# US 6,298,144 B1 · Device for and method of detecting motion in an image

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- Number: US 6,298,144 B1
- Document ID: US6298144B1
- Status: Granted
- Kind: B1
- Application number: 09/081,608
- Filed: 1998-05-20
- Granted: 2001-10-02
- Earliest claimed: 1998-05-20
- Assignees: The United States of America as represented by the National Security Agency
- Inventors: Leonard G. Pucker, II; David B. Sofge
- Web page: https://patentgrep.com/patent/US6298144B1

## CPC

- H04N 5/147: {Scene change detection}
- G06T 7/254: involving subtraction of images
- H04N 5/144: {Movement detection (for video coding H04N19/503; analysis of motion in general G06T7/20)}
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL

## Abstract

A device for and method of detecting motion between a reference image and a test image by acquiring the images; aligning the images; dividing the images into blocks; masking certain blocks; differencing corresponding blocks; median filtering the differences; low-pass filtering the outputs of the median filter; generating a normalized histogram for each output of the low-pass filter; generating a model of gaussian noise; calculating the distance between the noise model and each normalized histogram; comparing each distance calculated to a user-definable threshold; and determining if motion has occurred between the images if a certain number of distance calculations are at or above the user-definable threshold. If a scene is to be continuously monitored and no motion occurred between the previous reference image and the previous test image then a new test image is acquired and compared against the previous reference image as described above. If the scene is to be continuously monitored and motion has occurred between the previous reference image and the previous test image then replace the previous reference image with the previous test image, acquire a new test image, and compare the new test image to the new reference image as described above.

## Claims

### Claim 1

A method of detecting motion between a reference image and a test image, comprising the steps of:
a) acquiring the reference image;
b) acquiring the test image;
c) aligning the reference image and the test image;
d) dividing the reference image and the test image each into N×M blocks, where N and M are user-definable integers;
e) masking a user-definable number of blocks of the reference image and the test image;
f) differencing each pair of corresponding blocks in the reference image and the test image;
g) median filtering each result of the last step;
h) low-pass filtering each result of the last step;
i) generating a normalized histogram for each result of the last step;
j) generating a model of gaussian noise;
k) calculating a distance between the model of gaussian noise and each result of step (i);
l) comparing the results of the last step to a user-definable threshold; and
m) determining that no motion has occurred between the reference image and the test image if a user-definable number of results of the last step where below the user-definable threshold, otherwise determining that motion has occurred between the reference image and the test image.

### Claim 2 (depends on 1)

The method of claim 1, further including the step of discarding the test image, acquiring a new test image, and returning to step (c) if no motion has been determined in step (m), otherwise, replacing the reference image with the test image, acquiring a new test image, and returning to step (c).

### Claim 3 (depends on 1)

The method of claim 1, wherein said step of aligning the reference image and the test image is comprised of using an alignment technique selected from the group consisting of horizontal alignment, vertical alignment, and horizontal and vertical alignment.

### Claim 4 (depends on 1)

The method of claim 1, wherein said step of generating a model of gaussian noise comprises generating a model of gaussian noise for noise commonly encountered in sonograms.

### Claim 5 (depends on 1)

The method of claim 1, wherein said step of generating a model of gaussian noise comprises generating a model of gaussian noise for noise commonly encountered in radar images.

### Claim 6 (depends on 1)

The method of claim 1, wherein said step of calculating a distance comprises calculating a distance using a distance calculation selected from the group consisting of a Kullback-Leibler “goodness of fit” test, a chi-square test, a Kolmogorov-Smirnov test, and an Anderson-Darling test.

### Claim 7 (depends on 2)

The method of claim 2, wherein said step of aligning the reference image and the test image is comprised of using an alignment technique selected from the group consisting of horizontal alignment, vertical alignment, and horizontal and vertical alignment.

### Claim 8 (depends on 7)

The method of claim 7, wherein said step of generating a model of gaussian noise comprises generating a model of gaussian noise for noise commonly encountered in sonograms.

### Claim 9 (depends on 8)

The method of claim 8, wherein said step of generating a model of gaussian noise comprises generating a model of gaussian noise for noise commonly encountered in radar images.

### Claim 10 (depends on 9)

The method of claim 9, wherein said step of calculating a distance comprises calculating a distance using a distance calculation selected from the group consisting of a Kullback-Leibler “goodness of fit” test, a chi-square test, a Kolmogorov-Smirnov test, and an Anderson-Darling test.

### Claim 11

A device for detecting motion between a reference image and a test image, comprising:
a) an image grabber, having a first input for acquiring the reference image and the test image, having a second input, having a first output for transmitting the reference image, and having a second output for transmitting the test image;
b) an image aligner, having a first input connected to the first output of said image grabber, having a second input connected to the second output of said image grabber, having a first output for transmitting the aligned reference image, and having a second output for transmitting the aligned test image;
c) a block divider, having a first input connected to the first output of said image aligner, having a second input connected to the second output of said image aligner, having a first output for transmitting a divided reference image, and having a second output for transmitting a divided test image;
d) a masker, having a first input connected to the first output of said block divider, having a second input connected to the second output of said block divider, having a third input for receiving a control signal that indicates which blocks should be masked, having a first output for transmitting un-masked blocks of the reference image, and having a second output for transmitting a un-masked blocks of the test image;
e) a differencer, having a first input connected to the first output of said masker, having a second input connected to the second output of said masker, and having an output for transmitting blocks that represent the differences between the blocks of the reference image and corresponding blocks of the test image;
f) a median filter, having an input connected to the output of said differencer, and having an output;
g) a low-pass filter, having an input connected to the output of said median filter, and having an output;
h) a histogram generator, having an input connected to the output of said low-pass filter, and having an output;
i) a distance calculator, having a first input connected to the output of said histogram generator, having a second input for receiving a model of gaussian noise, and having an output;
j) a comparator, having a first input connected to the output of said distance calculator, having a second input for receiving a user-definable threshold, and having an output; and
k) a controller, having a first input connected to the output of said comparator, having a second input for receiving a user-definable number, and having an output connected to the second input of said image grabber.

### Claim 12 (depends on 11)

The device of claim 11, wherein said low-pass filter is comprised of a two-dimensional infinite impulse response filter.

### Claim 13 (depends on 11)

The device of claim 11, wherein said distance calculator implements distance calculations selected from the group consisting of a Kullback-Leibler “goodness of fit” test, a chi-square test, a Kolmogorov-Smirnov test, and an Anderson-Darling test.

### Claim 14 (depends on 12)

The device of claim 12, wherein said distance calculator implements distance calculations selected from the group consisting of a Kullback-Leibler “goodness of fit” test, a chi-square test, and an Anderson-Darling test.