10mm 12mm 140DEG PIR Sensor Module ROHS Round PIR Motion Sensor
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|PIR Motion Sensor Fresnel Lens
|10mm 12mm 15mm 30mm 40mm
10mm 12mm PIR Sensor Module,
140DEG Passive Infrared PIR Sensor Module,
ROHS round PIR Motion Sensor
Passive Infrared Sensor PIR Motion Sensor Fresnel Lens 10mm 12mm 15mm 27mm 40mm
Description Of The PIR Motion Sensor Fresnel Lens
Fresnel lenses are mostly thin sheets made of polyolefin materials. One side of the lens surface is smooth, and the other side is engraved with concentric circles from small to large. Fresnel lens is equivalent to infrared and visible light convex lens in many cases, the effect is better, but the cost is much lower than ordinary convex lens. Fresnel lenses can be classified according to optical design or structure. The Fresnel lens has two functions: one is focusing; the other is to divide the detection area into a number of bright and dark areas, so that moving objects entering the detection area can be detected in the PIR (Passive Infrared Detector) in the form of temperature changes. ) Produces a changing pyro-infrared signal.
Features Of The PIR Motion Sensor Fresnel Lens
* Wide angle
* Long sensor distance
* Small size
* All kinds of focus
* Different shapes available
* Completed model
Example Specifications 8140-2 Of The PIR Motion Sensor Fresnel Lens
Fresnel Lens Selection List Of The PIR Motion Sensor Fresnel Lens
Function Of The PIR Motion Sensor Fresnel Lens
1) The Fresnel lens uses the special optical principle of the lens to produce an alternating "blind zone" and "high-sensitivity zone" in front of the detector to improve its detection and reception sensitivity. When someone walks by the lens, the infrared rays emitted by the human body will alternately enter the “high-sensitivity area” from the “blind area”, so that the received infrared signal is input in the form of sudden strong and weak pulses, thereby increasing its energy amplitude .
2) The Fresnel lens has two functions: one is focusing, that is, the pyro-infrared signal is refracted (reflected) on the PIR, and the second is to divide the detection area into several bright and dark areas, so that it can enter the detection area A moving object can produce a changing pyro-infrared signal on the PIR in the form of a temperature change. Fresnel lens, simply means that there are equidistant teeth on one side of the lens, through these teeth, the optical bandpass (reflection or refraction) of the specified spectral range can be achieved. Bandpass optical filters for traditional polished optical equipment are expensive to manufacture.
3) Fresnel lenses can greatly reduce costs. The typical example is PIR. PIR is widely used in alarms. If you take one and take a look, you will find that there is a small plastic cap on each PIR. This is the Fresnel lens. The inside of the little hat is engraved with teeth. This Fresnel lens can limit the frequency peak of incident light to about 10 microns (the peak of infrared radiation from the human body). The Fresnel lens can focus the light passing through the narrow-band interference filter on the photosensitive surface of the silicon photoelectric secondary detector. The Fresnel lens cannot be wiped with any organic solution (such as alcohol, etc.). Distilled water can be used first when removing dust Or rinse with ordinary clean water, then wipe with absorbent cotton.
4) Current camera focusing screens are all frosted frosted glass Fresnel lenses, which have the advantage of being bright and uniform in brightness. When the focus is not accurate, the image on the focusing screen is not clear. In order to coordinate with more precise focusing, a split image and micro-ring device are generally installed in the center of the focusing screen. When the focus is not accurate, the image of the subject in the center of the focusing screen splits into two images.
5) When the two split images are merged into one, it indicates that the focus is accurate. The standard focusing screen of an AF SLR machine generally does not have a split image device, but a small rectangular frame is engraved to indicate the AF area, and some focusing screens are also engraved with partial or spot metering areas. When the early AF SLRs were focusing in a dark environment, it was often difficult to see the focus frame, and it was difficult to determine which point the camera used as the focus point. The focus point on the focusing screen of the new generation SLR camera would glow, or there would be a focusing sound. Prompt to confirm the focus in a complex environment.
6) Different types of focusing screens have different purposes. For portraits, it is better to use split-image focusing screens. Focusing screens with horizontal and vertical lines or scales are suitable for building photography and document copying; there is no split-image in the middle part but only micro-edge focusing The screen is suitable for small aperture lens, it will not have the shortcomings of split image which is bright and black. The focus screen of many SLR cameras can be replaced by the user. Also known as threaded lens.