Can be set,
It is possible to perform stable image formation.

The control timing of the sequential AE control has been described above, but next, the method of calculating the developing bias DC value Vn will be described. The calculation of the bias DC value is carried out in the zero-cross interrupt processing shown in FIG. High voltage transformer used in this example
The development bias specification of 38 is the control signal 10 as shown in FIG.
It is linearly controlled from -50 to -600V with respect to ~ 15V.
In this embodiment, in order to obtain this control signal, pulse width modulation (PW
M) pulse is output, and the level is converted into a control signal by inputting this pulse to an integrator. The state is first
Shown in Figure 15. In this embodiment, the duty ratio of the pulse is prepared in 43 divisions, and the developing bias DC value control signal is controlled. Therefore, the minimum resolution of the developing bias DC value is (600-50) /44=12.5V. In this way, proper image density control is realized by successively outputting the pulses having the duty ratio corresponding to the developing bias value calculated by the bias calculation routine shown in FIG. 8 from the one-output boat.

Next, the contents of the bias calculation routine shown in FIG. 8 will be described with reference to FIG. After the document is moving forward, after passing the image sensor, the average value is calculated for each output of sampling 8 times when the power supply frequency is 50 Hz and 10 times when it is 60 Hz, and the average value is the magnification shown in Fig. 13 as described above. It is corrected to the data at the same size by a linear expression showing a function. That is, assuming that the average value Vn when the magnification is x%, the data Vn when the magnification is 100% is Becomes This is the magnification correction process in FIG.

The light amount correction process is performed next. In the photosensitive drum (PC drum) embodying the present invention, as shown in FIG. 19, the Light potential rises and the contrast decreases as the number of copies increases. In order to correct this, as shown in FIG. 7, the light amount of the halogen lamp which is the original exposure lamp is selected by the switches 44 and 45.
In other words, as the number of copies progresses, the Li
As the ght potential rises, the lighting voltage of the halogen lamp is increased to mitigate the decrease in contrast. This lighting voltage is selected by the switch 4 shown in FIG.
Four types of voltage can be selected by combining 4,45, and the microcomputer 7 can
8 bit information is transmitted to the A ₁ converter 46, and the D / A converter converts this information into an analog value and outputs it, thereby giving a halogen lamp lighting voltage control signal to the lamp regulator LR1. Therefore, assuming that the standard lighting voltage is E ₀ and the other three lighting voltages are E1, E2, and E3 (representatively El), the calculated value Vn obtained by the magnification correction processing is Vn ′ and Vn ′ after light amount correction.
Is Is obtained as.

This light amount correction process determines the document density shown in FIG. 17, and the final process of the flow in FIG. 16, that is, the light amount correction value V
The calculation of the developing bias DC value for n'is executed. First
Figure 8 shows the situation. Referring to FIG. 18, by controlling the developing bias DC value linearly with respect to the density between the reflected light amount Q = 0.76 of the standard density original and the dark original Q = 0.5 corresponding to the newspaper, the dark original is darkened. Characters are clearly reproduced on a thin original without covering. However, by setting an upper limit on the bias value for documents that are darker than newspapers and setting a lower limit for documents that are brighter than standard-density documents, excessive control of the background over-blurring or over-fogging can be prevented. ing. Also, the photosensitive drum (PC drum) 108 used in this embodiment has a latent image potential curve with respect to the exposure amount as the number of copies increases as shown in FIG.
Since it tends to rise from 51 to 52, it is necessary to make the control value (lower limit value mentioned above) of the developing bias for the standard original variable as shown in FIG. 18, which is shown in FIG. It is realized by volume 35. In addition, the change over time of the photosensitive drum shown in FIG. 19 changes so as to reduce the contrast between the Light potential (V _L ) and the Dark potential (V _D ), so as shown in FIG. It is also necessary to change the variable width of the developing bias control between the originals with the lapse of time. In this embodiment, the variable width is controlled from min 90V to max 180V by the volume control 36 shown in FIG.

According to the present embodiment, it is possible to optimally reproduce the image corresponding to the density of the original, and since the sequential control is performed within the same original, it is possible to perform image control that follows the change in density within the same original. Therefore, the waste of the transfer paper due to the miscopy is eliminated and an efficient copying function is realized.

In the present embodiment, the optical system moving type copying machine has been described as an example, but the present invention is also applicable to a document table moving type copying machine.
It can also be applied to an apparatus for copying while flowing a document.

[Brief description of drawings]

FIG. 1 is a schematic view of an image recording apparatus of the present invention, FIG. 2 is an explanatory view of a cause of a problem to be solved by the present invention, FIG. 3 is an enlarged view of a document end of FIG. 2, and FIG. FIG. 5 is a timing chart showing a specific example of the present invention, FIG. 6 is a sectional view of a copying machine to which the present invention is applied, and FIG. 7 is a document density detection circuit diagram according to the present invention. FIG. 8 is an interrupt routine flowchart, FIG. 9 is a diagram showing waveforms of each part of the present invention, FIG. 10 is a timing chart of the present invention, FIG.
Figure 12 shows the correspondence between AE sensor output sampling classification and development bias output DC value, and Figure 13 shows the copy magnification and
FIG. 14 shows the relationship between the AE sensor output, FIG. 14 shows the specifications of the developing bias DC value of the high-voltage transformer, FIG. 15 shows the relationship between the developing bias control pulse and the developing bias control signal, and FIG. 16 shows the AE. Bias value calculation flowchart in control, FIG. 17 is a diagram showing the relationship between the document reflected light amount Q and the AE sensor output, FIG. 18 is a diagram showing the document reflected light amount Q and the developing bias DC value, and FIG. 19 is a photosensitive drum It is a figure which shows the sensitivity change by the time-dependent change of. Reference numeral 1 is a document, 1A and 1B are the rear end of the document, 3 is a light source, 5 is a density detecting sensor, 16 is a white plate, 19 is a developing bias control means, 20 is a microcomputer, and W is a predetermined width for detecting the document density.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-60-38751 (JP, A) JP-A-60-26367 (JP, A) JP-A-60-26365 (JP, A) JP-A-59- 142573 (JP, A) JP 59-42551 (JP, A) JP 56-156841 (JP, A)

Claims (1)

[Claims] 1. An image forming means for forming an image on a photoconductor based on an original, a detecting means for scanning the original to detect the density of the original for each predetermined width, and a density of the original detected by the detecting means. And a density control unit that controls the image forming condition of the image forming unit based on the above, the density control unit is configured so that the density control unit, in regions other than the end regions of the document set in the scanning direction of the document, The image forming condition is controlled on the basis of the region corresponding to each of the predetermined widths of the document, and the edge region of the document set in the scanning direction of the document is adjacent to the set edge region of the document. A copying apparatus, wherein the image forming condition is controlled based on a width region.