Mr. Allan Bereczki Profile

KEYWORDS: Diodes, Crystals, Absorption, Neodymium lasers, Raman spectroscopy, Laser crystals, Semiconductor lasers, Beam shaping, Mirrors, Output couplers

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Proceedings Article | 16 February 2018 Presentation + Paper

Dynamically stable operation of a 100-watt level CW single frequency ring laser at 1064 nm

Niklaus Wetter, Allan Bereczki, Amauri Ferreira

Proceedings Volume 10518, 1051811 (2018) https://doi.org/10.1117/12.2290480

KEYWORDS: Resonators, Nd:YAG lasers, Rod lasers, Diodes, Mirrors, Continuous wave operation, Laser resonators, Laser applications, Semiconductor lasers

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Proceedings Article | 15 February 2018 Presentation + Paper

Quasi-three level Nd:YLF fundamental and Raman laser operating under 872-nm and 880-nm direct diode pumping

Niklaus Wetter, Allan Bereczki, João Pedro Fonseca Paes

Proceedings Volume 10511, 105111S (2018) https://doi.org/10.1117/12.2290444

KEYWORDS: Crystals, Neodymium lasers, Output couplers, Diodes, Mirrors, Continuous wave operation, Laser crystals, Laser applications, Absorption, Raman scattering

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Proceedings Article | 8 September 2006 Paper

Design, fabrication, and characterization of Fresnel lens array with spatial filtering for passive infrared motion sensors

Giuseppe Cirino, Robson Barcellos, Spero Morato, Allan Bereczki, Luiz Neto

Proceedings Volume 6343, 634323 (2006) https://doi.org/10.1117/12.707928

KEYWORDS: Sensors, Infrared sensors, Positron emission tomography, Target detection, Fresnel lenses, Point spread functions, Infrared radiation, Laser marking, Laser engraving, Pyroelectric detectors

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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.

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