JP3991933B2 - Image reading device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image reading apparatus.
[0002]
[Prior art]
Conventionally, in an image reading apparatus such as an image scanner, a technique for automatically determining a document size using an image sensor used for reading a document is known. According to the technique described in Patent Document 1, optical density is measured for a plurality of determination areas on a document table by sampling output signals of pixels of a predetermined linear image sensor, and a document is based on the result. Determine the size.
[0003]
[Patent Document 1]
JP 9-191370 A
[0004]
[Problems to be solved by the invention]
However, since the optical path from the multiple judgment areas on the document table to the linear image sensor varies depending on the manufacturing tolerances of the optical system, sampling is performed based on the output signal of the pixel of the predetermined linear image sensor. The area on the platen that is being used varies from one apparatus to another. Therefore, in the conventional image reading apparatus, the document size may be erroneously determined due to the manufacturing tolerance of the optical system. An object of the present invention is to provide an image reading apparatus which has been created to solve such a problem, and which improves the accuracy of document size determination.
[0005]
[Means for Solving the Problems]
To achieve the above object, an image reading apparatus according to the present invention includes a transparent document table on which a document is placed on a board surface, and an image sensor that reads the document by photoelectric conversion in a plurality of discretely arranged pixels. A first optical system that forms a reflected light image of the document placed on the document table on the light receiving surface of the image sensor, and a plurality of the first optical systems that are spaced apart from each other on the surface of the document table and aligned in the main scanning direction When a first optical path from the first determination area to a predetermined pixel of the image sensor is formed by the first optical system, a predetermined distance in the sub-scanning direction from the first determination area on the surface of the document table A second optical system that forms a second optical path from the separated second determination region to a predetermined pixel of the image sensor, at least the image sensor, the first optical system, and a part of the second optical system; Mounted Carriage moving means for reciprocating the carriage in the sub-scanning direction, and sampling the output signals of the plurality of pixels of the image sensor to obtain the optical density of the first determination area and the optical density of the second determination area. Document size determination means for measuring and determining the size of the document placed on the surface of the document table based on the measured optical density of the first determination region and the measured optical density of the second determination region; A magnification measuring means for measuring the magnification of the first optical system, wherein the carriage moving means is a position where the first optical path and the second optical path are formed at the same time, and is located at the second optical system. On the other hand, the carriage is moved to a position where the magnification measurement result of the first optical system can be applied, and the document size determining means is configured to detect a plurality of image sensors when the carriage is at the position. Sampling the output signal of the pixel in the sampling, it is changed in accordance with pixel sampling object corresponding to the first determination area and the second determination area to the measurement result of the magnification measuring means. The accuracy of document size determination can be improved by changing the pixel of the image sensor that is the target of sampling the output signal to determine the document size in accordance with the magnification of the optical system.
[0006]
Furthermore, not only a plurality of first determination areas that are separated from each other on the surface of the document table and are arranged in the main scanning direction, but also a second determination area that is spaced a predetermined distance from the first determination region in the sub-scanning direction on the surface of the document table By measuring the optical density, various document sizes can be distinguished from each other even when the orientation of the document placed on the document table is not constant. The optical system further includes a second optical system that forms an optical path from the second determination region to a predetermined pixel of the image sensor when an optical path from the plurality of first determination regions to the predetermined pixel of the image sensor is formed. Thus, the length of the document in the sub-scanning direction can be determined in a short time without translating the main scanning line of the image sensor in the sub-scanning direction.
[0007]
Further, the accuracy of determining the length of the document in the sub-scanning direction is improved by changing the pixel of the image sensor to be sampled to measure the optical density of the second determination region according to the measurement result of the magnification measuring unit. be able to.
The image reading apparatus according to the present invention further includes a document cover provided so as to be swingable from a posture in which the platen surface of the document table is opened to a posture in which the platen surface of the document platen is covered. A change in the amount of light incident on a predetermined pixel of the image sensor by the first optical system and the second optical system, wherein the document cover covers the platen surface of the document platen from a posture in which the platen surface of the document platen is opened The size of the document placed on the platen surface of the document table is determined based on the change in the amount of light during the period when the document is swung.
In the image reading apparatus according to the present invention, the document size determination means may specify a minimum-size document whose size can be determined from an edge on the document table board surface for a plurality of areas on the document table board surface. It is determined whether or not the document is covered in the order in which the document falls within the placement range.
[0008]
The functions of the plurality of means provided in the present invention are realized by hardware resources whose functions are specified by the configuration itself, hardware resources whose functions are specified by a program, or a combination thereof. The functions of the plurality of means are not limited to those realized by hardware resources that are physically independent of each other.
The present invention can be specified not only as an apparatus invention but also as a program invention, a recording medium recording the program, and a method invention.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples.
FIG. 2 is a top view of the image scanner 14 as an image reading apparatus according to an embodiment of the present invention. 3, 4, and 5 are schematic cross-sectional views of the image scanner 14. The image scanner 14 is a so-called flat bed type having a generally rectangular transparent document table 30 formed of a glass plate or the like on the upper surface of the housing 20. A manuscript such as a photograph or a document is placed on the platen 30 on the platen. The document abuts on the end surfaces 22 and 32 of the L-shaped document guide 24 provided at the edge of the document table 30, so that the corner of the document is positioned at the corner of the document table 30 corresponding to the origin. To be positioned. As shown in FIG. 11, a white reference plate 84 is provided on the back surface of the document guide 24. The white reference plate 84 is formed with two optical magnification measurement marks 80 and 82 for measuring the optical magnification of the first optical system 46 (see FIG. 4) and the second optical system 58 (see FIG. 5). By design, the pixels of the image sensor 54 on which the two optical magnification measurement marks 80 and 82 are imaged by the first optical system 46 (p4 and p6 are illustrated in FIG. 11) are preliminarily stored as reference information described later. It is remembered.
[0010]
The document cover 16 is connected to the housing 20 by a hinge 17 so as to be swingable from a posture in which the platen surface of the document platen 30 is opened (fully open posture) to a posture covering the platen surface of the document platen 30 (fully closed posture). FIG. 2 shows the fully open posture of the document cover 16. The document cover 16 holds the document placed on the document table 30 and covers the document table 30 so that light other than the light emitted from the main lamp 34 and the LED 36 does not illuminate the document. Further, the movable member 12 of the attitude sensor 41 for detecting the attitude of the document cover 16 protrudes from the vicinity of the swing axis of the document cover 16 on the upper surface of the housing 20.
[0011]
In the following description, the posture I shown in FIG. 3 is called a fully open posture, and the posture III is called a fully closed posture. Posture II is called an intermediate posture. The attitude sensor 41 is a sensor that detects a change in the attitude of the document cover 16. The movable member 12 of the attitude sensor 41 is biased by a spring 38 in a direction protruding from the upper surface of the housing 20. When the document cover 16 is in the intermediate position, the movable member 12 comes into contact with the document cover 16, and when the document cover 16 further approaches the fully closed position from the intermediate position, the movable member 12 is pushed into the inside of the housing 20. Detected.
[0012]
As shown in FIG. 4, the carriage 28 is accommodated in the housing 20 so as to be reciprocally movable in parallel with the surface of the document table 30. The carriage 28 includes a linear image sensor 54, a first optical system 46, and a part of the second optical system 58, and is slidably locked to a guide shaft or the like parallel to the surface of the document table 30. Yes. The longitudinal axis of the guide shaft extends in the X direction (sub-scanning direction) in FIG. 4, and the carriage 28 is pulled by, for example, a belt to convey the linear image sensor 54 and the like in the sub-scanning direction.
[0013]
The linear image sensor 54 reads the document M by photoelectrically converting the reflected light of the document M placed on the document table 30. Specifically, the linear image sensor 54 has a plurality of pixels such as photodiodes arranged in a straight line in the direction perpendicular to the paper surface in FIG. 4 and emits light in a predetermined wavelength region such as visible light, infrared light, and ultraviolet light. The electric charge obtained by photoelectric conversion is accumulated for a certain period of time, and the electric charge accumulated in accordance with the amount of received light for each pixel is transferred to a floating capacitor using a CCD (Charge Coupled Device), a MOS transistor switch or the like. The charge transferred to the floating capacitor is output as a voltage signal.
[0014]
The first optical system 46 includes a main lamp 34 as a light source, mirrors 50, 44, 42 and 48, and a lens 52. The main lamp 34 is composed of a tube illumination device such as a xenon lamp, and is mounted on the carriage 28 with a longitudinal axis extending parallel to the longitudinal axis of the linear image sensor 54. The main lamp 34 irradiates the back side of the document table 30 from the inside of the housing 20. The mirrors 50, 44, 42, 48 and the lens 52 are linear from the region on the main scanning line parallel to the longitudinal axis of the linear image sensor 54 as shown by the broken line in FIG. An optical path T to the image sensor 54 is formed.
[0015]
As shown in FIG. 5, the second optical system 58 includes an LED (Light Emitting Diode) 36, mirrors 51, 56, 49 and 48, and a lens 52. The mirror 48 and the lens 52 are used both as the first optical system 46 and the second optical system 58. The LED 36 is arranged at a position to irradiate a determination area H on the surface of the document table 30 that is separated from the end surface 22 of the document guide 24 extending in the main scanning direction by a predetermined distance in the sub-scanning direction X. The determination area H is an area set for determining the length of the document in the sub-scanning direction, and a specific position thereof will be described later. The mirrors 51, 56, 49, 48 and the lens 52 form an optical path R from the determination region H to the linear image sensor 54 as indicated by a broken line in FIG. The LED 36 and the mirrors 56 and 51 are arranged at positions where there is no hindrance to the movement of the carriage 28. Since the first optical system 46 and the second optical system 58 can simultaneously form an optical path from at least two regions separated from each other in the sub-scanning direction to the image sensor 54, the document 28 can be kept stationary while the carriage 28 is stationary. It is possible to determine the length in the sub-scanning direction. As a result, even when the orientation of the document placed on the document table 30 is not constant, various document sizes can be distinguished from each other in a short time.
[0016]
FIG. 6 is a block diagram showing the image scanner 14.
The main scanning drive unit 72 is a drive circuit that outputs drive pulses necessary for driving the linear image sensor 54 to the linear image sensor 54. The main scanning drive unit 72 includes, for example, a synchronization signal generator, a drive timing generator, and the like.
[0017]
The sub-scanning drive unit 74 includes a belt locked to the carriage 28, a motor and a gear train for rotating the belt, a drive circuit, and the like. When the sub-scanning drive unit 74 pulls the carriage 28 with a belt, the main scanning line extending in the direction perpendicular to the paper surface of FIG. 4 moves in the sub-scanning direction perpendicular to the main scanning line.
[0018]
The AFE unit 60 includes an analog signal processing unit, an A / D converter, and the like. The analog signal processing unit subjects the electrical signal output from the linear image sensor 54 or the photodiode 33 to amplification, noise reduction processing, and the like, and outputs the result. The A / D converter quantizes the output signal output from the analog signal processing unit and outputs an output signal in a digital representation having a predetermined bit length. In the following description, the output signal is assumed to be 8 bits long, that is, expressed in 256 gradations.
The digital image processing unit 62 performs processing such as shading correction, gamma correction, defective pixel interpolation by a pixel interpolation method, and image signal sharpening on the output signal output from the AFE unit 60 to create image data. .
[0019]
The control unit 70 includes a CPU 66, a ROM 64 and a RAM 68. The CPU 66 executes computer programs stored in the ROM 64 and controls each unit of the image scanner 14. The CPU 66 also functions as a magnification measurement unit and a document size determination unit by executing a computer program stored in the ROM 64. The ROM 64 is a memory that stores a computer program executed by the CPU 66, a determination table (see FIG. 17) used for determining the document size, reference information for measuring the magnification of the optical system, and other various programs and data. . These programs and various data may be downloaded and input from a predetermined server via a network, or may be read and input from a computer-readable storage medium such as a removable memory (not shown). The RAM 68 is a memory that temporarily stores programs and data.
[0020]
FIG. 7A is a schematic diagram showing the posture sensor 41, and FIG. 7B is a waveform diagram of an output signal of the posture sensor 41. The attitude sensor 41 is a sensor that detects the attitude of the document cover 16. The posture sensor 41 includes a movable member 12, a spring 38 that biases the movable member 12 to protrude from the housing 20, a posture detection LED 76, and a photodiode 40 that detects light emitted from the posture detection LED 76. Note that an optical path for allowing the light emitted from the attitude detection LED 76 to reach the linear image sensor 54 may be provided, and the light emitted from the attitude detection LED 76 may be detected by the linear image sensor 54. The output signal of the attitude sensor 41 changes before and after the original cover 16 swings to the intermediate attitude. Therefore, when the output signal of the posture sensor 41 is determined at predetermined time intervals, the timing when the document cover 16 is in the intermediate posture can be detected.
[0021]
Next, the operation of the image scanner 14 will be described.
FIG. 1 is a flowchart showing the entire processing until the original is read by the image scanner 14. First, the optical magnification is measured by measuring the position of the optical magnification measurement marks 80 and 82, and a pixel for sampling an output signal is set to determine the document size according to the measured optical magnification (S100). ). Next, a change in the output signal of the sampling target pixel accompanying the operation of closing the document cover 16 is detected (S200). Next, the document size is determined based on the change in the output signal of the sampling target pixel (S300). Next, an area corresponding to the determined document size is read (S400). Hereinafter, these processes will be described in detail.
[0022]
FIG. 8 is a flowchart showing processing for setting pixels of the image sensor to be sampled according to the optical magnification of the optical system.
First, a white reference for shading correction is set by reading an area where the optical magnification measurement marks 80 and 82 are not formed on the white reference plate 84 (S110). Next, the positions of the optical magnification measurement marks 80 and 82 are measured based on the output signal of the linear image sensor 54 obtained by reading the optical magnification measurement marks 80 and 82 (S120). Next, the measured position of the optical magnification measurement mark is compared with the positions of the optical magnification measurement marks 80 and 82 indicated by the reference information stored in advance in the ROM 64, and the sampling target pixel is set based on the comparison result (S130). ). Here, the process of setting the sampling target pixel will be described in detail.
[0023]
FIG. 9 is a plan view of the document table 30. Frames A5H to WLT in the drawing represent the document sizes shown in FIG. When determining the document size, it is not necessary to detect the light amount change for all the pixels of the linear image sensor 54, and it is sufficient to detect the light amount change only for the pixels on which the reflected light in the specific determination region on the document table 30 is incident. . The pixels of the linear image sensor 54 whose output signal should be sampled to determine the document size are pixels on which light enters the determination areas A to H via the first optical system 46 and the second optical system 58. In order to prevent erroneous determination, it is desirable that each determination region corresponds to a plurality of continuous pixels.
[0024]
Determination areas A to G as first determination areas are areas for determining the length of the document in the main scanning direction. The positions in the sub-scanning direction of the determination areas A to G are sub-scanned from the end surface 22 of the document guide within a range shorter than the shortest sub-scanning length of the standard paper size to be determined (within 148 mm in the example of FIG. 10). It is set so as to be aligned in a straight line in the main scanning direction at a position slightly apart in the direction. Specifically, the positions of the determination areas A to G in the main scanning direction are determined based on, for example, the document size shown in FIG. 10 when the distance from the end surface 32 of the document guide 24 to the determination areas A to G is set to the following range. can do.
[0025]
0mm <A <148mm
148mm <B <182mm
184.15mm <C <210mm
210mm <D <215.9mm
215.9 mm <E <257 mm
266.7 mm <F <279.4 mm
279.4 mm <G <297 mm
[0026]
The determination area H as the second determination area is an area for determining the length of the document in the sub-scanning direction. Specifically, the determination area H is, for example, at an arbitrary position in the area on the document table 30 that is covered with an A4 vertical size (A4V) original and is not covered with a letter vertical size (LTV) original. Is set. That is, it is set at an arbitrary position within a region of 279.4 mm or more and 297 mm or less in the sub-scanning direction from the origin Q and 0 mm or more and 210 mm or less from the origin Q in the main scanning direction. The origin Q is set on the board surface immediately below the corner formed by the end faces 22 and 32 of the L-shaped document guide 24. If it is not necessary to determine the length in the sub-scanning direction because all document sizes can be determined only by the length in the main scanning direction, it is not necessary to detect a change in the amount of light for the pixel corresponding to the determination region H. is there. In that case, the second optical system 58 described above is also unnecessary.
[0027]
FIG. 11 and FIG. 12 are perspective views for explaining processing for changing the pixel to be sampled according to the magnification of the optical system. When the optical magnification measurement marks 80 and 82 are read to measure the positions of the optical magnification measurement marks 80 and 82, the positions of the optical magnification measurement marks 80 and 82 are specified in association with the pixel numbers of the image sensor 54. The reference information stored in the ROM 64 in advance includes the numbers of the pixels (p4, p6) corresponding to the optical magnification measurement marks 80, 82 in design and the pixels (p1, p2) corresponding to the determination areas A to H in design. , P5, which is illustrated in the figure). The numbers of the pixels (illustrated in the drawing as p3 and p7) identified by reading the optical magnification measurement marks 80 and 82 and the pixels (p4 and p6) corresponding to the optical magnification measurement marks 80 and 82 indicated by the reference information. By comparing the numbers, the magnification error of the optical system can be specified. When the magnification error of the optical system is specified, the number obtained by changing the number of the pixels (p1, p2, p5) corresponding to the determination areas A to H indicated by the reference information according to the magnification error of the optical system is changed. It is set as the number of the pixel (illustrated by p8, p9, and p10). The processing for setting the sampling target pixel has been described above.
[0028]
Next, processing for determining the document size will be described. First, the principle of detecting the document size will be described. The document size determination method is not limited to the method described below, and any method may be used as long as the document size is determined using an image reading image sensor.
[0029]
FIG. 13 plots pixel output signals for one line for the timing when the document cover 16 is in the fully closed position and the timing when the document cover 16 is in the intermediate position when no document is placed on the document table 30. It is a graph. When the document cover 16 is in the fully closed posture, the radiated light of the main lamp 34 is reflected by the document cover 16 and enters the inside of the housing 20 from the document table 30. On the other hand, when the document cover 16 is in the intermediate position, the amount of reflected light of the main lamp 34 incident on the linear image sensor 54 from the document table 30 is reduced as compared with the fully closed position for all the pixels because the light diffuses. To do. In the intermediate posture, most of the light reflected at the position on the document cover 16 and close to the swing axis is incident on the linear image sensor 54, and most of the light reflected at a position far from the swing axis is It does not enter the linear image sensor 54. For this reason, as the pixel is farther from the swing axis of the document cover 16, the amount of decrease in the amount of received light becomes larger. Further, the main lamp 34 has a higher brightness near the center in the longitudinal direction and a lower brightness at both ends. Therefore, at the timing when the document cover 16 is in the intermediate position, the light reception amount is the highest at a pixel slightly closer to the swing axis than the center. growing.
[0030]
On the other hand, when the determination area on the board is covered with the document, each pixel of the linear image sensor 54 where light enters from the determination area covered with the document is in the fully closed position or the intermediate position. Regardless of this, the reflected light of the original M irradiated by the main lamp 34 is always received. In the pixel that receives the reflected light of the document M, the reflected light of the document M irradiated by the main lamp 34 hardly changes even when the document cover 16 is in the fully closed position or the intermediate position, so that the amount of received light is almost the same. It is constant.
For this reason, the difference between the output signal at the timing when the document cover 16 is in the fully closed posture or the timing immediately before it and the output signal at the timing of the intermediate posture is small in the pixels corresponding to the determination area covered by the document. The pixel corresponding to the determination area that is not covered by the document becomes large.
[0031]
Therefore, a predetermined threshold value Y is set to the change width between the output signal at the timing when the document cover 16 is in the fully closed posture or the timing immediately before it and the output signal at the timing when the document cover 16 is in the intermediate posture, and an output signal corresponding to a certain pixel. If the change width is smaller than the threshold value Y, it can be determined that the determination area corresponding to the pixel is covered with the document. That is, when the document cover 16 swings from the fully open position to the fully closed position, if the magnitude of the change in the amount of received light is determined for a certain pixel, the determination area on the surface of the document table 30 corresponding to that pixel is covered with the document. It can be determined whether or not. In this determination method, it is possible to determine whether or not the determination area on the surface of the document table 30 corresponding to the pixel is covered with the document without considering the change width of the received light amount of the pixels other than the pixel.
[0032]
FIG. 14 is a flowchart showing a flow of processing for detecting a light amount change, and FIG. 15 is a time chart for explaining timings for detecting the light amount change. Hereinafter, processing for detecting a change in the output signal of the sampling target pixel will be described with reference to FIGS. 14 and 15.
In S205, the output signal of the posture sensor 41 is monitored at predetermined time intervals to detect the timing when the document cover 16 is in the intermediate posture.
[0033]
In S210, the main lamp 34 is turned on.
In S215, the process waits until the time t1 elapses after the main lamp 34 is turned on. When the main lamp 34 is a xenon lamp, the time t1 is about 10 milliseconds, for example.
In S220, the LED 36 is turned on. The reason why the main lamp 34 is lit at a timing earlier than the timing at which the LED 36 is lit is that the main lamp 34 takes a longer time than the LED 36 to stably emit light having the maximum luminance.
[0034]
In S225, the linear image sensor 54 accumulates charges for the period t2 while the carriage 28 is stationary, detects the accumulated charges, and samples the output signal of the pixel set as the sampling target pixel. At this time, since the light in the determination region H enters the pixels near the end of the linear image sensor 54 via the second optical system 58, the determination is performed together with the determination regions A to G even when the carriage 28 is stationary. The optical density in region H is also measured.
[0035]
In S230, the LED 36 is turned off once in order to prevent deterioration.
In S235, the number of times of reading is determined. If the reading is the first time, the process proceeds to S240. If the reading is the second time, the process proceeds to S250.
In S240, the output signal of the pixel sampled for the first time in S225 is stored in the RAM 68. Specifically, for example, an average value for each pixel, for example, an average value of output signals of 20 pixels corresponding to one determination area is stored in the RAM 68.
In S245, the process waits until the time t3 elapses after the LED 36 is turned off. Here, the time t3 is a time estimated as a time required for the user to rotate the document cover 16 from the intermediate posture to the fully closed posture, and specifically, for example, about 1000 milliseconds.
[0036]
In S250, the main lamp 34 is turned off. Even if it is light of the same luminance, the human eye feels more dazzling when it shines for a moment compared to when it shines longer, and generally when the time is about 200 milliseconds or more, the degree of feeling dazzling becomes smaller. For this reason, it is desirable that the lighting time t4 of the main lamp 34 is at least 200 milliseconds. Note that the main lamp 34 may be turned off once after the first reading, similar to the LED 36.
[0037]
In S255, the output signal of the pixel sampled for the second time is stored in the RAM 68. Specifically, for example, an average value for each of the determination areas A to H, for example, an average value of output signals of 20 pixels corresponding to one determination area is stored in the RAM 68.
In S260, a change width between the first output signal and the second output signal is obtained for the sampled pixel.
FIG. 16 is a flowchart showing a flow of processing for determining the size of the document placed on the surface of the document table 30 based on the detection result of the change width between the first output signal and the second output signal. .
[0038]
In S305, in order to determine the length of the document size in the sub-scanning direction, it is determined whether or not the change width of the output signal of the pixel corresponding to the determination region H is equal to or greater than a predetermined value (for example, 15 or greater). If the change width is equal to or greater than the predetermined value, it is determined that the determination area H is covered with the document cover 16 and the process proceeds to S310. If it is less than the predetermined value, the determination area H is determined to be covered with the original and the process proceeds to S315. .
[0039]
In S310, a value indicating “document cover” is set in a flag for storing whether the determination area H is covered by the document cover 16 or the document.
In S315, a value indicating “original” is set in the above-described flag.
In S320, 1 is set to the variable P indicating the number assigned to the determination area. Here, it is assumed that numbers 1 to 7 are assigned to the determination areas A to G in the order of A to G.
[0040]
In S325, it is determined whether or not the change width of the output signal is equal to or greater than a predetermined value (for example, 100 or more) for the pixel corresponding to the determination region to which the number set in the variable P is assigned. If it is less than the predetermined value, it is determined that the determination area to which the number set in the variable P is assigned is covered with the document, and the process proceeds to S330. If it is equal to or greater than the predetermined value, it is determined that the document cover 16 is covered, and the process proceeds to S340.
In S330, 1 is added to the variable P.
In S335, it is determined whether or not the value of the variable P is 8. If not 8, the process returns to S325 and the process is repeated until the value of the variable P becomes 8. If it is 8, the process proceeds to S340.
[0041]
In S340, the document size is determined. Specifically, the determination is performed as follows using the determination table shown in FIG. “◯” in FIG. 17 indicates that the area is covered with the document, and “X” indicates that the area is covered with the document cover. For example, if an A4-size original is placed, the determination areas A to C and H are covered with the original, and the determination areas D to G are covered with the original cover. Therefore, if the flag is “original” and 4 corresponding to the determination area D is set in the variable P, it can be determined that the original size is A4 vertical size. Similarly, all other document sizes can be uniquely specified.
[0042]
In the above description, the determination is performed in order from the determination area A until the change width becomes equal to or larger than the predetermined value. However, the determination may be performed in the reverse order from the determination area G until the change width becomes less than the predetermined value. .
Further, in the above description, the change width is obtained for all the determination areas in S260 of FIG. 14, but each time the change width is sequentially obtained for the determination areas A to G, whether or not the change width is equal to or greater than a predetermined value. It may be determined, and the processing for obtaining the change width may be terminated when the value becomes a predetermined value or more. As a result, it is not necessary to obtain the change width for the determination areas after the determination area, and the document size can be determined in a shorter time.
[0043]
According to the image scanner 14 according to the embodiment of the present invention described above, the pixels of the image sensor 54 that are the target of sampling the output signal to determine the document size are the pixels of the first optical system 46 and the second optical system 58. By changing according to the magnification, the accuracy of determining the document size can be improved. Specifically, the document size determination accuracy can be improved in the main scanning direction by changing the pixel numbers associated with the determination regions A to G according to the magnification of the first optical system 46. Further, by changing the number of the pixel associated with the determination region H according to the magnification of the second optical system 58, the accuracy of determining the document size can be improved in the sub-scanning direction.
[0044]
Further, according to the image scanner 14, whether or not the determination area on the surface of the document table 30 is covered with the original M can be determined without considering the change width of the received light amount of the pixels other than the pixels corresponding to the determination area. Can be determined. That is, according to the image scanner 14, as described in the flowchart of FIG. 16, the determination area change width is determined in order from the determination area A, and if a determination area covered by the document cover 16 is found, the subsequent steps are performed. It is not necessary to make a determination on the determination region. Therefore, the correct document size can be determined without necessarily inspecting all of the plurality of determination areas. Therefore, the document size can be reliably determined in a short time.
[0045]
Further, the linear image sensor 54 may be conveyed by the carriage 28 in the sub-scanning direction so as to receive the reflected light of the determination region H. In this case, the second optical system 58 is not necessary. In addition, a separate image sensor may be provided immediately below the determination region H, and the change width of the determination region H may be determined based on the output of the separately provided image sensor.
[Brief description of the drawings]
FIG. 1 is a flowchart according to an embodiment of the present invention.
FIG. 2 is a top view of the image reading apparatus according to the embodiment of the present invention.
FIG. 3 is a schematic diagram according to an embodiment of the present invention.
FIG. 4 is a schematic diagram according to an embodiment of the present invention.
FIG. 5 is a schematic diagram according to an embodiment of the present invention.
FIG. 6 is a block diagram according to an embodiment of the present invention.
FIG. 7 is a schematic diagram according to an embodiment of the present invention.
FIG. 8 is a flowchart according to an embodiment of the present invention.
FIG. 9 is a plan view according to an embodiment of the present invention.
FIG. 10 is a schematic diagram according to an embodiment of the present invention.
FIG. 11 is a schematic diagram according to an embodiment of the present invention.
FIG. 12 is a schematic diagram according to an embodiment of the present invention.
FIG. 13 is a graph according to an example of the present invention.
FIG. 14 is a flowchart according to an embodiment of the present invention.
FIG. 15 is a time chart according to an embodiment of the present invention.
FIG. 16 is a flowchart according to an embodiment of the present invention.
FIG. 17 is a schematic view according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Image scanner (image reading apparatus), 12 Document stand, 13 Document cover, 15 Linear image sensor (image sensor), 21 1st optical system, 22 Main lamp (light source), 31 2nd optical system, 44 Subscanning drive part (Sub-scanning means), 50 control section (detection means, document size determination means)

Claims (3)

A transparent platen on which the document is placed on the surface;
An image sensor that reads the original by photoelectric conversion with a plurality of discretely arranged pixels;
A first optical system that forms a reflected light image of a document placed on the document table on a light receiving surface of the image sensor;
When the first optical system forms a first optical path from a plurality of first determination areas spaced apart from each other on the surface of the document table and arranged in the main scanning direction to the predetermined pixel of the image sensor, A second optical system that forms a second optical path from a second determination area spaced from the first determination area by a predetermined distance in the sub-scanning direction on the surface of the document table to a predetermined pixel of the image sensor;
Carriage moving means for reciprocating a carriage in which at least a part of the image sensor, the first optical system, and the second optical system are mounted in a sub-scanning direction;
Sampling output signals of a plurality of pixels of the image sensor to measure the optical density of the first determination area and the optical density of the second determination area, and measuring the measured optical density of the first determination area And document size determination means for determining the size of the document placed on the surface of the document table based on the optical density of the second determination region;
A magnification measuring means for measuring the magnification of the first optical system;
The carriage moving means is a position where the first optical path and the second optical path are simultaneously formed, and a position where the magnification measurement result of the first optical system can be applied to the second optical system. Moving the carriage,
The document size determination means samples output signals of a plurality of pixels of the image sensor when the carriage is at the position, and in this sampling, sampling targets corresponding to the first determination area and the second determination area The image reading apparatus is characterized in that the pixel is changed according to the measurement result of the magnification measuring means. A document cover provided so as to be swingable from a posture in which the platen surface of the platen is opened to a posture covering the platen surface of the platen;
The document size determination means is a change in the amount of light incident on a predetermined pixel of the image sensor by the first optical system and the second optical system, and the document cover is in a position in which the document surface of the document table is opened. The image reading apparatus according to claim 1, wherein the size of the document placed on the platen surface of the document table is determined based on a change in light amount during a period of swinging to a posture covering the platen surface of the document table.   The document size determination means includes a plurality of regions on the platen surface of the document table, in order from the edge on the platen surface of the document table toward the designated placement range of the minimum size document that can be determined in size. The image reading apparatus according to claim 2, wherein it is determined whether or not the image is covered.

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