Search results for "Lens"

Systematic Redshift of the Fe III UV Lines in Quasars. Measuring Supermassive Black Hole Masses under the Gravitational Redshift Hypothesis

2018

We find that the Fe III$\lambda\lambda$2039-2113 spectral feature in quasars appears systematically redshifted by amounts accountable under the hypothesis of gravitational redshift induced by the central supermassive black hole. Our analysis of 27 composite spectra from the BOSS survey indicates that the redshift and the broadening of the lines in the Fe III$\lambda\lambda$2039-2113 blend roughly follow the expected correlation in the weak limit of Schwarzschild geometry for virialized kinematics. Assuming that the Fe III UV redshift provides a measure of $M_{BH}\over R$ (${\Delta \lambda\over \lambda}\simeq{3\over2}{G\over c^2} {M_{BH}\over R}$) and using different estimates of the emittin…

Size of the accretion disk in the gravitationally lensed quasar SDSS J1004+4112 from the statistics of microlensing magnifications

2016

We present eight monitoring seasons of the four brightest images of the gravitational lens SDSS J1004+4112 observed between December 2003 and October 2010. Using measured time delays for the images A, B and C and the model predicted time delay for image D we have removed the intrinsic quasar variability, finding microlensing events of about 0.5 and 0.7 mag of amplitude in the images C and D. From the statistics of microlensing amplitudes in images A, C, and D, we have inferred the half-light radius (at {\lambda} rest = 2407 {\AA}) for the accretion disk using two different methods, $R_{1/2}=8.7^{+18.5}_{-5.5} \sqrt{M/0.3 M_\odot}$ (histograms product) and $R_{1/2} = 4.2^{+3.2}_{-2.2} \sqrt{…

Contact lenses: do they really change the opticalperformance?

1996

Abstract In this investigation the quality of two types of optical correction, hydrogel contact lenses and ophthalmic lenses, wascompared by measuring the modulation transferfunction (MTF) of the correcting lens plus visual optics system using an objective method. A merit function was defined in order to allow the direct comparison between the optical performance with the two corrections. A study on 10 subjects was undertaken, measuring the MTF of both corrections by using the double pass method. The results show that the optical quality of contact lenses was higher than that with ophthalmic lenses. The contrast sensitivity function (CSF) and visual acuity (VA) were determined as subjective…

Validation of a method for measuring the retinal thickness with Shack–Hartmann aberrometry in an artificial eye

2015

In Shack–Hartmann aberrometry, it is assumed that a wave front emerges from a single point focused on a retina. However, the retina is a multi-layered structure and reflections may occur from several layers. This may result in several overlapping spot patterns on the CCD due to different vergences of the outgoing wave fronts. The amount by which these spot patterns are displaced may contain information about the retinal thickness. In this study, we perform simulations of formation of double spots in a living eye and also apply this method to measure the thickness of an artificial retina with a simple structure. We also compare the results obtained with artificial eye and compare them to the…

Metacoatings for wavelength-scale, high-numerical-aperture plano–concave focusing lenses

2016

We design plano–concave silicon lenses with coupled gradient-index plasmonic metacoatings for ultrawide apertured focusing utilizing a reduced region of ∼20λ2. The anomalous refraction induced in the planar input side of the lens and in the boundary of the wavelength-scale focal region boosts the curvature of the emerging wavefront, thus significantly enhancing the resolution of the tightly focused optical wave. The formation of a light tongue with dimensions approaching those of the concave opening is here evidenced. This scheme is expected to have potential applications in optical trapping and detection.

Sub-wavelength and non-periodic holes array based fully lensless imager

2011

Abstract We present a novel concept for microscopic imaging. The proposed microscope-like device does not include an objective lens neither a condenser. Instead, a metallic plate of sub-wavelength hole-array with a varying pitch is used to illuminate the inspected object that is mounted very close to it. As a result, the transmitted spectrum through each hole differs from the others and therefore, each spot of the detected object is illuminated with a unique spectrum. By measuring a single spectrum that is the sum of all the spectra that are transmitted through the sample and by using spectral decomposition algorithms, the spatial transmission pattern of the object can be extracted.

Brightness induction in a chromatic center?achromatic surround configuration

1997

Nonsymmetric Fourier transforming with an anamorphic system

1984

The idea of obtaining a nonsymmetric Fourier transform with crossed cylindrical lenses of different focal lengths is presented. The anamorphic rotation-variant system produces a scaled Fourier transform F(u,mv) of an object f(x,y), where m is a scaling constant. The system performs controlled angular magnification of an object spectrum. It is shown that the super resolution in one direction is gained by reducing the number of degrees of freedom of the optical message in the other. Experimental results are shown where the scaling constant m of up to 10 has been obtained.

White-light implementation of the Wigner-distribution function with an achromatic processor.

2010

A temporally incoherent optical processor that combines diffractive and refractive components is proposed for performing two different operations simultaneously: an achromatic image along an axis and an achromatic one-dimensional Fourier transformation along the orthogonal axis. These properties are properly employed to achieve the achromatic white-light display of the Wigner-distribution function associated with a one-dimensional real signal, with high redundancy and variable scale.

Superresolved imaging in digital holography by superposition of tilted wavefronts

2006

A technique based on superresolution by digital holographic microscopic imaging is presented. We used a two dimensional (2-D) vertical-cavity self-emitting laser (VCSEL) array as spherical-wave illumination sources. The method is defined in terms of an incoherent superposition of tilted wavefronts. The tilted spherical wave originating from the 2-D VCSEL elements illuminates the target in transmission mode to obtain a hologram in a Mach-Zehnder interferometer configuration. Superresolved images of the input object above the common lens diffraction limit are generated by sequential recording of the individual holograms and numerical reconstruction of the image with the extended spatial frequ…