JP4706293B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine, a printer, a facsimile machine, and a multifunction machine of these.

  Some image forming apparatuses include a photosensitive drum and a developing device as a set of image forming units, and a plurality of sets thereof are arranged in tandem. Such a tandem type image forming apparatus includes a photosensitive drum of each image forming unit. An electrostatic latent image is formed by exposing each of the body drums, and the electrostatic latent image is developed by a developing device to form a toner image of a predetermined color for each image forming unit. IBT (Intermediate Belt Transfer) module After each toner image is primarily transferred to the belt, the toner image is secondarily transferred to paper (recording paper, recording medium) by a secondary transfer unit, and fixed by a fixing device to form a color image.

  Since image reproducibility fluctuates due to changes in the environment in which the device is placed and deterioration of the photosensitive drum and developer over time, the image density can be controlled by monitoring the image density to control the image density. The method of keeping in place is widely performed. Various specific configurations of the method have been proposed. For example, without outputting a dedicated sheet for density measurement, the density of the image density measurement patch after fixing is measured, and the measurement result is reflected in the density measurement result of the density measurement patch in the unfixed state to form an image. A technique for obtaining a high-quality image by controlling conditions is disclosed (for example, see Patent Document 1).

JP 2003-173063 A (page 7, FIG. 9)

  Here, some image forming apparatuses include a secondary fixing device (high gloss processing device) in order to increase the image glossiness on the paper after the primary fixing. When measuring the density of the image density measurement patch in such an image forming apparatus, there may be a case where the above-described technique cannot measure the density accurately. That is, the density of the image density measurement patch is detected and measured as a combined light amount of the light amount directly reflected from the toner surface and the light amount that enters the toner and then returns to the color material. Since the amount of directly reflected light depends on the glossiness of the toner surface, the detected density of the image density measurement patch after high gloss processing varies depending on the magnitude of the glossiness. For this reason, it is difficult to measure the exact density of the patch on the paper with the above-described conventional technology, and there is a risk that the control of the image forming conditions cannot be performed accurately.

The present invention has been made to solve the technical problems as described above. The object of the present invention is to control the image forming conditions and the fixing conditions in consideration of the glossiness. It is to obtain high image quality.
Another object is to increase the accuracy of control of image forming conditions and fixing conditions for high glossy paper.

For this purpose, an image forming apparatus to which the present invention is applied includes an image forming unit that forms a toner image under predetermined image forming conditions and transfers the toner image to a sheet, and a toner image transferred to the sheet by the image forming unit. Fixing means for fixing under a predetermined fixing condition; first measuring means for measuring the amount of specularly reflected light and / or diffusely reflected light by irradiating the toner image in a state before being fixed by the fixing means; and paper by the fixing means A second measuring unit that measures the amount of specularly reflected light by irradiating the toner image after being fixed thereon; a predetermined image forming condition and a predetermined amount based on the measurement results of the first measuring unit and the second measuring unit; viewed contains a control unit, the controlling the fixing condition, the first measuring means and second measuring means measures the same area of the toner image, the control means, the measurement of the same area by the first measuring means In the result Zui calculates the proper value of the second measuring means, characterized in that to control the predetermined fixing condition based on the measurement result in the same region by proper value and second measuring means calculated.
Here, the image forming apparatus further includes a high gloss processing unit that performs high gloss processing under a predetermined gloss processing condition after being fixed by the fixing unit, and the second measurement unit calculates the image density after the high gloss processing by the high gloss processing unit. The measurement and control unit controls a predetermined image forming condition and a predetermined fixing condition or / and a predetermined gloss processing condition based on the measurement result by the first measuring unit and the second measuring unit. be able to.

From another point of view, the image forming apparatus to which the present invention is applied includes an image forming unit that forms a toner image under a predetermined image forming condition and transfers the toner image onto a sheet, and a toner image that is transferred onto the sheet by the image forming unit. A primary fixing means for fixing the toner image under a predetermined primary fixing condition, a secondary fixing means for fixing the paper fixed by the primary fixing means under a predetermined secondary fixing condition, and a state before being fixed by the secondary fixing means. First measurement means for measuring the image density of the toner image, second measurement means for measuring the image density of the paper after being fixed by the secondary fixing means, first measurement means, and second measurement means Control means for controlling at least one of a predetermined image forming condition, a predetermined primary fixing condition, and a predetermined secondary fixing condition on the basis of the measurement result of the above.
Here, the image forming apparatus further includes conversion means for converting the measurement result by the first measurement means into the image density of the paper after being fixed by the secondary fixing means, and the control means replaces the measurement result by the second measurement means. In addition, it is possible to use the conversion result by the conversion means.

Further, from another point of view of the present invention, an image forming apparatus to which the present invention is applied includes an image forming unit that forms a toner image under a predetermined image forming condition and transfers the toner image to a sheet, and the image forming unit transfers the sheet to the sheet. Fixing means for fixing the toner image under a predetermined fixing condition; first measuring means for measuring the amount of specularly reflected light irradiated on the toner image after being fixed by the fixing means; and fixing by the fixing means A second measuring unit that measures the amount of diffusely reflected light applied to the toner image in a state after being applied, and a predetermined image forming condition or / or based on a measurement result by the first measuring unit and the second measuring unit And control means for controlling predetermined fixing conditions.
Here, the first measuring unit and the second measuring unit measure the same region in the toner image. In addition, the first measuring means and the second measuring means are integrally formed.

  Further, from another point of view of the present invention, an image forming apparatus to which the present invention is applied includes an image forming unit that forms a toner image under a predetermined image forming condition according to an instruction content, and transfers the toner image onto a sheet. Fixing means for fixing a predetermined number of times of fixing on a sheet on which a toner image has been transferred by the means under a predetermined fixing condition, and an image density of the paper on which fixing is performed less than the predetermined number of fixing times Based on the value converted by the conversion means, the conversion means for converting the image density measured by the measurement means into the image density of the paper when fixing is performed for a predetermined number of times, And control means for controlling predetermined image forming conditions and predetermined fixing conditions in the instruction content.

  Further, from another point of view of the present invention, the image forming condition and fixing condition control method to which the present invention is applied is that after a toner image is formed under a predetermined image forming condition and transferred to a sheet according to the instruction content. An image forming condition and a fixing condition control method for controlling a predetermined image forming condition and a predetermined fixing condition of an image forming apparatus that performs fixing for a predetermined number of times in accordance with an instruction content under a predetermined fixing condition. , Measure the image density of the paper that has been fixed a number of times less than the predetermined number of fixings according to the instruction content, determine whether the measured image density of the paper is within a predetermined threshold, and measure When it is determined that the image density of the printed paper is not within the predetermined threshold, the image density of the paper that has been fixed less than the number of times of fixing related to the paper is measured again after density adjustment, and is measured or remeasured. Paper image When it is determined that the degree is within a predetermined threshold, the image density is converted to the image density of the paper when fixing is performed a predetermined number of times, and the predetermined content in the instruction content is converted based on the converted image density. The image forming conditions and / or predetermined fixing conditions are controlled.

  According to the present invention, the image forming conditions are controlled while taking the glossiness into account, so that a higher quality image can be obtained.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
First Embodiment First, an image forming apparatus according to a first embodiment will be described with reference to FIGS.
FIG. 1 is a diagram showing the overall configuration of the image forming apparatus according to the first embodiment, and shows a so-called tandem type digital color printer. An image forming apparatus shown in FIG. 1 includes an image processing system 10 that forms an image corresponding to gradation data of each color, a sheet conveyance system 40 that conveys a recording medium (a sheet member such as paper), and the like. For example, an IPS (Image Processing System) 50 and a controller 55 that are connected to a personal computer, an image reading apparatus, and the like and perform predetermined image processing on received image data, and a double-sided original or a single-sided original An image reading device (document reading device, IIT (Image Input Terminal)) 60 for reading an image, and a gloss processing device (high gloss processing device, which glosses the toner image surface (recording surface) on the recording medium to make it glossy. Secondary fixing device) 70. Moreover, the control part 80 which controls operation | movement of each apparatus (each part) is provided.

  The image processing system 10 includes four image forming units 11Y, 11M, yellow (Y), magenta (M), cyan (C), and black (K) arranged in parallel at a certain interval in the horizontal direction. 11C and 11K. Further, the transfer unit 20 that multiplex-transfers toner images of respective colors formed on the photosensitive drums 12 of the image forming units 11Y, 11M, 11C, and 11K onto the intermediate transfer belt 21, and the image forming units 11Y, 11M, 11C, and 11K. Is provided with a ROS (Raster Output Scanner) 30 which is an optical system unit for irradiating a laser beam. Further, the image (toner image) on the recording medium secondarily transferred by the transfer unit 20 is fixed to the main body 1 on the recording medium using heat and pressure roller 29a and pressure roller 29b, for example. A fixing device 29 is provided. Further, each of the image forming units 11Y, 11M, 11C, and 11K includes a developing device 13 and a small charger 14 called a BCR (Bias Charge Roll) (see FIG. 2). In addition, toner cartridges 19Y, 19M, 19C, and 19K are provided for supplying toner of each color to the developing device 13 of the image forming units 11Y, 11M, 11C, and 11K.

  Each color toner supplied to the toner cartridges 19Y, 19M, 19C, and 19K is melted, kneaded, pulverized, classified, or polymerized with polyester resin, colorant (dye, sublimation dye), charge control material, and the like. It is manufactured by. In order to transfer the toner image formed on the image bearing member onto the intermediate transfer member or the recording medium, an external additive having releasability can be added. In consideration of offset resistance, fixing properties, and sharp melt properties, color toners using a polyester resin as a binder resin are particularly preferable.

  On the other hand, the transfer unit 20 includes a drive roller 22 that drives an intermediate transfer belt 21 that is an intermediate transfer member, a tension roller 23 that applies a certain tension to the intermediate transfer belt 21, and a toner image of each superimposed color on a recording medium. A backup roller 24 for the next transfer and a cleaning device 25 for removing residual toner and the like existing on the intermediate transfer belt 21 are provided. The intermediate transfer belt 21 is wound around the drive roller 22, the tension roller 23, and the backup roller 24 with a constant tension, and is driven to rotate by a dedicated drive motor (not shown) having excellent constant speed. The drive roller 22 is driven to circulate at a predetermined speed in the direction of the arrow. As the intermediate transfer belt 21, for example, a belt whose resistance is adjusted with a belt material (rubber or resin) that does not cause charge-up is used. The cleaning device 25 includes a cleaning brush 25a and a cleaning blade 25b, and removes residual toner, paper dust, and the like from the surface of the intermediate transfer belt 21 after the toner image transfer process is completed, and performs the next image forming process. It is comprised so that it may prepare for.

  In addition to a semiconductor laser and a modulator (not shown), the ROS 30 includes a polygon mirror 31 that deflects and scans laser light (LB-Y, LB-M, LB-C, and LB-K) emitted from the semiconductor laser. In the example shown in FIG. 1, since the ROS 30 is provided below the image forming units 11Y, 11M, 11C, and 11K, there is a risk of contamination due to dropping of toner or the like. Accordingly, the ROS 30 is provided with a rectangular parallelepiped frame 32 for sealing each constituent member, and a glass window 33 through which the laser light (LB-Y, LB-M, LB-C, LB-K) passes. Is provided above the frame 32 to enhance the shielding effect together with the scanning exposure.

  The sheet conveyance system 40 includes a sheet feeding device 41 that stacks and supplies a recording medium (sheet) on which an image is recorded, a nudger roller 42 that picks up and supplies the recording medium from the sheet feeding device 41, and a recording medium that is supplied from the nudger roller 42. Are provided with a feed roller 43 that separates and conveys the recording medium one by one, and a conveyance path 44 that conveys the recording medium separated one by one by the feed roller 43 toward the image transfer unit. Further, a registration roller 45 that conveys the recording medium conveyed through the conveyance path 44 in time toward the secondary transfer position, and a backup roller 24 that is provided at the secondary transfer position and is in pressure contact with the recording medium. And a secondary transfer roller 46 for secondary transfer of the image. Further, a discharge tray (not shown) on which the recording medium on which the toner image is fixed and discharged by the fixing device 29 is stacked, and after the toner image is fixed by the fixing device 29, the gloss processing device 70 described later performs gloss processing and discharges. And a discharge tray 48 (see FIG. 2) on which the recording medium to be loaded is loaded. Further, a branching portion 49 (see FIG. 2) is provided in front of the paper discharge tray 48 for switching the recording medium conveyance path.

  Next, the operation of the image forming apparatus shown in FIG. 1 will be described. The color material reflected light image of the original read by the image reading device 60 and the color material image data formed by a personal computer (not shown) are, for example, R (red), G (green), and B (blue). It is input to the IPS 50 as 8-bit reflectance data. In IPS 50, the input reflectance data is subjected to predetermined image processing such as various image editing such as shading correction, position shift correction, brightness / color space conversion, gamma correction, frame deletion, color editing, and moving editing. Is done. The image data that has been subjected to image processing is converted into color material gradation data of four colors of yellow (Y), magenta (M), cyan (C), and black (K), and is output to the ROS 30.

In the ROS 30, laser light (LB-Y, LB-M, LB-C, LB-K) emitted from a semiconductor laser (not shown) is changed to f-θ according to the input color material gradation data. The light is emitted to the polygon mirror 31 through a lens (not shown). In the polygon mirror 31, the incident laser light is modulated in accordance with gradation data of each color, deflected and scanned, and image forming units 11Y, 11M, 11C, and 11K through an imaging lens (not shown) and a plurality of mirrors. The photosensitive drum 12 is irradiated. On the photosensitive drums 12 of the image forming units 11Y, 11M, 11C, and 11K, the surface charged by the charger 14 is scanned and exposed to form an electrostatic latent image. The formed electrostatic latent image is developed as a toner image of each color of yellow (Y), magenta (M), cyan (C), and black (K) in each of the image forming units 11Y, 11M, 11C, and 11K. Is done.
The toner images formed on the photosensitive drums 12 of the image forming units 11Y, 11M, 11C, and 11K are multiple-transferred onto an intermediate transfer belt 21 that is an intermediate transfer member. At this time, the black image forming unit 11 </ b> K that forms a black toner image is provided on the most downstream side in the moving direction of the intermediate transfer belt 21, and the black toner image is finally transferred to the intermediate transfer belt 21. Is done.

  On the other hand, in the sheet conveying system 40, the nudger roller 42 rotates in synchronization with the image formation timing, and a recording medium of a predetermined size is supplied from the paper feeding device 41. The recording medium separated one by one by the feed roller 43 is conveyed to the registration roller 45 through the conveyance path 44 and is temporarily stopped. Thereafter, the registration roller 45 rotates in accordance with the movement timing of the intermediate transfer belt 21 on which the toner image is formed, and the recording medium is conveyed to the secondary transfer position formed by the backup roller 24 and the secondary transfer roller 46. . On the recording medium conveyed from the lower side to the upper side at the secondary transfer position, the toner images in which the four colors are multiplexed are sequentially transferred in the sub-scanning direction using a pressing force and a predetermined electric field. The recording medium on which the toner image of each color is transferred is discharged to the discharge tray 47 after being subjected to a fixing process with heat and pressure by the fixing device 29. Further, for example, when gloss processing such as a digital camera photograph is required, the branching unit 49 is operated to switch the transport path, whereby the recording medium is transported to the gloss processing device 70 and subjected to gloss processing, and then the discharge tray. 48 is discharged.

Next, the gloss processing device 70 will be described.
As shown in FIG. 2, the gloss processing device 70 includes a fixing roll 70a, a pressure roll 70b, a fixing belt 70c, a cooling device 70d, a peeling roll 70e, and a tension roll 70f. The fixing belt 70c is stretched around a peeling roll 70e and a tension roll 70f. The fixing belt 70c is further circulated by following the rotating fixing roll 70a. The fixing roll 70a is rotated in the transport direction by a driving device (not shown).

The fixing belt 70c is a member in which, for example, a highly smooth coating layer made of fluorine rubber, silicon rubber, or the like is formed on the surface of an endless film made of thermosetting polyimide. The thickness of the coating layer of the fixing belt 70c is desirably about 35 μm, and the thickness of the polyimide base layer is desirably about 70 μm.
The recording medium is heated in the fixing nip region formed by the fixing roll 70a and the pressure roll 70b via the fixing belt 70c. As a result, the toner and the image receiving layer of the recording medium are in a molten state on the recording medium, and in this state, the toner image surface of the recording medium is finished smoothly by being in close contact with the fixing belt 70c.
The cooling device 70d is provided on the inner peripheral surface of the fixing belt 70c in a section between the fixing roll 70a and the peeling roll 70e. The cooling device 70d contacts the inner peripheral surface of the fixing belt 70c and absorbs heat of the fixing belt 70c. As a result, the recording medium heated in the nip region is cooled. Although the cooling temperature of the cooling device 70d varies depending on the type of toner and recording medium used, it is desirable to cool the recording medium so that the toner image surface of the recording medium is about 60 to 80 ° C.
By cooling the recording medium in this manner, the toner and the image receiving layer on the surface of the recording medium, which will be described later, are solidified while maintaining smoothness, so that the recording medium can be easily peeled off from the fixing belt 70c.

  Here, the tension roll 70f is provided to correct a bias (a phenomenon in which the fixing belt 70c moves toward one end of the tension roll 70f) that occurs when the fixing belt 70c is continuously circulated. It has been. One end of the central axis of the tension roll 70f is fixed (hereinafter referred to as “fixed end”), and the other end is movable with respect to the fixing roll 70a (hereinafter referred to as “moving end”). Called). For example, when the fixing belt 70c is gradually biased toward the fixed end, the bias is corrected by moving the moving end. On the contrary, when the fixing belt 70c is gradually biased toward the moving end, the bias is corrected by moving the moving end in the opposite direction.

The peeling roll 70e rotates following the movement of the fixing belt 70c. By changing the moving direction of the fixing belt 70c by stretching the peeling roll 70e while winding the fixing belt 70c, the recording medium is naturally peeled at this position by the rigidity of the recording medium itself. The outer diameter of the peeling roll 70e and the winding angle α of the fixing belt 70c are determined according to the rigidity of the recording medium and the adhesive force between the recording medium and the fixing belt 70c.
The fixing roll 70a is a member in which a release layer made of a PFA tube or the like is formed around a metal core having high thermal conductivity. Further, a heat source such as a halogen lamp is provided inside the core of the fixing roll 70a. The surface of the fixing roll 70a is heated to a predetermined temperature (120 to 190 ° C. in this embodiment, depending on the melting temperature of the toner and the image receiving layer). As a result, the toner image surface of the conveyed recording medium is heated in the nip region.

In the pressure roll 70b, an elastic body layer made of silicon rubber or the like having a rubber hardness of about 40 ° is coated around a metal core having high thermal conductivity. A release layer similar to the release layer of the fixing roll 70a is formed on the surface of the pressure roll 70b. Further, a heat source such as a halogen lamp is provided inside the core of the pressure roll 70b, and the surface of the pressure roll 70b is heated to a predetermined temperature. The pressure roll 70b heats the conveyed recording medium from the back surface in the nip region and presses it with a predetermined pressure in the direction of the fixing roll 70a.
Note that a cutting device for cutting the edge portions on the four sides of the recording medium fixed with high smoothness and high gloss may be provided. In other words, before discharging to the discharge tray 48, it may be considered that the edge of the four sides of the recording medium is cut so that an image is printed on the entire surface of the recording medium so as to perform so-called borderless printing. It is done.

FIG. 2 is a schematic configuration diagram for explaining various sensors built in the main body 1 of the image forming apparatus.
As shown in FIG. 2, each developing device 13 of the image forming units 11Y, 11M, 11C, and 11K detects the internal toner density and keeps the toner density (mixing ratio of toner and magnetic carrier) constant. ATC (Auto Toner Concentration Control) sensor (toner density detection sensor) 91 is attached. A patch density sensor 92 for measuring the density of the toner image on the intermediate transfer belt 21 (toner image density) is attached downstream of the image forming unit 11K and upstream of the tension roller 23. A patch density sensor 93 that measures the density of the toner image transferred to the recording medium is attached between the fixing device 29 and the backup roller 24. In addition, a patch density sensor 94 that measures the image density of the recording medium that has been glossy processed by the gloss processing apparatus 70 is attached between the gloss processing apparatus 70 and the discharge tray 48.

FIG. 3 is a block diagram of the IPS 50, the controller 55, and the control unit 80.
As illustrated in FIG. 3, the IPS 50 includes an automatic tone correction LUT (Look Up Table) calculation unit 51, a copy LUT synthesis unit 52, and a copy LUT application unit 53. The controller 55 also includes an automatic gradation correction LUT 56 for printing, an IOT (ADC (Auto Density Control)) LUT 57, a printer LUT synthesis unit 58, and a printer LUT application unit 59. Further, the control unit 80 controls the toner based on the detection result of the Vh (BCR voltage) control unit 81 for controlling the charging potential Vh or the BCR voltage of the charger 14 (see FIG. 2) and the ATC sensor 91 (see FIG. 2). And a toner cartridge controller 82 for controlling the cartridges 19Y, 19M, 19C, and 19K and detecting an empty test. Further, the control unit 80 is based on the detection result of the LD light quantity control unit 83 that controls the LD light quantity of the ROS 30 based on the detection result of the patch density sensor 92 (see FIG. 2) and the patch density sensor 92 (see FIG. 2). And a gradation control unit 84 that outputs a gradation control signal to the IOT (ADC) LUT 57.
Here, in general, when image data handled in a computer is output by an image output device such as a printer, various types of image processing such as color conversion processing, halftone processing, gradation correction processing, and the like are performed on the image data. Applied. In this gradation correction processing, the density characteristics and colorimetric characteristics of the output result when the input values are sequentially changed depend on the output characteristics of the image output device such as the printer engine or the toner color material. This is a process of performing gradation correction according to the output characteristics on the input image data and converting the input image data into output image data for obtaining a desired output result. Here, the desired gradation image output is an output in which the density characteristics and colorimetric characteristics of the output result for the input image data are linear or similar, and no density jump or density inversion occurs. I mean.
Such gradation correction processing is normally performed based on a gradation correction curve that defines the relationship between input image data and output image data. Then, one gradation correction curve is created in advance for the same model and the same mode according to the output characteristics of the image output apparatus, and this is an image processing apparatus that performs gradation correction processing, for example, in a computer that handles image data or its The image data is held and stored in an image processing apparatus in the image output apparatus that outputs image data.

As shown in FIG. 3, the automatic gradation correction LUT calculation unit 51 of the IPS 50 acquires gradation correction data from the image reading apparatus (IIT) 60, and the copy LUT synthesis unit 52 and the automatic gradation correction LUT 56 for printing. Output to. The copy LUT combining unit 52 combines the copy LUT using information from the automatic gradation correction LUT calculating unit 51 and the IOT (ADC) LUT 57 and outputs the combined LUT to the copy LUT applying unit 53. The copy LUT application unit 53 outputs a control signal to the ROS 30 (see FIG. 1). The IOT (ADC) LUT 57 acquires a gradation control signal from the gradation controller 84 of the controller 80.
The printer LUT combining unit 58 combines the printer LUT using information from the automatic print gradation correction LUT 56 and the IOT (ADC) LUT 57 and outputs the combined LUT to the printer LUT applying unit 59.

FIG. 4 is a flowchart showing a procedure for controlling the toner density and the glossiness. FIG. 5 is a graph showing the relationship between the image density and the glossiness, where the vertical axis represents the image density SNR output and the horizontal axis represents the glossiness.
As shown in FIG. 4, a control patch is formed on the intermediate transfer belt 21 by the control unit 80 (step 101), and the toner image density of the control patch on the intermediate transfer belt 21 is determined by a patch density sensor 92 (see FIG. 2). (Step 102). Then, based on the detection result of the patch density sensor 92 (see FIG. 2), it is determined whether or not toner image density control is necessary (step 103). That is, the control unit 80 compares the detection result S ₁ of the patch density sensor 92 (see FIG. 2) with a predetermined target value T ₁ (value based on the input image density (Cin)%), and the difference Δ ₁ (= S ₁₋ T ₁ ) is calculated, and it is determined whether or not the difference Δ ₁ is within an allowable range. When it is determined that the toner image is within the allowable range, the toner image density control is not necessary. However, when it is determined that the toner image exceeds the allowable range, the toner image density control factor is controlled (step 104). Return to. As shown in FIG. 5, when the toner amount is large or small, the toner amount can be adjusted to an appropriate value by controlling the toner image density.
An example of the toner image density control factor here is the toner density in the developing device 13, the exposure light amount of the photosensitive drum 12 by the ROS 30, the developing bias, the charging voltage of the photosensitive drum 12 by the charger 14, and the image digital. At least one of the signals. As described above, by detecting the toner image density of the control patch before being transferred to the recording medium, necessary toner amount correction is performed to control the toner image density to a predetermined target value. It is also conceivable to detect the toner image density of the unfixed control patch transferred to the recording medium by the patch density sensor 93 (see FIG. 2). It is also conceivable that the toner image density of the control patch fixed by the fixing device 29 is detected by a patch density sensor (not shown).

  After performing necessary corrections on the toner image density, the control unit 80 calculates an appropriate image density after secondary fixing (gloss processing) corresponding to the detected toner image density of the control patch (step 105). That is, a process for obtaining the image density of the control patch after the gloss process from the toner density detected by the patch density sensor 92 is performed. The toner image density before the gloss process (on the intermediate transfer belt 21) and the image density after the gloss process have a linear relationship as shown in FIG. Therefore, if the relationship between the two is ascertained in advance through experiments or the like and a conversion table is prepared, for example, the image density after gloss processing can be obtained from the toner image density before gloss processing.

Thereafter, the control unit 80 detects the toner image density of the control patch on the paper after the secondary fixing (gloss processing) by the patch density sensor 94 (step 106), and controls the glossiness based on the calculation result and the detection result. Is determined whether it is necessary (step 107). That is, the difference Δ ₂ is allowed after the difference Δ ₂ (= S ₂ −T ₂ ) is calculated by comparing the detection result S ₂ of the patch density sensor 94 (see FIG. 2) with the calculated appropriate concentration T _2. It is determined whether it is within the range. When it is determined that the value is within the allowable range, the process ends as it is. When it is determined that the value exceeds the allowable range, the gloss control factor is controlled (step 108), and then the process returns to step 101. That is, when the allowable range is exceeded, as shown in FIG. 5, it is a case where the glossiness is insufficient or the glossiness is excessive. By controlling the glossiness control factor, an appropriate glossiness can be obtained. .
Examples of the gloss control factor include fixing conditions such as the fixing temperature, fixing speed, and fixing pressure of the fixing device 29. The glossiness can be controlled by any one or a combination thereof. Further, in the case of a configuration in which the secondary fixing is not illustrated in which surface treatment is performed by overcoating the coating agent on the recording medium fixed by the fixing device 29, the amount of the coating agent can be used as a glossiness control factor.

  The flowchart shown in FIG. 4 is summarized as follows. Comparing the measured image density before primary fixing with a predetermined target value and correcting the image forming conditions, image data, etc. so that the same reading density is obtained, so that the toner amount of the image becomes a predetermined target value. Control. Further, the glossiness of the image after secondary fixing is calculated from the measured image density value after secondary fixing (gloss processing) and the measured image density value before primary fixing. The calculated glossiness value of the secondary fixed image is compared with a specified target glossiness value, and glossiness control factors such as fixing temperature, fixing speed, and fixing pressure are controlled so as to obtain the same glossiness value.

As described above, in the present embodiment (first embodiment), in an image forming apparatus that performs primary fixing and secondary fixing (gloss processing) on a toner image formed on a recording medium, the image density before primary fixing The image density on the recording medium after the secondary fixing is measured, and the image forming conditions, the fixing conditions and / or the gloss processing conditions are controlled to control the density and the glossiness with high accuracy. The density of the image includes the amount of light directly reflected from the toner surface on the recording medium (which depends on the glossiness of the toner surface) and the amount of light that enters the toner and then reflects back to the color material (color material). And the amount of light that depends on the amount of toner). That is, in the density detection before fixing, although the toner amount can be detected, the density changes depending on the fixing surface state (glossiness). On the other hand, in the density detection after fixing, both the toner amount and the fixing surface quality are detected. A combination of conditions results in a density value. For this reason, when detecting the density of a fixed image, it is difficult to accurately measure the amount of toner on the recording medium depending on the level of glossiness.
Therefore, after measuring the toner amount accurately by measuring the density of the toner image (toner itself) before fixing with a stable glossiness, the density of the toner image after fixing is measured. Thus, the toner amount and the glossiness are accurately measured based on the above information. In other words, the toner amount on the recording medium and the fixing surface state (glossiness) information can be obtained by detecting the density values before and after fixing. And by controlling with each control factor based on these information, the image quality of the target toner amount and toner glossiness can be ensured.

As the density measurement value before the primary fixing, the measurement value by the patch density sensor 92 that measures the toner image density on the intermediate transfer belt 21 or the patch density sensor 93 that measures the toner image density on the unfixed recording medium is used. be able to. Further, as the density measurement value before primary fixing, the value of the toner image density on the photosensitive drum 12 can be used.
Furthermore, a configuration is also conceivable in which the toner amount and the glossiness are each accurately measured based on the density measurement values after primary fixing and the density measurement values after secondary fixing. Further, a configuration is also conceivable in which the toner amount and the glossiness are each accurately measured based on the density measurement values before primary fixing and the density measurement values before secondary fixing.

Here, as the patch density sensor 92 for detecting the toner amount of the toner image before the primary fixing, a regular reflection type optical sensor and / or a diffuse reflection amount sensor can be used. In the case of a regular reflection type optical sensor, it is standardized by the amount of reflected light from the toner-free portion of each toner image carrier. In the case of the diffuse reflection amount sensor, the density can be detected with high accuracy by using the reflected light amount from the toner image on each toner image carrier standardized by the reflected light amount from the internal reference reflecting plate as a detection signal.
Further, a diffuse reflection amount sensor can be used as the patch density sensor 94 that detects the image density after fixing, and a regular reflection amount sensor can be used as the sensor that detects the image glossiness after fixing.

Second Embodiment Next, an image forming apparatus according to a second embodiment will be described with reference to FIGS. This embodiment is different from the first embodiment in which the image density of the fixed recording medium is measured at one place, and the measurement is performed at two places. The same parts (portions) as those in the first embodiment will be described using the same reference numerals. In the present embodiment, the basic configuration is the same as that of the first embodiment, and therefore, different points will be mainly described below.
FIG. 6 is a schematic configuration diagram for explaining various sensors built in the main body 1 of the image forming apparatus according to the second embodiment.
As shown in FIG. 6, each developing device 13 of the image forming units 11Y, 11M, 11C, and 11K detects the internal toner density and keeps the toner density (mixing ratio of toner and magnetic carrier) constant. ATC sensor 91 is attached. In addition, a patch density sensor 94 that measures the image density of the recording medium that has been glossy processed by the gloss processing apparatus 70 is attached between the gloss processing apparatus 70 and the discharge tray 48. That is, unlike the case of the first embodiment, a patch density sensor (refer to reference numerals 92 and 93 in FIG. 2) is provided that measures the toner image density of the intermediate transfer belt 21 and the unfixed toner image density on the recording medium. Not.

FIG. 7 is a schematic configuration diagram of the patch density sensor 94. Note that the configuration of the patch density sensor 94 described below can also be applied to the patch density sensor 94 in the first embodiment described above.
As shown in FIG. 7, the patch density sensor 94 is a regular reflection / diffuse reflection sensor, and a light emitting element 94a for irradiating the patch with illumination light and a regular reflection light component of the reflection light reflected by the patch. And a light receiving element 94c for detecting a diffuse reflected light (diffuse reflected light) component of the reflected light reflected by the patch. The patch density sensor 94 includes a lens 94d positioned on the light receiving surface of the light receiving element 94c for diffusely reflected light, the light emitting element 94a, the light receiving elements 94b and 94c, and the lens 94d so that the optical axis has a predetermined relationship. And a casing 94e that holds the head so as to always satisfy the above.

The patch density sensor 94 is configured to standardize the light receiving element 94c, and reflects a light from the light emitting element 94a and causes the light receiving element 94c to detect the reflected light, and the light receiving element 94c. Includes a reference plate optical path switching member (shutter) 94g for selecting one of reflected light from the patch and reflected light from the reference plate 94f. That is, when the shutter 94g is at the solid line position, the reflected light from the patch is received by the light receiving element 94c, while when the shutter 94g is at the broken line position, the reflected light from the reference plate 94f is received by the light receiving element 94c. The
The light receiving element 94c can be standardized by the amount of light reflected from the reference plate 94f when the shutter 94g is at the position of the broken line. Further, the standardization of the light receiving element 94b can be performed by the amount of reflected light at the toner-free portion. By performing such standardization with the reflected light amount of the non-toner image forming portion of the recording medium itself having a reflected light amount, the accuracy can be improved particularly for a highlight portion where the influence of the surface condition on the recording medium is large in density information. You can measure improvement.
The above-described configuration can also be said as follows. That is, the diffuse reflection density of the image on the recording medium is measured by projecting (irradiating) the toner image on the recording medium at a predetermined angle and being symmetrical with respect to the projection angle and a vertical line (vertical line) with respect to the recording sheet. The light receiving element is arranged at a position where the light reflected in other directions is not received. In other words, this light receiving element is provided with a light receiving element that receives a small amount of light that diffuses and reflects the projected (irradiated) light from the toner, and monitors the amount of reflected light from the reference reflecting plate other than the recording medium or the amount of emitted light. The image density information on the recording medium is obtained by standardizing the amount of received light.

  In the patch density sensor 94, a single light emitting element 94a for irradiating the patch with illumination light is shared, the regular reflection light component due to the light is detected by the light receiving element 94b, and the diffuse reflection light component due to the light is detected as the light receiving element. 94c is detected. It is also conceivable that the light receiving element and the light emitting element have opposite configurations. That is, a common light receiving element (not shown) is provided at the position of the light emitting element 94a, and a light emitting element (not shown) is provided at each position of the light receiving element 94b and the light receiving element 94c in FIG.

FIG. 8 is a diagram for explaining the amount of specularly reflected light and diffusely reflected light with respect to incident light when the angle with respect to the toner layer is changed. When (a) is an incident angle A = 20 degrees, (b) is incident. The angle A = 85 degrees is shown.
As shown in FIG. 8A, when the incident angle A is 20 degrees, the amount reflected on the surface of the toner layer (regular reflection light amount) is 4%, and the amount that advances into the toner layer (diffuse reflection light amount). Is 96%. Further, as shown in FIG. 8B, when the incident angle A is 85 degrees, the amount reflected on the surface of the toner layer is 60%, and the amount proceeding into the toner layer is 40%. As described above, the larger the angle of the surface of the recording medium with respect to the normal direction (the angle A from the normal direction is more than 50 degrees and close to 90 degrees), most of the irradiated light is in the toner layer. Since the light is reflected from the surface, the amount of specular reflection increases. Then, most of the irradiated light is reflected on the surface of the toner layer, and the glossiness can be measured with high accuracy without entering the toner layer and reproducing the color and density.

FIG. 9 is a graph for explaining the relationship between the amount of diffuse reflection and the amount of toner. The vertical axis represents the amount of diffuse reflection and the horizontal axis represents the amount of toner on the recording medium. FIG. 10 is a graph for explaining the relationship between the regular reflection light amount and the glossiness, where the vertical axis represents the regular reflection light amount on the recording medium and the horizontal axis represents the toner amount on the recording medium. FIG. 11 is a diagram showing the amount of reflected light for each gloss level, and FIG. 12 shows the relationship between the amount of specularly reflected light and the amount of diffusely reflected light when the toner image on the recording medium is irradiated with light. FIG.
As shown in FIG. 9, as the amount of toner increases, the amount of diffusely reflected light also increases. The diffuse reflection output is an output that depends on the toner amount rather than the glossiness. Further, as shown in FIG. 10, if a toner amount of a certain amount or more is fixed on the recording medium, the regular reflection output substantially depends on the glossiness. As shown in FIG. 11, this dependency can also be said from the fact that when the toner amount is the same, the amount of specular reflection increases as the glossiness increases. Therefore, regarding the toner amount range depending on the toner amount, the information accuracy as the glossiness can be improved by limiting the toner amount by the output value of the diffused light amount.

As described above, the toner image density can be representatively detected by the diffuse reflection light amount, and the glossiness can be representatively detected by the regular reflection light amount.
Here, in addition, as shown in FIG. 12, when the light from the light emitting element 94a is applied to the patch on the recording medium, the light reflected from the surface of the toner layer of the patch reflects the irradiated light itself. Does not develop color (form density). Further, when the light emitted from the light emitting element 94a enters the toner layer, the light is diffusely reflected by the color material contained in the toner to form a color (form density). By receiving only the regular reflection light quantity from the surface of the toner layer, it is possible to measure the glossiness of the toner layer accurately regardless of the density (toner amount).

FIG. 13 is a flowchart showing a procedure for controlling the toner density and the glossiness. FIG. 14 is a graph showing the relationship between the toner amount and the amount of diffusely reflected light. The vertical axis represents the toner amount on the recording medium, and the horizontal axis represents the diffusely reflected light amount on the recording medium. FIG. 15 is a graph showing the relationship between the image gloss level and the regular reflection light amount, where the vertical axis represents the image gloss level on the recording medium and the horizontal axis represents the regular reflection light amount on the recording medium.
As shown in FIG. 13, a control patch is formed on the intermediate transfer belt 21 (step 201), and the regular reflection light quantity and diffuse reflection of the control patch on the glossy processed recording medium are detected by the patch density sensor 94 (see FIG. 6). The amount of light is detected (step 202). Then, the control unit 80 uses the diffuse reflection light amount detected by the patch density sensor 94 (see FIG. 6). Patch density (toner amount) = fd_M (diffuse reflection light amount)
Thus, the patch density is calculated (step 203). Specifically, the toner amount can be obtained from the curve shown in FIG. FIG. 14 shows low glossiness, intermediate glossiness, and high glossiness, and although the toner amount slightly varies depending on the glossiness, the toner amount is diffusely reflected. Since it is almost represented by the amount of light, many people can grasp it.
Based on the calculated patch density, the control unit 80 determines whether or not toner image density control is necessary (step 204). That is, the detection result S ₃ of the patch density sensor 94 (see FIG. 6) is compared with a predetermined target value T ₃ (value based on the input image density (Cin)%), and the difference Δ ₃ (= S ₃ −T ₃ ). Is calculated, it is determined whether or not the difference Δ ₃ is within an allowable range. When it is determined that the toner image is within the allowable range, the toner image density control is not necessary. However, when it is determined that the toner image exceeds the allowable range, the toner image density control factor is controlled (step 205), and the process returns to step 201. . The toner image density control factor is the same as that described in the first embodiment, and a description thereof will be omitted.

After performing necessary corrections on the toner image density, the image glossiness = fr (regular reflection light amount, diffuse reflection light amount) using the regular reflection light amount and diffuse reflection light amount detected by the patch density sensor 94 (see FIG. 6).
= Fr1 (regular reflection light amount, toner amount)
= Fr1 (regular reflected light amount, fd_M (diffuse reflected light amount))
Thus, the image glossiness is calculated (step 206). Specifically, the image glossiness can be obtained from the line shown in FIG. FIG. 15 illustrates four cases where the toner amount is different, but all illustrate cases where the toner amount is within an appropriate range. The toner amount is obtained by fd_M (diffuse reflected light amount) as shown in FIG.
Then, the control unit 80 determines whether or not glossiness control is necessary based on the calculated image glossiness (step 207). That is, the difference Δ ₄ is allowed after the difference Δ ₄ (= S ₄ −T ₄ ) is calculated by comparing the detection result S ₄ of the patch density sensor 94 (see FIG. 6) with the calculated appropriate density T _4. It is determined whether it is within the range. When it is determined that the value is within the allowable range, the process ends as it is. When it is determined that the value exceeds the allowable range, the gloss control factor is controlled (step 208), and then the process returns to step 201. The glossiness control factor is the same as that described in the first embodiment, and thus the description thereof is omitted.

  As described above, in this embodiment, the amount of toner that forms an image on a recording medium is substantially represented by the amount of diffusely reflected light (the light of the specular reflection component needs to be selectively excluded). It is noted that the gross gloss on the surface of the layer can be detected almost representatively by the amount of specular reflection (the diffuse reflection component needs to be selectively eliminated). In addition, regarding the image density represented by the amount of diffusely reflected light from the image on the recording medium, even if the image is formed with the same toner amount, the image fixing conditions and the gloss processing conditions (surface treatment state / gloss level magnitude) ) Greatly changes, and it is difficult to measure the correct toner amount only from the diffused light quantity information. For this reason, the density (toner amount) and the glossiness information are read from the image on the recording medium after fixing through the regular reflection light amount and the diffuse reflection light amount, respectively, and both are controlled to a target quality using individual control factors.

In the present embodiment, since one patch density sensor 94 is equipped with sensing means capable of measuring with the respective light amounts of regular reflection and diffuse reflection, the patch density sensor 94 can be made one. This can contribute to reducing the cost. Further, since the same location can be detected simultaneously by one patch density sensor 94, the amount of specular reflection and diffuse reflection are not affected by noise such as a change in surface reflectance due to a change in the surface condition of the recording medium. Information on the amount of light can also be obtained.
In a device having a scanner, the specular reflection / diffuse reflection sensor is added to the light emission / light reception relationship used for normal reading in the scanner, and the amount of specular reflection (in general, even if some diffuse light is included, is very small). Yes, or the sensing means which is deficient of only the diffusely reflected light amount (because specularly reflected light is generally stronger than diffused light) may be added to the apparatus.

Third Embodiment Next, an image forming apparatus according to a third embodiment will be described with reference to FIGS. In the third embodiment, when the image density of the paper to be measured is high glossy or the like (from the density measurement principle of IIT (CCD) as the image reading means), there is a concern about the measurement error. The image density of a sheet having a lower glossiness is measured, and the measurement result is converted into the image density of a sheet that could not be measured due to high gloss. Then, an image forming condition, a fixing condition, and the like are to be controlled based on the converted image density.
The same parts (portions) as those in the first embodiment will be described using the same reference numerals. In the present embodiment, since the basic configuration has a part common to the first and second embodiments, the following description will be focused on differences.
First, the background about the third embodiment will be described.
FIG. 16 is a graph showing the relationship between the input image signal and the target image density in the standard image quality mode and in the high image quality mode, where the vertical axis is the target image density and the horizontal axis is the input image signal. FIG. 17 is a graph showing the relationship between the input image signal and the image density at the number of times of fixing. The vertical axis is the image density and the horizontal axis is the input image signal.
As shown in FIG. 16, when the standard image quality mode is compared with the high image quality mode in which fixing is performed a plurality of times for the purpose of improving density and gloss, the target image density is high even if the input image signal is the same. As shown in FIG. 17, the image density increases as the number of times of fixing increases.
Thus, the image density correction for each of the standard image quality mode and the high image quality mode must use individual correction parameters. That is, the test pattern at the time of fixing once is read by the image reading means for density correction in the standard image quality mode, and the test pattern at the time of fixing multiple times is read individually by the image reading means for density correction in the high image quality mode, It is necessary to obtain correction parameters for image forming conditions in each mode.

FIG. 18 is a graph for explaining the difference in density when the same image is measured by the image reading means and the calibrated density measuring device (Xrite), where the vertical axis is the image density and the horizontal axis is the input image. Signal.
As shown in FIG. 18, the relationship between the input image signal and the image density obtained by measuring the density of the same multiple-time fixing test pattern by the image reading means or the calibrated density measuring device in the image forming apparatus is particularly high on the high density side. An error has occurred. This is because the CCD (Charge Coupled Device) characteristics in the image reading means are not particularly detectable at high density and high gloss, and the reading variation is larger than that of a calibrated density measuring device. The CCD characteristics include low directivity of incident light, a single light receiving surface, and weak reflected light intensity from the high density image area, so that the influence of dark current increases and the S / N ratio is increased. It can be easily reduced, and the reading error is large or high density detection beyond a certain level cannot be detected, and the resolution is lowered when the range is expanded.

  The present embodiment has been made in view of the background as described above, and is characterized in that it uses image information of a once-fixed image that can be read for image condition correction of a twice-fixed image. This will be specifically described below.

FIG. 19 is a flowchart showing a procedure for controlling the toner density and the glossiness. FIG. 20 is a diagram showing an example of a UI (User Interface) screen (not shown), and FIG. 21 is a graph showing a density conversion table, where the vertical axis is the image density at the time of fixing twice and the horizontal axis is fixed once. Image density. FIG. 22 is a graph showing the relationship between the input image signal and the image density, where the vertical axis is the image density and the horizontal axis is the input image signal. FIG. 23 is a graph showing the relationship between the input image signal and the output image signal, where the vertical axis is the output image signal and the horizontal axis is the input image signal.
As shown in FIG. 19, when the user operates a UI (not shown) to enter the on-paper gradation correction mode (step 301), the control unit 80 switches to the screen shown in FIG. As the image quality mode, there are a standard image quality mode with one fixing operation and a high image quality mode with two fixing operations. The user selects either one as the correction target mode (step 302) and presses the execution button (step 303). Here, the case where the user selects the high image quality mode will be described below.
Then, the control unit 80 forms a predetermined built-in pattern on the recording medium (step 304). That is, a predetermined built-in pattern stored in a storage unit (not shown) of the image forming apparatus is called up. Then, a latent image having a predetermined built-in pattern is formed on the photosensitive drum 12 (see FIG. 1) under image forming conditions for high image quality. The formed latent image is developed and then transferred onto the intermediate transfer belt 21. A predetermined built-in pattern is transferred from the intermediate transfer belt 21 to a recording medium, and a fixing operation is performed once to perform print discharge.
The user places a print of the built-in pattern of “fix once” on the platen of the image reading device 60 (see FIG. 1) (step 305), presses a start button (not shown) of the image forming device, and presses the image reading device 60 (FIG. 1). The scan is started (see step 306). Then, the control unit 80 determines whether or not the print is placed in an appropriate position and direction based on the read image information, and determines whether or not the image is appropriate for correction (step 307). . If the determination result is NG, a warning display (print reset display) is output to a UI (not shown) so that the print is correctly set (step 308), and scanning is performed again.
If the determination result is OK, each color gradation density of the printed built-in pattern (one-time fixing mode) is detected (step 309). Then, using the graph shown in FIG. 21, the detected once-fixed image density of each gradation is converted into twice-fixed image density (step 310). After that, as shown in FIG. 22, the image density at the time of twice fixing after conversion and the target density are compared (step 311), and as shown in FIG. The LUT (image forming condition) of the output image signal is corrected (step 312). In this way, the LUT for twice fixing can be corrected without detecting the built-in pattern for twice fixing.
The control unit 80 inquires of the user through the UI whether or not to perform correction in another mode (step 313). If the user gives an instruction to perform correction in another mode, the process returns to step 302, and if the user gives an instruction not to perform correction in another mode (correction in other mode). Is not instructed), the on-paper gradation correction mode is terminated (step 314).

  As for the third embodiment, the following application examples are also conceivable. That is, in other words, the image information of an image having a fixed number smaller than n that can be read is used for correcting the image condition of the image fixed n times. In other words, a readable density threshold is provided in the image reading means, and the image information of the once-fixed image is used for correcting the image condition of the twice-fixed image if the read density of the twice-fixed image is equal to or higher than the density threshold. Hereinafter, application examples will be described with reference to FIGS. 24 and 25. FIG.

FIG. 24 is a flowchart showing a procedure for controlling the toner density and the glossiness. FIG. 25 is a table showing the relationship between the number of fixing times and the reading density upper limit value in the image reading device 60 (see FIG. 1).
As shown in FIG. 24, the user operates a UI (not shown) to enter the on-paper gradation correction mode (step 401), designates the image quality mode (step 402), and presses the execution button (step 403). As the image quality mode here, a mode up to n times fixing can be designated. That is, it is not limited to fixing twice, but includes fixing by a larger number of times. Here, a case where the user designates the fixing mode five times (n = 5) will be described below.
Then, a predetermined built-in pattern fixed in the designated mode five times is formed on the recording medium (step 404). The user places “n times fixing”, that is, a print on which a built-in pattern of 5 times fixing is formed on the platen of the image reading device 60 (see FIG. 1) (step 405), and presses a start button (not shown) of the image forming device, Scanning is started by the image reading device 60 (see FIG. 1) (step 406). Next, it is determined whether or not the patch density based on the image information read by the image reading device 60 (see FIG. 1) is lower than a threshold value (step 407). That is, as shown in FIG. 25, determination is made using the reading density upper limit value of each color determined for each number of fixings as a threshold value. Here, according to FIG. 25, as the number of times of fixing increases, the upper limit of density that can be guaranteed by the image reading means decreases. The reason for this is as follows. In other words, when there is a concern about measurement errors due to high gloss, etc., in addition to setting an upper limit of density that guarantees reading accuracy, the greater the number of fixings, the greater the contribution of glossiness at the same density. This is because the read guarantee density is lower than the upper limit value of the read guarantee density at the previous fixing.
When the patch density based on the read image information is larger than the threshold value of each color in the five-time fixing, it is determined that accurate density measurement is difficult for the built-in pattern for the five-time fixing. It is difficult to perform accurate density measurement to detect a gradation patch as it is, and a predetermined built-in pattern is formed in a mode in which the number of fixing times is smaller than a designated fixing mode. That is, after confirming that n is greater than 1 (step 408) and changing the setting to n = 4 (n = n−1) (step 409), the process returns to step 404 to perform a series of procedures again. . Specifically, a built-in pattern for four times fixing is formed on a recording medium and output (step 404), the recording medium is placed on the platen (step 405), and a start button is pressed to start scanning (step 406). Then, the magnitude relationship between the patch density and the predetermined threshold value is determined (step 407). When the patch density is smaller than the threshold value of each color in the four-time fixing, accurate density measurement is possible. When the patch density is larger than the threshold value of each color in the one-time (n = 1) fixing, it is determined that scanning by the image reading device 60 (see FIG. 1) is impossible (step 410), and the process ends.
When the patch density is smaller than the threshold value of each color in the four-time fixing, the process proceeds to the next step. Since the next steps, steps 411 to 418, are the same in contents as steps 307 to 314 in FIG. 19 described above, description thereof will be omitted.
In this way, by obtaining the correction parameters for each mode combination, it is possible to perform on-paper gradation correction with high accuracy according to the number of times of fixing.

  As the above-described correction, the correction between the input image signal and the output image signal is performed. However, it is also conceivable that the image forming condition other than this is corrected. For example, at least one or more of toner density, photosensitive member charging potential, photosensitive member exposure light quantity, developing bias, number of fixings, fixing temperature, fixing pressure, fixing time, etc. are corrected from the image information obtained by the image reading means. Configure.

  The first to third embodiments have been described with the color tandem machine. However, the present invention can be applied to a 4-cycle machine or a monochrome machine (K single-color machine). Although the intermediate transfer method has been described, the present invention can also be applied to a direct transfer method. The image reading device 60 can use an externally connected scanner, a fixed image sensor, or the like in addition to being provided in the image forming apparatus. In addition to the built-in pattern, the test pattern may be input from the outside of the image forming apparatus. Also, if the test pattern used when the tone correction on the paper is outside the density threshold, a warning that the tone correction on the paper cannot be performed is issued on the UI, and a different test pattern is output. It may be possible to give a display to the user to confirm whether it is good or not. It is also conceivable that a single fixing device is provided so that a plurality of fixings for high image quality mode are performed by a paper conveying means (such as a conveying path for a reversal recording material) that can pass through one fixing device twice or more. It is done.

1 is a diagram illustrating an overall configuration of an image forming apparatus according to a first embodiment. It is a schematic block diagram for demonstrating the various sensors incorporated in the main body of the image forming apparatus. It is a block diagram of IPS, a controller, and a control part. 5 is a flowchart illustrating a procedure for controlling toner density and glossiness. It is a graph which shows the relationship between image density and glossiness. It is a schematic block diagram for demonstrating the various sensors incorporated in the main body of the image forming apparatus which concerns on 2nd Embodiment. It is a schematic block diagram of a patch density sensor. It is a figure for demonstrating the regular reflection light quantity and diffuse reflection light quantity with respect to incident light at the time of changing the angle with respect to a toner layer. It is a graph for demonstrating the relationship between a diffuse reflected light quantity and a toner amount. It is a graph for demonstrating the relationship between a regular reflection light quantity and glossiness. It is a figure which shows the reflected light amount for every glossiness. It is a figure which shows the relationship between the regular reflection light quantity and the diffuse reflection light quantity in the total reflection light quantity when light is irradiated to the toner image on a recording medium. 5 is a flowchart illustrating a procedure for controlling toner density and glossiness. It is a graph which shows the relationship between a toner amount and a diffuse reflected light quantity. It is a graph which shows the relationship between image glossiness and a regular reflection light quantity. 6 is a graph showing a relationship between an input image signal and a target image density in a standard image quality mode and a high image quality mode. It is a graph which shows the relationship between the input image signal and image density in the frequency | count of fixing. It is a graph for demonstrating the difference in the density | concentration at the time of measuring the same image with an image reading means and the calibrated density measuring device. 5 is a flowchart illustrating a procedure for controlling toner density and glossiness. It is a figure which shows an example of UI screen. It is a graph which shows a density conversion table. It is a graph which shows the relationship between an input image signal and image density. It is a graph which shows the relationship between an input image signal and an output image signal. 5 is a flowchart illustrating a procedure for controlling toner density and glossiness. 6 is a table showing a relationship between the number of times of fixing and a reading density upper limit value in the image reading apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 21 ... Intermediate transfer belt, 60 ... Image reading apparatus, 70 ... Gloss processing apparatus, 91 ... ATC sensor, 92, 93, 94 ... Patch density sensor, 94a ... Light emitting element, 94b, 94c ... Light receiving element, 94d ... Lens, 94e ... Case, 94f ... Reference plate, 94g ... Shutter

Claims (2)

Image forming means for forming a toner image under predetermined image forming conditions and transferring the toner image onto a sheet;
Fixing means for fixing the toner image transferred to the paper by the image forming means under predetermined fixing conditions;
First measuring means for measuring the amount of specularly reflected light and / or diffusely reflected light by irradiation of the toner image in a state before being fixed by the fixing means;
Second measuring means for measuring the amount of specular reflection due to irradiation of the toner image after being fixed on the paper by the fixing means;
Control means for controlling the predetermined image forming conditions and the predetermined fixing conditions based on measurement results by the first measuring means and the second measuring means;
Only including,
The first measuring means and the second measuring means measure the same region in the toner image;
The control means calculates an appropriate value of the second measuring means based on a measurement result of the same area by the first measuring means, and the calculated appropriate value and the same area by the second measuring means An image forming apparatus that controls the predetermined fixing condition based on the measurement result . The image forming apparatus according to claim 1 , wherein the first measurement unit and the second measurement unit are integrally configured.

Images