Deep learning method for pinhole array color image reconstruction.

The following paper proposes a combination of a supervised encoder-decoder neural network with coded apertures. Coded apertures provide improved sensitivity and signal-to-noise ratio (SNR) in planar images. The unique array design of this method overcomes the spatial frequency cutoff found in standard multi-pinhole arrays. In this design, the pinholes were positioned to minimize loss in spatial frequencies. The large number of pinholes results in significant overlapping on the detector. To overcome the overlapping issue, reconstruction of the object from the obtained image is done using inverse filtering methods. However, traces of duplications remain leading to a decline in SNR, contrast, and resolution. The proposed technique addresses the challenge of image distortion caused by the lack of accuracy in the inverse filter methods, by using a deep neural network. In this work, the coded aperture is combined with a deep convolutional neural network (CNN) to remove noise caused by pinhole imaging and inverse filter limitations. Compared to only using Wiener filtering, the proposed method delivers higher SNR, contrast, and resolution. The imaging system is presented in detail with experimental results that illustrate its efficiency.

Gamma Radiation Imaging System via Variable and Time-Multiplexed Pinhole Arrays.

Biomedical planar imaging using gamma radiation is a very important screening tool for medical diagnostics. Since lens imaging is not available in gamma imaging, the current methods use lead collimator or pinhole techniques to perform imaging. However, due to ineffective utilization of the gamma radiation emitted from the patient's body and the radioactive dose limit in patients, poor image signal to noise ratio (SNR) and long image capturing time are evident. Furthermore, the resolution is related to the pinhole diameter, thus there is a tradeoff between SNR and resolution. Our objectives are to reduce the radioactive dose given to the patient and to preserve or improve SNR, resolution and capturing time while incorporating three-dimensional capabilities in existing gamma imaging systems. The proposed imaging system is based on super-resolved time-multiplexing methods using both variable and moving pinhole arrays. Simulations were performed both in MATLAB and GEANT4, and gamma single photon emission computed tomography (SPECT) experiments were conducted to support theory and simulations. The proposed method is able to reduce the radioactive dose and image capturing time and to improve SNR and resolution. The results and method enhance the gamma imaging capabilities that exist in current systems, while providing three-dimensional data on the object.

Remote optical sensing in otolaryngology: middle ear effusion detection.

Otitis Media (OM) is related to a group of inflammatory diseases of the middle ear (ME) commonly encountered, worldwide. A method based on a simple device, which can be used by medical staff and non-experts to detect OM is presented. The method is based on detection of tympanic membrane (TM) vibrations. A laser beam is pointed on an infra-sonic stimulated TM with fast camera capturing the back scattered secondary speckle patterns. A camera enables inspection of the frequency and amplitude of the changes in TM characteristics obtained by analysis of the spatial-temporal statistics of the speckle patterns. The results may provide information that express ME effusion.

Demonstration of a Speckle Based Sensing with Pulse-Doppler Radar for Vibration Detection.

In previous works, an optical technique for extraction and separation of remote static vibrations has been demonstrated. In this paper, we will describe an approach in which RF speckle movement is used to extract remote vibrations of a static target. The use of conventional radar Doppler methods is not suitable for detecting vibrations of static targets. In addition, the speckle method has an important advantage, in that it is able to detect vibrations at far greater distances than what is normally detected in classical optical methods. The experiment described in this paper was done using a motorized vehicle, which engine was turned on and off. The results showed that the system was able to distinguish between the different engine states, and in addition, was able to determine the vibration frequency of the engine. The first step towards real time detection of human vital signs using RF speckle patterns is presented.

2D mono detection spatially super-resolved microwave imaging for radar applications.

In this paper, we present an advanced two-dimensional (2D) novel microwave photonic approach to super-resolved radar imaging. Unlike synthetic aperture radar that requires movement to improve resolution by synthetically increasing the antenna's dimensions, our super-resolved imaging solution not only does not require movement to synthetically increase the antenna's dimensions, it also allows this super-resolved sensing with only a single (mono) detector. The operation principle is based upon phased array antennas, which consist of four radiating horn antennas that generate a projected plane at the far field zone. The setting of an appropriate phase to each one of the antenna inputs causes scanning of the projected structured electromagnetic beam over the imaged object. The summing of each azimuth cut of the reflections received from the object at different frequencies can spatially reconstruct the high resolution image of the object despite the fact that the receiving was done with a small size antenna with only a mono detector. Following several CST simulations, experiments, and Matlab code-based simulations, we are able to demonstrate reconstruction results having a satisfying resolution enhancement factor.

Neural networks within multi-core optic fibers.

Hardware implementation of artificial neural networks facilitates real-time parallel processing of massive data sets. Optical neural networks offer low-volume 3D connectivity together with large bandwidth and minimal heat production in contrast to electronic implementation. Here, we present a conceptual design for in-fiber optical neural networks. Neurons and synapses are realized as individual silica cores in a multi-core fiber. Optical signals are transferred transversely between cores by means of optical coupling. Pump driven amplification in erbium-doped cores mimics synaptic interactions. We simulated three-layered feed-forward neural networks and explored their capabilities. Simulations suggest that networks can differentiate between given inputs depending on specific configurations of amplification; this implies classification and learning capabilities. Finally, we tested experimentally our basic neuronal elements using fibers, couplers, and amplifiers, and demonstrated that this configuration implements a neuron-like function. Therefore, devices similar to our proposed multi-core fiber could potentially serve as building blocks for future large-scale small-volume optical artificial neural networks.

Optical remote sensor for peanut kernel abortion classification.

In this paper, we propose a simple, inexpensive optical device for remote measurement of various agricultural parameters. The sensor is based on temporal tracking of backreflected secondary speckle patterns generated when illuminating a plant with a laser and while applying periodic acoustic-based pressure stimulation. By analyzing different parameters using a support-vector-machine-based algorithm, peanut kernel abortion can be detected remotely. This paper presents experimental tests which are the first step toward an implementation of a noncontact device for the detection of agricultural parameters such as kernel abortion.

Noncontact speckle-based optical sensor for detection of glucose concentration using magneto-optic effect.

We experimentally verify a speckle-based technique for noncontact measurement of glucose concentration in the bloodstream. The final device is intended to be a single wristwatch-style device containing a laser, a camera, and an alternating current (ac) electromagnet generated by a solenoid. The experiments presented are performed in vitro as proof of the concept. When a glucose substance is inserted into a solenoid generating an ac magnetic field, it exhibits Faraday rotation, which affects the temporal changes of the secondary speckle pattern distributions. The temporal frequency resulting from the ac magnetic field was found to have a lock-in amplification role, which increased the observability of the relatively small magneto-optic effect. Experimental results to support the proposed concept are presented.

Lensless three-dimensional integral imaging using variable and time multiplexed pinhole array.

We present a multivariable coded aperture (MVCA) for lensless three-dimensional integral imaging (3D II) systems. The new configuration is based on a time multiplexing method using a variable pinholes array design. The system provides higher resolution 3D images with improved light intensity and signal to noise ratio as compared to single-pinhole system. The MVCA 3D II system configuration can be designed to achieve high light intensity for practical use as microlenslets arrays. This new configuration preserves the advantages of pinhole optics while solving the resolution limitation problem and the long exposure time of such systems. The three-dimensional images are obtained with improved resolution, signal to noise ratio, and light efficiency. This integral imaging lensless system is characterized by large depth of focus, simplicity, and low cost.

Light intensity and SNR improvement for high-resolution optical imaging via time multiplexed pinhole arrays.

In this paper, we present a novel method for pinhole optics with variable pinhole arrays. The imaging system is based on a time multiplexing method using variable and moving pinhole arrays. The improved resolution and signal-to-noise ratio are achieved with improved light intensity in the same exposure time, compared with that of a one-pinhole system. This new configuration preserves the advantages of pinhole optics while solving the resolution limitation problem and the long exposure time of such systems. The system also can be used as an addition to several existing optical systems, which use visible and invisible light and x-ray systems.

RF-photonic chirp encoder and compressor for seamless analysis of information flow.

In this paper we realize an RF photonic chirp compression system that compresses a continuous stream of incoming RF data (modulated on top of an optical carrier) into a train of temporal short pulses. Each pulse in the train can be separated and treated individually while being sampled by low rate optical switch and without temporal loses of the incoming flow of information. Each such pulse can be filtered and analyzed differently. The main advantage of the proposed system is its capability of being able to handle, seamlessly, high rate information flow with all-optical means and with low rate optical switches.

All-optical axial super resolving imaging using a low-frequency binary-phase mask.

In this paper we present a new approach for obtaining all-optical axial super-resolving imaging by using a non-diffractive binary phase mask inserted at the entrance pupil of an imaging lens. The designed element is tested numerically and experimentally on various practical testing benches and eventually is inserted into the lens of a cellular phone camera.

Passive and periodically ultra fast RF-photonic spectral scanner.

In this paper we present passive photonic device performing periodic and ultra fast spectral analysis of RF signals modulated on optical carrier. The spectral scanning is demonstrated in two approaches. First by passing the light through a couple of special bulk periscopes that split the beam into a set of parallel channels or combine a set of channels into one beam. One surface of each periscope is coated with high reflectivity coating such that the set of parallel beams travel several times through the structure due to their partial back reflection in each passage through the periscope. In each passage in the system the channel experience different delay in comparison with the original signal. This relative delay is accumulative and it is generated by placing glass bars with different length for each one of the channels. This structure realizes Finite Impulse Response (FIR) filter that performs the spectral scanning. The second approach involves similar configuration but it is realized with fibers and Y couplers rather than bulk optics. In this case the filter that performs the spectral scanning is an Infinite Impulse Response (IIR) filter having much sharper spectral sampling capability.

Radio frequency photonic filter for highly resolved and ultrafast information extraction.

We present a method and devices for highly resolved carrier and information extraction of optically modulated radar signals. The extraction is done by passing the optical beam through a monitoring path that constitutes a finite impulse response filter. Replications of the monitoring signal realize the required spectral scan of the filter. Despite the fact that the filter configuration is fixed, each replication experiences different spectral filtering. The radar carrier is detected by observing the energy fluctuations in a low-rate output detector. The RF information is extracted by positioning a low-rate tunable filter at the detected carrier frequency.

Optical characteristics of the compound PLZT.

We present a summary of measured characteristics of lanthanum-doped lead zirconium titanate (PLZT) compound in its mechanical housing. It is expected that the PLZT device will be used as the main component in an ultrafast electro-optic switch. We have performed several experiments to measure and calculate the following characteristics: optical power transmission, thermodynamic effects, switching speed, and dc drift phenomenon.

Time multiplexing superresolution based on interference grating projection.

In a previous work done by the authors, it was shown that the superresolution concept based on two moving gratings could be effected by a physical grating attached to the object and a virtual grating. This concept was shown to be very efficient and exhibited features that are helpful in removing some artifacts caused when coherent illumination is used. Furthermore, it simplifies the optical and mechanical modules of the super-resolving system by removing the need for mechanical movement of one grating. However, the system still required the need for moving the first (encoding) grating attached to the input. In this study the encoding grating is replaced by use of a projected grating. This approach simplifies the need for attaching the grating to the input object and thus new applications, such as remote sensing can be considered. The theoretical concept is demonstrated and experimental results are shown.