This paper describes a new test bench for measuring the modulation transfer function of an infrared focal plane array. The system is based on the use of a plane target made with a continuously self-imaging grating (CS...
详细信息
ISBN:
(纸本)0819449350
This paper describes a new test bench for measuring the modulation transfer function of an infrared focal plane array. The system is based on the use of a plane target made with a continuously self-imaging grating (CSIG)(1) that projects in polychromatic light a biperiodic pattern of small and non-diffracting spots called a nondiffracting array.
One result of the recent advances in different components of imaging systems technology is that these systems have become more resolution-limited and less noise-limited. The most useful tool utilized in characterizati...
详细信息
One result of the recent advances in different components of imaging systems technology is that these systems have become more resolution-limited and less noise-limited. The most useful tool utilized in characterization of resolution-limited systems is the modulation transfer function (MTF). Our goal is to use the MTF as an image quality measure of image compression implemented by the JPEG (Joint Photographic Experts Group) algorithm and transmitted MPEG (Motion Picture Experts Group) compressed video stream through a lossy packet network. Although we realize that the MTF is not an ideal parameter with which to measure image quality after compression and transmission due to the nonlinearity shift-variant process, we examine the conditions under which it can be used as an approximated criterion for image quality. The advantage of using the MTF of the compression algorithm is that it can be easily combined with the overall MTF of the imaging system. (C) 2001 Society of Photo-Optical Instrumentation Engineers.
Pyroelectric infrared sensor arrays are imaging devices for infrared radiation that utilize the temperature dependence of the remanent in polarization in pyroelectric materials. We use the finite element method for th...
详细信息
Pyroelectric infrared sensor arrays are imaging devices for infrared radiation that utilize the temperature dependence of the remanent in polarization in pyroelectric materials. We use the finite element method for the calculation of the coupled thermo-electro-mechanical fields for an instance of a linear sensor array, derive the modulation transfer function from the simulation data, and compare the result to an analytical solution.
This paper describes a new test bench for measuring the modulation transfer function of an infrared focal plane array. The system is based on the use of a plane target made of eight gratings that projects in polychrom...
详细信息
ISBN:
(纸本)0819437751
This paper describes a new test bench for measuring the modulation transfer function of an infrared focal plane array. The system is based on the use of a plane target made of eight gratings that projects in polychromatic light a biperiodic pattern of small and non-diffracting spots called a nondiffracting array.
Although there are various methods to measure the modulation transfer function (MTF) of charge-coupled devices (CCD). the interferometric fringe pattern method has advantages over others, such as canted slit sources, ...
详细信息
ISBN:
(纸本)9780819470096
Although there are various methods to measure the modulation transfer function (MTF) of charge-coupled devices (CCD). the interferometric fringe pattern method has advantages over others, such as canted slit sources, bar targets, knife-edge, laser-speckle patterns, random noise pattern, etc. Our interferometric method is relatively simple and versatile: It requires no critical optics and no focusing or precision alignment, the entry array is tested, the contrast ratio of the test pattern is high enough, the spatial frequency of the fringe pattern can vary continuously. Our method generates the formation of a sinusoidal intensity fringe pattern by the interference of two monochromatic plane waves, and straightforward projects it onto the CCD array under test. The construction of the experimental device is based on the Fresnel Double-Mirror structure. A 2.5 mw He-Ne laser with the wavelength of 632.8 nm is used as the light source, the laser beam is spatially filtered by a 10 mu m pinhole and expanded to a diameter of 30 mm, and the resulting wave front is divided by two mirrors, which incline to each other at a small angle, and interfered. One of the mirrors is rotatable to vary the frequency of the pattern. The CCD array is mounted on a stage, which is also rotatable to make that the CCD array takes different angle with the fringe pattern direction, to receive the patterns. With the method we provided, the spatial frequency can be extended to some 2 times the Nyquist frequency of the CCD array to study the aliasing effect. In the Cartesian coordinates, the x- and y- axis MTFs (at angle 0 degrees and 90 degrees) of the CCD array were measured, the other three MTFs (at angle 26.56 degrees, 45 degrees and 63.44 degrees), which nobody has done before, were also tested offering a more comprehensive characterization of the CCD array.
Owing to the ability of generating designated spectrums as special requirements, spectrum-controllable light source has attracted huge interesting in several fields, e.g. medical science, industrial detection, defense...
详细信息
ISBN:
(纸本)9781628417999
Owing to the ability of generating designated spectrums as special requirements, spectrum-controllable light source has attracted huge interesting in several fields, e.g. medical science, industrial detection, defense-related testing. In principle, optical performance of a spectrum-controllable light source can be predicted by some transferfunctions of the corresponding system, e.g. modulation transfer function (MTF). Unfortunately, the aforementioned research work is still lacking at present although it is meaningful for the optical design and evaluation of this new kind of light sources. Hence, a MTF model for a modified version of our previously-proposed spectrum-controllable light source system based on a Digital Micromirror Device (DMD) and an Offner dispersion configuration with a convex grating is deduced as an example. Related preliminary analyses have been present in this paper as well.
Based on the statistical properties of laser speckle, the response for laser speckle passing through a linear shift- invariant system is studied. This paper presents a method for testing the modulationtransfer functi...
详细信息
ISBN:
(纸本)0819423009
Based on the statistical properties of laser speckle, the response for laser speckle passing through a linear shift- invariant system is studied. This paper presents a method for testing the modulation transfer function (MTF) of charge-coupled devices below the Nyquist frequency. A new scattering microcrystalline glass material generates laser speckle. The instrument is designed and test results show that this technique is a variable MTF measurement approach. The difference of the results of each test is within 0.03.
In this paper, we consider the measurement of modulation transfer function (MTF) by means of spatially random, noise-like targets. We begin our discussion with the concept of shift-invariance and the measurement of MT...
详细信息
ISBN:
(纸本)0819417742
In this paper, we consider the measurement of modulation transfer function (MTF) by means of spatially random, noise-like targets. We begin our discussion with the concept of shift-invariance and the measurement of MTF in pixelated systems. We then proceed to the methods for generation of these noise targets, using both laser speckle and transparency-based techniques.
During the Spaceborne Imaging Radar (SIR-B) mission in October 1984, the on-board synthetic aperture radar (SAR) acquired data in the vicinity of Hurricane Josephine. In this paper, ocean wave spectra computed from th...
详细信息
During the Spaceborne Imaging Radar (SIR-B) mission in October 1984, the on-board synthetic aperture radar (SAR) acquired data in the vicinity of Hurricane Josephine. In this paper, ocean wave spectra computed from the SAR imagery are compared with Ocean Data Gathering Project (ODGP) model forecasts. Because the apparent propagation direction of the dominant wave system rotated over 90-degrees along the pass, the data set affords a unique opportunity to observe the same wave system as imaged by different SAR imaging mechanisms. It is shown here that, for the SIR-B geometry, the wavenumbers and propagation directions extracted from the wave spectra are not strongly dependent upon the exact nature of the SAR imaging mechanisms. However, the estimation of ocean significant wave height (SWH) requires accurate knowledge of such mechanisms. The spatial variation of SWH as estimated from SAR derived wave spectra and ODGP model spectra compare most favorably when the phase of the hydrodynamic portion of the SAR modulation transfer function is approximately 90-degrees past the long wave crest.
In conjunction with recent atmospheric modulation transfer function (MTF) measurements for desert and mountain locations, the distribution of optical turbulence within the planetary boundary layer was measured by usin...
详细信息
In conjunction with recent atmospheric modulation transfer function (MTF) measurements for desert and mountain locations, the distribution of optical turbulence within the planetary boundary layer was measured by using tower, aircraft, and acoustic sounder techniques. Diurnal variations in the atmospheric turbulence within 1–3 km above the surface dominate the MTF observations. During convective, daylight hours, desert and mountain boundary layers are found to be similar. The magnitudes of optical turbulence ( C n 2 ) are comparable, and similar thermal plume structures are observed. In addition, optical turbulence is found to have a simple (Δ θ ) 4/3 dependence on the air–surface temperature difference. At night, the cool ground surface produces turbulent, stratified layers above a desert that are not observed for a mountain. The effects of tower height above the ground are investigated theoretically and experimentally. MTF measurements made 2 and 8 m above the desert during the day are in good agreement with theoretical models. We observe interrelationships between the turbulent boundary layer and the atmospheric MTF that can be applied to the selection of both astronomical and solar telescope site locations.
暂无评论