JP5198306B2 - Image forming apparatus - Google Patents

Description

  The present invention belongs to the technical field of image forming apparatuses such as copiers and multi-function peripherals, and particularly relates to a technique for detecting toner consumption.

  Various techniques for detecting toner consumption in an image forming apparatus such as a copying machine or a multifunction machine have been proposed (for example, Patent Documents 1 and 2 below).

  In Patent Document 1 below, for each pixel, the input signal value of the pixel is multiplied by a weighting coefficient, the multiplied value is added to all the pixels, and the toner consumption of the output image is calculated based on the integrated value. In addition, a configuration in which the weighting coefficient is variable is disclosed.

  Further, in Patent Document 1 below, “in the halftone gamma correction process, a toner patch is formed on a photosensitive member or a transfer belt with a halftone pattern (tone) based on a predetermined fixed input value. Read the amount of reflected light from the toner patch with a reading device such as an optical sensor .... Then, the sensor output value of the read toner patch is compared with a reference target value that is a target value, and a correction amount is calculated. Then, the current halftone gamma correction table is corrected in accordance with the calculated correction amount, thereby controlling to always obtain a constant halftone gamma characteristic ([0013] ]) ”.

  Further, in Patent Document 2 below, an image forming apparatus that performs development using a two-component developer containing toner and a carrier is provided with the configuration of Patent Document 1, and a magnetic permeability sensor installed in a developing tank. The toner concentration of the toner and carrier contained in the two-component developer in the developing tank is detected, and a correction coefficient is set in consideration of the toner density in the developing tank that affects the toner adhesion amount. And a technique for calculating the toner consumption based on the weighting coefficient.

  Further, Patent Documents 1 and 2 below describe a configuration for calculating a toner consumption amount based on image data processed by the halftone correction processing unit.

JP 2006-023392 A JP 2008-96735 A

  However, since the halftone gamma characteristics change every time halftone gamma correction processing is performed throughout the use period of the image forming apparatus, in Patent Documents 1 and 2, every time the halftone gamma characteristics are corrected. A process of rewriting the weighting coefficient is required.

  The image data after processing by the halftone correction processing unit is image data processed so as to obtain a target density according to the current characteristics and development characteristics of the photoreceptor. On the other hand, for the calculation of the toner consumption amount, for example, an arithmetic expression set based on the characteristics of the photoconductor and the development characteristics at the time of factory shipment is used.

  Therefore, from the image data after processing by the halftone correction processing unit processed so as to obtain the target density according to the current characteristics and development characteristics of the photoreceptor, for example, characteristics and development characteristics of the photoreceptor at the time of factory shipment Even if the toner consumption amount is calculated using an arithmetic expression set based on the above, an accurate toner consumption amount is not calculated, and the actual toner consumption amount has a large error.

  For example, when the image data is “50” at the time of factory shipment, it is assumed that the target density “100” is obtained, and an arithmetic expression for toner consumption is set based on the assumption. In this case, when the density correction performed at a certain timing after factory shipment reveals that the density measured for the image data “50” is “120”, the obtained density is “100”. Thus, the image data is corrected from “50” to “30”, for example, by halftone correction processing.

  However, since the image data “30” is image data processed so as to obtain the target density “100” according to the current characteristics and development characteristics of the photoconductor, the image data is “50”. When the toner consumption amount is calculated using an arithmetic expression set on the assumption that the target density “100” is obtained, a toner consumption amount greatly different from the actual toner consumption amount is calculated.

  Furthermore, since the amount of developer consumed varies depending on the electrostatic latent image even if the toner density is the same, the density patch pattern used for density correction is the density level used during normal image formation. If the screen is created by means different from the screen used in the tone processing, a large error occurs in the calculated toner consumption.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of detecting a more accurate toner consumption with a simple configuration.

According to the first aspect of the present invention, there is provided an image forming unit that forms an image on a recording medium using a developer, and a halftone γ correction that performs a halftone γ correction process using a halftone γ correction table on image data. And a pseudo halftone processing unit for performing pseudo halftone processing using a screen on the image data after halftone gamma correction processing or the image data of the density correction image output from the halftone gamma correction processing unit A density correction image forming operation on the image carrier using the screen, and the halftone γ based on the density of the density correction image formed on the image carrier. A density correction processing unit that performs density correction processing for correcting the correction table; and a consumption amount calculation unit that calculates a consumption amount of the developer based on image data before the halftone γ correction processing by the halftone γ correction processing unit. Comprising the image data One pixel is composed of a plurality of blocks, and each block is assigned a block number corresponding to the block position in one pixel, and the screen associates the block number with the output time of the laser beam. The pseudo-halftone processing unit compares the pixel value of the pixel of interest in the density correction image with the threshold value of the screen, and based on the comparison result, the pixel of interest By executing the pseudo halftone process for determining the output time of the laser light of a plurality of blocks included in each of the pixels of the density correction image, by determining the output time of the laser light of each block constituting The density correction processing unit uses a laser light output time determined by the pseudo halftone processing unit for the image data of the density correction image, By irradiating over beam which is an image forming apparatus for forming operation of the density correction image by carried to the image forming unit performs the density correction process of the image bearing member.

  According to the present invention, since the consumption amount of the developer is calculated based on the image data before the halftone γ correction processing by the halftone γ correction processing unit, the halftone γ correction by the halftone γ correction processing unit is performed. There is almost no large error in the calculated value related to the developer consumption as in the prior art for calculating the developer consumption from the processed image data.

  Further, even if the toner density is the same, the developer consumption varies depending on the difference in the electrostatic latent image. Therefore, the density patch pattern used for density correction is the screen used for the actual density gradation processing. However, in this embodiment, the screen used in the pseudo halftone process that is performed at the time of normal image formation is used. Since the density correction process is performed using the density patch pattern, the density patch pattern used in the density correction is compared with a configuration using a density patch pattern created by means different from the screen used in the pseudo halftone process. With a simple configuration, more accurate developer consumption can be calculated.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the consumption calculation unit is a pixel of each pixel indicated by image data before halftone γ correction processing by the halftone γ correction processing unit. A storage unit that stores in advance a correspondence between a value and a weighting factor set in advance for each pixel value, and a weighting factor corresponding to the pixel value of each pixel indicated by the image data input to the halftone γ correction processing unit Is derived from the correspondence relationship stored in the storage unit, the derived weighting factor is multiplied by the pixel value of each pixel indicated by the image data, and a correction unit that outputs the multiplication value, An integration unit that integrates multiplication values output from the correction unit, and a calculation unit that calculates the consumption amount of the developer based on the integration value of the integration unit.

  According to the present invention, when the image data input to the halftone γ correction processing unit is acquired, a weighting factor corresponding to the pixel value of each pixel indicated by the image data is derived from the table, and the pixel value Since the multiplication values obtained by multiplying the weighting coefficients are integrated and the consumption amount of the developer is calculated based on the integrated value, the image data after the halftone γ correction processing by the halftone γ correction processing unit is used. Compared to the conventional technique for calculating the consumption amount of the developer, the consumption amount of the developer can be calculated more accurately.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the pseudo halftone processing unit holds in advance a plurality of screens corresponding to image forming conditions of the image forming unit. Then, pseudo halftone processing using a screen corresponding to the image forming condition of the image forming unit that is currently set is performed on the image data output from the halftone γ correction processing unit or the image data of the density correction image. The density correction processing section performs the density correction processing for each screen.

  According to the present invention, since the density correction processing is performed for each screen, it is possible to have the halftone γ correction table corresponding to each screen. Therefore, regardless of which screen is used for the pseudo halftone process, an appropriate halftone γ correction process can be performed and an accurate toner consumption amount can be calculated.

  The density correction processing by the density correction processing unit is predetermined when the main power of the image forming apparatus is turned on and in the image forming apparatus, as in the invention described in claim 4. The density correction processing may be performed at least one of the image forming operations performed on the number of recording media, or the image forming operation may be performed as in the invention according to claim 5. An environment detection unit that detects an environment of the apparatus is further provided, and the density correction processing unit performs the density correction processing when the environment detected by the environment detection unit changes beyond a predetermined amount of change. It is good to do so.

  According to the present invention, more accurate toner consumption can be detected with a simple configuration.

1 is a schematic configuration diagram of a copying machine as an embodiment of an image forming apparatus according to the present invention. 1 is a block diagram illustrating an example of an electrical configuration of a copying machine. It is a figure which shows an example of (gamma) correction curve. (A) is a figure which shows an example of a screen, (b) is a figure which shows the arrangement | sequence matrix used by screen processing. (A) is a figure for demonstrating the setting method of the on-duty about each block when performing a screen process using a screen, when the pixel value of a focused pixel is comparatively small "75", (b) These are diagrams showing an example of an image formed on a sheet when screen processing is performed using a screen when the pixel value of a pixel is “75”. (A) is a figure for demonstrating the setting method of the on-duty about each block when performing a screen process using a screen, when the pixel value of a focused pixel is relatively large "140", (b) These are diagrams showing an example of an image formed on a sheet when screen processing is performed using a screen when the pixel value of a pixel is “140”. FIG. 6 is a graph showing a relationship between a pixel value indicated by pixel data output from a pseudo halftone processing unit and a toner consumption amount. It is a figure which shows the table which a weighting coefficient table memory | storage part memorize | stores. It is a flowchart which shows a density correction process. 5 is a flowchart illustrating an image forming operation performed after density correction processing. 6 is a flowchart illustrating a toner consumption calculation process.

  Hereinafter, an image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a copying machine which is an embodiment of an image forming apparatus according to the present invention.

  As shown in FIG. 1, the copying machine 1 includes image forming units 2M, 2C, 2Y, and 2K for each color of C (cyan), M (magenta), Y (yellow), and K (black). Forming section 2) is arranged in the main body.

  The image forming unit 2 forms (prints) a color image on a sheet. The image forming units 2M, 2C, 2Y, and 2K respectively include a photosensitive drum 3 made of, for example, amorphous silicon, and the photosensitive drum 3. Are provided with a charging unit 4, an exposure unit 5, a developing unit 6, and a photosensitive member cleaning unit 7.

  The charging unit 4 uniformly charges the entire surface of the photosensitive drum 3 to a predetermined potential. The exposure unit 5 irradiates the surface of the photosensitive drum 3 with a laser beam generated based on image data transmitted from a storage unit 40 (see FIG. 2) to be described later and the like on the surface of the photosensitive drum 3. An electrostatic latent image is formed.

  The developing unit 6 makes the electrostatic latent image appear as a toner image by attaching the toner (developer) supplied from the toner supply unit 8 to the electrostatic latent image formed on the photosensitive drum 3. Is. The photosensitive member cleaning unit 7 removes toner remaining on the surface of the photosensitive drum 3 without being transferred to the intermediate belt 10 after the primary transfer of a toner image to the intermediate belt 10 described later is completed.

  Below the image forming unit 2, an intermediate transfer roller 9 (primary transfer roller) and an intermediate belt (intermediate transfer belt) 10 for performing an intermediate transfer (primary transfer) of a toner image that has become apparent on the surface of the photosensitive drum 3. Is arranged. The intermediate belt 10 is composed of a predetermined intermediate belt 10 and is endlessly rotated by the drive rollers 11 to 13 while being pressed against the photosensitive drum 3 by the intermediate transfer roller 9 disposed to face each of the photosensitive drums 3. It is configured.

  The toner images of the respective colors formed on the photosensitive drum 3 are transferred and superimposed on the intermediate belt 10 that is rotated endlessly in order of cyan, magenta, yellow, and black at the same timing. As a result, a color image composed of four colors C, M, Y, and K is formed on the intermediate belt 10.

  A secondary transfer roller 14 is provided via the intermediate belt 10 at a position facing the drive roller 13. The secondary transfer roller 14 transfers a color image on the intermediate belt 10 to a sheet by a transfer bias from a control unit 33 (see FIG. 2) described later.

  In addition, the copying machine 1 includes a paper feeding unit 15 that feeds paper toward the image forming unit 2. The paper feed unit 15 includes a paper feed cassette 151 that stores paper of each size, a transport path 152 that is a path for transporting the paper, a transport roller 153 that transports the paper in the transport path 152, and the like. The sheets taken out one by one from the paper cassette 151 are conveyed toward the position of the image forming unit 2, that is, the secondary transfer roller 14. The paper feeding unit 15 conveys the paper subjected to the secondary transfer process to the fixing unit 16 and discharges the paper subjected to the fixing process to the paper discharge tray 17 at the upper part of the copying machine main body.

  A fixing unit 16 is provided at an appropriate position downstream of the secondary transfer roller 14 in the conveyance path 152. The fixing unit 16 fixes the toner image transferred to the paper. The fixing unit 16 includes a heat roller 161 and a pressure roller 162, melts toner on the paper by the heat of the heat roller 161, and applies pressure by the pressure roller 162 to fix the toner on the paper.

  In addition, the copying machine 1 includes a static elimination cleaning 18. The neutralization cleaning 18 removes (collects) the toner (residual toner) on the intermediate belt 10. The neutralization cleaning 18 includes a cleaning electrode (not shown) and a cleaning brush (rotating brush), and a cleaning bias having a polarity opposite to the charged charge of the toner is applied to the cleaning brush by the cleaning electrode. The toner is removed by moving the toner to the cleaning brush.

  A document reading unit 20 and a document feeding unit 24 are provided at the top of the copying machine 1. The document reading unit 20 includes a scanner unit 21 including a CCD (Charge Coupled Device) sensor and an exposure lamp, and a document table 22 and a document reading slit 23 made of a transparent member such as glass.

  In the CCD, for example, three photoelectric conversion element arrays in which a plurality of photoelectric conversion elements are arranged in the main scanning direction are arranged in the sub scanning direction, for example, and an R (red) filter is arranged in one column. This is a line sensor having a configuration in which a G (green) filter is disposed in one column of the B, and a B (blue) filter is disposed in the other column. In the following description, three photoelectric conversion elements arranged in the sub-scanning direction in which R (red), G (green), and B (blue) filters are respectively arranged are referred to as one pixel. At this time, image data of each color component of R (red), G (green), and B (blue) is output from one pixel.

  The scanner unit 21 is configured to be movable by a drive unit (not shown). When reading a document placed on the document table 22, the scanner unit 21 is moved along the document surface at a position facing the document table 22 to scan the document image. The image data acquired while scanning is output to the control unit 33 (see FIG. 2). Further, when reading a document fed by the document feeding unit 24, the document is moved to a position facing the document reading slit 23, and is synchronized with the document feeding operation by the document feeding unit 24 via the document reading slit 23. The image of the original is acquired and the image data is output to the control unit 33.

  The document feeder 24 includes a document placement unit 25 for placing a document, a document discharge unit 26 for discharging a document whose image has been read, and a document placed on the document placement unit 25. A document transport mechanism 27 including a paper feed roller, a transport roller (not shown), and the like for feeding the paper one by one to a position facing the document reading slit 23 and discharging it to the document discharge section 26 is provided. The document transport mechanism 27 further includes a sheet reversing mechanism (not shown) that reverses the document and reversely transports the document to a position facing the document reading slit 23, and images on both sides of the document are passed through the document reading slit 23. Reading is possible from the scanner unit 21.

  The document feeder 24 is provided so as to be rotatable with respect to the main body so that the front side thereof can move upward. By moving the front side of the document feeder 24 upward to open the upper surface of the document table 22, the operator can place a read document, for example, a book in a spread state, on the upper surface of the document table 22. It has become.

  FIG. 2 is a block diagram illustrating an example of an electrical configuration of the copying machine 1. As shown in FIG. 2, the copying machine 1 includes a network I / F unit 30, a storage unit 40, a user interface unit 50, an image forming unit 2, and a control unit 33.

  The network I / F unit 30 controls transmission / reception of various data to / from an information processing apparatus (external device) such as a PC (personal computer) connected via a network such as a LAN. The storage unit 40 temporarily stores image data transmitted from a PC or the like via the network I / F unit 30 and image data obtained by the reading operation of the document reading unit 20.

  The user interface unit 50 is provided in the front part of the copier 1 and functions as an input key for inputting various instructions by the user or displays predetermined information. The image forming unit 2 corresponds to the image forming unit 2 shown in FIG. 1, and forms (prints) an image on a sheet based on image data stored in the storage unit 40 or the like. The density sensor 19 measures the density of the density patch formed on the intermediate belt 10, and is mainly used during density correction processing described later.

  The control unit 33 reads a ROM (Read Only Memory) for storing various control programs, a RAM (Random Access Memory) having a function of temporarily storing data and a function as a work area, and the control program and the like from the ROM. And a dedicated hardware circuit such as an ASIC (Application Specific Integrated Circuit), etc., which transmits and receives various control signals to each of the above-described units and controls the operation of the entire copying machine 1.

  The control unit 33 includes an image processing unit 331, a halftone γ correction processing unit 332, a pseudo halftone processing unit 333, a density correction processing unit 334, and a counting unit 335.

  The image processing unit 331 performs shading correction for correcting variation in image data caused by uneven illumination of the light source with respect to the document or sensitivity variation of each light receiving sensor in the CCD with respect to the image data received from the document reading unit 20. CCD line correction for correcting a shift due to the line sensor interval of each color component, chromatic aberration correction for correcting a color shift due to a difference in wavelength of each RGB color, and characteristics of an optical system (not shown) of the scanner unit 21, MTF correction that corrects “blurring” of incident light to the CCD by the system and converts it into sharp image data, color correction that performs correction to remove mixed color components included in pixel values of RGB colors for each pixel, etc. Various correction processes are performed. After these processes, the image processing unit 331 outputs C (cyan), M (magenta), and Y (yellow). K (black) image data of each color is output.

  The halftone γ correction processing unit 332 performs halftone γ correction processing for changing the tone characteristics of image data for each of the C, M, Y, and K color components. FIG. 3A shows the relationship between the pixel values indicated by the pixel data input from the image processing unit 331 to the halftone γ correction processing unit 332 on the horizontal axis and the image density on the vertical axis (hereinafter, development characteristics). The graph L1 indicated by a dotted line is a graph showing an ideal relationship, and the graph L2 is a graph showing the relationship when an error occurs. FIG. 3B shows a graph L3 showing a halftone γ correction curve used in the halftone γ correction process.

  As shown in FIG. 3A, the halftone γ correction processing is performed when the actual development characteristics (for example, development characteristics shown by the graph L2) are different from the target development characteristics (graph L1). As shown in FIG. 5, each pixel value indicated by each pixel data (hereinafter referred to as input pixel data) input to the halftone γ correction processing unit 332 is, for example, a target development characteristic (graph L1) set at the time of factory shipment. The brightness (color saturation) of the image is adjusted by converting (processing) so as to obtain the halftone γ correction curve as shown in FIG. 3 (b). Is done.

  For example, as shown in FIG. 3B, when the pixel value indicated by certain pixel data (input pixel data) acquired from the image processing unit 331 is “50”, the halftone γ correction processing unit 332 The ideal value of the density is “100”. If the actually measured image density is increased to “150”, the image density is suppressed to obtain an image density of “100”. The input pixel data having a pixel value of “50” is converted into pixel data (output pixel data) having a smaller pixel value, for example, a pixel value of “30”.

  In the present embodiment, the halftone γ correction processing unit 332 holds the relationship between the input image data and the output image data indicated by the halftone γ correction curve in the halftone γ correction table storage unit 3321 as a halftone γ correction table. When the image data is input to the halftone γ correction processing unit 332, the output image data corresponding to the input image data is stored in the halftone γ correction table stored in the halftone γ correction table storage unit 3321. Derived by reference, the input image data is converted into the derived output image data, and is output to the pseudo halftone processing unit 333 in the subsequent stage.

  As will be described later, the halftone γ correction table is updated each time density correction processing by the density correction processing unit 334 is performed. This density correction processing is performed when the image forming operation is performed on a predetermined number of sheets in the image copying machine 1 when the main power source of the copying machine 1 is turned on. In the case where a temperature detection unit and a humidity detection unit for detection are provided, the detection is performed at at least one timing when a change in temperature and humidity around the copying machine 1 exceeds a predetermined amount of change. It is good to.

  The pseudo halftone processing unit 333 performs pseudo halftone processing described below. The copying machine 1 performs an image forming operation using a block having a predetermined size (hereinafter referred to as a large block) as an image constituent unit (one pixel). Further, the copying machine 1 divides the large block into a plurality of small blocks arranged in a matrix, and performs a process of performing light irradiation operation based on the PWM signal for each small block according to the pixel value of the pixel. By carrying out, it is configured to express the density gradation of the image of one pixel. The size of the small block corresponds to the number of screen lines, and corresponds to the printing accuracy of the copying machine 1.

  In the pseudo halftone process, a screen for determining the output time of the laser beam for each small block (the on-duty value of the PWM signal (pulse signal) output to the exposure unit 5 for each small block) is used. . An example of this screen is shown in FIG. FIG. 4B shows a case where the matrix of small blocks set for one large block is a matrix composed of a total of 16 small blocks of 4 (rows) × 4 (columns). FIG. 16 is a diagram showing an array matrix in which numbers (in this case, numbers “0” to “15”) for indicating the block positions of the small blocks in the large block are assigned to the 16 small blocks.

  As shown in FIG. 4A, in the copying machine 1 of the present embodiment, a plurality of on-duty values r1 to r15 are set as on-duty values of the PWM signal (pulse signal) output to the exposure unit 5. ing. The on-duties r1 to r15 are values set so as to increase from 0% at a constant rate in order from r1, where r1 is 0 (%) and r15 is 100 (%). The on-duty of this screen is represented by a 4-bit digital signal. For each combination of the on-duty values r1 to r15 and the block position of each small block in the large block, a threshold value for the pixel value indicated by the pixel data input to the pseudo halftone processing unit 333 is set. Yes.

The pseudo halftone processing unit 333 has a screen storage unit 3331 for storing such a screen in advance. Then, the pseudo halftone processing unit 333 pays attention to the image data pixel by pixel, and uses the screen stored in the screen storage unit 3331 to set the pixel value X of the target pixel and each small block on the screen. Compared with the threshold value Y, and for each small block,
Y ≦ X (1)
The on-duty corresponding to the maximum threshold value among the threshold values Y satisfying is set as the on-duty of the pulse signal for the small block.

  Assume that the pixel value of the target pixel is “75”, for example. In this case, when the pseudo halftone process is performed using the screen shown in FIG. 4A, as shown in FIG. 5A, all threshold values set in the blocks “0” to “3” are set. Since it is smaller than the pixel value of the target pixel, the pseudo halftone processing unit 333 sets “r15” as the on-duty for these blocks.

  For the blocks “4” to “7”, only the threshold values corresponding to the on-duty “r1” to “r3” are smaller than the pixel value of the target pixel. “R3” is set as the on-duty for. Since all the threshold values set in the blocks “8” to “15” do not satisfy the formula (1), the pseudo halftone processing unit 333 sets the on-duty for these blocks to “0”. .

  In FIG. 5A, a threshold value of the pixel value of “75” or less of the pixel of interest is surrounded by a bold line. FIG. 5B shows an example of an image formed on a sheet when pseudo halftone processing is performed using the screen shown in FIG. 4A when the pixel value of the pixel is “75”. FIG.

  Next, it is assumed that the pixel value of the target pixel is “140”. In this case, when the pseudo halftone process is performed using the screen shown in FIG. 4A, as shown in FIG. 6A, all threshold values set in the blocks “0” to “7” are set. Since it is smaller than the pixel value of the target pixel, the pseudo halftone processing unit 333 sets “r15” as the on-duty for these blocks.

  For the blocks “8” to “11”, only the threshold values corresponding to the on-duty “r1” to “r3” are smaller than the pixel value of the target pixel. “R3” is set as the on-duty for. Since all threshold values set in the blocks “12” to “15” do not satisfy the formula (1), the pseudo halftone processing unit 333 sets the on-duty for these blocks to “0”. .

  In FIG. 6A, the threshold value of the pixel value of “140” or less of the pixel of interest is shown surrounded by a thick line. Further, FIG. 6B is formed on the sheet when the pseudo halftone process is performed using the screen shown in FIG. 4A when the pixel value of the pixel is “140”. It is a figure which shows an example of an image. The pseudo halftone processing unit 333 performs the above processing as pseudo halftone processing.

  The density correction processing unit 334 performs density correction processing described below. In the copying machine 1 according to the present embodiment, the characteristics of the photosensitive drum 3, the development bias, the exposure, and the like as long as the respective parts constituting the copying machine 1 maintain the same state as at the time of reference (for example, at the time of factory shipment) The relationship between the density parameter value such as the amount or the charging bias and the toner density of the toner image formed on the intermediate belt 10 is also substantially the same as that at the reference time, and the developing bias and the like are set to a predetermined value. When the developing operation is performed with the density parameter value, a toner image having the desired toner density is formed on the intermediate belt 10.

  However, when a change such as a change with time occurs in each part constituting the copying machine 1, the relationship between the value of the developing bias and the toner density of the toner image formed on the intermediate belt 10 is the reference time. Depending on the relationship, a toner image having a desired toner density may not be obtained even if the developing operation is performed with the predetermined parameter value. The density correction processing unit 334 performs processing for correcting the change in density.

  The density correction processing unit 334 first outputs a plurality of density patches having different densities to the intermediate belt 10 as a test when the main power supply of the copying machine 1 is turned on as described above. The density correction processing unit 334 causes the density sensor 19 to measure the density of the density patch formed on the intermediate belt 10 in this way, and based on the comparison between the density value of the density patch and a predetermined reference value, the density parameter It is checked whether the relationship between the value and the toner density of the toner image formed on the intermediate belt 10 has changed from that at the reference time.

  When the density correction processing unit 334 detects that the relationship between the density parameter value and the toner density has changed, the image forming operation can be stably performed even if the photosensitive drum 3 changes over time. In order to maintain a good state, density correction processing for adjusting the halftone γ correction table is performed.

  Here, the density correction processing unit 334 of the present embodiment forms the density patch formed on the intermediate belt 10 using the screen stored in the screen storage unit 3331 of the pseudo halftone processing unit 333.

  That is, in this embodiment, the target density of the density patch to be formed on the intermediate belt 10 is set in advance. For example, 10 (%), 30 (%), 50 (%), 70 (%), and 100 (%). Conventionally, image data corresponding to each density is generated in advance as density patch image data and stored in a predetermined storage unit. When performing density correction processing, the control unit reads the density patch from the storage unit. Image data is read out and the image forming operation based on the image data is executed by the image forming unit. In the present embodiment, the target density is obtained when the pseudo halftone process is performed. The pixel value obtained in advance is stored in advance in the density correction pixel data storage unit 3341 of the density correction processing unit 334 as density correction pixel data.

  When the density correction processing unit 334 forms a density patch on the intermediate belt 10 to perform the density correction process, the density correction processing unit 334 simulates the density correction pixel data stored in the density correction pixel data storage unit 3341. Output to the halftone processing unit 333.

  Accordingly, the pseudo halftone processing unit 333 derives an on-duty value for each small block from the pixel value indicated by each density correction pixel data output from the density correction processing unit 334 using the screen. The image forming unit 2 forms a density patch on the intermediate belt 10 based on the on-duty value.

  The density correction processing unit 334 causes the density sensor 19 to measure the density of each density patch formed on the intermediate belt 10, and outputs the halftone γ correction table stored in the halftone γ correction table storage unit 3321. The image data is rewritten based on the measured density of each density patch.

  The count unit 335 outputs image data (image data sequentially output from the image processing unit 331) immediately before being input to the halftone γ correction processing unit 332 when the image forming operation is performed by the image forming unit 2. The toner consumption is calculated based on the pixel values indicated by the image data, and the weight coefficient table storage unit 3351, the image data correction unit 3352, the integration unit 3353, and the toner consumption calculation unit 3354. Is provided.

  The weighting coefficient table storage unit 3351 stores a table indicating a correspondence relationship between each pixel value of image data captured by the counting unit 335 and a weighting coefficient for the pixel value.

  As shown by a graph L4 in FIG. 7, the toner consumption amount is not proportional to the pixel value indicated by the pixel data output from the pseudo halftone processing unit 333, but has a non-linear relationship as shown by a graph L5. Become. In this embodiment, the toner consumption required for a certain pixel value is used as a reference, and a weighting factor for the pixel value for eliminating the difference between the toner consumption required for each pixel value and the reference toner consumption is: For example, it is obtained in advance for each pixel value at the time of factory shipment.

The weighting coefficient table storage unit 3351 stores a table indicating the correspondence between each pixel value of image data that can be output from the image processing unit 331 and the weighting coefficient. FIG. 8 shows an example of the table. As shown in FIG. 8, a weighting factor r ₁ is associated with the pixel value g ₁ indicated by the image data output from the image processing unit 331 in the table, and is output from the image processing unit 331. A weight coefficient r ₂ is associated with the pixel value g ₂ indicated by the image data.

When the image data correction unit 3352 receives image data (pixel data) from the image processing unit 331, the image data correction unit 3352 corrects the image data using a table stored in the weight coefficient table storage unit 3351. That is, when the pixel value indicated by the image data output from the image processing unit 331 is, for example, the pixel value g ₁ , the image data correction unit 3352 derives a weighting factor r ₁ corresponding to the pixel value g ₁ from the table. , Multiplying the pixel value g ₁ by the weighting factor r ₁ . Further, when the pixel value indicated by the image data output from the image processing unit 331 is, for example, the pixel value g _2, the image data correction unit 3352 derives a weighting factor r ₂ corresponding to the pixel value g ₂ from the table The pixel value g ₂ is multiplied by the weighting factor r ₂ . The image data correction unit 3352 outputs data indicating the multiplication value to the integration unit 3353.

  The integration unit 3353 integrates pixel values (multiplication values) indicated by data sequentially output from the image data correction unit 3352.

  The toner consumption amount calculation unit 3354 calculates the toner consumption amount from the integration value calculated by the integration unit 3353 using a predetermined calculation formula. Further, the toner consumption amount calculation unit 3354 calculates the total toner consumption amount by adding the toner consumption amount calculated this time to the cumulative value of the toner consumption amount until the previous time.

  FIG. 9 is a flowchart showing the density correction process. Here, it is assumed that the density correction processing is performed when the main power supply of the copying machine 1 is turned on.

  As shown in FIG. 9, when the main power supply of the copying machine 1 is turned on (YES in step # 1), the density correction processing unit 334 performs density correction processing stored in the density correction pixel data storage unit 3341. The pixel data is output to the pseudo halftone processing unit 333, and the pseudo halftone processing using the screen stored in the screen storage unit 3331 is executed by the pseudo halftone processing unit 333. Based on the output, the image forming unit 2 performs an operation of forming a density patch on the intermediate belt 10 (step # 2), and causes the density sensor 19 to measure the density of the density patch formed on the intermediate belt 10 (step # 3). ).

  Then, the density correction processing unit 334 determines whether or not the density indicated by the density information received from the density sensor 19 has changed from the appropriate range (step # 4), and when it has changed (in step # 4). YES), the halftone γ correction table is rewritten based on the density, and the series of density correction processing is completed (step # 5). On the other hand, when the density has not changed from the appropriate range (NO in step # 4). Then, the series of density correction processing is terminated without performing Step # 5.

  FIG. 10 is a flowchart showing an image forming operation performed after the density correction processing.

  As shown in FIG. 10, when image data is output from the scanner unit 21 (YES in step # 11), the image processing unit 331 performs various correction processes such as shading correction and color correction on the image data. Then (step # 12), the halftone γ correction processing unit 332 performs halftone γ correction processing using the halftone γ correction table rewritten by the density correction processing unit 334 (step # 13).

  Next, the pseudo halftone processing unit 333 performs pseudo halftone processing using the screen stored in the screen storage unit 3331 for the image data after the halftone γ correction processing by the halftone γ correction processing unit 332. The image data after the pseudo halftone process is output to the image forming unit 2 (step # 14), and the image forming unit 2 forms the image on the sheet based on the image data after the pseudo halftone process. Operation is performed (step # 15).

  FIG. 11 is a flowchart illustrating a toner consumption calculation process.

  As shown in FIG. 11, when image data is output from the scanner unit 21 (YES in step # 21), the image processing unit 331 performs various correction processes such as shading correction and color correction on the image data. Then (step # 22), the image data correction unit 3352 of the counting unit 335 acquires the image data after the correction processing (step # 23).

  The image data correction unit 3352 corrects each pixel data using the weighting coefficient stored in the weighting coefficient table storage unit 3351 with respect to the acquired image data (step # 24), and the integration unit 3353 The corrected pixel data is accumulated in the image data correction unit 3352 (step # 25).

  The toner consumption amount calculation unit 3354 determines whether or not the pixel data integration process for a series of documents has been completed (step # 26), and if not completed (NO in step # 26), step # 21. On the other hand, if completed (YES in step # 26), the toner consumption amount is calculated based on the integrated value of the pixel data by the integration unit 3353, and the cumulative value of the toner consumption amount is calculated (step # 27). ).

  With the configuration as described above, in this embodiment, the toner consumption amount is calculated immediately before being input to the halftone γ correction processing unit 332 instead of the image data after the halftone γ correction processing by the halftone γ correction processing unit 332. By performing based on the image data, it is possible to calculate the toner consumption more accurately than in the conventional configuration.

  That is, as described above, the image data after the halftone γ correction processing by the halftone γ correction processing unit 332 is set so as to obtain a target density according to the current characteristics and development characteristics of the photosensitive drum 3. For the calculated image data, for example, an arithmetic expression set based on the characteristics and development characteristics of the photosensitive drum 3 at the time of factory shipment is used to calculate the toner consumption.

  Therefore, from the image data after the halftone γ correction processing by the halftone γ correction processing unit 332 so that the target density can be obtained according to the current characteristics and development characteristics of the photosensitive drum 3, for example, at the time of shipment Even if the toner consumption is calculated using an arithmetic expression set based on the characteristics and development characteristics of the photosensitive drum 3, the accurate toner consumption is not calculated, and there is a large error from the actual toner consumption. It will be a thing.

  On the other hand, in the image processing in the image processing unit 331, since the values of various parameters are not affected by the characteristics of the photosensitive drum 3 and the development characteristics, the image data output from the scanner unit 21 is not changed. If they are the same, substantially the same image data is output as the image data after image processing by the image processing unit 331 both at the time of factory shipment and after that.

  Therefore, in the present embodiment, image data after image processing by the image processing unit 331 (image data before halftone γ correction processing by the halftone γ correction processing unit 332) is used as image data used for calculating the toner consumption. By adopting it, it is possible to calculate the toner consumption more accurately than in the conventional configuration.

  Further, even if the toner density is the same, the developer consumption varies depending on the difference in the electrostatic latent image. Therefore, the density patch pattern used for density correction is the screen used for the actual density gradation processing. However, in this embodiment, the pseudo halftone processing unit 333 implements the density patch used for density correction. Since it was created using the screen used in the pseudo halftone process, the density patch pattern used in the density correction was created by means different from the screen used in the pseudo halftone process performed during normal image formation. Compared to the case of using a density patch pattern, more accurate toner consumption can be calculated.

  In this case, the following modifications may be employed instead of or in addition to the embodiment.

  [1] In the first embodiment, one type of screen is stored in the screen storage unit 3331, and the configuration in which pseudo halftone processing is performed using this screen has been described. A plurality of screens are stored in the screen storage unit 3331 in accordance with the image forming conditions of the image forming unit 2 including image attributes such as an image area and image quality modes such as high image quality mode / low image quality mode. In some cases, pseudo halftone processing is performed on the image data output from the halftone γ correction processing unit 332 using a screen corresponding to the image forming conditions of the image forming unit that is currently set.

  In this case, the density correction processing may be performed for each screen (a halftone γ correction table is created). Even when there are a plurality of screens and halftone γ correction tables in this way, C For each color of (cyan), M (magenta), Y (yellow), and K (black), pixel data may be integrated to calculate the toner consumption.

  [2] The density correction processing is performed when the main power supply of the copying machine 1 is turned on, when an image forming operation is performed on a predetermined number of sheets in the image copying machine 1, In the case where an environment detection unit such as a temperature detection unit or a humidity detection unit that detects the environment, for example, temperature or humidity, is provided, changes in the temperature and humidity around the copying machine 1 exceed a predetermined amount of change. In addition to at least one timing at a certain time, when a personal computer is communicably connected to the copier 1, density correction is performed when a user issues an instruction to start density correction processing via the personal computer. Processing may be performed.

DESCRIPTION OF SYMBOLS 1 Copier 2 Image forming part 21 Scanner part 331 Image processing part 332 Halftone gamma correction processing part 3321 Halftone gamma correction table storage part 333 Pseudo halftone processing part 3331 Screen storage part 334 Density correction processing part 3341 Density correction pixel data Storage unit 335 Count unit 3351 Weight coefficient table storage unit 3352 Image data correction unit 3353 Integration unit 3354 Toner consumption calculation unit

Claims (5)

An image forming unit that forms an image on a recording medium using a developer;
A halftone γ correction processing unit for performing halftone γ correction processing using a halftone γ correction table on image data;
A pseudo halftone processing unit that performs pseudo halftone processing using a screen on image data after halftone γ correction processing or image data of density correction images output from the halftone γ correction processing unit;
The halftone γ correction table is formed based on the density of the density correction image formed on the image carrier by causing the image forming unit to perform a density correction image forming operation on the image carrier using the screen. A density correction processing unit that performs density correction processing for correcting
A consumption amount calculation unit that calculates the consumption amount of the developer based on the image data before the halftone γ correction processing by the halftone γ correction processing unit ,
One pixel of the image data is composed of a plurality of blocks, and each block is given a block number corresponding to a block position in one pixel,
The screen is data that associates the block number with a plurality of threshold values associated with output times of laser light,
The pseudo halftone processing unit compares the pixel value of the target pixel in the image for density correction with the threshold value of the screen, and based on the comparison result, the output time of the laser light of each block constituting the target pixel By determining, execute a pseudo halftone process for determining the output time of the laser light of a plurality of blocks included in each pixel of the image for density correction,
The density correction processing unit uses the output time of the laser light determined by the pseudo halftone processing unit for the image data of the density correction image, and irradiates a laser beam to density correction image on the image carrier. The image forming apparatus performs the density correction processing by causing the image forming unit to perform the image forming operation . The consumption calculation unit
A storage unit for preliminarily storing a correspondence relationship between a pixel value of each pixel indicated by image data before the halftone γ correction processing by the halftone γ correction processing unit and a weighting factor set in advance for each pixel value;
A weighting factor corresponding to a pixel value of each pixel indicated by image data input to the halftone γ correction processing unit is derived from the correspondence relationship stored in the storage unit, and the derived weighting factor is A correction unit that multiplies the pixel value of each pixel indicated by the image data and outputs the multiplication value;
An integration unit for integrating the multiplication values output from the correction unit;
The image forming apparatus according to claim 1, further comprising: a calculating unit that calculates a consumption amount of the developer based on an integrated value of the integrating unit. The pseudo halftone processing unit holds a plurality of screens corresponding to the image forming conditions of the image forming unit in advance, and the image data output from the halftone γ correction processing unit or the image data of the density correction image In contrast, pseudo halftone processing using a screen corresponding to the image forming conditions of the image forming unit that is currently set,
The image forming apparatus according to claim 1, wherein the density correction processing unit performs the density correction process for each screen.   The density correction processing unit is configured to display the density at least one of when a main power source of the image forming apparatus is turned on and when an image forming operation is performed on a predetermined number of recording media in the image forming apparatus. The image forming apparatus according to claim 1, wherein correction processing is performed. An environment detection unit for detecting the environment of the image forming apparatus;
4. The density correction processing unit performs the density correction processing when the environment detected by the environment detection unit changes beyond a predetermined amount of change. 5. The image forming apparatus described in 1.

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