JP2014181909A - Imaging unit, colorimetric device, image forming apparatus, colorimetric system, and distance measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a colorimetric device capable of obtaining stable image data from a subject of colorimetry to perform accurate colorimetry, an image forming apparatus, a colorimetric system, and a colorimetric method.SOLUTION: A colorimetric camera 20 includes: a sensor unit (two-dimensional image sensor 27) that photographs a predetermined imaging object area including a subject area; a light path length changing member that is arranged between the sensor unit and the subject area, and transmits light; an illumination light source 30 that illuminates the imaging object area, and causes regular reflection light to enter the sensor unit, the reflection light having transmitted through the light path length changing member, having been regularly reflected in the subject area, and having further transmitted through the light path length changing member; and a distance calculation unit 46 that calculates a distance from the sensor unit to the subject area on the basis of an image of the regular reflection light (white streaks) included in a photographed image that is output from the sensor unit (two-dimensional image sensor 27).

Description

  The present invention relates to an imaging unit, a color measurement device, an image forming apparatus, a color measurement system, and a distance measurement method.

  In an image forming apparatus such as a printer, processing called color management is performed in order to improve output reproducibility with respect to input by suppressing variations in output due to device-specific characteristics. Color management improves the reproducibility of an output image by performing color conversion between a standard color space and a device-dependent color based on a device profile (ICC profile) that describes device-specific characteristics. When generating or modifying a device profile, an image forming apparatus actually forms a test pattern in which color charts (patches) of a large number of reference colors are arranged on a recording medium, and applies to each patch included in the test pattern. Perform colorimetry.

  A spectrocolorimeter is widely used as a color measuring device for measuring the color of a patch. Since the spectral colorimeter can obtain spectral reflectance for each wavelength, it can perform highly accurate color measurement. However, since the spectrocolorimeter is an expensive device, it is desired to perform high-precision colorimetry using a cheaper device.

  As an example of a method for realizing high-precision colorimetry at low cost, RGB values of colorimetric objects included in an image (hereinafter referred to as “captured image”) obtained by performing image-capturing with a colorimetric object as a subject. Is converted to a color value in the standard color space. For example, Patent Document 1 uses a two-dimensional image sensor to simultaneously capture a colorimetric target patch and a reference chart including a plurality of reference patches whose colorimetric values are known in advance, and are included in the captured image. There is described a color measurement device configured to calculate a color measurement value of a color measurement target patch based on an RGB value of the color measurement target patch and an RGB value of a reference patch.

  However, in the color measurement device described in Patent Document 1, if the distance to the color measurement target patch varies during imaging of the color measurement target patch, the calculated color measurement value may change. Therefore, it is desired to measure the distance to the color measurement target patch before calculating the color measurement value of the color measurement target patch so that the correct color measurement value can be calculated.

  The present invention has been made in view of the above, and provides an imaging unit, a color measuring device, an image forming apparatus, a color measuring system, and a distance measuring method capable of measuring a distance to a subject to be color measured. The purpose is to do.

  In order to solve the above-described problems and achieve the object, the present invention provides a sensor unit that captures a predetermined imaging target region including a subject region, and a light that is disposed between the sensor unit and the subject region. A light transmissive member that illuminates the area to be imaged, and the specularly reflected light that has passed through the light transmissive member, reflected regularly at the subject area, and transmitted through the light transmissive member is incident on the sensor unit. An illumination light source to be operated; and a distance calculation unit that calculates a distance from the sensor unit to the subject region based on the image of the regular reflection light included in the captured image output by the sensor unit. To do.

  According to the present invention, it is possible to measure the distance to a subject to be colorimetric.

FIG. 1 is a perspective view illustrating the inside of the image forming apparatus. FIG. 2 is a top view showing an internal mechanical configuration of the image forming apparatus. FIG. 3 is a diagram for explaining an example of a lifting mechanism that lifts and lowers the carriage. FIG. 4 is a diagram for explaining an arrangement example of the recording heads mounted on the carriage. FIG. 5A is a longitudinal sectional view of the colorimetric camera (a sectional view taken along line X1-X1 in FIG. 5-3). FIG. 5B is a longitudinal sectional view of the colorimetric camera (cross sectional view taken along line X2-X2 in FIG. 5-3). FIG. 5C is a top view of the inside of the color measurement camera seen through. FIG. 5-4 is a plan view of the bottom surface of the housing as viewed from the X3 direction in FIG. 5-1. FIG. 5-5 is a longitudinal sectional view of the colorimetric camera. FIG. 5-6 is a schematic diagram of a white spot image obtained by specular reflection light and an image obtained by binarizing the white spot image. FIG. 6 is a diagram illustrating a specific example of the reference chart. FIG. 7 is a block diagram illustrating a schematic configuration of a control mechanism of the image forming apparatus. FIG. 8 is a block diagram illustrating a configuration example of the control mechanism of the colorimetric camera. FIG. 9 is an explanatory diagram illustrating an example of a method for calculating a subject distance by the distance calculation unit. FIG. 10 is a diagram illustrating an example of a captured image output from the two-dimensional image sensor of the sensor unit when the subject distance is measured. FIG. 11 is a flowchart illustrating an example of a procedure for calculating the subject distance. FIG. 12 is an explanatory diagram for explaining another example of a method for calculating a subject distance by the distance calculation unit. FIG. 13 is a flowchart illustrating another example of the procedure for calculating the subject distance. FIG. 14 is a diagram for explaining processing for obtaining a reference colorimetric value and a reference RGB value and processing for generating a reference value linear transformation matrix. FIG. 15 is a diagram illustrating an example of the initial reference RGB values. FIG. 16 is a diagram for explaining the outline of the color measurement process. FIG. 17 is a diagram for describing processing for generating a linear conversion matrix between reference RGB. FIG. 18 is a diagram illustrating the relationship between the initial reference RGB value and the colorimetric reference RGB value. FIG. 19 is a diagram for explaining basic colorimetry processing. FIG. 20 is a diagram for explaining basic colorimetry processing. FIG. 21A is a longitudinal sectional view of a colorimetric camera according to a first modification. FIG. 21B is a longitudinal sectional view of the colorimetric camera of the first modification. FIG. 22 is a longitudinal sectional view of a colorimetric camera of a second modification. FIG. 23 is a longitudinal sectional view of a colorimetric camera of a third modification. FIG. 24 is a longitudinal sectional view of a colorimetric camera according to a fourth modification. FIG. 25 is a longitudinal sectional view of a colorimetric camera of a fifth modification. FIG. 26 is a longitudinal sectional view of a colorimetric camera according to a sixth modification. FIG. 27A is a longitudinal sectional view of a colorimetric camera of a seventh modified example. FIG. 27-2 is a plan view of the bottom surface of the housing of the colorimetric camera of the seventh modification when viewed from the X4 direction in FIG. 27-1. FIG. 28 is a diagram showing a schematic configuration of the color measurement system.

  Exemplary embodiments of an imaging unit, a color measurement device, an image forming device, a color measurement system, and a distance measurement method according to the present invention will be described below in detail with reference to the accompanying drawings. In the embodiments described below, an inkjet printer is illustrated as an example of an image forming apparatus to which the present invention is applied. However, the present invention is widely applied to various types of image forming apparatuses that output an image to a recording medium. Applicable.

<Mechanical configuration of image forming apparatus>
First, the mechanical configuration of the image forming apparatus 100 according to the present embodiment will be described with reference to FIGS. 1 to 4. FIG. 1 is a perspective view illustrating the inside of the image forming apparatus 100 according to the present embodiment. FIG. 2 is a top view illustrating a mechanical configuration inside the image forming apparatus 100 according to the present embodiment. FIG. FIG. 4 is a diagram for explaining an example of an elevating mechanism that moves up and down, and FIG. 4 is a diagram for explaining an arrangement example of the recording head 6 mounted on the carriage 5.

  As shown in FIG. 1, the image forming apparatus 100 according to the present embodiment reciprocates in the main scanning direction (arrow A direction in the figure) and is intermittently conveyed in the sub-scanning direction (arrow B direction in the figure). A carriage 5 for forming an image on the recording medium P is provided. The carriage 5 is supported by a main guide rod 3 extending along the main scanning direction. The carriage 5 is provided with a connecting piece 5a. The connecting piece 5 a engages with the sub guide member 4 provided in parallel with the main guide rod 3 to stabilize the posture of the carriage 5.

  As shown in FIG. 2, the carriage 5 includes a recording head 6y that discharges yellow (Y) ink, a recording head 6m that discharges magenta (M) ink, a recording head 6c that discharges cyan (C) ink, and black. (Bk) A plurality of recording heads 6k that discharge ink (hereinafter, the recording heads 6y, 6m, 6c, and 6k are collectively referred to as “recording heads 6”) are mounted. The recording head 6 is mounted on the carriage 5 so that the ejection surface (nozzle surface) faces downward (the recording medium P side).

  A cartridge 7, which is an ink supply body for supplying ink to the recording head 6, is not mounted on the carriage 5 and is disposed at a predetermined position in the image forming apparatus 100. The cartridge 7 and the recording head 6 are connected by a pipe (not shown), and ink is supplied from the cartridge 7 to the recording head 6 through this pipe.

  The carriage 5 is connected to a timing belt 11 stretched between a driving pulley 9 and a driven pulley 10. The drive pulley 9 is rotated by driving the main scanning motor 8. The driven pulley 10 has a mechanism for adjusting the distance to the driving pulley 9 and has a role of applying a predetermined tension to the timing belt 11. The carriage 5 reciprocates in the main scanning direction when the timing belt 11 is fed by driving the main scanning motor 8. The movement of the carriage 5 in the main scanning direction is controlled based on an encoder value obtained when the encoder sensor 13 provided on the carriage 5 detects the mark on the encoder sheet 14 as shown in FIG.

  In addition, the image forming apparatus 100 according to the present embodiment includes a maintenance mechanism 15 for maintaining the reliability of the recording head 6. The maintenance mechanism 15 performs cleaning and capping of the ejection surface of the recording head 6 and discharging unnecessary ink from the recording head 6.

  As shown in FIG. 2, a platen 16 is provided at a position facing the ejection surface of the recording head 6. The platen 16 is for supporting the recording medium P when ink is ejected from the recording head 6 onto the recording medium P. The image forming apparatus 100 according to the present embodiment is a wide-width machine in which the moving distance of the carriage 5 in the main scanning direction is long. For this reason, the platen 16 is configured by connecting a plurality of plate-like members in the main scanning direction (movement direction of the carriage 5). The recording medium P is nipped by a conveyance roller driven by a sub-scanning motor 12 (see FIG. 7) described later, and is intermittently conveyed on the platen 16 in the sub-scanning direction.

  When the recording medium P is a stiff sheet or a folded sheet, the recording medium P may be lifted from the platen 16 and conveyed. At this time, if the recording medium P comes into contact with the ejection surface of the recording head 6, the recording head 6 may be damaged. In view of this, the image forming apparatus 100 includes a lifting mechanism that lifts and lowers the carriage 5 as a countermeasure for the recording medium P that easily floats from the platen 16, and is used when the recording medium P that easily lifts is used. In this case, the distance between the recording medium P and the ejection surface of the recording head 6 can be increased. The raising / lowering of the carriage 5 refers to the movement of the carriage 5 in the direction of approaching and separating from the recording medium P.

  For example, as shown in FIG. 3, the lifting mechanism is configured to lift the carriage 5 by displacing the eccentric cam 18 by driving the carriage lifting motor 17. That is, the gear 17 a attached to the rotation shaft of the carriage lifting / lowering motor 17 rotates the shaft 18 a of the eccentric cam 18 by the rotation of the carriage lifting / lowering motor 17. Since the shaft 18a is provided at a position displaced from the center of the eccentric cam 18, the eccentric cam 18 is displaced when the shaft 18a rotates. Since the carriage 5 is in contact with the eccentric cam 18, the carriage 5 moves up and down in the direction indicated by the arrow in the drawing as the eccentric cam 18 is displaced. Note that the lifting mechanism shown in FIG. 3 is merely an example, and any configuration may be used as long as it can raise and lower the carriage 5.

  The recording head 6 includes a plurality of nozzle arrays, and forms an image on the recording medium P by ejecting ink from the nozzle arrays onto the recording medium P transported on the platen 16. In this embodiment, in order to secure a large width of an image that can be formed on the recording medium P by one scan of the carriage 5, as shown in FIG. 4, the upstream recording head 6 and the downstream recording head are provided on the carriage 5. The head 6 is mounted. Further, the recording head 6k that discharges black ink is mounted on the carriage 5 as many times as the recording heads 6y, 6m, and 6c that discharge color ink. The recording heads 6y and 6m are arranged separately on the left and right. This is because the color stacking order is adjusted by the reciprocating operation of the carriage 5 so that the color does not change between the forward path and the return path. Note that the arrangement of the recording heads 6 shown in FIG. 4 is an example, and is not limited to the arrangement shown in FIG.

  Each of the above-described constituent elements constituting the image forming apparatus 100 of the present embodiment is disposed inside the exterior body 1. The exterior body 1 is provided with a cover member 2 that can be opened and closed. At the time of maintenance of the image forming apparatus 100 or when a jam occurs, the cover member 2 can be opened to perform work on each component provided inside the exterior body 1.

  The image forming apparatus 100 according to the present embodiment intermittently conveys the recording medium P in the sub-scanning direction, and moves the carriage 5 in the main scanning direction while the conveyance of the recording medium P in the sub-scanning direction is stopped. However, ink is ejected from the nozzle row of the recording head 6 mounted on the carriage 5 onto the recording medium P on the platen 16 to form an image on the recording medium P (image forming unit).

  In particular, at the time of adjusting the color of the image forming apparatus 100, ink is actually ejected from the nozzle row of the recording head 6 mounted on the carriage 5 onto the recording medium P on the platen 16, and a large number of colorimetric patches CP. A test pattern is formed. Then, color measurement is performed on each color measurement target patch CP included in the test pattern. Each colorimetric object patch CP included in the test pattern is an image obtained when the image forming apparatus 100 outputs a reference color patch, and reflects output characteristics unique to the image forming apparatus 100. Therefore, a device profile describing characteristics unique to the image forming apparatus 100 can be generated or modified using the colorimetric values of these colorimetric target patches CP. Then, by performing color conversion between the standard color space and the device-dependent color based on this device profile, the image forming apparatus 100 can output an image with high reproducibility.

  The image forming apparatus 100 of this embodiment includes a colorimetric camera (imaging unit, colorimetric device) 20 for performing colorimetry on each colorimetric target patch CP included in a test pattern formed on a recording medium P. The color measurement camera 20 takes a color measurement target patch CP included in a test pattern formed on the recording medium P by the image forming apparatus 100 as a subject, and simultaneously images the color measurement target patch CP and a reference chart 400 described later. Then, the colorimetric camera 20 calculates the colorimetric value of the colorimetric target patch CP by using the RGB value of the colorimetric target patch CP obtained by imaging and the RGB value of each reference patch included in the reference chart 400.

  As shown in FIGS. 2 and 3, the colorimetric camera 20 is fixed to the carriage 5 and reciprocates in the main scanning direction together with the carriage 5. When the colorimetric camera 20 moves to a position facing each colorimetric object patch CP included in the test pattern formed on the recording medium P on the platen 16, each colorimetric object patch CP is displayed on the reference chart 400. Take an image at the same time. Note that the simultaneous imaging here means that one frame of image data including the colorimetric target patch CP and the reference chart 400 is acquired. That is, even if there is a time difference in data acquisition for each pixel, if the image data including the color measurement target patch CP and the reference chart 400 is acquired in one frame, the color measurement target patch CP and the reference chart 400 are simultaneously captured. It will be done.

<Specific examples of colorimetric cameras>
Next, a specific example of the colorimetric camera 20 will be described in detail with reference to FIGS. 5A to 5D are diagrams illustrating specific examples of the colorimetric camera 20, and FIG. 5A is a longitudinal sectional view of the colorimetric camera 20 (cross-sectional view taken along line X1-X1 in FIG. 5-3). FIG. 5B is a longitudinal sectional view of the colorimetric camera 20 (cross-sectional view taken along line X2-X2 in FIG. 5C), and FIG. 5C is a top view of the colorimetric camera 20 seen through. FIGS. 5-4 are plan views of the bottom surface of the housing as viewed from the X3 direction in FIG.

  The colorimetric camera 20 includes a housing 23 configured by combining a frame body 21 and a substrate 22. The frame body 21 is formed in a bottomed cylindrical shape in which one end side which is the upper surface of the housing 23 is opened. The substrate 22 is fastened to the frame body 21 by a fastening member 24 and integrated with the frame body 21 so as to close the open end of the frame body 21 and configure the upper surface of the housing 23.

  The housing 23 is fixed to the carriage 5 so that the bottom surface portion 23a faces the recording medium P on the platen 16 with a predetermined gap d. On the bottom surface 23 a of the housing 23 facing the recording medium P, an opening 25 for enabling the subject (color measurement target patch CP in color adjustment) formed on the recording medium P to be photographed from the inside of the housing 23. Is provided.

  A sensor unit 26 that captures an image is provided inside the housing 23. The sensor unit 26 includes a two-dimensional image sensor 27 such as a CCD sensor or a CMOS sensor, and an imaging lens 28 that forms an optical image of an imaging target region of the sensor unit 26 on the sensor surface of the two-dimensional image sensor 27. The two-dimensional image sensor 27 is mounted on, for example, the inner surface (component mounting surface) of the substrate 22 so that the sensor surface faces the bottom surface portion 23 a side of the housing 23. The imaging lens 28 is fixed in a state of being positioned with respect to the two-dimensional image sensor 27 so as to maintain a positional relationship determined according to the optical characteristics thereof.

  A reference chart 400 is disposed on the inner surface of the bottom surface 23a of the housing 23 facing the sensor unit 26 so as to be adjacent to the opening 25 provided in the bottom surface 23a. The reference chart 400 is imaged together with the color measurement target patch CP by the two-dimensional image sensor 27 of the sensor unit 26 when the color measurement target patch CP is measured. That is, the reference chart 400 is arranged on the bottom surface portion 23 a of the housing 23 so as to be included in the imaging target region of the sensor unit 26 together with the color measurement target patch CP outside the housing 23. Of the imaging target area of the sensor unit 26, an area outside the housing 23 that is imaged through the opening 25 is referred to as a subject area. Details of the reference chart 400 will be described later.

  In addition, an illumination light source 30 that illuminates an imaging target region of the sensor unit 26 is provided inside the housing 23. For example, an LED (Light Emitting Diode) is used as the illumination light source 30. In the present embodiment, two LEDs are used as the illumination light source 30. These two LEDs used as the illumination light source 30 are mounted on the inner surface of the substrate 22 together with the two-dimensional image sensor 27 of the sensor unit 26, for example. However, the illumination light source 30 only needs to be disposed at a position where the subject (color measurement target patch CP) and the reference chart 400 can be illuminated, and is not necessarily mounted directly on the substrate 22. Moreover, in this embodiment, although LED is used as the illumination light source 30, the kind of light source is not limited to LED. For example, an organic EL or the like may be used as the illumination light source 30. When the organic EL is used as the illumination light source 30, illumination light close to the spectral distribution of sunlight can be obtained, so that improvement in colorimetric accuracy can be expected.

  In the present embodiment, as shown in FIG. 5C, the projection on the bottom surface portion 23a when two LEDs used as the illumination light source 30 are vertically looked down from the substrate 22 side to the bottom surface portion 23a side of the housing 23. These two LEDs are arranged so that the position is within the region between the opening 25 and the reference chart 400 and is symmetric with respect to the sensor unit 26. In other words, the opening 25 is formed at a position where a line connecting two LEDs used as the illumination light source 30 passes through the center of the imaging lens 28 of the sensor unit 26 and is symmetrical with respect to a line connecting the two LEDs. And a reference chart 400 are arranged. By arranging the two LEDs used as the illumination light source 30 in this way, the color measurement target patch CP outside the housing 23 and the reference chart KC inside the housing 23 are illuminated under substantially the same conditions. Can do.

  By the way, in order to illuminate the color measurement target patch CP outside the housing 23 under the same illumination condition as the reference chart 400 arranged inside the housing 23, external light is used when the sensor unit 26 performs imaging. It is necessary to illuminate the color measurement target patch CP with only the illumination light from the illumination light source 30 so as not to hit the CP. In order to prevent external light from hitting the colorimetric target patch CP, the gap d between the bottom surface portion 23a of the housing 23 and the recording medium P is reduced, and external light directed to the colorimetric target patch CP is exposed to the housing. It is effective to be shielded by 23. However, if the gap d between the bottom surface portion 23a of the housing 23 and the recording medium P is made too small, the recording medium P will come into contact with the bottom surface portion 23a of the housing 23 and the image cannot be captured properly. There is a fear. Therefore, the gap d between the bottom surface 23a of the housing 23 and the recording medium P is a small value in a range where the recording medium P does not contact the bottom surface 23a of the housing 23 in consideration of the flatness of the recording medium P. It is desirable to set to. For example, if the gap d between the bottom surface portion 23 a of the housing 23 and the recording medium P is set to about 1 mm to 2 mm, the recording medium P does not contact the bottom surface portion 23 a of the housing 23 and the recording medium P It is possible to effectively prevent external light from hitting the formed colorimetric object patch CP.

  An optical path length changing member 31 is arranged inside the housing 23 so as to close the opening 25 from the inner surface side. The optical path length changing member 31 is an optical element (light transmitting member) having a refractive index n (n is an arbitrary number) having a sufficient transmittance with respect to the light (illumination light) of the illumination light source 30. The optical path length changing member 31 is disposed in the light path between the colorimetric target patch CP outside the housing 23 and the sensor unit 26, and the imaging surface of the optical image of the colorimetric target patch CP is used as a reference chart 400. It has a function to bring the optical image closer to the image plane. In other words, in the colorimetric camera 20 of the present embodiment, the optical path length changing member 31 is disposed in the light path between the colorimetric target patch CP and the sensor unit 26, thereby providing a colorimetric target outside the housing 23. The imaging surface of the optical image of the patch CP and the imaging surface of the reference chart 400 inside the housing 23 are both matched with the sensor surface of the two-dimensional image sensor 27 of the sensor unit 26.

When light passes through the optical path length changing member 31, the optical path length is extended according to the refractive index n of the optical path length changing member 31, and the image appears to float. The image floating amount C can be obtained by the following equation, where Lp is the length of the optical path length changing member 31 in the optical axis direction.
C = Lp (1-1 / n)

Further, if the distance between the principal point of the imaging lens 28 of the sensor unit 26 and the reference chart 400 is Lc, the front focal plane of the optical image transmitted through the principal point of the imaging lens 28 and the optical path length changing member 31 ( The distance L to the imaging surface can be obtained by the following equation.
L = Lc + Lp (1-1 / n)

  Here, when the refractive index n of the optical path length changing member 31 is 1.5, L = Lc + Lp (1/3), and the optical path length of the optical image transmitted through the optical path length changing member 31 is the same as that of the optical path length changing member 31. The length can be increased by about 1/3 of the length Lp in the optical axis direction. In this case, for example, if Lp = 9 [mm], L = Lc + 3 [mm], so that the difference between the distance from the sensor unit 26 to the reference chart 400 and the distance to the colorimetric target patch CP is 3 mm. If the imaging is performed in the state, the rear focal plane (imaging plane) of the optical image of the reference chart KC and the rear focal plane (imaging plane) of the optical image of the color measurement target patch CP are both of the sensor unit 26. It can be matched with the sensor surface of the two-dimensional image sensor 27.

  As described above, the image forming apparatus 100 according to the present embodiment forms an image on the recording medium P by ejecting ink from the nozzle row of the recording head 6 mounted on the carriage 5 onto the recording medium P on the platen 16. It is the structure to do. For this reason, when ink is ejected from the nozzle array of the recording head 6, mist-like minute ink particles (hereinafter, such minute ink particles are referred to as “mist”) are generated. When mist generated during image formation enters the housing 23 from the outside of the housing 23 of the colorimetric camera 20 provided fixed to the carriage 5 through the opening 25, the mist enters the housing 23. There is a concern that the mist that has entered may adhere to the sensor unit 26, the illumination light source 30, the optical path length changing member 31, and the like, so that accurate RGB values cannot be obtained at the time of adjustment for performing color measurement of the color measurement target patch CP. Therefore, in the colorimetric camera 20 of the present embodiment, the mist generated during image formation is placed inside the housing 23 by disposing the mist prevention glass 32 in the opening 25 provided in the bottom surface portion 23a of the housing 23. Prevent entry.

  The mist prevention glass 32 is a transparent optical element (light transmission member) having a sufficient transmittance with respect to the light (illumination light) of the illumination light source 30 and is a plate having a size capable of covering the entire opening 25. It is formed in a shape. The mist prevention glass 32 is attached to a slit formed along the bottom surface portion 23 a of the housing 23 and closes the entire surface of the opening 25 provided in the bottom surface portion 23 a of the housing 23. The slit in which the mist prevention glass 32 is mounted opens at the side surface of the housing 23. The mist prevention glass 32 can be inserted from the side surface portion of the housing 23 and attached to the slit. Moreover, the mist prevention glass 32 can also be removed from the side part of the housing | casing 23, and replacement | exchange is possible suitably.

  Here, FIG. 5-5 is a longitudinal sectional view of the colorimetric camera 20, and is a sectional view at the same position as the longitudinal sectional view of the colorimetric camera 20 shown in FIG. FIG. 5-6 is a schematic diagram of a white spot image (left side) obtained by specular reflection light and an image obtained by binarizing the white spot image (right side).

As shown in FIG. 5-5, the illumination light source 30 according to the present embodiment causes the two-dimensional image sensor 27 to receive specularly reflected light that is specularly reflected by the subject.
On the sensor surface of the two-dimensional image sensor 27 of the sensor unit 26, the pixel value is saturated at the position where the specularly reflected light of the illumination light source 30 is incident, and the image data is in a white-out state as shown in FIG. It becomes. This is utilized in the present embodiment. In other words, the image data when the regular reflection light is incident is binarized to obtain the position or size of the “white spot”. A reference value of the position or size of the white spot is stored in advance, and the distance is measured from the fluctuation of the value. More details are as follows.

  When the illumination light source 30 illuminates the imaging target area of the sensor unit 26, white spots appear in the subject area included in the illuminated imaging target area. The position and size of the white spots change according to the distance between the illumination light source 30 and the subject area. In other words, since the positional relationship between the illumination light source 30 and the sensor unit 26 is fixed, if the distance between the sensor unit 26 and the subject region included in the imaging target region changes, the subject region under illumination by the illumination light source 30 The position and size of white spots appearing on the screen change. The colorimetric camera 20 of the present embodiment uses this property to capture an image in which white spots are reflected by the sensor unit 26, and based on this white background image, the distance from the illumination light source 30 to the subject region That is, the distance from the sensor unit 26 to the subject area (hereinafter, this distance is referred to as “subject distance”) is measured. A specific example of the method for measuring the subject distance will be described later.

  However, the illumination light source 30 may be arranged in a predetermined range near the center of the subject area (hereinafter, this range is referred to as “color measurement target area”) at a position where no white spots are reflected. desirable. That is, it is desirable that the illumination light source 30 is provided at an appropriate position so that white spots are reflected in the peripheral portion of the subject area excluding the color measurement target area.

  In the present embodiment, when calculating a colorimetric value of a subject such as the colorimetric target patch CP, the image data of the colorimetric target region included in the captured image output from the sensor unit 26 is averaged as described later. The RGB values of the colorimetric target patch CP are obtained. At this time, if white spots appear in the color measurement target area, the correct RGB value of the color measurement target patch CP cannot be obtained, and there is a concern that an error may occur in the color measurement value. As described above, if the illumination light source 30 is arranged at a position where white spots are not reflected in the colorimetry target region, such a problem can be avoided in advance.

<Specific examples of reference chart>
Next, the reference chart 400 arranged inside the housing 23 of the colorimetric camera 20 will be described in detail with reference to FIG. FIG. 6 is a diagram illustrating a specific example of the reference chart 400.

  A reference chart 400 illustrated in FIG. 6 includes a plurality of reference patch rows 401 to 404 in which colorimetric patches are arranged, a dot diameter measurement pattern row 406, a distance measurement line 405, and a chart position specifying marker 407.

  The reference patch arrays 401 to 404 include a reference patch array 401 in which YMCK primary color reference patches are arranged in gradation order, a RGB secondary color reference patch in reference gradation order, and a gray scale. A reference patch array (achromatic color gradation pattern) 403 in which the reference patches are arranged in gradation order, and a reference patch array 404 in which tertiary color reference patches are arrayed. The dot diameter measurement pattern row 406 is a geometric shape measurement pattern row in which circular patterns of different sizes are arranged in order of size, and is used for measuring the dot diameter of an image recorded on the recording medium P. it can.

  The distance measurement line 405 is formed as a rectangular frame surrounding the plurality of reference patch rows 401 to 404 and the dot diameter measurement pattern row 406. The chart position specifying markers 407 are provided at the positions of the four corners of the distance measuring line 405 and function as markers for specifying the positions of the respective reference patches. By specifying the distance measurement line 405 and the chart position specifying markers 407 at the four corners from the image data of the reference chart 400 imaged by the sensor unit 26, the position of the reference chart 400 and the position of each reference patch or pattern are determined. Can be identified.

  Each reference patch constituting the reference patch rows 401 to 404 for colorimetry is used as a color reference reflecting the imaging conditions of the colorimetric camera 20. The configuration of the colorimetric reference patch arrays 401 to 404 arranged in the reference chart 400 is not limited to the example shown in FIG. 6, and any reference patch array can be applied. . For example, a reference patch that can specify a color range as wide as possible may be used, and the YMCK primary color reference patch row 401 and the grayscale reference patch row 403 are used in the image forming apparatus 100. It may be composed of patches of colorimetric values of ink. The RGB secondary color reference patch row 402 may be configured with patches of colorimetric values that can be developed with ink used in the image forming apparatus 100, and further, colorimetric values such as Japan Color are used. A predetermined reference color chart may be used.

  In the present embodiment, the reference chart 400 having the reference patch rows 401 to 404 having a general patch (color chart) shape is used. However, the reference chart 400 is not necessarily limited to such reference patch rows 401 to 404. It may not be the form which has. The reference chart 400 may be configured so that a plurality of colors that can be used for colorimetry are arranged so that their positions can be specified.

  Since the reference chart 400 is disposed on the bottom surface portion 23a of the housing 23 of the colorimetric camera 20 so as to be adjacent to the opening 25, the reference chart 400 can be imaged simultaneously with the colorimetric target patch CP by the sensor unit 26.

  The mechanical configuration of the colorimetric camera 20 described above is merely an example, and is not limited to this configuration. The colorimetric camera 20 of the present embodiment only needs to be configured to capture an image using at least the two-dimensional image sensor 27, and various modifications and changes can be made to the above configuration.

<Schematic configuration of control mechanism of image forming apparatus>
Next, a schematic configuration of the control mechanism of the image forming apparatus 100 of the present embodiment will be described with reference to FIG. FIG. 7 is a block diagram illustrating a schematic configuration of a control mechanism of the image forming apparatus 100.

  As shown in FIG. 7, the image forming apparatus 100 according to the present embodiment includes a CPU 101, a ROM 102, a RAM 103, a recording head driver 104, a main scanning driver 105, a sub scanning driver 106, and a control FPGA (Field-Programmable Gate Array) 110. A recording head 6, a colorimetric camera 20, an encoder sensor 13, a main scanning motor 8, and a sub-scanning motor 12. The CPU 101, ROM 102, RAM 103, print head driver 104, main scanning driver 105, sub scanning driver 106, and control FPGA 110 are mounted on the main control board 120. The recording head 6, the encoder sensor 13, and the colorimetric camera 20 are mounted on the carriage 5 as described above.

  The CPU 101 governs overall control of the image forming apparatus 100. For example, the CPU 101 uses the RAM 103 as a work area, executes various control programs stored in the ROM 102, and outputs control commands for controlling various operations in the image forming apparatus 100.

  The recording head driver 104, the main scanning driver 105, and the sub scanning driver 106 are drivers for driving the recording head 6, the main scanning motor 8, and the sub scanning motor 12, respectively.

  The control FPGA 110 controls various operations in the image forming apparatus 100 in cooperation with the CPU 101. The control FPGA 110 includes, for example, a CPU control unit 111, a memory control unit 112, an ink ejection control unit 113, a sensor control unit 114, and a motor control unit 115 as functional components.

  The CPU control unit 111 communicates with the CPU 101 to transmit various information acquired by the control FPGA 110 to the CPU 101 and inputs a control command output from the CPU 101.

  The memory control unit 112 performs memory control for the CPU 101 to access the ROM 102 and the RAM 103.

  The ink discharge control unit 113 controls the operation of the print head driver 104 in accordance with a control command from the CPU 101, thereby controlling the discharge timing of ink from the print head 6 driven by the print head driver 104.

  The sensor control unit 114 performs processing on sensor signals such as encoder values output from the encoder sensor 13.

  The motor control unit 115 controls the main scanning motor 105 driven by the main scanning driver 105 by controlling the operation of the main scanning driver 105 in accordance with a control command from the CPU 101, and moves the carriage 5 in the main scanning direction. Control the movement of. In addition, the motor control unit 115 controls the sub-scanning motor 106 driven by the sub-scanning driver 106 by controlling the operation of the sub-scanning driver 106 in accordance with a control command from the CPU 101, and records on the platen 16. Controls the movement of the medium P in the sub-scanning direction.

  Each of the above-described units is an example of a control function realized by the control FPGA 110, and various other control functions may be realized by the control FPGA 110. Moreover, the structure which implement | achieves all or one part of said control function with the program run by CPU101 or another general purpose CPU may be sufficient. Further, a configuration in which a part of the control function is realized by dedicated hardware such as another FPGA different from the control FPGA 110 or an ASIC (Application Specific Integrated Circuit) may be used.

  The recording head 6 is driven by a recording head driver 104 whose operation is controlled by the CPU 101 and the control FPGA 110, and ejects ink onto the recording medium P on the platen 16 to form an image.

As described above, the colorimetric camera 20 images the colorimetric target patch CP included in the test pattern together with the reference chart 400 during the color adjustment of the image forming apparatus 100, and the colorimetric target patch obtained from the captured image. Based on the RGB value of the CP and the RGB value of each reference patch of the reference chart 400, the colorimetric value of the color measurement target patch CP (the colorimetric value in the standard color space, for example, in the L ^* a ^* b ^* color space L ^* a ^* b ^* value (hereinafter, L ^* a ^* b ^* is expressed as “Lab”) is calculated. The colorimetric values of the colorimetric target patch CP calculated by the colorimetric camera 20 are sent to the CPU 101 via the control FPGA 110.

  The encoder sensor 13 outputs an encoder value obtained by detecting the mark on the encoder sheet 14 to the control FPGA 110. This encoder value is sent from the control FPGA 110 to the CPU 101 and used, for example, to calculate the position and speed of the carriage 5. The CPU 101 generates and outputs a control command for controlling the main scanning motor 8 based on the position and speed of the carriage 5 calculated from the encoder value.

<Configuration of colorimetric camera control mechanism>
Next, the control mechanism of the colorimetric camera 20 will be specifically described with reference to FIG. FIG. 8 is a block diagram illustrating a configuration example of the control mechanism of the colorimetric camera 20.

  As shown in FIG. 8, the colorimetric camera 20 includes a two-dimensional image sensor 27, an illumination light source 30, a light source drive controller 40, a timing signal generator 41, a frame memory 42, an averaging processor 43, and a colorimetric calculator 44. , A nonvolatile memory 45, a distance calculation unit 46, and a distance adjustment unit 47. Each of these units is mounted on a substrate 22 that constitutes the upper surface of the housing 23 of the colorimetric camera 20, for example.

  The two-dimensional image sensor 27 converts light incident from the imaging target area illuminated by the illumination light source 30 through the imaging lens 28 into an analog signal, and outputs a captured image of the imaging target area. The two-dimensional image sensor 27 AD-converts an analog signal obtained by photoelectric conversion into digital image data, and performs various types of image data conversion such as shading correction, white balance correction, γ correction, and image data format conversion. A function for performing image processing is incorporated, and an image obtained by image processing is output as a captured image. Various image processing on the image data may be performed partly or entirely outside the two-dimensional image sensor 27.

  The light source drive control unit 40 generates a light source drive signal for driving the illumination light source 30 and supplies the light source drive signal to the illumination light source 30. In the present embodiment, as described above, two LEDs arranged with the sensor unit 26 interposed therebetween are used as the illumination light source 30. The light source drive control unit 40 drives the illumination light source 30 so that both of the two LEDs are lit when performing color measurement of the color measurement target patch CP. Further, when the light source drive control unit 40 measures the subject distance described above, one of the two LEDs (incident angle θ when “white spot” caused by specular reflection light is reflected on the imaging surface increases). The illumination light source 30 is driven so that the light is turned on.

  The timing signal generation unit 41 generates a timing signal for controlling the timing of starting imaging by the two-dimensional image sensor 27 and supplies the timing signal to the two-dimensional image sensor 27. In the present embodiment, imaging is performed by the two-dimensional image sensor 27 of the sensor unit 26 not only when the color measurement target patch CP is measured but also when the subject distance is measured. The timing signal generation unit 41 generates a timing signal for controlling the timing of the start of imaging by the two-dimensional image sensor 27 at the time of color measurement of the color measurement target patch CP and the measurement of the subject distance, and supplies the timing signal to the two-dimensional image sensor 27. To do.

  The frame memory 42 temporarily stores the captured image output from the two-dimensional image sensor 27.

  When the color measurement target patch CP is color-measured, the averaging processing unit 43 outputs a subject area from a captured image output from the two-dimensional image sensor 27 of the sensor unit 26 and temporarily stored in the frame memory 42. A colorimetry target region set near the center and a region where each reference patch of the reference chart 400 is projected are extracted. Then, the averaging processing unit 43 averages the extracted image data of the color measurement target region and outputs the obtained value to the color measurement calculation unit 44 as the RGB value of the color measurement target patch CP. Are averaged, and the obtained values are output to the colorimetric calculation unit 44 as RGB of each reference patch.

  The color measurement calculation unit 44 measures the color measurement target patch CP based on the RGB value of the color measurement target patch CP obtained by the processing of the averaging processing unit 43 and the RGB value of each reference patch of the reference chart 400. Calculate the color value. The colorimetric value of the colorimetric target patch CP calculated by the colorimetric calculation unit 44 is sent to the CPU 101 on the main control board 120. A specific example of the process in which the colorimetric calculation unit 44 calculates the colorimetric value of the colorimetric target patch CP will be described later in detail.

  The nonvolatile memory 45 stores various data necessary for the colorimetric calculation unit 44 to calculate the colorimetric values of the colorimetric target patch CP and various data necessary for the distance calculation unit 46 to calculate the subject distance. To do.

  When measuring the subject distance, the distance calculation unit 46 outputs “white spots” due to specularly reflected light that is output from the two-dimensional image sensor 27 of the sensor unit 26 and temporarily stored in the frame memory 42. ”To calculate the subject distance. Hereinafter, a specific example of how the distance calculation unit 46 calculates the subject distance will be described.

<First method>
The distance calculation unit 46 is, for example, a sensor unit when measuring the white spot position in the captured image when the subject distance is set as a predetermined reference distance (hereinafter, this distance is referred to as “reference subject distance”) and the subject distance. The subject distance can be calculated based on the positions of white spots in the captured image output from the 26 two-dimensional image sensors 27.

  FIG. 9 is an explanatory diagram for explaining an example of a method for calculating a subject distance by the distance calculation unit 46, and an imaging surface (a surface on which the above-described subject region is present) by the sensor unit 26 is changed from the imaging surface IA_r due to a change in the subject distance. The change in the position of the white spot when changing to the imaging surface IA_a is shown. The imaging surface IA_r represents the imaging surface by the sensor unit 26 when the subject distance is the reference subject distance Dr, and the imaging surface IA_a represents the imaging surface by the sensor unit 26 at the subject distance Da to be measured. . The point α in FIG. 9 is the center of gravity of the white spot on the imaging surface IA_r, and the point β is output from the two-dimensional image sensor 27 when measuring the center of gravity of the white spot on the imaging surface IA_a, that is, the subject distance Da. This is the position of the center of gravity of the white spot in the captured image.

The amount of change a (the α point and the β point) of the center of gravity of the white spot due to the imaging surface changing from the imaging surface IA_r to the imaging surface IA_a (that is, the subject distance changing from the reference subject distance Dr to the subject distance Da). The relationship of the following formula (1) is established for the distance between α and β when projected onto the same imaging surface.
tan θ = a / (| Da−Dr |) (1)
However, (theta) is the incident angle of the illumination light with respect to imaging surface IA_r and IA_a.

  Although illustration of the mist prevention glass 32 is omitted in FIG. 9, even if the mist prevention glass 32 is interposed between the optical path length changing member 31 and the imaging surface of the sensor unit 26, the principle is not changed. Absent. For this reason, the mist prevention glass 32 is not considered here.

  From the above equation (1), even if the subject distance Da to be measured changes, if the tan θ, the reference subject distance Dr, and the coordinates of the α point in the captured image are known, the imaging output from the two-dimensional image sensor 27 The subject distance Dr can be calculated based on the coordinates of the center of gravity position (β point in FIG. 9) included in the image. If the subject distance Dr can be calculated, the change amount (| Da−Dr |) of the actual subject distance Da with respect to the reference subject distance Dr can also be obtained.

  Therefore, when the image forming apparatus 100 is shipped from the factory, for example, tan θ and the coordinates of the α point are obtained by the following method. The reference subject distance Dr can be set in advance such that the gap d between the bottom surface 23a of the casing 23 of the colorimetric camera 20 and the recording medium P described above is an optimal value (for example, about 1 mm to 2 mm). That's fine.

  First, the carriage lift motor 17 is driven to set the subject distance to the reference subject distance Dr. Then, the illumination light source 30 (one of the two LEDs) is turned on, and the imaging target area of the two-dimensional image sensor 27 is illuminated by the illumination light from the illumination light source 30. In this state, by capturing an image with the two-dimensional image sensor 27, a captured image in which specularly reflected light is reflected in the subject region is obtained. White spots are detected from the captured image and the coordinates of the center of gravity position (α point) are obtained. A specific example for obtaining the coordinates of the center of gravity position of the outline will be described later.

  Next, the carriage lifting / lowering motor 17 is driven to set the subject distance to a distance Da ′ obtained by adding (or subtracting) a known value to the reference subject distance Dr. Then, the image is picked up by the two-dimensional image sensor 27 in the same manner as described above, and the coordinates (β ′ point position) of the blank gravity center position are obtained from the picked-up image. Then, tan θ is calculated by the above equation (1) using the obtained position (x1, y1) of the α point and position (x2, y2) of the β ′ point.

  The coordinates of the tan θ and α points obtained by performing the above processing at the time of factory shipment of the image forming apparatus 100 are stored in the nonvolatile memory 45 of the colorimetric camera 20 together with the predetermined reference subject distance Dr. deep. At the time of measuring the subject distance Da, the distance calculation unit 46 obtains the coordinates of the center of gravity position (β point) of the white spot from the captured image output from the two-dimensional image sensor 27, and the obtained coordinates of the β point and the non-volatile The subject distance Da is calculated by the above equation (1) using tan θ stored in advance in the memory 45 or the like, the reference subject distance Dr, and the coordinates of the α point.

  FIG. 10 is a diagram illustrating an example of a captured image output from the two-dimensional image sensor 27 of the sensor unit 26 when the subject distance Da is measured. In the drawing, I_ta represents an image of the entire imaging target region of the sensor unit 26, I_400 represents an image of the reference chart 400, and I_oa represents an image of the subject region.

  When measuring the subject distance Da, as described above, the illumination light source 30 (one of the two LEDs) is turned on, and the imaging target region of the two-dimensional image sensor 27 is illuminated by the illumination light from the illumination light source 30. In this state, by picking up an image with the two-dimensional image sensor 27, a picked-up image as shown in FIG. 10 is obtained in which the white spot I_sa is reflected in the image I_oa in the subject area. In FIG. 10, the white spot I_sr observed in the captured image at the reference subject distance Dr is also shown as a comparison target of the white spot I_sa, but actually, it appears in the image I_oa of the subject area. Are only white spots I_sa.

  The distance calculator 46 outputs the center of gravity position (β point) of the white spot I_sa from the captured image shown in FIG. 10 output from the two-dimensional image sensor 27 and temporarily stored in the frame memory 42 by, for example, the following method. ).

  First, the distance calculation unit 46 binarizes the image I_oa in the subject area and sets the value as f (x, y). Then, using the obtained f (x, y), the coordinates β (x2, y2) of the gravity center position (β point) of the white spot I_sa are obtained. However, it converts from resolution to distance. Note that the coordinates α (x1, y1) of the gravity center position (α point) of the white spot I_sr can also be obtained by a similar method when the image forming apparatus 100 is shipped from the factory.

Incidentally, the coordinates α (x1, y1) of the center of gravity position (α point) in the image range of n × m pixels are obtained by the following equations (2) and (3).
x1 = Ix / M (2)
y1 = Iy / M (3)
However,
(Ix, Iy are first moments, M is mass).
Therefore, for the above n and m, appropriate values may be used that will include an α point (β point) in the image range of n × m pixels in the image of the subject area.

  The distance calculation unit 46 calculates the coordinates β (x2, y2) of the β point obtained by the above method, the tan θ stored in advance in the nonvolatile memory 45, the reference subject distance Dr, and the coordinates α (x1, x1) of the α point. Based on y1), the subject distance Da is calculated by the above equation (1). The distance calculation unit 46 obtains the coordinates of the coordinates β (x2, y2) of the β points from the plurality of captured images captured while changing the horizontal position of the colorimetric camera 20, and uses the average value thereof. The subject distance Da may be calculated.

  Next, a flow of a series of processing when calculating the subject distance Da by the above method will be described with reference to FIG. FIG. 11 is a flowchart illustrating an example of a procedure for calculating the subject distance Da.

  When calculating the subject distance Da, first, in step S101, the light source drive control unit 40 turns on the illumination light source 30 (one of the two LEDs). Then, the timing signal generator 41 inputs a timing signal to the two-dimensional image sensor 27 and starts imaging by the two-dimensional image sensor 27.

  Next, in step S102, the distance calculation unit 46 extracts the image I_oa of the subject area from the captured image output from the two-dimensional image sensor 27 and temporarily stored in the frame memory 42. In step S103, the distance calculation unit 46 obtains the coordinates β (x2, y2) of the center of gravity position (β point) of the white spot I_sa by the method described above for the image I_oa of the subject area extracted in step S102. .

  In step S104, the distance calculation unit 46 reads tan θ, the reference subject distance Dr, and the coordinates α (x1, y1) of the center of gravity position (α point) of the white spot I_sr stored in the nonvolatile memory 45 or the like. Based on the coordinates (x2, y2) of the β point obtained in step S103, the tan θ read from the nonvolatile memory 45, the reference subject distance Dr, and the coordinates α (x1, y1) of the α point, The subject distance Da is calculated by the equation (1), and the process is terminated.

<Second method>
In the above method, the distance calculation unit 46 calculates the subject distance Da based on the position of the white spot I_sr when the subject distance is the reference subject distance Dr and the position of the white spot I_sa when measuring the subject distance Da. Like to do. However, the distance calculation unit 46, based on the size (area) of the white spot I_sr when the subject distance is the reference subject distance Dr and the size (area) of the white spot I_sa when measuring the subject distance Da, The subject distance Da can also be calculated.

  FIG. 12 is an explanatory diagram for explaining another example of the method for calculating the subject distance by the distance calculation unit 46, and shows the variation of the blank area on the imaging surface due to the variation of the subject distance. IA_r and IA_a in FIG. 12 represent imaging surfaces similar to those in FIG. In FIG. 12, S_r represents a white area on the imaging surface IA_r, and a point S_a represents a white area on the imaging surface IA_a, that is, an image output from the two-dimensional image sensor 27 when measuring the subject distance Da. It represents the area of white spots in the image.

When the imaging surface changes from the imaging surface IA_r to the imaging surface IA_a (that is, the subject distance changes from the reference subject distance Dr to the subject distance Da), the white area changes from S_r to S_a. At this time, the relationship between the subject distance and the white area is expressed by the following formula (7). Therefore, if the reference subject distance Dr and S_r are known, the white spot in the captured image obtained when the subject distance Da is measured is obtained. The subject distance Dr can be calculated based on the area S_a.
If the subject distance Dr can be calculated, the change amount (| Da−Dr |) of the actual subject distance Da with respect to the reference subject distance Dr can also be obtained.

  Therefore, when the image forming apparatus 100 is shipped from the factory, the white area S_r in the captured image at the reference subject distance Dr is obtained and stored in the nonvolatile memory 45 or the like. The reference subject distance Dr may be determined in advance as the distance at which the gap d is an optimum value (for example, about 1 mm to 2 mm), as in the above-described example.

  When measuring the subject distance Da, as described above, the illumination light source 30 (one of the two LEDs) is turned on, and the imaging target region of the two-dimensional image sensor 27 is illuminated by the illumination light from the illumination light source 30. In this state, by picking up an image with the two-dimensional image sensor 27, a picked-up image as shown in FIG. 10 is obtained in which the white spot I_sa is reflected in the image I_oa in the subject area.

  The distance calculation unit 46 extracts the image I_oa of the subject area from the captured image shown in FIG. 10 output from the two-dimensional image sensor 27 and temporarily stored in the frame memory 42. Then, the image I_oa of the subject area is binarized, and the total value of the black portions of the obtained binary image (the number of black pixels in the image area of n × m pixels including white spots) is calculated as the white spot I_sa. Obtained as area S_a. Note that the area S_r of the white spot I_sr can also be obtained by a similar method when the image forming apparatus 100 is shipped from the factory.

  Based on the area S_a of the white spot I_sa obtained by the above method and the reference subject distance Dr and the area S_r of the white spot I_sr stored in advance in the nonvolatile memory 45 or the like, the distance calculating unit 46 The subject distance Da is calculated according to 7). The distance calculation unit 46 obtains the area S_a of the white spot I_sa from each of the plurality of captured images taken while changing the horizontal position of the colorimetric camera 20, and calculates the subject distance Da using the average value. You may do it.

  Next, a flow of a series of processes when calculating the subject distance Da by the above method will be described with reference to FIG. FIG. 13 is a flowchart illustrating an example of a procedure for calculating the subject distance Da.

  When calculating the subject distance Da, first, in step S201, the light source drive control unit 40 turns on the illumination light source 30 (one of the two LEDs). Then, the timing signal generator 41 inputs a timing signal to the two-dimensional image sensor 27 and starts imaging by the two-dimensional image sensor 27.

  Next, in step S202, the distance calculation unit 46 extracts the image I_oa of the subject area from the captured image output from the two-dimensional image sensor 27 and temporarily stored in the frame memory 42. In step S203, the distance calculation unit 46 obtains the area S_a of the whiteout I_sa by the above-described method for the subject region image I_oa extracted in step S202.

  In step S204, the distance calculation unit 46 reads the reference subject distance Dr and the area S_r of the white spot I_sr stored in the nonvolatile memory 45 or the like. Then, based on the area S_a of the white spot I_sa obtained in step S203, the reference subject distance Dr read from the nonvolatile memory 45 or the like, and the area S_r of the white spot I_sr, the subject distance Da is calculated by the above equation (7). Then, the process ends.

  Returning to FIG. 8, the distance adjustment unit 47 adjusts the subject distance by driving the carriage lifting motor 17 based on the subject distance Da calculated by the distance calculation unit 46. For example, the distance adjustment unit 47 performs colorimetry at a position where the subject distance becomes the reference subject distance Dr based on the change amount (| Da−Dr |) of the subject distance Da calculated by the distance calculation unit 46 with respect to the reference subject distance Dr. The carriage lifting / lowering motor 17 is driven so that the camera 20 is arranged.

  The colorimetric camera 20 of this embodiment performs colorimetry on the colorimetric target patch CP in a state where the subject distance is adjusted by the distance adjustment unit 47. That is, after the recording medium P on which the test pattern including the colorimetric target patch CP is formed is set on the platen 16 and the carriage elevating motor 17 is driven by the distance adjusting unit 47 to adjust the subject distance, the illumination light source 30 (Both of two LEDs) are turned on, and the imaging target area of the two-dimensional image sensor 27 is illuminated with illumination light from the illumination light source 30. In this state, by capturing an image with the two-dimensional image sensor 27, a captured image including the colorimetric target patch CP and the reference chart 400 is obtained.

  Then, the RGB value of the color measurement target patch CP and the RGB value of each reference patch of the reference chart 400 are obtained from the captured image by the averaging processing unit 43. Then, the colorimetric calculation unit 44 calculates the colorimetric value of the colorimetric target patch CP based on the RGB value of the colorimetric target patch CP and the RGB value of each reference patch of the reference chart 400.

  As described above, the colorimetric camera 20 of the present embodiment calculates the subject distance Da before performing the colorimetric measurement of the colorimetric target patch CP, and adjusts the subject distance to be, for example, the reference subject distance Dr. An image including the colorimetric target patch CP is captured. Then, based on the RGB value of each reference patch of the reference chart 400 of the color measurement target patch CP obtained from the captured image, the color measurement value of the color measurement target patch CP is calculated. Therefore, according to the colorimetric camera 20 of the present embodiment, it is possible to prevent inconvenience that the colorimetric value calculated due to the change in the subject distance is changed, and calculate the correct colorimetric value of the colorimetric target patch CP. can do.

  Note that the colorimetric camera 20 of the present embodiment adjusts the subject distance when the colorimetric target patch CP is measured using the subject distance Da calculated by the distance calculation unit 46, so that the colorimetric target patch CP is adjusted. The correct colorimetric value is obtained. However, instead of this, a correct colorimetric value can be obtained by providing a correction unit that corrects the colorimetric value calculated by the colorimetric calculation unit 44 based on the subject distance Da calculated by the distance calculation unit 46. You may be made to do.

  In the case of this configuration, a correction parameter for correcting the colorimetric value according to the subject distance is obtained in advance and stored in the nonvolatile memory 45 or the like. The correction unit reads the correction parameter corresponding to the subject distance Da calculated by the distance calculation unit 46, and corrects the color measurement value calculated by the color measurement calculation unit 44 using the correction parameter. The correction unit does not correct the colorimetric value calculated by the colorimetric calculation unit 44, but the RGB value of the colorimetric target patch CP output from the averaging processing unit 43 and each reference patch of the reference chart 400. The RGB values may be corrected according to the subject distance Da calculated by the distance calculation unit 46.

<Patch color measurement method>
Next, a specific example of the color measurement method of the color measurement target patch CP by the image forming apparatus 100 according to the present embodiment will be described in detail with reference to FIGS. The color measurement method described below performs pre-processing that is performed when the image forming apparatus 100 is in an initial state (when the image forming apparatus 100 is in an initial state due to manufacturing, overfall, or the like) and color adjustment of the image forming apparatus 100. Colorimetric processing performed at the time of adjustment.

  FIG. 14 is a diagram for explaining processing for obtaining a reference colorimetric value and a reference RGB value and processing for generating a reference value linear transformation matrix. These processes shown in FIG. 14 are implemented as a preprocess. In the preprocessing, a reference sheet KS on which a plurality of reference patches KP are formed is used. The reference patch KP of the reference sheet KS is equivalent to the patch of the reference chart 400 provided in the colorimetric camera 20.

  First, at least one of Lab values and XYZ values (both Lab values and XYZ values in the example of FIG. 14) that are colorimetric values of a plurality of reference patches KP of the reference sheet KS is assigned to each patch number. Correspondingly, it is stored in a memory table Tb1 provided in, for example, a non-volatile memory 45 mounted on the substrate 22 of the colorimetric camera 20. The colorimetric value of the reference patch KP is a value obtained in advance by colorimetry using the spectroscope BS or the like. If the colorimetric value of the reference patch KP is known, that value may be used. Hereinafter, the colorimetric values of the reference patch KP stored in the memory table Tb1 are referred to as “reference colorimetric values”.

  Next, the reference sheet KS is set on the platen 16 and the movement of the carriage 5 is controlled, so that the colorimetric camera 20 takes an image using a plurality of reference patches KP of the reference sheet KS as subjects. Then, the RGB values of the reference patch KP obtained by imaging with the colorimetric camera 20 are stored in the memory table Tb1 of the nonvolatile memory 45 in correspondence with the patch numbers. That is, in the memory table Tb1, the colorimetric values and RGB values of the plurality of reference patches KP arranged on the reference sheet KS are stored in correspondence with the patch numbers of the respective reference patches KP. Hereinafter, the RGB values of the reference patch KP stored in the memory table Tb1 are referred to as “reference RGB values”. The reference RGB value is a value reflecting the characteristics of the colorimetric camera 20.

  When the reference colorimetric values and the reference RGB values of the reference patch KP are stored in the memory table Tb1 of the non-volatile memory 45, the CPU 101 of the image forming apparatus 100 stores the XYZ values that are the reference colorimetric values of the same patch number and the reference RGB values. A reference value linear conversion matrix for converting these values into each other is generated and stored in the nonvolatile memory 45. When only Lab values are stored as reference colorimetric values in the memory table Tb1, after converting Lab values to XYZ values using a known conversion formula for converting Lab values to XYZ values, a reference value linear conversion matrix Should be generated.

  Further, when the colorimetric camera 20 captures a plurality of reference patches KP on the reference sheet KS, the reference chart 400 provided in the colorimetric camera 20 is also captured at the same time. The RGB values of each patch of the reference chart 400 obtained by this imaging are also stored in the memory table Tb1 of the nonvolatile memory 45 in association with the patch number. The RGB values of the patches of the reference chart 400 stored in the memory table Tb1 by this preprocessing are referred to as “initial reference RGB values”. FIG. 15 is a diagram illustrating an example of the initial reference RGB values. FIG. 15A shows a state in which the initial reference RGB value (RdGdBd) is stored in the memory table Tb1, and the initial reference Lab value obtained by converting the initial reference RGB value (RdGdBd) into the Lab value together with the initial reference RGB value and (RdGdBd). It shows that the initial reference XYZ value (XdYdZd) converted into the value (Ldadbd) and the XYZ value is also stored in association with each other. FIG. 15B is a scatter diagram in which initial reference RGB values of each patch of the reference chart 400 are plotted.

  After the above preprocessing is completed, the image forming apparatus 100 controls the main scanning motor 8, the sub-scanning motor 12, and the recording head under the control of the CPU 101 based on image data input from the outside, print settings, and the like. 6 is driven to form an image on the recording medium P by ejecting ink from the recording head 6 while intermittently transporting the recording medium P in the sub-scanning direction and moving the carriage 5 in the main scanning direction. . At this time, the amount of ink ejected from the recording head 6 may change depending on the characteristics inherent to the device or changes over time. When this ink ejection amount changes, the color differs from the color of the image intended by the user. As a result, the color reproducibility deteriorates. Therefore, the image forming apparatus 100 performs a color measurement process for obtaining a color measurement value of the color measurement target patch CP formed on the recording medium P at a predetermined timing for color adjustment. Then, a device profile is generated or corrected based on the colorimetric value of the colorimetric target patch CP obtained by the colorimetric processing, and color adjustment is performed based on the device profile. To increase.

  FIG. 16 is a diagram for explaining the outline of the color measurement process. When performing color adjustment, the image forming apparatus 100 first ejects ink from the recording head 6 onto the recording medium P set on the platen 16 to form a test pattern in which a large number of colorimetric target patches CP are arranged. To do. Hereinafter, the recording medium P on which the test pattern is formed is referred to as an “adjustment sheet CS”. The adjustment sheet CS is formed with a colorimetric target patch CP reflecting output characteristics at the time of adjustment of the image forming apparatus 100, in particular, output characteristics of the recording head 6. Note that image data for forming a test pattern is stored in advance in the nonvolatile memory 45 or the like.

  Next, as shown in FIG. 16, the image forming apparatus 100 sets the adjustment sheet CS on the platen 16 or holds the adjustment sheet CS on the platen 16 without discharging the sheet when the adjustment sheet CS is created. In the state, the two-dimensional image sensor 27 of the colorimetric camera 20 captures an image while moving the carriage 5 on the adjustment sheet CS in the main scanning direction. Then, the RGB value of the colorimetric target patch CP is obtained from the captured image output from the two-dimensional image sensor 27 by the processing by the averaging processing unit 43. Further, since the two-dimensional image sensor 27 images the reference chart 400 simultaneously with the color measurement target patch CP to be measured, the RGB value of each patch included in the reference chart 400 can also be obtained. Hereinafter, the RGB value of the color measurement target patch CP to be measured is referred to as “color measurement target RGB value”, and the RGB value of the patch in the reference chart 400 is referred to as “color measurement reference RGB value (RdsGdsBds)”. The “color measurement reference RGB value (RdsGdsBds)” is stored in the nonvolatile memory 45 or the like.

  The colorimetric calculation unit 44 of the colorimetric camera 20 performs processing for converting the colorimetric object RGB values into the initialization colorimetric object RGB values (RsGsBs) using a reference RGB linear conversion matrix to be described later (step S10). . The initialization colorimetric object RGB values (RsGsBs) are the imaging conditions of the colorimetric camera 20 that are generated from the colorimetry object RGB values from the initial state where preprocessing is performed to the adjustment time when performing colorimetry processing. This eliminates the influence of a change with time, for example, a change with time of the illumination light source 30 and a change with time of the two-dimensional image sensor 27.

  Thereafter, the colorimetric calculation unit 44 performs basic colorimetry processing, which will be described later, on the initialization colorimetry target RGB values (RsGsBs) converted from the colorimetry target RGB values (step S20), thereby performing colorimetry. A Lab value that is a colorimetric value of the target colorimetric object patch CP is acquired.

  FIG. 17 is a diagram illustrating processing for generating a linear conversion matrix between reference RGB. FIG. 18 is a diagram illustrating a relationship between an initial reference RGB value and a colorimetric reference RGB value. The colorimetric calculation unit 44 generates a reference inter-RGB linear conversion matrix to be used for this conversion before performing the process (step S10) of converting the colorimetric target RGB values into the initialization colorimetric target RGB values (RsGsBs). That is, as shown in FIG. 17, the colorimetric calculation unit 44, the initial reference RGB value (RdGdBd) obtained as preprocessing when the image forming apparatus 100 is in the initial state, and the colorimetric time reference obtained at the time of adjustment. The RGB values (RdsGdsBds) are read from the nonvolatile memory 45, and a reference RGB linear conversion matrix for converting the colorimetric reference RGB values RdsGdsBds into the initial reference RGB values RdGdBd is generated. Then, the colorimetric calculation unit 44 stores the generated reference RGB linear conversion matrix in the nonvolatile memory 45.

  In FIG. 18, the thinly drawn points in FIG. 18A are points where the initial reference RGB values RdGdBd are plotted in the rgb space, and the filled points are points where the colorimetric reference RGB values RdsGdsBds are plotted in the rgb space. It is. As can be seen from FIG. 18A, the value of the colorimetric reference RGB value RdsGdsBds varies from the value of the initial reference RGB value RdGdBd, and the direction of variation in the rgb space is shown in FIG. 18B. As shown, the directions are generally the same, but the direction of deviation differs depending on the hue. As described above, the factors that cause the RGB value to change even if the patches of the same reference chart 400 are imaged include the temporal change of the illumination light source 30 and the temporal change of the two-dimensional image sensor 27.

  As described above, when the colorimetric value is obtained using the colorimetric target RGB value obtained by imaging the colorimetric target patch CP in a state where the RGB value obtained by imaging by the colorimetric camera 20 is fluctuating, There is a possibility that an error occurs in the colorimetric value by the fluctuation amount. Therefore, between the initial reference RGB value RdGdBd and the colorimetric reference RGB value RdsGdsBds, using an estimation method such as a least square method, the colorimetric reference RGB value RdsGdsBds is converted into the initial reference RGB value RdGdBd between the reference RGB values. A linear transformation matrix is obtained, and using this reference RGB linear transformation matrix, the colorimetric object RGB values obtained by imaging the colorimetric object patch CP with the colorimetric camera 20 are converted into initialized colorimetric object RGB values RsGsBs. The converted color measurement target RGB values RsGsBs are processed, and a color measurement value of the color measurement target patch CP can be obtained with high accuracy by executing a basic color measurement process described later.

  This linear conversion matrix between RGB may be not only a first-order but also a higher-order nonlinear matrix. If the nonlinearity is high between the rgb space and the XYZ space, a higher-order matrix can be obtained. , Conversion accuracy can be improved.

  As described above, the colorimetric calculation unit 44 converts the colorimetric target RGB values obtained by imaging the colorimetric target patch CP into initialization colorimetric target RGB values (RsGsBs) using a reference RGB linear conversion matrix. After that (step S10), the basic colorimetric processing of step S20 is performed on the initialization colorimetric target RGB values (RsGsBs).

  19 and 20 are diagrams for explaining basic colorimetric processing. The colorimetric calculation unit 44 first reads the reference value linear conversion matrix generated in the preprocessing and stored in the nonvolatile memory 45, and uses the reference value linear conversion matrix to determine the initialization colorimetric target RGB values (RsGsBs). It is converted into 1XYZ value and stored in the nonvolatile memory 45 (step S21). FIG. 19 shows an example in which the initialization colorimetric target RGB values (3, 200, 5) are converted to the first XYZ values (20, 80, 10) by the reference value linear conversion matrix.

  Next, the colorimetric calculation unit 44 converts the first XYZ value converted from the initialization colorimetric target RGB value (RsGsBs) in step S21 into a first Lab value using a known conversion formula, and the nonvolatile memory 45 (Step S22). FIG. 19 shows an example in which the first XYZ values (20, 80, 10) are converted into the first Lab values (75, −60, 8) by a known conversion formula.

  Next, the colorimetric calculation unit 44 searches for a plurality of reference colorimetric values (Lab values) stored in the memory table Tb1 of the nonvolatile memory 45 in the preprocessing, and out of the reference colorimetric values (Lab values). Then, a set of a plurality of patches (neighboring color patches) having a reference colorimetric value (Lab value) close to the first Lab value in the Lab space is selected (step S23). As a method for selecting a patch having a short distance, for example, the distance from the first Lab value is calculated for all reference colorimetric values (Lab values) stored in the memory table Tb1, and the patch is calculated for the first Lab value. A method of selecting a plurality of patches having Lab values that are close in distance (in FIG. 19, Lab values that are hatched) can be used.

  Next, as shown in FIG. 20, the colorimetric calculation unit 44 refers to the memory table Tb1, and for each of the neighboring color patches selected in step S23, the RGB value paired with the Lab value (reference RGB) Value) and XYZ values are extracted, and a combination of RGB values and XYZ values is selected from the plurality of RGB values and XYZ values (step S24). Then, the colorimetric calculation unit 44 obtains a selected RGB value linear conversion matrix for converting the RGB values of the selected combination (selected set) into XYZ values using the least square method or the like, and obtains the selected RGB value linear The conversion matrix is stored in the nonvolatile memory 45 (step S25).

  Next, the colorimetric calculation unit 44 converts the initialization colorimetric object RGB values (RsGsBs) into the second XYZ values using the selected RGB value linear conversion matrix generated in step S25 (step S26). Further, the colorimetric calculation unit 44 converts the second XYZ value obtained in step S26 into a second Lab value using a known conversion formula (step S27), and converts the obtained second Lab value into the colorimetric target patch CP. Is the final colorimetric value. The image forming apparatus 100 generates or corrects a device profile based on the colorimetric values obtained by the above colorimetric processing, and performs color adjustment based on the device profile, thereby improving the color reproducibility of the output image. be able to.

  The colorimetric camera 20 described above has a configuration in which the reference chart 400 is provided in the housing 23 and the two-dimensional image sensor 27 of the sensor unit 26 captures the colorimetric target patch CP and the reference chart 400 at the same time. . However, as described above, the initial reference RGB values and the colorimetric reference RGB values obtained by imaging the reference chart 400 are the colorimetric cameras with respect to the colorimetric object RGB values obtained by imaging the colorimetric object patch CP. This is used to eliminate the influence of the time-dependent change of the 20 imaging conditions, for example, the change of the illumination light source 30 and the change of the two-dimensional image sensor 27 over time. That is, for the initial reference RGB value and the colorimetric reference RGB value obtained by imaging the reference chart 400, the above-described reference RGB linear conversion matrix is calculated, and the colorimetric target RGB is calculated using the reference RGB linear conversion matrix. This value is used to convert the value to an initialization colorimetric object RGB value (RsGsBs).

  Therefore, if the temporal change in the imaging condition of the colorimetric camera 20 is negligible with respect to the required colorimetric accuracy, the colorimetric target patch using the colorimetric camera 20 having the configuration in which the reference chart 400 is omitted. You may make it calculate the colorimetric value of CP. In this case, the process of converting the colorimetric object RGB values into the initialization colorimetric object RGB values (step S10 in FIG. 16) is omitted, and the basic colorimetry process (step S20 in FIG. 16) is performed on the colorimetric object RGB values. 19 and 20) are performed.

<Modification of colorimetric camera>
Next, modified examples (first to eighth modified examples) of the colorimetric camera 20 of the present embodiment will be described. In the following, the color measurement camera 20 of the first modification is the color measurement camera 20A, the color measurement camera 20 of the second modification is the color measurement camera 20B, the color measurement camera 20 of the third modification is the color measurement camera 20C, and the fourth. The colorimetric camera 20 of the modified example is the colorimetric camera 20D, the colorimetric camera 20 of the fifth modified example is the colorimetric camera 20E, the colorimetric camera 20 of the sixth modified example is the colorimetric camera 20F, and the colorimetric camera of the seventh modified example. The camera 20 is referred to as a colorimetric camera 20G, and the colorimetric camera 20 of the seventh modified example is referred to as a colorimetric camera 20H. Note that, in each modification, the same reference numerals are given to the same components as those of the colorimetric camera 20 described above, and redundant description is omitted.

<First Modification>
21A and 21B are longitudinal sectional views of the colorimetric camera 20A of the first modified example, and are sectional views at the same position as the longitudinal sectional view of the colorimetric camera 20 shown in FIG. . FIG. 21A shows the positions of the first mirror 51 and the second mirror 52 when the subject distance is measured, and FIG. 21B shows the first mirror 51 and the first mirror 51 when the colorimetric target patch CP is measured. The position of the two mirrors 52 is shown.

  As described above, the colorimetric camera 20 of the present embodiment calculates the subject distance based on the variation of the white spot position (coordinate of the center of gravity position) and the size (area). Here, the variation in the position and size of the white spot with respect to the variation in the subject distance increases as the incident angle of the illumination light with respect to the imaging surface of the sensor unit 26 increases. That is, when the subject distance is measured, it is expected that the measurement accuracy of the subject distance can be improved by increasing the incident angle of the illumination light with respect to the imaging surface. Therefore, in the colorimetric camera 20A of the first modified example, the first mirror 51 and the second mirror 52 are provided inside the housing 23, and the illumination light from the illumination light source 30 is supplied to the first mirror 51 when the subject distance is measured. The incident angle of the illumination light with respect to the imaging surface can be increased by reflecting the light with the second mirror 52.

  The first mirror 51 has a structure that can be rotated about a rotating shaft 51a, and one surface is a mirror surface that reflects light. The surface opposite to the mirror surface is black that absorbs light. Similarly, the 2nd mirror 52 is a structure which can be rotated using the rotating shaft 52a as a fulcrum, and one surface is made into the mirror surface which reflects light. The surface opposite to the mirror surface is black that absorbs light.

  In the colorimetric camera 20A of the first modification, when the subject distance is measured, for example, the light source drive control unit 40 controls the first mirror 51 and the second mirror 52 with the rotation axes 51a and 52a as fulcrums, respectively. To the position shown in FIG. Here, the surfaces of the first mirror 51 and the second mirror 52 facing the illumination light source 30 are mirror surfaces. Thereby, after the illumination light from the illumination light source 30 is reflected by the first mirror 51, it is further reflected by the second mirror 52 and enters the imaging surface. The incident angle of the illumination light at this time is equivalent to the case where the illumination light source 30 is provided at the position of the second mirror 52, and the incident angle of the illumination light can be made larger than that of the colorimetric camera 20 described above. it can.

  In the color measurement camera 20A of the first modification, when performing color measurement of the color measurement target patch CP, the first mirror 51 and the second mirror 52 are reversed with the rotation axes 51a and 52a as fulcrums, respectively. The position shown in FIG. Thereby, the illumination light from the illumination light source 30 enters the imaging surface without being reflected by the first mirror 51 and the second mirror 52.

  As described above, in the color measurement camera 20A of the first modified example, when measuring the subject distance, the illumination light from the illumination light source 30 is reflected by the first mirror 51 and the second mirror 52 and is incident on the imaging surface. Therefore, the incident angle of the illumination light with respect to the imaging surface can be increased to improve the measurement accuracy of the subject distance.

<Second Modification>
FIG. 22 is a longitudinal sectional view of the colorimetric camera 20B of the second modification, and is a sectional view at the same position as the longitudinal sectional view of the colorimetric camera 20 shown in FIG.

  The color measurement camera 20B of the second modified example is a distance measurement illumination light source 53 that is turned on when the subject distance is measured, separately from the illumination light source 30 (first light source) that is turned on when the color measurement target patch CP is measured. This is an example in which (second light source) is provided. For example, as shown in FIG. 22, the distance measuring illumination light source 53 is provided at a position relatively close to the optical path length changing member 31 on the side surface of the frame body 21.

  In the color measurement camera 20B of the second modification, the light source drive control unit 40 turns on the distance measurement illumination light source 53 without turning on the illumination light source 30 when measuring the subject distance. As described above, since the distance measuring illumination light source 53 is provided at a position relatively close to the optical path length changing member 31 on the side surface of the frame body 21, the incident angle of the illumination light from the distance measuring illumination light source 53 is This is larger than the colorimetric camera 20 described above.

  As described above, in the color measurement camera 20B of the second modified example, when measuring the subject distance, the illumination light source 53 for distance measurement provided separately from the illumination light source 30 is turned on to increase the incident angle of the illumination light with respect to the imaging surface. Therefore, as in the case of the colorimetric camera 20A of the first modification, the measurement accuracy of the subject distance can be improved.

<Third Modification>
FIG. 23 is a longitudinal sectional view of a colorimetric camera 20C of the third modification, and is a sectional view at the same position as the longitudinal sectional view of the colorimetric camera 20 shown in FIG.

  In the color measurement camera 20 </ b> C of the third modification, an opening 54 is provided on the bottom surface 23 a of the housing 23, which is different from the opening 25 for imaging the color measurement target patch CP. The reference chart 400 is arranged so as to close the opening 54 from the outside of the housing 23. That is, in the colorimetric camera 20 described above, the reference chart 400 is arranged on the inner surface side facing the sensor unit 26 of the bottom surface part 23a of the housing 23, whereas in the colorimetric camera 20C of the third modification example. The reference chart 400 is arranged on the outer surface side of the bottom surface 23a of the housing 23 facing the recording medium P.

  Specifically, for example, a recess having a depth corresponding to the thickness of the reference chart 400 is formed on the outer surface side of the bottom surface portion 23 a of the housing 23 so as to communicate with the opening 54. The reference chart 400 is mounted in the recess with the surface on which each reference patch is formed facing the sensor unit 26 side. For example, the bottom surface portion 23a of the housing 23 is formed with an adhesive or the like. It is joined to.

  In the color measurement camera 20 </ b> C of the third modified example configured as described above, the reference chart 400 is arranged on the outer surface side of the bottom surface portion 23 a of the housing 23, so that the sensor unit is compared with the color measurement camera 20 described above. Thus, the difference between the optical path length from the sensor 26 to the colorimetric object patch CP and the optical path length from the sensor unit 26 to the reference chart 400 can be reduced.

<Fourth Modification>
FIG. 24 is a longitudinal sectional view of the colorimetric camera 20D of the fourth modified example, and is a sectional view at the same position as the longitudinal sectional view of the colorimetric camera 20 shown in FIG. 5-1.

  In the color measurement camera 20D of the fourth modified example, the reference chart 400 is arranged on the outer surface side of the bottom surface portion 23a of the housing 23, similarly to the color measurement camera 20C of the third modified example. However, in the colorimetric camera 20C of the third modified example, the reference chart 400 is joined to the bottom surface portion 23a of the housing 23 by an adhesive or the like and integrated with the housing 23, whereas the fourth modified example. In the colorimetric camera 20D, the reference chart 400 is detachably held with respect to the housing 23.

  Specifically, for example, similarly to the colorimetric camera 20C of the third modified example, a recessed portion communicating with the opening 54 is formed on the outer surface side of the bottom surface portion 23a of the housing 23, and the reference chart 400 of the reference chart 400 is formed in this recessed portion. The end is attached. The color measurement camera 20 </ b> D of the fourth modified example includes a holding member 55 that holds the reference chart 400 with the end portion mounted in the recess from the outer surface side of the bottom surface portion 23 a of the housing 23. The holding member 55 is detachably attached to the bottom surface portion 23 a of the housing 23. Therefore, in the colorimetric camera 20D of the fourth modified example, the reference chart 400 can be taken out by removing the holding member 55 from the bottom surface portion 23a of the housing 23.

  As described above, in the colorimetric camera 20D of the fourth modified example, the reference chart 400 is detachably held with respect to the housing 23, and the reference chart 400 can be taken out. When 400 is deteriorated, the operation of replacing the reference chart 400 can be easily performed. Further, in the colorimetric camera 20D of the fourth modified example, when the correction data for shading correction described above is obtained, the reference chart 400 is taken out and a white reference plate is placed instead. If the image is captured by the two-dimensional image sensor 27, correction data for shading correction can be easily obtained.

<Fifth Modification>
FIG. 25 is a longitudinal sectional view of a colorimetric camera 20E of the fifth modification, and is a sectional view at the same position as the longitudinal sectional view of the colorimetric camera 20 shown in FIG.

  In the color measurement camera 20E of the fifth modification, the mist prevention glass 32 that closes the opening 25 of the housing 23 is omitted, and the opening 25 of the housing 23 is closed by the optical path length changing member 31.

  In the colorimetric camera 20E of the fifth modification, the opening 25 of the housing 23 is blocked by the optical path length changing member 31, so that the mist prevention glass 32 is provided inside the housing 23 as in the case where the mist prevention glass 32 is provided. Mist can be prevented from entering. In the case of this modification, there is a concern that mist or dust may adhere to the exposed portion of the optical path length changing member 31 exposed to the outside from the opening 25, so before performing color measurement of the color measurement target patch CP. It is desirable to keep the optical path length changing member 31 in a clean state by wiping off dirt adhering to the exposed portion of the optical path length changing member 31.

<Sixth Modification>
FIG. 26 is a longitudinal sectional view of a colorimetric camera 20F of a sixth modification, and is a sectional view at the same position as the longitudinal sectional view of the colorimetric camera 20 shown in FIG. 5-1.

  In the colorimetric camera 20F of the sixth modification, the optical path length changing member 31 inside the housing 23 is omitted.

  As described above, the optical path length changing member 31 has a function of changing the optical path length from the sensor unit 26 to the colorimetric target patch CP to match the optical path length from the sensor unit 26 to the reference chart 400. However, if the difference between these optical path lengths is within the range of the depth of field of the sensor unit 26, even if there is a difference in the optical path length, both the colorimetric object patch CP and the reference chart 400 are in focus. Images can be taken.

  The difference between the optical path length from the sensor unit 26 to the color measurement target patch CP and the optical path length from the sensor unit 26 to the reference chart 400 is generally a value obtained by adding the gap d to the thickness of the bottom surface portion 23a of the housing 23. . Therefore, if the gap d is set to a sufficiently small value, the difference between the optical path length from the sensor unit 26 to the colorimetric object patch CP and the optical path length from the sensor unit 26 to the reference chart 400 is determined as the object field of the sensor unit 26. The depth can be within the range, and the optical path length changing member 31 can be omitted to reduce the component cost.

  Note that the depth of field of the sensor unit 26 is determined according to the aperture value of the sensor unit 26, the focal length of the imaging lens 28, the distance between the sensor unit 26 and the subject, and the like. It is. In the colorimetric camera 20F of the present modification, when the gap d between the bottom surface portion 23a of the housing 23 and the recording medium P is set to a sufficiently small value, for example, about 1 mm to 2 mm, the subject ( The sensor unit 26 is designed so that the difference between the optical path length to the color measurement target patch CP) and the optical path length from the sensor unit 26 to the reference chart 400 is within the depth of field.

<Seventh Modification>
FIG. 27A is a longitudinal sectional view of a colorimetric camera 20G of the seventh modified example, and is a sectional view at the same position as the longitudinal sectional view of the colorimetric camera 20 shown in FIG. FIG. 27-2 is a plan view of the bottom 23a of the housing 23 as viewed from the X4 direction in FIG. 27-1. In FIG. 27-2, the vertical projection position of the illumination light source 30 on the bottom surface portion 23a of the housing 23 (the position projected when looking down perpendicular to the bottom surface portion 23a) is indicated by a broken line.

  In the color measurement camera 20G of the seventh modified example, the bottom surface portion 23a of the housing 23 is positioned on a perpendicular line that is perpendicular to the bottom surface portion 23a from the sensor portion 26 (that is, the optical axis center of the sensor portion 26). An opening 25G is provided, and the color measurement target patch CP is imaged through the opening 25G. That is, in the colorimetric camera 20G of the seventh modified example, the opening 25G for imaging the colorimetric target patch CP outside the housing 23 is provided so as to be positioned substantially at the center in the imaging target region of the sensor unit 26. It has been.

  In the color measurement camera 20G of the seventh modification, the reference chart 400 imaged together with the color measurement target patch CP by the sensor unit 26 is arranged on the bottom surface portion 23a of the housing 23 so as to surround the opening 25G. Has been. For example, the reference chart 400 is formed in an annular shape centered on the opening 25G, and is bonded to the inner surface side of the bottom surface portion 23a of the housing 23 with the surface opposite to the surface on which the reference patch is formed as an adhesive surface. It is bonded with a material or the like and is held in a fixed state with respect to the housing 23.

  Further, in the colorimetric camera 20G of the seventh modified example, as the illumination light source 30, four LEDs arranged at the four corners on the inner peripheral side of the frame body 21 constituting the side wall of the housing 23 are used. These four LEDs used as the illumination light source 30 are mounted on the inner surface of the substrate 22 together with the two-dimensional image sensor 27 of the sensor unit 26, for example. By arranging the four LEDs used as the illumination light source 30 in this way, the color measurement target patch CP that is the subject and the reference chart KC can be illuminated under substantially the same conditions.

  In the color measurement camera 20G of the seventh modified example configured as described above, the opening 25G for imaging the color measurement target patch CP outside the housing 23 is provided in the sensor portion 26 in the bottom surface portion 23a of the housing 23. Since the reference chart 400 is disposed so as to be provided on the vertical line from the side and further surround the periphery of the opening 25G, the colorimetric object patch CP and the reference chart 400 can be imaged more appropriately.

<Other variations>
In the above-described embodiment, the colorimetric camera 20 has a function of calculating the colorimetric value of the colorimetric target patch CP. However, the colorimetric value of the colorimetric target patch CP is outside the colorimetric camera 20. You may make it calculate. For example, the CPU 101 and the control FPGA 110 mounted on the main control board 120 of the image forming apparatus 100 can be configured to calculate the colorimetric values of the colorimetric target patch CP. In this case, the color measurement camera 20 sends the color measurement target patch CP and the RGB values (or image data) of the reference chart 400 to the CPU 101 and the control FPGA 110 instead of the color measurement values of the color measurement target patch CP. Become. That is, the colorimetric camera 20 is configured as an imaging unit that does not have a function of calculating a colorimetric value.

  In the above-described embodiment, the colorimetric camera 20 is moved on the recording medium P on which the test pattern is formed using the mechanism of the image forming apparatus 100. However, the colorimetric camera 20 is connected to the image forming apparatus. A configuration may be adopted in which the recording medium P is separated from the recording medium P and moved on the recording medium P on which the test pattern is formed by a unique moving mechanism. In other words, the embodiment described above is an example in which the image forming apparatus 100 is provided with a function as a color measuring device. However, the color measuring device is configured as an independent device different from the image forming device 100, and this color measuring device. Thus, the colorimetric value of the colorimetric target patch CP included in the test pattern formed by the image forming apparatus 100 may be calculated.

  In the embodiment described above, the image forming apparatus 100 including the colorimetric camera 20 has a function of calculating the colorimetric value of the colorimetric target patch CP. The calculation of the value is not necessarily executed inside the image forming apparatus 100. For example, as shown in FIG. 28, an image forming system (colorimetric system) in which the image forming apparatus 100 and the external apparatus 500 are communicably connected is constructed, and the colorimetric value of the colorimetric target patch CP is calculated. The color calculation value may be calculated in the external apparatus 500 by providing the function of the color calculation unit 44 to the external apparatus 500. That is, the color measurement system includes an imaging unit 200 (a configuration in which the color measurement camera 20 is excluded from the color measurement camera 20 described above) provided in the image forming apparatus 100 and a color measurement calculation unit 44 provided in the external apparatus 500. And a communication unit 600 that connects the imaging unit 200 and the colorimetric calculation unit 44 (the image forming apparatus 100 and the external apparatus 500). As the external device 500, for example, a computer called DFE (Digital Front End) can be used. The communication unit 600 can use communication using a network such as a LAN or the Internet, in addition to wired or wireless P2P communication.

  In the case of the above configuration, for example, the image forming apparatus 100 uses the communication unit 600 for the RGB value of the colorimetric target patch CP obtained from the captured image of the imaging unit 200 and the RGB value of each reference patch of the reference chart 400. To the external device 500. The external apparatus 500 calculates the colorimetric value of the colorimetric target patch CP using the RGB value of the colorimetric target patch CP received from the image forming apparatus 100 and the RGB value of each reference patch of the reference chart 400. A device profile describing the characteristics of the image forming apparatus 100 is generated or modified based on the colorimetric values of the color target patch CP. Then, the external apparatus 500 transmits this device profile to the image forming apparatus 100 using the communication unit 600. The image forming apparatus 100 holds the device profile received from the external apparatus 500, and when performing image formation, the image forming apparatus 100 corrects the image data based on the device profile and performs image formation based on the corrected image data. . Thereby, the image forming apparatus 100 can perform image formation with high color reproducibility.

  Further, the external apparatus 500 may hold the device profile of the image forming apparatus 100 generated based on the colorimetric values of the colorimetric target patch CP, and the external apparatus 500 may correct the image data. That is, the image forming apparatus 100 transmits image data to the external apparatus 500 when performing image formation. The external apparatus 500 corrects the image data received from the image forming apparatus 100 based on the device profile of the image forming apparatus 100 held by itself, and transmits the corrected image data to the image forming apparatus 100. The image forming apparatus 100 forms an image based on the corrected image data received from the external apparatus 500. Thereby, the image forming apparatus 100 can perform image formation with high color reproducibility.

  In addition, instead of transmitting the RGB value of the color measurement target patch CP and the RGB value of each reference patch of the reference chart 400 from the image forming apparatus 100 to the external apparatus 500, the captured image itself of the imaging unit 200 is transmitted. May be. In this case, the external device 500 obtains the RGB value of the color measurement target patch CP and the RGB value of each reference patch of the reference chart 400 from the captured image received from the image forming apparatus 100, and measures using the obtained RGB value. A colorimetric value of the color target patch CP is calculated.

  Note that the control functions of the respective parts constituting the image forming apparatus 100 and the colorimetric camera 20 according to the present embodiment described above can be realized using hardware, software, or a combined configuration of both. When the control function of each unit constituting the image forming apparatus 100 and the colorimetric camera 20 according to the present embodiment is realized by software, the processor included in the image forming apparatus 100 or the colorimetric camera 20 executes a program describing a processing sequence. To do. The program executed by the processor is provided by being incorporated in advance in, for example, the image forming apparatus 100 or a ROM in the color measurement apparatus. In addition, a computer-readable recording medium such as a CD-ROM, a flexible disk (FD), a CD-R, a DVD (Digital Versatile Disc), etc., in which the program executed by the processor is an installable or executable file. It may be recorded and provided.

  Further, the program executed by the processor may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. The program executed by the processor may be configured to be provided or distributed via a network such as the Internet.

  Although specific embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments as they are, and various modifications and changes are made without departing from the scope of the invention in the implementation stage. It can be embodied.

5 Carriage 6 Recording Head 17 Carriage Lifting Motor 20 Colorimetric Camera (Imaging Unit, Colorimetric Device)
26 Sensor unit 27 Two-dimensional image sensor 30 Illumination light source 40 Light source drive control unit 31 Optical path length changing member 32 Mist prevention glass 44 Color measurement calculation unit 46 Distance calculation unit 47 Distance adjustment unit 51 First mirror 52 Second mirror 53 For distance measurement Illumination light source 100 Image forming apparatus 200 Imaging unit 500 External apparatus

JP 2012-63270 A

Claims (13)

A sensor unit for imaging a predetermined imaging target area including a subject area;
A light transmitting member that is disposed between the sensor unit and the subject region and transmits light;
An illumination light source that illuminates the imaging target area, and that makes regular reflection light that is transmitted through the light transmission member, specularly reflected by the subject area, and further transmitted through the light transmission member enter the sensor unit;
A distance calculation unit that calculates a distance from the sensor unit to the subject region based on the image of the regular reflection light included in the captured image output by the sensor unit;
An imaging unit comprising:   The imaging unit according to claim 1, wherein the illumination light source causes light to be incident on a position where the light is regularly reflected outside a predetermined range in the subject area.   The distance calculation unit includes a position of the regular reflected light image in the captured image when the distance is a reference distance, and a position of the regular reflected light image in the captured image when the distance is calculated. The imaging unit according to claim 1, wherein the distance is calculated based on the distance.   The distance calculation unit includes a size of the image of the regular reflection light in the captured image when the distance is set as a reference distance, and a size of the image of the regular reflection light in the captured image at the time of calculating the distance. The imaging unit according to claim 1, wherein the distance is calculated based on the distance.   When calculating the distance by the distance calculation unit, the light source drive control unit is configured to illuminate the imaging target area to the illumination light source that is common to the illumination light source that illuminates the imaging target area when imaging a subject. The imaging unit according to any one of claims 1 to 4. The illumination light source includes a light source that illuminates the imaging target region when imaging a subject, and a mirror that reflects light of the light source in an arbitrary direction to change the path of the light,
The said light source drive control part changes the path | route of the light from the said light source by the said mirror in the path | route different from the time of imaging | photography of a to-be-photographed object at the time of calculation of the said distance by the said distance calculating part. Imaging unit.   2. The illumination light source comprising: a first light source that illuminates the imaging target area when imaging a subject; and a second light source that illuminates the imaging target area when calculating the distance. The imaging unit according to any one of?   The imaging unit according to claim 1, further comprising a distance adjustment unit that adjusts the distance based on a difference between the distance calculated by the distance calculation unit and a reference distance. The imaging unit according to any one of claims 1 to 8,
A colorimetric apparatus comprising: a colorimetric calculation unit that calculates a colorimetric value of a subject included in the subject region based on the captured image.   The colorimetric apparatus according to claim 9, further comprising a correction unit that corrects the colorimetric value based on the distance calculated by the distance calculation unit. A colorimetric device according to claim 9 or 10,
An image forming unit for forming an image,
The image forming apparatus, wherein the subject is an image formed by the image forming unit. The imaging unit according to any one of claims 1 to 8,
A colorimetric system comprising: a colorimetric calculation unit that calculates a colorimetric value of a subject included in the subject region based on the captured image. A sensor unit for imaging a predetermined imaging target area including a subject area;
A light transmitting member that is disposed between the sensor unit and the subject region and transmits light;
An illumination light source that illuminates the imaging target area, and that makes regular reflection light that is transmitted through the light transmission member, specularly reflected by the subject area, and further transmitted through the light transmission member enter the sensor unit;
A distance measurement method executed by an imaging unit comprising:
A step in which the sensor unit images the imaging target area illuminated by the illumination light source;
Calculating a distance from the sensor unit to the subject region based on the image of the specularly reflected light included in the captured image output by the sensor unit;
The distance measuring method characterized by including.