Image measuring device and image forming device

Abstract

In order to automatically detect the density of color patches formed on a sheet inside an image forming device, it is necessary to detect the position of the color patches. Therefore, it is necessary to provide a sensor that detects reference marks or paper edges without contacting the sheet, separate from the color measurement sensor. This makes the device complicated and increases costs. The carriage 34 holding the colorimetric sensor 40 is configured to be movable between at least a first position and a second position where the distance from the sheet is different in a direction perpendicular to the sheet surface, and detects a reference mark on the sheet being conveyed at the first position, and detects a color calibration image at the second position. At the second position, a gap maintaining member is provided to keep the distance between the sheet and the carriage 34 constant, and the distance from the sheet surface is changed at the second position.

Description

[Technical Field]

[0001] The present invention relates to an image measuring device including a color measuring device that measures the color of an image formed on a sheet, and to an image measuring device for an image forming apparatus. [Background technology]

[0002] In recent years, the market for electrophotographic and inkjet digital printers has been expanding in the printing industry. Digital printers are also required to provide image quality (hereinafter referred to as image quality) equivalent to that of conventional offset printers. Color reproducibility is particularly important in image quality. Furthermore, color stability and consistency in the recorded image are also required.

[0003] Therefore, color calibration of a recorded image recorded on a sheet, which is a recording medium, may be performed by an image measuring device. The image measuring device acquires colorimetric data obtained by measuring the color of a color measurement test pattern. Color calibration is performed by using this colorimetric data.

[0004] In color proofing work, the task of an operator removing a sheet with a printed test pattern and measuring the color requires skill and time, especially in roll-to-roll printing machines. Therefore, Patent Documents 1 and 2 disclose a printer that uses a color measurement sensor installed inline within the device, improving the detection accuracy of detecting patch images formed on a sheet.

[0005] The colorimetric sensor in Patent Document 2 discloses a movable color sensor. By moving the color sensor in the main scanning direction, the number of patch images arranged on one sheet can be increased, thereby reducing the number of sheets required for color management. Furthermore, by detecting the color of the entire area of ​​the sheet in the main scanning direction, image uniformity can be improved. However, in the configuration in which the colorimetric sensor is movable as disclosed in Patent Document 2, the distance between the colorimetric sensor and the sheet can change as the colorimetric sensor moves, resulting in low color detection accuracy.

[0006] Therefore, Patent Document 1 discloses a configuration in which the colorimetric sensor has a roller member that can roll freely in the part facing the sheet, and during color measurement, the colorimetric sensor moves while in contact with the sheet to detect color. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2021-75002 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-53346 Summary of the Invention [Problem to be solved by the invention]

[0008] When measuring the color of a patch image, a mechanism is required to determine which part of the sheet the patch image is recorded in. For example, when forming a patch image, a reference mark is recorded at the same time, and the position of the patch image can be identified from the position of the reference mark detected by a sensor.

[0009] Here, when detecting the reference mark, it is necessary to detect the sheet while it is being conveyed, so the sensor had to be positioned at a predetermined distance to avoid contact with the sheet. Furthermore, it is desirable for the colorimetric sensor to be in contact with the sheet, as explained in Patent Document 2. This means that it is necessary to provide both a reference mark detection sensor that detects the image in a spaced-apart state while the sheet is being conveyed, and a colorimetric sensor that detects the image while in contact with the sheet when it is stopped, which makes the device complicated and increases costs.

[0010] An object of the present invention is to provide an image measuring device and an image forming device in which the colorimetric sensor can also detect reference marks, thereby simplifying the device, reducing costs, and further miniaturizing the device. [Means for solving the problem]

[0011] In order to achieve the above-mentioned object, the present invention provides an image measuring device capable of measuring an image formed on a sheet and arranged opposite a transported sheet, the image measuring device comprising: a colorimetric means including a sensor capable of detecting an image; the colorimetric means having at least a first position and a second position at which the distance from the sheet differs in a direction perpendicular to the sheet surface; a moving means for moving between the first position and the second position; and a gap retaining member for maintaining a constant gap between the sheet and the colorimetric means, the colorimetric means detecting an image on the sheet at the first position and the second position, detecting a position reference image during sheet transport at the first position, and detecting a color calibration image while sheet transport is stopped at the second position, and the distance between the colorimetric means and the sheet surface at the second position is smaller than the distance between the colorimetric means and the sheet surface at the first position. [Effects of the Invention]

[0012] As described above, the present invention allows the colorimetric sensor to also detect the reference marks, which simplifies the device and reduces costs. It also allows the device to be made more compact.

[0013] Furthermore, it is possible to suppress sheet lift and perform accurate color measurement. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a principal cross-sectional view illustrating an image forming apparatus equipped with an image measuring device according to the present invention. [Figure 2] 1 is a perspective view illustrating an image measuring device according to the present invention. [Figure 3] 1 is a schematic diagram for explaining the operation of an image measuring device according to a first embodiment of the present invention; [Figure 4] 3A to 3C are diagrams for explaining the colorimetric operation of the image measuring device according to the first embodiment of the present invention. [Figure 5]3A to 3C are diagrams for explaining the colorimetric operation of the image measuring device according to the first embodiment of the present invention. [Figure 6] 3A to 3C are diagrams for explaining the colorimetric operation of the image measuring device according to the first embodiment of the present invention. [Figure 7] 3A to 3C are diagrams for explaining the colorimetric operation of the image measuring device according to the first embodiment of the present invention. [Figure 8] 4 is a flowchart for explaining a color measurement operation of the image measuring device according to the first embodiment of the present invention. [Figure 9] 10A and 10B are schematic diagrams for explaining a separating operation of the image measuring device according to the second embodiment of the present invention. [Figure 10] 10A and 10B are schematic diagrams for explaining a contact operation of an image measuring device according to a second embodiment of the present invention. [Figure 11] 10A and 10B are cross-sectional views for explaining the contact and separation operation of the image measuring device according to the second embodiment of the present invention. [Figure 12] 10 is a flowchart for explaining a color measurement operation of an image measuring device according to a second embodiment of the present invention. [Figure 13] 10A and 10B are schematic diagrams for explaining a separating operation of the image measuring device according to the third embodiment of the present invention. [Figure 14] 10A and 10B are schematic diagrams for explaining a contact operation of an image measuring device according to a third embodiment of the present invention. [Figure 15] 10A and 10B are cross-sectional views for explaining the contact and separation operation of the image measuring device according to the third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] (First embodiment) An embodiment of the present invention will be described in detail below with reference to the drawings. First, the top of the device in FIG. 1 is defined as the upside (Z), the longitudinal direction (X) from right to left, and the sheet width direction (Y) from the front to the back of the page perpendicular to the sheet transport direction. The image forming apparatus 1 in this example is a high-speed inkjet line printer using a so-called roll-to-roll system, in which a continuous sheet is unwound and then wound back onto a roll after printing. The inkjet system ejects tiny ink droplets onto a sheet to form an image using dots. The paper feed / discharge system of the present invention is not limited to the roll-to-roll system, and the present invention can also be applied to electrophotographic image forming apparatuses. The electrophotographic system, for example, in a full-color laser beam printer, is an image forming system in which toners of black, cyan, magenta, and yellow colors are developed onto an electrostatic latent image formed on a photoreceptor, and the resulting image is transferred to a sheet via a transfer belt or the like and thermally fixed by a fixing device.

[0016] (Image forming device) 1 is a schematic cross-sectional view showing the internal configuration of an image forming apparatus 1. The image forming apparatus of this embodiment includes the following units inside: an unwinding roll unit 2, a first dancer unit 3, a first main conveyor unit 4, a meandering correction unit 5, a conveyance detection unit 6, a mark sensor unit 7, a recording unit 8, a first scanner unit 9, a first drying unit 10, a second drying unit 11, a cooling unit 12, a second scanner unit 13, a second main conveyor unit 14, a second dancer unit 15, a take-up roll unit 16, and a maintenance unit 17. A sheet S is conveyed along a sheet conveyance path indicated by a solid line in the figure, and is processed by each unit.

[0017] The unwinding roll unit 2 is a unit for holding and supplying a continuous sheet wound in a roll. The unwinding roll unit 2 is configured to store an unwinding roll and be rotated in the direction of arrow A1 by a motor (not shown), thereby unwinding and supplying the sheet S. Note that the number of rolls that can be stored is not limited to one, and two or three or more rolls may be stored, and the sheet S may be selectively unwound and supplied.

[0018] The first dancer section 3 is a unit for applying a constant sheet tension between the unwinding roll section 2 and the first main conveying section 4. The first dancer section 3 applies sheet tension by a tension applying means (not shown).

[0019] The first main conveying unit 4 is a unit that feeds the sheet S to a meandering correction unit 5, a conveying detection unit 6, a mark sensor unit 7, a recording unit 8, a first scanner unit 9, a first drying unit 10, a second drying unit 11, a cooling unit 12, and a second scanner unit 13, which are arranged in the following order along the sheet conveying path (sheet S), and also applies tension to the sheet between the first main conveying unit 4 and the second main conveying unit 14. The first main conveying unit 4 rotates by driving a motor (not shown), and conveys the sheet S under tension.

[0020] The meandering correction unit 5 is a unit for correcting meandering in the sheet width direction when the sheet S is conveyed under tension. The meandering correction unit 5 is configured to include a meandering correction roller 5a and a meandering detection sensor (not shown) that detects meandering of the sheet S. The meandering correction roller 5a can change its inclination relative to the sheet S using a motor (not shown), and corrects meandering of the sheet S based on measurements by the meandering detection sensor. At this time, the sheet S wraps around the meandering correction roller 5a, thereby improving the meandering correction function.

[0021] The transport detection unit 6 is a unit for detecting tension when transporting the sheet S under tension between the first main transport unit 4 and the second main transport unit 14. The transport detection unit 6 is also a unit for detecting the speed of the sheet S in order to control the image formation timing of the recording unit 8.

[0022] The mark sensor unit 7 is a unit for detecting marks printed on the sheet S in advance in order to control the image formation timing of the recording unit 8.

[0023] The recording unit 8 is a sheet processing unit that performs recording processing on the conveyed sheet S from above using multiple recording heads 22 to form an image on the sheet S. The conveyance path in the recording unit 8 is formed by multiple guide rollers 23 arranged in an arc-shaped configuration that convex upward, and a certain amount of tension is applied to the sheet S, ensuring clearance with the recording heads 22. The recording heads 22 are arranged in a line along the conveyance direction. In this example, in addition to four colors (Bk (black), Y (yellow), M (magenta), and C (cyan)), a total of eight line-type recording heads are provided, corresponding to reaction liquids and three spot colors. Note that the number of colors and the number of recording heads 22 are not limited to eight. The inkjet method can be a method using heating elements, a method using piezoelectric elements, a method using electrostatic elements, a method using MEMS elements, or the like. Ink of each color is supplied to the recording head from an ink tank (not shown) via an ink tube.

[0024] The first scanner unit 9 is a unit that reads the image formed on the sheet S by the recording unit 8 during printing, detects misalignment and density of the image, and corrects the printing.

[0025] The first drying unit 10 and the second drying unit 11 are units that reduce the liquid content of the ink applied to the sheet S in the recording unit 8, thereby improving the fixation of the ink to the sheet S. The second drying unit 11 is located downstream of the first drying unit 10 in the sheet conveyance direction. The first drying unit 10 and the second drying unit 11 heat the recorded sheet S to dry the applied ink. Inside the first drying unit 10 and the second drying unit 11, hot air is applied to at least the ink-applied side of the sheet S passing through, drying the ink-applied surface of the sheet S. Note that the drying method may be a combination of a method that applies hot air, a method that irradiates the surface of the sheet S with electromagnetic waves (such as ultraviolet or infrared rays), and a conductive heat transfer method through contact with a heating element.

[0026] The winding guide roller 29 is a roller that wraps around the surface of the sheet S downstream of the recording unit 8 opposite the ink application surface at a fixed winding angle, since it is necessary to block the effect of the hot air from the first drying unit 10 on the recording unit 8. In this example, two winding guide rollers 29 are arranged between the first scanner unit 9 and the first drying unit 10, and the sheet S is folded back approximately parallel at the top and bottom of the device. The first drying unit 10 is arranged below the recording unit 8, and the second drying unit 11 is arranged below the transport detection unit 6 and mark sensor unit 7 described above.

[0027] The cooling section 12 cools the sheet S that has been fixed in the first drying section 10 and the second drying section 11, solidifying the softened ink and suppressing the amount of temperature change in the sheet S in downstream processes of the image forming apparatus. Inside the cooling section 12, air at a temperature lower than that of the sheet S is blown onto at least the ink-applied surface side of the passing sheet S, thereby cooling the ink-applied surface of the sheet S. Note that the cooling method is not limited to the method of blowing air, and may also be a conductive heat transfer method using contact with a heat dissipation member, or a combination thereof.

[0028] The second scanner unit 13 is a unit that reads the test image formed on the sheet S by the recording unit 8 before printing, detects misalignment and density of the image, and corrects the printing.

[0029] The second main conveyance unit 14 is a unit that conveys the sheet S together with the first main conveyance unit 4 while applying tension to the sheet S, and adjusts the tension of the sheet S. The second main conveyance unit 14 is rotated by a motor (not shown), and the tension of the sheet S is adjusted by a clutch (not shown) that can control the torque connected to the drive connection in accordance with the tension value detected by the conveyance detection unit 6 through a tension control unit (not shown). Note that, as an additional configuration for adjusting the tension of the sheet S, a configuration for controlling the speed of the second main conveyance unit 14 by the conveyance detection unit 6 may be added. In this case, there are two tension control methods: a torque control method that controls the torque value transmitted from the clutch, and a speed control method that controls the roller speed of the second main conveyance unit 14. The tension control methods can be switched depending on the purpose, or both can be used simultaneously.

[0030] The second dancer section 15 is a unit for applying a constant sheet tension between the second main conveying section 14 and the winding roll section 16. The second dancer section 15 applies sheet tension by a tension applying means (not shown).

[0031] The winding roll unit 16 is a unit for winding the recorded sheet S onto a core, and is rotated in the direction of arrow A2 by a motor (not shown) to wind the sheet S. The number of retrievable rolls is not limited to one, and a configuration may be adopted in which two or three or more cores are provided and the sheet S is recovered by selectively switching between them. Note that, depending on the content of the post-recording processing, instead of winding the continuous sheet onto a core, a cutter may be used to cut the continuous sheet and the cut sheets S may be stacked.

[0032] The control unit 21 is a unit that controls each part of the entire image forming apparatus. The control unit 21 has a CPU, a storage device, a controller equipped with various control units, an external interface, and an operation unit 24 through which the user performs input and output. The operation of the image forming apparatus 1 is controlled based on commands from the controller or a host device 25 such as a host computer connected to the controller via an external interface.

[0033] The maintenance unit 17 is a unit equipped with a mechanism for restoring the ejection performance of the recording head 22. Examples of such mechanisms include a cap mechanism for protecting the ink ejection surface of the recording head 22, a wiper mechanism for wiping the ink ejection surface, and a suction mechanism for negatively sucking ink from the ink ejection surface inside the recording head 22. The maintenance unit also has a drive mechanism and rails (not shown) that are reciprocable horizontally along the rails, moving directly below the recording head when maintenance is performed, and moving to a position away from directly below the recording head when maintenance is not performed.

[0034] (color measurement unit) A detailed description will be given of the second scanner unit 13, which is a characteristic configuration of this embodiment. The second scanner unit 13 is capable of reading a recording image recorded with ink ejected from the recording head 22 and performing color calibration when recording the image.

[0035] 2 is a perspective view of the color measurement unit 30 provided inside the second scanner unit 13, seen from the upstream side in the transport direction. When color measurement is performed by the color measurement unit 30, a test pattern 47, which is an image for color calibration, and a reference mark 48 (see FIG. 4), which is a position reference image indicating a measurement reference position, are recorded on the sheet S by the recording head 22 before the color measurement is performed. Then, the color measurement unit 30 reads the recorded reference mark 48 and test pattern 47, and performs color calibration using the color measurement data obtained thereby.

[0036] The colorimetry unit 30 has two pairs of conveying rollers 31 and 32 that convey a sheet. It also has a first motor 33 for rotating and driving the pairs of conveying rollers 31 and 32. The first motor 33 drives the pairs of conveying rollers 31 and 32 using two drive belts (not shown) and pulleys (not shown). By changing the diameter of these pulleys (not shown), the downstream pair of conveying rollers 32 rotates at a faster peripheral speed than the upstream pair of conveying rollers 31, preventing slack in the reading portion of the conveyed sheet. A torque limiter (not shown) is provided on the shaft of the pair of conveying rollers 32 to absorb the speed difference. A platen 38 is provided on the back side of the sheet. A carriage 34, which is a colorimetry device, holds a colorimetry sensor and is movable along a first guide member 37 in the Y direction by a second motor 35, which is a drive source, and a drive belt 36, which is a drive force transmission device. By switching the rotation direction of the second motor 35 between forward and reverse, color measurement can be performed while the device is reciprocating in the Y direction.

[0037] The color measurement operation will be described in detail with reference to FIG. 3. FIG. 3 is a schematic diagram illustrating the movement of the carriage 34 in the Y direction, viewed from the upstream side in the sheet conveyance direction in the positive X direction. The carriage 34 is configured to be movable in the direction of arrow A3, and holds a color measurement sensor 40, which is a sensor that acquires data for color calibration. An example of the state after the carriage 34 has moved in the Y direction is illustrated by the area surrounded by a two-dot chain line 34a. A spectrophotometer is used as the color measurement sensor 40 that reads the image on the surface of the opposing sheet S, but a CCD, CMOS, or other sensor may also be used. Calibration is also performed by reading a white reference plate 46.

[0038] The carriage 34 includes a compression spring 41 as a biasing means, and gap maintaining members including a first roller member 42, a second roller member 43, a sleeve 45, and a spring stopper 39. The first guide member 37 is a metal rod with a shaft-like shape extending linearly in the Y direction. The first guide member may be, for example, a rail-like member formed by bending a metal plate into an L-shape or a cylindrical member. The sleeve 45 is movable integrally with the carriage 34 in the Y direction and engages with the carriage 34 so that the carriage 34 can slide and move while being guided in the Z direction. The first guide member 37 penetrates the sleeve 45, allowing for smooth sliding movement. The sleeve 45 also supports one seating surface of the compression spring 41, which absorbs the repulsive force in the Z direction. The other end of the compression spring 41 absorbs the repulsive force at a spring stopper 39 formed integrally with the carriage 34. With the above configuration, the repulsive force of the compression spring 41 biases the carriage 34 in the negative Z direction. The second guide member 44 is a member for guiding the movement of the carriage 34, and is an axial or rail-shaped member fixed to the color measurement unit 30, and is arranged parallel to the first guide member 37 as shown in Fig. 3, and is composed of an area 44a far from the sheet surface in the Z direction and areas 44b and 44c close to the sheet surface. Here, the heights of the guide surfaces, which are the surfaces of area 44b and area 44c that come into contact with the first roller member 42, are the same height in the Z direction from the sheet surface, and area 44a is configured to be higher by height Z1 shown in Fig. 3.

[0039] When the carriage 34 is in area 44a as shown in Figure 3, the first roller member 42 is biased by a spring force and abuts against area 44a of the second guide member 44. In this state, the carriage 34 is spaced apart from the sheet S, the second roller member 43 is not in contact with the sheet surface, and the spatial distance therebetween is Z2. Here, the relationship Z1 > Z2 holds. Hereinafter, this is referred to as the "first position" and "position 1."

[0040] When the carriage 34 is moved in the Y direction, the first roller member 42 moves along the slope that connects the region 44a of the second guide member 44 to the region 44b. As described above, because of the relationship Z1 > Z2, the second roller member 43 comes into contact with the sheet S due to the biasing force of the spring while moving along the slope. On the opposite side of the carriage 34 across the sheet S, a platen 38 having a support surface that supports the sheet is provided, and supports the backside of the sheet biased by the second roller member 43 of the carriage 34. In the position 34a shown in FIG. 3, the first roller member 42 is spaced apart from the region 44b of the second guide member 44. Hereinafter, this is referred to as the "second position" and "position 2."

[0041] When calibrating the colorimetric sensor 40, the carriage 34 is moved to the area 44c of the second guide member 44. The white reference plate 46 is at approximately the same height as the sheet surface, and the second roller member 43 comes into contact with the white reference plate. This position is outside the area of ​​the sheet in the Y direction, and is also the "standby position" where the carriage 34 is kept on standby when colorimetric measurement is not being performed, such as during printing.

[0042] As described above, the carriage 34 having the color measurement sensor 40 has three positions, "position 1," "position 2," and "standby position," whose distances from the sheet S differ in the Z direction.

[0043] 4, 5, 6, and 7 are diagrams illustrating the operation for acquiring data for color calibration drawn on sheet S, and are views of the sheet surface viewed in the minus Z direction from a direction perpendicular to the sheet surface. A test pattern 47 for color calibration and a reference mark 48 are recorded on sheet S. The sheet is transported in the direction of arrow A4, and reference mark 48 is recorded in the plus X direction of test pattern 47 and outside the area of ​​test pattern 47 in the Y direction.

[0044] To start colorimetry, the carriage 34 moves from the "standby position" described above to "position 2" shown in Figure 4. At position 2, the carriage 34 is separated from the sheet S and does not obstruct the transport of the sheet S. At position 2, the reference mark 48 recorded on the sheet being transported can be read, and when the reference mark 48 is detected, the position where the test pattern 47 is recorded is calculated from pre-programmed information to determine the reading start position. The transport of the sheet S is stopped at a position where the first row L1 of the test pattern 47 is on the scanning movement line of the colorimetric sensor 40.

[0045] 5 is a diagram illustrating the operation of reading the first row of test pattern 47. After conveyance of sheet S is stopped, carriage 34 is moved in the direction of arrow A5, and the Z direction position of carriage 34 relative to sheet S moves to the aforementioned "position 1" due to the configuration described in FIG. 3. Carriage 34 abuts on the sheet surface via second roller members 43, which rotate freely and move while rolling. Therefore, measurements can be performed with the distance between colorimetric sensor 40 and the sheet surface kept as constant as possible, enabling accurate measurements without variation in colorimetric results.

[0046] After scanning the first row of the test pattern 47, the carriage 34 continues to move in the Y direction and stops at the position shown in FIG. 6, where the second roller members 43 that contact the sheet have passed the sheet area and are no longer in contact with the sheet. Because the second roller members 43 and the sheet S are no longer in contact, the sheet S can be transported without resistance. The sheet S is transported in the direction of arrow A6 by one row of the test pattern 47 and then stops again. The above operation is the same when scanning in the positive Y direction, i.e., odd-numbered rows.

[0047] When scanning the second row of the test pattern 47, the carriage 34 is moved in the direction of arrow A7 shown in FIG. 7. After scanning the second row, the carriage 34 is moved to the position shown in FIG. 4, i.e., position 2. At position 2, the carriage 34 is spaced apart from the sheet S, so it is possible to transport the sheet. The above operation is the same when scanning in the minus Y direction, i.e., the even-numbered rows. After that, scanning of the third and subsequent rows of the test pattern 47 is a repetition of the steps shown in FIGS. 4 to 7. After scanning the final row is complete, the carriage 34 is moved to the standby position.

[0048] The series of color measurement operations explained in Figures 4 to 7 will be explained in a flowchart in Figure 8. This color measurement operation is performed when color calibration is required, such as before the start of a print job.

[0049] According to this embodiment, in an inkjet image forming apparatus equipped with a colorimetric sensor 40 that measures the color of an image on a sheet S, the colorimetric sensor 40 is capable of detecting both a reference mark 48 indicating the reference position for measurement and a test pattern 47 for colorimetric measurement, thereby enabling simplification of the apparatus and reduction in costs.

[0050] (Second embodiment) Next, a second embodiment will be described, in which a carriage 34 equipped with a colorimetric sensor 40 similar to that of the first embodiment is moved away from and brought into contact with a sheet by a means different from that of the first embodiment. Other components similar to those of the first embodiment will not be shown in the drawings or will be described with the same reference numerals in the drawings.

[0051] The characteristic configuration of this embodiment will be described below with reference to Figures 9, 10, 11, and 12. Figure 9 shows a state in which the carriage 34 is separated from the sheet S, Figure 10 shows a state in which the carriage 34 is biased against the sheet S, Figure 11 is a side view from the Y direction illustrating the carriage separation mechanism, and Figure 12 is a flowchart illustrating the operation.

[0052] In this embodiment, movement of the carriage 34 in the color measurement unit 60 in the Z direction, i.e., the movement of the carriage 34 toward and away from the sheet, is performed by rotating the motor 50. A rotating shaft 51 is connected to the motor 50, and rotation is controlled in the direction of arrow A8. The motor 50 is fixed to a frame (not shown) of the color measurement unit 60, and the rotating shaft 51 is rotatably held by a bearing. Two eccentric cams 52 are fixed to the rotating shaft 51 in the same phase. When the eccentric cams 52 rotate due to the rotation of the motor 50, the movable shaft 55 that it abuts moves up and down in the Z direction. The movable shaft 55 is a shaft-shaped member that guides movement of the carriage 34 in the Y direction and is engaged with the frame (not shown) of the color measurement unit 60 so that it can slide a predetermined amount only in the Z direction. The carriage 34 has a compression spring 41 as a biasing means, a roller member 43 as a gap maintaining member, a sleeve 45, and a spring stopper 39. When the movable shaft 55 moves in the Z direction due to the rotation of the eccentric cam 52, the movable shaft 55 biases the sliding member 56, and the carriage 34 moves in the Z direction while compressing the compression spring 41. As in the first embodiment, the carriage 34 is biased toward the seat surface by the action of the compression spring 41. The sliding member 56 is configured to slide smoothly relative to the movable shaft 55, so there is no impediment to the movement of the carriage 34 in the Y direction.

[0053] When transporting the sheet S, as shown in FIG. 9, the carriage 34 is held at "position 2," which is a "second position" separated from the sheet. At position 2, the carriage 34 is not in contact with the sheet surface and does not affect the transport of the sheet. At position 2, a space Z3 is created between the roller members 43 and the sheet surface. At position 2, the colorimetric sensor 40 moves to a Y-direction position where the reference mark 48 can be read, and detects the reference mark 48.

[0054] When calibrating the colorimetric sensor 40, the carriage 34 is moved to a position where the colorimetric sensor 40 faces the white reference plate 46. The eccentric cam 52 is rotated so that the carriage 34 is at position 1. The white reference plate 46 is at approximately the same height as the sheet surface, and the roller members 43 come into contact with the white reference plate. This position is outside the sheet area in the Y direction, and is also a "standby position" where the carriage 34 is kept on standby when colorimetric measurement is not being performed, such as during printing.

[0055] After detecting the reference mark 48, the conveyance of the sheet S is stopped at a position where the first row L1 of the test pattern 47 is on the scanning path of the colorimetric sensor 40, as in the first embodiment described with reference to FIG. 4. After the carriage 34 moves in the Y direction and arrives at the measurement start position of the test pattern 47, the motor 50 rotates to bring the carriage 34 into contact with the sheet S. The compression spring 41 of the carriage 34 applies pressure, causing the eccentric cam 52 to rotate and the movable shaft 55 to lower, moving the carriage 34 in the Z direction toward the sheet surface. FIG. 10 shows the "Position 1" state in which the roller member 43 contacts the sheet surface. On the opposite side of the carriage 34 across the sheet S, a platen 38 is provided with a support surface that supports the sheet S. This supports the sheet, which is biased by the roller member 43 of the carriage 34, from the backside. The sliding member 56 and the movable shaft 55 are separated, resulting in a clearance Z4. The relationship between Z3 and Z4 shown in FIG. 9 is configured so that Z3 > Z4.

[0056] The color measurement operation in this embodiment will be described below. After scanning one row in the Y direction shown in FIG. 5, the movement in the Y direction is stopped, and the motor 50 is rotated to move the carriage 34 away from the sheet surface. The position at which the movement in the Y direction is stopped may be a position where the sheet S and the carriage 34 overlap as viewed from the Z direction. In this embodiment, the carriage 34 can be moved away at any position in the Y direction, so there is no need to move it to a standby position outside the sheet area as in the first embodiment (FIG. 6). This makes it possible to shorten the length of the color measurement unit 30 in the Y direction, which in turn makes it possible to reduce the size of the image forming apparatus body.

[0057] FIG. 12 is a flowchart showing the color measurement operation in this embodiment described above.

[0058] In the configuration shown in this embodiment, as in the first embodiment, in an inkjet image forming apparatus equipped with a colorimetric sensor 40 that measures the color of an image on a sheet S, the colorimetric sensor 40 can detect both a reference mark 48 that indicates a measurement reference position and a colorimetric test pattern 47, thereby simplifying the apparatus and reducing costs. Furthermore, since the carriage 34 can be separated from the sheet at any position, it is possible to transport the sheet without retracting the carriage outside the sheet width area, thereby making it possible to reduce the size of the apparatus.

[0059] (Third embodiment) This embodiment will be described using FIGS. 13, 14, and 15. A rail member 54, which serves as a sheet contact member, is provided between the sheet S and the roller member 43. The rail member 54 is made of a thin resin or metal and extends across the entire Y-axis of the sheet. It also has a longitudinal slit 54a (window) in the center, as shown in FIG. 15, through which the colorimetric sensor 40 detects an image of the sheet surface. The rail member 54, a characteristic feature of this embodiment, can be applied to both the first and second embodiments. FIGS. 13 and 14 are views in the X-axis direction showing a configuration in which the rail member 54 has been added to the configuration of the first embodiment, and FIG. 15 is a cross-sectional view in the Y-axis direction showing a configuration in which the rail member 54 has been added to the configuration of the second embodiment. The rail member 54 is biased in the positive Z-axis direction by a compression spring 53. As shown in FIGS. 13 and 15, when the carriage 34 is in position 2, where it is spaced apart from the sheet S, the rail member 54 is also spaced apart from the sheet S due to the action of the compression spring 53. Therefore, the rail member 54 and the sheet S do not come into contact with each other when the sheet S is being conveyed. As shown in FIG. 14, when the carriage 34 is in position 1 and abuts against the sheet S, the biasing force of the compression spring 41 that biases the carriage 34 is set to be greater than the biasing force of the compression spring 53 that lifts the rail member 54. This causes the roller member 43 to abut against the rail member 54, and the rail member 54 abuts against the sheet surface. As shown in FIG. 15, the width of the roller member 43 is greater than the width of the slit 54a, and the roller member 43 rolls and moves on the rail member 54 when scanning in the Y direction. By including the rail member 54, even if the sheet surface is wavy or curled, the distance between the colorimetry unit 40 and the sheet surface can be maintained constant by pressing down on the sheet, thereby enabling accurate detection. The thickness of the rail member 54 is manufactured with high precision and does not affect the detection results of the colorimetry sensor 40.

[0060] In the configuration shown in this embodiment, the provision of the rail members 54 makes it possible to prevent the sheet from floating, thereby obtaining accurate color measurement results.

[0061] In the present invention, the colorimetric sensor that detects the density detection patches on the conveyed sheet also reads the position detection marks. The colorimetric sensor can move the distance from the sheet surface to at least two stages, and detects the patches and the position detection marks at both positions. [Explanation of symbols]

[0062] 1. Image forming device 6. Transport detection unit 7 Mark sensor section 8 Recording section 21 Control Unit 22 Recording head 23 Guide roller 30 color measurement units 31 conveying roller pair 32 conveying roller pair 34 Carriage 36 conveyor belt 40 Colorimetric Sensor 60 color measurement units

Claims

1. An image measuring device capable of measuring an image formed on a sheet and disposed opposite the conveyed sheet, a color measurement means including a sensor capable of detecting an image; The color measurement means has at least a first position and a second position where the distance from the sheet is different in a direction perpendicular to the sheet surface, a moving means for moving the device between the first position and the second position; a gap maintaining member for maintaining a constant gap between the sheet and the color measurement means; the color measurement means detects an image on a sheet at the first position and the second position; detecting a position reference image during sheet conveyance at the first position; detecting a color proof image while the sheet is stopped at the second position; 10. An image measuring device according to claim 9, wherein the distance between the color measurement means and the sheet surface at the second position is smaller than the distance between the color measurement means and the sheet surface at the first position.

2. 2. The image measuring device according to claim 1, wherein the gap holding member is a roller-shaped member that is freely rotatable in the direction of movement of the color measuring means.

3. 3. The image measuring device according to claim 1, wherein a measurement position for measuring the color calibration image is determined based on the position of the position reference image detected at the first position.

4. 4. The image measuring device according to claim 1, wherein the color measuring means has a biasing means that biases the sheet in a direction perpendicular to a sheet surface at the second position.

5. 5. The image measuring device according to claim 1, wherein the first position is a position where the gap retaining member is spaced apart from the sheet surface, and the second position is a position where the gap retaining member is in contact with the sheet surface.

6. 5. The image measuring device according to claim 1, wherein the first position is a position where the gap retaining member is spaced from the sheet surface, and the second position is a position where the gap retaining member is in contact with a sheet contact member that is in contact with the sheet surface.

7. 7. The image measuring device according to claim 1, further comprising a drive source and a drive force transmission means for enabling the color measurement means to move in a direction perpendicular to the sheet conveying direction and along the sheet surface at the second position.

8. 8. The image measuring device according to claim 7, further comprising a first guide member and a second guide member formed in the shape of an axis or a rail to guide the movement of the colorimetric means, wherein the first guide member and the second guide member both engage with or come into contact with the colorimetric means to guide the movement of the colorimetric means.

9. The image measuring device of claim 8, wherein the first guide member and the second guide member have guide surfaces for guiding the movement of the colorimetric means, and at least one of the first guide member and the second guide member is configured so that the height of the guide surface from the sheet surface is partially different in a direction perpendicular to the sheet surface.

10. The image measuring device of claim 8, wherein at least one of the first guide member and the second guide member is configured to be movable in a direction perpendicular to the sheet surface so that the distance from the sheet surface can be changed, and the image measuring device has a cam member that contacts the movably configured guide member, a rotation shaft that rotates the cam member, and a drive source that rotates the rotation shaft at a predetermined timing.

11. 11. The image measuring device according to claim 7, wherein, at the second position, the color measurement means moves back and forth in the sheet width direction, and the color calibration image is read one row at a time during each of the forward movement and the return movement.

12. 12. The image measuring device according to claim 11, wherein the color measurement means moves to the first position or a position where it does not come into contact with the sheet when the color measurement means transports the sheet to read the next row of the color proof image.

13. 13. The image measuring device according to claim 1, wherein the color measuring means is a spectrophotometer.

14. an image forming means for forming an image; a conveying unit that unwinds and conveys the rolled sheet; a support surface for supporting the seat; an image measuring device having a colorimetric sensor disposed opposite the sheet, which reads the patch image for color calibration and the mark for detecting the reference position recorded on the sheet by the image forming means; Within the image measuring device, the colorimetric sensor is configured to be movable between a first position spaced apart from a sheet surface and a second position where the colorimetric sensor is biased in a direction perpendicular to the sheet surface and abuts against the sheet surface or a member abutting against the sheet surface via a roller member, the color measurement sensor has a moving means that is movable in a direction perpendicular to a sheet conveying direction and along a sheet surface at the first position; determining a measurement position of the color calibration patch by detecting the reference position detection mark during sheet conveyance at the first position; an image forming apparatus, characterized in that, while the sheet transport is stopped at the second position, the color calibration patch is measured while moving in a direction perpendicular to the sheet transport direction and along the sheet surface, and the output image by the recording head is corrected.

15. 15. The image forming apparatus according to claim 14, wherein the image forming means is an ink-jet type having a recording head that ejects ink to record an image on a sheet.

16. 15. The image forming apparatus according to claim 14, wherein said image forming means is an electrophotographic system in which toner is developed on a photosensitive member, and an image is transferred and fixed onto a sheet.

Images