星载高分辨力、大视场高光谱成像仪光学设计

根据高分辨力,大视场的要求,考虑到市售探测器的限制,提出了视场分离分光的方法,分析了视场分离分光的原理.利用此方法设计了一个星载高分辨力、大视场高光谱成像仪光学系统,该系统由11.42°远心离轴三反消像散(TMA)望远系统和2个Offner凸面光栅光谱成像系统组成,运用光学设计软件CODE V对高光谱成像仪光学系统进行...     

复合材料薄壁梁的固有特性分析

本文采用复合材料薄壁梁的高次翘曲理论对复合材料薄壁梁的固有特性进行了分析,讨论了单闭室复合材料薄壁梁的高次翘曲,剖面分层对结构的固有特性的影响。数例表明,复合材料薄壁梁的高次翘曲函数和分层对结构的固有特性具有一定的影响。     

椭偏仪测量光学参数实验

以云母波片为例,根据椭偏测量相位原理,利用椭偏仪的温控装置,对不同温度下云母波片的延迟量进行测量,再根据延迟量与最大双折射率的数学关系,得到相应温度下云母波片的最大双折射率从而验证椭偏测量法是切实、可行的,也是可靠的。     

基于晶体双折射的光学FIR滤波器设计

提出建立在晶体双折射基础上，由晶体延迟片堆组成的光学FIR（Finite Impulse Response)滤波器设计方法，用以实现任意形状光谱输出。从FIR信号理论出发，建立了光学FIR滤波器数学模型，并分析了它与FIR滤波器的映射关系。在给出“输出反向传递法”来完成其光学实现同时，还以G／M滤波器设计实例证明其优良的光谱特性及角度特性。     

合肥800MeV同步辐射源光谱特性的测量

本文介绍了测量合肥国家同步辐射实验室８００ＭｅＶ同步辐射源光谱功率分布的原理、装置和方法，并对实验结果进行误差分析。     

纳米SiO2的光学特性研究

纳米SiO2的独特结构使其表现出一些特殊的光学特性，但文献对其紫外区光学性质的报道不一致。本文对几种不同类型的纳米SiO2进行了紫外—可见光谱测试，结果表明纳米SiO2在紫外—可见光范围内具有较强的光反射性能，但在λ=230nm附近有一强度不一的吸收峰，该吸收峰的强度可能与纳米SiO2的结构和表面状态有关。     

海水光谱吸收/散射系数测量仪的研制

在克服了由于海水的光谱吸收和散射很小的难点下,研制成功具有高分辨和高精度能力的室外现场测试仪器,其结构紧凑合理,测量装置构思精巧,测试过程完全自动化,克服环境和测试条件的多变性带来的影响,实现了海水吸收系数与散射系数的瞬态测量。现场海水光谱吸收/散射系统测量装置为国内首创,填补了国内空白。     

连续矩形板横向振动固有特性的计算

本文给出了中间有任意个平行于边界的单向和双向连续支承矩形板的横向振动特性的一个近似算法,将基函数选择为梁函数与多项式函数的叠加,利用李兹法近似求解固有频率,公式简单、易程序化,且有较好的精度。本文最后给出了几个算例,并与已有结果进行了比较。     

基于高光谱成像技术的绿松石在线鉴别系统研发

为了避免常见的绿松石处理品及伪品入药,本文针对药用绿松石原矿样品,利用高光谱成像技术开展了绿松石在线鉴别系统的研发.依据全国各地有代表性的天然绿松石原矿样品的高分辨光谱数据,获取了标准谱线,并验证了其普适性.针对市面上常见的绿松石伪品和处理品,分析了在400 nm～1000 nm和400 nm～600 nm范围内的相关...     

桥梁结构边界条件变异对固有振动特性的影响分析

针对实际桥梁结构复杂的边界条件，分析其对结构固有振动特性的影响因素。采用解析的方法分析简支梁在纵向不同程度的约束效应，以及简支梁、连续梁支承处不同刚度弹性扭转约束对结构自振特性的影响，并提出利用有限元分析来考虑复杂结构的边界条件变异影响的方法。最后以重庆轻轨PC梁以及一中承式拱桥的实测及计算固有频率结果验证了实际边界条件变化对固有频率的显著影响。     

Chlorophyll-based model of seawater optical properties

A one-parameter model of the inherent optical properties of biologically stable waters is proposed. The model is based on the results of in situ measurements of inherent optical properties that have been conducted at different seas and oceans by a number of researchers. The results of these investigations are processed to force this model to agree satisfactorily with an established regression model that connects the color index with the chlorophyll concentration. The model couples two concentrations of colored dissolved organic matter (concentrations of humic and fulvic acids) and two concentrations of suspended scattering particles (concentrations of terrigenic and biogenic particles) with the chlorophyll concentration. As a result, this model expresses all inherent properties of seawater by a single parameter, the concentration of chlorophyll.     

A prototype optical encoder system with nanometer measurement capability

Optical gratings are becoming available with precision down to the 2 nm level, or below. Such gratings can be employed to make highly accurate measuring tools such as optical encoders and coordinate measuring tools which can find numerous applications in precision machining applications and integrated circuit industry such as image placement inspection. Such tools are significantly less expensive than interferometers because of the relaxed mechanical tolerances required on the associated stages. In this paper, a novel prototype optical encoder system is developed for grating-based measurement tools with nanometer accuracy. The location of the grating was determined with an error of 0.09 nm. This is comparable to the accuracy of state-of-the-art interferometers, but at much lower cost.     

Deriving inherent optical properties from water color: a multiband quasi-analytical algorithm for optically deep waters

For open ocean and coastal waters, a multiband quasi-analytical algorithm is developed to retrieve absorption and backscattering coefficients, as well as absorption coefficients of phytoplankton pigments and gelbstoff. This algorithm is based on remote-sensing reflectance models derived from the radiative transfer equation, and values of total absorption and backscattering coefficients are analytically calculated from values of remote-sensing reflectance. In the calculation of total absorption coefficient, no spectral models for pigment and gelbstoff absorption coefficients are used. Actually those absorption coefficients are spectrally decomposed from the derived total absorption coefficient in a separate calculation. The algorithm is easy to understand and simple to implement. It can be applied to data from past and current satellite sensors, as well as to data from hyperspectral sensors. There are only limited empirical relationships involved in the algorithm, and they are for less important properties, which implies that the concept and details of the algorithm could be applied to many data for oceanic observations. The algorithm is applied to simulated data and field data, both non-case1, to test its performance, and the results are quite promising. More independent tests with field-measured data are desired to validate and improve this algorithm.     

Miniature endoscope for simultaneous optical coherence tomography and laser-induced fluorescence measurement

We have designed a multimodality system that combines optical coherence tomography (OCT) and laser-induced fluorescence (LIF) in a 2.0-mm-diameter endoscopic package. OCT provides approximately 18-microm resolution cross-sectional structural information over a 6-mm field. LIF spectra are collected sequentially at submillimeter resolution across the same field and provide histochemical information about the tissue. We present the use of a rod prism to reduce the asymmetry in the OCT beam caused by a cylindrical window. The endoscope has been applied to investigate mouse colon cancer in vivo.     

Uncertainties associated to measurements of inherent optical properties in natural waters

Monte Carlo simulations are used to explain and quantify the errors in inherent optical properties (IOPs) (absorption and attenuation coefficients) measured using the WET Labs AC-9 submarine spectrophotometer, and to assess correction algorithms. Simulated samples with a wide range of IOPs encountered in natural waters are examined. The relative errors on the measured absorption coefficient are in general lower than 25%, but reach up to 100% in highly scattering waters. Relative errors on attenuation and scattering coefficients are more stable, with an underestimation mainly driven by the volume scattering function. The errors in attenuation and scattering spectral shapes are small.     

Uncertainties of inherent optical properties obtained from semianalytical inversions of ocean color

We present a method to quantify the uncertainties in the in-water constituent absorption and backscattering coefficients obtained from an inversion of remotely sensed reflectance (rrs). We first find a set of positive inversion solutions within a given uncertainty range around the values of the inverted rrs. The uncertainties of the solutions are then computed based on the statistics of these solutions. We demonstrate the uncertainty calculation algorithm using a specific semianalytic inversion model applied to both a field and a simulated data set. When the associated uncertainties are taken into account, the inverted parameters are generally within the uncertainties of the measured (or simulated) parameters, highlighting the success of the inversion and the method to obtain uncertainties. The specific inversion we use, however, fails to retrieve two spectral parameters within a usable range. The method presented is general and can be applied to all existing semianalytical inversion algorithms.     

Uniqueness in remote sensing of the inherent optical properties of ocean water

We examine the problem of uniqueness in the relationship between the remote-sensing reflectance (Rrs) and the inherent optical properties (IOPs) of ocean water. The results point to the fact that diffuse reflectance of plane irradiance from ocean water is inherently ambiguous. Furthermore, in the 400 < lambda < 750 nm region of the spectrum, Rrs(lambda) also suffers from ambiguity caused by the similarity in wavelength dependence of the coefficients of absorption by particulate matter and of absorption by colored dissolved organic matter. The absorption coefficients have overlapping exponential responses, which lead to the fact that more than one combination of IOPs can produce nearly the same Rrs spectrum. This ambiguity in absorption parameters demands that we identify the regions of the Rrs spectrum where we can isolate the effects that are due only to scattering by particulates and to absorption by pure water. The results indicate that the spectral shape of the absorption coefficient of phytoplankton, a(ph)(lambda), cannot be derived from a multiparameter fit to Rrs(lambda). However, the magnitude and the spectral dependence of the absorption coefficient can be estimated from the difference between the measured Rrs(lambda) and the best fit to Rrs(lambda) in terms of IOPs that exclude a(ph)(lambda).     

Parameterization of the inherent optical properties of Murchison Bay, Lake Victoria

Lake Victoria, Africa's largest freshwater lake, suffers greatly from negative changes in biomass of species of fish and also from severe eutrophication. The continuing deterioration of Lake Victoria's ecological functions has great long-term consequences for the ecosystem benefits it provides to the countries bordering its shores. However, knowledge about temporal and spatial variations of optical properties and how they relate to lake constituents is important for a number of reasons such as remote sensing, modeling of underwater light fields, and long-term monitoring of lake waters. Based on statistical analysis of data from optical measurements taken during half a year of weekly cruises in Murchison Bay, Lake Victoria, we present a three-component model for the absorption and a two-component model for the scattering of light in the UV and the visible regions of the solar spectrum along with tests of their ranges of validity. The three-component input to the model for absorption is the chlorophyll-a (Chl-a), total suspended materials concentrations, and yellow substance absorption, while the two-component input to the model for scattering is the Chl-a concentration and total suspended materials.     

Oceanic inherent optical properties: proposed single laser lidar and retrieval theory

It is suggested that an economical airborne lidar having a single laser can retrieve the three principal inherent optical properties of the ocean. Only three time-resolved backscattering receiver channels are required: (i) elastic (on-wavelength), (ii) inelastic (water Raman), and (iii) inelastic [chromophoric dissolved organic matter (CDOM) fluorescence channel to remove the CDOM fluorescence interference from the Raman channel].     

Comparison of the ocean inherent optical properties obtained from measurements and inverse modeling

A model developed recently by Loisel and Stramski [Appl. Opt. 39, 3001-3011 (2000)] for estimating the spectral absorption a(lambda), scattering b(lambda), and backscattering b(b)(lambda) coefficients in the upper ocean from the irradiance reflectance just beneath the sea surface R(lambda, z = 0(-)) and the diffuse attenuation of downwelling irradiance within the surface layer ?K(d)(lambda)?(1) is compared with measurements. Field data for this comparison were collected in different areas including off-shore and near-shore waters off southern California and around Europe. The a(lambda) and b(b)(lambda) values predicted by the model in the blue-green spectral region show generally good agreement with measurements that covered a broad range of conditions from clear oligotrophic waters to turbid coastal waters affected by river discharge. The agreement is still good if the model estimates of a(lambda) and b(b)(lambda) are based on R(lambda, z = 0(-)) used as the only input to the model available from measurements [as opposed to both R(lambda, z = 0(-)) and ?K(d)(lambda)?(1) being measured]. This particular mode of operation of the model is relevant to ocean-color remote-sensing applications. In contrast to a(lambda) and b(b)(lambda) the comparison between the modeled and the measured b(lambda) shows large discrepancies. These discrepancies are most likely attributable to significant variations in the scattering phase function of suspended particulate matter, which were not included in the development of the model.