Reading device and control method

Abstract

To facilitate relatively easily, a change of reading resolution while correcting errors of a conveying roller.SOLUTION: A reading device includes a conveyance roller for conveying a medium, reading means for reading an image of the medium conveyed by the conveyance roller, detection means for detecting a rotation phase of the conveyance roller, storage means that corresponds to the rotation phase of the conveyance roller and stores an index value corresponding to the amount conveyed by the conveyance roller per a unit angle of rotation, and timing control means for selecting the index value on the basis of the detection result of the detection means and controlling reading timing of the reading means on the basis of a result of a comparison between a cumulative value of the index values and a threshold value corresponding to the reading resolution.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a reading device and a control method. [Background technology]

[0002] There is known a reading device that reads an image on a sheet-like document while transporting the document. In such a reading device, for example, an encoder detects the rotation of a transport roller that transports the document. Then, the timing of reading by a reading element such as a CCD sensor or a CIS is controlled based on the detection result according to the reading resolution. Meanwhile, the transport roller has a diameter error and eccentricity. Therefore, the amount of document transport per unit pulse period of the encoder varies, which causes distortion of the read image. Patent Document 1 discloses a recording device that focuses on the influence of the diameter error and eccentricity of the transport roller on the detection signal of the encoder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-839 A Summary of the Invention [Problem to be solved by the invention]

[0004] It is necessary for a reading device to be able to change the resolution of the read image. It is possible to reduce the resolution of an image read at a fixed resolution by post-processing such as image thinning or averaging. However, it is necessary to read an image at a fixed resolution, and it is also necessary to store the data of the read image.

[0005] The present invention provides a technique that allows the reading resolution to be changed relatively easily while correcting errors in the transport roller. [Means for solving the problem]

[0006] According to the present invention, A conveying roller for conveying the medium; a reading unit for reading an image on the medium conveyed by the conveying roller; A detection means for detecting a rotation phase of the conveying roller; a storage means for storing an index value corresponding to a rotational phase of the transport roller and corresponding to a transport amount of the transport roller per unit rotation angle; a timing control means for selecting the index value based on the detection result of the detection means, and for controlling the reading timing of the reading means based on a comparison result between an accumulated value of the index value and a threshold value corresponding to a reading resolution. A reading device is provided, characterized in that Effect of the Invention

[0007] According to the present invention, it is possible to provide a technique that allows the reading resolution to be changed relatively easily while correcting the error of the transport roller. [Brief description of the drawings]

[0008] [Figure 1] 1A is a side view of a reading device according to an embodiment of the present invention, and FIG. [Diagram 2] (A) is an explanatory diagram of the detection unit, and (B) is an explanatory diagram of the phase region. [Diagram 3] FIG. [Figure 4] FIG. [Diagram 5] FIG. 1A is an explanatory diagram of a calibration chart, and FIG. 1B is a diagram showing an example of the chart reading results. [Figure 6] 13A and 13B are diagrams showing examples of chart reading results. [Figure 7] FIG. 1A is a diagram showing an example of pixel identification, and FIG. 1B is a diagram showing an example of index values. [Figure 8] 6 is a flowchart showing an example of processing by a control unit. [Figure 9] FIG. 4 is a functional block diagram of a timing control circuit. [Figure 10]4A and 4B are timing charts showing an example of generation of a read timing signal. [Figure 11] 6 is a flowchart showing an example of processing by a control unit. [Figure 12] 6 is a flowchart showing an example of processing by a control unit. [Figure 13] 6 is a flowchart showing an example of processing by a control unit. [Figure 14] FIG. 4 is a functional block diagram of a timing control circuit. [Figure 15] 11 is a timing chart showing an example of threshold correction. [Figure 16] 6 is a flowchart showing an example of processing by a control unit. [Figure 17] 6 is a flowchart showing an example of processing by a control unit. [Figure 18] 6 is a flowchart showing an example of processing by a control unit. [Figure 19] 13A and 13B are diagrams illustrating a change in the period of threshold correction. [Figure 20] 6 is a flowchart showing an example of processing by a control unit. [Figure 21] 13A and 13B are diagrams illustrating a change in the period of threshold correction. [Figure 22] 13A and 13B are diagrams illustrating a change in the period of threshold correction. [Figure 23] 13A and 13B are diagrams illustrating a change in the period of threshold correction. [Figure 24] 6 is a flowchart showing an example of processing by a control unit. [Diagram 25] FIG. 4 is a functional block diagram of a timing control circuit. [Figure 26] FIG. 4 is a functional block diagram of a set control circuit. [Figure 27] 11 is a timing chart showing an example of threshold correction. [Figure 28] 11 is a timing chart showing an example of threshold correction. [Figure 29] FIG. 4 is a functional block diagram of a timing control circuit. [Diagram 30] 11 is a timing chart showing an example of threshold correction. [Diagram 31]6 is a flowchart showing an example of processing by a control unit. [Diagram 32] 6 is a flowchart showing an example of processing by a control unit. [Diagram 33] 4A and 4B are flowcharts showing an example of processing by a control unit. [Diagram 34] 11 is a timing chart showing an example of threshold correction. [Diagram 35] 11 is a timing chart showing an example of threshold correction. [Diagram 36] 6 is a flowchart showing an example of processing by a control unit. [Figure 37] 6 is a flowchart showing an example of processing by a control unit. [Figure 38] 6 is a flowchart showing an example of processing by a control unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a number of features, not all of these features are essential to the invention, and the features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0010] First Embodiment <Outline of the device> 1(A) and 1(B) are schematic diagrams of a reading device 1 according to an embodiment of the present invention, with FIG. 1(A) being a side view and FIG. 1(B) being a plan view. The reading device 1 is a device that reads an image on a medium 100. The medium 100 is, for example, a sheet-like original such as paper, and the image is characters, figures, photographs, etc. on the medium 100.

[0011] The reading device 1 includes transport rollers 6 and 7 and nip rollers 9 and 10 as a transport mechanism for the medium 100, and the medium 100 is transported in a D1 direction (transport direction). The D2 direction is a direction intersecting the D1 direction, and in this embodiment, is a direction perpendicular to the D1 direction, and is the width direction of the medium 100. The transport rollers 6 and 7 extend in the D2 direction and rotate synchronously by the driving force of the transport motor 5. The driving force of the transport motor 5 is transmitted to the transport roller 6 via a transmission belt 8b, and is also transmitted from the transport roller 6 to the transport roller 7 via a transmission belt 8a. The transport roller 6 is disposed upstream of the transport roller 7 in the D1 direction.

[0012] The nip roller 9 and the nip roller 10 extend in the direction D2. The nip roller 9 is in pressure contact with the transport roller 6, and the nip roller 10 is in pressure contact with the transport roller 7. The medium 100 is conveyed in the direction D1 by the rotation of the transport roller 6 while being sandwiched between the transport roller 6 and the nip roller 9. Similarly, the medium 100 is conveyed in the direction D1 by the rotation of the transport roller 7 while being sandwiched between the transport roller 7 and the nip roller 10. The medium 100 is conveyed through a state in which it is conveyed by the transport roller 6 and the nip roller 9, a state in which it is conveyed by the transport roller 6 and the nip roller 9, a state in which it is conveyed by the transport roller 7 and the nip roller 10, and a state in which it is conveyed by the transport roller 7 and the nip roller 10.

[0013] The reading unit 2 reads an image of the medium 100 conveyed by the conveying rollers 6 and 7. In this embodiment, the reading unit 2 includes a plurality of sensor units 2A to 2C. The sensor units 2A to 2C are contact image sensor (CIS) units extending in the D2 direction. Each of the sensor units 2A to 2C includes a photodiode array 4, two rows of LED light sources 3, and a lens array (not shown) arranged in the D2 direction. The LED light sources 3 are arranged on the upstream side and downstream side of the photodiode array 4 in the D1 direction, respectively, and irradiate light onto the medium 100. The photodiode array 4 includes a plurality of light receiving elements (reading elements) arranged in the D2 direction that receive reflected light from the medium 100. The LED light source 3 is a three-color LED array having light emitting elements of three colors, Red (R), Green (G), and Blue (B).

[0014] The sensor units 2A to 2C are disposed between the conveying roller 6 and the conveying roller 7 in the D1 direction. The sensor units 2A to 2C are disposed in a staggered manner. Specifically, the sensor unit 2A is disposed upstream in the D1 direction with respect to the sensor units 2B and 2C, and in the center in the D2 direction. The sensor units 2B and 2C are disposed at the same position in the D1 direction, and are spaced apart from each other in the D2 direction. In the D2 direction, the sensor unit 2B is disposed shifted relative to the sensor unit 2A, and the sensor unit 2C is also disposed shifted relative to the sensor unit 2A. In the D2 direction, one end of the reading area of ​​the sensor unit 2A overlaps with the center end of the reading area of ​​the sensor unit 2B, and the other end of the reading area of ​​the sensor unit 2A overlaps with the center end of the reading area of ​​the sensor unit 2C.

[0015] In this embodiment, the sensor units 2A to 2C each have a reading area with a width of A4 size. The sensor units 2A to 2C are arranged in a staggered pattern, so that an image on the medium 100 having a width wider than A4 size can be read. In this case, the images read by the sensor units 2A to 2C are combined into a single image. Note that although the reading unit 2 is configured with a plurality of sensor units 2A to 2C in this embodiment, it may be configured with a single sensor unit.

[0016] The sensor units 2A to 2C are disposed facing a white platen 11, and the medium 100 is transported between the sensor units 2A to 2C and the platen 11. By maintaining a constant distance between the medium 100 and each of the sensor units 2A to 2C, the occurrence of image blurring can be suppressed, and by making the color of the platen 11 uniform, the occurrence of color unevenness in the read image can be prevented.

[0017] A leading edge detection sensor 12 that detects the leading edge of the medium 100 to be read is disposed upstream of the transport roller 6 in the D1 direction. In addition, a trailing edge detection sensor 13 that detects the trailing edge of the medium 100 is disposed downstream of the sensor units 2B and 2C and upstream of the transport roller 7 in the D1 direction. The leading edge detection sensor 12 and the trailing edge detection sensor 13 are, for example, optical sensors.

[0018] The reading device 1 includes a detection unit 20 that detects the rotation phase of the transport roller 6. The configuration of the detection unit 20 will be described with reference to FIG. 2(A). The detection unit 20 includes a code wheel 21 fixed coaxially to the shaft of the transport roller 6, an optical encoder sensor 22, and an optical HP sensor 23. The code wheel 21 has a disk shape, and rotates once for each rotation of the transport roller 6. The code wheel 21 has a slit portion 21a on the outer periphery thereof, in which a number of slits are formed at equal pitches in the circumferential direction, and a non-transmitting region 21b is formed inside the slit portion 21a in a range of 180 degrees in the circumferential direction. The non-transmitting region 21b is a region that blocks the transmission of light (other portions are transmissive regions through which light passes).

[0019] The encoder sensor 22 switches its output signal between Hi and Low as the slits of the slit portion 21a pass through the slits. When the transport roller 6 rotates and the code wheel 21 rotates accordingly, the encoder sensor 22 outputs two-phase pulses of phases A and B as shown in FIG. 3. Each rising edge of the two-phase pulse is taken as a reference signal. In this embodiment, the number of reference signals (number of pulses) when the code wheel 21 rotates once is 51200 pulses. Therefore, the reference signal is output for each rotation of 360 degrees / 51200 as a unit rotation angle. If the transport roller 6 is an ideal roller with a perfectly circular cross section and no eccentricity, the transport amount of the medium 100 per rotation angle equivalent to one pulse (360 degrees / 51200 ≈ 0.007 degrees) is transport amount = circumference of the transport roller 6 / 51200.

[0020] It is necessary to set a reference rotational position in order to identify the rotational phase of the conveying roller 6. The HP sensor 23 switches its output signal between Hi and Low (called a reset signal) when the non-transparent region 21b passes through it. The rotational position at which the non-transparent region 21b passes through the HP sensor 23 (the rotational position at which the output of the HP sensor 23 switches) is set as the reference position (in other words, the home position of the conveying roller 6).

[0021] <Control circuit> The control circuit provided in the reading device 1 will be described with reference to Fig. 4. The reading device 1 includes a control unit 14. The control unit 14 includes a CPU 15, which is a processor that executes the processes described below, and a timing control circuit 16 that controls the reading timing of the reading unit 2, and is responsible for controlling the reading device 1. The CPU 15 is connected to storage devices (ROM 17, RAM 18). The storage devices store programs executed by the CPU 15 and various data, and the RAM 18 provides a work area for the CPU 15.

[0022] When the leading edge detection sensor 12 detects that the medium 100 has been set, the CPU 15 starts driving the transport motor 5 and also causes the timing control circuit 16 to start generating a read timing signal. The timing control circuit 16 generates the read timing signal based on the reference signal. The read timing signal is input to the LED driver 32.

[0023] When the LED driver 32 receives a read timing signal, it causes the LED light source 3 to emit light. The LED light source 3 is a three-color LED array having light-emitting elements of three colors, Red (R), Green (G), and Blue (B), and when it receives a read timing signal, it causes the light-emitting elements to emit light in the order of R → G → B. In synchronization with the emission of the light-emitting elements, the photodiode array (PD array) 4 is exposed to light and receives reflected light from the medium 100. The photodiode array 4 outputs an output voltage that changes from each light-receiving element depending on the intensity of the received light. The output voltage is input to the read data processing circuit 31. The read data processing circuit 31 has an AD converter, and the output voltage is converted into a digital signal. The read data processing circuit 31 buffers the output voltage after AD conversion in the RAM 18 as read data for each pixel. The read data is stored separately for the sensor units 2A to 2C.

[0024] This line-by-line reading in the D2 direction is repeated from the leading end to the trailing end of medium 100 in the D1 direction, thereby storing image data of the read image in RAM 18. As medium 100 continues to be transported, and trailing end detection sensor 13 detects the passing of the trailing end of medium 100, CPU 15 issues a command to timing control circuit 16 to stop generating the read timing signal. After medium 100 has been transported a distance equivalent to the distance between trailing end detection sensor 13 and transport roller 7, CPU 15 stops transport motor 5. This completes one reading operation.

[0025] When the reading operation is completed, the images read by the sensor units 2A to 2C are combined to generate one image. Specifically, the images read by the sensor units 2B and 2C are offset by the number of lines corresponding to the distance between the sensor unit 2A and the sensor units 2B and 2C in the D1 direction and superimposed on the image read by the sensor unit 2A. As a result, eleven images are formed. At this time, a process may be performed on the pixel area where the read image of the sensor unit 2A overlaps with the read images of the sensor units 2B and 2C to make the seams of the images less noticeable. For example, a gradation process or a process of averaging data between pixels may be performed. When the formation of the image is completed, a display indicating that the reading is completed may be displayed on the operation panel 30 such as a touch panel. In addition, the image data may be transmitted to another device such as a user's personal computer via the interface (I / F) 19.

[0026] In this example, the images read by the sensor units 2A to 2C are combined after the reading of the medium 100 is completed, but the images may be combined in parallel with the reading.

[0027] <Error correction for transport rollers> If the transport roller 6 is an ideal roller with a perfectly circular cross section and no eccentricity, the number of pulses of the reference signal will match the amount of transport of the medium 100 by the transport roller 6. If it is determined from the number of pulses of the reference signal that the medium 100 has been transported by the amount corresponding to the desired reading resolution and the reading operation of the reading unit 2 is performed, a read image at that reading resolution can be obtained.

[0028] However, in reality, the conveying roller 6 has a diameter error and eccentricity. Therefore, a deviation occurs between the number of pulses of the reference signal and the conveying amount of the medium 100. If the error is periodic, such as when the conveying roller 6 is eccentric, the conveying amount varies depending on the rotation phase, with one revolution of the conveying roller 6 being one period. This may cause the read image to be distorted. Furthermore, in the case where the sensor units 2A to 2C are arranged with a shift in the D1 direction as in this embodiment, when the read images of each sensor unit are combined, periodic image shift occurs in the overlapping portions of each read image. Therefore, in this embodiment, a read timing signal in which the error of the conveying roller 6 is corrected is generated from the reference signal.

[0029] As shown in Fig. 2(A) and Fig. 2(B), the code wheel 21 is divided into a plurality of rotational phase regions at equal pitches in the circumferential direction, and the correction content per pulse of the reference signal is set for each phase region. There is no limit to the number of divisions, but in this embodiment, it is divided equally into 32 phase regions. To identify each phase region, region numbers R0 to R31 are assigned in order from the above-mentioned reference position. Each region is distinguished by the number of pulses of the reference signal. Phase region R0 is in the range of 1599 pulses from the reference position. Phase region R1 is in the range of 1600 pulses to 3199 pulses. A unit phase region may be referred to as phase region R.

[0030] The correction content is defined by an index value corresponding to the conveyance amount of the conveying roller 6 per unit rotation angle. In the case of this embodiment, the unit rotation angle is a rotation angle equivalent to one pulse (360 degrees / 51200 ≒ 0.007 degrees). In the case of this embodiment, the index value is quantified in the form of a correction value that corrects the amount of counting for one time when counting the number of pulses of the reference signal. To facilitate understanding, a hypothetical specific example will be described.

[0031] It is assumed that in order to achieve a desired reading resolution, the reading unit 2 performs one reading operation every time the medium 100 is transported 10 mm. It is also assumed that, if the transport roller 6 is an ideal roller, 1000 pulses of the reference signal are output when the medium 100 is transported 10 mm. When the count value of the reference signal reaches 1000, it is sufficient to output the reading timing signal once.

[0032] However, in reality, when the reference signal is outputted at 1000 pulses due to eccentricity of the conveying roller 6, the medium 100 is conveyed by 11 mm. If the count value of the reference signal is 1000 and the read timing signal is outputted once, the medium will be read at a lower resolution than the desired reading resolution. Therefore, one reference signal is counted as, for example, 1.101 times. This value is used as the index value. When the reference signal is outputted at 909 pulses, the count value becomes 909×1.101=1000.81 (>1000), and the read timing signal is outputted once. At this time, the conveying amount of the medium 100 is 11 mm×909 / 1000=9.999 mm, which is approximately 10 mm. In this way, the error of the conveying roller 6 can be corrected.

[0033] The index value is set for each of the phase regions R0 to R31. The index value to be set can be calculated in advance using a specific calibration chart and stored in the ROM 17. An example of the index value setting process will be described below.

[0034] <Example of index value setting> FIG. 5(A) is an explanatory diagram of a calibration chart 101. The chart 101 is composed of a plurality of thin lines L printed on a sheet. Each thin line L is inclined at 45° with respect to the D1 direction, and the interval between adjacent thin lines L is a distance W in each of the D1 direction and the D2 direction. In this embodiment, it is assumed that the maximum reading resolution of the reading device 1 is 600 dpi. 50 lines correspond to one phase area (1600 pulses), and W=(1 inch / 600)×50.

[0035] With the chart 101 having such a configuration, if the transport roller 6 is an ideal roller, when the chart 101 is transported by an amount equivalent to the phase region R, adjacent thin lines L will be located at the same position in the direction D2 on the same pixel (light receiving element) of the sensor units 2A to 2C. A specific example will be described.

[0036] Fig. 5(B) shows, for example, the detection result of the sensor unit 2B. Here, an example is shown in which the thin line L1 (see Fig. 5(A)) is located above the 1000th pixel (light receiving element) of the photodiode array 4 when the transport roller 6 is located at the home position. Since the thin line L1 overlaps the 1000th pixel, the amount of reflected light is the smallest at the 1000th pixel, resulting in a small output voltage.

[0037] Fig. 6(A) illustrates an example in which the conveying roller 6 is an ideal roller and the chart 101 is conveyed 50 lines from the state shown in Fig. 5(B). In other words, the conveying roller 6 rotates from the start to the end of phase region R0. In this case, the thin line L2 (see Fig. 5(A)) adjacent to the thin line L1 overlaps with the 1000th pixel, and similar to the example in Fig. 5(B), the 1000th pixel has the least amount of reflected light.

[0038] Fig. 6(B) illustrates an example in which the conveying roller 6 has an eccentricity or the like and conveys the chart 101 by 50 lines from the state shown in Fig. 5(B). In this case, the conveying roller 6 rotates from the start to the end of phase region R0. The pixels that overlap with the thin line L2 shift, and the area between the 993rd pixel and the 994th pixel overlaps with the thin line L2. This means that the conveying roller 6 is conveyed by approximately 6 pixels more with the same amount of rotation than when it is an ideal roller.

[0039] An index value is calculated from this deviation amount. Specifically, as shown in FIG. 7A, a quadratic function approximation curve is calculated using three values: the pixel with the least amount of reflected light (in this example, the 994th pixel) and its two neighboring pixels, numbered 993 and 995. Then, the pixel with the minimum value of the approximation curve is calculated. In the example of FIG. 7A, the pixel with the minimum value is calculated as 993.612. Therefore, it is shifted by 6.38 pixels from the 1000th pixel, and the chart 101 has been conveyed by that amount. In other words, the conveyance magnification is 1.004 times, and in this embodiment, this magnification value 1.004 is treated as the index value of the region R0. The same calculation is performed for all phase regions from region R0 to R31 to calculate the index value of all phase regions. The calculation result is stored in the ROM 17. FIG. 7B shows an example of the information to be stored. In the illustrated example, the index value is set for each of the phase regions R0 to R31. Decimal and hexadecimal numbers are written together. The stored index value may be a 24-bit fixed-point value with a 4-bit integer part and a 20-bit fractional part.

[0040] 8 shows an example of processing executed by the control unit 14, and in particular, an example of index value setting processing mainly executed by the CPU 15. The setting processing is aimed at correcting errors in the transport roller 6, so it only needs to be performed once when the reading device 1 starts to be used for the first time. However, it may also be performed after the first use to update the index value. The timing of the update may be after the transport roller 6 is replaced, or it may be set as a condition that a predetermined time has passed or a predetermined number of readings have been reached, regardless of whether the transport roller 6 has been replaced.

[0041] In S1, the user sets the chart 101 in the reading device 1, which is detected by the leading edge detection sensor 12. In S2, the index values ​​for all phase regions are temporarily set to 1.0. This is to prevent the reading timing from being corrected by the index value in the operation of calculating the index value.

[0042] In S3, a threshold value T corresponding to the reading resolution is set. Here, a threshold value corresponding to the maximum reading resolution of the reading device 1 is set. In this embodiment, the maximum reading resolution is set to 600 dpi, and the corresponding threshold value T is set to 32. The threshold value T=32 means that a reading timing signal of 600 dpi is generated by dividing the reference signal by 32 for the paper resolution of the medium, 19200 dpi.

[0043] In S4, the chart 101 is read. While the chart 101 is transported by the transport rollers 6 and 7, a read timing signal is generated and reading is performed by the reading unit 2 every time the number of pulses of the reference signal is counted 32 times. Since the index value is set to 1.0, a read timing signal is generated every time the number of pulses of the reference signal is counted 32 times in all phase regions. The read images are stored sequentially in the RAM 18 so that they can be referenced after reading is completed.

[0044] Once the reading is complete, the process moves on to the calculation of the index value. In S5, the variable n, which indicates the number of the phase region, is set to 0. In S6, the reading result of one line corresponding to the start position of phase region Rn is read from RAM 18. For example, when n=0, the reading result of one line at the start position of phase region R0 is read. In S7, the pixel with the highest density (lowest amount of received light) is identified from the image of one line that has been read. The variable indicating the number of the identified pixel is Dpix.

[0045] In S8, the read result of one line corresponding to the start position of phase region Rn+1 is read from RAM 18. For example, when n=0, the read result of one line at the start position of phase region R1 is read. In S8, from the image of one line read out, the pixel with the highest density (lowest amount of light received) among the pixels around Dpix is ​​identified. A variable representing the number of the identified pixel is set as Dpix'. When searching for Dpix', for example, Dpix may be used as a reference and a search may be made in order from adjacent pixels of Dpix in a direction away from Dpix, or a search may be made in order from pixels a predetermined value away from Dpix in a direction toward Dpix.

[0046] In S10, the index value of the phase region Rn is calculated. A quadratic function approximation curve is obtained from three pixels including those before and after Dpix, as shown in FIG. 7(A), and the minimum value of the approximation curve is obtained. Similarly, a quadratic function approximation curve is obtained from three pixels including those before and after Dpix', as shown in FIG. 7(A), and the minimum value of the approximation curve is obtained. If the difference between the two minimum values ​​is Dif, the index value Emag(n) of the phase region Rn can be obtained by the following formula. Emag(n)=1+((Dpix-Dpix') / 1600) Here, 1600 is the number of pulses of the reference signal in the unit phase region R.

[0047] In S11, it is determined whether n=31 (whether index value setting has been completed for all phase regions). If n=31 is not true, the process proceeds to S12, n is incremented by one, and the process returns to S6. In S13, the calculated index value is stored in ROM 203 for each phase region R. The stored information is as shown in FIG. 7(B). This completes the process.

[0048] <Reading timing control> The control of the read timing using the index value will now be described with reference to Fig. 9, which is a functional block diagram of the timing control circuit.

[0049] The timing control circuit 16 receives a reference signal from the encoder sensor 22 and a reset signal from the HP sensor 23. A period counter 501 operates as a counter that counts up every time a reference signal is input, and clears the count value up to that point when a reset signal is input. A region selection unit 502 selects the current phase region R by referring to the count value of the period counter 501. An index value selection unit 503 selects an index value Emag corresponding to the phase region R selected by the region selection unit 502, and acquires it from the ROM 17.

[0050] Each time a reference signal is input, calculation unit 504 adds the index value selected by index value selection unit 503 to the current cumulative value. Also, each time a reading timing signal is output, calculation unit 504 subtracts threshold value T held in holding unit 505 from the current cumulative value. Threshold value T corresponding to the reading resolution is set in holding unit 505 by CPU 15. Calculation unit 504 outputs the current cumulative value to comparison unit 506.

[0051] Comparator 506 compares the accumulated value output from calculator 504 with threshold T held in holder 505, and outputs an L-level signal to D flip-flop 507 if the accumulated value is less than threshold T, or outputs an H-level signal if the accumulated value is equal to or greater than threshold T. The output signal from comparator 506 is held by D flip-flop 507 for a predetermined clock (CLK) period. The H-level signal output from D flip-flop 507 is output as a read timing signal.

[0052] When the read timing signal is output, the calculation unit 504 subtracts the threshold value T from the current cumulative value, so that the output signal of the comparison unit 506 becomes L level. The read timing signal is output for only one clock (CLK) period.

[0053] By repeating this operation, the timing control circuit 16 can generate a reading timing signal according to the desired resolution and medium transport amount. Figure 10(A) is a timing chart showing an example of changes in the reference signal, cumulative value (ΣEmag), index value (Emag), and reading timing signal when the reading resolution is 600 dpi (threshold T=32).

[0054] In the illustrated example, the index value is set to 0.99 in phase region Rn. Each time a reference signal is input, the cumulative value (ΣEmag) is incremented by 0.99, and when 33 pulses are input, the cumulative value (32.67) > threshold value T. At this timing, a read timing signal is output, and the threshold value T is subtracted from the cumulative value (ΣEmag = 0.67).

[0055] After that, the cumulative value (ΣEmag) is added by 0.99 each time the reference signal is input, but when the phase region R changes from phase region Rn to phase region Rn+1, the index value becomes 1.01 and the cumulative value (ΣEmag) is added by 1.01 each time. When the cumulative value (ΣEmag)=32.65, the read timing signal is output again. In this manner, the read timing signal is generated. The read timing signal is generated based on the magnification of the actual transport amount of the medium 100 relative to the reference signal, so that the period of the read timing signal corresponds to the distance that the medium 100 has actually moved. In this embodiment, the threshold value T is subtracted from the cumulative value when the read timing signal is output. Therefore, even if the transport amount becomes longer, an error is unlikely to occur.

[0056] To change the reading resolution, the threshold value T can be changed, and the index value can be used as is. By changing the threshold value T, it is possible to output reading timing signals corresponding to various cycles. Note that the cycle of the reading timing signal changes with the cycle of the reference signal being one resolution unit, so in this embodiment, 600 dpi has the smallest value of threshold T (T=32), and the resulting jitter is 1 / 32=3.125%. To reduce the jitter, this can be done by reducing the cycle of the reference signal relative to the cycle of the reading timing signal.

[0057] Fig. 10(B) shows an example where the reading resolution is 300 dpi. The threshold value T is set to 64. The index value is set to 0.99 in the phase region Rn. Each time a reference signal is input, the accumulated value (ΣEmag) is added by 0.99, and when 65 pulses are input, the accumulated value (64.35) > threshold value T. At this timing, a read timing signal is output, and the threshold value T is subtracted from the accumulated value (ΣEmag = 0.35).

[0058] After that, the cumulative value (ΣEmag) is increased by 0.99 each time a reference signal is input, but when phase region R changes from phase region Rn to phase region Rn+1, the index value becomes 1.01 and the cumulative value (ΣEmag) is increased by 1.01 each time. When the cumulative value (ΣEmag) reaches 64.65, a read timing signal is output again. In this manner, the read timing signal is generated. Note that each read pixel on one line may be changed according to the read resolution, or may be thinned out after reading without being changed.

[0059] <Example of reading control> FIG. 11 shows an example of processing executed by the control unit 14, and shows an example of processing when reading the medium 100. Each step in the example processing is mainly executed by the CPU 15. When the reading device 1 is started, an initial processing is executed in S21. In the initial processing, the index value of each phase region R stored in the ROM 17 is read out and set in the index value selection unit 503. In addition, after the count value of the period counter 501 is cleared, the start of counting is set. When the start of counting is set, the period counter 501 counts up the count value every time a reference signal is input, and repeats the operation of resetting the count value by inputting a reset signal.

[0060] In the initial process, the conveying motor 5 is driven to position the conveying roller 6 at the home position. This is an operation for associating the conveying roller 6 with the phase region R, and it is sufficient to perform this operation once after startup.

[0061] In S22, it is determined whether the medium 100 to be read has been set based on the detection result of the leading edge detection sensor 12. If it is determined that the medium 100 has been set, the process proceeds to S23. In S23, a prescan operation is performed on the medium 100. The prescan operation is a preparation operation for determining the reading width by detecting the width (D2 direction) of the set medium 100 and for determining the intensity of each light source during reading from the amount of reflected light from each of the RGB light sources 5. In order to reduce the operation time, in the prescan operation, the leading edge of the medium 100 is read at a high transport speed (for example, 5 inches / sec) and a low resolution setting (for example, 100 dpi) regardless of the actual reading resolution.

[0062] 12 is a flowchart showing a processing example of the pre-scan operation in S23. Initial settings are performed in S31. The accumulated value (ΣEmag) of the calculation unit 504 is cleared, and the threshold value T is set to 192. With this setting, a reading timing signal is generated at a reading resolution of 100 dpi from the start of rotation of the conveying motor 5.

[0063] In S32, the carry motor 5 is rotated so that the carry speed of the medium 100 is 5 inches / sec. The rotation speed of the carry motor 5 can be controlled by feeding back the output of the encoder sensor 16. In addition, as the carry motor 5 rotates, a reference signal from the encoder sensor 16 is input to the timing control circuit 16.

[0064] S33 to S37 show the operation of the timing control circuit 16. While the conveying motor 5 is being driven, as described above, each time a reference signal is input (S33), the index value Emag for each phase region R is added by the calculation unit 504, and when it becomes equal to or greater than the threshold value T (=192), the operation of outputting a read timing signal is repeated. Each time a read timing signal is output, the reading unit 2 reads the image on the medium 100 one line at a time, and the image is stored in the RAM 18.

[0065] In S38, it is determined whether the movement amount of the medium 100 has reached a predetermined value (for example, 100 mm), and when the movement amount reaches the predetermined value, the conveying motor 5 is stopped in S39. When the conveying motor 5 is stopped, each read image is combined, and the combined image is stored in the RAM 18 (S40).

[0066] Next, in S41, CPU 15 extracts the upper part from the combined image. Specifically, the combined image is read from RAM 18 and the leading edge position and width of medium 100 are identified. The leading edge position and width are found by detecting the edges of the combined image and extracting a straight line from the outermost part of the combined image.

[0067] Also, the combined image is separated into R, G, and B images, and a histogram is generated for each. Then, the light receiving intensity of the most frequently occurring pixel is compared between RGB, so that white balance can be achieved during actual reading. Then, based on the comparison result, the current flowing for each RGB color in the LED driver 32 may be changed, or the light emission time may be changed. Alternatively, the same result can be obtained by changing the exposure time of the photodiode array 4 for each RGB. When an image on the platen 11 outside the medium 100 is used as the image area for generating the histogram, white balance can be achieved based on the white color of the platen 11. When an image inside the medium 100 is used, white balance can also be achieved based on the surface color of the medium 100.

[0068] If the information extracted in S41 (the leading edge position and width of the medium, and white balance) is not normal, the conveying motor 5 may be rotated in the reverse direction to eject the medium 100, and the user may be prompted to recheck via the operation panel 30. Alternatively, the medium 100 may not be ejected, and predetermined parameters may be set as values ​​for the white balance, etc.

[0069] 11, when the prescan operation of S23 is completed, the process proceeds to S24 to adjust the leading edge position of the medium 100. Here, the transport motor 5 is rotated in the reverse direction to position the leading edge position of the medium 100 detected in the prescan of S23 in front of the sensor unit 2A (upstream position).

[0070] In S25, the selection of a reading mode by the user is accepted via the operation panel 30. The multiple types of reading modes include modes with different reading resolutions. Settings such as white balance may differ depending on the reading mode. Note that, in this embodiment, the selection of the reading mode is accepted after prescanning (S23), but the selection may be accepted before prescanning.

[0071] In S26, the threshold value T is set according to the result of the selection of the reading mode in S25. If a reading mode with a reading resolution of 600 dpi is selected, T=32, and if a reading mode with a reading resolution of 300 dpi is selected, T=64. The threshold value T is set based on the relationship between the paper resolution corresponding to the reference signal (19200 dpi in this embodiment) and the reading resolution. Once setting of the threshold value T is completed, reading of the image on the medium 100 is started in S27. FIG. 13 is a flowchart showing the flow of this process.

[0072] In S51, the accumulated value (ΣEmag) of the calculation unit 504 is cleared. In S52, the drive of the transport motor 5 is started to transport the medium 100. The drive speed of the transport motor 5 may be set according to the selected reading mode. For example, when a 600 dpi reading mode is selected, the transport motor 5 is driven so as to transport the medium 100 at 1 ips.

[0073] S53 to S57 show the operation of the timing control circuit 16. While the conveying motor 5 is being driven, as described above, each time a reference signal is input (S53), the index value Emag for each phase region R is added by the calculation unit 504 (S54), and when it becomes equal to or greater than the threshold value T, a read timing signal is output (S56, S57). Each time a read timing signal is output, the reading unit 2 reads the image of the medium 100 one line at a time, and the read image for each of the sensor units 2A to 2C is stored in the RAM 18. This operation is repeated until the rear end of the medium 100 is detected.

[0074] When the trailing edge detection sensor 13 detects the passage of the medium 100 in S58, the CPU 15 stops the carry motor 5 to stop reading. When the carry motor 5 stops, the pulse output from the encoder sensor 16 stops, and the reference signal input to the timing control circuit 16 ends. This ends reading. Note that in this embodiment, the reference signal is input to the timing control circuit 16 in synchronization with the drive of the carry motor 5, but motor control and reading control may be executed independently. In this case, a gate may be provided inside or outside the timing control circuit 16.

[0075] When the reading of the medium 100 is completed by the above process, the read images of each of the sensor units 2A to 2C are combined to generate a single image as described above. When the generation is completed, the user is notified via the operation panel 30 and prompted via the I / F 19 to instruct image transfer.

[0076] If it is determined in S28 of FIG. 11 that a certain period of time has elapsed without the next medium 100 being set, the process ends.

[0077] In this embodiment, by generating the reading timing signal as described above, it is possible to read the image on the medium 100 while correcting the error of the conveying roller 6. Furthermore, since the reading resolution can be changed by changing the threshold value T and there is no need to change the index value, the reading resolution can be changed relatively easily. Furthermore, even in the case where the sensor unit 2A is separated from the sensor units 2B and 2C in the D1 direction as in this embodiment, it is possible to prevent periodic image misalignment from occurring in the overlapping portions of the images when the read images of the respective sensor units are combined.

[0078] Second Embodiment The threshold value T may be corrected at a specific timing. Fig. 14 is a functional block diagram of the timing control circuit 16 of this embodiment. A configuration different from the timing control circuit 16 of the first embodiment shown in Fig. 9 will be described.

[0079] The timing control circuit 16 of this embodiment can correct the threshold value T corresponding to the reading resolution, which is held in the holding unit 513, by the correction value held in the holding unit 514. The correction of the threshold value T is applied at a substantially constant period and only to the generation period of one reading timing signal. To achieve this, a period counter 511, a period holding unit 512, a holding unit 515, and a period comparison unit 516 are provided.

[0080] Period counter 511 is a counter that counts up every time a reference signal is input, and the count value is denoted as VCount. Period holding unit 512 holds a period setting value (count threshold) that specifies the timing for correcting threshold value T. Period comparison unit 516 outputs an L level signal when the count value of period counter 511 is smaller than the period setting value of period holding unit 512, and outputs an H level signal when the count value of period counter 511 is equal to or greater than the period setting value.

[0081] When period comparison unit 516 outputs an H-level signal, holding unit 515 holds a value obtained by adding the correction value held in holding unit 514 to the threshold value T held in holding unit 513 (corrected threshold value T=threshold value T+correction value). When period comparison unit 703 is outputting an H-level signal, if a reference signal is input, a reset signal is input from the AND circuit to period counter 511, and the count value of period counter 511 is cleared. As a result, period comparison unit 703 outputs an L-level signal. Thereafter, the same process is repeated.

[0082] When a read timing signal is output from D flip-flop 507, the corrected threshold value T in holding unit 515 is set in threshold value holding unit 505, and the corrected threshold value T is input to comparison unit 506. In addition, the original threshold value T is set in holding unit 515 from holding unit 513.

[0083] The above operation is repeated every time a reference signal is input. As a result, when a read timing signal is output after the period specified by the period setting value set in the period holding unit 512 has elapsed, the threshold value T compared with the cumulative value (ΣEmag) in the comparator 506 is replaced with the corrected threshold value T for one period (one interval) until the next read timing signal is output.

[0084] 15 is a timing chart showing an example of how the threshold value T is corrected. In this example, the cycle setting value of the cycle holding unit 512 is 10240, and the correction value held in the holding unit 514 is set as -1. Therefore, when the reference signal is input 10240 times, the threshold value T is decremented by one until the next read timing signal is output. The threshold value held in the holding unit 505 is represented as held value A, and the threshold value held in the holding unit 515 is represented as held value B.

[0085] When the VCount value reaches the cycle setting value, held value B is set to the corrected threshold value = 31 (= 32 - 1). With threshold value T = 32 held as held value A, the accumulated value (ΣEmag) becomes 32 or greater and a read timing signal is output. As a result, held value A is updated with held value B, and threshold value T = 31 remains until the next read timing signal is output. Held value B returns to its original value of 32.

[0086] This operation makes it possible to apply vertical magnification correction of the read image while maintaining the error correction of the conveying roller 6 described in the first embodiment. In the vertical magnification correction, it is possible to correct the image length error (vertical magnification error) caused by the slippage of the conveying roller 6 caused by the type of medium 100 and the conveying speed. For example, according to an experiment conducted by the inventors, it has been confirmed that the read image of the thick glossy paper is shorter by 0.01% even when the same image is displayed on plain paper and thick glossy paper at the same conveying speed. It has also been confirmed that there is a difference of about 0.2% in the conveying amount between plain paper when conveyed at 7.5 ips and when conveyed at 0.6 ips. Even with the same type of medium, an error may occur in the conveying amount depending on the usage environment such as temperature and humidity. Such errors can be identified from the experimental results, and vertical magnification correction can be realized by setting the correction value of the threshold T and the correction period according to the identified contents.

[0087] The reading start control in this embodiment will be described with reference to Fig. 16. The process different from the reading start control in the first embodiment in Fig. 13 will be described.

[0088] When the process starts, the accumulated value (ΣEmag) of the calculation unit 504 is cleared in S51. After that, the vertical magnification correction operation is started in S61. In parallel, in S60, the process waits for the elapse of a wait time for the vertical magnification correction setting operation (S71 and S74 described later) to be completed. After that, the same process as the example of FIG. 13 is executed from S52.

[0089] 17 is a flowchart showing a processing example of the vertical magnification correction operation in S61. Initial settings are performed in S71. Here, a cycle setting value is set in cycle holding unit 512, and a correction value is set in holding unit 514. These values ​​may be preset corresponding to the type of medium 100 by having the user select the type of medium 100 when selecting the reading mode, or the values ​​may be stored in ROM 17 and read out.

[0090] As an example of the value, for example, when the index value setting process is performed, the vertical magnification ratio of thick glossy paper to plain paper is -0.01%. When thick glossy paper is selected as the medium 100, 10000 is set as the period setting value in the period holding unit 512, and -1 is set as the correction value in the holding unit 514. As a result, the threshold value T is subtracted by one while the read timing signal is output approximately every 10000 times of input of the reference signal. For example, in the case of a 600 dpi reading mode, the timing control circuit 16 normally operates with the threshold value T=32, but the threshold value becomes 31 only for one section of the read timing signal every 10000 times of input of the reference signal. As a result, the number of times the medium 100 is read increases, and the length of the image finally formed in the D1 direction becomes longer.

[0091] In S74, VCount is cleared to 0. When a reference signal is input in S75, VCount is incremented by one by the cycle counter 511 in S76. In S77, it is determined whether VCount has reached the cycle setting value in the cycle holding unit 512. If it has reached the cycle setting value, the process proceeds to S78, and if it has not reached the cycle setting value, the process returns to S75. In S78, the corrected threshold value T is held in the holding unit 515.

[0092] When it is determined in S71 that a read timing signal has been output, the value held in holding unit 515 in S72 is held in holding unit 505 and used as threshold value T. In S73, threshold value T held in holding unit 513 is held in holding unit 515. The above operations are repeated.

[0093] In this embodiment, in addition to the effects of the first embodiment, vertical magnification correction can be performed, so that errors caused by differences in the medium 100 and differences in the transport speed can be easily corrected.

[0094] <Third embodiment> When performing vertical magnification correction as in the second embodiment, at least one of the cycle setting value of the cycle holding unit 512 and the correction value of the threshold T may be changed midway. FIG. 18 is a flowchart showing one example. A process different from the example of FIG. 17 will be described. In this embodiment, the processes of S79 to S82 are executed. In S79, it is determined whether or not a condition for changing the correction value is satisfied, and if satisfied, the process proceeds to S80. In S80, VCount is cleared to 0. In S81, a new cycle setting value is set in the cycle holding unit 512, and a new correction value is set in the holding unit 514. In S82, the threshold T held in the holding unit 513 in S73 is held in the holding unit 515. As described above, the new cycle setting value and correction value set in S81 are used in the subsequent operations.

[0095] An example of the change condition in S79 is a change in the transport state of the medium 100. In the reading device 1 of this embodiment, the medium 100 changes from a state in which it is transported only by the upstream transport rollers 6 to a state in which it enters the downstream transport rollers 7 and is transported by the transport rollers 6 and 7. The timing at which the medium 100 enters the transport rollers 7 may be considered as the establishment of the change condition. If the distance between the trailing end detection sensor 13 and the downstream transport rollers 7 is known in advance, the change condition may be considered as the establishment of a predetermined number of reference signal inputs after the trailing end detection sensor 13 detects the medium 100.

[0096] <Fourth embodiment> In a configuration in which the sensor units 2A to 2C are arranged with a shift in the D1 direction, if the threshold value T is made changeable by a correction value as in the third embodiment, this may affect the read image. Here, the relationship between the read image and the timing of switching the transport state will be described with reference to Figures 19(A) and 19(B).

[0097] FIG. 19A is a diagram in which an image 902 read by the sensor unit 2A and an image 903 read by the sensor units 2B and 2C are arranged over time. In the reading device 1, the sensor unit 2A and the sensor units 2B and 2C are arranged in a so-called staggered pattern at a distance in the D1 direction. The sensor unit 2A starts reading the medium 100 conveyed by the conveying roller 6 first. Thereafter, the conveyance of the medium 100 progresses, and when the leading end of the medium 100 reaches the sensor units 2B and 2C, the sensor units 2B and 2C start reading the medium 100. The conveyance of the medium 100 further progresses, and at the timing when the leading end of the medium 100 enters the conveying roller 7, the conveying state of the medium 100 changes so that the medium 100 is conveyed by the two conveying rollers 6 and 7. For this reason, the conveying state of the image 902 read by the sensor unit 2A differs between the time when the leading end of the medium 100 passes the sensor unit 2A and enters the conveying roller 7 and the time when the leading end of the medium 100 enters the conveying roller 7.

[0098] On the other hand, the image 903 read by the sensor units 2B and 2C has a different transport state for the medium 100 before and after the timing when the leading edge of the medium 100 passes the sensor units 2B and 2C and enters the transport rollers 7. For this reason, the area of ​​the image read by the sensor units 2B and 2C by the timing TS when the transport state is switched is shorter than the image read by the sensor unit 2A by the distance LS1 between the sensor unit 2A and the sensor units 2B and 2C in the D1 direction.

[0099] Here, assume that vertical magnification correction is performed in the reading operation during the period until the timing TS at which the transport state is switched. The lengths of the images to which vertical magnification correction is applied are different between the sensor unit 2A and the sensor units 2B and 2C. Therefore, the number of timings TA1 at which vertical magnification correction occurs in this transport state differs between the image 902 read by the sensor unit 2A and the image 903 read by the sensor units 2B and 2C.

[0100] In addition, if the vertical magnification correction operation is continued by changing parameters such as the vertical magnification correction period setting value at timing TS, an image to which vertical magnification correction has been applied is read at intervals of timing TA2 of vertical magnification correction performed under a different transport state.

[0101] As described above, the images read by the sensor units 2A to 2C are combined into one image by offsetting the data for the number of lines corresponding to the distance LS1 in the transport direction between the sensor unit 2A and the sensor units 2B and 2C. Fig. 19(B) shows the combined image. Therefore, when the parameters for the vertical magnification correction are changed in accordance with the change in the transport state, images affected by different vertical magnification corrections are combined so as to overlap at the joint 906 of the area 906 with a length corresponding to the distance LS1.

[0102] In such an area where images affected by different vertical magnification corrections overlap, if the condition is met that the timing of each vertical magnification correction is aligned in the D1 direction, image degradation may occur at the seam 906 of the combined images.

[0103] For example, if vertical magnification correction is performed so that the vertical magnification ratio is -0.01% until the timing TS when the transport state is changed, the timing TA1 of vertical magnification correction occurs once every 10,000 reference signals, as described above. If the vertical magnification ratio is then changed to +0.01% in accordance with the change in the transport state and vertical magnification correction is performed, the timing TA2 of vertical magnification correction also occurs once every 10,000 reference signals. In this case, the correction values ​​are set to values ​​with opposite positive and negative values.

[0104] In this case, when performing vertical magnification correction with a vertical magnification ratio of -0.01%, the threshold value of the timing signal is changed from 32 to 31 for only one section at the timing TA1 of vertical magnification correction, which occurs once every 10,000 times of the reference signal. Therefore, the timing at which the read timing signal is generated changes so that the interval between the timing signals is narrower for that section than for the sections before and after it. In other words, at the timing TA1 of vertical magnification correction, the read operation is performed in a shorter time than usual.

[0105] Conversely, when performing vertical magnification correction with a vertical magnification ratio of +0.01%, the threshold value of the timing signal is changed from 32 to 33 for only one section at the timing TA2 of vertical magnification correction, which occurs once every 10,000 times of the reference signal. As a result, the timing at which the reading timing signal is generated changes so that the interval is wider for that section than the sections before and after it. In other words, at the timing TA2 of vertical magnification correction, the reading operation is performed for a longer time than usual. This leads to an increase or decrease in the light emission time of the LED light source 5 or the exposure time of the photodiode array 4 of the sensor unit 2A and the sensor units 2B and 2C, which may affect the density of the read image.

[0106] Here, in the reading operation of Fig. 18, when changing the parameters of the vertical magnification correction in accordance with the change in the transport state, Vcount is cleared (S80). Therefore, the cycle of the vertical magnification correction is lost at the transition timing TS of the transport state. Specifically, as shown in Fig. 19(A), the cycle is shifted by the interval Ld between the transition timing TS of the transport state and the timing of the vertical magnification correction performed immediately before the transition timing TS of the transport state.

[0107] Assume that the distance LS1, which corresponds to the number of lines by which the scanned image is offset, is arranged at an interval that cancels the shift in period caused by the interval Ld. In this case, in the joint of the area 906, the timing TA1 of the vertical magnification correction where the vertical magnification ratio is -0.01% and the timing TA2 of the vertical magnification correction where the vertical magnification ratio is +0.01% are aligned in the D1 direction. The condition for this to be true is, for example, when the remainder of dividing the distance LS1 by the smaller value of the period of the timing TA1 or the period of the timing TA2 matches or approximates the interval Ld.

[0108] When such conditions are met, lines read at shorter intervals by sensor units 2B and 2C and lines read at longer intervals by sensor unit 2A are joined together, making the effects of differences in line thickness and density more likely to become apparent at the joints.

[0109] As a countermeasure, the process in FIG. 20 can be adopted instead of the process in FIG. 18. To explain the process different from the process in FIG. 18, in the process in FIG. 20, the process of S80' is executed instead of S80 in FIG. 18. In S80', an initial value X is set to Vcount. At this time, the initial value X may be a negative value. In this way, when the transport state of the medium 100 changes, Vcount is counted from the initial value, and vertical magnification correction is executed at the timing of the cycle setting value-initial value X.

[0110] For example, as shown in Fig. 21(A), an initial value X is set to a value that sets the start timing of vertical magnification correction after the timing TS of switching the transport state to an interval Td. This makes it possible to prevent the timings of vertical magnification correction with different correction directions from aligning at the joint of the area 906 when combining images read by each of the sensor units 2A to 2C as shown in Fig. 21(B). Here, if the value of the interval Td is set to a value of the shorter half period of the timing TA1 or timing TA2 of the vertical magnification correction, the respective correction timings can be shifted to the maximum extent.

[0111] Fig. 22(A) is a diagram in which an image 902 read by the sensor unit 2A and images 903 read by the sensor units 2B and 2C are arranged in the order of elapsed time, similar to Fig. 19(A), except that the distance LS2 between the sensor unit 2A and the sensor units 2B and 2C is in the relationship LS2>LS1.

[0112] Even in this case, in order to form the final read image, the data is offset by the distance LS2 between the sensor unit 2A and the sensor units 2B and 2C. However, as shown in Fig. 22B, the timing TA2 of the vertical magnification correction between the sensor unit 2A and the sensor units 2B and 2C is not aligned in the D2 direction at the joint of the area 909. The same is true for the timing TA1.

[0113] This situation occurs when the interval LS2 between the sensor unit 2A and the sensor units 2B and 2C is not a multiple of the period of the timing TA1 of the vertical magnification correction. In other words, the closer the interval LS2 between the sensor unit 2A and the sensor units 2B and 2C is to a multiple of the period of the timing TA1 of the vertical magnification correction, the easier it is for the timing of the vertical magnification correction with the same correction direction to be aligned in the D1 direction. Note that the timing of the vertical magnification correction with different correction directions described above is independent of this condition and is not aligned in this example.

[0114] Next, in order to prevent the timing TA1 and the timing TA2 from being aligned, multiple timing control circuits 16 may be provided. In this case, one timing control circuit 16 may be assigned to the sensor unit 2A, and one timing control circuit 16 may be assigned to the sensor units 2B and 2c (two in total). If the sensor unit 2A and the sensor units 2B and 2C can be controlled independently, it becomes possible to shift the timing of starting vertical magnification correction after the timing TS at which the transport state is switched only in the sensor unit 2A.

[0115] In this case, as shown in Fig. 23(A), in the timing control circuit 16 of the sensor unit 2A, the initial value X is set so that the start timing of the timing TA2 of the vertical magnification correction is the interval Td. As a result, as shown in Fig. 23(B), when the read images are combined, the timing TA2 of the vertical magnification correction is aligned in the D1 direction at the joint of the area 909.

[0116] Here, the value of the interval Td is obtained by subtracting the remainder of dividing the interval LS by the period of the timing TA2 of the vertical magnification correction from the period of the timing TA2 of the vertical magnification correction. This ensures that the timing TA2 of the vertical magnification correction is aligned in the D1 direction even after the images read by each sensor unit are combined into one image, minimizing the effect of the vertical magnification correction on the read image.

[0117] In this example, the timing TA2 of the vertical magnification correction of the sensor unit 2A is shifted, but the same effect can be obtained even if the timing TA2 of the vertical magnification correction of the sensor units 2B and 2C is shifted.

[0118] In the example of FIG. 20, the start timing of the vertical magnification correction is shifted by setting the initial value X to VCount in S80', but the processing example of FIG. 24 can also be adopted. In the processing example of FIG. 24, the initial value Y is set to VCount in S74' instead of S74. Before the transport state is switched, that is, at the timing when reading of the medium 100 is started, the start timing of the vertical magnification correction is shifted in the timing control circuit 16 of the sensor unit 2A. This allows the timing TA1 of the vertical magnification correction to be aligned in the D1 direction when the read images are combined into one. The processing of S74' may be adopted in the timing control circuits 16 of the sensor units 2B and 2C. The initial value Y may be set in relation to the initial value X, and furthermore, in the example of FIG. 24, the initial value X may not be set to VCount in S80' and may be reset.

[0119] <Fifth embodiment> When performing vertical magnification correction as in the second to fourth embodiments, a plurality of correction values ​​of the threshold T may be prepared and applied. The cycle for applying the correction value may be set individually for each correction value. Fig. 25 is a functional block diagram of the timing control circuit 16 of this embodiment. A configuration different from the timing control circuit 16 of the second embodiment shown in Fig. 14 will be described.

[0120] The timing control circuit 16 of this embodiment is provided with two holding units 514A and 514B as a configuration equivalent to the holding unit 514 in Fig. 14. The holding units 514A and 514B each hold a correction value for correcting the threshold value T corresponding to the reading resolution, which is held in the holding unit 513. The correction value held in the holding unit 514A is represented as correction value A, and the correction value held in the holding unit 514B is represented as correction value B.

[0121] The set control circuit 600 is a circuit that controls the correction timing of the threshold T. FIG. 26 is a functional block diagram of the set control circuit 600. The set control circuit 600 has two sets of configurations corresponding to the period counter 511, period holding unit 512, and period comparison unit 516 of FIG. 14. The period counter 511A, period holding unit 512A, and period comparison unit 516A control the application timing of the correction value A of the holding unit 514A. The period counter 511B, period holding unit 512B, and period comparison unit 516B control the application timing of the correction value B of the holding unit 514B. The two sets of configurations function in the same manner as the period counter 511, period holding unit 512, and period comparison unit 516 of FIG. 14. The count value of the period counter 511A is represented as VCount A, and the count value of the period counter 511B is represented as VCount B.

[0122] 27 is a timing chart showing an example in which the threshold value T is corrected. In this example, the period setting value of the period holding unit 512A is 10240, and the period setting value of the period holding unit 512B is 5293. Correction value A and correction value B are both -1. The signal output by the period comparing unit 516A is referred to as correction flag A (correction notification A), and the signal output by the period comparing unit 516B is referred to as correction flag B (correction notification B).

[0123] 27, when correction flag A and correction flag B go to H level at the same time, correction value A and correction value B are simultaneously applied to threshold T and set in holding unit 515. Then, when the next read timing signal is output, held value A in holding unit 505 becomes 30, and threshold T is corrected from 32 to 30.

[0124] In this manner, in this embodiment, it is possible to apply a plurality of correction values ​​A and B. In the example of Fig. 27, correction value A and correction value B are applied simultaneously, but since the period setting values ​​of period holding units 512A and 512B are different, either correction value A or correction value B may be applied depending on the timing.

[0125] 27, multiple correction values ​​A and B are simultaneously applied, resulting in a total correction amount of the threshold T of −2. There are cases where the threshold T changes suddenly, affecting the image.

[0126] FIG. 28 shows another example. In this example, the cycle setting value of the cycle holding unit 512A is 10240, and the cycle setting value of the cycle holding unit 512B is 5293. The correction value A and the correction value B are both -0.5, and are set to a value (a value of 1 or less, a decimal) that is less than the resolution of the reference signal. In the example of FIG. 28, the correction flag A and the correction flag B are simultaneously set to the H level, so that the correction value A and the correction value B are simultaneously applied to the threshold T and set in the holding unit 515. However, the total correction amount of the correction value A and the correction value B is -1. By outputting the next reading timing signal, the held value A of the holding unit 505 becomes 31, and the threshold T is corrected from 32 to 31. It is possible to suppress a sudden change in the threshold T.

[0127] Sixth Embodiment Fig. 29 is a functional block diagram of the timing control circuit 16 of this embodiment. The timing control circuit 16 of this embodiment is obtained by adding a correction regulation unit 516 to the timing control circuit 16 of the fifth embodiment shown in Fig. 25, and other configurations are the same as those of the timing control circuit of Fig. 25.

[0128] The function of the correction regulating unit 516 will be described with reference to Fig. 30. Fig. 30 is a timing chart showing an example in which the threshold value T is corrected. In this example, the cycle setting value of the cycle holding unit 512A is 10240, and the cycle setting value of the cycle holding unit 512B is 5293. The correction value A and the correction value B are both -1.

[0129] In the example of Fig. 30, correction flag A and correction flag B are both at the H level at the same time. However, when the total correction amount is equal to or greater than the upper limit (equal to or greater than correction value MAX (=|1|: absolute value 1)), correction regulating unit 516 applies only one of the correction values ​​to threshold T. In the example shown, correction value A + correction value B = -1, and the absolute value is equal to or greater than 1. For this reason, correction regulating unit 516 corrects threshold T with correction value A, but does not reflect correction value B.

[0130] As a result, in section T4 between the next read timing signals, the threshold T is corrected from 32 to 31. The correction flag B corresponding to the correction value B that was not reflected is maintained at the H level. Therefore, the correction value B is applied in section T5 between the next read timing signals, and the threshold T is corrected from 32 to 31. This process makes it possible to reflect the correction values ​​A and B in the correction of the threshold T while suppressing abrupt changes in the threshold T.

[0131] 31 to 33B are flowcharts showing a processing example of the vertical magnification correction operation in this embodiment for realizing the example of FIG. 30, and are processing examples replacing those in FIGS.

[0132] In S101, initial settings are performed. Here, cycle setting values ​​are set in cycle holding units 512A and 512B, respectively. In addition, correction value A is set in holding unit 514A, and correction value B is set in holding unit 514B. Thereafter, threshold setting processing (S102), notification processing (S103), and notification processing (S104) are executed in parallel.

[0133] First, the notification process of S103 will be described with reference to Fig. 33(A). In S131, VCount A of cycle counter 511A is cleared. When a reference signal is input in S132, the process proceeds to S133, where VCount A is incremented by one. In S134, cycle comparator 516A determines whether VCount A has reached the cycle setting value of cycle holding unit 512A, and if it has reached the setting, the process proceeds to S135, and if it has not reached the setting, the process returns to S132. In S135, cycle comparator 516A outputs H-level correction flag A (correction notification A), and the arrival of the correction timing is notified to holding unit 515.

[0134] Next, the notification process of S104 will be described with reference to Fig. 33(B). In S141, VCount B of cycle counter 511B is cleared. When a reference signal is input in S142, the process proceeds to S143, where VCount B is incremented by one. In S144, cycle comparator 516B determines whether VCount B has reached the cycle setting value of cycle holding unit 512B, and if it has reached the setting, the process proceeds to S145, and if it has not reached the setting, the process returns to S142. In S145, cycle comparator 516B outputs correction flag B (correction notification B) at H level, and the arrival of the correction timing is notified to holding unit 515.

[0135] Next, the threshold set process of S102 will be described with reference to Fig. 32. In S111, it is determined whether or not a read timing signal has been output. When the read timing signal has been output, in S112, it is determined whether or not both correction notifications A and B have been notified from the set control circuit 600 to the holding unit 515. In other words, it is determined whether or not the application of correction value A and correction value B to threshold value T overlaps. If both have been notified, proceed to S113, and if neither have been notified, proceed to S119.

[0136] In S113, it is determined whether the absolute value of the total correction amount (=correction value A+correction value B) is equal to or greater than correction value MAX. If the total correction amount is equal to or greater than correction value MAX, the process proceeds to S114. If the total correction amount is less than correction value MAX, the process proceeds to S117. In S114, a value (corrected threshold T=threshold T+correction value A) obtained by adding correction value A held in holding unit 514A to threshold T held in holding unit 513 is held in holding unit 515. Note that correction value A is prioritized here, but correction value B may also be prioritized. In S115, correction notification A is cleared (correction flag A is set to L level). Correction notification B is not cleared (correction flag B is maintained at H level).

[0137] In S117, a value (corrected threshold T=threshold T+correction value A+correction value B) obtained by adding the correction value A held in holding unit 514A and the correction value A held in holding unit 514B to the threshold T held in holding unit 513 is held in holding unit 515. In S118, correction notification A and correction notification B are cleared (both correction flags A and B are set to the L level).

[0138] In S119, it is determined whether or not the set control circuit 600 has notified the holding unit 515 of either the correction notification A or the correction notification B. If the notification has been made, the process proceeds to S121, and if the notification has not been made, the process proceeds to S120. In S121, a value obtained by adding the correction value to be notified to the threshold value T held in the holding unit 513 is held in the holding unit 515. Specifically, when the correction notification A has been made, a value obtained by adding the correction value A held in the holding unit 514A to the threshold value T held in the holding unit 513 (corrected threshold value T=threshold value T+correction value A) is held in the holding unit 515. When the correction notification B has been made, a value obtained by adding the correction value B held in the holding unit 514B to the threshold value T held in the holding unit 513 (corrected threshold value T=threshold value T+correction value B) is held in the holding unit 515. In S120, the threshold value T held in the holding unit 513 is held in the holding unit 515.

[0139] The value held in holding unit 515 in S116 is held in holding unit 505 and used as threshold value T. The above operations are repeated.

[0140] Seventh Embodiment Next, another function of the correction regulating unit 516 of the sixth embodiment will be described with reference to Fig. 34. The configuration of the timing control circuit 16 is similar to that of the sixth embodiment.

[0141] 34 is a timing chart showing an example in which the threshold T is corrected. In this example, an operating waveform is shown when the index value Emag and the correction value of the threshold T are values ​​in the same direction. The values ​​in the same direction are when the index value Emag>1 and the correction value of the threshold T is a negative value, or when the index value Emag≦1 and the correction value of the threshold T is a positive value. The cycle setting value of the cycle holding unit 512A is 10240, and the correction value A is −1.

[0142] 34, the correction flag A (correction notification A) becomes H level, and 31 is set as the stored value B in the storage unit 515. After that, when the index value Emag is 1.03, in the section T6 between the read timing signals, in terms of the resolution unit of the reference signal, when the reference signal is input 30 times (600 dpi - 9600 dpi), the read timing signal is output, and the change from the threshold value T (32) is large.

[0143] 35 shows an example of selecting a threshold value by the correction regulating unit 516. In the illustrated example, the cycle setting value of the cycle holding unit 512A is 10240, and the correction value A is -1. When the correction flag A (correction notification A) transitions to the H level, the index value (NEXT_Emag) for generating the next reading timing signal is 1 or more, so the correction value A is not reflected in the holding unit 515. When the next index value becomes less than 1 (NEXT_Emag=0.99), the correction value A is reflected in the holding unit 515. Specifically, the value (corrected threshold T=threshold T+correction value A) obtained by adding the correction value A held in the holding unit 514A to the threshold T held in the holding unit 513 is held in the holding unit 515.

[0144] As a result, in the section T6 between the read timing signals, when the reference signal is input 31 times (600 dpi - 9600 dpi) in terms of the resolution unit of the reference signal, the read timing signal is output. Also, in the section T7, when the reference signal is input 32 times, the read timing signal is output. This prevents the threshold T from changing suddenly.

[0145] 36 to 38 are flowcharts showing an example of processing of the vertical magnification correction operation of this embodiment that realizes the example of FIG. 35. For simplicity of explanation, FIGS. 36 to 38 will explain the case of only vertical magnification correction related to correction value A, unlike the examples of FIGS. 31 to 33 of the sixth embodiment. However, similar processing is also applied when there are multiple vertical magnification corrections, such as when both correction values ​​A and B are applied. Conversely, the processing described below can also be applied to a configuration in which multiple correction values ​​are not used and a correction regulating unit 516 is provided in the configuration of the timing control circuit 16 as shown in FIG. 14.

[0146] In S102, initial settings are performed. Here, a cycle setting value is set in cycle holding unit 512A. Also, a correction value A is set in holding unit 514A. Thereafter, a threshold setting process (S202) and a notification process (S203) are executed in parallel.

[0147] First, the notification process of S203 will be described with reference to Fig. 38. In S221, VCount A of cycle counter 511A is cleared. When a reference signal is input in S222, the process proceeds to S223, where VCount A is incremented by one. In S224, cycle comparator 516A determines whether VCount A has reached the cycle setting value of cycle holding unit 512A, and if it has reached the setting, the process proceeds to S225, and if it has not reached the setting, the process returns to S2222. In S225, cycle comparator 516A outputs H-level correction flag A (correction notification A), and the arrival of the correction timing is notified to holding unit 515.

[0148] Next, the threshold value setting process in S202 will be described with reference to Fig. 37. In S211, it is determined whether or not a read timing signal has been output. When the read timing signal has been output, in S212, it is determined whether or not a correction notification A has been sent from the set control circuit 600 to the holding unit 515. If it has been sent, the process proceeds to S213, and if it has not been sent, the process proceeds to S217.

[0149] In S213, it is determined whether or not a predetermined condition is satisfied. One of the predetermined conditions is that the correction value A<0 and the index value (NEXT_EMAG) between the next read timing signals is ≦1 (condition 1). Another of the predetermined conditions is that the correction value A>0 and the index value (NEXT_EMAG) between the next read timing signals is>1 (condition 2). If either condition 1 or condition 2 is satisfied, the process proceeds to S214, and if not, the process proceeds to S217. In other words, in S213, it is determined that the vertical magnification correction by the correction value A and the reflected contents of the index value do not overlap.

[0150] In S214, the threshold value T held in holding unit 513 is added to the correction value A held in holding unit 514A, and the value (corrected threshold value T=threshold value T+correction value A) is held in holding unit 515. In S215, correction notification A is cleared (correction flag A is set to L level). In S217, threshold value T held in holding unit 513 is held in holding unit 515. In S216, the value held in holding unit 515 is held in holding unit 505 and used as threshold value T. The above operations are repeated.

[0151] As described above, in this embodiment, when the correction value of the threshold T and the reflection timing of the index value overlap, it is possible to prevent abrupt increases and decreases in the reading timing, and the impact on the image can be minimized. This is particularly effective in a configuration in which the medium 100 is conveyed from a state where it is conveyed only by the conveying rollers 6 to a state where the medium 100 enters the conveying rollers 7, as in this embodiment, and the setting of the vertical magnification correction can be simplified.

[0152] <Other embodiments> The present invention can also be realized by a process in which a program for realizing one or more functions of the above-mentioned embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) for realizing one or more functions.

[0153] <Disclosure of the embodiment> The above embodiment discloses the following inventions.

[0154] Item 1. A conveying roller for conveying the medium; a reading unit for reading an image on the medium conveyed by the conveying roller; A detection means for detecting a rotation phase of the conveying roller; a storage means for storing an index value corresponding to a rotational phase of the transport roller and corresponding to a transport amount of the transport roller per unit rotation angle; a timing control means for selecting the index value based on the detection result of the detection means, and for controlling the reading timing of the reading means based on a comparison result between an accumulated value of the index value and a threshold value corresponding to a reading resolution. A reading device comprising:

[0155] Item 2. The reading device according to item 1, The index value is set for each of a plurality of phase regions of the conveying roller. A reading device comprising:

[0156] Item 3. The reading device according to item 1 or 2, the detection means outputs a reference signal for each rotation of the conveying roller by the unit rotation angle; the threshold value corresponds to a count value of the reference signal, the index value is a corrected value obtained by correcting a count value of the reference signal in one cycle in accordance with the transport amount of the transport roller. A reading device comprising:

[0157] Item 4. A reading device according to any one of items 1 to 3, the timing control means outputs a read timing signal to the reading means when the accumulated value reaches the threshold value; A reading device comprising:

[0158] Item 5. Item 5. A reading device according to item 4, When the accumulated value reaches the threshold value, the timing control means subtracts the threshold value from the accumulated value. A reading device comprising:

[0159] Item 6. A reading device according to any one of items 1 to 5, The threshold value is changed in response to a change in the reading resolution. A reading device comprising:

[0160] Item 7. The reading device according to item 1, a setting means for setting the index value based on a result of reading the calibration chart by the reading means and storing the index value in the storage means; A reading device comprising:

[0161] Item 8. A reading device according to any one of items 1 to 7, The reading means includes a plurality of sensor units spaced apart in a conveying direction of the conveying roller, and each sensor unit includes a plurality of reading elements arranged in a direction intersecting the conveying direction. A reading device comprising:

[0162] Item 9. Item 5. A reading device according to item 4, The timing control means after a predetermined period corresponding to the rotation of the conveying roller has elapsed, when the reading timing signal is output, the corrected threshold value is compared with the cumulative value until the next reading timing signal is output; A reading device comprising:

[0163] Item 10. Item 9. A reading device according to item 9, At least one of the predetermined period or the correction amount of the threshold value is set according to the type of the medium. A reading device comprising:

[0164] Item 11. Item 9. A reading device according to item 9, At least one of the predetermined period or the correction amount of the threshold value is set according to a usage environment of the reading device. A reading device comprising:

[0165] Item 12. Item 9. A reading device according to item 9, the reading means includes a plurality of sensor units spaced apart in a conveying direction of the conveying roller, the timing control means includes a counting means that repeats the predetermined period, The initial value of the counting means is changed in a predetermined case. A reading device comprising:

[0166] Item 13. Item 13. A reading device according to item 12, a second transport roller is provided downstream of the transport roller in the transport direction of the medium; The predetermined case is when the medium reaches the second transport roller. A reading device comprising:

[0167] Item 14. Item 5. A reading device according to item 4, The timing control means after a first period corresponding to the rotation of the conveying roller has elapsed, when the reading timing signal is output, the threshold value corrected by a first correction value is compared with the cumulative value until the next reading timing signal is output; after a second period corresponding to the rotation of the conveying roller has elapsed, when the reading timing signal is output, the threshold value corrected by a second correction value is compared with the cumulative value until the next reading timing signal is output; A reading device comprising:

[0168] Item 15. Item 9. A reading device according to item 9, The timing control means A regulating means for regulating the correction of the threshold value is provided. A reading device comprising:

[0169] Item 16. Item 16. A reading device according to item 15, the regulating means selects whether or not to regulate based on the corrected value of the threshold value and the index value. A reading device comprising:

[0170] Item 17. Item 15. A reading device according to item 14, The timing control means a regulating means for regulating the threshold value from being simultaneously corrected by the first correction value and the second correction value; A reading device comprising:

[0171] Item 18. Item 18. A reading device according to item 17, the regulating means regulates the correction of the threshold value when a total correction amount for the threshold value at one time is equal to or greater than an upper limit value. A reading device comprising:

[0172] Item 19. Item 18. A reading device according to item 17, the regulating means regulates the correction of the threshold by selecting either the first correction value or the second correction value and correcting the threshold. A reading device comprising:

[0173] Item 20. A control method for a recording device including a transport roller for transporting a medium, a reading means for reading an image of the medium transported by the transport roller, a detection means for detecting a rotational phase of the transport roller, and a storage means for storing an index value associated with the rotational phase of the transport roller and corresponding to a transport amount of the transport roller per unit rotation angle, the control method including a timing control step of selecting the index value based on a detection result of the detection means, and controlling a reading timing of the reading means based on a comparison result between an accumulated value of the index value and a threshold value corresponding to a reading resolution, A control method comprising:

[0174] The invention is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention.

Claims

1. A transport roller for transporting the medium; a reading unit for reading an image on the medium conveyed by the conveying roller; A detection means for detecting a rotation phase of the conveying roller; a storage means for storing an index value corresponding to a rotational phase of the transport roller and corresponding to a transport amount of the transport roller per unit rotation angle; a timing control means for selecting the index value based on the detection result of the detection means, and for controlling the reading timing of the reading means based on a comparison result between an accumulated value of the index value and a threshold value corresponding to a reading resolution. A reading device comprising:

2. 2. The reading device according to claim 1, The index value is set for each of a plurality of phase regions of the conveying roller. A reading device comprising:

3. 2. The reading device according to claim 1, the detection means outputs a reference signal for each rotation of the conveying roller by the unit rotation angle; the threshold value corresponds to a count value of the reference signal, the index value is a corrected value obtained by correcting a count value of the reference signal in one cycle in accordance with the transport amount of the transport roller. A reading device comprising:

4. 2. The reading device according to claim 1, the timing control means outputs a read timing signal to the reading means when the accumulated value reaches the threshold value; A reading device comprising:

5. 5. The reading device according to claim 4, When the accumulated value reaches the threshold value, the timing control means subtracts the threshold value from the accumulated value. A reading device comprising:

6. 2. The reading device according to claim 1, The threshold value is changed in response to a change in the reading resolution. A reading device comprising:

7. 2. The reading device according to claim 1, a setting means for setting the index value based on a result of reading the calibration chart by the reading means and storing the index value in the storage means; A reading device comprising:

8. 2. The reading device according to claim 1, the reading means includes a plurality of sensor units spaced apart in a conveying direction of the conveying rollers, Each sensor unit includes a plurality of reading elements arranged in a direction intersecting the transport direction. A reading device comprising:

9. 5. The reading device according to claim 4, The timing control means after a predetermined period corresponding to the rotation of the conveying roller has elapsed, when the reading timing signal is output, the corrected threshold value is compared with the cumulative value until the next reading timing signal is output; A reading device comprising:

10. 10. The reading device according to claim 9, At least one of the predetermined period or the correction amount of the threshold value is set according to the type of the medium. A reading device comprising:

11. 10. The reading device according to claim 9, At least one of the predetermined period or the correction amount of the threshold value is set according to a usage environment of the reading device. A reading device comprising:

12. 10. The reading device according to claim 9, the reading means includes a plurality of sensor units spaced apart in a conveying direction of the conveying rollers, the timing control means includes a counting means for repeating the predetermined period; The initial value of the counting means is changed in a predetermined case. A reading device comprising:

13. 13. A reading device according to claim 12, a second transport roller is provided downstream of the transport roller in the transport direction of the medium; The predetermined case is when the medium reaches the second transport roller. A reading device comprising:

14. 5. The reading device according to claim 4, The timing control means after a first period corresponding to the rotation of the conveying roller has elapsed, when the reading timing signal is output, the threshold value corrected by a first correction value is compared with the cumulative value until the next reading timing signal is output; after a second period corresponding to the rotation of the conveying roller has elapsed, when the reading timing signal is output, the threshold value corrected by a second correction value is compared with the cumulative value until the next reading timing signal is output; A reading device comprising:

15. 10. The reading device according to claim 9, The timing control means A regulating means for regulating the correction of the threshold value is provided. A reading device comprising:

16. 16. A reading device according to claim 15, the regulating means selects whether or not to regulate based on the corrected value of the threshold value and the index value. A reading device comprising:

17. 15. A reading device according to claim 14, The timing control means a regulating means for regulating the threshold value from being simultaneously corrected by the first correction value and the second correction value; A reading device comprising:

18. 18. A reading device according to claim 17, the regulating means regulates the correction of the threshold value when a total correction amount for the threshold value at one time is equal to or greater than an upper limit value. A reading device comprising:

19. 18. A reading device according to claim 17, the regulating means regulates the correction of the threshold by selecting either the first correction value or the second correction value and correcting the threshold. A reading device comprising:

20. A control method for a recording device including a transport roller for transporting a medium, a reading means for reading an image of the medium transported by the transport roller, a detection means for detecting a rotational phase of the transport roller, and a storage means for storing an index value associated with the rotational phase of the transport roller and corresponding to a transport amount of the transport roller per unit rotation angle, the control method including a timing control step of selecting the index value based on a detection result of the detection means, and controlling a reading timing of the reading means based on a comparison result between an accumulated value of the index value and a threshold value corresponding to a reading resolution, A control method comprising:

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