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Angular aperture

About: Angular aperture is a research topic. Over the lifetime, 1771 publications have been published within this topic receiving 27257 citations.


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Journal ArticleDOI
TL;DR: In this paper, it is shown that it is not necessary to resolve the speckles when making measurements in speckle interferometry, and the results lead to the conclusion that, especially when the total camera noise is low enough, lens apertures up to f /2 can be used.
Abstract: Speckle interferometry has long proven its usefulness for measuring the deformation and contours of objects with rough surfaces. Nevertheless, the influence of a parameter as important as the lens aperture of the imaging system on the result of the measurement is still not precisely known. Generally, it is stated that the speckles must be resolved by the camera and that therefore the lens aperture number should be large enough (e.g., f /11 or f /16 for typical applications with a standard CCD). It is shown, theoretically as well as experimentally, that it is not necessary to resolve the speckles when making measurements in speckle interferometry. The joint probability distribution of the pixel modulation and the pixel background intensity, which determines the percentage of valid pixels, is investigated for different lens aperture numbers, i.e., for different numbers of speckles per pixel. The comparison between theory and the experimental counterpart enables a number of speckles per pixel to be determined for any given aperture number and pixel size. It appears that the average pixel modulation remains high enough even with a relatively large number of speckles per pixel. The results lead to the conclusion that, especially when the total camera noise is low enough, lens apertures up to f /2 can be used. Thus, measurements are less constrained by limited laser power and decorrelation effects.

14 citations

Patent
06 Aug 1993
TL;DR: A high-resolution synthetic aperture, adaptive optics system includes an imaging system having a plurality of optical elements including at least a primary mirror which is a section of the aperture to be synthesized, and a detector for receiving the radiation collected by the primary mirror as mentioned in this paper.
Abstract: A high-resolution synthetic aperture, adaptive optics system includes an imaging system having a plurality of optical elements including at least a primary mirror which is a section of the aperture to be synthesized, and a detector for receiving the radiation collected by the primary mirror; and a device for rotating the primary mirror section through a number of angular positions about the aperture being synthesized to obtain a plurality of component images of an object, at least one from each of the positions; a device for sensing distortion of an incident wavefront; and a device responsive to distortions of the wavefront for locally adjusting at least one of the optical elements to correct distortions in the wavefront.

14 citations

Journal ArticleDOI
TL;DR: Theoretical and experimental studies of optical filtering which utilize anisotropic and noncollinear acoustooptic interaction in a Y-cut LiNbO 3 waveguide are reported in this article.
Abstract: Theoretical and experimental studies of optical filtering which utilize anisotropic and noncollinear acoustooptic interaction in a Y -cut LiNbO 3 waveguide are reported. A guided-light beam from either an He-Ne laser at 6328 A or an argon laser at around 5000 A, propagating at an angle centering around 70° from the Z(c) axis of the LiNbO 3 crystal, was Bragg diffracted by the surface acoustic wave with 500 MHz center frequency and propagating at 16° from the x axis of the crystal. High optical resolving power, large optical angular aperture, and good spatial separation between the filtered light and the unfiltered light have been simultaneously achieved. An optical passband of 16 A and an angular aperture of 9° have been measured for the case in which the undiffracted and diffracted light propagate in TE 0 mode and TM 0 mode, respectively. Furthermore, by varying the acoustic frequency from 350 to 670 MHz, the filtered optical wavelength may be tuned from 8300 to 5000 A.

14 citations

Journal ArticleDOI
TL;DR: In this article, the Fraunhofer diffraction of a Laguerre-Gaussian (LG) beam incident on a dynamic superposed dual-triangular aperture is analyzed experimentally and theoretically.
Abstract: We investigate the Fraunhofer diffraction of a Laguerre-Gaussian (LG) beam incident on a dynamic superposed dual-triangular aperture. The evolution of the diffraction pattern from this aperture is analyzed experimentally and theoretically. A special aperture, called the hex-star triangular aperture, demonstrates interesting diffraction patterns. Further, the diffraction properties of integer, half-integer, and fractional orders of topological charges at the Fraunhofer zone are studied by using the hex-star triangular aperture. This study can provide additional information to enhance the understanding of the diffraction properties of the LG beam transmitted through a complex aperture. (C) 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)

14 citations

Patent
29 Mar 1995
TL;DR: The gradient index (GRIN) lens elements are bi-convex and/or meniscus type lens elements as discussed by the authors, which are used in a lens system to correct monochromatic and chromatic lens aberrations.
Abstract: Axial gradient index of refraction lens elements are used in a lens system, for instance for a photographic objective lens, to correct monochromatic and chromatic lens aberrations, thereby reducing the number of lens elements required to achieve good optical performance in the overall lens design compared to for instance a lens system using aspheric lenses. The gradient index (GRIN) lens elements are bi-convex and/or meniscus type lens elements. The large refractive index gradients as well as large dispersion value gradients provide aberration correction in the overall lens system. A high aperture ratio lens system uses six lens elements where the first and last lens elements are positive power lens elements having refractive index and/or dispersion gradients along the optical axis.

14 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20234
20224
20217
20207
20195
201811