Jehad Khoury

Homodyne and heterodyne imaging through a scattering medium.

We introduce a novel two-dimensional (2D) homodyne and heterodyne technique for imaging objects through or embedded in a scattering medium. Our imaging approach is based on heterodyning of light with different Doppler broadenings that is scattered from objects of two different textures or from an opaque object and a textured scattering medium. We report on the initial demonstration of pulling signals out of noise for an object hidden behind a scattering medium. Enhancements of signal-to-noise ratio of the order of 50 have been achieved by use of a 2D holographic phase-sensitive detector. We also discuss the experimental feasibility of this approach for objects embedded in a scattering medium.

Optically driven microelectromechanical-system deformable mirror under high-frequency AC bias

A new, optically addressed deformable mirror device is demonstrated. The device consists of a pixellated metalized polymeric membrane mirror supported above an optically addressed photoconductive substrate. A conductive transparent ZnO layer is deposited on the back side of the substrate. A very high-frequency AC bias is applied between the membrane and the back electrode of the device. The membrane is deformed when the back of the device is illuminated because of impedance and bias redistribution between two cascaded impedances. We fabricated, demonstrated, and modeled the operation of this device.

Speckle velocimetry by means of holographic time-integrative correlation

We develop the theory of the speckle velocimeter that is based on use of a photorefractive real-time hologram in four-wave mixing as a time-integrative correlator. The theory of the speckle velocimeter has been developed for the time correlation between the far-field spectrum of light scattered from the diffuser and the reference wave that is Doppler shifted. Our theoretical derivation shows that it is possible to extract the velocity with minor processing of the output correlation.

Performance evaluation of photorefractive two-beam coupling joint transform correlator

The performance of a novel joint transform correlator (JTC) based on photorefractive (PR) two-beam coupling (TBC) is analyzed by determining the dependence of relevant figures of merit such as the discrimination ratio, the peak-to-correlation plane energy ratio, and the peak-to-noise ratio on the PR gain coefficient and pump-probe beam ratio for a variety of reference and signal images. In this scheme, spatially separated reference and signal images constitute the pump, which transfers energy to a weak probe in a novel image processing setup where the PR polymer serves as the spatial filter in the Fourier plane.

A mapping approach for distortion correction in sinusoidally scanned images

We have developed a mapping algorithm for correcting sinusoidally scanned images from their distortions. Our algorithm is based on an approximate relationship between linear and sinusoidal scanning. Straightforward implementation of this algorithm showed that the mapped image has either missing lines or redundant lines. The missing lines were filled by fusing the mapped image with its median filtered version. The implementation of this algorithm shows that it is possible to retrieve up to 96.43% of the original image, as measured by the recovered energy.

Optimal synthetic aperture radar image correlation using enhanced scattering centers in holographic data storage

We prove that for gray-level or binarized synthetic aperture radar (SAR) images with enhanced scattering centers, the DC-blocked phase-only filter is the optimal, as well as the most practical, solution for SAR image recognition. Our correlation algorithm, which employs various power laws to enhance the scattering centers, was examined for images with different complexity using the moving and stationary target acquisitions and recognition (MSTAR) data base. For standard recognition problems, which represent 95% of the cases (intermediate level of noise and sufficient number of scattering centers on the target), we found that our proposed approach improves the correlation even when utilizing binary templates extracted from the region of interest and binary inputs. For more complex problems (representing nearly 5% of the cases), a further improvement in our correlation recognition approach is needed.

Multipurpose mean-square-error filter for processing obscured images

We develop a generalized minimum mean-square-error image processing filter for recognition and retrieval of noisy, blurred and obscured images. We examined the performance of this filter in four modes: (1) the well-known mean-square- error correlation filter; (2) the phase-only mean-square- error correlation filter; (3) the matched mean-square-error correlation filter, and (4) the image retrieving filter. Our simulation result show that it is possible to retrieve and recognize blurred images that are 90 percent obscured and whose signal-to-noise ratio is 0.1.

Demultiplexing and phase-locking via a self-pumped phase-conjugate mirror

We demonstrate a new type of time-integrative photorefractive device using self-pumped phase conjugation. This device can be used for most of the applications related to time-integrative devices, such as demultiplexors and phase-sensitive detectors. A new device for angular multiplexing-to-frequency multiplexing conversion is proposed. By combining this new device with frequency demultiplexing, we show a new architecture for retrieving holograms from different holographic storages and for performing various arithmetic operations on the retrieved information.

Wiener-like correlation filters

We introduce a new, to our knowledge, design for a Wiener-like correlation filter, which consists of cascading a phase-only filter (POF) with a photorefractive Wiener-like filter. Its performance is compared with that of the POF and the Wiener correlation filter (WCF). Correlation results show that for intermediate and higher levels of noise this correlation filter has a peak-to-noise ratio that is larger than that of either the POF or the WCF while still preserving a correlation peak that is almost as high as that of the POF.

An FPGA-based method for a reconfigurable and compact scanner controller

An essential part of a LADAR system is the scanner component. The physical scanner and its electrical controller must often be as compact as possible to meet the stringent physical requirements of the system. It is also advantageous to have a reconfigurable electrical scanner controller. This can allow real-time automated dynamic modifications to the scanning characteristics. Via reconfiguration, this can also allow a single scanner controller to be used on multiple physical scanners with different resonant frequencies and reflection angles. The most efficient method to construct a compact scanner with static or dcynamic re-configurability is by using an FPGA-based system. FPGAs are extremely compact, reconfigurable, and can be programmed with very complex algorithms. We show here the design and testing of such an FPGA-based system has been designed and tested. We show here this FPGA-based system is able to drive scanners at arbitrary frequencies with different waveforms and produce appropriate horizontal and vertical syncs of arbitrary pulse width. Several programmable constants are provided to allow re-configurability. Additionally we show how very few essential components are required so the system could potentially be compacted to approximately the size of a cell phone.