Image reading device, image forming device, and calibration support method

Abstract

To provide an image reading device that can reduce a frequency of execution of calibration and timely execute calibration when a change requiring it is detected.SOLUTION: An image reading device 1 comprises: an optical sensor 21 that scans an object to be read 70 placed on a contact glass 210 to acquire an image; a carriage 20 that carries the optical sensor 21 and moves in a sub-scanning direction; a reference scale 81 that is a reference for calculating dimensions on the basis of the image acquired by the optical sensor 21; calibration means that converts the dimensions of the image acquired by the optical sensor 21 into the actual dimensions; detection means that detects a change in movement characteristics when the carriage 20 moves; means that determines if the change in the movement characteristics of the carriage 20 is a change with time; and notification means that encourages a user to execute calibration on the basis of the determination.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an image reading apparatus, an image forming apparatus, and a calibration support method. [Background technology]

[0002] Image reading devices that optically read the shape of an object are known. The image reading device includes a mounting surface member such as glass and a scanning and acquiring unit that scans along the mounting surface to acquire image information of an object placed on the mounting surface. Known scanning and acquiring units include, for example, a scanning and acquiring unit that has a drive mechanism that moves a carriage holding an optical sensor along a guide rod or the like.

[0003] As an image reading device, one with sufficient reading accuracy that can also meet the demand for use as a measuring device has been proposed (see, for example, Patent Document 1).

[0004] Patent Document 1 discloses a calibration method for improving reading accuracy, in which a reference scale having graduations formed on a hard member is read by a flatbed scanner to obtain calibration data. It describes that by measuring the positional information of the image of the graduations in the read image of this reference scale, it is possible to accurately identify the correspondence between the distance in the read image and the distance on the placement surface. Summary of the Invention [Problem to be solved by the invention]

[0005] In the method of Patent Document 1, the image of the reference scale is acquired at a timing different from the timing when the image of the object to be read is read, and therefore there is a problem with the accuracy of measuring the dimensions of the object to be read from the image of the object to be read.

[0006] Furthermore, the carriage holding the optical sensor is supported so that it can slide on the guide rod, but because a gap is provided during the product design process, skew (tilt in the main scanning direction) is unavoidable, which poses the problem of making it difficult to accurately correct the amount of deviation of the reading range from the position of the reference scale.

[0007] To address this issue, a calibration method is being considered in which the amount of misalignment is obtained in advance using a separate correction means such as a plane gauge, and the amount of correction for the scanned image is calculated.Since the amount of carriage skew changes over time due to component wear and installation environment conditions, it is necessary to perform calibration periodically to maintain scanning accuracy. However, setting up a reference scale or a plane gauge each time calibration is performed makes the operation complicated and reduces workability.

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an image reading device that can reduce the frequency of calibration and can perform calibration at an appropriate time when a change requiring calibration is detected. [Means for solving the problem]

[0009] In order to solve the above problem, the image reading device of the present invention is characterized by comprising an optical sensor that scans an object to be read placed on a contact glass to obtain an image, a carriage that carries the optical sensor and moves in the sub-scanning direction, a reference scale that serves as a basis for calculating dimensions based on the image obtained by the optical sensor, a calibration means that converts the dimensions of the image obtained by the optical sensor into actual dimensions, a detection means that detects changes in the movement characteristics as the carriage moves, a means for determining whether the change in the movement characteristics of the carriage is due to time, and a notification means that prompts the user to perform calibration based on the determination. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an image reading device that can reduce the frequency of calibration and can perform calibration at an appropriate time when a change requiring calibration is detected. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram illustrating an example of a configuration of an image forming apparatus according to the present invention. [Figure 2] 1 is a perspective view showing an example of a configuration of an image forming apparatus according to the present invention; [Figure 3] 1 is an explanatory diagram of an optical system provided in a scanner unit as an embodiment of an image reading device according to the present invention. [Figure 4] 1 is a plan view showing an example of a configuration of an image reading device according to the present invention; [Figure 5] FIG. 5 is a schematic diagram of a cross section taken along the line AA in FIG. [Figure 6] FIG. 10 is an explanatory diagram of the skew of the scanner unit. [Figure 7] FIG. 4 is an explanatory diagram showing an example of a calibration execution state in the image reading device according to the present invention. [Figure 8] FIG. 10 is a schematic diagram of a read image of a main scanning direction reference scale. [Figure 9] 10 is a graph showing a change in length per pixel detected by a sub-scanning direction reference scale. [Figure 10] 10 is a graph showing the difference between the first and Nth times in the graph of FIG. 9. [Figure 11] 10 is a graph showing an example of a change detected when the amount of skew of the scanner unit changes. [Figure 12] 10 is a graph showing a change in length per pixel detected by a pair of sub-scanning direction reference scales. [Figure 13] 13 is a graph showing the difference between the first and Nth times in the graph of FIG. 12. [Figure 14] FIG. 2 is a block diagram showing an example of a hardware configuration of a control unit included in the image forming apparatus. [Figure 15]FIG. 2 is a functional block diagram illustrating an example of a functional configuration of the image forming apparatus. [Figure 16] 10 is a flowchart illustrating a calibration support method for determining whether to perform calibration of an image reading device. DETAILED DESCRIPTION OF THE INVENTION

[0012] The image reading device, image forming device, and calibration support method of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the following embodiments, and other modifications, additions, corrections, deletions, and other changes can be made within the scope of what a person skilled in the art can conceive. Any aspect is within the scope of the present invention as long as it achieves the functions and effects of the present invention.

[0013] FIG. 1 is a schematic diagram showing an example of the configuration of an image forming apparatus according to the present invention, and FIG. 2 is a perspective view showing an example of the configuration of an image forming apparatus according to the present invention.

[0014] The image forming apparatus 1 of this embodiment includes an image forming unit 100 as an image recording means, and an image reading unit 200 which is an image reading device according to the present invention as an image reading means. The image forming apparatus 1 also includes an operation panel 2 which is a notification means for displaying notifications to the user and which receives instructions and operations from the user.

[0015] The image forming unit 100 records (forms) an image on a recording material, namely, paper P. The image forming unit 100 of this embodiment is a tandem image forming apparatus in which image forming units 10 for each color, yellow (Y), magenta (M), cyan (C), and black (K), are arranged along the rotation direction of an intermediate transfer belt 31 serving as an intermediate transfer body. Each image forming unit 10 is equipped with a photosensitive member 11 serving as a latent image carrier.

[0016] Each image forming unit 10 also includes a charging device around the photoconductor 11 as charging means for uniformly charging the photoconductor surface to a predetermined potential. Each image forming unit 10 also includes an optical writing device around the photoconductor 11 as electrostatic latent image forming means for writing an electrostatic latent image on the photoconductor surface uniformly charged by the charging device by exposing the surface to light in accordance with image information. Each image forming unit 10 also includes a developing device around the photoconductor 11 as developing means for creating a toner image by developing the electrostatic latent image on the photoconductor by applying toner of each color (Y, M, C, K) to the electrostatic latent image on the photoconductor. Each image forming unit 10 also includes a primary transfer device around the photoconductor 11 as primary transfer means for transferring the toner image on the photoconductor to the intermediate transfer belt 31. Each image forming unit 10 also includes a cleaning device around the photoconductor 11 as cleaning means for removing residual toner from the photoconductor.

[0017] The color toner images formed on the photoconductors 11 are primarily transferred onto the intermediate transfer belt 31 by the primary transfer device so as to be superimposed on each other, forming color toner images on the intermediate transfer belt 31. The color toner images on the intermediate transfer belt 31 are transported to an opposing area (secondary transfer area) to the secondary transfer device 30 as the intermediate transfer belt 31 rotates.

[0018] Meanwhile, below the image forming unit 100, a paper feed unit 60 is provided as a feed unit that feeds paper P. In this embodiment, the paper feed unit 60 is composed of two paper feed trays 61a and 61b, but the number of paper feed trays is not limited to this. The paper feed unit 60 feeds paper P one sheet at a time using a pickup roller 62 from one of the paper feed trays 61a and 61b selected in accordance with an instruction from the control unit 150 of the image forming unit 100. Then, the paper P is transported to the secondary transfer area by a transport roller pair 63 along a transport path indicated by a dashed line in the figure.

[0019] The color toner image on the intermediate transfer belt 31 is secondarily transferred by the secondary transfer device 30 onto a sheet of paper P, which is conveyed by a pair of conveying rollers 63 at a predetermined timing in the secondary transfer region. The sheet of paper P on which the color toner image has been formed is then conveyed to a fixing device 40 as a fixing means, where the color toner image is fixed onto the sheet of paper P by the action of heat and pressure. After the fixing, the sheet of paper P is conveyed along a conveyance path indicated by a dashed line in the figure, and is discharged onto a sheet discharge tray 50 as a discharge section.

[0020] The image reading unit 200 is provided with a pressure plate 202 that can be opened and closed relative to the contact glass 201 and serves as a pressing member that presses the object 70 to be read that is placed on the contact glass 201 against the upper surface of the contact glass 201. The pressure plate 202 is supported by a hinge 203 so that it can be opened and closed. When acquiring image information of the object 70 to be read, the object 70 to be read is set on the contact glass 201, the pressure plate 202 is closed, and the reading operation is performed.

[0021] The image reading unit 200 includes an optical sensor that scans the object 70 to obtain an image, and a carriage 20 that moves in the sub-scanning direction and that has an optical sensor 21 (see FIG. 3) mounted thereon. The optical sensor 21 is an image sensor that irradiates light onto the object 70 to be read placed on the contact glass 201 and acquires an optical image based on the reflected light. The carriage 20 moves from the home position 20a in the sub-scanning direction indicated by the arrow D in the figure so that the optical sensor 21 scans the object 70 to be read.

[0022] The optical sensors 21 are arranged in a line in the main scanning direction, which is perpendicular to the sub-scanning direction as the direction in which the carriage 20 moves. The image reading unit 200 is configured to acquire the entire object 70 as an image by scanning the object 70 while moving the line serving as the reading position of the optical sensor 21 in the sub-scanning direction. The image reading unit 200 also includes an ADF that conveys a sheet-like object to be read.

[0023] Fig. 3 is a diagram showing an overview of the optical system mounted on the carriage 20. As shown in Fig. 3, light from a light source mounted on the carriage 20 is reflected by the reading object 70, and the reflected light enters the reduction optical system via optical path h and is reflected by the first mirror 23a. Note that the light source is not shown in Fig. 3. The light reflected by the first mirror 23a is reflected by the second mirror 23b, the third mirror 23c, the fourth mirror 23d, the fifth mirror 23e, and the sixth mirror 23f, passes through the reflecting lens 22, and enters the optical sensor 21. The optical sensor 21 is, for example, a CCD sensor.

[0024] Based on the light detected by the optical sensor 21, the image of the object 70 to be read is converted into an electrical signal and subjected to predetermined processing in the control unit 150. In this way, image data of the object 70 to be read is generated.

[0025] Fig. 14 is a block diagram showing an example of the hardware configuration of a control unit 150 included in an image forming apparatus. As shown in Fig. 14, the image forming apparatus of this embodiment includes a configuration similar to that of a general server or a personal computer (PC). That is, a central processing unit (CPU) 310, a random access memory (RAM) 320, a read only memory (ROM) 330, a hard disk drive (HDD) 340, and an interface (I / F) 350 are connected via a bus 390, and a display unit 360, an operation unit 370, and a dedicated device 380 are connected to the I / F 350. The dedicated device 380 includes an image forming unit 100 and an image reading unit (image reading device) 200.

[0026] The CPU 310 is a computing unit that controls the overall operation of the image forming apparatus. The RAM 320 is a volatile storage medium that allows high-speed reading and writing of information and is used as a work area when the CPU 310 processes information. The ROM 330 is a read-only nonvolatile storage medium that stores programs such as firmware. The HDD 340 is a nonvolatile storage medium that allows reading and writing of information and stores an OS (Operating System), various control programs such as an applied voltage control program, application programs, etc.

[0027] The I / F 350 connects and controls various hardware, networks, etc. to the bus 390. The display unit 360 is a visual user interface that allows the user to check the status of the image forming apparatus 1 including the image reading unit 200, which is an image reading device, and is realized by a display device such as an LCD (Liquid Crystal Display). The operation unit 370 is a user interface that allows a user to input information to the image forming apparatus 1. The functions of the operation unit 370 and the display unit 360 may be realized by the same member, for example, the operation panel 2 shown in FIG. The dedicated device 380 includes an image forming unit 100 and an image reading unit 200 .

[0028] In such a hardware configuration, a software control unit is configured by reading a program stored in a storage medium such as ROM 330, HDD 340, or an optical disk (not shown) into RAM 320, and having CPU 310 perform calculations in accordance with the program loaded into RAM 320. The combination of the software control unit configured in this way and hardware configures a functional block that realizes the functions of image forming apparatus 1 according to this embodiment.

[0029] Fig. 15 is a functional block diagram showing an example of the functional configuration of an image forming apparatus, in which electrical connections are indicated by solid arrows and the flow of paper or document stacks is indicated by dashed arrows. 15 , the image forming apparatus 1 according to this embodiment includes a control unit 150, a paper feed table 96, a print engine 95, a paper output tray 50, an ADF (Auto Document Feeder) 93, a scanner engine 92, a scanning paper output tray 91, an operation panel 2, and a network I / F 97. The control unit 150 also includes a main control unit 151, an engine control unit 152, an image processing unit 153, an operation display control unit 154, and an input / output control unit 155.

[0030] The paper feed table 96 feeds transfer paper to the print engine 95, which is an image forming unit. The print engine 95 is an image forming unit that forms and outputs an image on the paper conveyed from the paper feed table 96. A specific embodiment of the print engine 95 is an electrophotographic image forming mechanism, which corresponds to the image forming unit indicated by reference numeral 100 in FIG. 1. The paper on which the image has been formed by this print engine 95 is discharged to the paper discharge tray 50. The print engine 95 is realized by a dedicated device 380 shown in FIG. 14.

[0031] The ADF 93 automatically transports a sheet-like object to a position where it can be read by the scanner engine 92, which executes the main processing in the image reading device. The scanner engine 92 is a document reading unit that includes a photoelectric conversion element that converts optical information into an electrical signal, and optically scans and reads a document that has been automatically transported by the ADF 93 or an object to be read that has been placed on the contact glass 201, to generate image information. The document is automatically conveyed by the ADF 93 and read by the scanner engine 92, and then discharged onto a scanning paper discharge tray 91. The ADF 93 and the scanner engine 92 are realized by a dedicated device 380 shown in FIG.

[0032] The operation panel 2 is an output interface that visually displays the status of the image forming apparatus or image reading apparatus, and also serves as an input interface when the user directly operates the image forming apparatus or image reading apparatus or inputs information as a touch panel. In other words, the operation panel 2 has a function to display images for receiving operations by the user. The operation panel 2 is realized by a display unit 360 and an operation unit 370 shown in FIG. 14.

[0033] The network I / F 97 is an interface that enables the image forming apparatus 1 to communicate with other devices, such as an administrator terminal or a PC (Personal Computer), via a network. The image forming apparatus 1 according to this embodiment receives various control commands from the terminal connected via the network I / F 97. The network I / F 97 is realized by the I / F 350 shown in FIG. 14.

[0034] Control unit 150 is configured by a combination of software and hardware. Specifically, control programs such as firmware stored in nonvolatile storage media such as ROM 330 and HDD 340 are loaded into RAM 320, and control unit 150 is configured by software control configured by CPU 310 performing calculations in accordance with those programs and hardware such as integrated circuits.

[0035] The main control unit 151 controls each unit included in the control unit 150 and issues commands to each unit of the control unit 150. The main control unit 151 also controls the input / output control unit 155 and accesses other devices via the network I / F 97 and the network. The engine control unit 152 controls or drives the drive units such as the print engine 95 and the scanner engine 92.

[0036] Image processing unit 153 generates drawing information as output information based on image information described in PDL (Page Description Language) or the like, for example, document data or image data included in an input print job, under the control of main control unit 151. This drawing information is information such as CMYK bitmap data, and is information used by print engine 95, which is an image forming unit, to draw an image to be formed in an image forming operation. Furthermore, the image processing unit 153 processes information input from the scanner engine 92 to generate image data. This image data is information that is stored in the image forming apparatus 1 as a result of the scanner operation or is transmitted to another device via the network I / F 97 and the network.

[0037] An operation display control unit 154 displays information on the operation panel 2 or notifies the main control unit 151 of information input via the operation panel 2. An input / output control unit 155 inputs signals and commands input via the network I / F 97 and the network to the main control unit 151.

[0038] The calibration in the image reading device according to the present invention will be described below. The image reading device 200 of the present invention comprises an optical sensor 21 that scans a reading object 70 placed on a contact glass 201 to acquire an image, a carriage 20 that is mounted with the optical sensor 21 and moves in the sub-scanning direction, a reference scale that serves as a basis for calculating dimensions based on the image acquired by the optical sensor 21, a calibration means that converts the dimensions of the image acquired by the optical sensor 21 into actual dimensions, a detection means that detects changes in the movement characteristics as the carriage 20 moves in the sub-scanning direction, a means that determines whether the change in the movement characteristics of the carriage 20 is due to time, and a notification means that prompts the user to perform calibration based on the determination. The functions of the calibration means, detection means, judgment means, and notification means are realized by the control unit 150 (image processing unit 153, main control unit 151, and operation display control unit 154) of the image forming apparatus shown in Figures 1, 14, and 15.

[0039] 4 and 6 are plan views showing an example of the configuration of an image reading device according to the present invention, and FIG. 5 is a schematic view of the cross section AA in FIG. FIG. 4 shows the carriage 20 in the home position. The image reading device includes a motor 27 that is the drive source for the carriage 20, a timing pulley 28 attached to the motor shaft, a timing belt 26, and a guide rod 24. The carriage 20 moves along the guide rod 24 in the sub-scanning direction indicated by arrow D in the figure.

[0040] As shown in FIG. 5, the carriage 20 also has a sliding member 25 that slides on the guide rod 24, and a fixed portion 29 that holds the timing belt 26. The carriage 20 is supported by a sliding member 25 so that it can slide on the guide rod 24, but as shown in Figure 5, a gap G occurs between the sliding member 25 and the guide rod 24 due to processing in the product design. And because it is separated from the fixing part 29 that fixes the timing belt 26, it is inevitable that a skew (inclination in the main scanning direction) will occur in the rotation direction of the pulling direction of the timing belt 26. The gap G increases over time due to wear and tear, and as a result, the amount of skew of the carriage 20 also increases over time.

[0041] FIG. 6 is a diagram showing a schematic diagram of a state in which the carriage 20 is skewed. For example, if the guide rod 24 is installed not in the center of the main scanning direction but closer to one end in the main scanning direction, the skew amount S of the carriage 20 increases toward the end in the main scanning direction as shown in FIG. 6 (S1 <S2)。

[0042] The amount of skew of the carriage 20 changes over time due to wear of the sliding members 25 and other factors, the installation environment, and other conditions, so calibration must be performed periodically to maintain reading accuracy. An example of calibration is shown in Fig. 7. Fig. 7 is a plan view showing a state in which a correction value is calculated using a reference scale 81 and a flat gauge 82 in an image reading device.

[0043] The reference scale 81 is a component that places a "scale" that functions as a dimensional measurement standard on the reading surface of the contact glass. As shown in Figure 7, a reference position 83 for placing an object to be read on the contact glass is also shown. The reference scale 81 is positioned outside the range in which the optical sensor 21 scans the object to be read and acquires an image, but inside the maximum range in which the carriage 20 can move, and has a main scanning reference scale 81a arranged along the main scanning direction, and one or more sub-scanning reference scales 81b arranged along the sub-scanning direction. In the example of FIG. 7, a pair (two) of sub-scanning reference scales 81b are provided facing each other on both ends in the main scanning direction, but it may also be possible to provide one only on one end in the main scanning direction.

[0044] The reference scale 81 is used to calibrate the optical sensor 21, and therefore needs to have a scale on its underside (the carriage 20 side). On the other hand, placing the reference scale 81 on the upper side of the contact glass (the surface on which the object to be read is placed) improves the accuracy of the calibration of reading by the optical sensor 21. The reference scale 81 may be placed on both the upper and lower sides of the contact glass. Placing the reference scale 81 on both sides allows the user to visually recognize the position of the reference scale 81, and also allows the optical sensor 21, which faces upward from the lower side of the contact glass, to simultaneously acquire images of the reference scale 81 and the object to be read.

[0045] It is desirable that the surface of the reference scale 81 located on the carriage 20 side have a different color for displaying the scale and the color of the part where the scale is formed, so as not to reflect light from the light source mounted on the carriage 20. For example, the lines that display the scale can be made white by polishing the stainless steel, and the contrast of the lines in the image can be enhanced to make them easier to identify. Even if the material of the reference scale 81 is SUS and the scale is formed in black, no problem occurs in the process of acquiring an image simultaneously with the object to be read.

[0046] It should be noted that there is a tendency for positional deviation to be greater in the movement direction of the carriage 20 (sub-scanning direction) than in the optical direction (main scanning direction) in which the optical sensor 21 mounted on the carriage 20 optically reads the object to be read. Therefore, in order to improve measurement accuracy, the scale intervals of the sub-scanning direction scale 81b can be made narrower (finer) than the scale intervals of the main scanning direction scale 81a.

[0047] As mentioned above, the amount of skew of the carriage 20 changes over time, so accurate dimensions cannot be obtained using only the information from the reference scale 81. Therefore, it is necessary to perform periodic calibration using a flat gauge 82 that has scales in the main scanning direction and the sub-scanning direction (X / Y directions). As shown in FIG. 7, by using the flat gauge 82, for example, it is possible to obtain lengths X1 to X4 in the sub-scanning direction and lengths Y1 to Y3 in the main scanning direction. Then, the length X in the sub-scanning direction of the reference scale is compared with the obtained lengths X1 to X4, and the difference is stored as the correction amount. Similarly, the length Y in the main scanning direction of the reference scale is compared with the obtained lengths Y1 to Y3, and the difference is stored as the correction amount.

[0048] The reference scale 81 is permanently installed, but the flat gauge 82 must be set up each time calibration is performed. Installing a flat gauge complicates operation and reduces workability, so it is preferable to reduce the frequency at which calibration is performed and to allow it to be performed in a timely manner only when a change requiring calibration is detected. Therefore, the image reading device of this embodiment determines whether the change in the movement characteristics when the carriage 20 moves in the sub-scanning direction is due to time or is temporary due to vibration of the device, etc., and notifies the user to perform calibration based on the determination result. Specifically, if it is determined that the change in the movement characteristics of the carriage 20 is due to time, the notification means notifies the user to perform calibration, and if it is determined that the change in the movement characteristics of the carriage 20 is not due to time, the image is acquired again.

[0049] FIG. 16 is a flowchart showing a calibration support method for determining whether calibration should be performed in the image reading device of this embodiment. First, the pressure plate 202 is opened (S001) in order to place the object 70 to be read on the placement surface of the contact glass 201. The pressure plate 202 includes the ADF 93, and is a member that covers the contact glass 201 to hold the object 70 when it is placed on the contact glass 201. Next, the object to be read 70 is placed on the placement surface of the contact glass 201 (S002).

[0050] Next, an instruction to start the reading process is given from the operation panel 2 (S003), and the reading process starts. After the reading starts, the carriage 20 starts to operate, and as the carriage 20 moves, the optical sensor 21 simultaneously acquires images of the object 70 to be read and the reference scale 81, and stores the images in a storage area.

[0051] Next, the portion of the image of the reference scale 81 contained in the acquired image is identified and compared with a previously acquired image of the reference scale, for example, an image of the reference scale 81 acquired during the previous calibration run, and the difference is detected as a change in the movement characteristics of the carriage 20 (S004). A change in the movement characteristics of the carriage 20 can be detected as a change in the amount of skew when the carriage 20 moves in the sub-scanning direction, or as a change in the movement speed of the carriage when the carriage moves in the sub-scanning direction.

[0052] If it is determined that there is a change in the movement characteristics of the carriage 20 (S005), it is determined whether this is a change over time (S006). If it is determined that the change in the movement characteristics of the carriage 20 is a change over time, the notification means notifies the user to perform calibration (S007), and if it is determined that the change in the movement characteristics of the carriage 20 is not a change over time, the process returns to step S004 and an image is acquired again. If it is determined in step S005 that there is no change in the movement characteristics of the carriage 20, the process ends without any notification.

[0053] In the image reading device of this embodiment, changes in the movement characteristics of the carriage 20 can be detected based on the inclination of the image of the acquired main-scanning reference scale 81a or the length per pixel of the image of the acquired sub-scanning reference scale 81b. The change in the movement characteristics of the carriage 20 is, for example, a change in the amount of skew when the carriage 20 moves in the sub-scanning direction, or a change in the movement speed when the carriage moves in the sub-scanning direction.

[0054] To detect the movement characteristics of the carriage 20, an image of the reference scale 81 is acquired and saved when an image of the object 70 to be read is acquired, and the newly acquired image of the reference scale 81 is compared with the image of the reference scale 81 acquired during the previous calibration, and the difference is detected as a change in the movement characteristics of the carriage 20.

[0055] As a method for determining whether the change in the movement characteristics of the carriage 20 has occurred over time, for example, a threshold value can be set for the difference obtained by comparing a newly acquired image of the reference scale 81 with the image of the reference scale 81 acquired during the previous calibration, and when that difference exceeds the threshold value at least two consecutive times, it can be determined that the change in the movement characteristics of the carriage 20 has occurred over time.

[0056] In addition, a threshold value is set for the difference obtained by comparing the newly acquired image 81 of the reference scale with the image of the reference scale 81 acquired during the previous calibration, and when the threshold value is exceeded continuously within a predetermined range in the sub-scanning direction, it can be determined that the change in the movement characteristics of the carriage 20 is over time.

[0057] A specific example of determining whether the change in the movement characteristics of the carriage 20 is due to time will be described below.

[0058] (First embodiment) A method for detecting a change in the movement characteristics of the carriage 20 based on the inclination of the acquired image 810 of the main scanning reference scale 81a will be described. The method of this embodiment compares a newly acquired image of the main scanning reference scale 81a with the image of the main scanning reference scale 81a acquired during the previous calibration, and detects the difference as a change in the movement characteristics of the carriage 20. The change in the movement characteristics of the carriage 20 can be detected as a change in the amount of skew when the carriage 20 moves in the sub-scanning direction.

[0059] 8A and 8B are diagrams showing schematic representations of scanned images of the main scanning direction reference scale 81a, with FIG. 8A showing a scanned image 810 obtained during calibration and FIG. 8B showing a newly acquired image 811. In this embodiment, the tilt amounts of scanned image 810 in FIG. 8A and scanned image 811 in FIG. 8B are compared to obtain the difference. A threshold is set for the difference, and if a change in the tilt amount exceeds the threshold, it is determined that the movement characteristics of the carriage 20 have changed. If the difference exceeds the threshold at least two times in a row, it can be determined that the change in the movement characteristics of the carriage 20 has occurred over time.

[0060] In addition, by saving the amount of tilt of the image of the main scanning reference scale 81a and comparing it with the amount of tilt of the previous image when a new image of the main scanning reference scale 81a is acquired, it is possible to determine whether the change in the amount of skew is temporary or has occurred over time. If the skew amount is gradually changing, it is likely that this is a change over time due to wear of the drive components, etc., so the user is prompted to perform calibration. On the other hand, if the change in skew amount is sudden and not continuous, it is likely that this is not a change over time, so the image is read again.

[0061] (Second embodiment) A method for detecting a change in the movement characteristics of the carriage 20 based on the length per pixel of the acquired image of the sub-scanning reference scale 81b will be described. The method of this embodiment compares the length per pixel of the newly acquired image 81b of the sub-scanning reference scale with the length per pixel of the image of the sub-scanning reference scale 81b acquired during the previous calibration run, and detects the difference as a change in the movement characteristics of the carriage 20. The change in the movement characteristics of the carriage 20 can be detected as a change in the amount of skew when the carriage 20 moves in the sub-scanning direction.

[0062] In the first embodiment described above, only changes in the area on one end side of the sub-scanning side where the main-scanning reference scale 81a is arranged can be detected, but according to this embodiment, changes can be widely detected across the entire area where the sub-scanning reference scale 81b is arranged.

[0063] 9 is a graph showing the change in length per pixel detected by the sub-scanning direction reference scale 81b, plotting data obtained from scanned images at different times. The vertical axis of the graph represents pixel length, and the horizontal axis represents position in the sub-scanning direction. The thin solid line in the graph represents data from the first scan (e.g., the previous time calibration was performed), and the solid line represents data from the Nth (N>1) scan (e.g., data from any scan after calibration was performed). FIG. 10 is a graph of the difference between the first and Nth measurements in FIG. 9, and the vertical and horizontal axes of the graph have the same ranges as those in FIG. The graph in Fig. 10 shows a pattern in which the change in pixel length falls within a narrow, fixed range between L1 and L2. In the example of Fig. 10, if the lower threshold of the difference is set to L1 and the upper threshold is set to L2, the change in pixel length does not exceed the threshold, and it is not determined that the change in the movement characteristics of the carriage 20, i.e., the change in the amount of skew when the carriage 20 moves in the sub-scanning direction, is due to time.

[0064] In addition, by detecting the difference between the image dimensions and the actual dimensions of the image acquired during calibration and the image acquired during subsequent image reading, and comparing the two, changes in the carriage movement characteristics can be detected. In this case, too, a predetermined threshold is used, and if the difference exceeds the threshold, it is determined whether the carriage movement characteristics are time-dependent.

[0065] FIG. 11 shows an example of a graph in which a change in the movement characteristics of the carriage 20, that is, a change in the amount of skew when the carriage 20 moves in the sub-scanning direction, is observed and the change is determined to be over time. In the case of a change over time due to wear of the drive member or the like, an overall change in length is detected as shown in Figure 11. In the example of Figure 11, if the lower threshold value of the difference is L1 and the upper threshold value is L2, the difference exceeds threshold value L2 continuously within a predetermined range in the sub-scanning direction, so it is determined that the change in the movement characteristics of the carriage 20 has occurred over time. On the other hand, a temporary change due to vibration of the device or the like will result in a graph showing fluctuations where only a part of the image suddenly exceeds the threshold. In this case, the image will need to be acquired again.

[0066] (Third embodiment) As in the example of FIG. 7, it is preferable that a pair of sub-scanning reference scales 81b are provided at both ends in the main scanning direction. For example, when the guide rod 24 is installed not at the center in the main scanning direction but closer to one end in the main scanning direction, as shown in FIG. 6, the skew amount S of the carriage 20 increases as it goes toward the end side in the main scanning direction (S1 < S2). Therefore, depending on the method of setting the threshold value that serves as a reference for detecting changes in the skew amount as a movement characteristic, there are cases where the change cannot be detected, or a notification prompting the execution of calibration is issued even though calibration is not originally necessary. As in the present embodiment, by detecting changes using two sub-scanning reference scales 81b, changes in the movement characteristics of the carriage 20 can be detected more accurately.

[0067] A method for detecting changes in the movement characteristics of the carriage 20 based on the length per pixel of the images of a pair (two) of acquired sub-scanning reference scales 81b will be described. Changes can also be detected using the images acquired for each of the two sub-scanning reference scales 81b, but the stored data will be doubled. Therefore, by using the difference in the length per pixel obtained from the image of one sub-scanning reference scale 81b and the image of the other sub-scanning reference scale 81b as the data to be stored, an increase in the data volume can be suppressed.

[0068] FIG. 12 is a graph showing changes in the difference in the length per pixel detected by a pair of sub-scanning direction reference scales, and is a plot of data obtained from read images at different timings. The vertical axis of the graph represents the length of the pixel, the horizontal axis represents the position in the sub-scanning direction, the thin solid line in the graph represents the data at the first scan (for example, at the time of the previous calibration execution), and the solid line represents the data at the Nth scan (N > 1) (for example, data at an arbitrary read time after the calibration is performed). FIG. 13 is a graph of the differences at the first and Nth times in FIG. 12, and the vertical and horizontal axes of the graph are in the same range as in FIG. 12. The graph in Figure 13 shows that the change in pixel length is within a certain range and does not exceed a predetermined threshold, so the change in the movement characteristics of the carriage 20, i.e., the change in the amount of skew when the carriage 20 moves in the sub-scanning direction, is not judged to be over time.

[0069] The processes exemplified in the first to third embodiments are realized by calculation processes executable by the main control unit 151 and image processing unit 153 of the control unit 150. In the above processes, the image processing unit 153 executes a process for identifying each image portion of the simultaneously acquired images of the object to be read 70 and the reference scale 81. The result of this process is passed to the main control unit 151, and the information required to calculate the dimensions of the object to be read 70 is collected, so the main control unit 151 executes a dimension calculation process. That is, the functional block including the main control unit 151 and the image processing unit 153 constitutes a dimension calculation unit.

[0070] The image reading device 200 can simultaneously acquire images of the object to be read 70 and the reference scale 81 by using a carriage 20 equipped with an optical sensor 21 below the contact glass 201. To enable this simultaneous acquisition, the reference scale 81 is positioned so that the reading (measurement) range when the object to be read 70 is a three-dimensional object can be set to a range different from the area when the object to be read is flat.

[0071] For example, the maximum read length of the read object 70 is set to 297 mm in the main scanning direction and 420 mm in the sub-scanning direction. The maximum range within which the carriage 20 can move and which can be read by the optical sensor 21 is set to 306 mm in the main scanning direction and 435 mm in the sub-scanning direction. Then, the reference scale 81 is placed at a position outside the maximum read length and inside the maximum readable range in both the main scanning direction and the sub-scanning direction. With this configuration, an image of the reference scale 81 and an image of the object 70 to be read can be acquired simultaneously, thereby significantly improving the accuracy of dimension measurement.

[0072] The image reading device and calibration support method according to the present invention reduce the frequency of calibration of the image reading device and can perform calibration in a timely manner when a change requiring calibration is detected. Furthermore, since the image forming device according to the present invention is equipped with the image reading device according to the present invention, the frequency of performing complicated calibration operations is reduced, and a decrease in workability can be suppressed. [Explanation of symbols]

[0073] 1. Image forming device 20 carriages 21 Optical Sensor 24 Guide rod 25 Sliding member 26 Timing belt 29 Fixed part 70 Reading object 81 Reference Scale 81a Main scanning reference scale 81b Sub-scanning reference scale 100 Image forming unit 150 control section 200 Image reader 201 Contact Glass 202 Pressure Plate [Prior art documents] [Patent documents]

[0074] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-203386

Claims

1. An image reading device comprising: an optical sensor that scans an object to be read placed on a contact glass to obtain an image; a carriage that carries the optical sensor and moves in a sub-scanning direction; a reference scale that serves as a basis for calculating dimensions based on the image obtained by the optical sensor; a calibration means that converts the dimensions of the image obtained by the optical sensor into actual dimensions; a detection means that detects changes in the movement characteristics as the carriage moves; a means that determines whether the change in the movement characteristics of the carriage is due to time; and a notification means that prompts a user to perform calibration based on the determination.

2. When it is determined that the change in the carriage movement characteristics is due to time, the notification means notifies the user to perform calibration; 2. The image reading device according to claim 1, wherein when it is determined that the change in the carriage movement characteristics is not due to aging, the image is acquired again.

3. the reference scale is disposed outside a range in which the optical sensor scans the object to be read and acquires an image, and inside a maximum range in which the carriage can move; 3. The image reading device according to claim 1, further comprising a main scanning reference scale arranged along the main scanning direction, and one or more sub-scanning reference scales arranged along the sub-scanning direction.

4. 4. The image reading device according to claim 3, wherein a change in the movement characteristics of the carriage is detected based on the inclination of the image of the main scanning reference scale acquired or the length per pixel of the image of the sub scanning reference scale acquired.

5. 5. An image reading device according to claim 1, wherein the change in the carriage movement characteristics is either a change in the amount of skew when the carriage moves in the sub-scanning direction, or a change in the carriage movement speed when the carriage moves in the sub-scanning direction.

6. An image reading device as described in any one of claims 1 to 5, characterized in that an image of the reference scale is acquired and saved when an image of the object to be read is acquired, the newly acquired image of the reference scale is compared with the previously acquired image of the reference scale, and the difference is detected as a change in the movement characteristics of the carriage.

7. 7. The image reading device according to claim 6, wherein a threshold value is set for the difference, and when the difference exceeds the threshold value at least twice consecutively, it is determined that the change in the carriage movement characteristics is due to time.

8. 7. The image reading device according to claim 6, wherein a threshold value is set for the difference, and when the threshold value is exceeded continuously within a predetermined range in the sub-scanning direction, it is determined that the change in the movement characteristics of the carriage is due to time.

9. An image forming apparatus comprising the image reading device according to any one of claims 1 to 8.

10. A calibration support method for an image reading device comprising: an optical sensor that scans an object placed on a contact glass to acquire an image; a carriage that carries the optical sensor and moves in a sub-scanning direction; a reference scale that serves as a reference for calculating dimensions based on the image acquired by the optical sensor; a calibration means that converts the dimensions of the image acquired by the optical sensor into actual dimensions; a detection means that detects changes in movement characteristics when the carriage moves; a means that determines whether the change in movement characteristics of the carriage is due to time; and a notification means, When it is determined that the change in the carriage movement characteristics is due to time, the notification means notifies the user to perform calibration; A calibration support method characterized in that, when it is determined that the change in the carriage movement characteristics is not due to time, the image is acquired again.

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