Search results for "Point spread function"
showing 10 items of 75 documents
Myopic astigmatism correction: comparison of a Toric Implantable Collamer Lens and a bioptics technique by an adaptive optics visual simulator.
2013
Purpose To compare the optical and visual quality of a simulated Toric Implantable Collamer Lens (TICL) and a bioptics technique to treat high myopic astigmatism. Methods An adaptive optics visual simulator was used to simulate the vision after TICL implantation and a bioptics procedure from the wavefront aberration pattern for moderate and high-myopic astigmatism. Visual acuity (VA) at different contrasts and contrast sensitivity (CS) at 10, 20 and 25 cycles degree−1 were measured for 3 and 5-mm pupils. Modulation Transfer Function (MTF) and Point Spread Function (PSF) were calculated for a 5-mm pupil. Results At a 3-mm pupil we only found statistically significant differences in VA betwee…
The INTEGRAL IBIS/ISGRI System Point Spread Function and Source Location Accuracy
2003
The imager on board INTEGRAL (IBIS) presently provides the most detailed sky images ever obtained at energies above 30 keV. The telescope is based on a coded aperture imaging system which allows to obtain sky images in a large field of view 29deg x 29deg with an angular resolution of 12'. The System Point Spread Function of the telescope and its detailed characteristics are here described along with the specific analysis algorithms used to derive the accurate point-like source locations. The derived location accuracy is studied using the first in-flight calibration data on strong sources for the IBIS/ISGRI system. The dependence of the calibrated location accuracy with the signal to noise r…
Color difference threshold of chromostereopsis induced by flat display emission
2015
The study of chromostereopsis has gained attention in the backdrop of the use of computer displays in daily life. In this context, we analyze the illusory depth sense using planar color images presented on a computer screen. We determine the color difference threshold required to induce an illusory sense of depth psychometrically using a constant stimuli paradigm. Isoluminant stimuli are presented on a computer screen, which stimuli are aligned along the blue–red line in the computer display CIE xyY color space. Stereo disparity is generated by increasing the color difference between the central and surrounding areas of the stimuli with both areas consisting of random dots on a black backgr…
Superresolved imaging of remote moving targets.
2006
We present a superresolving approach that allows one to exceed the diffraction limit and recover highly resolved contours of moving targets from a sequence of low-resolution images. The presented approach is suitable for remote sensing applications. The resolution decoding algorithm that is used to recover the high-resolution features of the target can be run partially via optical means and that way can be used to reduce the required computational complexity.
One-dimensional iterative algorithm for three-dimensional point-spread function engineering.
2001
We present a new method with which to binarize pupil filters designed to control the three-dimensional irradiance distribution in the focal volume of an optical system. The method is based on a one-dimensional iterative algorithm, which results in efficient use of computation time and in simple, easy to fabricate binary filters. An acceptable degree of resemblance between the point-spread function of the annular binary filter and that of its gray-tone counterpart is obtained.
Lightfield microscopy, an emerging tool for real-time 3D imaging
2020
Integral, or lightfield, microscopy offers the possibility of capturing and processing in real time multiple views of 3D fluorescent samples captured with a single shot. In this contribution we review the recent advances in lightfield microscopy and enunciate the forthcoming challenges.
Flux and color variations of the quadruply imaged quasar HE 0435-1223
2011
aims: We present VRi photometric observations of the quadruply imaged quasar HE 0435-1223, carried out with the Danish 1.54m telescope at the La Silla Observatory. Our aim was to monitor and study the magnitudes and colors of each lensed component as a function of time. methods: We monitored the object during two seasons (2008 and 2009) in the VRi spectral bands, and reduced the data with two independent techniques: difference imaging and PSF (Point Spread Function) fitting.results: Between these two seasons, our results show an evident decrease in flux by ~0.2-0.4 magnitudes of the four lensed components in the three filters. We also found a significant increase (~0.05-0.015) in their V-R …
Diffractive corneal inlay for presbyopia
2017
[EN] A conceptually new type of corneal inlays for a customized treatment of presbyopia is presented. The diffractive inlay consists on a small aperture disc having an array of micro-holes distributed inside the open zones of a Fresnel zone plate. In this way, the central hole of the disc lets pass the zero order diffraction and produces an extension of the depth of far focus of the eye, while the diffracted light through the holes in the periphery produce the near focus. Additionally, the micro-holes in the inlay surface fulfill the essential requirement of allowing the flow of nutrients through it to the cells of the corneal stroma. Theoretical and optical-bench experimental results for t…
Imaging Performance of a Diffractive Corneal Inlay for Presbyopia in a Model Eye
2019
[EN] In this work we evaluated the imaging properties of the Diffractive Corneal Inlay (DCI), a novel type of corneal implant working by diffraction that we proposed for the treatment of presbyopia. ZEMAX OpticStudio software was employed for the numerical assessment, with simulations performed in a human-based eye model. In the ray tracing analysis, we used the Modulation Transfer Function (MTF), the Area under the MTF (AMTF), and the Point Spread Function (PSF). The theoretical performance of the DCI under different situations was evaluated in comparison with a commercially available pinhole based corneal inlay. Finally, real images were obtained experimentally in vitro in a model eye wit…
Multitemporal fusion of Landsat/TM and ENVISAT/MERIS for crop monitoring
2013
Abstract Monitoring Earth dynamics using current and future satellites is one of the most important objectives of the remote sensing community. The exploitation of image time series from sensors with different characteristics provides new opportunities to increase the knowledge about environmental changes and to support many operational applications. This paper presents an image fusion approach based on multiresolution and multisensor regularized spatial unmixing. The approach yields a composite image with the spatial resolution of the high spatial resolution image while retaining the spectral and temporal characteristics of the medium spatial resolution image. The approach is tested using …