Search results for "Sensor"

In vitro optical quality differences between multifocal apodized diffractive intraocular lenses.

2013

Purpose To compare the in vitro optical quality of multifocal apodized intraocular lenses (IOLs) at different focal points. Setting University of Valencia, Valencia, Spain. Design Experimental study. Methods The Acrysof Restor +3.0 diopter (D) multifocal IOL with 2 main foci (bifocal IOL) and the Finevision multifocal IOL with 3 main foci (trifocal IOL) were evaluated. The optical quality was quantified using the modulation transfer function (MTF) at 7 focal points and for 3.0 mm and 4.5 mm apertures. The through-focus MTF at 10 focal points of the IOLs was also recorded. Results For the 0.0 D and −2.5 D focal points, the bifocal IOL showed the highest MTF values for pupil sizes as well as …

Stimulus-induced gamma activity in the electrocorticogram of freely moving rats: the neuronal signature of novelty detection.

2009

To investigate the cortical activity pattern associated with the exploration and identification of a novel object we recorded the intracranial electrocorticogram (ECoG) in the barrel cortex of freely moving adult rats using wireless technology. We report here that the exploration and detection of a novel object correlate with a transient increase of synchronized oscillatory activity in the 40–47 Hz frequency band. This specific cortical activity pattern occurs 200–300 ms after the first sensory contact with the novel stimulus and decreases in power in the subsequent recording sessions with the same object. During the first explorative session the increase in 40–47 Hz is associated with a si…

Fourier analysis of the stimuli for pattern-induced flicker colors.

1992

Pattern-induced flicker colors (PIFCs) were observed and color matched in rotating discs from which higher-harmonic Fourier components in the square-wave temporal luminance functions of a conventional black-and-white Benham disc had been removed. Since both reddish-brown and blue PIFCs were visible with purely sinusoidal stimuli they cannot result from differences in temporal stimulus shape or pattern and do not provide evidence for a temporal coding theory of color. Green PIFCs differed in that they did require the presence of additional harmonics. In a second experiment the luminance means upon which the sinusoidal PIFC stimuli were imposed were varied. The results show that color is dete…

Simulation of propagation characteristics of ultrasonic guided waves in fractured long bone

2008

Using ultrasonic guided waves (GW) to assess fractures in long bones has gained considerable attention. This paper focuses on using an improved hybrid boundary element method (HBEM) to analyze and calculate reflection coefficients (RC) and transmission coefficients (TC) of low-order GWs for cracks with different depth-to-width ratios (d/w) in fractured long bones. The results showed that the primary received modes, which include the transmitted and reflected modes, are the same as the incident modes. For some values of d/w, the TC of different GW always had local maxima at adjacent frequencies. For some other cracks with different d/w, most of the TC curves had local maxima of which frequen…

Quantum Stochastic Resonance in a Micromaser

1998

We demonstrate that quantum stochastic resonance allows for the noise-controlled synchronization of quantum jumps between the metastable states of the quantized radiation field in a micromaser. Under readily accessible experimental conditions optimal synchronization is achieved at a finite temperature $T\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}500\mathrm{mK}$ of the environment.

Reconfigurable Shack-Hartmann sensor without moving elements.

2010

We demonstrate wavefront sensing with variable measurement sensitivity and dynamic range by means of a programmable microlens array implemented onto an off-the-shelf twisted nematic liquid crystal display operating as a phase-only spatial light modulator. Electronic control of the optical power of a liquid lens inserted at the aperture stop of a telecentric relay system allows sensing reconfigurability without moving components. Results of laboratory experiments show the ability of the setup to detect both smooth and highly aberrated wavefronts with adequate sensitivity.

An optical pulse modulator based on an all-fiber mirror

1996

Self-referenced phase reconstruction proposal of Ghz bandwidth non-periodical optical pulses by in-fiber semi-differintegration

2011

Abstract We propose two new techniques able to retrieve the phase profile of a given temporal optical pulse based on the use of in-fiber semi-differintegral operators, where by semi-differintegration we mean either a 0.5th-order differentiation or integration. In both cases, the signal's temporal phase can be obtained by simple dividing two temporal intensity profiles, namely the intensities of the input and output pulses of a spectrally shifted semi-differintegral operator. In both cases, we obtained simple analytical expressions for the phase profile. The techniques are self-referenced and well-suited for real-time applications. We numerically prove the viability of these proposals.

Operation of transition-edge sensors with excess thermal noise

2006

The superconducting transition-edge sensor (TES) is currently one of the most attractive choices for ultra-high resolution calorimetry in the keV x-ray band, and is being considered for future ESA and NASA missions. We have performed a study on the noise characteristics of Au/Ti bilayer TESs, at operating temperatures around ~100 mK, with the SQUID readout at 1.5 K. Experimental results indicate that without modifications the back-action noise from the SQUID chip degrades the noise characteristics significantly. We present a simple and effective solution to the problem: by installing an extra shunt resistor which absorbs the excess radiation from the SQUID input, we have reduced the excess …

DEPFET Macropixel Detectors for MIXS: First Electrical Qualification Measurements

2010

The Mercury Imaging X-ray Spectrometer (MIXS) is one of the instruments on board the Mercury Planetary Orbiter of the fifth European Space Agency (ESA) cornerstone mission BepiColombo. This spectrometer comprises two instruments and allows imaging X-ray spectroscopy of the Mercurian surface. The focal plane arrays for the energy and spatial resolved detection of X-rays are based on depleted P-channel FET (DEPFET) macropixel detectors. We report on the first electrical qualification measurements of DEPFET macropixel flight hardware, which are done at room temperature. The measurement of the transistor properties of all DEPFET pixels allows the selection of 100% electrically defect-free devic…