偏振相移技术在DIC显微术中的应用研究

微分干涉（DIC）显微技术使用诺曼斯基棱镜完成光束的分割、合成、最后发生干涉,将样品上各个部分折射率、厚度的变化率或表面起伏的不同转化为像面上光强的差别,一般情况下,无法进行定量测量。文章将激光偏振相移技术应用于DIC显微术中,建立并推导出光学数学模型。该模型利用无限远光学系统优化系统光路,使系统减小了因为使用激光光源、     

基于微分干涉相衬的相位分析法研究

通过对微分干涉相衬显微定量测量方法进行研究,提出了一种更有效的相位分析法。即在不对双光束干涉光路进行改造或处理的前提下,通过对光学成像进行处理而得到理想的结果。即把图像中的光强信号转变成相位信号,并通过维纳滤波对噪声进行了消除,最后获得表面微观形貌定量参数。     

A quantitative method for analysing AFM images of the outer surfaces of human hair

Cuticle step height is an important parameter for the quantitative assessment of human hair. This paper describes a novel, computational method for the rapid calculation of step heights from atomic force microscope images obtained from large numbers of specimens. Such an approach is necessary to allow a statistical analysis of the inherently wide distribution of cuticle step heights characteristic of a single hair sample. The method described will be of use to cosmetic formulation chemists and forensic scientists and also to dermatologists in the field of disease diagnosis.     

Multimodal microscopy by digital image processing

A matching algorithm is proposed for aligning microscope images obtained using different modalities, making use of cross-correlations of outputs from Prewitt's edge filter. Brightfield, phase contrast and differential interference contrast microscope images of algal and bacterial cells from an experimental, high-rate algal pond are used for illustration. The information content of multimodal images is explored using principal components analysis and colour displays, and an image which represents optical thickness is constructed digitally.     

分级淬火热处理双相钢在拉伸变形时的应变分配

采用亚微米级分辨率的数字图像相关(DIC)方法,探究了分级淬火得到的马氏体体积分数分别为33.8%和58.3%双相钢在不同拉伸变形量下的应变分配规律。结果表明:两种双相钢在不同变形量下的微观应变分配规律相似,应变分布都很不均匀,且变形量较大时应变分布不均匀性更为显著;在马氏体体积分数较小的双相钢中,应变在铁素体和马氏体间分配的不均匀性更显著;微区内存在应变集中的变形带,变形带主要分布在铁素体上,在块状马氏体间的较窄铁素体区域出现的概率比较大;在马氏体上或相界面处也有少量应变集中的变形带,马氏体体积分数较小时沿相界面扩展的变形带数量较多;马氏体体积分数较大时变形带穿过马氏体的概率更大。     

Re-evaluation of differential phase contrast (DPC) in a scanning laser microscope using a split detector as an alternative to differential interference contrast (DIC) optics

In this paper, differential phase imaging (DPC) with transmitted light is implemented by adding a suitable detection system to a standard commercially available scanning confocal microscope. DPC, a long‐established method in scanning optical microscopy, depends on detecting the intensity difference between opposite halves or quadrants of a split photodiode detector placed in an aperture plane. Here, DPC is compared with scanned differential interference contrast (DIC) using a variety of biological specimens and objective lenses of high numerical aperture. While DPC and DIC images are generally similar, DPC seems to have a greater depth of field. DPC has several advantages over DIC. These include low cost (no polarizing or strain‐free optics are required), absence of a double scanning spot, electronically variable direction of shading and the ability to image specimens in plastic dishes where birefringence prevents the use of DIC. DPC is also here found to need 20 times less laser power at the specimen than DIC.     

Confocal differential interference contrast (DIC) microscopy: including a theoretical analysis of conventional and confocal DIC imaging

A technique for obtaining differential interference contrast (DIC) imaging using a confocal microscope system is examined and its features compared to those of existing confocal differential phase contrast (DPC) techniques as well as to conventional Nomarski DIC. A theoretical treatment of DIC imaging is presented, which takes into account the vignetting effect caused by the finite size of the lens pupils. This facilitates the making of quantitative measurements in DIC and allows the user to identify and select the most appropriate system parameters, such as the bias retardation and lateral shear of the Wollaston prism.     

Reconstruction of optical pathlength distributions from images obtained by a wide-field differential interference contrast microscope

An image processing algorithm is presented to reconstruct optical pathlength distributions from images of nonabsorbing weak phase objects, obtained by a differential interference contrast (DIC) microscope, equipped with a charge-coupled device camera. The method is demonstrated on DIC images of transparent latex spheres and unstained bovine spermatozoa. The images were obtained with a wide-field DIC microscope, using monochromatic light. After image acquisition, the measured intensities were converted to pathlength differences. Filtering in the Fourier domain was applied to correct for the typical shadow-cast effect of DIC images. The filter was constructed using the lateral shift introduced in the microscope, and parameters describing the spectral distribution of the signal-to-noise ratio. By varying these parameters and looking at the resulting images, an appropriate setting for the filter parameters was found. In the reconstructed image each grey value represents the optical pathlength at that particular location, enabling quantitative analysis of object parameters using standard image processing techniques. The advantage of using interferometric techniques is that measurements can be done on transparent objects, without staining, enabling observations on living cells. Quantitative use of images obtained by a wide-field DIC microscope becomes possible with this technique, using relatively simple means.     

Comparative morphology of leaf epidermis in eight populations of Atlas Pistachio (Pistacia atlantica Desf., Anacardiaceae)

A comparative analysis was undertaken to conduct a micromorphological study of Pistacia atlantica leaves by comparing different populations grown under different climatic conditions. Leaf epidermis of eight wild populations was investigated under scanning electron microscope. Micromorphological characteristics (epidermis ornament, stomata type, waxes as well as trichomes) of the adaxial and abaxial leaf surfaces were examined. The epidermis ornament varied among populations and leaf surface, the abaxial leaf surface is reticulate with a striate surface. Messaad site shows a smooth uneven surface. The adaxial leaf surface is smooth but several ornamentations can be seen. The leaflet is amphistomatic; the stomata appeared to be slightly sunken. A variety of stomatal types were recorded; actinocytic and anomocytic types are the most frequent. The indumentum consisted of glandular and nonglandular trichomes. Unicellular glandular trichomes are recorded for P. atlantica leaves in this study. Their density is higher in Oued safene site, located at the highest altitude in comparison with the other populations. The wax occurred in all the sites and its pattern varied according to the populations studied, particularly between Berriane and Messaad. The morphological variability exhibited by the eight populations of P. atlantica may be interpreted as relevant to the ecological plasticity and the physiological mechanisms involved are discussed in this report.     

An evaluation of methods for preparing easily damaged cuticular surfaces of plants for scanning electron microscopy

Techniques were tested to ascertain the best method for preparing the surfaces of delicate plant cuticles for microscopic examination at magnifications not exceeding 10,000. Using scanning electron microscopy, comparative examinations were made of cuticles of fresh material, ambient dried, freeze dried, critical point dried, and frozen material kept at low temperature. Micrographs were compared with material examined using light microscopy which acted as a control at low magnification. Cuticles of the leaves of runner bean, Coleus and the petals of Nicotiana, showed best surface preservation and least wrinkling when frozen, held at low temperature, and examined on a cryostage.