Image reading device and control method thereof

Abstract

To provide an image reading device that can appropriately determine a size of a document from data acquired by a line sensor when a platen is closed.SOLUTION: An image reading device of the present invention comprises: a document glass on which a document is placed; a platen that rotates to an opening position for opening the document glass and a closing position for closing the document glass; a line sensor that has an image pickup device extending in a main scanning direction, and reads the document placed on the document glass and outputs data; and a detection sensor that detects that the platen is at a middle position between the opening position and the closing position, and the image reading device determines a size of the document on the basis of, the data from the line sensor. The image reading device has an operation unit that calculates second data from coefficient data and first data acquired by the line sensor when the detection sensor detects that the platen is at the middle point, and determines presence or absence of the document from the second data and third data acquired by the line sensor when the line sensor is at the closing position.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to an image reading apparatus and a control method thereof. [Background technology]

[0002] There is known an image reading device that uses a line sensor to read an original placed on a platen with the platen closed, and that can detect the size of the original placed on the platen. In Patent Document 1, data is obtained by the line sensor at different opening and closing positions when the platen is closed, and the size of the original is determined by comparing the obtained data with a predetermined threshold value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-219780 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when a predetermined threshold is used, there is a possibility that the size of the document may be erroneously detected due to changes in the speed at which the pressure plate is closed. The present invention provides an image reading device that can appropriately determine the size of the document from data acquired by a line sensor when the pressure plate is closed. [Means for solving the problem]

[0005] The image reading device of the present invention comprises a document platen on which a document is placed, a line sensor having an image sensor extending in the main scanning direction and reading the document placed on the document platen and outputting data, a pressure platen that rotates on a rotation axis that intersects the main scanning direction to an open position that opens the document platen and a closed position that closes it, and a detection sensor that detects when the pressure platen is in an intermediate position between the open position and the closed position, and is an image reading device that determines the size of the document based on data from the line sensor, and is characterized in that it has a calculation unit that calculates second data from first data acquired by the line sensor when the detection sensor detects that the pressure platen is in the intermediate position and coefficient data that changes depending on the distance from the rotation axis, and determines the presence or absence of a document from third data acquired by the line sensor and the second data when the line sensor is in the closed position. Effect of the Invention

[0006] According to the present invention, it is possible to provide an image reading device that can appropriately determine the size of a document from data acquired by a line sensor when the pressure plate is closed. [Brief description of the drawings]

[0007] [Figure 1] FIG. 2 is a perspective view showing the appearance of a scanner unit. [Diagram 2] 5A and 5B are diagrams illustrating the relationship between the opening and closing positions of the pressure plate and a position detection sensor. [Diagram 3] 6 is a diagram showing the relationship between the open / closed position of the pressure plate and the output of a photointerrupter. FIG. [Figure 4] FIG. 4 is a top view showing the positional relationship between the document platen and the line sensor. [Diagram 5] FIG. 2 is a system block diagram of the MFP. [Figure 6] 5A and 5B are schematic diagrams showing the relationship between a document size and a detection position. [Figure 7] FIG. 13 is a diagram showing output data from a line sensor when a white original is not placed. [Figure 8] FIG. 11 is a diagram showing output data from a line sensor when a white original is placed. [Figure 9] 10 is a flowchart illustrating an operation of detecting a document size. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the following embodiment does not limit the present invention, and not all of the combinations of features described in the present embodiment are necessarily essential to the solution of the present invention. Note that the same configurations will be described with the same reference numerals. Also, the relative arrangements, shapes, etc. of the components described in the embodiments are merely examples, and are not intended to limit the scope of the present invention to only those. Therefore, the present invention can be embodied in various other forms, and various omissions, substitutions, combinations, and modifications can be made within the scope of the invention.

[0009] (First embodiment) In the first embodiment, a configuration of a multi-functional peripheral (MFP) having an image reading device and a printing device will be described. This MFP is not limited to a specific printing method, and may be any of an electrophotographic method, an inkjet method, and a thermal transfer method.

[0010] <Scanner unit> Here, a case will be described where the image reading device is a scanner unit 10 installed on the top of the main body of the MFP. FIG. 1 is a perspective view showing the exterior of the scanner unit 10. The scanner unit 10 is provided with a document table 11 on which a document is placed. A user places a document with the document surface facing the document table 11. A pressure plate 12 for pressing the document placed on the document table 11 is rotatably provided on the upper side of the document table 11. The pressure plate 12 can be rotated by the rotation shaft of the hinge portion 71 between an open position where the document table 11 is opened and a closed position where the document table 11 is closed relative to the document table 11. A white plate 13, which is close to white in color, is attached to the surface of the pressure plate 12 that presses the document.

[0011] FIG. 2 is an explanatory diagram for explaining the relationship between the opening / closing positions of the pressure plate and the position detection sensor. FIG. 3 is a diagram showing the relationship between the opening / closing positions of the pressure plate 12 and the output of the photointerrupter. The pressure plate 12 is provided with a position detection sensor 20 for detecting the opening / closing position. The position detection sensor 20 is composed of a first photointerrupter 21, a second photointerrupter 22, and a shutter section 23. The first photointerrupter 21 and the second photointerrupter 22 each have a light receiving element and a light emitting element. The shutter section 23 rotates with the opening / closing operation of the pressure plate 12 to block the first photointerrupter 21 or the second photointerrupter 22 depending on the opening / closing position of the pressure plate 12. The photointerrupter outputs an L level, which is a low output, when the light receiving element is in a state where it can receive light from the light emitting element, and outputs an H level, which is a high output, when the light receiving element is in a state where it cannot receive light from the light emitting element. The photointerrupter can detect the open position where the pressure platen 12 opens the platen 11, the closed position where the pressure platen 12 closes the platen 11, and intermediate positions between the open and closed positions. The position detection sensor 20 may be an encoder disposed on the rotating shaft. In the case of an encoder, the open / closed position of the pressure platen 12 can be obtained more precisely.

[0012] FIG. 2(a) shows the relationship between the photointerrupter and the shutter section 23 when the pressure plate 12 is in the open position. The light receiving elements of the first photointerrupter 21 and the second photointerrupter 22 are in a state where they can receive light from the light emitting element. Therefore, the output of the first photointerrupter 21 and the output of the second photointerrupter 22 are at the L level. FIG. 2(b) shows the relationship between the photointerrupter and the shutter section 23 when the pressure plate 12 is in the intermediate position. The light receiving element of the first photointerrupter 21 is blocked by the shutter section 23 and cannot receive light from the light emitting element, while the light receiving element of the second photointerrupter 22 is in a state where it can receive light. Therefore, the output of the first photointerrupter 21 is at the H level, and the output of the second photointerrupter 22 is at the L level. The intermediate position is a position where the angle between the pressure plate 12 and the document table 11 is, for example, 30°. FIG. 2(c) shows the relationship between the photointerrupter and the shutter section 23 when the pressure plate 12 is in the closed position. The light receiving elements of the first photointerrupter 21 and the second photointerrupter 22 are blocked by the shutter section 23 and cannot receive light from the light emitting elements. Therefore, the output of the first photointerrupter 21 and the output of the second photointerrupter 22 are at H level. The closed position is a position where the angle between the pressure plate 12 and the document table 11 is, for example, 5°. The angles of the open position, intermediate position, and open position may be other angles as long as they are smaller in this order. Also, the intermediate position may be detected by a photointerrupter, and the open position or closed position may be detected by another sensor.

[0013] The accuracy of detection of the opening / closing position of the pressure plate 12 may vary by several degrees due to the influence of mechanical errors and the like. In addition, the opening / closing position of the pressure plate 12 varies depending on the opening / closing speed when the user closes the pressure plate 12. Furthermore, there is a time lag between when the position detection sensor 20 detects the opening / closing position of the pressure plate 12 and when it acquires data from the line sensor. This embodiment makes it possible to determine the presence or absence of a document even when the opening / closing speed of the pressure plate 12 varies. As a result, it becomes more likely that the size of the document can be determined correctly.

[0014] FIG. 4 is a top view showing the positional relationship between the document table and the line sensor. A carriage unit 31 is disposed below the document table 11 of the scanner unit 10. The carriage unit 31 is equipped with components such as a light source (LED), a light guide, a lens array, and a line sensor 32, and can optically read an image of a document placed on the document table 11. The line sensor 32 mounted on the carriage unit 31 extends in a main scanning direction that is a direction intersecting with the rotation axis. The line sensor 32 outputs data for one line in the main scanning direction of the document by an imaging element extending in the main scanning direction. The data is, for example, in an array format for each line. The output data is subjected to image processing, and the document can be read by acquiring image data. Note that in this embodiment, a contact optical system using a CIS (contact image sensor) is used, but other methods such as a reduction optical system may be used. The main scanning direction may be parallel to the rotation axis.

[0015] The carriage unit 31 has a movement mechanism that moves in a sub-scanning direction intersecting with the main scanning direction. When in a standby state, the carriage unit 31 waits at a home position (HP). After a user places an original on the platen 11 with the original abutment position as a reference, various operations are executed according to the user's instructions. During an original size detection operation to determine the size of the original, the carriage unit 31 moves in the sub-scanning direction to a predetermined position A that is a distance D away from the home position. During a reading operation to read an image of the original, the carriage unit 31 can continuously obtain output data for each line in the main scanning direction of the original while moving in the sub-scanning direction from the home position. The carriage unit 31 moves to the end of the original in the sub-scanning direction, and image processing is performed on the obtained output data, so that the entire original can be read as image data.

[0016] The reflective photosensor 32 is a sensor that detects the presence or absence of a document in the sub-scanning direction. The reflective photosensor 32 includes a light-emitting unit 33 and a light-receiving unit 34, and the light emitted from the light-emitting unit 33 is reflected by the document and received by the light-receiving unit 34. The light-receiving unit 34 outputs a voltage according to the amount of light received. When the pressure plate 12 is in the intermediate position or the closed position, the light from the light-emitting unit 34 is acquired by the light-receiving unit 35. When there is a change in the light acquired by the light-receiving unit 34 at the intermediate position or the closed position, it is determined that there is no document, and when there is no change, it is determined that there is a document. Note that, although a reflective photosensor is used in this embodiment, the method is not limited to a specific one as long as it can detect the presence or absence of a document.

[0017] FIG. 5 is a system block diagram of the MFP. The printer 54 or the scanner unit 10 is controlled by the control unit 50 based on instructions from the operation unit 53 or an external control device (not shown). Parameters necessary for controlling the scanner unit 10 or the printer 54 are held in the RAM 51. Also, programs for executing the operation of reading the document, the operation of printing the image, and the operation of detecting the document size are held in the ROM 52. Furthermore, the ROM 52 holds a document size reference table for determining the document size and coefficient data for calculating threshold data for determining the presence or absence of the document. The control unit 50 executes various controls based on the parameters held in the RAM 51. Also, the control unit 50 has a calculation unit 56 for calculating threshold data for determining the presence or absence of the document. The operation unit 53 is provided with various buttons, and the user can manually perform any operation. The display unit 55 is a touch panel, and the user can check the information notified on this display unit 55 and perform any operation.

[0018] When recording the scanned document on a recording medium, the user places the document on document table 11 of scanner unit 10. When the start button on operation unit 53 is pressed, scanner unit 10 acquires output data from the line sensor. The acquired output data is subjected to image processing in control unit 50, and the document is read as image data. The image processing includes shading correction for correcting variations in the sensitivity of the line sensor. The image data is then output to printer 54, and the image is recorded on a recording medium.

[0019] <Document size detection operation> Here, a description will be given of an original size detection operation for detecting the size of an original placed on the original table 11. After the presence or absence of an original is determined in the main scanning direction and the sub-scanning direction, the size of the original is determined from the determination result of the presence or absence of an original and an original size reference table.

[0020] FIG. 6 is a schematic diagram showing the relationship between the document size and the detection position for detecting the presence or absence of the document. The line sensor 32 has a plurality of detection positions P1 to P5, P7. The detection positions P1 to P5, P7 indicate detection positions according to the document size in the main scanning direction of the line sensor 32. The relationship between the detection positions and the document size is as follows. P1 corresponds to A5R, P2 corresponds to B5R, P3 corresponds to A5, A4R, P4 corresponds to B5, B4, and P5 corresponds to A4, A3. Note that the detection positions P1 to P5, P7 may not each correspond to one imaging element, but may each correspond to the center of a range consisting of a predetermined number of imaging elements of the line sensor 32. Furthermore, the detection position P6 indicates the detection position of the reflective photosensor 33. The presence or absence of a document larger than B5R can be detected by P6. The detection position P7 is outside the area where the document is placed. In this embodiment, the maximum size that can be detected is set to A3 size. Therefore, detection position P7 is a position where documents do not overlap even when an A3 size document, which is the maximum size, is placed on document table 11. It should be noted that detection position P7 is not necessarily required to practice the present invention.

[0021] The size of the document is determined based on the output data from the line sensor 32 and a document size reference table stored in the ROM 52. For example, if P1 to P3 indicate that a document is present, P4 to P5 and P7 indicate that a document is not present, and P6 indicates that a document is not present, the control unit 50 can determine that the document size is A5. Also, if P1 to P3 indicate that a document is present, P4 to P5 and P7 indicate that a document is not present, and P6 indicates that a document is present, the control unit 50 can determine that the document size is A4R.

[0022] The presence or absence of a document in the main scanning direction is determined using output data from the line sensor 32. When closing the pressure plate 12, the control unit 50 acquires output data from the line sensor 32 when the pressure plate 12 is in an intermediate position and when it is in a closed position. The output data is array data corresponding to the output values ​​of the imaging elements arranged continuously in the main scanning direction of the line sensor 32. However, in this embodiment, the positions of the output data corresponding to the detection positions (P1 to P5, P7) are used as the output data. Note that at each detection position, the output value of the imaging element may be the average of multiple imaging elements in the vicinity of each detection position.

[0023] The output data from the line sensor 32 changes according to the intensity of the light input to the imaging element. The amount of light reflected by the detection object and entering the imaging element increases as the detection object approaches white and the distance between the detection object and the imaging element is shorter. Also, the greater the amount of light entering the imaging element, the greater the output value from the imaging element. On the other hand, the amount of light entering the imaging element decreases as the detection object approaches black and the distance between the detection object and the imaging element is longer, or when there is no detection object. In this case, the output value from the imaging element decreases. Note that the difference between the on-state data acquired when the LED of the carriage unit 31 is turned on during the document size detection operation and the off-state data acquired when the LED is turned off may be used as new output data. This output data can cancel the effects of external light.

[0024] The output data obtained from the line sensor 32 when the pressure plate 12 is at an intermediate position during closing is used as reference data for calculating threshold data for judging the presence or absence of a document. Using the reference data and coefficient data stored in advance in the ROM 52, the calculation unit 56 calculates threshold data for judging the presence or absence of a document. The coefficient data is a value set for each detection position of the line sensor 32. The coefficient data is monotonically larger (may include a part of the same value) as it is farther from the hinge portion 71 in the main scanning direction because the pressure plate is at an intermediate position. Note that, in some cases where the output is inverted, the coefficient data may be monotonically smaller (may include a part of the same value) as it is farther from the hinge portion 71 in the main scanning direction. In this embodiment, the threshold data is calculated by multiplying the reference data and the coefficient data. However, the calculation method may be addition, or a combination of addition and multiplication. Note that the coefficient data may be calculated from design values, etc., may be values ​​adjusted at the time of shipment from the factory, or may be values ​​adjusted by a serviceman at the time of installation.

[0025] The output data at the closed position obtained from the line sensor 32 when the pressure plate 12 is in the closed position is used to determine whether or not a document is present. Specifically, the output data at the closed position is compared with threshold data. At the detection positions (P1 to P5), when the output value at the closed position is greater than the threshold, it is determined that no document is present, and when the output value at the closed position is less than or equal to the threshold, it is determined that a document is present. In the calculation of this embodiment, a threshold is calculated for each calculation, instead of a fixed threshold, so that a threshold level shading process is not required. The threshold level shading process is a process of adjusting threshold data for determining whether or not a document is present for each individual sensor in order to correct the sensitivity variation of the line sensor 32. That is, in the conventional method of using a preset threshold, it is necessary to execute the threshold level shading process.

[0026] Here, the output data from line sensor 32 will be described in detail. Fig. 7 is a diagram showing output data from line sensor 32 when no white original is placed on platen 11. Fig. 8 is a diagram showing output data from line sensor 32 when a white original is placed on platen 11. Arrows indicate detection positions (P1 to P5) of line sensor 32 in the main scanning direction that correspond to the original size. (a) is when pressure plate 12 is in an intermediate position, and (b) is when pressure plate 12 is in a closed position. The solid line indicates output data from line sensor 32, and the dotted line indicates threshold data for determining the presence or absence of an original, calculated from the output data when pressure plate 12 is in an intermediate position.

[0027] In the output data of FIG. 7(a), since the pressure plate 12 is inclined at the midpoint, the output value is higher near the hinge portion 71 where the distance to the white plate 13 is closer. On the other hand, the output value is lower farther from the hinge portion 71 where the distance to the white plate 13 is greater. The output data at the midpoint is used as reference data. In FIG. 7(b), the distance between the white plate 13 and the line sensor 32 is closer, so the output data is uniform. The threshold data for determining whether or not a document is present is calculated from the reference data and coefficient data acquired at the midpoint as described above. Note that, as the threshold data, the closer to the hinge portion 71 the predetermined magnification is, the higher the magnification is, as the farther from the hinge portion 71 the document is. In this way, the threshold data for determining whether or not a document is present can be made constant. Since the output data is higher than the threshold data, it is determined that no document is present.

[0028] In the output data of FIG. 8(a), the output value is high in the portion where the white original S is placed. On the other hand, the output value is low in the portion where the white original S is not placed. However, in the portion where the white original S is not placed, the hinge portion 71, which is closer to the white plate 13 because the pressure plate 12 is inclined at the midpoint, has a higher output value. The output data acquired at the midpoint is used as reference data. In FIG. 8(b), the distance between the white plate 13 and the line sensor 32 is closer, so the output data is high not only in the portion where the white original S is placed, but also in the portion where it is not placed. The presence or absence of an original at the detection position can be determined by the threshold data shown by the dotted line obtained from the reference data and the coefficient data. It is determined that an original is not present where the output data is higher than the threshold data.

[0029] When the user opens and closes the pressure plate 12 quickly, the pressure plate 12 approaches the closed position from the intermediate position, and the output data from the line sensor 32 becomes high. Therefore, in a conventional document size detection operation that refers to a preset absolute threshold value, the document size may be erroneously detected. In this embodiment, the threshold data for determining the presence or absence of a document is calculated every time. Therefore, even if the opening and closing position of the pressure plate 12 is different from the expected one, the threshold data is calculated according to the opening and closing position of the pressure plate 12, and therefore erroneous detection of the presence or absence of a document can be prevented.

[0030] For recording media with high transmittance such as tracing paper, the difference in output value from the imaging element between the portion with the document and the portion without the document is small, making it easy to make a false detection. Therefore, by adjusting the value of the coefficient data so that it is possible to determine that a document is present even on a recording medium with high transmittance such as tracing paper, it is possible to make it possible to detect the document size regardless of the recording medium. The coefficient data may be set according to the type of recording medium of the document.

[0031] The presence or absence of an original in the sub-scanning direction is determined using a reflective photosensor 33. When the position detection sensor 20 detects that the pressure plate 12 is in an intermediate position, the control unit 50 starts acquiring an output value from the reflective photosensor 33. Acquisition of the output value continues at a predetermined time interval until the position detection sensor 20 detects that the pressure plate 12 is in the closed position. At this time, the first output value is set as the sub-scanning reference. If the sub-scanning reference indicates that an original is present and the subsequent detection results do not change from that indicating that an original is present, it is determined that an original is present. If the sub-scanning reference indicates that an original is not present and the subsequent detection results change to that an original is present, it is determined that an original is not present.

[0032] In this embodiment, no new hardware is required to be added to the conventional technology. Therefore, the presence or absence of a document in the RAM 51 may be determined by predetermined threshold data without omitting the threshold level shading processing operation. By doing so, it is possible to switch between the document size detection operation of the present invention and the conventional document size detection operation. This is to enable the use of the one with better accuracy depending on the type of document, etc.

[0033] In this way, the size of the document can be determined by combining the result of the presence or absence of the document in the main scanning direction from the line sensor 32 mounted on the carriage unit 31 and the result of the presence or absence of the document from the reflective photosensor 33 .

[0034] Here, the above-mentioned document size detection operation will be described with reference to the flowchart of FIG.

[0035] In step S201, the position detection sensor 20 continuously detects the open / closed position of the pressure plate 12. When the user opens the pressure plate 12 and the position detection sensor 20 detects the open position, the process proceeds to S202.

[0036] In step S202, the carriage unit 31 at the home position (HP) moves in the sub-scanning direction to position A where the document size detection operation is performed.

[0037] In step S203, the control unit 50 turns on the power supply of the line sensor 32 to make it possible to detect the document size.

[0038] In step S204, when the position detection sensor 20 detects that the pressure plate 12 is in the intermediate position (for example, the state of FIG. 8(a)), the process proceeds to step S205. This process is continued until the position detection sensor 20 detects the intermediate position.

[0039] In step S205, the reflective photosensor 33 starts the document size detection operation in the sub-scanning direction.

[0040] In step S206, the control unit 50 causes the line sensor 32 to execute a reading operation, and obtains output data serving as reference data from the line sensor 32. The reference data is temporarily stored in the RAM 51.

[0041] In step S207, the calculation unit 56 calculates threshold data for detecting the document from the reference data and the coefficient data.

[0042] In step S208, when the position detection sensor 20 detects that the pressure plate 12 is in the closed position, the process proceeds to step S209. This step is continued until the position detection sensor 20 detects the closed position.

[0043] In step S209, the control unit 50 causes the line sensor 32 to perform a reading operation and obtains output data from the line sensor 32 in the closed position.

[0044] In step S210, the control unit 50 determines the presence or absence of a document at each detection position from the data acquired at each detection position in the main scanning direction and the sub-scanning direction.

[0045] In step S211, the control unit 50 compares the determination result of the presence or absence of the document at each detection position with the document size reference table, and determines the document size.

[0046] In step S212, the control unit 50 judges whether the document size has been determined. If the document size has been determined, the process proceeds to step S213. If the document size has not been determined, the process proceeds to step S214.

[0047] In step S213, the control unit 50 displays the determined document size on the display unit 55, and notifies the user of the detection result of the document size.

[0048] In step S214, the control unit 50 displays on the display unit 55 that the document size could not be determined. In this case, a further display may be displayed to prompt the user to select the document size. This completes the document size detection operation.

[0049] In this embodiment, in the document size detection operation of the image reading device, output data is obtained from the line sensor when the pressure plate 12 is in the midway position and the closed position. Threshold data for determining the presence or absence of a document is calculated from the output data when the pressure plate 12 is in the midway position, and the presence or absence of a document in the main scanning direction is detected by comparing the threshold data with the output data when the pressure plate 12 is in the closed position. In this way, the document size can be determined with a configuration that is less dependent on the opening and closing speed of the pressure plate 12.

[0050] Second Embodiment In the first embodiment, the position detection sensor 20 detects two positions of the pressure plate 12, the intermediate position and the closed position. In the second embodiment, a configuration in which the position detection sensor 20 does not need to detect the closed position will be described. Note that the following mainly describes characteristic parts of the second embodiment, and parts that overlap with the first embodiment will be omitted.

[0051] As in the first embodiment, when the pressure plate 12 is detected to be in the intermediate position, the output data from the line sensor 32 is acquired as reference data, and the threshold data is calculated. In the second embodiment, the position sensor 20 determines that the pressure plate 12 is in the closed position after a predetermined time has elapsed since the position sensor 20 detected the intermediate position. In other words, the output data from the line sensor 32 is acquired as output data at the closed position after a predetermined time has elapsed since the intermediate position was detected. As in the first embodiment, the presence or absence of an original in the main scanning direction is determined from the threshold data and the output data at the closed position. As a result, the size of the original placed on the platen 11 can be determined. The predetermined time is the time from when the position sensor 20 detects the closed position to when the user completely closes the pressure plate 12, and is a time that is sufficient for this series of operations. In addition, the counter function built into the control unit 50 is used as a method for counting the predetermined time. The counter function allows the time elapsed since the position sensor 20 detected the intermediate position to be counted. As a result, the photointerrupter 22 for detecting the closed position can be reduced, and the size of the original can be detected with an inexpensive configuration that is less dependent on the opening and closing speed of the pressure plate.

[0052] In another embodiment of the second embodiment, the pressure plate 12 is determined to be in the closed position from the line sensor 32 and the reflective photosensor 33. First, as in the first embodiment, when the position detection sensor 20 detects the intermediate position, output data from the line sensor 32 is acquired as reference data. Threshold data for determining the presence or absence of a document is calculated from the acquired reference data. Even after the intermediate position is detected, output values ​​are acquired from each detection position of the line sensor 32 and the reflective photosensor 33 at regular time intervals, and the amount of change in the output values ​​is continued to be monitored. The output data of the line sensor 32 when the amount of change in all output values ​​becomes equal to or less than a predetermined amount of change is compared with the threshold data as output data at the closed position. As a result, the presence or absence of a document at each detection position can be determined, and the document size of the document placed on the document table 11 can be determined. The time interval is, for example, 10 msec intervals after the intermediate position of the pressure plate 12 is detected. If the output value at the detection position is equal to or less than the predetermined amount of change 10 times in a row, the pressure plate 12 is determined to be in the closed position. In this case, the document size can be determined approximately 100 msec after the pressure plate 12 is closed. As a result, it is possible to reduce the waiting time of users with an inexpensive configuration.

[0053] As another embodiment of the second embodiment, it is possible to determine that the pressure plate 12 is in the closed position using the output value of the detection position P7 of the line sensor 32. The detection position P7, which is outside the area where the original is placed, does not overlap with the original even if an A3 size original, which is the maximum original size, is placed on the original. Therefore, the output value of the detection position P7 continues to change depending on the opening / closing position of the pressure plate 12 when the pressure plate 12 is closed. Then, when the pressure plate 12 is in the closed position, the output value stops changing. Therefore, it is possible to detect that the pressure plate 12 is in the closed position.

[0054] It should be noted that the pressure plate 12 can be detected to be in the closed position using the detection positions P1 to P5 and the detection position P6 in the sub-scanning direction, without using the detection position P7 of the line sensor 32. For example, when an A4-sized document is placed on the document table 11, the detection positions P1 to P5 overlap with the document, but the detection position P6 does not overlap with the document. Therefore, the output value of the detection position P6 in the sub-scanning direction continues to change until the pressure plate 12 is in the closed position. When the pressure plate 12 is in the closed position, the output value does not change, so it is possible to detect that the pressure plate 12 is in the closed position. On the other hand, when an A3-sized document is placed on the document table 11, the document overlaps at all of the detection positions P1 to P5 and P6, and the output value does not change depending on the opening and closing position of the pressure plate 12. Therefore, the pressure plate 12 may be in the closed position before it is completely closed. The presence or absence of a document can be determined by acquiring output data as the closed position after the pressure plate 12 reaches an intermediate position and before it reaches the closed position, and comparing it with the threshold data. In this way, the photointerrupter 22 for detecting the closed position can be eliminated, and the document size can be detected with a cheaper configuration that is less dependent on the opening and closing speed of the pressure plate.

[0055] As described above, the document size can be determined with a configuration that is less dependent on the opening and closing speed of the pressure plate. [Explanation of symbols]

[0056] 11 Manuscript holder 12 Pressure Plate 20 Detection sensor 31 Line sensor 56 Arithmetic section

Claims

1. a manuscript table on which a manuscript is placed; a line sensor having an image sensor extending in a main scanning direction, reading an original placed on the platen and outputting data; a pressure plate that rotates about a rotation axis that intersects with the main scanning direction and that rotates to an open position where the document table is opened and a closed position where the document table is closed; a detection sensor that detects that the pressure plate is in an intermediate position between the open position and the closed position, and determines a size of a document based on data from the line sensor, a calculation unit that calculates second data from first data acquired by the line sensor when the detection sensor detects that the pressure plate is at the intermediate position and coefficient data that changes depending on the distance from the rotation shaft, an image reading device that determines the presence or absence of an original from third data and the second data acquired by the line sensor when the line sensor is in the closed position;

2. 2. The image reading device according to claim 1, wherein the first data, the second data, and the third data correspond to positions of different document sizes on the line sensor.

3. 3. The image reading device according to claim 1, wherein the coefficient data increases or decreases as the distance from the rotation axis increases.

4. 4. The image reading device according to claim 1, wherein the detection sensor detects that the pressure plate is in the closed position.

5. 4. The image reading device according to claim 1, wherein the determination is made as to whether the pressure plate is in the closed position based on the lapse of a predetermined time after it is detected that the pressure plate is in the intermediate position.

6. 4. An image reading device according to claim 1, wherein the pressure plate is determined to be in the closed position based on a change in data acquired by the line sensor after detecting that the pressure plate is in the intermediate position.

7. 7. The image reading apparatus according to claim 6, wherein the change in the data is a change in the output of the image pickup element of the line sensor that is outside an area where a document is placed.

8. 8. The image reading apparatus according to claim 1, wherein a size of the document in the main scanning direction is determined from the third data and the second data.

9. 9. The image reading apparatus according to claim 1, further comprising a photosensor for determining a size of the document in a sub-scanning direction intersecting the main scanning direction.

10. 10. The image reading device according to claim 1, wherein when the pressure plate is in the closed position, the data acquired by the line sensor while moving is corrected.

Images