Effects of compression on soft tissue optical properties

Tissue optical properties are necessary parameters for prescribing light dosimetry in photomedicine. In many diagnostic or therapeutic applications where optical fiber probes are used, pressure is often applied to the tissue to reduce index mismatch and increase light transmittance. In this paper, we have measured in vitro optical properties as a function of pressure with a visible-IR spectrophotometer. A spectral range of 400-1800 mm with a spectral resolution of 5 nm was used for all measurements. Skin specimens of a Hispanic donor and two Caucasian donors were obtained from the tissue bank. Bovine aorta and sclera, and porcine sclera came from a local slaughter house. Each specimen, sandwiched between microscope slides, was compressed by a spring-loaded apparatus. Then diffuse reflectance and transmittance of each sample were measured at no load and at approximately 0.1, 1, and 2 kgf/cm². Under compression, tissue thicknesses were reduced up to 78%. Generally speaking, the reflectance decreased while the overall transmittance increased under compression. The absorption and reduced scattering coefficients were calculated using the inverse adding doubling method. Compared with the no-load controls, there was an increase in absorption and scattering coefficients among most of the compressed specimens     

Investigation of optical clearing of gastric tissue immersed with hyperosmotic agents

In order to understand the role of water desorption and the mass transport process in the optical clearing effect on gastric tissues with the application of hyperosmotic agents, the porcine stomach tissues (pyloric mucosa) applied topically with glycerol and dimethyl sulfoxide (DMSO) are investigated with optical coherence tomography (OCT) and the near infrared reflectance spectroscopy. Three solutions of 80% and 50% glycerol, and 50% DMSO are studied, each of which shows significant improvement in light transmittance and, thus, reduction of the light scattering of tissue. It is found that, among the solutions investigated, 80% glycerol achieves the best clearing effect on improvement of both the light penetration and imaging contrast. More detailed microstructures of the mucosal layer can be observed for glycerol treatment, while these structures are not resolvable by the conventional OCT. Light transmittance is increased by approximately 23% and diffuse reflectance decreased by approximately 24% at 30 min after the topical application of 80% glycerol. 50% DMSO is more effective than 50% glycerol only at the beginning stage; thereafter the rate of optical clearing is slowed down with time. Although DMSO can enhance the light transmittance and thus reduce the scattering, it has a negligible effect on the imaging contrast improvement. The mass transport process of agent to tissue accounts for the different clearing effects for glycerol and DMSO, respectively. It is concluded that the optical clearing by the hyperosmotic agent is strongly correlated with the water desorption kinetics induced by agent and the agent mass transport process within tissue. In other words, the tissue dehydration induced by agent and the refractive index matching between the agent and the main scattering components within tissue facilitated by the agent mass transport are responsible for optical clearing effects.     

传像光纤束透过率测量方法研究

光学纤维的传光特性不同于一般的成像光学系统,透过率的测量方法也不同。区别在于,测量传像光纤束透过率时不能采用平行光束,而测量成像光学系统透过率时,即可以采用会聚光束,又可以采用平行光束,只要不拦光即可。光在光纤束中遵循全反射的传光原理,而光在成像光学系统中遵循折、反射传光原理。通过对细小口径传像光纤束透过率的测量方法进行了实验、检测研究,得到一个新的测量光纤束透过率的方法。此方法完全不同于目前国标中光纤束透过率测量方法,又区别于成像光学系统透过率的测量方法。测量传像光纤束透过率时,要求光在光纤束中既要避免拦光现象又要满足全反射条件。我们根据光纤束传光原理研制了一个测量连接装置加到光谱仪的测量光路里,构成一个光纤束透过率测量光路系统。该测量法的重心在测量连接装置上。用该测量法成功地完成了细小口径成像光纤束透过率参数的测量,测量结果与设计预期值接近,测量准确度满足用户使用要求。     

应用微结构配光材料的格栅灯光学性能研究

运用挤出压印成型制备了表面添加微结构的PS漫反射板和PMMA扩散板,测试了漫反射板的反射率和漫反射率及扩散板的透光率和雾度。基于前期制备的微结构配光材料,将其应用在格栅灯上,测试了格栅灯的光学性能。微结构配光材料提高了格栅灯的光效,同时保障了光线均匀性。     

Effect of thermal damage on the in vitro optical and fluorescence characteristics of liver tissues

Thermal energy generated by radio-frequency current or other means may be employed in treating liver tumors by means of thermal coagulation when conventional resection is impossible. Currently, these thermal energy-based therapeutic procedures suffer from the lack of an adequate feedback control system, making it difficult to determine the optimal therapeutic endpoint. In this study, the potential of optical spectroscopy to provide such an objective endpoint for these procedures is presented. Freshly harvested canine liver samples were exposed to 50/spl deg/C, 60/spl deg/C, and 70/spl deg/C water baths for times ranging from 0 to 60 min. Transmission and reflectance were measured from each sample using an integrating sphere and the optical properties of each sample were accordingly derived. Excitation-emission matrices were recorded from the samples using a spectrofluorometer to identify the intrinsic fluorescence characteristics of native and thermally coagulated liver tissues. In addition, fluorescence and diffuse reflectance spectra were separately obtained from the samples prepared using a portable spectroscopic system. Results of this study show that fluorescence and optical properties of liver tissues exhibit clear and consistent changes through the thermal coagulation process. Specifically, the primary peak in the fluorescence spectra from liver tissues shifts from 480 nm in the native state to 510 nm in the fully coagulated state. In addition, a three- to fourfold increase in the absolute intensity of the diffuse reflectance spectra is observed upon complete coagulation of liver tissues. These dynamic spectral features indicate that fluorescence and diffuse reflectance spectroscopy may provide a direct measure of the biochemical and structural changes associated with tissue thermal damage in the liver.     

Sized-fiber reflectometry for measuring local optical properties

Sized-fiber spectroscopy describes a device and method for measuring absorption and reduced scattering properties of tissue using optical fibers with different diameters. The device used in this paper consists of two fibers with diameters of 200 and 600 μm. Each fiber emits and collects its own backscattered light. Backscattered light measurements for solutions with absorption coefficients of 0.1-2.0 cm ^-1 and reduced scattering coefficients of 5-50 cm^-1 demonstrate that the device is most sensitive for the highest scattering materials. Monte Carlo simulations suggest the device is insensitive to the fiber illumination characteristics and that the light returning to the fiber is nearly uniform over all directions. Finally, experiments and Monte Carlo simulations of the sized-fiber device indicate that 50% of the signal arises from roughly 1.2 and 1.9 reduced mean-free paths for the 200- and 600-μm fibers, respectively     

Determination of epithelial tissue scattering coefficient using confocal microscopy

Most models of light propagation through tissue assume the scattering properties of the various tissue layers are the same. The authors present evidence that the scattering coefficient of normal cervical epithelium is significantly lower than values previously reported for bulk epithelial tissue. They estimated the scattering coefficient of normal and precancerous cervical epithelium using measurements of the reflectance as a function of depth from confocal images. Reflectance measurements were taken from ex vivo cervical biopsies and fit to an exponential function based upon Beer's law attenuation. The mean scattering coefficients derived were 22 cm/sup -1/ for normal tissue and 69 cm/sup -1/ for precancerous tissue. These values are significantly lower than previously reported for bulk epithelial tissues and suggest that scattering of bulk tissue is dominated by the stroma. They also suggest that computational models to describe light propagation in epithelial tissue must incorporate different scattering coefficients for the epithelium and stroma. Further, the lower scattering of the epithelium suggests greater probing depths for fiber optic probes used by optical diagnostic devices which measure reflectance and fluorescence in epithelial tissue. The difference in scattering between normal and precancerous tissue is attributed to increased nuclear size, optical density, and chromatin texture. The scattering coefficients measured here are consistent with predictions of numerical solutions to Maxwell's equations for epithelial cell scattering.     

Magnetorefractive Effect for Co/Ru Multilayer Film with Antiferromagnetic Interlayer Exchange Coupling

The spin‐dependent scattering of conduction electron in metallic magnetic multilayers was investigated to reveal the optical properties which corresponded to the magnetization state. From the measurement of magnetorefractive effect in antiferro‐magnetically exchange coupled Co/Ru multilayers, it was found that (1) the transmittance varied around 1% at wavelength of 1550 nm during the parallel/antiparallel spin alignment changes, (2) as a result of number of repetition and Co thickness for the multilayers, transmittance difference between the parallel and antiparallel spin alignment states had trade‐off relationship with the magnitude of transmittance, and (3) asymmetric Co/Ru/Co stacking structure brought different interlayer exchange coupling fields in each layer, which resulted in magnetic field sensitive transmittance.     

半透明介质内辐射与导热复合换热过程熵产分析

本文用数值模拟方法对一维半透明介质内辐射与导热复合换热过程进行了热力学分析，给出了参与性介质中辐射与导热复合换热过程的无因次熵产公式和熵产数公式，分析了辐射—导热参数、光学厚度、散射反照率、壁面黑度对熵产数的影响。结果表明，在整个系统中，熵产数满足热力学第二定律，从而证明了无因次熵产公式及熵产数公式的正确性。最后从熵产数的角度分析了系统中的功损。     

Electrically induced light scattering performances of lanthanum-modified lead zirconate titanate transparent ceramics

A series of lanthanum-modified lead zirconate titanate (PLZT) ceramics of Zr/Ti (70/30) with different La concentration (La?=?7.6, 7.8, 8.0 mole %) were prepared by a hot pressing process. The performances of electrically induced light scattering for PLZT (X/70/30) ceramics were investigated and analyzed systematically. All samples are crystallized into a single perovskite phase. The PLZT (7.6/70/30) sample exhibits a ferroelectric behavior while both PLZT (7.8/70/30) and PLZT (8.0/70/30) samples show an antiferroelectric behavior. The phase transition temperature (T _c ) of the PLZT (X/70/30) ceramics shifts slightly from ~86?°C to ~89?°C with the increasing of La concentration at 1?kHz. All three ceramic samples exhibit a high transmittance, i.e., greater than 60?%, with a thickness of 0.4?mm over a wide range of wavelength band, from visible to near IR. The PLZT (X/70/30) ceramics exhibit three different types of light scattering behavior depending on the La concentration (examined at ???=?632.8?nm). Among them, PLZT (8.0/70/30) presents a unique applicable auto-switchable property with a low threshold value of electric field and high transmittance. Noticeably, the contrast ratio increases correspondingly with the thickness of the sample, and the contrast ratio aroused by the transverse electric field is about twice as big as that aroused by the longitudinal one. The light scattering properties of the PLZT (8.0/70/30) ceramic may represent a creative application in optical modulators.     

Optical and electrical properties of ZnO thin film containing nano-sized Ag particles

Low-temperature crystallized ZnO thin film was achieved by sol–gel process using zinc acetate dihydrate and 2-methoxyethanol as starting precursor and solvent, respectively. Ag nanoparticles were prepared with uniform size at 4.4 nm by spontaneous reduction method of Ag 2-ethylhexanoate in dimethyl sulfoxide (DMSO). The optical and electrical properties of ZnO thin films containing various contents of Ag-nanoparticles were monitored. Light scattering and charge emission and scattering behaviors of Ag nanoparticles in ZnO film were found. The incorporation of Ag nanoparticles into Al-doped ZnO film was also investigated. The optical transmittance was not degraded but the increase of electrical sheet resistance was found. The effect of Al-dopant on the transmittance and electrical sheet resistance of ZnO film was found too great to distinguish the positive effect of the incorporation of Ag nanoparticles into Al-doped ZnO thin films.     

多光路光散射扬尘检测方法研究

针对传统扬尘传感器在测量方法中测量精度低、长期户外测量精度保持性差的不足,在Mie光散射原理基础上,研究了一种多光路扬尘检测方法,设计了一套面向建筑工地扬尘检测的光学扬尘浓度测量系统。介绍了扬尘监测系统的光学测量原理,研究了新方法中光通量和离子浓度计算方法,并对检测系统参数进行了优化分析。设计了多光路激光扬尘检测系统,分析了光透过率与粉尘层厚度之间关系。对所设计系统以国控点数据为基础进行了对比实验,实验结果表明新方法相对国控点数值最大偏差8.5%,较PPD4NS检测精度明显提高。     

Dielectric surface flashover in vacuum at 100 K

Cryogenic components in high power electrical systems and in power electronics gain more and more importance. The behavior of insulators for cryogenic conditions, however, is virtually unknown. In a fast coaxial setup, dielectric test sample and electrodes in vacuum are cooled to <100 K and flashover is characterized using fast electrical and optical diagnostics. Three consecutive development stages for flashover in self-breakdown mode with a gap distance of 0.5 cm can be distinguished: (1) a fast current rise to mA amplitudes within ~2 ns, probably associated with field emission, followed by, (2) a slow current rise to ~5 to 10 A amplitude with duration of 40 ns to 1 μs, associated with secondary emission avalanche saturation, and (3) a transition to a rapid gaseous ionization above the sample caused by electron induced outgassing, leading to impedance-limited current amplitudes of ⩽300 A. Phase (1) shows a higher final current at lower temperature, which is probably due to a higher initial velocity of the secondary electrons, the duration of phase (2) is a decreasing function of breakdown voltage and only slightly dependent on temperature, which points to a weak temperature dependence of the outgassing process. Flashover potentials show a slight increase at lower temperature     

Intraoperative application of optical spectroscopy in the presenceof blood

A simple but effective method of spectral processing was developed to minimize or remove the effects of the presence of superficial blood on tissue optical spectra and, hence, enhance the performance of optical-spectroscopic-based in vivo tissue diagnosis and surgical guidance. This spectral-processing algorithm was developed using the principles of absorption-induced light attenuation wherein the ratio of fluorescence intensity (F) and the hth power of diffuse reflectance intensity (Rd) at a given emission wavelength λ_m is immune to spectral distortions induced by the presence of blood on the tissue surface. Here, the exponent h is determined by the absorption coefficients of whole blood at the excitation and emission wavelengths. The theoretical basis of this spectral processing was verified using simulations and was experimentally validated. Furthermore, the optical spectra of brain tissues collected in vivo was processed using this algorithm to evaluate its impact on brain tissue differentiation using combined fluorescence and diffuse reflectance spectroscopy. Based on the simulation, as well as experimental results, it was observed that using F/Rd^h h can effectively reduce or remove spectral distortions induced by superficial blood contamination on tissue optical spectra. Thus, optical spectroscopy can also be used intraoperatively for applications such as surgical guidance of tumor resection     

镀膜玻璃在线质量检测系统的研究和实现

基于光学的色散原理,本文研制了一种可以在线检测镀膜玻璃光学性质的仪器。该仪器采用光纤作为传光载体,利用线阵CCD与光栅的配合完成对玻璃透射和反射光谱测量。光纤对光的发射和接收避免了杂散光的干扰噪声;光栅和高灵敏度的线阵CCD可实现高精确度的光谱采集。通过计算机强大的计算能力,可以实现透射率、反射率、各种色差测量和显示,如CIE1931色坐标（x,y）以及CIE1976色坐标（U,V,W）等,并且能够反馈给生产线,实现对镀膜玻璃光学特性的在线检测及生产线的自动控制。     

Inverse method 3-D reconstruction of localized in vivofluorescence-application to Sjogren syndrome

The development of specific fluorescently labeled cell surface markers have opened the possibility of specific and quantitative noninvasive diagnosis of tissue changes. We are developing a fluorescence scanning imaging system that can perform a “noninvasive optical biopsy” of the Sjogren syndrome (SS) which may replace the currently used histological biopsy. The diagnosis of SS is based on the quantification of the number of topical preadministered fluorescent antibodies which specifically bind to the lymphocytes infiltrating the minor salivary glands. We intend to scan the lower lip, and for each position of the scan, generate a two-dimensional (2-D) image of fluorescence using a charge-coupled device (CCD) camera. We have shown previously that our diffuse fluorescent photon migration theory predicts adequately the positions and strengths of one and two fluorescent targets embedded at different depths in tissue-like phantoms. An inverse reconstruction algorithm based on our theoretical findings has been written in C⁺⁺ and uses 2-D images to predict the strength and location of embedded fluorophores. However, due to large numbers of variables, which include the optical properties of the tissue at the excitation and emission wavelengths, and the positions and strengths of an unknown number of fluorophore targets, the validity of the final result depends on assumptions (such as the number of targets) and the input values for the optical parameters. Our results show that the number of fluorophore targets reconstructed for each scan is limited to two, and at least the scattering coefficient at the excitation wavelength is needed a priori to obtain good results. The latter can be obtained by measurements of spatially resolved diffuse reflectance at the excitation wavelength that provides the product of the absorption and scattering coefficients     

Characteristics of spectral-hole burning of InAs self-assembledquantum dots

Spectral-hole burning of InAs self-assembled quantum dots (QDs) embedded in pin-diode was observed. At 5 K, a narrow hole with width of less than 1 mm was observed and the hole depth increased as electric field increased with the writing light power of 8 mW. The hole was observed up to 40 K. The spectral hole was broadened as the writing light power increases from 8 to 20 mW. Spectral-hole width at the 8 mW was well fitted with the convolution integral of Gaussian distribution for reading light and Lorentzian distribution for absorption change taking into account homogeneous broadening of InAs QDs of ⩽80 μeV. Spectral-hole lifetime at the 8 mW was estimated to be in the order of 10^-6 s. Optical absorption spectrum of 15-stacked InAs QD structure was also observed at 77 K and 300 K     

Three‐dimensional analysis of light transmittance characteristics in many index ellipsoids connected in series

The three‐dimensional optical technique has been applied to analysis of the experimental results related to magnetic wave scattering phenomena. Recently, we have developed an ideal equation for analyzing the three‐dimensional transmittance character of light scattered due to many index ellipsoids. The index ellipsoids are arranged directly along the light axis in series. In this case, the index ellipsoid size and the gap distance between each index ellipsoid and neighbor one are considered as a calculation condition. By using an analysis equation devised by us, we have sought to determine the condition under which the light can be passed through many transparent mediums with high efficiency. From the numerical calculations, the condition for maximum transmittance of light 100% is obtained when a spherical and elliptic index ellipsoids are alternately arranged with respect to each other. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(3): 12–18, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20311     

Electrooptic planar deflector switches with thin-film PLZT active elements

First prototypes of electrooptic (EO) planar deflector switches (PDSs) are fabricated with hybrid integration on Si substrates. Planar optical modules, made in silica-on-silicon technology, consist of input and output (I/O) waveguide microlenses facing each other and slab waveguides in between. The modules interconnect the I/O fibers with laterally collimated light beams less than 400 /spl mu/m in width at distances up to 100 mm with losses lower than 3 dB. Thin lead lanthanum zirconium titanate (PLZT) films with prism-shaped electrodes grown on SrTiO/sub 3/ substrates form the deflector elements. The PLZT films are more than 10 /spl mu/m thick with EO coefficients about 40 pm/V. The deflector assembly technology provides chip vertical positioning accuracy better than 1 /spl mu/m. The deflector chips are attached to the optical substrates with thermo-compression flip-chip bonding. The optical power losses of the modules with test silica chips can be as low as 3.6 dB. However, the lowest module losses achieved with PLZT are about 10 dB. The channel-to-channel switching operations are demonstrated at about 40 V and switching times less than 500 ns.