JP2017063334A - Image reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce wrong detection even in an environment in which light quantity of disturbance light varies when the size of an original is detected.SOLUTION: An image reading device comprises: an original platen on which an original is placed; an original platen cover which is opened and closed with respect to the original; an optical cover opening sensor 23 which detects that an opening/closing angle of the original platen cover passes a predetermined angle from a closed state; a CCD line sensor 92 which records distribution variation of incident light in a fixed period when detecting passage of the original platen cover; and an operation control part 52b which controls an operation of the CCD line sensor 92 according to an angle that the cover opening sensor 23 detects. The operation control part 52b executes a first read operation for recording a first luminance distribution at an original width detection position at a change up to a first angle, and a second read operation for recording a second luminance distribution while moving the CCD line sensor 92 in a sub-scanning direction over a predetermined range including the original width detection position when the opening/closing angle is changed up to a second angle.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image reading apparatus that is provided in a scanner, a copier, a FAX apparatus, a multifunction peripheral, or the like and optically reads a document placed on a document table.

  2. Description of the Related Art Conventionally, there has been known an image reading apparatus that is provided in a scanner, a copier, a FAX apparatus, a multifunction machine, or the like and optically reads a document placed on a document table. In this image reading apparatus, if the document size is erroneously determined, the image cannot be read accurately and image data is lost. Therefore, a document size detection mechanism for detecting the size of the document to be read is generally used. Has been implemented.

  As a mechanism for detecting the document size, there is a mechanism that detects by a CCD image sensor (Charge Coupled Device). As a method for detecting the document size, the document platen is placed at the timing when the pressure plate is opened and when the platen is closed. There is a technique for discriminating between a document portion and a non-document portion by utilizing a difference in brightness of reflected light caused by irradiation of light and reflection of a pressure plate (see Patent Document 1).

  The technique disclosed in Patent Document 1 is based on the following. That is, in the non-document portion, the platen is dark when the platen is open, and when the platen is closed, the reflection of the platen becomes brighter. Regardless, since the reflected light from the original does not fluctuate, the brightness of the original does not change by the opening / closing operation. In the method disclosed in Patent Document 1 described above, under this precondition, the amount of change in luminance is compared with a predetermined threshold value for each main scanning position, and a position below (or above) the threshold value is compared with a document portion and a non-document. It is determined that the boundary is a part boundary.

JP 2007-174221 A

  However, in the opening / closing operation of the pressure plate, the document shift occurs in the sub-scanning direction in the process of closing the pressure plate, and the position of the document read is different depending on before and after the opening / closing operation when reading the luminance at a predetermined main scanning position. The brightness may change, and in this case, the document size may not be detected accurately by the above method. In detail, for example, when the pressure plate is opened, the black portion of the original is read, and then when the pressure plate is closed, the original is displaced, and in this state, a different portion of the original, for example, a portion without an image (white portion) is read. In this case, a large change occurs in the luminance difference between the data obtained at the first time and the second time, and the main scanning position of the document portion may be erroneously determined as a non-document portion. In particular, document misalignment is likely to occur when the pressure plate is opened due to the bounce of the pressure plate, and is more likely to occur as the closing speed of the pressure plate increases, and the amount of displacement tends to increase.

  Therefore, the present invention solves the above-described problems, and even when the document size is detected by the opening / closing operation of the pressure plate when detecting the document size, the document size, particularly the document, is detected. An object of the present invention is to provide an image reading apparatus capable of reducing erroneous detection of the width size.

  In order to achieve the above object, a first feature of an image reading apparatus according to the present invention is an image reading apparatus for optically reading a document, the document table on which the document is placed, and the document table A pressure plate that opens and closes, first angle detection means for detecting that the opening and closing angle of the pressure plate has changed from an open state to a first angle, and the pressure plate has changed from the first angle to a second angle. Irradiating light toward the document placed on the document table in a middle angle region between the first angle and the second angle; The luminance distribution along the main scanning direction of the reflected light is recorded as the first luminance distribution, and light is emitted toward the original placed on the original table in a small angle area equal to or smaller than the second angle. The luminance distribution along the main scanning direction of the reflected light is A document width based on a result of comparison between the reading means for recording as a degree distribution, a driving means for moving the reading means in a sub-scanning direction orthogonal to the main scanning direction, and the first luminance distribution and the second luminance distribution Document width detecting means for detecting, and an operation control section for controlling the operation of the reading means and the driving means in accordance with the angle detected by the angle detecting means, the operation control section opening and closing the pressure plate A first reading operation for recording the first luminance distribution by the reading unit at the document width detection position when the angle detecting unit detects that the angle has changed to the first angle; When the angle detection unit detects that the opening / closing angle has changed to the second angle, the reading unit is moved in the sub-scanning direction over a predetermined range including the document width detection position. It is to be executed and a second reading operation for recording the distribution.

  A second feature of the image reading apparatus according to the present invention is that, in the second reading operation, the reading means calculates a minimum luminance value along the sub-scanning direction for each main scanning position. It is to be recorded as two luminance distributions.

  A third feature of the image reading apparatus according to the present invention is further provided with a closing speed measuring unit that measures a speed at which the pressure plate is closed, and the operation control unit is a speed at which the pressure plate is measured which is measured by the closing speed measuring unit. Accordingly, the position or size of the predetermined range is changed.

  According to the first feature of the image reading apparatus according to the present invention, the pressure plate opening / closing angle is a “medium angle region” between the first angle and the second angle from the open state, and further from the first angle. When a transition is made to a “small angle region” of an angle of 2 or less, light is irradiated toward the original, and the distribution of reflected light in each region is recorded as a first luminance distribution and a second luminance distribution. At this time, in the second reading operation for recording the second luminance distribution, the reading unit is moved in the sub-scanning direction over a predetermined range including the document width detection position. As a result, even in a situation where the document shift occurs in the middle of closing the pressure plate, the reflected light can be acquired while moving the reading unit over the range where the document shifts, and the luminance distribution can be recorded. By detecting fluctuations in the luminance distribution, accurate document width detection can be performed.

  According to the second feature of the image reading apparatus of the present invention, in the second reading operation, the result of calculating the minimum value of luminance along the sub-scanning direction for each main scanning position is recorded as the second luminance distribution. Thus, it is possible to accurately detect the boundary between the original portion and the non-original portion when the deviation occurs.

  According to the third feature of the image reading apparatus according to the present invention, in a situation where document deviation is expected to be small, it is possible to take measures such as narrowing the reading range of document width detection, and read preparation time (next) The increase in time until the reading operation can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view schematically showing a schematic configuration of an image forming apparatus including an image reading apparatus according to an embodiment, (a) is a front view of the entire apparatus, and (b) is a side view of an image reading apparatus portion. . It is a block diagram which shows the image reading apparatus part which concerns on embodiment. (A) is explanatory drawing which shows schematic structure of a platen cover, (b) is explanatory drawing which shows the relationship between a detection angle area | region and an angle sensor. (A) is a block diagram showing a characteristic functional unit of the image reading apparatus according to the embodiment, (b) is a block diagram showing a functional unit of the reading control unit. 5 is a flowchart illustrating an image reading operation according to the embodiment. FIG. 3 is a top view illustrating a configuration of a document table according to the embodiment. (A) is a top view showing the position of the carriage in the configuration of the document table according to the embodiment, (b) is a side view thereof, and (c) shows the relationship between the closing speed of the pressure plate and the reading position PB. It is a table. It is explanatory drawing which shows the procedure of the detection method of the brightness | luminance variation which concerns on embodiment. 5A and 5B are explanatory diagrams of document width detection according to the embodiment, in which FIG. 5A illustrates a pressure plate open state, FIG. 5B illustrates a luminance distribution in a range of reading positions PB to PC in a closed state, and FIG. The luminance distribution at the reading position PA is shown, and (d) shows the luminance distribution change at the reading position PA before and after opening and closing. It is explanatory drawing of the document width detection which concerns on embodiment, and shows a pressure plate closed state (with a shift | offset | difference).

  Embodiments of the present invention will be described below with reference to the drawings. Throughout the drawings, the same or equivalent parts and components are denoted by the same or equivalent reference numerals. However, it should be noted that the drawings are schematic and different from the actual ones. Moreover, the part from which the relationship and ratio of a mutual dimension differ also in between drawings is contained. Further, the embodiment described below exemplifies an apparatus or the like for embodying the technical idea of the present invention, and the technical idea of the present invention is to arrange the components and the like as follows. It is not something specific. The technical idea of the present invention can be variously modified within the scope of the claims.

(Configuration of image reading apparatus)
FIG. 1 is an explanatory view schematically showing a schematic configuration of an image forming apparatus including an image reading apparatus 1 according to the present invention, and FIG. 2 is a block diagram schematically showing a schematic configuration of an image reading apparatus portion. . The image reading apparatus 1 according to the present embodiment employs a flat bed method in which a read original is fixed and read. As shown in FIGS. 1 and 2, the image reading apparatus 1 uses a scanner 20 that optically reads a document as a base, and forms an image based on image data output from the scanner 20 on a recording medium such as paper. It is provided in the upper part of the main body 10 of the forming apparatus.

  The apparatus main body 10 includes a paper feed unit 102, an image forming unit 103, a paper discharge unit 104, and a control circuit 150. The paper feed unit 102 includes a paper feed tray 106 on which a large number of sheets can be stacked, and a paper feed roller 107 that takes out the stacked sheets one by one and conveys them at a predetermined paper feed timing. This unit supplies the paper to the image forming unit 103 at a predetermined paper feed timing while restricting the transport direction of the paper taken out in step 1 along the transport path.

  The image forming unit 103 corrects the skew of the paper supplied from the paper supply unit 102 and feeds the skew-corrected paper in accordance with a predetermined printing timing. Corresponding to a photosensitive drum and a developing device, an inkjet head in the inkjet system, and a printing drum in the stencil printing system, an image forming unit 112 that prints a desired image on a sheet fed from the registration roller 108, and an annular conveyance belt 109 and a conveying belt roller 110 that rotates the conveying belt 109 in a predetermined direction are provided with a conveying unit 111 that conveys a sheet, and an image is conveyed while the sheet supplied from the sheet feeding unit 102 is conveyed by the conveying unit 111. This is a unit for printing a desired image by the forming means 112.

  The paper discharge unit 104 includes a paper discharge tray 105 that discharges the printed paper and a plurality of paper discharge roller pairs 115 that convey the paper that has been printed to the paper discharge tray 105, and printing is performed in the image forming unit 103. This is a unit for discharging and stacking finished sheets outside the apparatus. The control circuit 150 includes a CPU, a signal processing device, a communication processing device, and the like. Furthermore, the power supply circuit 160 includes a power supply device that supplies power to each unit.

  As shown in FIG. 2, the scanner 20 includes a document table 21, a document table cover 22, an auto sheet feeder 24, a cover open sensor 23, and the like. The document table 21 is a document table made of transparent glass or the like, on which a document P to be read is placed. The document table cover 22 is provided on the upper side of the document table 21. The document table cover 22 is a pressure plate that opens and closes with respect to the document table 21 and presses the document P placed on the document table 21. The surface of the document table cover 22 that holds the document P is white or a color close to white. The auto sheet feeder 24 is an automatic document feeder (ADF) that is integrated with the document table cover 22 and automatically sends a document to the document table 21.

  The cover open sensor 23 is an angle detection unit that detects the open / close state and the angle of the document table cover 22, and detects that the open / close angle of the document table cover 22 is closed from the open state to the first angle. It functions as angle detection means and second angle detection means for detecting that the document table cover 22 is closed from the first angle to the second angle. Specifically, the cover open sensor 23 is provided in the vicinity of the connection portion between the scanner 20 main body and the document table cover 22, and indicates whether or not the document table cover 22 has reached a predetermined angle with respect to the document table 21. To detect.

  More specifically, the cover open sensor 23 is in the scanner 20 in the vicinity of the support shaft for opening and closing the document table cover 22, and the optical sensors 233 and 234 are mechanisms for detecting a plurality of stages of opening angles of the document table cover 22. Yes, the sensor flag 235 moves up and down depending on the opening angle of the document table cover 22, and blocks the light of the optical sensors 233 and 234 when reaching a certain angle, so that the opening angle of the document table cover 22 becomes the optical sensors 233 and 234. Detected by.

  In this embodiment, the optical sensors 233 and 234 are used as the sensors. However, the present invention is not limited to this, and it is only necessary to detect the position of the sensor flag 235 linked to the document table cover 22. A photocoupler, which is similar photoelectric conversion means, may be used. For example, a magnet is provided at a position corresponding to the sensor flag 235, and the state of the sensor flag 235 is detected by detecting the magnet with a magnetic sensor. The structure to detect may be sufficient.

The scanner 20 is also provided with a white reference plate 26 that acquires data for performing shading correction at a predetermined position on the home position side of the document table 21.
As shown in detail in FIG. 6, the image reading unit 25 includes a CCD line sensor 92 in which image reading elements such as CCDs are arranged on a line, an exposure lamp 94 as a light source, a CCD line sensor 92, and an exposure lamp 94. A carriage 25a, a motor for conveying the carriage 25a, and the like are provided. The image reading unit 25 irradiates the original P placed on the original table 21 or the original fed by the auto sheet feeder 24 with light from the exposure lamp 94 onto the original, and the reflected light is applied to the CCD 92 or the like. By receiving the light with the image pickup device, an image is read from the document, and image data corresponding to the read image is output to the control circuit 150 as job data.

  Next, the document detection angle of the document table cover 22 and the angle detection of the document table cover 22 will be described. FIG. 3A is a side view for explaining the position of the document table cover, and FIG. 3B is an explanatory diagram showing the document size detection position of the document table cover and the detection state of the sensor.

  In the open state, the document table cover 22 is in an open position indicated by a solid line in FIG. In the closed state, the document table cover 22 is in a closed position indicated by a two-dot chain line. The document table cover 22 opens and closes with respect to the document table 21 by rotating about one side of the rear side as a central axis.

  The first angle is the position of the document table cover 22 indicated by a broken line in FIG. 3A, and is the position where the angle θ formed by the document table cover 22 and the document table 21 becomes the angle θ1. The first angle θ1 is smaller than the angle formed by the document table cover 22 and the document table 21 in the open position. When the position reaches the second angle θ1 in the process of closing the document table cover 22, the optical sensor 233 of the cover open sensor 23 determines that the open / close state of the document table cover 22 has changed.

  The second angle is a position of the document table cover 22 indicated by a one-dot chain line in FIG. 3A, and is a position where an angle θ formed by the document table cover 22 and the document table 21 becomes an angle θ2. The second angle θ <b> 2 is an angle smaller than the first angle θ <b> 1 and is detected by the optical sensor 234. In the present embodiment, the position of the document table cover 22 is classified into three areas. Specifically, as shown in FIG. 3B, the area where the document table cover 22 is located is a small angle region in which the angle formed by the document table cover 22 and the document table 21 is smaller than the second angle θ2, The angle formed between the table cover 22 and the document table 21 is larger than the first angle θ1, and the angle formed between the document table cover 22 and the document table 21 is located between the small angle region and the large angle region. Divided into three angular regions.

  Whether it is located in any of these areas is determined by the detection result of the cover open sensor 23. Specifically, when the document cover 22 reaches the first angle θ1 that moves from the large angle region to the medium angle region by the cover open sensor 23, the medium angle sensor (optical sensor 233) changes from the OFF state to the ON state. Thus, when the second angle θ2 that moves from the medium angle region to the small angle region is reached, the small angle sensor (optical sensor 234) is changed from the OFF state to the ON state.

(Configuration of reading control unit)
FIG. 4A is a block diagram illustrating a characteristic function unit of the image reading apparatus 1, and FIG. 4B is a block diagram illustrating a function unit of the reading control unit. For simplicity, functional parts that are not important in the description of the present embodiment are omitted.

  As shown in FIG. 4A, the control circuit 150 includes a CPU 50, a RAM 30, a flash memory 40, an input / output interface 80, an FeRAM 60, a USB interface 70, and a system bus 150a that connects each unit. .

  The flash memory 40 stores program and configuration circuit information in a nonvolatile manner. The RAM 30 is a work area for the CPU 20. The CPU 20 virtually constructs a functional module according to the program recorded in the flash memory 40.

  The image reading unit 25 includes a document size detection sensor 91 for detecting the size of the document P placed on the document table 21. As shown in FIG. 6, the document size detection sensor 91 includes document length detection size sensors 91a to 91d that detect the length of the document in the sub-scanning direction. The document length detection size sensors 91a to 91d are light emitting elements. And a light receiving element, each of which is arranged at a position corresponding to a standard size.

  The image reading unit 25 includes a CCD 92 that optically reads an image, a motor 93 that drives lenses and mirrors of an optical system, and an exposure lamp 94 that is illumination that irradiates the original. In the CCD 92, the light receiving elements are arranged in a line along the main scanning direction, and each light receiving element reads the reflected light from the original and reads the image, and the light receiving elements reflect the light from the original P. It also has a function of determining the document width by detecting light and disturbance light incident on the document table 21 and detecting the luminance distribution on the line with the original position of the document as the origin. In the present embodiment, the standard size of the document is detected from the combination of the document width in the main scanning direction detected by the CCD 92 and the document length in the sub-scanning direction detected by the sensors 91a to 91d.

  On the other hand, various programs and data are recorded in the flash memory 40 shown in FIG. 4, and this program includes circuit information for constructing a logic circuit necessary for image reading processing, and a reading control unit. 52 circuit information is also included. In the FeRAM 60, various adjustment values unique to the body of the image reading apparatus 1 are recorded in a nonvolatile manner. Connected to the USB interface 70 is a USB cable for connecting the printer as the host device and the image reading apparatus 1.

  The CPU 50 is an integrated circuit that can virtually configure a functional module such as a logic circuit by loading a program. In this embodiment, the scanner controller 51 and the reading control unit 52 are constructed by loading a program. In the present embodiment, the “module” refers to a functional unit that is configured by hardware such as an apparatus or a device, software having the function, or a combination thereof, and achieves a predetermined operation.

  The scanner controller 51 is a module that executes control related to the carriage 25 a and controls operations of devices such as the CCD 92, the motor 93, and the exposure lamp 94 included in the image reading unit 25. On the other hand, the reading control unit 52 is a module that executes document size determination and calculation processing necessary for image reading when reading an image. In the present embodiment, the reading control unit 52 includes a function of detecting luminance fluctuation of ambient light. ing.

  The carriage 25a is a unit that mounts and moves the CCD 92 and the exposure lamp 94, and is moved horizontally in the sub-scanning direction by the motor 93. More specifically, as shown in FIGS. 7A and 7B, the carriage moves to the carriage position according to the state of the image reading apparatus 1 and the stage of the reading operation. During standby, the document table 21 is retracted to the home position P1 that is separated from the glass surface of the document table 21 in the sub-scanning direction. The home position P1 is located behind the origin that is the abutting position (leftward in the y-axis direction in FIG. 7A), and corresponds to an AF window provided at a position where the document passes during the auto feeder operation. This position also serves as a pre-disturbance light detection position. At the time of shading correction, it moves to the shading reading position P2. The shading reading position P2 is a position corresponding to the white reference plate 26 adjacent to the document table 21 side of the home position P1, and by reading the white reference plate 26, data for performing shading correction is acquired.

  In this embodiment, when the document size is detected, the document moves to the reading position PA. This reading position PA is a position moved to the end side to some extent from the origin along the sub-scanning direction below the glass surface of the document table 21. In addition, reading positions PB and PC are arranged before and after the reading position PA.

These distances from the butting positions of the reading positions PA, PB, PC are as follows:
Reading position PC ≦ reading position PA ≦ reading position PB
It has become. In this embodiment, when the presence of the document table cover 22 is detected by the small angle sensor (optical sensor 234) following the first reading operation, the second reading operation is performed. After moving to PB, the range of the PC is read from the reading position PB while moving the carriage 25a to the top side. The read data extracts the minimum luminance in the sub-scanning direction for each main scanning position.

(Configuration of reading control unit)
FIG. 4B is a block diagram illustrating an internal configuration of the reading control unit 52. As shown in the figure, the reading control unit 52 mainly includes an operation control unit 52b, a reading unit 52a, a document size detection unit 52c, an angle determination unit 52e, and data as modules corresponding to document size detection. An analysis unit 52d and a closing speed measurement unit 52f are provided.

  The reading unit 52a is a module that analyzes the distribution of reflected light included in the image data read by the CCD 92 at each opening / closing angle, and includes a luminance distribution recording unit 52g. The luminance distribution recording unit 52g is a module that records each open / close angle and the distribution data of the reflected light at the time of the angle, records the distribution data of the reflected light in the medium angle region, and in the small angle region. It functions as a reading means for recording the distribution data of the reflected light.

  The reading unit 52a includes a data analysis unit 52d. The data analysis unit 52d records the result of calculating the minimum luminance value along the sub-scanning direction for each main scanning position in the second reading operation as the second luminance distribution.

  The document size detection unit 52c is a module that detects the width and length of a document from each data detected or analyzed by each module of the reading control unit 52. The document size detection unit 52c has a function as document width detection means, and compares the recording in the medium angle region and the recording in the small angle region when detecting the document size, and based on the comparison result. Thus, document width detection is performed in which a portion with a large change in brightness is set as a non-document portion.

  The angle determination unit 52e is a module that determines an angle area based on the opening / closing angle of the document table cover 22 detected by the optical sensors 233 and 234. When the document size is detected, the document table cover 22 is opened to the first angle θ1. And that the document table cover 22 has changed from the first angle θ1 to the second angle θ2.

  The angle determination unit 52e in the present embodiment includes a closing speed measurement unit 52f. The closing speed measuring unit 52f is a module that measures the speed at which the document table cover 22 is closed, and measures the elapsed time from when the first angle θ1 is detected until the second angle θ2 is detected. The angular velocity during the closing operation of the document table cover 22 is calculated from the angle change per unit time from the angle θ1 to the second angle θ2.

  The operation control unit 52b is a module that comprehensively controls the operation of each module in the reading control unit 52. In the operation control unit 52b, data from each sensor is input, and each module in the reading control unit 52 is input. Sorted. Specifically, sensor detection results and read image data are input from the document size detection sensor 91 and the CCD 92 through the scanner controller 51, and the opening / closing angle of the document table cover 22 is input from the cover open sensor 23.

  In particular, in this embodiment, the operation control unit 52b controls the reading unit 52a and the scanner controller 51 according to the angle detected by the angle determination unit 52e. More specifically, when the angle determination unit 52e detects that the opening / closing angle of the document table cover 22 has changed to the first angle θ1, the first reading operation for recording the first luminance distribution is executed at the reading position PA. To do. Next, when the angle determination unit 52e detects that the opening / closing angle of the document table cover 22 has changed to the second angle θ2, the carriage 25a is moved in the sub-scanning direction over the reading range RBC including the reading position PA. A second reading operation for recording the luminance distribution is executed. At this time, the operation control unit 52b changes the position or size of the range RBC according to the closing speed of the document table cover 22 measured by the closing speed measuring unit 52f.

(Operation control in size reading processing)
The characteristic operation control at the time of image reading of the image reading apparatus 1 according to the present embodiment having the document width detecting function described above will be described. FIG. 5 is a flowchart showing an operation at the time of image reading.

  First, when the size reading process is started, a loop process is performed until the first angle θ1 is detected (“N” in S101). Then, when it is detected that the opening / closing angle of the document table cover 22 has changed from the open state to the first angle θ1 (“Y” in S101), light is irradiated toward the document in the middle angle region, and the reflection is performed. A first reading process for recording a first luminance distribution, which is a light distribution, is executed (S102). The first reading process is performed at a reading position PA that is a document width detection position shown in FIGS.

  Further, it is waited by loop processing to detect that the document table cover 22 has changed from the first angle θ1 to the second angle θ2 (“N” in S103), and when the second angle θ2 is detected. (“Y” in S103), the closing speed is measured (S104). In the closing speed measurement in step S104, the elapsed time from when the first angle θ1 is detected until the second angle θ2 is detected is measured, and the unit time from the first angle θ1 to the second angle θ2 is reached. The angular velocity at the time of the closing operation of the document table cover 22 is calculated from the change in the angle.

  Next, based on this closing speed, in the present embodiment, the position or size of the second reading range RBC is set (S105). More specifically, as the reading position PB is moved to the end side with respect to the reading position PA, the reading range RBC in the closed state becomes wider and becomes more resistant to document misalignment, as shown in FIG. When the pressure plate is quickly closed (elapsed time is short), there is a high possibility that the amount of displacement will be large. Therefore, the amount of movement of the reading position PB toward the end side is increased according to the speed at which the pressure plate is closed. Give priority to actions that are wider and have better countermeasures against slippage. On the other hand, when closing the pressure plate slowly, it is assumed that the amount of displacement is small or there is no displacement, and the amount of movement toward the end side is made small or 0 (PA = PB), giving priority to the speed of the reading operation. .

  Thereafter, over the second reading range BC (including the reading position PA) set in step S105, light is emitted toward the document while moving the carriage 25a in the sub-scanning direction, and the luminance distribution of the reflected light is recorded. A second reading process is executed (S106). At this time, in the present embodiment, the result of calculating the minimum value of luminance along the sub-scanning direction is recorded as the second luminance distribution for each main scanning position.

  Then, document width detection processing is performed based on the difference in luminance distribution obtained by the processing in step S106 (S107). In the document width detection process according to the present embodiment, a difference between the second luminance distribution obtained by extracting the minimum luminance value for each main scanning position and the first luminance distribution is calculated, and the luminance difference is compared with a predetermined threshold value. Document width detection is performed based on the result.

(Details of document width detection method)
Details of the document width detection method in step S107 will be described. In the present embodiment, a pressure plate opening / closing difference method for detecting a document edge from a difference in luminance distribution depending on presence / absence of reflection on a reflection plate on a back surface of a pressure plate in a pressure plate open state and a pressure plate closed state where the pressure plate is closed than this state. Use. In the pressure plate open / close difference method, a state where the angle between the document table 21 and the document table cover 22 is in the large angle region or the medium angle region is referred to as a “pressure plate open state”, and a state in the small angle region is referred to as a “pressure plate closed state”. When the platen cover 22 moves from the large angle region to the small angle region through the medium angle region, the brightness of the document table cover 22 is determined based on the comparison result between the luminance distributions obtained in the medium angle region and the small angle region. A portion with a large change is defined as a non-original portion.

  More specifically, as shown in FIG. 8D, when the light source is turned on when the pressure plate is located in the large angle and medium angle regions, as shown in FIG. Reflected light from the document table cover 22 is not reflected on the non-document portion of the document, and the brightness is low. If the light source is turned on when the document table cover 22 is closed and reaches a small angle area as shown in FIG. 6B, the front side area A2 non-original is shown in FIG. The reflected light from the pressure plate is reflected in the portion, and the brightness increases. In the present embodiment, at the time of the second reading operation in step S106, after moving to the reading position PB, the carriage 25a is moved to the top side while reading the range of the PC from the reading position PB, and at each sub-scanning position. A second luminance distribution is generated by extracting the minimum luminance in the scanning direction.

  The difference between the second luminance distribution in the small angle region (FIG. 8A) and the luminance distribution in the large angle / medium angle region (FIG. 8C), that is, “reading of the closed state of the light source ON” − “ By calculating “reading of open state of light source ON”, a luminance distribution difference as shown in FIG. 8E is obtained. In the luminance distribution difference, the value is small because there is no change in the reflected light from the document in the region A1, and the value is large in the region A2 because the amount of reflected light is changed.

  Then, as shown in FIG. 8F, the edge of the document is searched by comparing the luminance distribution difference and the predetermined threshold value with the position away from the abutting position (front side) as the starting point. The part where the difference is less than the threshold is defined as the document edge.

  More specifically, for example, as shown in FIG. 9A, when a document including both a black portion having a high print density and a white portion having a low print density or not printed is grounded and read, When the document table cover 22 is opened, the white portion of the original is abutted against the top side, and the reading position PA is located in the black portion of the original.

  In this state, when the first reading operation is executed at the reading position PA, as shown in FIG. 9B, the reflected light from the document table cover 22 is not reflected on the non-document portion of the front side area A2, and the brightness is increased. Is a low value (luminance 0), while the rear area A1 has a higher luminance (luminance 20) than the area A2 while the luminance is low in the black portion of the document. Next, when the pressure plate is closed, as shown in FIG. 10A, it is assumed that the document is displaced in the sub-scanning direction by the closing operation. In the illustrated example, the white portion of the document is reflected at the reading position PA.

  In this state, after the carriage 25a is moved to the size detection position PB, the PC range is read from the size detection position PB while moving the carriage 25a to the top side. At this time, the minimum luminance in the sub-scanning direction is extracted for each main scanning position, and the luminance of the original portion is only the original black portion even if both the original black portion and the original white portion are included in the reading range RBC. It is the same as the time value (luminance 20). On the other hand, the reflected light from the pressure plate is reflected in the non-document portion on the front side area A2, and the brightness increases to 200.

  Then, by calculating the difference between the second luminance distribution in the closed state (FIG. 10B) and the first luminance distribution in the open state (FIG. 9B), as shown in FIG. 9C. The luminance distribution difference is obtained. In the brightness distribution difference, the brightness difference is 0 because there is no change in the reflected light from the document in the area A1, and the brightness difference is 200 in the area A2 because the amount of reflected light changes. It has become. Finally, by comparing the brightness distribution difference and the predetermined threshold value with a position away from the abutting position (front side) as a starting point, as shown in FIG. Is detected, and it is determined that there is a document in the area A1, and the width is detected as the document width.

(Action / Effect)
According to the present embodiment, in the second reading operation for recording the second luminance distribution in the small angle region, the carriage 25a is moved in the sub-scanning direction over the range RCB including the document width detection position, so that the pressure plate is being closed. Even in a situation where document deviation occurs, the reflected light can be acquired while moving the carriage 25a over the range where the document is displaced, and the luminance distribution can be recorded, and fluctuations in the luminance distribution are detected due to document deviation. Thus, accurate document width detection can be performed.

  Further, in the second reading operation, the result of calculating the minimum value of the luminance along the sub-scanning direction for each main scanning position is recorded as the second luminance distribution, so that the original portion and the non-original portion at the time of deviation are recorded. The boundary of the part can be detected with high accuracy. Further, in a situation where document deviation is expected to be small, an increase in the read preparation time can be reduced because measures such as narrowing the reading range of document width detection are taken.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiment.

θ1 ... first angle θ2 ... second angle A1 ... rear side area A2 ... front side area P ... document P1 ... home position P2 ... shading reading position PA to PC ... document size detection position 1 ... image reading device 10 ... device body 20 ... Scanner 21 ... Document table 22 ... Document table cover 23 ... Cover open sensor 24 ... Auto sheet feeder 25 ... Image reading unit 25a ... Carriage 26 ... White reference plate 30 ... RAM
40 ... Flash memory 50 ... CPU
DESCRIPTION OF SYMBOLS 51 ... Scanner controller 52 ... Reading control part 52a ... Reading part 52b ... Operation control part 52c ... Original size detection part 52d ... Data analysis part 52e ... Angle determination part 52f ... Closing speed measurement part 52g ... Luminance distribution recording part 60 ... FeRAM
DESCRIPTION OF SYMBOLS 70 ... USB interface 80 ... Input / output interface 91 ... Document size detection sensor 91a-d ... Document length detection size sensor 92 ... CCD line sensor 93 ... Motor 94 ... Exposure lamp 102 ... Paper feeding unit 103 ... Image forming unit 104 ... Ejecting paper Numeral 105 ... Discharge tray 106 ... Feed tray 107 ... Feed roller 108 ... Registration roller pair 109 ... Conveying belt 110 ... Conveying belt roller 111 ... Conveying means 112 ... Image forming means 115 ... Discharge roller pair 150 ... Control circuit 150a ... System bus 160 ... Power supply circuit 232 ... Moving part 233 ... Optical sensor (medium angle sensor)
234 ... Optical sensor (small angle sensor)
235 ... Through hole 236 ... Photo interrupter

Claims (3)

An image reading apparatus for optically reading a document,
A document table on which the document is placed;
A pressure plate that opens and closes with respect to the document table;
First angle detecting means for detecting that the opening / closing angle of the pressure plate has changed from the open state to the first angle;
Second angle detecting means for detecting that the pressure plate has changed from the first angle to a second angle;
In a medium angle region between the first angle and the second angle, light is emitted toward the document placed on the document table, and a luminance distribution along the main scanning direction of the reflected light is obtained. In addition to recording as a first luminance distribution, in a small angle region equal to or less than the second angle, light is irradiated toward the document placed on the document table, and the luminance along the main scanning direction of the reflected light Reading means for recording the distribution as a second luminance distribution;
Driving means for moving the reading means in a sub-scanning direction orthogonal to the main scanning direction;
Document width detection means for performing document width detection based on a comparison result between the first brightness distribution and the second brightness distribution;
An operation control unit for controlling operations of the reading unit and the driving unit according to an angle detected by the angle detecting unit;
The operation control unit includes:
A first reading operation for recording the first luminance distribution by the reading unit at the document width detection position when the angle detecting unit detects that the opening / closing angle of the pressure plate has changed to the first angle; ,
When the angle detection means detects that the opening / closing angle of the pressure plate has changed to the second angle, the reading means is moved in the sub-scanning direction over a predetermined range including the document width detection position, And a second reading operation for recording the second luminance distribution.   2. The reading unit according to claim 1, wherein a result of calculating a minimum value of luminance along a sub-scanning direction is recorded as the second luminance distribution for each main scanning position in the second reading operation. The image reading apparatus described in 1. Further comprising a closing speed measuring means for measuring the speed of closing the pressure plate,
3. The image reading according to claim 1, wherein the operation control unit changes the position or size of the predetermined range according to a closing speed of the pressure plate measured by the closing speed measuring unit. apparatus.