Image acquiring method and image acquiring apparatus

1. An image acquiring method, in which an image of a subject is photographed using stroboscopic light as external illumination, comprising the steps of:

comparing, in terms of color change, an image of said subject acquired without using the stroboscopic light and images of said subject acquired by using a plurality of different kinds of stroboscopic light; and

selecting one kind of stroboscopic light which has the least color change from among said plurality of different kinds of stroboscopic light, thereby finally acquiring the image of said subject.

2. The image acquiring method according to claim 1 , wherein said plurality of different kinds of stroboscopic light have colors changed along a black body radiation locus and that a point on the black body radiation locus corresponding to a color of said one kind of stroboscopic light which has the least color change between said image acquired without using said stroboscopic light and each of said images acquired using said plurality of different kinds of stroboscopic light is obtained, and said one kind of stroboscopic light having the color determined by said point is used to finally acquire the image.

3. The image acquiring method according to claim 1 , wherein an inverse number correlated color temperature of said one kind of stroboscopic light used when the image is finally acquired is in a range of ±50 mired with respect to the inverse number correlated color temperature of a black body radiation locus corresponding to the color of said one kind of stroboscopic light which has the least color change.

4. The image acquiring method according to claim 1 , wherein, when said color change is determined, a color of each image is decomposed into a luminance signal and a chromaticity signal, and a magnitude of said color change is determined using a difference in the chromaticity signal.

5. The image acquiring method according to claim 1 , wherein said comparison in terms of color change comprises the steps of:

calculating difference values of colors between said image acquired without using the stroboscopic light and said images acquired by using a plurality of different kinds of stroboscopic light with respect to pixels of each image;

calculating a total sum of said difference values of the pixels;

comparing said total sum of each image; and

one kind of stroboscopic light with which the value of the total sum becomes least is selected as a stroboscopic light which has the least color change from among said plurality of different kinds of stroboscopic light.

6. An image acquiring method, comprising the steps of:

photographing a reference object or a subject using a plurality of different kinds of stroboscopic light as external illumination and without using stroboscopic light to acquire first images photographed respectively with said plurality of different kinds of stroboscopic light and a second image photographed without the stroboscopic light;

determining a color change between said second image and each of said first images to obtain color changes of said first images, respectively;

comparing said color changes of said first images photographed respectively with said plurality of different kinds of stroboscopic light;

selecting one stroboscopic light in which said color change is least from among said plurality of different kinds of stroboscopic light; and

thereby acquiring a final image of the subject.

7. The image acquiring method according to claim 6 , wherein said acquiring step of the final image is a step of photographing said subject using said one stroboscopic light to acquire said final image when said first images and said second image are acquired by photographing said reference object or a step of determining as said final image one image of said first images which is acquired by photographing said subject using said one stroboscopic light when said first images and said second image are acquired by photographing said subject.

8. The image acquiring method according to claim 6 , wherein an inverse number correlated color temperature of said one kind of stroboscopic light used when the image is finally acquired is in a range of ±50 mired with respect to the inverse number correlated color temperature of a black body radiation locus corresponding to the color of said one kind of stroboscopic light which has the least color change.

9. The image acquiring method according to claim 6 , wherein said comparison in terms of color change comprises the steps of:

calculating difference values of colors between said second image and each of said first images with respect to pixels of each image;

calculating a total sum of said difference values of the pixels;

comparing said total sum of each image; and

one kind of stroboscopic light with which the value of the total sum becomes least is selected as a stroboscopic light which has the least color change from among said plurality of different kinds of stroboscopic light.

10. An image acquiring apparatus for photographing an image of a subject using stroboscopic light as external illumination, comprising:

photographing means for photographing the image of the subject;

a stroboscopic lamp for emitting a plurality of different kinds of stroboscopic light having different colors;

means for obtaining color change between an image of said subject acquired without using the stroboscopic light and each of images of said subject acquired using said plurality of different kinds of stroboscopic light; and

stroboscopic light color selecting means for selecting one kind of stroboscopic light which has the least color change for finally acquiring the image of said subject from among said plurality of different kinds of stroboscopic light.

11. The image acquiring apparatus according to claim 10 , wherein said plurality of different kinds of stroboscopic light emitted from the stroboscopic lamp have the colors changed along a black body radiation locus and that said stroboscopic light color selecting means selects said one kind of stroboscopic light for finally acquiring the image, based on a point on the black body radiation locus corresponding to a color of said one kind of stroboscopic light having the least color change between said image acquired without using the stroboscopic light and said images acquired using said plurality of different kinds of stroboscopic light.

12. The image acquiring apparatus according to claim 10 , wherein an inverse number correlated color temperature of said one kind of stroboscopic light selected by said stroboscopic light color selecting means is in a range of ±50 mired with respect to the inverse number correlated color temperature of a black body radiation locus corresponding to the color of said one kind of stroboscopic light having the least color change.

13. The image acquiring apparatus according to claim 10 , further, comprising:

decomposing means for decomposing the color of each image into a luminance signal and a chromaticity signal and that said color change is obtained by determining a magnitude of said color change using only a difference in the chromaticity signal.

14. The image acquiring apparatus according to claim 10 , wherein

said means for obtaining color change calculates a difference values of colors between said image acquired without using the stroboscopic light and each of said images acquired by using a plurality of different kinds of stroboscopic light with respect to pixels of each image and calculates a total sum of said difference values of the pixels, and compares said total sum of each image; and said stroboscopic light color selecting means selects one kind of stroboscopic light with which the value of the total sum becomes least, as a stroboscopic light which has the least color change from among said plurality of different kinds of stroboscopic light.