JPH03233576A - Adjusting method for digital copying machine - Google Patents

Abstract

PURPOSE:To perform copying operation with proper characteristics at all times by reading a copy which is outputted once by an image forming device by an image input device again, comparing image information of the copy with the image information of the document, and controlling an image formation parameter in such a direction that the difference is eliminated. CONSTITUTION:The document is read by an image reader 1, an image is formed on recording paper by the image forming device 8 according to the read image information to obtain the copy, and the image information is stored in a storage device 18. Then the copy is read again by the image reader 1, the read image information is compared with the image information stored in the storage device 18, and the image formation parameter of the image forming device 8 is varied so that the difference between both the pieces of image information is eliminated. Consequently, even when there is variation or variance in the characteristics of the image forming device itself, they are compensated automatically and the copying operation is performed with proper characteristics at all times.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention first converts a document image into electrical image information,
The present invention relates to an adjustment method in a digital copying apparatus that outputs an image after performing desired image processing by an image processing apparatus.

[Conventional technology]

In digital copying machines, original images are transferred to a CCD (i.e.
1E load-coupled element) It is read by an image reading device using an image sensor or the like and converted into image information. After this image information is subjected to image quality adjustments such as density, contrast, and gradation in an image processing device, an image is formed on recording paper using an image forming device such as a laser printer.

[Problem to be solved by the invention]

In this digital copying apparatus, image quality can be adjusted not only in the image processing device but also in each of the image reading device and the image forming device. Therefore, if the image quality of the final copy is not satisfactory and it is desired to adjust the image quality, there are three devices to be adjusted.

However, it is often impossible to determine which device should be adjusted just by looking at the final copy. For this reason,
For example, if the image of the final copy is faded due to poor adjustment of the image forming device, if you make a mistake in judgment and make adjustments using the image reading device or image processing device when the image forming device should be making adjustments, For example, the toner is used in a state where the toner concentration is abnormally higher than the normal state. For this reason, the inside of the copying device is likely to be contaminated with toner, which is undesirable from the viewpoint of maintainability. Further, there are cases where the photoreceptor is used in a state where the charged potential is abnormally high, and in this case, the photoreceptor is likely to deteriorate, which is not preferable from the viewpoint of life span and the like.

In addition, in color copying machines, yellow magenta,
Colors are reproduced by superimposing three colors (cyan) or four colors (black and black), but in the case of color, the density of each color varies (and appears as a color difference.The human eye is sensitive to the density of black and white images. In color copying machines, it is necessary to further stabilize the density reproduction characteristics of each color.However, in electrophotography, since triboelectric charging and corona discharge are used, It inherently contains unstable elements, and it is difficult to improve its stability.Also, methods have been proposed to change the development characteristics in response to changes in the external environment, such as temperature and humidity. ,
Since the development characteristics vary depending on the image density of the original and the environmental history of each copying device, they cannot be corrected in a regular manner.

It is also possible to perform color adjustment by adjusting each density component of yellow, magenta, and cyan, but this adjustment requires a skilled person with knowledge of color separation, and moreover, Even in this case, it was necessary to make several test prints. Therefore, it has been practically impossible for general users to perform color adjustment for characteristic correction.

Further, if a user who is not accustomed to adjustment makes the adjustment inappropriately, it becomes extremely difficult to restore the original characteristics.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to automatically adjust the copying apparatus so that copying operations can always be performed with appropriate characteristics.

[Means to solve the problem]

In order to achieve the above object, the adjustment method for a digital copying apparatus of the present invention reads a document with an image reading device, forms an image on recording paper with an image forming device based on the image information obtained by reading, and obtains a copy. At the same time, the image information is stored in a storage device, the copy is read again by the image reading device, and the image information obtained by reading is compared with the image information stored in the storage device, so that the difference between the two image information is eliminated. The method is characterized in that image forming parameters in the image forming apparatus are changed in the direction.

Further, in the adjustment method for a digital copying apparatus of the present invention, a reference document for image quality adjustment on which a reference density has been formed is read by an image reading device, and the density obtained by reading is read as a base 111 degrees stored in the main body of the copying apparatus. The image reading device and the image processing device installed after the image reading device are adjusted in a direction that reduces the difference in image density, and the photoreceptor is exposed in the image forming device according to the standard exposure pattern. forming an electrostatic latent image on the surface, determining image forming parameters that make the exposure light amount vs. surface potential characteristic linear and ensuring a standard contrast based on the surface potential of the electrostatic latent image;
forming a copy based on a reference exposure pattern using the image forming parameters, reading the copy with the image reading device, and comparing the density obtained by reading with a reference density stored in the main body of the copying device; It is characterized by controlling image forming parameters so that the difference in image density is small.

〔Example〕

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, features of the present invention will be specifically described based on examples with reference to the drawings.

FIG. 1 is a schematic sectional view of a digital copying apparatus according to a first embodiment of the present invention, which includes a black and white image reading device, an image processing device, and an image forming device.

FIG. 2 is a block diagram showing a signal system and a control system in the copying apparatus.

As shown in FIG. 3, the image reading device 1 of this apparatus includes a self-focusing lens 3, such as a SELFOC (registered trademark) lens, disposed below the platen glass 2. Line image sensor 4. N light lamp5. It mainly consists of a carriage 6 on which these are placed and a scanning system (not shown) for moving this carriage 6, and its reading width is, for example, 297 mm. The exposure lamp 5 also includes a lamp drive circuit 5a for adjusting the exposure amount.
(See Figure 2) are connected. The output of the image sensor 4 is supplied to the image processing device 7 via an amplifier 4a whose sensitivity is adjustable.

The image processing device 7 is provided with, for example, a gradation correction circuit 7a and the like, and after being subjected to predetermined image processing there, the image is supplied to the image forming device 8. Although various processes are actually performed in the image processing device 7, only the gradation correction circuit 7a is shown in FIG. 2 to simplify the explanation.

In the image forming apparatus 8, as shown in FIG. 4, a charger 10 is arranged close to the surface of a drum-shaped photoreceptor 9 that rotates in the direction of the arrow. The photoreceptor 9 is, for example, a negatively charged organic photoreceptor having a diameter of 84 mm and sensitive to infrared rays with a wavelength of 800 nm, and rotates at a circumferential speed of 160 mm/sec. In addition, the charger 10 has, for example, 3
It consists of a scorotron with a 0 μm diameter tungsten wire 10a stretched thereon and a grid 10b. Here, the high voltage power supply 3a (see FIG. 2) that applies a high voltage to the wire 10a is of a constant current type, and the wire t
The current value to Oa is variable according to a control signal from a CPU (central processing unit) 18. In addition, the grid 10b
The voltage of the grid power supply 8b that applies a grid bias to is also variable in the same way.

On the downstream side of the charger 10 (see FIG. 4), an exposure device 11 equipped with, for example, a semiconductor laser lla having a wavelength of 800 nm and a scanning optical system (not shown) is disposed, and the exposure device 11 is provided with a scanning optical system (not shown). The image signal is supplied to the semiconductor laser lla via the laser drive circuit 11b,
The intensity of the laser beam is modulated according to the image signal. The photoreceptor 9 is irradiated with this laser light, and an electrostatic latent image corresponding to the original image is formed on the surface of the photoreceptor 9. Note that the exposure device 11 is not limited to this configuration, and may use a combination of a He-Ne laser and its scanning optical system.
Alternatively, an exposure system using an LED (light emitting diode) may be used. Note that in this apparatus, it is assumed that the portion corresponding to the non-image portion is exposed to light.

Further, a surface electrometer 12 for measuring the surface position of the photoreceptor 90 after exposure is arranged downstream of this exposure section. The output of this surface electrometer 12 is supplied to the CPU 18 and compared with a reference potential, and depending on the comparison result, the high voltage power supply 8
a, Grid power supply Bb, Laser drive circuit 11b
etc. are controlled.

A developing device 13 that uses a two-component developer consisting of toner and carrier, for example, is arranged downstream of the surface electrometer 12. Note that the developing bias value from the bias power supply 8C applied to the developing roll 13a is variable according to a control signal from the CPU 18.

Further, on the downstream side of the developing device 13, a reflective density sensor 14, which has an integrated infrared light emitting section and a light receiving section, is disposed, for example. The output of the density sensor 14 is supplied to the CPU 18, and the output of the CPU 18 controls the toner dispenser 13b, thereby controlling the amount of toner supplied to the developing device 13. In addition, concentration sensor 1
The sensor 4 is not limited to a reflective type, and a density sensor that is placed inside the developing machine 13 and detects changes in magnetic permeability may be used.

On the downstream side of the concentration sensor 14, a corona transfer type transfer device 15. A glue-leaning device 16 using a blade cleaning method and a static eliminator 17 employing a photostatic neutralization method using a tungsten lamp are arranged in sequence.

Further, although not shown, a fixing device of a heat roll fixing type, for example, is provided to fix the toner transferred to the paper in the transfer device 15.

Furthermore, an operation panel 19 is connected to the CPU 18 and is used for inputting to the copying machine and displaying responses from the copying machine.

Next, the image quality adjustment operation in the above-mentioned copying apparatus will be explained with reference to the flowchart shown in FIG. In this embodiment, image quality adjustment is performed in four modes: image reading 7 image processing adjustment mode, electrophotographic section setup mode, sampling mode, and image output adjustment mode.

First, the image reading 7 image processing adjustment mode will be explained.

In the first embodiment, two types of reference patches are used for image quality adjustment in the image reading device 1. That is, as shown in FIG. 6, on a sheet of paper having a width equal to or greater than the reading width of the image reading device 1, a plurality of sheets of paper having different densities uniform over a width equal to or greater than the reading width are printed. The first reference patch set P is printed, and a plurality of second reference patch sets P having different densities are printed at other locations, and this is used as a reference document for image quality adjustment.

In the first embodiment, the reference document for image quality adjustment is A3 size, and the density of the first reference patch P is 1.5 and 0.0.
1, and the density of the second reference patch P2 is 0.01°O.
J, 0.6.0.9.1.2.1.5 standard manuscript is used.

First, the illumination system and sensitivity are corrected using the first reference patch P1. That is, a reference document Di for image quality adjustment is placed on the platen glass 2, and the first reference patch P is read by the image sensor 4 (step 101). and,
Maximum density D□ of the density output obtained by reading (see Figure 7)
and minimum concentration 0. .

The CPU 18 controls the light intensity of the exposure lamp 5 of the image reading device 1 and the amplifier 4 so that the image is reproduced without saturation.
The sensitivity of a is adjusted (step 102).

In addition, if there is a reference patch for shading correction on a part of the back side of the platen glass 2, or if you do not place an original on the platen and use it as a substitute for a high-density patch, and use an ordinary blank sheet of paper as a substitute for a low-density patch, etc. , the first reference patch P1 does not need to be printed in advance.

Next, read the second reference patch P2 (see Figure 8).
(Step 103), the output of each density after image processing is
In U13, the correction coefficient of the gradation correction circuit 7a of the image processing device 7 is changed by comparing it with the value stored in advance (step 104).

The adjustment in the image reading device 1 is completed by the processing in the image reading 7 image processing adjustment mode described above.

Next, the electrophotographic section setup mode in the image forming apparatus 8 will be explained.

First, for example, the standard n stored in the CPU 18
The laser drive circuit 11b is driven by the light pattern to modulate the laser light from the semiconductor laser lla.

This creates an electrostatic latent image on the photoreceptor 9, and the corotron current value, grid bias value, laser light amount, etc. are adjusted based on the potential of the electrostatic latent image.

In this electrophotography department setup mode, first,
U18 controls the grid power supply 8b to determine two levels of the grid voltage V, and the laser drive circuit 11b controls the laser light intensity (laser output) for each grid voltage level.
The surface potential of the photoreceptor 9 was measured by the surface electrometer 12 at a total of 20 levels.
Point measurement is performed (step 105).

Figure 9 shows an example of surface potential measurement, where the grid voltage V is 640v and 750v, and the laser output is 0 to about 1.
The power was changed in 10 steps within the range of mW.

Next, for each grid voltage, the maximum light amount value that maintains a substantially linear relationship between the laser light amount and the surface potential is calculated (step 106). Next, as shown in Fig. 10, the surface potential when the amount of light at each grid voltage is 0 (the relationship between the surface potential between points A and A and the surface potential of the amount of light at each grid voltage is a substantially linear relationship). From the surface potential (between points 0 and 1) at the maximum light intensity value that maintains (Step 107).

Furthermore, the surface potential of the solid patterned portion under the calculated conditions is calculated (step 108), and an appropriate developing bias value is determined (step 109).

Through the above-described processing, the laser output, grid voltage, and development bias are determined so that the relationship between the laser output and the surface potential is linear and a standard contrast can be obtained.

Next, a sampling mode in which a toner image is actually formed based on the base M/An light pattern and outputted onto recording paper will be described.

In this sampling mode, the CPU 18 controls the laser drive circuit 11b and the grid power supply 8b so that the laser light intensity, grid voltage, and development bias values calculated in the setup mode described above are obtained.

The bias power supply 8C is controlled and image forming conditions of the image forming apparatus 8 are set (step 110). Then, for example, the laser drive circuit 11b is driven by the basic Iff light pattern stored in the CPU 18 to drive the semiconductor laser lla.
modulates the laser light from the For example, the reference exposure pattern has an area ratio of 100%.

Five batches of 75%, 50%, 25%, and 0% are prepared, and a reference pattern is printed on recording paper under the above image forming conditions to obtain a copy sample (step 111).

Next, in the image output adjustment mode, this copy sample is read by the image reading device 1 (step 112), and after image processing is performed by the image processing device 7, the CPU 1g compares it with a reference value, and based on the comparison result, the density sensor 14 is adjusted. Change the reference value (step 113). For example, when the density of the copy sample is low, the base t$ density set in the CPU 18 is set to a lower value, and the time point at which toner supply from the toner dispenser 13C is started is determined. Hurry up.

By automatically sequentially executing the above four modes of image reading 7 image processing adjustment mode, electrophotography department setup mode, sampling mode, and image output adjustment mode, image reading device 11 image processing device 7 and image forming device 8 can be adjusted appropriately.

Next, when copying a document, the copying apparatus is set to the normal copy mode, and image reading, image processing, and image output are performed based on the parameters obtained in each of the adjustment modes described above.

That is, in the image reading device 1, the illumination system and sensitivity are corrected so that saturation of the density does not occur, so the image reading device 1 can read the density of the document faithfully. Further, in the image processing device 7, for example, gradation correction is correctly adjusted to a predetermined characteristic, so that the density reproducibility of the entire copying device is improved. Furthermore, in the image forming apparatus 8, feedback is applied to the grid potential for each copy cycle so that the dark area potential measured by the surface electrometer 12 is approximately constant with respect to the reference value, and the developed density for the dark area batch is adjusted to the density. The amount of toner supplied is controlled so that the output is read by the sensor 14 and becomes approximately constant with respect to a reference value. This allows the density of the original to be faithfully reproduced. In addition, since the adjustment state of each device such as the image reading device 11, the image processing device 73, and the image forming device 8 becomes appropriate, it is possible to use the device in the best condition in terms of internal contamination and the life of the photoreceptor.

In addition, in the above-mentioned embodiment, a two-component development method was employed, but a one-component development method may also be employed. in this case,
Since there is no need to control the toner density, a density sensor is not required. The difference between one-component development method and two-component development method is that
There is no adjustment factor such as toner concentration for changes in development characteristics due to aging or environmental changes. For this reason, a reference pattern is printed, its density is read by the image reading device 11 and the image processing device 7, and if there is a difference from the reference, the reference contrast value is changed according to the difference and the density is read from the information in the setup mode. What is necessary is to calculate and adjust an appropriate developing bias value, grid voltage value, and exposure amount.

Furthermore, instead of the scorotron, a normal corotron without a grid can be used as the charger 10. In this case, the charging potential may be controlled by the corotron current value or the voltage applied to the corotron wire.

Next, a copying apparatus according to a second embodiment of the present invention having a full-color image reading device, an image processing device, and an image forming device will be described with reference to FIG.

Note that the basic configuration and operation are the same as those of the first embodiment shown in FIGS. 1 to 5, so corresponding members and the like are given the same reference numerals and redundant explanation will be omitted.

Hereinafter, differences from the first embodiment described above will be mainly described.

In the second embodiment shown in FIG. 11, a color image sensor is used as the image sensor of the image reading device 1.

In the second embodiment as well, the first. A reference document for image quality adjustment having a second patch set is used, but it is different from the reference document of the first embodiment.

That is, this reference document is A3 size, and the first reference patch is black and white, that is, the density is 2.0 and 0.0.
1, and the second reference patch has cyan, magenta, yellow, and black densities of 0.01.0.5°1.0.
1.5.2.0 is used.

Similar to the first embodiment, the first reference patch corrects the illumination system and sensitivity of the image reading device 1, and the second reference patch changes the coefficients of the gradation correction circuit of the image processing device 7. It is.

In the second embodiment, the developing machines of the image forming apparatus 30 are cyan, magenta, yellow, and black developing machines 1.
3C, 13M, 13Y, and 13, each color toner image is formed on the photoreceptor 9 every time the photoreceptor 901 rotates. A messini-shaped transfer drum 31 is arranged to face the photoreceptor 9 , and the recording paper P fed from the paper feed tray 32 is attracted to the transfer drum 31 by the discharge of the adsorption corotron 33 . While the photoreceptor 9 rotates four times, it remains attracted to the transfer drum 31, and the toner images of each color on the photoreceptor 9 are sequentially and multiple-transferred onto the recording paper P by the corona discharge of the transfer corotron 34. A full color image is formed. The recording paper P on which this full-color image has been formed is peeled off from the transfer drum 31 by a peeling corotron 35 and fixed by a fixing device 36.

In the second embodiment shown in FIG. 11, in the electrophotographic unit setup mode, the grid voltage and laser light amount that provide a reference contrast are determined for each developing machine. In addition, an appropriate developing bias is also determined for each developing machine. Also sampling mode.

The image forming apparatus adjustment mode is also similar to the first embodiment except that processing is performed for each developing machine.

Therefore, according to the second embodiment shown in FIG. 11, in a color copying apparatus where poor adjustment results in noticeable deterioration in image quality, it is possible to make a certain adjustment without depending on the subjectivity of the adjuster, and the image quality is improved by the machine. difference, the difference in parameter values can be minimized.

Next, a third embodiment of the present invention will be described with reference to the flowchart of FIG. 13. The basic configuration is as follows.
This is similar to the second embodiment shown in FIG. Further, the circuit configuration is similar to the block diagram shown in FIG. 2.

In the third embodiment, an image quality adjustment mode key (not shown), which is usually covered with a cover, is provided on a part of the operation panel 19.
is provided. When this image quality adjustment mode key is pressed, "
A message will be displayed that says "Post the original" (
Step 201). Therefore, when the adjuster places the original on the platen glass 2 of the image reading device 1 of the color copying machine shown in FIG. 11 and presses the copy start key provided on the operation panel 19, the copying operation starts. Color information of the original is collected and stored. That is, first, n of the original image
The color is read by the image reading device tl (step 202), and after the nth color is subjected to predetermined image processing by the image processing device 7 (step 203), it is supplied to the image forming device 8, where the nth color is exposed, developed, and Transfer is performed (step 204). Note that n is any one of 1 to 4, and represents any one of cyan, magenta, yellow, and black. In addition, in parallel with this, the integrated density of the n-th color is calculated (step 20
5), the result is stored in, for example, a RAM (Random Access Memory) built into the CPU UlB (step 206). By repeating the above process for four colors while incrementing the value of n, an adjustment copy is formed by multiple transfer of four colors, and the R
AM stores color information for each color of the original, that is, integral values of the respective color-separated densities Orl to Or4.

When n>4 (step 20?), a message ``Put a copy'' is displayed on the display device (not shown) of the single work panel 19 (step 208). Therefore, the adjuster places the copy on the platen glass 2 and presses the copy start key provided on the operation panel 19. As a result, reading (step 209) and image processing (step 210) are performed for each color while incrementing the value of n, and in parallel, the integrated density is similarly calculated for each color for copying. (Step 211),
Integral value Cpl of each density obtained by color-separating the copy in RAM
~Cp4 is stored (step 212).

When n>4 (step 213), the copy density integral values Cpl to Cp4 and the original density integral values Orl to Or4 are compared for each color, and the process parameters are changed according to the comparison result (step 213). 21
4). In the third embodiment, the process parameter means a reference potential with respect to the dark potential, and in normal process control, the dark potential measured by the surface electrometer 12 is approximately equal to the reference potential. Feedback is applied to the grid potential of the charger 10 for each copy cycle so as to keep it constant. Further, the developing bias value is set to a predetermined value for each color corresponding to the reference potential.

For example, when Cpl > Orl, that is, when the density of the first color of the copy is darker than the original, αI: Calculate the coefficient and change the reference potential v1.

Also, when Cpl=Orl, V+=V+ And when Cpl<Orl, shall be.

Note that the same applies to the second to fourth colors. However, the coefficients are α2 to α4.

As described above, in the third embodiment, when a document is read and copied, image information of the document is collected and stored temporarily, and then a copy is read and image information is collected again. Compared with the previous image information, the process parameters are changed in a direction that reduces the difference. This makes it possible to obtain copies that are faithful to the original, regardless of differences in environmental history, variations in characteristics, etc. of each copying device.

In the third embodiment, the integrated value of each density obtained by color-separating the original image is used as the color information, but the invention is not limited to this, and for example, an exposure lamp for a color copier using three-color phosphor You can also use a fluorescent lamp to illuminate the document surface with light of each color, perform color separation, and expose the light onto the photoreceptor, and then use the integrated value of the reflected light after color separation from the document surface as color information. good.

〔Effect of the invention〕

As described above, according to the present invention, - the copy output by the star image forming device is read again by the image input device, the image information of this copy is compared with the reference value or the image information of the original, and the difference is eliminated. The image forming parameters in the image forming apparatus are controlled in this direction. Therefore, even if the characteristics of the image forming apparatus change, the image forming parameters are changed in a direction that compensates for the change in characteristics. As a result, even if there are changes or variations in the characteristics of the image forming apparatus itself, these are automatically compensated for and do not affect the output image. Furthermore, since the image processing device and image forming device of the image processing device 1 of the copying device are properly trimmed, each device is not used in an unreasonable operating state.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a black-and-white copying apparatus according to a first embodiment of the present invention, FIG. 2 is a block diagram showing a signal system and control system in the copying apparatus, and FIG. 3 is a main part of a document reading device. 4 is a partial sectional view showing the main parts of the image forming apparatus, FIG. 5 is a flowchart showing an example of a method for adjusting a copying device according to the present invention, and FIG. 6 is a partial sectional view showing a reference original for image quality adjustment. An explanatory diagram showing an example, FIGS. 7 and 8 are waveform diagrams showing the output when a reference document for image quality adjustment is read by a document reading device, and FIG. 9 is a waveform diagram showing the laser output and photoconductor surface potential in the image forming device. 10 is an explanatory diagram showing the procedure for determining the grid voltage and laser output to obtain the reference contrast in the image forming apparatus.
The figure is a schematic sectional view of a color copying apparatus according to a second embodiment of the invention, and FIG. 12 is a flowchart for explaining the operation of a color copying apparatus according to a third embodiment of the invention. 1: Image reading device 2 Nibraten glass 3: Lens 4: Image sensor 4a: Amplifier
5: fi light lamp 5a: lamp drive circuit 6: carriage 7: image forming device 8; image forming device 8b negative power supply 9: photoreceptor 10a: wire 11: i light device 11b: laser drive circuit 13, 13C, 13M, 13Y , 13K:13a
: Developing roll 14: Density sensor 16: Cleaning device Ill: CPU 30: Image forming device 32: Paper feed tray 34: Transfer corotron 36: Fixing device 7a: Tone correction circuit 8a: High voltage power supply 8c; Bias power supply 10: Charger 10b Nigellid 11a: Semiconductor laser 12: Surface electrometer developing device 13b: Toner dispenser 15: Transfer device 17: Static eliminator 19: Operation panel 31: Transfer drum 33: Adsorption corotron 35: Peeling corotron

Claims (1)

[Claims] 1. A document is read by an image reading device, an image is formed on a recording paper by an image forming device based on the image information obtained by the reading, a copy is obtained, and the image information is stored in a storage device. , the copy is read again by the image reading device, the image information obtained by the reading is compared with the image information stored in the storage device, and the image forming parameters in the image forming device are adjusted so that the difference between the two image information disappears. 1. A method for adjusting a digital copying device, characterized by changing. 2. Read the standard document for image quality adjustment on which the standard density has been formed using an image reading device, compare the density obtained by reading with the standard density stored in the copying device, and adjust the density in the direction that reduces the difference between the two densities. The image reading device and the image processing device provided after the image reading device are adjusted, and the photoreceptor is exposed in the image forming device according to a standard exposure pattern to form an electrostatic latent image on the photoreceptor. Based on the surface potential of the electrostatic latent image, determine image forming parameters that make the exposure light amount vs. surface potential characteristic linear and ensure the standard contrast, use the image forming parameters to form a copy based on the standard exposure pattern, and The copy apparatus is characterized in that the copy is read by the image reading device, the density obtained by reading is compared with a reference density stored in the main body of the copying apparatus, and image forming parameters are controlled in a direction that reduces the difference between the two densities. How to adjust a digital copying device.