Patent Description:
In recent years, there has been known a technique for determining the authenticity of a document by reading, with invisible light, invisible information embedded in the document for the purpose of document security.

<CIT> (<CIT>) assumes application to sensors, disclosing a technique for detecting an object with sensitivity to a visible spectrum, and for detecting an object and a pupil with sensitivity to an invisible (or near-infrared (NIR)) spectrum.

<CIT> assumes application to security cameras, disclosing a technique for monitoring with sensitivity to visible to invisible (i.e., NIR) spectra at night.

<CIT> relates to an image processing device, an imaging device, an image processing method, and an image processing program, and more particularly, to a technology for performing a point image restoration process on the basis of a point spread function on a visible light image and a near-infrared light image.

<CIT> discloses an image processing device that enables a visible image and a near-infrared image to be generated with a simple configuration.

<CIT> relates to a method and an electronic device for producing a composite image.

<CIT> relates to an imaging device and an imaging system having higher visibility.

<CIT> relates to image processing, and more particularly, to fusing an RGB image with a near infrared image from among images obtained using a multi-spectral filter array.

<CIT> relates to an imaging apparatus that is capable of capturing a synthesized image of a visible-spectrum image and an infrared-spectrum image resulting from an infrared-fluorescing substance.

<CIT> relates to an image reading apparatus and an image scanning method in each of which a document is read (scanned) so as to prepare image data for the document.

<CIT> provides an image processing apparatus that includes an image acquisition unit that acquires a visible light image and a non-visible light image corresponding to the visible light image, and a noise reduction unit that reduces noises of the visible light image by using the non-visible light image.

<CIT> relates to digital image sensing art for acquiring image data using an image sensing element as an image sensor.

Visible and invisible images exhibit different image characteristics at the time of reading, and therefore, the visible and invisible images are to be subjected to different image correction processes.

Typical techniques suppose correction of a mixed image constructed of the visible and invisible images. However, the typical techniques do not suppose independent usage of the visible and invisible images. In short, the typical techniques have difficulties in providing users with the visible and invisible images in qualities suitable for each image.

In light of the above-described problems, it is a general object of the present disclosure to restore an invisible image quality to be equivalent to a visible image quality, thereby providing users with the images.

The invention is set out by the appended set of claims. The embodiments and/or examples of the following description which are not covered by the claims, are provided for illustrative purpose only and are only intended to assist the reader in understanding the present invention. However, such embodiments and/or examples which are not covered by the claims do not form part of the present invention that is solely defined by the claims. Accordingly, the image is separated into a visible image and an invisible image before different image correction processes are performed on the visible image and the invisible image, respectively. Accordingly, the invisible image quality is restored to be equivalent to the visible image quality. Thus, the images are providable to users.

A more complete appreciation of the embodiments and many of the attendant advantages and features thereof can be readily obtained and understood from the following detailed description with reference to the accompanying drawings, wherein:.

However, the disclosure of the present specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve a similar result.

Although the embodiments are described with technical limitations with reference to the attached drawings, such description is not intended to limit the scope of the disclosure and not all of the components or elements described in the embodiments of the present disclosure are indispensable to the present disclosure.

In a later-described comparative example, embodiment, and exemplary variation, for the sake of simplicity like reference numerals are given to identical or corresponding constituent elements such as parts and materials having the same functions, and redundant descriptions thereof are omitted unless otherwise required.

Referring to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, embodiments of the present disclosure are described below.

Now, a description is given of a first embodiment of the present disclosure.

<FIG> is a block diagram illustrating a system configuration of an image processing apparatus <NUM> according to the first embodiment.

The image processing apparatus <NUM> according to the present embodiment is an image forming system generally called a multifunction peripheral, printer, or product (MFP) having at least two of copying, printing, scanning, and facsimile functions.

An image processing apparatus <NUM> illustrated in <FIG> includes a reading unit <NUM> serving as an image reading device, an image correction processing unit <NUM>, a bus controller <NUM>, a hard disk drive (HDD) <NUM>, a central processing unit (CPU) <NUM>, a memory <NUM>, a plotter <NUM> serving as an image forming device, a plotter interface (I/F) <NUM>, a control panel <NUM>, a line I/F <NUM>, an external I/F <NUM>.

The reading unit <NUM> includes an image sensor (or line sensor) <NUM> and a light source <NUM> as illustrated in <FIG>. The reading unit <NUM> further includes an analog-to-digital (A/D) converter and drive circuits that drive the image sensor <NUM>, the light source <NUM>, and the A/D converter. The reading unit <NUM> scans a document placed and acquires the density information of the document. From the density information, the reading unit <NUM> generates and outputs <NUM>-bit red, green, and blue (RGB) digital image data of <NUM> dots per inch (dpi). The reading unit <NUM> uses a xenon lamp or a light emitting diode (LED) as the light source <NUM>.

The image correction processing unit <NUM> processes the digital image data output from the reading unit <NUM>. Then, the image correction processing unit <NUM> outputs the image data thus processed. A detailed description thereof is deferred.

The bus controller <NUM> controls a data bus that exchanges various kinds of data such as image data and control commands in the image processing apparatus <NUM>. The bus controller <NUM> also functions as a bridge between a plurality of bus standards. In the present embodiment, the bus controller <NUM>, as an application specific integrated circuit (ASIC), is connected to each of the image correction processing unit <NUM> and the CPU <NUM> via a peripheral component interconnect express (PCI-Express) bus while being connected to the HDD <NUM> via an advanced technology attachment (ATA) bus.

The HDD <NUM> is a large-sized storage device, as used in, e.g., a personal computer, for storing electronic data. In the image processing apparatus <NUM>, the HDD <NUM> mainly stores digital image data and associated information of the digital image data (e.g., setting mode). In the present embodiment, the HDD <NUM> is connected to the bus controller <NUM> through ATA bus connection standardized by extending integrated drive electronics (IDE).

The CPU <NUM> is a microprocessor that generally controls the image processing apparatus <NUM>. In the present embodiment, the CPU <NUM> is a recently widespread integrated CPU having a single CPU core with additional functions. Specifically, in the present embodiment, the CPU <NUM> is an integrated CPU having a connecting function with a general-purpose standard I/F and a bus connecting function using a crossbar switch.

The memory <NUM> is a volatile memory that stores temporarily exchanged data so as to absorb, e.g., a speed difference in connecting a plurality of bus standards and a processing speed difference of a connected component. In addition, the memory <NUM> temporarily stores, e.g., programs and intermediate processing data when the CPU <NUM> controls the image processing apparatus <NUM>. In the present embodiment, the memory <NUM> is a dual inline memory module (DIMM). The DIMM is used in standardized personal computers.

In response to cyan, magenta, yellow, and black (CMYK) digital image data, the plotter <NUM> outputs an image on a recording medium according to the CMYK digital image data, through an electrophotographic process using a laser beam or with an inkjet.

In response to the CMYK digital image data transmitted via the general-purpose standard I/F as an integrated part of the CPU <NUM>, the plotter I/F <NUM> performs bus bridging for outputting the CMYK digital image data to an I/F dedicated to the plotter <NUM>. The PCI-Express bus is the general-purpose standard I/F used in the present embodiment.

The control panel <NUM> is an interface between the image processing apparatus <NUM> and, e.g., users. The control panel <NUM> includes, e.g., a liquid crystal display (LCD) provided with a touch panel, and a key group including various processing mode setting keys, numeric keys, and a start key. The control panel <NUM> displays, on the LCD, various statuses and operating instructions of the image processing apparatus <NUM>. The control panel <NUM> also detects inputs from the users via the touch panel and the key switch group. In the present embodiment, the control panel <NUM> is connected to the CPU <NUM> via the PCI-Express bus.

The line I/F <NUM> connects the PCI-Express bus and a telephone line. The line I/F <NUM> enables the image processing apparatus <NUM> to exchange various kinds of data with a facsimile machine <NUM>, which is an image output device (or image processor), via the telephone line. The facsimile machine <NUM> is a general facsimile machine that exchanges image data with the image processing apparatus <NUM> via the telephone line.

The external I/F <NUM> connects the PCI-Express bus and a computer <NUM>, such as a personal computer, as an image output device (or image processor). The external I/F <NUM> enables the image processing apparatus <NUM> to exchange various kinds of data with the computer <NUM>. In the present embodiment, the external I/F is connected to the computer <NUM> via a network such as Ethernet (registered trademark). That is, the image processing apparatus <NUM> is connected to the network via the external I/F <NUM>. Note that the computer <NUM> transmits various instructions and exchanges image data with the image processing apparatus <NUM> via application software and drivers installed in the computer <NUM>.

Referring now to <FIG>, a description is given of reading of a visible image by the reading unit <NUM>.

<FIG> is a graph illustrating spectral sensitivity characteristics of the image sensor <NUM> of the reading unit <NUM> described above.

As illustrated in <FIG>, the image sensor <NUM>, provided with a color filter, of the reading unit <NUM> has a sensitivity to a visible spectrum such as RGB and to an invisible spectrum not less than about <NUM>.

<FIG> is a graph illustrating a spectrum of the light source <NUM> of the reading unit <NUM>.

In the present example, <FIG> illustrates a spectrum of a xenon lamp. As illustrated in <FIG>, the xenon lamp has a weak spectral intensity in a near-infrared (NIR) spectrum, which is an invisible spectrum.

That is, a visible image read by the reading unit <NUM> with the image sensor <NUM> and the light source <NUM> is an image subjected to visible light together with NIR light.

Referring now to <FIG>, a description is given of difficulties that the typical techniques face in reading a visible image as described above.

<FIG> is a plan view of an edge image. <FIG> is a graph-based diagram illustrating relationships between a signal level and a position. <FIG> is a graph illustrating the relationship between the signal level and the position after image correction. <FIG> is a graph illustrating the relationship between the signal level and the position after image separation.

Specifically, <FIG> illustrate intensity images of visible and invisible signal components when the edge image illustrated in <FIG> is read. In short, <FIG> illustrate signal level images.

The reading unit <NUM> includes a lens that is designed optimally for reading a visible image while keeping the image quality. Signal levels of readings from the reading unit <NUM> depend on the wavelength due to the light amount of the light source <NUM> and the spectral sensitivity characteristics of the image sensor <NUM>. Compared to the visible signal level, the NIR signal level stays low. In addition, an upper graph of <FIG> illustrates a great difference between the visible signal level and the NIR signal level.

That is, as illustrated in <FIG>, a visible image, a NIR image, and a composite or synthesis image constructed of visible and NIR images (hereinafter referred to as a visible and NIR image) exhibit different signal characteristics from each other.

<FIG> illustrate a typical case in which a composite or synthesis image is optimized and then separated into images.

Specifically, <FIG> illustrates a signal characteristic of the visible and NIR image subjected to image correction, such as modulation transfer function (MTF) correction. In other words, <FIG> illustrates the signal characteristic of the visible and NIR image corrected to be equivalent to a visible image.

As illustrated in <FIG>, the visible and NIR image corrected with an optimum parameter exhibits a given MTF characteristic. However, as illustrated in <FIG>, when the composite image corrected as illustrated in <FIG> is separated into the visible image and the NIR image, the separated NIR image keeps in a low signal level. That is, the NIR signal component fails to achieve a target MTF characteristic. In short, a typical optimization of a composite image does not achieve an optimum correction of a single image after image separation.

In the image processing apparatus <NUM> according to the present embodiment, the reading unit <NUM> reads a visible image in a general document scanning, which is a main operation of the reading unit <NUM>. On the other hand, the reading unit <NUM> reads an invisible image in an authenticity determination scanning. Since visible and invisible images have different kinds of information, the visible and invisible images may be used separately, rather than as a composite image.

To address such a situation, according to the present embodiment, the image processing apparatus <NUM> separates the visible and NIR images from each other, and then corrects the visible and NIR images thus separated. Note that separating a composite image into a single visible image and a single invisible image is defined as image separation.

The present embodiment describes and illustrates the NIR image as an invisible image. Alternatively, the invisible image may be an ultraviolet image.

<FIG> is a block diagram illustrating a configuration of the reading unit <NUM> and the image correction processing unit <NUM> in the image processing apparatus <NUM>.

As illustrated in <FIG>, the reading unit <NUM> includes an image separating unit <NUM> in addition to the image sensor <NUM> and the light source <NUM> described above. The image sensor <NUM> is a charge-coupled device (CCD) photovoltaic device. As described above, the light source <NUM> is a xenon lamp or an LED.

The image correction processing unit <NUM> includes a gamma correcting unit <NUM>, a spatial filtering unit <NUM>, a color correcting unit <NUM>, and an image correction control unit <NUM>.

The gamma correcting unit <NUM> converts a gamma (γ) characteristic of RGB image data received from the reading unit <NUM> into a predetermined characteristic (e.g., <NUM>/<NUM>^).

The spatial filtering unit <NUM> corrects the MTF characteristic of the reading unit <NUM> and converts a frequency characteristic of read image to prevent moire, thereby clarifying and smoothing images. The spatial filtering unit <NUM> unifies the sharpness of the RGB image data into a predetermined characteristic. For example, when a reference chart is scanned, the spatial filtering unit <NUM> converts lines per inch (lpi) to be a predetermined MTF characteristic value for each given image quality mode.

The color correcting unit <NUM> unifies the colors of RGB image data into RGB image data values of a predetermined characteristic, such as standard Red Green Blue (sRGB) and optional Red Green Blue (opRGB). In the present embodiment, the color correcting unit <NUM> converts the color space to be the standard color space, for example. Note that the present embodiment employs a three-dimensional lookup method as a color converting method.

The image correction control unit <NUM> sets process parameters for the gamma correcting unit <NUM>, the spatial filtering unit <NUM>, and the color correcting unit <NUM>.

The image correction control unit <NUM> includes a controller such as a CPU and storage devices such as a read only memory (ROM) and a random access memory (RAM). Thus, the image correction control unit <NUM> has a hardware configuration using a general computer. The CPU operating according to programs stored in the storage devices causes the image correction control unit <NUM> to execute various processes.

The programs executed by the image correction control unit <NUM> is carried by a computer-readable carrier medium, such as a compact disc read-only memory (CD-ROM), a flexible disk (FD), a compact disc-recordable (CD-R), or a digital versatile disk (DVD), in an installable or executable format file. Thus, the programs are providable.

Alternatively, the programs executed by the image correction control unit <NUM> may be stored in a computer connected to a network such as the Internet and downloaded via the network, thus being providable. Alternatively, the programs executed by the image correction control unit <NUM> may be provided or distributed via a network such as the Internet. Alternatively, the programs executed by the image correction control unit <NUM> may be incorporated into, e.g., a ROM, in advance, thus being providable.

Note that the image correction control unit <NUM> may be implemented by hardware such as an integrated circuit (IC).

Image data having characteristics unified by the color correcting unit <NUM> and the gamma correcting unit <NUM> that correct the scanner characteristics of the reading unit <NUM> basically is stored inside the image processing apparatus <NUM>. The image data stored inside the image processing apparatus <NUM> is converted into image signals suitable for the characteristics of an output destination when the image data is reused thereafter.

With continued reference to <FIG>, a description is given of the image separation performed before the image correction. As illustrated in <FIG>, the reading unit <NUM> irradiates a document with light from the light source <NUM>. The reading unit <NUM> reads the reflected light from the document with the image sensor <NUM>. Thus, the reading unit <NUM> reads an image of the document. A signal indicating the image thus read is input into the image separating unit <NUM>. In response to the signal, the image separating unit <NUM> separates the image into visible and NIR images. The separated image data is input into the image correction processing unit <NUM>.

As illustrated in <FIG>, the image separating unit <NUM> prepares three RGB channels and a NIR-dedicated channel. Thus, the present embodiment enables simultaneous processing by use of different channels, that is, visible RGB channels and NIR-dedicated channel.

In the image correction processing unit <NUM>, the gamma correcting unit <NUM>, the spatial filtering unit <NUM>, and the color correcting unit <NUM> process the separated images or image signals input from the image separating unit <NUM>. Specifically, in the image correction processing unit <NUM>, for example, the gamma correcting unit <NUM> changes the background removal correction intensities. The spatial filtering unit <NUM> changes the MTF correction intensities. The color correcting unit <NUM> changes the color conversion coefficients.

Further, with the process parameters set by the image correction control unit <NUM>, the image correction processing unit <NUM> corrects the separated images with different intensities according to the image type. That is, when correcting a visible image, the image correction processing unit <NUM> performs an image correction process suitable for the visible image. On the other hand, when correcting a NIR image, the image correction processing unit <NUM> performs an image correction process suitable for the NIR image.

<FIG> is a block diagram illustrating a way of the image separation.

As illustrated in <FIG>, the image separating unit <NUM> includes the light source <NUM>. The image separating unit <NUM> controls the light source <NUM> that emits light upon scanning, thereby performing the image separation. Specifically, the light source <NUM> includes a visible light source 63A and an invisible light source 63B.

<FIG> illustrate conditions of the visible light source 63A and the invisible light source 63B switched therebetween upon the image separation.

Specifically, <FIG> is a graph illustrating spectral sensitivity characteristics of the image sensor <NUM>. As described above with reference to <FIG>, the image sensor <NUM> of the reading unit <NUM> has a sensitivity to a visible spectrum such as RGB and to a NIR spectrum not less than about <NUM>.

<FIG> is a graph illustrating a relationship between an emission intensity of the visible light source 63A and a wavelength. <FIG> is a graph illustrating a relationship between an emission intensity of the invisible light source 63B and the wavelength.

The visible light source 63A of the light source <NUM> is a light source that does not have an emission intensity in the NIR spectrum not less than about <NUM>. On the other hand, the invisible light source 63B of the light source <NUM> is a light source that has an emission intensity in a spectrum of from about <NUM> to about <NUM>. With such a configuration, the image separating unit <NUM> emits light with the visible light source 63A of the light source <NUM> upon a scanning operation. Upon another scanning operation, the image separating unit <NUM> emits light with the invisible light source 63B of the light source <NUM>. Thus, the image separating unit <NUM> outputs visible and NIR images as output images.

Note that, to acquire both the visible image and the NIR image, the reading unit <NUM> scans the image twice by switching between the visible light source 63A and the invisible light source 63B. Alternatively, the reading unit <NUM> may scan the image once while sequentially switching between and turning on the visible light source 63A and the invisible light source 63B, thereby acquiring the visible and invisible images at one time.

The image correction processing unit <NUM> corrects the images thus acquired. In the image correction processing unit <NUM>, the image correction control unit <NUM> changes process parameters according to the image type (i.e., visible image or invisible image) or a user mode. Accordingly, the image correction processing unit <NUM> performs an optimal image correction for each mode and image type.

Referring now to <FIG>, a description is given of control executed by the image correction control unit <NUM>.

<FIG> is a block diagram illustrating a configuration of the image correction processing unit <NUM>.

Specifically, <FIG> illustrates an image correcting process performed by the image correction control unit <NUM> to match the image characteristics.

The image correction control unit <NUM> corrects visible and invisible images to match an image characteristic of the visible image and an image characteristic of the invisible image. In other words, the visible and invisible images corrected exhibit identical image characteristics. Specifically, the image correction control unit <NUM> sets process parameters corresponding to the image characteristics of the visible and invisible images so as to match the image characteristics of the visible and invisible images, thus correcting the visible and invisible images. The image qualities matched as described above enable users to equally handle the visible and invisible image outputs.

As illustrated in <FIG>, the image correction control unit <NUM> includes an image characteristic difference retaining unit <NUM> and a parameter setting unit <NUM> to match the image characteristics. Specifically, the image characteristic difference retaining unit <NUM> retains an image characteristic difference between the visible and invisible images, that is, a difference between the image characteristic of the visible image and the image characteristic of the invisible image. The parameter setting unit <NUM> sets parameters for the gamma correcting unit <NUM> and the like. The image correction control unit <NUM> sets parameters for the gamma correcting unit <NUM>, the spatial filtering unit <NUM>, and the color correcting unit <NUM> according to the image characteristic difference retained by the image characteristic difference retaining unit <NUM>. The image correction control unit <NUM> sets parameters so as to absorb the image characteristic difference between the visible and invisible images, thereby attaining closer image qualities of the visible and invisible images after image processing.

Now, a description is given of the parameter setting according to the image characteristic difference. In the present embodiment, the spatial filtering unit <NUM> restores the MTF with an MTF intensity difference between the visible and invisible images, that is, a difference between an MTF intensity of the visible image and an MTF intensity of the invisible image, thereby equalizing the MTF intensities of the visible and invisible images.

Referring now to <FIG>, a description is given of determination of an MTF restoration intensity by use of an MTF characteristic.

Initially with reference to <FIG>, a description is given of an MTF issue in visible image reading and invisible image reading.

<FIG> is a diagram illustrating an input document that includes black, green, and blue letters as an image. <FIG> is a diagram illustrating RGB images of the input document acquired by visible image reading. <FIG> is a diagram illustrating a NIR image of the input document acquired by invisible image reading.

Black letters printed with black ink or black toner generally have a characteristic of absorbing the NIR component. Therefore, as illustrated in <FIG>, the black letter printed on the document remains as an image. General scanners that mainly read visible spectrum images are optically designed to be optimized for the visible spectrum. Therefore, unlike the visible spectrum images, invisible spectrum images read by such general scanners are blurred as illustrated in <FIG>, compared to the visible spectrum images, due to aberration of the lens.

Referring now to <FIG>, a description is given of spatial filtering.

The spatial filtering includes edge enhancement and dot smoothing on an input image, thereby correcting the image quality.

A description is now given of MTF correction by acutance improvement.

<FIG> is a graph illustrating MTF characteristics of visible and invisible images.

As illustrated in <FIG>, the invisible image exhibits an MTF characteristic inferior to the MTF characteristic of the visible image because of a relatively large aberration of the lens. In addition, the degradation of the MTF is greater as the spatial frequency is higher. Note that the MTF is measurable by a general method.

<FIG> is a graph illustrating an MTF characteristic difference between the visible and invisible images, that is, a difference between an MTF characteristic of the visible image and an MTF characteristic of the invisible image.

As illustrated in <FIG>, the MTF characteristic difference is generated for each spatial frequency.

<FIG> is a graph illustrating frequency characteristics of spatial filters according to the MTF characteristic difference.

In the present embodiment, the spatial filtering unit <NUM> performs filtering such that a spatial filter for the invisible image has a frequency characteristic according to the MTF characteristic difference, with respect to a frequency characteristic of a spatial filter set for the visible image. After the spatial filtering, the MTF characteristics become equivalent between the visible image and the invisible image. The spatial filter for the invisible image has a frequency characteristic to absorb the MTF characteristic difference between the visible and invisible images. Specifically, the spatial filtering unit <NUM> superimposes data of the MTF characteristic difference on the characteristic of the spatial filter for the visible image, thereby generating the spatial filter. The filter size may limit the filters that can be generated. In such a case, a spatial filter may be generated that absorbs the difference simply at a typical spatial frequency.

With such a configuration, the invisible image, which is blurred greater than the visible image, is corrected simply for the difference in blurring degree of the visible and invisible image. Thus, the invisible image has a quality equal to the visible image.

According to the present embodiment, the image separating unit <NUM> separates an image into a visible image and an invisible image. Then, the image correction processing unit <NUM> performs different image correction processes on the visible image and the invisible image, respectively. Accordingly, the invisible image quality is restored to be equivalent to the visible image quality. Thus, the images are providable to users.

In addition, according to the present embodiment, simply selecting an appropriate light source enables the image separation with a simple configuration and a reduced cost.

Further, according to the present embodiment, the visible and invisible images have identical qualities by changing a correction intensity according to the difference between the visible and invisible images.

Note that, in the present embodiment, the image separating unit <NUM> prepares the NIR-dedicated channel in addition to the three RGB channels. However, the channels are not limited to the RGB channels and the NIR-dedicated channel.

<FIG> is a block diagram illustrating a variation of the configuration of the reading unit <NUM> and the image correction processing unit <NUM> of <FIG>.

As illustrated in <FIG>, the image separating unit <NUM> may execute NIR processing by use of the RGB channels as common channels. In the present example of <FIG>, the image separating unit <NUM> executes the NIR processing by use of the G channel.

Alternatively, the channel for transmission of the NIR data may be the R channel or the B channel. Such use of a visible channel as a common channel to transmit visible and invisible image data prevents an increase in size of the image processing circuit.

The image correction control may be altered according to a mode selected by, e.g., a user.

<FIG> is a block diagram illustrating another variation of the configuration of the reading unit <NUM> and the image correction processing unit <NUM> of <FIG>.

As described above with reference to <FIG>, the reading unit <NUM> reads a visible image in the general document scanning. On the other hand, the reading unit <NUM> reads an invisible image in the authenticity determination scanning. In short, the reading unit <NUM> reads a visible or invisible image depending on the scanning purpose. For example, as described above with reference to <FIG>, in a case in which the signals are subjected to peak normalization to maximize the dynamic range, the signal levels of the separated visible and NIR images are different from the signal levels of visible and NIR images read separately. To address such a situation, the image correction control may be altered.

In order to alter the image correction control, for example, the reading unit <NUM> includes a mode selecting unit <NUM> as illustrated in <FIG>. The mode selecting unit <NUM> has a mode selecting function that allows, e.g., a user to select a mode to acquire a given image. According to the mode selected by the user, the mode selecting unit <NUM> causes the image sensor <NUM> to acquire the given image. Meanwhile, the mode selecting unit <NUM> switches between the process parameters for the image correction processes that are executed after the image separation of the given image acquired.

By contrast, when the user desires to acquire visible and NIR images and selects a visible/NIR scan mode, the mode selecting unit <NUM> turns on the visible light source 63A and the invisible light source 63B (in this case, a NIR light source) of the light source <NUM> so that the image sensor <NUM> acquires a composite image including the visible (i.e., RGB) image and the NIR image. The image separating unit <NUM> performs the image separation on the composite image acquired. In the subsequent image correction process, the image correction processing unit <NUM> corrects the visible image and the NIR image with a parameter B and a parameter B', respectively.

Although the image correction processing unit <NUM> receives the visible and NIR images from the image separating unit <NUM> like the example described above with reference to <FIG>, the image correction processing unit <NUM> of the present variation corrects the visible and NIR images with the process parameters changed by the image correction control unit <NUM> of the image correction processing unit <NUM> according to the mode selected by the user.

Referring now to <FIG>, a description is given of a second embodiment of the present disclosure.

Unlike the image processing apparatus <NUM> according to the first embodiment, the image processing apparatus <NUM> according to the second embodiment performs the image separation by use of an optical filter such as a spectrum cut filter. A redundant description of identical features in the first and second embodiments is herein omitted; whereas a description is now given of features of the second embodiment different from the features of the first embodiment.

<FIG> is a block diagram illustrating a configuration of the reading unit <NUM> and the image correction processing unit <NUM> of the image processing apparatus <NUM> according to the second embodiment.

As illustrated in <FIG>, the image separating unit <NUM> includes an optical filter <NUM> (e.g., spectrum cut filter) to perform the image separation. Examples of the optical filter <NUM> include an infrared cut filter and a visible spectrum cut filter.

Each of <FIG> illustrates a graph of a spectrum of a filter.

Specifically, <FIG> is a graph illustrating a spectrum of an infrared cut filter.

Infrared cut filters exhibit a characteristic of cutting an image in the invisible spectrum not less than about <NUM>. The image separating unit <NUM> causes the infrared cut filter to cut an invisible spectrum image from a visible read image, thereby acquiring an image including a visible spectrum alone.

<FIG> is a graph illustrating a spectrum of a visible spectrum cut filter.

Visible spectrum cut filters exhibit a characteristic of cutting an image in the visible spectrum less than about <NUM>. The image separating unit <NUM> causes the visible spectrum cut filter to cut a visible spectrum image from a NIR read image, thereby acquiring an image including a NIR spectrum alone.

When the image separating unit <NUM> uses the optical filter <NUM> as described above, the light source <NUM> turns on the visible light source 63A and the invisible light source 63B at one time.

Thus, the present embodiment enhances a simple lighting control of the light source <NUM> according to the mode. The present embodiment also enhances reduction of the user waiting time with image acquisition by a single scan.

Referring now to <FIG>, a description is given of a third embodiment of the present disclosure.

Unlike the image processing apparatus <NUM> according to the first embodiment, the image processing apparatus <NUM> according to the third embodiment performs the image separation by image processing. A redundant description of identical features in the first and third embodiments is herein omitted; whereas a description is now given of features of the third embodiment different from the features of the first embodiment.

<FIG> is a block diagram illustrating a configuration of the reading unit <NUM> and the image correction processing unit <NUM> of the image processing apparatus <NUM> according to the third embodiment.

As illustrated in <FIG>, the reading unit <NUM> of the image processing apparatus <NUM> turns on the visible light source 63A and the invisible light source 63B of the light source <NUM> at one time to irradiate a document with light. The reading unit <NUM> reads the reflected light from the document with the image sensor <NUM>. Then, visible and NIR signals indicating visible and invisible images read at one time are input into the image separating unit <NUM> together with a white signal indicating an image read so as to include a full spectrum.

The image separating unit <NUM> performs, e.g., masking operation by use of the visible and NIR signals and the white signal thus input, thereby separating the signals into RGB signals and a NIR signal.

The image correction processing unit <NUM> corrects the visible and NIR images thus separated by the image separating unit <NUM>.

Note that the image separating unit <NUM> may be included in the image correction processing unit <NUM>.

Thus, the present embodiment omits the need to provide an optical filter (e.g., spectrum cut filter), thereby reducing costs. In addition, according to the present embodiment, the reading unit <NUM> turns on the visible light source 63A and the invisible light source 63B of the light source <NUM> at one time to read an image with a single scan, thereby reducing the user waiting time.

Referring now to <FIG>, a description is given of a fourth embodiment of the present disclosure.

Unlike the image processing apparatus <NUM> according to the first embodiment, the image processing apparatus <NUM> according to the fourth embodiment performs the image separation by image processing. A redundant description of identical features in the first and fourth embodiments is herein omitted; whereas a description is now given of features of the fourth embodiment different from the features of the first embodiment.

<FIG> is a block diagram illustrating a configuration of the reading unit <NUM> and the image correction processing unit <NUM> of the image processing apparatus <NUM> according to the fourth embodiment.

In the reading unit <NUM> of the image processing apparatus <NUM> illustrated in <FIG>, the image sensor <NUM> is provided with a visible spectrum cut filter <NUM>. Visible spectrum cut filters exhibit a characteristic of cutting an image in the visible spectrum less than about <NUM>. By using the visible spectrum cut filter <NUM> in NIR image reading, the reading unit <NUM> acquires an image including a NIR spectrum alone.

As illustrated in <FIG>, the reading unit <NUM> of the image processing apparatus <NUM> turns on the visible light source 63A and the invisible light source 63B of the light source <NUM> at one time to irradiate a document with light. The reading unit <NUM> reads the reflected light from the document with the image sensor <NUM>. Then, visible and NIR signals indicating visible and invisible images read at one time are input into the image separating unit <NUM> together with a NIR signal indicating a NIR image.

The image separating unit <NUM> performs, e.g., masking operation by use of the visible and NIR signals and the NIR signal thus input, thereby separating the signals into RGB signals and a NIR signal.

Thus, according to the present embodiment, the reading unit <NUM> turns on the visible light source 63A and the invisible light source 63B of the light source <NUM> at one time to read an image with a single scan, thereby reducing the user waiting time.

Referring now to <FIG>, a description is given of a fifth embodiment of the present disclosure.

Unlike the image processing apparatus <NUM> according to the first embodiment, the image processing apparatus <NUM> according to the fifth embodiment determines a bleed-through removal intensity by use of a bleed-through intensity characteristic. A redundant description of identical features in the first and fifth embodiments is herein omitted; whereas a description is now given of features of the fifth embodiment different from the features of the first embodiment.

Initially, a description is given of the parameter setting according to the image characteristic difference. In the present embodiment, the gamma correcting unit <NUM> performs the bleed-through removal by use of a bleed-through intensity difference between the visible and invisible images, that is, a difference between a bleed-through intensity of the visible image and a bleed-through intensity of the invisible image, thereby equalizing the bleed-through intensities of the visible and invisible images.

Referring now to <FIG>, a description is given of the determination of the bleed-through removal intensity by use of the bleed-through intensity characteristic in the image processing apparatus <NUM> according to the fifth embodiment.

Initially with reference to <FIG>, a description is given of a bleed-through issue in visible image reading and invisible image reading.

<FIG> is a diagram illustrating front and back sides of an input document.

As illustrated in <FIG>, the front side of the input document includes black letters A, B, C, and D. The back side of the input document includes black letters E, F, G, and H.

<FIG> is a diagram illustrating an R image of the input document acquired by visible image reading. Although <FIG> illustrates the R read image alone, G and B read images are substantially the same as the R read image.

<FIG> is a diagram illustrating a NIR image of the input document acquired by invisible image reading. As illustrated in <FIG>, the invisible (or NIR) image reading exhibits a greater bleed-through than a bleed-through in the visible image reading.

Referring now to <FIG>, a description is given of bleed-through removal by gamma correction by use of the image characteristic difference between the visible and invisible images.

<FIG> is a graph illustrating a general gamma correction.

The gamma correction converts pixel values with a conversion table of an output pixel value to an input pixel value being <NUM> to <NUM>. The gamma correction may also whiten a document background.

<FIG> is a graph illustrating acquired bleed-through characteristics of a target scanner.

The bleed-through characteristics indicate a relationship between the document density and the read pixel value obtained when reading the density from the back side of the document. For example, the bleed-through characteristics are acquired, as visible and invisible bleed-through characteristics, from the relationship between the document density and the read pixel value upon visible and invisible image scanning of a white front side of a patch document, which bears a gradation on a back side. A gamma correction table may be generated to fill a characteristic difference between the visible and invisible bleed-through characteristics.

<FIG> is a graph illustrating a gamma correction by use of the characteristic difference according to the fifth embodiment.

In the present embodiment, firstly, the gamma correcting unit <NUM> acquires, from the bleed-through characteristics, a read pixel value maxrgb of a solid-density visible image and a read pixel value maxi, of a solid-density invisible image. The gamma correcting unit <NUM> adjusts a gamma correction table for an invisible image (hereinafter referred to as an invisible image gamma correction table) such that the output pixel value with an input pixel value maxi, approaches the output pixel value with an input pixel value maxrgb.

In addition, the gamma correcting unit <NUM> adjusts a background removal threshold value of the invisible image gamma correction table with a background removal amount thir for the invisible image. The background removal amount thir is a read pixel value acquired by the invisible image reading with respect to the document density removed from the background of the visible image. Note that, in <FIG>, thrgb represents a background removal amount for the visible image.

Thus, the present embodiment adjusts a gamma of a portion of the invisible image exhibiting lower background removal intensity and contrast than those of the visible image, thereby equalizing the bleed-through intensities of the visible and invisible images.

Referring now to <FIG>, a description is given of a sixth embodiment of the present disclosure.

Unlike the image processing apparatus <NUM> according to the first embodiment, the image processing apparatus <NUM> according to the sixth embodiment includes an image synthesizing unit <NUM> in the image correction processing unit <NUM> to incorporate an invisible image into a visible image. A redundant description of identical features in the first and sixth embodiments is herein omitted; whereas a description is now given of features of the sixth embodiment different from the features of the first embodiment.

<FIG> is a block diagram illustrating a configuration of the image correction processing unit <NUM> of the image processing apparatus <NUM> according to the sixth embodiment.

As illustrated in <FIG>, the image correction processing unit <NUM> of the image processing apparatus <NUM> includes the image synthesizing unit <NUM> that incorporates an invisible image into a visible image.

In contrast to visible images, invisible images are in a spectrum without a human visual sensitivity. Therefore, the invisible images are generally treated as data without color information. The image synthesizing unit <NUM> synthesizes visible and invisible images corrected. Such image synthesis reduces the data amount stored by, e.g., users. In addition, since the synthesized image is treated as a general RGB image, image handling is simplified.

Referring now to <FIG>, a description is given of a synthesizing process performed by the image synthesizing unit <NUM> according to the sixth embodiment.

<FIG> is a block diagram illustrating a configuration of the image synthesizing unit <NUM> in the image correction processing unit <NUM> according to the sixth embodiment. The image synthesizing unit <NUM> places an invisible image into a blank area, thereby synthesizing visible and invisible images.

When a visible image and an invisible image are synthesized so as to overlap each other, the invisible image affects the visible image. As a consequence, the synthesized image is hard for users to read. To address such a situation, the image synthesizing unit <NUM> detects a blank area in a visible image. The image synthesizing unit <NUM> then moves an invisible image into the blank area detected. Thus, the image synthesizing unit <NUM> synthesizes the visible and invisible images. That is, the image synthesizing unit <NUM> superimposes invisible information on an area that does not affect the visible image, thereby enhancing the readability for, e.g., users. In addition, the present embodiment omits the need for, e.g., a user to designate a synthesis position for each document, thereby enhancing user-friendliness.

As illustrated in <FIG>, the image synthesizing unit <NUM> includes a blank area detecting unit <NUM> and a synthesizing unit <NUM>. In response to setting the detection of a blank area ON by, e.g., a user, the blank area detecting unit <NUM> detects a blank area in an input RGB image (i.e., visible image). The blank area detecting unit <NUM> outputs the blank area thus detected to the synthesizing unit <NUM>.

The synthesizing unit <NUM> extracts an image area from an input NIR image (i.e., invisible image) to place the image area in the blank area detected.

Referring now to <FIG>, a description is given of a way of the image synthesis with detection of a blank area.

<FIG> is a diagram illustrating an input document image. The document includes a visible image area and an invisible image embedded area. In the invisible image embedded area of <FIG>, the star mark indicates a visible image. The letter "V" inside the star mark is an invisible image embedded as a latent image in the visible image.

<FIG> is a diagram illustrating a visible image of the input document acquired by visible image reading. In the visible image reading, visible information of the document is read.

<FIG> is a diagram illustrating an invisible image of the input document acquired by invisible image reading. In the invisible image reading, the embedded letter "V" is read. <FIG> illustrates an area including the letter "V" as a block to be extracted.

<FIG> is a diagram illustrating a blank-area synthesized image in which the invisible image is placed in a blank area of the visible image. Specifically, <FIG> illustrates the block including the letter "V" placed at the center of the blank area detected by the blank area detecting unit <NUM>. Note that the synthesis position to place the invisible image is not limited to the center of the blank area. That is, the synthesis position can be anywhere in the blank area. When a plurality of blank areas is detected, the invisible image may be placed in a largest blank area or a closest blank area. In short, the synthesis position is not limited to a specific blank area. When the blank area is smaller than the incorporated image (i.e., block including the letter "V"), the block may be placed at the center of the blank area while overlapping a peripheral image. Alternatively, the block may be placed at an original position regardless of the blank area detected.

Thus, according to the present embodiment, incorporation of the invisible image into the visible image generates a visible image with invisible information. In addition, the present embodiment reduces the data amount stored by, e.g., users, and simplifies the image handling. The present embodiment also provides hardware advantages because the images can be handled in a typical processing system.

Further, in the present embodiment, the image synthesizing unit <NUM> recognizes a blank area and places an image in the blank area. Thus, the image synthesizing unit <NUM> places invisible image information at a position that does not affect a visible image. Furthermore, the present embodiment omits the need for, e.g., a user to designate the synthesis position, thereby enhancing user-friendliness.

Referring now to <FIG>, a description is given of a seventh embodiment of the present disclosure.

Unlike the image processing apparatus <NUM> according to the sixth embodiment, the image processing apparatus <NUM> according to the seventh embodiment determines a color of an invisible image subjected to the image synthesis, according to a color selection by, e.g., a user. A redundant description of identical features in the first to seventh embodiments is herein omitted; whereas a description is now given of features of the seventh embodiment different from the features of the first to sixth embodiments.

<FIG> is a block diagram illustrating a configuration of the image correction processing unit <NUM> of the image processing apparatus <NUM> according to the seventh embodiment.

As illustrated in <FIG>, the image synthesizing unit <NUM> receives color information indicating a color selected by, e.g., a user. The image synthesizing unit <NUM> colors a NIR image (i.e., invisible image) according to the color information before synthesizing the NIR image and an RGB image (i.e., visible image). By incorporating the NIR image (i.e., invisible image) of a user-desired color into the RGB image (i.e., visible image), the image synthesizing unit <NUM> renders the visible information and the invisible information of the document clearly distinguishable in the synthesized image.

Referring now to <FIG>, a description is given of an image synthesizing process performed by the image synthesizing unit <NUM> according to the seventh embodiment.

<FIG> is a block diagram illustrating a configuration of the image synthesizing unit <NUM> in the image processing apparatus <NUM> according to the seventh embodiment.

As illustrated in <FIG>, the image synthesizing unit <NUM> includes a synthesis position determining unit <NUM> and the synthesizing unit <NUM>. When, e.g., a user desires to designate an image synthesis position, the user inputs synthesis position setting information. The synthesis position determining unit <NUM> determines coordinates of the synthesis position and outputs position information to the synthesizing unit <NUM>.

The synthesizing unit <NUM> extracts an image area from a NIR image (i.e., invisible image) received. Then, the synthesizing unit <NUM> performs the image synthesizing process based on the position information.

Referring now to <FIG>, a description is given of a way of the image synthesis with designation of the synthesis position.

<FIG> is a diagram illustrating an input document. The document includes a visible image area and an invisible image embedded area. In the invisible image embedded area of <FIG>, the star mark indicates a visible image. The letter "V" inside the star mark is an invisible image embedded as a latent image in the visible image.

<FIG> is a diagram illustrating a visible image of the input document acquired by visible image reading. In the visible image reading, the visible information of the document is read.

<FIG> is a diagram illustrating a position-designated synthesized image in which the invisible image is positioned as designated by, e.g., a user. In a case in which the user does not designate the synthesis position, the images are located and synthesized as in the input document. In the present embodiment, the visible and invisible images are synthesized at identical positions. In such a case, the invisible image overlapping the visible image causes difficulties for users in reading a visible read image. To address such a situation, the present embodiment allows the users to set, in advance, a synthesis area to place an invisible image, thereby moving the invisible image to a given position (e.g., (x, y) coordinates in <FIG>). Accordingly, the present embodiment enhances the readability for the users.

As described above, in the present embodiment, the image synthesizing unit <NUM> colors an invisible image as desired by, e.g., a user, thereby rendering the visible information and the invisible information of a document clearly distinguishable.

In addition, the image synthesizing unit <NUM> places an invisible image at a position designated by, e.g., a user. In other words, the image synthesizing unit <NUM> moves the invisible image to a position where the invisible image is easy to read.

Note that, in the embodiments described above, the image processing apparatus <NUM> has been described as applicable to an MFP having at least two of copying, printing, scanning, and facsimile functions. Alternatively, the image processing apparatus <NUM> may be applied to a copier, a printer, a scanner, a facsimile machine, or the like.

Alternatively, the image processing apparatus <NUM> may be applied to applications in various fields, such as inspection in a factory automation (FA) field.

Alternatively, the image processing apparatus <NUM> may be applied to a bill scanner that discriminates bills and used to prevent the forgery. Alternatively, the image processing apparatus <NUM> may be applied to an apparatus that reads visible and invisible images and performs some processing in a subsequent step.

Claim 1:
An image processing apparatus (<NUM>) comprising:
a light source (<NUM>) configured to emit light upon scanning a document, the light source (<NUM>) comprising a visible light source (63A) and an invisible light source (63B),
an image sensor (<NUM>) configured to read a visible spectrum and an invisible spectrum of an image of the scanned document;
an image separating unit (<NUM>) configured to separate the image read into a visible image and an invisible image; and
an image correction processing unit (<NUM>) configured to perform different image correction processes on the visible image and the invisible image, respectively,
characterized in that
the image correction processing unit (<NUM>) comprises an image correction control unit (<NUM>) comprising:
an image characteristic difference retaining unit (<NUM>) configured to retain an image characteristic difference between the visible and invisible images; and
a parameter setting unit (<NUM>) configured to set parameters according to the image characteristic difference retained by the image characteristic difference retaining unit (<NUM>);
wherein the image correction control unit (<NUM>) corrects visible and invisible images to match an image characteristic of the visible image and an image characteristic of the invisible image.