JP2010261861A - Spectral characteristics acquisition apparatus, image evaluation apparatus, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spectral characteristics acquisition apparatus, an image evaluation apparatus and an image forming apparatus for simultaneously acquiring the brightness information on an image by the same sensor, reading data at a high speed, and for eliminating the alignment of a position, at which a light indicating spectral color information and brightness information is observed, when a spectral characteristic of an object to be read is measured over the entire width. <P>SOLUTION: The spectral characteristics acquisition apparatus includes a light irradiation means for irradiating the object to be read with a light; a light division means for dividing at least a part of a diffusion/reflection light of the light irradiated from the light irradiation means to the object to be read; a light receiving means for acquiring the diffused/reflected light divided by the light division means and the diffusion/reflection light which is not divided by the light division means. In the light-receiving means, a spectral sensor array includes a plurality of spectral sensors arrayed in one direction; the spectral sensor has N pixels (N is an interger≥2) arrayed in one direction. At least a part of the pixels among the N pixels are required so as to receive lights having different spectral characteristics. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a spectral characteristic acquisition apparatus that acquires spectral characteristics of an image formed on an image bearing medium, an image evaluation apparatus that includes the spectral characteristic acquisition apparatus, and an image forming apparatus that includes the image evaluation apparatus.

  There are many image products in the market such as printers, copiers, high value-added products such as printers, copiers and communication functions, and commercial printers. Electrophotographic, ink jet, and thermal methods are also used in image forming methods. And so on. In the field of production printing, digitization of both sheet-fed machines and continuous book machines has progressed, 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. 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).

  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.

  Also, in the above prior art, there is no one that obtains color information to be measured without positional deviation and simultaneously obtains image brightness information, and for image inspection such as remapping the obtained color information on the image. None of the necessary configurations and measures are taken.

  In view of the above points, when measuring the spectral characteristics of the object to be read in full width, the brightness information of the image can be acquired at the same time by the same sensor, and high-speed data reading can be performed. It is an object of the present invention to provide a spectral characteristic acquisition device, an image evaluation device, and an image forming device that do not require alignment of an observation position of light representing information.

  The spectral characteristic acquisition apparatus includes a light irradiating unit that irradiates light to an object to be read, a spectroscopic unit that divides at least a part of the diffusely reflected light of the light irradiated to the object to be read from the light irradiating unit, And a light receiving means for acquiring the diffuse reflected light spectrally separated by the spectroscopic means and the diffuse reflected light not spectrally divided by the spectroscopic means, wherein the light receiving means includes a plurality of spectral sensors in one direction. The spectroscopic sensor array is configured to have N (N is a natural number of 2 or more) pixels arranged in one direction, and at least a part of the N pixels is arranged. The pixel is required to receive light having different spectral characteristics.

  According to the disclosed technology, when measuring the spectral characteristics of the object to be read in full width, the brightness information of the image can be simultaneously acquired by the same sensor, and high-speed data reading can be performed. It is possible to provide a spectral characteristic acquisition device, an image evaluation device, and an image forming device that do not require alignment of the observation position of light representing information.

It is a figure which illustrates the spectral characteristic acquisition apparatus which concerns on 1st Embodiment. It is a figure which illustrates typically the section structure of a filter array. It is a figure which illustrates the spectral transmittance of a filter array. It is a figure which illustrates typically the pixel structure of a line sensor. It is a figure which illustrates the spectral characteristic acquisition apparatus which concerns on 2nd Embodiment. FIG. 6 is a diagram schematically illustrating a part of FIG. 5 in an enlarged manner. It is a figure which shows an example of the structure of a pinhole array. It is a figure which shows the other example of the structure of a pinhole array. It is a figure for demonstrating arrangement | positioning of a diffraction element. It is a figure which illustrates the spectral characteristic acquisition apparatus which concerns on 4th Embodiment. It is a figure for demonstrating arrangement | positioning of a diffraction element. 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 which illustrates the spectral characteristic acquisition apparatus which concerns on 6th Embodiment. It is a figure which illustrates the image evaluation apparatus which concerns on 7th Embodiment. It is a figure which illustrates the image forming apparatus which concerns on 8th Embodiment.

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

<First Embodiment>
FIG. 1 is a diagram illustrating a spectral characteristic acquisition apparatus according to the first embodiment. Referring to FIG. 1, the spectral characteristic acquisition apparatus 10 includes a line illumination light source 11, a collimator lens 12, an imaging optical system 13, a filter array 14, and a line sensor 15. Reference numeral 90 denotes an image bearing medium (paper or the like).

  The line illumination light source 11 has a function of irradiating light. As the line illumination light source 11, for example, a white LED (Light Emitting Diode) array having intensity over almost the entire visible light region 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, it is preferable that the line illumination light source 11 emits light in a wavelength region necessary for spectroscopy and can be illuminated uniformly over the entire observation region. The collimating lens 12 has a function of collimating the light emitted from the line illumination light source 11 onto the image bearing medium 90 (as parallel light). The line illumination light source 11 and the collimating lens 12 constitute a typical example of the light irradiation means according to the present invention. However, the collimating lens 12 can be omitted.

  The imaging optical system 13 is composed of a plurality of lenses, and has a function as an imaging unit that forms an image on the line sensor 15 through the filter array 14 with the diffuse reflection light of the light irradiated on the image bearing medium 90. Have. The filter array 14 has a function of splitting and transmitting a part of incident light and a function of transmitting a part of incident light without splitting. The imaging optical system 13 and the filter array 14 constitute a typical example of the spectroscopic means according to the present invention.

  The line sensor 15 is composed of a plurality of pixels, and functions as a light receiving unit that acquires a diffused and reflected light amount in a predetermined wavelength band incident through the filter array 14 and a diffused and reflected light amount that is not dispersed. Have As the line sensor 15, 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.

  Here, the filter array 14 and the line sensor 15 will be described in more detail. FIG. 2 is a diagram schematically illustrating a cross-sectional structure of the filter array. 2, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof may be omitted. Referring to FIG. 2, the filter array 14 is formed on the first reflective layer 17 formed on the glass substrate 16, the spacer layer 18 having a stepped shape, and the spacer layer 18. And a second reflective layer 19. The first reflective layer 17, the spacer layer 18, and the second reflective layer 19 constitute a Fabry-Perot interference filter. Since the thickness of the spacer layer 18 varies depending on the location, a filter array having a plurality of spectral transmission characteristics can be obtained. Can be realized.

  The filter array 14 includes a plurality of filters 14 a, 14 b, 14 c, etc., that diverge diffusely reflected light irradiated on the image bearing medium 90 in one direction. In each of the filters 14a, 14b, 14c, etc., the number of steps of the spacer layer 18 is (N-1) (N is a natural number of 2 or more, and so on). The (N-1) steps of the spacer layer 18 constitute (N-1) types of wavelength-specific filters having different transmission wavelength characteristics. In the example of FIG. 2, N = 7.

  Further, a transmission part 16x is formed so as to be adjacent to the filters 14a, 14b, 14c and the like. The transmission part 16x is a part which has no spectral characteristics such as no filter is formed or an ND (Neutral Density) filter is formed of aluminum (Al) or the like. In the transmission part 16x, the brightness information including the color information of the image is transmitted as it is and received by a predetermined pixel of the line sensor 15. Note that the ND (Neutral Density) filter is a filter having no spectral characteristic and a function of reducing the amount of incident diffuse reflection light.

As the material of the first reflective layer 17 and the second reflective layer 19, it is preferable to use aluminum (Al), silver (Ag), or the like having high reflectivity over the entire visible light region. The material of the spacer layer 18, a high silicon dioxide transmittance to visible light (SiO ₂₎ or the like can be used. As an example, the spectral transmittance of the filter array 14 when silver (Ag) having a thickness of 30 nm is used as the first reflective layer 17 and the second reflective layer 19 and silicon dioxide (SiO ₂ ) is used as the spacer layer 18 is shown. This is illustrated in FIG. FIG. 3 is a diagram illustrating the spectral transmittance of the filter array. In FIG. 3, the numerals shown indicate the thickness of the spacer layer 18. Referring to FIG. 3, the spacer layer 18 has a thickness that is modulated in increments of 15 nm from 90 nm to 165 nm depending on the location, thereby realizing a filter array having different spectral transmittances depending on the location.

  In this way, it is possible to realize a filter array in which a plurality of (N-1) types of wavelength-specific filters having different transmittances and a plurality of pairs of one transmission part are arranged. In the example of FIG. 2, N = 7 (the number of steps of the staircase that is a wavelength-specific filter is six, and the number of transmission parts is one). In FIG. 2, the spacer layer 18 has a stepped shape, but the spacer layer 18 may have a wedge shape. The filter array configuration is not limited to the Fabry-Perot interference filter, but a configuration using a dielectric multilayer film having a different film configuration depending on the location, a configuration in which a plurality of absorbing dyes are applied, and a configuration consisting of a photonic crystal structure It is possible to use as many existing inventions as possible. Further, it is preferable that the filter array 14 and the line sensor 15 are integrated in order to prevent the influence of displacement due to impact or vibration.

  FIG. 4 is a diagram schematically illustrating the pixel structure of the line sensor. 4, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof may be omitted. Referring to FIG. 4, the line sensor 15 has a pixel structure in which a plurality of pixels are arranged in a line in the Y direction (the depth direction in FIG. 1). The line sensor 15 constitutes a spectroscopic sensor array in which a plurality of spectroscopic sensors 15a, 15b, 15c, and the like, each having a group of N pixels arranged in parallel in the Y direction, are arranged in the Y direction. The spectroscopic sensors 15a, 15b, 15c and the like have (N-1) pixels that receive light having different spectral characteristics and one pixel that receives non-split light arranged in the Y direction.

  The value of N, which is the number of pixels constituting the spectroscopic sensors 15a, 15b, 15c, etc., is the number of transmission parts in the number (N-1) of filters by wavelength constituting the filters 14a, 14b, 14c, etc. of the filter array 14. It corresponds to the number added by one. In the example of FIG. 4, N = 7. Of the N pixels constituting the spectral sensors 15a, 15b, 15c, etc., (N-1) pixels have different spectral characteristics separated by the filters 14a, 14b, 14c, etc. of the filter array 14 (N -1) The light enters. In addition, one of the N pixels constituting the spectroscopic sensors 15a, 15b, 15c and the like is incident on one pixel which is not split from the transmission part 16x. However, the number of pixels on which the non-spectrized light from the transmission part 16x is incident is not necessarily one, and may be K (K is a natural number, the same applies hereinafter). In this case, the spectroscopic sensors 15a, 15b, 15c and the like are spectrally separated from (NK) pixels that receive light having different spectral characteristics (N−K ≧ 2, K is a natural number, the same applies hereinafter). In this configuration, K pixels that receive light that has not been received are provided.

  Returning to FIG. 1, the image on the image carrier medium 90 that is the object to be read is obtained in the depth direction (Y direction in FIG. 1) of the image carrier medium 90 by the light irradiation means constituted by the illumination light source 11 and the collimator lens 12. Illuminated in a wide line. Diffuse reflected light from the image on the image bearing medium 90 is guided to the line sensor 15 by the spectroscopic means constituted by the imaging optical system 13 and the filter array 14.

  In the optical system illustrated in FIG. 1, the illumination light emitted from the illumination light source 11 is incident on the image bearing medium 90 at an angle of approximately 45 degrees, and the line sensor 15 diffuses and reflects in the vertical direction from the image bearing medium 90. Is a so-called 45/0 optical system. However, the configuration of the optical system is not limited to that illustrated in FIG. 1. For example, the illumination light emitted from the illumination light source 11 is perpendicularly incident on the image carrier medium 90, and the line sensor 15 is connected to the image carrier medium 90. It may be a so-called 0/45 optical system or the like that receives light diffusing in the direction of 45 degrees from.

  As described above, the spectral characteristic acquisition device according to the first embodiment receives (N−K) pixels arranged in a predetermined direction and receiving light having different spectral characteristics and non-split light. A spectral sensor having K pixels for receiving light acquires spectral characteristics using a line sensor (light receiving means) constituting a plurality of spectral sensor arrays arranged in the predetermined direction. As a result, it is possible to simultaneously acquire the color information dispersed by the filter and the brightness information of the image not through the filter.

  In addition, since spectral characteristics can be acquired without using a sensor having a two-dimensional pixel structure with a slow readout speed, high-speed data readout is possible.

  In addition, in a conventional spectral characteristic acquisition apparatus having a configuration in which a plurality of wavelength bands are photographed by different imaging systems and synthesized later, the necessity of alignment of observation positions of the respective imaging systems, or the observation position The problem of misalignment arises and the configuration becomes complicated. Since the spectral characteristic acquisition apparatus according to the first embodiment has a configuration composed of one line of line sensors, the observation position is not misaligned, so that alignment is not necessary. As a result, a highly accurate spectral characteristic acquisition device can be realized with a simple configuration.

  That is, according to the first embodiment, when measuring the spectral characteristics of the reading object in the full width, the brightness information of the image is simultaneously acquired by the same sensor, and high-speed data reading can be performed. It is possible to realize a spectral characteristic acquisition device that does not require alignment of observation positions of light representing color information and brightness information.

<Second Embodiment>
In the second embodiment, an example of a spectral characteristic acquisition apparatus different from the first embodiment is shown. Hereinafter, the description of the parts common to the first embodiment will be omitted, and description will be made focusing on the parts different from the first embodiment.

  FIG. 5 is a diagram illustrating a spectral characteristic acquisition apparatus according to the second embodiment. FIG. 6 is a diagram schematically illustrating a part of FIG. 5 in an enlarged manner. 5 and 6, the same components as those in FIGS. 1 to 4 are denoted by the same reference numerals, and the description thereof may be omitted. 5 and 6, the spectral characteristic acquisition apparatus 20 includes a line illumination light source 11, a collimator lens 12, a line sensor 15, a diffraction element 21 as a diffraction means, and an imaging optical as an imaging means. It has a system 22, a pinhole array 23, and a SELFOC lens 24 as a second imaging means.

  The illumination optical system (line illumination light source 11 and collimator lens 12) is not shown, but is exactly the same as that described in FIG. 1, and the illumination optical system irradiates at an angle of 45 degrees from the depth direction (X direction) of the drawing. Is equipped.

  A dotted line in FIG. 5 schematically shows a typical optical path of diffusely reflected light from the image bearing medium 90. An image on the image bearing medium 90 is formed on the pinhole array 23 by the SELFOC lens 24. The image on the pinhole array 23 is dispersed or transmitted by the imaging optical system 22 and the diffraction element 21 and then formed on the pixels of the line sensor 15.

The diffraction element 21 is disposed close to the line sensor 15, and (N−1) pieces of the line sensor 15 are diffracted by diffracting the incident light, as schematically shown by the dotted line in FIG. 6. Lights having different spectral characteristics are incident on the pixels 15b _{2 to} 15b ₇ (N = 7 in the example of FIG. 6). Further, by transmitting incident light, light that has not been split is incident on _one pixel 15b ₁ of the line sensor 15. Thus, the pinhole array 23, the imaging optical system 22, and the diffraction element 21 constitute a typical example of the spectroscopic means according to the present invention.

  The diffractive element 21 is formed by periodically forming a sawtooth structure on a transparent substrate, for example. Assuming that the period of the sawtooth portion of the diffraction element 21 is p, light having a wavelength λ incident on the diffraction element 21 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 21 into a sawtooth shape as shown in FIG. In addition to the sawtooth shape, it is possible to take a stepped shape. If the pixel period d of the line sensor 15 is 10 μm, the visible light is reduced to approximately 6 pixels when the period p of the diffraction element 21 is 10 μm and the distance between the diffraction part of the diffraction element 21 and the line sensor 15 is 2 mm. It is possible to enter by spectroscopic. Also, by receiving transmitted light that does not undergo zero-order diffracted by the pixel 15b _1, it is possible to obtain the brightness information of the image.

  FIG. 7 is a diagram showing an example of the structure of the pinhole array. Referring to FIG. 7, the pinhole array 23 has a structure in which rectangular slits 23b, which are a plurality of openings through which light is transmitted, are arranged in a row. The light beam from one slit 23b takes the dotted optical path shown in FIG. 6 and enters the N pixels of the line sensor 15. One slit 23b corresponds to one spectroscopic sensor, and one slit 23b and N pixels are in an imaging relationship.

  Furthermore, since the slit 23b and the N pixels are formed in parallel, it can correspond to the spectroscopic sensor array. As the pinhole array 23, it is possible to use a blackened metal plate with a hole or a glass substrate with a black member such as chromium or carbon-containing resin formed in a predetermined shape. .

  FIG. 8 is a diagram showing another example of the structure of the pinhole array. Referring to FIG. 8, the pinhole array 23 has a structure in which rectangular slits 23d, which are a plurality of openings through which light passes, are arranged in a row. The slit 23d has a plurality of sizes, and the position of the pinhole array 23 can be switched according to a desired wavelength resolution. The shape of the opening is not limited to a rectangle, and may be an ellipse, a circle, or other shapes.

  In FIG. 5, the SELFOC lens 24 is not necessarily required, and the pinhole array 23 and the image bearing medium 90 may be arranged close to each other.

  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 spectral characteristic acquisition apparatus according to the second embodiment includes at least a pinhole array, an imaging unit, and a diffractive element as a diffractive unit as a spectroscopic optical system. As a result, the light emitted from the slits constituting the pinhole array is diffracted by the diffraction element, and the light having different wavelength distribution is guided to the (N−K) pixels of the line sensor, and the pinhole array is constituted. Of the light emitted from the slit, it is possible to guide transmitted light that does not undergo 0th-order diffraction to K pixels, and it is possible to realize a high-accuracy spectral characteristic acquisition device that does not require alignment at high speed. .

  In addition, the spectral characteristic acquisition apparatus according to the second embodiment includes a second imaging unit that forms an image of the reading object on the pinhole array. As a result, it is possible to limit the light incident on the slit of the pinhole array to light scattered from within a certain range of the reading object, and obtain spectral characteristics with higher spatial resolution of the target area measured by each spectroscopic sensor An apparatus can be realized.

<Third Embodiment>
In the third embodiment, a method of blocking diffracted light other than the desired order in the spectral characteristic acquisition apparatus 20 according to the second embodiment will be described. Hereinafter, the description of the parts common to the first embodiment and the second embodiment will be omitted, and the description will be focused on the parts different from the first embodiment and the second embodiment.

  FIG. 9 is a diagram for explaining the arrangement of the diffractive elements, and shows a state in which the line sensor 15 and the light incident on the line sensor 15 are viewed from the incident surface side. 9, the same components as those in FIGS. 1 to 8 are denoted by the same reference numerals, and the description thereof may be omitted. As shown in FIG. 9, in order to block diffracted light other than non-diffracted light (0th-order light) A and + 1st-order light B, which is desired diffracted light, the diffractive element has a diffraction sensor whose diffraction direction is a line sensor. It is preferable that 15 N pixels are arranged so as not to be parallel to the direction in which the N pixels are arranged (Y direction).

  In FIG. 9, in addition to non-diffracted light (0th-order light) A and + 1st-order light B, which are desired diffracted light, the desired diffracted light is weaker than + 1st-order light B as light that passes through the diffraction element. -First order light C, + secondary light D, -secondary light E, etc. are generated. As shown in FIG. 9, the diffraction direction of the diffraction element is inclined in the X direction by a minute angle β with respect to the pixel arrangement direction (Y direction) of the line sensor 15. As a specific arrangement of the diffraction elements at this time, the sawtooth shape of the diffraction element 21 shown in FIG. 6 is arranged in a direction inclined in the X direction by an angle β from the pixel arrangement direction (Y direction) of the line sensor 15. You just have to do it. As a result, non-diffracted light (0th-order light) A and + 1st-order light B, which are desired diffracted lights, enter the pixels of the line sensor 15, but −1st-order light C and + second-order light D that are not desired diffracted lights. , -Secondary light E or the like can be arranged so that it hardly enters. Further, it is possible to acquire image brightness data by non-diffracted light (0th order light) A.

  Hereinafter, an example of a method for determining the minute angle β will be described. Since the value of the angle β depends on the optical layout, it is not uniquely determined. For example, the width in the height direction of the light receiving surface of the line sensor 15 that is a light receiving element, the distance between the diffraction element 21 and the light receiving surface of the line sensor 15, and image formation It is determined by the magnification of the optical system 22, the pinhole diameter of the pinhole array 23, α, p in the formula (Equation 1), and the like.

  Here, since the non-diffracted light (0th order light) is not diffracted, the incident angle α in the formula (Equation 1) becomes θm (m = 0) as it is, and the distance between the light receiving surface of the line sensor 15 and the diffraction element 21. Is imaged at a position divided by sin α. On the other hand, the imaging position of the + 1st order light differs from wavelength to wavelength according to the equation (Equation 1). For example, when measuring wavelengths up to 700 nm, the distance between the light receiving surface of the line sensor 15 and the diffraction element 21 is expressed by sinθm (m = 1) Form an image at the divided position. Note that the width of the light receiving surface of the line sensor 15 necessary for measurement also depends on the size of the image on the light receiving surface of the line sensor 15, and the pinhole diameter of the pinhole array 23 and the magnification of the imaging optical system 22. A measurement area is required outside the non-diffracted light (0th order light) and the + 1st order light by an amount corresponding to the approximate spot radius on the light receiving surface of the line sensor 15 determined by

  In addition, the angle β must be determined so that the diffraction images of the adjacent pinholes in the pinhole array 23 do not overlap with the same pixel on the light receiving surface of the line sensor 15. It depends on the distance between them and the height of the light receiving surface of the line sensor 15. The height of the light receiving surface of the line sensor 15 is related to its own non-diffracted light (0th order light), secondary light, and adjacent pinholes in the pinhole array 23 by setting the angle β. This is because the non-diffracted light (0th-order light) and the diffracted image from the light beam propagate outside the line sensor 15 so as not to enter the same pixel.

As a specific method for determining the angle β, there is a method in which the width in the height direction of the light receiving surface of the line sensor 15 is defined first, and an angle at which unnecessary light is not imaged on the line sensor 15 is known. As an example, consider the case where a commercially available PD array (pixel horizontal width is 50 μm and height width is 500 μm) is used for the line sensor 15. In this case, the angle β differs depending on how the width of the measurement area of the non-diffracted light (0th order light) and the primary light is defined (how many pixels are applied). It can be determined that β = tan ⁻¹ (50 μm × number of pixels / 500 μm).

  In the above specific example, the angle β is determined after defining the width of the line sensor 15 in the light receiving surface height direction. However, after the angle β is determined, the width of the line sensor 15 in the light receiving surface height direction is determined. It is also possible to specify. In this case, for example, a line sensor having a plurality of lines called a TDI (Time Delayed Integration) line sensor is used. Then, the angle β is first determined, and then the width of the light receiving surface of the TDI line sensor is defined, and then the number of stages used by the TDI line sensor may be adjusted.

  In FIG. 9, since the sensor configuration acquires non-diffracted light (0th-order light) A and + 1st-order light B, the spectroscopic sensor 15a and the like acquire non-diffracted light (0th-order light) A and + 1st-order light B. Therefore, the number of pixels is necessary. A value obtained by dividing the total number of pixels of the line sensor 15 by the number of pixels necessary for one set of spectroscopic sensors such as the spectroscopic sensor 15a is the number of spectroscopic sensors obtained from the line sensor 15, and the brightness information of the image is also the spectroscopic sensor. Will be obtained.

  Since the spectral characteristic acquisition device 20 acquires color information and image brightness information by a single optical system, the color information and image brightness information can be acquired as position information that completely matches. Further, by providing the spectral characteristic acquisition device 20 with an image inspection means, high-resolution image inspection can be performed. Image inspection can be performed by ordinary image processing and image recognition technology, and by a processing circuit (not shown) having a dedicated processor, a method such as inter-image difference between the image acquired by the spectral characteristic acquisition device 20 and the reference image, pattern matching, or the like. Image inspection is possible.

  As described above, according to the third embodiment, the same effects as those of the first embodiment and the second embodiment are obtained, but the following effects are further obtained. That is, in the spectral characteristic acquisition device according to the third embodiment, the diffraction element that is the diffractive means has a diffraction direction that is not parallel to the direction in which the N pixels of the line sensor are arranged. By arranging in this way, it becomes possible to make only non-diffracted light (0th-order light) A and + 1st-order light B, which are desired diffracted light, enter the line sensor. As a result, light that may cause noise is less incident on the line sensor, and a more accurate spectral characteristic acquisition device can be provided.

  In addition, image inspection such as verification can be executed from image brightness information using normal image processing and image recognition technology, and highly reliable images and image products can be provided.

<Fourth embodiment>
In the fourth embodiment, an example of a spectral characteristic acquisition apparatus different from the first to third embodiments is shown. Hereinafter, the description of the parts common to the first embodiment to the third embodiment will be omitted, and the description will focus on the parts different from the first embodiment to the third embodiment.

  FIG. 10 is a diagram illustrating a spectral characteristic acquisition apparatus according to the fourth embodiment. 10, the same components as those in FIG. 5 are denoted by the same reference numerals, and the description thereof may be omitted. Referring to FIG. 10, the spectral characteristic acquisition device 30 includes a line illumination light source 11, a collimating lens 12, a line sensor 15, a diffraction element 21 that is a diffraction unit, and an imaging optical system 22 that is an imaging unit. , A pinhole array 23, a SELFOC lens 24 as second imaging means, a line illumination light source 31, a collimating lens 32, an imaging optical system 33, and a conveying means (not shown).

  The line illumination light source 31 and the collimating lens 32 are illumination optical systems having functions similar to those of the line illumination light source 11 and the collimating lens 12. The line illumination light source 31 and the collimating lens 32 constitute a typical example of the second light irradiation means according to the present invention. However, the collimating lens 32 can be omitted. The imaging optical system 33 has the same function as the imaging optical system 22. The transport unit (not shown) has a function of transporting the image bearing medium 90 in the arrow direction (X direction).

  In the spectral characteristic acquisition device 30, when the image bearing medium 90 is conveyed in the arrow direction (X direction), the line illumination light source 11 is turned on with the spectral sensor array arranged in the direction perpendicular to the paper surface (Y direction). Then, diffuse reflected light from the image bearing medium 90 is input to the line sensor 15 via the SELFOC lens 24, the pinhole array 23, the imaging optical system 22, and the diffraction element 21, and spectral information is acquired. Further, the line illumination light source 31 is turned on, and the diffuse reflected light from the image bearing medium 90 is input to the line sensor 15 only through the imaging optical system 33 (not through the diffraction element), and the brightness information of the image is obtained. get.

  That is, the N pixels such as the spectroscopic sensors 15a, 15b, and 15c receive light having different spectral characteristics from the spectroscopic means including the diffractive element 21 and the second light including the line illumination light source 31 and the like. In this configuration, the diffused reflected light that is not spectrally separated from the light applied to the image bearing medium 90 that is the object to be read from the irradiation means is also received.

  When acquiring spectral information, the resolution is reduced only by pixels (for example, 7 pixels) used for the spectral sensors 15a, 15b, 15c, etc., but the pixel resolution of the line sensor 15 can be applied to the brightness information of the image as it is. Thus, image information can be acquired with high resolution.

  FIG. 11 is a diagram for explaining the arrangement of the diffractive elements, and shows a state in which the line sensor 15 and the light incident on the line sensor 15 are viewed from the incident surface side. 11, the same components as those in FIG. 9 are denoted by the same reference numerals, and the description thereof may be omitted. In the third embodiment, the brightness information of the image is obtained using the non-diffracted light (0th order light) A. However, in the fourth embodiment, the light that does not pass through the diffraction element is used. Get brightness information. Therefore, as shown in FIG. 11, the spectral sensors 15a, 15b, 15c and the like can be configured to receive only the + 1st order light B, and the resolution when acquiring spectral information can be improved. Become.

  In FIG. 11, in order to block the diffracted light other than the + 1st order light B which is the desired diffracted light, the diffraction element (not shown) has a diffraction direction of the line sensor 15 of the diffraction element (not shown). The pixels are arranged so as to be inclined in the X direction by a minute angle γ so as to be non-parallel to the direction in which N pixels are arranged (Y direction). As a result, the + 1st order light B, which is the desired diffracted light, enters the pixel of the line sensor 15, but the non-diffracted light (0th order light) B that is not the desired diffracted light, the -1st order light C, and the + secondary light D. , -Secondary light E or the like can be arranged so that it hardly enters. Since the method for determining the minute angle γ is the same as the method for determining the minute angle β described above, the description thereof is omitted.

  In FIG. 11, since the sensor configuration acquires only the + 1st order light B, the spectroscopic sensor 15a and the like require the number of pixels for acquiring only the + 1st order light B. A value obtained by dividing the total number of pixels of the line sensor 15 by the number of pixels necessary for one set of spectroscopic sensors such as the spectroscopic sensor 15a is the number of spectroscopic sensors obtained from the line sensor 15, and the brightness information of the image is also the spectroscopic sensor. Will be obtained.

  By providing the spectral characteristic acquisition device 30 with an image inspection means, a high-resolution image inspection can be performed. Image inspection can be performed by normal image processing and image recognition technology. By a processing circuit (not shown) having a dedicated processor, an image difference between the image acquired by the spectral characteristic acquisition device 30 and a reference image and a method such as pattern matching are used. Image inspection is possible. The spectral characteristic acquisition device 30 acquires color information and image brightness information by using an independent optical system, so that it is difficult to completely match the observation positions of the two, but image inspection with high resolution is possible. It becomes. Image inspection can be performed by normal image processing and image recognition technology, and image processing can be performed by a method such as inter-image difference from the reference image and pattern matching by a processing circuit (not shown) having a dedicated processor.

  As described above, according to the fourth embodiment, the same effects as those of the first to third embodiments are obtained, but the following effects are further obtained. That is, in the spectral characteristic acquisition device according to the fourth embodiment, the diffraction elements are arranged so that the diffraction direction of the diffraction elements is not parallel to the direction in which the N pixels of the line sensor are arranged. As a result, only the + 1st order light B, which is the desired diffracted light, can be incident on the line sensor. Also, the brightness information of the image can be acquired using light that does not pass through the diffraction element by dividing the optical axis. As a result, the brightness information of the image can be acquired with high resolution.

  In addition, since the character information to be inspected with the brightness information of the image requires a higher resolution than the color information, the resolution of the line sensor is applied only to the brightness information of the image by dividing the optical axis. It is possible to provide a spectral characteristic acquisition device that can perform image inspection with high resolution.

<Fifth embodiment>
In the fifth embodiment, spectral characteristic acquisition having processing for estimating a spectral distribution by estimation means such as Wiener estimation while minimizing the number of bands (for example, N or (NK)) in multiband spectroscopy. An example of an apparatus is shown.

  In multiband spectroscopy, the more the number of bands, the better because it is possible to obtain detailed measurement results of the spectral distribution. However, when the number of pixels of the line sensor 15 is constant, the number of spectral sensors that can be arrayed decreases as the number of bands (number of N) increases. Therefore, it is preferable that the spectral characteristic acquisition 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 bands. 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 will be 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 includes a matrix R in which spectral distributions are stored for a large number (n) of samples whose spectral distributions are known in advance, as shown in Expressions (3) to (5), and the same samples. It is obtained by minimizing the square norm ‖ · ‖2 of the error using the least square method from the matrix V storing v when measured by this measuring apparatus.

The transformation matrix G, which is the regression coefficient matrix of the regression equation from V to R, where V is the explanatory variable and R is the objective variable, is expressed using the Moore-Penrose generalized inverse matrix that gives the least-squares 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. 12 is a diagram illustrating the spectral distribution of the toner image used in the simulation. FIG. 13 is a diagram illustrating a simulation result. Referring to FIG. 13, 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 bands is 6 or more, the error of the spectral estimation value is sufficiently small, indicating that a suitable spectral sensor array can be realized. The 0th order light acquired by the spectroscopic sensor array is received on the line sensor at a certain distance from the + 1st order light, so that the number of pixels required for the spectroscopic sensor 15a and the like can be increased. .

  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. That is, the spectral characteristic acquisition apparatus according to the fifth embodiment includes spectral characteristic estimation means that estimates a wavelength distribution with higher wavelength resolution and higher density based on outputs from N pixels. As a result, even if the number of bands is, for example, about six in the visible light wavelength region, a substantially continuous spectral distribution can be estimated.

  In particular, when measuring an image formed by an 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 spectral A characteristic acquisition device can be realized.

  In addition, by applying estimation processing, the number of bands can be minimized and optimized, and the number of spectral sensors can be maximized with respect to the total number of pixels of the line sensor, thereby providing a highly integrated spectral characteristic acquisition device. be able to.

<Sixth Embodiment>
In the first to fifth embodiments, an example in which one-dimensional spectral characteristics (color information) and image brightness information are acquired has been described. In the sixth embodiment, two-dimensional spectral characteristics (color information) are obtained. An example of acquiring spectral characteristics (color information) and image brightness information will be described. In the spectral characteristic acquisition apparatus 10 shown in FIG. 1, a conveyance unit that conveys the image carrying medium 90 in the X direction of FIG. 1 is provided, and the linear (one-dimensional) spectral characteristic and image brightness are conveyed while conveying the image carrying medium 90. By continuously acquiring depth information, two-dimensional spectral characteristics (color information) and image brightness information can be acquired.

  Further, instead of the configuration in which the spectral characteristic acquisition apparatus 10 shown in FIG. 1 is provided with a conveying means, a method of scanning by driving the spectral sensor array or a scanning optical system incorporated in the spectral sensor array is measured by the scanning optical system. By the method of scanning the position, two-dimensional spectral characteristics (color information) and image brightness information can be acquired. An example of a configuration for acquiring two-dimensional spectral characteristics (color information) and image brightness information is shown below, but the description of the parts common to the first to fifth embodiments is omitted. The description will focus on the differences from the first to fifth embodiments.

  FIG. 14 is a diagram illustrating a spectral characteristic acquisition apparatus according to the sixth embodiment. 14, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof may be omitted. Referring to FIG. 14, the spectral characteristic acquisition device 40 includes a first traveling body 41, a second traveling body 42, an imaging optical system 13, a filter array 14, and a line sensor 15. The first traveling body 41 and the second traveling body 42 constitute a representative example of the moving means according to the present invention.

  The first traveling body 41 includes a line illumination light source 11, a collimating lens 12, and a first mirror 41a, and is configured to be able to travel in the X direction by a drive mechanism (not shown). The first mirror 41 a has a function of reflecting the diffuse reflected light of the light irradiated from the line illumination light source 11 through the collimator lens 12 to the image carrier medium 90 in the direction of the second mirror 42 a. As the first mirror 41a, for example, a reflecting mirror whose surface is coated with a metal film or the like can be used.

  The second traveling body 42 includes a second mirror 42a and a third mirror 42b, and is configured to be able to travel in the X direction by a drive mechanism (not shown). However, the second traveling body 42 is configured to move, for example, by half of the distance traveled by the first traveling body 41. The second mirror 42a has a function of reflecting the diffusely reflected light reflected by the first mirror 41a in the direction of the third mirror 42b. The third mirror 42 b has a function of reflecting the diffusely reflected light reflected by the second mirror 42 a in the direction of the imaging optical system 13. As the second mirror 42a and the third mirror 42b, for example, a reflecting mirror whose surface is coated with a metal film or the like can be used. The second traveling body 42 moves, for example, by half the distance traveled by the first traveling body 41 to continuously change the measurement location, thereby acquiring two-dimensional spectral characteristics (color information) and image brightness information. be able to. The spectral characteristic acquisition device 40 does not include a transport unit that transports the image bearing medium 90 in the X direction.

  As described above, according to the sixth embodiment, the same effects as those of the first to fifth embodiments are obtained, but the following effects are further obtained. That is, the spectral characteristic acquisition apparatus according to the sixth embodiment includes a moving unit that scans the image bearing medium. As a result, two-dimensional spectral characteristics (color information) and image brightness information of the image bearing medium are obtained by continuously acquiring spectral data and image brightness information in one direction while scanning on the image bearing medium. Can be obtained.

<Seventh embodiment>
In the seventh embodiment, an example in which an image evaluation apparatus is configured using a plurality of spectral characteristic acquisition apparatuses will be described. FIG. 15 is a diagram illustrating an image evaluation apparatus according to the seventh embodiment. Referring to FIG. 15, an image evaluation apparatus 50 is an image evaluation apparatus that measures an image produced on an image carrying medium 90 by, for example, an electrophotographic image forming apparatus over the entire width, and is shown in FIG. A plurality of spectral characteristic acquisition devices 20 are arranged in the Y direction. By configuring the image evaluation device 50 in this way, it is possible to acquire a wider range of spectral characteristics (color information) and image brightness information.

  Although the illumination optical system (line illumination light source 11 and collimating lens 12) is not shown in FIG. 14, the illumination optical system is more oblique than the paper depth direction (X direction) which is exactly the same as that described in FIG. A plurality of illumination optical systems that irradiate at 45 degrees may be arranged in the Y direction by the same number as that of the spectral characteristic acquisition device 20, or a plurality of illumination optical systems may be arranged in the Y direction by a smaller number than the spectral characteristic acquisition device 20. It is good also as the structure which was made, and it is good also as only one.

  The image evaluation apparatus 50 further includes an image evaluation unit 51 and a conveyance unit (not shown). The image evaluation unit 51 combines the outputs from the plurality of spectral characteristic acquisition devices 20 to calculate color measurement data such as XYZ and L * a * b *, and the image formed on the image carrier medium 90 in a plurality of colors. It has a function to evaluate the color. The transport unit (not shown) has a function of transporting the image bearing medium 90 in the X direction. The image evaluation apparatus 50 also performs spectral image data and measurement over the entire image forming unit on the image bearing medium 90 based on speed information from an encoder sensor or the like that is known or attached to a conveying means (not shown). Color data can be calculated. Further, the plurality of spectral characteristic acquisition devices 20 can be positioned by collating image brightness information with reference images and digital data.

  In the image evaluation apparatus 50, the spectral characteristic acquisition apparatus 10, 30, or 40 may be used instead of the spectral characteristic acquisition apparatus 20.

  As described above, according to the seventh embodiment, by configuring an image evaluation apparatus using a plurality of spectral characteristic acquisition apparatuses according to the present invention, image brightness information can be obtained simultaneously with spectral characteristics (color information). It is possible to obtain an image evaluation apparatus that can be acquired and that is not affected by the positional deviation at high speed.

  In addition, off-line image inspection is possible and high-quality images can be applied. At the same time, high-quality images and images can be fed back by feeding back color information and image brightness information to image products at the development stage. Products can be provided.

<Eighth embodiment>
In the eighth embodiment, an example of an image forming apparatus having the image evaluation apparatus according to the seventh embodiment will be described. FIG. 16 is a diagram illustrating an image forming apparatus according to the eighth embodiment. Referring to FIG. 16, the image forming apparatus 80 includes an image evaluation apparatus 50 according to the seventh embodiment, a paper feed cassette 81a, a paper feed cassette 81b, a paper feed roller 82, a controller 83, and scanning. An 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 evaluation device 50 is installed at the subsequent stage of the fixing roller 87.

  As described above, according to the eighth embodiment, the image evaluation apparatus according to the seventh embodiment is installed at a predetermined position of the image forming apparatus, so that the high quality without color variation over the entire image area. An image can be provided, and automatic color calibration can be performed, so that the image forming apparatus can be stably operated. Further, since it is possible to acquire image information over the entire image, it is possible to store inspections and print data, and to provide a highly reliable image forming apparatus.

  Further, the image evaluation apparatus according to the seventh embodiment can acquire color information in the image plane in two dimensions without any positional deviation between the line sensors. It can be reduced by one-scan control within the light source output of the writing scanning optical system and image processing such as gamma correction before printing. In the IJ method, color unevenness can be reduced by directly controlling the amount of ink discharged 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.

  In addition, it is possible to simultaneously perform inspections of image quality such as color unevenness in the image plane and print contents such as character information, and an image product with high image quality, high reliability, and high stability can be provided.

  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 replacements are made to the above-described embodiment without departing from the scope described in the claims. Can be added.

  For example, in the spectral characteristic acquisition device 30 according to the fourth embodiment, instead of the diffraction element 21, the imaging optical system 22, the pinhole array 23, and the Selfoc lens 24, the imaging optical system 13 and the filter array 14 are used. May be used. However, in this case, the filters 14a, 14b, 14c and the like constituting the filter array 14 do not need to have the transmission part 16x. That is, the filters 14a, 14b, 14c, and the like have N types of wavelength-specific filters that are arranged in one direction and have different transmission wavelength characteristics, and the N types of wavelength-specific filters have the spectral characteristics of the N pixels of the spectroscopic sensor. The light guide may be configured to guide different lights.

10, 20, 30, 40 Spectral characteristic acquisition device 11, 31 Line illumination light source 12, 32 Collimating lens 13, 22, 33 Imaging optical system 14 Filter array 14a, 14b, 14c Filter 15 Line sensor 15a, 15b, 15c Spectroscopic sensor _{15b 1, 15b 2, 15b 3} , 15b 4, 15b 5, 15b 6, 15b 7 pixel 16 glass substrate 16x transmissive portion 17 first reflection layer 18 a spacer layer 19 a second reflective layer 21 diffraction element 23 pinhole array 23a , 23c Light-shielding portion 23b, 23d Slit 24 Selfoc lens 41 First traveling body 41a First mirror 42 Second traveling body 42a Second mirror 42b Third mirror 50 Image evaluation device 51 Image evaluation means 80 Image forming device 81a Paper cassette 81b Paper cassette 82 Paper roller 83 controller 84 scanning optical system 85 photoconductor 86 the intermediate transfer member 87 fixing roller 88 discharge rollers 90 image carrying medium A non-diffracted light (0 order light)
B + 1st order light C -1st order light D + 2nd order light E -2nd order light

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

Claims (15)

A light irradiation means for irradiating the reading object with light;
A spectroscopic unit that splits at least part of the diffusely reflected light of the light irradiated on the reading object from the light irradiating unit;
A light receiving means for acquiring the diffuse reflected light dispersed by the spectroscopic means and the diffuse reflected light not spectrally divided by the spectroscopic means,
The light receiving means constitutes a spectral sensor array in which a plurality of spectral sensors are arranged in one direction,
The spectroscopic sensor has N pixels (N is a natural number of 2 or more) arranged in one direction, and at least some of the N pixels receive light having different spectral characteristics. Spectral characteristics acquisition device.   The spectroscopic sensor includes (N−K) pixels that receive light having different spectral characteristics from each other (N−K ≧ 2, K is a natural number), and K pixels that receive light that is not dispersed. Item 2. The spectral characteristic acquisition device according to Item 1. The spectroscopic means includes an image forming means for forming an image of the diffusely reflected light on the light receiving means,
A filter array in which a plurality of filters for dispersing the diffuse reflected light are arranged in one direction,
The filter has (NK) kinds of wavelength-specific filters having different transmission wavelength characteristics and K transmission parts having no wavelength dependency, which are arranged in one direction.
3. The spectral characteristic according to claim 2, wherein the wavelength-specific filter guides light having different spectral characteristics from each other to the (N−K) pixels, and the transmission part guides light not split into the K pixels. 4. Acquisition device.   The spectral characteristic acquisition apparatus according to claim 3, wherein a filter is not formed in the transmission part, or a filter having no spectral characteristic and having a function of reducing the amount of incident light is formed. The spectroscopic means includes a hole array in which a plurality of openings are arranged in a line in a light shielding member,
Imaging means for forming an image on the hole array on the light receiving means;
The spectral characteristic acquisition apparatus according to claim 2, further comprising: a diffracting unit that guides diffracted light having different spectral characteristics to the (N−K) pixels and guides light that is not diffracted to the K pixels. . A second light irradiation means for irradiating the reading object with light;
The N pixels of the spectroscopic sensor receive light incident from the spectroscopic unit and having different spectral characteristics from each other, and the light irradiated on the reading object from the second light irradiation unit is not split The spectral characteristic acquisition apparatus according to claim 1, which also receives diffuse reflected light. The spectroscopic means includes an image forming means for forming an image of the diffusely reflected light on the light receiving means,
A filter array in which a plurality of filters for dispersing the diffuse reflected light are arranged in one direction,
The filter has N kinds of wavelength-specific filters arranged in one direction and having different transmission wavelength characteristics,
The spectral characteristic acquisition apparatus according to claim 6, wherein the wavelength-specific filter guides light having different spectral characteristics to the N pixels. The spectroscopic means includes a hole array in which a plurality of openings are arranged in a line in a light shielding member,
Imaging means for forming an image on the hole array on the light receiving means;
The spectral characteristic acquisition apparatus according to claim 6, further comprising diffraction means for guiding diffracted light having different spectral characteristics from each other to the N pixels.   The spectral characteristic acquisition apparatus according to claim 5, further comprising a second imaging unit between the reading object and the hole array.   The spectral characteristic acquisition according to claim 5, 8, or 9, wherein the diffracting means is arranged so that a diffraction direction is non-parallel to a direction in which the N pixels of the light receiving means are arranged. apparatus.   The spectral characteristic acquisition apparatus according to any one of claims 1 to 10, further comprising spectral characteristic estimation means for estimating a higher density spectral characteristic based on outputs from the N pixels.   The spectral characteristic acquisition apparatus according to claim 1, further comprising a moving unit that scans the object to be read. An image evaluation apparatus for evaluating the color and brightness of an image formed in a plurality of colors on an image bearing medium,
The spectral characteristic acquisition device according to any one of claims 1 to 12,
Conveying means for conveying the image bearing medium;
An image evaluation apparatus comprising: an image evaluation unit that evaluates the color and brightness of the image based on the color information of the image and the brightness information of the image acquired by the spectral characteristic acquisition apparatus.   The image evaluation apparatus according to claim 13, wherein a plurality of the spectral characteristic acquisition apparatuses are mounted in a direction perpendicular to a direction in which the conveyance unit conveys the image bearing medium.   An image forming apparatus equipped with the image evaluation apparatus according to claim 13.