JPH0815943A - Color image forming device - Google Patents

Abstract

PURPOSE:To provide a color image forming device capable of forming an image and also capable of adjusting the reproducibility of the image under the same conditions as an actual image. CONSTITUTION:The image forming device transfers images in separate colors to an intermediate transfer body 32, and transfers the superimposed images to a transfer material all at once. In the entire image formation area of a photoreceptor 20, a test pattern is formed together with an image part, and the density of the test pattern is detected in highlight, middle, and shadow parts each, and the result of the detection is corrected to adjust the quantity of light for writing, thereby improving the color reproducibility of the image. Thus, the trial printing and, at the same time, the check of the color reproducibility can be achieved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus, and more particularly to an image forming apparatus capable of color tone control.

[0002]

2. Description of the Related Art Generally, a copying machine, a printer, a facsimile or the like is known as a color image forming apparatus capable of forming an image of two or more colors. Among color image forming apparatuses, in an apparatus using an electrostatic copying method, a color separation process of an original image, an electrostatic latent image forming process of color separated colors, a development of a color complementary to the color separated color Each step of the visible image processing step with the agent and the transfer step to the intermediate transfer body is repeated for each separated color, and the visible image of each color is superimposed on the intermediate transfer body, and then transferred to a transfer material such as transfer paper. It is designed to be transferred at once.

By the way, in a color image forming apparatus, the color reproducibility of an image formed is adjusted. The reason for adjusting the color reproducibility of such an image is to prevent the color misregistration with the original document from being left due to the deterioration of the developer, the deterioration of the photoreceptor over time, and the change of the usage environment. is there. An example of an apparatus for adjusting such color reproducibility is an apparatus described in Japanese Patent Laid-Open No. 4-558868. In the apparatus described in the above publication, it is possible to select, as the operation of the apparatus, a normal mode for performing a normal color copying step and a test mode for performing an image color reproducibility adjusting step. When the test mode is selected, the reproducibility is adjusted by using the following configuration. That is, the adjusting unit includes an optical fiber arranged on the discharge side of a transfer sheet on which an image is fixed after the image is collectively transferred, and an optical detector circuit for converting light from the optical fiber into a separated color information signal. And a control unit connected to the photodetector circuit and having a comparison function. When the reproducibility is adjusted, the light from the optical fiber is converted into a color separation information signal by the photodetector and then input to the control unit. The control unit, to which the color separation information signal is input, inputs the measured value relating to the input separation color to the comparator, and calculates the difference from the expected value registered in the comparator. Then, a control signal is output to the color correction unit and the gradation correction unit so that the difference between the measured value and the expected value becomes less than or equal to a predetermined value. This brings the reproducibility of the measured image closer to the expected reproducibility.

Image formation in such a test mode is
The same processing as in the case of normal color copying is performed, but the test pattern is formed by replacing the image forming area of the transfer paper on which the normal original image is formed. That is, the test pattern is formed over the entire image forming area.

Further, instead of forming a test pattern in the entire image forming area, a structure in which a test pattern is formed in a portion other than the image forming area has also been proposed (for example, Japanese Patent Laid-Open No. Hei 4). -139776).

[0006]

However, in the above-mentioned apparatus, the comparison and monitoring of the image actually formed and the color reproducibility cannot be performed at the same time. To confirm the image reproducibility, it is also necessary to monitor the actual image, but since the entire image forming area is used as a test pattern, comparison judgment with the original image cannot be made, and it is simply within the image forming area. There is no choice but to refer to the state of the formed test pattern. Therefore, the impression based on the document image actually formed cannot be grasped. Moreover, in order to correct the reproducibility of the image, it is necessary to use a transfer material on which an original image is not formed, so that the transfer material is consumed in a large amount when adjusting the reproducibility.

Further, when a test pattern is formed outside the image forming area, it is possible to form an actual image and monitor color reproducibility, but on the other hand, other than the area where the image is actually formed. Since the test pattern was formed on the image forming area, the use environment could not be set under the same condition as the image forming area, and the color reproducibility in the image forming area could not be confirmed.

It is an object of the present invention to provide a color image forming apparatus capable of forming an image and adjusting the reproducibility of the image under the same conditions as the actual image. .

[0009]

In order to achieve this object, the invention of claim 1 separates the color of the original image for each color and forms an electrostatic latent image according to the color on the photoconductor. However, it is possible to repeatedly transfer the image of each color that has been subjected to visible image processing using a developer having a color complementary to the separated color to the intermediate transfer member, and collectively transfer and fix the superimposed image of each color. A color image forming apparatus capable of forming a test pattern in the image forming area on the photoconductor along with image formation, and a detection unit for detecting the state of the test pattern formed by the test pattern forming unit. And a control unit capable of adjusting color reproducibility in accordance with information from the detection unit.

According to a second aspect of the present invention, in the color image forming apparatus according to the first aspect, the test pattern forming means exposes the vicinity of the original image forming range within the image forming area in the same manner as the original image. The feature is that a test pattern row is formed in a direction along the moving direction of the body.

According to a third aspect of the present invention, in the color image forming apparatus according to the first aspect, the test pattern forming means forms the test pattern and the image at a different time from the time of forming a normal original image. It has a feature.

[0012]

According to the first aspect of the invention, since the test pattern can be formed together with the original image in the image forming area on the photoconductor, the reproducibility of the image, especially the test image of the original image, can be improved. Color reproducibility can be monitored and set at the same time.

According to the second aspect of the present invention, since the test pattern is formed along the moving direction of the photoconductor, the detection section of the control means need only be installed on this row.

Since the test pattern forming operation and the normal image forming operation can be separated from each other, the test pattern is not formed during the normal image forming.

[0015]

The details of one embodiment of the present invention will be described below.
FIG. 1 is a schematic diagram for explaining the overall configuration of a color image forming apparatus that is an embodiment of the present invention.

The color image forming apparatus 10 shown in FIG.
Are roughly divided into a writing section and an image forming section. As one example, the writing unit includes a semiconductor laser as a light source, and is configured by a polygon mirror 12, an fθ lens 14, and a reflecting mirror 16 which are rotatable by a drive motor 12a. In the writing unit, a laser beam is emitted from the semiconductor laser in response to an image information signal from a control unit (not shown), is scanned in the main scanning direction by the polygon mirror 12, and is imaged on the photoconductor through the fθ lens 14 and the reflecting mirror 16. To be done. An electrostatic latent image is formed by such image formation on the photoconductor, and the electrostatic latent image is formed for each color separated.

The image forming unit is of a type in which a flexible belt-shaped photoconductor 20 which is stretched over a pair of pulleys 22 and 24 is used. The belt-shaped photoconductor 20 is a drive pulley. It can be moved in the direction of the arrow shown by the lever 22. And
Around the belt-shaped photoreceptor 20, a charging device 26 for executing a copying process along the moving direction, an optical path from a writing device, a developing device 28, a transfer device and a cleaning device 30 are arranged. . One of the pulleys on which the belt-shaped photoconductor 20 is hung, that is, the pulley 24 located on the upper side in the drawing is in charge of the transfer device, and a transfer bias is applied thereto.

In the present embodiment, the developing device 28 is a cylinder 28 having an opening at a position facing the belt-shaped photoreceptor 20.
A, and a developing unit that is supported at a plurality of locations inside the cylinder and is rotatable around the center of the cylinder. Each developing unit contains a developer of a color having a complementary color relationship with the separation color, and when the electrostatic latent image of the separation color formed on the belt-shaped photoreceptor is subjected to visible image processing, the photoreceptor 20 The developer is supplied so as to face with. As a type of such a developing unit, for example, a magnetic developing method is used in which a magnetic developer is used, the developer forms a magnetic brush on the surface of the developing sleeve, and the magnetic brush is brought into contact with the belt-shaped photoreceptor 20. Has been adopted.

On the other hand, an intermediate transfer member 32 is arranged at the transfer position of the belt-shaped photosensitive member 20. The intermediate transfer member 32 is
It is configured by a belt that is stretched over a pair of pulleys, and a belt-shaped belt is formed at a position where a pulley 24, which is partially stretched between the pulleys and forms a transfer portion, is arranged. The photoconductor 20 is contacted.

The intermediate transfer member 32 includes a belt-shaped photosensitive member 20.
A visible image for each color corresponding to the separated color formed above is transferred and superimposed. Therefore, the belt-shaped photoreceptor 20
A bias roller 32A for applying a transfer bias is in contact with the side of the intermediate transfer member facing the pulley 24.
Images of all colors are transferred to such an intermediate transfer member 32. When all the images have been transferred to the intermediate transfer body 32, they are collectively transferred to a transfer material such as paper fed from the paper feeding device 34. Therefore, at a position corresponding to the transfer position on the intermediate transfer member 32, a bias device 36 for electrostatically transferring the transfer material to a position facing the intermediate transfer member 32 above the transfer material.
Are abutted.

The batch-transferred transfer material is subjected to image fixing by a fixing device 38 located behind the transfer position in the moving direction, and is discharged onto a paper discharge tray 42 by a paper discharge roller 40.

On the other hand, FIG. 2 shows a characteristic portion of this embodiment, and this portion is a portion used for detecting the test pattern formed on the transfer material.

The test pattern detector is the fixing device 38.
The light emitting member 44, which is located on the side where the transfer material is discharged from and emits the detection light toward the image surface of the transfer material, the photo sensor 46 for detecting the light reflected on the surface of the transfer material, and the reference roller 48. It is configured. The reference roller 48 is a rotatable roller arranged at a position above the transfer material transporting path so as to reflect the light from the light emitting member 44 and introduce the light into the photosensing sensor 46. Is shown in FIG.
As shown in FIG. 3, zones of each color described later are provided. FIG. 4 is a development view of the reference roller 48, which has a complementary color relationship with the three primary colors obtained when the color original is color-separated.
A state in which each color zone portion of cyan (C), magenta (M), yellow (Y), black (B) used for tone improvement and black and white development, and white (W) that is a basic color is evenly distributed. Is formed by. The reference roller 48 is a photo sensor 46 that detects an image density on a transfer material described later.
The photosensor 48 detects the amount of reflected light in each color zone having a reference density to register the detection potential at the initial stage, and to set the reference value for image density detection. Is set. The detection order of each color is black, cyan, magenta, yellow, and white, and when not detected, the white (W) color zone corresponds to the light emitting member 44 and the photosensor 46. ing.

FIG. 5 is a block diagram for explaining the configuration of the control unit 50 that executes the control for the image test.

The control section 50 can execute a normal color image forming operation and a test pattern forming operation.
For this reason, the control unit 50 is provided with a selector 52 for switching each of the above operations.

An I / F (interface) 56 is connected to the input side of the selector 52 via a recording converter 54 that operates during normal image formation. The I / F 56 has a complementary color relationship with the three primary colors. B (black) with
Four color signals of C (cyan), M (magenta), and Y (yellow) are input. Also the selector 52
A test signal generator 58 is connected to the input side of. The test signal generator 58 performs a writing process for forming a test pattern with the light intensity according to the detection voltage initialized by using the reference roller 48. As shown in FIG. 6, the laser beam from the test signal generator 58 is used for writing in three modes of highlight, middle and shadow, and is within an allowable error range (L1, L2) with respect to the target writing light. The amount of light within the display range) is used. A drive unit 60 of a semiconductor laser 62 which is a light source is connected to the output side of the selector 52.

Such switching of the operation of the selector 52 is carried out based on a command from the control device 64 for image testing which is composed of a microcomputer. Here, the control element 64 will be described. An A / D converter 66 is connected to the input side of the control element 64.
The photo sensor 46 is connected to the converter 66 via an amplifier 68. Further, on the input side of the control element 64, R for storing color adjustment data described later is stored.
The OM 70 is connected to output reference data necessary for color adjustment.

A timing selector 72 is connected to the output side of the control element 64, and this timing selector 7
A clock generator 74 is connected to 2 and applies a clock pulse to the selector 52.
The output of such a clock pulse is used to set the start time of forming a test pattern by emitting a laser beam, and it is possible to form a test pattern irrespective of the start of image formation or with a predetermined relationship. It has become.

The discrimination of each color by the photo sensor 46 will be described below. Photo sensor 46
As shown in FIG. 7, the color discrimination by the method uses the reflection density with respect to the wavelength of the light of the toner. As is clear from this figure, yellow (Y) has a characteristic of being sensitive to blue light (B), magenta (M) to green light, and cyan (C) to red light. The toner color can be determined based on the detection result of 1. In addition, black (B
Since r) is sensitive to the above-mentioned respective colors of red, green and blue, this state will be detected.

FIG. 8 is a diagram showing a response relationship between the RGB sensor and the ink color, and ON / OFF is indicated by high (H) and low (L).

As is apparent from the figure, the cyan toner responds only to the red (R) sensor and does not respond to the green (G) sensor and the blue (B) sensor. Magenta toner responds only to the green (G) sensor (R)
The sensor and the blue (B) sensor do not respond, and further, the yellow toner does not respond to the (R) sensor and the (G) sensor only to the blue (B) sensor. The black toner responds to all of the sensors of (B), (G), and (B), and the white toner corresponding to the color of the surface of the transfer material is of the (R), (G), and (B) sensors. Does not respond to all of.

On the other hand, in the ROM 70, as shown in FIG. 9, a correction curve forming basic data used for adjusting color reproducibility is registered. This correction curve shows the relationship between the reflection density and the writing light amount, and there are a plurality of correction curves for the highlight portion, the middle portion, and the shadow portion obtained by changing the light intensity at the time of writing, and five types of correction curves in the embodiment. Is registered. The reason for providing such a plurality of types of correction curves is that the deterioration of the photoreceptor such as the background stain is expected to occur over time. In FIG. 9, H1 to H5 are registered as highlight areas, M1 to M5 are registered as middle areas, and D1 to D5 are registered as shadow areas. As described with reference to FIG. 6, the setting of the writing light amount at this time uses the light amount within the allowable error range (the range displayed by L1 and L2) with respect to the target writing light in the highlight, middle and shadow. To be Further, as shown in FIG. 10, the test pattern formed with such a standard writing light amount has a transfer material moving direction (indicated by an arrow in the figure) having a size corresponding to the image forming area of the photoconductor.
Are arranged along. The entire surface of the transfer material is used as an image forming area, a part thereof is used as an image portion, and a plurality of test pattern patches P are formed in a slight range of the remaining portion. These test pattern patches P are cyan (C) toner used as a developer,
The magenta (M) toner, the yellow (Y) toner, and the black (B) toner are arranged in this order. As described with reference to FIG. 6, the pattern formed for each color toner has a maximum value (level 2) and a minimum value (level 2) that include an error from the target light amount at which the target density for shadow, middle and highlight is obtained. 1) and are formed respectively.

In the control element 64, the selection state of the selector 52 is set to the normal image forming state when the normal image forming is performed. In this state, the writing information for forming the electrostatic latent image of the color complementary to the color separated by the selector 52 is fetched through the I / F 56 and the recording converter 54, and the driving unit 60. The writing operation by the semiconductor laser is executed via the.

On the other hand, when forming the test pattern, the control element 64 outputs a start signal for forming the test pattern to the selector 52 via the timing selector 72. In the selector 52, the write signal corresponding to the image signal for each color from the test signal generator 58 is applied to the drive unit 60 at an arbitrary or predetermined timing by the timing selector 72, and the writing for each color by the semiconductor laser 62 is executed. It Control element 6 in this case
The test pattern formation by 4 is executed on the basis of, for example, the time when the image formation is repeated a predetermined number of times, or when a command is issued from the test pattern formation mode selection means installed on the operation panel (not shown).

Since this embodiment has the above-mentioned configuration,
The operation will be described below with reference to the flowchart showing the operation of the control element 64. First, in FIG.
After the initialization of the entire apparatus is executed, it is judged whether or not a test pattern formation is instructed (step 1). When the test pattern is not being formed but the normal image is being formed, the selector 52 is set to the normal image forming state, and the image writing signal input from the I / F 56 is transmitted via the recording converter 54 to the selector. It is input into 52 (step 2). As the processing for forming the electrostatic latent image for each color on the belt-shaped photoconductor 20, the selector 52 sets the light intensity through the drive unit 60, and the semiconductor laser 62 executes the writing processing (step 3). ).
The electrostatic latent image formed on the belt-shaped photoconductor 20 is subjected to visible image processing with a developer having a color complementary to the written color (step 4) and transferred to the intermediate transfer member 32 ( Step 5). After the transfer, the cleaned belt-shaped photoconductor 20 is again formed with an electrostatic latent image of a color different from that before, and the visible image processing of this latent image is repeated.

The images of the respective colors superimposed on the intermediate transfer member 32 are collectively transferred onto the transfer material (step 6), fixed as a color copy, and then discharged to the paper discharge tray 42 (step 7).

On the other hand, when the test pattern formation is instructed, the control element 64 issues an instruction for initialization setting of the photosensor 42 (step 8). This process is executed to determine the reference voltage of the photo sensor 42 with respect to the reference roller 44. Such processing is executed for each of the five colors set on the reference roller 44 (step 9).

When the initialization of the photosensor is completed, the composite signal from the recording converter 54 and the test signal generator 58 is output to the selector 52 (step 10).
When an image is formed, the timing selector 72 determines the test pattern formation position after the image formation is started, and writing is performed for each color at this position (step 11). The writing of the test pattern is performed by the light intensity for each color shown in FIG. The electrostatic latent image is subjected to an image forming process including a visible image process to a transfer to an intermediate transfer member by a developer having a complementary color relationship with each color (step 12), and after the visible image of each color is superimposed and transferred. After being collectively transferred to the transfer material (step 13) and fixed, the photosensor 42 is prepared to detect the density of each color of the test pattern formed near the image and observe the reproducibility (step 14). ).

The color reproducibility is determined by detecting the image density on the transfer material for each color. In the detection for each color, the density detection output is obtained by excluding the reference voltage obtained by the initial setting of the photo sensor 42 as described above. Then, regarding the detected potential corresponding to each detected color, the closest correction curve among the correction curves shown in FIG. 9 is selected. For example, the highlight section selects from correction curves H1 to H5 having output levels HO1 to HO5, and the middle section selects output levels MO1 to M5.
The correction curves M1 to M5 having O5 are selected, and in the shadow portion, the correction curves D0 to D5 having output levels DO1 to DO5 are selected (step 15). The difference between the selected correction curve and the actual detection output from the photosensor 42 is calculated to obtain an index, and the difference is erased to bring the semiconductor laser into a state in which the correction curve is matched. The output is changed (step 17). As a result, the intensity of light emitted from the semiconductor laser is changed. By performing such processing for each of the highlight, middle, and shadow states and then synthesizing the states, the writing light amount of the semiconductor laser used for writing is corrected (step 18).

As described above, the reproducibility is deteriorated even when the same writing light amount is used due to the deterioration of the photosensitive member with time or the change of use environment. The reproducibility is deteriorated by correcting the writing light amount of the semiconductor laser. Will be suppressed.

[0041]

As described above, according to the first aspect of the invention, since the writing light quantity can be corrected according to the deterioration of the photoconductor with time, the change of use environment, and the like, a stable color is always obtained. Reproducibility can be obtained. Moreover, since the test pattern can be formed together with the test printing of the image, it is possible to eliminate the waste of the used paper.

According to the second aspect of the present invention, the test pattern can be formed by the same method as the original image, and the test pattern is formed in the moving direction of the photoconductor. The number of sensors can be reduced because the sensors used to detect the pattern need only be on that row.

According to the third aspect of the present invention, since the test pattern is formed at a different time from the formation of the normal original image, an accident such that an unnecessary test pattern is erroneously formed during image formation is prevented. it can.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining the configuration of an image forming apparatus that is an embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining the configuration of a test pattern detection unit used in the device shown in FIG.

FIG. 3 is an external view of a reference roller used in the detection unit shown in FIG.

FIG. 4 is a development view of the reference roller shown in FIG.

5 is a block diagram for explaining a configuration of a control unit used in the device shown in FIG.

6 is a diagram showing a relationship between a writing light amount level in the detection unit shown in FIG. 2 and a detection level by a detection member,
(A) shows the relationship in the highlight part, (B) shows the relationship in the middle part, and (C) shows the relationship in the shadow part.

FIG. 7 is a diagram for explaining the relationship between the wavelength of light and the reflection density for performing color discrimination by the detection member.

FIG. 8 is a diagram for explaining a response result when discriminating between three primary colors and colors having a complementary color relationship.

9A and 9B are diagrams for explaining a correction curve used in the control unit shown in FIG. 5, where FIG. 9A is a correction curve in a highlight portion, and FIG. 9B is a correction curve in a middle portion (C). ) Indicates the correction curve in the shadow part.

10 is a plan view showing an image portion and a test pattern that are actually formed by the apparatus shown in FIG.

11 is a flow chart for explaining the operation of the control unit shown in FIG.

[Explanation of symbols]

 10 Color Image Forming Device 20 Belt-Shaped Photosensitive Member 32 Intermediate Transfer Body 38 Fixing Device 44 Light Emitting Member 46 Photosensor 48 Reference Roller 50 Control Section 52 Selector 58 Test Signal Generator 62 Semiconductor Laser 64 Control Element

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B41J 2/525 G03G 15/00 303 H04N 1/60 1/46 H04N 1/46 Z

Claims (3)

[Claims] 1. A color of an original image is separated for each color, an electrostatic latent image corresponding to the color is formed on a photoconductor, and an electrostatic latent image is formed by using a developer having a color complementary to the separated color. A color in which an image for each separated color obtained by subjecting an image to visible image processing is repeatedly transferred to an intermediate transfer member, and the superimposed images for each color can be collectively transferred and fixed.
In the image forming apparatus, a unit for forming a test pattern together with a normal image formation in the image forming area on the photoconductor, and a detection unit for detecting the state of the test pattern formed by the test pattern forming unit, A color image forming apparatus, comprising: a control unit capable of adjusting color reproducibility according to information from a detection unit. 2. The color image forming apparatus according to claim 1, wherein the test pattern forming means is arranged in the image forming area in the vicinity of the original image forming range in the moving direction of the photoconductor by the same method as the original image. A color image forming apparatus, wherein a test pattern row is formed in a direction along the color image forming apparatus. 3. The color image forming apparatus according to claim 1, wherein the test pattern forming means forms the test pattern and the image at a different time from the time of forming a normal original image. apparatus.