Pyroelectric Infrared Sensor Term definitions
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Pyroelectric infrared sensor
Pyroelectric infrared sensors detect changes in heat (infrared radiation) emitted from the human body and so on.
In other words, it is a sensor that generates a signal only when a temperature change occurs within its detection field.
Far Infrared
The spectrum of infrared wavelengths is distributed from 0.7μm to 1mm. Wavelengths of 0.7 to 2.5μm is called near infrared, 2.5 to 4μm is called middle infrared, and 4μm to 1mm is called far infrared.
The human body emits infrared energy whose peak wavelength is around 10 μm.
Pyroelectric effect
The sensor uses a thermal-type pyroelectric sensing element.
The pyroelectric effect is a phenomenon where the charge generated correlates to the amount of change,
when a temperature change occurs in a ferroelectric ceramic material, giving corresponding spontaneous polarization changes in the material.
Element type
[Element type]
The two light receivers are connected in series and in reverse polarity to each other.
External noise (such as ambient temperature changes) simultaneously input to the two electrodes causes the signals to cancel out each other, making the sensor resistant to ambient temperature changes.
This type of sensor is most often used to detect human presence.
when a temperature change occurs in a ferroelectric ceramic material, giving corresponding spontaneous polarization
changes in the material.
Quad:
A structure in which two sets of Dual-type sensor are placed in a single package. If the same lens is used for the sensor, the sensitivity within the detection area is increased in the Quad type, making it highly suited for detecting human presence.
The Quad type, unlike the Dual type, has sensitivity to movement in both horizontal and vertical directions.
Fresnel lens
Fresnel lens (a) is a type of flat lens consisting of concentrically arranged zones realized after removing the gray partsfrom a standard convex lens (b). It is typically thinner than an ordinary convex lens.
In addition, through the use of resin molding, multiple lenses can be formed onto one curved surface.
The Fresnel lens design permits selection of the desired angle and area within which detection occurs.
