Image reading apparatus having conveyance rollers conveying original sheet

In an image reading apparatus, it is judged whether an original sheet is a first sheet type, whose sheet length is longer than or equal to a first conveyance distance and shorter than a second conveyance distance, and a second sheet type, whose sheet length is longer than or equal to the second conveyance path, the first conveyance distance being a distance between a first conveyance roller and a second conveyance roller, the second conveyance distance being a distance between a supply roller and the second conveyance roller. At least one of a leading-edge arriving timing; a trailing-edge arriving timing; and a sub-scanning magnification is set dependently on the judged result. An image is read from the original sheet by using an image reading unit and a conveyance unit based on the set at least one of the leading-edge arriving timing; trailing-edge arriving timing; and sub-scanning magnification.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from Japanese Patent Application No. 2012-254697 filed Nov. 20, 2012. The entire content of this priority application is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an image reading apparatus for reading an image from an original sheet while conveying the original sheet.

BACKGROUND

There is conventionally known an image reading apparatus of a type that reads an image from an original sheet while conveying the original sheet, such as a Japanese Patent Application Publication No. 11-127301.

SUMMARY

It is conceivable that an image reading apparatus has a supply roller, first conveyance rollers, and second conveyance rollers in this order along a conveyance path in a conveying direction from its upstream side to its downstream. The supply roller sends out an original sheet placed on a sheet feed tray one sheet by one sheet to the conveyance path. This image reading apparatus can convey the original sheet by using the rollers if the length of the original sheet in the sheet conveying direction is longer than both of the distance along the conveyance path between the supply roller and the first conveyance rollers and the distance along the conveyance path between the first and second conveyance rollers.

According to this conceivable image reading apparatus, however, the conveyance speed of the original sheet will possibly vary dependently on the length of the original sheet along the conveyance path relative to the positions of the supply roller and the first and second conveyance rollers. So, the read out image data will possibly expand or contract in the conveying direction dependently on the size of the original sheet.

An object of the present invention is therefore to provide an image reading apparatus that reads an image from an original sheet while conveying the original sheet and that can restrain expansion and contraction of image data in the conveying direction.

In order to attain the above and other objects, the invention provides an image reading apparatus, including: a sheet feed tray; a supply roller; the conveyance unit; a discharged-sheet receiving unit; an image reading unit; and a control device. The supply roller is configured to rotate while being in contact with an original sheet placed on the sheet feed tray and to send out the original sheet one sheet by one sheet to a conveyance path. The conveyance unit includes a first conveyance roller and a second conveyance roller and configured to convey, along the conveyance path, the original sheet that has been sent out by the supply roller to the conveyance path, the conveyance unit conveying the original sheet by using the first conveyance roller and the second conveyance roller in succession in this order. The original sheet that has been conveyed by the conveyance unit is discharged into the discharged-sheet receiving unit. The image reading unit is disposed at a reading position along the conveyance path between the first conveyance roller and the second conveyance roller and configured to read an image, in a main scanning direction, from the original sheet conveyed by the conveyance unit at the reading position. The control device is configured to: judge whether the original sheet is either one of a first sheet type, whose sheet length in a conveying direction along the conveyance path is longer than or equal to a first conveyance distance and shorter than a second conveyance distance, and a second sheet type, whose sheet length in the conveying direction along the conveyance path is longer than or equal to the second conveyance path, the first conveyance distance being a distance between the first conveyance roller and the second conveyance roller along the conveyance path, the second conveyance distance being a distance between the supply roller and the second conveyance roller along the conveyance path; set at least one of a leading-edge arriving timing; a trailing-edge arriving timing; and a sub-scanning magnification dependently on the judged result, the leading-edge arriving timing indicating a timing when a leading edge of the original sheet in the conveying direction reaches the reading position, the trailing-edge arriving timing indicating a timing when a trailing edge of the original sheet in the conveying direction reaches the reading position, the sub-scanning magnification indicating an enlargement or reduction ratio in a sub-scanning direction orthogonal to the main scanning direction that is to be applied onto an image to be read by the image reading unit; and read an image from the original sheet by using the image reading unit and the conveyance unit based on the set at least one of the leading-edge arriving timing; the trailing-edge arriving timing; and the sub-scanning magnification.

DETAILED DESCRIPTION

An image reading apparatus according to embodiments of the invention will be described while referring to the accompanying drawings wherein like parts and components are designated by the same reference numerals to avoid duplicating description.

First Embodiment

1. Mechanical Configuration of Image Reading Apparatus

As shown inFIG. 1, an image reading apparatus1is a sheet-feed scanner that conveys, one sheet by one sheet, a plurality of original sheets G placed by a user on a sheet feed tray2to a sheet discharge portion4, and reads a conveyed original sheet G by using a first CIS30and a second CIS32contained in a main body3of the image reading apparatus1.

In the main body3of the image reading apparatus1, a conveyance path22is provided to connect the sheet feed tray2to the sheet discharge portion4. Around the conveyance path22, the following components are provided: a sheet feed roller40, a separation pad42, first conveyance rollers44, second conveyance rollers46, a switching plate48, the first CIS30, the second CIS32, a front sensor (referred to as F sensor, hereinafter)13, and a rear sensor (referred to as R sensor, hereinafter)14.

The sheet feed roller40rotates, while being in contact with the original sheet G placed on the sheet feed tray2, thereby sending out the original sheet G into the main body3. More specifically, the original sheets G are separated from one another due to a friction force of the separation pad42, and are sent out sheet one by one to the conveyance path22.

The sheet feed tray2is provided with a pickup roller50and a pickup pad52, which confront each other across the original sheet G placed on the sheet feed tray2. The pickup roller50and the pickup pad52assist the sheet feed roller40and the separation pad42in sending the original sheet G placed on the sheet feed tray2to the conveyance path22.

The conveyance rollers44and46are driven by a motor M (Refer toFIG. 3) to convey, along the conveyance path22, the original sheet G that has been drawn into the main body3. Along the conveyance path22, the first conveyance rollers44are disposed on the upstream side relative to the second conveyance rollers46in a conveyance direction D2, in which the original sheet G is conveyed. The conveyance direction D2is also referred to as a “sub-scanning direction D2.” A first conveyance distance L1is defined as a distance between the first conveyance rollers44and the second conveyance rollers46along the conveyance path22. A second conveyance distance L2is defined as a distance between the sheet feed roller40and the second conveyance rollers46along the conveyance path22. Original sheets G that can be conveyed by the image reading apparatus1of the present embodiment have sheet lengths, along the conveyance path22, that are longer than the first conveyance distance L1.

The first CIS30is disposed at a first reading position Y1that is between the first conveyance rollers44and the second conveyance rollers46on the conveyance path22. The first CIS30is for reading the front surface of a conveyed original sheet G at the first reading position Y1. The second CIS32is disposed at a second reading position Y2that is between the first reading position Y1and the second conveyance rollers46on the conveyance path22. The second CIS32is for reading a back surface of a conveyed original sheet G at the second reading position Y2.

The second conveyance rollers46are for discharging the original sheet G onto the sheet discharge portion4. The sheet discharge portion4includes a sheet discharge tray4A and a sheet discharge tray4B.

The switching plate48is disposed on the opposite side of the second conveyance rollers46with respect to the conveyance path22. The switching plate48switches between a first posture F1, at which the switching plate48extends along a straight path (referred to as S path, hereinafter)22A to the sheet discharge tray4A, and a second posture F2, at which the switching plate48extends along a U-turn path (referred to as U path, hereinafter)22B to the sheet discharge tray4B.

The S path22A and the U path22B diverge from the conveyance path22at a position Z4that is on the downstream side of a position Z3. At the position Z3, the conveyance path22reaches the second conveyance rollers46from the upstream side of the second conveyance rollers46in the conveyance direction D2. At the position Z4, the conveyance path22confronts the switching plate48. The S path22extends substantially linearly, and is used for conveying small sheets such as business cards and postcards. Part of the U path22B is bent or curved along the periphery of one of the second conveyance rollers46, and is used for conveying large sheets such as A4-size sheets.

The sheet discharge tray4A is configured from a discharge tray plate54that is part of an outer case of the main body3. The sheet discharge tray4B is formed by an upper portion of the outer case of the main body3.

The discharge tray plate54is pivotable to the main body3. The discharge tray plate54pivots from a closed state indicated by a solid line inFIG. 1to an opened state indicated by a two-dot chain line inFIG. 1. In the opened state, the discharge tray plate54serves as the sheet discharge tray4A. The switching plate48switches between the first and second postures F1and F2in interlocking relationship with the discharge tray plate54. That is, when the discharge tray plate54becomes the opened state, the switching plate48switches to the first posture F1. When the discharge tray plate54becomes the closed state, the switching plate48switches to the second posture F2. In the main body3, a tray plate detection sensor15is provided to detect the opened and closed states of the discharge tray plate54. The tray plate detection sensor15is being ON when the discharge tray plate54is in the closed state, and is being OFF when the discharge tray plate54is in the opened state.

When the switching plate48takes the first posture F1indicated by a two-dot chain line inFIG. 1, the original sheet G is conveyed along the S path22A, and is discharged onto the sheet discharge tray4A. On the other hand, when the switching plate48takes the second posture F2indicated by a solid line inFIG. 1, the original sheet G is conveyed along the U path22B, and is discharged onto the sheet discharge tray4B. In this way, the pickup roller50, the sheet feed roller40, the first conveyance rollers44, and the second conveyance rollers46constitute a conveyance unit56for conveying, along the conveyance path22, the original sheet G that has been placed on the sheet feed tray2.

The front sensor13is disposed at a detection position Y3in the sheet feed tray2. The front sensor13is being ON when an original sheet G is placed on the sheet feed tray2, and is being OFF when no original sheet G is placed on the sheet feed tray2. The rear sensor14is disposed at a detection position Y4between the first conveyance rollers44and the first reading position Y1along the conveyance path22. The rear sensor14is being ON when an original sheet G is passing through the detection position Y4on the conveyance path22, and is being OFF when no original sheet G is passing through the detection position Y4. Thus, the rear sensor14detects an original sheet G passing through the detection position Y4.

Furthermore, in the image reading apparatus1, a sheet size detection sensor16, a temperature sensor17, an operation unit11, and a display unit12are provided. The sheet size detection sensor16is disposed at the detection position Y3in the conveyance direction D2similarly to the front sensor13as shown inFIG. 2. The sheet size detection sensor16is being ON when an original sheet G placed on the sheet feed tray2is a large sheet, and is being OFF when the original sheet G is a small sheet. The temperature sensor17is for detecting a temperature T inside the apparatus1. The operation unit11(SeeFIG. 3) includes a power switch and various setting buttons, and receives operation instructions and reading settings inputted by a user. The display unit12(SeeFIG. 3) includes an LED or liquid crystal display, and is for displaying the state of the image reading apparatus1.

FIG. 2is a top view of the inside of the main body3. The conveyance path22has a predetermined width in a main scanning direction D1which is substantially orthogonal to the conveyance direction (sub-scanning direction) D2. The entire region of the conveyance path22in the main scanning direction D1is referred to as a “conveyance region H.” When an original sheet G is placed on the sheet feed tray2that is in connection with the conveyance path22, the original sheet G is positioned with its center in the main scanning direction D1being aligned with the center of the conveyance path22in the main scanning direction D1. When conveying a large sheet G on the conveyance path22, the entire part of the conveyance region H of the conveyance path22in the main scanning direction D1is used to convey the large sheet G. When conveying a small sheet G, only a center region MH of the conveyance region H is used to convey the small sheet G. The center region MH is part of the conveyance region H that is located in the center of the conveyance region H in the main scanning direction D1, and has a width H0in the main scanning direction D1. Hereinafter, in the conveyance region H, a region on the right side of the center region MH is referred to as a right region RH, and a region on the left side of the center region MH as a left region LH, as viewed from the upstream side in the conveyance direction D2.

The width of the discharge tray plate54in the main scanning direction D1is substantially equal to the width of the center region MH. Accordingly, onto the sheet discharge tray4A formed by the discharge tray plate54, a small sheet that is conveyed only by the center region MH is discharged. The front sensor13and the rear sensor14are disposed near the center of the center region MH in the main scanning direction D1at the detection position Y3and Y4, respectively. At the detection position Y3, the sheet size detection sensor16is disposed in the left region LH at a position near to the boundary between the left region LH and the center region MH.

The pickup roller50and the sheet feed roller40are each made up from one roller that is disposed in the center region MH in the main scanning direction D1. Each of the first conveyance rollers44includes three roller portions44A,44B, and44C that are arranged to rotate around the same rotation axis extending in the main scanning direction D1and in synchronization with each other. The three roller portions44A,44B, and44C constituting each of the first conveyance rollers44are disposed in the right region RH, the center region MH, and the left region LH, respectively. Similarly, each of the second conveyance rollers46includes three roller portions46A,46B, and46C that are arranged to rotate around the same rotation axis extending in the main scanning direction D1and in synchronization with each other. The three roller portions46A,46B, and46C constituting each of the second conveyance rollers46are disposed in the right region RH, the center region MH, and the left region LH, respectively.

When a small sheet such as a business card indicated by a dashed line inFIG. 7or a postcard indicated by a one-dot chain line is conveyed by the first conveyance rollers44and the second conveyance rollers46, the small sheet is conveyed by one of the three roller portions (roller portion44B,46B) in each of the first and second conveyance rollers44and46that are disposed in the center region MH. On the other hand, a large sheet such as an A4-size sheet indicated by a two-dot chain line inFIG. 7is conveyed by more than one roller portion in each of the first and second conveyance rollers44and46. More specifically, a large sheet such as an A4-size sheet is conveyed by all of the three roller portions44A-44C and46A-46C that constitute each of the first and second conveyance rollers44and46.

2. Electrical Configuration of Image Reading Apparatus

As shown inFIG. 3, the image reading apparatus1includes a central processing unit (referred to as CPU, hereinafter)20, a ROM26, a RAM27, a device control unit23, a first analog front end (referred to as AFE, hereinafter)24, a second AFE25, and a conveyance unit drive circuit28. To the above components, the operation unit11, the display unit12, and the sensors13to17are connected via a bus19. As indicated by a dotted line21inFIG. 3, the CPU20, the ROM26, and the RAM27constitute a control device for controlling the entire part of the image reading apparatus1.

The ROM26is prestored with various programs for controlling an operation of the image reading apparatus1. By executing the programs read from the ROM26, the CPU20controls each part in the image reading apparatus1and also performs a conveyance reading process according to the present embodiment as described later. The ROM26is further prestored with: the first conveyance distance L1and second conveyance distance L2; the width H0of the center region MH; and first step numbers PA, second step numbers PB, third step numbers PC, fourth step numbers PD, and sub-scanning magnifications HB, which will be described later.

The device control unit23is connected to the CISs30and32. Based on instructions outputted from the CPU20, the device control unit23transmits reading control signals to the CISs30and32. Each of the CISs30and32reads a corresponding surface of an original sheet G based on the reading control signal inputted from the device control unit23.

The first AFE24is connected to the first CIS30. The first AFE24converts analog read data outputted from the first CIS30into digital read data, i.e., digital gradation data. The first AFE24stores the converted gradation data in the RAM27via the bus19. The second AFE25is connected to the second CIS32. The second AFE25converts analog read data outputted from the second CIS32into digital read data, and stores the digital read data in the RAM27via the bus19.

The conveyance unit drive circuit28is connected to the motor M. Based on a pulse signal inputted from the CPU20, the conveyance unit drive circuit28drives the motor M to rotate. Upon receiving one pulse in the pulse signal, the motor M is driven to rotate by a predetermined one step's worth of rotation angle. As the motor M is driven by one step, the rollers constituting the conveyance unit56are rotated by predetermined angles, thereby conveying an original sheet G by a predetermined one step's worth of distance on the conveyance path22.

To convey the original sheet G, the CPU20transmits a pulse signal to the conveyance unit drive circuit28, whereupon the conveyance unit56conveys the original sheet G by a distance that is equivalent to a value determined by multiplying the number of pulses in the pulse signal and the predetermined one step's worth of distance. Hereinafter, the number of pulses in the pulse signal transmitted from the CPU20to the motor M is referred to as a step number.

In the conveyance unit56, in order to prevent an original sheet G conveyed along the conveyance path22from being wrinkled, when an original sheet G, which has been sent out by the sheet feed roller40to the conveyance path22, starts being conveyed by the first or second conveyance rollers44,46, as shown inFIGS. 10A-11B, the first conveyance rollers44apply the original sheet G with a driving force F1for moving the original sheet G in the conveyance direction D2, the second conveyance rollers46apply the original sheet G with a driving force F3for moving the original sheet G in the conveyance direction D2, and the sheet feed roller40applies the original sheet G with a restraining force F2for restraining the original sheet G from moving in the conveyance direction D2.

As shown inFIG. 10A, a large sheet such as an A4-size sheet is conveyed by the three roller portions44A-44C constituting each of the first conveyance rollers44. Therefore, the large sheet G is subjected to three driving forces F1and one restraining force F2when the large sheet G is conveyed. Contrarily, as shown inFIG. 10B, a small sheet such as a business card or postcard is conveyed by the one roller portion44B in each of the first conveyance rollers44. Therefore, the small sheet G is subjected to one driving force F1and one restraining force F2when the small sheet G is conveyed. That is, the number of the roller portions in the first conveyance rollers44that are used for conveying the small sheet G is fewer than that of the roller portions used for conveying the large sheet G. Therefore, in the total of the driving and restraining forces, the restraining force F2has a greater impact on a small sheet than on a large sheet.

Therefore, in the case of a small sheet such as a business card indicated by a dashed line inFIG. 7or a postcard indicated by a one-dot chain line, leading-edge arrival timings ST, at which a conveyance-direction leading edge of an original sheet G reaches the reading positions Y1and Y2, and trailing-edge arrival timings KT, at which a conveyance-direction trailing edge of the original sheet G reaches the reading position Y1and Y2, are delayed compared with a large sheet such as an A4-size sheet indicated by a two-dot chain line inFIG. 7. Moreover, the length of time required by one unit length of a small sheet to pass through each of the reading positions Y1and Y2is longer than that required by one unit length of a large sheet to pass through each of the reading positions Y1and Y2. Therefore, the sub-scanning magnifications HB for the CISs30and32need to be smaller for small sheets than for large sheets. The sub-scanning magnifications HB represent enlargement or reduction ratios that should be applied to: reading or scanning operations by the CISs30and32in the sub-scanning direction D2; or read data resulting from the reading or scanning operations by the CISs30and32in the sub-scanning direction D2.

An original sheet G of a first sheet type such as a business card indicated by a dashed line inFIG. 7, whose sheet length is shorter than the second conveyance distance L2, separates away from the sheet feed roller40before the original sheet G reaches the position Z3. Contrarily, an original sheet G of a second sheet type such as a postcard indicated by a one-dot chain line inFIG. 7or an A4-size sheet indicated by a two-dot chain line, whose sheet length is greater than or equal to the second conveyance distance L2, separates away from the sheet feed roller40after the original sheet G reaches the position Z3.

That is, the original sheet G of the second sheet type is conveyed by both of the first conveyance rollers44and the second conveyance rollers46after separating from the feed roller. Contrarily, the original sheet G of the first sheet type is conveyed only by the first conveyance rollers44after separating from the sheet feed roller40.

Therefore, as shown inFIG. 11A, while an original sheet G of the second sheet type such as a postcard or A4-size sheet is subjected to the restraining force F2, there is some period of time, during which the original sheet G is subjected to both of the driving forces F1and F3. On the other hand, as shown inFIG. 11B, while an original sheet G of the first sheet type such as a business card is subjected to the restraining force F2, there is no period of time, during which the original sheet G is subjected to both of the driving forces F1and F3. Accordingly, compared to the second sheet type, the original sheet of the first sheet type is more affected by the restraining force F2while the original sheet is subjected to the restraining force F2.

Accordingly, the leading-edge arrival timings ST and the trailing-edge arrival timings KT for the original sheets of the first sheet type are delayed in comparison with those for the original sheets of the second sheet type. The sub-scanning magnifications HB for the original sheets of the first sheet type need to be set smaller than those for the original sheets of the second sheet type.

Thus, appropriate values for the parameters such as the leading-edge arrival timings ST, trailing-edge arrival timings KT, and sub-scanning magnifications HB vary depending on whether or not the sheet length of an original sheet G to be read is shorter than the second conveyance distance L2. So, according to the image reading apparatus1of the present embodiment, the conveyance reading process described below includes a process of setting parameters depending on the sheet length of an original sheet G to be read.

It is noted that as shown inFIG. 2, the original sheet G has to be conveyed by a distance X1along the conveyance path22after the leading edge of the original sheet G has reached the detection position Y4and until the leading edge of the original sheet G reaches the first reading position Y1. The first step number PA is defined as the number of steps (pulses) required for the leading edge of the original sheet G to reach the first reading position Y1after reaching the detection position Y4.

The original sheet G has to be conveyed also by the distance X1along the conveyance path22after the trailing edge of the original sheet G has reached the detection position Y4and until the trailing edge of the original sheet G reaches the first reading position Y1. The second step number PB is defined as the number of steps (pulses) required for the trailing edge of the original sheet G to reach the first reading position Y1after reaching the detection position Y4.

The original sheet G has to be conveyed by a distance X2along the conveyance path22after the leading edge of the original sheet G has reached the detection position Y4and until the leading edge of the original sheet G reaches the second reading position Y2. The third step number PC is defined as the number of steps (pulses) required for the leading edge of the original sheet G to reach the second reading position Y2after reaching the detection position Y4.

The original sheet G has to be conveyed also by the distance X2along the conveyance path22after the trailing edge of the original sheet G has reached the detection position Y4and until the trailing edge of the original sheet G reaches the second reading position Y2. The fourth step number PD is defined as the number of steps (pulses) required for the trailing edge of the original sheet G to reach the second reading position Y2after reaching the detection position Y4.

3. Conveyance Reading Process

The following describes the conveyance reading process for an original sheet G with reference toFIGS. 4 to 8. According to the present embodiment, a front surface of an original sheet G is read by the first CIS30.FIG. 4is a flowchart showing the conveyance reading process that the CPU20performs in accordance with a prescribed program. The CPU20starts the process after the CPU20confirms by using the front sensor13that an original sheet G has been placed on the sheet feed tray2and a conveyance reading instruction for the original sheet G is inputted by a user through the operation unit11.

After starting the conveyance reading process, the CPU20receives reading settings, such as a type of the original sheet G and a surface of the original sheet G to be read, which have been inputted by the user together with the conveyance reading instruction (S2). Then, the CPU20checks the state of the tray plate detection sensor15and sheet size detection sensor16. More specifically, the CPU20first checks whether the tray plate detection sensor15is being ON. If the tray plate detection sensor15is being ON (S4: YES), i.e. if the discharge tray plate54is in the closed state, the CPU20detects that the original sheet G is to be conveyed along the U path22B.

Then, the CPU20checks whether the sheet size detection sensor16is being ON (S6). If the sheet size detection sensor16is being ON (S6: YES), the state of the tray plate detection sensor15is consistent with the state of the sheet size detection sensor16because it is known that the original sheet G to be conveyed along the U path22B is a large sheet. In this case, the CPU20turns ON a U path flag, indicating that the original sheet G is to be conveyed along the U path22B (S10). Then, the CPU20performs a reading process described later (S18).

On the other hand, if the sheet size detection sensor16is being OFF (S6: NO), the CPU20detects that the original sheet G to be conveyed along the U path22B is a small sheet. If a small sheet is conveyed along the U path22B, the original sheet is apt to be jammed in a curved portion along the periphery of one of the second conveyance rollers46on the U path22B. So, the CPU20displays, on the display unit12, an error message saying, “Open the discharge tray plate because the discharge tray plate is closed,” before starting to convey the original sheet G (S12). Then, the CPU20ends the conveyance reading process.

If the tray plate detection sensor15is OFF (S4: NO), i.e. if the discharge tray plate54is in the opened state, the CPU20detects that the original sheet G is to be conveyed along the S path22A. Then, the CPU20checks whether the sheet size detection sensor16is being ON (S8). If the sheet size detection sensor16is being OFF (S8: NO), the state of the tray plate detection sensor15is consistent with the state of the sheet size detection sensor16because it is known that the original sheet G to be conveyed along the S path22A is a small sheet. In this case, the CPU20turns ON an S path flag, indicating that the original sheet G is to be conveyed along the S path22A (S14). Then, the CPU20performs the reading process (S18).

On the other hand, if the sheet size detection sensor16is ON (S8: YES), the CPU20detects that the original sheet G to be conveyed along the S path22A is a large sheet. If a large sheet is conveyed along the S path22A, the large sheet cannot be discharged onto the sheet discharge tray4B, and becomes jammed. Therefore, the CPU20displays, on the display unit12, an error message saying, “Close the discharge tray plate because the discharge tray plate is opened,” before starting to convey the original sheet G (S16). Then, the CPU20ends the conveyance reading process.

The following describes the reading process.FIG. 5is a flowchart showing the reading process. In the reading process, the CPU20first instructs the conveyance unit56to convey an original sheet G (S22). Then, a parameter setting process is executed to set parameters such as the leading-edge arrival timing ST, trailing-edge arrival timing KT, and sub-scanning magnification HB for the first CIS30(S24).

In setting the parameters for the first CIS30, the CPU20first compares a sheet length of the sheet type that has been set in S2with the first conveyance distance L1and second conveyance distance L2stored in the ROM26(S44). The CPU20regards the sheet length of the sheet type set in S2as the sheet length of the original sheet G to be read. If the sheet length of the original sheet G is greater than or equal to the first conveyance distance L1, and is less than the second conveyance distance L2(S44: YES), the CPU20determines that the original sheet G is of the first sheet type. In this case, based on the fact that the original sheet G is of the first sheet type, the CPU20sets in S46the first step number PA into PA3(T) corresponding to the first sheet type, and sets the second step number PB into PB3(T) corresponding to the first sheet type. As a result, the leading-edge arrival timing ST for the first CIS30is set to such a timing, at which a length of time that is determined by multiplying a cycle of the pulse signal by the number PA3(T) will have passed since the leading edge of the original sheet G reaches the detection position Y4. The trailing-edge arrival timing KT for the first CIS30is set to such a timing, at which a length of time that is determined by multiplying the cycle of the pulse signal by the number PB3(T) will have passed since the trailing edge of the original sheet G reaches the detection position Y4. Furthermore, the CPU20sets in S46the sub-scanning magnification HB for the first CIS30into HB3(T) corresponding to the first sheet type, based on the number of steps (pulses) required for the original sheet G of the first sheet type to pass through the first reading position Y1along the conveyance path22.

Parameters such as the first step number PA and second step number PB for the first CIS30, the third step number PC and fourth step number PD for the second CIS32, and sub-scanning magnification HBs for the first and second CISs30and32are affected by the temperature T inside the apparatus. This is because in the image reading apparatus1, as the temperature T inside the apparatus increases, each roller swells, resulting in an increase in the conveyance speed of the original sheet G. As the temperature T inside the apparatus decreases, each roller becomes smaller in size, resulting in a decrease in the conveyance speed of the original sheet G. That is, in the image reading apparatus1, the conveyance speed of the original sheet G is affected by the temperature T inside the apparatus.

Therefore, parameters such as the first step number PA and second step number PB for the first CIS30, the third step number PC and fourth step number PD for the second CIS32, and sub-scanning magnification HB for the first and second CISs30and32are set for each temperature range and are prestored in the ROM26.FIG. 8shows the sub-scanning magnification HB for each of the CISs30and32and for each temperature range, as a correction value that is determined by correcting a predetermined standard sub-scanning magnification that is set in advance.FIG. 8also shows each of the first step number PA and the second step number PB for the first CIS30and for each temperature range as a correction value that is obtained by correcting a predetermined standard step number for the CIS30and by converting the corrected result into a distance. In this example, the first step number PA and the second step number PB are set to be equal with each other.FIG. 8also shows each of the third step number PC and the fourth step number PD for the CIS32and for each temperature range as a correction value that is obtained by correcting a predetermined standard step number for the CIS32and by converting the corrected result into a distance. In this example, the third step number PC and the fourth step number PD are set to be equal with each other.

As shown inFIG. 8, the first step number PA and the second step number PB are set so that the first step number PA and the second step number PB become smaller as the temperature range becomes higher. The third step number PC and the fourth step number PD are set so that the third step number PC and the fourth step number PD become smaller as the temperature range becomes higher. The sub-scanning magnification HB is set so that the sub-scanning magnification HB becomes greater as the temperature range becomes higher.

So, in S46, the CPU20refers to the table shown inFIG. 8, and sets the first step number PA, the second step number PB, and the sub-scanning magnification HB for the first CIS30based on the sheet type of the original sheet G to be read (first sheet type) and the temperature T inside the apparatus that is detected in S42.

On the other hand, if the sheet length of the original sheet G is greater than or equal to both of the first conveyance length L1and the second conveyance length L2(S44: NO), it is known that the original sheet G is of the second sheet type. So, the CPU20further judges whether the sheet type set in S2belongs to a small or large sheet.

More specifically, the CPU20compares a sheet width of the sheet type set in S2with the width H0of the center region MH that is stored in the ROM26(S48). The CPU20regards the sheet width of the sheet type set in S2as the sheet width of the original sheet G to be read. If the sheet width of the original sheet G to be read is less than or equal to the width H0of the center region MH (S48: NO), the CPU20determines that the original sheet G is of a third sheet type that belongs to a small sheet such as a postcard. In this case, based on the fact that the original sheet G is of the third sheet type and based on the temperature T inside the apparatus detected in S42, the CPU20sets the first step number PA into PA2(T), the second step number PB into PB2(T), and the sub-scanning magnification HB into HB2(T) by referring to the table inFIG. 8(S50).

On the other hand, if the sheet width of the original sheet G is greater than the width H0of the center region MH (S48: YES), the CPU20determines that the original sheet G is of a fourth sheet type that belongs to a large sheet such as an A4-size sheet. In this case, based on the fact that the original sheet G is of the fourth sheet type and based on the temperature T inside the apparatus detected in S42, the CPU20sets the first step number PA into PA1(T), the second step number PB into PB1(T), and the sub-scanning magnification HB into HB1(T) by referring to the table inFIG. 8(S52).

As shown inFIG. 8, in the same temperature range, the first step numbers PA1(T), PA2(T), and PA3(T) are set so that the numbers PA1(T), PA2(T), and PA3(T) are arranged in an ascending order, with the number PA1(T) being the smallest, and the number PA3(T) being the largest among the three numbers PA1(T), PA2(T), and PA3(T). Similarly, the second step numbers PB1(T), PB2(T), and PB3(T) are set so that the numbers PB1(T), PB2(T), and PB3(T) are arranged in an ascending order, with the number PB1(T) being the smallest, and the number PB3(T) being the largest among the three numbers PB1(T), PB2(T), and PB3(T). The sub-scanning magnifications HB1(T), HB2(T), and HB3(T) are set so that the values HB1(T), HB2(T), and HB3(T) are arranged in a descending order, with the value HB1(T) being the largest, and the value HB3(T) being the smallest among the three values HB1(T), HB2(T), and HB3(T).

Then, based on the surface to be read that is set in S2, the CPU20checks whether or not both of front and back surfaces of the original sheet G are to be read (S54). According to the present embodiment, only the front surface of the original sheet G is to be read. Therefore, the CPU20does not perform a process (S56to S64) of setting parameters to be used for reading by the second CIS32(S54: NO), and ends the parameter setting process.

The CPU20then returns to the reading process. In the reading process, the CPU20uses the rear sensor14to detect the position of the original sheet G being conveyed (S26: NO). When the rear sensor14is turned ON indicating that the leading edge of the original sheet G has reached the detection position Y4(S26: YES), the CPU20further conveys the original sheet G by the first step number PA that has been set in S24(S28: NO). When the original sheet G has been conveyed by the first step number PA (S28: YES), the CPU20instructs the first CIS30to read the front surface of the original sheet G (S30). It is noted that the first CIS30scans the original sheet G to read an image from the original sheet G and generates read data indicative of the read image, and the CPU20enlarges or reduces the read data at the sub-scanning magnification HB set in S24. Or, the CPU20controls the first CIS30so that the first CIS30scans the original sheet G to read an image from the original sheet G, while enlarging or reducing the image at the sub-scanning magnification HB set in S24.

The CPU20continues reading the original sheet G until the rear sensor14is turned OFF (S32: NO). When the rear sensor14is turned OFF, indicating that the trailing edge of the original sheet G has reached the detection position Y4(S32: YES), the CPU20further conveys the original sheet G by the second step number PB that has been set in S24(S34: NO). When the original sheet G has been conveyed by the second step number PB (S34: YES), the CPU20stops reading the surface of the original sheet G (S36). The CPU20discharges the original sheet G onto a sheet discharge tray4A or4B corresponding to the sheet size thereof, and stops conveying the original sheet G (S38), and ends the reading process.

After returning to the conveyance reading process, the CPU20uses the front sensor13to detect whether or not there is any original sheet G left on the sheet feed tray2to read (S20). If there is some original sheet G left to read (S20: YES), the CPU20repeats the process of S4and subsequent processes. If there is no original sheet G left to read (S20: NO), the CPU20ends the conveyance reading process.

4. Operations of the Present Embodiment

(1) The image reading apparatus1of the present embodiment makes a determination as to whether an original sheet G is of a first or second sheet type. Based on the determination result, the image reading apparatus1sets parameters such as the first step number PA, second step number PB, and sub-scanning magnification HB for the first CIS30, and reads the original sheet G by using the set parameters. The sheet length of the first sheet-type original sheet G is shorter than the second conveyance distance L2. So, while the original sheet G of the first sheet type is being sent out by the sheet supply roller40, the original sheet G is conveyed only by the first conveyance rollers44. Therefore, the conveyance speed is likely to become slower compared with the second sheet-type original sheet G. This is because the sheet length of the second sheet-type original sheet G is longer than or equal to the second conveyance distance L2, and therefore while the original sheet G of the second sheet type is being sent out by the sheet supply roller40, there is some period of time, during which the original sheet G of the second sheet type is conveyed by both of the first and second conveyance rollers44and46.

The image reading apparatus switches the values of the parameters depending on whether the original sheet G is of the first or second sheet type. More specifically, the first step number PA and second step number PB for the first sheet-type original sheet are set to be larger than those for the second sheet-type original sheet; the sub-scanning magnification HB for the first sheet-type original sheet is set to be smaller than that for the second sheet-type original sheet. Accordingly, even if the conveyance speed becomes slower due to the sheet length of the original sheet G, by reading an image from the original sheet G by using the thus set parameters, it is possible: to correct expansion or contraction generated in image data that has been outputted from the first CIS30; or to prevent the first CIS30from generating such image data that includes expansion or contraction in the sub-scanning direction D2. In this manner, it is possible to restrain expansion or contraction of resultant image data obtained by the image reading apparatus1.

(2) After determining that the original sheet G is of the second sheet type, the image reading apparatus1of the present embodiment further determines whether the original sheet G is of the third or fourth sheet type. Based on the determination result, the image reading apparatus1sets parameters such as the first step number PA, second step number PB, and sub-scanning magnification HB for the first CIs30, and reads the original sheet G by using the set parameters. The sheet width of the third sheet-type original sheet G is shorter than the width H0of the center region MH, and therefore the original sheet G of the third sheet type is conveyed only by one roller portion among the three roller portions constituting each of the first conveyance rollers44. Therefore, the conveyance speed is likely to become slower compared with the fourth sheet-type original sheet G. This is because the sheet width of the fourth sheet-type original sheet G is longer than the width H0of the center region MH, and therefore the original sheet G of the fourth sheet type is conveyed by the three roller portions constituting each of the first conveyance rollers44.

The image reading apparatus switches the values of the parameters depending on whether the original sheet G is of the third or fourth sheet type. More specifically, the first step number PA and second step number PB for the third sheet-type original sheet are set to be larger than those for the fourth sheet-type original sheet; the third step number PC and fourth step number PD for the third sheet-type original sheet are set to be larger than those for the fourth sheet-type original sheet; and the sub-scanning magnification HB for the third sheet-type original sheet is set to be smaller than that for the fourth sheet-type original sheet. Accordingly, even if the conveyance speed becomes slower due to the sheet width of the original sheet G, by reading an image from the original sheet G by using the thus set parameters, it is possible: to correct expansion or contraction generated in image data that has been outputted from the first CIS30; or to prevent the first CIS30from generating such image data that includes expansion or contraction in the sub-scanning direction D2. In this manner, it is possible to restrain expansion or contraction of resultant image data obtained by the image reading apparatus1.

(3) The image reading apparatus1of the present embodiment detects the temperature T inside the apparatus when reading the original sheet G. Based on the detected temperature T, the image reading apparatus1sets parameters such as the first step number PA, second step number PB, and sub-scanning magnification HB for the first CIS30, and reads the original sheet G by using the set parameters. Accordingly, even if the conveyance rollers44and46swell or contract due to changes in the temperature T inside the apparatus, and therefore the conveyance speed changes, by reading an image from the original sheet G by using the thus set parameters, it is possible: to correct expansion or contraction generated in image data that has been outputted from the first CIS30; or to prevent the first CIS30from generating such image data that includes expansion or contraction in the sub-scanning direction D2. In this manner, it is possible to restrain expansion or contraction of resultant image data obtained by the image reading apparatus1.

(4) The image reading apparatus1of the present embodiment detects the sheet size of an original sheet G to be read based on the reading settings that are detected in S2prior to the reading process of S18. Therefore, in the reading process, based on the detected sheet size, the image reading apparatus1can determine whether the original sheet G is of the first or second sheet type, or of the third or fourth sheet type.

Second Embodiment

A second embodiment will be described with reference toFIGS. 4,6, and9. The present embodiment is different from the first embodiment in that, in the conveyance reading process, both surfaces of an original sheet G are read by the first CIS30and the second CIS32. The same contents as those of the first embodiment will not be described below.

1. Conveyance Reading Process

As shown inFIG. 4, after starting the conveyance reading process, the CPU20detects the reading settings which are received together with the conveyance reading instruction (S2). According to the present embodiment, the reading settings are such that both of the front and back surfaces of an original sheet G are to be read. The CPU20executes the process of S4and subsequent processes, and performs the reading process if the judgment result in S6is affirmative or the judgment result in S8is negative.

FIG. 9is a flowchart showing the reading process of the present embodiment. In the reading process, the CPU20first instructs the conveyance unit56to convey the original sheet G (S72), and performs a parameter setting process to set parameters, such as the leading-edge arrival timing ST, trailing-edge arrival timing KT, and sub-scanning magnification HB, for each of the first CIS30and second CIS32(S74).

As shown inFIG. 6, in the parameter setting process, the CPU20first detects the temperature T inside the apparatus by using the temperature sensor17(S42). Then, the CPU20performs the process in S44to S52to set parameters for reading by the first CIS30. Incidentally, the process of setting the parameters for the first CIS30is the same as that of the first embodiment, and therefore will not be described again.

Then, based on the surface to be read that is set in S2, the CPU20checks whether or not both of the front and back surfaces of the original sheet G are to be read (S54). According to the present embodiment, both of the front and back surfaces of the original sheet G are to be read. Therefore, the CPU20performs the process (S56to S64) of setting parameters to be used for reading by the second CIS32(S54: YES). More specifically, the CPU20sets: the parameters including the leading-edge arrival timing ST, trailing-edge arrival timing KT, and sub-scanning magnification HB for the second CIS32; or parameters that are used to set the parameters ST, KT, and HB for the second CIS32. In this example, the CPU20sets: the third step number PC that is a parameter used for setting the parameter ST for the second CIS32; the fourth step number PD that is a parameter used for setting the parameter KT for the second CIS32; and the parameter HB for the second CIS32.

In setting the parameters for the second CIS32, the CPU20first compares a sheet length of the sheet type that has been set in S2with the first conveyance distance L1and second conveyance distance L2stored in the ROM26(S56). If the sheet length of the original sheet G is greater than or equal to the first conveyance distance L1, and is less than the second conveyance distance L2(S56: YES), the CPU20determines that the original sheet G is of the first sheet type. In this case, based on the fact that the original sheet G is of the first sheet type and based on the temperature inside the apparatus detected in S42, the CPU20sets in S58the third step number PC into PC6(T) corresponding to the first sheet type, and sets the fourth step number PD into PD6(T) corresponding to the first sheet type by referring to the table inFIG. 8. As a result, the leading-edge arrival timing ST for the second CIS32is set to such a timing, at which a length of time that is determined by multiplying the cycle of the pulse signal by the number PC6(T) will have passed since the leading edge of the original sheet G reaches the detection position Y4. The trailing-edge arrival timing KT for the second CIS32is set to such a timing, at which a length of time that is determined by multiplying the cycle of the pulse signal by the number PD6(T) will have passed since the trailing edge of the original sheet G reaches the detection position Y4. In S58, referring to the table inFIG. 8, the CPU20further sets the sub-scanning magnification HB for the second CIS32into HB6(T) corresponding to the first sheet type, based on the number of steps (pulses) required for the original sheet G of the first sheet type to pass through the second reading position Y2along the conveyance path22.

On the other hand, if the sheet length of the original sheet G is greater than or equal to both of the first conveyance length L1and the second conveyance length L2(S56: NO), it is known that the original sheet G is of the second sheet type. So, the CPU20further compares a sheet width of the sheet type set in S2with the width H0of the center region MH that is stored in the ROM26(S60). If the sheet width of the original sheet G to be read is less than or equal to the width H0of the center region MH (S60: NO), the CPU20determines that the original sheet G is of a third sheet type that belongs to a small sheet such as a postcard. In this case, based on the fact that the original sheet G is of the third sheet type and based on the temperature T inside the apparatus detected in S42, the CPU20sets the third step number PC into PC5(T), the fourth step number PD into PD5(T), and the sub-scanning magnification HB into HB5(T) by referring to the table inFIG. 8(S62).

On the other hand, if the sheet width of the original sheet G is greater than the width H0of the center region MH (S60: YES), the CPU20determines that the original sheet G is of a fourth sheet type that belongs to a large sheet such as an A4-size sheet. In this case, based on the fact that the original sheet G is of the fourth sheet type and based on the temperature T inside the apparatus detected in S42, the CPU20sets the third step number PC into PC4(T), the fourth step number PD into PD4(T), and the sub-scanning magnification HB into HB4(T) by referring to the table inFIG. 8(S64). Then, the CPU20ends the parameter setting process.

In this example, the third step number PC and the fourth step number PD are set to be equal with each other. In addition, as shown inFIG. 8, in the same temperature range, the third step numbers PC4(T), PC5(T), and PC6(T) are set so that the numbers PC4(T), PC5(T), and PC6(T) are arranged in an ascending order, with the number PC4(T) being the smallest, and the number PC6(T) being the largest among the three numbers PC4(T), PC5(T), and PC6(T). Similarly, the fourth step numbers PD4(T), PD5(T), and PD6(T) are set so that the numbers PD4(T), PD5(T), and PD6(T) are arranged in an ascending order, with the number PD4(T) being the smallest, and the number PD6(T) being the largest among the three numbers PD4(T), PD5(T), and PD6(T). The sub-scanning magnifications HB4(T), HB5(T), and HB6(T) are set so that the values HB4(T), HB5(T), and HB6(T) are arranged in a descending order, with the value HB4(T) being the largest, and the value HB6(T) being the smallest among the three values HB4(T), HB5(T), and HB6(T).

The CPU20then returns to the reading process. In the reading process, the CPU20uses the rear sensor14to detect the position of the original sheet G being conveyed (S76: NO). When the rear sensor14is turned ON indicating that the leading edge of the original sheet G has reached the detection position Y4(S76: YES), the CPU20further conveys the original sheet G by the first step number PA that has been set in the parameter setting process of S74(S78: NO). When the original sheet G has been conveyed by the first step number PA (S78: YES), the CPU20instructs the first CIS30to read the front surface of the original sheet G (S80). The CPU20controls the first CIS30to read the surface of the original sheet G, while executing an enlargement or reduction process by using the sub-scanning magnification HB that has been set in the parameter setting process of S74. Or, the CPU20executes, onto the read data that has been acquired by the first CIS30, an enlargement or reduction process by using the sub-scanning magnification HB that has been set in the parameter setting process of S74.

The CPU20further continues conveying the original sheet G so that the original sheet G will have been conveyed by the third step number PC since the rear sensor14turned ON, the third step number being set in the parameter setting process of S74(S82: NO). When the original sheet G has been conveyed by the third step number PC since the rear sensor14turned ON (S82: YES), the CPU20instructs the second CIS32to read the back surface of the original sheet G (S84). It is noted that the second CIS32scans the original sheet G to read an image from the original sheet G and generates read data indicative of the read image, and the CPU20enlarges or reduces the read data at the sub-scanning magnification HB set in S74. Or, the CPU20controls the second CIS32so that the second CIS32scans the original sheet G to read an image from the original sheet G, while enlarging or reducing the image at the sub-scanning magnification HB set in S74.

The CPU20continues reading the original sheet G until the rear sensor14is turned OFF (S86: NO). When the rear sensor14is turned OFF, indicating that the trailing edge of the original sheet G has reached the detection position Y4(S86: YES), the CPU20further conveys the original sheet G by the second step number PB that has been set in the parameter setting process of S74(S88: NO). When the original sheet G has been conveyed by the second step number PB (S88: YES), the CPU20stops reading by the first CIS30of the front surface of the original sheet G (S90).

The CPU20further continues conveying the original sheet G so that the original sheet G will have been conveyed by the fourth step number PD since the rear sensor14turned OFF, the fourth step number being set in the parameter setting process of S74(S92: NO). When the original sheet G has been conveyed by the fourth step number PD since the rear sensor14turned OFF (S92: YES), the CPU20stops reading by the second CIS32of the back surface of the original sheet G (S94). The CPU20discharges the original sheet G onto a sheet discharge tray4A or4B corresponding to the sheet size thereof, and stops conveying the original sheet G (S96), and ends the reading process.

After returning to the conveyance reading process, the CPU20uses the front sensor13to detect whether or not there is any original sheet G left on the sheet feed tray2to read (S20). If there is some original sheet G left to read (S20: YES), the CPU20repeats the process of S4and subsequent processes. If there is no original sheet G left to read (S20: NO), the CPU20ends the conveyance reading process.

2. Operations of the Present Embodiment

When reading both surfaces of the original sheet G by using the first CIS30and the second CIS32, the image reading apparatus1of the present embodiment can restrain expansion or contraction of image data that will possibly occur at each CIS due to the sheet length or sheet width. In particular, even though the first reading position Y1where the first CIS30is disposed along the conveyance path22is different from the second reading position Y2where the second CIS32is disposed, the difference is taken into account in restraining expansion or contraction of image data.

Other Embodiments

(1) For example, according to the above-described embodiments, the image reading apparatus1has a scanner function. However, the present invention is not limited to this example. For example, the present invention may be applied to a multifunction peripheral having a printer function, copy function, facsimile function, and other functions.

(2) According to the above embodiments, the image reading apparatus1has a single CPU20that executes various processes in the conveyance reading process. However, the present invention is not limited to this example. For example, a plurality of CPUs may be employed each for executing each part in the conveyance reading process. Or, one or more hardware circuit such as ASIC (Application Specific Integrated Circuit) may be employed for executing each part in the conveyance reading process. Or, one or more CPU and one or more ASIC may be employed to execute each part in the conveyance reading process.

(3) The program executed by the CPU20is not necessarily stored in the ROM26. The program may be stored in the CPU20or any other storage device.

(4) According to the above embodiments, based on the positional relationship between the conveyance rollers44and46of the image reading apparatus1, a business card serves as an example of the first sheet-type original sheet G, a postcard serves as an example of the third sheet-type original sheet G, and an A4-size sheet serves as an example of the fourth sheet-type original sheet G. However, the present invention is not limited to this example. For example, if the positional relationship between the conveyance rollers44and46is changed, a postcard may belong to the first sheet-type original sheets G, and an A4-size sheet may belong to the third sheet-type original sheets G.

(5) According to the above embodiments, in determining whether the original sheet G is of the third or fourth sheet type, the size of the original sheet is detected based on the reading settings. However, the present invention is not limited to this example. For example, based on the state of the sheet size detection sensor16, a determination may be made as to whether the original sheet G is a small or large sheet. If the state of the sheet size detection sensor16is consistent with the state of the tray plate detection sensor15, a determination may be made as to whether the original sheet G is a small or large sheet based on the state of the tray plate detection sensor15, instead of the state of the sheet size detection sensor16.

(6) According to the above embodiments, first, a determination is made as to whether the original sheet G is of the first or second sheet type. If it is determined that the original sheet G is of the second sheet type, then another determination is made as to whether the original sheet G is of the third or fourth sheet type. However, only a determination as to whether the original sheet G is of the first sheet type or of the second sheet type may be executed. Or, only a determination as to whether the original sheet G is of the third sheet type or the fourth sheet type may be executed.

(7) According to the above embodiments, in the process (S56to S64) of setting parameters for the second CIS32, judging processes the same as those in S44and S48in the process (S44-S52) of setting parameters for the first CIS30are executed in S56and S60. However, the present invention is not limited to this example. For example, the results of determination in S44and S48may be temporarily stored, and used in S58and S60.

(8) According to the above embodiments, the width H0of the center region MH is used as a single threshold value in determining whether the original sheet G is of the third or fourth sheet type. However, a plurality of threshold values may be used for the determination. A plurality of threshold values may be used in determining, among three or more sheet types, which type the original sheet is.