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

mechanical Mechanical may refer to: Machine * Machine (mechanical), a system of mechanisms that shape the actuator input to achieve a specific application of output forces and movement * Mechanical calculator, a device used to perform the basic operations ...

or electronic methods. When it is done by natural organisms, it is called motion 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, microwave and tomographic motion detection) *Sound (microphones, other acoustic sensors) *Kinetic energy (

triboelectric The triboelectric effect (also known as triboelectric charging) is a type of contact electrification on which certain materials become electrically charged after they are separated from a different material with which they were in contact. Rub ...

, 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

motion In physics, motion is the phenomenon in which an object changes its position with respect to time. Motion is mathematically described in terms of displacement, distance, velocity, acceleration, speed and frame of reference to an observer and m ...

can be electronically identified are optical and acoustic.

Infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of Light, visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from ...

light or

laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The ...

technology can be used for optical detection. Motion-detection devices such as PIR motion detectors have a sensor that detects a disturbance in the

infrared spectrum Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

. A signal can then activate an alarm, and/or a

camera A camera is an optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), with ...

to capture an image or video of the event. 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 In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific problems or to perform a computation. Algorithms are used as specifications for performing ...

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.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.

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. Motion controllers are also used for video game consoles as game controllers. A camera can also allow the body's movements to be used for control, such as in the Kinect system.

References

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External links

Relational Motion Detection

Motion Detection Algorithms In Image Processing

Presence and Absence detection explained

Motion detection sample algorithm realization video
Security Motion in computer vision