JPH10123886A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To warn a user for preparations of renewal parts, etc., before the corrected state of printing gradation reaches a limit, at the time of correcting the printing gradation by printing a test pattern, so as to detect a gradation density. SOLUTION: A reference output means 13 allows an image forming means 102 to form a fixed multi-level printed image for the test pattern, its gradation density is detected by a gradation detecting means 104 and then, a gradation correcting means 105 corrects the printing gradation of the image forming means 102. In such a case, when the corrected state reaches a specific state just before the limit, a warning output means 106 outputs a prescribed warning, to inform the user, so that he or she can immediately recognize that a gradation correction is just before the limit. Thus, the renewal parts can be prepared for instance before the gradation correction reaches the limit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus capable of correcting a gradation of a printed image.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus for forming a multi-gradation print image by an electrophotographic method has been used in a laser printer or a digital copying machine. Such an image forming apparatus receives an external input of multi-gradation image data, transfers toner to printing paper by electrophotography according to the image data, and prints the multi-gradation printing image on the surface of the printing paper. Formed.

As described above, a printer section of an image forming apparatus for forming a printed image by an electrophotographic method has a photosensitive member such as a photosensitive drum or a photosensitive belt, and the photosensitive member is moved in a state where the surface thereof is movable. keeping. A charging device, an exposing device, a developing device, a transfer device, and the like are sequentially arranged on the surface of such a photoconductor, and a conveyance path of a printing paper is located in a gap between the transfer device and the photoconductor. ing.

When the above-mentioned printer unit forms a printed image by electrophotography, the surface of a photosensitive body that moves sequentially is charged by corona discharge of a charger, and the surface of the charged photosensitive body corresponds to image data. The exposed electrostatic latent image is exposed by an exposure device, and the electrostatic latent image on the surface of the photoconductor is developed with toner supplied from a developing device to form a printed image. At this time, the printing paper is sequentially conveyed by the paper conveyance belt, the feed roller, and the like in synchronization with the above-described operation. Electrotransferred.

However, in the above-described image forming apparatus,
The reproducibility of the gradation density of the printed image may be reduced due to the deterioration with time or the environmental change of each part. In particular, in the case of an image forming apparatus that forms a color image with a plurality of color toners,
When the image formation is repeated, the toners of the respective colors are mixed with each other, and the reproducibility of the gradation density of the printed image is reduced for each color. In addition, in the case of an image forming apparatus that forms a color image as described above, the deterioration of the reproducibility of the gradation density of each color occurs as the deterioration of the color balance of the print image, and the deterioration of the print quality is remarkable.

To solve such a problem, Japanese Patent Application Laid-Open No.
In the image forming apparatus described in Japanese Patent Application Laid-Open No. 189362 and the like, a predetermined multi-tone test pattern can be printed for each color, and a print image of the multi-tone test pattern is illuminated by a light emitting diode. It is detected by a photo sensor, and the print gradation of the printer unit is corrected based on the output signal. Further, when the correction state of the print gradation reaches a predetermined limit state, a warning lamp informs and outputs that further gradation correction is impossible.

[0007]

The image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 60-189362 can correct the print gradation for each color, and can maintain good print quality of a color image. . In addition, since a warning is output when the gradation correction reaches the limit state, the user can call a service engineer to perform part replacement or the like before reaching the state where correction is impossible.

However, since a warning is output when the gradation correction reaches the limit state, further gradation correction cannot be executed at this point. For this reason, there is a possibility that the print quality deteriorates before the maintenance work is executed, and the deteriorated image is printed. In particular, the fact that the gradation correction has reached the limit state is detected when the test pattern is printed out and the density is detected.
At this point, the deterioration of the print quality may exceed the limit of the gradation correction.

In view of recent demands for color printing, it is difficult to assume that image printing will continue in a state in which print quality has deteriorated, and generally until maintenance is performed and print quality is restored. Printing has been stopped.
However, in the above-described image forming apparatus, since the warning is not issued until the gradation correction reaches the limit state, if the printing operation is stopped at this point, the restart of the printing operation is extremely delayed.

[0010]

According to the first aspect of the present invention, there is provided an image forming apparatus, comprising: an image input means for receiving an external input of multi-tone image data; Image forming means for forming a multi-gradation print image by transferring toner; reference output means for causing the image forming means to form a predetermined multi-gradation test pattern print image; Tone detection means for detecting the tone density, tone correction means for correcting the print tone of the image forming means in accordance with the tone density of the detected test pattern, and a predetermined state in which the correction state is just before the limit And a warning output means for notifying and outputting a predetermined warning when the predetermined time is reached. Therefore, when the external input of the multi-tone image data is received by the image input means, the image forming means transfers the toner to the recording medium by electrophotography in accordance with the image data, and forms the multi-tone print image. As a result, a recording medium on which a multi-tone image is printed is output. Further, when the reference output means causes the image forming means to form a print image of a predetermined multi-tone test pattern, the tone density of the print image of the test pattern is detected by the tone detection means.
Since the print gradation of the image forming unit is corrected by the gradation correcting unit in accordance with the gradation density of the test pattern detected in this manner, the image forming unit thereafter corrects the print gradation appropriately. The image printing is executed in the state where the printing is performed. When the printing gradation of the image forming unit is corrected by the gradation correcting unit in this way, when the correction state reaches a predetermined state immediately before the limit, a predetermined warning is notified and output by the warning output unit. The user is notified that the tone correction of the image forming means by the means is immediately before the limit.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, when a correction request for print gradation is issued after the correction state reaches a predetermined limit state, the image forming means is forcibly stopped. Forcibly stopping means is provided. Therefore, if the correction state has reached the predetermined limit state, no further correction of print gradation is possible. However, when a print gradation correction request is issued in such a state, the image forming unit is forcibly stopped by the forcible stop unit, and thus image printing is not executed in a state where necessary gradation correction cannot be performed.

According to a third aspect of the present invention, there is provided the image forming apparatus according to the second aspect, wherein the warning output means includes a predetermined warning different from the time immediately before the limit when the image forming means is forcibly stopped. Is output. Therefore, even when the image forming unit is forcibly stopped, a predetermined warning different from the case immediately before the limit is notified and output by the warning output unit, so that the user is notified that the tone correction is immediately before the limit. After that, for example, it is also notified that the necessity of gradation correction has occurred even though the gradation correction is already in the limit state.

The invention described in claim 4 is the first to third aspects of the present invention.
The image forming apparatus according to any one of the preceding claims, wherein the image forming means includes a photosensitive member having a movable surface, a charger for charging the surface of the photosensitive member, and image data on the charged surface of the photosensitive member. An exposure device that exposes the corresponding electrostatic latent image, a developing device that develops the exposed electrostatic latent image with toner to form a print image, a medium conveyance unit that sequentially conveys a recording medium, and a photoconductor. Transfer means for transferring a print image formed on the surface to the surface of the recording medium, wherein the gradation detection means detects the gradation density of the print image of the test pattern on the surface of the photoconductor. Therefore, when the image forming means forms a print image on a recording medium, the movable surface of the photoreceptor is charged by the charger, and the surface of the charged photoreceptor is charged on the surface of the photoreceptor by the exposure device. The latent image is exposed, the exposed electrostatic latent image is developed with toner supplied from a developing device to form a printed image, and the printed image formed on the surface of the photoconductor is sequentially conveyed by a medium conveying unit. The recording medium is transferred to the surface of the recording medium to be transferred. Since the detection of the gradation density of the print image of the test pattern by the gradation detection means is performed on the surface of the photoconductor,
The printed image of the test pattern does not need to be transferred to the recording medium.

[0014] The invention according to claim 5 provides the invention according to claims 1 to 3.
The image forming apparatus according to any one of the preceding claims, wherein the image forming means includes a photosensitive member having a movable surface, a charger for charging the surface of the photosensitive member, and image data on the charged surface of the photosensitive member. An exposure device that exposes the corresponding electrostatic latent image, a developing device that develops the exposed electrostatic latent image with toner to form a print image, a medium conveyance unit that sequentially conveys a recording medium, and a photoconductor. Transfer means for transferring a print image formed on the surface to the surface of the recording medium, wherein the gradation detecting means detects the gradation density of the print image of the test pattern on the surface of the recording medium. Therefore, when the image forming means forms a print image on a recording medium, the movable surface of the photoreceptor is charged by the charger, and the surface of the charged photoreceptor is charged on the surface of the photoreceptor by the exposure device. The latent image is exposed, the exposed electrostatic latent image is developed with toner supplied from a developing device to form a printed image, and the printed image formed on the surface of the photoconductor is sequentially conveyed by a medium conveying unit. The recording medium is transferred to the surface of the recording medium to be transferred. Since the detection of the gradation density of the print image of the test pattern by the gradation detection means is performed on the surface of the recording medium, the detection result reflects the characteristics of the transfer means and the recording medium.

The invention according to claim 6 is the first to third aspects of the present invention.
The image forming apparatus according to any one of the preceding claims, wherein the image forming means includes a photosensitive member having a movable surface, a charger for charging the surface of the photosensitive member, and image data on the charged surface of the photosensitive member. An exposure device that exposes the corresponding electrostatic latent image, a developing device that develops the exposed electrostatic latent image with toner to form a printed image, and a recording medium that is electrostatically attracted to a circulating surface and conveyed sequentially An endless medium transport belt, and a transfer unit that transfers a print image formed on the surface of the photoconductor to the surface of the recording medium and the medium transport belt. The gradation density of the print image of the test pattern on the surface of the medium transport belt is detected. Therefore, when the image forming means forms a print image on a recording medium, the movable surface of the photoreceptor is charged by the charger, and the surface of the charged photoreceptor is charged on the surface of the photoreceptor by the exposure device. The latent image is exposed, the exposed electrostatic latent image is developed with toner supplied from a developing device to form a print image, and the print image formed on the surface of the photoconductor is circulated through a medium transport belt. Is transferred to the surface of the recording medium sequentially conveyed by the transfer means. Since the detection of the gradation density of the print image of the test pattern by the gradation detection means is performed on the surface of the medium transport belt, the detection result reflects the characteristics of the transfer means, and the print image of the test pattern is recorded on the recording medium. There is no need to transcribe.

The invention according to claim 7 is the first to third aspects of the present invention.
The image forming apparatus according to any one of the preceding claims, wherein the image forming means includes a photosensitive member having a movable surface, a charger for charging the surface of the photosensitive member, and image data on the charged surface of the photosensitive member. An exposure device that exposes the corresponding electrostatic latent image, a developing device that develops the exposed electrostatic latent image with toner to form a print image, and a print image that is formed on the surface of the photoconductor is movable. An intermediate transfer body that is transferred to the surface, a medium transporting unit that sequentially transports the recording medium, and a transfer unit that transfers a print image that has been transferred to the surface of the intermediate transfer body to the surface of the recording medium. The tone detecting means detects the tone density of the printed image of the test pattern on the surface of the intermediate transfer member. Therefore, when the image forming means forms a print image on a recording medium, the movable surface of the photoreceptor is charged by the charger, and the surface of the charged photoreceptor is charged on the surface of the photoreceptor by the exposure device. The latent image is exposed, the exposed electrostatic latent image is developed with toner supplied from a developing device to form a printed image, and the printed image formed on the surface of the photoreceptor is freely circulated through the intermediate transfer member. The printed image on the surface of the intermediate transfer body is transferred to the surface of the recording medium sequentially conveyed by the medium conveying means by the transfer means. Since the detection of the gradation density of the print image of the test pattern by the gradation detection means is performed on the surface of the intermediate transfer body, the detection result reflects the characteristics of the intermediate transfer body, and the print image of the test pattern is recorded. There is no need to transfer to media.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. Note that directions such as front and rear, up and down, and the like in the present embodiment are shown for the sake of convenience for simplification of description, and do not limit the directions of actual installation and use of the apparatus.

First, as shown in FIG. 3, a color copying machine 1 as an image forming apparatus according to the present embodiment has a main body control section 2, and the main body control section 2 includes an operation section 3, Scanner unit 4, image processing unit 5, printer unit 6, color sensor 7
Etc. are connected. The scanner unit 4 and the image processing unit 5 are also connected to each other, and the printer unit 6 is connected to the image processing unit 5.

The structure of the printer section 6 will be described below. First, as shown in FIG. 2, an endless transfer belt 9 that electrostatically attracts and sequentially conveys a printing paper 8 as a recording medium is circulated freely by a pair of guide rollers 10 as a medium conveying belt of a medium conveying unit. The first to fourth printing stations 11 to 14 are arranged in order at a position facing the transfer belt 9 which is stretched and stretched linearly.

These printing stations 11 to 14 are:
A charging charger 17 as a charging device, a laser scanner 18 as an exposing device, a developing device 19, and the like are provided on a peripheral surface of a photosensitive drum 16 as a photosensitive member opposed to a transfer charger 15 as a transferring means via the transfer belt 9. The laser scanner 18 is configured to face the laser light source 2.
The correction optical system 22 is arranged on the scanning optical path of the polygon mirror 21 arranged opposite to the polygon mirror 0. In each of the developing devices 19 of the first to fourth printing stations 11 to 14, a yellow toner, a magenta toner, a cyan toner, and a black toner (not shown) are individually stored as color toners.

Further, a laser driver 2 is connected to the laser scanner 18 of each of the first to fourth printing stations 11 to 14.
3 are connected, and as shown in FIG.
A motor driver 25 is connected to the drive motor 24,
A video controller 26 is connected to these drivers 23 and 25. The charging charger 17, the transfer charger 15, a belt charger 27 for removing electricity from the transfer belt 9, a developing charger 28 for charging toner stored in the developing device 19, a toner replenisher 29, and a fixing device (not shown) Each of the heaters 30 has a high-voltage power supply 31 to 3
4, the driver circuit 35 and the control unit 36 are connected,
The fixing device is also provided with a thermistor 37.

Further, the photosensitive drum 16, the transfer belt 9, the developing device 19, the fixing device, a paper feeding device 38,
Each of the registration rollers (not shown) and the like has a drive motor 3
9 to 44 are connected, and the drive motors 39 to 42, which are DC (Direct Current) motors, are connected to a microcomputer 45 of the main body control unit 2 via a driver circuit 46, and the drive motors, which are pulse motors, are connected. The motors 43 and 44 are connected to a driver circuit 47 of the main body control unit 2. Further, the video control unit 26, the high-voltage power supplies 31 to 34, the driver circuit 35, the control unit 36, the thermistor 37, and the like of the printer unit 6 described above are also connected to the microcomputer 45 of the main body control unit 2. Have been.

Next, the structure of the main body control unit 2 will be described below. First, the microcomputer 45 includes a paper ejection sensor 48, a paper end sensor 49, a registration sensor 50, a cassette size sensor 51, a toner sensor 5
2 to 55 are connected. Note that the paper ejection sensor 4
8 detects discharge of the printing paper 8 to the outside of the machine, and the paper end sensor 49 detects a paper feed cassette (not shown).
The presence or absence of the printing paper 8 stored in the printer is detected. The registration sensor 50 detects a sheet feeding state to a registration roller, and the cassette size sensor 51 detects a size of a sheet feeding cassette. The toner sensors 52 to 55 are
The presence or absence of the color toner stored in the developing device 19 is detected. The microcomputer 45 has a RAM (Rando
m AccessMemory), ROM (Read Only Memory) and I / F
(Central Process)
ssing unit), and necessary programs are formed as software installation and firmware.

Next, the structure of the color sensor 7 will be described below. As shown in FIG. 2, the color sensor 7 is disposed at a position facing a side near the end of the transfer belt 9 of the printer unit 6, and as shown in FIG.
B-LED (Blue-Light Emitting
Diode) 56, G-LED (Green
-LED) 57, R-LED (Red-LE) which is the third light emitting element
D) 58 and one phototransistor 5 as a light receiving element
9.

As shown in FIG. 7, the B-LED 56
Since the emission wavelength peak is located at about 460 (nm), it is located in the region of 400 to 500 (nm), and the emission is blue. Since the peak of the emission wavelength of the G-LED 57 is located at about 530 (nm), this is 500 to 600 (n).
m), and its emission is green. The R-LED 58 has an emission wavelength peak of about 600.
(nm), it will be located in the region of 600-700 (nm) and its emission is red. For this reason,
The LEDs 56 to 58 have different emission wavelength peaks as the three primary colors of light. In addition, the phototransistor 59 has sensitivity at a wavelength of 400 to 700 (nm) at the light receiving wavelength, and thus has sensitivity over the entire emission wavelength of the LEDs 56 to 58.

Then, as shown in FIG.
The transistor arrays 60 are individually connected to the cathodes 6 to 58.
Is connected to the output port of the microcomputer 45 of the main body control unit 2. A resistor 79 is connected to the anode of the B-LED 56, and the G-LED 56
Variable resistors 80 and 81 are connected to the anodes of 57 and the R-LED 58, respectively. Therefore, the G
Since the power applied to the LED 57 and the R-LED 58 can be changed by the amount of current, the G-LE
The light emission intensity of D57 and the R-LED 58 can be varied. Further, the phototransistor 59 includes:
A resistor 61 for converting the output signal from a current amount to a voltage value
And an amplifier 62 for amplifying an output signal. The amplifier 62 is connected to an A / D (Analog / Digital) input terminal of the microcomputer 45 of the main body control unit 2.

As shown in FIG. 4, the image processing unit 5 includes a γ conversion unit 63, a masking processing unit 64, a UCR processing unit 65, a multi-value processing unit 66, a buffer memory (not shown), and the like. The γ conversion unit 63 is connected to the scanner unit 4, and the multi-value processing unit 66 is connected to the printer unit 6. The image processing unit 5 includes:
By each of the parts 63 to 66, γ conversion, masking processing,
By sequentially executing UCR processing, multi-value processing, and the like, RGB (Red, Green, Blue) image data is converted to YMCK (Y
ellow, Magenta, Cyanide, Black).

The γ conversion section 63 has a data memory (not shown) such as a ROM, and stores therein a γ of image data.
Conversion data of a γ curve used for conversion is recorded. This conversion data is individually prepared for each color of YMCK, and is set in four stages for each color. The four-stage conversion data for each of the four colors is recorded one by one in 16 data memories, and a changeover switch (not shown) for selecting one of the four data memories is provided for each color. ing. Since the switch is set by the main body control unit 2, one of the four-stage conversion data for each color is used for γ conversion.

The operation section 3 is formed by a keyboard (not shown) for receiving an input operation of various data such as copy conditions and a display (not shown) for displaying and outputting various data such as operation guidance. I have. The display of the operation unit 3 is provided with at least two warning lamps. By turning on these warning lamps, “immediately before the limit of gradation correction” and “impossibility of gradation correction” are separately performed. Notification is output.

In the color copying machine 1 of the present embodiment, as described above, a control program for causing the main body control unit 2 and the like to execute various processing operations is set in advance as software. In response to the above, various functions are realized as various means by the main body control unit 2 executing operation control and the like of each unit. As various means as described above, the color copying machine 1 of the present embodiment
As shown in FIG. 1, mode switching means (not shown), image input means 101, image forming means 102, reference output means 1
03, a gradation detection unit 104, a gradation correction unit 105, a warning output unit 106, a forced stop unit 107, and the like.

The mode switching means operates the color copier 1 according to the present embodiment by causing the main body control unit 2 to switch and set a plurality of operation programs in response to an input operation on the keyboard of the operation unit 3. The mode is switched to at least a copy mode and an adjustment mode. The image input unit 101 operates the operation unit 3 under the copy mode setting.
When a predetermined input operation is executed on the keyboard, the main body control unit 2 causes the scanner unit 4 to read and scan the read original, thereby accepting an external input of image data. Under the setting of the copy mode, the image forming means 102 corresponds to the externally input full-color image data by the image processing section 5 and the printer section 6 which are controlled by the main body control section 2 as described above. Then, a color toner is appropriately transferred to the printing paper 8 by electrophotography to form a multi-tone full-color print image.

However, the image forming means 102 forms a print image of a test pattern in accordance with the operation control of the reference output means 103 when the adjustment mode is set. That is, the reference output means 103 stores the image data of the multi-tone test pattern in the ROM of the main body control unit 2 and operates the operation unit 3 under the setting of the adjustment mode.
When a predetermined input operation is performed on the keyboard, the operation of the image processing unit 5 and the printer unit 6 is controlled by the main body control unit 2 to form a print image of a test pattern on the surface of the transfer belt 9.

As shown in FIG. 8, the print image of this test pattern is composed of a large number of patch images 67 to 78, and is located outside the position where the printing paper 8 is attracted.
Is formed on the side edge of the transfer belt 9 detected by These patch images 67 to 78 are multi-tone test patterns for each color by forming a horizontally long rectangular image in order of high density, medium density and low density with each of the color toners. .

Specifically, a high density Y (Yellow) 67, a medium density Y68, a low density Y69, which is a yellow pattern, a high density M (Magenta) 70, which is a magenta pattern, and a medium density M
71, low density M72, high density C (C
yanide) 73, medium density C74, low density C75, high density K (Black) 76 which is a black pattern, medium density K77,
Low concentration K78.

The gradation detecting means 104 controls the operation of the color sensor 7 by the main body control unit 2 under the setting of the adjustment mode, and detects the gradation density of the patch images 67 to 78 of each color by the color sensor 7. I do. In other words, when the color sensor 7 detects the patch images 67 to 78, the LED 56 by the transistor array 60 is used.
The driving of .about.58 is controlled by the microcomputer 45. As a result, the yellow patch image 6
7-69, the B-LED 56 is turned on. For the magenta patch images 70-72, the G-LED 56 is turned on.
The LED 57 is turned on, and the cyan patch images 73 to
75, the R-LED 58 is turned on, and for the patch images 76 to 78 of black, the G-LE
D57 is turned on.

Further, a point in time before the patch images 67 to 78 reach the position of the color sensor 7, a point in time when the color sensor 7 faces a gap between the patch images 67 to 78, When the LED 78 has passed the position of the color sensor 7, the LED 5
6 to 58 are turned on, and the patch images 67 to 78 are turned on.
When a predetermined time has passed since the LED passed the position of the color sensor 7, all of the LEDs 56 to 58 that are emitting light are turned off.

The tone correcting means 105 controls the operation of the image processing section 5 by the main body control section 2 in accordance with the tone density detected for each color from the patch images 67 to 78 as described above. Thus, the print gradation of the image forming unit 102 is corrected. More specifically, as described above, the γ conversion unit 63 of the image processing unit 5 includes γ used for γ conversion.
Since the conversion data of the curve is prepared in four stages for each color, the print gradation by the printer unit 6 is corrected for each color by switching and setting this conversion data.

The warning output unit 106 recognizes the correction state of the print gradation as described above by the main body control unit 2,
When the correction state reaches a predetermined state immediately before the limit, a predetermined warning is notified and output by the operation unit 3. Further, when the above-described gradation correction reaches a predetermined limit state, a predetermined warning different from the case immediately before the limit is notified and output by the operation unit 3.

More specifically, in the γ conversion section 63, the conversion data of the first stage having the slowest γ curve is initially set for each color at the time of product shipment. This is executed as a setting for switching to the converted data. At this time, when the conversion data of the third stage of the γ conversion unit 63 is set even for one color, this is recognized by the main body control unit 2 as the correction state immediately before the limit, and the “grayscale correction limit” of the operation unit 3 is set. The "just before" warning lamp is lit.

If the conversion data of the fourth stage, which is the last stage, is switched, this is recognized as the limit state of the gradation correction. Then, the warning lamp of "Tone correction is impossible" of the operation unit 3 is turned on. The forcible stopping means 1
07, when the main body control unit 2 detects that the gradation correction cannot be executed as described above, the operation control of the printer unit 6 and the like is set to a stop state, whereby the image formation by the image forming unit 102 is performed. Is forcibly stopped.

In the color copying machine 1 of the present embodiment, the G-LED 5 is controlled by the variable resistors 80 and 81.
7 and the R-LED 58, the output intensity of the phototransistor 59 when the black intermediate density patch image 77 is illuminated by the B-LED 56, the G-LED 57 and the R-LED
The phototransistor 59 when illuminated by 58
Are adjusted to be equal to each other. More specifically, since the brightness of the B-LED 56 is physically lower than that of the G-LED 57 or the R-LED 58, the drive current of the B-LED 56 is smaller than that of the G-LED 57 or the R-LED 58. The driving current of the LED 58 is relatively increased.

Further, the amplifier 62 connected to the phototransistor 59 of the color sensor 7 detects that the maximum output intensity when the color sensor 7 reads the patch images 67 to 78 is a voltage slightly lower than the power supply voltage. The degree of amplification is set to be as follows. More specifically, the power supply voltage of the amplifier 62 is 15 (V), and the color sensor 7
The output voltage of each of the low-density patch images 69 and 7 of each color
Even when reading 2,75,78, it is about 1.0 (V).

Therefore, the amplification of the amplifier 62 is performed so that the output voltage of the amplifier 62 when the color sensor 7 reads the patch images 67 to 78 becomes 14 (= 15-1) (V) at the maximum. The degree is set to 14 times. In addition,
As a result of setting the amplification degree of the amplifier 62 in this way, the color sensor 7 detects the high-density patch images 67, 70, 73,
The output voltage of the amplifier 62 when reading 76 is about 5 (V).

In such a configuration, in the color copying machine 1 of the present embodiment, when a copy mode is set as an operation mode, a document (not shown) is
Is read to generate RGB image data, and the RGB image data is
The image data is converted into CK image data, and based on the YMCK image data, a printing paper
Print a color image on At this time, the main body control unit 2 controls the above-described scanner unit 4, image processing unit 5, and printer unit 6 based on the setting data input from the operation unit 3.

More specifically, when a color image of a document is copied onto the printing paper 8 as described above, the document is set on the scanner unit 4 and a predetermined input operation is performed on the operation unit 3.
Then, the main body control unit 2 drives and controls the scanner unit 4 in accordance with the copy conditions input to the operation unit 3, so that the scanner unit 4 reads the color image of the original and performs image processing on the 8-bit RGB image data. Output to section 5. At this time, the image processing unit 5 outputs a horizontal synchronizing signal S-LSYNC, an image clock S-STROBE, and a vertical synchronizing signal FGATE to the scanner unit 4 under the control of the main body control unit 2 to synchronize with these signal outputs. Then, the scanner unit 4 outputs the image data to the image processing unit 5.

Next, as shown in FIG. 4, the image processing section 5 to which the image data has been input, responds to the image processing mode designation signal transmitted from the main body control section 2 and performs γ conversion, masking processing, UCR The input RGB 8-bit image data is converted into YMCK 1-bit image data by sequentially executing image processing such as processing and multi-value processing by pulse width modulation, and this image data is controlled by the main unit. The horizontal synchronizing signal P-LSYNC and the image clock P-ST
Output to the printer unit 6 together with ROBE. At this time, in order to output image data corresponding to the interval of the printer unit 6,
The image processing unit 5 temporarily stores the output image data in a buffer memory. When the user performs an input operation to execute the editing process on the operation unit 3 as desired, the image processing unit 5 controls the image processing unit 5 to perform the scaling process, the trimming, the color It also performs editing processing such as conversion and mirroring.

Next, when the image data is the horizontal synchronizing signal P-LSY
The printer unit 6 output together with the NC and the image clock P-STROBE outputs the laser light from the first to fourth printing stations 11 to 14 according to the image data in synchronization with the horizontal synchronization signal P-LSYNC and the image clock P-STROBE. 20 is driven to emit light to form an electrostatic latent image on the circumferential surface of the photosensitive drum 16 that rotates sequentially.
At the first to fourth printing stations 11 to 14, the electrostatic latent image on the photosensitive drum 16 is developed with yellow toner, magenta toner, cyan toner and black toner, and the printing paper 8 conveyed sequentially by the transfer belt 9. Are sequentially transferred with the voltage applied to the transfer charger 15. This printing paper 8
Is printed with a single color image of yellow toner, magenta toner, cyan toner and black toner. The printing paper 8 on which the color image has been formed by the overprinting is heat-pressed by a fixing device and then discharged outside the machine. I do.

The color copier 1 of the present embodiment prints a high-quality color image on the printing paper 8 in the copy mode as described above.
With the lapse of time, the print density and gradation of a specific color toner may decrease. Therefore, in order to solve such a problem, for example, when performing the initial setting, when performing the end processing, when detecting a fixed cycle, when performing the maintenance work, and the like, the processing operation of the adjustment mode as the operation mode. Is executed.

In this adjustment mode, patch images 67 to 78 whose print densities sequentially change with each of the color toners.
Is printed on the transfer belt 9, and these patch images 67 to 7
8 is read by the color sensor 7 as a multi-tone test pattern. The conversion operation of the image processing unit 5 is adjusted based on the output signal of the color sensor 7, and the print gradation of image formation by the printer unit 6 is corrected for each color.

More specifically, when the print density of the color toner is tested as described above, the image data of the patch images 67 to 78 preset as a test pattern in the main body control unit 2 is read. Then, as shown in FIGS. 2 and 8, the first to fourth printing stations 11 to 14 of the printer unit 6 form three patch images for each of the four colors of YMCK on the side edges of the transfer belt 9 circulating sequentially. 67-7
8 are printed in order, so that these patch images 67 to
Reference numeral 78 sequentially reaches the position of the color sensor 7 according to the circulation of the transfer belt 9.

The color sensor 7 detects the patch images 67 to
Before 78 arrives, all LEDs 56-58
Is turned on, and immediately before the first yellow patch image 67 reaches the position of the color sensor 7, the G-LED 57 and the R-
The LED 58 and the LED are turned off, and as shown in FIG.
Only lighting of D56 is continued. The yellow patch images 67 to 69 illuminated by the B-LED 56 are read by the phototransistor 59 of the color sensor 7, and when these patch images 67 to 69 pass the position of the color sensor 7, the yellow and magenta At the position of the gap between the patch images 69 and 70, the G-LED 57 and the R-LE
D58 is lit again, so that at this point all L
The EDs 56 to 58 are turned on.

Similarly, as shown in FIGS. 11 to 16, G is applied to the magenta patch images 70 to 72.
-The other than the LED 57 is turned off, and the cyan patch image 73
, The G-LED 57 is turned off for black patch images 76 to 78.
Are turned off. That is, in the gap between the patch images 72 and 73 between magenta and cyan and the gap between the patch images 75 and 76 between cyan and black, all the LEDs 56 to 58
Lights up.

Even when the black patch image 78 has passed, all the LEDs 56 to 58 are turned on.
This is turned off when both the end of the adjustment mode and the elapse of the predetermined time are confirmed. When the adjustment mode is continued without ending, or when the adjustment mode is restarted before the elapse of a predetermined time, the printing of the above-described patch images 67 to 78 is performed while all the LEDs 56 to 58 remain lit. And detection are repeated.

That is, before the adjustment mode starts, the LED 5
Since the temperature of 6 to 58 is prevented from lowering, the adjustment mode is always started well. Moreover, even in such a state, if a predetermined time has elapsed, all the LEDs 56 to 58 are turned off, so that when the adjustment mode is restarted for a long time, unnecessary power consumption is prevented and the consumption of the LEDs 56 to 58 is reduced. Is done.

Further, the color copying machine 1 of the present embodiment
In order to control the turning on and off of the LEDs 56 to 58 as described above, the main body controller 2 controls the driving motor 4 of the transfer belt 9.
0, the reference clock synchronized with the operation of the driver circuit 46 is counted.
The EDs 56 to 58 are driven. Similarly, LEDs 56 to 58
The main body controller 2 reads the output signals of the phototransistor 59 at the timing when the center of the patch images 67 to 78 arrives at the reading position of the color sensor 7 because the patch images 67 to 78 illuminated by are read by the phototransistor 59. .

At this time, the phototransistor 59 of the color sensor 7 outputs the patch images 67 to 78, as shown in FIG.
And outputs a current proportional to the amount of light. This amount of current is converted to a voltage value by a resistor 61 and then amplified by an amplifier 62 of the main body control unit 2 so that the microcomputer 45 Is output to

The microcomputer 45 detects the amount of change in print density for each color as a print gradation based on the output signal of the color sensor 7 as shown in FIG.
This is compared with a preset reference value, as indicated by 0 or the like. Since the print densities of the patch images 67 to 78 are set to change in three steps for each color, if the difference between the two densities satisfies the reference value, it is determined that the print gradation is appropriate. No gradation correction is performed.

However, when the comparison result between the change amount of the print density and the reference value is lower than the reference value, the γ conversion unit 6 sets the change amount of the output data to be larger than the change amount of the input data.
Change the setting of 3. In other words, as described above, by setting the data memory in which the conversion data of the γ curve of each color is individually recorded by the changeover switch, the γ conversion unit is used so that the conversion data having a sharper γ curve is used for the γ conversion. Change the setting of 63.

In the color copying machine 1 according to the present embodiment, since the above-described gradation correction is sequentially performed with the YMCK toner, the printing process of the specific color toner is performed by the aging of the color toner and the photosensitive drum 16. Even if the reproducibility of the key is reduced,
This can be corrected individually for each of the color toners, and the color balance of the printed image can be maintained well.

Further, in the color copying machine 1 of the present embodiment, when the above-described gradation correction is executed, the third stage of the four-stage converted data is selected by turning on the third changeover switch. Then, the warning lamp of the operation unit 3 is turned on to notify the user that "immediately before the limit of the gradation correction".
For this reason, the user can immediately recognize that the gradation correction is just before the limit, and prepare a replacement part before the gradation correction reaches the limit.

In the color copying machine 1 of the present embodiment, further gradation correction cannot be executed in the limit state in which the fourth stage of the four-stage converted data is selected by turning on the fourth switch. It is. Therefore, when a print gradation correction request is issued in such a state, the operation state of the printer unit 6 and the like is set to forcible stop by the main body control unit 2, and a predetermined warning lamp of the operation unit 3 is turned on, and the The user is notified that "tone adjustment cannot be performed."

That is, although image printing is performed in a state where the print gradation is corrected to the limit, image printing is not performed in a state where correction is necessary from the limit state, so that an image that cannot be used with low quality is printed out. Instead, wasteful consumption of the printing paper 8 and toner is prevented. In addition, when the image printing is forcibly stopped, the user is notified that the gradation correction is not executable, so that the user can recognize the cause of the automatic stop of the image printing and replace the parts. Etc. can be executed quickly.

In the color copying machine 1 according to the present embodiment, one of the changeover switches of the γ conversion section 63 is turned on for each color. When the occurrence of a failure is detected, a predetermined warning lamp of the operation unit 3 is turned on, and the printer unit 6 and the like are set in a stopped state.

In the color copying machine 1 according to the present embodiment, the patch images 67 to 78 to be printed with the color toner in multiple gradations as described above are provided by the LEDs 56 to 5 of the color sensor 7.
8 illuminates with light of a complementary color.
Can read the print gradation of the patch images 67 to 78 with high accuracy, and
, The print gradation of the color toner can be satisfactorily corrected.

Further, the LEDs 56 to 5 of the color sensor 7
8, the luminance fluctuates immediately after lighting due to temperature rise,
In the color copying machine 1 of the present embodiment, the patch images 67 to
Since all the LEDs 56 to 58 are turned on before 78 reaches the position of the color sensor 7, these LEDs
The patches 56 to 58 can illuminate the patch images 67 to 78 in a state where the emission luminance does not fluctuate stably at a high temperature. For this reason, the phototransistor 59 of the color sensor 7 can detect the print density of the patch images 67 to 78 with high accuracy, and the color copying machine 1 of the present embodiment can improve the print density of the printer unit 6 Can be corrected.

Furthermore, since all the LEDs 56 to 58 are turned on even at the positions of the gaps between the patch images 67 to 78, the luminous brightness of these LEDs 56 to 58 can be stabilized very well. The color copying machine 1 according to the present embodiment
Then, in order to simplify the processing, all of the LEDs 56 to 58 are turned on only at the gaps where the colors of the patch images 67 to 78 change, but the present invention is not limited to the above embodiment. It is also possible to light the LEDs 56 to 58 at the positions of the respective gaps of the patch images 67 to 78.

Even when the black patch image 78 passes, all the LEDs 56 to 58 are turned on. Therefore, even when the processing operation in the adjustment mode is restarted, the patch images 67 to 78 are firstly detected by the color sensor 7. It can be read well. In addition, when the adjustment mode is ended, when it is confirmed that the predetermined time has been exceeded, all the LEDs are turned off.
Since the lights 56 to 58 are turned off, the LEDs 56 to 58 are not left as they are.

Further, in the color copying machine 1 of the present embodiment, when detecting to correct the print gradation as described above, the patch images 67 to 78, which are the test patterns, are transferred to the transfer belt 9 as the medium transport belt. Are formed on the side edges of the patch image 67 to be detected without consuming the printing paper 8 as a recording medium for the print gradation correction work.
The characteristics and the like of the transfer charger 15 can be reflected on the 78 print gradations.

The present invention is not limited to the above-described embodiment, but allows various modifications. For example, in the color copying machine 1 having the above-described structure, it is also possible to form a test pattern on the surface of the printing paper 8 and detect the print gradation. In this case, printing is performed to detect the print gradation. Although the paper 8 is consumed, the characteristics of the printing paper 8 can be reflected on the detected print gradation, so that the print gradation can be detected more favorably.

It is also possible to detect the print gradation of the test pattern on the surface of the photosensitive drum 16. In this case, the detected print gradation cannot reflect the characteristics of the transfer charger 15 or the like. The paper 8 is not consumed. Also, the first to fourth printing stations 11
Since the print gradation detection work can be executed in parallel in steps # 14 to # 14, the work can be completed more quickly.

In particular, the color copying machine 1 of the present embodiment has a structure having the transfer belt 9 which is a medium transport belt as a medium transport means, and this is used for printing a test pattern. In the case of an image forming apparatus having no medium transport belt, it is preferable to detect the print gradation of the test pattern on the surface of the recording medium or the photoconductor as described above.

When the image forming apparatus has an intermediate transfer member that mediates toner transfer between the photosensitive member and the printing paper, it is possible to detect the print gradation of the test pattern on the surface of the intermediate transfer member. In this case, the characteristics of the intermediate transfer member can be reflected on the detected print gradation, and the recording medium is not consumed.

In the present embodiment, it has been described that the color balance of the color copying machine 1 is maintained in good condition by individually detecting and correcting the print gradations of the four color toners. Is not limited to the above form,
For example, the present invention can be applied to maintaining good printing gradation of a black and white laser printer.

In the color copying machine 1 of the present embodiment, a plurality of data memories in which γ-curve conversion data are individually recorded are switched by the changeover switch in order to correct the print gradation. For example, it is also possible to switch a plurality of conversion data recorded in one data memory by specifying an address, or to change parameters using one conversion data as an arithmetic expression.

[0075]

According to the first aspect of the present invention, there is provided an image forming apparatus comprising:
Image input means for receiving an external input of multi-tone image data; image forming means for forming a multi-tone print image by transferring toner to a recording medium by electrophotography in accordance with the image data; Reference output means for forming a print image of a multi-tone test pattern on the image forming means, tone detection means for detecting the tone density of the test pattern print image, and corresponding to the tone density of the detected test pattern A tone correction means for correcting the print tone of the image forming means, and a warning output means for notifying and outputting a predetermined warning when the correction state reaches a predetermined state immediately before the limit, thereby providing a predetermined multi-level Since the print gradation is corrected in accordance with the gradation density of the print image of the tone test pattern, the print gradation of the image print can be properly maintained against deterioration with time of each part. Complement of gradation When the state reaches the predetermined state immediately before the limit, a predetermined warning is notified and output, so that the user can immediately recognize that the gradation correction is immediately before the limit, and before the gradation correction reaches the limit. You can prepare replacement parts.

According to the image forming apparatus of the present invention,
When a correction request for print gradation is issued after the correction state reaches a predetermined limit state, a forced stop unit for forcibly stopping the image forming unit is provided, so that image printing is executed in a state where the gradation correction is in a limit state. However, since the image printing is not executed in a state where the gradation correction is required beyond the limit, it is possible to automatically prevent the printing of an image that cannot be used with a low quality and to prevent the wasteful consumption of printing paper and toner. be able to.

In the image forming apparatus according to the third aspect of the present invention,
The warning output unit outputs a predetermined warning that is different from the case immediately before the limit even when the image forming unit is forcibly stopped, and is different from the case immediately before the limit when the image printing is forcibly stopped. Since the predetermined warning is output as a notification, it is possible to make the user recognize the reason for the automatic stop of the image printing.

In the image forming apparatus according to the fourth aspect,
The image forming means includes a photosensitive member having a movable surface, a charger for charging the surface of the photosensitive member, and an exposing device for exposing an electrostatic latent image corresponding to image data to the charged surface of the photosensitive member.
A developing unit that develops the exposed electrostatic latent image with toner to form a print image; a medium transport unit that sequentially transports a recording medium; and a print image formed on the surface of the photoconductor is transferred to the surface of the recording medium. And a transfer unit for causing the test pattern to detect the gradation density of the test pattern on the surface of the photoreceptor so that the test pattern gradation can be quickly consumed without consuming the recording medium. The concentration can be detected.

According to the image forming apparatus of the present invention,
The image forming means includes a photosensitive member having a movable surface, a charger for charging the surface of the photosensitive member, and an exposing device for exposing an electrostatic latent image corresponding to image data to the charged surface of the photosensitive member.
A developing unit that develops the exposed electrostatic latent image with toner to form a print image; a medium transport unit that sequentially transports a recording medium; and a print image formed on the surface of the photoconductor is transferred to the surface of the recording medium. And a transfer unit for causing the transfer unit to record the test pattern gradation density on the test pattern by detecting the gradation density of the print image of the test pattern on the surface of the recording medium. The characteristics of the medium can be reflected, and the gradation density of the test pattern can be detected more favorably.

In the image forming apparatus according to the present invention,
The image forming means includes a photosensitive member having a movable surface, a charger for charging the surface of the photosensitive member, and an exposing device for exposing an electrostatic latent image corresponding to image data to the charged surface of the photosensitive member.
A developing unit that develops the exposed electrostatic latent image with toner to form a printed image; an endless medium transport belt that electrostatically attracts a recording medium to a circulating surface and sequentially transports the recording medium; Transfer means for transferring the formed print image to the surface of the recording medium and the medium conveyance belt, wherein the gradation detection means detects the gradation density of the print image of the test pattern on the surface of the medium conveyance belt By doing
The gradation density of the test pattern can be detected without consuming the recording medium, and the characteristics of the transfer unit can be reflected on the detection result of the gradation density of the test pattern.

According to the image forming apparatus of the present invention,
The image forming means includes a photosensitive member having a movable surface, a charger for charging the surface of the photosensitive member, and an exposing device for exposing an electrostatic latent image corresponding to image data to the charged surface of the photosensitive member.
A developing device that forms a printed image by developing the exposed electrostatic latent image with toner, an intermediate transfer body on which the printed image formed on the surface of the photoreceptor is transferred to a movable surface, and a recording medium are sequentially arranged. A medium transporting means for transporting, and a transfer means for transferring a print image transferred on the surface of the intermediate transfer body to the surface of the recording medium, and the gradation detecting means has a test pattern of the test pattern on the surface of the intermediate transfer body. By detecting the gradation density of the printed image, the gradation density of the test pattern can be detected without consuming the recording medium. Can be reflected.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a logical structure of a main part of a color copying machine as an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a perspective view showing an internal structure of the color copying machine.

FIG. 3 is a block diagram showing a physical structure of the color copying machine.

FIG. 4 is a block diagram illustrating a circuit structure of an image processing unit of the color copying machine.

FIG. 5 is a block diagram illustrating a circuit structure of an image processing unit.

FIG. 6 is a block diagram illustrating a circuit structure of a color sensor.

FIG. 7 is a characteristic diagram showing a relationship between an emission wavelength of a color sensor and an output voltage ratio.

FIG. 8 is a plan view illustrating a formation position of a patch image, which is a test pattern, on a transfer belt, which is a medium transport belt.

FIG. 9 is a flowchart showing the first half of the first yellow part of the processing operation in which the color copying machine detects and corrects the print gradation of the test pattern.

FIG. 10 is a flowchart showing the second half of the first yellow part of the processing operation in which the color copying machine detects and corrects the print gradation of the test pattern.

FIG. 11 is a flowchart illustrating a first half of a magenta portion of a processing operation in which a color copying machine detects and corrects a print gradation of a test pattern.

FIG. 12 is a flowchart illustrating the latter half of the magenta portion of the processing operation in which the color copying machine detects and corrects the print gradation of the test pattern.

FIG. 13 is a flowchart illustrating the first half of the cyan part of the processing operation in which the color copying machine detects and corrects the print gradation of the test pattern.

FIG. 14 is a flowchart illustrating the second half of the cyan part of the processing operation in which the color copying machine detects and corrects the print gradation of the test pattern.

FIG. 15 is a flowchart showing the first half of the last black portion of the processing operation in which the color copying machine detects and corrects the print gradation of the test pattern.

FIG. 16 is a flowchart showing the latter half of the last black part of the processing operation in which the color copying machine detects and corrects the print gradation of the test pattern.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus 8 Recording medium 9 Medium conveyance belt 15 Transfer means 16 Photoconductor 17 Charger 18 Exposure device 19 Developing device 67-78 Test pattern 101 Image input means 102 Image forming means 103 Reference output means 104 Gradation detection means 105 floor Tone correction means 106 Warning output means 107 Forced stop means

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI G03G 15/01 113 B41J 3/00 B H04N 1/407 H04N 1/40 101E

Claims (7)

[Claims] An image input means for receiving an external input of multi-gradation image data, and an image forming apparatus for forming a multi-gradation print image by transferring toner to a recording medium by electrophotography in accordance with the image data Means, reference output means for causing the image forming means to form a print image of a predetermined multi-tone test pattern, tone detection means for detecting the tone density of the print image of the test pattern, and the detected test pattern Tone correction means for correcting the print gradation of the image forming means in accordance with the gradation density of, and a warning output means for informing and outputting a predetermined warning when the correction state reaches a predetermined state immediately before the limit,
An image forming apparatus comprising: 2. An image according to claim 1, further comprising a forced stop means for forcibly stopping the image forming means when a print gradation correction request is issued after the correction state reaches a predetermined limit state. Forming equipment. 3. The image forming apparatus according to claim 2, wherein the warning output unit outputs a predetermined warning different from the case immediately before the limit even when the image forming unit is forcibly stopped. 4. An image forming means, comprising: a photoreceptor having a movable surface, a charger for charging the surface of the photoreceptor, and exposing an electrostatic latent image corresponding to image data to the charged surface of the photoreceptor. An exposure device, a developing device that develops the exposed electrostatic latent image with toner to form a print image, a medium conveyance unit that sequentially conveys a recording medium, and a print image formed on the surface of the photoconductor. And a transfer unit for transferring the image on the surface of the recording medium, wherein the gradation detecting unit detects a gradation density of a print image of a test pattern on the surface of the photoconductor. 3. The image forming apparatus according to any one of 3. 5. An image forming means comprising: a photoreceptor having a movable surface; a charger for charging the surface of the photoreceptor; and an electrostatic latent image corresponding to image data is exposed on the charged surface of the photoreceptor. An exposure device, a developing device that develops the exposed electrostatic latent image with toner to form a print image, a medium conveyance unit that sequentially conveys a recording medium, and a print image formed on the surface of the photoconductor. And a transfer unit for transferring the image on the surface of the recording medium, wherein the gradation detecting unit detects a gradation density of a print image of a test pattern on the surface of the recording medium. 3. The image forming apparatus according to any one of 3. 6. An image forming means, comprising: a photoreceptor having a movable surface, a charger for charging the surface of the photoreceptor, and exposing an electrostatic latent image corresponding to image data to the charged surface of the photoreceptor. An exposing device, a developing device that develops an exposed electrostatic latent image with toner to form a printed image, an endless medium transport belt that electrostatically attracts a recording medium to a circulating surface and sequentially transports the recording medium, Transfer means for transferring a print image formed on the surface of the photoreceptor to the surface of the recording medium and the medium transport belt, wherein the gradation detecting means comprises a test pattern on the surface of the medium transport belt. 4. The image forming apparatus according to claim 1, wherein a gradation density of the print image is detected. 7. An image forming means, comprising: a photosensitive member having a movable surface; a charger for charging the surface of the photosensitive member; and exposing an electrostatic latent image corresponding to image data to the charged surface of the photosensitive member. Exposing device, developing device that develops the exposed electrostatic latent image with toner to form a printed image, and an intermediate transfer member that transfers the printed image formed on the surface of the photoreceptor to a movable surface And a medium transport unit for sequentially transporting a recording medium, and a transfer unit for transferring a print image transferred on the surface of the intermediate transfer body to the surface of the recording medium. 4. The image forming apparatus according to claim 1, wherein a gradation density of a print image of a test pattern on a surface of the intermediate transfer body is detected.