JP6733346B2 - Image reading apparatus, image forming apparatus, and image reading method - Google Patents

Description

The present technology relates to an image reading device, an image forming device, and an image reading method that generate image information from a reading target by sequentially switching and irradiating lights having different wavelength characteristics.

Image reading apparatuses that optically read image information from an arbitrary reading target are widely used. Such an image reading apparatus is often mounted as a part of an image forming apparatus such as a copying machine, a facsimile machine, and a multi-function machine.

A configuration using a line sensor is adopted as one of typical configurations in which an image reading apparatus optically reads image information from a reading target. Specifically, the line sensor continuously acquires images from the surface to be imaged of the reading target while relatively moving the line sensor, which is an imaging element, and the reading target at a constant speed. Examples of the structure for relative movement include a structure for moving a document, a structure for moving a carriage equipped with a line sensor, and a structure for moving both.

As a line sensor used in such a configuration, a so-called CCD (Charge Coupled Device) reading method, a 3-line CIS (Contact Image Sensor) reading method, a 1-line CIS reading method, etc. It has been known.

In the CCD reading method and the 3-line CIS reading method, light having a relatively wide wavelength range (typically, white light) is applied to a reading object, and reflected light generated by reflection on the reading object is received by a light receiving element. By using a color filter arranged in the vicinity of, to separate into a plurality of wavelength components (generally, three primary colors of red, green, and blue) and receive the separated wavelength components in parallel, Image signals for each color are acquired and color image data is generated by processing these image signals. Such a method may be referred to as a color filter method.

On the other hand, in the 1-line CIS reading method, a plurality of light sources that emit light (typically, red light, green light, and blue light) having wavelength characteristics different from each other are arranged, and a line sensor and a reading target are provided. These light sources are sequentially turned on in a predetermined order while relatively moving between them at a constant speed, and a light receiving element having sensitivity to any wavelength of light from a plurality of light sources is used. The image signals for each color are acquired by sequentially reading the image signals in association with the light irradiation timing, and these image signals are processed to generate color image data and the like. Such a method may be referred to as a light source switching method/light source sequential method.

The 1-line CIS reading method is inferior in color reproducibility to the CCD reading method or the 3-line CIS reading method in principle, but the number of necessary light receiving elements is small. Is advantageous to

Regarding color reproducibility, for example, there is a prior art focusing on an original included in a portion marked with a highlighter pen or the like.

For example, Japanese Unexamined Patent Publication No. 10-107970 (Patent Document 1) prints with a commercially available yellow-colored, pink (magenta)-type, cyan-typed fluorescent pen, or a similar fluorescent ink. An object of the present invention is to solve the problem that when a document image is copied, it is reproduced in a color far from the color of the document image. Specifically, the density of the image data of M, C, Y, Bk is reduced (equivalent to increasing the density of R, G, B) according to the fluorescence component detected when the ultraviolet light is irradiated. It is disclosed that the problem that the fluorescent color looks dimmer than it looks on the copy output is solved by performing.

Further, regarding the configuration of irradiating with ultraviolet rays, Japanese Patent Laid-Open No. 2004-127235 (Patent Document 2) is a device for illuminating, reading, and interpreting a mark appearing on a machine readable zone (MRZ) of a document. , A document reader in which the indicia is visible only under illumination by invisible light. Specifically, Japanese Patent Laid-Open No. 2004-127235 (Patent Document 2) includes an ultraviolet light source reading unit having an ultraviolet light cut filter and a visible light source reading unit having visible light of a plurality of wavelengths, and a passport. Disclosed is a configuration in which the detection of fluorescent marks such as banknotes and the acquisition of visible light images are performed independently.

JP, 10-107970, A JP, 2004-127235, A

The above-mentioned Japanese Patent Laid-Open No. 10-107970 (Patent Document 1) only provides a solution to the problem "fluorescent color appears dimmer than visually observed" that may occur in the CCD reading method or the 3-line CIS reading method. However, it does not solve the problem relating to color reproducibility that occurs in the 1-line CIS scanning method as described later.

Japanese Unexamined Patent Application Publication No. 2004-127235 (Patent Document 2) is directed to a technique for detecting an invisible mark that is previously given to a passport, a bill, or the like, and has a problem regarding color reproducibility in an image reading apparatus. Is not like solving.

The present technology improves color reproducibility in a configuration in which a single line sensor is used to detect reflected light generated by the irradiation while sequentially switching and irradiating light having different wavelength characteristics to a reading target. One purpose is to provide a new configuration.

According to one aspect of the present invention, an image reading device for reading image information from a reading target is provided. The image reading device emits a red light source that emits light containing a red wavelength component, a green light source that emits light containing a green wavelength component, a blue light source that emits light containing a blue wavelength component, and a light containing an ultraviolet component. A light emitting unit including an ultraviolet light source that generates light, a light guide for uniformizing the light emitted from the light emitting unit and irradiating the reading target, and the brightness of each region of the reflected image generated by the irradiation of the light to the reading target. A photoelectric conversion unit that outputs the indicated value, a cut filter that is arranged on the optical path from the reading target to the photoelectric conversion unit, and that blocks the ultraviolet component, and emits any light from the light emitting unit in a predetermined order. In addition, the control unit that generates the image information to be read by processing the output values sequentially output from the photoelectric conversion unit in association with the wavelength characteristics of the corresponding light. The process of generating the image information of the reading target is performed by using the light from the ultraviolet light source from at least one of the output values output when the reading target is irradiated with light from the red light source, the green light source, and the blue light source. It includes a first correction process for subtracting a component corresponding to an output value when the object to be read is irradiated.

Preferably, the first correction process is a red light source, a green light source, or a blue light source, and a light having a wavelength at least partially overlapping with a wavelength of fluorescence that can be generated when the reading target is irradiated with light from an ultraviolet light source. Is applied to the output value corresponding to the light source that generates.

Preferably, the first correction processing subtracts a component corresponding to the output value when the reading target is irradiated with the light from the ultraviolet light source from the output value when the reading target is irradiated with the light from the blue light source. Processing.

Preferably, in the process of generating the image information of the reading target, the first correction process is not applied among the output values output when the reading target is irradiated with light from the red light source, the green light source, and the blue light source. It further includes a second correction process for adding a component corresponding to the output value when the reading object is irradiated with the light from the ultraviolet light source to at least one of the output values.

Preferably, in the process of generating image information of the reading target, the output value when the reading target is irradiated with light having a short wavelength is larger than the output value when the reading target is irradiated with light from the ultraviolet light source. It includes the process of subtracting the value multiplied by the coefficient.

Preferably, the wavelength of the light from the ultraviolet light source is set so as not to overlap with the wavelength of the light from the blue light source.

Preferably, the peak emission wavelength of the light from the ultraviolet light source is 370 nm or less.
Preferably, the intensity of the wavelength component of 370 nm or more of the light from the ultraviolet light source is 1/2 or less of the peak intensity of the light from the blue light source.

Preferably, the predetermined order is set so that the blue light source and the ultraviolet light source emit light at least continuously.

An image forming apparatus according to another aspect of the present invention includes an image reading apparatus that reads image information from a reading target, and an image forming unit that forms an image based on the image information read by the image reading apparatus. The image reading device emits a red light source that emits light containing a red wavelength component, a green light source that emits light containing a green wavelength component, a blue light source that emits light containing a blue wavelength component, and a light containing an ultraviolet component. A light emitting unit including an ultraviolet light source that generates light, a light guide for uniformizing the light emitted from the light emitting unit and irradiating the reading target, and the brightness of each region of the reflected image generated by the irradiation of the light to the reading target. A photoelectric conversion unit that outputs the indicated value, a cut filter that is arranged on the optical path from the reading target to the photoelectric conversion unit, and that blocks the ultraviolet component, and emits any light from the light emitting unit in a predetermined order. In addition, the control unit that generates the image information to be read by processing the output values sequentially output from the photoelectric conversion unit in association with the wavelength characteristics of the corresponding light. The process of generating the image information of the reading target is performed by using the light from the ultraviolet light source from at least one of the output values output when the reading target is irradiated with light from the red light source, the green light source, and the blue light source. It includes a first correction process for subtracting a component corresponding to an output value when the object to be read is irradiated.

According to still another aspect of the present invention, an image reading method for reading image information from a reading target is provided. The image reading method includes a red light source that emits light containing a red wavelength component, a green light source that emits light containing a green wavelength component, a blue light source that emits light containing a blue wavelength component, and a light containing an ultraviolet component. And a step of generating any light in a predetermined order from a light emitting unit including a generated ultraviolet light source. The light emitted from the light emitting unit is uniformized by the light guide and then is irradiated to the reading target. A cut filter for blocking the ultraviolet component is arranged on the optical path from the reading target to the photoelectric conversion unit. The image reading method includes a step of storing an output value, which is sequentially output from the photoelectric conversion unit, indicating an intensity of each region of a reflected image generated by irradiation of light on a reading target in association with a wavelength characteristic of corresponding light, and storing the output value. Generating image information to be read from the output value. The step of generating the image information of the reading target is performed by using the light from the ultraviolet light source from at least one output value output from the red light source, the green light source, and the blue light source. Includes a step of subtracting a component corresponding to an output value when the object to be read is irradiated.

According to the present technology, color reproducibility is improved in a configuration in which a single line sensor is used to detect reflected light generated by the irradiation while sequentially switching and irradiating light having different wavelength characteristics to a reading target. Can be improved.

FIG. 3 is a schematic diagram showing an external configuration example of an image forming apparatus including the image reading apparatus according to the present embodiment. It is a schematic diagram showing an example of section composition of an image reading device according to this embodiment. It is a schematic diagram which shows the structural example of the 1-line CIS reading system according to related technology. It is a schematic diagram for explaining the wavelength characteristic of the reflected light generated from the drawing portion by the fluorescent dye. FIG. 6 is a diagram for explaining processing when a read target including a drawing portion with a fluorescent dye is read by a 1-line CIS reading method and a 3-line CIS reading method, respectively. FIG. 3 is a schematic diagram showing an example of a reproduction result of image information read by a 1-line CIS reading method and a 3-line CIS reading method from a reading object having a drawing portion containing a fluorescent dye. FIG. 3 is a schematic diagram showing a configuration example of a reading unit of the image reading device according to the present embodiment. FIG. 8 is a diagram showing an example of wavelength characteristics (spectrum) of each light source and an ultraviolet cut filter which configure the light emitting unit shown in FIG. 7. It is a figure which shows an example of the reading result using the reading part which concerns on related technology. FIG. 6 is a diagram showing an example of a wavelength characteristic (spectrum) of reflected light generated when each light source is turned on for an original including a mark portion made of yellow fluorescent ink by the image reading device according to the present embodiment. 7 is a table showing correction effects of the first fluorescence correction method according to the present embodiment. 7 is a table showing correction effects of the third fluorescence correction method according to the present embodiment. FIG. 7 is a diagram showing an example of a combination of correction coefficients used in the fluorescence correction method according to the present embodiment. 3 is a schematic diagram showing a hardware configuration example relating to image reading in the image reading device according to the present embodiment. FIG. It is a schematic diagram which shows an example of a functional structure of the fluorescence correction processing part of the image processing part shown in FIG. 7 is a flowchart showing an image reading processing procedure in the image reading device according to the present embodiment. FIG. 6 is a schematic diagram for explaining a preferable lighting sequence of light sources in a fluorescence correction process in the image reading device according to the present embodiment. It is a figure which shows the example of the wavelength characteristic of the UV light source used for the image reading device according to this Embodiment.

Embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the same or corresponding parts in the drawings are designated by the same reference numerals and the description thereof will not be repeated.

<A. Device configuration>
Next, a device configuration of the image reading device and the image forming device including the image reading device according to the present embodiment will be described. Hereinafter, as a typical example, the image forming apparatus 1 implemented as a multi-functional peripheral (MFP) including an image reading apparatus will be described. The invention is not particularly limited to this, and it may be implemented as a copying machine or a facsimile including an image reading device, or the image reading device may be implemented as a single device.

(A1: image forming apparatus)
FIG. 1 is a schematic diagram showing an external configuration example of an image forming apparatus including an image reading apparatus according to the present embodiment. Referring to FIG. 1, image forming apparatus 1 according to the present embodiment has a plurality of functions such as a copy function, a scanner function, a printer function, and a fax function, and can be used in a LAN (Local Area Network), a telephone line, or the like. You can send and receive data over the network. That is, the image forming apparatus 1 can output the image information (image data) read from the reading target to another computer via the network as a scanner function or a copy function, and can output the image information (image data) to another computer via the network as a printer function or a fax function. Image information (image data) can be obtained from another computer, and printing or fax transmission based on the image data can be performed.

When the image reading apparatus is mounted on the image forming apparatus, any method may be adopted for the image forming unit (print engine) of the image forming apparatus. For example, an electrophotographic system (monochrome system or color system), an inkjet system, a heat-sensitive system, a thermal transfer system and the like can be mentioned. FIG. 1 shows, as a typical example, an image forming apparatus 1 employing an electrophotographic method.

The image forming apparatus 1 includes an image forming section 5, a sheet feeding section 6 arranged below the image forming section 5, and an image reading apparatus 4 arranged above the image forming section 5.

The image reading device 4 reads image information from a reading target and outputs image data and the like, and mainly includes a reading main body 2 and an automatic document feeder 3. The user can directly place one original on the reading main body 2 to read the image information, or place one or a plurality of originals on the automatic original conveying unit 3 to continuously transfer the image information. It can also be read. In this continuous reading operation, the reading main body 2 and the automatic document feeder 3 operate in synchronization with each other, so that the originals placed in the automatic document feeder 3 are fed one by one toward the reading main body 2. The reading main body 2 reads image information when a document passes through a predetermined position and generates image data.

The paper feed unit 6 stores paper as a recording medium and supplies the stored recording media to the image forming unit 5 one by one in response to the image forming operation in the image forming unit 5.

The image forming unit 5 forms an image on the recording medium supplied from the paper feeding unit 6 based on the image data read by the image reading device 4, the image data acquired via the network, the image data directly input, and the like. Form. In this way, the image forming unit 5 prints arbitrary image data on the recording medium. As a typical example, the image forming unit 5 forms an image based on the image information read by the image reading device 4. The recording medium on which the image is formed by the image forming unit 5 is output to the paper discharge unit 7 between the image forming unit 5 and the reading main body unit 2.

An operation panel 8 having a plurality of keys or buttons is provided on the front side (the side operated by the user) of the image forming apparatus 1. The operation panel 8 receives an operation instruction from a user and outputs the received operation instruction to the image forming unit 5 or the like.

(A2: image reading device)
Next, the device configuration of the image reading device 4 shown in FIG. 1 will be described in more detail. FIG. 2 is a schematic diagram showing a cross-sectional configuration example of image reading device 4 according to the present embodiment.

In the configuration example of the image reading device 4 shown in FIG. 2, image information can be read from both sides of a document. Specifically, the automatic document feeder 3 has a paper feed tray 31 on which one or a plurality of documents 70 are placed. The originals 70 placed in the paper feed tray 31 are sent to the original conveyance path 30 one by one from the uppermost one by the pickup roller 32 and the paper feed roller pair 33. In the document conveyance path 30, the document 70 is conveyed by the intermediate roller pair 34 to the registration roller pair 35. The registration roller pair 35 functions as a skew feeding correction roller, corrects the transported document 70 to its original posture, and sends the document 70 toward the first transport roller pair 36 at a predetermined timing. The original 70 is sent out onto the slit glass 21 which is the carrying and reading surface of the reading main body 2 by the first carrying roller pair 36, and passes over the slit glass 21 by the reading roller 42.

When the document 70 passes over the slit glass 21, the first reading unit 22 located below the slit glass 21 reads the image information on the downward surface (front surface) of the document 70.

A second transport roller pair 37, a second reading unit 38, a third transport roller pair 39, and a paper discharge roller 40 are arranged on the document transport path 30 on the transport downstream side of the slit glass 21. The original 70 that has passed over the slit glass 21 is sent to a position right below the second reading unit 38 by the second pair of transport rollers 37. When the document 70 passes directly below the second reading unit 38, the image information on the upward surface (back surface) of the document 70 is read.

The document 70 that has passed directly below the second reading unit 38 is discharged onto the paper discharge tray 41 by the third transport roller pair 39 and the paper discharge roller 40.

A slit glass 21 and a platen glass 23 are provided on the upper surface of the reading main body 2. The first reading unit 22 is arranged inside the reading main body unit 2. The first reading unit 22 is used to read the image information of the surface of the document 70 passing on the slit glass 21 and/or the image information of the document 70 arranged on the platen glass 23. When reading the image information of the document 70 passing on the slit glass 21, the scanning unit 24 and the traveling unit 25 are placed in a fixed state. On the other hand, when reading the image information of the document 70 placed on the platen glass 23, the scanning unit 24 and the traveling unit 25 move in the sub-scanning direction Y, so that the range read by the first reading unit 22 is sequentially changed. To do.

The scanning unit 24 and the traveling unit 25 are supported by a pair of support rails 46 arranged in the reading main body 2, and slide and move by the power of an actuator (not shown).

The second reading unit 38 is fixedly arranged in the automatic document feeder 3. The second reading unit 38 reads the image information on the back surface of the document 70 conveyed by the reading roller 43. The reading roller 43 also has a function as a white reference body for shading correction, as well as a function of conveying the document 70.

The first reading unit 22 and the second reading unit 38 include a light source for emitting light toward the surface of the document to be read, and a line sensor for receiving the reflected light generated by the reading target. The line sensor is composed of a plurality of photoelectric conversion elements arranged along the main scanning direction, and outputs an output value according to the brightness (light intensity) of the incident reflected light. That is, the line sensor converts an optical reflection image generated on the reading target into an electric image signal and outputs the electric image signal.

In image reading device 4 according to the present embodiment, CIS is used as a line sensor for at least one of first reading unit 22 and second reading unit 38. In particular, the first reading unit 22 and/or the second reading unit 38 adopts the 1-line CIS reading method.

It is not necessary to adopt the 1-line CIS reading method for both the first reading unit 22 and the second reading unit 38, and the 1-line CIS reading method may be adopted for only one of them, or the image reading is performed. The device 4 may employ only one of the first reading unit 22 and the second reading unit 38.

<B. Newly Discovered Issues>
Next, a related configuration example of the 1-line CIS reading method will be described, and a newly discovered problem in the related configuration example will be described. In the following description, the first reading unit 22 and the second reading unit 38 shown in FIG. 2 may be collectively referred to as the “reading unit 22”.

(B1: Related configuration example)
FIG. 3 is a schematic diagram showing a configuration example of a 1-line CIS reading method according to related art. The reading unit 22# of the 1-line CIS reading system sequentially switches and irradiates light having different wavelength characteristics to the reading target, and sequentially reflects reflected images generated from the reading target by a common light receiving element (photoelectric conversion element). Image information is generated by combining the detected results.

More specifically, the reading unit 22# according to the related art illustrated in FIG. 3 includes a light emitting unit 220# that emits light for irradiating a target surface to be read, and light emitted from the light emitting unit 220#. A light guide 222 for uniformizing and irradiating the object to be read, a line sensor 226, and an imaging lens 224 for forming a reflected image from the object to be read on a detection surface on the line sensor 226.

The light emitting unit 220# is a light emitting unit for generating light of each color of red, green, and blue that irradiates the reading target. The light emitting unit 220# includes a red light source (hereinafter, also referred to as “R light source”) 220R that generates light including a red wavelength component, and a green light source (hereinafter, “G light source”) that generates light including a green wavelength component. 220G, and a blue light source (hereinafter, also referred to as “B light source”) 220B that generates light including a blue wavelength component.

The light guide 222 is disposed integrally with or close to the light emitting unit 220# so as to spatially smooth (uniformize) the light emitted from the light emitting unit 220#, and Directs light in the direction of the object to be read.

As the line sensor 226, a CIS in which a plurality of photoelectric conversion elements are arranged along the main scanning direction is used. The line sensor 226 is a kind of sensor group in which monochrome sensors are arranged in a line, and each photoelectric conversion element has a size corresponding to the brightness (brightness/light intensity) of an image incident on each photoelectric conversion element. The signal of is output.

The imaging lens 224 is an imaging optical system for shortening the focal length of the line sensor 226. For example, an SLA (Selfoc Lens Array) in which a plurality of gradient index lenses are arranged along the main scanning direction is used. Can be used. The SLA is an imaging optical system capable of forming one continuous image as a whole on the line sensor 226.

In the reading unit 22# shown in FIG. 3, a single line sensor 226 (an array of monochrome sensors) is used to sequentially switch the light sources emitted from the light emitting unit 220#, so that a plurality of images included in the reflected image from the reading target can be obtained. The wavelength components of are separated in time. That is, the R light source 220R, the G light source 220G, and the B light source 220B included in the light emitting section 220# are sequentially switched to emit light, thereby sequentially acquiring the line data for each color of R, G, and B. Since there is no mechanism for wavelength separation when acquiring this line data, it is considered that the light of the same wavelength as the light emitted from the light source when each line data was acquired was received, and the wavelength component Are separated in time.

The electric signal output from the line sensor 226 is given to an image processing unit (not shown), and is subjected to analog signal processing, A/D (Analog to Digital) conversion, shading correction, image compression processing, etc., and digitized image data. Is output as. In the processing for outputting the image data, the line data for each color is multiplied by the wavelength characteristic of the corresponding light source, so that the spectrum of the reflected image and the color image information of the reflected image can be reproduced.

(B2: Newly discovered problem)
Next, a new problem relating to color reproducibility discovered by the inventors of the present application that may occur when image information is read using a 1-line CIS reading type reading unit as shown in FIG. 3 will be described.

When the image information of the original is read by using the reading unit of the 1-line CIS reading method as shown in FIG. 3, if there is an area drawn by the fluorescent dye in the original, the area of the area of the read image information is read. The inventor of the present application has newly discovered that there is a problem peculiar to the 1-line CIS reading method that the color becomes lighter than the original color and disappears. For example, a document marked with a commercially available highlighter pen or the like includes an area for drawing with a fluorescent dye, and in the image data read from such a document, the color of the target area is light. Or disappears and disappears.

Such a phenomenon is due to a combination of the property of fluorescence and the principle of the 1-line CIS reading system. The reason why such a phenomenon occurs will be described below. FIG. 4 is a schematic diagram for explaining the wavelength characteristic of the reflected light generated from the drawing portion with the fluorescent dye. FIG. 5 is a diagram for explaining the processing when the reading target including the drawing portion with the fluorescent dye is read by the 1-line CIS reading method and the 3-line CIS reading method, respectively.

Generally, a fluorescent dye absorbs a specific wavelength or a component in a specific wavelength range specific to each dye, and emits light (fluorescence) having a wavelength shorter than the absorbed wavelength. For example, a fluorescent dye that emits red or yellow fluorescence having a long wavelength in visible light absorbs a component such as blue having a shorter wavelength of visible light and emits red or yellow.

FIG. 4 shows an example in which the original 70 including the drawing portion 72 traced by the highlighter pen is irradiated with blue light. In this case, the reflected light generated from the drawing portion 72 mainly contains the yellow wavelength component.

FIG. 5A shows a process of reading the image information by using the reading unit 22# of the 1-line CIS reading method with the original 70 shown in FIG. 4 as the reading target. As described with reference to FIG. 4, when the B light source 220B is turned on, the reflected light mainly including the yellow wavelength component is generated from the document 70 to be read. Since the color sensor is not attached to the line sensor 226 of the reading unit 22#, when the reflected light mainly including the yellow wavelength component is incident, the B light source 220B is irradiated with an electric signal corresponding to the brightness of the incident reflected light. It is output as a detection value (B signal) at that time. However, since the reflected light that has entered the line sensor 226 is approximately yellow light, the output B signal has an erroneous detection result.

That is, since the reading unit 22# of the 1-line CIS reading system does not have a mechanism (for example, a color filter or the like) for separating the light in which the reflected light and the fluorescence are mixed by color, the fluorescence included in the received light. Since the B light source 220B capable of separating the components is the output from the line sensor 226 during lighting, it is erroneously determined as reflected light of blue light.

As a result, for the yellow drawing that should be originally obtained, the output when blue light that should be absorbed by the fluorescent dye is excessively expressed by the fluorescent dye, and as a result, the total output of the image signals for each color As a value, the luminance may be larger than the original value, that is, reproduced as a light color close to white, or the calculated luminance may be too large and disappear.

As a comparative example, FIG. 5B shows a process of reading image information from a similar reading target using the reading unit 22## of the 3-line CIS reading system. The reading unit 22## of the 3-line CIS reading system uses a white light source (hereinafter, also referred to as “W light source”) 220W that generates white light having a relatively wide wavelength range, and replaces the monochrome line sensor 226. The imaging lenses 224R, 224G, 224B and the line sensors 226R, 226G, 226B are arranged. Color filters 227R, 227G, and 227B are attached to the line sensors 226R, 226G, and 226B, and have detection sensitivity for each color of R, G, and B.

When such a 3-line CIS reading method is adopted, when reflected light including a yellow wavelength component is incident, the line sensor 226R having detection sensitivity for red light and the line sensor 226G having detection sensitivity for green light are used. , Respectively, the detection values (R signal and G signal) are output, and the drawing portion including the fluorescent dye is basically reproduced correctly from these R signal and G signal.

FIG. 6 is a schematic diagram showing an example of a reproduction result of image information read by a 1-line CIS reading method and a 3-line CIS reading method from a reading object having a drawing portion containing a fluorescent dye. FIG. 6A shows an example of a document 70 having a drawing portion 72 containing a fluorescent dye as a reading target.

FIG. 6B shows an example of the result of reading image information from the original 70 shown in FIG. 6A using the 1-line CIS reading type reading unit 22# as shown in FIG. 5A. Show. In the reproduced image 80 thus reproduced, the drawing portion 82 corresponding to the drawing portion 72 containing the fluorescent dye becomes thin as a whole.

On the other hand, in FIG. 6C, image information is read from the original 70 shown in FIG. 6A by using the reading unit 22## of the 3-line CIS reading method as shown in FIG. 5B. An example of the read result is shown. In this reproduced image 90, the color tone of the drawing portion 92 corresponding to the drawing portion 72 containing the fluorescent dye may change.

When the reading unit 22## of the three-line CIS reading method is used, "fluorescent color is dull than it looks on the copy output as disclosed in Japanese Patent Laid-Open No. 10-107970 (Patent Document 1). Although there is a possibility that a situation such as "visible" may occur, the problem that "the fluorescent color is faint on the copy output and disappears" that occurs when the reading unit 22# of the 1-line CIS reading system is used cannot occur. That is, the above-mentioned Japanese Patent Application Laid-Open No. 10-107970 (Patent Document 1) does not suggest any new problem regarding color reproducibility discovered by the inventors of the present application as described above, and will be described later. However, it does not suggest any solution to the new problem.

The image reading apparatus including the reading unit of the 1-line CIS reading method according to the present embodiment improves the reading accuracy of the drawing portion including the fluorescent dye and improves the color reproducibility in consideration of the new problems described above. The purpose is to raise.

When comparing the unit costs of the line sensors of the CCD reading system, the 3-line CIS reading system, and the 1-line CIS reading system, the CCD reading system, the 3-line CIS reading system, and the 1-line CIS reading system decrease in order. That is, it is important to solve the problems inherent in the 1-line CIS reading method in order to reduce the cost.

<C. Image reading device configuration>
Next, an example of an image reading apparatus capable of solving the above-described new problem regarding color reproducibility discovered by the inventors of the present application will be described.

In the image reading device 4 according to the present embodiment, in addition to the light source (R light source, G light source, B light source) for acquiring the original image signal for each color, in addition to the above-described new problems, Mainly, another light source for generating the fluorescent component from the fluorescent dye is arranged, and a process of detecting and correcting the fluorescent component generated by the light irradiation from the other light source is adopted.

More specifically, in a 1-line CIS reading type image reading device, in addition to a normal light source (R light source, G light source, B light source), a light source that emits light in an ultraviolet region wavelength and reflection from a reading target A cut filter that blocks ultraviolet components of light is additionally arranged. Then, by correcting the image signal for each color (reading intensity in each color) by using the fluorescent component from the reading target detected when the reading target is irradiated with light from the ultraviolet light source, the color for the fluorescent color is corrected. Improves reproducibility and readability.

FIG. 7 is a schematic diagram showing a configuration example of reading unit 22 of image reading device 4 according to the present embodiment. Referring to FIG. 7, reading unit 22 of image reading device 4 according to the present embodiment employs a 1-line CIS reading type line sensor, and sequentially reads light having different wavelength characteristics with respect to a reading target. Image information is generated by switching and irradiating and synthesizing the results obtained by sequentially detecting the reflected image generated from the reading target by the common light receiving element (photoelectric conversion element).

More specifically, the reading unit 22 uniformizes the light emitted from the light emitting unit 220 and the light emitted from the light emitting unit 220 and irradiates the reading target. Light guide 222, a line sensor 226, an imaging lens 224 for forming a reflected image from a reading object on a detection surface on line sensor 226, and a cut filter 228 for blocking an ultraviolet component.

The light emitting unit 220 is a light emitting unit for generating light of each color of red, green, and blue for irradiating the reading target. The light emitting unit 220 includes a red light source (R light source) 220R, a green light source (G light source) 220G, and a blue light source (B light source) 220B, as well as an ultraviolet light source (hereinafter, referred to as “UV Also referred to as a “light source.”) 220 UV.

The light guide 222 is arranged integrally with or close to the light emitting unit 220, spatially smoothes (uniformizes) the light generated from the light emitting unit 220, and reads the light from the light emitting unit 220. Orient in the direction of the target. The light guide 222 is a member for guiding the light generated by the light emitting unit 220 to the reading target. The light guide 222 is typically made of a resin such as acrylic or an optical material such as glass.

As the line sensor 226, a CIS in which a plurality of photoelectric conversion elements are arranged along the main scanning direction is used. The line sensor 226 is a kind of sensor group in which monochrome sensors are arranged in a line, and each photoelectric conversion element has a size corresponding to the brightness (brightness/light intensity) of an image incident on each photoelectric conversion element. The electric signal of is output. The line sensor 226 is a photoelectric conversion element that converts the optical image formed by the imaging lens 224 into a potential signal, and each area of the reflected image generated by irradiating the reading target with light (on the light receiving surface of each photoelectric conversion element). Equivalent to a photoelectric conversion unit that outputs a value indicating the luminance.

Note that the technical idea according to the present invention is not limited to the name of CIS, and may be a configuration in which a common photoelectric conversion unit is used to temporally separate a plurality of wavelength components included in a reflected image from a reading target. For example, it can be applied to any configuration.

For example, the line sensor 226 may be configured using a CCD without a color filter attached. Further, the array of light receiving elements (photoelectric conversion elements) of the line sensor 226 is not limited to one row, and may be a plurality of rows.

The electric signal output from the line sensor 226 is given to an image processing unit described later to perform analog signal processing, A/D (Analog to Digital) conversion, correction processing according to the present embodiment (fluorescence correction processing described later), It is output as digitized image data after undergoing shading correction, image compression processing, and the like. In the processing for outputting the image data, the line data for each color is multiplied by the wavelength characteristic of the corresponding light source, so that the spectrum of the reflected image and the color image information of the reflected image can be reproduced.

The imaging lens 224 is an imaging optical system for shortening the focal length of the line sensor 226. For example, an SLA (Selfoc Lens Array) in which a plurality of gradient index lenses are arranged along the main scanning direction is used. Can be used. The SLA is an imaging optical system capable of forming one continuous image as a whole on the line sensor 226.

The cut filter 228 is a band pass filter or a band cut filter that blocks ultraviolet components, and is arranged on the optical path from the reading target to the line sensor 226 that is a photoelectric conversion unit. As a result, the ultraviolet component between the reading target and the photoelectric conversion element is blocked on the optical path of the light emitting unit 220 that generates the ultraviolet component light. In the configuration example shown in FIG. 7, an example is shown in which it is arranged between the reading target and the imaging lens 224, but it may be arranged between the imaging lens 224 and the line sensor 226.

The image reading device 4 reads the image data corresponding to the wavelength component of the light emitted from the light emitting unit 220 by the potential signal from the photoelectric conversion element when each light source of the light emitting unit 220 is sequentially made to emit light. ..

FIG. 8 is a diagram showing an example of wavelength characteristics (spectrum) of each light source and the ultraviolet cut filter constituting the light emitting unit 220 shown in FIG. 7. Referring to FIG. 8, R light source 220R, G light source 220G, and B light source 220B generate light having wavelength characteristics such that their respective peak emission wavelengths correspond to red, green, and blue.

The UV light source 220UV is a light emitting means for generating light of an ultraviolet component, and emits light having wavelength characteristics whose peak emission wavelength is in the ultraviolet region. The light emitted by the UV light source 220UV may be any light as long as it contains a component in the ultraviolet range, and may also contain a component in the visible range. That is, the spectrum of the light generated by the UV light source 220UV may include the ultraviolet region to the visible region. However, it is preferable that the light generated by the UV light source 220UV and the light generated by the R light source 220R do not overlap in the wavelength range. That is, the wavelength of the light from the UV light source 220UV is preferably set so as not to overlap the wavelength of the light from the R light source 220R. Even if there are overlapping wavelength ranges between the light from the UV light source 220UV and the light from the R light source 220R, there is no substantial problem if the intensity difference is sufficiently large.

FIG. 8 also shows the cutoff characteristics of the cut filter 228. The cut filter 228 prevents light (ultraviolet light) from the UV light source 220UV from directly entering the line sensor 226. The light from the UV light source 220UV is used to generate a fluorescent component from the reading target, and when the generated fluorescent component and the light from the UV light source 220UV enter the line sensor 226 in a mixed state, the fluorescent light is emitted. It becomes impossible to estimate the intensity of components. Therefore, as the cut filter 228, one having a cutoff characteristic that can cut off substantially all of the light from the UV light source 220UV is adopted.

However, the cut filter 228 does not need to completely block the light from the UV light source 220UV, and any cut filter 228 can be used as long as the intensity of the light (ultraviolet light) after transmission can be made equal to or lower than the detection sensitivity of the line sensor 226. The cut filter 228 may be adopted.

<D. Overview of reading results and correction processing>
Next, the correction process in the image reading apparatus according to the present embodiment will be described while comparing with the 1-line CIS reading method according to the related art.

(D1: Read result)
First, the result of actually reading an image in four types of areas in a document using the reading unit 22# according to the related art shown in FIG. 3 is shown below.

FIG. 9 is a diagram illustrating an example of a reading result using the reading unit according to the related art. In the read result shown in FIG. 9, the lines are (1) a blank space, (2) a black character, (3) a mark part of general yellow ink not containing a fluorescent component, and (4) a mark part of yellow fluorescent ink, respectively. The output value from the photoelectric conversion element forming the sensor 226 is shown.

In FIG. 9, when the R light source 220R, the G light source 220G, and the B light source 220B are sequentially turned on only once, the respective output values output from the photoelectric conversion elements corresponding to a certain specific pixel are S_R, S_G, and S_B. I am trying. The output value is standardized in the range of 0 to 255.

Further, the column of "reading result of 1-line CIS (related technology)" shows the reading result finally output by combining the corresponding output values S_R, S_G, and S_B.

As shown in FIG. 9, (1) a blank space, (2) a black character, and (3) a mark portion made of a general yellow ink containing no fluorescent component was read as a visual appearance of the color and read. The colors match, and there is no problem when the reading unit 22# according to the related art is used.

On the other hand, in (4) the mark portion made of the yellow fluorescent ink, the visual appearance of the color does not match the read color.

In general, yellow fluorescent ink contains a fluorescent dye that emits yellow fluorescence and a yellow dye that mainly absorbs a blue wavelength component, and emits white light (that is, red light, green light, and blue light). When it is illuminated with all-inclusive light, it looks visually bright yellow. To reproduce this visual appearance, ideally S_R=S_G=255 and S_B=0.

However, in FIG. 9, the value of S_B greatly exceeds the ideal “0” and becomes “130”. Both S_R and S_G are "230", which are generally appropriate values. However, when color reproduction is performed using S_B, which has an apparently large value, the drawing portion that should originally appear bright yellow is It is read as pale yellow, which is close to white. The image reading device according to the present embodiment solves such a problem of color reproducibility by performing a correction process described below.

FIG. 10 is a diagram showing an example of a wavelength characteristic (spectrum) of reflected light generated when each light source is turned on for an original including a mark portion made of yellow fluorescent ink by the image reading device according to the present embodiment. FIG. 10A shows a spectrum of reflected light obtained when the R light source 220R is turned on, and FIG. 10B shows a spectrum of reflected light obtained when the G light source 220G is turned on. FIG. 10C shows a spectrum of reflected light obtained when the B light source 220B is turned on, and FIG. 10D shows a spectrum of reflected light obtained when the UV light source 220UV is turned on.

As shown in FIG. 10A, when red light having a wavelength longer than that of yellow light is applied to the reading target, no fluorescence is emitted from the fluorescent dye. On the other hand, as shown in FIGS. 10(B) and 10(C), when green light and blue light having a shorter wavelength than yellow light are respectively irradiated to the reading target, fluorescence is emitted from the fluorescent dye. ..

When ultraviolet light from the UV light source 220UV is applied to the reading target, more fluorescent components are generated. Since the cut filter 228 is arranged in front of the line sensor 226, the ultraviolet light from the UV light source 220UV is not detected by the line sensor 226. That is, the output value S_UV output from the line sensor 226 when the UV light source 220UV is turned on indicates the magnitude of the fluorescent component contained in the reflected light generated from the reading target.

Note that FIG. 10 shows an example in which a red light from the R light source 220R does not generate a fluorescent component, but a fluorescent dye or the like excited by the red light from the R light source 220R is also assumed. The output value from the line sensor 226 when 220R is turned on can be a value including the fluorescent component.

The image reading device 4 according to the present embodiment generates one of the lights from the light emitting unit 220 in a predetermined order, and corresponds each output value sequentially output from the line sensor 226 (photoelectric conversion unit). The image information to be read is generated by processing in association with the wavelength characteristic of the light to be read. That is, the image reading device 4 is based on the output value from the photoelectric conversion element obtained when the four light sources including the R light source 220R, the G light source 220G, the B light source 220B, and the UV light source 220UV are sequentially turned on one by one, The image information in one column in the main scanning direction is read.

As shown in FIG. 10, depending on the relationship between the wavelength of the light generated by each light source and the characteristics of the fluorescent dye, when each light source is turned on, a fluorescent component having a different wavelength from the light emitted by the lighting is emitted. It can be detected in excess. The excessively detected output value is corrected by using the output value obtained when the UV light source 220UV is turned on. More specifically, from at least one output value (photoelectric conversion element output value) of the output values respectively output when the light from the R light source 220R, the G light source 220G, and the B light source 220B is applied to the reading target, Image information of the reading target is generated by performing a correction process of reducing a component according to an output value (photoelectric conversion element output value) when the light from the UV light source 220UV is emitted to the reading target.

As described above, in the image reading device 4, the photoelectric conversion element output value when the light source corresponding to the ultraviolet component is turned on is set to any one of when the R light source, the G light source, and the B light source are turned on. Correction is performed by subtracting from the output value of the photoelectric conversion element of a color or more.

Hereinafter, such correction processing is also referred to as “fluorescence correction processing”, and the content of the fluorescence correction processing will be described.

Note that the name “fluorescence correction processing” is for convenience, and the correction processing when a substance having the same characteristics as the fluorescent substance is present in the reading target can also be included in the technical scope of the present invention.

(D2: First fluorescence correction method)
As shown in FIG. 10 described above, the reflected light that enters the line sensor 226 when the B light source 220B is turned on contains more fluorescent components than the reflected components. This fluorescent component may reduce color reproducibility. Therefore, the output value S_B obtained when the B light source 220B is turned on is corrected using a value that reflects the magnitude of the fluorescent component, that is, the output value S_UV obtained when the UV light source 220UV is turned on. Become. Specifically, a correction formula according to the following correction formula (1) can be used.

I_B=S_B-α_B×S_UV (1)
Here, the correction coefficient α_B is a coefficient based on the ratio between the fluorescent component generated when the UV light source 220UV is turned on and the fluorescent component generated when the B light source 220B is turned on. Since the purpose is to remove the fluorescence component from the output value obtained when the B light source 220B is turned on, the correction coefficient α_B>0 is set.

As described above, in the image reading device 4, the photoelectric conversion element output value when the B light source is turned on is corrected using the photoelectric conversion element output value when the light source corresponding to the ultraviolet component is turned on.

The correction coefficient α_B may be predetermined based on actual measurement values obtained when the UV light source 220UV and the B light source 220B irradiate the reading target with light. Alternatively, generally, since the peak spectra of the light generated by the B light source 220B and the light generated by the UV light source 220UV are close to each other, it is considered that the excitation characteristics of the fluorescent dye are also similar, and therefore the light emitted from the B light source 220B is similar. The correction coefficient α_B is preferably a fixed value that is close to 1, on the assumption that the intensity of the light source and the intensity of the light from the UV light source 220UV are substantially equal.

Alternatively, when the user can previously specify the type of the fluorescent dye included in the reading target, or when the type of the fluorescent dye included in the reading target can be determined by some method, the correction is performed according to the type of the fluorescent dye. The value of the coefficient α_B may be dynamically changed.

FIG. 11 is a table showing the correction effect of the first fluorescence correction method according to the present embodiment. In FIG. 11, similar to FIG. 9 described above, (1) blank space, (2) black character, (3) mark portion with general yellow ink not containing fluorescent component, (4) mark portion with yellow fluorescent ink, The reading result of is shown.

In FIG. 11, when the R light source 220R, the G light source 220G, the B light source 220B, and the UV light source 220UV are sequentially turned on only once, the respective output values output from the photoelectric conversion element corresponding to a certain specific pixel are S_R. , S_G, S_B, S_UV. Further, the R, G, and B values of the pixels of the read image data after correction are set to I_R, I_G, and I_B. Both values are standardized in the range of 0-255.

When no correction process is performed, I_R=S_R, I_G=S_G, I_B=S_B.

The fluorescent component does not occur in any of the (1) margins, (2) black characters, and (3) the mark portion made of general yellow ink that does not include the fluorescent component, so the output value S_UV= obtained when the UV light source 220UV is turned on. It becomes 0. Since the ultraviolet light from the UV light source 220UV is blocked by the cut filter 228, it does not appear in the output value S_UV from the line sensor 226. As a result, even when the above-mentioned correction formula (1) is applied, the value of the correction term becomes zero, so that there is no adverse effect due to the correction. That is, with respect to these drawing portions, it is possible to obtain a reading result that matches the visual appearance of the colors as in the reading unit 22# according to the related art.

Further, (4) for the mark portion made of the yellow fluorescent ink, the output value S_B obtained when the B light source 220B is turned on is corrected according to the correction equation (1) described above, so that the value of the correction value I_B is originally It is possible to obtain a reading result “yellow” that is closer to the value “1” and is closer to the “vivid yellow” by visual observation. That is, it can be seen that by applying the first fluorescence correction method, the fluorescence component is reproduced with the brightness that can be distinguished from white, and the visibility is improved.

Such a first fluorescence correction method and a second fluorescence correction method described later can generate fluorescence when the reading target of the R light source 220R, the G light source 220G, and the B light source 220B is irradiated with light from the UV light source 220UV. Is preferably applied to an output value corresponding to a light source that generates light having a wavelength that at least partially overlaps with the wavelength of. As a typical example, in the first fluorescence correction method, according to the output value when the light from the B light source 220B is applied to the reading target, the output value when the reading target is irradiated with the light from the UV light source 220UV is used. The process of reducing the component is executed.

As described above, by applying the first fluorescence correction method according to the present embodiment, the color reproducibility of the reading target that does not generate the fluorescent component is improved while maintaining the color reproducibility of the reading target that does not generate the fluorescent component. it can.

(D3: Second fluorescence correction method)
In the first fluorescence correction method described above, the process of correcting the output value S_B obtained when the B light source 220B is turned on with the output value S_UV obtained when the UV light source 220UV is turned on has been described. Depending on the type, it may be preferable to correct the output value S_G obtained when the G light source 220G is turned on. In this case, the following correction formula (2) can be used in the same manner as the above correction formula (1).

I_G=S_G-α_G×S_UV (2)
Here, the correction coefficient α_G may be set to any positive or negative value. That is, the correction coefficient α_G<0 is set when the correction is performed in the sense of the first fluorescence correction method described above, while the correction coefficient α_G< is set when the correction is performed in the meaning of the third fluorescence correction method described later. Set to 0. The value of the correction coefficient α_G may be set as appropriate according to the wavelength of the fluorescent component to be read.

(D4: Third fluorescence correction method)
As shown in the correction effect of the first fluorescence correction method described above (see FIG. 11), by correcting the output value S_B obtained when the B light source 220B is turned on, the reading result of the drawing portion including the fluorescent dye is visually checked. You can get closer to the colors you see in. Further, in order to realize color reproducibility close to visual appearance, it may be preferable to correct the output value S_R obtained when the R light source 220R is turned on. In this case, the following correction formula (3) can be used.

I_R=S_R-α_R×S_UV (3)
Here, in order to reproduce the reflected light including the fluorescent component as a brighter color, it is necessary to increase the brightness of the red component. Therefore, in the correction equation (3), the correction coefficient α_R<0 is set. This is to add the fluorescence component generated when light (that is, green light and blue light) obtained by removing red light from white light is irradiated to the output value S_R obtained when the R light source 220R is turned on. It is intended for.

As described above, in the image reading apparatus 4, the photoelectric conversion element output value of any one or more colors having a wavelength longer than that of the light emitted from the B light source, which performs correction for subtracting the photoelectric conversion element output value, is converted into an ultraviolet ray. Correction is performed to add the photoelectric conversion element output value when the component light source is turned on.

As the correction coefficient α_R, a fixed value based on the wavelength characteristics of each light source may be adopted.
Alternatively, the correction coefficient α_R may be predetermined based on actual measurement values obtained when the UV light source 220UV, the B light source 220B, and the G light source 220G respectively irradiate the reading target with light.

Further alternatively, if the user can previously specify the type of fluorescent dye included in the reading target, or if it is possible to determine the type of fluorescent dye included in the reading target by some method, depending on the type of fluorescent dye, The value of the correction coefficient α_R may be dynamically changed.

FIG. 12 is a table showing correction effects of the third fluorescence correction method according to the present embodiment. In FIG. 12, similar to FIGS. 9 and 11, (1) a blank space, (2) a black character, (3) a mark portion made of a general yellow ink containing no fluorescent component, and (4) a yellow fluorescent ink. The reading result of the mark part is shown. FIG. 12 shows a reading result when the correction equations (1) and (3) are applied and the correction coefficients are set to α_B=1 and α_R=−1.

As shown in FIG. 12, by applying the third fluorescence correction method, in addition to (1) a blank space, (2) black characters, and (3) a mark portion made of general yellow ink that does not contain a fluorescent component, (4 ) It can be seen that it is possible to obtain a reading result that matches the visual appearance of the color even for the mark portion made of the yellow fluorescent ink. That is, by using the third fluorescence correction method, it is possible to reproduce the hue and saturation closer to the visual color as the read result.

(D5: correction coefficient)
The first fluorescence correction method to the third fluorescence correction method described above can be summarized in the following correction equations.

I_B=S_B-α_B×S_UV (1)
I_G=S_G-α_G×S_UV (2)
I_R=S_R-α_R×S_UV (3)
In general, a fluorescent dye absorbs a component in a specific wavelength or a specific wavelength range and generates a light (fluorescence) having a wavelength shorter than the absorbed wavelength, and However, it is preferable that an appropriate correction be performed. Therefore, it is preferable to set the correction coefficient depending on the wavelength.

FIG. 13 is a diagram showing an example of a combination of correction coefficients used in the fluorescence correction method according to the present embodiment. As shown in FIG. 13, it is preferable to set the magnitude of the corresponding correction coefficient according to the length of the wavelength of the light emitted from each light source. Note that, in the above-described third fluorescence correction processing, the purpose is to add a value according to the fluorescence component to the output value S_R, so the correction coefficient α_R is set to a negative value.

In this way, when performing correction processing on the output values S_R, S_G, and S_B when the R light source 220R, the G light source 220G, and the B light source 220B are sequentially switched to emit light, the output value when the light source having a short wavelength is emitted. The value obtained by multiplying the output value when the UV light source 220UV that emits ultraviolet light is emitted is increased by a larger value, while the output value when a light source having a longer wavelength is emitted UV that generates ultraviolet light. A value obtained by reducing the coefficient by which the output value when the light source 220UV is generated is multiplied (a negative value may be included) is subtracted.

In the fluorescence correction method according to the present embodiment, the output value when the reading target is irradiated with light having a short wavelength is multiplied by a larger coefficient with respect to the output value when the reading target is irradiated with light from the UV light source 220UV. You may make it include the process of reducing the value. By determining the magnitude of the correction coefficient depending on the length of the wavelength, it is possible to realize the correction that reflects the characteristics of the fluorescent dye.

Furthermore, these correction coefficients may be predetermined fixed values, or all or part of them may be dynamically changed. For example, if the user can previously specify the type of fluorescent dye included in the reading target, or if the type of fluorescent dye included in the reading target can be determined by some method, all Alternatively, some correction coefficient values may be dynamically determined.

<E. Control configuration and control method>
Next, a control configuration and a control method for realizing image reading according to the present embodiment will be described.

(E1: Hardware configuration example)
FIG. 14 is a schematic diagram showing a hardware configuration example relating to image reading in image reading device 4 according to the present embodiment. FIG. 14 shows a block diagram of the reading main body 2 and its peripheral circuits. As an example, FIG. 14 shows a configuration example in which the controller board 60 arranged in the reading main body unit 2 (see FIGS. 1 and 2) and the image processing unit 50 cooperate to realize a control function. ..

In the configuration shown in FIG. 14, the control function (the controller board 60 and the image processing unit 50) causes the light emitting unit 220 to generate any light in a predetermined order, and causes the line sensor 226 (photoelectric conversion unit) to generate light. Image information to be read is generated by processing the output values that are sequentially output in association with the wavelength characteristics of the corresponding light.

The controller board 60 controls the irradiation timing of the light from the light emitting unit 220 and acquires the electric signal output from the line sensor 226 (photoelectric conversion element) according to the irradiation timing of each light. More specifically, the controller board 60 includes a timing control unit 62, a light emission control unit 64, and a signal acquisition unit 66.

The timing control unit 62 determines the timing of the light emitted from the light emitting unit 220 based on the conveyance speed of the document to be read and the like, gives the timing to the light emission control unit 64, and the electrical signal input from the signal acquisition unit 66. It is output as one of the output values S_R, S_G, S_B, and S_UV according to the type of the light source that is emitting light at that time.

The light emission control unit 64 configures the light emission unit 220 in accordance with a command from the timing control unit 62. The R light source 220R, the G light source 220G, the B light source 220B, and the UV light source 220UV (typically, an LED (Light Emitting Diode)). Selectively drive one of the two. The signal acquisition unit 66 activates the photoelectric conversion element forming the line sensor 226 in accordance with a command from the timing control unit 62 to acquire an electric signal indicating a reflected image incident from the reading target, and the acquired electric signal. The signal is output to the timing control unit 62.

The image processing unit 50 receives the output values S_R, S_G, S_B, and S_UV from the controller board 60, and outputs the image data that is the read result. More specifically, the image processing unit 50 includes a fluorescence correction processing unit 52, an edge detection unit 54, and a color correction unit 56.

The fluorescence correction processing unit 52 executes the above-described fluorescence correction processing on the output values S_R, S_G, S_B, and S_UV from the controller board 60, and the correction values I_R, I_G, and I_B indicating the corrected image information. To generate. Typically, the fluorescence correction processing unit 52 has at least one of output values S_R, S_G, and S_B output when the light from the R light source 220R, the G light source 220G, and the B light source 220B is emitted to the reading target. From the output value, the component corresponding to the output value S_UV when the light from the UV light source 220UV is applied to the reading target is subtracted.

The edge detection unit 54 and the color correction unit 56 reproduce the image information based on the correction values I_R, I_G, and I_B from the fluorescence correction processing unit 52, and execute necessary input image processing to obtain the final image data. Output as. An image forming process or the like is executed based on the output image data.

In FIG. 9, as an example, in the fluorescence correction processing unit, a signal for each color output from the reading main body unit 2 is given to the image processing unit 50, and the input image processing is performed after the fluorescence correction processing is first executed. To be executed. By executing the fluorescence correction processing in the preceding stage of such general input image processing, it is possible to use various existing input image processing (for example, processing for RGB image data) without changing it. Further, the image processing unit 50 is configured to execute the fluorescence correction processing and the input image processing, so that a single semiconductor device including other input image processing (for example, ASIC (Application Specific Integrated Circuit)) Since it can be mounted with, the device configuration can be simplified and the cost can be reduced.

Note that some or all of the functions of the fluorescence correction processing unit 52 and the input image processing (such as the edge detection unit 54 and the color correction unit 56) included in the image processing unit 50 may be implemented in the reading main body unit 2. Alternatively, the functions shown in FIG. 14 may be realized by using a single system board or the like, or a part of the functions shown in FIG. 14 may be realized by a hard-wired circuit and the remaining functions may be executed by a processor. You may make it implement|achieve by doing.

The present invention does not limit the mounting form of the image reading apparatus, and those skilled in the art will appropriately mount the image reading apparatus using any technique that is actually available.

(E2: Functional configuration of fluorescence correction processing unit)
Next, an example of the functional configuration of the fluorescence correction processing section 52 of the image processing section 50 shown in FIG. 14 will be described. FIG. 15 is a schematic diagram showing an example of the functional configuration of the fluorescence correction processing section 52 of the image processing section 50 shown in FIG. The functional configuration of the fluorescence correction processing unit 52 shown in FIG. 15 may be realized by a hard-wired circuit or may be realized by executing a program by a processor.

With reference to FIG. 15, the fluorescence correction processing unit 52 has, as its components, output value buffers 522R, 522G, 522B, 522UV for storing output values S_R, S_G, S_B, S_B from the controller board 60, and subtraction. It includes the units 524R, 524G and 524B and the multipliers 526R, 526G and 526B.

As a correction for red, the multiplier 526R outputs a correction amount obtained by multiplying the output value S_UV when the UV light source 220UV stored in the output value buffer 522UV is turned on by the correction coefficient α_R to the subtractor 524R. The subtractor 524R subtracts the correction amount from the subtractor 524R from the output value S_R when the R light source 220R stored in the output value buffer 522R is turned on, and outputs it as the output value correction value I_R.

Similarly, for the corrections relating to green and blue, the subtractor 524G and the multiplier 526G, and the subtractor 524B and the multiplier 526B cooperate with each other to execute the processing, thereby realizing the fluorescence correction processing.

(E3: processing procedure)
Next, an image reading processing procedure in image reading device 4 according to the present embodiment will be described. FIG. 16 is a flowchart showing an image reading processing procedure in image reading device 4 according to the present embodiment. The steps shown in FIG. 16 may be implemented by the image processing unit 50 and the controller board 60 in cooperation with each other, or may be implemented by the program of the control device executing the program.

With reference to FIG. 16, when the image reading timing for the reading target arrives (YES in step S2), image reading device 4 selects one of the plurality of light sources constituting light emitting unit 220 according to a predetermined order. A light source is selected (step S4), and the light to be read is irradiated with the light from the selected light source (step S6). That is, the image reading device 4 causes the light emitting unit 220 including the R light source 220R, the G light source 220G, the B light source 220B, and the UV light source 220UV to generate any light in a predetermined order.

At the same time, the output value is obtained from the line sensor 226 and is stored in association with the selected light source and the current reading position (step S8). That is, in the image reading device 4, the output value indicating the brightness of each region of the reflected image generated by the irradiation of light on the reading object, which is sequentially output from the line sensor 226 (photoelectric conversion unit), corresponds to the wavelength characteristic of light (that is, , Color) and store.

Then, the image reading device 4 determines whether the output values corresponding to the plurality of light sources forming the light emitting unit 220 are aligned for one line (step S10). That is, it is determined whether or not a set of output values when the R light source 220R, the G light source 220G, the B light source 220B, and the UV light source 220UV are respectively turned on is already acquired.

When the output values corresponding to the plurality of light sources forming the light emitting unit 220 are not aligned for one line (NO in step S10), the image reading device 4 advances by ¼ dot from the current reading position. The read position is set as a new reading position (step S12), and it is determined whether the newly set reading position is within the valid range of the reading target (step S14). That is, it is determined whether or not the reading of the target surface of the reading target is completed. It should be noted that since reading is performed four times for reading one line (one dot in the sub-scanning direction), the reading position advances by 1/4 dot per lighting.

If the newly set reading position is within the effective range of the reading target (YES in step S14), the processes of step S4 and subsequent steps are repeated. On the other hand, when the newly set reading position is outside the effective range of the reading target (NO in step S14), the image reading process ends.

On the other hand, when the output values corresponding to the plurality of light sources forming the light emitting unit 220 are aligned for one line (YES in step S10), the image reading device 4 determines the image to be read from the stored output values. Generate information. When generating the image information to be read, the above-mentioned fluorescence correction is performed. More specifically, the image reading device 4 multiplies the output value S_UV when the UV light source 220UV is turned on by the correction coefficients α_R, α_G, and α_B to calculate the correction amount of each color (step S16) and outputs the output value. The correction values I_B, I_G, and I_B are calculated by subtracting the corresponding correction amounts from S_R, S_G, and S_B (step S18). Then, the processing from step S12 onward is executed.

The image information is acquired from the reading target according to the processing procedure as described above.
(E4: Light source lighting sequence)
Next, a preferable lighting sequence of the light sources in the fluorescence correction process in image reading device 4 according to the present embodiment will be described. FIG. 17 is a schematic diagram for explaining a preferable lighting sequence of the light sources in the fluorescence correction processing in image reading device 4 according to the present embodiment.

FIG. 17A shows a reading range when each light source is turned on during an image reading operation in the image reading device 4. Generally, in the one-line CIS reading method, when reading each line (each dot), the relative movement between the original and the line sensor is continuously performed without stopping. In association with this continuous relative movement, a plurality of light sources are sequentially turned on to acquire an image signal for each color. Therefore, as shown in FIG. 17A, reading is performed between light sources whose light emission order is adjacent. A predetermined amount of displacement (1/3 dot when three light sources are used, 1/4 dot when four light sources are used) occurs in the position.

Strictly considering, the output values S_R, S_G, S_B, and S_UV from the line sensor 226 mean values in different reading ranges of the reading target. Regarding the output values S_R, S_G, and S_B used for the image data, the reading position error can be corrected in consideration of the continuity in the sub-scanning direction, but the output value S_UV used only for the fluorescence correction processing is , It is difficult to make a correction that reflects the continuity in the sub-scanning direction.

Therefore, the B light source 220B, which has a short wavelength and is easily affected by the fluorescent component, and the UV light source 220UV, which measures the size of the fluorescent component, are adjacent to each other in the order of light emission, which is unique to the 1-line CIS reading method. It is possible to reduce the influence of the reading position error on the image quality. That is, of the four light sources of red, green, blue, and ultraviolet rays, the ultraviolet light source and the blue light source may be made to emit light in a continuous order.

In this way, the lighting order of the light sources is determined such that the B light source 220B and the UV light source 220UV emit light at least continuously, so that the accuracy of fluorescence correction can be improved.

<F. Wavelength characteristics of UV light source>
Next, the wavelength characteristic of UV light source 220UV used in image reading device 4 according to the present embodiment will be described.

As described above, in image reading device 4 according to the present embodiment, UV light source 220UV is used for measuring the size of the fluorescent component generated from the reading target. Therefore, it is preferable that the ultraviolet light emitted from the UV light source 220UV does not overlap the wavelength of the light source used for original image reading. That is, it is preferable that the UV light source 220UV for generating the light of the ultraviolet component does not overlap the emission wavelength of the B light source 220B. Therefore, for example, it is preferable to employ the UV light source 220UV that emits light having the following wavelength characteristics. FIG. 18 is a diagram showing an example of wavelength characteristics of the UV light source 220UV used in the image reading device 4 according to the present embodiment. FIG. 18 conceptually shows spectra of light generated by the UV light source 220UV and the B light source 220B.

In FIG. 18(A), there is no overlap between the wavelength characteristics of the ultraviolet light generated by the UV light source 220UV and the wavelength characteristics of the blue light generated by the B light source 220B, and each light is completely separated in terms of wavelength. The following is an example. As shown in FIG. 18A, the ultraviolet light and the visible light with which the reading target is irradiated are spectrally separated. That is, the wavelength of the light from the UV light source 220UV may be set so as not to overlap with the wavelength of the light from the B light source 220B. By using the UV light source 220UV that emits ultraviolet light having such wavelength characteristics, the accuracy of fluorescence correction can be improved.

FIG. 18B shows an example in which the peak emission wavelength of the ultraviolet light generated by the UV light source 220UV is 370 nm or less. As described above, by using the UV light source 220UV that emits ultraviolet light having a peak emission wavelength in the ultraviolet region, it is possible to suppress the wavelength interference with the blue light generated by the B light source 220B. That is, the peak emission wavelength of the light from the UV light source 220UV for generating the light of the ultraviolet component may be 370 nm or less.

FIG. 18C shows an example in which the intensity of ultraviolet light generated by the UV light source 220UV at 370 nm is ½ or less of the peak emission intensity of blue light generated by the B light source 220B. As described above, by using the UV light source 220UV having an emission characteristic sufficiently separated from the peak emission wavelength of blue light, it is possible to suppress the interference with the blue light generated by the B light source 220B on the wavelength. That is, the intensity of the wavelength component of 370 nm or more of the light from the UV light source 220UV for generating the light of the ultraviolet component may be ½ or less of the peak emission intensity of the B light source 220B.

Even if the UV light source 220UV separated in the spectrum cannot be prepared for the blue light generated by the B light source 220B, as shown in FIG. If the visible light component of the UV light source 220UV is sufficiently small as shown in (4), it is possible to prevent the visible component of the ultraviolet light from being generated and being erroneously excessively detected as the fluorescent component. That is, by adopting the UV light source 220UV having such a wavelength characteristic, it is possible to improve the correction accuracy of the fluorescence correction in the image reading device according to the present embodiment.

<G. Advantage>
In the image reading apparatus adopting the 1-line CIS reading method according to the present embodiment, in addition to the general three light sources (R light source, G light source, B light source), a UV light source that generates ultraviolet light and a reading target By adding a cut filter that cuts the ultraviolet light contained in the reflected light of, when the light from each light source is irradiated to the reading target by using the fluorescent component generated from the reading target when the ultraviolet light is radiated By correcting the obtained image signal, it is possible to improve the color reproducibility of the fluorescent color and improve the readability.

According to the image reading apparatus adopting the 1-line CIS reading method according to the present embodiment, the color reproducibility with respect to the drawing range of the reading object including the fluorescent dye is equivalent to that of the CCD reading method and the 3-line CIS reading method. Therefore, as compared with these reading methods, it is possible to realize a configuration having equivalent performance and lower cost.

The embodiments disclosed this time are to be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and is intended to include meanings equivalent to the claims and all modifications within the scope.

DESCRIPTION OF SYMBOLS 1 image forming apparatus, 2 main body section, 3 automatic document conveying section, 4 image reading apparatus, 5 image forming section, 6 sheet feeding section, 7 sheet discharging section, 8 operation panel, 21 slit glass, 22 first reading section (reading section) Part), 23 platen glass, 24 scanning unit, 25 traveling unit, 30 document transport path, 31 paper feed tray, 32 pickup roller, 33 paper feed roller pair, 34 intermediate roller pair, 35 registration roller pair, 36 first transport roller Pair, 37 Second conveyance roller pair, 38 Second reading unit, 39 Third conveyance roller pair, 40 Paper ejection roller, 41 Paper ejection tray, 42, 43 Reading roller, 46 Support rail, 50 Image processing unit, 52 Fluorescence correction Processing unit, 54 edge detection unit, 56 color correction unit, 60 controller board, 62 timing control unit, 64 light emission control unit, 66 signal acquisition unit, 70 document, 72, 82, 92 drawing portion, 80, 90 reproduced image, 220 Light emitting part, 220B, 220G, 220R, 220UV light source, 222 light guide, 224, 224R, 224G, 224B imaging lens, 226, 226R, 226G, 226B line sensor, 227R, 227G, 227B color filter, 228 cut filter, 522R, 522G, 522B, 522UV output value buffer, 524R, 524G, 524B subtractor, 526R, 526G, 526B multiplier.

Claims (11)

An image reading device for reading image information from an object to be read,
A red light source that generates light including a red wavelength component, a green light source that generates light including a green wavelength component, a blue light source that generates light including a blue wavelength component, and an ultraviolet light source that generates light including an ultraviolet component. A light emitting unit including
A light guide for uniformizing the light generated from the light emitting unit and irradiating the reading target.
A photoelectric conversion unit that outputs a value indicating the brightness of each region of the reflected image generated by irradiating the reading target with light,
A cut filter for blocking the ultraviolet component, which is arranged on the optical path from the reading target to the photoelectric conversion unit,
While generating any light from the light emitting unit in a predetermined order, each output value sequentially output from the photoelectric conversion unit, by processing in association with the wavelength characteristics of the corresponding light, And a control unit for generating image information to be read,
The process of generating the image information of the reading target is at least one of output values output when the red light source, the green light source, and the light from the blue light source are emitted to the reading target, respectively, An image reading apparatus including a first correction process for reducing a component corresponding to an output value when light from the ultraviolet light source is applied to the reading target. The first correction process is a wavelength at least partially overlapping with a wavelength of fluorescence that can be generated when the reading target is irradiated with light from the ultraviolet light source among the red light source, the green light source, and the blue light source. The image reading apparatus according to claim 1, wherein the image reading apparatus is applied to an output value corresponding to a light source that generates light having a. The first correction process is a component corresponding to the output value when the reading target is irradiated with the light from the ultraviolet light source with respect to the output value when the reading target is irradiated with the light from the blue light source. The image reading apparatus according to claim 1, which is a process for reducing The process of generating the image information of the reading target is the first correction process among output values output when the reading target is irradiated with light from the red light source, the green light source, and the blue light source. The second correction process of adding a component according to an output value when the reading target is irradiated with light from the ultraviolet light source, to at least one of output values to which is not applied. The image reading device according to any one of 3 above. The process of generating the image information of the reading target is performed so that the output value when the reading target is irradiated with light having a short wavelength is larger than the output value when the reading target is irradiated with the light from the ultraviolet light source. The image reading apparatus according to claim 1, further comprising a process of subtracting a value obtained by multiplying a large coefficient. The image reading device according to claim 1, wherein the wavelength of the light from the ultraviolet light source is set so as not to overlap with the wavelength of the light from the blue light source. The image reading device according to claim 1, wherein a peak emission wavelength of light from the ultraviolet light source is 370 nm or less. The image reading device according to claim 1, wherein the intensity of the wavelength component of 370 nm or more of the light from the ultraviolet light source is ½ or less of the peak intensity of the light from the blue light source. The image reading apparatus according to claim 1, wherein the predetermined order is determined so that the blue light source and the ultraviolet light source emit light at least continuously. An image forming apparatus,
An image reading device that reads image information from a reading target,
An image forming unit that forms an image based on image information read by the image reading device,
The image reading device,
A red light source that generates light including a red wavelength component, a green light source that generates light including a green wavelength component, a blue light source that generates light including a blue wavelength component, and an ultraviolet light source that generates light including an ultraviolet component. A light emitting unit including
A light guide for uniformizing the light generated from the light emitting unit and irradiating the reading target.
A photoelectric conversion unit that outputs a value indicating the brightness of each region of the reflected image generated by irradiating the reading target with light,
A cut filter for blocking the ultraviolet component, which is arranged on the optical path from the reading target to the photoelectric conversion unit,
While generating any light from the light emitting unit in a predetermined order, each output value sequentially output from the photoelectric conversion unit, by processing in association with the wavelength characteristics of the corresponding light, And a control unit for generating image information to be read,
The process of generating the image information of the reading target is at least one of output values output when the red light source, the green light source, and the light from the blue light source are emitted to the reading target, respectively, An image forming apparatus including a first correction process for reducing a component corresponding to an output value when light from the ultraviolet light source is applied to the reading target. An image reading method for reading image information from a reading target,
A red light source that generates light including a red wavelength component, a green light source that generates light including a green wavelength component, a blue light source that generates light including a blue wavelength component, and an ultraviolet light source that generates light including an ultraviolet component. From a light emitting unit including a step of generating any light in a predetermined order, the light generated from the light emitting unit is irradiated onto the reading target after being uniformized by a light guide, On the optical path from the reading target to the photoelectric conversion unit, a cut filter for blocking the ultraviolet component is arranged,
Sequentially output from the photoelectric conversion unit, a step of storing the output value indicating the luminance of each region of the reflected image generated by the light irradiation to the reading target in association with the wavelength characteristic of the corresponding light,
Generating image information to be read from the stored output value,
The step of generating the image information of the reading object, from the red light source, the green light source, from at least one output value of the output values respectively output when the light from the blue light source is irradiated to the reading object, An image reading method comprising a step of subtracting a component corresponding to an output value when the light from the ultraviolet light source is applied to the reading object.