1. Articles from aip.scitation.org

  2. 1-16 of 16
    1. Comparison of laser triangulation, phase shift triangulation and swept source optical coherence Tomography for nondestructive inspection of objects with micrometric accuracy

      Comparison of laser triangulation, phase shift triangulation and swept source optical coherence Tomography for nondestructive inspection of objects with micrometric accuracy

      We compare the performance of laser triangulation, phase shift triangulation and swept source optical coherence tomography (SSOCT) for quantitative nondestructive inspection. Measurement accuracies of these three optical 3D imaging techniques can be reduced to a few tens of micrometers or less, making it possible to locate and geometrically characterize defects at the micrometric scale. We consider surfaces with different optical properties and we discuss the ability of these techniques to reconstruct the surface profiles. For opaque surfaces, the three techniques provide very similar results. For semi-transparent and transparent surfaces, the accuracy achieved by SSOCT relies on the capability of detecting ...

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    2. Synthetic optical holography for in-depth imaging of optical vortices in speckle patterns

      Synthetic optical holography for in-depth imaging of optical vortices in speckle patterns

      In this paper, we report a novel approach based on a lensless Synthetic Optical Holography (SOH) that is aimed to recover the complex scattered field from buried surfaces at different wavelengths with sub-nanometric spectral resolution, without affecting the phase retrieval in depth. The proposed technique is applied to characterize and image the field scattered from a rough embedded surface of a microfluidic channel. The real and imaginary part of the random complex field revealed the presence of 2D optical vortices at each location in which a phase singularity is located. A statistical study of optical vortices is presented and the ...

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    3. Perspective: Current challenges and solutions of Doppler optical coherence tomography and angiography for neuroimaging

      Perspective: Current challenges and solutions of Doppler optical coherence tomography and angiography for neuroimaging

      The nervous system, based on a complex network of nerves and cells, carries messages by transmitting signals to and from different parts of the body. The supply of blood flow in the nervous system is critical to maintain physiological functions. Optical coherence tomography (OCT) has the ability to noninvasively image the microvascular networks and accurately quantify the blood flow in vivo with high spatial and temporal resolutions in three dimensions. It has been used to measure changes in blood supplies and assess physiological functions before and after occurrences of diseases, drug administration, and external stimulation in the nervous system, especially ...

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    4. Imaging and visualization of the polarization state of the probing beam in polarization-sensitive optical coherence tomography

      Imaging and visualization of the polarization state of the probing beam in polarization-sensitive optical coherence tomography

      We propose a simple and efficient method of color-encoded Stokes parameters to visualize the polarization states for polarization-sensitive optical coherence tomography (PS-OCT) of biological tissue. In this method, polarization states of the probing light are detected and described in the Stokes domain. Three primary colors of red, green, and blue are used to code Stokes parameters of Q, U, and V, respectively, which can be used to represent and visualize each unique polarization state. A strategy that uses the polarization state as the PS-OCT imaging parameter is first introduced to obtain high contrast images of the birefringent samples. Then, color-based ...

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    5. An ultraslim all-fiber microendoscope for depth-resolved imaging

      An ultraslim all-fiber microendoscope for depth-resolved imaging

      We demonstrate an ultraslim all-fiber microendoscope for depth-resolved imaging that integrates a gradient-index (GRIN) fiber and an imaging fiber bundle. The desired imaging depth is achieved through a high-precision adjustment of the length of the GRIN fiber. A fusion splicing of this fiber to an imaging fiber bundle, with provisions for a carefully tailored adiabatic conical transition region, keeps these fiber components robustly aligned, enabling a high-quality image transmission with no compromise on fiber-probe flexibility. With the maximum outer diameter of this microendoscope scalable down to ≈50  μ m, the range of envisaged applications spans from depth-resolved brain imaging, deep optical ...

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    6. Deep imaging in highly scattering media by combining reflection matrix measurement with Bessel-like beam based optical coherence tomography

      Deep imaging in highly scattering media by combining reflection matrix measurement with Bessel-like beam based optical coherence tomography

      Multiple scattering in biomedical tissue limits the imaging depth within a range of 1–2 mm for conventional optical imaging techniques. To extend the imaging depth into the scattering medium, a computational method based on the reflection matrix measurement has been developed to retrieve the singly back-scattered signal light from the dominant detrimental multiple-scattered background. After applying singular value decomposition on the measured matrix in the post-process, the target image underneath the turbid media is clearly recovered. To increase the depth of focus of the incident light by elongating the focal spot along the optical axis, a digital grating pattern ...

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    7. Adapting a commercial spectral domain optical coherence tomography system for time-locked displacement and physiological measurements

      Adapting a commercial spectral domain optical coherence tomography system for time-locked displacement and physiological measurements

      Measuring vibration within the cochlear partition is important to understand sound transduction and nonlinear amplification within the cochlea. Here we describe the customization of a commercially available Spectral Domain Optical Coherence Tomography system, the Thorlabs Telesto, for displacement measurements in the cochlea using a technique called Spectral Domain Phase Microscopy (SDPM). The paper describes the SDOCT data analysis pipeline composed of background subtraction, interpolation, and spectral shaping of the raw photodetector data, followed by the implementation of SDPM for vibration measurements. It also details the software and hardware modification necessary to couple the Telesto to a Tucker-Davis Technologies data acquisition ...

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    8. Denoising and segmentation of retinal layers in optical coherence tomography images

      Denoising and segmentation of retinal layers in optical coherence tomography images

      Optical Coherence Tomography (OCT) is an imaging technique used to localize the intra-retinal boundaries for the diagnostics of macular diseases. Due to speckle noise, low image contrast and accurate segmentation of individual retinal layers is difficult. Due to this, a method for retinal layer segmentation from OCT images is presented. This paper proposes a pre-processing filtering approach for denoising and segmentation methods for segmenting retinal layers OCT images using graph based segmentation technique. These techniques are used for segmentation of retinal layers for normal as well as patients with Diabetic Macular Edema. The algorithm based on gradient information and shortest ...

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    9. Photoacoustic signal attenuation analysis for the assessment of thin layers thickness in paintings

      Photoacoustic signal attenuation analysis for the assessment of thin layers thickness in paintings

      This study introduces a novel method for the thickness estimation of thin paint layers in works of art, based on photoacoustic signal attenuation analysis (PAcSAA). Ad hoc designed samples with acrylic paint layers (Primary Red Magenta, Cadmium Yellow, Ultramarine Blue) of various thicknesses on glass substrates were realized for the specific application. After characterization by Optical Coherence Tomography imaging, samples were irradiated at the back side using low energy nanosecond laser pulses of 532 nm wavelength. Photoacoustic waves undergo a frequency-dependent exponential attenuation through the paint layer, before being detected by a broadband ultrasonic transducer. Frequency analysis of the recorded ...

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    10. In vivo oral imaging with integrated portable photoacoustic microscopy and optical coherence tomography

      In vivo oral imaging with integrated portable photoacoustic microscopy and optical coherence tomography

      Oral diseases, especially oral cancers, are becoming serious health problems in humans. To image vasculatures and structures simultaneously in the human oral cavity which are tightly associated with various oral diseases, we develop a dual-modality portable optical resolution photoacoustic microscopy (ORPAM) and optical coherence tomography (OCT) system. This system utilizes a new rotary scanning mechanism and a compact design of the imaging head, making it portable and free of translation of the imaging interface or samples. Through the phantom experiments, both modalities yield high lateral resolutions of 8.1  μ m (ORPAM) and 8.56  μ m (OCT), respectively. The axial resolutions ...

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    11. Quantitative angle-insensitive flow measurement using relative standard deviation OCT

      Quantitative angle-insensitive flow measurement using relative standard deviation OCT

      Incorporating different data processing methods, optical coherence tomography (OCT) has the ability for high-resolution angiography and quantitative flow velocity measurements. However, OCT angiography cannot provide quantitative information of flow velocities, and the velocity measurement based on Doppler OCT requires the determination of Doppler angles, which is a challenge in a complex vascular network. In this study, we report on a relative standard deviation OCT (RSD-OCT) method which provides both vascular network mapping and quantitative information for flow velocities within a wide range of Doppler angles. The RSD values are angle-insensitive within a wide range of angles, and a nearly linear ...

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    12. Development of a combined OCT-Raman probe for the prospective in vivo clinical melanoma skin cancer screening

      Development of a combined OCT-Raman probe for the prospective in vivo clinical melanoma skin cancer screening

      A combined optical coherence tomography (OCT)-Raman probe was designed and built into a spectral domain OCT head, and its performance was evaluated and compared to the most common Raman probe setups, based on a fiber bundle and confocal free space optics. Due to the use of the full field of view of an OCT scanning lens, the combined probe has a superior performance within maximum permissible exposure limits, compared to the other two probes. Skin Raman spectra, recorded in vivo , further prove the feasibility of the OCT-Raman probe for the future in vivo clinical applications in skin cancer screening.

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    13. Longitudinal shear wave imaging for elasticity mapping using optical coherence elastography

      Longitudinal shear wave imaging for elasticity mapping using optical coherence elastography

      Shear wave measurements for the determination of tissue elastic properties have been used in clinical diagnosis and soft tissue assessment. A shear wave propagates as a transverse wave where vibration is perpendicular to the wave propagation direction. Previous transverse shear wave measurements could detect the shear modulus in the lateral region of the force; however, they could not provide the elastic information in the axial region of the force. In this study, we report the imaging and quantification of longitudinal shear wave propagation using optical coherence tomography to measure the elastic properties along the force direction. The experimental validation and ...

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    14. Dynamically focused optical coherence tomography for endoscopic applications

      Dynamically focused optical coherence tomography for endoscopic applications

      We report a demonstration of a small liquid-filled polymer lens that may be used to dynamically provide scanning depth focus for endoscopic optical coherence tomography (OCT) applications. The focal depth of the lens is controlled by changing the hydraulic pressure within the lens, enabling dynamic focal depth control without the need for articulated parts. The 1 mm diameter lens is shown to have resolving power of 5 μm, and can enable depth scans of 2.5 mm, making it suitable for use with OCT-enabled optical biopsy applications.

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    15. Geometric & radiometric vignetting associated with a 72-facet, off-axis, polygon mirror for swept source optical coherence tomography (SS-OCT)

      Geometric & radiometric vignetting associated with a 72-facet, off-axis, polygon mirror for swept source optical coherence tomography (SS-OCT)

      Optical Coherence Tomography (OCT) has a broad range of applications in 2D and volumetric imaging of micron scale structures typically used on inaccessible objects such as the retina of the eye. This report focuses on Swept Source OCT (SS-OCT), favoured for its faster scanning speeds and therefore faster data acquisition (highly favourable when imaging live patients). SS-OCT relies on the scanning of a narrow laser line at speeds typically in excess of 100 kHz. We have employed Zemax TM ray tracing software to simulate one method of splitting the spectrum of a broadband, near-infrared source, into its component wavelengths by ...

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    16. Volumetric Doppler angle correction for ultrahigh-resolution optical coherence Doppler tomography

      Volumetric Doppler angle correction for ultrahigh-resolution optical coherence Doppler tomography

      Ultrahigh-resolution optical coherence Doppler tomography (μODT) demonstrates great potential for quantitative blood flow imaging owing to its large field of view and capillary resolution. However, μODT only detects the axial flow velocity and requires Doppler angle correction to retrieve the absolute velocity. Although methods for Doppler angle tracking of single or few large vessels have been reported, a method that enables angle correction of the entire 3D microvascular networks remains a challenge. Here, we present a method based on eigenvalue analysis of 3D Hessian matrix to retrieve the orientation of each tubular vessel. As the algorithm is voxel based, it ...

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    1-16 of 16
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