JP2006053305A - Image forming apparatus and program for the apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase accuracy in the measurement of the densities of density correction patches by restraining cumulative errors in sampling position, and to prevent erroneous measurement caused by inadvertence and erroneous recognition of trigger patches. <P>SOLUTION: In the image forming apparatus, a density measuring sensor 27 measures the densities of the density correction patches PC, PM, PY, and PK formed on an intermediate transfer belt 25, and image forming conditions relating to the image density are corrected using the densities measured. When the density correction patches PC, PM, PY, and PK are formed in an array in the scanning direction of the density measuring sensor 27, the plurality of trigger patches TP1 to TP3 of different patterns are formed in the array of the patches. When the measurement values of the density measuring sensor 27 are sampled, the trigger patches TP1 to TP3 are identified. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, a digital composite apparatus, etc., and a program for the image forming apparatus, and in particular, measures the density of a density correction patch formed on an image carrier with a density measuring sensor. The present invention relates to an image forming apparatus and an image forming apparatus program for correcting an image forming condition related to the image density based on the measured density.

  The configuration of an image forming apparatus to which the present invention can be applied will be described using a digital color copying machine (4-cycle color laser printing system) as an example. However, the image forming apparatus of the present invention is not limited to the four-cycle color laser printing method, and can also be applied to a printing method such as a tandem color laser printing method, a monochrome laser printing method, and an ink jet printing method.

FIG. 4 is an explanatory diagram showing the configuration of a digital color copying machine (4-cycle color laser printing system).
As shown in this figure, the digital color copying machine includes a scanner unit 10, a print unit 20, a recording medium transport unit 30, and a control unit (not shown) that controls these operations. Yes.

  The scanner unit 10 includes a contact glass 11 on which a document to be copied is placed, first and second optical system traveling bodies 12 and 13 that travel along the lower surface thereof, and these optical system traveling bodies 12 and 13. And an imaging element 15 such as a CCD that receives the reflected light of the original and converts it into an electrical signal via the condenser lens 14.

  The first optical system traveling body 12 is provided with an exposure lamp 16 that exposes and scans the document, and a first mirror 17 that reflects reflected light from the document toward the second optical system traveling body 13, and the second optical system. The traveling body 13 is provided with a second mirror 18 and a third mirror 19 that reflect the reflected light from the first optical system traveling body 12 toward the condenser lens 14.

  The first optical system traveling body 12 and the second optical system traveling body 13 are traveled by a stepping motor (not shown). The first optical system traveling body 12 is normally in the standby position shown in FIG. 4 and moves in the direction indicated by the arrow F in FIG. 4 during exposure scanning, and the moving direction is switched at a return position determined according to the document size. , Move in the direction of arrow R and return to the standby position. The second optical system traveling body 13 is moved by a distance 1/2 that of the first optical system traveling body 12 at a speed that is 1/2 that of the first optical system traveling body 12.

  The print unit 20 includes a photosensitive drum 21. The photosensitive drum 21 is rotationally driven in the direction of the arrow in FIG. 4 by a main motor (not shown). Around the photosensitive drum 21, in order of the rotation direction, a charger 22 for charging the photosensitive layer of the photosensitive drum 21, a laser unit 23 for forming an electrostatic latent image on the photosensitive layer, and an electrostatic latent image Developing device 24 (C, M, Y, K) for each color (C: cyan, M: magenta, Y: yellow, K: black) and a toner image formed on the photosensitive layer. An intermediate transfer belt (intermediate transfer member) 25 to which toner is transferred and a photosensitive member cleaner 26 for removing residual toner on the photosensitive drum 21 are disposed.

  The intermediate transfer belt 25 is rotationally driven in the direction of the arrow in FIG. 4 by a main motor (not shown). Around the intermediate transfer belt 25, a density measurement sensor 27 (for example, a reflection type optical sensor) that measures the density of the toner image transferred to the intermediate transfer belt 25 and a toner image transferred to the intermediate transfer belt 25 are recorded. A transfer roller 28 for transferring to the medium and a transfer belt cleaner 29 for removing residual toner on the intermediate transfer belt 25 are disposed.

  The recording medium transport unit 30 includes a paper feeding roller 32 that feeds the recording medium in the paper feeding cassette 31, and a registration roller 33 that feeds the recording medium sent by the paper feeding roller 32 to the intermediate transfer belt 25 at a predetermined timing. A conveying belt 35 that sends the recording medium after the toner image is transferred to the fixing roller 34; and a discharge roller 37 that sends the recording medium after the toner image is fixed by the fixing roller 34 to the discharge tray 36. Yes.

  In the four-cycle color laser printing type digital color copying machine configured as described above, four color toner images are formed in four cycles by using one photosensitive drum 21 when performing color copying. The toner images of the respective colors are sequentially transferred to the intermediate transfer belt 25, and then transferred collectively from the intermediate transfer belt 25 to the recording medium.

Normally, in this type of digital color copying machine, image density correction is performed in order to stabilize gradation reproducibility (see, for example, Patent Document 1).
A conventional image density correction procedure will be described below.

(1) After the photosensitive layer of the photosensitive drum 21 is charged by the charger 22, the laser unit 23 is driven based on the predetermined density correction patch data, and the density correction patch is placed on the photosensitive drum 21. The electrostatic latent image is formed.
(2) The electrostatic latent image formed on the photosensitive drum 21 is visualized as a toner image using the developing device 24 of the corresponding color.
(3) The toner image of the density correction patch is transferred to the intermediate transfer belt 25 by a predetermined transfer voltage.
(4) The above processing is repeated for each color developing device 24 (C, M, Y, K), and density correction patches for each color are formed on the intermediate transfer belt 25.
(5) The density measurement sensor 27 measures the density of the density correction patch formed on the intermediate transfer belt 25.
(6) The image forming conditions related to the image density are corrected based on the measured density. Examples of the image forming condition relating to the image density include the exposure intensity of the laser unit 23 and the developing bias of the developing device 24.
JP 2003-186278 A

  5A to 5E are explanatory diagrams showing various patch formation patterns. In FIG. 5, the density measurement sensor is illustrated as scanning each density correction patch from top to bottom. The density correction patches for each color are arranged in the order C, M, Y, K from the top, but this order is arbitrary.

  5A to 5E, four color correction patches PC, PM, PY, and PK are formed so as to be aligned in the scanning direction of the density measurement sensor. The density correction patches PC, PM, PY, and PK for each color include a plurality of patches Pa to Ph having different color values (density), and the measured values of the density measuring sensor are the patches Pa to Ph. It is sampled with a period narrower than the width.

  The density correction patches PC, PM, PY, and PK shown in FIG. 5A are drawn in order from patches Pa to Ph having the smallest color value. When the density correction patches PC, PM, PY, and PK are configured in this way, since the change in the measured density at the patch head position is small, it is difficult to recognize the patch head position based on the measurement value of the density measurement sensor. Become.

  There is also a method of generating a measurement timing signal based on the formation timing of the density correction patches PC, PM, PY, and PK and starting sampling of the density measurement value in accordance with this signal. Due to slippage of the transfer belt or the like, there is a possibility that a large deviation occurs in the sampling start position.

  The density correction patches PC, PM, PY, and PK shown in FIG. 5B are drawn in order from patches Pa to Ph having the largest color values. When the density correction patches PC, PM, PY, and PK are configured in this way, the change in the measured density at the patch head position becomes large. Therefore, the patch head position can be recognized based on the measurement value change of the density measurement sensor. It becomes possible.

For example, preliminary sampling (sampling for patch position detection) is started from a position sufficiently before the head position of the density correction patches PC, PM, PY, and PK, and the main sampling (density) Sampling for measurement) can be started.
However, this method has a restriction that a patch having a large color value must always be placed at the head of the density correction patches PC, PM, PY, and PK.

  5 (c) and 5 (d), trigger patches TP are formed at a predetermined interval in the vicinity of the head position of the patch row composed of density correction patches PC, PM, PY, and PK. When such a trigger patch TP is formed, the top position of the patch row is recognized with high accuracy regardless of the order of arrangement of the color values in the density correction patches PC, PM, PY, and PK, and the main sampling is started with good timing. be able to.

  However, in the above method, even if the main sampling is started in a timely manner, a slight deviation is accumulated near the rear end of the patch row, and there is a large error in the sampling position and the number of samples in each patch Pa to Ph. As a result, there is a possibility of making an error in the aggregation processing and the representative value calculation based on each sampling measurement data.

  It should be noted that the sampling timing that should have been synchronized once deviates slightly toward the rear end because the image carrier is not moving at a uniform speed due to uneven rotation or slippage. This is because the total circumference of the carrier is not necessarily an integral multiple of the sampling clock, and there are subtle individual differences in the total circumference of the image carrier and the sampling clock.

  Therefore, as shown in FIG. 5E, it is proposed to form a plurality of trigger patches TP in a patch row composed of a plurality of density correction patches PC, PM, PY, and PK. In this way, when measuring the density of the density correction patches PC, PM, PY, and PK, the sampling clock can be reset a plurality of times based on the trigger patches TP formed in the patch array. Accumulated position errors can be suppressed.

  However, as a result of experiments by the present inventors, it has been found that there is a possibility that measurement errors may occur even when the above-described patch formation pattern is applied. This is probably because sampling was not started from the correct position due to a detection error of the trigger patch TP. For example, if the trigger patch TP is overlooked, or if some of the density correction patches PC, PM, PY, and PK are mistaken for the trigger patch TP, an error occurs in the subsequent sampling position, making correct density measurement difficult. Become.

In the patch formation pattern shown in FIG. 5 (e), it is possible to determine the measurement error as described above by checking the appearance period of the trigger patch TP. It is necessary to perform sampling from
When the density measurement sensor can identify the colors of the density correction patches PC, PM, PY, and PK, while recognizing the position of the patch row based on the color information and density information of the density measurement sensor, Sampling is also possible, but in many image forming apparatuses, the patch image is irradiated with invisible light such as infrared rays, and a reflective optical sensor that detects the amount of reflected light is used to detect the surface particle size. Since a sensor for specifying the density is used, it is difficult to recognize the position of the patch row based on the color information.

  The present invention has been considered in view of the above circumstances, and it is possible not only to accurately measure the density of the density correction patch while suppressing the accumulated error of the sampling position, but also due to an oversight or misidentification of the trigger patch. An object of the present invention is to provide an image forming apparatus and a program for the image forming apparatus that can prevent mistakes.

  In order to achieve the above object, the image forming apparatus of the present invention measures the density of the density correction patch formed on the image carrier with the density measuring sensor, and based on the measured density, the image forming condition relating to the image density An image forming apparatus for correcting the density, and a patch forming unit that forms a plurality of density correction patches arranged in a scanning direction of the density measurement sensor on the carrier, and a measurement value of the density measurement sensor is set to a predetermined value. Density measurement means for sampling at the timing of the sample, and extracting or calculating a representative value from the sampled measurement value, and density correction means for correcting an image forming condition related to image density based on the representative value, and forming the patch The means forms a plurality of trigger patches having different image patterns in a patch row composed of a plurality of the density correction patches, and the density measuring means includes the trigger Detects the patch, it is constituted to identify each trigger patch on the basis of the image pattern.

With this configuration, the sampling timing is reset based on a plurality of trigger patches formed in the patch row, thereby suppressing the accumulated error of the sampling position and increasing the density measurement accuracy of the density correction patch. Can do.
In addition, since the plurality of trigger patches are drawn with different image patterns, it is easy to specify the position of each density correction patch, and it is possible to prevent measurement errors caused by oversight or misidentification of the trigger patches.

Further, in the image forming apparatus of the present invention, the density measuring unit specifies the position of the density correction patch based on the trigger patch formed in front of and / or behind the density correction patch. It is as.
With this configuration, even if the front trigger patch is overlooked, the position of the density correction patch can be specified based on the rear trigger patch, and necessary sampling data can be acquired retrospectively.

In the image forming apparatus of the present invention, the trigger patch includes a plurality of bar images formed at predetermined intervals in the scanning direction of the density measurement sensor, and the number of bar images between the trigger patches. , The width and / or the interval are different.
With this configuration, trigger patches having different image patterns can be easily formed, and the trigger patches can be distinguished by simple identification processing.

In the image forming apparatus of the present invention, the trigger patch is formed in the vicinity of the head position of each density correction patch.
With this configuration, the formation position of each density correction patch and the sampling position can be synchronized with higher accuracy.

In the image forming apparatus of the present invention, the image carrier is a photosensitive drum, an intermediate transfer member, or a recording medium.
With this configuration, it is possible to measure the patch density on the photosensitive drum, the intermediate transfer member, or the recording medium with high accuracy and improve the accuracy of image density correction.

The image forming apparatus program according to the present invention measures the density of the density correction patch formed on the image carrier with a density measuring sensor and corrects the image forming condition related to the image density based on the measured density. A program for the image forming apparatus, wherein when forming the plurality of density correction patches arranged in the scanning direction of the density measurement sensor on the carrier, a patch array including a plurality of density correction patches A plurality of trigger patches having different image patterns are formed, the measurement values of the density measurement sensor are sampled at a predetermined timing, and the representative values are extracted or calculated from the sampled measurement values. The patch is detected, each trigger patch is identified based on the image pattern, and the image forming condition relating to the image density is determined based on the representative value. It is constituted to correct the.
With this configuration, the existing image forming apparatus can be operated as the image forming apparatus of the present invention by changing the program.

As described above, according to the present invention, the sampling timing is reset based on a plurality of trigger patches formed in the patch array, thereby suppressing the accumulated error of the sampling position and measuring the density of the density correction patch. Accuracy can be increased.
In addition, since the plurality of trigger patches are drawn with different image patterns, it is easy to specify the position of each density correction patch, and it is possible to prevent measurement errors caused by oversight or misidentification of the trigger patches. For example, even if the front trigger patch is overlooked, the position of the density correction patch can be specified based on the rear trigger patch, and necessary sampling data can be acquired retrospectively.

Embodiments of the present invention will be described below with reference to the drawings.
A configuration of an image forming apparatus according to an embodiment of the present invention will be described with reference to FIG.
FIG. 1 is a block diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention.

  However, although the image processing apparatus shown in FIG. 1 shows the configuration of a copying machine as a specific example, the image forming apparatus according to the present embodiment is not limited to a copying machine. For example, a printer, a facsimile, a digital composite Device (multifunction peripheral (MFP)) and the like.

  Further, as a printing method of the image forming apparatus according to the present invention, a color laser printing method (including a 4-cycle method and a tandem method), a monochrome laser printing method, an ink jet printing method, a sublimation type thermal transfer printing method, a melt type thermal transfer printing. Method, dot impact printing method, and the like.

  As shown in FIG. 1, the image forming apparatus 1 according to the present embodiment includes a scanner unit 10, a print unit 20, a recording medium transport unit 30, a storage unit 40, and a control unit 50. Yes. For the scanner unit 10, the print unit 20, and the recording medium transport unit 30, the same configuration as that of the image forming apparatus shown in FIG. 4 is applied, and the reference numerals and descriptions in FIG. 4 are used.

  The storage unit 40 stores programs and data. The data stored in the storage unit 40 includes image data read by the scanner unit 10 and various image forming condition data related to printing of the image data. Further, the image forming condition data includes parameters relating to image density such as the exposure intensity of the laser unit 23 and the developing bias of the developing device 24, and these parameters are the correction targets of the image density correction process described later. Become.

The control unit 50 includes at least a patch forming unit 51, a density measuring unit 52, and a density correcting unit 53 as a functional configuration realized by a program.
The patch forming unit 51 charges the photosensitive layer of the photosensitive drum 21 with the charger 22, and then drives the laser unit 23 based on the predetermined patch data to electrostatically charge the patch on the photosensitive drum 21. A latent image is formed. The electrostatic latent image formed on the photosensitive drum 21 is visualized as a toner image using the developing device 24 of the corresponding color, and then transferred to the intermediate transfer belt 25 by a predetermined transfer voltage. The The patches formed by the patch forming unit 51 include a density correction patch and a trigger patch, and the position of the density correction patch is specified based on detection of the trigger patch.

  The density measuring means 52 samples the measurement value of the density measuring sensor 27 using a sampling clock having a predetermined period. This sampling includes preliminary sampling for detecting the trigger patch and main sampling for detecting the density of the density correction patch, and the sampling clock is reset when the trigger patch is detected.

The density correction unit 53 corrects parameters related to image density, such as the exposure intensity of the laser unit 23 and the development bias of the developing device 24, based on the measured patch density.
Hereinafter, a procedure of image density correction processing using the patch forming unit 51, the density measuring unit 52, and the density correcting unit 53 will be described.

FIG. 2 is a flowchart showing a procedure of image density correction processing according to the embodiment of the present invention.
As shown in this figure, in the image density correction process, first, the head color (for example, cyan) is set in the patch color variable (S101), and then the patch formation process (S102: patch formation means 51) is executed. In the patch forming process, a patch image including a plurality of types of densities (color values) is formed on the photosensitive drum 21 by using the color developing device 24 set in the patch color variable, and this patch image is intermediately transferred. Transfer to the belt 25.

  When the patch forming process is completed, the next color is set in the patch color variable (S103), and the patch forming process (S102) is executed again. When patch formation processing is completed for all colors (S104), density measurement processing (S105: density measurement means 52) and density correction processing (S106: density correction means 53) are executed, and image density correction processing ends. .

FIG. 3 is an explanatory diagram showing a patch formation pattern according to the embodiment of the present invention.
As shown in this figure, in this embodiment, four color correction patches PC, PM, PY, and PK are formed so as to be aligned in the scanning direction of the density measurement sensor 27. The density correction patches PC, PM, PY and PK for each color include a plurality of patches Pa to Ph having different color values (density). Further, a plurality of trigger patches TP are formed in a patch row composed of density correction patches PC, PM, PY, and PK. In the example shown in FIG. 3, trigger patches TP are formed in the vicinity of the head positions of the density correction patches PC, PM, and PY.

  In this way, the sampling clock can be reset at the head position of each density correction patch PC, PM, PY, and the accumulated error at the sampling position can be refreshed. That is, in the present invention, since at least two trigger patches TP are arranged in the patch row, a conventional patch formation pattern in which one trigger patch TP is arranged in the vicinity of the head of the patch row (FIG. 5C). , (D)), it is possible to suppress the accumulated error at the sampling position and measure the densities of the density correction patches PC, PM, PY, and PK with high accuracy.

  The number of trigger patches TR is not particularly limited as long as it is two or more. When there are the same number of density correction patches PC, PM, PY, PK, more than the density correction patches PC, PM, PY, PK, and less than the density correction patches PC, PM, PY, PK Can be considered. For example, in the example shown in FIG. 3, the trigger patch TP corresponding to the black density correction patch PK is omitted. In FIG. 3, only trigger patches TP corresponding to cyan and yellow density correction patches PC and PY are arranged, or only trigger patches TP corresponding to cyan and black density correction patches PC and PK are arranged. You may arrange. When the intermediate trigger patch TP is omitted, the density correction patches PC, PM, PY, PK may be left blank, or blanks may be filled.

  The plurality of trigger patches TP according to the present invention are drawn with different image patterns. In this way, by identifying each trigger patch TP based on the image pattern, not only can the positions of the respective density correction patches PC, PM, PY, PK be accurately identified, It becomes possible to prevent measurement errors due to misidentification. For example, a measurement error due to an oversight of the trigger patch TP can be prevented by determining the density measurement processing procedure as follows.

(1) Sampling of measured values is started with sufficient margin from the front position of the patch row composed of density correction patches PC, PM, PY, and PK, and the sampling data is sequentially stored.
(2) When the trigger patch TP of interest is detected without error, the measured values of the density correction patches PC, PM, PY, and PK located behind it are extracted with reference to the detection timing.
(3) If the subsequent trigger patch TP is detected without detecting the target trigger patch TP, it is determined that the target trigger patch TP is overlooked, and the subsequent trigger patch is detected. Using the timing at which TP is detected as a reference, the positions of density correction patches PC, PM, PY, and PK in front of them are specified. Then, necessary sampling data is acquired retrospectively from the stored sampling data.

  The image pattern of the trigger patch TP is not particularly limited as long as it can be identified. However, it is preferable that the trigger patch TP is composed of a plurality of bar images formed at predetermined intervals in the scanning direction of the density measurement sensor 27. In this way, each trigger patch TP can be identified only by making the number, width, interval, etc. of the bar images different. For example, in the example shown in FIG. 3, the first trigger patch TP1 is composed of four bar images with a narrow width and interval, and the second trigger patch TP2 is three with a medium width and interval. The third trigger patch TP3 is composed of two bar images having a wide width and interval.

  Identification of the trigger patch TP can be performed based on a rapid change in the density measurement value and the appearance interval. For example, in the example shown in FIG. 3, when the measurement value change from the image carrier level to the trigger patch level appears four times at short intervals, the first trigger patch TP1 is identified. If the measured value change appears three times at a short interval, it is identified as the second trigger patch TP2, and if the above measured value change appears twice at a short interval, the third trigger is detected. Can be identified as the patch TP3.

  According to the image forming apparatus of the present embodiment configured as described above, patch formation for forming a plurality of density correction patches PC, PM, PY, and PK arranged in the scanning direction of the density measurement sensor 27 on the carrier. Means 51, the measurement value of the density measurement sensor 27 is sampled at a predetermined timing, a density measurement means 52 for extracting or calculating a representative value from the sampled measurement value, and image formation relating to the image density based on the representative value Density correction means 53 for correcting the conditions, and the patch forming means 51 forms a plurality of trigger patches TP1 to TP3 in a patch row composed of a plurality of density correction patches PC, PM, PY, PK. Each time the trigger patches TP1 to TP3 are detected, the sampling timing is reset, thereby suppressing the accumulated error of the sampling position and for density correction. Pitch PC, PM, PY, can increase the density measurement precision of PK.

  In addition, since the plurality of trigger patches TP1 to TP3 are drawn in different image patterns, the density correction patches PC, PM, and PY are identified by identifying the trigger patches TP1 to TP3 based on the image pattern. The position of the PK can be easily identified, and measurement errors caused by oversight or misidentification of the trigger patches TP1 to TP3 can be prevented.

  Further, the positions of the density correction patches PC, PM, PY, and PK can be specified based on the trigger patches TP1 to TP3 formed in front of or behind the density correction patches PC, PM, PY, and PK. Even if the trigger patches TP1 to TP3 are overlooked, the positions of the density correction patches PC, PM, PY, and PK are specified based on the rear trigger patches TP1 to TP3, and necessary sampling data is acquired retrospectively. Can do.

  Further, the trigger patches TP1 to TP3 are composed of a plurality of bar images formed at predetermined intervals in the scanning direction of the density measurement sensor 27, so that only the number, width, interval, etc. of the bar images are changed. The trigger patches TP1 to TP3 having different image patterns can be easily formed, and the trigger patches TP1 to TP3 can be distinguished by a simple identification process.

Next, an image forming apparatus program will be described.
The density measurement / density correction function of the computer (image forming apparatus) in the above-described embodiment is realized by an image forming apparatus program stored in a storage unit (for example, ROM).

The program for the image forming apparatus is read by the control means (CPU) of the computer to send commands to each component of the computer and perform predetermined processing, for example, patch formation processing of the patch formation means, density measurement processing of the density measurement means Then, the density correction process of the density correction unit is performed.
Thus, the density measurement / density correction function is realized by the cooperation of the program for the image forming apparatus as software and each component of the computer (image forming apparatus) as the hardware resource.

The image forming apparatus program for realizing the density measurement / density correction function is stored in a computer ROM, hard disk, or the like, or a computer-readable recording medium such as an external storage device or a portable recording medium. Can be stored.
The external storage device is a memory expansion device that incorporates a storage medium such as a CD-ROM and is externally connected to the image forming apparatus. On the other hand, the portable recording medium is a recording medium that can be mounted on a recording medium driving device (drive device) and is portable, and refers to, for example, a flexible disk, a memory card, a magneto-optical disk, and the like.
The program recorded on the recording medium is loaded into a RAM of a computer and executed by a CPU (control means / control unit). By this execution, the function of the image forming apparatus of the present embodiment described above is realized.

Needless to say, the present invention is not limited to the embodiment. For example, the image carrier is not limited to an intermediate transfer belt, but includes an intermediate transfer roller, a photosensitive drum, a recording medium, and the like.
Further, the shape, number, interval, and the like of the density correction patch can be arbitrarily changed.

  The present invention is applied to an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a digital composite apparatus. In particular, it is suitable for an image forming apparatus that measures the density of a density correction patch formed on an image carrier with a density measuring sensor and corrects image forming conditions related to the image density based on the measured density.

1 is a block diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. It is a flowchart which shows the procedure of the image density correction process which concerns on embodiment of this invention. It is explanatory drawing which shows the patch formation pattern which concerns on embodiment of this invention. It is explanatory drawing which shows the structure of a digital color copying machine (4 cycle color laser printing system). (A)-(e) is explanatory drawing which shows various patch formation patterns.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Scanner part 20 Print part 21 Photoconductor drum 22 Charger 23 Laser unit 24 Developing device 25 Intermediate transfer belt 26 Photoconductor cleaner 27 Density measurement sensor 28 Transfer roller 29 Transfer belt cleaner 30 Recording medium conveyance part 40 Storage part 50 Control Unit 51 Patch Formation Unit 52 Density Measurement Unit 53 Density Correction Unit PC, PM, CY, CK Density Correction Patches TP1 to TP3 Trigger Patch

Claims (6)

An image forming apparatus that measures the density of a density correction patch formed on an image carrier with a density measuring sensor and corrects image forming conditions related to the image density based on the measured density.
Patch forming means for forming a plurality of the density correction patches arranged in the scanning direction of the density measurement sensor on the carrier;
A concentration measurement unit that samples the measurement value of the concentration measurement sensor at a predetermined timing, and extracts or calculates a representative value from the sampled measurement value;
A density correction unit that corrects an image forming condition related to the image density based on the representative value;
The patch forming means forms a plurality of trigger patches with different image patterns in a patch row composed of a plurality of density correction patches,
The image forming apparatus, wherein the density measuring unit detects the trigger patch and identifies each trigger patch based on the image pattern. The image according to claim 1, wherein the density measuring unit specifies the position of the density correction patch based on the trigger patch formed in front of and / or behind the density correction patch. Forming equipment. The trigger patch is composed of a plurality of bar images formed at predetermined intervals in the scanning direction of the density measurement sensor, and the number, width and / or interval of the bar images between the trigger patches are different. The image forming apparatus according to claim 1, wherein: The image forming apparatus according to claim 1, wherein the trigger patch is formed in the vicinity of a head position of each density correction patch. The image forming apparatus according to claim 1, wherein the image carrier is a photosensitive drum, an intermediate transfer member, or a recording medium. A program for an image forming apparatus that measures the density of a density correction patch formed on an image carrier with a density measuring sensor and corrects image forming conditions related to the image density based on the measured density.
When forming a plurality of the density correction patches arranged in the scanning direction of the density measurement sensor on the carrier, a plurality of triggers having different image patterns in a patch row composed of the plurality of density correction patches. Let the patch form,
The measurement value of the concentration measurement sensor is sampled at a predetermined timing, and when the representative value is extracted or calculated from the sampled measurement value, the trigger patch is detected and each trigger patch is based on the image pattern. Identify
An image forming apparatus program for correcting an image forming condition related to an image density based on the representative value.