JP3575259B2 - Image forming device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus for forming an image on a recording medium, such as an electrophotographic or ink-jet printer, a copying machine, and the like, and more particularly, to an image forming apparatus having a calibration function of an image forming process.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an image forming apparatus has been calibrated to improve the image quality of an image formed on a sheet. In particular, in an electrophotographic image forming apparatus in which an image is formed through an image forming process including a plurality of steps such as charging, exposing, developing, and transferring, an image finally formed on a sheet is formed for each step. Various controls are performed to enhance the image quality.
[0003]
Examples of such an image forming apparatus include those disclosed in JP-A-3-87768 and JP-A-4-193576.
[0004]
The image forming apparatus disclosed in JP-A-3-87768 monitors a developed image formed on a photoreceptor as an image carrier, and controls each process so that the developed image becomes a predetermined developed image. By calibrating the apparatus, the image quality of the image formed on the paper is improved.
[0005]
The image forming apparatus disclosed in Japanese Patent Application Laid-Open No. Hei 4-193576 monitors the toner density after transfer, and controls each process so that the toner density becomes a predetermined toner density to calibrate the apparatus. The image quality of the image formed on the paper is improved.
[0006]
However, since the image forming apparatuses disclosed in JP-A-3-87768 and JP-A-4-193576 all control a process in an intermediate stage of image formation to calibrate the apparatus, There is no guarantee that the image quality of the image actually obtained by the user, that is, the fixed image (final image) itself will be improved, and there will be an error between the image quality of the image (intermediate image) and the image quality of the final image based on the process controlled in the intermediate stage. Is likely to occur.
[0007]
As a conventional image forming apparatus for solving this problem, there are, for example, those disclosed in JP-A-4-366165 and JP-A-4-55868.
[0008]
An image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 4-369165 forms a reference image on a sheet using an image forming unit, and detects the reference image using an image detection unit provided in the image forming apparatus. This controls each process to calibrate the apparatus. According to this apparatus, since the apparatus can be calibrated by controlling the fixing step, which is the final step, the error between the reference image and the final image is reduced, and the image quality can be improved.
[0009]
The image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 4-55868 forms a test pattern in which a color band is inserted between a start pattern and a stop pattern on paper, and tests reflected light from the test pattern. The image quality is improved by calibrating the apparatus so that the difference between the level of the reflected light read by the pattern detection unit and the reference value is reduced. According to this device, the device can be calibrated even when the image reading unit is not provided unlike a printer.
[0010]
[Problems to be solved by the invention]
However, according to the conventional image forming apparatuses disclosed in JP-A-4-366165 and JP-A-4-55868, the characteristics of the detection unit change due to aging or temperature change. In order to perform the above, it is necessary to appropriately calibrate the detection unit using the reference concentration, but the above publication does not describe what is used as the reference concentration.
[0011]
It is conceivable that a white reference plate is provided and its density is used as the reference density.However, the white reference plate becomes soiled with the passage of time, and the correct reference density cannot be detected stably. No, image quality deteriorates. In order to avoid this, there is a problem that regular maintenance is required.
It is also conceivable to use the density of the paper background as the reference density.However, the background of the paper may be stained by fogging of the residual toner. In this case, the correct reference density cannot be detected. And the image quality deteriorates.
[0012]
SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an image forming apparatus which enables maintenance-free operation, performs calibration of the apparatus with high accuracy and stability, and improves the image quality of an image formed on a recording medium.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the present invention conveys a recording medium to a predetermined position by a conveying mechanism and forms an image on the recording medium, wherein an image for calibration or a recording image is formed on the recording medium. An image forming unit to be formed; a density of a ground of the recording medium on which the image for calibration and the recording image are not formed by the image forming unit; and the calibration unit formed on the recording medium by the image forming unit. Detecting means for detecting the density of the image, controlling image forming conditions of the image forming means based on the density of the ground of the recording medium and the density of the calibration image detected by the detecting means, An image forming apparatus comprising: a control unit for setting a density to a desired density.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows an electrophotographic image forming apparatus according to a first embodiment of the present invention. The image forming apparatus 1 charges, exposes, develops, transfers, and fixes an image for device calibration or an image to be output to a user (hereinafter, referred to as a “recorded image”) on a sheet P in an image forming position according to a mode. Image forming unit 2 formed through the predetermined image forming process, the density of the ground of the sheet P not passing through the image forming position at the density detecting position, and the calibration of the apparatus formed on the sheet P by the image forming unit 2. A detection unit 3 for detecting the density of the image for use; and a paper transport mechanism 4 for transporting the paper P to the image forming unit 2, the detection unit 3, and the like. In the figure, P ₀ represents a paper that has not passed through the image forming position, P ₁ denotes a sheet apparatus for calibration image has been formed, P ₂ denotes a sheet recording image is formed.
[0015]
The image forming unit 2 includes an image carrier 20 on which an electrostatic latent image is formed, a charging unit 21 for uniformly charging the surface of the image carrier 20, and an image signal on the charged image carrier 20 based on an image signal. Exposure unit 22 that forms an electrostatic latent image on image carrier 20 by performing exposure, developing unit 23 that develops the electrostatic latent image with toner, and transfer unit that transfers the developed toner image onto paper P 24, and a fixing unit 25 for fixing the toner image on the paper P.
[0016]
Paper transport mechanism 4 includes a paper feed tray 40 for feeding a sheet P ₀ before image formation, a first discharge tray 41A to the paper P ₁ the apparatus for calibration image has been formed is ejected, the recorded image There the sheet P ₂ is formed and a second discharge tray 41B to be discharged. Paper feed tray 40 includes a paper feed roller 40a for feeding the sheet P ₀ one by one from the paper feed tray 40 by the driving of the feed motor, not shown. A main transport path 42 extending from the paper feed tray 40 to the first discharge tray 41A is formed, and between the first branch point 42a and the junction 42b on the main transport path 42 via an image forming position. A sub-conveyance path 43 is formed, and a recovery conveyance path 44 returning to the paper feed tray 40 is formed from a second branch point 42c of the main conveyance path 42, and is formed from a third branch point 42d of the main conveyance path 42. A branch conveyance path 45 reaching the second paper discharge tray 41B is formed. A first gate that switches the transport direction of the paper P to a first branch point 42a, a second branch point 42c, and a third branch point 42d of the main transport path 42 by driving a gate driving unit (not shown). 46a, a second gate 46b and a third gate 46c are arranged. A plurality of transport rollers 47 for transporting the paper P by driving a paper transport motor (not shown) are provided in each of the main transport path 42, the sub transport path 43, the recovery transport path 44, and the branch transport path 45. . Further, a reflection plate 5 such as a white plate or a black plate is provided at a position facing the detection unit 3 with the main transport path 42 interposed therebetween to reduce a density detection error due to a variation in the thickness of the paper P.
[0017]
FIG. 2 shows the detection unit 3. The detection unit 3 is disposed behind the fixing unit 25 (see FIG. 1) on the main transport path 42 in the process direction, and emits light at an angle of 45 degrees with respect to the detection surface Pa of the paper P. Is arranged at an angle of 90 degrees with respect to the detection surface Pa, and the light diffusely reflected on the detection surface Pa of the paper P is input through the condenser lens 31, and the input light is photoelectrically converted into an electric signal. And a photodiode 32 that outputs a detection signal. If the thickness of the paper P is not uniform, the reflectance (transmittance) of light is different, so that a variation in the thickness causes a density detection error. However, the provision of the reflection plate 5 on the back side of the paper P Accordingly, the light transmitted through the sheet P is reflected by the reflection plate 5 and transmitted again through the sheet P, thereby reducing the density detection error.
[0018]
FIG. 3 shows a control system of the device 1. The device 1 has a control unit 10 for controlling the entire device 1. The control unit 10 has a program memory 11 for storing a program of the control unit 10 and a device calibration device for forming a device calibration image. An image memory 12 that stores an image signal, a recorded image signal for forming a recorded image, and the like; an image processing unit 13 that performs predetermined processing on the image signal from the image memory 12; the image forming unit 2; The unit 3 and the paper transport mechanism 4 are connected.
[0019]
Based on the detection signal from the detection unit 3, the control unit 10 controls the image forming conditions, that is, the image processing unit 13, the charging unit 21, the exposure unit 22, the developing unit 23, the transfer unit 24, and the fixing unit of the image forming unit 2. The operation of each part or part of 25 is controlled.
[0020]
Next, the operation of the present apparatus 1 will be described with reference to FIG. The following description is based on the assumption that the background color of the paper P is white.
[0021]
Figure 4 illustrates the operation of detecting the density of the density and the device calibration image of the land of the sheet P ₀ by the detection unit 3 (reference image). As shown in the figure, the device calibration image forms a plurality of density patterns 6a, 6b, and 6c having different densities along the transport direction 7 of the paper P so as to pass through a density detection position immediately below the detection unit 3. ing. Further, the density patterns 6a, 6b, 6c are formed so as to have densities of, for example, 0.30, 0.80, 1.55 when the density of the reference image is 0.00.
[0022]
(1) Device Calibration Mode When the operator turns on the power of the present device 1, the control unit 10 executes the device calibration mode according to the program stored in the program memory 11 as described below.
[0023]
First, the control unit 10, in order to detect the density of the reference image, to feed the sheet P ₀ from the paper feed tray 40 by driving the feed motor and the paper transporting motor (not shown) of the paper transport mechanism 4, the main transfer Supply to the road 42. At the same time, the control unit 10 controls the gate drive unit (not shown) of the paper transport mechanism 4 to operate the first gate 46 a so that the paper P ₀ from the paper feed tray 40 is transported to the sub transport path 43. Let it. Sheet P ₀ supplied to the main conveying path 42 is conveyed from the first branching point 42b by the rotation of the conveying roller 47 by the driving of the paper conveying motor to sub-passage 43, the confluence without passing through the image forming position Proceed to 42b and pass through the density detection position immediately below the detection unit 3. White paper P ₀ of the left without passing through the image forming position, it passes through the concentration detection position, the concentration of the land of the sheet P ₀ detected by the detection unit 3 is outputted to the control unit 10 as a detection signal .
[0024]
As the sheet P ₁ that following the sheet P ₀ where no image is formed device calibration image is formed, as shown in FIG. 4, it passes through the density detection position directly below the detection unit 3 continuously, controlled The unit 10 controls the sheet transport mechanism 4 and the image forming unit 2. That is, the control unit 10 causes the feeding paper P ₀ from the paper feed tray 40 as described above is supplied to the main transport path 42. At the same time, the control unit 10 operates the first gate 46a so that the paper P ₀ from the paper feed tray 40 and controls the gate driver (not shown) of the paper transport mechanism 4 is conveyed to the image forming position . Sheet P ₀ supplied to the main conveying path 42 is conveyed to the image forming position.
[0025]
At the same time, the control unit 10 reads out the device calibration image signal from the image memory 12, performs predetermined processing on the device calibration image signal by the image processing unit 13, and based on the processed device calibration image signal. The image forming unit 2 is controlled. The image forming unit 2 forms a device calibration image on the paper P. That is, the exposure unit 22 of the image forming unit 2 forms an electrostatic latent image on the image carrier 20 that is uniformly charged by the charging unit 21 based on the image signal for device calibration. The developing unit 23 develops the electrostatic latent image with toner, the transfer unit 24 transfers the developed toner image onto the paper P, and the fixing unit 25 fixes the toner image on the paper P. In this way, an apparatus calibration image composed of a plurality of density patterns 6a, 6b, 6c as shown in FIG. The sheet P ₁ the apparatus for calibration image has been formed passes through the density detection position. When the sheet P ₁ passes through the concentration detection position, the density pattern 6a of the sheet P ₁ by the detection unit 3, 6b, the concentration of 6c is detected is output to the control unit 10 as a detection signal. The sheet P ₀ the concentration of the earth is detected, return to the paper feed tray 40 again through the collecting path 44 by the operation of the second gate 46c by the gate driver. On the other hand, the sheet P ₁ in which the concentration of device calibration image is detected, the second and third gate 46c by the gate driver, is discharged to the first paper discharge tray 41A by the operation of 46d.
[0026]
Next, the control unit 10, a detection signal indicative of the concentration of the ground of the output white paper P ₀ from the detection unit 3, and density patterns 6a, 6b, the image forming unit based on a detection signal indicative of the concentration of 6c Calibrate 2. That is, the output voltage of the detection unit 3 when reading the ground of a blank sheet of paper P ₀ on which no image is formed is V ₀ , and the output voltage of the detection unit 3 when reading the density patterns 6a, 6b, and 6c is respectively When V ₁ , V ₂ , and V ₃ are set, V ₁ / V ₀ , V ₂ / V ₀ , and V ₃ / V ₀ have predetermined values, respectively, so that the image processing unit 13 and the image forming unit 2 have different values. The operation of each part or a part of the charging unit 21, the exposure unit 22, the developing unit 23, the transfer unit 24, and the fixing unit 25 is controlled.
[0027]
(2) Normal Mode When the device calibration mode ends and the operator performs settings necessary for printing, the control unit 10 executes the normal mode according to the program stored in the program memory 11. In the normal mode, the control unit 10 reads out a recording image signal from the image memory 12 and controls each unit of the image forming unit 2 based on the recording image signal. At the same time, the paper P ₀ is conveyed from the paper feed tray 40 to the image forming position, the recording image by the image forming unit 2 is formed. Sheet P ₃ which recorded images are formed, the second and third gate 46c by the gate driver, is discharged to the second sheet discharge cassette 41B by the operation of 46d.
[0028]
Next, effects of the present device 1 having the above configuration will be described.
(B) to detect the concentration of the land of the sheet P, because the image is using the sheet P ₀ is not formed, it is possible to eliminate detection error due to fog or the like. That is, the marginal portion of the sheet on which the image has been formed through the image forming process may have a small amount of residual toner that should not originally exist. For this reason, if the correction of the device calibration image is performed based on the density of the ground in the margin of the paper on which the image has been formed through the image forming process, the correction will be performed correctly due to the influence of the density of the ground due to fog. Can not. Therefore, the paper P ₀ the image is not formed at all is not present the head, it is possible to accurately detect the concentration of the land of the paper.
For detecting the concentration of the land of (b) paper, because of the use of paper P ₀ that has not passed through the image forming position, for reading the concentration of the land of the sheet to the sheet P to form a device calibration image There is no need to provide a blank portion, and more density patterns can be formed. As a result, the density detection accuracy is improved.
(C) for conveying the paper P ₀ blank to a concentration detection position, because of the use of sub-passage 43 which does not pass through the image forming position, the toner used for image formation because it can avoid the sheet P is soiled And the density of the reference image can be detected with high accuracy.
In (d) equipment calibration mode, the concentration of the land of blank paper P ₀ the image is not formed at all, since the read and concentration of device calibration image continuously, a change in the ambient temperature detection unit 3 And the effects of aging and the like can be reduced.
After the detection of the concentration of the land of (e) the sheet P ₀ has ended, since the recovered paper P ₀ of the blank to the feed tray 40, since it can reuse sheet P ₀ that the recovered as an image forming paper And resource saving can be achieved.
(F) Since the reflection plate 5 is provided on the back surface of the paper P at the density detection position, the light transmitted through the paper P is diffusely reflected by the reflection plate 5, transmitted again through the paper P, and made incident on the photodiode 32. In addition, it is possible to reduce a density detection error due to a variation in the thickness of the sheet P.
(G) Since the device sheet P ₂ the calibration sheet P ₁ on which an image is formed recorded image is formed is collected in a separate tray, when forming the recording image in succession, the middle in even calibrate the image forming unit 2, for prevent the sheets P ₁ the apparatus for calibration image is formed between the paper P ₂ which recorded image is formed is mixed, divided work sheet P _1, P ₂ Can be omitted.
[0029]
Next, a second embodiment of the present invention will be described. In the first embodiment, the paper P ₀ for detecting the density of the ground of the paper P and the paper P ₁ for detecting the density of the apparatus calibration image are different from each other. In the second embodiment, the same paper P is used. That is, in this second embodiment, after detecting the concentration of the land of the sheet P ₀ is transported from the paper feed tray 40 to the paper P ₀ to the concentration detecting position via the sub-passage 43, the sheet P ₀ through the collecting path 44 is recovered, so that the collected paper P ₀ and conveyed to the image forming position as it is to form a device calibration image, detecting the concentration of device calibration image is transported to the concentration detection position I have to. According to the second embodiment, it is possible to reduce the paper error between the density of the land of the sheet P _0. That is, there is a difference between sheets in the density of the ground of the paper, and the difference between the sheets in the density of the ground may be large when the manufacturing lot is different. Therefore, when the sheet P ₁ to form a sheet P ₀ and apparatus calibration image for detecting the concentration of the land of the paper are different, if the sheet between difference of the concentration of the land of the paper causes the concentration detection error There is. Therefore, by adopting the configuration of the second embodiment, it is possible to reduce an error between sheets in the density of the background of a sheet.
[0030]
Next, a third embodiment of the present invention will be described. In the third embodiment, the sheet P ₀ that has not passed through the image forming position by using a plurality detects the concentration of a plurality of earth, is obtained by the reference density and the average value. As a result, it is possible to determine the density of the ground with higher accuracy, and it is possible to eliminate the influence of unevenness in the density of the ground itself.
[0031]
Next, a fourth embodiment of the present invention will be described. In the fourth embodiment, the detection unit 3, also detecting the concentration of the land of the margin portion of the paper P ₁ the apparatus for calibration image has been formed, the control unit 10, the land of the paper density and the paper P The degree of fogging by the image forming unit 2 is obtained by comparing with the density of the ground in the margin portion ₁ . Because the degree of head which varies depending on the charging voltage or the like, the degree of fogging by the image forming unit 2, when calibrating the image forming unit 2 so that the recording image of the desired concentration on the paper P ₂ is formed Data.
[0032]
FIG. 5 shows an electrophotographic image forming apparatus according to a fifth embodiment of the present invention. The image forming apparatus 1 is disposed in front of the image forming position, a first detection unit 3A that detects the concentration of the land of the sheet P ₀ where no image is formed, it is disposed behind the image forming position, device The first embodiment has a second detection unit 3B for detecting the density of the calibration image, and two reflectors 5 arranged at positions facing the first and second detection units 3A and 3B, respectively. Unlike the first embodiment, the sub-transport path 43, the first and second gates 46a and 46b, and the recovery transport path 44 are not provided, and the other configuration is the same as that of the first embodiment.
[0033]
Next, the operation of the fifth embodiment will be described.
(1) Device Calibration Mode When the operator turns on the power of the present device 1, the control unit 10 executes the device calibration mode according to the program stored in the program memory 11. First, the control unit 10 controls the paper transport mechanism 4 to feed the paper P ₀ from the paper feed tray 40 and supplies the paper P ₀ to the main transport path 42. The paper P ₀ supplied to the main transport path 42 has the ground density of the paper P ₀ detected by the first detection unit 3A disposed in front of the image forming position, and is output to the control unit 10 as a detection signal. . Subsequently, the control section 10 conveys the sheet P ₀ the concentration of the earth is detected in the sheet P ₀ to the image forming position, and controls the image forming unit 2 for forming a device calibration image on the sheet P _0. Paper P ₁ the apparatus for calibration image has been formed, the concentration of the second detection unit 3B by a device calibration image disposed behind the image forming position is detected is output to the control unit 10 as a detection signal. Sheet P ₁ in which the concentration of device calibration image is detected is discharged to the first discharge tray 41A by the operation of the gate 46d by the gate driver. Next, the control unit 10 calibrates the image forming unit 2 based on the detection signals from the first and second detection units 3A and 3B.
[0034]
(2) Normal Mode When the device calibration mode ends and the operator performs settings necessary for printing, the control unit 10 executes the normal mode according to the program stored in the program memory 11. The control unit 10, the paper feed tray 40 and controls the paper transport mechanism 4 by feeding a sheet P ₀ and conveyed to the image forming position, and controls the image forming unit 2 forms a recording image on the sheet P ₀ . Sheet P ₃ which records the image is formed is discharged to the second sheet discharge cassette 41B by the operation of the gate 46d by the gate driver.
[0035]
According to the fifth embodiment, the auxiliary transport path 43, the first and second gates 46a and 46b, and the recovery transport path 44 are not required, and the configuration can be simplified as compared with the first embodiment. .
[0036]
Note that the present invention is not limited to the above-described embodiment, and various modes are possible. For example, the present invention can be applied to a method other than the electrophotographic method, for example, an image forming apparatus of an ink jet method.
Further, in the above embodiment, the case where a single color image is formed has been described. However, the present invention can be applied to a color image forming apparatus. In this case, the detection unit 3 and the density pattern 6 may be provided for each color.
Also, without collecting the paper P ₀ the concentration of the earth is detected in the sheet feeding tray 40, it may be discharged to a dedicated third discharge tray.
[0037]
【The invention's effect】
As described above, according to the image forming apparatus of the present invention, a recording image having a desired density is formed on a recording medium based on the density of the ground of the recording medium where no image is formed and the density of the calibration image. Since the image forming conditions of the image forming unit are controlled so that the image is formed, it is possible to eliminate an error in detecting the density of the ground due to fogging or the like. Therefore, there is no need to provide a white reference plate or the like, so that maintenance-free operation is possible. In addition, since the density of the ground of the recording medium free from fog or the like is used as the reference density, the apparatus can be calibrated with high accuracy and stability. As a result, the image quality of the image formed on the recording medium can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a detection unit according to the first embodiment of the present invention.
FIG. 3 is a block diagram illustrating a control system of the image forming apparatus according to the first embodiment of the present invention.
FIG. 4 is a diagram for explaining an operation of the image forming apparatus according to the first embodiment of the present invention.
FIG. 5 is a schematic configuration diagram of an image forming apparatus according to a fifth embodiment of the present invention.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 image forming apparatus 2 image forming units 3, 3 A, 3 B detecting unit 4 paper transport mechanism 5 reflectors 6 a, 6 b, 6 c density pattern 10 control unit 11 program memory 12 image memory 13 image processing unit 20 image carrier 21 charging unit 22 Exposure unit 23 Developing unit 24 Transfer unit 25 Fixing unit 30 Light source 31 Condensing lens 32 Photodiode 40 Feed tray 40a Feed roller 41A First discharge tray 41B Second discharge tray 42 Main transport path 42a First Branch point 42b Merging point 42c Second branch point 42d Third branch point 43 Sub-transport path 44 Circulating transport path 45 Branch transport path 46a First gate 46b Second gate 46c Third gate 46d Gate 47 Transport roller P paper P ₂ recording picture sheet P ₁ device calibration image that is not via the sheet Pa detected face P ₀ image forming position is formed Paper but formed

Claims (14)

In an image forming apparatus that conveys a recording medium to a predetermined position by a conveyance mechanism and forms an image on the recording medium,
Image forming means for forming a calibration image or a recorded image on the recording medium,
Detection for detecting the density of the ground of the recording medium where the image for calibration and the recorded image are not formed by the image forming means, and the density of the image for calibration formed on the recording medium by the image forming means Means,
Control means for controlling the image forming conditions of the image forming means based on the density of the ground of the recording medium and the density of the calibration image detected by the detection means to make the density of the recorded image a desired density; An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein the transport mechanism transports the recording medium, the density of which is detected on the ground of the recording medium, to the detecting unit without passing through the image forming unit. 2. The transport mechanism according to claim 1, wherein the transport mechanism continuously transports the recording medium in which the density of the ground of the recording medium is detected and the recording medium in which the density of the calibration image is detected to the detection unit. Image forming apparatus. The image forming apparatus according to claim 1, wherein the transport mechanism includes a collection unit that collects the recording medium whose density of the recording medium is detected by the detection unit. The recording medium collected by the collection unit is transported to the image forming unit to be used for forming the calibration image, and the recording medium on which the calibration image is formed by the image forming unit is transported to the detection unit. The image forming apparatus according to claim 4, wherein The transport mechanism includes a storage unit that stores the recording medium on which the calibration image or the recording image is formed,
2. The image forming apparatus according to claim 1, wherein the collecting unit collects the recording medium whose density of the recording medium has been detected by the detecting unit into the storage unit. 3. The conveyance mechanism conveys the recording medium, for which the density of the recording medium is detected by the detection unit, to the image forming unit to form the calibration image, and the calibration image is formed by the image forming unit. The image forming apparatus according to claim 1, wherein the recording medium on which the image is formed is transported to the detection unit. The image forming apparatus according to claim 1, wherein the transport mechanism includes a discharge tray from which the recording medium whose density of the calibration image is detected by the detection unit is discharged. The transport mechanism includes a first discharge tray from which the recording medium whose density of the calibration image has been detected by the detection unit is discharged, and a recording medium on which the recording image is formed by the image forming unit is discharged. The image forming apparatus according to claim 1, further comprising a second discharge tray to be used. The transport mechanism includes a first discharge tray from which the recording medium whose density of the calibration image has been detected by the detection unit is discharged, and a recording medium on which the recording image is formed by the image forming unit is discharged. 2. The image forming apparatus according to claim 1, further comprising: a second discharge tray to be discharged; and a third discharge tray from which the recording medium whose density on the recording medium is detected by the detection unit is discharged. 3. . The detection unit includes a light source that irradiates the recording medium with light, a light detection sensor that detects light reflected on the recording medium by irradiation of light from the light source, and the recording medium that is conveyed to the detection unit. 2. The image forming apparatus according to claim 1, further comprising: a reflector disposed at a position facing the light source and the light detection sensor with the light interposed therebetween and reflecting light emitted from the light source and transmitted through the recording medium. The detection means detects the density of the ground in the margin of the recording medium on which the calibration image is formed,
The control unit compares the density of the background of the recording medium on which the image for calibration and the recorded image are not formed by the image forming unit with the density of the background of the margin, and determines the degree of fog by the image forming unit. The image forming apparatus according to claim 1, wherein the image forming apparatus obtains the following. The image forming apparatus according to claim 1, wherein the detection unit includes a single detection element that detects the density of the ground of the recording medium and detects the density of the calibration image. 2. The image forming apparatus according to claim 1, wherein the detection unit includes a first detection element that detects the density of the ground of the recording medium, and a second detection element that detects the density of the calibration image. 3. .

Images