The modulation transfer function (MTF) quantitatively describes the ability of an optical or imaging system to reproduce contrast at various spatial frequencies. The ISO 12233 edge-based method adopted diagonal MTF me...
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The modulation transfer function (MTF) quantitatively describes the ability of an optical or imaging system to reproduce contrast at various spatial frequencies. The ISO 12233 edge-based method adopted diagonal MTF measurement for sampled imaging systems by analyzing the gradient of a slanted edge captured by the system and estimating MTF as a function of spatial frequency perpendicular to the edge. Pixels in a region of interest (ROI) are projected into a quarter-pixel wide bin array on a horizontal or vertical axis, yielding a $4\times $ oversampled edge spread function. However, the accuracy and precision of MTF estimates can degrade considerably at high spatial frequencies for certain edge angles because of the clustering of the projection paths at or around specific locations on the bin array axis. Thus, a novel edge-based method, Omni-sine, was proposed to overcome this limitation by optimizing a noninteger oversampling ratio based on the edge angle. The accuracy and precision of the proposed method were demonstrated through computer simulations using synthesized edge images and through actual measurements with a machine vision camera. Implementing the Omni-sine method does not affect the real-time nature of the edge-based measurement and facilitates MTF anisotropy measurements using multiple nonrectangular ROIs with slanted starburst charts.
The ensemble average of the transferfunction of an optical system that corrects wavefront tilt in real time is termed the average short-exposure modulation transfer function (SEMTF). Most of the previous studies rega...
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The ensemble average of the transferfunction of an optical system that corrects wavefront tilt in real time is termed the average short-exposure modulation transfer function (SEMTF). Most of the previous studies regarding this topic neglect the influences of type of tilt. The difference between Zernike tilt (Z-tilt) and gradient tilt (G-tilt) is introduced in SEMTF. Fried-type analytical but less accurate forms that assume tilt is uncorrelated with residual phase and numerical but accurate double-integral forms that discard the above assumption have been derived. The double-integral forms can achieve both high accuracy and rapid computation speed without neglecting the location dependency of the tilt-corrected phase structure function. For the sake of generality, telescope aperture is set to be annular, and circular formulae can be obtained by setting the obstruction ratio to be zero.
Topobathymetric scanning lidar deployed on unmanned aircraft systems is a powerful tool for high-resolution mapping of the dynamic interface between topography and bathymetry. However, standardized methods for empiric...
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Topobathymetric scanning lidar deployed on unmanned aircraft systems is a powerful tool for high-resolution mapping of the dynamic interface between topography and bathymetry. However, standardized methods for empirical resolution validation have not been widely adopted across lidar applications. While theoretical models of idealized lidar sampling resolution can be used to describe topographical resolution, misrepresented or unknown behaviors in an instrument, platform, or environment can degrade expected performance or introduce georeferencing inaccuracies. Furthermore, bathymetric resolution is strongly dependent on water surface and column conditions. Thus, only empirical methods for evaluating resolution will provide reliable estimates for both topographic and bathymetric surveys. Presented is an extension of standard modulation transfer function (MTF) methods used by passive imaging systems applied to high-resolution scanning lidar. Compact retroreflectors characterized as point and line sources are employed to empirically assess effective lidar system resolution through MTF analysis in topographic and bathymetric scenes. These targets enable MTF analyses using height measurements without reliance on intensity data, promoting widespread applicability among lidar systems. Empirical MTFs calculated using these targets are compared against theory-derived counterparts as empirical measurements elucidate influences by elements that are unknown or difficult to model. Simulated point cloud data were incorporated into theoretical MTF descriptions to better represent empirically-derived topographic MTFs, revealing mirror pointing uncertainties in the across-track axis. Similarly, theoretical bathymetric MTFs augmented with simulated, subaqueous data enabled water surface slope estimation using empirical measurements of submerged retroreflector targets, where rough water surfaces strongly influenced beam steering and the corresponding point spread MTFs.
The resolution characteristic can be obtained by the modulation transfer function （MTF） of a GaAs/GaA1As photocathode. After establishing the theoretical model of GaAs（100）-oriented atomic configuration and the fo...
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The resolution characteristic can be obtained by the modulation transfer function （MTF） of a GaAs/GaA1As photocathode. After establishing the theoretical model of GaAs（100）-oriented atomic configuration and the formula for the ionized impurity scattering of the non-equilibrium carriers, this paper calculates the trajectories of photoelectrons in a photocathode. Thus the distribution of photoelectron spots on the emit-face is obtained, which is namely the point spread function. The MTF is obtained by Fourier transfer of the line spread function obtained from the point spread function. The MTF obtained from these calculations is shown to depend heavily on the electron diffusion length, and enhanced considerably by decreasing the electron diffusion length and increasing the doping concentration. Furthermore, the resolution is enhanced considerably by increasing the active-layer thickness, especially at high spatial frequencies. The best spatial resolution is 860 lp/mm, for the GaAs photocathode of doping concentration 1 ×10^19 cm 3 electron diffusion length 3.6 μm and the active-layer thickness 2 μm, under the 633-nm light irradiated. This research will contribute to the future improvement of the cathode＇s resolution for preparing a high performance GaAs photocathode, and improve the resolution of a low light level image intensifier.
We measured the modulation transfer function for microjetted microlenses with diameters ranging between 109 and 490 mu m and with focal lengths ranging between 135 and 540 mu m. We found that single-drop 100-mu m-diam...
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We measured the modulation transfer function for microjetted microlenses with diameters ranging between 109 and 490 mu m and with focal lengths ranging between 135 and 540 mu m. We found that single-drop 100-mu m-diameter microlenses perform close to their theoretical cutoff frequency. However, the larger lenses made with multiple droplets have a cutoff frequency that is 35% of the theoretical value. We interpret this as an illustration of the rapid increase in spherical aberration as the diameter of a lens increases. (C) 1999 Optical Society of America.
The modulation transfer function of a source-encoded Hadamard transform imaging system including beam condensing optics is derived. The effects of diffraction, convolution with the encoding apertures, mask motion, and...
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The modulation transfer function of a source-encoded Hadamard transform imaging system including beam condensing optics is derived. The effects of diffraction, convolution with the encoding apertures, mask motion, and focus errors are considered explicitly. The derived equations are shown to describe resolution of Hadamard transform photothermal deflection imagers with up to 30× condensing optics.
We investigate electrically tunable liquid crystal (LC) microlenses and microprisms based on double dielectric optically hidden (DDOH) layers. Comparative theoretical study of the spatial resolution limits in the crea...
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We investigate electrically tunable liquid crystal (LC) microlenses and microprisms based on double dielectric optically hidden (DDOH) layers. Comparative theoretical study of the spatial resolution limits in the creation of a spatially modulated electric field by the DDOH layer is conducted. Both the depth of the resulting optical phase modulation and its deviation from the desired wavefront are obtained for sine and sawtooth geometries of the DDOH layer's structure. A comparison is provided with the standard LC reorientation approach using patterned electrodes. (C) 2017 Optical Society of America
The modulation transfer function (MTF) is one of the main criteria for judging the image quality of an imaging system. Together with the well-known optical transferfunction, the MTF can be regarded as an objective ba...
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The modulation transfer function (MTF) is one of the main criteria for judging the image quality of an imaging system. Together with the well-known optical transferfunction, the MTF can be regarded as an objective basis reflecting the comprehensive performance of an imaging interferometer. In order to improve the imaging quality of a modified spatially modulated imaging interferometer (MSMII) with large optical path difference, the boundary conditions of an incident ray, at full field of view, along the x and y directions, respectively, are first calculated by the method of prism expansion, and then the exact expression of the pupil function of the MSMII is given. The two-dimensional MTF of the MSMII is obtained by the Fourier transform. Compared with previous studies, this work gives the two-dimensional MTF for the MSMII, and analyzes the effects of various parameters on the MTF. The optimal values of the incident angle i together with the acute angels beta(1) and beta(2) are chosen as i = 0 degrees and beta(1) = beta(2) = 45 degrees, respectively. If so, a high MTF is obtained, i.e. the imaging quality of the MSMII can satisfy the need of detecting upper atmospheric wind fields.
modulation transfer function (MTF) is the ability of an imaging system to faithfully image a given object. The MTF of an imaging system quantifies the ability of the system to resolve or transfer spatial frequencies. ...
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modulation transfer function (MTF) is the ability of an imaging system to faithfully image a given object. The MTF of an imaging system quantifies the ability of the system to resolve or transfer spatial frequencies. In this paper we will discuss the detail MTF measurements of a 1024 x 1024 pixel multi-band quantum well infrared photodetector and 320 x 256 pixel long-wavelength InAs/GaSb superlattice infrared focal plane arrays. (c) 2013 Elsevier B.V. All rights reserved.
We measured the modulation transfer function (MTF) of a short multimode fiber (SMMF) probe and proposed the optical model including the thin random phase screen (TRPS) to explain degradations of imaging characteristic...
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We measured the modulation transfer function (MTF) of a short multimode fiber (SMMF) probe and proposed the optical model including the thin random phase screen (TRPS) to explain degradations of imaging characteristics. SMMF is a graded index multimode fiber for optical communication. That length is 8.8 mm and the diameter of core is 50 mu m. With the wavelength of 780 nm, for spatial frequencies from128 lp/mm to 228 lp/mm MTFs were measured at 0.179-0.062 in reflection images and these contrasts were 19% to contrasts without TRPS. With parameters of sigma(phi) of 1.5 rad and W of 2-3.5 mu m calculated results almost correspond to measured ones. Dependences of contrasts on wavelength were also measured. With the spatial frequency of 200 lp/mm, at the wavelength of 0.8 mu m the contrast decreased to 17% due to TRPS and at that of 0.5 mu m the contrast decreased to 6%. Measured dependences of contrasts on wavelength with the spatial frequency of 228 lp/mm approximately correspond to calculation results with 200 lp/mm. These basic characteristics are useful to design the imaging optics by means of SMMF.
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