JP5652183B2 - Image characteristic measuring apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an image characteristic measuring apparatus using a spectroscopic sensor array that makes it possible to acquire spectral data of an object at once on a line, and mainly evaluates an image formed by an image forming apparatus. Therefore, the present invention relates to an image characteristic measuring apparatus having a mechanism for accurately detecting the position and orientation of a spectral sensor array itself in order to obtain spectral reflectance over the entire width of the image and accurately perform color measurement.

  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. User needs are also changing from monochrome printing to color printing, with multi-dimensional and high-definition images. Consumers such as high-quality photo printing, catalog printing, and advertisements that respond to personal preferences for invoices, etc. With the diversification of service forms that can be delivered to customers, the demand for high image quality and color reproduction is 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 formation 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 points are measured with a spectrometer and calibrated. Something to do is launched on the market.

  These techniques are preferably executed over the entire image in order to cope with image variations between pages and within pages.

  As an evaluation technique for measuring the full width of an image, for example, techniques disclosed in Patent Documents 1 to 6 have been proposed.

  Patent Document 1 discloses “a measuring device and a scanning device for photoelectrically measuring a measurement object based on pixels”. That is, a plurality of line-shaped light receiving elements are arranged, a mechanism for moving the measurement object relative to the detection system is set, and the spectral characteristics of the full width are measured. At this time, the light shielding wall is set so that crosstalk of reflected light from the detection target region does not occur between the light receiving elements.

  Patent Document 2 discloses “a full-width array spectrophotometer, a method of full-width scanning color analysis of a color inspection target, and a method of full lateral scanning color analysis of a color print sheet”. That is, continuous irradiation is performed with light sources having different wavelength bands over the entire width of the image, and reflected light is acquired to acquire the spectral characteristics of the entire width.

  Patent Document 3 discloses a “color ink density detection method and color ink density detection apparatus for printed matter”. That is, the entire width of the printing surface is irradiated with light, the density of a specific area is detected by a line sensor camera, and the density is compared with the reference density.

  Patent Document 4 discloses an “image processing apparatus and method”. That is, the original and the specific original are scanned a plurality of times, and the similarity is determined from processing such as inter-image logical sum for common color information.

  Patent Document 5 discloses a “multicolor printed image density detecting device on a printing sheet”. That is, light is irradiated to the entire width of the printing surface, and the spectral characteristics of the full width are obtained by a combination of a CCD having a two-dimensional pixel structure and a diffractive element or a refractive element.

  Patent Document 6 discloses a “color measurement device and image forming apparatus”. That is, a multiband spectroscopic sensor that irradiates an image with illumination light from a plurality of light sources having different emission wavelengths and obtains reflected light with a single light receiving unit is formed. At that time, 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.

  By the way, when trying to measure the color of an image at the full width, it is possible to irradiate a plurality of light limited to different wavelength bands and take an image with an area sensor, or relatively image the measurement system and the test subject 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 the 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.

  In the prior art, with respect to Patent Document 1, it is a line-shaped measurement system and has a general configuration capable of measuring the color of the image to be examined in full width, but reduces the positional deviation of the image obtained in each wavelength band. There is no way to do this.

  With regard to Patent Document 2, in the configuration in which reflected light from a test object by continuous irradiation light from light sources having different wavelength bands is acquired, a shift in the time axis occurs, and the same part of the test object is measured. Impossible. 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. In addition, a configuration using a plurality of rows of detectors filtered with different colors has been described. However, as described above, there arises a problem due to image positional deviation between a plurality of colors.

  With respect to Patent Document 3, the configuration for acquiring color information in the full width is the same, but it is considered that the representative value is obtained by the process of averaging the density of the detected region, and the color distribution of the test object cannot be guaranteed.

  With respect to Patent Document 4, a document and a test object are determined by comparison between images in each wavelength band, but color variation of the test object cannot be specified. Further, 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.

  Patent Document 5 shows a configuration in which color information of a full width is measured by using a CCD having a two-dimensional pixel structure and acquiring image data in one direction and spectral data in the other direction. However, in a CCD having a two-dimensional pixel structure, the reading speed is remarkably slow with respect to the line sensor due to restrictions on data reading characteristics, so that there is a great restriction on the speed of acquiring color information of the object.

  With respect to Patent Document 6, visible light and ultraviolet light are irradiated on paper, and the influence of paper on ultraviolet light can be removed. However, the spectroscopic measurement is possible only at one place because of 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 while the time-division lighting is on, and color measurement at the same location is impossible. In addition, since the measurement is performed at only one location, 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, image color distribution, and both Since it takes a lot of time, it can be said that it is impossible to acquire such information.

  In addition, in the spectroscopic measurement, there is generally a method in which a diffraction element such as a grating or a prism is used, and the spectral information is acquired by acquiring the intensity of each wavelength band split by the diffraction element. However, when trying to acquire color information on a line at once using a diffractive element, crosstalk of 0th order light, ± 1st order diffracted light, ± 2nd order diffracted light, etc., and crosstalk between adjacent diffracted images are problems. Become.

  The inventors have applied for a patent (Japanese Patent Application No. 2009-081986) that avoids this problem, arranges spectrometers in a line, and makes it possible to acquire spectral information over the entire width of the image. That is, as a “spectral characteristic acquisition device, image evaluation device, and image forming device”, a bandpass filter or a diffraction element is used to cross adjacent color information, zero-order light, ± first-order diffraction image, and ± second-order diffraction image. A plurality of spectroscopic measurement sensors are configured on the line sensor without talk.

  More specifically, after illuminating the image to be measured and dividing the diffuse reflected light, which is color information, into regions using a pinhole array, etc., a bandpass filter and a light-shielding wall are used in combination, and multiple bands from each pinhole array are used. In addition to being able to arrange and configure multiple spectrometers by acquiring spectral information with a line sensor, diffraction is performed by rotating diffused reflected light divided by a pinhole array etc. by a predetermined angle around the optical axis. By forming a diffraction image diffracted by the element and having an angle on the optical axis on a line sensor, it is possible to construct a spectroscopic sensor array that does not cause cross-talk between adjacent color information of each image and each diffraction pattern, It has a very effective configuration as a sensor that enables simultaneous measurement of spectral measurement of the full width of the image.

  However, in the above technique, since the relative position and relative posture of the spectroscopic sensor with respect to the measurement object depend on mechanical positioning on the drawing, adjustment for satisfying the optical condition is indispensable. In this respect, since the spectroscopic sensor is a passive element, it is difficult to secure an index indicating what position and in what posture the spectroscopic sensor itself is fixed.

  An image characteristic measuring apparatus that performs spectroscopic measurement with the full width of the image can be easily increased even when the measurement target is wide with the full width of the image and the angle deviation of the apparatus is small. Is important.

  The present invention has been proposed in view of the above-described conventional problems, and an object of the present invention is to accurately execute spectroscopic measurement as color information of an image on an image carrier, which is an object, with the full width of the image. To provide an image characteristic measuring apparatus and an image forming apparatus that have a mechanism for detecting a relative position with respect to an object in a spectroscopic sensor array and can acquire diffuse reflected light that is optimal image color information in the entire image width. It is in.

  In order to solve the above-described problems, in the present invention, as described in claim 1, the first light irradiation for irradiating a predetermined region of the image on the image carrier that is a measurement object is performed. Means, a first imaging means for condensing the reflected light from the measurement object of the light irradiated by the first light irradiation means, and the measurement object by the first imaging means. Area dividing means for dividing an area by an aperture row installed at an image-related position; and second imaging means for collecting reflected light from the measurement object that has been divided into areas by passing through the aperture row; Spectroscopic means for splitting the light divided by the second imaging means through the aperture row so that the diffraction images do not overlap with each other, and splitting the area from each of the spectrally split apertures An array of light receiving means for receiving the emitted light, the aperture row and the second connection. A second light irradiating means for irradiating light from above between the means; and a reflecting means for reflecting light from the second light irradiating means in the direction of the aperture row, the aperture row and the reflection The gist of the image characteristic measuring apparatus is that the distance between the second light irradiation means via the means and the distance between the aperture row and the entrance pupil of the second imaging means are the same.

  According to a second aspect of the present invention, in the image characteristic measuring apparatus according to the first aspect of the present invention, a light source rotating unit that rotates the second light irradiating unit may be provided.

  In addition, as described in claim 3, in the image characteristic measuring apparatus according to claim 1 or 2, the second light irradiation unit includes a plurality of light sources, and a plurality of the openings are provided. It may be possible to irradiate directed light.

  In addition, as described in claim 4, in the image characteristic measuring apparatus according to any one of claims 1 to 3, the first imaging unit, the region dividing unit, and the second imaging unit. Means, the spectroscopic means, the arrayed light receiving means, the second light irradiating means, and the reflecting means may have moving means that can rotate and move in parallel.

  According to a fifth aspect of the present invention, the image characteristic measuring device according to any one of the first to fourth aspects is mounted, and the moving unit relatively moves the image characteristic measuring device and the measurement object. The image forming apparatus can be configured.

  In the image characteristic measuring apparatus and the image forming apparatus of the present invention, in order to accurately execute spectral measurement as the color information of the image on the image carrier that is the object with the full width of the image, the spectral sensor array is connected to the object. A mechanism for detecting the relative position is provided, and diffuse reflected light, which is optimal image color information, can be acquired over the entire image width.

It is a figure which shows the structural example of the image characteristic measuring apparatus concerning one Embodiment of this invention. It is a figure which shows the more detailed structural example of the optical system for normal image specific measurement. It is a figure which shows the example of the relationship between a 1st image formation means and an area | region division means. It is a figure which shows the example of the mode of the light which passes a 1st image formation means. It is a figure which shows the example of the relationship between a spectroscopy means and an array-form light-receiving means. It is a figure which shows the example of the image formation on an array-like light-receiving means. It is a figure which shows the example which inclines the image formation on an array-like light-receiving means. It is a figure which shows the example of the image formation inclined on the array-like light-receiving means. It is a figure which shows the example of the measured spectral distribution. It is a figure which shows the example of the measurement result of the color difference with respect to the number of bands. It is a figure which shows the other structural example of an image characteristic measuring apparatus. It is a figure which shows the other structural example of a reflection means. It is FIG. (1) which shows the specific structural example of a 2nd light irradiation means. It is FIG. (2) which shows the specific structural example of a 2nd light irradiation means. It is a figure which shows the example of the outgoing angle of the light beam from the 1st image formation means by the light which propagated back from the 2nd light irradiation means. It is a figure which shows the example of the measurement result which shows the relationship between the light passage position of an area division means, and the outgoing angle of a light beam. It is a figure which shows the example of the divergence angle of the light beam from the 1st image formation means by the light which propagated back from the 2nd light irradiation means. It is a figure which shows the example of the measurement result which shows the relationship between the light passage position of an area division means, and the divergence angle of a light beam. It is a figure which shows the example of the test chart for positioning adjustment. It is a figure which shows the structural example of the image forming apparatus carrying an image characteristic measuring device.

  Hereinafter, preferred embodiments of the present invention will be described.

  FIG. 1 is a diagram showing a configuration example of an image characteristic measuring apparatus 100 according to an embodiment of the present invention. FIG. 2 is a diagram showing a more detailed configuration example of a normal image specific measurement optical system (an optical system in which an adjustment member is omitted) in the image characteristic measurement apparatus 100, and is viewed from above in FIG. It is drawn with the right end at the top.

  In FIG. 1 and FIG. 2, the first light irradiation means 101, which is a line illumination light source such as an LED array or a collimating lens, displays an image on the measurement surface 102 of an image carrier such as paper as a measurement object in a line shape. Illuminate with illumination light. The first light irradiation means 101 is a white light source having an intensity over almost the entire visible light region. As a light source used for the first light irradiation means 101, a fluorescent lamp such as a cold cathode tube or a lamp light source can be used in addition to an LED array or the like. It is desirable that the light source emits light in a wavelength region necessary for spectroscopy and can be illuminated uniformly throughout the entire observation region.

  Diffuse reflected light from the measurement surface 102 is reflected by the first imaging means 103 such as a microlens array or a selfoc lens array, and the reflected light from an image such as an aperture array such as a pinhole array or a slit array is converted into a region. A primary image is formed on the area dividing means 104 to be divided. The SELFOC lens may have a configuration in which a microlens array is applied or a primary image forming system is omitted and the aperture array and the paper are arranged close to each other. When a Selfoc lens array is applied, periodic bright and dark areas may occur due to mismatch between the hole pitch of the pinhole array and the lens array pitch. The pinhole array and slit array can be made by using a blackened metal plate with holes, or a glass substrate with black members such as chromium or carbon-containing resin formed in a predetermined shape. It is. The shape of the opening is not limited to a circle or a rectangle, but may be an ellipse or other shapes.

  The light beam that has passed through the region dividing means 104 passes through the second imaging means 105 composed of a plurality of lenses, and then passes through a transmissive grating, etc., if an adjustment reflecting means 112 described later is removed from the optical path. Are guided to the arrayed light receiving means 107 by a linear sensor or the like.

  The light flux from each aperture of the region dividing unit 104 is imaged by the second imaging unit 105 and dispersed by the spectroscopic unit 106, and then the intensity of a plurality of wavelength bands can be acquired by a plurality of pixels of the arrayed light receiving unit 107. Become.

  However, in the configuration using the SELFOC lens array for the first image forming unit 103, the diffused light from the measurement surface 102 goes straight and passes through the end of the region dividing unit 104 when the measurement target paper is wide. It is conceivable that the received light does not couple to the second imaging means 105. Therefore, for example, as shown in FIG. 3, a slit 103b is provided on the measurement surface 102 side of the microlens 103a of the first imaging means 103 so that the center positions of the microlens 103a and the pinhole 104a of the area dividing means 104 coincide. The slit 103b is made to coincide with the center of the microlens 103a and the pinhole 104a at the center of the optical system, and only the position of the slit 103b is gradually shifted from the center of the microlens 103a and the pinhole 104a toward the end. Thus, it is preferable to define the light passing position. In this case, as shown in FIG. 4, the light that has passed through the micro lens 103a can be bent toward the second imaging means 105 through the pinhole (104a).

Returning to FIG. 1 and FIG. 2, the spectroscopic means 106 is disposed in the vicinity of the arrayed light receiving means 107. FIG. 5 is a diagram showing an example of the relationship between the spectroscopic means 106 and the array-like light receiving means 107. As shown schematically by the broken lines in the figure, the incident light is diffracted by the spectroscopic means 106 to receive the array-like light. Light having different spectral characteristics is incident on N (N: number of bands) pixels of the spectral sensor (line sensor) constituting the means 107. As the spectroscopic means 106, one in which a sawtooth-shaped structure is periodically formed on a transparent substrate can be applied. When the period of the sawtooth portion of the spectroscopic unit 106 and p, the light of wavelength λ to be incident at an angle α to the spectroscopic means 106 is diffracted at an angle theta _m that is expressed by the following equation.

sinθ _m = mλ / p + sinα
Here, m is called the order of the diffraction grating, and can take a positive or negative integer value.

  As the shape of the spectroscopic means 106, the sawtooth shape as shown in FIG. 5 can increase the intensity of the + 1st order diffracted light, which is the most desirable. In addition to the sawtooth shape, it is possible to take a stepped shape. Further, if the pixel period d of the arrayed light receiving means 107 is 10 μm, the visible light is split into about 6 pixels when the diffraction element period p is 10 μm and the distance between the spectroscopic means 106 and the arrayed light receiving means 107 is 2 mm. It is possible to enter.

  However, when diffracted in the array direction (x direction in FIG. 2) of the elements of the arrayed light receiving means 107, the light beam is 0th order light, second order diffraction image, diffraction image of adjacent light beam transmitted through adjacent aperture, etc. Are overlapped on the linear sensor, causing crosstalk as shown in FIG. 6, making accurate spectral measurement difficult. Therefore, by rotating the spectroscopic means 106 in a plane perpendicular to the optical axis z of the optical system in FIG. 2 or setting the angle of the teeth of the diffractive element, as shown in FIGS. It is possible to obtain the intensity of each wavelength band by eliminating crosstalk. Here, FIG. 8 shows a state in which the diffraction element of the spectroscopic means 106 is tilted by 10 [deg], but the optimum angle can be determined from conditions such as optical elements and layout.

  In this embodiment, since it is necessary to acquire diffraction images from ultraviolet light and infrared light, diffraction performance from about 350 nm to about 800 nm is necessary. Of course, the grating frequency and blaze of the spectroscopic means 106 in FIG. By setting the angle, it is possible to acquire diffraction images in the visible region and outside the visible region. In addition, although the peak diffraction efficiency is somewhat lower than that of a sawtooth diffraction grating, the use of a holographic diffraction grating makes it possible to ensure a certain diffraction performance in a wide wavelength region in the visible region and outside the visible region. .

  In the present embodiment, when each spectroscopic sensor constituting the arrayed light receiving means 107 is an individual unit, the number of pixels constituting the unit is the pitch and diameter of the pinhole array constituting the area dividing means 104 of FIG. Depends on the magnification of the second imaging means 105, the pitch of the diffraction elements constituting the spectroscopic means 106, the installation distance from the arrayed light receiving means 107, etc., but the number of units configured on the arrayed light receiving means 107, the wavelength range to be measured It is possible to effectively apply the superiority of the overall layout of the present case, which can be flexibly adjusted according to the above conditions.

  When acquiring color information of an image formed with color toner in the present embodiment, a set of elements constituting a spectroscopic measurement system in the visible region on the arrayed light receiving means 107 in the wavelength range of 400 nm to 700 nm. Thus, a multiband spectroscopic sensor is configured. In multiband spectroscopy, the more the number of bands, the more detailed measurement results of the spectral distribution can be obtained, which is preferable. However, when the number of pixels of the arrayed light receiving means 107 is constant, the number of pixels used in one set of spectroscopic sensors increases as the number of bands increases, and the number of spectroscopic sensors that can be arrayed decreases. It will be. Therefore, it is preferable that the spectroscopic sensor of the present embodiment has processing for estimating the spectral distribution by an estimation method such as Wiener estimation while minimizing the number of bands.

  Many methods have been proposed for this spectral estimation process, and details are described in Non-Patent Document 1, for example.

An example of a technique for estimating a spectral distribution from an output v _i from one spectroscopic sensor is shown. From a row vector v storing signal outputs v _i (i = 1 to N) from N pixels constituting one spectroscopic sensor and a conversion matrix G, spectral reflectances (for example, 400 to 400) The row vector r storing 31) of 700 [nm] and 10 [nm] pitch is expressed by the following equation.

r = Gv
The transformation matrix G includes a matrix R storing spectral distributions for a large number (n) of samples whose spectral distributions are known in advance, and v when similar samples are measured by the image characteristic measuring apparatus 100 of the present embodiment. It is obtained from the stored matrix V by minimizing the square norm of error 誤差 · ‖ ² using the least square method.

_{R = [r 1, r 2} , ···, r n]
V = [v ₁ , v ₂ ,..., V _n ]
e = ‖R-GV‖ ² → min
The regression coefficient matrix G of the regression equation from V to R, where V is the explanatory variable and R is the objective variable, is expressed as Calculated.

G = RV ^T (VV ^T ) ⁻¹
Here, the superscript “T” represents the transpose of the matrix, and the superscript “−1” represents the inverse matrix. By storing G obtained in this manner, 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 at the time of actual measurement.

  A simulation in which a toner image (after fixing) output by an electrophotographic image forming apparatus is read by the image characteristic measuring apparatus 100 of the present embodiment to estimate a spectral distribution and calculate a color difference as an estimation error from the estimated spectral distribution. Went. 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. The spectral distribution of the toner image actually used in the simulation is as shown in FIG. FIG. 10 shows the simulation result. FIG. 10 shows that there is no significant difference in the estimated value error when the number of bands N is 6 or more. By setting the number of pixels required for each spectroscopic sensor at each position to be 6 or more, although there is a difference in accuracy between the spectroscopic sensors, it is possible to perform spectroscopic measurement with high accuracy over the entire area.

  Next, returning to FIG. 1, a configuration for adjustment added to the configuration of the optical system for normal image specific measurement described above will be described.

  In FIG. 1, a reflecting means 112 such as a mirror is disposed at 45 ° obliquely upward between the area dividing means 104 and the second imaging means 105, and a second light source such as an LED or a xenon light source is provided from above the entire optical system. The light irradiation means 111 is installed. The distance between the region dividing unit 104 and the second light irradiation unit 111 is made to coincide with the distance between the region dividing unit 104 and the entrance pupil plane of the second imaging unit 105. The entrance pupil plane corresponds to the position P in FIG.

  Further, the entire optical system other than the measurement surface 102 in FIG. 1 can be moved and rotated relative to the measurement surface 102 in the optical axis direction, and individual members can also be moved and rotated. The first light irradiation means 101 may be fixed on the measurement surface 102 side. In order to facilitate movement and rotation of the entire optical system, as shown in FIG. 11, an entrance pupil plane that rotates a member other than the measurement plane 102 (the first light irradiation means 101 may be excluded) as a unit. Further, a rotation stage 121 whose rotation center is coincident with each other and a moving stage 122 that moves the entire optical system together with the rotation stage 121 in a direction perpendicular to the measurement surface 102 in the optical axis direction (left-right direction in the figure) may be provided.

  Further, in FIG. 1 (also in FIG. 11), it is assumed that the reflecting means 112 is attached only at the time of adjustment, and the reflecting means 112 is removed at the time of normal image characteristic measurement. However, as shown in FIG. Is switched between a position indicated by a solid line (at the time of adjustment) and a position indicated by a broken line (at the time of normal image characteristic measurement) around the rotation axis 112a, so that the reflection means 112 does not have to be removed from the apparatus. Thereby, it is possible to easily adjust the relative posture and the relative position shift with respect to the position shift over time.

  FIG. 13 is a diagram showing a specific configuration example of the second light irradiation means 111, as viewed from the left side direction of FIG. In FIG. 13, the light irradiation element 111a of the second light irradiation means 111 is disposed on the rotation stage 111c, and the rotation stage 111c is rotatable around the emission end of the light irradiation element 111a. Thereby, it is possible to selectively irradiate the entire range of the region dividing unit 104 and the first imaging unit 103 with a single light source.

  FIG. 14 is a diagram illustrating another specific configuration example of the second light irradiation unit 111. In FIG. 17, two light irradiation elements 111a and 111b are provided on the rotation stage 111c, and the intersection of the optical axes in the emission direction of the light irradiation elements 111a and 111b is made to coincide with the rotation center of the rotation stage 111c. As a result, it is possible to simultaneously detect the imaging state of light at a plurality of positions on the measurement surface 102, and it is possible to adjust the position and orientation without deviation in the entire optical system.

  Returning to FIG. 1 (also in FIG. 11), at the time of adjustment, the light from the second light irradiation means 111 is irradiated in the direction of each pinhole of the area dividing means 104 via the reflection means 112. By observing the image formation on the measurement surface 102 of the light that has passed through the region dividing means 104 and the first image formation means 103, the distance and posture between the measurement surface 102 and the entire optical system can be clarified. The image may be observed visually or by an imaging means 113 such as a CCD camera that images the measurement surface 102. The arrangement of the image pickup means 113 may be anywhere as long as other members do not obstruct the image pickup as long as there is no regular reflection light from the first light irradiation means 101. The imaging unit 113 is not only for imaging from the optical system side of the measurement surface 102 but also arranges the imaging unit on the measurement surface 102 and directly images light that has passed through the first imaging unit 103. There may be.

FIG. 15 is a diagram showing an example of the exit angle of the light beam from the first imaging unit 103 by the light that has propagated back from the second light irradiation unit 111. Since the outgoing light from the first imaging means 103 is in principle parallel light, it should reach perpendicular to the measurement surface 102, but there is an angle shift between the optical system and the measurement surface 102. Deviations such as θ ₁ and θ _{2 in} FIG. This deviation can be observed as the movement of the imaging on the measurement surface 102 by moving the entire optical system in the optical axis direction, and the emission angle can be calculated from the movement amount of the entire optical system and the movement amount of the imaging. it can. FIG. 16 is a diagram showing an example of a measurement result showing the relationship between the light passing position of the region dividing means 104 and the light beam emission angle. The emission angle is changed from left (Left) to the center (Center) and to the right (Right). From the fact that it fluctuates almost linearly, it can be seen that the entire optical system has an angular deviation with respect to the measurement surface 102. For this reason, an operation of rotating the entire optical system so as to cancel out the angle shift according to the angle is performed. In a state where there is no angle shift, the emission angle is substantially constant and the plot of FIG. 16 is substantially horizontal. Therefore, if the state can be confirmed, the adjustment of the emission angle is completed.

  FIG. 17 is a diagram showing an example of the divergence angle of the light beam from the first image forming means 103 by the light propagating back from the second light irradiation means 111. The light emitted from the first image forming means 103 should in principle be parallel light. However, if there is a deviation in the position of the first image forming means 103 in the optical axis direction, the light does not become parallel light, and ω1 in the figure. , .Omega.2 changes in the light diameter (divergence angle). This variation can be observed as a change in the size of the image on the measurement surface 102 by moving the entire optical system in the optical axis direction, and the divergence angle is calculated from the amount of movement of the entire optical system and the size change of the image. Can do. FIG. 18 is a diagram showing an example of a measurement result showing the relationship between the light passing position of the region dividing means 104 and the divergence angle of the light beam.

  When there is a divergence angle, the diameter of the light on the measurement surface 102 changes depending on the relative distance between the entire optical system and the measurement surface 102. Therefore, the light can be adjusted by adjusting the relative distance between the entire optical system and the measurement surface 102. The diameter is adjusted to a predetermined size. In addition, it can also adjust so that it may become parallel light without a divergence angle by adjusting the relative position with respect to the 2nd image formation means 105 or the 2nd light irradiation means 111 of the 1st image formation means 103. FIG. In this case, adjustment of the relative distance between the entire optical system and the measurement surface 102 is not important. In the state where there is no divergence angle, the divergence angle is substantially constant and the plot of FIG. 18 is substantially horizontal.

  FIG. 19 is a diagram showing an example of a test chart for positioning adjustment. That is, when the image characteristic measuring apparatus 100 is used alone, when a print paper conveyance mechanism that is an object of image characteristic measurement is used, the paper feed direction (y direction orthogonal to the x direction in FIG. 2) is determined by this test chart. And the positioning in the direction perpendicular to it (the x direction in FIG. 2). The positioning based on the test chart can also be used when an image characteristic measuring apparatus 100 as will be described later is mounted on the image forming apparatus. FIG. 19 shows a test chart in which pattern images are formed by the number of sensors, and positioning is completed by confirming that each pattern image can be accurately detected.

  FIG. 20 is a diagram illustrating a configuration example of an image forming apparatus 200 in which the image characteristic measuring apparatus 100 is mounted. In FIG. 20, an image forming apparatus 200 includes paper feed trays 201 and 202, a paper feed roller 203, a controller 204, a scanning optical system 205, a photosensitive unit 206, an intermediate transfer member 207, a fixing unit 208, a paper discharge roller 209, and the like. The image characteristic measuring apparatus 100 described above is installed, for example, at the rear stage of the fixing unit 208. Further, if it is a type in which a finisher unit can be attached to the image forming apparatus 200, the image characteristic measuring device 100 can be provided externally on that part.

  The image characteristic measuring apparatus 100 of the present embodiment uses spectroscopic measurement, and can acquire color information in the image plane in two dimensions without positional deviation between the spectroscopic sensors constituting the apparatus. By feeding back, in the electrophotographic method, color unevenness in the image plane can be reduced by image processing such as one-scan control of the light source output of the writing scanning optical system and gamma correction before printing. In the ink jet method, it is possible to reduce color unevenness by directly controlling the ink discharge amount according to the head position.

As described above, according to the present embodiment, there are the following advantages.
(1) In the image characteristic measurement apparatus, light is propagated back in the optical system of the spectroscopic sensor that acquires diffuse reflected light from the object at a plurality of positions, and the relative position and orientation of the measurement object and the spectroscopic sensor are determined over the entire image width. By having a detection mechanism, it is possible to optimize the relative position and orientation between the spectroscopic sensor and the object, and measure the color information of the image formed by the color material such as color toner over the full width of the two-dimensional image. can do.
(2) By rotating a light source that reversely propagates light in the optical system of the spectroscopic sensor array, each sensor of the spectroscopic sensor array detects a relative position and posture with respect to an object, and performs optimum positioning in the spectroscopic sensor array as a whole. It can be carried out.
(3) It is possible to detect the relative positions and orientations of the plurality of sensors constituting the spectroscopic sensor array and the measurement object, and it is possible to perform optimum positioning over the entire spectroscopic sensor array.
(4) A mechanism for correcting the position and orientation of the image characteristic measuring apparatus is provided, and the reliability of spectroscopic measurement can be ensured.
(5) By mounting the image characteristic measuring device on the image forming device, the color information and transparent color material information of the image on the image carrier conveyed in the image product are measured with high accuracy, and the color variation of the image and When there is a non-formed portion of the transparent image, feedback correction can be performed.

  The present invention has been described above by the preferred embodiments of the present invention. While the invention has been described with reference to specific embodiments, various modifications and changes may be made to the embodiments without departing from the broad spirit and scope of the invention as defined in the claims. Obviously you can. In other words, the present invention should not be construed as being limited by the details of the specific examples and the accompanying drawings.

DESCRIPTION OF SYMBOLS 100 Image characteristic measuring apparatus 101 1st light irradiation means 102 Measurement surface 103 1st image formation means 103a Micro lens 103b Slit 104 Area division means 104a Pinhole 105 2nd image formation means 106 Spectroscopic means 107 Array-like light reception means 111 Second light irradiation means 111a, 111b Light irradiation element 111c Rotating stage 112 Reflecting means 112a Rotating shaft 113 Imaging means 121 Rotating stage 122 Moving stage 200 Image forming apparatus 201, 202 Paper feeding tray 203 Paper feeding roller 204 Controller 205 Scanning optical system 206 Photosensitive unit 207 Intermediate transfer member

Special table 2008-518218 gazette JP 2005-315883 A JP 2002-310799 A Japanese Patent No. 3566334 JP 2003-139702 A Japanese Patent Laid-Open No. 2005-265752

“Analysis and Evaluation of Digital Color Images”, The University of Tokyo Press, Yoichi Miyake, February 25, 2000, p. 154-p. 157

Claims (5)

A first light irradiation means for irradiating a predetermined region of the image on the image carrier that is a measurement object;
First imaging means for condensing the reflected light from the measurement object of the light irradiated by the first light irradiation means;
An area dividing means for dividing an area by an aperture row installed at a position substantially in an imaging relationship with the measurement object by the first imaging means;
A second imaging means for condensing the reflected light from the measurement object divided into regions through the aperture row;
A spectroscopic means for spectroscopically splitting the light divided through the aperture row collected by the second imaging means so that the diffraction images do not overlap each other;
An arrayed light receiving means for receiving the divided light from each of the apertures,
Second light irradiation means for irradiating light from above between the aperture row and the second imaging means;
Reflecting means for reflecting light from the second light irradiation means in the direction of the aperture row,
The distance between the aperture row and the second light irradiating means via the reflecting means is the same as the distance between the aperture row and the entrance pupil of the second imaging means. Characteristic measuring device. The image characteristic measuring apparatus according to claim 1,
An image characteristic measuring apparatus comprising light source rotating means for rotating the second light irradiation means. In the image characteristic measuring device according to claim 1 or 2,
The second light irradiating means has a plurality of light sources, and is capable of irradiating light toward the plurality of openings. In the image characteristic measuring device according to any one of claims 1 to 3,
The whole of the first image forming means, the area dividing means, the second image forming means, the spectroscopic means, the array light receiving means, the second light irradiation means and the reflecting means can be rotated and moved in parallel. An image characteristic measuring apparatus comprising a moving means. An image forming apparatus comprising the image characteristic measuring apparatus according to claim 1, and having a moving unit that relatively moves the image characteristic measuring apparatus and a measurement object.