JP5499767B2 - Image characteristic measuring method, image characteristic measuring apparatus, image evaluation apparatus, and image forming apparatus - Google Patents

Description

  The present invention relates to an image characteristic measuring method, an image characteristic measuring apparatus, an image evaluation apparatus having the image characteristic measuring apparatus, and an image forming apparatus having the image characteristic measuring apparatus.

  In recent years, in the field of production printing, both sheet-fed machines and continuous book machines have been digitized, and many products such as electrophotographic systems and inkjet systems have been put on the market. As user needs shift from monochrome printing to color printing, multi-dimensional images and high-definition and high-density printing are promoted, high-quality photo printing, catalog printing, and advertisements that respond to individual preferences for invoices, etc. With the diversification of service forms that can be delivered to customers, demands for high image quality, guarantee of personal information, and color reproduction are also increasing.

  As a technology that supports high image quality, the electrophotographic system is equipped with a density sensor that detects the toner density before fixing on the intermediate transfer member and photoconductor to stabilize the toner supply amount. Regardless of the method, the output image is captured by a camera or the like and inspected by character recognition or difference detection based on the difference between images. For color reproduction, a color patch is output, and one or more color measurements are performed with a spectrometer. Things to do have been put on the market.

  These techniques are preferably executed over the entire image in order to cope with image variations between pages and within pages. In addition, there is an increasing demand for high image quality, catalogs, etc., such as glossiness, decoration of characters and images, and overall coating, because users themselves present commercial advantages over other users. In the image forming method, it is possible to provide glossiness by adding a transparent toner or the like, and to create a matte tone or metallic tone image in electrophotography.

  Examples of evaluation techniques for measuring the full width of an image are shown below. For example, a mechanism for moving a measurement object relative to the detection system by arranging a plurality of line-shaped light receiving elements is set, and the spectral characteristics of the full width are measured. In this case, a technique for setting a light shielding wall so that crosstalk of reflected light from a detection target region does not occur between light receiving elements is disclosed (for example, see Patent Document 1).

  Further, a technique is disclosed in which continuous irradiation is performed with light sources having different wavelength bands over the entire width of an image, and reflected light is acquired to acquire spectral characteristics of the entire width (see, for example, Patent Document 2).

  In addition, a technique is disclosed in which light is irradiated to the entire width of the printing surface, the density of a specific area is detected by a line sensor camera, and the density is compared with a reference density (see, for example, Patent Document 3).

  Further, a technique is disclosed in which a document and a specific document are scanned a plurality of times, and similarity is determined from processing such as inter-image logical sum for common color information (see, for example, Patent Document 4).

  In addition, a technique is disclosed in which light is irradiated to the entire width of the printing surface and the spectral characteristics of the full width are acquired by a combination of a CCD having a two-dimensional pixel structure and a diffractive element or a refractive element (see, for example, Patent Document 5).

  In addition, a multiband spectroscopic sensor that irradiates an image with illumination light from a plurality of light sources having different emission wavelengths and acquires reflected light with a single light receiving unit is formed. At that time, a technique has been disclosed in which an ultraviolet light source is provided to detect the influence of the fluorescent material contained in the paper and remove it from the color measurement result (see, for example, Patent Document 6).

  However, when trying to measure the color of an image at its full width, it is possible to irradiate multiple light limited to different wavelength bands and take an image with an area sensor, or while taking an image with a line sensor, In general, a moving configuration or a configuration in which a plurality of imaging systems are set and a wavelength band of reflected light from a test object incident on the imaging system is limited can be considered. At that time, in the images corresponding to a plurality of acquired wavelength bands, if there is a shift in the position to be tested between the images, it is impossible to accurately measure the color information at each position of the test target. It becomes possible.

  Here, as a method of accurately measuring color information from a plurality of images in different wavelength bands, a method of comparing the intensity of the reflected light amount acquired at the position of the subject of each image with a reference current image or document data, There is a method of estimating continuous spectral characteristics by applying Wiener estimation or the like from the intensity of the amount of reflected light acquired at the position of the test object in each image. For this reason, when a different position in each image is used as an object to be examined, an error occurs in comparison with a reference or estimation of continuous spectral characteristics.

  The technique disclosed in Patent Document 1 is a line-shaped measurement system, and has a general configuration capable of measuring the color of an image to be examined with the full width. However, the positional deviation of the image obtained in each wavelength band is detected. There was a problem that there was no way to reduce it.

  In the technique disclosed in Patent Document 2, the time axis is generated in the configuration in which the reflected light from the test object by continuous irradiation light from light sources having different wavelength bands is generated, and the same location of the test object is obtained. It is impossible to measure. Even if a plurality of combinations of the light source and the light receiving system are provided in the configuration, there is a possibility that the test target position of each image having a different wavelength band may be shifted.

  The technique disclosed in Patent Document 3 has the same configuration for acquiring color information over the entire width, but is considered to be a representative value by the process of averaging the density of the detected region. There was a problem that could not be guaranteed.

  Although the technique disclosed in Patent Document 4 determines a document and a test object by comparing each other by calculation between images for each wavelength band, color variation of the test object cannot be specified. In addition, there is a problem that even if the image is reconstructed from the color information of the image obtained individually, it cannot be determined whether the color variation has occurred in the actual test object.

  In the technique disclosed in Patent Document 5, the reading speed is significantly slowed down with respect to the line sensor due to restrictions on the data reading characteristics of a CCD having a two-dimensional pixel structure. Etc.) has a problem that there is a great restriction on the speed of acquiring the color information.

  The technique disclosed in Patent Document 6 irradiates paper with visible light and ultraviolet light so that the influence of the paper on the ultraviolet light can be removed. However, the spectroscopic measurement is possible only at one place due to the configuration of the measurement optical system, but the light source must be turned on in a time-sharing manner. It is impossible to measure in the state that is done. This is because the paper moves during time-division lighting and color measurement at the same location is impossible. In addition, since the measurement is performed at only one place, even if the paper is stopped and measured, in order to determine the influence of ultraviolet light reflected from the paper at an arbitrary position, the color distribution of the image, and both. Since it takes an enormous amount of time, there is a problem that it is practically impossible to acquire such information.

  Furthermore, in order to add value to an output image in printers and printing machines, a function of coating the entire image or a part thereof with a transparent color material has been developed. For example, a transparent toner has almost no absorption wavelength band in the visible range. For this reason, an image that is a subject of spectroscopic measurement is usually slightly smaller than the amount of diffusely reflected light of the paper that is the image bearing medium, but the spectral reflectance distribution exhibits substantially the same value. For this reason, in the prior art, even if an image made of color toners such as yellow, cyan, and magenta can be detected, the distribution of the transparent toner cannot be detected. In addition, an image made of transparent toner exhibits its effect by improving glossiness and ensuring uniformity in areas other than areas formed by other color toners, and by mixing with and around the image made of color toner. It does not make sense in the measurement of, and must be measured as a two-dimensional area. In the prior art, it is impossible to measure the image formation state on the entire surface of an image made of color toner and transparent toner at the same location.

  The present invention has been made in view of the above points, and is an image characteristic measuring method, an image characteristic measuring apparatus, an image, and the like that can acquire color information of a measurement object and value-added information such as glossiness in full width. It is an object to provide an evaluation apparatus and an image forming apparatus.

In this image characteristic measurement method, a light irradiation step of irradiating a medium with light including visible light and non-visible light, and diffuse reflected light from the medium irradiated by the light irradiation step, A region dividing step for dividing the region into a plurality of regions; a spectroscopic step for dispersing the diffused reflected light divided into the plurality of regions by the region dividing step outside the visible region and the visible region; and N arranged in one direction A spectral sensor array having a plurality of (N is a natural number of 2 or more) pixels and having a visible light receiving region and an invisible light receiving region are arranged in correspondence with the plurality of regions. Receiving the diffusely reflected light dispersed in the visible region in a visible light receiving region, and receiving the diffused reflected light dispersed outside the visible region in the invisible light receiving region, and receiving the light The diffusion reaction in the visible range received by The color of the plurality of regions is measured by the light reception intensity of light, and the state of the color material exhibiting transparency of the plurality of regions is measured by the light reception intensity of the diffusely reflected light outside the visible range received in the light receiving step. Is a requirement.

The image characteristic measurement apparatus includes a light irradiation unit that irradiates a medium with light including visible light and non-visible light, and diffuse reflected light from the medium irradiated by the light irradiation unit. A region dividing unit that divides the light into a plurality of regions, a spectroscopic unit that divides the diffusely reflected light divided into the plurality of regions by the region dividing unit outside the visible region and the visible region, and N arranged in one direction A visible light receiving region that has the number of pixels (N is a natural number of 2 or more) and receives the diffusely reflected light dispersed in the visible region; and a non-visible light that receives the diffusely reflected light dispersed outside the visible region It is a requirement that a spectral sensor including a light receiving region includes a plurality of spectral sensor arrays arranged corresponding to the plurality of regions.

  According to the disclosed technology, an image characteristic measuring method, an image characteristic measuring apparatus, an image evaluation apparatus, and an image forming apparatus capable of acquiring color information of a measurement object and added value information such as glossiness in full width are provided. can do.

It is a figure which illustrates the image characteristic measuring device concerning a 1st embodiment. It is a figure which expands and schematically illustrates a part of FIG. It is the photograph (the 1) which shows the state which looked at the light which injects into a line sensor from the entrance plane side. FIG. 6 is a diagram (part 1) for describing the arrangement of diffraction elements. It is FIG. (2) for demonstrating arrangement | positioning of a diffraction element. It is the photograph (the 2) which shows the state which looked at the light which injects into a line sensor from the entrance plane side. It is a figure which illustrates the spectral distribution of the toner image used for simulation. It is a figure which illustrates a simulation result. It is a figure for demonstrating a filter. It is a perspective view which shows typically a mode that the optical system of the image characteristic measuring device which concerns on 4th Embodiment was seen from the image carrier medium side. It is a perspective view which shows typically a mode that the optical system of the image characteristic measuring device which concerns on 5th Embodiment was seen from the image carrier medium side. It is a figure which illustrates the image evaluation apparatus which concerns on 6th Embodiment. It is a figure which illustrates the image forming apparatus which concerns on 7th Embodiment.

  Hereinafter, embodiments will be described with reference to the drawings.

<First Embodiment>
FIG. 1 is a diagram illustrating an image characteristic measuring apparatus according to the first embodiment. FIG. 2 is a diagram schematically illustrating a part of FIG. 1 in an enlarged manner. Referring to FIGS. 1 and 2, the image characteristic measuring apparatus 10 includes a line illumination light source 11, a selfoc lens 13, a pinhole array 14, an imaging optical system 15, a diffraction element 16, and a line sensor 17. And have. Reference numeral 90 denotes an image bearing medium (paper or the like). An image is formed in a predetermined area on the image bearing medium 90.

  In the following description, specularly reflected light is reflected light that is reflected at the same angle as the incident angle of the irradiation light irradiated from the line illumination light source 11 to the image bearing medium 90 (that is, incident light). If the angle is θ, it refers to reflected light having a reflection angle of π−θ, and diffuse reflected light refers to reflected light other than regular reflected light.

  The line illumination light source 11 has a function of irradiating the image bearing medium 90 and a predetermined area of the image on the image bearing medium 90 with irradiation light including light in the visible range and light outside the visible range. The line illumination light source 11 is disposed at a position where the irradiation light is incident on the image bearing medium 90 at an angle of approximately 45 degrees. As the line illumination light source 11, for example, an LED (Light Emitting Diode) array can be used. As the line illumination light source 11, a fluorescent lamp such as a cold cathode tube, a lamp light source, or the like may be used.

  However, the line illumination light source 11 emits light in a wavelength region necessary for spectroscopy (including light in the visible region and light outside the visible region) and can be uniformly illuminated over the entire observation region. Is preferred. A collimating lens, a cylindrical lens, or the like may be provided on the optical path between the line illumination light source 11 and the image bearing medium 90. The line illumination light source 11 is a typical example of the light irradiation means according to the present invention. Of course, the light irradiation means may include a collimating lens, a cylindrical lens, or the like.

  The SELFOC lens 13 forms an image (condensed light) on the pinhole array 14 of diffuse reflection light of the irradiation light irradiated from the line illumination light source 11 to the image bearing medium 90 and a predetermined region of the image on the image bearing medium 90. ) Function. The diffuse reflection light from the image bearing medium 90 and a predetermined region of the image on the image bearing medium 90 is imaged on the pinhole array 14 by the Selfoc lens 13 and divided into regions. Instead of the Selfoc lens 13, a microlens array may be applied. Alternatively, a configuration in which a homogeneous optical element such as a tapered rod array is integrally arranged with the pinhole array 14 may be adopted. The Selfoc lens 13, the microlens array, and the tapered rod array are typical examples of the first imaging unit according to the present invention.

  It is necessary to examine the suitability of the Selfoc lens array 13 based on the shading performance based on the hole pitch and lens array pitch of the pinhole array 14, the position of the imaging optical system 15 in the subsequent stage, and the optical characteristics. By adopting a configuration in which the pinhole array 14 and the image bearing medium 90 are arranged close to each other, it is possible to eliminate the Selfoc lens 13 and the microlens array.

  The pinhole array 14 has a structure in which, for example, a plurality of openings (for example, rectangular slits) through which light is transmitted are arranged in a row in a light shielding portion, and an image bearing medium of irradiation light irradiated by the line illumination light source 11 90 and a function of dividing diffusely reflected light from a predetermined area of the image on the image bearing medium 90 into a plurality of areas. Hereinafter, the pinhole array 14 having a structure in which slits are arranged in a row will be described as an example. A light beam incident on each slit of the pinhole array 14 is divided into a plurality of regions. One slit corresponds to one spectroscopic sensor (described later), and one slit and the N pixels of the spectroscopic sensor are in an imaging relationship. Furthermore, since the slits and N pixels are formed in parallel, it is possible to cope with a spectroscopic sensor array (described later).

  As the pinhole array 14, a blackened metal plate with holes or a glass substrate with a black member such as chromium or carbon-containing resin formed in a predetermined shape can be used. . The slit may have a plurality of sizes. In this case, the position of the pinhole array 14 can be switched according to the desired wavelength resolution. The shape of the opening is not limited to a rectangle, and may be an ellipse, a circle, or other shapes. The pinhole array 14 is a typical example of area dividing means according to the present invention.

  The imaging optical system 15 includes a plurality of lenses, and forms (condenses) each image divided into a plurality of regions on the pinhole array 14 on the line sensor 17 via the diffraction element 16. Have The imaging optical system 15 is a typical example of the second imaging means according to the present invention.

  The diffractive element 16 is disposed in the vicinity of the line sensor 17 and diffracts incident light to diffract incident light as schematically shown by the dotted line in FIG. Light having different spectral characteristics is incident on the N pixels. The diffractive element 16 has a function of dispersing each image divided into a plurality of regions on the pinhole array 14 in the visible region and outside the visible region. The diffractive element 16 is obtained by periodically forming a sawtooth structure on a transparent substrate, for example. The diffraction element 16 is a typical example of the spectroscopic means according to the present invention.

  The line sensor 17 is composed of a plurality of pixels, and has a function of acquiring a diffused reflection light amount in a predetermined wavelength band incident through the diffraction element 16. As the line sensor 17, for example, a metal oxide semiconductor device (MOS), a complementary metal oxide semiconductor device (CMOS), a charge coupled device (CCD), a contact image sensor (CIS), or the like can be used.

  The line sensor 17 has a pixel structure in which a plurality of pixels are arranged in a line in the X direction. The line sensor 17 constitutes a spectroscopic sensor array in which a plurality of spectroscopic sensors 17a, 17b, 17c, etc., each having a group of N pixels arranged in parallel in the X direction, are arranged in the X direction. The spectral sensors 17a, 17b, 17c and the like have N pixels that receive light having different spectral characteristics arranged in the X direction.

  The value of N, which is the number of pixels constituting the spectroscopic sensors 17a, 17b, 17c, etc. corresponds to the number of wavelength regions that are spectrally separated by the diffraction element 16. In the example of FIG. 2, N = 6. N light beams having different spectral characteristics are incident on N pixels constituting the spectral sensors 17a, 17b, 17c and the like.

  In the image characteristic measuring apparatus 10 shown in FIG. 1, a dotted line schematically shows a typical optical path of diffuse reflected light from the image bearing medium 90. The light emitted from the line illumination light source 11 (which may pass through a collimator lens or the like) has a line shape that spreads in a predetermined area of the image on the image carrier medium 90 and the image carrier medium 90 that is an object to be read. Illuminated. Diffuse reflected light from the image bearing medium 90 and a predetermined area of the image on the image bearing medium 90 is imaged on the pinhole array 14 by the SELFOC lens 13 and divided into areas. The region-divided image on the pinhole array 14 is dispersed by the diffraction element 16 and imaged on the pixels of the line sensor 17 by the imaging optical system 15.

  Here, if the period of the sawtooth-shaped portion of the diffraction element 16 is p, light having a wavelength λ incident on the diffraction element 16 at an angle α is diffracted to an angle θm expressed by the equation (Equation 1). In the equation (Equation 1), m is the order of the diffraction grating, and can be a positive or negative integer value.

By making the shape of the diffractive element 16 into a sawtooth shape as shown in FIG. 2, it is possible to increase the intensity of the + 1st order diffracted light, which is most desirable. In addition to the sawtooth shape, it is possible to take a stepped shape. Further, if the pixel period d of the line sensor 17 is 10 μm, the visible light is reduced to approximately 6 pixels when the period p of the diffraction element 16 is 10 μm and the distance between the diffraction part of the diffraction element 16 and the line sensor 17 is 2 mm. It is possible to enter by spectroscopic.

  FIG. 3 is a photograph (No. 1) showing a state in which light incident on the line sensor is viewed from the incident surface side. FIG. 3 shows a direction in which the diffraction element 16 has the diffraction direction of the diffraction element 16 in a plane (XY plane) perpendicular to the optical axis (Z direction) of the entire optical system and the pixels of the line sensor 17 are arranged. It is an example in the case of being arranged so as to be parallel to (X direction). In the example of FIG. 3, non-diffracted light (0th-order light), + second-order light, -second-order light, and diffraction images of adjacent light fluxes that have passed through adjacent apertures overlap on the line sensor to cause crosstalk, It is difficult to obtain accurate spectral characteristics.

  Therefore, in order to block non-diffracted light (0th order light) and other diffracted light other than the desired order, the diffractive element has a surface in which the diffraction direction of the diffractive element is perpendicular to the optical axis (Z direction) of the entire optical system. Within (in the XY plane) a predetermined angle with respect to the direction in which the pixels of the line sensor 17 are arranged so as to be non-parallel to the direction in which the pixels of the line sensor 17 are arranged (X direction) As is preferred). This will be described with reference to FIGS.

  FIG. 4 is a diagram for explaining the arrangement of the diffraction elements, and shows a state in which the line sensor 17 and the light incident on the line sensor 17 are viewed from the incident surface side. As shown in FIG. 4, in order to block the diffracted light other than the + 1st order light B which is the desired diffracted light, the diffractive element has a diffraction direction of the diffractive element on the optical axis (Z direction) of the entire optical system. In a vertical plane (in the XY plane), the N pixels of the line sensor 17 are arranged so as to be non-parallel to the direction (X direction) in which the N pixels of the line sensor 17 are arranged. It is preferably arranged (with a predetermined angle β) with respect to the direction.

  In FIG. 4, as the light transmitted through the diffraction element, in addition to the + 1st order light B that is the desired diffracted light, the desired diffracted light is weaker than the non-diffracted light (0th order light) A and the + 1st order light B. -First order light C, + secondary light D, -secondary light E, etc. are generated. As shown in FIG. 4, the diffraction direction of the diffraction element is in a plane (in the XY plane) perpendicular to the optical axis (Z direction) of the entire optical system, and with respect to the pixel arrangement direction (X direction) of the line sensor 17. It is tilted by a minute angle β. The minute angle β needs to be determined so that a certain + secondary light D does not enter the same pixel as the adjacent + first order light B.

  In order to incline the diffraction direction as shown in FIG. 4, for example, the entire diffraction element 16 shown in FIG. 2 is X in the XY plane perpendicular to the optical axis (Z direction) of the entire optical system as shown in FIG. What is necessary is just to rotate only the minute angle (beta) with respect to the axis | shaft. In addition, without rotating the entire diffraction element 16, the tooth angle of the diffraction element 16 may be tilted by a minute angle β with respect to the X axis in the XY plane perpendicular to the optical axis (Z direction) of the entire optical system. Good. As a result, the + 1st order light B that is the desired diffracted light is incident on the pixels of the line sensor 17, but the non-diffracted light (0th order light) A and −1st order light C that are not the desired diffracted light, and the + secondary light D , -Secondary light E or the like can be arranged so that it hardly enters.

  FIG. 6 is a photograph (No. 2) showing a state in which light incident on the line sensor is viewed from the incident surface side. FIG. 6 shows the diffraction element 16 in which the diffraction direction of the diffraction element 16 is in a plane (XY plane) perpendicular to the optical axis (Z direction) of the entire optical system, and N pixels of the line sensor 17 are arranged. This is an example in the case of being arranged so as to have a minute angle β (angle β = 10 [deg]) with respect to the direction (X direction). As shown in FIG. 6, the occurrence of crosstalk as shown in FIG. 3 can be prevented by setting the angle β to a predetermined value. Although FIG. 6 shows an example in which the diffraction element 16 is tilted by β = 10 [deg], the optimum value of the angle β can be determined from conditions such as the optical element to be used, the layout of the optical element, and the like.

  The image characteristic measuring apparatus 10 needs to acquire a diffraction image from ultraviolet light to infrared light. Therefore, the diffraction element 16 has a grating frequency and a blaze angle set so as to have diffraction performance corresponding to wavelengths from about 350 nm to about 800 nm, and can acquire diffraction images outside the visible region and the visible region. Further, as the diffraction element 16, a holographic diffraction grating can be applied instead of the sawtooth diffraction grating. Although the holographic diffraction grating has a somewhat lower peak diffraction efficiency than the sawtooth diffraction grating, it is possible to ensure a certain diffraction performance in the visible region and in a wide wavelength region outside the visible region.

  The image characteristic measuring apparatus 10 requires the following wavelength range. First, in order to acquire color information of an image using color materials such as yellow (Y), magenta (M), and cyan (C), for example, color toner, a wavelength range of about 400 nm to about 700 nm is required. Second, in order to distinguish between paper and the transparent toner distribution area, that is, the presence / absence of a transparent image formed by the transparent toner, a wavelength range from about 350 nm to about 400 nm in a short wavelength region from the ultraviolet region to the visible region is required. Become. Thirdly, in order to distinguish the black toner region from the other color toners, the transparent toner and the paper, a wavelength range from the long wavelength region in the visible region to about 700 nm or more in the infrared region is required. As described above, the light including the visible region is necessary for obtaining the color information of the measurement object, and the light including the visible outside region is necessary for obtaining the value-added information such as glossing of the measurement object.

  As a factor for determining these wavelength ranges, spectral measurement for obtaining color information of an image can be performed at about 400 nm to about 700 nm, but when only transparent toner is distributed, spectral information of diffuse reflected light at the exposed portion of the paper. On the other hand, the difference between the spectral information in the region where the transparent toner is distributed is small, and it is difficult to separate the two, and the state of the image formed with the transparent toner cannot be detected. Therefore, utilizing the fact that the light absorption wavelength band of the resin constituting the toner is in the ultraviolet region, the presence or absence of a transparent image is identified from the received light intensity of the diffraction image in the wavelength range of about 350 nm to about 400 nm. That is, if the received light intensity of the diffraction image in the wavelength range of about 350 nm to about 400 nm is high, it can be separated as an image area where the paper is exposed and if it is low, the presence or absence of a transparent image can be detected.

  A spectral reflectance of about 30 to 40% in the ultraviolet region of general paper is obtained, and the spectral reflectance of the resin constituting the toner is 10% or less. Therefore, it is possible to determine whether the received light intensity of the diffraction image is high or low using these values as indices. For example, if the spectral reflectance is 20% or more, it can be determined that the received light intensity of the diffraction image is high, and if the spectral reflectance is less than 20%, the received light intensity of the diffraction image is low. However, when the visible wavelength is shorter, for example, when the wavelength is 400 nm, the difference between the spectral reflectance of general paper and the spectral reflectance of the resin constituting the toner may be as small as about 10%. In such a case, a step of measuring the spectral reflectance difference between the paper to be used and the transparent image region in advance is separately provided, and a threshold value for determining the level of received light intensity of the diffraction image may be set based on the measurement result. . Note that, in the infrared region, there is no absorption wavelength band in which a remarkable difference is seen in the characteristics of paper, color toner (yellow, magenta, cyan, etc.), and transparent toner. However, since black toner absorbs carbon, which is a constituent material, in the infrared region, the presence or absence of black toner can be separated and identified from paper and other toner images from the received light intensity of the diffraction image in the infrared region. Become.

  The number N of pixels constituting the spectroscopic sensors 17a, 17b, 17c, etc. is the pitch and diameter of the pinhole array 14, the magnification of the imaging optical system 15, the pitch of the diffraction element 16, and the installation distance between the diffraction element 16 and the line sensor 17. However, it can be flexibly adjusted according to conditions such as the number of units configured on the line sensor 17 and the wavelength range to be measured.

  For the acquisition of value-added information such as glossiness for images formed with transparent toner, wavelengths from ultraviolet light to the short wavelength range of the visible range are applied, but the received light intensity of the diffraction image is limited to a specific wavelength. The simplest method is to determine the presence or absence of a transparent image. However, since there are fluctuations in the spectral characteristics of paper due to additives such as fluorescent materials, it is desirable to apply multiple wavelengths in order to increase reliability.

  Further, black toner detection from the long wavelength region of the visible region to the infrared region can be applied to distinguish between a black image formed with yellow, magenta, and cyan and a black image formed with black toner. When feedback to an image evaluation apparatus and an image forming apparatus to be described later, it is possible to develop detailed image correction.

  In the optical system illustrated in FIG. 1, the irradiation light emitted from the line illumination light source 11 is incident on the image bearing medium 90 at an angle of approximately 45 degrees, and the line sensor 17 diffuses from the image bearing medium 90 in the vertical direction. This is a so-called 45/0 optical system that receives reflected light. However, in the image characteristic measuring apparatus according to the present embodiment, the configuration of the optical system is not limited to that illustrated in FIG. 1. For example, the irradiation light emitted from the line illumination light source 11 is applied to the image carrier medium 90. A so-called 0/45 optical system or the like that receives light that is incident perpendicularly and is diffusely reflected by the line sensor 17 in the direction of 45 degrees from the image bearing medium 90 may be used.

  As described above, according to the first embodiment, the spectral data of the light (diffuse reflected light) scattered from the predetermined region of the image on the image bearing medium and the image bearing medium that is the measurement target can be obtained at high speed. By obtaining with high accuracy without causing errors due to alignment between colors, color information of images formed with color toners and value added information such as glossiness formed with transparent toners, etc. are obtained over the entire image width. An image characteristic measurement device and an image characteristic measurement method that enable measurement can be realized.

  In addition to the color information of the image on the image bearing medium, value-added information such as gloss can be measured simultaneously and at the full width of the image. By revealing in the same way as information, it is possible to evaluate the image quality and contribute to improving the image quality and improving the image quality.

<Second Embodiment>
In the second embodiment, an example of an image characteristic measurement apparatus having processing for estimating spectral distribution by estimation means such as Wiener estimation while minimizing the number of N is shown.

  In multiband spectroscopy, the larger the number of N, the more preferable it is possible to obtain a detailed measurement result of the spectral distribution. However, when the number of pixels of the line sensor 17 is constant, the number of spectral sensors that can be arrayed decreases as the number of N increases. Therefore, it is preferable that the image characteristic measurement apparatus has a process (spectral estimation process) of estimating the spectral distribution by an estimation means such as Wiener estimation while minimizing the number of N. Many methods have been proposed for spectral estimation processing, and details are described in, for example, “Analysis and Evaluation of Digital Color Images: University of Tokyo Press: p154-p157” which is a non-patent document.

  An example of a technique for estimating the spectral distribution from the output vi from one spectroscopic sensor is shown below. From the row vector v storing the signal outputs vi (i = 1 to N) from the N pixels constituting one spectroscopic sensor and the conversion matrix G, the spectral reflectance (for example, 400 to 700 nm) of each wavelength band. The row vector r storing 31 of 10-nm pitch is expressed by the equation (Equation 2).

The transformation matrix G is a matrix R that stores spectral distributions for a large number (n) of samples whose spectral distributions are known in advance, as shown in the equations (Equation 3) to (Equation 5). It is obtained by minimizing the square norm of error ‖ · ‖2 from the matrix V storing v when measured by this measuring apparatus, using the least square method.

A transformation matrix G, which is a regression coefficient matrix of a regression equation from V to R, where V is an explanatory variable and R is an objective variable, is expressed using a Moore-Penrose generalized inverse matrix that gives a squared least norm solution of the matrix V. It is calculated as (Equation 6).

Here, the superscript T represents the transpose of the matrix, and the superscript -1 represents the inverse matrix. By storing the conversion matrix G obtained in this way, the spectral distribution r of an arbitrary object to be measured is estimated by taking the product of the conversion matrix G and the signal output v during actual measurement.

  As an example, a toner image output by an electrophotographic image forming apparatus is read by the spectral sensor array according to the present embodiment, a spectral distribution is estimated, and a color difference that is an estimation error is calculated from the estimated spectral distribution. It was. In the simulation, the color difference (ΔE) between the color measurement result when the value of N is changed and the color measurement result obtained from a more detailed spectroscopic device is obtained.

  FIG. 7 is a diagram illustrating the spectral distribution of the toner image used in the simulation. FIG. 8 is a diagram illustrating a simulation result. Referring to FIG. 8, it can be seen that when N is 6 or more, there is no significant difference in the error of the estimated value. This result depends largely on the object to be read and the spectral distribution of the signal received by the sensor, so it may not be true in all cases, but to measure the output results of image forming devices such as toner, When the number of N is 6 or more, the error of the spectral estimation value is sufficiently small, indicating that a suitable spectral sensor array can be realized.

  As described above, according to the second embodiment, the same effects as those of the first embodiment are obtained, but the following effects are further obtained. That is, the image characteristic measuring apparatus according to the second embodiment has spectral characteristic estimation means for estimating a wavelength distribution with higher wavelength resolution and higher density based on outputs from N pixels. As a result, even if the number of N is, for example, about 6 in the visible range, a substantially continuous spectral distribution can be estimated.

  In particular, when measuring an image formed by the image forming apparatus, it is possible to efficiently estimate a substantially continuous spectral distribution when the value of N is 6 or more, and a highly accurate image. A characteristic measuring device can be realized.

<Third Embodiment>
In the third embodiment, an example of an image characteristic measuring apparatus in which a filter that shields light in a predetermined wavelength range is provided on the front surface of the incident surface of the line sensor 17 will be described.

  FIG. 9 is a diagram for explaining the filter, and shows a state in which the line sensor 17, the light incident on the line sensor 17, and the filters 18b, 18c, 19b, and 19c are viewed from the incident surface side. As shown in FIG. 9, in the image characteristic measuring apparatus according to the third embodiment, filters 18b, 18c, 19b, and 19c that shield light in a predetermined wavelength range are provided on the front surface of the incident surface of the line sensor 17. It has been.

  In FIG. 9, filters 18 b and 18 c are filters that shield light in a wavelength range of 400 nm or less, and are provided in front of a region (visible light receiving region) that receives a visible diffraction image of the line sensor 17. . The filters 18b and 18c are typical examples of the ultraviolet light shielding means according to the present invention. The filters 19b and 19c are filters that shield light in the wavelength range of 700 nm or less, and are in front of the long wavelength side of the visible range of the line sensor 17 and the region receiving infrared diffraction images (infrared light receiving region). Is provided. The filters 19b and 19c are typical examples of visible light shielding means according to the present invention.

  By providing the filters 18b, 18c, 19b, and 19c, crosstalk between the + first order light B (first order diffraction image) and the + second order light D (second order diffraction image) can be eliminated. As can be seen from the above formula (Equation 1), for example, + second order light (second order diffraction image) of 330 nm light is imaged on + 1st order light (first order diffraction image) of 660 nm light, and spectral information of 660 nm is obtained. This is an error factor. That is, in FIG. 9, if the wavelength of the + 1st order light B is 660 nm, the + secondary light D of the 330 nm light cross-talks with the + 1st order light B.

  In this case, if filters 18b and 18c that shield light in the wavelength range of 400 nm or less are provided in front of the region (visible light receiving region) that receives the diffraction image in the visible region of the line sensor 17, it is an error factor. It can block + secondary light D of 330 nm light, and can receive only + 1st order light B of 660 nm. Similarly, if filters 19b and 19c that shield light in a wavelength range of 700 nm or less are provided in front of a region (infrared light receiving region) that receives the diffraction image in the infrared region of the line sensor 17, the visible factor that is an error factor is provided. The + secondary light D of the light is shielded, and only the desired + first order light B can be received. As a result, spectral information in a wide wavelength range can be acquired with high accuracy without crosstalk.

  As described above, according to the third embodiment, the same effects as those of the first embodiment are obtained, but the following effects are further obtained. That is, by providing a filter that shields light in a predetermined wavelength range in front of the incident surface of the line sensor, + 1st order light (first order diffraction image) and 1st order light (first order diffraction image) in the measurement range are provided. It is possible to eliminate crosstalk with + second order light (second order diffraction image) on the short wavelength side to be superimposed, and to realize an image characteristic measuring apparatus and an image characteristic measuring method having higher accuracy and higher reliability. it can.

<Fourth embodiment>
In the fourth embodiment, an example of an image characteristic measuring apparatus provided with an optical path branching unit that splits diffuse reflected light from a predetermined area of an image on the image bearing medium 90 and the image bearing medium 90 into two optical paths is shown. .

  FIG. 10 is a perspective view schematically showing a state in which the optical system of the image characteristic measuring apparatus according to the fourth embodiment is viewed from the image bearing medium side. As shown in FIG. 10, the optical system of the image characteristic measuring apparatus according to the fourth embodiment is different from the optical system of the image characteristic measuring apparatus shown in FIG. A sensor 27 is added. The line sensor 27 is the same as the line sensor 17, but is given another reference for convenience of explanation.

  In FIG. 10, the light emitted from the line illumination light source 11 (which may pass through a collimating lens or the like) is on an image carrier medium (not shown) and an image carrier medium (not shown) that are reading objects. A predetermined area of the image is illuminated in a broad line shape. Diffuse reflected light from an image bearing medium (not shown) and a predetermined region of the image on the image bearing medium (not shown) is imaged on the pinhole array 14 by the SELFOC lens 13 and divided into regions. The region-divided image on the pinhole array 14 enters the optical path branching means 20 via the imaging optical system 15 (optical path P). As the optical path branching unit 20, for example, a beam splitter or the like can be used.

  Part of the diffusely reflected light incident on the optical path branching unit 20 passes through the optical path branching unit 20 and enters the line sensor 17 via the diffraction element 16 (optical path Q). That is, part of the diffuse reflected light is dispersed by the diffraction element 16 and imaged on the pixels of the line sensor 17 by the imaging optical system 15. On the other hand, the remaining part of the diffusely reflected light that has entered the optical path branching unit 20 is reflected by the optical path branching unit 20 and enters the line sensor 27 via the diffraction element 26 (optical path R). That is, the remainder of the diffusely reflected light is dispersed by the diffraction element 26 and imaged on the pixels of the line sensor 27 by the imaging optical system 15.

  For example, a diffraction image receiving system including the diffraction element 16 and the line sensor 17 acquires a diffraction image in the visible range, and a diffraction image receiving system including the diffraction element 26 and the line sensor 27 acquires a diffraction image outside the visible range. In the state where there is no crosstalk of the diffraction image, it is possible to identify the color information, the distribution state of the transparent image, and the black toner.

  In order to obtain a diffraction image in the visible range with a diffraction image light receiving system including the diffraction element 16 and the line sensor 17, for example, a method in which the diffraction element 16 is shaped to increase the diffraction efficiency in the visible range, or the incidence of the diffraction element 16 is incident. For example, a method of providing a filter that passes only a diffraction image in a visible region before or after incidence can be used. Similarly, in order to obtain a diffraction image outside the visible range with a diffraction image light receiving system including the diffraction element 26 and the line sensor 27, for example, a method of forming the diffraction element 26 in a shape that lowers the diffraction efficiency in the visible range, For example, a method of providing a filter that allows only the diffraction image outside the visible range to pass before or after the incidence of 26 can be used. As a result, the line sensor 17 can receive only the diffraction image in the visible region, and the line sensor 27 can receive the ultraviolet light from the short wavelength side of the visible region and the infrared light from the long wavelength side of the visible region. It becomes possible to acquire spectral information in a wide wavelength range with high accuracy without crosstalk.

  As described above, according to the fourth embodiment, the same effects as in the first embodiment can be obtained, but the following effects can be further achieved. That is, by branching the optical path for acquiring a diffraction image outside the visible region and the visible region, the + 1st order light (first order diffraction image) in the measurement range and the short wavelength side superimposed on the + 1st order light (first order diffraction image) It is possible to eliminate crosstalk with + 2nd order light (second order diffraction image), and an image characteristic measuring apparatus and an image characteristic measuring method having higher accuracy and higher reliability can be realized.

<Fifth embodiment>
In the fifth embodiment, an example of an image characteristic measuring apparatus provided with an image bearing medium and a light receiving element array that receives specularly reflected light from a predetermined region of an image on the image bearing medium is shown.

  FIG. 11 is a perspective view schematically showing a state in which the optical system of the image characteristic measuring apparatus according to the fifth embodiment is viewed from the image bearing medium side. As shown in FIG. 11, the optical system of the image characteristic measuring apparatus according to the fifth embodiment is obtained by adding a light receiving element array 21 to the optical system of the image characteristic measuring apparatus shown in FIG. . The light receiving element array 21 is, for example, a photodetector (PD) array, a CCD linear sensor, or the like, and is arranged at a position where it can receive regular reflection light from an image bearing medium and a predetermined region of the image on the image bearing medium. The light receiving element array 21 is arranged so that the elements constituting the light receiving element array 21 are arranged in the main scanning direction (X direction in FIG. 11), and the positions of the elements constituting the light receiving element array 21 are in the X direction. It is preferable that the position of each pinhole in the pinhole array 14 coincides with the position in the X direction.

  In FIG. 11, the light emitted from the line illumination light source 11 (which may pass through a collimating lens or the like) is on an image carrier medium (not shown) and an image carrier medium (not shown) as reading objects. A predetermined area of the image is illuminated in a broad line shape. Diffuse reflected light from an image bearing medium (not shown) and a predetermined region of the image on the image bearing medium (not shown) is imaged on the pinhole array 14 by the SELFOC lens 13 and divided into regions. The region-divided image on the pinhole array 14 is dispersed by the diffraction element 16 and imaged on the pixels of the line sensor 17 by the imaging optical system 15. On the other hand, regular reflection light from an image bearing medium (not shown) and a predetermined region of the image on the image bearing medium (not shown) is imaged on the pixels of the light receiving element array 21.

  As described above, according to the fifth embodiment, the same effects as those of the first embodiment are obtained, but the following effects are further obtained. In other words, by providing an image bearing medium and a light receiving element array that receives specularly reflected light from a predetermined area of the image on the image bearing medium, it is possible to add color information such as color toner and gloss by transparent toner. It is possible to realize an image characteristic measuring apparatus and an image characteristic measuring method capable of acquiring gloss distribution information of an image to be measured in association with value information.

  In each of the above embodiments, for example, the measurement region of the image characteristic measurement apparatus shown in FIGS. 1, 10, and 11 is set to be larger than the effective image formation width of the paper that is the image carrier medium to be measured. However, the optical system may be arranged so that measurement can be performed for the exposed portion of the paper. For example, in continuous printing such as production printing, a difference between the exposed portion of the paper and the toner image forming portion can be separated by providing a forming portion such as a paper exposed portion and a basic patch outside the effective image area. It becomes possible. With such a configuration, it is possible to improve the reliability of obtaining an identification index between paper and transparent toner in the ultraviolet region from the short wavelength side of the visible region. In this case, the magnification of the imaging optical system 15 is determined from the width of the line sensor 17 and the measurement region, and the number of spectral sensors is determined from the number of pixels necessary for the spectral sensor. The measurement pitch on the image bearing medium is determined by the number of spectral sensors.

<Sixth embodiment>
In the sixth embodiment, an example of an image evaluation apparatus equipped with the image characteristic measurement apparatus described in the first to fifth embodiments is shown.

  FIG. 12 is a diagram illustrating an image evaluation apparatus according to the sixth embodiment. An image evaluation apparatus 60 shown in FIG. 12 is obtained by integrating the image characteristic measurement apparatus 10 shown in FIG. Since the configuration of the optical system and the function of each optical element are as described in the first embodiment, the description thereof is omitted here.

  The image evaluation device 60 is configured to be movable in the Y direction by a moving means (not shown). As the image evaluation device 60 moves in the Y direction, the relative positional relationship with the image carrier medium 90 changes continuously, so that the linear (one-dimensional) color of the image carrier medium 90 and the distribution state of the transparent image Can be measured continuously. That is, it is possible to measure the color of the entire surface of the image bearing medium 90 and the distribution state (two-dimensional) of the transparent image. Of course, the optical system shown in FIGS. 9 to 11 may be used instead of the optical system shown in FIG. For example, if the optical system shown in FIGS. 9 and 10 is used, crosstalk can be eliminated, so that measurement with higher accuracy and reliability can be achieved. Further, if the optical system shown in FIG. 11 is used, specularly reflected light from the image bearing medium can be received, so that it is possible to acquire gloss information that is aligned with the color and transparent image distribution information. .

  Note that the moving means (not shown) may not be configured to move the image evaluation device 60 in the Y direction as long as the relative positional relationship between the image evaluation device 60 and the image bearing medium 90 can be changed. I do not care. For example, the moving means (not shown) may be configured such that the image evaluation apparatus 60 is fixed and the image bearing medium 90 is movable in the Y direction.

  As described above, according to the sixth embodiment, the same effect as that of the first embodiment is obtained, but the following effect is further obtained. That is, by moving the image evaluation device equipped with the image characteristic measurement device and the image carrier medium as the measurement object relatively, the linear (one-dimensional) color of the image carrier medium and the distribution state of the transparent image are changed. It becomes possible to measure continuously, and the color of the entire image of the image bearing medium and the distribution state (two-dimensional) of the transparent image can be measured.

  In addition, since the color information of the entire image on the image bearing medium and the formation area of the transparent image can be evaluated with high accuracy, off-line image inspection and evaluation can be performed, and at the same time, the color to image products at the development stage. It is possible to provide high-quality images and image products by feeding back information and the formation state of transparent images.

<Seventh embodiment>
In the seventh embodiment, an example of an image forming apparatus having the image evaluation apparatus according to the sixth embodiment is shown. FIG. 13 is a diagram illustrating an image forming apparatus according to the seventh embodiment. Referring to FIG. 13, the image forming apparatus 80 includes an image characteristic measuring apparatus 10 according to the first embodiment, a paper feed cassette 81a, a paper feed cassette 81b, a paper feed roller 82, a controller 83, A scanning optical system 84, a photosensitive member 85, an intermediate transfer member 86, a fixing roller 87, and a paper discharge roller 88 are included. Reference numeral 90 denotes an image bearing medium (paper or the like).

  In the image forming apparatus 80, the image carrier medium 90 transported by the guides (not shown) and the paper feed rollers 82 from the paper feed cassettes 81a and 81b is exposed to the photosensitive member 85 by the scanning optical system 84, and the color material is applied and developed. Is done. The developed image is transferred onto the intermediate transfer member 86 and then from the intermediate transfer member 86 onto the image bearing medium 90. The image transferred onto the image bearing medium 90 is fixed by the fixing roller 87, and the image bearing medium 90 formed with the image is ejected by the ejection roller 88. The image characteristic measuring apparatus 10 is installed at the subsequent stage of the fixing roller 87.

  Needless to say, the optical system of the image characteristic measuring apparatus 10 may be replaced with the optical system shown in the above-described embodiments.

  As described above, according to the seventh embodiment, by installing the image characteristic measuring device at a predetermined position of the image forming apparatus, the color information and the transparency of the image on the image bearing medium conveyed in the image product can be obtained. Color material information can be measured with high accuracy, and feedback correction can be performed when there is a color variation of an image and a non-formed portion of a transparent image.

  In addition, it is possible to measure the color unevenness in the image plane and evaluate the formation state of the transparent image, and at the same time, measure the color unevenness between the images and the formation unevenness of the transparent image. It becomes possible to provide an image product with high image quality, high reliability, and high stability by revealing the region and correcting process parameters and the like.

  Further, in the electrophotographic image forming apparatus, it is possible to reduce color unevenness in the image plane by image processing such as one-scan control of light source output of the writing scanning optical system and gamma correction before printing. Also, in the IJ image forming apparatus, it is possible to reduce color unevenness in the image plane by directly controlling the ink ejection amount according to the head position. At the same time, it is possible to perform defect inspection on the print contents such as personal information from the brightness information of the image.

  The preferred embodiment has been described in detail above. However, the present invention is not limited to the above-described embodiment, and various modifications and substitutions may be made to the above-described embodiment without departing from the scope described in the claims. Can be added.

DESCRIPTION OF SYMBOLS 10 Image characteristic measuring device 11 Line illumination light source 13 Selfoc lens 14 Pinhole array 15 Imaging optical system 16, 26 Diffraction element 17, 27 Line sensor 17a, 17b, 17c Spectral sensor 18b, 18c, 19b, 19c Filter 20 Optical path branch Means 21 Light receiving element array 25 Frame 60 Image evaluation device 80 Image forming device 81a Paper feed cassette 81b Paper feed cassette 82 Paper feed roller 83 Controller 84 Scanning optical system 85 Photoconductor 86 Intermediate transfer body 87 Fixing roller 88 Paper discharge roller 90 Image bearing Medium A Non-diffracted light (0th order light)
B + 1st order light C-1st order light D + secondary light E-2nd order light P, Q, R Optical path α, β, θ Angle

Special table 2008-518218 gazette JP 2005-315883 A JP 2002-310799 A Japanese Patent No. 3566334 JP 2003-139702 A

Claims (9)

A light irradiation step of irradiating the medium with light including light in the visible region and light outside the visible region;
A region dividing step of dividing the diffusely reflected light from the medium irradiated by the light irradiation step into a plurality of regions;
A spectroscopic step of dispersing the diffusely reflected light divided into the plurality of regions by the region dividing step in the visible region and outside the visible region;
A plurality of spectroscopic sensors having N (N is a natural number of 2 or more) pixels arranged in one direction and having a visible light receiving region and an invisible light receiving region are arranged corresponding to the plurality of regions. A light receiving step of receiving the diffuse reflected light dispersed in the visible region by a visible light receiving region and receiving the diffuse reflected light dispersed outside the visible region by an invisible light receiving region by the spectral sensor array; Have
The color of the plurality of regions is measured by the received light intensity of the diffuse reflected light in the visible region received in the light receiving step,
An image characteristic measuring method for measuring a state of a color material exhibiting transparency in the plurality of regions based on a received light intensity of the diffusely reflected light outside the visible region received in the light receiving step. A first imaging step of condensing the diffusely reflected light of the light from the medium on a region dividing unit that performs the region dividing step;
The image characteristic measuring method according to claim 1, further comprising: a second imaging step of condensing the diffusely reflected light divided into the plurality of regions by the region dividing step on the corresponding spectral sensors. The visible light receiving region is an infrared light receiving region that receives infrared light,
An ultraviolet light blocking step for blocking a second-order diffraction image of ultraviolet light irradiated on the visible light receiving region;
The image characteristic measuring method according to claim 1, further comprising: a visible light blocking step of blocking a second-order diffraction image of visible light irradiated on the infrared light receiving region. An optical path branching step for branching the diffusely reflected light divided into the plurality of regions by the region splitting step;
The spectroscopic step includes a first spectroscopic step of splitting one of the diffusely reflected light branched in the optical path branching step in the visible range, and the other diffused reflected light branched in the optical path branching step of the visible light. A second spectroscopic step of performing spectroscopy outside the region,
In the light receiving step, the diffuse reflected light split in the visible region by the first spectroscopic step is received by a first spectroscopic sensor array in which a plurality of spectroscopic sensors are arranged corresponding to the plurality of regions. The diffuse light reflected by the first light receiving step and the second spectral step outside the visible range is a second spectral sensor array in which a plurality of spectral sensors are arranged corresponding to the plurality of regions. A second light receiving step for receiving light,
The color of the plurality of regions is measured by the received light intensity of the diffusely reflected light dispersed in the visible region received in the first light receiving step,
The image according to any one of claims 1 to 3, wherein a state of a color material exhibiting transparency in the plurality of regions is measured based on a received light intensity of the diffusely reflected light outside the visible region received in the second light receiving step. Characteristic measurement method.   5. A specularly reflected light amount acquiring step of acquiring, by a light receiving element array, a specularly reflected light amount at a position corresponding to an area dividing unit that executes the region dividing step of the light irradiated by the light irradiation step. The image characteristic measuring method according to claim 1.   The received light intensity of diffusely reflected light reflected and dispersed outside the image forming area on the medium and the received light intensity of specularly reflected light reflected outside the image forming area on the medium are acquired. The image characteristic measuring method according to one item. A light irradiation means for irradiating the medium with light including light in the visible range and light outside the visible range;
Area dividing means for dividing diffusely reflected light from the medium irradiated by the light irradiating means into a plurality of areas;
Spectroscopic means for dispersing the diffusely reflected light divided into the plurality of areas by the area dividing means in the visible region and outside the visible region;
A visible light receiving region that has N pixels (N is a natural number of 2 or more) arranged in one direction and receives the diffusely reflected light dispersed in the visible region, and the diffused light dispersed outside the visible region An image characteristic measuring apparatus comprising: a spectral sensor array including a plurality of spectral sensors each having a visible light receiving region that receives reflected light, and a plurality of spectral sensors arranged corresponding to the plurality of regions. An image characteristic measuring device according to claim 7;
An image evaluation apparatus comprising: a moving unit that changes a relative positional relationship between the image characteristic measurement apparatus and the measurement object. An image characteristic measuring device according to claim 7;
An image forming apparatus that measures the entire surface of a measurement object that moves relatively in the image forming apparatus with respect to the image characteristic measuring apparatus, and performs feedback correction when there is a color variation amount and a transparent image formation variation.