Biomedical subjects

David Abookasis

Publications and source records attributed to David Abookasis.

7 recordsLinked to original sources

PubMed2006

Three types of computer-generated hologram synthesized from multiple angular viewpoints of a three-dimensional scene.

We describe various techniques to synthesize three types of computer-generated hologram (CGH): the Fresnel-Fourier CGH, the Fresnel CGH, and the image CGH. These holograms are synthesized by fusing multiple perspective views of a computer-generated scene. An initial hologram is generated in the computer as a Fourier hologram. Then it can be converted to either a Fresnel or an image hologram by computing the desired wave propagation and imitating an interference process of optical holography. By illuminating the CGH, a 3D image of the objects is constructed. Computer simulations and experimental results underline the performance of the suggested techniques.

Journal Article↗

PubMed2006

Performance comparison of iterative algorithms for generating digital correlation holograms used in optical security systems.

An optical security system based on a correlation between two separate binary computer-generated holograms has been developed and experimentally tested. The two holograms are designed using two different iterative algorithms: the projection- onto constrained sets algorithm and the direct binary search (DBS) algorithm. By placing the ready-to-use holograms on a modified joint transform correlator input plane, an output image is constructed as a result of a spatial correlation between the two functions coded by the holograms. Both simulation and experimental results are presented to demonstrate the system's performance. While we concentrate mainly on the DBS algorithm, we also compare the performance of both algorithms.

Journal Article↗

PubMed2006

Stereoscopic imaging through scattering media.

We develop and experimentally test a method for three-dimensional imaging of hidden objects in a scattering medium. In our scheme, objects hidden between two biological tissues at different depths from the viewing system are recovered, and their three-dimensional locations are computed. Analogous to a fly's two eyes, two microlens arrays are used to observe the hidden objects from different perspectives. At the output of each lens array we construct the objects from several sets of many speckled images with a previously suggested technique that uses a reference point. The differences of the reconstructed images in both arrays with respect to the reference point yield the information regarding the relative depth among the various objects.

Journal Article↗

PubMed2005

Watermarks encrypted in a concealogram and deciphered by a modified joint-transform correlator.

We describe an electro-optical method of deciphering a watermark from a recently invented encoded image termed a concealogram. The watermark is revealed as a result of spatial correlation between two concealograms, one containing the watermark and the other containing the deciphering key. The two are placed side by side on the input plane of a modified joint-transform correlator. When the input plane is illuminated by a plane wave, the watermark image is reconstructed on part of the correlator's output plane. The key function deciphers the concealed watermark from the visible picture only when the two specific concealograms are matched. To illustrate the system's performance, both simulation and experimental results are presented.

Journal Article↗

PubMed2004

NOISE 2 imaging system: seeing through scattering tissue with a reference point.

We propose a fly-eye-like imaging system for seeing objects embedded in scattering media. Objects are recovered from many speckled images observed by a digital camera through a microlens array. Each microlens in the array generates a speckle image of the object buried between two layers of chicken breast tissue. In the computer each image is Fourier transformed jointly with an image of the speckled pointlike source captured under the same conditions. A set of the squared magnitudes of the Fourier-transformed pictures is accumulated to form a single average picture. This final picture is again Fourier transformed, resulting in the reconstruction of the hidden object.

Animals↗

PubMed2004

Noninvasive optical imaging by speckle ensemble.

We propose a new method imaging through scattering media. An object hidden between two biological tissues (chicken breast) is reconstructed from any speckled images obtained from the output of a multichannel optical imaging system. The effect of multiple imaging is achieved with a microlens array. Each lens is the array projects a different speckled image onto a digital camera. The set of speckled images from the entire array is first shifted to a common center and then accumulated into a single average picture.

Animals↗

PubMed2003

Computer-generated holograms of three-dimensional objects synthesized from their multiple angular viewpoints.

Synthesizing computer-generated holograms (CGHs) of a general three-dimensional (3D) object is usually a heavy computational task. We propose and demonstrate a new algorithm for computing CGHs of 3D objects. In our scheme, many different angular projections of computer-designed 3D objects are numerically processed to yield a single two-dimensional complex matrix. This matrix is equivalent to the complex amplitude of a wave front on the rear focal plane of a spherical lens when the object is located near the front focal point and illuminated by a plane wave. Therefore the computed matrix can be used as a CGH after it is encoded to a real positive-valued transparency. When such CGH is illuminated by a plane wave, a 3D real image of the objects is constructed. The number of computer operations are equivalent to those of a two-dimensional Fourier CGH. Computer and optical constructions of 3D objects, both of which show the feasibility of the proposed approach, are described.

Journal Article↗