Motion detection is the action of sensing physical movement in a given area.
Motion can be detected by measuring change in speed or vector of an object or objects in the field of view. In Physics, motion means a constant change in the location of a body This can be achieved either by mechanical devices that physically interact with the field or by electronic devices that quantifies and measures changes in the given environment.
When motion detection is accomplished by natural organisms, it is called motion perception. Motion perception is the process of inferring the speed and direction of elements in a scene based on visual, vestibular and proprioceptive inputs
Mechanical devices
A tripwire is a simple form of motion detection. A tripwire is a passive Triggering mechanism usually/originally employed for military purposes although its principle has been used since prehistory for methods of trapping If a moving object steps into the tripwire's field of view (i. e. trips the wire), then a simple sound device (e. g. bells) may alert the user. A glass filled to the brim so that surface tension causes a convex meniscus can be placed on top of an object to detect if the object has moved. For the work of fiction see Surface Tension (short story. Surface tension is a property of the surface of a Liquid that causes it to For other uses see Meniscus (anatomy and lens (optics. Meniscus, plural menisci, from the Greek for "crescent"
Mechanical motion detection devices can be simple to implement, but at the same time, they can be defeated easily by interrupting the devices' mechanics (e. g. by "cutting the wire" or "drinking the water"). Electronic motion sensing devices, such as motion detectors, can prevent such mechanical intervention. A motion detector is a device that contains a physical mechanism or electronic sensor that quantifies motion that can be either integrated with or connected to other devices
Electronic devices
The principal methods by which motion can be electronically identified are optical detection and acoustical detection. Infrared light or laser technology may be used for optical detection. Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of A laser is a device that emits Light ( Electromagnetic radiation) through a process called Stimulated emission. Motion detection devices, such as motion detectors, have sensors that detect movement and send a signals to a sound device that produces an alarm or switch on an image recording device. There are motion detectors which employ cameras connected to a computer which stores and manages captured images to be viewed later or viewed over a computer network. A camera is a device used to capture images either as still Photographs or as sequences of moving images ( Movies or Videos. A computer is a Machine that manipulates data according to a list of instructions. A computer network is a group of interconnected Computers. Networks may be classified according to a wide variety of characteristics
The chief applications for such detection are (a) detection of unauthorized entry, (b) detection of cessation of occupancy of an area to extinguish lighting and (c) detection of a moving object which triggers a camera to record subsequent events. The motion detector is thus a linchpin of electronic security systems, but is also a valuable tool in preventing the illumination of unoccupied spaces. A motion detector is a device that contains a physical mechanism or electronic sensor that quantifies motion that can be either integrated with or connected to other devices Over-illumination is the presence of lighting intensity ( Illuminance) beyond that required for a specified activity
A simple algorithm for motion detection by a fixed camera compares the current image with a reference image and simply counts the number of different pixels. In Mathematics, Computing, Linguistics and related subjects an algorithm is a sequence of finite instructions often used for Calculation In Digital imaging, a pixel ( pict ure el ement is the smallest piece of information in an image Since images will 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. Flicker is visible fading between cycles displayed on video displays especially the refresh interval on Cathode ray tube (CRT based computer screens. A charge-coupled device ( CCD) is an analog Shift register, that enables the transportation of analog signals (electric charges through successive stages (capacitors In Statistics, the terms Type I error (also α error, or false positive) and type II error ( β error, or a false negative
More complex algorithms are necessary to detect motion when the camera itself is moving, or when the motion of a specific object must be detected in a field containing other movement which can be ignored. An example might be a painting surrounded by visitors in an art gallery. An art gallery or art museum is a space for the exhibition of art, usually Visual art.
References
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