Search

Diabetic foot is a well-known problem among patients suffering from peripheral arterial diseases (PAD). This article presents an optical sensor for contactless measurement of the anatomical site based on laser speckle techniques. The sensor illuminates the inspected tissue and analyzes the captured back-reflected light from the time-changing speckle patterns. An occlusion test was implemented to provide a statistical parameter to differentiate between a low perfused and a healthy foot. A clinical study of 15 subjects was conducted. The video was analyzed by two methods: dynamic laser speckle (DLS) and laser speckle contrast analysis (LASCA). Data analysis included several classification models, where the KNN model exhibited maximum performance. These findings suggest that a simple and inexpensive system for PAD monitoring can be designed for home use and/or in community clinics.

Photoacoustics is a promising technique for in-depth imaging of biological tissues. However, the lateral resolution of photoacoustic imaging is limited by size of the optical excitation spot, and therefore by light diffraction and scattering. Several super-resolution approaches, among which methods based on localization of labels and particles, have been suggested, presenting promising but limited solutions. This work demonstrates a novel concept for extended-resolution imaging based on separation and localization of multiple sub-pixel absorbers, each characterized by a distinct acoustic response. Sparse autoencoder algorithm is used to blindly decompose the acoustic signal into its various sources and resolve sub-pixel features. This method can be used independently or as a combination with other super-resolution techniques to gain further resolution enhancement and may also be extended to other imaging schemes. In this paper, the general idea is presented in details and experimentally demonstrated.

Diabetic foot is a well-known problem among patients suffering from peripheral arterial diseases (PAD). An optical sensor was built for a contactless measurement of the anatomical site, composing of a diode-laser and a high-speed camera. The laser illuminates the inspected tissue and the back reflected light forms time changing speckle patterns. We used second order autocorrelation function (ACF) decay time as merit for blood flow estimation. Clinical study with 15 subjects was conducted. An occlusion test was introduced to provoke a statistical parameter to distinguish between low perfused and a healthy foot.

The ability to remotely extract temperature from a specific location using back scattered light analysis is very applicable. In this paper we present the first step towards remote sensing of temperature by using several approaches based upon conventional neural network analysis of the back scattered speckle patterns, analysis of the speckle patterns decorrelation time constant and Photoplethysmogram measurements.

The angle of a rotating diffuser was evaluated by tracking the speckle pattern produced from an incoherent thermal radiation source demonstrating the use of an incoherent source for speckle-based sensing.

We present speckle and Michelson interference based photonic technique for performing depth measurement and elastography of a tissue. Photons from different depths of the tissue are separated by analyzing the flickering frequencies of collected speckles.

We will present how one can use the spatial-temporal analysis of secondary speckle patterns that are generated when laser light is back scattered from a tissue in order to measure the nano-vibrations (tilting associated vibrations) occurring in the tissue and in order to map its elastography. In addition to the fundamental nano-vibrations sensing capability, the proposed configuration allows by applying time multiplexing approach also to perform separation of photons coming from different depths of the tissue while externally stimulating the tissue via infra-sonic vibration. This yields a tomographic capability. The proposed configuration uses a modulated laser that allows combining a speckle pattern tracking method for surface tilting changes sensing with a Mach–Zehnder interferometer-based speckle patterns configuration to achieve z-axis detection (movement of the whole surface in the z direction). We will also show several methods for setup modulation to down convert high temporal frequencies to allow their sampling with a slow rate camera. As to be demonstrated in the experimental validation, the different elastographic layers (that were represented in our experiments by different concentrations of the agarose) have different temporal flickering and thereafter different temporal-spectral distribution which allows to extract their different elastographic characters.

We present novel optical approach based on statistical analysis of temporal laser speckle patterns for tissue in-depth flow characteristics. An ability to distinguish between Brownian motion of particles and laminar flow is well proved. The main steps in the post processing algorithm and the in-vivo and in-vitro experimental results are presented and demonstrated.

A method for fast non-scanning remote photoacoustic imaging is presented and experimentally demonstrated. The approach is based on speckle contrast measurement, proceeding the previously developed method for speckle contrast based photoacoustic detection. This previously developed method is now presented without the need for raster scanning of the sample, an advantage rarely found in optical photoacoustic detection, and offers 50 times faster as well as a simpler remote photoacoustic scheme in respect to interferometric available solutions.

In this study, the authors discuss in detail the implementation of all-optical orthogonal frequency-division multiplexing system based on discrete wavelet packet transform (DWPT) by using silicon-on-insulator (SOI) cascaded Mach–Zehnder interferometers (MZIs). DWPT can be used in the multiplexing and de-multiplexing of data channels in coherent optical communication in order to improve spectral efficiency excluding a cyclic prefix. DWPT and inverse-DWPT may be realised in an integrated-photonic MZI platform. They demonstrated experimentally the post-fabrication tuning of 1 × 4 cascaded MZI de-multiplexing filters. Tuning procedures effectively overcome fabrication tolerances and meet the target transfer function of the devices. The fabrication platform represents an essential stepping-stone toward the all-optical realisation of DWPT-based multiplexing.

A novel method for optimizing fast camera parameters to sense flow dynamics is presented. A wide-field statistic of the temporal auto-correlation intensity function from sample back-scattered laser light can be obtained from the high-end fast cameras that have come on to the market in recent years. Although these statistics can reveal flow dynamics within different sample regions, these cameras can be very costly. Here we investigated the impact of several key camera features such as camera frame rate, sensor exposure time, etc, on the output data (auto-correlation decay time and function fit models). The post-processing algorithm steps are described in detail, followed by the findings from in-vitro and in-vivo experiments investigating ways to re-leaf the camera parameters. The experimental results define fast-camera minimum specification requirements for the correct monitoring of normal blood flow conditions. These findings thus contribute to a better understanding of the impact of each parameter on speckle statistics and can contribute to customizing cheaper hardware to specific needs without compromising on accuracy.

A non-contact optical method based on laser speckle contrast analysis in IR for monitoring of blood pulsation is compared to remote PPG. Suggested method show superiority at anatomic sites with week pulsation.

A novel optical approach based on statistical analysis of spatial laser speckle pattern for tissue in-depth flow characteristics is presented. Properties such as flow orientation and speed can be estimated. In-vitro experimental results are demonstrated.

Middle ear effusion (MEE) is related to a group of inflammatory diseases of the middle ear. There are two main groups of otitis media (OM): The first group refers to acute OM (AOM), typically expressed by pain and elevated temperature of an acute onset, related to an infection of the middle ear that is caused by known pathogens (viruses and bacteriae). The second group, refers to OM with effusion (OME), has a rather benign course and is mainly presented with hearing loss. These two disorders share a significant impact upon public health and both demand appropriate diagnosis and specific treatment [1].

A novel method for non-contact and continuous detection of photoacoustic signals is presented and experimentally demonstrated. The approach is based on analysis of the contrast of time-varying speckle patterns, and suggests a more robust alternative in respect to interferometric and refractometric available solutions.

Silicon-photonic devices are tuned by selective photo removal of chalcogenide glass upper claddings. Phase delays in Mach-Zehnder interferometers and coupling ratios of ring resonators are adjusted. The transfer functions of devices remain stable following trimming.

The rapid post-fabrication trimming of the group index in hybrid chalcogenide-on-silicon Mach-Zehnder interferometers is demonstrated. Index changes of 0.065 are achieved through photo-induced mass transfer in an As10Se90 layer.

A hybrid Mach-Zehnder interferometer with directly bonded LiNbO3 on silicon-on-insulator waveguides is designed and demonstrated. The transfer function of the device shows a pi phase shift subject to an external field of 0.5 V/micro-meter

Orthogonal frequency-division multiplexing (OFDM) is a promising modulation technique well known in wireless and wired communication. Conventional OFDM implementation utilizes Fourier transform in order to generate orthogonal subcarriers. We proposed the novel hierarchal architecture for 1Tbps transmission of the optical signal based on dual polarization transmission based on the Discrete Wavelet Packet Transform (DWPT) and Inverse Discrete Wavelet Packet Transform (IDWPT). The novel system of Wavelet Packet Transform (WPT) OFDM permits to avoid CP, to increase significantly the transmission distance and to improve the system spectral efficiency (SE) as compared to the conventional coherent optical OFDM (CO-OFDM).

Silicon photonic devices are tuned by selective photo removal of upper chalcogenide glass layers. Phase delays in cascaded interferometer filters and couplers of ring resonators are arbitrarily adjusted. Responses remain stable following trimming.