JP2013117632A - Image processing system and correction method for image forming condition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the color of a patch image by appropriately reproducing observing conditions so that light is transmitted from the image non-formation side of a sample, when correcting image forming conditions according to the result of the color measurement of the patch image.SOLUTION: The image processing system comprises: a surface side emitting part 92 that emits light to a surface with respect to a sample in which a patch image is formed on a recording medium; a rear side emitting part 83 that emits light to the rear side; and a surface side light receiving part 91 that receives light reflected from the sample and light transmitted from this sample. A quantity of light emitted from the rear side emitting part 83 is controlled according to the quantity of light emitted from the surface side emitting part 92. To measure color, light is emitted from the surface side emitting part 92, and light is received by the surface side light receiving part 91 while a controlled quantity of light is emitted from the rear side emitting part 83. From the result of the color measurement, the image forming conditions for the image forming apparatus that has formed the patch image are corrected.

Description

  The present invention relates to an image processing apparatus that corrects an image forming condition of an image forming apparatus by feeding back a color measurement result of a patch image formed on a recording medium, and an image forming condition correcting method.

  2. Description of the Related Art Conventionally, so-called electrophotographic image forming apparatuses such as a laser beam printer and a copying machine that form an image by scanning an image carrier with laser light are known. In general, an electrophotographic image forming apparatus forms an image through a plurality of processes such as charging, exposure, development, transfer, and fixing.

  Here, an electrophotographic process in a general electrophotographic image forming apparatus will be described. In the apparatus, the photosensitive member is uniformly charged by the charging process provided in the apparatus based on the input image data, and the photosensitive member is exposed in accordance with the image signal by an exposure unit including a laser light source. As a result, an electrostatic latent image is formed on the photoreceptor. Thereafter, the electrostatic latent image on the photoconductor is developed by a development process to become a toner image, and the toner image on the photoconductor is transferred to a recording medium by a transfer process. The toner image transferred to the recording medium is fixed by a fixing process to form an image.

  The density of an image output from an image forming apparatus is required to be highly stable regardless of the installation environment of the apparatus and changes with time. However, since an electrophotographic image forming apparatus performs an electrostatic phenomenon as described above, the apparatus may be affected by environmental conditions in which the apparatus is placed, such as temperature and humidity, or deterioration over time of a photoconductor or developer. The output state of itself changes. That is, there is a problem that the density reproducibility is low.

  Therefore, in an electrophotographic image forming apparatus, feedback control is performed to keep the image density optimal. In this feedback control, the laser intensity during the exposure process is controlled, and patch images with different potential differences are formed on the recording medium. Here, the potential difference is Vcont obtained from the difference between Vl and Vdc when the potential changed by the laser is Vl and the development bias component of the development process is Vdc in the later-described exposure process. Vl is controlled by changing the laser intensity of the exposure process, and patch images with different potential differences Vcont are formed. Then, the color of the patch image formed on the recording medium is measured using a measuring instrument mounted on the image forming apparatus. With respect to the density obtained by the color measurement, an error from a target density predetermined for each medium is obtained, and a desired density is obtained by controlling the laser intensity of the exposure process based on the error.

  Here, a general concentration measurement method will be described. First, an irradiation unit that irradiates light onto a sample image (hereinafter referred to as a sample) on a recording medium and a light receiving unit that measures light reflected from the recording medium are arranged at positions based on predetermined geometric conditions. For example, as a geometric condition of the sample to be colorimetric and the irradiation unit / light receiving unit, light is irradiated from an angle of 45 ° with respect to the normal line of the sample and received at an angle of 0 ° with respect to the normal line of the sample, so-called 45 Suppose that the geometric condition of / 0 is used. The irradiating unit and the light receiving unit are arranged under a 45/0 geometric condition, and the amount of reflected light of the sample whose reflectance is known and the amount of reflected light of the image formed on the recording medium are measured. Then, the reflectance of the image formed on the recording medium is calculated based on the measured light quantity, and the density is obtained from the reflectance.

  Here, FIG. 1 shows a conceptual diagram of general sample measurement. This figure shows a state in which a sample composed of a recording medium 2006 and an image 2007 formed on the surface thereof is placed on a backing 2002 as a reflector background. The light measured by the light receiver 2005 includes not only the light 2008 irradiated from the light source 2001 and reflected from the sample, but also the light 2009 reflected from the backing 2002 located on the back surface (non-image forming surface) of the recording medium 2006. Therefore, when the reflectance of the backing 2002 changes, the reflectance of the sample measured by the light receiver 2005 also changes.

  In the conventional image forming apparatus, when the color of the sample on which the image is formed on the recording medium is measured, the type of backing located on the back surface (non-image forming surface) of the recording medium is not particularly considered. Therefore, even after density correction by feedback of the measured density value, when the user actually observes the printed matter, the target density cannot be reproduced depending on the backing used for the correction. For example, when the reflectance of the backing 2002 used for the sample measurement at the time of density correction is higher than the reflectance of the backing at the time of observation, the density actually observed of the printed matter formed after the density correction is It might be higher than the target concentration. On the contrary, when the reflectance of the backing at the time of observation is higher than the reflectance of the backing 2002 at the time of sample measurement, the density observed in the printed matter after density correction may be lower than the target density. there were.

  Therefore, a method has been proposed in which the backing part is detachable at the time of sample measurement and the target density is reproduced regardless of the observation conditions by changing the reflectance of the backing 2002 according to the user's application (e.g., patent document). 1).

JP 2008-275587

  However, even if a backing having a high reflectance is used when measuring the sample, the light 2009 reflected from the backing 2002 passes through the sample, and the amount of light is inevitably smaller than the amount of light irradiated on the sample surface. Therefore, no matter what kind of backing is used, the amount of light irradiated on the front surface (image forming surface) of the sample should be equal to the amount of light irradiated from the back surface (non-image forming surface). I can't. Therefore, for example, under the condition that the user observes only one printed material by hand, the amount of light transmitted from the back surface of the printed material is larger than that at the time of color measurement of the sample using the backing, and the density of the observed printed material. May be lower than the correction target. That is, it is difficult to measure the concentration of the sample on the assumption of observation conditions where there is transmitted light from the back surface (non-image forming surface) of the sample.

  In view of the above problems, the present invention provides an observation in which there is transmitted light from the non-image forming surface of the sample when correcting the image forming condition according to the color measurement result of the sample on which the patch image is formed on the recording medium. The purpose is to measure the color of a patch image by appropriately reproducing the conditions.

  As a means for achieving the above object, an image forming apparatus of the present invention comprises the following arrangement.

  That is, the first irradiation means for irradiating the image forming surface with light on the sample having the patch image formed on the recording medium, and the non-image forming surface which is the back surface of the image forming surface with respect to the sample. Irradiated from the second irradiation means for irradiating, the first light receiving means for receiving the reflected light from the sample and the transmitted light transmitted through the sample on the image forming surface side of the sample, and the second irradiation means. A light amount control means for controlling the light quantity of the light according to the light quantity emitted from the first irradiating means, the sample is irradiated with light from the first irradiating means, and the second A first colorimetric unit for measuring the color of the sample by receiving light from the first light-receiving unit in a state in which the light whose light amount is controlled by the light amount control unit is irradiated from the irradiation unit; The patch image was formed from the colorimetric result of the sample by the colorimetric means. And having a correction means for correcting image forming conditions in the image forming apparatus.

  According to the present invention, when correcting the image forming condition according to the colorimetric result of the patch image, the patch image is measured by appropriately reproducing the observation condition where there is transmitted light from the non-image forming surface of the sample. It becomes possible to color.

Conceptual diagram showing a general sample concentration measurement method, Sectional drawing which shows schematic structure of the image forming apparatus in 1st Embodiment, FIG. 2 is a block diagram illustrating a functional configuration of the image forming apparatus according to the first embodiment. The conceptual diagram of the density correction data in 1st Embodiment, The figure showing the structure of the print data in 1st Embodiment. The figure which shows the example of an observation environment in 1st Embodiment, The figure which shows the structural example of the color separation LUT in 1st Embodiment. A flowchart showing density correction processing in the first embodiment; The figure which shows the structural example at the time of the colorimetry in 1st Embodiment. The flowchart which shows the backing setting process in 1st Embodiment, Sectional drawing which shows schematic structure of the image forming apparatus in 2nd Embodiment, The figure which shows the structural example which concerns on the colorimetry in 2nd Embodiment. A flowchart showing density correction processing in the second embodiment; It is a flowchart which shows the detail of the light quantity control process in 2nd Embodiment.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. The following embodiments do not limit the present invention related to the scope of claims, and all combinations of features described in the present embodiments are essential to the solution means of the present invention. Not necessarily.

  In the present invention, when the image forming conditions are corrected by feeding back the color measurement result of the sample on which the patch image is formed on the recording medium, the amount of light irradiated onto the non-image forming surface of the sample is particularly reduced. An example of performing colorimetry that reproduces observation conditions that are equivalent to the amount of irradiation light will be shown.

  For this purpose, first, a first irradiating means for irradiating the sample with light on the image forming surface and a second irradiating means for irradiating the sample with light on the non-image forming surface which is the back surface of the image forming surface. Have. Furthermore, it has 1st light-receiving means which light-receives the reflected light from a sample, and the transmitted light which permeate | transmitted this sample by the image formation surface side of this sample. Then, after controlling the amount of light emitted from the second irradiating means to be equal to the amount of light emitted from the first irradiating means, the first color measuring means measures the color of the sample. Do. That is, in a state where the sample is irradiated with light from the first irradiating means and the light after light quantity control is irradiated from the second irradiating means, the first light receiving means receives light and the sample is colorimetrically measured. To do. Then, based on the color measurement result, the image forming conditions in the image forming apparatus that formed the patch image are corrected.

  Furthermore, it is possible to perform colorimetry that reproduces the observation conditions such that the amount of light applied to the non-image forming surface of the sample is smaller than the amount of light applied to the image forming surface. That is, the second colorimetric means measures the sample by receiving light from the first light-receiving means in a state where a backing is set for the sample according to the observation conditions and light is emitted from the first irradiation means. Similarly, the image forming condition is corrected from the color measurement result.

<First Embodiment>
Apparatus Configuration FIG. 2 is a cross-sectional view showing a schematic configuration of the image forming apparatus in the present embodiment. The image forming apparatus of the present embodiment includes a photosensitive drum 1 as an image carrier, a charging unit 2 for forming an electrostatic latent image, and an exposure unit 3. The exposure unit 3 includes a laser oscillator 31, a polygon mirror 32, and an Fθ lens 33, and irradiates the surface of the photosensitive drum 1 with laser light emitted from the laser oscillator 31 based on the input halftone image signal. An electrostatic latent image is formed on the surface. The formed electrostatic latent image is developed as a toner image when a bias voltage is applied by the developing unit 4 and toner adheres thereto. The developing unit 4 is a four-cycle type in the example of FIG. 2 and includes developing devices 4Y, 4M, 4C, and 4 that store developers (toners) of yellow, magenta, cyan, and black. Further, the image on the photosensitive drum 1 developed by the developing unit 4 is heated and applied to the transfer unit 5 for transferring to the recording medium S using the intermediate transfer member 51 and the transfer belt 52, and to the recording medium S that has been transferred. A fixing unit 71 for performing a fixing process with pressure is provided. The toner remaining on the photosensitive drum 1 after development is removed by the cleaner 6.

  The image forming apparatus of the present embodiment further measures a surface-side irradiation unit 92 that irradiates light on the surface side (image forming surface side) of the recording medium S after fixing, and the light that is irradiated and reflected from the recording medium S. A front surface side light receiving unit 91. Note that the front side irradiation unit 92 and the front side light receiving unit 91 are movable, and move according to a user input so that the measurement position can be changed. Furthermore, a black backing part 81 and a white backing part 82 fixedly installed as a background at the time of measurement, and a back side irradiation part 83 for irradiating light to the back side (non-image forming side) of the recording medium are provided. Yes. It is assumed that the black backing portion 81 and the white backing portion 82 conform to the ISO standard black backing reflectance and the white backing reflectance, respectively. However, the black backing portion 81 and the white backing portion 82 do not necessarily conform to the ISO standard, and it is sufficient that the reflectance of the black backing portion 81 is lower than the reflectance of the white backing portion 82. Further, the configuration of the backing portion in the present embodiment is not limited to the example including the black backing portion 81 and the white backing portion 82 as described above, and a backing portion that reproduces the reflectance of the paper may be added.

  FIG. 3 is a block diagram illustrating a functional configuration of the image forming apparatus according to the present embodiment. In the figure, reference numeral 500 denotes a printer driver, and 510 denotes an image forming unit. The printer driver 500 includes a data input unit 501 and an observation condition input unit 502, and creates image data to be printed by the image forming unit 510 based on the input data. Hereinafter, processing in the printer driver 500 will be described in detail.

  First, the data input unit 501 allows the user to select which image data or density correction data is to be input. Here, the image data is general image data to be actually printed, and the density correction data is a patch image (hereinafter also simply referred to as a patch) used for correcting image forming conditions described later. ) For creating data.

  When input of image data is selected, creation of image data to be printed by the image forming unit 510 is executed, and the created image data is passed to the observation condition input unit 502. The image data input here or data before the image data is edited can be captured via various media. For example, image data such as JPEG format captured by a digital camera can be captured via a CF card. Also, image data such as TIFF format read by a scanner can be imported. Furthermore, data on the web can be taken in via the Internet. For example, sRGB standard image data (input image signal values) R, G, and B are created by performing editing, processing, and the like on the captured image data through an application.

  On the other hand, when the input of density correction data is selected, the density correction data stored in advance in the printer driver 500 is transferred to the observation condition input unit 502 as input data. In the density correction data used in the present embodiment, the laser intensity to be irradiated and the type of color material to be recorded are described as exposure conditions in an exposure processing unit 513 to be described later. FIG. 4 shows a conceptual diagram of density correction data. As shown in the figure, the density correction data constitutes a plurality of patch images, the upper part of the text written in each patch indicates the type of color material, and the lower part indicates the laser intensity. In this embodiment, in order to correct the laser intensity so as to realize the maximum density according to the medium, as shown in FIG. 4, the density correction data is 60% to 100% for each CMYK ink color. ] Shows an example of changing the laser intensity in increments of 10 [%]. Of course, the density correction data is not limited to the example of the image patch shown in FIG. 4, and the laser intensity step may be wider than 10 [%] or the number of patches may be increased. For example, FIG. 4 shows an example of a patch image when four colors of toner are used, but the number of patches may be increased when six colors of toner are used.

  As described above, image data (or density correction data) is input from the data input unit 501 to the observation condition input unit 502. Hereinafter, processing in the observation condition input unit 502 will be described. In the observation condition input unit 502, the user sets conditions for observing an image (hereinafter, printed matter) formed on the recording medium, and attaches this to the image data, so that the print data that is actually input to the image forming unit 510 Create

  FIG. 5 shows the configuration of print data in this embodiment. As shown in the figure, the print data is composed of observation conditions and image data. In the observation condition input unit 502, the user selects conditions for observing the printed matter using an input device such as a touch panel (not shown) or a keyboard. Although not shown, the print data is also given normal printing conditions such as the type of recording medium (media information) to be printed and the number of copies to be printed.

  In this embodiment, as the observation condition of the printed matter, the light amount of the front surface irradiation light irradiated on the surface of the printed matter is Y1 (first light amount), and the light amount of the rear surface irradiation light irradiated from the back surface is Y2 (second light amount). The following three conditions are prepared.

Y1 ≒ Y2 ... Condition (1)
Y1> Y2 ... Condition (2)
Y1 >> Y2 ... Condition (3)
That is, the condition (1) indicates an observation condition (first condition) where Y1 and Y2 are substantially equal. Conditions (2) and (3) indicate observation conditions (second conditions) in which Y1 is larger than Y2. In the condition (3), Y1 is larger than Y2 as in the condition (2), but the difference is much larger than that in the condition (2). Specifically, the condition (3) may be used if the difference between Y1 and Y2 is greater than or equal to a predetermined value, and the condition (2) may be used if the difference is less than the predetermined value.

  Among the above conditions (1) to (3), the one closest to the condition when the user actually observes the printed matter is selected. Here, an example of selecting observation conditions for an actual observation environment is shown. For example, in an environment where uniform light is radiated, such as in an office environment, when observing a printed matter with a single sheet as shown in FIG. Condition (1) is selected considering that the amount of light is almost the same. In addition, when observing a plurality of printed materials as shown in FIG. 6B, it is considered that the amount of light emitted from the back surface of the printed material on the uppermost surface is smaller than the light emitted from the front surface. Select 2). In addition, as shown in FIG. 6 (c), when the printed material is attached to a wall such as a mount or concrete having a high basis weight, the amount of light emitted from the back surface is smaller than the light emitted from the front surface of the printed material. Select condition (3) considering that it is extremely small.

  Note that the observation conditions are not limited to the three patterns of the above conditions (1) to (3), and the relationship between the front side irradiation light and the rear side irradiation light on the printed material may be shown. For example, a condition of Y1 <Y2 may be assumed as in the case where a printed material is attached to the light emitter. In addition, an observation condition that specifically indicates an observation state by the user may be prepared, such as when using a single printed material or when using multiple printed materials.

  As described above, the print data in which the viewing condition is given to the image data is supplied to the image processing unit 511 of the image forming unit 510 in accordance with a print instruction from the user. Then, the image processing unit 511 first determines whether or not the image data input by the data input unit 501 is density correction data. In the case of density correction data, the image processing unit 511 inputs the input print data as it is to the charging processing unit 512 without performing color conversion processing and halftone processing described later.

  On the other hand, when the image data input by the data input unit 501 is not density correction data but normal image data, the image processing unit 511 performs the following color conversion processing and half-processing based on the input print data. Perform tone processing. First, color conversion processing is performed to obtain the amount of color material of color separation data CMYK corresponding to the combination of toners that reproduce the color represented from the RGB information of each pixel recorded in the image data portion of the print data. In the present embodiment, this color conversion processing is performed by using an interpolation operation together with a color separation look-up table (LUT) whose correspondence relationship with R, G, B is predetermined, and the output is 8 bits for each color of CMYK. Suppose there is. FIG. 7 shows an example of the color separation LUT. As shown in the figure, 8-bit output color material amounts C, M, Y, and K are determined for 8-bit input data R, G, and B in the color separation LUT of the present embodiment. C, M, Y, and K are not limited to 8 bits, and may be 4 bits. After the color conversion process, a known halftone process is performed on the color material amount of each toner. That is, the color material amount of each toner of C, M, Y, and K is converted into, for example, a 1-bit halftone image signal that can express a halftone by area gradation, and is input to the charging processing unit 512.

  The charging processing unit 512 to which the halftone image signal is input uses a charging roller disposed on the surface of the photosensitive drum 1 as the charging unit 2 and a charging bias electric wire that applies a charging bias to the charging roller. Charge the drum 1 surface uniformly.

  Next, the exposure processing unit 513 irradiates the surface of the photosensitive drum 1 with the laser light emitted from the laser oscillator 31 based on the halftone image signal using the laser oscillator 31, the polygon mirror 32, the Fθ lens 33, and the like. A latent image is formed. Then, the development processing unit 514 develops the electrostatic ray image using each color developing device 4Y, 4M, 4C, 4K to obtain a toner image. Then, in the transfer processing unit 515, first, the toner image on the photosensitive drum 1 is primarily transferred onto the intermediate transfer member 51, which is an image carrier formed in a cylindrical shape. Then, using the transfer belt 52 provided below the intermediate transfer member 51, the four-color toner images primarily transferred onto the intermediate transfer member 51 are collectively transferred to a recording medium. The fixing processing unit 516 heats and pressurizes the recording medium onto which the toner image is secondarily transferred, and fixes the toner image on the recording medium. In this way, an image is formed on the recording medium.

  If the data input from the printer driver 500 is image data designated by the user, the processing is terminated when the image is fixed on the recording medium as described above. On the other hand, when the data input from the printer driver 500 is density correction data, the density correction unit 517 performs density correction processing after the fixing process. That is, the reflectance for each patch is measured from a recording medium on which a plurality of patches corresponding to the density correction data are fixed, and the reflectance is fed back to the exposure processing unit 513, thereby correcting or forming the image forming conditions. Perform image density correction. Details of this density correction processing will be described below.

Density Correction Processing The density correction processing in the density correction unit 517 will be described in detail using the flowchart of FIG. Here, as described above, color measurement is performed on the patch image formed on the recording medium in accordance with the density correction data, using illumination from the front surface and illumination from the back surface via the recording medium. Therefore, hereinafter, the recording medium and the patch image formed on the surface thereof are collectively referred to as “sample” and described.

  First, in S1001, the amount of light emitted from the front side irradiation unit 92 is measured. Specifically, first, the reflectance Rw of the white backing portion 82 installed in the image forming apparatus is measured under the geometric condition 45/0. Here, the geometric condition indicates the relative relationship between the position of the sample and the irradiation unit / light receiving unit at the time of color measurement. Light is irradiated from an angle of 45 ° with respect to the normal line of the sample, and 0 ° When receiving light at an angle, it is expressed as 45/0. In this embodiment, it is assumed that the reflectance Rw of the white backing portion 82 is known and stored in advance in the image forming apparatus. Then, the light amount Ydst of the light irradiated from the front side irradiation unit 92 and reflected from the white backing unit 82 is measured by the front side light receiving unit 91. From the reflectance Rw and the light amount Ydst measured as described above, the irradiation light amount Ysrc from the surface side irradiation unit 92 is calculated using the following equation (1).

Ysrc = Ydst / Rw (1)
In the present embodiment, an example in which the amount of light emitted from the front side irradiation unit 92 is measured using the white backing unit 82 is shown. However, if the reflectance of the sample to be measured is known, the surface of the surface is measured by measuring the black backing unit 81. The irradiation light amount of the side irradiation unit 92 may be calculated. In addition to the backing unit, a calibration sample may be mounted on the apparatus. Further, a light receiving unit different from the surface side light receiving unit 91 may be prepared, and the irradiation light quantity may be directly measured from the surface side irradiation unit 92.

  Next, in step S1002, a backing used for color measurement is set by moving the front side light receiving unit 91 and the front side irradiation unit 92 based on the observation conditions recorded in the print data. Hereinafter, the movement process for each observation condition will be described with reference to FIGS. 9 and 10. FIG. 9 shows the positional relationship between the front side light receiving unit 91 and the front side irradiation unit 92 with respect to the black backing unit 81, the white backing unit 82, and the back side irradiation unit 83. FIG. 10 is a flowchart showing details of the backing setting process in S1002.

  First, in S1201, the observation conditions are determined, and the process branches according to the conditions (1) to (3).

  First, in the case of the condition (1) (Y1≈Y2), control is performed so that each component has the arrangement shown in FIG. That is, first in S1202, the front side light receiving unit 91 is moved to the upper part of the back side irradiation unit 83, and then in S1203, the front side light receiving unit 91 is moved to the position where the geometrical condition 45/0 is reached. Move. Then, by turning on the back side irradiation unit 83 in S1204 and receiving light by the front side light receiving unit 91, the back side irradiation unit 83 is set so that the amount of the received light is equivalent to Ysrc measured in S1001. Control. In step S1205, the back side irradiation unit after the control is turned on so that light is emitted with the same amount of light as Ysrc. By substituting the irradiation light from the back side irradiation unit 83 controlled in this way as a backing at the time of color measurement, the amount of light irradiated from the front surface to the sample is equivalent to the light amount irradiated from the back surface. Color measurement is possible under certain conditions.

  Next, in the case of the condition (2) (Y1> Y2), control is performed so that each component has the arrangement shown in FIG. That is, first, in S1206, the front side light receiving unit 91 is moved to the upper part of the white backing unit 82, and then in S1207, the front side light receiving unit 91 is moved to the position that satisfies the geometric condition 45/0 with the moved front side light receiving unit 91. Move. As a result, the white backing portion 82 becomes a backing at the time of color measurement, and color measurement can be performed under a condition in which the amount of light irradiated from the back surface is smaller than the amount of light irradiated from the front surface of the sample.

  Further, in the case of the condition (3) (Y1 >> Y2), control is performed so that the respective components are arranged as shown in FIG. That is, first the front side light receiving unit 91 is moved to the upper part of the black backing unit 81 in S1208, and then the front side light receiving unit 92 is moved to the position where the geometrical condition 45/0 with the front side light receiving unit 91 is moved in S1209. Move. As a result, the black backing portion 81 becomes a backing at the time of color measurement, and color measurement can be performed under a condition in which the amount of light irradiated from the back surface is extremely smaller than the amount of light irradiated from the front surface of the sample. This is because, since the reflectance of the black backing portion 81 is smaller than the reflectance of the white backing portion 82, the reflection component from the backing corresponding to the irradiation light from the back surface of the sample is reduced.

  When the backing according to the observation condition is set in S1002 as described above, in S1003, an unmeasured patch is set as a sample at the colorimetric position by the set backing, as shown in FIG. The recording medium on which the patch as shown in FIG. In S1004, the density of the patch installed at the colorimetric position in S1003 is measured. In this embodiment, the density value is calculated by measuring the reflectance of the patch. Specifically, first, the surface side irradiation unit 92 is turned on, and the surface side light receiving unit 91 receives light reflected from the sample. If the amount of received light is Ysam, the reflectance Rsam of the sample is obtained by the ratio of Ysam and Ysrc calculated in S1001. Using these, the concentration Dsam is calculated from the following equation (2).

Dsam = -log (Rsam) =-log (Ysam / Ysrc) (2)
In this embodiment, an example is shown in which the density is calculated from the reflectance. However, the density calculation method is not limited to this example, and a value corresponding to the density may be calculated using a formula other than the above equation (2). .

  The calculated density is held in a predetermined memory in the image forming apparatus. For example, in the patch example shown in FIG. 4 in the present embodiment, the laser intensity at the time of the exposure process is 5 patterns, and the color material is 4 patterns of CMYK. Therefore, if the laser intensity is represented by i having a value of 0 to 4 and the color material is represented by j having a value of 0 to 3, 20 patterns of Dij {i = 0 to 4, j = 0 to 3} A memory area for storing the density value of the patch is secured in the apparatus. Each time a sample corresponding to each patch is measured, the corresponding density value is updated.

  In step S1005, it is determined whether or not the density has been measured for all patches formed in the recording medium. If the density measurement for all patches has been completed, the process proceeds to S1006. If it has not been completed, the process returns to S1003 to perform measurement processing for the unmeasured patch.

  In S1006, the laser intensity for reproducing the target density Dt is specified. First, based on the media information recorded in the print data, the target density Dt corresponding to the media information stored in advance in the image forming apparatus is read. Here, for example, the maximum density for the medium is applied as the target density Dt. Next, of the densities Dij measured in S1004, two patches that interpolate Dt are specified. Based on the density of the two specified patches and the two laser intensities when the two patches are recorded, the laser intensity Lp that realizes the density of Dt is calculated using a known linear interpolation method. For example, a laser that achieves Dt when the density of a patch showing a density lower than the target density Dt is D0, the laser intensity is Lp0, the density of a patch showing a density higher than Dt is D1, and the laser intensity is Lp1. The intensity Lp is obtained by the following equation (3).

Lp = Lp0 + (Dt−D0) / (D1−D0) × (Lp1−Lp0) (3)
The interpolation method is not limited to the linear interpolation method, and a non-linear interpolation method such as a spline interpolation method may be used.

  In step S1007, density correction is performed. That is, the laser intensity used in the exposure processing unit 513 is changed to the laser intensity Lp calculated in S1006.

  As described above, according to the present embodiment, the backing used for the color measurement of the sample is changed according to the observation conditions specified by the user. Thereby, the color measurement can be performed by reproducing the relationship between the amount of irradiation light from the front surface and the amount of irradiation light from the back surface of the sample so as to be equivalent to that during actual observation. As a result, the target density can be reproduced regardless of the conditions observed by the user, including the case where there is transmitted light from the back surface of the sample, and the density reproducibility in the image forming apparatus is improved.

Second Embodiment
Hereinafter, a second embodiment according to the present invention will be described. In the first embodiment described above, a plurality of backing parts (81, 82) and a back side irradiation part (83) for irradiating light from the back side of the sample are provided, and at the time of color measurement according to observation conditions designated by the user. An example of changing the backing used was shown. This makes it possible to control the relationship between the amount of light irradiated from the front surface and the amount of light irradiated from the back surface of the sample. In the second embodiment, the control is realized by a different method. That is, in the second embodiment, an example is shown in which the relationship between the amount of light irradiated on the surface of the sample and the amount of light transmitted from the back is controlled by adjusting the amount of light irradiated from the back surface of the sample.

Apparatus Configuration FIG. 11 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to the second embodiment. In the drawing, the configuration for forming the sample is the same as that in FIG. 2 described in the first embodiment, and thus the description thereof is omitted. However, the configuration for measuring the color of the sample is different from that in the first embodiment. . That is, in the second embodiment, as a light emitting unit used when measuring the color of a sample, a front side irradiation unit 992 that is a first irradiation unit and a back side irradiation unit 982 that is a second irradiation unit are provided. Yes. In addition, as a light receiving unit for measuring reflected light intensity and transmitted light intensity from the sample, a front side light receiving unit 991 as a first light receiving unit and a back side light receiving unit 981 as a second light receiving unit are provided. Yes. The surface side irradiation unit 992 and the surface side light receiving unit 991 for measuring the reflected light from the sample are arranged so as to satisfy the 45/0 geometric condition. Note that the functional configuration of the image forming apparatus in the second embodiment is the same as that in FIG. 3 described in the first embodiment, and a description thereof will be omitted.

  FIG. 12 shows a configuration of a color measuring unit including the light emitting unit and the light receiving unit in the second embodiment. As shown in the figure, when measuring a sample on which a color material (patch) is formed on a recording medium, light 1301 is irradiated from the surface side irradiation unit 992, and the reflected light 1303 is irradiated on the surface side. The light is received by the surface side light receiving unit 991 installed at the positions of 992 and 45/0. At this time, light 1304 adjusted as a backing according to the observation conditions is also emitted from the back side irradiation unit 982, and transmitted light 1305 from the sample is received by the front side light receiving unit 991. That is, the front-side light receiving unit 991 can simultaneously reproduce the reflected light 1303 from the sample surface and the transmitted light 1305 from the sample back surface (backing), thereby reproducing the observation conditions for the sample. The back side light receiving unit 981 receives the light 1301 emitted from the front side irradiating unit 992 directly or through a sample and measures the light amount in order to control the light amount of the back side irradiating unit 982. Used for.

Density Correction Processing Hereinafter, density correction processing in the density correction unit 517 of the second embodiment will be described in detail with reference to the flowchart of FIG.

  First, in S1401, the light amount Ysrc of the light emitted from the front side irradiation unit 992 is measured. For example, when the light irradiated from the front side irradiation unit 992 is received by the back side light receiving unit 981, the light amount Ysrc of the irradiation light can be specified. Note that this measurement method is not limited to the above example. For example, as in the first embodiment, a sample with a known reflectance is mounted on the apparatus, and the amount of light Ysrc of the irradiation light from the surface side irradiation unit 992 is set to the surface. You may specify using the side light-receiving part 991.

  Next, in S1402, in order to determine the target light amount of the back side irradiation unit 982, whether the observation condition recorded in the print data is the condition (1) (Y1≈Y2) or other conditions Is determined. If the condition (1) is satisfied, the process proceeds to S1403. Otherwise, the process proceeds to S1407.

  First, processing when the observation condition is the condition (1) (Y1≈Y2) will be described. In the case of condition (1), the amount of light emitted from the back side irradiation unit 982 is controlled so that the amount of light emitted from the front surface and the amount of light emitted from the back surface of the sample are equal. For this purpose, first, in S1403, the light irradiated from the back side irradiation unit 982 is received by the front side light receiving unit 991, and the light amount Yt of the irradiation light is equal to the light amount Ysrc of the irradiation light from the surface measured in S1401. Control to become. In S1404, the recording medium is moved so that a patch whose density is not measured among the patches (FIG. 4) formed on the recording medium is placed at the colorimetric position. In step S1405, the density of the patches installed at the colorimetric position is measured in the same manner as in step S1004 in the first embodiment described above. Until it is determined in step S1406 that all patch densities on the recording medium have been measured. , S1404 to S1405 are repeated. When all patch densities have been measured, the laser intensity for reproducing the target density Dt is specified in S1412, and density correction is performed by feeding back the laser intensity to the exposure processing unit 513 in S1413.

  Next, processing when the observation condition is the condition (2) (Y1> Y2) or the condition (3) (Y1 >> Y2) will be described. In the case of the condition (2) or the condition (3), the amount of light emitted from the back side irradiation unit 982 is controlled so that the amount of light irradiated from the back surface becomes smaller than the amount of light irradiated from the front surface. For this purpose, first in S1407, an unmeasured patch on the recording medium is set at the colorimetric position as in S1404. In step S1408, the transmittance of the patch and recording medium installed at the colorimetric position, that is, the sample of the patch is measured. Here, the transmittance of the sample indicates the ratio between the light amount Ysrc of the irradiation light from the front side irradiation unit 992 measured in S1401 and the light amount Ytran of the light transmitted to the back side of the sample. That is, Ysrc is irradiated from the front side irradiation unit 992, and the light amount Ytran of the light transmitted through the sample is received by the back side light receiving unit 981, whereby the transmittance T of the sample is calculated from the following equation (4).

T = Ytran / Ysrc (4)
Next, in S1409, the amount of light irradiated by the back side irradiation unit 982 is adjusted so as to approach the observation conditions specified by the user. Here, the light amount control in S1409 will be described with reference to the flowchart of FIG.

  First, in S1301, based on the transmittance T of the sample calculated in S4108 and the reflectance Rb of the reference backing stored in advance in the image forming apparatus for each observation condition, a virtual reflectance Rg for the incident light on the sample is stored. Is calculated from the following equation (5). That is, the virtual reflectance Rg indicates the reflectance that will be obtained when the sample is measured using the reference backing. In other words, it represents the proportion of the light Ysrc irradiated from the front side irradiation unit 992 that will be irradiated from the back surface of the sample under the observation conditions specified by the user.

Rg = T × Rb (5)
Here, as the reference backing reflectance Rb, for example, when the observation condition is the condition (2) (Y1> Y2), the reflectance of the white backing defined in the ISO standard is used. When the observation condition is the condition (3) (Y1 >> Y2), the black backing reflectance defined by the ISO standard is used as the reflectance Rb. The calculation of the virtual reflectance Rg is not limited to the example of the above formula (5), and the reflectance Rg in the condition (2) is higher than the reflectance Rg in the condition (3). It suffices if it can be calculated to

  Next, using the virtual reflectance Rg calculated in S1301, adjustment is made so that the amount of light irradiated by the back side irradiation unit 982 approaches the observation condition specified by the user. For this purpose, first, in S1302, the target light amount Yt to be irradiated by the back side irradiation unit 982 is calculated by the following equation (6).

Yt = Ysrc × Rg (6)
As shown in Equation (6), the light amount Ysrc of the light irradiated from the front side irradiation unit 992 is multiplied by the virtual reflectance Rg, so that the light amount of the backside irradiation light under the observation conditions specified by the user is obtained. It is reproduced.

  Then, in order to realize the calculated target light amount Yt, the sample installed when measuring the transmittance T of the sample in S1303 is once removed from the colorimetric position together with the recording medium. In step S1304, the light emitted from the back side irradiation unit 982 is directly received by the front side light receiving unit 991, so that the amount of light emitted from the back side irradiation unit 982 is adjusted to be the target light amount Yt. Thereafter, in S1305, the sample removed from the colorimetric position in S1304 is returned to the colorimetric position, whereby the colorimetric preparation for the patch is completed.

  Although an example in which the recording medium is moved before and after the light amount control of the back side irradiation light in S1304 (S1303, S1305) is shown here, the present invention is not limited to this example. For example, by multiplying the right side of the above equation (6) by the transmittance T as the target light amount Yt, the light amount of the irradiation light from the back surface can be controlled without moving the recording medium, that is, through the sample. Is also possible.

  As described above, when the light amount control of the back side irradiation light by the back side irradiation unit 982 is completed, the process proceeds to S1410. In S1410, the light irradiated from the front surface side irradiation unit 992 and the light irradiated from the back surface side irradiation unit 982 are received by the front surface side light receiving unit 991, so that the same as S1004 in the first embodiment described above, Measure the patch density of the sample at the colorimetric position.

  In step S1411, it is determined whether the density has been measured for all patches formed on the recording medium. If the density of all the patches has been measured, the process proceeds to S1412. If unmeasured patches remain, the process returns to S1407. As described above, the laser intensity for reproducing the target density Dt is specified in S1412, and this is fed back to the exposure processing unit 513 in S1413 to perform density correction.

  As described above, according to the second embodiment, the amount of irradiation light from the back surface is controlled according to the observation conditions specified by the user. Thereby, the color measurement can be performed by reproducing the relationship between the amount of irradiation light from the front surface and the amount of irradiation light from the back surface of the sample so as to be equivalent to that during actual observation. As a result, the target density can be reproduced regardless of the conditions observed by the user, including the case where there is transmitted light from the back surface of the sample, and the density reproducibility in the image forming apparatus is improved.

<Other embodiments>
In the first and second embodiments described above, an example has been shown in which whether data input to the image forming apparatus is image data or density correction data is classified according to a user instruction. However, the present invention is not limited to this example, and the density correction may be performed by recording density correction data in a blank portion where image data is recorded. Further, even when the density correction data is not designated by the user, the density correction data may be automatically output periodically to perform density correction.

  In addition, the example in which the laser intensity of the exposure unit is controlled with the maximum density for each medium as the target density has been described. However, the density gradation correction may be performed based on the measurement values of a plurality of density patches as well as the maximum density. good.

  In the first embodiment, as shown in FIG. 2, the surface side light receiving unit 91 and the surface side irradiating unit 92 constituting the measuring unit are moved according to the set backing position. On the contrary, the measurement unit may be fixedly set and the backing may be moved.

  The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media. The processor or computer (or CPU, MPU, etc.) of the system or apparatus reads out and executes the program.

Claims (14)

A first irradiating means for irradiating the image forming surface with light on a sample on which a patch image is formed on a recording medium;
A second irradiation means for irradiating the sample with light on a non-image forming surface which is the back surface of the image forming surface;
First light receiving means for receiving reflected light from the sample and transmitted light transmitted through the sample on the image forming surface side of the sample;
A light amount control means for controlling the amount of light emitted from the second irradiation means in accordance with the amount of light emitted from the first irradiation means;
Light reception by the first light receiving means in a state in which the sample is irradiated with light from the first irradiation means and light whose light amount is controlled by the light quantity control means from the second irradiation means. First colorimetric means for performing colorimetry on the sample by performing
Correction means for correcting image forming conditions in the image forming apparatus that formed the patch image from the colorimetric result of the sample by the first colorimetric means;
An image processing apparatus comprising:   The light quantity control means controls the light quantity of light emitted from the second irradiation means to be equal to the light quantity of light emitted from the first irradiation means. An image processing apparatus according to 1. Furthermore, it has a backing setting means for arranging a backing having a predetermined reflectance on the non-image forming surface of the sample,
The light amount control means includes
The backing disposed by the backing setting means is irradiated with light from the first irradiating means, and the reflected light is received by the first light receiving means, thereby measuring the amount of the irradiated light. ,
The first light receiving unit directly receives the light emitted from the second irradiating unit so that the amount of light emitted from the second irradiating unit is equivalent to the measured light amount. The image processing apparatus according to claim 2, wherein the image processing apparatus is controlled as follows. Further, when observing an image formed on the recording medium, a first light amount applied to the image forming surface of the recording medium and a second light amount applied to the non-image forming surface of the recording medium. An observation condition input means for inputting an observation condition indicating a relationship;
In a state in which a backing is placed on the sample by the backing setting means and light is emitted from the first irradiating means, light is received by the first light receiving means, and a second colorimetric measurement is performed on the sample. Color means, and
When the observation condition indicates a first condition in which the first light amount and the second light amount are substantially equal, the sample is measured by the first colorimetric means, and the observation condition is the first condition. 4. The image processing apparatus according to claim 3, wherein the color measurement of the sample is performed by the second color measurement unit when a first light quantity indicates a second condition larger than the second light quantity. .   When the observation condition indicates the second condition, the backing setting means determines whether the first light amount and the second light amount indicated by the second condition from a plurality of backings having different reflectances. The image processing apparatus according to claim 4, wherein a backing having a reflectance corresponding to the difference is set.   The said backing setting means sets a backing with a small reflectance, so that the difference of the said 1st light quantity and said 2nd light quantity which the said 2nd condition shows is large. Image processing device.   If the difference between the first light amount and the second light amount indicated by the second condition is greater than or equal to a predetermined value, the backing setting means sets a black backing that conforms to an ISO standard, and the difference is the predetermined amount The image processing apparatus according to claim 6, wherein if it is less than the value, white backing conforming to the ISO standard is set. The backing setting means sets one according to the second condition from a plurality of fixedly installed backings,
The first irradiating unit and the first light receiving unit are configured to be able to irradiate light on the backing disposed by the backing setting unit and receive reflected light from the backing, or the sample without using the backing. The image processing apparatus according to any one of claims 5 to 7, wherein the image processing apparatus moves to a position where irradiation of light on the sample and reception of reflected light from the sample can be performed. Further, when observing an image formed on the recording medium, a first light amount applied to the image forming surface of the recording medium and a second light amount applied to the non-image forming surface of the recording medium. Having an observation condition input means for inputting an observation condition indicating a relationship;
The image processing apparatus according to claim 1, wherein the light amount control unit controls a light amount of light emitted from the second irradiation unit according to the observation condition.   The observation condition includes a first condition in which the first light amount and the second light amount are substantially equal, and a second condition in which the first light amount is larger than the second light amount. The image processing apparatus according to claim 9. Furthermore, it has a second light receiving means for receiving the light emitted from the first irradiation means on the non-image forming surface side of the sample,
The light amount control means includes
The light emitted from the first irradiation means is received by the second light receiving means to measure the amount of the emitted light,
The sample is irradiated with light from the first irradiation means, and the transmittance of the sample is measured by receiving the transmitted light with the second light receiving means.
The image processing apparatus according to claim 9 or 10, wherein a light amount of light emitted from the second irradiation unit is controlled from the measured light amount and transmittance.   12. The image processing apparatus according to claim 1, wherein the first light receiving unit and the first irradiation unit are installed at a position satisfying a geometrical condition of 45/0 with respect to each other. . Light amount control means, colorimetry means, and correction means, irradiation of light to the image forming surface and non-image forming surface of a sample on which a patch image is formed on a recording medium, reflected light from the sample, and the sample A method for correcting image forming conditions in an image forming apparatus capable of receiving transmitted light that has passed through
The light amount control means controls the amount of light irradiated to the non-image forming surface of the sample according to the amount of light irradiated to the image forming surface;
The colorimetric means irradiates the image forming surface and the non-image forming surface of the sample with light at the controlled light amount, and reflects light from the sample and transmitted light transmitted through the sample on the image forming surface side. Measure the sample color by receiving light,
An image forming condition correcting method, wherein the correcting unit corrects an image forming condition in an image forming apparatus on which the patch image is formed from a colorimetric result of the sample.   A program for causing a processor of an image forming apparatus to function as each unit of the image forming apparatus according to any one of claims 1 to 12 when executed by a processor of the image forming apparatus.

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