Search results for "Aperture synthesis"
showing 10 items of 13 documents
Super resolved optical system for objects with finite sizes using circular gratings
2015
We present a real time all optical super resolution method for exceeding the diffraction limit of an imaging system which has a circular aperture. The resolution improvement is obtained using two fixed circular gratings which are placed in predetermined positions. The circular gratings generate synthetic circular duplications of the aperture, thus they are the proper choice for a circular aperture optical system. The method is applicable for both spatially coherent and incoherent illuminations, as well as for white light illumination. The resolution improvement is achieved by limiting the object field of view. The proposed method is presented analytically, demonstrated via numerical simulat…
3D integral imaging display by smart pseudoscopic-to-orthoscopic conversion (SPOC).
2010
Previously, we reported a digital technique for formation of real, non-distorted, orthoscopic integral images by direct pickup. However the technique was constrained to the case of symmetric image capture and display systems. Here, we report a more general algorithm which allows the pseudoscopic to orthoscopic transformation with full control over the display parameters so that one can generate a set of synthetic elemental images that suits the characteristics of the Integral-Imaging monitor and permits control over the depth and size of the reconstructed 3D scene.
Enhanced viewing-angle integral imaging by multiple-axis telecentric relay system
2009
One of the main limitations of integral imaging is the narrow viewing angle. This drawback comes from the limited field of view of microlenses during the pickup and display. We propose a novel all-optical technique which allows the substantial increase of the field of view of any microlens and therefore of the viewing angle of integral-imaging displays.
Random angular coding for superresolved imaging.
2010
In this paper, we present a new approach capable of working under coherent and incoherent illumination for achieving superresolution by random coding of the object's angular information. By placing two static random masks in optically conjugate planes inside an aperture-limited imaging setup, one may obtain a transmitted image containing spatial resolution higher than the one obtained without the masks. As the most noticeable fact, the superresolution effect is obtained without imposing any restrictions either in the time domain or in the field-of-view domain but rather only in the dynamic range of the camera device. Experimental verifications for the proposed technique with incoherent illu…
Resolution and field of view improvement in digital holography using a VCSEL source array
2011
We describe a new implementation capable to produce superresolution (SR) and object field of view (FOV) improvement in digital lensless Fourier holography. The method provides synthetic aperture (SA) generation using angular multiplexing incoming from a Vertical Cavity Surface Emitting Laser (VCSEL) source array. SR imaging in a single exposure is obtained after proper digital processing of a multiplexed hologram coming from the incoherent addition of multiple sub-holograms, each one corresponding with a different source of the VCSEL array. FOV improvement in addition with SR imaging is achieved by recording a set of individual holograms obtained by sequential activation of the VCSEL source…
Single-step superresolution by interferometric imaging
2009
The use of vertical-cavity surface-emitting laser (VCSEL) arrays for implementation of incoherent source superresolution is presented. The method uses an interferometer setup to obtain superresolution in a single step. The novelty of the method relies on the use of a VCSEL array as the light source, which provides a set of coherent sources which are mutually incoherent. The technique accomplishes the transmission of several spatial frequency bands of the object's spectrum in parallel by use of spatial multiplexing that occurs because of the tilted illumination of the source array. The recording process is done by interference of each frequency band with a complementary set of reference plan…
Transversal superresolution with noncontact axial movement of periodic structures
2007
We present an innovative approach that allows superresolved images to be obtained by axial moving of two gratings and time integrating in the detector plane. The two gratings do not have to be in contact with either the object or the detector, and both are positioned between the object and the image planes. One of the main applications for the proposed approach in contrast to previously discussed time multiplexing superresolving methods is that it may fit well to superresolved imaging of remote objects, since both gratings are not in contact with either the object or the detector planes.
Multi-epoch VLTI-PIONIER imaging of the supergiant V766 Cen
2017
Context. The star V766 Cen (=HR 5171A) was originally classified as a yellow hypergiant but lately found to more likely be a 27-36 M red supergiant (RSG). Recent observations indicated a close eclipsing companion in the contact or common-envelope phase. Aims. Here, we aim at imaging observations of V766 Cen to confirm the presence of the close companion. Methods. We used near-infrared H-band aperture synthesis imaging at three epochs in 2014, 2016, and 2017, employing the PIONIER instrument at the Very Large Telescope Interferometer (VLTI). Results. The visibility data indicate a mean Rosseland angular diameter of 4.1 ± 0.8 mas, corresponding to a radius of 1575 ± 400 R. The data show an ex…
Synthetic aperture superresolution with multiple off-axis holograms
2006
An optical setup to achieve superresolution in microscopy using holographic recording is presented. The technique is based on off-axis illumination of the object and a simple optical image processing stage after the imaging system for the interferometric recording process. The superresolution effect can be obtained either in one step by combining a spatial multiplexing process and an incoherent addition of different holograms or it can be implemented sequentially. Each hologram holds the information of each different frequency bandpass of the object spectrum. We have optically implemented the approach for a low-numerical-aperture commercial microscope objective. The system is simple and rob…
Holography and Superresolution
2013
The capability of improving the spatial resolution of imaging systems is usually known as superresolution. Some methods provide improve resolution by playing with the imaging part of the system and without modifying the optical parameters of the imaging lenses. And others act over the geometry, shape and size of sampling pixels in the detection array. The former strategy allows optical superresolution while the latter provide geometrical superresolution. In this contribution, we will review the state of the art in optical superresolution approaches understood as the possibility to overcome the limited resolving power of imaging systems beyond the bounds imposed by Abbe's diffraction theory.…