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.

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.

Optical configuration of pigmented lesion detection by frequency analysis of skin speckle patterns.

In this paper we present a novel approach of realizing a safe, simple, and inexpensive sensor applicable to pigmented lesions detection. The approach is based on temporal tracking of back-reflected secondary speckle patterns generated while illuminating the affected area with a laser and applying periodic pressure to the surface via a controlled vibration source. When applied to pigmented lesions, the technique is superior to visual examination in avoiding many false positives and resultant unnecessary biopsies. Applying a series of different vibration frequencies at the examined tissue and analyzing the 2-D time varying speckle patterns in response to the applied periodic pressure creates a unique signature for each and different pigmented lesion. Analyzing these signatures is the first step toward detection of malignant melanoma. In this paper we present preliminary experiments that show the validity of the developed sensor for the classification of pigmented lesions.

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.