Motion detector
First Claim
1. A method of detecting motion activity by means of a detector, the method comprising for each of a series of frames,obtaining an ultrasonic signal derived from a transmitted ultrasonic signal;
- deriving an activity signal based on a difference between the obtained signal in a present frame and in at least one previous frame;
determining a peak value of the activity signal in a first time window of the frame;
determining a peak value of the activity signal in a second time window of the frame, wherein the second time window is different from the first time window;
calculating a ratio of the peak value of the activity signal in the first time window of the frame to the peak value of the activity signal in the second time window of the frame;
comparing the calculated ratio with a threshold value; and
determining that, in frames in which the calculated ratio exceeds the threshold values, there is motion of an object relative to the detector.
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Accused Products
Abstract
An ultrasonic motion activity detector is configured to, in each of a series of frames: obtain an ultrasonic signal derived from a transmitted ultrasonic signal; derive an activity signal based on a difference between the obtained signal in a present frame and at least one previous frame; determine a peak value of the activity signal in a first time window of the frame; determine a peak value of the activity signal in a second time window of the frame, wherein the first time window is different from the second time window; calculate a ratio of the peak value of the activity signal in the first time window of the frame to the peak value of the activity signal in the second time window of the frame; and compare the calculated ratio with a threshold value, and, in frames in which the calculated ratio exceeds the threshold value, determine that there is motion of an object relative to the detector.
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Citations
20 Claims
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1. A method of detecting motion activity by means of a detector, the method comprising for each of a series of frames,
obtaining an ultrasonic signal derived from a transmitted ultrasonic signal; -
deriving an activity signal based on a difference between the obtained signal in a present frame and in at least one previous frame; determining a peak value of the activity signal in a first time window of the frame; determining a peak value of the activity signal in a second time window of the frame, wherein the second time window is different from the first time window; calculating a ratio of the peak value of the activity signal in the first time window of the frame to the peak value of the activity signal in the second time window of the frame; comparing the calculated ratio with a threshold value; and determining that, in frames in which the calculated ratio exceeds the threshold values, there is motion of an object relative to the detector. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 20)
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17. An ultrasonic motion activity detector comprising modules to, in each of a series of frames:
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obtain an ultrasonic signal derived from a transmitted ultrasonic signal; derive an activity signal based on a difference between the obtained signal in a present frame and at least one previous frame; determine a peak value of the activity signal in a first time window of the frame; determine a peak value of the activity signal in a second time window of the frame, wherein the first time window is different from the second time window; calculate a ratio of the peak value of the activity signal in the first time window of the frame to the peak value of the activity signal in the second time window of the frame; compare the calculated ratio with a threshold value, and, in frames in which the calculated ratio exceeds the threshold value, determine that there is motion of an object relative to the detector. - View Dependent Claims (18, 19)
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Specification