Infrared analysis is a well-established tool for measuring composition and purity of various materials in industrial-, medical-and environmental applications. Traditional spectrometers, for example Fourier Transform Infrared (FTIR) Instruments are mainly designed for laboratory use and are generally, too large, heavy, costly and delicate to handle for remote applications. With important advances in the miniaturization, ruggedness and cost efficiency we have designed and created a new type of a micromirror spectrometer that can operate in harsh temperature and vibrating environments This device is ideally suited for environmental monitoring, chemical and biological applications as well as detection of biological warfare agents and sensing in important security locations In order to realize such compact, portable and field-deployable spectrometers we have applied MOEMS technology. Thus our novel dual detector micro mirror system is composed of a scanning micro mirror combined with a diffraction grating and other essential optical components in order to miniaturize the basic modular set-up. Especially it periodically disperses polychromatic radiation into its spectral components, which are measured by a combination of a visible (VIS) and near infrared (NIR) single element detector. By means of integrated preamplifiers high-precise measurements over a wide dynamic wavelength range are possible. In addition the spectrometer, including the radiation source, detectors and electronics can be coupled to a minimum-volume liquid or gas-flow cell. Furthermore a SMA connector as a fiber optical input allows easy attachment of fiber based probes. By utilizing rapid prototyping techniques, where all components are directly integrated, the micro mirror spectrometer is manufactured for the 700 -1700 nm spectral range. In this work the advanced optical design and integration of the electronic interface will be reviewed. Furthermore we will demonstrate the performance of the system and present characteristic measurement results. Finally advanced packaging issues and test results of the device will be discussed.
Mid infrared spectroscopy has been developed to a powerful and essential method of material analysis, with a steadily increasing number of industrial and scientific application fields. The so called spectral fingerprint range enables identification of chemical compounds by their unique spectral pattern. To provide a suitable miniaturized and portable MIR spectrometer solution at an affordable price, an existing MEMS NIR spectrometer module which already bases on micro system technology has been expanded in its wavelength range. The developed spectrometer belongs to the category of scanning grating spectrometers. Main component is a fast oscillating micro-mirror which moves sinusoidal with high mechanical precision enabling a high stability of according wavelength axis. This is supported by a highly precise optical tracking of the actual motion. Mono-crystalline silicon guarantees a long-life operation with no wear even under harsh environmental conditions. Spectral sign al acquisition is realized by using a TE-cooled MCT single element detector assisted by low noise trans-impedance amplifier. With the help of integrated logic components a data pre-processing takes place, such as averaging, offset subtraction, detector transfer characteristic correction and noise shaping. Due the compact and flexible setup, the spectrometer is suitable for the use in various applications, such as process control in chemical industry, gas mixture analysis or liquid verification. The portability of the device opens up new application possibilities in mobile environment. The advances of the promising technology and its specific applications will be described in this paper. Advanced performance issues of the device be reviewed in detail
Quantitative determination of gas compositions are important for operation and control of different industrial processes, e.g. in thermo process line operations. Changing gas conditions are affecting such processes significantly. Thus direct measurement of these gases enables adjustment of variable gas composition very fast and precisely and can improve process and product quality. Traditional analyzers, designed primarily for laboratory use, are too large, too delicate, and too costly to deploy. Cost efficient devices can however measure individual parameters (e.g. IR absorption at a specific wavelength, heat conductivity etc.) of gases and compositions can be derived directly by calculating it online. To bridge the gap between these traditional and expensive gas analyzers and favorable, cost-effective gas measurements, we have developed a low cost MEMS-based gas analyzer system. By using near infrared spectroscopy, individual components of the mixed gas can be determined quantitatively. Also disadvantages of existing cost-effective systems like selectivity, sensitivity and measurement time is avoided. Requirements of a suitable system are precise determination and adoption of the overall optical system as well as a high wavelength stability, which represents one important condition for exact chemometric evaluation. Likewise a robust and exact spectral evaluation procedure is important. Other challenges are MEMS design and packaging as well as optimization of insensitivity against vibrations and thermal stress. In this paper, the application of MEMS analyzer in gas measuring is described and above mentioned challenges will be discussed. To demonstrate the performance of the whole system, measurement results of gas mixtures will be shown
The spectroscopy market is enduring and growing one, in which the near infrared spectroscopy by means of the advances plays an important and indispensable role. Some nameable advances are the noninvasive character, the rapidity, which allows real-time measurements or the flexible sampling and sample presentation. To establish near infrared spectroscopic methods and tests at a wide variety of applications new technological innovations are necessary. One of these technological innovations is a modern scanning micro mirror spectrometers. We have developed a small sized, light weight MOEMS-spectrometers for different spectral regions which are due to the optical parameters less expensive, more flexible and offer better performance than traditional spectrometers even yet. The central component of the optical set-up is a large area scanning micro mirror, which oscillates in resonance with 250Hz. Thus, to record a single spectrum only 4 milliseconds are necessary. One of the important factors of NIR spectroscopy, which affects qualitative and quantitative determination, is the sample presentation. For optimal signal processing different sample presentation techniques such as transmission and flow cells, integrating spheres and attenuated total reflection (ATR) probes were realized. Consequently in combination with chemometric methods e.g. partial least square or principal component analysis several applications could be performed and investigated. This article describes the principles and the advances of the promising technology as well as some realized applications. Furthermore influences of the sample presentation and calibration procedures will be discussed closer
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