Difference image generation device, difference image generation method, and computer readable media

1. A difference image generation device comprising:

a measurement unit that measures a variation width of pixel values of a difference image signal obtained by performing subtraction processing on first and second input image signals; and

a scaling unit that performs a scaling operation on each pixel value of the difference image signal based on a measurement result of the variation width so that the difference image signal can be represented in grayscale using a predetermined bit width, and outputs a difference image signal subjected to the scaling;

wherein the measurement unit calculates the variation width based on a maximum value and a minimum value of the difference image signal measured within a predetermined signal range of the first and second input image signals.

2. The difference image generation device according to claim 1 , wherein the measurement unit is configured to measure the variation width in at least one frame image of the first and second input image signals.

3. The difference image generation device according to claim 2 , wherein

each of the first and second input image signals includes a sequence of frame images, and

the scaling unit is configured to perform the scaling operation by applying the measurement result of the variation width to a frame image subsequent to the at least one frame image in which the variation width is measured.

4. The difference image generation device according to claim 2 , wherein the measurement unit measures the variation width for a measurement period of two or more frame images.

5. The difference image generation device according to claim 2 , wherein

the measurement unit measures the variation width for each frame image, and

the scaling unit performs the scaling operation for each frame image based on the measurement result of the variation width for each frame image obtained by the measurement unit.

6. The difference image generation device according to claim 1 , wherein, when the variation width of the difference image signal exceeds a magnitude that can be represented in grayscale using the predetermined bit width, the scaling unit performs a right bit shift on the difference image signal.

7. The difference image generation device according to claim 1 , wherein, when the variation width of the difference image signal has a magnitude that can be represented in grayscale using a bit width smaller than the predetermined bit width, the scaling unit performs a left bit shift on the difference image signal.

8. The difference image generation device according to claim 1 , further comprising an addition unit that adds an offset based on a minimum value of the difference image signal to each of the pixel values of the difference image signal so that a minimum value of the difference image signal subjected to the scaling becomes zero.

9. A difference image generation method comprising:

measuring, by a measurement unit, a variation width of pixel values of a difference image signal obtained by performing subtraction processing on first and second input image signals; and

scaling, by a scaling unit, each pixel value of the difference image signal based on a measurement result of the variation width so that the difference image signal can be represented in grayscale using a predetermined bit width;

wherein the measuring includes calculating the variation width based on a maximum value and a minimum value of the difference image signal measured within a predetermined signal range of the first and second input image signals.

10. The method according to claim 9 , wherein the measurement of the variation width is performed for at least one frame image of the first and second input image signals.

11. The method according to claim 10 , wherein

each of the first and second input image signals includes a sequence of frame images, and

the scaling comprises scaling a subsequent frame image based on a measurement result of the variation width for a previous frame image.

12. The method according to claim 10 , wherein the measurement is performed for a measurement period of two or more frame images.

13. The method according to claim 9 , wherein the scaling comprises performing a right bit shift on the difference image signal when the variation width of the difference image signal exceeds a magnitude that can be represented in grayscale using the predetermined bit width.

14. The method according to claim 9 , wherein the scaling comprises performing a left bit shift on the difference image signal when the variation width of the difference image signal has a magnitude that can be represented in grayscale using a bit width smaller than the predetermined bit width.

15. The method according to claim 9 , further comprising adding an offset based on a minimum value of the difference image signal to each of the pixel values of the difference image signal so that a minimum value of the difference image signal subjected to the scaling becomes zero.

16. A tangible computer readable medium embodying instructions for causing a computer system to perform a difference image generation method, the method comprising:

measuring a variation width of pixel values of a difference image signal obtained by performing subtraction processing on first and second input image signals; and

scaling each pixel value of the difference image signal based on a measurement result of the variation width so that the difference image signal can be represented in grayscale using a predetermined bit width;

wherein the measuring includes calculating the variation width based on a maximum value and a minimum value of the difference image signal measured within a predetermined signal range of the first and second input image signals.

17. The difference image generation device according to claim 1 , wherein the second image signal is obtained by image processing of the first image signal.

18. The method according to claim 9 , wherein the second image signal is obtained by image processing of the first image signal.

19. The tangible computer readable medium according to claim 16 , wherein the second image signal is obtained by image processing of the first image signal.