JP5059327B2 - Illumination device for image reading apparatus - Google Patents

Description

The present invention relates to lighting equipment of the image reading apparatus for illuminating an original is read object.

Conventionally, a document that has been transported on or placed on a document table made of a transparent member such as glass or the like is illuminated with light from an illumination device disposed below the document table , and this is optically detected. The reflected light from the original is imaged on a photoelectric conversion element such as a CCD, and the accumulated charge amount corresponding to the amount of received light is output as an electrical analog signal, which is converted into a digital signal, An image reading apparatus that acquires data is known.

  In the conventional image reading apparatus as described above, it is possible to image the reflected light of the light irradiated onto the document surface, and to arrange the light source on the optical path where the reflected light from the document goes to the photoelectric conversion element. difficult. Therefore, the conventional image reading apparatus is configured to illuminate the document surface from an oblique direction by the illumination device and form an image of light reflected from the document surface on the photoelectric conversion element.

  When the surface of the document is illuminated obliquely as in the conventional image reading apparatus, if the surface of the document or the like to be read has unevenness, a shadow caused by the unevenness is generated. The shadow generated in this way appears as a shadow in the read image.

Therefore, as a configuration of the illuminating device, the illuminating device that moves along the sub-scanning direction is provided with the same light source facing the sub-scanning direction, and the same light source facing the center of the facing same light source. By illuminating the reading area to be read of the original image of the original placed on the upper platen glass at a position from both sides in the sub-scanning direction , even in the portion where the original surface is uneven, the shadow is not reflected on the read image. There is provided a technique capable of suppressing the occurrence of (a black image).

  In the conventional image reading apparatus as described above, when reading the image of the document placed on the document table, the end of the document is abutted against the butting plate provided at the end of the document table. The document surface is scanned by an illumination device that moves in a predetermined direction (so-called sub-scanning direction).

  As shown in FIG. 5, since a slight gap is formed between the end of the document placed on the document table and the butting plate in a state of being butted against the butting plate, for example, the A direction and the B direction. Even if the illumination is performed from the two directions, a shadow is likely to occur in the read image near the gap. Therefore, in the conventional image reading apparatus, in order to avoid the gap between the document and the abutting plate from appearing as a shadow on the scanned image, the image in a predetermined range is trimmed from the abutting plate on the scanned image. Yes.

  Similarly, as shown in FIG. 6, when a shadow is generated near the end of the document placed on the document table on the side not abutted against the abutting plate, due to the thickness or bending of the document. There is. However, unlike the above-described gap between the butting plate and the document edge, the range in which the shadow is generated depends on the size of the document and cannot be grasped in advance. Therefore, there is no processing such as trimming the image within a predetermined range to prevent the occurrence of shadows on the image near the end on the side that is not abutted against the abutting plate. There was a case where a shadow near the part appeared.

Also as described above, in the conventional image reading apparatus, in order to suppress the generation of the original shadow on the readout image, the area to be read of the document (the reading area) with respect to the normal of the platen glass and it has a configuration that illuminated by the same light source from symmetrical manner bi-directional. However, the light source used for illuminating the document in the image reading apparatus is a relatively expensive light source such as a xenon lamp. Therefore, there is a need for an illumination device that can contribute to cost reduction while suppressing the occurrence of shadows on a read image without increasing the number of such expensive light sources installed.

  The present invention has been made to solve the above-described problems, and an image reading apparatus capable of reading an image of a document placed on a document table is placed on the document table with a low-cost and simple configuration. It is an object of the present invention to provide a technique for suppressing the occurrence of a shadow on a read image in the vicinity of an end portion on the side that does not abut against an abutting plate for positioning a document.

In order to solve the above-described problems, an illumination device of an image reading apparatus according to the present invention is provided on a document table on which a document is placed and one end side in the sub-scanning direction of the document table, and is placed on the document table. An image of the original placed on the original table and placed on the original table by being moved in the sub-scanning direction is disposed below the original table and a butting plate for positioning one end of the original to be abutted. An image reading sensor for reading, and the image reading sensor has an imaging optical system that forms an image on the image pickup unit of reflected light that is irradiated from the first and second illumination units and reflected by the document image. In the image reading apparatus, the illumination is provided in the image reading sensor and illuminates while moving the reading area of the document placed on the document table in the sub-scanning direction according to the movement of the image reading sensor in the sub-scanning direction. A device comprising: Illuminating the reading area of the document placed on the table, and the first illumination unit reflected light from the original surface is guided to the imaging section, of the document placed on the document table The reading area is illuminated simultaneously with the first illuminating unit, and reflected light from the document surface is guided to the imaging unit, and is arranged opposite to the first illuminating unit in the sub-scanning direction across the imaging unit. is, the red LED as the light source is composed of a white type light guide tube equipped with a three green LED and blue LED, the first the first bandwidth emission color than the illumination unit irradiates the wider illumination light The first illuminating unit and the second illuminating unit that are opposed to each other along the sub-scanning direction, and the one side in the sub-scanning direction is the arrangement side of the abutting plate. Then, the first illumination unit is arranged on one end side in the sub-scanning direction, and the second illumination unit is It is characterized in that arranged on the other end side of the scanning direction.

  As described above in detail, according to the present invention, in an image reading apparatus capable of reading an image of a document placed on a document table, positioning of the document placed on the document table with a low cost and simple configuration. Therefore, it is possible to provide a technique for suppressing the occurrence of a shadow on the read image in the vicinity of the end portion on the side that does not abut against the abutment plate.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is an overall configuration diagram for explaining an illumination device of an image reading apparatus and an image reading apparatus including the same according to the present embodiment. The image reading apparatus 1 according to the present embodiment is installed in an image processing apparatus (MFP: Multi Function Peripheral) M as shown in FIG.

An image processing apparatus M shown in FIG. 1 includes an image reading apparatus 1 and an image forming apparatus 2. In the image forming apparatus 2, image data received from an external device or a document is read by the image reading apparatus 1. Image forming processing (print processing, copy processing, etc.) based on the image data read from is possible. In addition, the image processing apparatus M includes a central processing unit ( CPU ) 105 and a memory 106 that are shared by the image reading apparatus 1 and the image forming apparatus 2.

The image reading apparatus 1 is an image reading sensor including an illuminating device that illuminates a document, an optical system for imaging reflected light from a document surface illuminated by the illuminating device, and an imaging unit ( CIS: Contact Image Sensor). ) Moving (scanning) 120 in the sub-scanning direction R to perform manual placement reading (see FIG. 2) for reading the image of the document placed on the platen glass 109, and moving in the F direction, which is the sub-scanning direction. an automatic document reading read by CIS120 stationary image of the document conveyed at a predetermined position P by the automatic document reader (ADF (auto document Feeder)) is possible.

In the case of performing read manually placed in the image reading apparatus 1, with respect to the abutment plate 107 provided on one end of the platen in the sub-scanning direction so as to be orthogonal to the predetermined direction, placed on the document table By abutting and positioning the end of the original to be read, the original surface can be read without tilting the original with respect to the main scanning direction and the sub-scanning direction.

FIG. 3 is a configuration diagram showing details of the CIS 120 in the image reading apparatus 1 according to the present embodiment. As shown in the figure, the CIS 120 includes a first illumination unit 121, a second illumination unit 122, an optical system 125, and an imaging unit 126, and is disposed below the document table glass 109 .

In the image reading apparatus 1 according to the present embodiment, the CIS 120 is physically moved relative to the original surface of the original to be read in the predetermined direction R to read the image in the sub-scanning direction, and the photoelectric component constituting the imaging unit 126 is read. By performing image reading in the main scanning direction (normal direction with respect to the paper surface of FIG. 1) by the conversion element, image reading of a document within a predetermined reading area is realized.

The first illuminating unit 121 includes a light emitting element ( LED ) array including a yellow / green (YG type) light emitting element ( LED ) as a light source, and is inclined from the document surface by a predetermined angle. Illuminates the reading area of the document. Thus, the 1st illumination part 121 irradiates the illumination light of a single wavelength.

The 2nd illumination part 122 is comprised from the white type light guide tube provided with three of a red light emitting element ( LED ) , a green light emitting element ( LED ), and a blue light emitting element ( LED ) as a light source. As shown in FIG. 3, the first illumination unit 121 and the second illumination unit 122 are arranged to face each other along the sub-scanning direction R, and face each other along the sub-scanning direction as shown in FIG. 3. The first illuminating unit 121 and the second illuminating unit 122 to be arranged arrange the first illuminating unit 121 on one end side in the sub-scanning direction when the arrangement side of the butting plate 107 is one end side in the sub-scanning direction. The second illumination unit 122 is arranged on the other end side in the sub-scanning direction.
Then, the first illumination unit 121 and the second illumination unit 122 illuminate the reading area of the document image through the document glass plate 109 positioned above. The first illuminating unit 121 and the second illuminating unit 122 illuminate the reading area of the document image located at the center between both sides in the sub-scanning direction.
The second illumination unit 122 emits illumination light having a wider emission color bandwidth (multi-wavelength) than the first illumination unit 121.

Thus, in the illumination device of the image reading apparatus according to this embodiment, by illuminating from the line symmetry of two positions with respect to the reading area of the document, regardless of the presence or absence of irregularities on the original surface, the shadow It is the structure which can obtain the reading image without. In addition, when performing manual placement reading by moving the CIS 120 in the sub-scanning direction , the CIS 120 scans the document placed with one end abutted against the abutting plate 107 of the document table , and the sub-scan is performed. When the end of scanning is reached, the second illumination unit 122 illuminates the other end of the document. That is, the other end of the sheet can be irradiated with irradiation light having a wide emission color bandwidth by the second illumination unit 122 , so that a shadow due to the color of the image in the reading area of the document in the vicinity of the end portion appears. Therefore, it is possible to prevent the difference in the direction (to obtain effective reflected light from more colors on the image), and as a result, it is possible to suppress the occurrence of shadows in the read image near the edge.

The optical system 125 is composed of a SELFOC lens (registered trademark) , and is irradiated from the first illuminating unit 121 and the second illuminating unit 122 and reflected by the reading region of the document (downward arrow in FIG. 3). To the predetermined imaging position. Here, an example in which the entire optical system 125 is arranged on the CIS 120 is shown.

The imaging unit 126 is configured by a photoelectric conversion element or the like, and images the light guided to a predetermined imaging position by the optical system 125. The image of the document imaged by the imaging unit 126 is stored in the memory 106 and transmitted to an external device that can communicate with the image forming apparatus 2 or the image processing apparatus M as necessary.

The image processing apparatus M includes a light emission control unit 124. The light emission control unit 124 mixes the illumination light from the first illumination unit 121 and the illumination light from the second illumination unit 122, so that the spectral characteristic (wavelength distribution) of the illumination light on the document surface is The first emission ratio is substantially the same as the spectral characteristic (predetermined wavelength distribution) of a white light source composed of any one of a xenon lamp, a halogen lamp, an LED, a fluorescent lamp, and electroluminescence ( EL ) . Each light source which comprises each of the illumination part 121 of this and the 2nd illumination part 122 is made to light-emit. Information on the predetermined light emission ratio of each light source described above is held in the light emission control unit 124 or the memory 106.

  FIG. 4 is a diagram showing the spectral characteristics of the yellow-green LED constituting the first illumination unit 121 and the red LED, green LED, and blue LED constituting the second illumination unit 122. Thus, in the present embodiment, two types of yellow-green LEDs that constitute the first illumination unit 121 and red LEDs, green LEDs, and blue LEDs (three-wavelength white type) that constitute the second illumination unit 122 are provided. The irradiation light of the illumination unit having different spectral characteristics is combined to form irradiation light close to the ideal spectral characteristics (for example, the spectral characteristics of a white xenon lamp). Thus, one can be realized by an inexpensive light source without using the same light source having ideal spectral characteristics, which can contribute to cost reduction of the entire apparatus.

Further, the light emission control unit 124 receives the amount of light received by the imaging unit 126 of the light irradiated from the first illumination unit 121 and reflected from the document surface, and reflected from the document surface irradiated from the second illumination unit 122. The first illuminating unit 121 and the second illuminating unit 122 are configured with a light emission ratio (light emission ratio for irradiating intensity setting) at which the amount of received light (light reception intensity) at the imaging unit 126 becomes substantially the same. Each light source can also emit light. In this way, by causing the light sources constituting the first illumination unit 121 and the second illumination unit 122 to emit light so that the amounts of light received by the imaging unit 126 are substantially the same, shadows caused by unevenness on the document surface are caused. Can effectively be suppressed from appearing in the read image. Here, the light emission control unit 124 determines the ratio of the light emission amounts (light emission intensity) of the first illumination unit 121 and the second illumination unit 122.
Light amount of first illumination unit 121: Light amount of second illumination unit 122 = 2: 3
It is said.

In the present embodiment, the second illumination unit 122 is arranged in a position slightly separated from the optical system 125 in the sub-scanning direction R than the first illumination unit 121. By arranging the second illumination unit 122 at a position farther from the optical system 125 in this way, the end portion of the document not placed on the abutting plate 107 placed on the document table is placed in the predetermined direction R. It is possible to illuminate from a closer angle, and it is possible to suppress the occurrence of shadows in the read image near the edge.

As described above, the illumination device of the image reading apparatus according to the present embodiment is configured to include the first illumination unit 121, the second illumination unit 122, and the light emission control unit 124, and is placed on the document table. It has a function of illuminating while scanning the read area of the original document in a predetermined direction.

  As described above in detail, according to the present embodiment, a configuration using a light source such as a light guide tube normally used in a reading optical system and a light source such as an LED array that is less expensive than a light source such as a light guide tube By doing so, it is possible to provide an illumination device capable of realizing high-quality image reading at low cost. In addition, by arranging a light source with a wide wavelength band on the side farther than the original abutting plate in the sub-scanning direction, the generation of shadows on the scanned image near the end of the original that is not abutted against the abutting plate is suppressed. Therefore, it is possible to provide a low-cost and high-quality image reading apparatus to the user.

  Although the present invention has been described in detail according to particular embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall configuration diagram for explaining an illumination device of an image reading device according to an embodiment and an image reading device including the same. It is a figure for demonstrating the operation | movement of CIS at the time of manual placement reading. It is a block diagram which shows the detail of CIS120 in the image reading apparatus 1 by this Embodiment. It is a figure which shows the spectral characteristic of the yellow green LED which comprises the 1st illumination part 121, and the red LED, green LED, and blue LED which comprise the 2nd illumination part 122, and the target spectral characteristic. It is a figure for demonstrating the shadow which appears on a reading image. It is a figure for demonstrating the shadow which appears on a reading image.

107 abutting plate, 120 CIS, 121 first illumination unit, 122 second illumination unit, 124 light emission control unit, 125 optical system, 126 imaging unit.

Claims (3)

An original platen on which an original is placed; an abutting plate that is provided on one end side in the sub-scanning direction of the original platen and that positions one end of the original placed on the original platen so as to position the original; and An image reading sensor which is arranged below the document table and moves in the sub-scanning direction and reads an image of the document placed on the document table by an image pickup unit ; the image reading sensor includes first and second image reading sensors; the image reading apparatus which have the imaging optical system for imaging on the imaging unit the light reflected by the original image is irradiated from the illumination unit of, provided in the image reading sensor, the sub scanning of the image reading sensor An illumination device for illuminating a reading area of a document placed on the document table while moving in a sub-scanning direction according to movement in a direction;
Illuminating the reading area of the document placed on the platen, said first illumination unit which reflected light from the original surface is guided to the imaging unit, said to be placed on said platen The reading area of the document is illuminated simultaneously with the first illumination unit, and reflected light from the document surface is guided to the imaging unit, and in the sub-scanning direction with respect to the first illumination unit across the imaging unit It is arranged to face each other and is composed of a white type light guide tube provided with three red LEDs, green LEDs and blue LEDs as a light source, and irradiates illumination light having a wider emission color bandwidth than the first illumination unit. wherein the second illumination unit has, the second illumination unit and the first illumination unit which face each other along the sub-scanning direction, the sub-scanning direction of one arrangement side of the abutment plate The first illumination unit is disposed on one end side in the sub-scanning direction, and the second illumination unit is Part illumination device of an image reading apparatus disposed on the other end side in the sub-scanning direction. The illumination device of the image reading device according to claim 1 ,
By the irradiation light from the second illumination unit and the light irradiated from the first illumination unit are mixed, the image reading apparatus was the same as the wavelength distribution of white color light source irradiating light to the document image Lighting device. 3. The illumination device of the image reading apparatus according to claim 1, wherein the imaging optical system is disposed between the first illumination unit and the second illumination unit in the sub-scanning direction, and The illumination unit of the image reading device is arranged in a position farther from the imaging optical system than the first illumination unit in the sub-scanning direction.

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