Optical system of infrared intrusion detector
Jan. 30, 2021
Infrared imaging technology can be divided into active infrared imaging and passive infrared imaging. Passive infrared imaging uses the infrared radiation emitted by the object to capture the image of the object. Active infrared imaging irradiates an object with an infrared radiation source and using the reflected infrared radiation to capture the image of the object. Infrared intrusion detectors are often used for civil security and military security.
The passive infrared intrusion detection system
The passive infrared intrusion detection system is mainly composed of an optical system and a pyroelectric sensor. The optical system is usually composed of multiple sets of optical lenses and mirrors to form a flabelliform protective area overlooking downwards. While opening the fan-shaped viewing angle, it also takes into account target detection in far, middle and near areas. In order to detect the infrared moving target, the thermal energy radiation of the moving target needs to be reflected on the thermoelectric element. The scene on the scene is imaged on the surface of the pyroelectric sensor through optical lenses and optical mirrors to form an infrared image. The optical system of the passive infrared detector does not require high imaging accuracy, whether it affects the contour accuracy.
In the absence of a moving target, these overlapping images reflect the thermal energy radiation of the scene background. The continuous static thermal radiation will not cause thermoelectric output. When a moving target enters the prevention area, it will destroy the thermoelectric balance formed by the background, and produce a thermoelectric output reflecting the movement law of the target.
The active infrared intrusion detection system
The active infrared intrusion detection system is mainly composed of a transmitter and a receiver. Under the excitation of the power supply, the infrared light-emitting diode at the transmitter emits a modulated infrared beam (beam wavelength is between 0.8-0.95μm), which is transformed into parallel light by the optical system (mainly composed of spherical lenses) . This light beam is received by the receiver. The light signal is converted into an electrical signal by the infrared photoelectric sensor at the receiver. Under normal circumstances, the receiving end receives a stable optical signal. When someone invades, the infrared beam is blocked and the infrared signal received by the receiver changes.
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