Motion detection

Motion detectionis 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 eithermechanicalorelectronicmethods.^[1]When it is done by natural organisms, it is calledmotion perception.

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 andtomographicmotion 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 atypewriteruse 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 whichmotioncan be electronically identified are optical and acoustic.Infraredlight orlasertechnology can be used for optical detection. Motion-detection devices such asPIR motion detectorshave a sensor that detects a disturbance in theinfrared spectrum.A signal can then activate an alarm, and/or acamerato capture an image or video of the event.^[3]^[4]

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 simplealgorithmfor 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, cameraflicker,andCCD 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 ispanning,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 anart gallery.With a panning camera, models based onoptical floware 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. Anoccupancy sensordetects the entry or movement of a person or thing within a certain space.

Motion controllersare also used forvideo game consolesasgame controllers.A camera can also allow the body's movements to be used for control, such as in theKinectsystem.

References

^"motion detection".Retrieved26 January2015.
^Amin, Moeness (2017-09-14).Radar for Indoor Monitoring: Detection, Classification, and Assessment.CRC Press.ISBN 978-1-4987-8200-5.
^Video motion detection (VMD)Archived2011-10-23 at theWayback Machine
^Mechanisms of visual motion
^Bewley, A., Guizilini, V., Ramos, F., & Upcroft, B. (2014).Online Self-Supervised Multi-Instance Segmentation of Dynamic Objects.In International Conference on Robotics and Automation (pp. 1296–1303). Hong Kong, China: IEEE.doi:10.1109/ICRA.2014.6907020

External links

[1] "motion detection".Retrieved26 January2015.

[2] Amin, Moeness (2017-09-14).Radar for Indoor Monitoring: Detection, Classification, and Assessment.CRC Press.ISBN 978-1-4987-8200-5.

[3] Video motion detection (VMD)Archived2011-10-23 at theWayback Machine

[4] Mechanisms of visual motion

[5] Bewley, A., Guizilini, V., Ramos, F., & Upcroft, B. (2014).Online Self-Supervised Multi-Instance Segmentation of Dynamic Objects.In International Conference on Robotics and Automation (pp. 1296–1303). Hong Kong, China: IEEE.doi:10.1109/ICRA.2014.6907020

[1]

[2]

[3]

[4]

[5]