Abstract
This paper presents an experimental setup to measure the horizontal centering error of a pre-built pyroelectric infrared (PIR) sensor module, in which a dual-element PIR sensor is aligned at the focal point of a single-zone Fresnel Lens. In the setup, the sensor module was placed facing a modulated infrared radiating source and turned over a range of horizontal angles. The position of the optical axis of the sensor module was determined based on the analysis of the output response of the sensor at turned angles. Thus, the horizontal centering error of the module is defined as the difference between the mechanical axis of the housing and the found optical axis. For the prebuilt sensor module, with the specific available equipment, the measurement of the centering error of the module achieved a resolution of 0.02 degrees.
Highlights
The Pyroelectric Effect, in which a temperature change in a specific material leads to an output of an electric charge, has been known about for a long time [1]
pyroelectric infrared (PIR) sensors, which work based on the pyroelectric effect, are featured with their ability to detect intrusions from specific heat sources in their fields of view (FOV) [2]
The PIR sensor is usually assembled with a Fresnel lens—a flat, converted type of plano-convex lens [3]—which plays a role of the objective in order to concentrate infrared (IR) radiation emitted from a heat source onto the sensor surface and, as a result, to magnify the output signal of the sensor
Summary
The Pyroelectric Effect, in which a temperature change in a specific material leads to an output of an electric charge, has been known about for a long time [1]. The sensor and the lens usually work in the mid-infrared wavelength range Such assembly of the sensor and the lens should be considered as a non-imaging Electro-Optical (EO) system. The layout of our measurement system is illustrated, whereby the moving vehicle’s speed is defined by the length of the time delay between two output signals of those sensor modules when the vehicle passes across their FOV. In such a measurement system, the parallelism of the optical axes of the two sensor modules is critical for the measurement result, as the vehicles may travel at various distances from the measurement system.
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