JP5402740B2 - Spectral characteristic acquisition device, image evaluation device, and image forming device - Google Patents

Description

  The present invention relates to a spectral characteristic measuring apparatus for acquiring spectral characteristics of an image formed on the surface of a measurement object, an image evaluation apparatus including the spectral characteristic acquiring apparatus, and an image forming apparatus.

  In recent years, full-color image forming apparatuses (printers, copiers, etc.) such as electrophotographic systems and inkjet systems have demanded high image quality for color images printed on recording media such as paper, and color reproducibility. Improvement is one of the important technical issues.

  Therefore, in order to improve the color reproducibility of the printed color image, the spectral characteristics are measured over the entire area of the printed color image, and image formation is performed so that optimum color reproducibility can be obtained based on this measurement information. A method for controlling a process has been conventionally performed. As an apparatus for acquiring spectral characteristics over the entire area (full width) of a color image printed on a recording medium, for example, an apparatus (full width array spectrophotometer) described in Patent Document 1 is known.

  In Patent Document 1, a surface of a moving object to be measured is continuously illuminated over a whole area (full width) of an image on the surface of the object to be measured with a plurality of light sources having different emission colors, and each reflected light from the image is reflected. Is received and imaged by a line sensor having a plurality of multi-color photodetectors, and spectral characteristics at each position of the image on the measurement surface are acquired (estimated) based on a plurality of image data output from the line sensor. ) Is disclosed.

  By the way, as in Patent Document 1, illumination is continuously performed over the entire area (full width) of the image on the surface of the object to be measured with a plurality of different light sources, and the diffuse reflected light from the surface to be measured corresponds to each color light corresponding to the line sensor. In the configuration in which the image is picked up by the detector, a time lag occurs at the time of image pick-up by each color light detector due to the continuous illumination of each light source, so that the measurement is performed at different positions with respect to the image on the moving object. For this reason, since the relative positional shift of each image acquired by each color light detector corresponding to the line sensor occurs, an acquisition error of the spectral characteristics due to this positional shift occurs, so that the spectrum can be stably and accurately detected. It was difficult to get the characteristics.

  SUMMARY An advantage of some aspects of the invention is that it provides a spectral characteristic acquisition device, an image evaluation apparatus, and an image forming apparatus that can stably and accurately acquire spectral characteristics.

The spectroscopic characteristics acquisition unit of claim 1 in order to achieve the object, a pinhole array comprising multiple openings by the light irradiating means Ru passes the reflected light of the irradiated light to the measurement object, wherein an imaging means for the light passing through the plurality of openings of the pinhole array each Ru is focused, and the diffraction means for diffracting each were imaged light by the imaging means, the light is diffracted in the previous SL diffraction means the has a light receiving means for receiving, respectively, a, is characterized in that before Kiyuizo means is an array of erecting equal-magnification optical system.

Spectroscopic characteristics acquisition unit of claim 2 has a reduced focusing means for focusing said by reducing the reflected light of the object to be measured or these light to the plurality of openings of the pinhole array, the fused small The light condensing means has at least image side telecentric characteristics.

Magnification is spectroscopic characteristics acquisition unit of claim 3, comprising a plurality of focusing means for respectively condensing the light of reflected light from a plurality of locations of the object to be measured in the plurality of openings of the pinhole array It has a condensing means.

The spectroscopic characteristics acquisition unit of claim 4, said equal-magnification focusing means, wherein a plurality of openings of the pinhole array, but that it is arranged on the incident surface and an exit surface of the same optical element It is a feature.

The spectral characteristic acquisition apparatus according to claim 5, wherein an image-side numerical aperture of the plurality of condensing units of the equal magnification condensing unit is a single unit of the erecting equal magnification imaging optical system constituting the imaging unit. It is characterized by being at least twice the object-side numerical aperture.

  The spectral characteristic acquisition apparatus according to claim 6 is characterized in that the equal-magnification focusing means is an array of erecting equal-magnification imaging optical systems.

An image evaluation apparatus according to a seventh aspect includes a spectral characteristic acquisition apparatus according to any one of the first to sixth aspects, and a moving unit that changes a relative position between the spectral characteristic acquisition apparatus and the object to be measured. and output information from the spectroscopic characteristics acquisition unit, based on, is characterized by having a calculating means for calculating a spectral distribution or colorimetry results at a plurality of positions of the object to be measured.

  The image forming apparatus according to claim 8 is an image forming apparatus that forms an image on a recording medium and outputs the image. The image evaluation apparatus according to claim 7 is mounted, and the image evaluation apparatus outputs the image from the image forming apparatus. It is characterized in that an image on a recording medium is evaluated.

  According to the spectral characteristic acquisition apparatus of the first aspect of the present invention, the imaging unit is an array of an erecting equal-magnification imaging optical system, so that imaging is performed on a plurality of apertures of the pinhole array and the light receiving unit. Since the positioning accuracy of the means in the direction perpendicular to the optical axis is greatly relaxed and a relatively compact optical system can be realized, a highly accurate spectral characteristic acquisition device can be provided at a lower cost.

  According to the spectral characteristic acquisition apparatus of the second aspect of the present invention, there is a reduction condensing means for reducing and condensing the diffuse reflected light from the object to be measured at a plurality of openings of the pinhole array, Since the light means has at least image side telecentric characteristics, the object to be measured and the spectral characteristic acquisition device can be measured in a non-contact manner with a certain distance. In addition, since all the optical axes that pass through the plurality of apertures of the pinhole array are incident on the diffractive means substantially perpendicularly, the optical system in the imaging means, the diffractive means, and the light receiving means has almost the same characteristics from the central part to the peripheral part. Therefore, it is possible to perform highly accurate measurement stably up to the peripheral part.

  According to the spectral characteristic acquisition apparatus of the third aspect of the present invention, the diffused reflected light beam from each position on the surface of the object to be measured passes through the plurality of openings of the pinhole array through the equal-magnification condensing means. Therefore, all the optical axes passing through the plurality of openings can be made parallel. As a result, the 45/0 arrangement used in the conventional spectrocolorimeter is possible, and the spectral characteristics closer to those of the conventional spectrocolorimeter can be measured.

  According to the spectral characteristic acquisition apparatus of the fourth aspect of the present invention, the plurality of apertures of the equal-magnification condensing means and the pinhole array are arranged on the incident surface and the exit surface of the same optical member, so that There is no change in relative position error due to changes, vibrations, etc., and spectral characteristics can be measured stably over a long period of time with high accuracy.

  According to the spectral characteristic acquisition apparatus of the fifth aspect of the present invention, the image-side numerical apertures of the plurality of condensing means of the equal-magnification condensing means are set to the erecting equal-magnification imaging optical system constituting the imaging means. By making the numerical aperture at least twice that of the single object side, all the light beams that have passed through the plurality of apertures of the pinhole array are imaged at one point by two or more erecting equal magnification imaging optical systems. As a result, even if the pitch of the plurality of apertures and the pitch of the erecting equal-magnification imaging optical system are different, the optical characteristics are substantially the same, and the spectral characteristics can be measured stably and with high accuracy.

  According to the spectral characteristic acquisition apparatus of the sixth aspect of the present invention, by setting the equal magnification condensing means as an array of erecting equal magnification imaging optical systems, the image side numerical aperture of the equal magnification condensing means is reduced. This can be enlarged, and this is imaged by an imaging means that is an array of the same erecting equal-magnification imaging optical system, so that most of the light flux that has passed through the aperture of the pinhole array is imaged on the light receiving means. It becomes possible. Thereby, since the light utilization efficiency is further increased, the spectral characteristics can be stably measured with high accuracy even if the light irradiation means is relatively weak.

  According to an image evaluation apparatus as set forth in claim 7 of the present invention, the spectral characteristic acquisition apparatus according to any one of claims 1 to 6, and the relative position between the spectral characteristic acquisition apparatus and the object to be measured. Since the moving means for changing and the calculating means for calculating the spectral distribution or the colorimetric result at a plurality of positions of the object to be measured based on the output information from the spectral characteristic acquisition device, the moving recording medium The spectral distribution or color at a plurality of positions of the image formed above can be continuously evaluated with high accuracy.

  According to the image forming apparatus according to claim 8 of the present invention, the image evaluation apparatus according to claim 7 is mounted on the image forming apparatus that forms and outputs an image on a recording medium, and the image is evaluated by the image evaluation apparatus. By evaluating the image on the recording medium output from the forming apparatus, the spectral characteristics of the image on the output recording medium can be continuously measured with high accuracy.

Schematic which shows the structure of the spectral characteristics acquisition apparatus which concerns on Embodiment 1 of this invention. The figure which shows the pinhole array in which the some opening was formed. The figure which shows the state in which the diffraction image diffracted by the diffraction element was imaged along the inclination direction which has an angle with respect to the longitudinal direction of a light receiving sensor. Schematic which shows the structure of the spectral characteristics acquisition apparatus which concerns on Embodiment 2 of this invention. Schematic which shows the structure of the spectral characteristics acquisition apparatus which concerns on Embodiment 3 of this invention. Schematic which shows the structure of the image evaluation apparatus provided with the spectral characteristic acquisition apparatus which concerns on Embodiment 4 of this invention. FIG. 10 is a schematic diagram illustrating a configuration of a printer as an example of an image forming apparatus including an image evaluation apparatus according to a fifth embodiment of the invention.

Hereinafter, the present invention will be described based on the illustrated embodiments.
<Embodiment 1>
FIG. 1 is a schematic diagram illustrating a configuration of a spectral characteristic acquisition apparatus according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the spectral characteristic acquisition apparatus 1 according to the present embodiment has a width of a sheet-like object 2 on which an image is formed on a surface that moves in one direction (from top to bottom in FIG. 1). A line light irradiation device 3 that irradiates light along a direction (a direction orthogonal to the paper surface of FIG. 1) and a measurement object 2 of light irradiated from the line light irradiation device 3 toward the measurement object 2 are formed. A first imaging optical system 4 disposed on an axis for receiving diffusely reflected light from the image surface, a plurality of minute openings 5a formed in the pinhole array 5, and a second imaging optical system. 6, a diffraction element 7 and a light receiving sensor 8 are provided.

  Note that the DUT 2 in this embodiment is, for example, paper (paper) on which a color image (toner image) is printed on the surface output from an electrophotographic full-color printer or the like.

  The line light irradiation device 3 emits light from an angle direction inclined by 45 degrees with respect to the normal direction of the object to be measured 2 in the entire width direction of the surface of the object to be measured 2 (direction perpendicular to the paper surface of FIG. 1). It arrange | positions so that it may irradiate in a line form. The wavelength band of light emitted from the line light irradiation device 3 is visible light of about 400 to 700 nm. As the line light irradiation device 3, for example, an LED array irradiation device in which a plurality of white LEDs are arranged along the width direction of the surface of the DUT 2 can be used.

  The first imaging optical system 4 reduces the diffuse reflected light from an image (not shown) formed on the object 2 to be measured, which is irradiated from the line light irradiation device 3 toward the object 2 to be measured. This is an optical system that forms an image of diffusely reflected light beams on a plurality of minute openings 5 a formed in the pinhole array 5.

  For example, as shown in FIG. 2, the pinhole array 5 has a plurality of substantially circular openings 5 a which are light transmission regions on a blackened metal plate corresponding to the entire width direction of the surface of the object to be measured 2. Are arranged in a row. In the present embodiment, the shape of the opening of the pinhole array 5 is substantially circular. However, the shape is not limited to this, and may be oval or rectangular.

  The second imaging optical system 6 binds the diffusely reflected light beam imaged at each opening 5 a of the pinhole array 5 to the surface of the light receiving sensor 8 provided along the entire width direction of the object 2 to be measured. An erecting equal-magnification imaging optical system array (for example, a SELFOC lens array manufactured by Nippon Sheet Glass Co., Ltd.), and a refractive index dispersion type rod lens capable of imaging at erecting equal magnification is the width of the object 2 to be measured. It is arranged along the entire direction.

  The diffractive element 7 is a transmissive diffractive element disposed in the optical path between the second imaging optical system 6 and the light receiving sensor 8, and the light beam that has passed through each opening 5 a of the pinhole array 5 is converted into a pinhole. The diffraction is performed non-parallel to the arrangement direction of the openings 5a of the array 5. That is, the diffraction element 7 is tilted so that the diffraction axis of the diffraction element 7 has a predetermined angle (diffraction axis angle) with respect to the width direction of the DUT 2 (the arrangement direction of the openings 5a of the pinhole array 5). Is arranged. Thereby, for example, as shown in FIG. 3, the diffraction images a <b> 1 and a <b> 2 diffracted by the diffraction element 7 are along an inclination direction having an angle θ (the diffraction axis angle) with respect to the longitudinal direction of the light receiving sensor 8. Imaged.

  In FIG. 3, a0 is a 0th-order light that is a transmission image transmitted through the diffraction element 7, a1 and a2 are primary-light and secondary-light diffraction images, and in the figure, the primary-light a2 diffraction image is An image is formed on the surface of a predetermined number (six in the figure) of a plurality of pixels (light receiving elements) 9 constituting the light receiving portion of the light receiving sensor 8. In the present embodiment, as shown in FIG. 3, only the diffracted image a1 of the first-order light among the diffracted images diffracted by the diffractive element 7 is out of the plurality of pixels 9 arranged in a line shape of the light receiving sensor 8. The relative positions of the pinhole array 5 and the light receiving sensor 8 are adjusted so as to form an image on a predetermined number (six in the figure) of pixels (pixels indicated by oblique lines).

  In the present embodiment, the diffracted image a1 of the primary light is received by the six pixels of the light receiving sensor 8. However, the present invention is not limited to this, and the grating pitch of the diffractive element 7 and the distance between the light receiving sensor 8 and the like. By adjusting, the number of pixels that receive the diffraction image a1 of the primary light can be increased. By increasing the number of pixels that receive the diffracted image a1 of the primary light, it is possible to improve the measurement resolution and measurement accuracy when measuring the spectral characteristics of the image based on the pixel output signal from each pixel.

  Further, by adjusting the pitch of each opening 5a of the pinhole array 5 so that the diffraction image does not overlap on the plurality of pixels 9 constituting the light receiving portion of the light receiving sensor 8, a plurality of lines arranged in a line shape are adjusted. A plurality of primary light diffraction images can be formed on the pixel 9. Thus, a plurality of positions of the image formed on the object to be measured 2 can be obtained by dividing each pixel area that receives each diffraction image as one unit and dividing the pixel output signal from each pixel into each unit. Spectral characteristics at can be measured.

  As the diffractive element of the diffractive element 7, it is preferable to use a diffractive element having a high diffraction efficiency at a predetermined order, such as a transmissive blazed diffraction grating. As a result, the light utilization efficiency is improved, and a decrease in measurement accuracy due to incidence of other orders of diffracted light on the plurality of pixels 9 arranged in a line can be reduced.

  A plurality of square-shaped pixels 9 constituting the light-receiving portion of the light-receiving sensor 8 shown in FIG. 3 are arranged in a line along the entire width direction of the DUT 2, and each pixel has a received light quantity. A corresponding pixel output signal, that is, an electric signal corresponding to the spectral characteristics of the image formed on the DUT 2 is output.

  In the present embodiment, the shape of each pixel constituting the light receiving unit of the light receiving sensor 8 is a square. However, the shape is not limited to this, and may be a rectangle or an ellipse.

  Next, the operation of the spectral characteristic acquisition device 1 will be described.

  As shown in FIG. 1, the moving object to be measured (paper) is line-shaped from an angle direction inclined by 45 degrees over the entire width direction of the object to be measured 2 from the line light irradiation device (LED array irradiation device) 3. The light L1 is irradiated. Then, diffusely reflected light L 2 from the surface of an image (not shown) formed on the DUT 2 is incident on the first imaging optical system 4. The first imaging optical system 4 reduces the incident diffuse reflected light L 2 and forms an image of the light beam L 3 on a plurality of minute openings 5 a formed in the pinhole array 5.

  Then, the light beam L 4 that has passed through each opening 5 a of the pinhole array 5 is incident on the second imaging optical system 6. The second imaging optical system 6 images the incident light beam L4 on the surface of the light receiving sensor 8 by setting the incident light beam L4 as an erect equal magnification.

  At this time, as shown in FIG. 3, the diffraction element 7 disposed on the optical path between the second imaging optical system 6 and the light receiving sensor 8 is inclined at a predetermined angle (diffraction axis angle). A diffracted image a1 diffracted by the diffraction element 7 is formed on a predetermined number (six pixels in the figure) of pixels (pixels indicated by oblique lines) among a plurality of pixels (light receiving elements) 9 constituting the light receiving unit. The

  The spectral characteristics of the image formed on the DUT 2 can be acquired (measured) from the pixel output signal corresponding to the received light amount output from each pixel on which the diffraction image a1 is formed.

  As described above, the spectral characteristic acquisition apparatus 1 according to the present embodiment uses an array of erecting equal-magnification imaging optical systems as the second imaging optical system 6, and thus the second imaging optical system 6. The influence on the measurement accuracy due to the position error in the direction perpendicular to the optical axis is greatly mitigated. Thereby, it is possible to acquire (measure) spectral characteristics stably and accurately over a long period of time by suppressing a decrease in measurement accuracy due to an assembly error or a change with time during manufacturing.

  Further, by using an erecting equal-magnification imaging optical system array for the second imaging optical system 6, the conjugate length of the second imaging optical system 6 can be shortened to several tens of millimeters. Compared with the use of a general imaging lens for the imaging optical system 6, the entire optical system from the pinhole array 5 to the light receiving sensor 8 becomes compact. Thereby, the rigidity of the entire optical system from the pinhole array 5 to the light receiving sensor 8 is increased, and a decrease in measurement accuracy due to the influence of vibration or the like can be suppressed.

  In the present embodiment, it is desirable that the first imaging optical system 4 has image side telecentric characteristics. As a result, the DUT 2 and the spectral characteristic acquisition device 1 can be measured in a non-contact manner with a certain distance. Furthermore, the emission direction of the light beam passing through all the openings 5a of the pinhole array 5 is substantially parallel to the optical axis, and the optical characteristics of the central part and the peripheral part of the optical system from the pinhole array 5 to the light receiving sensor 8 are substantially the same. Therefore, the spectral characteristics can be acquired (measured) stably and accurately up to the peripheral portion.

  In the present embodiment shown in FIG. 1, a 45/0 arrangement in which measurement is performed in the normal direction by irradiating with the line light irradiation device 3 from the direction of 45 degrees with respect to the normal direction of the surface to be measured 2. However, the present invention is not limited to this, and a 0/45 arrangement may be employed in which the line light irradiation device 3 irradiates the measurement object 2 from the normal direction of the measurement surface and performs measurement from the 45 degree direction.

<Embodiment 2>
FIG. 4 is a schematic diagram illustrating a configuration of a spectral characteristic acquisition apparatus according to Embodiment 2 of the present invention. In addition, the same code | symbol is attached | subjected to the same member as the spectral characteristic acquisition apparatus of Embodiment 1, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 4, the spectral characteristic acquisition device 1 a according to this embodiment corresponds to each opening 5 a of the pinhole array 5 instead of the first imaging optical system 4 provided in the first embodiment. Thus, the lens array 10 is arranged. In this embodiment, the object to be measured (from the lens array 10 to the pinhole array 5, the imaging optical system 6a (corresponding to the second imaging optical system 6 of the first embodiment), the diffraction element 7, and the light receiving sensor 8). Paper) 2 is set to the same width as the measurement range of the surface to be measured. Other configurations are the same as those of the first embodiment.

  In the spectral characteristic acquisition device 1a of the present embodiment, when the moving object (paper) 2 is irradiated with the line-shaped light L1 from the line light irradiation device 3 over the entire width direction of the object 2 to be measured, the object to be measured is measured. The diffuse reflected light L2 in the normal direction from the surface of an image (not shown) formed on the object 2 is incident on the lens array 10. The lens array 10 reduces the incident diffusely reflected light L <b> 2 and focuses the light beam L <b> 3 on a plurality of minute openings 5 a formed in the pinhole array 5.

  Then, the light beam L4 that has passed through each opening 5a of the pinhole array 5 enters the imaging optical system 6a. The imaging optical system 6a images the incident light beam L4 on the surface of the light receiving sensor 8 by setting the incident light beam L4 as an erect equal magnification.

  At this time, as in the first embodiment, as shown in FIG. 3, the diffractive element 7 disposed on the optical path between the imaging optical system 6a and the light receiving sensor 8 is tilted to a predetermined angle (diffraction axis angle). Therefore, the diffracted image a1 diffracted by the diffractive element 7 is on a predetermined number (six pixels in the figure) of pixels (lightly hatched pixels) among a plurality of pixels (light receiving elements) 9 constituting the light receiving unit. Is imaged.

  Thus, in the present embodiment, the lens array 10 to the pinhole array 5, the imaging optical system 6a, the diffraction element 7, and the light receiving sensor 8 are the same as the measurement range of the measurement surface of the measurement object (paper) 2. Since the width is set, the luminous flux of the diffusely reflected light L2 in the normal direction from the surface of the image (not shown) formed on the object 2 to be measured 2 is the pixel 9 of the light receiving sensor 8 without its optical axis being inclined. To reach. Thereby, each array unit from the lens array 10 to the pinhole array 5, the imaging optical system 6a, the diffraction element 7, and the light receiving sensor 8 has a 45/0 arrangement used in a general spectrocolorimeter. Therefore, measurement close to that of a conventional spectrocolorimeter can be performed.

  In the present embodiment shown in FIG. 4, a 45/0 arrangement in which measurement is performed in the normal direction by irradiating with the line light irradiation device 3 from a direction of 45 degrees with respect to the normal direction of the surface to be measured 2. However, the present invention is not limited to this, and a 0/45 arrangement may be employed in which the line light irradiation device 3 irradiates the measurement object 2 from the normal direction of the measurement surface and performs measurement from the 45 degree direction.

  In the present embodiment, the lens system 10 is used as the optical system for condensing light on the pinhole array 5, so that the pinhole array can be formed from the surface to be measured (image formed on the object 2 to be measured). The distance up to 5 can be shortened to several millimeters to several tens of millimeters, and a more compact spectral characteristic acquisition device 1a can be provided.

  Furthermore, in the present embodiment, the lens array 10 and the pinhole array 5 may be integrated. For example, an element in which the lens array 10 is configured on the incident surface side of one glass surface and the pinhole array 5 is configured on the output surface side is suitable. Since the relative position fluctuation of each condensing lens of the lens array 10 and each aperture of the pinhole array 5 has a great influence on the measurement accuracy, this effect can be obtained by integrating the lens array 10 and the pinhole array 5. Can be reduced.

  In this embodiment, when the opening pitch of the pinhole array 5 and the pitch of the array of the imaging optical system 6a are different, these array units are not exactly the same optical characteristics. Therefore, it is preferable that the image-side numerical aperture of the lens array 10 as a condensing lens is at least twice the object-side numerical aperture of the erecting equal-magnification image element alone of the imaging optical system 6a.

  Thereby, all the light beams that have passed through the respective openings of the pinhole array 5 are imaged through two or more imaging optical systems (erecting equal-magnification image elements) 6a. Therefore, the difference in optical characteristics of each array unit from the lens array 10 to the pinhole array 5 and the imaging optical system 6a is reduced, and the spectral characteristics can be acquired (measured) stably and accurately.

<Embodiment 3>
FIG. 5 is a schematic diagram showing a configuration of a spectral characteristic acquisition apparatus according to Embodiment 3 of the present invention. In addition, the same code | symbol is attached | subjected to the same member as the spectral characteristic acquisition apparatus of Embodiment 2, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 5, the spectral characteristic acquisition device 1 b according to the present embodiment is erecting as a condensing unit for each opening 5 a of the pinhole array 5 instead of the lens array 10 provided in the second embodiment. In this configuration, the double-magnification optical system array 11 is arranged. Other configurations are the same as those of the first embodiment.

  As described above, in the present embodiment, the erecting equal-magnification image optical system array 11 is arranged as the light condensing means to each opening 5a of the pinhole array 5, so that the image of the light converging means is compared with a normal lens array. The side numerical aperture can be increased. Most of the light beams that have passed through the openings 5a of the pinhole array 5 can be imaged on the pixels 9 of the light receiving sensor 8 by the imaging optical system (erecting equal magnification image element) 6a. Therefore, the light utilization efficiency is further improved, and spectral characteristics can be acquired (measured) stably and accurately even with relatively weak light irradiation.

<Embodiment 4>
FIG. 6 is a schematic diagram illustrating a configuration of an image evaluation apparatus including a spectral characteristic acquisition apparatus according to Embodiment 4 of the present invention.

  As shown in FIG. 6, the image evaluation apparatus 20 according to the present embodiment includes, for example, the spectral characteristic acquisition apparatus 1 of the first embodiment and a calculation unit 12. The calculation unit 12 can be realized by software on a computer. As the spectral characteristic acquisition apparatus, the optical characteristic acquisition apparatuses 1a and 1b of the second and third embodiments may be used.

  In the image evaluation apparatus 20 according to the present embodiment, first, spectral characteristics of an image formed on the measurement object 2 are acquired (measured) by the spectral characteristic acquisition apparatus 1.

  That is, the measurement position of the object to be measured (paper) 2 that moves at a constant speed in the direction of arrow A by the rotational drive of the pair of transport rollers 21 and 22 is from an angle direction inclined by 45 degrees with respect to the normal direction. The line-shaped light L <b> 1 is irradiated from the line light irradiation device (LED array irradiation device) 3 over the entire width direction of the DUT 2. Then, diffusely reflected light L 2 from the surface of an image (not shown) formed on the DUT 2 is incident on the first imaging optical system 4. The first imaging optical system 4 reduces the incident diffuse reflected light L 2 and forms an image of the light beam L 3 on a plurality of minute openings 5 a formed in the pinhole array 5.

  Then, the light beam L 4 that has passed through each opening 5 a of the pinhole array 5 is incident on the second imaging optical system 6. The second imaging optical system 6 images the incident light beam L4 on the surface of the light receiving sensor 8 by setting the incident light beam L4 as an erect equal magnification. At this time, as shown in FIG. 3, the diffraction element 7 disposed on the optical path between the second imaging optical system 6 and the light receiving sensor 8 is tilted at a predetermined angle. The diffracted image a1 thus formed is formed on a predetermined number (six pixels in the figure) of pixels (light-slashed pixels) among a plurality of pixels (light-receiving elements) 9 constituting the light-receiving unit.

  A pixel output signal (spectral characteristic acquisition information) corresponding to the received light amount output from each pixel on which the diffraction image a1 is formed corresponds to a plurality of measurement positions as the object to be measured (paper) 2 moves. Then, it is continuously output to the calculation unit 12.

  Then, the arithmetic unit 12 responds to the pixel output signals (spectral characteristic acquisition information) at a plurality of input measurement positions from the lens array 10 to the pinhole array 5, the imaging optical system 6a, the diffraction element 7, and the light receiving sensor 8. After the separation processing is performed on the spectral characteristic information of each array unit up to the above, each is converted into a spectral distribution or a value of the XYZ color system. In general, a method of estimating a spectral distribution from a multiband image can be applied. For example, it is described in "Tokumura Tokumichi, Haneishi Hideaki, Miyake Yoichi," Estimation of Spectral Reflectance from Multiband Images by Multiple Regression Analysis ", Optics Vol. 27, No. 7, PP. The method is applicable.

  The calculation unit 12 refers to a sample of a plurality of colors with known spectral reflectances, and calculates a conversion matrix for estimating a spectral reflectance distribution from pixel output signals (spectral characteristic acquisition information) at a plurality of input measurement positions. , Calculated by the winner estimation method. Then, by storing the calculated conversion matrix, the spectral reflectance distribution of each array unit is calculated from the spectral characteristic information at an arbitrary measurement position of the object to be measured (paper) 2 using the conversion matrix. .

  Thereafter, the object color may be converted into a uniform color space, for example, an L * a * b * color system value. Further, the color difference from the reference data derived in advance may be evaluated.

  The evaluation result obtained by the calculation unit 12 can be displayed on a display device or printed on paper by a printer or the like and shown to the user.

  As described above, since the image evaluation apparatus 20 according to the present embodiment includes the spectral characteristic acquisition apparatus 1 (or spectral characteristic acquisition apparatuses 1a and 1b), the spectral characteristics are acquired (measured) stably and accurately over a long period of time. Thus, highly accurate image evaluation can be performed.

<Embodiment 5>
FIG. 7 is a schematic diagram illustrating a configuration of a printer as an example of an image forming apparatus including an image evaluation apparatus according to Embodiment 5 of the present invention.

  As shown in FIG. 7, the printer (image forming apparatus) 30 according to the present embodiment includes, for example, the image evaluation apparatus 20 of the fourth embodiment on the downstream side in the transport direction of the fixing device 34.

  As shown in FIG. 7, the printer (image forming apparatus) 30 of the present embodiment includes four image forming units 31a, 31b, 31c, 31d, an exposure device 32, an intermediate transfer belt 33, a fixing device 34, and a paper feed cassette 35a. , 35b and the like.

  Each of the image forming units 2a, 2b, 2c, and 2d has a photosensitive drum 36, a charger 37, a developing device 38, a primary transfer roller 39, and a photosensitive drum cleaning device 40 (note that the image forming unit). Reference numerals for these members in 31b, 31c, and 31d are omitted). Each developing device 38 of the image forming units 31a, 31b, 31c, and 31d contains Y (yellow), M (magenta), C (cyan), and K (black) toners as developers. .

  The endless belt-like intermediate transfer belt 33 is stretched between a plurality of rollers (a driving roller 41, a secondary transfer counter roller 42, a first driven roller 43, and a second driven roller 44) and driven. The roller 41 is driven to rotate in the direction of arrow a. Each primary transfer roller 39 as a primary transfer member of each of the image forming units 31a, 31b, 31c, and 31d is in contact with the photosensitive drum 36 with the intermediate transfer belt 33 interposed therebetween, and is a secondary transfer counter roller. 39 is in contact with the secondary transfer roller 45 with the intermediate transfer belt 33 interposed therebetween.

  The fixing device 34 includes a fixing roller 46 and a pressure roller 47 that are in pressure contact with each other. Further, between the secondary transfer portion (between the secondary transfer counter roller 42 and the secondary transfer roller 45) and the fixing nip (between the fixing roller 46 and the pressure roller 47) of the fixing device 34, the secondary transfer portion. An endless belt-like transport belt 50 is provided for transporting and guiding the transfer material onto which the toner image has been transferred to the fixing nip. In the vicinity of the discharge conveyance path 51 on the downstream side of the fixing device 34, the image evaluation device 20 including the spectral characteristic acquisition device described in the fourth embodiment is installed.

  During the printing operation (image forming operation) of the printer (image forming apparatus) 30, the surface of each photosensitive drum 36 that is rotationally driven at a predetermined process speed of the image forming units 31a, 31b, 31c, and 31d 37 are uniformly charged. Then, after exposure is performed by the exposure device 32 in accordance with the input image data to form an electrostatic latent image, development is performed by each developing device 38, thereby each color (yellow, magenta, cyan, black). A toner image is formed on the surface of each photosensitive drum 36.

  The toner images of the respective colors formed on the surfaces of the photosensitive drums 36 of the image forming units 31 a, 31 b, 31 c, and 31 d are transferred onto the surface of the intermediate transfer belt 33 that moves in the direction of the arrow a by the rotational driving of the driving roller 41. Transfer is performed (primary transfer) so as to be sequentially superimposed by the respective primary transfer rollers 39 to which a transfer bias is applied. The residual toner remaining on the surface of each photoconductor drum 36 after the primary transfer is removed by each photoconductor drum cleaning device 40.

  Then, the paper P as a recording medium fed one by one from the selected one of the paper feed cassettes 35a and 35b is transported to the registration roller 49 through the transport path 48 and temporarily stopped. Then, the registration roller 49 is rotated at a predetermined timing to convey the sheet to the secondary transfer portion between the secondary transfer counter roller 42 and the secondary transfer roller 45, and the intermediate transfer is performed by the secondary transfer roller 45 to which a transfer bias is applied. The full-color toner image carried on the surface of the transfer belt 33 is transferred (secondary transfer) to the surface of the paper.

  The sheet on which the toner image has been transferred is conveyed to the fixing device 34 by the moving conveying belt 50, and is heated and pressurized by the fixing nip between the fixing roller 46 and the pressure roller 47 of the fixing device 34, and is applied to the surface of the sheet. A full-color toner image is fixed. The sheet on which the full-color toner image is fixed is discharged onto a discharge tray 53 through a discharge conveyance path 51 provided with a plurality of discharge roller pairs 52a, 52b, and 52c.

  At this time, as described in the fourth embodiment, the spectral characteristics of the color image of the paper surface output to the discharge conveyance path 51 can be continuously measured by the image evaluation device 20 installed in the vicinity of the discharge conveyance path 51. it can.

  Then, the spectral characteristic data measured by the image evaluation apparatus 20 is compared with the reference data derived in advance, and when the spectral characteristic data measured by the comparison result exceeds a predetermined reference value, for example, The user is notified by a warning sound or the like, and the printing operation of the printer (image forming apparatus) 30 is stopped. As a result, it is possible to minimize the output of an image that does not satisfy the predetermined quality.

  When the spectral characteristic data measured by the comparison result exceeds a predetermined reference value, the control unit inputs the comparison result to a control unit (not shown) of the printer (image forming apparatus) 30 so that the control unit By correcting and controlling the printing operation (image forming operation) based on the input comparison result, it is possible to stably output a high-quality image.

1, 1a, 1b Spectral characteristic acquisition device 2 Object to be measured 3 Line light irradiation device 4 First imaging optical system 5 Pinhole array 6 Second imaging optical system 6a Imaging optical system 7 Diffraction element 8 Light receiving sensor 9 Pixel 10 Lens array 11 Erect life-size image optical system array 12 Arithmetic unit 20 Image evaluation apparatus 30 Printer (image forming apparatus)

JP 2005-315883 A

Claims (8)

A pinhole array comprising multiple openings Ru passes the reflected light of light emitted to the object to be measured by the light irradiation means,
An imaging unit that Ru is respectively image light that has passed through the plurality of openings of the pinhole array,
Diffraction means for diffracting the light imaged by the imaging means ;
Anda receiving means for receiving the light is diffracted respectively in the previous SL diffraction means,
Spectroscopic characteristics acquisition unit, characterized in that before Kiyuizo means is an array of erecting equal-magnification optical system. Have reduced condensing means for focusing said by reducing the reflected light of the object to be measured or these light to the plurality of openings of the pinhole array, the fused small condensing means to at least the image-side telecentricity The spectral characteristic acquisition apparatus according to claim 1. Claims, characterized in that it has a magnification focusing means consisting of a plurality of focusing means for respectively condensing the light of reflected light from a plurality of locations of the object to be measured in the plurality of openings of the pinhole array 1. The spectral characteristic acquisition device according to 1. Said magnification focusing means, wherein a plurality of openings of the pinhole array, but spectroscopic characteristics acquisition unit according to claim 3, characterized in that it is arranged on the incident surface and an exit surface of the same optical element . The image side numerical aperture of the plurality of condensing means of the equal magnification condensing means is at least twice the object side numerical aperture of the erecting equal magnification imaging optical system alone constituting the image forming means. The spectral characteristic acquisition apparatus according to claim 3 or 4,   4. The spectral characteristic acquisition apparatus according to claim 3, wherein the equal magnification condensing means is an array of erecting equal magnification imaging optical systems. The spectral characteristic acquisition device according to any one of claims 1 to 6, a moving unit that changes a relative position between the spectral characteristic acquisition device and the object to be measured, output information from the spectral characteristic acquisition device , And an arithmetic means for calculating a spectral distribution or a colorimetric result at a plurality of positions of the object to be measured. In an image forming apparatus that forms and outputs an image on a recording medium,
An image forming apparatus comprising the image evaluation apparatus according to claim 7, wherein an image on a recording medium output from the image forming apparatus is evaluated by the image evaluation apparatus.

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