共查询到20条相似文献,搜索用时 31 毫秒
1.
干涉成像光谱技术是利用光的干涉原理获取目标光谱信息的一种成像技术。为研究其在强光下的干扰效果和机理,以大孔径静态成像光谱仪为典型对象,开展了相关仿真实验研究。以实际地物的图像和光谱信息为对象,仿真生成了原始干涉成像图案,并模拟830 nm单波长激光和超连续谱激光两种干扰源,分别研究不同辐照强度下的典型干扰效果,分析时假设光谱角大于30°时原始光谱信息丢失。基于本文的仿真模型,得到的相关结果表明,在830 nm的单波长激光干扰情况下,当干扰与目标成像峰值之比大于0.2∶1时原始光谱信息无法正确复原(光谱角大于30°),但模拟加入830 nm滤光片后,干扰效果被有效滤除。在超连续谱激光干扰情况下,不考虑饱和阈值时光谱角数值最终稳定在21°;考虑探测器饱和阈值为目标成像强度峰值3倍时,干扰与目标成像峰值之比大于2.1∶1时,原始光谱信息便无法分辨。该研究可能为同类型光谱仪的激光辐照效应和损伤机理的后续研究,以及光谱成像系统的激光防护和性能优化提供参考。 相似文献
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An acousto-optic tunable filter that is insensitive to the polarization of incident light is studied both theoretically and experimentally. The fundamental possibility of designing an acousto-optic filter of nonpolarized light is demonstrated. The filter operates in the visible range of electromagnetic waves with λ=480–750 nm and provides a high spatial and temporal resolution. The number of resolvable spots of the filtered image reaches a value of 400×400 with the spectral bandwidth of the device being Δλ=1.7 nm. The results of the processing of optical images formed by arbitrarily polarized light beams are discussed. An acousto-optic filter based on a TeO2 crystal can be used in optics and spectroscopy in the processing of light beams with an arbitrary polarization, as well as in analyzing optical images formed by light beams whose polarization varies with time. 相似文献
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Laser-Induced Fluorescence at 488 nm Excitation for Detecting Benign and Malignant Lesions in Stomach Mucosa 总被引:1,自引:0,他引:1
Silveira L Betiol Filho JA Silveira FL Zângaro RA Pacheco MT 《Journal of fluorescence》2008,18(1):35-40
This work aims the detection of the histopathologic alterations of in vitro human gastric mucosa using spectral informations
from laser-induced fluorescence spectroscopy (LIFS) technique with excitation at 488 nm (argon laser). A total of 108 biopsies
with endoscopic diagnosis of gastritis and gastric cancer were obtained at the antral gastric region, from 35 patients with
dyspeptic digestive complaints. The biopsies were collected during the endoscopic examination. On each biopsy fragment the
autofluorescence spectrum was collected in two random points, through a fiber-optic catheter coupled to the excitation laser.
The fluorescence emission spectra collected by the fibers were directed to the spectrograph and detected by the CCD camera.
The spectra were then separated in groups (N, normal; LI, light inflammation; MI, moderated inflammation; CA, adenocarcinoma),
based on the histopathology. The ratio between the emission wavelengths 550 and 600 nm was used as a diagnostic parameter.
Analysis of fluorescence spectra was able to identify the normal tissue from adenocarcinoma lesions with 100% of sensibility
and specificity. The ratio intensities between inflammation (light and moderated), although presented significantly statistical
differences when compared to the normal mucosa, do not furnish enough sensibility and specificity for use as an identification
method due to high variations. LIFS, with excitation of 488 nm, could be used in the differentiation of normal tissue and
neoplasic lesions, assisting a less invasive diagnosis. 相似文献
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Regularities of the wide-aperture mode of light diffraction by acoustic waves in crystals with different values of birefringence are considered. The diffraction has been investigated theoretically and experimentally with the aim of applying it in acousto-optic filters used in processing uncollimated optical beams and images. It is proved that the main filtration parameters depend on the birefringence of crystals used in processing luminous fluxes. By the example of wide-aperture filters based on paratellurite, magnesium fluoride, and potassium dihydrogen phosphate crystals, it is shown that the choice of crystals with high birefringence may increase the maximum attainable angular aperture and throughput of devices. It is also proved that application of crystalline compounds of mercury and tellurium (characterized by high optical anisotropy) in filters increases spectral resolution and improves the quality of filtered images. 相似文献
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Analysis of Spectral Reflectance Using Normalization Method from Endoscopic Spectroscopy System 总被引:2,自引:0,他引:2
Masao Sambongi Makoto Igarashi Takashi Obi Masahiro Yamaguchi Nagaaki Ohyama Masahiko Kobayashi Yasushi Sano Shigeaki Yoshida Kazuhiro Gono 《Optical Review》2002,9(6):238-243
Objective assessment of gastrointestinal mucosal color is extremely important in the endoscopic diagnosis of digestive tract disease. In this paper, we propose a method to clarify the spectral characteristics of gastric and colon cancer. A large number of spectral reflectance data of mucous membrane are measured by the endoscopic spectroscopy system (ESS) in the National Cancer Center Hospital East, Kashiwa, Japan and the Department of Internal Medicine, Self-Defense Force Center Hospital, Tokyo, Japan. We assume that early cancer appears primarily in the spectral data of short wavelength, because it is usually present in a superficial cell where short wavelength light is scattered more strongly than long wavelength light. To identify the features in the short wavelength components, the spectral reflectance was divided by the reflectance of a long wavelength. We investigated the possibility of distinguishing early cancer from normal spectral data through statistical analysis, employing the projection axis as the mean difference between them. Early cancer and normal spectral data were projected on the projection axis, and the Student’s T-test was applied to evaluate the mean of the distribution between these data. 相似文献
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A new method for larger size images recognition is proposed based on high-pass filtering and frequency spectrum correlation. The input images are first filtered by a high-pass filter. Then the filtered input images, which are overlapped rather than displaced from each other in the input plane, serve as the input images for frequency spectrum correlator. As a result, only one sharp correlation peak yields in the center of output plane when the target image matches with the reference image. More importantly, the method is especially suitable for larger size image recognition because of the input and correlation ways, which ensures better utilization of the space-bandwidth product and efficient utilization of the spatial light modulator and detector. Computer simulation results are presented to demonstrate the feasibility and effectiveness of this method. 相似文献
8.
Point pattern matching is an essential step in many image processing applications.This letter investigates the spectral approaches of point pattern matching,and presents a spectral feature matching algorithm based on kernel partial least squares(KPLS).Given the feature points of two images,we define position similarity matrices for the reference and sensed images,and extract the pattern vectors from the matrices using KPLS,which indicate the geometric distribution and the inner relationships of the feature points.Feature points matching are done using the bipartite graph matching method.Experiments conducted on both synthetic and real-world data demonstrate the robustness and invariance of the algorithm. 相似文献
9.
K. Guze M. Short H. Zeng M. Lerman S. Sonis 《Journal of Raman spectroscopy : JRS》2011,42(6):1232-1239
Raman spectroscopy has been effectively applied to clinically differentiate normal and cancerous mucosal tissues. Micro‐Raman spectroscopy provides a tool to better understand the molecular basis for the Raman clinical signal. The objective of the current study was to utilize micro‐Raman spectroscopy to define the molecular/spectral differences between normal and abnormal squamous cell carcinoma (SCC) in oral mucosa (in vitro). Understanding this may help in identifying unique spectra or may be useful for in vivo application of this technology. Micro‐Raman (confocal) spectroscopy was used to obtain molecular images of normal and SCC cells of human oral mucosa. Four fresh flashed‐frozen tumor and four matched normal tongue specimens were studied. The spectra covered a wavenumber range from 300 to 4000 cm−1 with a spectral resolution of 8 cm−1 and a spatial resolution of 1.0 µm. The cells were located within thin sections of tongue mucosa biopsies. The excitation wavelength of 515 nm was used. We were able to obtain Raman images with rich information about the spectroscopic and structural features within the cytoplasm, cell membrane, and cell nuclei. Significant spectral differences were observed between the Raman images of normal and malignant squamous cells. The heterogeneity of tumor cells within the abnormal tissue was also demonstrated. Spectral differences demonstrated between both tissue types have provided important information regarding the origins of specific signals within the cells of each tissue type. In our search for specific spectral biomarkers, we believe that a cell surface protein, greatly upregulated in SCC cells, was discovered at 1583 cm−1. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
10.
Richard G. Seasholtz Alvin E. Buggele Mark F. Reeder 《Optics and Lasers in Engineering》1997,27(6):543-570
Flow diagnostics based on molecular Rayleigh scattering are discussed along with the results of a feasibility study to non-intrusively measure flow properties in a small supersonic wind tunnel. The technique uses an injection seeded, frequency doubled Nd:YAG laser tuned to an absorption band of iodine. The molecular Rayleigh scattered light is filtered with an iodine cell to block light at the laser frequency. The Doppler-shifted Rayleigh scattered light that passes through the iodine cell is analyzed with a planar mirror Fabry-Perot interferometer used in a static imaging mode. An intensified CCD camera is used to record the images. The images are analyzed at several subregions, where the flow properties are determined. Each image is obtained with a single laser pulse, giving instantaneous measurements. 相似文献
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Optical imaging of an exposed cortex for brain function measurement is an attractive method for both clinical and physiological investigations. Spectral imaging of the exposed cortical tissue enables measurement of the activity-dependent changes in oxy- and deoxy-haemoglobin independently. Since the diffusely reflected light from the exposed cortex is highly scattered in the cortical tissue, the wavelength dependence of the optical properties of the tissue is likely to affect the images of oxy- and deoxy-haemoglobin changes obtained from the spectral images. In this study, the spectral images of the model of exposed cortical tissue are calculated by Monte Carlo simulation to investigate the influence of blurring by tissue scattering on the brain function measurement by the imaging. The images of the change in oxy- and deoxy-haemoglobin obtained from the spectral images at near infrared wavelengths are broadened and blurred due to the scattering in the cortical tissue. The influence of cross talk is more significant in the image calculated from the spectral images at the visible wavelengths. Inappropriate choice of the spectral range of images might increase cross talk and error in the images of oxy- and deoxy-haemoglobin changes. 相似文献
12.
Spatially resolved spectral interferometry for determination of subsurface structure 总被引:3,自引:0,他引:3
We describe an instrument capable of obtaining two-dimensional images of subsurface structure in real time with no moving parts. The technique is based on spectral interferometry and uses an imaging spectrograph to obtain spatially resolved spectra. A test sample consisting of microscope coverslips and a Ronchi grating was measured, illustrating the system's depth resolution of 38 mum and transverse resolution of at least 12.7 mum . The technique is readily adaptable to endoscopic delivery as well as three-dimensional real-time image acquisition. 相似文献
13.
Pantel R Jullian S Delille D Dutartre D Chantre A Kermarrec O Campidelli Y Kwakman LF 《Micron (Oxford, England : 1993)》2003,34(3-5):239-247
This paper presents a new technique using energy filtered TEM (EFTEM) for inelastic electron scattering contrast imaging of Germanium distribution in Si-SiGe nanostructures. Comparing electron energy loss spectra (EELS) obtained in both SiGe and Si single crystals, we found a spectrum area strongly sensitive to the presence of Ge in the range [50-100 eV]. In this energy loss window, EELS spectrum shows a smooth steeply shaped background strongly depending on Ge concentration. Germanium mapping inside SiGe can thus be performed through imaging of the EELS background slope variation, obtained by processing the ratio of two energy filtered TEM images, respectively, acquired at 90 and 60 eV. This technique gives contrasted images strongly similar to those obtained using STEM Z-contrast, but presenting some advantages: elastic interaction (diffraction) is eliminated, and contrast is insensitive to polycrystalline grains orientation or specimen thickness. Moreover, since the extracted signal is a spectral signature (inelastic energy loss) we demonstrate that it can be used for observation and quantification of Ge concentration depth profile of SiGe buried layers. 相似文献
14.
We demonstrated fast terahertz spectral computed tomography by using real-time line projection of a terahertz beam. Two types of cross-sectional images of continuously rotating samples have been measured in only a few seconds. From temporal data, a peak-to-peak sinogram and cross sections have been reconstructed using a filtered backprojection algorithm. Using fast Fourier transform from temporal data, spectral cross sections of the sample have been obtained. 相似文献
15.
惯性约束聚变中环孔编码图像恢复的改进维纳滤波方法 总被引:7,自引:0,他引:7
针对惯性约束聚变(ICF)中环形孔径编码图像的恢复问题提出了一种改进的维纳滤波方法。在传统的维纳滤波方法中,由于原图像和噪声是未知的,故通常是用某一待定常量来代替其中的噪声与信号的谱密度之比。这种近似忽视了信号与噪声本身的信息,从而造成丢失某些关键的细节,难以达到高质量的图像复原效果。在改进的方法中,首先采用传统维纳滤波方法求得初始估值,然后利用该初始值求得原图像及噪声的谱密度估值,进而利用这些新获得的信息构成改进的维纳滤波器对退化图像进行第二次滤波。实验表明,这种改进方法可以克服原方法的不足,突出图像的一些关键细节,提高图像的整体质量。在仿真实验中,恢复图像的均方误差降低了15%以上;在实际惯性约束聚变图像的解码恢复实验中,图像恢复效果亦有显著改善。该方法还可以推广到其他图像恢复的应用中。 相似文献
16.
《Journal of magnetic resonance. Series B》1995,106(2):122-130
The development and optimization procedures for obtaining high-quality three-dimensional spatial electron-paramagnetic-resonance images of large lossy samples at L band are described. Strategies for selecting optimized parameters for projection acquisition, instrumentation, and algorithms for correcting drifts in microwave frequency and inaccuracies in the static and gradient magnetic fields are described. Image reconstruction was performed using a two-stage filtered back-projection method with spectral deconvolution. With this instrumentation, correction algorithms, and image reconstruction method, spatially accurate 3D images of radical distribution were observed in complex phantoms using 0.5 mM nitroxide labels. The results indicate that high-quality images of lossy samples, including biological organs and tissues of up to 25 mm in size, could be obtained in a reasonable time with submillimeter resolution. 相似文献
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叶绿素含量是作物光合能力与营养评价的重要指标,因此快速检测作物叶绿素含量与分布可为作物营养动态分析与长势评估提供支持。基于RGB(Red, Green, Blue)和NIR(Near Infrared)多光谱图像的获取,开展玉米作物营养状态分布光谱学成像检测。构建了多光谱图像采集平台获取RGB和NIR图像,研究了基于光饱和校正算法的RGB图像的光饱和校正与NIR图像去噪方法,通过图像的匹配分割,冠层的提取校正,建立了基于冠层图像的作物SPAD值检测模型与分布成图。采集15株玉米植株RGB-NIR图像,并同步获取不同植株,不同位置共68个叶绿素含量指标SPAD值。首先对RGB图像进行光饱和校正,再对NIR图像进行滤波和图像增强,其次对RGB和NIR图像进行了SURF(speeded-up robust features)和RANSAC(random sample consensus)图像匹配,利用RGB图像的颜色特征,采用ExG(Extra Green)和OTSU算法生成分割掩模,对RGB图像和NIR图像进行分割提取,提取图像的R, G, B和NIR分量,利用4阶灰度板进行反射率校正,然后计算作物图像中像素级PSPAD值,并建立图像PSPAD值与叶绿素仪SPAD值的拟合模型,最后绘制作物SPAD分布图。通过HSI(Hue, Saturation, Intensity)彩色模型中的I分量直方图对比去饱和前后光分布范围,以作物SPAD值分布图验证光饱和校正算法对作物叶绿素含量分布检测提升的效果。RGB图像光饱和校正前I分量集中在[140~180]之间,光饱和校正后的RGB图像I分量集中在[85~130]之间, 校正了相机成像时产生模糊和RGB图像饱和。对分割后的RGB图像和NIR图像提取R,G,B,NIR分量进行4阶灰度板校正,相关系数分别为0.829,0.828,0.745和0.994,进而生成R,G,B和NIR四波段的反射率伪彩色图像,反射率RNIR>RC>RR>RB。体现了作物的在蓝光和红光区域吸收光,在绿光区域和近红外区域反射光的光谱特性。校正前后的R和NIR分量反射率计算图像PSPAD值拟合叶绿素含量指标SPAD值的模型结果显示,校正前R2为0.332 6,校正后R2为0.619 3,绘制作物的SPAD特征分布图,可为作物的营养动态快速分析与分布检测提供技术支持。 相似文献
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A voltage controlled multiple-stage tunable filter with broad continuous tuning range was studied in theory and experiment. Four liquid crystal retarders, two quartz plates with certain integral ratio phase retardations and five polarization films were assembled into a traditional Lyot filter. The tunable function was achieved by using the electro-birefringence effect of liquid crystal. The result of numerical simulation showed that the spectral resolution was ∼10 nm around bands of 500-700 nm; side forms rejection ratio and FWHM changed in contrast to considering and not considering the birefringence dispersion effect of liquid crystal and quartz; the shape of filtered light displayed by spectral photometer would be affected by spectrum bands of light source in spectral photometer. A four-stage tunable filter was made and tested, experiment results agreed with the numerical simulation results very well, the research results could be applied as reference for the study of broad spectrum tunable filters. 相似文献