Image reading device

Abstract

To provide an image reading device that can improve image quality. [Solution] The image reading device comprises a transport unit for transporting a document, a reading unit for reading the document transported by the transport unit, a reference plate positioned opposite the reading unit, and a control unit. The reading unit includes an image sensor and a light source. The control unit performs a light intensity adjustment process to adjust the light intensity of the light source based on the amount of light received by the image sensor when the light source irradiates light toward the reference plate, and an acquisition process to acquire a reference value used for shading correction based on the amount of light received by the image sensor when the light source irradiates light toward the reference plate.

Description

Technical Field

[0001] The present invention relates to an image reading apparatus.

Background Art

[0002] Patent Document 1 describes an image reading apparatus that executes a process of obtaining a reference value used for shading correction. The image reading apparatus improves image quality by performing shading correction based on the obtained reference value.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In such a reading apparatus, there is room for improvement in improving image quality.

Means for Solving the Problems

[0005] The image reading apparatus that solves the above problems includes a conveyance unit that conveys a document, a reading unit that reads the document conveyed by the conveyance unit, a reference plate positioned to face the reading unit, and a control unit. The reading unit has an image sensor and a light source. The control unit executes a light amount adjustment process of adjusting the light amount of the light source based on the amount of received light received by the image sensor when the light source irradiates the reference plate with light, and an acquisition process of obtaining a reference value used for shading correction based on the amount of received light received by the image sensor when the light source irradiates the reference plate with light.

Brief Description of the Drawings

[0006] [Figure 1]Figure 1 shows an example of an image reading device. [Figure 2] Figure 2 is a flowchart showing an example of the reading process. [Figure 3] Figure 3 is a flowchart showing an example of parallel processing. [Modes for carrying out the invention]

[0007] The following describes an embodiment of an image reading device with reference to the diagram. An image reading device is a device that reads images from original documents such as paper or film. <Image reading device> As shown in Figure 1, the image reading device 11 includes a document tray 12. The document tray 12 is configured to hold the document M1. The document M1 is set on the document tray 12 when it is placed on it. The document tray 12 is a so-called flatbed.

[0008] The document feeder 12 has a housing 13. When the document M1 is placed on the housing 13, the document M1 is set on the document feeder 12. The document tray 12 has one or more transparent plates. The document tray 12 has a first transparent plate 14 and a second transparent plate 15. The transparent plates are attached to the housing 13. The transparent plates constitute the top plate of the housing 13. The first transparent plate 14 and the second transparent plate 15 are positioned side by side with a gap between them. The first transparent plate 14 is a plate with a larger area than the second transparent plate 15. The first transparent plate 14 is a transparent plate on which the document M1 is placed. The document M1 is set on the document tray 12 by being placed on the first transparent plate 14.

[0009] The image reading device 11 includes a cover 16. The cover 16 is attached to the document glass 12. The cover 16 is positioned to overlap with the document glass 12. The cover 16 is positioned to overlap the document glass 12 both vertically and horizontally. The cover 16 is configured to open and close relative to the document glass 12. When the cover 16 is opened, transparent plates are exposed. Specifically, when the cover 16 is opened, a first transparent plate 14 and a second transparent plate 15 are exposed. Therefore, by opening the cover 16, the document M1 can be placed on the document glass 12. When the cover 16 is closed relative to the document glass 12, it presses down on the document M1 placed on the document glass 12 from above. In the state shown in Figure 1, the cover 16 is closed relative to the document glass 12. The document M1 is read by the image reading device 11 by being sandwiched between the document glass 12 and the cover 16.

[0010] The image reading device 11 includes an automatic paper feeder 17. The automatic paper feeder 17 is configured to automatically feed the original document M1. The automatic paper feeder 17 is attached to the cover 16. More specifically, the automatic paper feeder 17 is incorporated into the cover 16. The automatic paper feeder 17 is configured to hold the original document M1. The automatic paper feeder 17 is configured to feed the set original document M1 into the cover 16. The automatic paper feeder 17 is a so-called automatic document feeder.

[0011] The automatic paper feeder 17 forms a transport path 18. More specifically, the automatic paper feeder 17 forms a transport path 18 within the cover 16. The transport path 18 is the path through which the original document M1 is transported. The transport path 18 extends within the cover 16. When the cover 16 is closed, the transport path 18 extends to pass through a position facing the second transparent plate 15. The original document M1 is read by the image reading device 11 as it is transported along the transport path 18.

[0012] The automatic paper feeder 17 has a supply tray 19. The supply tray 19 is attached to the cover 16. The supply tray 19 extends from the cover 16. The supply tray 19 is configured to hold the document M1. The document M1 is set in the automatic paper feeder 17 when the document M1 is placed on the supply tray 19.

[0013] The automatic paper feeder 17 has a transport unit 20. The transport unit 20 is attached to the cover 16. The transport unit 20 is configured to transport the original document M1. The transport unit 20 transports the original document M1 loaded on the supply tray 19. The transport unit 20 transports the original document M1 along the transport path 18.

[0014] The transport unit 20 has one or more rollers. The transport unit 20 has, for example, a pick roller 21. The pick roller 21 transports the documents M1 loaded in the supply tray 19 one by one. In one example, the pick roller 21 contacts the uppermost document M1 among the multiple documents M1 loaded in the supply tray 19. The pick roller 21 feeds the uppermost document M1 among the multiple documents M1 one by one. The transport unit 20 has one or more transport rollers 22. In addition to the pick roller 21, the transport unit 20 has multiple transport rollers 22. The multiple transport rollers 22 are positioned along the transport path 18. The transport rollers 22 transport the documents M1 fed by the pick roller 21.

[0015] The automatic paper feeder 17 has an output tray 23. The output tray 23 is attached to the cover 16. The output tray 23 extends from the cover 16. The output tray 23 is configured to receive documents M1 ejected from the cover 16. The output tray 23 receives scanned documents M1.

[0016] The automatic paper feeder 17 may have a supply sensor 24. The supply sensor 24 is configured to detect the original document M1 loaded in the supply tray 19. The supply sensor 24 detects the presence or absence of the original document M1 loaded in the supply tray 19. The supply sensor 24 may be a contact sensor or an optical sensor.

[0017] The automatic paper feeder 17 may have a document sensor 25. The document sensor 25 is configured to detect the document M1 conveyed by the conveyance unit 20. The document sensor 25 is configured to detect the document M1 conveyed along the conveyance path 18. Specifically, the document sensor 25 is configured to detect the document M1 before reading. The document sensor 25 is located along the conveyance path 18. In one example, the document sensor 25 is located upstream of the position facing the second transparent plate 15 in the conveyance path 18 to detect the document M1. The document sensor 25 may be a contact sensor or an optical sensor.

[0018] The image reading device 11 includes one or more reading units. The image reading device 11 includes a first reading unit 26. The image reading device 11 may include a second reading unit 27. The reading unit is configured to read the document M1. The first reading unit 26 is configured to read the front surface of the document M1. The second reading unit 27 is configured to read the back surface of the document M1. By including the second reading unit 27 in addition to the first reading unit 26, the image reading device 11 can read both sides of the document M1.

[0019] The first reading unit 26 is attached to the document table 12. The first reading unit 26 is housed in the housing 13. The first reading unit 26 is configured to scan within the housing 13. The first reading unit 26 reads the document M1 through the transparent plate.

[0020] The first reading unit 26 reads the document M1 through the first transparent plate 14. At this time, the first reading unit 26 reads the document M1 placed on the first transparent plate 14. The first reading unit 26 moves along the first transparent plate 14 to read the document M1 placed on the first transparent plate 14. That is, the first reading unit 26 reads the document M1 set on the flatbed.

[0021] The first reading unit 26 reads the document M1 through the second transparent plate 15. At this time, the first reading unit 26 reads the document M1 conveyed by the conveying unit 20. The first reading unit 26 reads the document M1 conveyed through the conveyance path 18 through the second transparent plate 15 by being positioned at a position facing the second transparent plate 15. That is, the first reading unit 26 reads the document M1 set in the auto document feeder.

[0022] The second reading unit 27 is attached to the cover 16. The second reading unit 27 is located inside the cover 16. The second reading unit 27 is located along the conveyance path 18. In one example, the second reading unit 27 is located downstream of the first reading unit 26 in the conveyance path 18. The second reading unit 27 reads the document M1 conveyed through the conveyance path 18. That is, the second reading unit 27 reads the document M1 set in the auto document feeder.

[0023] The reading unit has one or more image sensors. The first reading unit 26 has one or more first image sensors 28. The second reading unit 27 has one or more second image sensors 29. The image sensor is configured to output an electrical signal corresponding to the amount of received light by receiving light. The image sensor is configured to perform so-called photoelectric conversion. The image sensor is, for example, a sensor including CMOS. One or more image sensors may be configured as a contact image sensor module. The reading unit may have a plurality of contact image sensor modules.

[0024] The image sensor is configured to receive light incident from a position facing the reading unit. The first image sensor 28 is configured to receive light incident from a position facing the first reading unit 26. The second image sensor 29 is configured to receive light incident from a position facing the second reading unit 27.

[0025] The reading unit has a light source. The first reading unit 26 has a first light source 30. The second reading unit 27 has a second light source 31. The light source is configured to emit light. In one example, the light source is configured to emit white light. The light source is, for example, an LED.

[0026] The light sources are configured to irradiate light toward a position opposite the reading unit. The first light source 30 is configured to irradiate light toward a position opposite the first reading unit 26. The second light source 31 is configured to irradiate light toward a position opposite the second reading unit 27. The first light source 30 irradiates light onto the document M1, for example, through the first transparent plate 14 or through the second transparent plate 15. The second light source 31 irradiates light onto the document M1 as it is being transported along the transport path 18, for example. When a light source irradiates light onto the document M1, the reflected light is incident on the image sensor due to reflection from the document M1. When the first light source 30 irradiates light onto the document M1, the reflected light is incident on the first image sensor 28. When the second light source 31 irradiates light onto the document M1, the reflected light is incident on the second image sensor 29. As a result, the document M1 is read.

[0027] The reading unit has a carriage. The first reading unit 26 has a first carriage 32. The second reading unit 27 has a second carriage 33. The carriage is equipped with an image sensor and a light source. The first carriage 32 is equipped with a first image sensor 28 and a first light source 30. The second carriage 33 is equipped with a second image sensor 29 and a second light source 31.

[0028] The first carriage 32 is configured to move within the housing 13. The first carriage 32 is configured to move between a home position P1 and a reading position P2. Home position P1 is the position where the first carriage 32 is waiting. Home position P1 is the position where the first carriage 32 is retracted from the first transparent plate 14. Home position P1 is the position where the first carriage 32 is retracted from the second transparent plate 15. Home position P1 is the position opposite the space between the first transparent plate 14 and the second transparent plate 15. Reading position P2 is the position where the transported document M1 is read. Reading position P2 is the position opposite the second transparent plate 15.

[0029] The first carriage 32 may move to a position other than the home position P1 and the reading position P2. The first carriage 32 is configured to move from a position facing the first transparent plate 14 to a position facing the second transparent plate 15. The first carriage 32 may also move to a position facing the first transparent plate 14. By moving along the first transparent plate 14, the first carriage 32 causes the first image sensor 28 to read the document M1 set on the document glass 12.

[0030] The second carriage 33 is fixed to the cover 16. Therefore, unlike the first carriage 32, the second carriage 33 is configured not to move. The second carriage 33 simply holds the second image sensor 29 and the second light source 31.

[0031] The image reading device 11 includes one or more reference plates. The image reading device 11 includes a first reference plate 34 and a second reference plate 35. The reference plates are plates that serve as a reference when calibrating the reading unit. The first reference plate 34 is the plate that serves as a reference when calibrating the first reading unit 26. The second reference plate 35 is the plate that serves as a reference when calibrating the second reading unit 27.

[0032] The reference plate is positioned to face the reading unit. The first reference plate 34 is positioned to face the first reading unit 26. The first reference plate 34 is positioned to face the first reading unit 26 located at home position P1. The first reference plate 34 is attached to the housing 13. The first reference plate 34 is positioned between the first transparent plate 14 and the second transparent plate 15. The second reference plate 35 is positioned to face the second reading unit 27. The second reference plate 35 is attached to the cover 16.

[0033] The reference plate is a plate used to obtain a reference value used for calibrating the reading unit. The reading unit obtains the reference value by reading the reference plate. The reference value is a value used for shading correction. Shading correction will be described later. The reference value may be used for purposes other than shading correction. The reference value is, for example, a reference value for white. The reference value is, for example, a value indicating the level at which the luminance value is 255 in a 256-level scale. The reference plate is, for example, a plate that exhibits white color. The reference plate reflects light emitted from the light source, and the reflected light is incident on the image sensor. As a result, the image sensor outputs the reference value.

[0034] The reference value may be the output value of the image sensor when the light source is on. The reference value may also be a value calculated based on the output value of the image sensor when the light source is on and the output value of the image sensor when the light source is off. When the light source is on, an output value indicating white is obtained from the image sensor. When the light source is off, an output value indicating black is obtained from the image sensor. The reference value may be obtained by subtracting the output value indicating black from the output value indicating white. In other words, the reference value may be a value obtained by offsetting the output value indicating black from the output value indicating white.

[0035] The reference plate is not limited to white; for example, it may be a plate that exhibits gray color. In this case as well, the reference value is obtained by the reading unit reading the reference plate. When the reading unit reads the reference plate, an output value indicating gray is obtained from the image sensor. The reference value is obtained by multiplying the ratio of the output value indicating gray to the initial value indicating gray by the initial value indicating white. The initial values ​​indicating gray and the initial values ​​indicating white are stored in advance in the image reading device 11.

[0036] The image reading device 11 includes a control unit 36. The control unit 36 ​​is configured to control the image reading device 11. The control unit 36 ​​controls the transport unit 20. The control unit 36 ​​controls the first reading unit 26 and the second reading unit 27. The control unit 36 ​​is housed in a housing 13. The control unit 36 ​​is located inside the housing 13. The control unit 36 ​​includes, for example, a control board for the image reading device 11.

[0037] The control unit 36 ​​is connected to the reading unit. The control unit 36 ​​acquires electrical signals from the image sensor. That is, the control unit 36 ​​acquires output values ​​from the image sensor. The control unit 36 ​​is configured to generate a read image from the output values. The control unit 36 ​​generates the read image by converting the output values ​​into brightness values ​​for each pixel.

[0038] The control unit 36 ​​has a control circuit 37. The control circuit 37 may have one or more processors that execute each process according to a computer program. The control circuit 37 may have one or more hardware circuits, such as ASICs, that execute at least some of the various processes. The control circuit 37 may have a circuit that includes a combination of processors and hardware circuits. The processor includes a CPU and memory such as ROM and RAM. The memory stores program code or instructions configured to cause the CPU to execute processes. The memory, i.e., computer-readable media, includes any readable media that can be accessed by a general-purpose or dedicated computer.

[0039] The control circuit 37 is configured to correct the read image. For example, the control circuit 37 performs shading correction on the read image. Shading correction is a process that corrects color unevenness in the read image. Shading correction is a process that corrects the gradation of pixels. Shading correction is a process that corrects the reading result of the reading unit. Therefore, shading correction is a process that calibrates the reading unit. In image sensors, sensitivity may change due to aging, environmental changes, etc. That is, in image sensors, the output of the electrical signal in response to the amount of light received may change. Also, in multiple image sensors, the sensitivity may differ from one another due to individual differences. Therefore, by correcting the gradation of the brightness value obtained from the image sensor, the reproducibility of the brightness value is ensured. In addition to shading correction, the control circuit 37 may also perform gamma processing on the read image, for example. This improves image quality.

[0040] The control unit 36 ​​has an analog front end 38. The analog front end 38 is connected to the reading unit. The analog front end 38 is connected to the first reading unit 26. The analog front end 38 is connected to the second reading unit 27.

[0041] The analog front-end 38 receives electrical signals from the image sensor. The analog front-end 38 is configured to amplify the electrical signals, remove noise from the electrical signals, and perform A / D conversion on the electrical signals. The analog front-end 38 includes hardware circuitry, such as an ASIC. The analog front-end 38 outputs the A / D converted electrical signals to the control circuit 37.

[0042] The analog front end 38 may be mounted on the same board as the control circuit 37. In this case, the analog front end 38 is not mounted on the carriage. The analog front end 38 generates heat as it processes electrical signals. By not mounting the analog front end 38 on the carriage, the heat generated from the analog front end 38 is less likely to reach the reading section. That is, the heat generated from the analog front end 38 is less likely to reach the first reading section 26 and the second reading section 27. This reduces the risk that the reading results of the reading section may change due to the effects of heat. This is because the output of the reading section may change depending on the ambient temperature.

[0043] The control unit 36 ​​is configured to perform calibration of the reading unit. In the reading unit, the output may change due to individual differences in elements, aging of elements, environmental factors, etc. In the reading unit, not only the sensitivity of the image sensor but also the output of the light source may change. Therefore, the control unit 36 ​​improves the reading image quality by calibrating the image sensor, light source, etc.

[0044] The control unit 36 ​​is configured to perform light intensity adjustment processing. Light intensity adjustment processing is the process of adjusting the light intensity of the light source. Light intensity adjustment processing is the process of adjusting the light intensity of the first light source 30. Light intensity adjustment processing may also include the process of adjusting the light intensity of the second light source 31. The light intensity of a light source may change due to aging deterioration, environmental factors, etc. For example, if the light intensity decreases, the read image tends to become darker. Therefore, the control unit 36 ​​improves image quality by adjusting the light intensity of the light source.

[0045] The light intensity adjustment process is a process that adjusts the light intensity of a light source based on the amount of light received by the image sensor when the light source irradiates light toward a reference plate. The light intensity adjustment process may also be a process that adjusts the light intensity of the light source based on a reference value. In the light intensity adjustment process, the control unit 36 ​​turns on the light source for a predetermined time. The control unit 36 ​​acquires the amount of light received by the image sensor by turning on the light source for a predetermined time. That is, the control unit 36 ​​acquires an output value from the image sensor. The control unit 36 ​​determines whether the output value is within a predetermined range. The predetermined range is determined by a threshold value. The threshold value is stored in the control unit 36 ​​in advance. If the output value is not within the predetermined range, the control unit 36 ​​adjusts the light intensity of the light source so that the output value is within the predetermined range. In one example, the control unit 36 ​​adjusts the light intensity of the light source so that the maximum or minimum value among the multiple output values ​​output from multiple image sensors is within the predetermined range. The control unit 36 ​​may also adjust the light intensity of the light source based on the proportion of output values ​​that are within the predetermined range. The control unit 36 ​​adjusts the light intensity of the light source by adjusting the lighting time of the light source. As the illumination time increases, the light intensity of the light source increases. The control unit 36 ​​extends the illumination time of the light source by, for example, reducing the transport speed of the document M1 by the transport unit 20 or reducing the movement speed of the first carriage 32. The control unit 36 ​​may also adjust the light intensity of the light source by adjusting the applied voltage to the light source. As the applied voltage increases, the light intensity of the light source increases.

[0046] The control unit 36 ​​is configured to perform an acquisition process. The acquisition process is the process of acquiring a reference value used for shading correction. The control unit 36 ​​acquires the reference value based on the amount of light received by the image sensor when the light source irradiates light toward a reference plate. The acquisition process is the process of acquiring a reference value from the first image sensor 28 that is used when correcting the gradation of the brightness value by the first image sensor 28. The acquisition process may also include the process of acquiring a reference value from the second image sensor 29 that is used when correcting the gradation of the brightness value by the second image sensor 29.

[0047] The control unit 36 ​​is configured to perform the acquisition process after the light intensity adjustment process. That is, the control unit 36 ​​acquires a reference value based on the amount of light received by the image sensor with the adjusted light intensity. If the acquisition process is performed before the light intensity adjustment process, shading correction may not be performed properly.

[0048] The control unit 36 ​​performs light intensity adjustment and acquisition processing when the reading of the document M1 begins. The control unit 36 ​​performs light intensity adjustment and acquisition processing before the reading unit reads the document M1. As a result, the reading unit can read the document M1 in a calibrated state.

[0049] The control unit 36 ​​performs light intensity adjustment processing and acquisition processing when it receives an instruction to start reading the document M1. The control unit 36 ​​starts reading the document M1 based on the user's instruction. The control unit 36 ​​starts reading the document M1 based on instructions input through the touch panel of the image reading device 11, an operating terminal connected to the image reading device 11, etc.

[0050] The control unit 36 ​​may perform a light intensity adjustment process before starting to transport the original document M1. The control unit 36 ​​may perform an acquisition process before starting to transport the original document M1. The control unit 36 ​​may start transporting the original document M1 after completing the acquisition process.

[0051] The control unit 36 ​​may perform the acquisition process after the transport of the original document M1 has started. In other words, the control unit 36 ​​may perform the transport of the original document M1 and the acquisition process in parallel. This allows the transport of the original document M1 to start earlier compared to when the light intensity adjustment process and the acquisition process are performed before the transport of the original document M1 starts. This improves processing efficiency. In addition, the time from inputting the reading instruction to the start of the transport of the original document M1 is shortened, which reduces stress for the user.

[0052] The control unit 36 ​​may stop the transport unit 20 after starting to transport the document M1, based on the detection result of the document sensor 25. When the transport and acquisition processes of the document M1 are performed in parallel, there is a risk that the document M1 may reach the second transparent plate 15 before the first reading unit 26 reaches the reading position P2. Therefore, the control unit 36 ​​may stop the transport unit 20 if the document sensor 25 detects the document M1 before the first reading unit 26 reaches the reading position P2. This reduces the risk that the document M1 may reach the second transparent plate 15 before the first reading unit 26 reaches the reading position P2. If the first reading unit 26 reaches the reading position P2 after the transport unit 20 has been stopped, the control unit 36 ​​restarts driving the transport unit 20. This ensures that the document M1 is read properly. The control unit 36 ​​determines the position of the first carriage 32, for example, by a linear encoder (not shown).

[0053] The control unit 36 ​​may perform light intensity adjustment and acquisition processing between documents M1. That is, the control unit 36 ​​may perform light intensity adjustment and acquisition processing after the reading of one document M1 is complete and before the reading of the next document M1 begins. In the image reading device 11, multiple documents M1 may be loaded into the supply tray 19. In this case, the image reading device 11 will read the multiple documents M1 one by one in succession. If the number of documents read increases, there is a risk that the sensitivity of the image sensor may change. Therefore, if light intensity adjustment and acquisition processing are performed between documents M1, image quality will be maintained. In one example, the control unit 36 ​​does not perform light intensity adjustment and acquisition processing between documents M1. This is because the analog front end 38 is not mounted on the carriage, so the reading unit is less affected by heat. Therefore, image quality is easily maintained even if light intensity adjustment and acquisition processing are not performed between documents M1.

[0054] <Reading process> Next, an example of the reading process will be described. The reading process is performed by the control unit 36. The reading process is initiated when a reading instruction is input from the user.

[0055] As shown in Figure 2, in step S11, the control unit 36 ​​moves the first carriage 32 to the home position P1. As a result, the first reading unit 26 faces the first reference plate 34.

[0056] In step S12, the control unit 36 ​​performs a light intensity adjustment process. That is, the control unit 36 ​​performs the light intensity adjustment process when the first reading unit 26 is in the home position P1. At this time, the control unit 36 ​​adjusts the light intensity of the first light source 30 based on the amount of light received by the first image sensor 28 as the first light source 30 irradiates the first reference plate 34 with light.

[0057] In step S13, the control unit 36 ​​starts transporting the document M1. After completing the light intensity adjustment process, the control unit 36 ​​starts driving the transport unit 20. As a result, the document M1 is fed from the supply tray 19.

[0058] In step S14, the control unit 36 ​​starts parallel processing. At this time, the control unit 36 ​​executes a program to perform parallel processing in parallel with the program to perform the reading process. Parallel processing is a process that is executed in parallel with the reading process. Parallel processing is executed in parallel with the transport of the document M1.

[0059] As shown in Figure 3, the control unit 36 ​​starts parallel processing after starting to transport the document M1. In step S21, the control unit 36 ​​performs the acquisition process. That is, the control unit 36 ​​performs the acquisition process when the first reading unit 26 is in the home position P1. At this time, the control unit 36 ​​acquires a reference value based on the amount of light received by the first image sensor 28, which is adjusted by the light source adjustment process.

[0060] In step S22, the control unit 36 ​​moves the first reading unit 26 to the reading position P2. That is, the control unit 36 ​​moves the first reading unit 26 to the reading position P2 after the light source adjustment process and the acquisition process are completed. At this time, the first reading unit 26 moves from the home position P1 to the reading position P2. When the first reading unit 26 reaches the reading position P2, the control unit 36 ​​terminates the parallel processing.

[0061] As shown in Figure 2, in step S15, the control unit 36 ​​determines whether the document sensor 25 has detected the document M1. If the document sensor 25 has not detected the document M1, the control unit 36 ​​repeats the process in step S15. After starting to transport the document M1, the control unit 36 ​​waits until the document sensor 25 detects the document M1. When the document sensor 25 detects the document M1, the control unit 36 ​​proceeds to step S16.

[0062] In step S16, the control unit 36 ​​determines whether the first reading unit 26 has reached the reading position P2. That is, the control unit 36 ​​determines whether parallel processing is complete. If the first reading unit 26 has reached the reading position P2, the control unit 36 ​​proceeds to step S17. If the first reading unit 26 has not reached the reading position P2, the control unit 36 ​​proceeds to step S18.

[0063] In step S17, the control unit 36 ​​reads the original document M1. At this time, the control unit 36 ​​reads the original document M1 with the first reading unit 26. In addition to the first reading unit 26, the control unit 36 ​​may also read the original document M1 with the second reading unit 27. The control unit 36 ​​ejects the original document M1 while reading it. Once the control unit 36 ​​has finished ejecting the original document M1, it terminates the reading process. If there is another original document M1, the control unit 36 ​​may start the reading process again. In this case, light intensity adjustment and acquisition processes may or may not be performed. If light intensity adjustment and acquisition processes are not performed, the first reading unit 26 can remain at the reading position P2.

[0064] In step S18, the control unit 36 ​​stops the transport of the document M1. At this time, the control unit 36 ​​stops the transport unit 20. In other words, the control unit 36 ​​stops the transport unit 20 if the document sensor 25 detects the document M1 before the first reading unit 26 reaches the reading position P2. This reduces the risk that the document M1 will pass over the second transparent plate 15 before the first reading unit 26 reaches the reading position P2.

[0065] In step S19, the control unit 36 ​​determines whether the first reading unit 26 has reached the reading position P2. That is, the control unit 36 ​​determines whether parallel processing has been completed. If the first reading unit 26 has not reached the reading position P2, the control unit 36 ​​repeats the process in step S19. The control unit 36 ​​waits until the first reading unit 26 reaches the reading position P2. When the first reading unit 26 reaches the reading position P2, the control unit 36 ​​proceeds to step S20.

[0066] In step S20, the control unit 36 ​​resumes transporting the document M1. At this time, the control unit 36 ​​resumes driving the transport unit 20. As a result, the document M1 is transported from the document sensor 25 toward the second transparent plate 15. After resuming the transport of the document M1, the control unit 36 ​​executes the process in step S17.

[0067] <Effects and Effects of the Examples> Next, the operation and effects of the above embodiment will be described. (1) The control unit 36 ​​performs a light intensity adjustment process to adjust the light intensity of the light source based on the amount of light received by the image sensor when the light source irradiates light toward the reference plate. The control unit 36 ​​also performs an acquisition process to acquire a reference value used for shading correction based on the amount of light received by the image sensor when the light source irradiates light toward the reference plate. With the above configuration, the control unit 36 ​​performs a light intensity adjustment process in addition to the acquisition process. This improves image quality.

[0068] (2) The control unit 36 ​​performs light intensity adjustment processing before the transport unit 20 starts transporting the original document M1. The control unit 36 ​​performs acquisition processing after the transport unit 20 starts transporting the original document M1. With the above configuration, compared to the case where the light intensity adjustment processing and acquisition processing are performed before the transport unit 20 starts transporting the original document M1, the transport of the original document M1 and the acquisition processing are performed in parallel, thus improving processing efficiency.

[0069] (3) The image reading device 11 is equipped with a document sensor 25. With the above configuration, the image reading device 11 can detect that the document M1 is being transported correctly. (4) The control unit 36 ​​performs light intensity adjustment processing and acquisition processing while the first reading unit 26 is in the home position P1. After the light intensity adjustment processing and acquisition processing are completed, the control unit 36 ​​moves the first reading unit 26 to the reading position P2. If the document sensor 25 detects the document M1 before the first reading unit 26 reaches the reading position P2, the control unit 36 ​​stops the transport unit 20. With the above configuration, the risk of the document M1 passing the position corresponding to the reading position P2 before the first reading unit 26 reaches the reading position P2 is reduced.

[0070] (5) The analog front end 38 is not mounted on the carriage. With the above configuration, the reading unit is less affected by the heat generated by the analog front end 38 compared to when the analog front end 38 is mounted on the carriage. As a result, the image quality is less likely to deteriorate.

[0071] <Technical philosophy> The technical concepts and their effects, as understood from the above-described examples, are explained below. (A) The image reading device comprises a transport unit for transporting a document, a reading unit for reading the document transported by the transport unit, a reference plate positioned opposite the reading unit, and a control unit. The reading unit includes an image sensor and a light source. The control unit performs a light intensity adjustment process to adjust the light intensity of the light source based on the amount of light received by the image sensor when the light source irradiates light toward the reference plate, and an acquisition process to acquire a reference value used for shading correction based on the amount of light received by the image sensor when the light source irradiates light toward the reference plate. According to the above configuration, the control unit performs the light intensity adjustment process in addition to the acquisition process. This improves image quality.

[0072] (B) In the above image reading device, the control unit may perform the light intensity adjustment process before the transport unit starts transporting the document, and perform the acquisition process after the transport unit starts transporting the document. With the above configuration, compared to the case where the light intensity adjustment process and the acquisition process are performed before the transport unit starts transporting the document, the document transport and the acquisition process are performed in parallel, thus improving processing efficiency.

[0073] (C) The image reading device may be equipped with a document sensor that detects the document being transported to the transport unit before it reaches the reading unit. With the above configuration, the image reading device can detect that the document is being transported correctly.

[0074] (D) In ​​the above image reading device, the reading unit has a carriage on which the image sensor and the light source are mounted, and is configured to move between a home position and a reading position by the carriage, and the control unit executes the light intensity adjustment process and the acquisition process when the reading unit is located at the home position, moves the reading unit to the reading position after the light intensity adjustment process and the acquisition process are completed, and may stop the transport unit if the document sensor detects a document before the reading unit reaches the reading position. With the above configuration, the risk of the document passing a position corresponding to the reading position before the reading unit reaches the reading position is reduced.

[0075] (E) The image reading device comprises a housing that accommodates the reading unit and the control unit, the reading unit has a carriage on which the image sensor and the light source are mounted, and the control unit has an analog front end connected to the reading unit, the analog front end does not have to be mounted on the carriage. With the above configuration, the reading unit is less affected by the heat generated from the analog front end compared to when the analog front end is mounted on the carriage. As a result, the image quality is less likely to deteriorate. [Explanation of Symbols]

[0076] 11…Image reading device, 12…Document glass, 13…Housing, 14…First transparent plate, 15…Second transparent plate, 16…Cover, 17…Automatic paper feeder, 18…Transport path, 19…Supply tray, 20…Transport unit, 21…Pick roller, 22…Transport roller, 23…Output tray, 24…Supply sensor, 25…Document sensor, 26…First reading unit, 27…Second reading unit, 28…First image sensor, 29…Second image sensor, 30…First light source, 31…Second light source, 32…First carriage, 33…Second carriage, 34…First reference plate, 35…Second reference plate, 36…Control unit, 37…Control circuit, 38…Analog front end, M1…Document, P1…Home position, P2…Scanning position.

Claims

1. A transport unit that transports the manuscript, A reading unit that reads the document being transported by the transport unit, A reference plate positioned opposite the reading unit, It comprises a control unit and, The reading unit is, Image sensor and It has a light source, The control unit, A light intensity adjustment process that adjusts the amount of light from the light source based on the amount of light received by the image sensor when the light source irradiates light toward the reference plate, An image reading device characterized by performing an acquisition process to acquire a reference value used for shading correction based on the amount of light received by the image sensor when the light source irradiates the reference plate with light.

2. The control unit, The light intensity adjustment process is performed before the transport unit starts transporting the document. The image reading device according to claim 1, characterized in that the acquisition process is performed after the transport unit starts transporting the original document.

3. The image reading device according to claim 2, further comprising a document sensor for detecting a document being transported to the transport unit but before it reaches the reading unit.

4. The reading unit has a carriage on which the image sensor and the light source are mounted, and is configured to move between a home position and a reading position by the carriage. The control unit, The reading unit is positioned at the home position when the light intensity adjustment process and the acquisition process are executed. After the light intensity adjustment process and the acquisition process are completed, the reading unit is moved to the reading position. The image reading device according to claim 3, characterized in that the transport unit is stopped if the document sensor detects a document before the reading unit reaches the reading position.

5. The enclosure comprises the reading unit and the control unit, The reading unit has a carriage on which the image sensor and the light source are mounted. The control unit has an analog front end connected to the reading unit, The image reading device according to any one of claims 1 to 4, characterized in that the analog front end is not mounted on the carriage.

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