IMAGE GENERATION APPARATUS, IMAGE GENERATION METHOD AND IMAGE GENERATION PROGRAM

• US 20120249801A1
• Filed: 12/01/2010
• Published: 10/04/2012
• Est. Priority Date: 12/14/2009
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Nozaki, Takeo
• Granted Patent: US 9,047,672 B2
• Time in Patent Office: Days
• US Class Current: 348/164
• CPC Class Codes: G06T 2207/10048 Infrared image
• CPC Class Codes: G06T 5/94 based on local image properties, e.g. for local contrast enhancement

Abstract

An image generation apparatus is provided with: a resolution sensitivity conversion unit which generates different weight-averaged images by performing convolution operations on the infrared image with plural different weighted-filter images, and generates a resolution-sensitivity-converted image by adding luminance differences between the weight-averaged images to luminance values of the infrared image; a luminance shift calculating unit which sets the most frequently appearing luminance value of the resolution-sensitivity-converted image to an intermediate value in an enlarged range and as an intermediate luminance value, and generates a luminance-shifted image obtained by linearly shifting luminance values of the resolution-sensitivity-converted image in such a manner that the shifting corresponds to the intermediate luminance value and the enlarged range; and a luminance arithmetic operation unit which generates an arithmetically processed image by performing an arithmetic operation based on luminance differences between corresponding positions of the luminance-shifted image and a reverse shifted image.

Claims

1. An image generation apparatus, comprising:

an optical unit which condenses infrared rays from an image capturing target containing a target object and acquires a specific wavelength band from the condensed infrared rays;

an uncooled infrared image sensor which generates an infrared image corresponding to a temperature of the image capturing target based on the wavelength acquired by the optical unit; and

an image processing unit which generates an arithmetically processed image by performing arithmetic processing on luminance values of the infrared image, wherein

the image processing unit comprises;

a resolution sensitivity conversion module which generates a plurality of different weight-averaged images corresponding to a plurality of weighted-filter image of different pixel numbers by performing a convolution operation of filter coefficients of each of the weighted-filter images and luminance values at corresponding positions in the infrared image, and generates a resolution-sensitivity-converted image by adding luminance differences of the pixels of the different weight-averaged images to respective luminance values of the corresponding pixels of the infrared image;

a luminance histogram arithmetic operation module which generates a luminance histogram that shows appearing frequency of the luminance value of each pixel that forms the resolution-sensitivity-converted image;

a luminance level adjusting module which sets a gradation range of the resolution-sensitivity-converted image to an enlarged range set in advance, sets a most frequently appearing luminance value that is a luminance value whose appearing frequency in the luminance histogram is the maximum to an intermediate value in the enlarged range as an intermediate luminance value, and generates a luminance-shifted image by linearly shifting each luminance value of the resolution-sensitivity-converted image by corresponding to the enlarged range and the intermediate luminance value; and

a luminance arithmetic operation processing module which generates a reverse shifted image in which light and shade of luminance levels of the luminance-shifted image are reversed, and generates the arithmetically processed image by performing arithmetic processing based on differences in the luminance values of the corresponding pixels in each of the reverse shifted image and the luminance-shifted image.

2. The image generation apparatus as claimed in claim 1, wherein

the luminance arithmetic operation processing module comprises:

a luminosity difference image setting function which calculates luminance level averaged values of the luminance-shifted image and the reverse shifted image, respectively, and sets one of the luminance-shifted image or the reverse shifted image as a high luminosity side image and the other image as a low luminosity side image, respectively, based on the luminance averaged values; and

a subtraction processing function which generates the arithmetically processed image by executing frequency value subtraction processing for subtracting a frequency value of each pixel at corresponding position of the low luminosity side image from the luminance value of each pixel of the high luminosity side image as the arithmetic operation processing.

3. The image generation apparatus as claimed in claim 1, wherein

the luminance arithmetic operation processing module comprises:

a luminosity difference image setting function which calculates luminance level averaged values of the luminance-shifted image and the reverse shifted image, respectively, and sets one of the luminance-shifted image or the reverse shifted image as a high luminosity side image and the other image as a low luminosity side image, respectively, based on the luminance averaged values; and

a division processing function which generates the arithmetically processed image by executing frequency value division processing for dividing the luminance value of each pixel of the high luminosity side image by a frequency value of each pixel at corresponding position of the low luminosity side image as the arithmetic operation processing.

4. The image generation apparatus as claimed in claim 1, wherein

the image processing unit comprises:

a filtering processing module which generates a filtering image by eliminating the luminance of the pixel in a luminance region less than the luminance frequency set in advance from the arithmetically processed image;

a contrast enlarging module which performs enlarging processing of contrast the filtering image based on the luminance values contained in the filtering image; and

a binarization processing module which performs processing for binarizing the pixel of the luminance level of equal to or more than a specific value in the arithmetically processed image.

5. The image generation apparatus as claimed in claim 2, wherein:

the luminance arithmetic operation processing module comprises

a luminosity difference image setting function which calculates luminance level averaged values of the luminance-shifted image and the reverse shifted image, respectively, and sets one of the luminance-shifted image or the reverse shifted image as a high luminosity side image and the other image as a low luminosity side image, respectively, based on the luminance averaged values, and

a division processing function which generates the arithmetically processed image by executing frequency value division processing for dividing the luminance value of each pixel of the high luminosity side image by a frequency value of each pixel at corresponding position of the low luminosity side image as the arithmetic operation processing; and

the image processing unit comprises

a filtering processing module which generates a filtering image by eliminating the luminance of the pixel in a luminance region less than the luminance frequency set in advance from the arithmetically processed image,

a contrast enlarging module which performs enlarging processing of contrast the filtering image based on the luminance values contained in the filtering image, and

a binarization processing module which performs processing for binarizing the pixel of the luminance level of equal to or more than a specific value in the arithmetically processed image.

6. An image generation method for generating an arithmetically processed image from an infrared image by using an image generation apparatus which comprises:

an uncooled infrared image sensor which condenses infrared rays from an image capturing target containing a target object and generates an infrared image from the infrared rays based on a temperature of the image capturing target; and

an image processing unit which performs arithmetic processing on luminance values of the infrared image, the method comprising;

generating weight-averaged images corresponding to a plurality of weighted-filter image of different pixel numbers by performing a convolution operation of filter coefficients of each of the weighted filter images and luminance values at corresponding positions in the infrared image, and generating a resolution-sensitivity-converted image by adding luminance differences of the pixels of the different weight-averaged images to respective luminance values of the corresponding pixels of the infrared image;

generating a luminance histogram that shows appearing frequency of the luminance value of each pixel that forms the resolution-sensitivity-converted image;

setting a gradation range of the resolution-sensitivity-converted image to an enlarged range set in advance;

setting a most frequently appearing luminance value that is a luminance value whose appearing frequency in the luminance histogram is the maximum to an intermediate value in the enlarged range as an intermediate luminance value;

generating a luminance-shifted image by linearly shifting each luminance value of the resolution-sensitivity-converted image by corresponding to the enlarged range and the intermediate luminance value; and

generating a reverse shifted image in which light and shade of luminance levels of the luminance-shifted image are reversed, and generating the arithmetically processed image by performing arithmetic processing based on differences in the luminance values of the corresponding pixels in each of the reverse shifted image and the luminance-shifted image.

7. A non-transitory computer readable recording medium storing an image generation program for generating an arithmetically processed image from an infrared image to be used in an image generation apparatus which comprises:

an uncooled infrared image sensor which condenses infrared rays from an image capturing target containing a target object and generates the infrared image from the infrared rays based on a temperature of the image capturing target; and

an image processing unit which performs arithmetic processing on luminance values of the infrared image, the program causing a computer to execute;

a resolution sensitivity conversion function which generates weight-averaged images corresponding to a plurality of weighted-filter image of different pixel numbers by performing a convolution operation of filter coefficients of each of the weighted-filter images and luminance values at corresponding positions in the infrared image, and generates a resolution-sensitivity-converted image by adding luminance differences of the pixels of the different weight-averaged images to respective luminance values of the corresponding pixels of the infrared image;

a luminance histogram arithmetic operation function which generates a luminance histogram that shows appearing frequency of the luminance value of each pixel that forms the resolution-sensitivity-converted image;

a luminance level adjusting function which sets a gradation range of the resolution-sensitivity-converted image to an enlarged range set in advance, sets a most frequently appearing luminance value that is a luminance value whose appearing frequency in the luminance histogram is the maximum to an intermediate value in the enlarged range as an intermediate luminance value, and generates a luminance-shifted image by linearly shifting each luminance value of the resolution-sensitivity-converted image by corresponding to the enlarged range and the intermediate luminance value; and

a luminance arithmetic operation processing function which generates a reverse shifted image in which light and shade of luminance levels of the luminance-shifted image are reversed, and generates the arithmetically processed image by performing arithmetic processing based on differences in the luminance values of the corresponding pixels in each of the reverse shifted image and the luminance-shifted image.

8. An image generation apparatus, comprising:

optical means for condensing infrared rays from an image capturing target containing a target object and acquiring a specific wavelength band from the condensed infrared rays;

an uncooled infrared image sensor means for generating an infrared image corresponding to a temperature of the image capturing target based on the wavelength acquired by the optical means; and

image processing means for generating an arithmetically processed image by performing arithmetic processing on luminance values of the infrared image, wherein

the image processing means comprises;

resolution sensitivity conversion means for generating a plurality of different weight-averaged images corresponding to a plurality of weighted-filter image of different pixel numbers by performing a convolution operation of filter coefficients of each of the weighted-filter images and luminance values at corresponding positions in the infrared image, and generating a resolution-sensitivity-converted image by adding luminance differences of the pixels of the different weight-averaged images to respective luminance values of the corresponding pixels of the infrared image;

luminance histogram arithmetic operation means for generating a luminance histogram that shows appearing frequency of the luminance value of each pixel that forms the resolution-sensitivity-converted image;

luminance level adjusting means for setting a gradation range of the resolution-sensitivity-converted image to an enlarged range set in advance, setting a most frequently appearing luminance value that is a luminance value whose appearing frequency in the luminance histogram is the maximum to an intermediate value in the enlarged range as an intermediate luminance value, and generating a luminance-shifted image by linearly shifting each luminance value of the resolution-sensitivity-converted image by corresponding to the enlarged range and the intermediate luminance value; and

luminance arithmetic operation processing means for generating a reverse shifted image in which light and shade of luminance levels of the luminance-shifted image are reversed, and generating the arithmetically processed image by performing arithmetic processing based on differences in the luminance values of the corresponding pixels in each of the reverse shifted image and the luminance-shifted image.