Volume 77, Issue 6 -

There is a large potential in the field of infrared absorption spectroscopy, particularly if multicomponent mixtures have to be analyzed. A microspectrometer for the spectral range 3–5 μm is presented, which is based on a pyroelectric detector with an integrated MEMS Fabry-Pérot filter. The influence of different optical set-ups on the spectral resolution and the signal-to-noise ratio are discussed.

In recent years, a flexible technology has been developed for the manufacturing of pyroelectric infrared detectors based on lithium tantalate (LiTaO 3 ) allowing the fabrication of detectors with very high signal-to-noise ratios and their customization for particular applications. In this way, ultrathin self-supporting LiTaO 3 layers with film thicknesses of less than 1 μm have been manufactured for high-performance detectors with a maximum specific detectivity D * of more than 5×10 9 cm Hz 1/2 W -1 .

A novel fiber optic sensor interrogation system is developed for the structural and thermal monitoring of Ariane launchers. It is based on a monolithic modulated-grating laser diode that is capable of switching between any two output wavelengths within less than ten nanoseconds. This makes the system very versatile since different sensors in the connected measurement channels can be read out in arbitrary sequence. Therefore sampling rates of single sensors can be adapted independently according to their application. The relation between frequency (wavelength) and time domain during read out of sensors is derived. Performance optimization due to “Time-of-Flight” and “Peak-Tracking” procedures and the consequences for different sample sequences are described. Issues arising from switching between different output wavelengths during operation of the system are discussed in detail and solutions based on software algorithms are presented.

Terahertz- and millimeter waves are electromagnetic waves with a frequency between 100 and 10000 Gigahertz. Most non-conductive materials are transparent at these frequencies, permitting a non-tactile 3D non-destructive testing of the inner structure of modern (plastic-composite-) materials with a sub-millimeter depth and spatial resolution. The all-electronic technology presented here delivers high-quality images in very short measurement times.

Ion mobility spectrometry is a convenient method for the fast detection of gases under atmospheric pressure conditions. Using 63 Ni as ionization source, signals of different substances can interfere, which leads to hardly interpretable spectra. Two-photon laser ionization can overcome such problems. The advantages of this method are demonstrated by the detection of various kinds of hydrocarbons and amines in the trace gas concentration range.

We have developed a new concept for low-cost optical encoders to come up to meet the increasing demand for inexpensive rotary sensors. The principal idea is to use a micro patterned plastic disc with metal coating, as it is used for Compact Discs or DVDs. Such encoder discs can be manufactured by an efficient injection compression moulding process. With this well established technique it is possible to achieve highly precise micro patterns while running a cost effective process for high volume production.