JP5655505B2 - Image processing apparatus and image reading apparatus used therefor - Google Patents

Description

  The present invention is directed to an image processing apparatus capable of generating a deepened image and an image reading apparatus used therefor.

  2. Description of the Related Art Conventionally, an apparatus having an image reading function such as a copying machine, a facsimile machine, an image scanner, and an industrial camera generally employs a configuration in which an image showing a subject is read by scanning the subject (typically, a document). ing. Such a scanning mechanism includes a light source for irradiating light on a subject, an imaging optical system for forming a reflected image from the subject, and a line sensor for reading the reflected image. These read the image showing the subject while changing the relative position to the subject.

  An imaging optical system has been adopted as a structure of a conventional image reading apparatus. This imaging optical system is constituted by, for example, a reduction optical system having a magnification of about 1/5. By adopting such a reduction optical system, the depth of field can be increased. However, in an image reading apparatus employing such a reduction optical system, the conjugate length becomes long and it is difficult to reduce the size of the apparatus.

  On the other hand, the use of a contact optical system is increasing as a structure of a smaller image reading apparatus. This close-contact optical system is composed of, for example, an equal-magnification compound-eye optical system configured by arranging one or more rows of gradient index lenses (selfoc lenses). By employing such a close-contact optical system, the conjugate length is significantly shortened, and the apparatus can be downsized. However, an image reading apparatus employing such a contact optical system has overlapping images due to the compound eye optical system, and the combined aperture angle becomes large, so that the depth of field becomes shallow.

  As the depth of field becomes shallow, there is a problem that the image quality is deteriorated for a subject having unevenness such as a binding margin portion of a book or a fold. For this reason, the application range of the image reading apparatus adopting the contact optical type is limited to applications where the depth of field may be shallow, such as an automatic document feeder (ADF).

  By the way, there is a technique for increasing the depth of an acquired image in an imaging device (typically an area sensor not having a light source) of a non-contact optical system such as a digital camera, instead of the image reading device as described above. Proposed.

  For example, Japanese Patent Application Laid-Open No. 2008-244982 (Patent Document 1) uses a spectral image sensor that can photoelectrically convert a subject image in which a focused image and a blurred image overlap each other with three colors of light. A configuration of an ultra-deep image generating apparatus that can generate a high-quality ultra-deep image without causing a lack of resolution, false color, or the like by imaging is disclosed. More specifically, Patent Document 1 employs an imaging optical system having a different focal length depending on the wavelength of light, and has the highest contrast among the R, G, and B outputs of the image signal output from the imaging device. A higher one is adopted as a luminance signal, a color difference signal is generated from the remaining output to obtain a luminance-color difference signal, and an ultra-depth image is calculated from these by ultra-depth processing. In this way, by adopting an imaging optical system having a different focal length depending on the wavelength of light and acquiring distance data (contrast data) for each part of the subject, an image with a longer depth is acquired.

  Non-Patent Document 1 also discloses a method for improving the depth of field using a small camera for a mobile phone.

JP 2008-244982 A

Frederic Guichard et al., “Extended depth-of-field using sharpness transport across color channels”, [online], 2009, the proceedings of Electronic Imaging 2009, [searched July 16, 2010], Internet <URL: http://www.dxo.com/var/dxo/storage/fckeditor/File/embedded/2009_EI_EDOF.pdf>

  However, the technique for increasing the depth as described above cannot be simply applied to an image reading apparatus employing a contact optical system. That is, in the contact optical system, a light source for reading an image has to be arranged, but in the non-contact optical system, such a light source is unnecessary. This light source is arranged with an incident angle with respect to the subject (original) in order to avoid interference with the imaging optical system. Further, since the light emitted from the light source diffuses, the illumination intensity distribution on the axis of the optical system does not become uniform, and takes a peak value at a certain position (depth).

  For this reason, when the position of the document surface to be read deviates from the illumination intensity peak position, such as when the document is placed at a position (long depth region) away from the top surface of the document table, the document surface is irradiated. The S / N characteristic of the read image deteriorates due to the insufficient amount of light. As a result, it becomes difficult to stably acquire distance data (contrast data) extracted for increasing the depth.

  Accordingly, the present invention has been made to solve such a problem, and an object of the present invention is to provide an image processing apparatus capable of achieving both the downsizing of the apparatus and the expansion of the depth of field, and an image used therefor. It is to provide a reader.

An image processing apparatus according to an aspect of the present invention includes an illumination unit that emits illumination light having a predetermined wavelength band on a document, and different spectral sensitivities for acquiring respective color images for a plurality of colors. The image acquisition means comprising a plurality of pixels having light and the light generated by reflection of the illumination light on the original are guided to the image acquisition means, and the image forming position is different between the plurality of colors by generating a predetermined chromatic aberration. And an image processing means for generating an image having a longer depth from a plurality of color images acquired by the image acquisition means. The magnitude relationship between the illumination intensity at the object point position of the first color and the illumination intensity at the object point position of the second color is between the output characteristic value of the first color and the output characteristic value of the second color. It is configured to be the opposite of the magnitude relationship.

  By adopting this configuration, it is possible to stabilize the distance data calculation process in the deepening process.

Preferably, the image forming unit includes a contact optical system.
Preferably, the shorter the wavelength, the higher the illumination intensity at the object point position. By adopting such a configuration, it becomes suitable for the actual use frequency.

  Preferably, a color having a longer wavelength is configured to have a larger output characteristic value.

  Preferably, the illumination unit includes a first light source that generates the first illumination light, and a second light source that generates the second illumination light including a wavelength longer than the wavelength band of the first illumination light, The image processing means calculates distance data from the color image of the color included in the wavelength band of the first and second illumination light and synthesizes the color image of the color included in the wavelength band of the first illumination light. Thus, an image having a long depth is generated. By adopting such a configuration, the depth of field can be expanded.

More preferably, the second light source generates infrared second illumination light.
Preferably, the imaging means includes an optical system configured by arranging one or more rows of gradient index lenses. By adopting such a configuration, a chromatic aberration optical system can be easily realized.

  Preferably, the image acquisition means includes silicon photodiodes that respectively acquire color images of red, green, and blue, and the illumination intensity at the blue object point position is twice the illumination intensity at the green object point position. Configured to be larger. By adopting such a configuration, distance data can be calculated and calculated even when a silicon photodiode having a relatively low sensitivity to a short wavelength is used.

  Preferably, the image processing unit calculates the distance to the document and corrects the brightness of the acquired plurality of color images based on the calculated distance. By adopting such a configuration, it is possible to correct uneven brightness even for a subject whose distance from the light source is not uniform.

An image reading apparatus according to another aspect of the present invention includes an illuminating unit that emits illumination light having a predetermined wavelength band on a document, and different spectroscopic units for acquiring respective color images for a plurality of colors. The image acquisition means composed of a plurality of pixels having sensitivity and the light generated by reflecting the illumination light on the original are guided to the image acquisition means, and a predetermined chromatic aberration is generated, so that the image forming position is set between the plurality of colors. Different imaging means. The magnitude relationship between the illumination intensity at the object point position of the first color and the illumination intensity at the object point position of the second color is between the output characteristic value of the first color and the output characteristic value of the second color. It is configured to be the opposite of the magnitude relationship.

  According to the present invention, both miniaturization of the apparatus and expansion of the depth of field can be achieved.

1 is a schematic configuration diagram of an image processing device according to an embodiment of the present invention. It is a perspective view which shows typically the reading unit according to embodiment of this invention. It is a top view which shows typically the reading unit according to embodiment of this invention. It is a side view which shows typically the reading unit according to embodiment of this invention. It is a schematic diagram which shows the image formation position in the reading unit according to the embodiment of the present invention. It is a figure showing the output characteristic value in the design example 1 of the reading unit according to embodiment of this invention. It is a figure showing the illumination intensity distribution characteristic in the design example 1 of the reading unit according to embodiment of this invention. It is a side view which shows typically the design example 2 of the reading unit according to embodiment of this invention. It is a schematic diagram which shows the image position in the design example 2 of the reading unit according to embodiment of this invention. It is a figure showing the output characteristic value in the design example 2 of the reading unit according to embodiment of this invention. It is a figure showing the illumination intensity distribution characteristic in the design example 2 of the reading unit according to embodiment of this invention. It is a flowchart showing the design method of the image scanner according to embodiment of this invention. It is a schematic diagram which shows the hardware constitutions of the control part in the image processing apparatus according to embodiment of this invention. It is a block diagram which shows the control structure in the control part of the image processing apparatus according to embodiment of this invention.

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

<A. Overview>
The image processing apparatus according to the present embodiment has an image reading mechanism that employs a contact optical system. In particular, by using the lengthening process together, it is possible to expand the range in which image reading is guaranteed (the direction away from the image scanner). A chromatic aberration optical system is employed to carry out such a lengthening process.

  However, since the S / N characteristic deteriorates by adopting the chromatic aberration optical system, the illumination intensity distribution and the sensor output characteristic are optimized so as to match the characteristic of the chromatic aberration optical system. By adopting such a configuration, the sensitivity of the image acquired at the in-focus position is increased, and the reconstruction process of the long depth image can be stabilized.

<B. Configuration of Image Processing Device>
The present invention can be applied to any apparatus as long as it has an image reading function. Specifically, the present invention is applied to a copying machine (Multi Function Peripheral), a facsimile, an image scanner, an industrial camera, and the like. Applied. Hereinafter, as a typical example of the image processing apparatus according to the present invention, a multi-function peripheral equipped with a plurality of functions such as a copying function, a printing function, a facsimile function, and an image scanner function will be described.

  FIG. 1 is a schematic configuration diagram of an image processing apparatus MFP according to the embodiment of the present invention. Referring to FIG. 1, image processing apparatus MFP includes an automatic document feeder 2, an image scanner 3, a print engine 4, and a paper feeder 5.

  The automatic document transport unit 2 is for performing continuous scanning of a document, and includes a document feed table 21, a delivery roller 22, a registration roller 23, a transport drum 24, and a paper discharge table 25. . The document to be scanned is placed on the document feed table 21 and is sent out one by one by the operation of the delivery roller 22. Then, the fed document is temporarily stopped by the registration roller 23 and the leading edge is adjusted, and then conveyed to the conveyance drum 24. Further, the original rotates integrally with the drum surface of the transport drum 24, and the image surface is scanned by the image scanner 3 described later in the process. Thereafter, the document is separated from the drum surface at a position approximately half the circumference of the drum surface of the transport drum 24 and is discharged to the discharge table 25.

  The image scanner 3 includes a reading unit 33 and a document table 35. The reading unit 33 reads an image of a document by changing a relative position with respect to the document as a subject with time. The reading unit 33 is arranged as a main component, a light source that irradiates light on a document, an image sensor that acquires an image generated by reflection of light emitted from the light source on the document, and a front stage of the image sensor. Imaging optical system. The detailed configuration of the reading unit 33 will be described later. The document to be scanned can also be placed on the document table 35.

  The original image acquired by the image scanner 3, that is, the electrical signal output from the image sensor, is subjected to various image processing by the control unit 10.

  In image processing apparatus MFP according to the present embodiment, control unit 10 generates a deepened image from a plurality of color images acquired by image scanner 3. Details of this processing will be described later.

  For example, the print engine 4 executes an electrophotographic image forming process. Specifically, full-color print output is possible. Specifically, the print engine 4 includes imaging (imaging) units 44Y, 44M, 44C, which generate toner images of yellow (Y), magenta (M), cyan (C), and black (K), respectively. Includes 44K. The imaging units 44Y, 44M, 44C, and 44K are arranged in that order along the transfer belt 27 that is stretched and driven in the print engine 4.

  The imaging units 44Y, 44M, 44C, and 44K include image writing units 43Y, 43M, 43C, and 43K, and photosensitive drums 41Y, 41M, 41C, and 41K, respectively. Each of the image writing units 43Y, 43M, 43C, and 43K includes a laser diode that emits a laser beam corresponding to each color image included in the target image data, and a corresponding photoconductive drum 41Y, 41M by deflecting the laser beam. , 41C, 41K, and polygon mirrors that expose the surfaces in the main scanning direction.

  Electrostatic latent images are formed on the surfaces of the photosensitive drums 41Y, 41M, 41C, and 41K by the above-described exposure by the image writing units 43Y, 43M, 43C, and 43K, and the electrostatic latent images correspond respectively. A toner image is developed by toner particles supplied from the toner units 441Y, 441M, 441C, and 441K.

  The color toner images developed on the surfaces of the photosensitive drums 41Y, 41M, 41C, and 41K are sequentially transferred to the transfer belt 27. Further, the toner image superimposed on the transfer belt 27 is further transferred to the recording paper supplied from the paper supply unit 5 in time.

  The toner image transferred onto the recording paper is fixed at a fixing portion disposed at the downstream portion and then discharged onto the tray 57.

  In parallel with the operation of the photosensitive drums 41Y, 41M, 41C, and 41K, the feeding rollers 52, 53, and 54 and the manual paper feeding unit 26 corresponding to the paper feeding cassettes of the paper feeding unit 5 that stores the recording paper, respectively. Among these, the part corresponding to the recording paper to be used for image formation operates to supply the recording paper. The supplied recording paper is conveyed by the conveying rollers 55 and 56 and the timing roller 51, and is fed to the photosensitive drum 41 so as to be synchronized with the toner image formed on the photosensitive drum 41.

  The transfer unit 45 applies a voltage of opposite polarity to the photosensitive drum 41 to transfer the toner image formed on the photosensitive drum 41 to a recording sheet. The static eliminator 46 removes the recording paper from which the toner image has been transferred, thereby separating the recording paper from the photosensitive drum 41. Thereafter, the recording paper on which the toner image is transferred is conveyed to the fixing device 47. The transfer device 45 may employ a transfer method using a transfer charger or a transfer roller instead of the transfer method using a transfer belt as shown in FIG. Alternatively, instead of the direct transfer method in which the toner image is directly transferred from the photosensitive drum 41 to the recording paper, an intermediate transfer member such as a transfer roller or a transfer belt is disposed between the photosensitive drum 41 and the recording paper. Transfer may be performed by a process of more than one stage.

  The fixing device 47 includes a heating roller 471 and a pressure roller 472. The heating roller 471 heats the recording paper to melt the toner transferred thereon, and the melted toner is fixed on the recording paper by the compression force between the heating roller 471 and the pressure roller 472. The Then, the recording paper is discharged to the tray 57. The fixing device 47 may employ a fixing method using a fixing roller or a non-contact fixing method instead of the fixing method using a fixing belt as shown in FIG.

  On the other hand, in the photosensitive drum 41 from which the recording paper has been separated, after the residual potential is removed, the residual toner is removed and cleaned by the cleaning unit 48. Then, the next image forming process is executed. For example, the cleaning unit 48 removes and cleans residual toner by using a cleaning blade, a cleaning brush, a cleaning roller, or a combination thereof. Alternatively, a cleaner-less system that collects residual toner using the photoconductive drums 41Y, 41M, 41C, and 41K instead of the cleaning unit 48 may be employed.

  The IDC sensor 49 detects the density of the toner image formed on the photosensitive drum 41. The IDC sensor 49 is a light intensity sensor typically composed of a reflection type photosensor, and detects the intensity of reflected light from the surface of the photosensitive drum 41.

<C. Image Scanner Configuration>
Next, the configuration of the image scanner 3 shown in FIG. 1 will be described.

  FIG. 2 is a perspective view schematically showing reading unit 33 according to the embodiment of the present invention. FIG. 3 is a top view schematically showing reading unit 33 according to the embodiment of the present invention. FIG. 4 is a side view schematically showing reading unit 33 according to the embodiment of the present invention.

  In this specification, the plane of the document table 35 (the surface on which the document is placed) is an XY plane (the main scanning direction is the X axis and the sub scanning direction is the Y axis). The orthogonal direction is the Z axis (the direction away from the reading unit 33 is positive).

  Referring to FIG. 2, a reading unit 33 that employs a close-contact optical system includes a plurality of gradient index lenses (selfoc lenses) 332, and a side plate 331 that holds the plurality of gradient index lenses 332 so as to be sandwiched therebetween. And a plurality of pixels 336 arranged on the substrate 335.

  The gradient index lens 332 guides reflected light from a document that is a subject placed on the document table 35 to a plurality of pixels 336 on the substrate 335. FIG. 2 shows a configuration in which a plurality of gradient index lenses 332 are arranged in one row along the X axis (main scanning direction), but a configuration in which the plurality of gradient index lenses 332 are arranged in a plurality of rows can also be adopted. As an example, such a gradient index lens 332 may employ a SELFOC lens array manufactured by Nippon Sheet Glass Co., Ltd. Note that a path through which reflected light is guided through a plurality of gradient index lenses 332 is formed in the same pixel 336. That is, the gradient index lens 332 constitutes a compound eye optical system at the same magnification.

  The plurality of pixels 336 are one-dimensionally arranged on the substrate 335 so as to correspond to the plurality of gradient index lenses 332. Note that the pixels 336 can be arranged over a plurality of columns. The plurality of pixels 336 have different spectral sensitivities, and can acquire respective color images for a plurality of colors. Typically, it is possible to generate color images (color planes) for three colors of “red (R)”, “green (G)”, and “blue (B)”. As will be described later, in addition to the colors included in these visible bands, those capable of acquiring an infrared (IR) color image may be employed.

  As the pixel 336, for example, a charge coupled device (CCD) image sensor, a complementary metal oxide semiconductor (CMOS) image sensor, a photodiode (PD) array, or the like can be used. When such a device is employed, a color filter having a corresponding spectral transmission characteristic is provided on the light incident surface in order to vary the spectral sensitivity. For example, a pixel 336 having red sensitivity characteristics can be realized by combining a color filter that mainly transmits a red wavelength component and a detection device.

  In particular, the gradient index lens 332 according to the present embodiment guides reflected light generated by reflection on a document to a plurality of pixels 336 and generates a predetermined chromatic aberration so that an imaging position is set between a plurality of colors. Make them different from each other. Chromatic aberration means the property of varying the refractive index depending on the wavelength of light propagating in the gradient index lens 332. Due to such chromatic aberration, for example, a position where a light wave having a red wavelength component is imaged, a position where a light wave having a green wavelength component is imaged, and a position where a light wave having a blue wavelength component is imaged are mutually It will be different.

  In other words, when observing from the pixel 336 for each sensitive color, focusing is performed at different positions in the Z-axis direction. Therefore, the distance from the reading unit 33 is obtained for each partial area by acquiring each color image for a plurality of colors and determining which color image is in focus for each partial area in the image. Can be estimated. Furthermore, it is possible to generate a deepened image by performing image processing on each color image and synthesizing them with each other.

  By employing a plurality of gradient index lenses 332 that are close contact optical systems as shown in FIG. 2, the conjugate length can be significantly shortened.

  Next, with reference to FIGS. 3 and 4, light sources 333 and 334, which are illumination means for irradiating an original with illumination light having a predetermined wavelength band, will be described.

  The light sources 333 and 334 are light sources that extend in parallel with the arrangement direction of the gradient index lens 332 and the pixels 336, and typically use LEDs (Light Emitting Diodes), rare gas fluorescent lamps, and the like that are aligned. Can do. Note that a configuration in which only one of the light sources 333 and 334 is provided may be employed. However, it is preferable to provide a plurality of light sources from the viewpoint of making the illuminance intensity distribution uniform.

  As shown in FIG. 4, the light (irradiation light) emitted from each of the light sources 333 and 334 is reflected by the original D placed on the original table 35, and the reflected light generated there is a gradient index lens. Guided to a plurality of pixels 336 through 332. In the plurality of pixels 336, a color image is generated for each color. Then, an image having a longer depth (hereinafter also referred to as a “long depth image”) is generated from these color images.

Hereinafter, the lengthening process for generating the long-depth image will be described.
<D. Lengthening process>
As described above, the deepening process is a means for solving the problem that the depth of field becomes shallow due to the adoption of the contact optical type, and a binding margin portion, a crease, etc. Even when an uneven document is placed, the contents can be read accurately.

  In order to realize such a deepening process, the reading unit 33 according to the present embodiment uses a gradient index lens 332 having chromatic aberration, so that the imaging positions are different among a plurality of colors. . That is, the refractive index distribution type lens 332 that is an imaging optical system is arranged to face the subject (original), and the refractive index distribution type lens 332 expresses chromatic aberration.

  FIG. 5 is a schematic diagram showing an imaging position in reading unit 33 according to the embodiment of the present invention. FIG. 5 is a diagram illustrating an example of image formation positions for red (R), green (G), and blue (B) viewed from the pixel 336. The image forming position of each color is expressed as an object distance (hereinafter also referred to as “color object distance”) L from the upper surface of the document table 35.

  In the example shown in FIG. 5, an image forming position is set in the order of blue (B), green (G), and red (R) from the surface of the document table 35. In the gradient index lens 332, chromatic aberration is expressed by utilizing the material properties thereof. As a characteristic of this chromatic aberration, the shorter the wavelength, the larger the refractive index. For this reason, the object distance of each color when forming an image on the surface of the document table 35 (on the Z axis), that is, the color object distance formed at that position is, in descending order, red (R)> green (G)> blue. (B).

  Further, the width of the color object distance (distance from R to B) indicates an approximate range in which a long-depth image can be generated. That is, this width corresponds to the depth of field at which image reading is guaranteed.

  In the example shown in FIG. 5, a book or a document is assumed as a subject, and the depth of field is designed to be 2 [mm] so that the image can be read even when there are irregularities (for example, folds). Yes.

  Then, the blue (B) imaging position with the shortest color object distance is set on the surface of the document table 35 so as to be a reference point of these depths of field. That is, the color object distance L (B) for blue (B) is set to 0 [mm]. On the other hand, the red (R) imaging position with the shortest color object distance is set at a position away from the surface of the document table 35 by the depth of field. That is, the color object distance L (R) = 2 [mm] for red (R). Then, the green (G) imaging position having an intermediate color object distance is set at the center of the depth of field. That is, the color object distance L (G) = 1 [mm] for green (G).

  In this manner, a long-depth image is generated from a plurality of color images acquired using the reading unit 33 having different image formation positions depending on colors. Hereinafter, an outline of the lengthening process for generating the long-depth image will be described.

(1) Image acquisition processing As shown in FIG. 5, a plurality of colors having different imaging characteristics (blurring conditions) using an imaging optical system having chromatic aberration that varies the imaging position (focal length) for each color. Get an image.

(2) Distance data calculation processing Based on the contrast data obtained by evaluating the contrast of the acquired color images, distance data for each minute region constituting the acquired image is calculated. More specifically, by comparing the degree of sharpness between the color images, it is determined which image forming position in the Z-axis direction the portion of the subject (document) corresponding to the minute area to be evaluated is determined. To do. Here, the fact that the contrast of the color image is maximized in the in-focus state is used. The distance distribution in the image can be obtained by repeating the distance data calculation process for all the minute regions constituting the image.

(3) Reconstruction process Using the acquired distance data for each minute region, each color image is sharpened, and a sharpened color image is reconstructed to generate a long-depth image.

  For the detailed contents of the deepening process, refer to the above-mentioned Patent Document 1, Non-Patent Document 1, and the like.

  In such a deepening process, in order to generate a long-depth image with high accuracy, it is necessary to accurately calculate distance data. That is, the distance data is desired to have a high S / N characteristic that is resistant to noise. Therefore, it is necessary to acquire image data so that the contrast ratio of the color image can be maintained at a sufficiently high value in the focused state.

  Therefore, the reading unit 33 according to the present embodiment is configured such that the magnitude relationship between the illumination intensities at the object point positions of each color is opposite to the magnitude relationship between the output characteristic values of the corresponding color image. Is done. That is, the magnitude relationship between the illumination intensity at the object point position of the first color and the illumination intensity at the object point position of the second color is between the output characteristic value of the color and the output characteristic value of the first color. It is configured to be the opposite of the magnitude relationship.

Hereinafter, a more specific design example will be illustrated.
<E. Design Example 1>
In the design example 1 described below, an RGB color CCD is used as the detection device (pixel 336) constituting the reading unit 33. In this RGB color CCD, a color filter corresponding to the spectral characteristics of the corresponding color is formed on the light incident side of the Si (silicon) photodiode formed on the substrate. Therefore, the sensitivity (spectral sensitivity) for each color of the RGB color CCD is obtained by multiplying the characteristics of the color filter and the characteristics of the Si photodiode.

  As the light sources 333 and 334, rare gas fluorescent lamps were used. In the spectral wavelength characteristic of the rare gas fluorescent lamp, there are peaks in each wavelength band corresponding to red (R), green (G), and blue (B), as will be described later. Further, as shown in FIG. 4, the light sources 333 and 334 are arranged so as to have different predetermined incident angles with respect to the subject.

  In reading unit 33 according to the present embodiment, the illumination intensity distribution on the optical system axis (Z axis) is determined to be optimized. The following two points are considered as the viewpoint for determining the illumination intensity distribution.

(1) Generation of a high-quality long-depth image (appropriate execution of a deepening process)
(2) Normal Document Reading with High Quality Hereinafter, these aspects will be described with reference to FIGS. Here, FIG. 6 is a diagram representing output characteristic values in design example 1 of reading unit 33 according to the embodiment of the present invention. FIG. 7 shows illumination intensity distribution characteristics in design example 1 of reading unit 33 according to the embodiment of the present invention.

(E1: Generation of a high-quality long-depth image)
In order to generate a high-quality long-depth image, it is necessary to increase the S / N characteristic for each color image acquired when a subject at each color object distance is imaged. For example, when looking at a subject at a color object distance L = 2 [mm], it is sufficient that the S / N characteristic of the R image acquired at that time is high, and other images (G images) acquired at the same timing. It is not necessary to increase the S / N characteristics of the (B and B images).

  Similarly, regarding a subject at the position of the color object distance L = 1 [mm], it is sufficient that the S / N characteristic of the G image acquired at that time is high, and the color object distance L = 0 [mm]. For the subject at the position, it is sufficient that the S / N characteristic of the BG image acquired at that time is high.

  Therefore, in the reading unit 33 according to the present embodiment, the deterioration of the S / N characteristic in the distance data (obtained in the lengthening process) caused by the sensitivity of the image sensor and the color characteristic difference between the light source intensities, the illumination intensity distribution It compensates by optimizing.

  More specifically, the output characteristics of the color in which the illumination intensity at each object point position (color object distance L (R), color object distance L (G), color object distance L (B)) is focused at that position. Determine based on the value.

  Here, the color output characteristic value will be described. The color output characteristic value is defined as an integrated value of the spectral wavelength characteristic of the light source and the spectral sensitivity of the image sensor.

  For example, if the light sources 333 and 334 have spectral wavelength characteristics as shown in FIG. 6A, and the image sensors of the respective colors have spectral sensitivity as shown in FIG. Separately, they are multiplied to obtain a wavelength characteristic as shown in FIG. Then, the output characteristic value of each color is obtained by integrating the wavelength characteristics of each color. The relationship between the output characteristic values between the colors shown in FIG. 6C is as follows: output characteristic value (B): output characteristic value (G): output characteristic value (R) = 0.48: 0.76: 1. . That is, the design example 1 is configured such that the color having a longer wavelength has a larger output characteristic value.

  As the illumination intensity distribution on the optical axis, in the case of a color having a relatively large output characteristic value, the illumination intensity at the corresponding object point position is relatively small. That is, the shorter the wavelength, the higher the illumination intensity at the object point position.

  In other words, as shown in FIG. 7, the magnitude relationship between the illumination intensities at the object point positions of the respective colors is opposite to the magnitude relationship between the output characteristic values of the corresponding colors (reverse relationship). Is done.

  As shown in FIG. 7, for example, in the design example 1 of the present embodiment, the color object point position of blue (B) when the blue (B) whose output characteristic value is relatively lower than other colors is seen. The illumination intensity is designed to be relatively strong at (color object distance L = 0 [mm]). By setting such an illumination intensity distribution, it is possible to suppress the deterioration of the S / N characteristic of each color image, and to stably calculate distance data for any color.

  In the design example 1 of the present embodiment, as an example, the output characteristic value (output characteristic value (B): output characteristic value (G): output characteristic value (R) = 0.48: 0.76: 1) of each color is used. Taking into consideration, the illumination intensity ratio between each color object point position is B (value at color object distance L (B) = 0 [mm]): G (color object distance L (G) = 1 [mm]. Value): color object distance L (R) = 2 [mm]) = 1: 0.6 or more: 0.4 or more.

(E2: high quality normal document reading)
In image processing apparatus MFP according to the present embodiment, not only a document table direct reading operation (for example, +0 [mm] from the top surface of the document table) but also an automatic document transport operation (for example, +0.2 [mm from the top surface of the document table). ]) Is possible.

  In consideration of these operations, in the reading unit 33, as shown in FIG. 7, a light intensity peak is set in the vicinity of the paper passing position of the automatic document conveying operation (for example, +0.2 [mm] from the upper surface of the document table). Has been. By setting the light intensity peak, the image scanner 3 can acquire an image having a high S / N characteristic not only in the original table direct reading operation but also in the automatic document conveying operation. In general, since the frequency of automatic document conveyance is high, a light intensity peak is set in the vicinity of the paper passing position in the automatic document conveyance operation.

<F. Design Example 2>
In design example 2 shown below, another color used for calculation of distance data (contrast data) that is not output as a long-depth image but is used to increase the depth is added. As a result, the range in which a long-depth image can be generated (distance data can be calculated) is expanded, that is, the depth of field at which image reading is guaranteed is deepened. In design example 2, as a typical example of another color, a wavelength in an IR (infrared) region having a longer wavelength is used.

  In Design Example 2 described below, a four-color CCD of R, G, B, and IR type is used as the detection device (pixel 336) constituting the reading unit 33. In this four-color CCD, a color filter corresponding to the spectral characteristics of the corresponding color is formed on the light incident side of the Si (silicon) photodiode formed on the substrate. Therefore, the sensitivity (spectral sensitivity) for each color of the four-color CCD is a product of the characteristics of the color filter and the characteristics of the Si photodiode.

  FIG. 8 is a side view schematically showing design example 2 of reading unit 33 according to the embodiment of the present invention. Referring to FIG. 8, a composite light source of a white LED and an infrared LED (IR-LED) was used as light sources 333A and 334A. That is, the light sources 333A and 334A mainly include a first light source (white LED) that generates visible light and a second light source that generates light including a wavelength (infrared band) longer than the wavelength band of visible light. Infrared LED). Further, as shown in FIG. 8, the light sources 333A and 334A are arranged to have different predetermined incident angles with respect to the subject.

  That is, the distance data is calculated from the color images included in the visible light region and the infrared region, and the color image included in the visible light region is combined to generate a long-depth image.

  FIG. 9 is a schematic diagram showing an imaging position in design example 2 of reading unit 33 according to the embodiment of the present invention.

  In the example illustrated in FIG. 9, an image forming position is set in the order of blue (B), green (G), red (R), and infrared (IR) from the surface of the document table 35. Similar to the first design example described above, since the chromatic aberration is expressed using the material properties of the gradient index lens 332, the infrared (IR) image is refracted more greatly. Also, the color image for infrared (IR) is not used for generating a long-depth image (only used for calculating distance data). Therefore, the object point position for infrared (IR) is set to be the farthest position from the standard document placement position. In design example 2, the color object distance of each color when forming an image on the surface of the document table 35 (on the Z axis) is, in order from the longest, infrared (IR)> red (R)> green (G)> blue. (B).

  Here, the width between the smallest color object distance and the longest color object distance (the distance from IR to B) corresponds to the depth of field that guarantees the calculation of the distance data.

  In design example 2, the same design values as the color object distances L (R), L (G), and L (B) for red (R), green (G), and blue (B) in design example 1 are adopted. At the same time, the infrared (IR) imaging position with the shortest color object distance is set to the position farthest from the surface of the document table 35. As an example, the color object distance L (IR) for infrared (IR) is set to 3 [mm].

  Also in the design example 2, the illumination intensity distribution on the optical system axis (Z axis) is determined in consideration of the two viewpoints as described above.

  Hereinafter, these aspects will be described with reference to FIGS. 10 and 11. Here, FIG. 10 is a diagram representing output characteristic values in design example 2 of reading unit 33 according to the embodiment of the present invention. In FIG. 10, the infrared (IR) characteristics are not described because of the scale. FIG. 11 shows illumination intensity distribution characteristics in design example 2 of reading unit 33 according to the embodiment of the present invention.

(F1: Generation of a high-quality long-depth image)
In order to generate a high-quality long-depth image, it is necessary to increase the S / N characteristic for each color image acquired when a subject at each color object distance is imaged.

  Therefore, in the reading unit 33 according to the present embodiment, the deterioration of the S / N characteristic in the distance data (obtained in the lengthening process) caused by the sensitivity of the image sensor and the color characteristic difference between the light source intensities, the illumination intensity distribution It compensates by optimizing.

  For example, if the light sources 333A and 334A have spectral wavelength characteristics as shown in FIG. 10A, and the image sensors of the respective colors have spectral sensitivity as shown in FIG. Separately, they are multiplied to obtain a wavelength characteristic as shown in FIG. Then, the output characteristic value of each color is obtained by integrating the wavelength characteristics of each color. The relationship between the output characteristic values between the colors shown in FIG. 10C is as follows: output characteristic value (B): output characteristic value (G): output characteristic value (R) = 0.42: 1: 0.94. .

  As the illumination intensity distribution on the optical axis, in the case of a color having a relatively large output characteristic value, the illumination intensity at the corresponding object point position is relatively small. That is, the shorter the wavelength, the higher the illumination intensity at the object point position.

  In other words, as shown in FIG. 11, the magnitude relationship between the illumination intensities at the object point positions of each color is opposite to the magnitude relationship between the output characteristic values of the corresponding colors (reverse relationship). Is done.

  As shown in FIG. 11, for example, in design example 1 of the present embodiment, when blue (B) whose output characteristic value is relatively lower than other colors is seen, the color object point position of blue (B) The illumination intensity is designed to be relatively strong at (color object distance L = 0 [mm]). By setting such an illumination intensity distribution, it is possible to suppress the deterioration of the S / N characteristic of each color image, and to stably calculate distance data for any color.

  In the design example 1 of this embodiment, as an example, output characteristic values (output characteristic value (B): output characteristic value (G): output characteristic value (R) = 0.42: 1: 0.94) of each color are used. In consideration, the illumination intensity of blue (B) at the color object distance L (B) = 0 [mm], and the illumination intensity and color of green (G) at the color object distance L (G) = 1 [mm]. It was set to be larger than twice for any of the red (R) illumination intensities at the object distance L (R) = 2 [mm]. By adopting such an illumination intensity ratio, distance data can be stably acquired even when a Si photodiode having a lower blue (B) detection sensitivity than other colors is used. That is, the illumination intensity at the blue object point position is configured to be greater than twice the illumination intensity at the green object point position.

(F2: high quality normal document reading)
Also in the design example 2 of the reading unit 33, as shown in FIG. 11, the light intensity peak is set near the paper passing position of the automatic document conveying operation (for example, +0.2 [mm] from the upper surface of the document table). . By setting the light intensity peak, the image scanner 3 can acquire an image having a high S / N characteristic not only in the original table direct reading operation but also in the automatic document conveying operation.

<G. Design Method>
Next, a design method of the image scanner (reading unit 33) including the above-described optimization of the illumination intensity distribution will be described. FIG. 12 is a flowchart representing a design method of the image scanner according to the embodiment of the present invention.

  Referring to FIG. 12, first, the depth of field of the reading unit 33 to be designed is determined (step S10). The depth of field is determined in consideration of the design position from the reading unit 33 to the subject and the allowable amount of positional deviation variation in the Z-axis direction of the subject. As described above, when both the mode for reading a document placed directly on the platen and the mode for reading a document automatically conveyed by the automatic document conveyance unit are supported, Since the distance from the reading unit 33 to the document in the mode is different, the depth of field is determined in consideration of these matters.

  Once the depth of field is determined, the imaging optical system is then determined (step S20). Specifically, the physical size and material properties of the gradient index lens are selected so that the focal length (imaging position) and the degree of chromatic aberration have appropriate values.

  Once the imaging optical system is determined, the type of light source is then determined (step S30). Specifically, a light source with an appropriate cost and product specifications is selected according to the characteristics of the image scanner to be designed. There is also a degree of freedom in the number of light sources. For example, the content is whether to employ an LED or a rare gas fluorescent lamp.

  Once the type of light source is determined, the spectral sensitivity of the image sensor is then determined (step S40). Specifically, the type, material, and color filter characteristics of the image sensor are determined.

  When the spectral sensitivity of the image sensor is determined, next, the illumination intensity distribution is optimized (step S50). Specifically, the position of the light source and the lens combined with the light source so that the magnitude relationship between the illumination intensities at the color object point positions is opposite to the magnitude relationship between the output characteristic values of the corresponding colors. The physical properties of the light source (in the case of a rare gas fluorescent lamp, the gas pressure and gas type to be sealed) are appropriately changed. Then, it is determined whether or not the illumination intensity distribution has been optimized (step S60).

  If the illumination intensity distribution cannot be optimized (NO in step S60), the processes in steps S40 and S50 are executed again. On the other hand, if the illumination intensity distribution cannot be optimized (YES in step S60), the design of the image scanner is completed.

  As described above, as in the present embodiment, the degree of freedom for optimizing the illumination intensity distribution is relatively high. That is, there are many factors that determine the spectral sensitivity of the image sensor, and there are many factors that determine the spectral wavelength characteristics of the light source. In addition, there are many factors that determine the position of the object point for each color. Therefore, as a means of optimizing the illumination intensity distribution, it may be necessary only to adjust the type and position of the light source. However, if the optimization is not sufficient, the system including the optical system and image sensor can be used. It is also possible to optimize as a whole.

<H. Brightness correction>
In addition to the above-described deepening process, it is possible to improve the quality of the long-depth image by correcting the brightness.

  For example, considering the case of reading a spread part of a book, the distance S from the document table 35 is not uniform within the subject. On the other hand, the illumination intensity of light emitted from the light source has an intensity distribution (in the Z-axis direction) corresponding to the distance S from the document table 35. Therefore, the brightness of each acquired color image varies according to the distance S from the document table 35, and when viewed as the entire image, the brightness becomes uneven.

  Therefore, the quality of the long-depth image can be further improved by correcting such unevenness in brightness using the distance data calculated in the above-described depth-enhancing process. In other words, the distance to the document is calculated, and the brightness of the acquired plurality of color images is corrected based on the calculated distance.

  As a specific mounting method, the surface illuminance correction coefficient is experimentally acquired in advance in association with the distance S from the document table 35 to the subject. Then, in the image processing apparatus MFP, an LUT (Look Up Table) that defines the relationship between the distance S and the surface illuminance correction coefficient (for example, digitized gain value) is prepared, and each acquired For a color image, for each minute area, a correction coefficient obtained by referring to the LUT from distance data calculated for the minute area is acquired, and a two-dimensional brightness is obtained using the acquired correction coefficient. Correct the unevenness.

  By adopting such a correction method, even if the subject includes a portion where the distance S from the document table 35 is different from each other, unevenness of brightness in the acquired color image is reduced, and a high-quality long length is achieved. A depth image can be generated.

<I. Configuration of control unit>
FIG. 13 is a schematic diagram showing a hardware configuration of control unit 10 in image processing apparatus MFP according to the embodiment of the present invention.

  Referring to FIG. 13, the control unit 10 includes a CPU (Central Processing Unit) 202 that is a processing unit, a RAM (Random Access Memory) 204 that is a storage unit, a ROM (Read Only Memory) 206, an EEPROM (Electrical Erasable and A programmable read only memory (HDD) 208 and an HDD (Hard Disk Drive) 210, and an external communication I / F (Interface) 212 and an internal communication I / F 214 which are communication units are included. These parts are connected to each other via an internal bus 216.

  In control unit 10, CPU 202 controls image processing apparatus MFP as CPU 202 expands and executes programs for executing various processes stored in advance in ROM 206 or the like in RAM 204 or the like.

  The RAM 204 is a volatile memory and is used as a work memory. More specifically, the RAM 204 temporarily stores image data to be processed and various variable data in addition to the program itself to be executed. EEPROM 208 is typically a non-volatile semiconductor memory, and stores various setting values such as the IP address and network domain of image processing apparatus MFP. The HDD 210 is typically a non-volatile magnetic memory, and stores print jobs received from the image processing apparatus, image information acquired by the image scanner 3, and the like.

  The external communication I / F 212 typically supports a general-purpose communication protocol such as Ethernet (registered trademark), and provides data communication with the personal computer PC and other image processing apparatuses via the network NW.

  The internal communication I / F 214 is connected to an operation panel or the like, receives a signal corresponding to a user operation on the operation panel, transmits the signal to the CPU 202, and displays a message or the like on the operation panel according to a command from the CPU 202. Send the necessary signals.

<J. Control structure>
FIG. 14 is a block diagram showing a control structure in control unit 10 of image processing apparatus MFP according to the embodiment of the present invention. With reference to FIG. 14, the control part 10 produces | generates a long depth image by performing the lengthening process.

  More specifically, the control unit 10 includes, as its control structure, an image buffer 102, an R image extraction unit 104, a G image extraction unit 106, a B image extraction unit 108, a distance data calculation unit 110, and an LUT 112. An R image correction unit 114, a G image correction unit 116, a B image correction unit 118, an R filter 124, a G filter 126, a B filter 128, and a reconstruction unit 130. The image buffer 102 is provided as a predetermined area included in the RAM 203 (FIG. 13). The other parts are typically provided by the CPU 201 (FIG. 13) developing a program in the RAM 203 (FIG. 13) and executing each command.

  The image buffer 102 holds image data output in parallel from the image sensor for a predetermined time.

  The R image extraction unit 104 extracts only the red (R) component from the image data held in the image buffer 102 to generate an R image. Then, the R image extraction unit 104 outputs the generated R image to the distance data calculation unit.

  Similarly, the G image extraction unit 106 extracts only the green (G) component from the image data held in the image buffer 102, and generates a G image. Then, the G image extraction unit 106 outputs the generated G image to the distance data calculation unit. In addition, the B image extraction unit 108 extracts only the blue (B) component from the image data held in the image buffer 102, and generates a B image. Then, the B image extraction unit 108 outputs the generated B image to the distance data calculation unit.

  Note that <F. As illustrated in the section of Design Example 2>, when the wavelength component of the IR region used for calculating the distance data is added, only the infrared (IR) component is extracted from the image data held in the image buffer 102. An IR image extraction unit 109 for extracting and generating an IR image is further provided.

  The image buffer 102, the R image extraction unit 104, the G image extraction unit 106, the B image extraction unit 108, and the IR image extraction unit 109 are parts that execute an image acquisition process.

  The distance data calculation unit 110 is a part that executes a distance data calculation process. That is, the distance data calculation unit 110 calculates distance data for each minute region constituting the acquired image based on the contrast data of the R image, the G image, and the B image. The distance data calculation unit 110 outputs a distribution of distances in the image showing the subject.

  The LUT 112 includes the <H. As described in “Brightness Correction”, this is a table storing correction coefficients for correcting two-dimensional brightness unevenness in each color image. More specifically, the LUT 112 holds the correspondence between the distance and the surface illuminance correction coefficient (by color image), and when the distance data calculated for each minute region in the image is input, Are output to the R image correcting unit 114, the G image correcting unit 116, and the B image correcting unit 118, respectively.

  The R image correction unit 114 corrects each minute region of the R image generated by the R image extraction unit 104 with the corresponding surface illuminance correction coefficient received from the LUT 112, and outputs the corrected R image to the R filter 124. To do.

  Similarly, the G image correcting unit 116 corrects each minute region of the G image generated by the G image extracting unit 106 with the corresponding surface illuminance correction coefficient received from the LUT 112, and converts the corrected G image into a G filter. To 126. Further, the B image correction unit 118 corrects each minute region of the B image generated by the B image extraction unit 108 with the corresponding surface illuminance correction coefficient received from the LUT 112, and converts the corrected B image into the B filter 128. Output to.

  When the R filter 124 receives the corrected R image from the R image correction unit 114, the R filter 124 sharpens each minute region of the R image based on the distance data of each minute region calculated by the distance data calculation unit 110. More specifically, the R filter 124 sequentially generates (selects) a filter (function) having characteristics corresponding to the distance data of each minute region, and corrects the image of each minute region using the filter.

  Similarly, when the G filter 126 receives the corrected G image from the G image correction unit 116, the G filter 126 sharpens each minute region of the G image based on the distance data of each minute region calculated by the distance data calculation unit 110. Turn into. When the B filter 128 receives the corrected B image from the B image correction unit 118, the B filter 128 sharpens each minute region of the B image based on the distance data of each minute region calculated by the distance data calculation unit 110. To do.

  Even if the IR image extraction unit 109 is provided, the IR image is not used for generating a long-depth image, and therefore the image correction unit and the filter are not provided.

  The reconstruction unit 130 reconstructs the sharpened R, G, and B images output from the R filter 124, the G filter 126, and the B filter 128, respectively, thereby generating an output image (long-depth image). To do.

  The R filter 124, the G filter 126, the B filter 128, and the reconstruction unit 130 are parts that perform reconstruction processing.

<K. Other Embodiments>
The above-described values such as the light source, the imaging optical system, the image sensor, the color filter characteristics, and the number of colors are merely design examples, and the present invention is not limited to these design examples.

  In the above-described design example, the configuration using a single light source having a predetermined wavelength band has been illustrated. However, by adopting an independent light source (for example, an LED for each color), the emission intensity is independent for each color. Therefore, the adjustment of the illumination intensity distribution on the axis of the optical system becomes easier.

  In the design example described above, since chromatic aberration is expressed by utilizing the material properties of the gradient index lens, an example is shown in which the color object distance L becomes smaller as the wavelength becomes shorter. However, the present invention is not limited to this, and the color object distance L may be reduced as the wavelength becomes longer. That is, it can be designed such that L (B)> L (G)> L (R).

  In the above-described embodiment, the configuration in which the imaging optical system forms an image on the image sensor is exemplified. However, as disclosed in Japanese Patent Application Laid-Open No. 2008-244982 (Patent Document 1), a bifocal lens or the like is employed. You can also

  Part or all of the functions realized by the programs according to the above-described embodiments may be configured by dedicated hardware. Further, the program executed by the CPU according to the above-described embodiment is processed by calling a required module at a predetermined timing in a predetermined arrangement among program modules provided as a part of a computer operating system (OS). May be executed. In that case, the program itself does not include the module, and the process is executed in cooperation with the OS. Therefore, a program that does not include such a module can also be included in the program according to the present invention.

<K. Effect>
According to the embodiment of the present invention, the two needs of downsizing the image reading device and increasing the depth of field can be solved simultaneously. As a result of the expansion of the depth of field, the design tolerance can be relaxed, and an image scanner using a reduction optical system and an image scanner using an imaging optical system are mounted on the front and back surfaces, respectively. Even if it exists, both the front surface and the back surface of the document can be read with high quality.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  2 Automatic Document Conveying Unit, 3 Image Scanner, 4 Print Engine, 5 Paper Feeding Unit, 10 Control Unit, 21 Document Feeding Stand, 22 Feeding Roller, 23 Registration Roller, 24 Conveying Drum, 25 Paper Discharging Stand, 26 Manual Feeding Paper section, 27 Transfer belt, 33 units, 35 Document table, 41, 41Y, 41M, 41C, 41K Photosensitive drum, 43Y, 43M, 43C, 43K Image writing section, 44Y, 44M, 44C, 44K Imaging (image forming) ) Unit, 45 Transfer device, 46 Static eliminator, 47 Fixing device, 48 Cleaning unit, 49 IDC sensor, 51 Timing roller, 52, 53, 54 Delivery roller, 55 Transport roller, 57 Tray, 102 Image buffer, 104, 106, 108, 109 Image extraction unit, 110 Distance data calculation unit, 114, 116, 1 18 Image correction unit, 124, 126, 128 filter, 130 reconstruction unit, 201, 202 CPU, 203, 204 RAM, 206, 208 ROM, 212, 214 Communication I / F, 216 Internal bus, 331 Side plate, 332 Refractive index Distributed lens, 333,333A light source, 335 substrate, 336 pixels, 441Y, 441M, 441C, 441K toner unit, 471 heating roller, 472 pressure roller, D original, MFP image processing apparatus, NW network, PC personal computer.

Claims (10)

Illuminating means for emitting illumination light having a predetermined wavelength band to a document;
Image acquisition means comprising a plurality of pixels having different spectral sensitivities for acquiring respective color images for a plurality of colors;
An imaging unit that guides light generated by reflection of the illumination light from the document to the image acquisition unit and generates a predetermined chromatic aberration to make the imaging positions different among the plurality of colors,
Image processing means for generating an image having a longer depth from a plurality of color images acquired by the image acquisition means,
The magnitude relationship between the illumination intensity at the object point position of the first color and the illumination intensity at the object point position of the second color is the output characteristic value of the first color and the output characteristic value of the second color. An image processing apparatus configured to be opposite to the magnitude relationship between the two.   The image processing apparatus according to claim 1, wherein the imaging unit includes a contact optical system.   The image processing apparatus according to claim 1, wherein a color having a shorter wavelength has a higher illumination intensity at the object point position.   The image processing apparatus according to claim 1, wherein a color having a longer wavelength has a larger output characteristic value. The illumination unit includes a first light source that generates first illumination light, and a second light source that generates second illumination light including a wavelength longer than the wavelength band of the first illumination light,
The image processing means calculates distance data from a color image of a color included in the wavelength band of the first and second illumination light and calculates a color image of a color included in the wavelength band of the first illumination light. The image processing apparatus according to claim 1, wherein the image having the longer depth is generated by combining the images.   The image processing apparatus according to claim 5, wherein the second light source generates the second illumination light in an infrared region.   The image processing apparatus according to claim 1, wherein the imaging unit includes an optical system configured by arranging one or more rows of gradient index lenses. The image acquisition means includes a silicon photodiode that acquires color images for red, green, and blue, respectively.
The image processing apparatus according to claim 1, wherein the illumination intensity at the blue object point position is configured to be greater than twice the illumination intensity at the green object point position.   The image processing apparatus according to claim 1, wherein the image processing unit calculates a distance to the document and corrects brightness of the plurality of acquired color images based on the calculated distance. Illuminating means for emitting illumination light having a predetermined wavelength band to a document;
Image acquisition means comprising a plurality of pixels having different spectral sensitivities for acquiring respective color images for a plurality of colors;
An imaging unit that guides light generated by reflection of the illumination light from the document to the image acquisition unit and generates a predetermined chromatic aberration to change the imaging position between the plurality of colors;
The magnitude relationship between the illumination intensity at the object point position of the first color and the illumination intensity at the object point position of the second color is the output characteristic value of the first color and the output characteristic value of the second color. An image reading apparatus configured to be opposite to the magnitude relationship between the two.

Images