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 signal 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.
Due to climate protection and increasing oil prices, renewable energy is becoming extremely important. Anaerobic digestion is a particular environmental and resource-saving way of heat and power production in biogas plants. These plants can be operated decentralized and independent of weather conditions and allow peak load operation. To maximize energy production, plants should be operated at a high efficiency. That means the entire installed power production capacity (e.g. CHP) and biogas production have to be used. However, current plant utilization in many areas is significantly lower, which is economically and environmentally inefficient, since the biochemical process responds to fluctuations in boundary conditions, e.g. mixing in the conditions and substrate composition. At present only a few easily accessible parameters such as fill level, flow rates and temperature are determined on-line. Monitoring of substrate composition occurs only sporadically with the help of laboratory methods. Direct acquisition of substrate composition combined with a smart control and regulation concept enables significant improvement in plant efficiency. This requires a compact, reliable and cost-efficient sensor. It is for this reason that a MEMS sensor system based on NIR spectroscopy has been developed. Requirements are high accuracy, which is the basic condition for exact chemometric evaluation of the sample as well as optimized MEMS design and packaging in order to work in poor environmental conditions. Another issue is sample presentation, which needs an exact adopted optical-mechanical system. In this paper, the development and application of a MEMS-based analyzer for biogas plants will be explained. The above mentioned problems and challenges will be discussed. Measurement results will be shown to demonstrate its performance.
Driven by the demand of miniaturized and highly integrated functionalities in the area of photonics and photonic circuits,
the metal or plasmon optics has become a promising method for manipulating light at the nanometer scale.
Especially the application of periodic sub wavelength hole structures within an opaque metal film on a dielectric
substrate holds many advantages for the realization of optical filters, since the variation of the hole diameter and the
periodicity allows a selective filter response.
This paper is concerned with the modeling, fabrication and characterization of a sub wavelength hole array for surface
plasmon enhanced transmission of light . The theoretical backgrounds as well as the basics of the simulation by
Finite-Difference Time-Domain (FDTD) are described for the target structure with a hole diameter of 180 nm and a
periodicity of 400 nm.
By using a double-molding technology via nanoimprint lithography the fabrication of this sub wavelength hole array
with a peak wavelength of 470 nm and full width at half maximum of 50 nm from a silicon nanopillar master is
demonstrated. In order to ensure the dimensional stability of the molded structures, characterization was consequently
done by means of a self made non-contact mode atomic force microscope.
Contactless measurement of temperatures has gained enormous significance in many application fields, ranging from
climate protection over quality control to object recognition in public places or military objects. Thereby measurement of
linear or spatially temperature distribution is often necessary.
For this purposes mostly thermographic cameras or motor driven temperature scanners are used today. Both are
relatively expensive and the motor drive devices are limited regarding to the scanning rate additionally. An economic
alternative are temperature scanner devices based on micro mirrors. The micro mirror, attached in a simple optical setup,
reflects the emitted radiation from the observed heat onto an adapted detector. A line scan of the target object is
obtained by periodic deflection of the micro scanner. Planar temperature distribution will be achieved by perpendicularly
moving the target object or the scanner device. Using Planck radiation law the temperature of the object is calculated.
The device can be adapted to different temperature ranges and resolution by using different detectors - cooled or uncooled
- and parameterized scanner parameters. With the basic configuration 40 spatially distributed measuring points
can be determined with temperatures in a range from 350°C - 1000°C.
The achieved miniaturization of such scanners permits the employment in complex plants with high building density or
in direct proximity to the measuring point. The price advantage enables a lot of applications, especially new application
in the low-price market segment
This paper shows principle, setup and application of a temperature measurement system based on micro scanners
working in the near infrared range. Packaging issues and measurement results will be discussed as well.
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.
Near Infrared (NIR) spectroscopy has developed to an important and useful analysis method over the past years. The existence of compact, portable devices offers a lot of applications possibilities, even in harsh environments. Compact devices, mostly based on detector arrays, are quite costly caused by the expensive Indium Gallium Arsenide (InGaAs) detector arrays. By using MOEMS the set-up can be realised much more efficiently. With an adapted optical set-up detector arrays can be replaced by single element detectors. We have realised a new miniaturised spectrometer based on a scanning micro mirror. The mirror is combined with a diffraction grating and other optical components. It periodically disperses the polychromatic radiation into its spectral components. The radiation is measured by an InGaAs-single element detector, which can be thermoelectrically cooled depending on the application. The radiation coupling is possible either directly or by using fiber optics. It allows an easy attachment of substance samples for reflectance measurements as well as attenuated total reflection (ATR) probes, cuvette holders and flow cells. Lowest noise preamplifiers enable high-precise measurements over a wide dynamic range. With a spectral range of 1000 - 2100 nm and a spectral resolution of approx. 12 nm the device is able to fulfill various requirements. Applications for food stuff industry; clinical chemistry and identification of polymers were tested and will be discussed. Furthermore we will show the advanced optical and mechanical design. In addition advanced performance issues and reliability test results of the device will be reviewed.
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.
Modern optical analytics require more and more compact and cost-effective modules for analysis of surfaces, solids, thin films, powders, pastes, gels, liquids and alike. Thereby a fast and non-invasive measurement is often necessary. Microsystem technology, more precisely Micro-Opto-Electro-Mechanical System (MOEMS) technology is suitable for the realization of such modules. Different miniaturized optical analyzers employing MOEMS have been developed at the Fraunhofer Institute for Reliability and Microintegration (IZM) in collaboration with the Center for Microtechnologies (ZfM) and the company COLOUR CONTROL Farbmesstechnik GmbH. These devices are based on the principle of spectral sensing in the infrared range. Due to the requirement of compact dimensions and short optical paths a high packaging accuracy is necessary. In the development process different setups with a continuous packaging improvement have been realized. The first packaging principle was based on particularly assembled laser-cut stainless steel sheets and optical standard components. The design requires exact positioning of the functional elements to attain a sufficient optical resolution. The reduction of the active components by means of monolithic combinations was one improvement. Further progress could be achieved by a package made of aluminum cast, whose models were provided using modern methods of rapid prototyping. Consequently adjustment tolerances will be minimized and the vibration stability will be increased. During the development process, simulations and characterization of the system are essential to obtain necessary improvements. Thereby an evaluation of the packaging accuracy regarding its influence on the defocus was made. According to precision and reproducibility, the optical and electrical performance are being tested.
In modern optical diagnostics there is an increasing interest in compact and cost-effective devices, i.e. for the analysis of surfaces, thin films, solids, powders, pastes, gels, liquids and alike. Therefore fast and non-invasive measurements are necessary. For the realization of such devices, micro system technology especially Micro-Opto-Electro-Mechanical System (MOEMS) technology is suitable. Hence two main miniaturized optical analyzer modules employing MOEMS have been developed. They are based on the principle of spectral sensing in the infrared range by means of a scanning
micro mirror with an integrated diffraction grating or in combination with a separate grating. Using these configurations it is possible to project a specific wavelength onto an exit slit in front of an infrared detector. The first packaging approach is based on assembled laser-cut stainless steel sheets and optical standard components. During the further development different setups with improved reliability and accuracy have been realized. Due to the requirement of
compact dimensions and short optical paths modern methods e.g. rapid prototyping were utilized to optimize packaging and optical setup and therefore the performance of the complete system. In this work the characteristics and the measurement results of different development levels will be reviewed. Furthermore we address issues, challenges and
performance optimization of MOEMS packaging with respect to ultra compact micro mirror spectrometers. Finally, the applications and the feasibility of such miniaturized spectrometer systems are discussed.
The field of microtechnology is an important industrial and scientific resource for the 21st century. There is a great interest in spectroscopic sensors in the near and middle infrared (NIR-MIR) wavelength regions (1 - 2.5 micrometers ; 2.5 - 4.5 micrometers ; 4 - 6 micrometers ). The potential for cheap and small devices for nondestructive, remote sensing techniques at a molecular level has stimulated the design and development of more compact analyzer systems. Therefore we will try to build analyzers using micro optical components such as micromirrors and embossed micro gratings optimized for the above mentioned spectral ranges. Potentially, infrared sensors can be used for rapid nondestructive diagnostics of surfaces, liquids, gases, polymers and complex biological systems including proteins, blood, cells and cellular debris as well as body tissue. Furthermore, NIR-MIR microsensing spectroscopy will be utilized to monitor the chemical composition of petrochemical products like gasoline and diesel. In addition, miniature analyzers will be used for rapid measuring of food, in particular oil, starch and meat. In this paper we will present an overview of several new approaches for subsurface and surface sensing technologies based on the integration of optical micro devices, the most promising sensors for biomedical, environmental and industrial applications, data processing and evaluation algorithms for classification of the results. Both scientific and industrial applications will be discussed.