1,720,972 research outputs found
Accuratezza enlle misure di spostamento e posizione con dispositivi optoelettronici in regime di rivelazione quantico e termico: un approccio unificato
No full textAmplitude and Phase Relationships of the Readout Signals in a Self-Mixing Interfereometer
No full textOn the Optical Concentration Achievable by a Non-imaging Microprism Array Combined to an Image Photodetector
No full textAn array of non-imaging micro-prisms can offer a substantial recovery of the sensitivity loss due to area fill-factor in photodetectors. This is especially true for device in which complex circuit functions are required, that consume a large fraction of pixel area, like e.g., CMOS sensors, image rengefinders, SPAD arrays, fluorescence analysers, etc. In this paper, after a general introduction, we evaluate the achievable concentration at asymptotically low NA (input/output area ratio) and high NA (inverse square of the input NA). Then, we present the results of a ray-tracing method for the fast and efficient calculation of the optical parameters of several types of prism concentrators, i.e., truncated cone, parabolic and compound parabolic, both reflective and refractive. Parameters considered are: power efficiency, effective concentration, channel crosstalk and power penalty for output gap
Self-Mixing Laser Diode Vibrometer for Very Low Frequency applications
No full textOptical vibrometer based on Laser Diode Self-Mix Interferometry (SMI) is the elective choice in non-invasive vibration monitoring. We present an instrument aimed at measurement of small amplitude (10 nm < s < 1 μm) vibrations at very low frequency, below 10–3 Hz. Intended application is in situ vibration monitoring of artwork, e.g. during 3D surface topography aimed at indentification of the original piece to counteract forgery of the artwork, or to prevent or detect theft during transportation before/after an
exhibition. In the intended application, long term stability and glitch-free operation are required. The proposed vibrometer exploits the fringe-lock configuration, and the advantages offered by the presence of the
feedback loop. In previous design with AC feedback only, glitches were observed because of fringe lock loss due to wavelength fluctuation induced by temperature fluctuation, even with TEC control of the Laser
Diode temperature
Uniformity of Concentration Factor and BFL in Microlens Array for Image Detectors Applications
No full textWe use an array of polymer microlenses spatially matched to an array of SPADs (Single Photon Avalanche Detector) to mitigate the loss of sensitivity due to the area fill-factor. The lens array is fabricated by polymer casting in a photoresist replica mold. We report results about reproducibility of concentration factor and back focal length within an individual 32x32 array. At a C factor of 35 and a focal length F=40 μm, the spread of concentration is < 6%, and the spread of BFL is <0.5 μm
RECUPERO DEL FILL-FACTOR IN RIVELATORI AD IMMAGINESPAD MEDIANTE MATRICI DI MICRO-LENTI
Full text linkUsing an array of 32x32 plano-convex micro-lenses, fabricated by co-polymer casting in a
photoresist replica mold, we achieve substantial recovery of the fill-factor loss in a SPADs
(Single Photon Avalanche Detectors) array of 32x32 pixels, 50-μm pitch, up to a factor of 38
Banco ottico per la caratterizzazione di matrici di microlenti
Full text linkWe describe in the following an Optical Test Bench suitable to measure both Concentration
and Back Focal Length of optical microlens arrays. Individual lens within an array can be
characterized without array repositioning. The Optical Test Bench is easy to use and PCcontrolled.
The reproducibility achieved is better than 0.15% for Concentration and less than
300nm for Back Focal Length
Very Low Frequency Self-Mixing Laser Diode Vibrometer
Full text linkWe present an optical vibrometer especially designed
to measure small amplitude (hundreds pm to several μm)
vibrations at very low frequency, down to 0.01 Hz. The
instrument is based on a Self-Mixing Interferometer of the
fringe-lock type, to achieve high sensitivity and a wide dynamic
range. As compared to previous design based on the same
principle, our vibrometer is free from fringe-lock loss due to
thermal drift of the laser wavelength; this result is obtained by
exploiting a separate DC feedback loop acting on the Laser
Diode bias. Experiments show a very good long-term stability,
glitch-free operation, with rms error of 100-pm/sqrt(Hz) over a
bandwidth from less than 20 Hz to 20 kHz
- …
