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Proceedings Paper

Design, fabrication, and characterization of Fresnel lens array with spatial filtering for passive infrared motion sensors
Author(s): Giuseppe A. Cirino; Robson Barcellos; Spero P. Morato; Allan Bereczki; Luiz G. Neto
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Paper Abstract

A cubic-phase distribution is applied in the design, fabrication and characterization of inexpensive Fresnel lens arrays for passive infrared motion sensors. The resulting lens array produces a point spread function (PSF) capable of distinguish the presence of humans from pets by the employment of the so-called wavefront coding method. The cubic phase distribution used in the design can also reduce the optical aberrations present in the system. This aberration control allows a high tolerance in the fabrication of the lenses and in the alignment errors of the sensor. In order to proof the principle, a lens was manufactured on amorphous hydrogenated carbon thin film, by well-known micro fabrication process steps. The optical results demonstrates that the optical power falling onto the detector surface is attenuated for targets that present a mass that is horizontally distributed in space (e.g. pets) while the optical power is enhanced for targets that present a mass vertically distributed in space (e.g. humans). Then a mould on steel was fabricated by laser engraving, allowing large-scale production of the lens array in polymeric material. A polymeric lens was injected and its optical transmittance was characterized by Fourier Transform Infrared Spectrometry technique, which has shown an adequate optical transmittance in the 8-14 μm wavelength range. Finally the performance of the sensor was measured in a climate-controlled test laboratory constructed for this purpose. The results show that the sensor operates normally with a human target, with a 12 meter detection zone and within an angle of 100 degrees. On the other hand, when a small pet runs through a total of 22 different trajectories no sensor trips are observed. The novelty of this work is the fact that the so-called pet immunity function was implemented in a purely optical filtering. As a result, this approach allows the reduction of some hardware parts as well as decreasing the software complexity, once the information about the intruder is optically processed before it is transduced by the pyroelectric sensor.

Paper Details

Date Published: 8 September 2006
PDF: 12 pages
Proc. SPIE 6343, Photonics North 2006, 634323 (8 September 2006); doi: 10.1117/12.707928
Show Author Affiliations
Giuseppe A. Cirino, HoloPhotonics Equipamentos Ltda. (Brazil)
Robson Barcellos, HoloPhotonics Equipamentos Ltda. (Brazil)
Spero P. Morato, LaserTools Tecnologia Ltda. (Brazil)
Allan Bereczki, LaserTools Tecnologia Ltda. (Brazil)
Luiz G. Neto, Univ. of São Paulo (Brazil)

Published in SPIE Proceedings Vol. 6343:
Photonics North 2006
Pierre Mathieu, Editor(s)

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