Reading device and reading device control method

Abstract

To provide a reading device that can appropriately read a document, and a method for controlling a reading device.SOLUTION: A reading device 11 comprises: a reading unit 31 that reads a document; and a control unit 35 that acquires image data including a document area and a background area from the reading unit. The control unit acquires document information on the document, and sets a background range indicating the range of a luminance value regarded as the background area based on the document information.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] Patent Document 1 describes a reading device that detects a document area based on a luminance value from image data obtained by reading a document. In such a reading device, it may be difficult to detect the document area from the image data depending on the type of document being read. If the reading device described in Patent Document 1 is unable to properly detect the document area, it suggests to the user an appropriate method for reading the document. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-140628 Summary of the Invention [Problem to be solved by the invention]

[0004] The reading device described in Patent Document 1 reads the document once and then proposes an appropriate method, which requires time and effort for the reading device to properly read the document. [Means for solving the problem]

[0005] A reading device that solves the above problem includes a reading unit that reads a document and a control unit that acquires image data including a document area and a background area from the reading unit, and the control unit acquires document information about the document and, based on the document information, sets a background range that indicates the range of brightness values ​​that are considered to be the background area.

[0006] A control method for a reading device that solves the above problem is a control method for a reading device that reads a document, and includes acquiring document information about the document and setting a background range that indicates a range of brightness values ​​that are considered to be a background area based on the document information. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a side view of the reading device in a first position. [Figure 2] FIG. 10 is a side view of the reading device in a second position. [Figure 3] FIG. 2 is a block diagram showing the electrical configuration of the reading device. [Figure 4] FIG. 10 is a schematic diagram showing an example of image data when a carrier sheet is not used. [Figure 5] FIG. 10 is a schematic diagram showing an example of image data when a carrier sheet is used. [Figure 6] 10 is a graph showing background estimates. [Figure 7] 10 is a table showing an example of the relationship between a background range and other information. [Figure 8] 10 is a graph showing a first background range. [Figure 9] 10 is a graph showing a second background range. [Figure 10] 10 is a table showing another example of the relationship between the background range and other information. [Figure 11] 10 is a graph showing a third background range. [Figure 12] 10 is a flowchart showing a setting process. [Figure 13] 10 is a graph showing a usage area of ​​a background estimation value. [Figure 14] FIG. 10 is a schematic diagram showing a difference in image data capacity. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of a reading device will be described below with reference to the drawings. The reading device is, for example, a sheet-fed scanner in which a fixed reading unit reads a document such as paper or film that is being conveyed. The reading device is not limited to a sheet-fed scanner, and may also be a flatbed scanner.

[0009] 1 and 2, the reading device 11 includes a housing 12 and a base 13. The housing 12 is supported by the base 13. The base 13 is installed on, for example, a horizontal surface. The housing 12 is configured to be rotatable with respect to the base 13.

[0010] The housing 12 has a supply port 14 and one or more discharge ports. The supply port 14 is an opening through which the original M1 is supplied. The original M1 enters the housing 12 through the supply port 14. The discharge port is an opening through which the original M1 is discharged. The original M1 is discharged from the housing 12 through the discharge port. In this example, the housing 12 has a first discharge port 15 and a second discharge port 16.

[0011] The housing 12 is configured to be able to change its position. For example, the position of the housing 12 is changed by rotating the housing 12 relative to the base 13. The housing 12 is changeable between, for example, a first position and a second position. In FIG. 1, the housing 12 is in the first position. In FIG. 2, the housing 12 is in the second position. The housing 12 is changed from the first position to the second position by rotating the housing 12 clockwise in FIG. 1. The inclination of the housing 12 relative to the base 13 changes between when the housing 12 is in the first position and when the housing 12 is in the second position. When the housing 12 is in the first position, the footprint of the reading device 11 is reduced compared to when the housing 12 is in the second position.

[0012] The reading device 11 includes a transport unit 17. The transport unit 17 is configured to transport the original M1. The transport unit 17 includes, for example, one or more rollers. The transport unit 17 includes, for example, a first roller pair 18, a second roller pair 19, and a third roller pair 20. The transport unit 17 transports the original M1 in the sub-scanning direction D1.

[0013] The reading device 11 includes a tray 21. The tray 21 extends from inside the housing 12 to outside the housing 12 through the supply port 14. An original M1 before being read is set on the tray 21. One or more originals M1 are stacked on the tray 21.

[0014] The reading device 11 includes one or more transport paths. The transport paths are paths along which the document M1 is transported by the transport unit 17. The transport paths extend within the housing 12. The reading device 11 includes, for example, a first transport path 22 and a second transport path 23.

[0015] The first transport path 22 extends from the supply port 14 toward the first discharge port 15. The first transport path 22 is the path indicated by the dashed line in FIG. 1. The first transport path 22 includes, for example, a shared portion 24. The shared portion 24 is a portion shared by the first transport path 22 and the second transport path 23. The shared portion 24 extends in a straight line or in a linear shape. The direction in which the shared portion 24 extends is the sub-scanning direction D1.

[0016] The first transport path 22 includes a curved portion 25. The curved portion 25 extends from the shared portion 24. The curved portion 25 is curved, for example, in a U-shape. The first transport path 22 is used, for example, when the housing 12 is in the first position. That is, when the housing 12 is in the first position, the document M1 is transported along the first transport path 22.

[0017] The second transport path 23 extends from the supply port 14 toward the second discharge port 16. The second transport path 23 is the path indicated by the dashed line in FIG. 2. The second transport path 23 includes, for example, a shared portion 24. The second transport path 23 is a path that is straight or extends in a straight line. The second transport path 23 does not include a curved portion 25. The second transport path 23 is used, for example, when the housing 12 is in the second position. In other words, when the housing 12 is in the second position, the document M1 is transported along the second transport path 23. In this example, in the reading device 11, the path along which the document M1 is transported is switched depending on the position of the housing 12.

[0018] The angle of the shared portion 24 with respect to the horizontal plane changes as the posture of the housing 12 changes. In this example, when the housing 12 is in the second posture, the angle of the shared portion 24 with respect to the horizontal plane is gentler than when the housing 12 is in the first posture.

[0019] In the reading device 11, the transport path suitable for transporting the original M1 varies depending on the type of the original M1. For example, when reading a thick original M1, it is preferable to use the second transport path 23. If the original M1 is thick, there is a risk of transport failure when the original M1 passes through the curved portion 25. Therefore, when reading a thin original M1, the first transport path 22 can be used. When reading a thin original M1, not only the first transport path 22 but also the second transport path 23 may be used. In other words, the use of the first transport path 22 is limited to the type of original M1. On the other hand, the use of the second transport path 23 is not limited to the type of original M1.

[0020] The reading device 11 may read the original M1 while the original M1 is sandwiched between a carrier sheet. In this case, the second transport path 23 is used. The carrier sheet is a sheet configured to sandwich the original M1 between transparent films. The carrier sheet is transported along the second transport path 23 together with the original M1 while sandwiching the original M1. By using the carrier sheet, the reading device 11 can read the original M1 even if the original M1 is extremely small in size, for example.

[0021] The reading device 11 includes a path switching member 26. The path switching member 26 is, for example, a flap. The path switching member 26 switches the path along which the original M1 is transported to the first transport path 22 or the second transport path 23. The path switching member 26 switches the path along which the original M1 is transported by blocking the first transport path 22 or the second transport path 23. When the path switching member 26 blocks the first transport path 22, the original M1 is transported along the second transport path 23. When the path switching member 26 blocks the second transport path 23, the original M1 is transported along the first transport path 22.

[0022] The path switching member 26 is interlocked with, for example, the posture of the housing 12. When the housing 12 is in the first posture, the path switching member 26 blocks the second transport path 23. When the housing 12 is in the second posture, the path switching member 26 blocks the first transport path 22. The path switching member 26 may be displaced regardless of the posture of the housing 12. In other words, the path may be switched by the path switching member 26 regardless of the posture of the housing 12.

[0023] The reading device 11 may include, for example, one or more sensors. The reading device 11 may include, for example, a sensor that detects the state of the document M1, a sensor that detects the state of the reading device 11, and the like.

[0024] The reading device 11 may include, for example, one or more posture detection sensors that detect the posture of the housing 12. The reading device 11 may include, for example, a first posture detection sensor 27 that detects that the housing 12 is in the first posture. The first posture detection sensor 27 is configured, for example, to detect the path switching member 26 that blocks the second transport path 23. Therefore, when the first posture detection sensor 27 detects the path switching member 26, it can be determined that the housing 12 is in the first posture.

[0025] The reading device 11 may include, for example, a second position detection sensor 28 that detects that the housing 12 is in the second position. The second position detection sensor 28 is configured to detect, for example, a path switching member 26 that blocks the first transport path 22. Therefore, when the second position detection sensor 28 detects the path switching member 26, it can be determined that the housing 12 is in the second position.

[0026] The reading device 11 may be configured to detect that the housing 12 is in the first position when the first position detection sensor 27 detects the path switching member 26, and to detect that the housing 12 is in the second position when the first position detection sensor 27 does not detect the path switching member 26. The reading device 11 may be configured to detect that the housing 12 is in the second position when the second position detection sensor 28 detects the path switching member 26, and to detect that the housing 12 is in the first position when the second position detection sensor 28 does not detect the path switching member 26. In this case, only one position detection sensor is required. The position detection sensor is not limited to a sensor that detects the path switching member 26, and may be, for example, a gyro sensor. If the position detection sensor is a gyro sensor, the reading device 11 may be provided with a separate sensor that detects the position of the path switching member 26.

[0027] The reading device 11 may include, for example, a size detection sensor 29 that detects the size of the document M1 set on the tray 21. The size detection sensor 29 is located, for example, on the tray 21. The size detection sensor 29 includes, for example, multiple optical sensors. The multiple optical sensors included in the size detection sensor 29 are arranged in a row on the tray 21. The size detection sensor 29 detects the size of the document M1 based on the detection results of the multiple optical sensors. For example, the larger the size of the document M1 set on the tray 21, the more optical sensors overlap with the document M1. In this way, the size detection sensor 29 detects the size of the document M1 depending on the number of optical sensors overlap with the document M1.

[0028] The reading device 11 may include a thickness detection sensor 30 that detects the thickness of the document M1 set on the tray 21. The thickness detection sensor 30 is located, for example, inside the housing 12. The thickness detection sensor 30 is, for example, an ultrasonic sensor or an optical sensor.

[0029] The reading device 11 includes one or more reading units 31. The reading units 31 are configured to read the original M1. The reading units 31 read the original M1 transported on the first transport path 22 and the original M1 transported on the second transport path 23. The reading units 31 are housed in the housing 12.

[0030] The reading device 11 includes, for example, two reading units 31. The two reading units 31 are positioned so as to sandwich the first transport path 22 between them. The two reading units 31 are positioned so as to sandwich the second transport path 23 between them. More specifically, the two reading units 31 are positioned so as to sandwich the shared portion 24 between them. The two reading units 31 face each other. The reading units 31 are elongated in the main scanning direction D2. The main scanning direction D2 is a direction different from the sub-scanning direction D1.

[0031] The two reading units 31 read different sides of the document M1. Of the two reading units 31, one reading unit 31 reads the front side of the document M1. Of the two reading units 31, the other reading unit 31 reads the back side of the document M1. In this way, the reading device 11 reads one side or both sides of the document M1.

[0032] The reading unit 31 has a light source 32. The light source 32 is, for example, an LED, a fluorescent lamp, etc. The light source 32 irradiates light toward the reading unit 31 facing it. The reading unit 31 has a plurality of image sensors 33. The plurality of image sensors 33 are arranged in the main scanning direction D2. The plurality of image sensors 33 are modularized. The image sensors 33 are, for example, contact-type image sensors. More specifically, the image sensors 33 are CMOS image sensors. The image sensors 33 photoelectrically convert the received light. The image sensors 33 output an output signal having a value corresponding to the amount of received light.

[0033] The image sensor 33 may be a monochrome sensor or a color sensor. The reading unit 31 may be configured to read the original M1 in full color. For example, the reading unit 31 may be configured to read the original M1 in three colors, RGB. The reading unit 31 may be configured to read the original M1 in grayscale.

[0034] The reading unit 31 has a background plate 34. The background plate 34 faces, for example, an image sensor 33 and a light source 32 of another reading unit 31. Light is irradiated onto the background plate 34 from the light source 32 of the opposing reading unit 31. The background plate 34 reflects the irradiated light. The light reflected by the background plate 34 is incident on the image sensor 33 of the reading unit 31 facing the background plate 34. The background plate 34 is read by the image sensor 33 together with the original M1. The background plate 34 is read by the image sensor 33 as a background together with the original M1.

[0035] For example, at least the surface of the background board 34 facing the image sensor 33 exhibits a color other than white or black. The background board 34 exhibits, for example, gray. The color of the background board 34 is preferably a color that allows the original M1 to be distinguished from the background when the image sensor 33 reads the background board 34 together with the original M1. For example, if the original M1 has a bluish background color and is frequently used, a color other than blue is preferably selected as the color. For example, if the original M1 has a greenish background color and is frequently used, a color other than green is preferably selected as the color. For example, if the original M1 has a reddish background color and is frequently used, a color other than red is preferably selected as the color. In this example, gray is used as an example of a color because it is easy to distinguish the original M1 from the background even if the original M1 is not limited to white but also exhibits chromatic colors such as blue, green, and red.

[0036] As shown in FIG. 3 , the reading device 11 includes a control unit 35. The control unit 35 controls the reading device 11. The control unit 35 controls, for example, the conveying unit 17 and the reading unit 31. The control unit 35 may be configured as a circuit including: α: one or more processors that execute various processes according to a computer program; β: one or more dedicated hardware circuits, such as application-specific integrated circuits, that execute at least some of the various processes; or γ: a combination thereof. The processor includes a CPU and memory, such as RAM and ROM, that stores program code or instructions configured to cause the CPU to execute processes. The memory, i.e., computer-readable medium, includes any readable medium that can be accessed by a general-purpose or dedicated computer.

[0037] The control unit 35 is configured to be able to communicate with a terminal 36 operated by a user. A driver 37 for communication with the reading device 11 is installed in the terminal 36. The terminal 36 is, for example, a personal computer, a smartphone, or the like.

[0038] The control unit 35 acquires manuscript information, which is information relating to the manuscript M1. Specifically, the control unit 35 acquires manuscript information, which is information relating to the manuscript M1 to be read. The control unit 35 may acquire the manuscript information based on a detection signal from a sensor, or may acquire the manuscript information from the terminal 36.

[0039] The document information includes, for example, posture information. The posture information is information indicating the posture of the housing 12. The posture information includes, for example, information indicating that the housing 12 is in a first posture or information indicating that the housing 12 is in a second posture.

[0040] The document information includes, for example, path information. The path information is information indicating a path along which the document M1 is transported. The path information includes, for example, information indicating that the document M1 is transported along the first transport path 22 or information indicating that the document M1 is transported along the second transport path 23.

[0041] The document information includes, for example, usage information. The usage information is information indicating whether a carrier sheet is used or not. The usage information includes, for example, information indicating that the document M1 is transported sandwiched between carrier sheets, or information indicating that the document M1 is transported without being sandwiched between carrier sheets.

[0042] The document information includes, for example, document size information. The document size information is information indicating the size of the document M1. The document information includes, for example, document thickness information. The document thickness information is information indicating the thickness of the document M1.

[0043] When the control unit 35 acquires the document information from the terminal 36, the document information is information input to the driver 37. That is, the document information is input by the user. The control unit 35 acquires, for example, posture information and path information from the detection signal of the first posture detection sensor 27 and the detection signal of the second posture detection sensor 28. The control unit 35 acquires, for example, document size information from the detection signal of the size detection sensor 29. The control unit 35 acquires, for example, document thickness information from the detection signal of the thickness detection sensor 30.

[0044] The control unit 35 may acquire usage information from the detection signal of the first attitude detection sensor 27 and the detection signal of the second attitude detection sensor 28. For example, the usage information may be linked to attitude information or path information. For example, when the original M1 is transported sandwiched between carrier sheets, the second transport path 23 is used. The control unit 35 may acquire usage information from the detection signal of the thickness detection sensor 30. The thickness detection sensor 30 can detect whether the original M1 set in the tray 21 is sandwiched between carrier sheets.

[0045] The control unit 35 acquires image data from the reading unit 31. More specifically, the control unit 35 receives a detection signal from the reading unit 31. The control unit 35 acquires image data by A / D converting the detection signal. When acquiring image data, the control unit 35 may perform shading correction, gamma correction, and the like on the detection signal.

[0046] 4, the image data 40 includes an original region 41 and a background region 42. The original region 41 is a region showing pixels generated by reading the original M1. The background region 42 is a region showing pixels generated by reading the background board 34.

[0047] The control unit 35 detects the document area 41 from the image data 40. More specifically, the control unit 35 detects the document area 41 by regarding pixels showing luminance values ​​included in the background range as the background area 42. The background range is a range of luminance values ​​in the image data 40 that are considered to be the background area 42. In this way, the document area 41 is cut out from the image data 40.

[0048] If the color of the original document M1 and the color of the background board 34 are similar, the luminance value of the original document area 41 in the image data 40 will be close to the luminance value of the background area 42. If the luminance value of the original document area 41 is close to the luminance value of the background area 42, it will be difficult to distinguish between the original document area 41 and the background area 42. In particular, if the background range is large, the luminance value of the original document area 41 will likely be included in the background area 42. In this case, the detection accuracy of the original document area 41 may decrease. For example, if a large background range is set for the reading device 11 in consideration of individual differences in the reading device 11, the detection accuracy of the original document area 41 may decrease.

[0049] If the original M1 is thick, when the original M1 passes between the two reading units 31, the original M1 may come into contact with the reading units 31, widening the gap between the reading units 31. In this case, the distance between the image sensor 33 and the background plate 34 facing it increases. Therefore, when reading a thick original M1, the luminance value of the background region 42 tends to be smaller than when reading a thin original M1. In other words, the background region 42 tends to be darker.

[0050] 5, when the original M1 is sandwiched between carrier sheets, the luminance value of the background region 42 is likely to be small, just as when a thick original M1 is being transported. When the original M1 is sandwiched between carrier sheets, the carrier sheet is transported together with the original M1, and the carrier sheet may come into contact with the reading units 31, which may increase the distance between the reading units 31.

[0051] When the original M1 is sandwiched between carrier sheets, the first pixels 43 generated by reading the background board 34 through the carrier sheet are included in the background region 42. The luminance value of the first pixels 43 is smaller than the luminance value of the second pixels 44 generated by reading the background board 34 without the carrier sheet. Therefore, when the original M1 is sandwiched between carrier sheets, the luminance value of the background region 42 is likely to be small. For this reason, it is preferable that the reading device 11 set a background range in accordance with the original M1.

[0052] 3, the control unit 35 has a storage unit 51. That is, the reading device 11 is equipped with the storage unit 51. The storage unit 51 is configured, for example, with a non-volatile memory. The storage unit 51 stores various programs executed by the control unit 35. In addition to the programs, the storage unit 51 stores, for example, background color data 52, white data 53, background estimation data 54, coefficient data 55, margin data 56, background range data 57, image data 40, and the like.

[0053] The background color data 52 and the white color data 53 are data for defining a background range. The background color data 52 and the white color data 53 are used to define background estimation data 54. The background color data 52 and the white color data 53 are set, for example, individually for each of the two reading units 31. The background color data 52 and the white color data 53 are stored in advance in the storage unit 51.

[0054] The background color data 52 and the white color data 53 are data based on background reference data, white reference data, and black reference data. The background reference data, white reference data, and black reference data are data acquired under the same conditions. For example, the background reference data, white reference data, and black reference data are acquired under the same temperature conditions.

[0055] The background reference data is acquired by the image sensor 33 reading the background board 34 while the light source 32 is on. The white reference data is acquired by the image sensor 33 reading a white reference chart while the light source 32 is on. The white reference chart is, for example, a white sheet. The black reference data is acquired by the image sensor 33 reading the background board 34 while the light source 32 is off. The background reference data, white reference data, and black reference data are data indicating the brightness values ​​detected by each of the multiple image sensors 33 using the method described above.

[0056] The background color data 52 is obtained by subtracting the luminance value indicated by the black reference data from the luminance value indicated by the background reference data. The white data 53 is obtained by subtracting the luminance value indicated by the black reference data from the luminance value indicated by the white reference data. The background color data 52 and the white data 53 are data indicating luminance values ​​corresponding to the multiple image sensors 33, respectively.

[0057] The background estimation data 54 is data for defining a background range. The background estimation data 54 is used to define background range data 57. The background estimation data 54 is calculated based on the background color data 52 and the white data 53. The background estimation data 54 is data indicating a luminance value estimated to be acquired when the multiple image sensors 33 read the background board 34. The calculation of the background estimation data 54 will be described later. In this example, the background estimation data 54 is acquired by calculation by the control unit 35, but the background estimation data 54 may also be stored in advance in the memory unit 51, for example.

[0058] The background estimation data 54 includes first background estimation data 58 and second background estimation data 59. The first background estimation data 58 is data indicating a luminance value for defining a background range. The first background estimation data 58 is data indicating a luminance value estimated to be acquired when the multiple image sensors 33 read the background board 34 without using a carrier sheet. The first background estimation data 58 is calculated based on the background color data 52 and the white data 53. The second background estimation data 59 is data indicating a luminance value for defining a background range. The second background estimation data 59 is data indicating a luminance value estimated to be acquired when the multiple image sensors 33 read the background board 34 with using a carrier sheet. The second background estimation data 59 is calculated based on the first background estimation data 58 and the coefficient data 55.

[0059] The coefficient data 55 is data for defining a background range. The coefficient data 55 is used to define second background estimation data 59. The coefficient data 55 is stored in advance in the storage unit 51. The coefficient data 55 is data indicating a coefficient by which the first background estimation data 58 is multiplied. The second background estimation data 59 is calculated by multiplying the luminance value indicated by the first background estimation data 58 by the value indicated by the coefficient data 55. Note that if the first background estimation data 58 and the second background estimation data 59 are stored in advance in the storage unit 51, the coefficient data 55 is unnecessary.

[0060] The margin data 56 is data for defining a background range. The margin data 56 is used to define the background range. The margin data 56 is pre-stored in the storage unit 51. The margin data 56 is data indicating a value to be added to a luminance value indicated by the background estimation data 54 and a value to be subtracted from a luminance value indicated by the background estimation data 54. The margin data 56 includes, for example, first margin data 61, second margin data 62, and common margin data 63.

[0061] The first margin data 61 is a value to be subtracted from the brightness value indicated by the background estimation data 54. The second margin data 62 is a value to be subtracted from the brightness value indicated by the background estimation data 54. The value indicated by the second margin data 62 is greater than the value indicated by the first margin data 61. The common margin data 63 is a value to be added to the brightness value indicated by the background estimation data 54.

[0062] The background range data 57 is data indicating a background range. That is, the background range data 57 is data indicating a range of brightness values ​​that is considered to be the background region 42 in the image data 40. The background range data 57 is determined, for example, based on the background estimation data 54 and the margin data 56. The background range data 57 is set by the control unit 35, for example, every time the reading unit 31 reads the original M1. That is, the background range data 57 is set for each original M1.

[0063] The control unit 35 executes the programs stored in the storage unit 51, thereby functioning as functional units such as an estimation unit 66, a background determination unit 67, and a detection unit 68. That is, the control unit 35 has the estimation unit 66, the background determination unit 67, and the detection unit 68.

[0064] The estimation unit 66 calculates a background estimation value based on the background color data 52 and the white data 53. The background estimation value is a luminance value that is estimated to be acquired when the multiple image sensors 33 read the background board 34.

[0065] The estimation unit 66 calculates a background estimation value for each image sensor 33. For example, if the reading unit 31 has N image sensors 33, the estimation unit 66 calculates N background estimation values. For example, if the reading unit 31 performs color scanning, the estimation unit 66 calculates a background estimation value for each of the three colors, RGB.

[0066] The estimation unit 66 estimates a first background estimation value and a second background estimation value. The first background estimation value is, for example, a luminance value estimated to be acquired when the multiple image sensors 33 read the background board 34 without using a carrier sheet. The second background estimation value is, for example, a luminance value estimated to be acquired when the multiple image sensors 33 read the background board 34 through a carrier sheet.

[0067] The estimation unit 66 calculates a first background estimation value based on, for example, the ratio between the background color data 52 and the white data 53. The estimation unit 66 sets the ratio of the background color data 52 to the white data 53 as the first background estimation value. The estimation unit 66 calculates the first background estimation value, for example, as follows. First background estimation value = 255 × (background color data / white data) The coefficient 255 indicates the maximum brightness value. This is because brightness values ​​are expressed in 256 levels from 0 to 255.

[0068] As shown in FIG. 6, the first background estimation value differs for each image sensor 33. For example, the first background estimation value of an image sensor 33 located at an edge in the main scanning direction D2 tends to be lower than the first background estimation value of an image sensor 33 located in the center. Therefore, the first background estimation value changes in an arch-like manner in the main scanning direction D2. This is a characteristic of contact-type image sensors. Individual differences in the image sensors 33 may cause the first background estimation value to locally increase or decrease. Color unevenness in the background board 34 may also cause the first background estimation value to locally increase or decrease.

[0069] The estimation unit 66 extracts the maximum value and the minimum value of the first background estimation value. It can be estimated that the range of values ​​equal to or less than the maximum value of the first background estimation value and equal to or greater than the minimum value of the first background estimation value is the luminance value output by the image sensor 33 when reading the background board 34 without using a carrier sheet. Therefore, the estimation unit 66 sets the range of values ​​equal to or less than the maximum value of the first background estimation value and equal to or greater than the minimum value of the first background estimation value as the first background estimation data 58. In other words, the estimation unit 66 stores the range of values ​​equal to or less than the maximum value of the first background estimation value and equal to or greater than the minimum value of the first background estimation value in the memory unit 51 as the first background estimation data 58.

[0070] The estimation unit 66 estimates a second background estimation value by multiplying the first background estimation value by a value indicated by coefficient data 55. The coefficient data 55 is, for example, a numerical value less than 1. The value indicated by the coefficient data 55 is a coefficient indicating the proportion of the brightness value that changes depending on the carrier sheet. Therefore, by multiplying the first background estimation value by the value indicated by coefficient data 55, a background estimation value when a carrier sheet is used, i.e., a second background estimation value, is calculated.

[0071] The estimation unit 66 extracts the maximum value and the minimum value of the second background estimation value. The range of values ​​equal to or less than the maximum value of the second background estimation value and equal to or greater than the minimum value of the second background estimation value can be estimated to be the luminance value output by the image sensor 33 reading the background board 34 through the carrier sheet. The maximum value of the second background estimation value is smaller than the maximum value of the first background estimation value. The minimum value of the second background estimation value is smaller than the minimum value of the first background estimation value.

[0072] The estimation unit 66 sets the range equal to or less than the maximum value of the first background estimation value and equal to or greater than the minimum value of the second background estimation value as second background estimation data 59. That is, the estimation unit 66 stores the range equal to or less than the maximum value of the first background estimation value and equal to or greater than the minimum value of the second background estimation value in the storage unit 51 as second background estimation data 59. The reason why the range equal to or less than the maximum value of the second background estimation value and equal to or greater than the minimum value of the second background estimation value is not set as second background estimation data 59 is because the second pixel 44 is included in the background region 42. Therefore, it can be said that the estimation unit 66 sets the second background estimation data 59 by multiplying the minimum value of the luminance value indicated by the first background estimation data 58 by the value indicated by the coefficient data 55.

[0073] 3, the background determination unit 67 determines background range data 57 based on the background estimation data 54. If the background estimation data 54 is used as the background range as is, there is a risk that the background region 42 will be detected as the document region 41 due to deterioration of the image sensor 33, the influence of the surrounding environment, etc. Therefore, the background determination unit 67 uses margin data 56 to include a margin in the brightness value indicated by the background estimation data 54. In this way, the background determination unit 67 determines the background range data 57.

[0074] The background determination unit 67 adds the margin indicated by the margin data 56 to the brightness value indicated by the background estimation data 54. As a result, the background determination unit 67 determines a range larger than the range of brightness values ​​indicated by the background estimation data 54 as the background range. Therefore, the background range is larger than the range of brightness values ​​indicated by the background estimation data 54. A specific method for determining the background range will be described later. The background determination unit 67 stores the determined background range in the memory unit 51 as background range data 57.

[0075] The detection unit 68 detects the document area 41 from the image data 40 based on the background range data 57. For example, when the reading unit 31 performs a color scan, the detection unit 68 considers pixels having brightness values ​​within the background range for all three RGB colors to be the background area 42. The detection unit 68 considers pixels having brightness values ​​outside the background range for any one of the three RGB colors to be the document area 41. In this way, the detection unit 68 detects the document area 41. By detecting the document area 41, the detection unit 68 can obtain information such as the position, size, and tilt of the document M1. This obtained information is transmitted from the control unit 35 to the driver 37, for example.

[0076] When the reading unit 31 performs color scanning, the detection unit 68 may regard pixels having a brightness value within the background range for any one of the three RGB colors as the background region 42. When a group of pixels having a brightness value outside the background range is equal to or larger than a predetermined size, the detection unit 68 may regard the pixels as the document region 41. The detection unit 68 may regard the pixels as the document region 41 by detecting edges in the group of pixels having a brightness value outside the background range.

[0077] Next, a method for determining the background range will be described. The background range is determined based on the background estimation data 54 and the margin data 56. Two examples will be described here. First, the example shown in FIG. 7 will be described. In the example shown in FIG. 7, when a carrier sheet is used, the original M1 is transported along the second transport path 23, and when a carrier sheet is not used, the original M1 is transported along the first transport path 22. Therefore, in the example shown in FIG. 7, the background range data 57 includes two background ranges.

[0078] 7, the background range data 57 includes a first background range and a second background range. The first background range is determined based on first background estimation data 58. The first background range is determined based on first margin data 61 and common margin data 63. The second background range is determined based on second background estimation data 59. The second background range is determined based on second margin data 62 and common margin data 63.

[0079] 8, the control unit 35 adds the value indicated by the common margin data 63 to the maximum brightness value indicated by the first background estimation data 58. This ensures a margin from the maximum brightness value indicated by the first background estimation data 58 by the value indicated by the common margin data 63. The margin ensured by the common margin data 63 is a common margin. The control unit 35 sets the value obtained by adding the common margin to the maximum brightness value indicated by the first background estimation data 58 as the maximum value of the first background range.

[0080] The control unit 35 subtracts the value indicated by the first margin data 61 from the minimum brightness value indicated by the first background estimation data 58. As a result, a margin of the value indicated by the first margin data 61 is secured from the minimum brightness value indicated by the first background estimation data 58. The margin secured by the first margin data 61 is the first margin. The control unit 35 determines the value obtained by subtracting the first margin from the minimum brightness value indicated by the first background estimation data 58 as the minimum value of the first background range. In other words, the control unit 35 determines the value obtained by subtracting the first margin from the minimum value of the first background estimation values ​​as the minimum value of the first background range.

[0081] 9, the control unit 35 adds the value indicated by the common margin data 63 to the maximum brightness value indicated by the second background estimation data 59. This ensures a margin from the maximum brightness value indicated by the second background estimation data 59 by the value indicated by the common margin data 63. The control unit 35 sets the value obtained by adding the common margin to the maximum brightness value indicated by the second background estimation data 59 as the maximum value of the second background range.

[0082] The control unit 35 subtracts the value indicated by the second margin data 62 from the minimum brightness value indicated by the second background estimation data 59. As a result, a margin of the value indicated by the second margin data 62 is secured from the minimum brightness value indicated by the second background estimation data 59. The margin secured by the second margin data 62 is the second margin. The second margin is larger than the first margin. The control unit 35 determines the value obtained by subtracting the second margin from the minimum brightness value indicated by the second background estimation data 59 as the minimum value of the second background range. In other words, the control unit 35 determines the value obtained by subtracting the second margin from the minimum value of the second background estimation value as the minimum value of the second background range.

[0083] The first background range is determined by determining a maximum value and a minimum value of the first background range. The second background range is determined by determining a maximum value and a minimum value of the second background range. The second background range is smaller than the minimum value of the first background range.

[0084] Next, an example shown in Fig. 10 will be described. In the example shown in Fig. 10, when a carrier sheet is used, the original M1 is transported along the second transport path 23, and when a carrier sheet is not used, the original M1 is transported along the first transport path 22 or the second transport path 23. Therefore, in the example shown in Fig. 10, the background range data 57 includes three background ranges.

[0085] 10, the background range data 57 includes a first background range, a second background range, and a third background range. The first background range is determined based on the first background estimation data 58, the first margin data 61, and the common margin data 63, as in the example shown in FIG. 7. The second background range is determined based on the second background estimation data 59, the second margin data 62, and the common margin data 63, as in the example shown in FIG. 7. The third background range is determined based on the first background estimation data 58. The third background range is determined based on the second margin data 62 and the common margin data 63.

[0086] 11, the control unit 35 adds the value indicated by the common margin data 63 to the maximum brightness value indicated by the first background estimation data 58. This ensures the common margin from the maximum brightness value indicated by the first background estimation data 58. The control unit 35 sets the value obtained by adding the common margin to the maximum brightness value indicated by the first background estimation data 58 as the maximum value of the third background range.

[0087] The control unit 35 subtracts the value indicated by the second margin data 62 from the minimum brightness value indicated by the first background estimation data 58. This ensures a second margin from the minimum brightness value indicated by the first background estimation data 58. The control unit 35 determines the value obtained by subtracting the second margin from the minimum brightness value indicated by the first background estimation data 58 as the minimum value of the third background range. In other words, the control unit 35 determines the value obtained by subtracting the second margin from the minimum value of the first background estimation value as the minimum value of the third background range.

[0088] The third background range is determined by determining a maximum value and a minimum value of the third background range. The third background range is larger than the first background range and smaller than the second background range. The minimum value of the third background range is smaller than the minimum value of the first background range and larger than the minimum value of the second background range.

[0089] The background range may be set in detail based on document size information, document thickness information, etc., without being limited to the examples shown in FIGS. 7 and 10. For example, the number of pieces of background estimation data 54 may be one, or three or more. The number of pieces of margin data 56 may be two or less, or four or more. Various background ranges can be determined by combining the background estimation data 54 and the margin data 56. The determined background range is stored in the memory unit 51 in association with the document information.

[0090] Next, a setting process for setting the background range will be described. For example, when a command to read the original M1 is input, the control unit 35 executes the setting process. By executing the setting process, the control unit 35 sets the background range based on the original information.

[0091] 12, the control unit 35 acquires document information in step S11. At this time, the control unit 35 acquires the document information from the first attitude detection sensor 27, the second attitude detection sensor 28, the size detection sensor 29, the thickness detection sensor 30, the driver 37, etc.

[0092] In step S12, the control unit 35 selects a background range based on the document information. At this time, the control unit 35 selects a background range associated with the acquired document information. First, consider the example shown in FIG.

[0093] As shown in FIG. 7, when the document information indicates that the document M1 is transported along the first transport path 22, the control unit 35 selects the first background area. When the document information indicates that the housing 12 is in the first position, the control unit 35 selects the first background area. When the document information indicates that a carrier sheet is not used, the control unit 35 selects the first background area. In the example shown in FIG. 7, when the document M1 is transported along the first transport path 22 and when the housing 12 is in the first position, a carrier sheet is not used. Therefore, the first background area is selected.

[0094] When the document information indicates that the document M1 is transported along the second transport path 23, the control unit 35 selects the second background range. When the document information indicates that the housing 12 is in the second position, the control unit 35 selects the second background range. When the document information indicates that a carrier sheet is used, the control unit 35 selects the second background range. In the example shown in FIG. 7, when the document M1 is transported along the second transport path 23 and when the housing 12 is in the second position, a carrier sheet is used. Therefore, the second background range is selected.

[0095] Next, consider the example shown in FIG. 10, when the document information indicates that the document M1 is transported along the first transport path 22, the control unit 35 selects the first background range. When the document information indicates that the housing 12 is in the first position, the control unit 35 selects the first background range. This is because a carrier sheet is not used when the document M1 is transported along the first transport path 22 and when the housing 12 is in the first position.

[0096] When the document information indicates that the document M1 is transported along the second transport path 23, the control unit 35 selects the second background range or the third background range. When the document information indicates that the housing 12 is in the second position, the control unit 35 selects the second background range or the third background range. This is because a carrier sheet may be used when the document M1 is transported along the second transport path 23 and when the housing 12 is in the second position.

[0097] When the document information indicates that the document M1 is transported on the second transport path 23 and that a carrier sheet is to be used, the control unit 35 selects the second background range. When the document information indicates that the housing 12 is in the second position and that a carrier sheet is to be used, the control unit 35 selects the second background range. This is because a carrier sheet is to be used.

[0098] When the document information indicates that the document M1 is transported through the second transport path 23 and that a carrier sheet is not used, the control unit 35 uses the third background area. When the document information indicates that the housing 12 is in the second position and that a carrier sheet is not used, the control unit 35 selects the third background area. This is because a carrier sheet is not used.

[0099] As shown in FIG. 12, the control unit 35 sets background range data 57 in step S13. At this time, the control unit 35 sets the selected background range. If the control unit 35 is connected to the terminal 36, the control unit 35 transmits the set background range data 57 to the driver 37. The background range data 57 transmitted to the driver 37 is used by the driver 37 for image processing. After completing the processing of step S13, the control unit 35 ends the setting process. After the setting process ends, reading of the original M1 is started. Based on the set background range data 57, the control unit 35 detects the original area 41 from the image data 40 obtained by reading the original M1.

[0100] According to the example shown in FIG. 7 , the control unit 35 sets the first background range when the usage information indicates that a carrier sheet is not used. The control unit 35 sets the first background range when the path information indicates that the document M1 is transported through the first transport path 22. The control unit 35 sets the first background range when the orientation information indicates that the housing 12 is in the first orientation. The control unit 35 sets the second background range when the usage information indicates that a carrier sheet is used. The control unit 35 sets the second background range when the path information indicates that the document M1 is transported through the second transport path 23. The control unit 35 sets the second background range when the orientation information indicates that the housing 12 is in the second orientation.

[0101] According to the example shown in FIG. 10 , the control unit 35 sets the first background range when the path information indicates that the document M1 is transported through the first transport path 22. The control unit 35 sets the first background range when the housing 12 is in the first position. The control unit 35 sets the second background range when the usage information indicates that a carrier sheet is used. The control unit 35 sets the third background range when the usage information does not include information indicating that a carrier sheet is not used and when the path information indicates that the document M1 is transported through the second transport path 23. The control unit 35 sets the third background range when the usage information indicates that a carrier sheet is not used and when the position of the housing 12 is in the second position.

[0102] As described above, the background range set for each document M1 changes based on the document information. This allows a background range appropriate for each document M1 to be set. In this way, the control method for the reading device 11 of this example includes acquiring document information and setting a background range based on the document information.

[0103] In this example, the control unit 35 reads out the background range from the storage unit 51 based on the acquired manuscript information, but for example, the control unit 35 may calculate the background range each time based on the manuscript information. In this case, the control unit 35 sets the calculated background range.

[0104] Next, the operation and effects of the above embodiment will be described. (1) The control unit 35 acquires document information about the document M1. Based on the document information, the control unit 35 sets a background range indicating a range of brightness values ​​that is considered to be the background region 42. According to the above configuration, the background range is set based on the document information, so that the document M1 can be read appropriately in accordance with the type of the document M1.

[0105] (2) When the usage information indicates that a carrier sheet is not used, the control unit 35 sets a first background range. When the usage information indicates that a carrier sheet is used, the control unit 35 sets a second background range. The minimum value of the second background range is smaller than the minimum value of the first background range.

[0106] When a carrier sheet is used, the luminance value of the background area 42 is likely to be smaller than when a carrier sheet is not used. Therefore, if the same background range is set when a carrier sheet is used and when a carrier sheet is not used, there is a risk that the document area 41 cannot be detected.

[0107] According to the above configuration, when a carrier sheet is used, a second background range is set. The minimum value of the second background range is smaller than the minimum value of the first background range. That is, a background range with a smaller minimum value is set in accordance with the smaller luminance value of the background area 42. This allows the document M1 to be read appropriately in accordance with the use of the carrier sheet.

[0108] (3) The control unit 35 sets a first background range when the path information indicates that the original M1 is transported through the first transport path 22. The control unit 35 sets a second background range when the path information indicates that the original M1 is transported through the second transport path 23. The minimum value of the second background range is smaller than the minimum value of the first background range.

[0109] Because the first transport path 22 includes a curved portion 25, depending on the thickness of the original M1, the original M1 may not be able to be transported along the first transport path 22. Therefore, the original M1 transported along the second transport path 23 is thicker than the original M1 transported along the first transport path 22. When reading a thick original M1, the luminance value of the background area 42 is likely to be smaller than when reading a thin original M1. Therefore, if the same background range is set when the original M1 is transported along the first transport path 22 and when the original M1 is transported along the second transport path 23, there is a risk that the original area 41 may not be detected.

[0110] According to the above configuration, when the original M1 is transported along the second transport path 23, a second background range is set. The minimum value of the second background range is smaller than the minimum value of the first background range. That is, a background range with a smaller minimum value is set in accordance with the smaller luminance value of the background region 42. This allows the original M1 to be read appropriately in accordance with the thickness of the original M1.

[0111] (4) When the posture information indicates that the housing 12 is in the first posture, the control unit 35 sets a first background range. When the posture information indicates that the housing 12 is in the second posture, the control unit 35 sets a second background range. According to the above configuration, a background range that matches the thickness of the document M1 is set according to the posture of the housing 12. This makes it possible to appropriately read the document M1 in accordance with the thickness of the document M1.

[0112] (5) The control unit 35 acquires background estimation values ​​indicating brightness values ​​estimated to be acquired when the multiple image sensors 33 read the background board 34. The control unit 35 determines the brightness value obtained by subtracting the first margin from the minimum value of the background estimation values ​​as the minimum value of the first background range. The control unit 35 determines the brightness value obtained by subtracting the second margin from the minimum value of the background estimation values ​​as the minimum value of the second background range. The second margin is a value greater than the first margin. With the above configuration, the background range includes a margin, so that the document area 41 can be appropriately detected even if the brightness values ​​of the image data 40 vary.

[0113] (6) The control unit 35 acquires document information based on the detection signal of the sensor. According to the above configuration, the control unit 35 can set the background range based on the detection signal of the sensor.

[0114] (7) The control unit 35 acquires the document information from the terminal 36. According to the above configuration, the control unit 35 can set the background range by acquiring document information from the terminal 36.

[0115] This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other within the scope of technical compatibility. As shown in FIG. 13, the control unit 35 may set a usage area for the background estimation value based on document size information. The usage area indicates the width of the background estimation value used to define the background range. The usage area limits the width of the background estimation value used. For example, the width of the background estimation value may be limited to match the width of the document M1.

[0116] When scanning a small original M1, the image sensors 33 located at the edges of the multiple image sensors 33 aligned in the main scanning direction D2 only scan the background board 34. Furthermore, the output of the image sensors 33 located at the edges tends to be smaller than that of the image sensors 33 located in the center of the multiple image sensors 33 aligned in the main scanning direction D2. For this reason, the control unit 35 sets the usage area based on the original size information and with the center in the main scanning direction D2 as the reference point.

[0117] When the usage area is set, the background estimate value of image sensor 33, which tends to have a small output, is not used to determine the background range. In the usage area, the difference between the maximum background estimate value and the minimum background estimate value is reduced. Therefore, the variation in the background estimate value in the usage area is reduced. This modification example has the following effects.

[0118] (8) The control unit 35 sets a usage area for the background estimated value based on the document size information, and sets a background range based on the background estimated value within the usage area. According to the above configuration, the usage area of ​​the background estimation value is set in accordance with the size of the original M1. By setting the usage area, the variation in the background estimation value is reduced. In other words, when setting the background range, the influence of the variation in the output of the image sensor 33 is reduced. As a result, the accuracy of the background range is improved.

[0119] 14, the control unit 35 may adjust the capacity used to store the image data 40 based on document size information. When scanning a document M1 that is short in the sub-scanning direction D1, the capacity used to store the image data 40 is smaller than when scanning a document M1 that is long in the sub-scanning direction D1. The control unit 35 may adjust the capacity used to store the image data 40 based not only on the size of the document M1 but also on the image quality when scanning the document M1.

[0120] The image data 40 includes, for example, an original area 71 and two margin areas 72. Therefore, the storage unit 51 reserves a capacity for the original area 71 and the two margin areas 72. The original area 71 is an area set according to the dimensions of the original M1 in the sub-scanning direction D1. When the orientation of the original M1 is not tilted with respect to the sub-scanning direction D1, the original M1 fits within the original area 71. The two margin areas 72 are adjacent to both ends of the original area 71 in the sub-scanning direction D1. When the original M1 is tilted with respect to the sub-scanning direction D1, part of the original M1 may extend beyond the original area 71. The part of the original M1 that extends beyond the original area 71 is located in the margin area 72. In other words, the margin area 72 is an area reserved so that the entire original M1 can be read even when the original M1 is tilted. The margin area 72 has a constant size regardless of the size of the original M1.

[0121] By changing the document area 71 to match the size of the document M1, when a small-sized document M1 is read, an unnecessary area 73 is generated in the image data 40 compared to when a large-sized document M1 is read. In other words, the capacity used to store the image data 40 can be reduced by the amount of the unnecessary area 73. This modification example provides the following effects.

[0122] (9) The control unit 35 adjusts the capacity of the storage unit 51 to store the image data 40 based on the document size information. According to the above configuration, for example, when the size of the original M1 is small, it is possible to reduce the capacity used to store the image data 40. As a result, the reduced capacity can be used for other functions.

[0123] The margin data 56 may have different values ​​for each of the three RGB colors, for example. The maximum value of the background range is common to the first background range, the second background range, and the third background range, but may be different. For example, the maximum value of the background range may be different by varying the margin added to the maximum value of the background estimate value.

[0124] The technical concepts and effects that can be understood from the above-described embodiment and modified examples will be described below. (A) A reading device includes a reading unit that reads a document and a control unit that acquires image data including a document region and a background region from the reading unit, and the control unit acquires document information about the document and sets a background range indicating a range of luminance values ​​that are considered to be the background region based on the document information. According to the above configuration, since the background range is set based on the document information, the document can be appropriately read in accordance with the type of document.

[0125] (B) In the above reading device, the document information includes usage information indicating whether or not a carrier sheet is used to hold the document, and the control unit sets a first background range when the usage information indicates that the carrier sheet is not used, and sets a second background range when the usage information indicates that the carrier sheet is used, and the minimum value of the second background range may be smaller than the minimum value of the first background range.

[0126] When a carrier sheet is used, the brightness value of the background area tends to be smaller than when a carrier sheet is not used. Therefore, if the same background range is set when a carrier sheet is used and when a carrier sheet is not used, there is a risk that the document area will not be detected.

[0127] According to the above configuration, when a carrier sheet is used, a second background range is set. The minimum value of the second background range is smaller than the minimum value of the first background range. That is, a background range with a smaller minimum value is set in accordance with the decrease in the luminance value of the background area. This allows the document to be read appropriately in accordance with the use of the carrier sheet.

[0128] (C) The reading device may include a first transport path that includes a curved portion and a second transport path that does not include the curved portion, and the document information may include route information that indicates the route along which the document will be transported, and the control unit may set a first background range when the route information indicates that the document will be transported along the first transport path, and set a second background range when the route information indicates that the document will be transported along the second transport path, and the minimum value of the second background range may be smaller than the minimum value of the first background range.

[0129] Because the first transport path includes a curved portion, some documents may not be able to be transported along the first transport path depending on their thickness. Therefore, documents transported along the second transport path are thicker than documents transported along the first transport path. When scanning a thick document, the luminance value of the background area tends to be smaller than when scanning a thin document. Therefore, if the same background range is set when a document is transported along the first transport path and when the document is transported along the second transport path, the document area may not be detected.

[0130] According to the above configuration, when the document is transported through the second transport path, a second background range is set. The minimum value of the second background range is smaller than the minimum value of the first background range. That is, a background range with a smaller minimum value is set in accordance with the decrease in the luminance value of the background area. This allows the document to be read appropriately in accordance with the thickness of the document.

[0131] (D) The reading device may include a housing that houses the reading unit, the housing being switchable between a first position and a second position, wherein when the housing is in the first position, the document is transported along the first transport path, and when the housing is in the second position, the document is transported along the second transport path, the document information includes position information that indicates the position of the housing, and the control unit may set the first background range when the position information indicates that the housing is in the first position, and set the second background range when the position information indicates that the housing is in the second position. According to the above configuration, a background range that matches the thickness of the document is set depending on the position of the housing. This makes it possible to properly read the document according to the thickness of the document.

[0132] (E) In the above reading device, the reading unit may have a plurality of image sensors arranged in a main scanning direction and a background board that is read by the image sensors as a background together with the document, and the control unit may acquire background estimates indicating luminance values ​​estimated to be acquired when the plurality of image sensors read the background board, and may set a luminance value obtained by subtracting a first margin from the minimum value of the background estimates as the minimum value of the first background range, and may set a luminance value obtained by subtracting a second margin from the minimum value of the background estimates as the minimum value of the second background range, the second margin being a value greater than the first margin. With the above configuration, the background range may include a margin, thereby enabling appropriate detection of the document area even when the luminance values ​​of the image data vary.

[0133] (F) In the above reading device, the document information may include document size information indicating the size of the document, and the control unit may set a usage area of ​​the background estimation value based on the document size information, and set the background range based on the background estimation value within the usage area.

[0134] In multiple image sensors lined up in the main scanning direction, the output of the image sensors located at the edges is usually likely to be lower than that of the image sensor located in the center. In other words, in the main scanning direction, the luminance value at the edges of the document is likely to be lower than that at the center of the document. With the above configuration, the usage area of ​​the background estimated value is set according to the size of the document. By setting the usage area, the variation in the background estimated value is reduced. In other words, when setting the background range, the influence of variation in the output of the image sensors is reduced. As a result, the accuracy of the background range is improved.

[0135] (G) The reading device may include a storage unit that stores the image data, and the document information may include document size information indicating the size of the document. The control unit may adjust the capacity used by the storage unit to store the image data based on the document size information. According to the above configuration, for example, when the document size is small, the capacity used to store the image data can be reduced. This allows the reduced capacity to be used for other functions.

[0136] (H) The reading device may include a sensor, and the control unit may obtain the document information based on a detection signal from the sensor. According to the above configuration, the control unit can set the background range based on the detection signal of the sensor.

[0137] (I) In the reading device, the control unit may acquire the document information from a terminal operated by a user. According to the above configuration, the control unit can set the background range by acquiring document information from the terminal operated by the user.

[0138] (J) A control method for a reading device is a control method for a reading device that reads a document, and includes acquiring document information about the document and setting a background range indicating a range of luminance values ​​that is considered to be a background area based on the document information. According to the above method, the same effects as those of the above-mentioned reading device can be obtained. [Explanation of symbols]

[0139] 11...reading device, 12...housing, 13...base, 14...supply port, 15...first discharge port, 16...second discharge port, 17...conveying section, 18...first roller pair, 19...second roller pair, 20...third roller pair, 21...tray, 22...first conveying path, 23...second conveying path, 24...shared portion, 25...curved portion, 26...path switching member, 27...first attitude detection sensor, 28...second attitude detection sensor, 29...size detection sensor, 30...thickness detection sensor, 31...reading section, 32...light source, 33...image sensor, 34...background plate, 35...control section, 36...terminal, 37...driver, 4 0...image data, 41...original area, 42...background area, 43...first pixel, 44...second pixel, 51...memory unit, 52...background color data, 53...white data, 54...background estimation data, 55...coefficient data, 56...margin data, 57...background range data, 58...first background estimation data, 59...second background estimation data, 61...first margin data, 62...second margin data, 63...common margin data, 66...estimation unit, 67...background determination unit, 68...detection unit, 71...original area, 72...margin area, 73...unnecessary area, D1...sub-scanning direction, D2...main scanning direction, M1...original.

Claims

1. a reading unit that reads a document; a control unit that acquires image data including a document area and a background area from the reading unit, The control unit Acquire document information relating to the document, the document information including usage information indicating whether a carrier sheet for sandwiching the document is used; When setting a background range indicating a range of brightness values ​​to be regarded as the background region based on the document information, a first background range is set when the usage information indicates that the carrier sheet is not used, and a second background range is set when the usage information indicates that the carrier sheet is used; A reading device, wherein the minimum value of the second background range is smaller than the minimum value of the first background range.

2. a first conveying path including a curved portion; a second transport path that does not include the curved portion, through which a document using the carrier sheet and a document that is thicker than a document transported through the first transport path are transported; the document information includes route information indicating a route along which the document is transported; The control unit When the path information indicates that the document is transported through the first transport path, the first background range is set; 2. The reading device according to claim 1, wherein the second background range is set when the path information indicates that the document is transported through the second transport path.

3. a reading unit that reads a document; a control unit that acquires image data including a document area and a background area from the reading unit; a first conveying path including a curved portion; a second transport path that does not include the curved portion, and through which a document that uses a carrier sheet that sandwiches the document and a document that is thicker than the document transported through the first transport path are transported; The control unit acquiring document information relating to the document, the document information including route information indicating a route along which the document is transported; When setting a background range indicating a range of brightness values ​​regarded as the background region based on the document information, a first background range is set when the path information indicates that the document is transported through the first transport path, and a second background range is set when the path information indicates that the document is transported through the second transport path; A reading device, wherein the minimum value of the second background range is smaller than the minimum value of the first background range.

4. a housing that houses the reading unit, the housing being switchable between a first position and a second position; When the housing is in the first position, the document is transported along the first transport path, When the housing is in the second position, the document is transported along the second transport path, the document information includes posture information indicating a posture of the housing, The control unit When the posture information indicates that the housing is in the first posture, the first background range is set; 4. The reading device according to claim 2, wherein the second background range is set when the orientation information indicates that the housing is in the second orientation.

5. the reading unit has a plurality of image sensors arranged in a main scanning direction and a background plate that is read as a background together with the document by the image sensors; The control unit acquiring background estimation values ​​indicating luminance values ​​estimated to be acquired when the plurality of image sensors read the background plate; a brightness value obtained by subtracting a first margin from the minimum value of the background estimated value is set as the minimum value of the first background range; a brightness value obtained by subtracting a second margin from the minimum value of the background estimated value is set as the minimum value of the second background range; 5. The reading device according to claim 1, wherein the second margin is greater than the first margin.

6. the document information includes document size information indicating a size of the document, The control unit setting a usage area of ​​the background estimation value based on the document size information; 6. The reading device according to claim 5, wherein the background range is set based on the background estimated value within the area of ​​use.

7. a storage unit that stores the image data; the document information includes document size information indicating a size of the document, 7. The reading device according to claim 1, wherein the control unit adjusts the capacity of the storage unit to store the image data based on the document size information.

8. Equipped with sensors, 8. The reading device according to claim 1, wherein the control unit acquires the document information based on a detection signal from the sensor.

9. 9. The reading device according to claim 1, wherein the control unit acquires the document information from a terminal operated by a user.

10. A method for controlling a reading device that reads a document, comprising: acquiring document information relating to the document, the document information including usage information indicating whether a carrier sheet for sandwiching the document is used; When setting a background range indicating a range of brightness values ​​to be regarded as a background area based on the document information, a first background range is set when the usage information indicates that the carrier sheet is not used, and a second background range is set when the usage information indicates that the carrier sheet is used, A method for controlling a reading device, wherein the minimum value of the second background range is smaller than the minimum value of the first background range.

11. A method for controlling a reading device that reads a document, comprising: acquiring document information relating to a document, the document information including route information indicating a route along which the document is transported; When setting a background range indicating a range of brightness values ​​regarded as a background region based on the document information, a first background range is set when the path information indicates that the document will be transported on a first transport path including a curved portion, and a second background range is set when the path information indicates that the document will be transported on a second transport path that does not include the curved portion and through which a document using a carrier sheet that sandwiches the document and a document that is thicker than the document transported on the first transport path are transported, A method for controlling a reading device, wherein the minimum value of the second background range is smaller than the minimum value of the first background range.

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