Motion detection
It has been suggested that this article be merged with Motion detector. (Discuss) Proposed since January 2024. |
Motion detection is the process of detecting a change in the position of an object relative to its surroundings or a change in the surroundings relative to an object. It can be achieved by either
Methods
Motion can be detected by monitoring changes in:
- Infrared light (passive and active sensors)
- Visible light (video and camera systems)
- Radio frequency energy (radar,[2] microwave and tomographic motion detection)
- Sound (microphones, other acoustic sensors)
- Kinetic energy (triboelectric, seismic, and inertia-switch sensors)
- Magnetism (magnetic sensors, magnetometers)
- Wi-Fi Signals (WiFi Sensing)
Mechanical
The most basic forms of mechanical motion detection utilize a switch or trigger. For example, the keys of a typewriter use a mechanical method of detecting motion, where each key is a switch that is either off or on, and each letter that appears is a result of the key's motion.
Electronic
The principal methods by which
This method's chief applications are:
- Detection of unauthorized entry
- Turning lights on/off when an area is entered/vacated
- Activating a camera to record new events (e.g. human activity)
A simple algorithm for motion detection by a fixed camera compares the current image with a reference image and monitors the number of different pixels. Since images naturally differ due to factors such as varying lighting, camera flicker, and CCD dark currents, pre-processing is useful to reduce the number of false positive alarms.
More complex algorithms are necessary to detect motion when the camera itself is panning, or when a specific object's motion must be detected in a field containing other, irrelevant movement—for example, a painting surrounded by visitors in an art gallery. With a panning camera, models based on optical flow are used to distinguish between apparent background motion caused by the camera's movement and that of independently moving objects.[5]
Devices
Motion detectors are often integrated components of systems that automatically perform tasks, or alert users of motion in an area. An occupancy sensor detects the entry or movement of a person or thing within a certain space.
References
- ^ "motion detection". Retrieved 26 January 2015.
- ISBN 978-1-4987-8200-5.
- ^ Video motion detection (VMD) Archived 2011-10-23 at the Wayback Machine
- ^ Mechanisms of visual motion