Showing papers on "Optical tomography published in 2014"
TL;DR: The different instrumentation, methodological approaches and schema for inverse image reconstructions for optical tomography, including luminescence and fluorescence modalities, are summarized, and limitations and key technological advances needed for further discovery research and translation are commented on.
Abstract: Emerging fluorescence and bioluminescence tomography approaches have several common, yet several distinct features from established emission tomographies of PET and SPECT. Although both nuclear and optical imaging modalities involve counting of photons, nuclear imaging techniques collect the emitted high energy (100–511 keV) photons after radioactive decay of radionuclides while optical techniques count low-energy (1.5–4.1 eV) photons that are scattered and absorbed by tissues requiring models of light transport for quantitative image reconstruction. Fluorescence imaging has been recently translated into clinic demonstrating high sensitivity, modest tissue penetration depth, and fast, millisecond image acquisition times. As a consequence, the promise of quantitative optical tomography as a complement of small animal PET and SPECT remains high. In this review, we summarize the different instrumentation, methodological approaches and schema for inverse image reconstructions for optical tomography, including luminescence and fluorescence modalities, and comment on limitations and key technological advances needed for further discovery research and translation.
170 citations
TL;DR: It is found that statistical sub-pixel detection methods can demonstrate a unique detection performance with up to five times enhanced sensitivity as compared to linear unmixing approximations, under the condition that the optical agent of interest is sparsely present within the tissue volume, as common when using targeted agents and reporter genes.
Abstract: Detection of intrinsic or extrinsically administered chromophores and photo-absorbing nanoparticles has been achieved by multi-spectral optoacoustic tomography (MSOT). The detection sensitivity of MSOT depends not only on the signal to noise ratio considerations, as in conventional optoacoustic (photoacoustic) tomography implementations, but also on the ability to resolve the molecular targets of interest from the absorbing tissue background by means of spectral unmixing or sub-pixel detection methods. However, it is not known which unmixing methods are optimally suited for the characteristics of multispectral optoacoustic images. In this work we investigated the performance of different sub-pixel detection methods, typically used in remote sensing hyperspectral imaging, within the context of MSOT. A quantitative comparison of the different algorithmic approaches was carried out in an effort to identify methods that operate optimally under the particulars of molecular imaging applications. We find that statistical sub-pixel detection methods can demonstrate a unique detection performance with up to five times enhanced sensitivity as compared to linear unmixing approximations, under the condition that the optical agent of interest is sparsely present within the tissue volume, as common when using targeted agents and reporter genes.
136 citations
TL;DR: An optical holographic micro-tomographic technique for imaging both the three-dimensional structures and dynamics of biological cells and measurements of morphological, chemical, and mechanical parameters at the individual cell level is presented.
Abstract: We present an optical holographic micro-tomographic technique for imaging both the three-dimensional structures and dynamics of biological cells. Optical light field images of a sample, illuminated by a plane wave with various illumination angles, are measured in a common-path interferometry, and thus both the three-dimensional refractive index tomogram and two-dimensional dynamics of live biological cells are measured with extremely high sensitivity. The applicability of the technique is demonstrated through quantitative and measurements of morphological, chemical, and mechanical parameters at the individual cell level.
119 citations
TL;DR: A reconstruction algorithm based on first Born approximation to generate three dimensional distribution of flow using the experimental data obtained from tissue simulating phantoms is developed.
Abstract: A novel tomographic method based on the laser speckle contrast, speckle contrast optical tomography (SCOT) is introduced that allows us to reconstruct three dimensional distribution of blood flow in deep tissues. This method is analogous to the diffuse optical tomography (DOT) but for deep tissue blood flow. We develop a reconstruction algorithm based on first Born approximation to generate three dimensional distribution of flow using the experimental data obtained from tissue simulating phantoms.
77 citations
TL;DR: 3-D RI tomograms of nonbiological samples such as polystyrene microspheres, as well as biological samples including human red blood cells and breast cancer cells, are presented.
Abstract: A simple and practical method to measure three-dimensional (3-D) refractive index (RI) distributions of biological cells is presented. A common-path self-reference interferometry consisting of a compact set of polarizers is attached to a conventional inverted microscope equipped with a beam scanning unit, which can precisely measure multiple 2-D holograms of a sample with high phase stability for various illumination angles, from which accurate 3-D optical diffraction tomograms of the sample can be reconstructed. 3-D RI tomograms of nonbiological samples such as polystyrene microspheres, as well as biological samples including human red blood cells and breast cancer cells, are presented.
77 citations
TL;DR: Accurate analysis of effects of small speed of sound variations demonstrates that accounting for differences in the speed ofsound allows improving optoacoustic reconstruction results in realistic imaging scenarios involving acoustic heterogeneities in tissues and surrounding media.
Abstract: Speed of sound difference in the imaged object and surrounding coupling medium may reduce the resolution and overall quality of optoacoustic tomographic reconstructions obtained by assuming a uniform acoustic medium. In this work, the authors investigate the effects of acoustic heterogeneities and discuss potential benefits of accounting for those during the reconstruction procedure.The time shift of optoacoustic signals in an acoustically heterogeneous medium is studied theoretically by comparing different continuous and discrete wave propagation models. A modification of filtered back-projection reconstruction is subsequently implemented by considering a straight acoustic rays model for ultrasound propagation. The results obtained with this reconstruction procedure are compared numerically and experimentally to those obtained assuming a heuristically fitted uniform speed of sound in both full-view and limited-view optoacoustic tomography scenarios.The theoretical analysis showcases that the errors in the time-of-flight of the signals predicted by considering the straight acoustic rays model tend to be generally small. When using this model for reconstructing simulated data, the resulting images accurately represent the theoretical ones. On the other hand, significant deviations in the location of the absorbing structures are found when using a uniform speed of sound assumption. The experimental results obtained with tissue-mimicking phantoms and a mouse postmortem are found to be consistent with the numerical simulations.Accurate analysis of effects of small speed of sound variations demonstrates that accounting for differences in the speed of sound allows improving optoacoustic reconstruction results in realistic imaging scenarios involving acoustic heterogeneities in tissues and surrounding media.
59 citations
TL;DR: The design, construction and performance of the second generation UCL time-resolved optical tomography system, known as MONSTIR II, are detailed and the efficacy of the system is demonstrated by performing multi-spectral imaging of a simple phantom.
Abstract: We detail the design, construction and performance of the second generation UCL time-resolved optical tomography system, known as MONSTIR II. Intended primarily for the study of the newborn brain, the system employs 32 source fibres that sequentially transmit picosecond pulses of light at any four wavelengths between 650 and 900 nm. The 32 detector channels each contain an independent photo-multiplier tube and temporally correlated photon-counting electronics that allow the photon transit time between each source and each detector position to be measured with high temporal resolution. The system's response time, temporal stability, cross-talk, and spectral characteristics are reported. The efficacy of MONSTIR II is demonstrated by performing multi-spectral imaging of a simple phantom.
44 citations
TL;DR: The cylindrical tube-shaped anomaly was clearly reconstructed in both simulation and phantom and recovered and assigned flow contrast changes in anomaly were found to be highly correlated, exhibiting promise of the ncDCT technique for 3-D imaging of deep tissue blood flow heterogeneities.
Abstract: This study extended our recently developed noncontact diffuse correlation spectroscopy flowmetry system into noncontact diffuse correlation tomography (ncDCT) for three-dimensional (3-D) flow imaging of deep tissue. A linear array of 15 photodetectors and two laser sources connected to a mobile lens-focusing system enabled automatic and noncontact scanning of flow in a region of interest. These boundary measurements were combined with a finite element framework for DCT image reconstruction implemented into an existing software package. This technique was tested in computer simulations and using a tissue-like phantom with anomaly flow contrast design. The cylindrical tube-shaped anomaly was clearly reconstructed in both simulation and phantom. Recovered and assigned flow contrast changes in anomaly were found to be highly correlated: regression slope = 1.00, R2 = 1.00, and p < 10−5 in simulation and regression slope ≥ 0.97, R2 ≥ 0.96, and p < 10−3 in phantom. These results exhibit promise of our ncDCT technique for 3-D imaging of deep tissue blood flow heterogeneities.
44 citations
TL;DR: This work investigates the use of discrete imaging models based on Kaiser-Bessel window functions for iterative image reconstruction in OAT, and calculates a closed-form expression for the pressure produced by a Kaiser- Bessel function to facilitate accurate computation of the system matrix.
Abstract: Optoacoustic tomography (OAT), also known as photoacoustic tomography, is an emerging computed biomedical imaging modality that exploits optical contrast and ultrasonic detection principles. Iterative image reconstruction algorithms that are based on discrete imaging models are actively being developed for OAT due to their ability to improve image quality by incorporating accurate models of the imaging physics, instrument response, and measurement noise. In this work, we investigate the use of discrete imaging models based on Kaiser-Bessel window functions for iterative image reconstruction in OAT. A closed-form expression for the pressure produced by a Kaiser-Bessel function is calculated, which facilitates accurate computation of the system matrix. Computer-simulation and experimental studies are employed to demonstrate the potential advantages of Kaiser-Bessel function-based iterative image reconstruction in OAT.
43 citations
TL;DR: Simulated analyses are reported for different geometrical and temporal parameters, showing that the new concept of restoring tomographic performance in temporal decorrelating forest scenarios through differential tomography is promising.
Abstract: Much interest is continuing to grow in advanced interferometric synthetic aperture radar (SAR) methods for full 3-D imaging, particularly of volumetric forest scatterers. Multibaseline (MB) SAR tomographic elevation beam forming, i.e., spatial spectral estimation, is a promising technique in this framework. In this paper, the important effect of temporal decorrelation during the repeat-pass MB acquisition is tackled, analyzing the impact on superresolution (MUSIC) tomography with limited sparse data. Moreover, new tomographic methods robust to temporal decorrelation phenomena are proposed, exploiting the advanced differential tomography concept that produces “space-time” signatures of scattering dynamics in the SAR cell. To this aim, a 2-D version of MUSIC and a generalized MUSIC method matched to nonline spectra are applied to decouple the nuisance temporal signal components in the spatial spectral estimation. Simulated analyses are reported for different geometrical and temporal parameters, showing that the new concept of restoring tomographic performance in temporal decorrelating forest scenarios through differential tomography is promising.
43 citations
TL;DR: The heterogeneity of x-rays energy deposition is included in the XLOT-EP reconstruction and improves the reconstruction accuracy, suggesting that there is a need to calculate the x-ray energy distribution for experimental XLOT imaging.
Abstract: X-ray luminescence optical tomography (XLOT) is an emerging hybrid imaging modality in which x-ray excitable particles (phosphor particles) emit optical photons when stimulated with a collimated x-ray beam. XLOT can potentially combine the high sensitivity of optical imaging with the high spatial resolution of x-ray imaging. For reconstruction of XLOT data, we compared two reconstruction algorithms, conventional filtered backprojection (FBP) and a new algorithm, x-ray luminescence optical tomography with excitation priors (XLOT-EP), in which photon propagation is modeled with the diffusion equation and the x-ray beam positions are used as reconstruction priors. Numerical simulations based on dose calculations were used to validate the proposed XLOT imaging system and the reconstruction algorithms. Simulation results showed nanoparticle concentrations reconstructed with XLOT-EP are much less dependent on scan depth than those obtained with FBP. Measurements at just two orthogonal projections are sufficient for XLOT-EP to reconstruct an XLOT image for simple source distributions. The heterogeneity of x-ray energy deposition is included in the XLOT-EP reconstruction and improves the reconstruction accuracy, suggesting that there is a need to calculate the x-ray energy distribution for experimental XLOT imaging.
TL;DR: Both phantom and human tissue tests indicate that this confocal acoustic radiation force optical coherence elastography system is able to sense the stiffness difference of samples and quantitatively map the elastic property of materials.
Abstract: We designed and developed a confocal acoustic radiation force optical coherence elastography system. A ring ultrasound transducer was used to achieve reflection mode excitation and generate an oscillating acoustic radiation force in order to generate displacements within the tissue, which were detected using the phase-resolved optical coherence elastography method. Both phantom and human tissue tests indicate that this system is able to sense the stiffness difference of samples and quantitatively map the elastic property of materials. Our confocal setup promises a great potential for point by point elastic imaging in vivo and differentiation of diseased tissues from normal tissue.
TL;DR: A reconstruction procedure based on the inversion of a time-domain forward model incorporating the spatial impulse response due to the shape of the transducer is presented, which is subsequently applied in a tomographic system based on a translation-rotation scan of a linear detector array.
Abstract: Image quality in 3-D optoacoustic (photoacoustic) tomography is greatly influenced by both the measurement system, in particular the number and spatial arrangement of ultrasound sensors, and the ability to account for the spatio-temporal response of the sensor element(s) in the reconstruction algorithm. Herein we present a reconstruction procedure based on the inversion of a time-domain forward model incorporating the spatial impulse response due to the shape of the transducer, which is subsequently applied in a tomographic system based on a translation-rotation scan of a linear detector array. The proposed method was also adapted to cope with the data-intensive requirements of high-resolution volumetric optoacoustic imaging. The processing of 2 · 10 4 individual signals resulted in well-resolved images of both ~ 200 μm absorbers in phantoms and complex vascular structures in biological tissue. The results reported herein demonstrate that the introduced model-based methodology exhibits a better contrast and resolution than standard back-projection and model-based algorithms that assume point detectors. Moreover, the capability of handling large datasets anticipates that model-based methods incorporating the sensor properties can become standard practice in volumetric opto acoustic image formation.
TL;DR: A direct method with structural priors for imaging pharmacokinetic parameters is presented, which uses a nonlinear objective function to efficiently model the measurement noise and utilizes theStructural priors to mitigate the ill-posedness of FMT.
Abstract: Images of pharmacokinetic parameters in dynamic fluorescence molecular tomography (FMT) have the potential to provide quantitative physiological information for biological studies and drug development. However, images obtained with conventional indirect methods suffer from low signal-to-noise ratio because of failure in efficiently modeling the measurement noise. Besides, FMT suffers from low spatial resolution due to its ill-posed nature, which further reduces the image quality. In this letter, we present a direct method with structural priors for imaging pharmacokinetic parameters, which uses a nonlinear objective function to efficiently model the measurement noise and utilizes the structural priors to mitigate the ill-posedness of FMT. The results of numerical simulations and in vivo mouse experiments demonstrate that the proposed method leads to significant improvements in the image quality.
TL;DR: A method for correcting motion artifacts in AO-OCT volume data after acquisition using simultaneously captured adaptive optics-scanning laser ophthalmoscope (AO-SLO) images to improve the accuracy of quantitative analyses of microscopic structures.
Abstract: Recent progress in retinal image acquisition techniques, including optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO), combined with improved performance of adaptive optics (AO) instrumentation, has resulted in improvement in the quality of in vivo images of cellular structures in the human retina. Here, we present a short review of progress on developing AO-OCT instruments. Despite significant progress in imaging speed and resolution, eye movements present during acquisition of a retinal image with OCT introduce motion artifacts into the image, complicating analysis and registration. This effect is especially pronounced in high-resolution datasets acquired with AO-OCT instruments. Several retinal tracking systems have been introduced to correct retinal motion during data acquisition. We present a method for correcting motion artifacts in AO-OCT volume data after acquisition using simultaneously captured adaptive optics-scanning laser ophthalmoscope (AO-SLO) images. We extract transverse eye motion data from the AO-SLO images, assign a motion adjustment vector to each AO-OCT A-scan, and re-sample from the scattered data back onto a regular grid. The corrected volume data improve the accuracy of quantitative analyses of microscopic structures.
TL;DR: It is shown, both in numerical and experimental gelatin phantom cases, that the proposed frame work to improve the reconstructed image characteristics using the basis pursuit deconvolution method yields better recovery of the target shapes compared to traditional method, without the loss of quantitativeness of the results.
Abstract: The image reconstruction problem encountered in diffuse optical tomographic imaging is ill-posed in nature, necessitating the usage of regularization to result in stable solutions. This regularization also results in loss of resolution in the reconstructed images. A frame work, that is attributed by model-resolution, to improve the reconstructed image characteristics using the basis pursuit deconvolution method is proposed here. The proposed method performs this deconvolution as an additional step in the image reconstruction scheme. It is shown, both in numerical and experimental gelatin phantom cases, that the proposed method yields better recovery of the target shapes compared to traditional method, without the loss of quantitativeness of the results.
TL;DR: In this article, a multi-wavelength luminescence cone beam XLT method with the structural a priori information is presented to relieve the severe ill-posedness problem in the cone beam X-ray computed tomography (XCT) system.
Abstract: X-ray luminescence tomography (XLT) is an imaging technology based on X-ray-excitable materials. The main purpose of this paper is to obtain quantitative luminescence concentration using the structural information of the X-ray computed tomography (XCT) in the hybrid cone beam XLT/XCT system. A multi-wavelength luminescence cone beam XLT method with the structural a priori information is presented to relieve the severe ill-posedness problem in the cone beam XLT. The nanophosphors and phantom experiments were undertaken to access the linear relationship of the system response. Then, an in vivo mouse experiment was conducted. The in vivo experimental results show that the recovered concentration error as low as 6.67% with the location error of 0.85 mm can be achieved. The results demonstrate that the proposed method can accurately recover the nanophosphor inclusion and realize the quantitative imaging.
TL;DR: A 3D tomography technique for in vivo observation of microscopic samples that combines flow in a microfluidic channel, illumination through a slit aperture, and a Fourier lens for simultaneous acquisition of multiple perspective angles in the phase-space domain is presented.
Abstract: We present a 3D tomography technique for in vivo observation of microscopic samples. The method combines flow in a microfluidic channel, illumination through a slit aperture, and a Fourier lens for simultaneous acquisition of multiple perspective angles in the phase-space domain. The technique is non-invasive and naturally robust to parasitic sample motion. 3D absorption is retrieved using standard back-projection algorithms, here a limited-domain inverse radon transform. Simultaneously, 3D differential phase contrast images are obtained by computational refocusing and comparison of complementary illumination angles. We implement the technique on a modified glass slide which can be mounted directly on existing optical microscopes. We demonstrate both amplitude and phase tomography on live, freely swimming C. elegans nematodes.
TL;DR: In this paper, the authors measured the attenuation of slow light modes in slotted photonic crystal waveguides and found that when the group index is close to 20, attenuation is below 300 dB cm−1.
Abstract: Using Optical Coherence Tomography, we measure the attenuation of slow light modes in slotted photonic crystal waveguides. When the group index is close to 20, the attenuation is below 300 dB cm−1. Here, the optical confinement in the empty slot is very strong, corresponding to an ultra-small effective cross section of 0.02 μm2. This is nearly 10 times below the diffraction limit at λ = 1.5 μm, and it enables an effective interaction with a very small volume of functionalized matter.
TL;DR: A powerful, accurate segmentation method with high stability and sensitivity, using an intelligent tracking kernel and a clustering mask based on the Gaussian mixture model (GMM), that yields robust, degradation-free tracking with highly sensitive pixel classification.
Abstract: Ophthalmology requires automated segmentation of retinal layers in optical coherence tomography images to provide valuable disease information. Sensitive extraction of accurate layer boundaries stable against local image quality degradation is necessary. We propose and demonstrate a powerful, accurate segmentation method with high stability and sensitivity. The method uses an intelligent tracking kernel and a clustering mask based on the Gaussian mixture model (GMM). Combining these concepts yields robust, degradation-free tracking with highly sensitive pixel classification. The kernel extracts boundaries by moving and matching its double faces with locally clustered images generated by GMM clustering. The cluster-guided motion of the kernel enables sensitive classification of structures on a single-pixel scale. This system targets seven major retinal boundaries. Then, using peak detection, additional two simple boundaries are easily grabbed in regions where their distinct features emerge sufficiently in the limited space remaining after the previous segmentation. Using these hybrid modes, successful segmentation of nine boundaries of eight retinal layers in foveal areas is demonstrated. A 0.909 fraction of a pixel difference appears between boundaries segmented manually and using our algorithm. Our method was developed for use with low-quality data, allowing its application in various morphological segmentation technologies.
TL;DR: A dual-mode tomography system based on capacitance sensor and gamma sensor was developed to capture oil–gas two-phase flow and two fusion methods, namely image fusion method and data fusion method, are proposed.
TL;DR: This paper presents an iterative reweighted l2-norm optimization incorporating anatomical structures in order to enhance the performance of bioluminescence tomography and evaluates the accuracy, robustness, and efficiency of the proposed method.
Abstract: Bioluminescence tomography is a promising tool in preclinical research, enabling noninvasive real-time in vivo imaging as well as quantitative analysis in small animal studies. Due to the difficulty of reconstruction, continuous efforts are still made to find more practical and efficient approaches. In this paper, we present an iterative reweighted l2-norm optimization incorporating anatomical structures in order to enhance the performance of bioluminescence tomography. The structure priors have been utilized to generate a heterogeneous mouse model by extracting the internal organs and tissues, which can assist in establishing a more precise photon diffusion model, as well as reflecting a more specific position of the reconstruction results inside the mouse. To evaluate the performance of the iterative reweighted approach, several numerical simulation studies including comparative analyses and multisource cases have been conducted to reconstruct the same datasets. The results suggest that the proposed method is able to ensure the accuracy, robustness, and efficiency of bioluminescence tomography. Finally, an in vivo experiment was performed to further validate its feasibility in a practical application.
Patent•
12 Mar 2014
TL;DR: Optical sensors, systems, and methods are described in this paper, which may be used to provide or analyze information about a subject, where the optical sensor may be placed in proximity to the subject and may include optical sources and optical detectors.
Abstract: Optical sensors, systems, and methods are described, which may be used to provide or analyze information about a subject. The optical sensor may be placed in proximity to the subject and may include optical sources and optical detectors. The optical sources may irradiate the subject with optical signals and the optical detectors can detect signals from the subject. Analysis of the detected signals can yield information about the subject.
TL;DR: It is shown that ultrasound frequency-dependent artifacts suppress multispectral features and complicate spectral analysis, and a wavelet decomposition is employed to perform spectral unmixing on a per-scale basis and showcase imaging of fine-scale features otherwise hidden by low frequency components.
Abstract: Multispectral optoacoustic tomography (MSOT) utilizes broadband ultrasound detection for imaging biologically-relevant optical absorption features at a range of scales. Due to the multiscale and multispectral features of the technology, MSOT comes with distinct requirements in implementation and data analysis. In this work, we investigate the interplay between scale, which depends on ultrasonic detection frequency, and optical multispectral spectral analysis, two dimensions that are unique to MSOT and represent a previously unexplored challenge. We show that ultrasound frequency-dependent artifacts suppress multispectral features and complicate spectral analysis. In response, we employ a wavelet decomposition to perform spectral unmixing on a per-scale basis (or per ultrasound frequency band) and showcase imaging of fine-scale features otherwise hidden by low frequency components. We explain the proposed algorithm by means of simple simulations and demonstrate improved performance in imaging data of blood vessels in human subjects.
TL;DR: In this article, the authors present sufficient conditions ensuring that the absorption and diffusion coefficients modeling light propagation can be uniquely and stably reconstructed from the corresponding available information, based on the analysis of linear elliptic systems of redundant partial differential equations.
Abstract: Ultrasound-modulated optical tomography is a hybrid imaging modality that aims to combine the high contrast of optical waves with the high resolution of ultrasound. We follow the model of the influence of ultrasound modulation on the light intensity measurements developed in Bal and Schotland (2010 Phys. Rev. Lett. 104 043902). We present sufficient conditions ensuring that the absorption and diffusion coefficients modeling light propagation can locally be uniquely and stably reconstructed from the corresponding available information. We present an iterative procedure to solve such a problem based on the analysis of linear elliptic systems of redundant partial differential equations.
TL;DR: The high spatial resolution, fast reconstruction speed, noise tolerance, and ability to detect small targets are indicative of the potential of the approach for detecting and locating fluorescence contrast-enhanced breast tumors in early growth stages, when they are more amenable to treatment.
Abstract: A near-infrared optical tomography approach for detection, three-dimensional localization, and cross-section imaging of fluorescent targets in a turbid medium is introduced. The approach uses multisource probing of targets, multidetector acquisition of diffusely transmitted fluorescence signal, and a non-negative matrix factorization based blind source separation scheme to obtain three-dimensional location of the targets. A Fourier transform back-projection algorithm provides an estimate of target cross section. The efficacy of the approach is demonstrated in an experiment involving two laterally separated small fluorescent targets embedded in a human breast tissue-simulating sample of thickness 60 times the transport mean free path. The approach could locate the targets within ∼1 mm of their known positions, and provide estimates of their cross sections. The high spatial resolution, fast reconstruction speed, noise tolerance, and ability to detect small targets are indicative of the potential of the approach for detecting and locating fluorescence contrast-enhanced breast tumors in early growth stages, when they are more amenable to treatment.
TL;DR: This work reports on the development of a highly sensitive optical receiver for heterodyne IR spectroscopy at the communication wavelength of 1.5 μm (200 THz) by use of a superconducting hot-electron bolometer, which is important for the resolution of narrow spectral molecular lines in the near-IR range for the study of astronomical objects.
Abstract: We report on the development of a highly sensitive optical receiver for heterodyne IR spectroscopy at the communication wavelength of 1.5 μm (200 THz) by use of a superconducting hot-electron bolometer. The results are important for the resolution of narrow spectral molecular lines in the near-IR range for the study of astronomical objects, as well as for quantum optical tomography and fiber-optic sensing. Receiver configuration as well as fiber-to-detector light coupling designs are discussed. Light absorption of the superconducting detectors was enhanced by nano-optical antennas, which were coupled to optical fibers. An intermediate frequency (IF) bandwidth of about 3 GHz was found in agreement with measurements at 300 GHz, and a noise figure of about 25 dB was obtained that was only 10 dB above the quantum limit.
Patent•
19 Nov 2014
TL;DR: In this paper, a method for improving an optical scanning holographic tomography effect, and belongs to the field of optical tomography, is proposed. But the method is not suitable for the use of optical imaging.
Abstract: The invention discloses a method for improving an optical scanning holographic tomography effect, and belongs to the field of optical tomography. The method can solve the defect in the conventional optical scanning technology that restored section images have louder out-of-focus noise, in real time. The method comprises the following steps: utilizing a random phase in the optics encryption technique, changing a certain pupil function in a conventional optical scanning holographic system into a stochastic phase pupil function, and equaling restore of out-of-focus layer images into decryption under the condition of mistakenly decrypting a secret key, thereby enabling the out-of-focus layer images overlaid on the restored section images to be gaussian white noise with statistical independence and greatly reducing the influence of the out-of-focus noise on the focus layer images. Meanwhile the out-of-focus noise can also be filtered through design of a gaussian filter, so that the longitudinal resolution of the system can be improved; besides, through the adoption of the method, the bandwidth of the optical transfer function is wider, and the transverse resolution of the restored section images can be higher.
TL;DR: In this paper, a hybrid radiosity-SP3 equation based reconstruction algorithm for bioluminescence tomography was proposed to provide an ideal solution for a specific problem of gastric cancer detection.
Abstract: To provide an ideal solution for a specific problem of gastric cancer detection in which low-scattering regions simultaneously existed with both the non- and high-scattering regions, a novel hybrid radiosity-SP3 equation based reconstruction algorithm for bioluminescence tomography was proposed in this paper. In the algorithm, the third-order simplified spherical harmonics approximation (SP3) was combined with the radiosity equation to describe the bioluminescent light propagation in tissues, which provided acceptable accuracy for the turbid medium with both low- and non-scattering regions. The performance of the algorithm was evaluated with digital mouse based simulations and a gastric cancer-bearing mouse based in situ experiment. Primary results demonstrated the feasibility and superiority of the proposed algorithm for the turbid medium with low- and non-scattering regions.
TL;DR: In this paper, a single-photon sensitive spectrometer in the visible range is presented, which allows to perform time-resolved and multiphoton spectral correlation measurements at room temperature, using a monochromator composed of two gratings, collimation optics, and an array of single photon avalanche diodes.
Abstract: We demonstrate a single-photon sensitive spectrometer in the visible range, which allows us to perform time-resolved and multi-photon spectral correlation measurements at room temperature. It is based on a monochromator composed of two gratings, collimation optics, and an array of single photon avalanche diodes. The time resolution can reach 110 ps and the spectral resolution is 2 nm/pixel, limited by the design of the monochromator. This technique can easily be combined with commercial monochromators and can be useful for joint spectrum measurements of two photons emitted in the process of parametric down conversion, as well as time-resolved spectrum measurements in optical coherence tomography or medical physics applications.