JP2010025473A - Image emphasizing device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To emphasize an object portion being observed from a photographed image. <P>SOLUTION: The image enhancement device includes: a first photographing means 11 for photographing a first image by a felt wavelength region; a second photographing means 12 for photographing a second image in the same field of view as the first image and with the same pixel number and the same resolution as the first image by a felt wavelength region different from the first felt wavelength region; a contrast image calculating means 13 for calculating the contrast between the first image and the second image and outputting it as a contrast image; and an emphasized image calculating means 14 for calculating an evaluation function predetermined by the contrast image and an emphasized contrast value predetermined as a value for emphasizing the observed object, and outputting it as an emphasized image. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image enhancement apparatus and an image enhancement method for enhancing an object part of interest from a captured image.

  There is an image processing apparatus that detects an image of an aircraft by capturing an infrared image in a high-speed flying object or the like that captures and tracks the aircraft. This image processing apparatus gives a threshold value for binarization of an image to obtain an aircraft image in a region where the temperature is higher than the threshold value, and bisects the image as a background image in a region where the temperature is low. Only the aircraft image of can be captured.

  In addition, for example, there is conventionally a technique for extracting a target using a near-infrared image captured by a first image sensor and a mid-infrared image captured by a second image sensor (for example, Patent Document 1). reference).

  However, “jet engine plume” (about 1000 to 2000 ° C.), which is higher than the temperature of the airframe (about 30 ° C.), is generated from the aircraft engine. In addition, an “heating element” (about 1700 ° C.) that is higher than the temperature of the aircraft may be dropped from the aircraft. In addition, there are “clouds” (about 10 ° C.) that are cooler than the temperature of the aircraft.

Therefore, when capturing a fuselage image, there is a risk of erroneous detection of the aircraft due to a jet engine plume, a heating element, a cloud, or the like existing in the imaging field of view, depending on the threshold value to be set. In addition, if the detection of the aircraft is wrong, there is a problem that the guidance accuracy of the high speed flying object is impaired.
JP-A-6-323788

  As described above, in the conventional method, when an object of interest (airframe) is detected from a captured image, the object of interest may not be detected accurately.

  Therefore, the present invention provides an image enhancement apparatus and an image enhancement method that accurately detect an object portion of interest from a captured image and emphasize the object portion of interest.

  An image enhancement apparatus according to a feature of the present invention is an image enhancement apparatus that generates an enhanced image in which an object of interest included in a captured image is enhanced, and includes a first image including the object of interest by a first sensitive wavelength region. The first image pickup means for picking up images and the second sensitive wavelength region different from the first sensitive wavelength region have the same field of view as the first image, the same number of pixels and the same resolution. A second imaging unit that captures two images, a contrast image calculation unit that calculates a contrast between the first image and the second image as a contrast image, a value that emphasizes the contrast image and the object of interest. And an enhanced image computing means for computing an enhanced image that enhances the object of interest contained in the captured image from the enhanced contrast value.

  An image enhancement method for generating an enhanced image by emphasizing an object of interest included in a captured image, the step of inputting a first image including the object of interest captured in a first sensitive wavelength region, and the first Inputting a second image having the same field of view as the first image and having the same number of pixels and the same resolution, which is imaged in a second sensitive wavelength region different from the sensitive wavelength region of The object of interest included in the captured image is calculated from the step of calculating the contrast between the first image and the second image as a contrast image, the contrast image, and an enhanced contrast value that is predetermined as a value that enhances the object of interest. Calculating an emphasized image to be emphasized.

  According to the present invention, it is possible to emphasize an object of interest from a captured image.

  Hereinafter, an image enhancement apparatus and an image enhancement method according to the best embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the image enhancement device 1 according to the present invention includes a first imaging unit 11 that captures a first image Aij with an infrared sensor, and an infrared ray having a wavelength different from that of the first imaging unit 11 in a sensitive wavelength region. From the second image pickup means 12 for picking up the second image Bij by the sensor, the contrast image calculation means 13 for calculating the contrast image Cij from the first image Aij and the second image Bij, and a preset enhanced contrast value Cref And an enhanced image computing means 14 for computing an enhanced image Dij that enhances the contrast image Cij.

  The first image pickup unit 11 and the second image pickup unit 12 include infrared sensors having the same imaging field of view, the number of pixels of the captured image, and the resolution, but having different sensitive wavelength regions. The images captured by the first captured image 11 and the second captured image 12 include “hot object”, “target object”, and “cold object”, respectively. Here, the “airframe” is the “target object”, the “jet engine plume” or “heating element” that is hotter than the airframe is the “hot object”, and the “cloud” or “rain” that is cooler than the airframe. Are referred to as “cold objects”.

  The first imaging unit 11 outputs the captured first image Aij to the contrast image calculation unit 13, and the second imaging unit 12 also outputs the captured second image Bij to the contrast image calculation unit 13. In the following description, the sensitive wavelength of the first imaging unit 11 is assumed to be the first wavelength, and the sensitive wavelength of the second imaging unit 12 is assumed to be the second wavelength that is longer than the first wavelength. Here, in the first image Aij and the second image Bij, the pixel of the x coordinate of the image is represented as i, and the pixel of the y coordinate is represented as j.

  An image level when an object having a different temperature at each wavelength is imaged will be described with reference to FIG. FIG. 2 represents the relative ratio of the image levels of the captured image in the case of black body radiation obtained using Planck's radiation law. FIG. 2 shows an example of the image level when the temperature of the high-temperature object is 800K, the temperature of the target object is 600K, the temperature of the low-temperature object is 500K, the first wavelength is 4 μm, and the second wavelength is 10 μm.

  As shown in FIG. 2, at the first wavelength, the image level of the low temperature object is “0.2”, the image level of the target object is “1”, and the image level of the high temperature object is “4”. At the second wavelength, the image level of the low temperature object is “0.2”, the image level of the target object is “0.7”, and the image level of the high temperature object is “1”. It depends on. FIG. 3A shows a comparison of image levels of the first image Aij and the second image Bij in each object in the case of FIG. As shown in FIG. 3A, it can be seen that in both images, the difference in image level is large in the high-temperature object portion, the difference in image level is small in the target object portion, and the image level is the same in the low-temperature object portion.

  The contrast image calculation means 13 calculates the contrast image Cij from the first image Aij and the second image Bij input by the following contrast calculation formula (Formula 1). Further, the contrast image calculation unit 13 outputs the calculated contrast image Cij to the emphasized image calculation unit 14.

Cij = (Aij−Bij) / (Aij + Bij) (Formula 1)
The contrast image Cij obtained by the calculation is also expressed with the x coordinate of the image as i and the pixel of the y coordinate as j. FIG. 3B shows an example of the image level of the contrast image Cij calculated from the first image Aij and the second image Bij described above with reference to FIG. In the example of FIG. 3B, in the contrast image Cij, the image level of the high temperature object is “0.60”, the image level of the object of interest is “0.18”, and the image level of the low temperature object is “0”.

  In the enhanced image calculation unit 14, the enhanced contrast value Cref is set based on the sensitive temperature of the first imaging unit 11 and the second imaging unit 12 and the temperature of the object of interest. When the contrast image Cij is input from the contrast image calculation means 13, the emphasized image calculation means 14 is set as the input contrast image Cij by the following emphasized image calculation expressions (Expression 2) and (Expression 3). The emphasized image Dij is calculated from the value Cref. Similarly to the other images, this enhanced image Dij is represented by the x coordinate of the image as i and the pixel of the y coordinate as j.

δij = | Cij−Cref | (Formula 2)
Dij = MAX (δij) −δij (Formula 3)
Specifically, the emphasized image calculation means 14 first obtains the evaluation image value δij by (Equation 2) using the emphasized contrast value Cref. Thereafter, the emphasized image computing means 14 obtains the maximum value MAX (δij) from the obtained evaluation image value δij, and obtains the emphasized image Dij for the target object using the evaluation function expression of (Expression 3). The evaluation function formula of (Formula 3) is expressed as shown in FIG.

  FIG. 3C shows an example of the image level of the emphasized image Dij calculated from the contrast image Cij described above with reference to FIG. The example of FIG. 3C is an example in which the enhanced contrast value Cref is set to “0.18” with respect to the contrast image Cij, and the image level of the high-temperature object is “0” in the enhanced image Dij. The image level of the object is “0.42”, and the image level of the low-temperature object is “0.24”. That is, it can be seen that the object of interest is emphasized in the enhanced image Dij. In setting Cref, a method of setting based on the value of the image level of the object of interest in the contrast image itself can be applied.

  Further, the enhanced image calculation means 14 outputs the calculated enhanced image Dij as a result of image enhancement processing in the image enhancement apparatus 1.

  Therefore, in the enhanced image Dij output from the enhanced image calculation means 14, the target object portion is emphasized, so that the target object can be easily distinguished.

  Here, Fig. 5 shows an example of the spectral characteristics of the infrared emission of the engine plume (Source: "The Infrared & Electro-Optical Systems Handbook", Vol.1, GJ Zissis, SPIE, 1993 Fig2.64). An example of the spectral characteristics of infrared radiation from a heating element (Source: “The Infrared & Electro-Optical Systems Handbook”, Vol. 1, GJ Zissis, SPIE, 1993 Fig2.79) is shown. As shown in FIGS. 5 and 6, even for a high-temperature object, the spectral characteristics of the engine plume and the heating element are irregular regardless of Planck's radiation law. For this reason, even if the temperature of the engine plume and the heating element are different, when an image is picked up by the imaging means having only one specific wavelength, there may be no difference in the image level between the engine plume part and the heating element part in the picked-up image. . Therefore, as described above, by comparing the captured images captured by the first imaging unit 11 and the second imaging unit 12 having different sensitive wavelength ranges, the aircraft that is the target object and the engine that is the high-temperature object from the captured image. In addition to distinguishing between plumes and heating elements, it is also possible to distinguish objects with different engine plumes and heating elements from high-temperature objects.

  In recent years, two-wavelength infrared sensors composed of sensors in the sensitive wavelength region with the same imaging field of view, the number of pixels and resolution, such as QWIP (Quantum Well Infrared Photodetector) have been developed. Is used as the first imaging unit 11 and the second imaging unit 12, the image enhancement device 1 can be easily configured.

  Further, although the evaluation function shown in (Expression 3) is used for the calculation of the emphasized image Dij, the present invention is not limited to this. For example, according to the statistical analysis of the contrast image Cij, when the image level of the evaluation image value δij is equal to or lower than a predetermined value, the value of the emphasized image Dij is forcibly set to “0”. It is possible to obtain an image that emphasizes the target object portion without departing from the gist of the above.

It is a block diagram explaining the structure of the image enhancement apparatus which concerns on the best embodiment of this invention. It is a figure explaining the relationship between the temperature of an object, and an image level. It is a figure explaining the image level of each image in the image enhancement apparatus of FIG. It is a figure explaining the enhancement of the image in the image enhancement apparatus of FIG. It is a figure explaining the spectral characteristic of an engine plume. It is a figure explaining the spectral characteristic of flare.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image emphasis apparatus 11 ... 1st imaging means 12 ... 2nd imaging means 13 ... Contrast image calculating means 14 ... Enhanced image calculating means
Aij ... 1st image
Bij ... second image
Cij: Contrast image
Cref: Enhanced contrast value
Dij ... Emphasized image δij ... Evaluation image value

Claims (4)

An image enhancement device that generates an enhanced image that emphasizes an object of interest included in a captured image,
First imaging means for capturing a first image including the object of interest by a first sensitive wavelength region;
Second imaging means for imaging a second image having the same field of view as the first image, the same number of pixels, and the same resolution by a second sensitive wavelength region different from the first sensitive wavelength region When,
Contrast image calculation means for calculating the contrast between the first image and the second image as a contrast image;
Enhanced image computing means for computing an enhanced image that enhances the noted object included in the captured image from the contrast image and an enhanced contrast value that is predetermined as a value that enhances the noted object;
An image enhancement apparatus comprising: The contrast image calculation means includes:
The ratio of the difference and sum of the image levels is calculated for each pixel of the first image and the second image, and a contrast image is generated with the ratio obtained for each pixel as the image level of each pixel. The image enhancement apparatus according to claim 1. The enhanced image calculation means includes
The difference value between the image level and the enhanced contrast value is calculated for each pixel of the contrast image, and the difference between the maximum difference value of all pixels and the difference value of the target pixel is calculated. The image enhancement apparatus according to claim 1, wherein an enhanced image is generated using the difference obtained in this way as an image level of the pixel. An image enhancement method for generating an enhanced image that emphasizes an object of interest included in a captured image,
Inputting a first image including the object of interest imaged in a first sensitive wavelength region;
The step of inputting a second image having the same field of view as the first image, the same number of pixels and the same resolution, taken in a second sensitive wavelength region different from the first sensitive wavelength region When,
Calculating a contrast between the first image and the second image as a contrast image;
Calculating an emphasized image for emphasizing the object of interest included in the captured image from the contrast image and an emphasis contrast value predetermined as a value for emphasizing the object of interest;
An image enhancement method comprising:

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