Security Camera Motion Detection Using Dual Averaging Circuits
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Solution Overview
Problem
Security cameras with motion detection functions often incorrectly identify motion due to environmental noise or small objects, leading to false determinations.
Innovation Solution
A security camera system that includes an image sensor, variation level computation circuits for long-term and short-term averaging, and a motion determining circuit to differentiate between desired and non-desired object motion by calculating and comparing average image variation levels, thereby setting a motion threshold to filter out noise and small objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If motion detection is performed using simple image comparison, then the detection response is fast and simple, but false detection occurs due to noise or small objects
Solution Approach 1:
The patent segments the motion detection process into multiple stages: first computing image variation levels for individual frames, then calculating long-term average levels (over M frames) and short-term average levels (over N frames, where M>N), and finally comparing these averages to determine motion. This segmentation allows the system to filter out transient noise while maintaining detection capability for actual motion events.
Solution Approach 2:
The patent performs preliminary computation of image variation levels and accumulates long-term average levels before final motion determination. By pre-calculating and storing average variation levels over extended periods (M frames), the system prepares filtered data that inherently reduces noise impact, enabling more reliable motion detection when comparison is finally made.
2Reliability
If long-term averaging is used to filter noise, then false detection is reduced, but the response time to detect actual motion increases
Solution Approach 1:
The patent applies different averaging characteristics to different time scales: long-term averaging (M frames) provides noise filtering for baseline comparison, while short-term averaging (N frames, where M>N) provides more responsive motion detection. By having two distinct averaging mechanisms with different temporal characteristics, the system achieves both noise rejection and timely response to actual motion events.
Solution Approach 2:
The patent dynamically adjusts the detection threshold by comparing current short-term average variation levels against historical long-term average levels. This dynamic thresholding adapts to changing environmental conditions and noise levels, allowing the system to maintain high reliability while responding quickly to genuine motion that deviates from the established baseline.
Data Source
AI summary
A security camera with a motion detection function, which comprises: an image sensor, configured to capture original images; a variation level computation circuit, configured to compute image variation levels of the original images; a long term computation circuit, configured to calculate a first average level for the image variation levels corresponding to M of the original images; a short term computation circuit, configured to calculate a second average level for the image variation levels corresponding to N of the original images, wherein M>N; and a motion determining circuit, configured to determine whether a motion of an object appears in a detection range of the image sensor according to a relation between the first average level and the second average level. By such security camera, the interference caused by noise or small object can be avoided. Accordingly, the motion detection of the security camera can be more accurate.