JP2005268909A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively provide an imaging apparatus, having simple configuration and capable of imaging an object, while applying color separation to the object into a plurality of colors. <P>SOLUTION: The imaging apparatus 1 is provided with three optical systems for applying color separation to an object P into three colors and to image the object P, whose distance from the imaging apparatus 1 is constant; and lenses 2R, 2G, 2B and RGB and color filters 3R, 3G, 3B located in front of three monochromatic image sensors 4R, 4G, 4B. Further, the optical system is configured so that an imaging area enters the visual field of the image sensors 4R, 4G, 4B. Since the reading of the images of the image sensors 4R, 4G, 4B can read the same imaging area, a color image of the object can be obtained, by combining the image signals outputted from the image sensors 4R, 4G, 4B. Further, when applying color separation to the image of the object into four or more colors, a plurality of optical systems at a fixed distance are likewise provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an imaging apparatus that captures a color image of a planar subject (object) located at a certain distance.

  Conventional color imaging devices using an image sensor include a single-plate type and a three-plate type as typical ones. In the former, for example, R, G, and B primary color filters, or Y, M, and C complementary color filters and G filters are attached to each pixel in a predetermined arrangement on the surface of the image sensor. R, G, B and color image signals have been obtained by processing the signals output from.

On the other hand, in the latter, for example, R, G, B images are formed in different directions by an optical system combining a prism and a half mirror, and a signal output from an image sensor attached at that position is processed. R, G, B and color image signals were obtained (for example, see Non-Patent Document 1).
Hiroo Takemura “CCD Camera Technology” Radio Engineer 1986

  The conventional single-plate color imaging device has a configuration in which color filters are attached to each pixel of the image sensor as described above. In order to obtain a color image signal of one pixel, at least R, G, B It is necessary to synthesize image signals for three pixels, or four pixels of Y, M, C, and G. Therefore, the conventional single-plate color imaging device has a problem that the resolution is lower than the number of pixels of the imaging element.

  On the other hand, the conventional three-plate color image pickup device needs to design an optical system with high accuracy by combining a prism and a half mirror, and the components are expensive. In addition, due to the characteristics of the half mirror, there is a problem that the sensitivity is not so good because the light use efficiency is low.

  In recent years, with the development of printing technology, technology for printing color images using four or more colors of ink has been used, and the color tone of color images is monitored during the production of such printed matter. In order to do this, it is necessary to color-separate and inspect the image of the object according to the number of inks used. However, in a single-plate color image pickup apparatus, the number of color filters provided in the image sensor increases, so that the resolution becomes lower than the number of pixels of the image pickup element. In addition, since the number of manufacturing steps increases, there is a problem that the color imaging device becomes very expensive particularly when the production amount is small. On the other hand, when a conventional three-plate type color imaging device is modified so that an image of an object can be separated into four or more colors, it is necessary to newly design an optical system using a prism and a half mirror. The technology cannot be used, and the components are more expensive.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an imaging apparatus capable of imaging a target object by color separation into a plurality of colors with a simple configuration at low cost.

  The present invention has the following configuration as means for solving the above problems.

(1) An imaging device that captures an image of an object located at a certain distance, an image sensor that images the object, a lens that forms an image of the object on the image sensor, and a specific wavelength component A plurality of image pickup units each including a filter that allows only the light to pass through,
An image processing unit that performs image processing of an object imaged by the image sensor,
The filters of the respective imaging units pass light of different wavelength components,
The image sensor of each imaging unit is arranged to image the same region of the object from an optically substantially same distance as the object,
The image processing unit synthesizes images of the same region of the object captured by the image sensors.

  In this configuration, each image sensor of the imaging unit is optically arranged at substantially the same distance as the object, and is arranged so as to image the same region of the object. In addition, the optical system can be configured without using a prism or a half mirror, so that the same region of the object can be imaged, and the apparatus configuration can be simplified.

  (2) One filter of the imaging unit is a filter that transmits infrared rays.

  In this configuration, since an infrared filter is provided, it is possible to extract an image of only a portion printed with black ink in a color image printed with a plurality of types of ink. Therefore, it is possible to easily grasp the black ink amount used when expressing the saturation.

  An imaging apparatus of the present invention is installed at a certain distance from an object, and includes a plurality of optical systems for imaging the object by separating the object into a plurality of colors, and each optical system has a lens on the front surface of the monochrome image sensor. Has a color filter. In addition, by synthesizing the image signal in the field of view of each image sensor, a color image of the object without deviation can be obtained. In addition, since the imaging apparatus according to the present invention has the above-described configuration, it is possible to reduce component costs and manufacturing costs.

  FIG. 1 is a schematic configuration diagram of an imaging apparatus according to an embodiment of the present invention. FIG. 1 shows a configuration for color separation into three colors of RGB in order to explain the basic operation of the imaging apparatus 1. As shown in FIG. 1, the imaging apparatus 1 arranges an optical system so that lenses 2R, 2G, and 2B and a filter imaging area enter. Accordingly, each image sensor can read out images in the same imaging area, and includes 3R, 3G, and 3B, image sensors 4R, 4G, and 4B output from each image sensor, an image processing circuit 5, and an output circuit 6. ing. The lens 2R forms an image of the object P on the image sensor 4R via the filter 3R. The lens 2G forms an image of the object P on the image sensor 4G via the filter 3G. The lens 2B forms an image of the object P on the image sensor 4B via the filter 3B. The filter 3R is a filter that transmits red component light. The filter 3G is a filter that transmits green component light. The filter 3B is a filter that transmits blue component light. The image sensors 4R, 4G, and 4B are monochrome image sensors, and have light receiving areas of approximately the same size. The image sensor 4R photoelectrically converts and outputs a red component image of the object P obtained through the lens 2R and the filter 3R. The image sensor 4G photoelectrically converts and outputs a green component image of the object P obtained through the lens 2G and the filter 3G. The image sensor 4B photoelectrically converts and outputs a blue component image of the object P obtained through the lens 2B and the filter 3B. The image processing circuit 5 combines the image data output from the image sensors 4R, 4G, and 4B to generate color image data, and outputs the color image data to the output circuit 6. The image processing circuit 5 outputs the image data output from the image sensors 4R, 4G, and 4B to the output circuit 6 as it is. The output circuit 6 outputs a color image signal of the object P, an image signal of a red component of the object P, an image signal of a green component of the object P, and an image signal of a blue component of the object P.

  The imaging device 1 according to the embodiment of the present invention is a device that captures a color image of the object P that is always located at a constant distance, and adopts a three-plate type (double-plate type) instead of a single-plate type. A high-resolution color image can be obtained. Further, as described above, the imaging device 1 always images the object P at a fixed distance, so that the optical system can be simplified without using a prism or a half mirror, and the component cost and manufacturing cost can be suppressed. can do.

The imaging apparatus 1 includes three different optical systems (imaging units) that separately capture R, G, and B images of the object P, and each optical system has an imaging area within the field of view of the image sensor. That is, in other words, the object P and each image sensor are arranged so as to be optically the same distance. Further, the lens and the image sensor of each optical system are arranged so that the image of the object P is formed at the substantially central portion of each image sensor, and an arbitrary one point image of the object P is each image sensor 4R. -It arrange | positions so that it may image at the substantially same position of 4G * 4B.

  Since the imaging device 1 is configured as described above, when the images of the image sensors 4R, 4G, and 4B are read out, the same imaging area can be read out, and the image signal output from each image sensor is read out by the image processing unit. A color image is obtained by combining in step 5.

  The image sensors 4R, 4G, and 4B used in the imaging apparatus 1 may be CCD image sensors or CMOS image sensors, and may be line sensors or area sensors.

  FIG. 2 is a diagram illustrating a state in which the imaging device images a target object. FIG. 2A shows a case where the image sensor of the imaging device is a line type image sensor, and FIG. 2B shows a case where the image sensor of the imaging device is an area type image sensor. FIG. 2 shows a side view and a front view of each image sensor.

  As shown in FIG. 2A, when the image sensor 4 is a line-type image sensor, if the object P is a printed material that continuously moves in the sub-scanning direction, the width direction of the object P (main scanning) By repeating scanning of a predetermined area in the direction), the entire image of the object P can be read.

  In addition, as shown in FIG. 2B, when an area type image sensor is used as the image sensors 4R, 4G, and 4B, it can be set to perform imaging with all pixels.

  Next, since the imaging apparatus of the present invention performs imaging in a state where the distance from the object is always constant, the same target is not limited to three imaging units (image sensors), and more than one imaging unit (image sensor). It can be configured to image an object. FIG. 3 is a diagram illustrating a schematic configuration of an imaging apparatus capable of color separation into four or more colors. As shown in FIG. 3A, for example, each image can be captured by color separation into four colors of R, G, B, and Ir. In the configuration shown in FIG. 3A, the image sensors 14R, 14G, 14B, and 14Ir are disposed optically at the same distance from the object P so as to face the object P. Each image can be picked up by separating the image into four colors of R, G, B, and Ir.

  In general, in overprinting of offset printing, an achromatic color is often expressed by mixing not only black (K) ink but also Y, M, and C inks in an appropriate amount. At this time, the ratio of each ink of Y, M, C, and K used for expressing an achromatic color is not constant. Therefore, even when trying to measure the ink amount (ink area) of four colors (YMCK), the mixing ratio of black and other color inks is not clear in the gray and black parts, and the conventional RGB (or YMCG) In an image pickup apparatus that picks up an image by color separation, the amount of each ink of YMCK cannot be obtained correctly.

  In the imaging apparatus of the present invention, as described above, an image of an object can be separated into four colors of R, G, B, and Ir and each image can be imaged, and the object is imaged via an infrared filter. Then, the amount of black ink can be measured, and each ink amount can be accurately decomposed. Therefore, the image pickup apparatus of the present invention can be used for inspection of a print defect of a color image printed using four colors of YMCK ink and monitoring of color tone. It should be noted that when performing a print defect inspection or color change monitoring of a color image printed using four colors of YMCK, color separation into five colors of Y, M, C, G, and Ir is performed. Also good.

  Further, the image pickup apparatus of the present invention can be used for color tone monitoring of a color image using a plurality of color inks. For example, as shown in FIG. 3B, light cyan (LC) and light magenta (LM) inks are used in addition to cyan, magenta, yellow, and black inks to create a smooth gradation image. The used printed matter can be separated into six colors and each image can be taken. In this case, the image pickup apparatus is provided with six optical systems, and the image sensors 24Y, 24M, 24C, 24B, 24LM, and 24LC are disposed at the same optical distance from the object P so as to face the object P. The image of the object P can be color-separated into six colors at approximately the center of each image sensor to capture each image. Such an imaging apparatus can be used for the purpose of monitoring the color tone of a printed material of six colors, for example. Further, the imaging device 1 can individually output the signals output by the image sensors without being combined, and compares the image data captured by the image sensors with the reference data, thereby performing defect inspection for each plate. It can be carried out. Furthermore, an image with a more correct color can be obtained by using a color image obtained by combining signals output from the image sensors.

  Since the image sensor has the ability to perform photoelectric conversion up to wavelengths in the near-infrared region, if infrared light is accepted as it is when a color image is captured, a signal having a correct color cannot be reproduced. Therefore, it is preferable to use an infrared cut filter for each color filter (excluding the infrared filter) used in the image sensor.

  The present invention can be applied to an application for reading a color image of a flat subject whose distance from the subject is constant. For example, it can be used in a quality inspection apparatus for printed matter.

1 is a schematic configuration diagram of an imaging apparatus according to an embodiment of the present invention. It is the figure which showed a mode that an imaging device imaged a target object. It is the figure which showed schematic structure of the imaging device which can color-separate into four or more colors.

Explanation of symbols

1-imaging device, 2R, 2G, 2B-lens,
3R / 3G / 3B-filter, 4R / 4G / 4B-image sensor,
5-image processing circuit, 6-output circuit

Claims (2)

An imaging device that captures an image of an object located at a certain distance,
A plurality of imaging units comprising: an image sensor that images an object; a lens that forms an image of the object on the image sensor; and a filter that passes only light of a specific wavelength component;
An image processing unit that performs image processing of an object imaged by the image sensor,
The filters of the respective imaging units pass light of different wavelength components,
The image sensor of each imaging unit is arranged to image the same region of the object from an optically substantially same distance as the object,
The image processing unit synthesizes images of the same region of the object captured by the image sensors.   The imaging apparatus according to claim 1, wherein one filter of the imaging unit is a filter that allows infrared rays to pass.

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