JP2005026949A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reader in which judgment error of a document size can be reduced. <P>SOLUTION: The image reader comprises a transparent document table 12, a document cover 13 covering the document table 12, an image sensor 15 having a plurality of light receiving elements arranged linearly and reading a document mounted on the surface of the document table by performing photoelectric conversion of light reflected on the document, and a subscanning means for translating a main scanning line parallel with the longitudinal axis of the image sensor 15 to the perpendicular subscanning direction. The image reader further comprises a means having at least two of a red light source 32r, a blue light source 32b and a green light source 32g and irradiating detection areas H, J and K on the surface of the document table 12 spaced apart in the subscanning direction from the main scanning line, a sensor having a light receiving element and outputting an electric signal by performing photoelectric conversion of light reflected on the detection area, and a means for judging the size of the document in the subscanning direction based on an electric signal outputted from the sensor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image reading apparatus.
[0002]
[Prior art]
Conventionally, a technique for automatically determining the size of a document in the sub-scanning direction by an image reading device such as an image scanner is known. A conventional image reading apparatus includes a light source that irradiates a detection area spaced apart from a main scanning line on the surface of a platen in the sub-scanning direction, and a sensor that photoelectrically converts reflected light from the detection area and outputs an electrical signal. The size in the sub-scanning direction is determined based on the electrical signal output from the sensor. When determining the size, the light source is turned on when the platen surface of the document table is open (open position), and the presence or absence of the document in the detection area is determined by comparing the value represented by the electrical signal output from the sensor with a preset threshold value. is doing. For example, when the document cover is in the open position, if there is a document on the detection area, the light emitted from the light source is reflected by the document, so that bright light is incident on the sensor. Light will enter. Therefore, the presence / absence of the document in the detection area can be determined by comparing the value represented by the electrical signal output from the sensor with the threshold value. If there is an original in the detection area, the size of the original in the sub-scanning direction is longer than the length specified by the position of the detection area, and if there is no original in the detection area, the size is determined to be shorter than the length specified by the position of the detection area. . In this way, the size of the document in the sub-scanning direction is determined.
[0003]
[Problems to be solved by the invention]
In a conventional image reading apparatus, a light source of one color such as a red LED is used as a light source for irradiating a detection region. When the light source is one color, there is a problem that an error in determining the document size occurs depending on the color of the document.
[0004]
FIG. 10 is a graph showing the relationship between the reflectance and the wavelength of light for each color. The graph shown in FIG. 10 is a result obtained by measuring a printed matter printed using a predetermined ink. The waveform shown in the graph varies depending on the nature of the ink, but generally has a waveform similar to that shown in FIG. For example, when the color of the original is red, the reflectance is small for light having a wavelength of approximately 575 nm or less, and the reflectance is high for light having a wavelength of 575 nm or more. Therefore, when the color of the original is red, light having a wavelength of 575 nm or more is likely to be reflected, so that bright light, that is, light having a high luminance is incident on the sensor. Light, that is, light with low luminance enters. As a result, if the color of the original is red, when light of 575 nm or less is emitted, light with low brightness is incident on the sensor even though the original is present, thereby erroneously determining that there is no original. Become. The same applies to other colors. Therefore, if the light source is one color, the wavelength of light is limited, and an original size determination error may occur depending on the original color.
[0005]
The present invention has been created in view of such a problem, and an object of the present invention is to provide an image reading apparatus capable of reducing an appreciation of determination of a document size.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, an image reading apparatus according to the present invention includes a transparent document table, a document cover that covers the document table, and a plurality of pixels arranged in a straight line. An image sensor that reads the document by photoelectrically converting reflected light of the placed document, and a sub-scanning unit that translates a main scanning line parallel to the longitudinal axis of the image sensor in a sub-scanning direction perpendicular thereto. An image reading apparatus having at least two light sources of a red light source, a blue light source, and a green light source, and irradiating a detection region spaced apart from the main scanning line on the surface of the document table in the sub scanning direction Means, a sensor having a pixel for photoelectrically converting reflected light from the detection area and outputting an electric signal, and determining a size of the document in the sub-scanning direction based on the electric signal output from the sensor Characterized in that it comprises a determining means. Since red, blue, and green light have different wavelength regions, it is possible to irradiate the original with light having different wavelengths when at least two of the red, blue, and green light sources are provided. Therefore, the reflectance is higher for more colors than when only one color is emitted, and the document size determination error can be reduced as compared with the case where only one color of light is emitted.
[0007]
Further, in the image reading apparatus according to the present invention, a transparent document table, a document cover that covers the document table, and a plurality of pixels arranged in a straight line, a reflection of the document placed on the surface of the document table. An image reading apparatus comprising: an image sensor that reads a document by photoelectrically converting light; and a sub-scanning unit that translates a main scanning line parallel to a longitudinal axis of the image sensor in a sub-scanning direction perpendicular thereto. A white light source that irradiates a detection region spaced apart from the main scanning line on the surface of the document table in the sub-scanning direction, and a sensor that photoelectrically converts reflected light from the detection region and outputs an electrical signal And determining means for determining the size of the document in the sub-scanning direction based on the electrical signal output from the sensor. When a white light source is provided, the entire visible region can be covered with one light source. Accordingly, since the reflectance is increased in almost all colors, it is possible to reduce document size determination errors.
[0008]
The image reading apparatus according to the present invention further includes an optical system that forms an optical path from the detection region to the image sensor, and the image sensor is used as the sensor. When an image sensor is used as a sensor, the cost of the image reading apparatus can be reduced as compared with a case where a sensor is separately provided.
Furthermore, in the image reading apparatus according to the present invention, the image sensor has a plurality of lines in which a plurality of pixels are linearly arranged at a predetermined interval, and the optical system reflects reflected light from a plurality of detection areas spaced apart from each other. It is characterized by reaching different lines. If multiple detection areas are provided apart from each other, the size can be determined based on electrical signals obtained by photoelectrically converting reflected light at different positions on the document. Can be further reduced. In addition, if a predetermined interval is provided between the lines, the reflected light of a certain detection area can surely reach only a specific line, so that erroneous determination due to the arrival of reflected light of another detection area is further reduced. it can.
[0009]
Further, in the image reading apparatus according to the present invention, based on the detection means for detecting the size of the document in the main scanning direction, the size in the sub-scanning direction determined by the determination means, and the size in the main scanning direction detected by the detection means. And document size determination means for determining the document size and orientation. According to this image reading apparatus, the document size and its direction can be determined.
[0010]
Further, in the image reading apparatus according to the present invention, the detection means designates a minimum-size original that can be determined from an edge portion on the original table surface for a plurality of areas on the original table surface. The size of the document in the main scanning direction is detected by determining whether or not the document is covered in the order in which the document is covered. When the document cover opens the platen surface of the platen, the pixels corresponding to the region covered by the white area of the document are more incident than the pixels corresponding to the region not covered by the document on the platen surface of the document platen. The amount of light to be increased always increases. Therefore, the document cover covers the surface of the platen in the order of the plurality of areas on the platen of the platen from the edge on the platen of the platen in the specified placement range of the minimum size original that can be determined. As a result of determining whether or not the area corresponding to the pixel is covered with the document by the amount of light incident on the pixel when it is open, if the first area covered by the document is found, The determination process can be omitted assuming that the document is covered.
[0011]
Further, in the image reading apparatus according to the present invention, the detection means corresponds to a range outside the designated placement range of the maximum size document within the range covered by the document cover on the platen surface of the document table and capable of determining the size. Based on the electrical signals output from the image sensor pixels and the image sensor pixels corresponding to the designated placement range of the maximum-size document, the main document of the document placed on the platen surface of the document table The size in the scanning direction is determined. A value represented by an electrical signal output from a pixel of the image sensor corresponding to a size outside the designated placement range of the maximum size document within the range covered by the document cover on the platen surface of the document table is a predetermined value. If it is above, it can discriminate | determine that the area | region on the board surface of the original plate corresponding to the said pixel is covered with the original. When it is determined that the document is covered, it can be determined that the size of the document cannot be determined.
[0012]
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.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples.
[0014]
(First Example)
1 and 2 are schematic views showing an image scanner 1 as an image reading apparatus according to a first embodiment of the present invention. The image scanner 1 is an image scanner capable of reading a color image, and is a so-called flat bed type image scanner having a document table on an upper surface of a rectangular parallelepiped main body.
[0015]
The document table 12 is formed of a substantially rectangular transparent member such as a glass plate. On the platen 12, originals such as photographs and documents are placed on the surface of the platen 12. The document is positioned at a predetermined position on the surface of the document table 12 by contacting two sides of an L-shaped document guide 16 (see FIG. 5) provided on the edge of the document table 12. At this time, if the document size is a standard size that can be determined, the document is positioned on a specified placement range corresponding to the standard size on the surface of the document table 12.
The document cover 13 is connected to the main body 11 so as to be swingable from a posture in which the platen surface of the document table 12 is opened by a hinge (fully open posture) to a posture in which the platen surface of the document platen 12 is covered (fully closed posture). The document cover 13 holds the document M placed on the document table 12 and covers the document table 12 so that light other than the light emitted from the main lamp 22, the red LED 32r, the blue LED 32b, and the green LED 32g does not illuminate the document. Is. The main body 11 is provided with an opening / closing sensor (not shown) for detecting the opening / closing of the document cover 13. When the user swings the document cover 13 from the fully open position to the fully closed position, the main body 11 is almost at the intermediate position. The detection signal is output to the control unit 50 described later.
[0016]
The carriage 14 is accommodated in the main body 11 so as to be reciprocally movable in parallel with the surface of the platen 12. The carriage 14 carries a part of the linear image sensor 15, the first optical system 21, and the second optical system 31, and is slidably locked to a guide shaft or the like parallel to the surface of the document table 12. . The longitudinal axis of the guide shaft extends in the X direction (sub-scanning direction) in FIG. 1, and the carriage 14 is pulled by, for example, a belt to linear image sensor 15, first optical system 21 (see FIG. 2), A part of the second optical system 31 (see FIG. 1) is transported in the sub-scanning direction. 1 and 2 show the carriage 14 in the standby position. Specifically, the standby position of the carriage 14 is set to a position where, for example, an area on a main scanning line passing through detection areas A to G, which will be described later, on the document table 12 can be read.
[0017]
The linear image sensor 15 as an image sensor reads a document by photoelectrically converting the reflected light of the document M placed on the document table 12. Specifically, the linear image sensor 15 has a plurality of pixel rows (lines) in which pixels such as photodiodes are arranged in a straight line in the direction perpendicular to the paper surface in FIG. Here, the predetermined interval is generally an interval of 8 pixels, and in the first embodiment, one pixel is about 0.04 mm, and the interval between lines is about 0.35 mm. The reason why the space is provided between the lines is to prevent light that should be incident only on one line from entering the adjacent line. For example, if there is a black ruled line wider than the width of the pixel on one detection area, the light will enter the adjacent line if there is no space between the lines, and the value represented by the electrical signal is low on either line. Because it becomes. By providing an interval between the lines, it is possible to further reduce the appreciation of the document size. A red, blue, or green color filter is formed for each line on the light receiving surface of the pixel, thereby enabling reading of a color image. The linear image sensor 15 is provided with an infrared cut filter for reducing near-infrared light that cannot be absorbed by the color filter, thereby reducing the influence of near-infrared light on color image reading. The pixel accumulates the charge obtained by photoelectric conversion of incident light for a certain period of time, and outputs the accumulated charge for each pixel according to the amount of received light as an electrical signal using a CCD (Charge Coupled Device), MOS transistor switch, or the like. To do. In general, the linear image sensor 15 often includes extra pixels that are not used for image reading in addition to pixels used for image reading, and the linear image sensor 15 also has extra pixels near the end of each line. . The linear image sensor 15 reads the original by photoelectrically converting reflected light of the original placed on the surface of the original table 12, and also performs main scanning of the original by photoelectrically converting reflected light from detection areas A to G described later. It is also used as detection means for detecting the size of the direction. Further, the remaining pixels of the linear image sensor 15 are used as sensors that photoelectrically convert reflected light in a detection region described later.
[0018]
As shown in FIG. 2, the first optical system 21 includes a main lamp 22, mirrors 23, 24, 25, 26 and a lens 27. The main lamp 22 is constituted by a tube illumination device such as a xenon lamp, and is mounted on the carriage 14 with a longitudinal axis extending parallel to the longitudinal axis of the linear image sensor 15. The main lamp 22 irradiates the back side of the document table 12 from the inside of the main body 11. The mirrors 23, 24, 25, 26 and the lens 27 are areas on the surface of the platen 12, as indicated by broken lines in FIG. 2, from areas on the main scanning line parallel to the longitudinal axis of the linear image sensor 15. An optical path T leading to the linear image sensor 15 is formed.
[0019]
The light source part 32 (refer FIG. 4) as an irradiation means is provided with red LED (Light Emitting Diode) 32r, green LED 32g, and blue LED 32b as a light source, as shown in FIG. The red LED 32r, the blue LED 32b, and the green LED 32g are regions below the plurality of detection regions H, J, and K that are regions on the surface of the document table 12 and that are separated from the edge extending in the main scanning direction of the document guide 16 in the sub scanning direction X. The detection areas H to K are irradiated from the back side. The detection areas H to K are areas set for determining the size of the document in the sub-scanning direction, and specific positions thereof will be described later. Since the image scanner 1 includes the three LEDs of the red LED 32r, the blue LED 32b, and the green LED 32g, reflected light having high luminance can be reflected by any one of the LEDs. For humans, it generally looks blue when the wavelength of light is in the range of 400 nm to 500 nm, generally green when it is in the range of 500 nm to 580 nm, and generally red when it is in the range of 610 nm to 750 nm. For example, according to the standards of the CIE (International Commission on Illumination), red is 700 nm, blue is 435.8 nm, and green is 546.1 nm. When CIE standard light is emitted, as shown in FIG. 10, cyan, magenta, and blue have blue light (435.8 nm) with high reflectance, and green has green light (546.1 nm) reflected. The rate is high. Similarly, yellow and red increase with red (700 nm) light. Note that yellow has a high reflectance even with green light, and white has a high reflectance with any light. For this reason, when the red LED 32r, the blue LED 32b, and the green LED 32g are provided, reflected light having high luminance can be reflected by light emitted from any of the LEDs other than black. Here, all colors include colors not shown in FIG. Since other colors not shown in FIG. 10 can be expressed by combinations of the colors shown in FIG. 10, if the reflectance increases for all the colors shown in FIG. 10, all other colors not shown in FIG. This is because the reflectance increases. As a result, it is possible to reduce document size determination errors due to the color of the document. However, since black has a low reflectance for any light in the visible region of approximately 400 nm to 700 nm, the possibility of erroneous determination remains when the color of the document is black.
[0020]
In the first embodiment, three LEDs of red, blue, and green are provided as light sources, but only two of them may be provided. Since red, blue, and green have different wavelength regions, the document can be irradiated with light of different wavelengths by providing at least two of the red, blue, and green light sources. Therefore, the reflectance is higher for more colors than when only one color is emitted, and the document size determination error can be reduced as compared with the case where only one color is emitted.
[0021]
In the above description, the CIE reference light is emitted as an example. However, the light emitted from the red LED 32r, the blue LED 32b, and the green LED 32g may not be the CIE reference light. Any light source may be used as long as it emits light that looks red, blue, and green.
The second optical system 31 includes a mirror 30, a mirror 29, a mirror 28, a mirror 24, and a lens 27. The mirror 24 and the lens 27 are used as both the first optical system 21 and the second optical system 31. The mirrors 30, 29, 28 and 24 form an optical path R from the detection areas H to K to the linear image sensor 15. As schematically shown in FIG. 3, the second optical system 31 causes the reflected light of the detection regions H to K to reach the remaining pixels on different lines of the linear image sensor 15. When the second optical system 31 is provided, the linear image sensor 15 can be used as a sensor, so that the cost can be reduced as compared with the case where a sensor is provided separately. Further, when the second optical system 31 is provided, it is possible to determine the size of the document in the sub-scanning direction without moving the carriage 14 from the standby position even when the linear image sensor 15 is used as a sensor. . Further, when the remaining pixels of the linear image sensor 15 are used as sensors, the detection areas A to G and the detection areas can be simultaneously read in a state where the carriage 14 is in the standby position. As a result, even when the orientation of the document placed on the document table 12 is not constant, various document sizes and orientations can be distinguished from each other in a short time.
[0022]
FIG. 4 is a block diagram illustrating a hardware configuration of the image scanner 1.
The main scanning drive unit 43 is mounted on a substrate fixed to the carriage 14. The main scanning drive unit 43 is a drive circuit that outputs a drive pulse necessary for driving the linear image sensor 15 to the linear image sensor 15. The main scanning drive unit 43 includes, for example, a synchronization signal generator, a driving timing generator, and the like.
[0023]
The sub-scanning drive unit 44 as sub-scanning means is configured by a belt locked to the carriage 14, a motor and a gear train for rotating the belt, a drive circuit, and the like, and is accommodated in the main body 11. The sub-scanning drive unit 44 pulls the carriage 14 with a belt, so that the main scanning line extending in the direction perpendicular to the paper surface in FIG. 1 is moved in parallel in the sub-scanning direction X perpendicular to the main scanning line.
[0024]
The analog front end (AFE) unit 41 includes an analog signal processing unit, an A / D converter, and the like. The analog signal processing unit performs amplification, noise reduction processing, and the like on the electric signal output from the linear image sensor 15 and outputs the electric signal. 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.
[0025]
The digital image processing unit 42 generates image data by performing 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 41. .
The control unit 50 includes a CPU 51, a ROM 52, and a RAM 53. The CPU 51 executes computer programs stored in the ROM 52 and controls each part of the image scanner 1. The CPU 51 also functions as a determination unit, a detection unit, and a document size determination unit by executing a computer program stored in the ROM 52. The ROM 52 is a memory that stores a computer program executed by the CPU 51, a determination table (see FIG. 8) used for determining a document size, 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. The RAM 53 is a memory that temporarily stores programs and data.
[0026]
The hardware configuration of the image scanner 1 has been described above. Next, a detection area provided for determining the size in the sub-scanning direction and a detection area provided for determining the size in the main scanning direction will be described.
FIG. 5 is a plan view of the document table 12. Frames A5H to WLT in the figure each represent a designated placement range corresponding to the document size shown in FIG.
[0027]
The detection areas H to K are small areas set for determining the size of the document in the sub-scanning direction. The detection areas H to K are areas that are covered with an A4 vertical size (A4V) original and are not covered with a letter vertical size (LTV) original on the original platen 12 as shown in the drawing, that is, from the origin Q. They are set apart from each other in an area of 279.4 mm or more and 297 mm or less in the sub-scanning direction and 0 mm or more and 210 mm or less from the origin Q in the main scanning direction. Here, the origin Q is set immediately below the corner formed by the two walls in contact with the document in the L-shaped document guide 16. If multiple detection areas are provided apart from each other, the size can be determined based on electrical signals obtained by photoelectrically converting reflected light at different positions on the document. Can be further reduced.
[0028]
The detection areas A to G and X are at a position slightly apart from the origin Q in the sub-scanning direction within a range shorter than the shortest sub-scanning size of the standard size to be determined (within 148 mm in the example of FIG. 6). In addition, the small area is set so as to be aligned on a straight line in the main scanning direction from the origin Q in the following range.
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
279 mm <X <width of the document table 12 in the main scanning direction
The plurality of ranges described above are ranges specified by the sizes in the main scanning direction of the plurality of document sizes shown in FIG. When the detection areas A to G are set in the above-described range, one detection area is set between a plurality of positions specified by the size in the main scanning direction as shown in FIG. However, in the first embodiment, B5 vertical size (B5V) and executive vertical size (EXV), and B5 horizontal size (B5H) and executive horizontal size (EXH) are only set to one of the sizes depending on the setting. It shall be readable. Therefore, in the first embodiment, it is not necessary to distinguish the B5 vertical size (B5V) and the executive vertical size (EXV) from each other, and no detection area is set between 182 mm and 184.15 mm. Similarly, no detection area is set between 257 mm and 266.7 mm. Reflected light in the detection areas A to G enters a predetermined pixel of the linear image sensor 15 via the first optical system 21. Note that if it is not necessary to determine the size in the main scanning direction because all document sizes can be determined only by the size in the sub-scanning direction, it is not necessary to process electrical signals for the pixels corresponding to the detection regions A to G. is there. The detection area X is set outside the designated placement range of the maximum paper size (A3 vertical) to be determined. The pixel of the image sensor corresponding to the outside of the designated placement range of the maximum size document capable of determining the size described in the claims corresponds to a pixel on which the reflected light of the detection region X is incident.
[0029]
Next, processing for determining the document size by the image scanner 1 will be described.
FIG. 7 is a flowchart showing a flow of processing in which the image scanner 1 detects the document size and orientation. This process is started by detecting the closing operation of the document cover 13 by the user with the open / close sensor while the carriage 14 is at the standby position. The process for detecting the document size and orientation is performed by the user pressing an automatic reading start button (not shown) for instructing the start of reading while the document cover 13 is open, or when the document cover 13 is opened. In the state where the reading is started, a reading start is instructed from a control device such as a personal computer connected to the image scanner 1.
[0030]
In S105, the control unit 50 detects that the operation of closing the document cover 13 is started by the open / close sensor, and turns on the red LED 32r, the blue LED 32b, the green LED 32g, and the main lamp 22 to start accumulation.
In S <b> 110, after a predetermined time has elapsed, the linear image sensor 15 outputs an electrical signal corresponding to the charge accumulated in the pixel to the AFE unit 41. The AFE unit 41 performs predetermined processing on the output electric signal and outputs an output signal in digital representation to the control unit 50.
[0031]
In S115, the presence or absence of documents in the detection areas A to G and X is determined. The control unit 50 compares the detection signals A to G and the output signal corresponding to the electrical signal output from the pixel corresponding to X among the output signals output from the AFE unit 41 with a preset threshold value, and detects the detection regions A to G. The presence / absence of a document in G is determined. Specifically, for each detection area, the average value of the output signals of the pixels corresponding to the detection area is obtained. If it is less than the threshold, it is determined that “no original”. In the determination of the presence / absence of a document, the determination of detection regions A to G is determined in the order of G to A following the determination of detection region X, and the determination processing for the remaining detection regions is omitted when it is determined that “there is a document”. . As a result, the processing time for determining the document size can be shortened. The determination may be performed in reverse order from the detection area A. In addition, when the average value of the output signals of a plurality of pixels corresponding to one detection region is compared with a threshold value, the population pixels may be selected so that one detection region has a spread in the sub-scanning direction. For example, an average of pixels corresponding to two points separated by 30 μm or more in the sub-scanning direction on the surface of the document table 12 may be obtained as an output signal of pixels corresponding to one detection region. Further, the population pixels may be selected so that one detection region extends in both the main scanning direction and the sub-scanning direction.
[0032]
In S120, the presence / absence of documents in the detection areas H to K is determined. The control unit 50 compares an output signal corresponding to the electrical signal output from the remaining pixels corresponding to the detection regions H to K among the output signals output from the AFE unit 41 with a threshold value.
For example, assume that the placed document size is A4 horizontal size (A4H). In this case, since there is no document in the detection areas H to K, the light emitted from the light source is not reflected by the document immediately before the document cover 13 is closed. Therefore, the light reaching the remaining pixels of each line is weak and dark light, and the value when the light is converted into a digital output signal is less than the threshold value. Therefore, the detection area is determined as “no document”.
[0033]
For example, it is assumed that the size of the placed document is A4 vertical size (A4V), and the color of the portion located in the detection areas H to K is blue. The blue light is weak and dark because the light emitted from the red LED 32r and the light emitted from the green LED 32g are low, but the light emitted from the blue LED 32b is high, so the remainder of each line It enters the pixel as strong and bright light. Therefore, the value when the light is converted into a digital output signal is equal to or greater than a preset threshold value. As a result, the detection area is determined to be “document present”.
[0034]
Further, for example, it is assumed that the placed document size is A4 vertical size (A4V) and a table using black ruled lines is printed on the document. Here, it is assumed that the ruled line is only on one detection area, and the color of the portion located in the other two detection areas of the document is a color other than black. In this case, the value represented by the electrical signal output by the remaining pixels of the line on which the reflected light of the ruled line is incident is a low value, and the other lines are high. If at least one of the values represented by the plurality of electrical signals is greater than or equal to the threshold value, the control unit 50 determines that the detection area is “document present”. Thereby, even if a black ruled line is positioned on one detection area, the document size can be accurately determined. Therefore, if a plurality of detection areas separated from each other are set, erroneous determination can be reduced as compared with the case where the presence / absence of a document is determined by one detection area.
[0035]
In S125, the size in the main scanning direction and the size in the sub-scanning direction are determined based on the presence / absence of the document in each detection area and the presence / absence of the document in the detection area, thereby determining the document size and orientation. Specifically, the determination is performed using the determination table shown in FIG. “◯” in FIG. 8 means that the area is “with a document”, and “X” means that the area is “without a document”. For example, suppose that the detection area is determined to be “document present” in the detection area C as a result of the determination. In this case, the size in the main scanning direction can be determined to be either the A5 horizontal size or the A4 vertical size according to FIG. In this way, the size in the main scanning direction is detected. Similarly, it can be determined that the size in the sub-scanning direction is any one from A vertical size (A4V) to double letter vertical size (WLT). As a result, the A4 vertical size is uniquely specified as the size that satisfies both. In this way, the document size and orientation are specified using the determination table. When the detection area X becomes “◯”, it means that the size exceeds the readable paper size, and therefore it is specified that the size cannot be determined.
[0036]
According to the image scanner 1 according to the first embodiment described above, the detection region is irradiated with the three LEDs of the red LED 32r, the blue LED 32b, and the green LED 32g. Accordingly, when a document is present in a portion located in the detection area, the brightness of the reflected light becomes high regardless of the color of the portion located in the detection area of the document other than black. Thereby, it can be determined that “there is a document”. Therefore, when the red LED 32r, the blue LED 32b, and the green LED 32g are provided, it is possible to reduce the appreciation of the document size.
[0037]
In the first embodiment, the remaining pixels of the linear image sensor 15 are used to determine the presence or absence of the document in the detection area. However, the pixels used for reading the document may be used. In addition, reflected light from different detection regions may be incident on different remaining pixels on one line of the linear image sensor 15. Further, a pixel may be provided separately from the linear image sensor 15 and a pixel provided separately may be used as the sensor.
[0038]
In the first embodiment, the image scanner 1 that can read a color image including a color filter has been described as an example. However, the present invention is applied to an image reading apparatus that does not include a color filter and can generate only monochrome image data. Also good.
[0039]
(Second embodiment)
The second embodiment is an example in which the detection area is irradiated with a white light source. In the second embodiment, substantially the same parts as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.
FIG. 9 is a schematic diagram showing the image scanner 2 of the second embodiment. The image scanner 2 of the second embodiment has a white LED 61 that emits white light as a white light source. The white light here means light including light of all wavelengths. However, the intensity of light of each wavelength included in the white light here is not necessarily equal. Note that a fluorescent tube lamp or the like may be used as the white light source.
[0040]
According to the image scanner 2 of the second embodiment, since the entire visible region can be covered with one light source, the reflectance increases for all colors except black. As a result, it is possible to reduce document size determination errors due to the color of the document.
Further, according to the image scanner 2 of the second embodiment, since only one LED is required, the number of parts of the light source, the size, the weight, and the number of work steps for assembling the light source can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an image reading apparatus according to a first embodiment of the present invention.
FIG. 2 is a schematic diagram of an image reading apparatus according to a first embodiment of the present invention.
FIG. 3 is a schematic diagram of an optical path according to the first embodiment of the present invention.
FIG. 4 is a block diagram according to a first embodiment of the present invention.
FIG. 5 is a plan view of a document table according to the first embodiment of the present invention.
FIG. 6 is a table showing document sizes according to the first embodiment of the present invention.
FIG. 7 is a flowchart according to the first embodiment of the present invention.
FIG. 8 is a determination table according to the first embodiment of the present invention.
FIG. 9 is a schematic diagram of an image reading apparatus according to a second embodiment of the present invention.
FIG. 10 is a graph showing the relationship between the wavelength of light and the reflectance for each color.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Image scanner (image reading apparatus), 2 Image scanner (image reading apparatus), 12 Document stand, 13 Document cover, 15 Linear image sensor (Image sensor, sensor, detection means), 24 Mirror (optical system), 27 Lens ( Optical system), 28 mirror (optical system), 29 mirror (optical system), 30 mirror (optical system), 32 light source unit (irradiation means), 32a red LED (light source), 32b blue LED (light source), 32g green LED (Light source), 61 white LED (light source), 44 sub-scanning drive unit (sub-scanning unit), 50 control unit (determination unit, detection unit, document size determination unit)

Claims (7)

A transparent document table, a document cover covering the document table, and a plurality of pixels arranged in a straight line, and reading the document by photoelectrically converting the reflected light of the document placed on the surface of the document table An image reading apparatus comprising: an image sensor; and a sub-scanning unit that translates a main scanning line parallel to the longitudinal axis of the image sensor in a sub-scanning direction perpendicular thereto.
An irradiation unit having at least two light sources among a red light source, a blue light source, and a green light source, and irradiating a detection region spaced apart from the main scanning line on the platen surface of the document table in the sub-scanning direction;
A sensor that has pixels and photoelectrically converts the reflected light of the detection region and outputs an electrical signal;
Determination means for determining the size of the document in the sub-scanning direction based on the electrical signal output from the sensor;
An image reading apparatus comprising: A transparent document table, a document cover covering the document table, and a plurality of pixels arranged in a straight line, and reading the document by photoelectrically converting the reflected light of the document placed on the surface of the document table An image reading apparatus comprising: an image sensor; and a sub-scanning unit that translates a main scanning line parallel to the longitudinal axis of the image sensor in a sub-scanning direction perpendicular thereto.
An irradiation unit having a white light source and irradiating a detection region spaced apart in the sub-scanning direction from the main scanning line on the platen surface of the document table;
A sensor that has pixels and photoelectrically converts the reflected light of the detection region and outputs an electrical signal;
Determination means for determining the size of the document in the sub-scanning direction based on the electrical signal output from the sensor;
An image reading apparatus comprising: An optical system that forms an optical path from the detection region to the image sensor;
The image reading apparatus according to claim 1, wherein the image sensor is used as the sensor. The image sensor has a plurality of lines in which a plurality of pixels are linearly arranged at a predetermined interval,
The image reading apparatus according to claim 3, wherein the optical system causes reflected light from a plurality of detection areas spaced apart from each other to reach different lines. Detection means for detecting the size of the document in the main scanning direction;
Document size determination means for determining the document size and orientation based on the size in the sub-scanning direction determined by the determination means and the size in the main scanning direction detected by the detection means;
The image reading apparatus according to claim 1, further comprising: The detecting means covers a plurality of areas on the platen surface of the platen in a sequence from the edge on the platen surface of the platen to the specified placement range of the minimum size document that can be determined in size. 6. The image reading apparatus according to claim 5, wherein the size of the document in the main scanning direction is detected by determining whether or not the document has been read. The detection means includes pixels of the image sensor corresponding to outside a designated placement range of a maximum-size document within a range covered by the document cover on the surface of the document table and capable of determining a size, and the maximum Determining the size in the main scanning direction of the document placed on the surface of the document table based on an electrical signal output from the pixel of the image sensor corresponding to the designated placement range of the document of the size; The image reading apparatus according to claim 6.

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