Pyroelectric Materials as Infrared Detectors

The infrared detector typically consists of four parts. The pyroelectric material is attached to two conducting elements, which are then connected to a voltage-measuring circuit.

Conductor

Pyroelectric

This conductor is coated in an absorbent material.

When an IR beam is fired at the pyroelectric, transmitting conductor allows the radiation in, while the absorbing conductor prevents it from leaving.

This increases the temperature of the pyroelectric.

To get a more useful, continual signal, the IR radiation needs to be pulsed.

As someone passes a detector, the heat energy they emit will vary. This gives a continuous pulse, and gives a voltage which can easily be detected.

Despite the simple nature of the previous animation, the set up is actually more complicated than that. The detector is sat in an arc of faceted mirrors.

Detector

Mirror

The radiation emitted as body heat passes through the detector, and reflects from the mirrors. At certain points, the incident and reflected waves interfere constructively. This results in a heating of the pyroelectric.