Topic
Speckle imaging
About: Speckle imaging is a research topic. Over the lifetime, 3730 publications have been published within this topic receiving 62354 citations.
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TL;DR: In this article, the authors used a slow read-rate bare CCD detector and thus had to deal effectively with additive noise in the speckle measurements, and demonstrated diffraction-limited imaging down to light levels approaching a few photons per specckle per resolution area.
Abstract: Results are presented from a horizontal path imaging experiment in which a 0.5-m telescope was focused on targets located at a range of 1 .2 km. The targets varied in complexity from simple binary letters to extended representations of satellites with gray scale and size variations. Imaging at a center wavelength of 0.7 μm, we found an atmospheric degradation factor of D / r 0 = 17, on average. We used a slow read-rate bare CCD detector and thus had to deal effectively with additive noise in the speckle measurements. Our image reconstruction algorithms are based on the use of the complex bispectrum, and we have demonstrated diffraction-limited imaging down to light levels approaching a few photons per speckle per resolution area. We have paid careful attention to the effects of additive noise on the reconstruction process and have shown that they can be adequately overcome. These results support the feasibility of high-resolution speckle imaging of high-earth-orbit satellites using CCDs.
32 citations
TL;DR: In this article, a diffractive beam shaper with a cylindrical lens and a vibrating motor was used to eliminate laser speckle on the projection screen, which can achieve uniformity and contrast of 78% and 5.5% respectively, which demonstrates the feasibility and potential of the proposed scheme.
Abstract: Currently the major issues in applying the laser as an illumination source for projectors are beam shaping and laser speckle. We present a compact total solution for both issues by using a diffractive beam shaper associated with a cylindrical lens for the illumination optics and a vibrating motor attached to the beam shaper to eliminate speckle on the projection screen. The diffractive beam shaper features a double-sided microlens array with a lateral shift to each other. The illumination pattern is free of zero diffraction order mainly due to the continuous and spherical surface relief of the lenslet, which can be accurately fabricated with diamond turning and injection molding without quantizing surface relief, so that the illumination pattern on the microdisplay can match the design very well with high diffraction efficiency. In addition, the vibration of the diffractive beam shaper in the longitudinal mode has been found effective for eliminating the dot pattern in the illumination and reducing laser speckle on the projection screen. The proposed laser illuminator has been implemented on a three-panel LCoS projector engine to replace the traditional UHP lamp. The uniformity and speckle contrast are measured to be 78% and 5.5% respectively, which demonstrates the feasibility and potential of the proposed scheme.
32 citations
TL;DR: A speckle processing prescription is described that should yield diffraction-limited performance for large telescopes in spite of atmospheric turbulence and at light levels as low as 100 photons/sec in the picture.
Abstract: A speckle processing prescription is described that should yield diffraction-limited performance for large telescopes in spite of atmospheric turbulence and at light levels as low as 100 photons/sec in the picture. The prescription involves rearranging the spatial frequency components of running glimpses of the scene according to the complex information (entropy) of those components. The imaginary part (phase) of the information is rendered unambiguous by maintaining track of the phase. A 2-D photon counter furnishes the raw observations. Comparisons and ramifications of the procedure are discussed.
32 citations
TL;DR: Numerical simulations investigate how non-Rayleigh and Rayleigh speckle fields affect the resolution and visibility for high-order thermal ghost imaging and show regardless of the speckled field used better resolution is achieved with the use of a higher-order and that sub-rayleigh speckingle fields lead to the best resolution regardless of ghost order.
Abstract: It has been recently demonstrated in experiments how to create non-Rayleigh speckle fields through the use of a phase-only spatial light modulator. These non-Rayleigh speckle fields possess high-order correlations which could play important roles in correlation-based optical imaging methods such as thermal ghost imaging, in which case the Gaussian moment theorem is no longer applicable. Through numerical simulations we investigated at how non-Rayleigh and Rayleigh speckle fields affect the resolution and visibility for high-order thermal ghost imaging. The results show regardless of the speckle field used better resolution is achieved with the use of a higher-order and that sub-Rayleigh speckle fields lead to the best resolution regardless of ghost order.
32 citations
15 Aug 1983
TL;DR: In this article, an analysis of the effects of photon noise on astronomical speckle image reconstruction using the Knox-Thompson algorithm is presented, and it is shown that the quantities resulting from the average are biased, but that the biases are easily estimated and compensated.
Abstract: Abstract An analysis of the effects of photon noise on astronomical speckle image reconstruction using the Knox-Thompson algorithm is presented. It is shown that the quantities resulting from the speckle average are biased, but that the biases are easily estimated and compensated. Calculations are also made of the convergence rate for the speckle average as a function of the source brightness. An illustration of the effects of photon noise on the image recovery process is included.
32 citations