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首页> 外文会议>Conference on Laser Applications to Chemical and Environmental Analysis, Feb 11-13, 2000, Santa Fe, New Mexico >A laser-based system for chemical imaging
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A laser-based system for chemical imaging

机译：基于激光的化学成像系统

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摘要

We are currently developing a real-time, laser-based method to provide in situ qualitative and quantitative assessment of hydrocarbon contaminants on metallic surfaces for surface cleaning verification. Many manufacturing techniques require the use of hydrocarbon lubricants that are removed from finished and intermediate products by techniques such as vapor degreasing and solvent cleaning. Not only is the cleaning process laborious and time consuming, commonly used organic solvents are toxic and generate expensive hazardous waste. A rapid surface analysis technique that differentiates hydrocarbons will mitigate these problems by allowing accurate assessment of the type and amount of surface contaminants throughout the cleaning process. The development of an on-line technique will eliminate the need to send process parts out to a separate laboratory, thereby eliminating processing delays. Overall, this will lead to improved alternative cleaning products and processes, and reduction of hazardous materials usage and handling. Currently, the detection of surface contaminants on reflective surfaces is most conveniently and rapidly done by Fourier transform infrared (FTIR) reflectance methods. These non-destructive, non-contacting optical techniques are sensitive to a wide range of organic and inorganic species, and can yield quantitative measurements with appropriate calibration. While an FTIR-based infrared reflectance analysis is able to characterize a very broad range of organic constituents and many inorganic species, a surface-probing FTIR instrument measures a spectrum at only a single small area on a sample, thus requiring broad area surveys to be done by sequentially probing many points. The rate of measurement by FTIR is constrained by the relatively low spectral brightness (compared to a laser) of the incandescent illumination sources used in an FTIR instrument, and makes it necessary to use relatively long integration times to achieve an acceptable signal-to-noise ratio. A position-sensitive FTIR technique also requires the computation of a Fourier transform at each point, further slowing the acquisition rate. A highly desirable characteristic of a cleaning verification instrument is the ability to rapidly survey large surface areas and to determine the location and amount of contaminants during the cleaning process. The laser and imaging system for this application were adapted from a previously developed laser imaging device that was designed for gas leak detection. The present design performs real-time imaging of a broad surface area by infrared laser illumination. Measurements at multiple wavelengths are made by tuning the laser and repeating the image acquisition at each desired wavelength. While detailed spectral maps of a surface can be generated over the laser tuning range, the primary intent of the system is to provide rapid areal surveys at a few key wavelengths that correspond to absorptions by specific contaminants. The specular reflectance is detected by an InSb focal plane array camera (256 x 256 pixels), which allows～65,000 surface points to be made on a timescale of 1/30th of a second.
机译：我们目前正在开发一种基于激光的实时方法，以对金属表面上的碳氢化合物污染物进行原位定性和定量评估，以进行表面清洁验证。许多制造技术要求使用通过诸如蒸汽脱脂和溶剂清洁之类的技术从成品和中间产品中去除的碳氢化合物润滑剂。清洁过程不仅费时费力，而且常用的有机溶剂是有毒的，会产生昂贵的危险废物。通过区分碳氢化合物的快速表面分析技术，可以在整个清洁过程中准确评估表面污染物的类型和数量，从而缓解这些问题。在线技术的发展将消除将过程零件发送到单独实验室的需要，从而消除了处理延迟。总体而言，这将导致改进的替代清洁产品和工艺，并减少有害物质的使用和处理。当前，通过傅里叶变换红外（FTIR）反射率方法最方便，最快速地完成反射表面上表面污染物的检测。这些非破坏性，非接触式光学技术对多种有机和无机物敏感，并且可以通过适当的校准进行定量测量。尽管基于FTIR的红外反射分析能够表征非常广泛的有机成分和许多无机物，但表面探测FTIR仪器只能在样品的单个小区域上测量光谱，因此需要进行广域测量通过依次探测许多点来完成。 FTIR的测量速率受FTIR仪器中使用的白炽灯光源相对较低的光谱亮度（与激光相比）的约束，因此必须使用较长的积分时间才能获得可接受的信噪比比。位置敏感的FTIR技术还需要在每个点上进行傅立叶变换的计算，从而进一步降低了采集速率。清洁验证仪器的高度期望的特性是能够在清洁过程中快速调查大表面积并确定污染物的位置和数量。用于此应用的激光和成像系统是从先前开发的用于气体泄漏检测的激光成像设备改编而来的。本设计通过红外激光照射对宽表面积进行实时成像。通过调谐激光器并在每个所需的波长处重复图像采集，可以在多个波长下进行测量。虽然可以在激光调谐范围内生成表面的详细光谱图，但该系统的主要目的是在与特定污染物的吸收相对应的几个关键波长下提供快速的面积测量。镜面反射率由InSb焦平面阵列相机（256 x 256像素）检测，可以在1/30秒的时间范围内制作约65,000个表面点。

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