Due to improvement in technology of laser diodes, now-a-days these have become an integral part of most of the physics and engineering undergraduate courses. Laser diodes, which generally have low coherence, are extensively used in various educational experiments due to their compactness, easy-to-operate and easy-to-handle as well as cost-effectiveness. Thus, knowledge about coherence length of beams from these laser diodes becomes important while designing experiments using these as light sources. Generally, students find it difficult to measure coherence length with most of the existing techniques. In present work an experimental arrangement using holographic optics is designed and demonstrated to measure ...

A high-speed, depth optical scanner with a longitudinal scan speed of up to and repetition rate of 28.5 kHz was designed. Optical low-coherence reflectometry is used in this non-contacting depth scanning method. A Michelson interferometer uses a glass cube which rotates at a speed of 427 000 rpm as an optical path length variation. Details of the adopted design, the precision glass cube positioning system (tripod), the experimental set-up, and some experimental results are discussed. This technique is especially well suited for biomedical applications in the field of optical tomography of tissues, e.g. skin, retina, etc where motion ...

Objective: Peripheral nerves serve as a link between the central nervous system and its targets. Altering peripheral nerve activity through targeted electrical stimulation is being investigated as a therapy for modulating end organ function. To support rapid advancement in the field, novel approaches to predict and prevent nerve injury resulting from the electrical stimulation must be developed to overcome the limitations of traditional histological methods. The present study aims to develop an optical imaging-based approach for real-time assessment of peripheral nerve injury associated with electrical stimulation.
 
 Approach: We developed an optical coherence tomography angiography system and a 3-D ...

We developed a near-infrared (NIR) superluminescent diode (SLD) based on self-assembled InAs quantum dots (QDs) and demonstrated high-axial-resolution optical coherence tomography (OCT) imaging using this QD-based SLD (QD-SLD). The QD-SLD utilized InAs QDs with controlled emission wavelengths as a NIR broadband light emitter, and a tilted waveguide with segmented electrodes was prepared for edge-emitting broadband electroluminescence (EL) spanning approximately 1–1.3 μm. The bandwidth of the EL spectrum was increased up to 144 nm at a temperature of 25 °C controlled using a thermoelectric cooler. The inverse Fourier transform of the EL spectrum predicted a minimum resolution of 3 ...

The aim of the study was to observe time-related changes in the optical properties of normal brain tissues as measured using cross-polarization optical coherence tomography (CP OCT). 32 ex vivo tissue samples from 16 animals (rats) were monitored under different external conditions, over a period of 1 hour after excision, to measure time-related optical changes. It was found that the optical properties of white matter were quite stable over the time scales of the experiments, while the optical properties of the gray matter could change significantly. However, these changes could be minimized by using fresh sections from samples that had ...

This paper reports on the characterization of a novel multi-channel Optical Coherence Tomography (MC-OCT) method capable of concurrent scanning at multiple sites along the sample arm length of a low coherence interferometer. For this study, a cascade of two wavelength-based beam splitters is used to split the sample arm beam into three channels, forming three imaging (sensing) units. Channel-specific free-space beam paths are introduced in the sample arm to ensure equal optical path lengths amongst the different sensing beams and hence, a single reference reflector is employed for simultaneous interrogation of signals reflected from samples (or from different spots of ...

Radiation-associated toxicities due to sophisticated ocular anatomy and shape variability of organs at risk (OARs) are major concerns during external beam radiation therapy (EBRT) of patients with intraocular cancer. A novel two-step image registration strategy between optical coherence tomography (OCT) and computed tomography (CT) images was proposed and validated to precisely localize the target in the EBRT of patients with intraocular cancer. Specifically, multiple features from OCT and CT images were extracted automatically, then spatial transformation based on thin-plate spline function was performed iteratively to achieve feature alignment between the CT and OCT images. Finally, an exclusive OR (XOR) algorithm ...

The method for vessel visualization from optical coherence tomography (OCT) data is presented. The method is based on high-frequency filtration of the normalized absolute values of the scattered field measured with OCT. It is shown that in contrast with optical coherence angiography based on the processing of complex values of a scattered field, the proposed processing does not require motion correction preprocessing while providing resulting angiographic images of comparable quality.

Despite our understanding that the microvasculature plays a multifaceted role in the development and progression of various conditions, we know little about the extent of this involvement. A need exists for non-invasive, clinically meaningful imaging modalities capable of elucidating microvascular information to aid in our understanding of disease, and to aid in the diagnosis/monitoring of disease for more patient-specific care. In this review article, a number of imaging techniques are summarized that have been utilized to investigate the microvasculature of skin, along with their advantages, disadvantages and future perspectives in preclinical and clinical settings. These techniques include dermoscopy, capillaroscopy ...

We reported an all single-mode fiber (SMF)-based polarization sensitive spectral domain optical coherence tomography (PSSDOCT) system with single input polarization state (IPS). In our design, polarization state was modulated only by four polarization controllers (PC) and a polarization beam splitter. To extract the phase retardance and optical axis orientation of sample, the Mueller matrix of the fiber system and sample is transferred to a new retardar by employing PCs with the advantage that the effects of fiber birefringence of SMFs and SMF components are corrected. The contribution of the multibackscattering in tissues to the orthogonal polarization interference signals is ...

The second most leading cause of death in women is breast cancer even after surgery 20%–30% patients require re-surgery for the removal of the incomplete malignant tissue. To reduce the risk of recurrence exact navigation during surgery is essential. In this paper, a multi-level ensemble model is developed to classify the normal and cancerous breast tissue using features extracted from optical coherence tomography images. Both A-line and B-scan features were extracted and the training data feature space was best-first search to select the best feature subset for each base classifier. To improve the performance of the model reverse active ...

Ovarian cancer has the lowest survival rate among all gynecologic cancers due to predominantly late diagnosis. Optical Coherence Tomography (OCT) has been applied successfully to experimentally image the ovaries in vivo; however, a robust method for analysis is still required to provide quantitative diagnostic information. Recently, texture analysis has proved to be a useful tool for tissue characterization; unfortunately, existing work in the scope of OCT ovarian imaging is limited to only analyzing 2D sub-regions of the image data, discarding information encoded in the full image area, as well as in the depth dimension. Here we address these challenges by ...

We demonstrate a new scheme for infrared spectroscopy with visible light sources and detectors. The technique relies on the nonlinear interference of correlated photons, produced via spontaneous parametric down conversion in a nonlinear crystal. Visible and infrared photons are split into two paths and the infrared photons interact with the sample under study. The photons are reflected back to the crystal, resembling a conventional Michelson interferometer. Interference of the visible photons is observed and it is dependent on the phases of all three interacting photons: pump, visible and infrared. The transmission coefficient and the refractive index of the sample in ...

Spectrally tunable illumination is widely used for spectral imaging, spectroscopy, spectral-domain optical coherence tomography and other applications. Most of swept-wavelength light sources are based on mechanical change of narrow-band filters or on a supercontinuum laser coupled with a tunable filter. Such commercially available sources suffer either from a limited number of spectral channels or from a spatial noise caused by parasitic interferences. Here, we describe an alternative solution, which is free from the mentioned disadvantages and provides speckle-free uniform illumination. It is based on acousto-optic (AO) diffraction of a wide-band light. AO tunable filters (AOTFs) are fully software-controlled solid-state devices ...

A finite impulse response filter, which shifts the focal plane in optical coherence tomography (OCT) images, is proposed. Since several OCT images with the focal plane in various positions can be fused into one image with increased lateral resolution, such a filter facilitates the creation of an OCT system with numerically increased lateral resolution, operating in real-time, i.e. showing one OCT B-scan with increased lateral resolution while collecting data for the next B-scan. Since the proposed real-time resolution enhancement method is phase-sensitive, the method for estimating and compensating phase shifts between consecutive B-scans during data acquisition is also discussed.

Optical Coherence Tomography (OCT) systems have huge potential for application beyond the traditional ophthalmology as general-purpose medical instrument for optical biopsy. The widening of the range of applications is expected to significantly increase production volume and, consequently, puts pressure on unit cost. This trend calls for a flexible and miniaturized system fabricated in a batch process. In this paper the different OCT configurations are compared for suitability in such an implementation. The required flexibility favors operation in the spectral domain, using a broadband light source in combination with a spectrometer, while the miniaturization and low unit-cost in batch fabrication can ...

We demonstrated non-destructive and non-contact measurement of semiconductor optical waveguide using optical coherence tomography with a visible broadband light source (vis-OCT). Vis-OCT can provide high axial and lateral resolutions of less than 1 µm, which were effective for measurement of optical waveguides with several-micrometer structure. We obtained cross-sectional images of ridge-type optical waveguides (RWGs) fabricated as test samples and measured the height and width of the RWGs. The height and width measured by vis-OCT were similar to these values measured by scanning electron microscopy. These results indicated that vis-OCT enables measurement of the height and width of optical waveguides without ...

The usability of time-domain optical coherence tomography equipped with a flexible endoscopic probe for detecting effusion in the tympanic cavity is shown in the clinical environment. The possibility of assessing the dynamic properties of effusion, particularly its contained scatterers' mobility, is shown in real clinical cases. A method of comparative assessment of scatterers' mobility is proposed.

Objective . Microgap formation between polymer-based resin system and teeth surfaces is undetectable by conventional x-rays. Therefore, this in vitro study was designed to assess the adaptation of polymeric dental fillings and microgap formation at the tooth floor using cross-polymerization optical coherence tomography (CP-OCT). Materials and Methods . Class-I cavities (4 mm diameter × 1.5 mm depth) were prepared in twenty extracted molar teeth and divided into two groups: ESQ and DI (n = 10). All groups were bonded with Tetric-N Bond universal (Ivoclar/Vivadent) in selective etching mode. Then, each group was restored with either Estelite ∑ Quick dental composite (ESQ; Tokuyama Dental ...

Optical coherence tomography (OCT) relies on ballistic back scattered photons to construct depth resolved optical slices of a specimen. However, the theory of OCT is generally math heavy and unintuitive. In this paper, we propose an approach, and show as many aspects of the OCT signal formation that can be described by using simple math and intuitive physics. The model allowing for simulating a semi-ideal OCT signal from an object with an arbitrary structure is presented.

Optical coherence tomography (OCT) is a noninvasive high-resolution diagnostic imaging modality that plays an increasingly important role in dermatology. Diagnosis of skin diseases using OCT requires both cellular-level high resolution and large area skin coverage. In practice, however, there exists a trade-off between the achievable spatial resolutions and the transverse scanning range. In this study, we report a Micro-OCT ( μ OCT) system that is capable of providing three-dimensional images of the skin at multiple spatial scales with both cellular-level resolution (1–2 μ m) mode and large area (~ mm 2 ) scanning mode. Specifically, in the cellular-level scanning mode, we achieve a transverse ...

We present a non-invasive three-dimensional depth-resolved micro-structure and micro-vasculature imaging of a human fingernail-fold with a swept-source optical coherence tomography (ssOCT) system at a 1064 nm center wavelength. A phase variance OCT angiography (OCTA) method was implemented for motion contrast OCT imaging. A Fourier-domain mode-locked light source with an A-scan rate of 1.7 MHz (1 700 000 A-scans s −1 ) was utilized for imaging. The experimental setup demonstrates OCT and OCTA imaging with an area of ~5 mm   ×   5 mm (within the Nyquist limit). Details of the ssOCTA system such as system parameters, scanning protocols, acquisition time, challenges, and ...

Moisture content is an important feature of fruits and vegetables. As 80% of apple content is water, so decreasing the moisture content will degrade the quality of apples (Golden Delicious). The computational and texture features of the apples were extracted from optical coherence tomography (OCT) images. A support vector machine with a Gaussian kernel model was used to perform automated classification. To evaluate the quality of wax coated apples during storage in vivo , our proposed method opens up the possibility of fully automated quantitative analysis based on the morphological features of apples. Our results demonstrate that the analysis of the ...