Microoptical components play an increasing role in different technology fields such as medical engineering, materials
and information processing, imaging and metrology. But their realization needs the combination of modern design
concepts with sophisticated processing technologies, new materials and design tools. Furthermore, the introduction of
ambitious processing technologies must be accompanied by effective metrology and inspection tools. Therefore, this
paper reports about the technologies for making microoptics at ITO. Because sophisticated measurement tools are an
indispensable part of the fabrication process, the paper describes our multi-scale inspection approach for the testing of
microstructures on wafer-scale level. Finally, some representative applications of microoptical components for advanced
measurement and imaging are explained.
Recent lithographic technologies allow for the fabrication of high period diffractive structures on planar and curved
optical surfaces with high precision. Such diffractive surfaces offer the optical designer extra degrees of freedom, which
are of special importance for optical systems, where light collection efficiency is important. We illustrate the usage and
benefit of diffractive elements within fast optical systems in various applications. For these hybrid design classes it is
mandatory to include the realistic as-built performance of the employed diffractive elements into the design phase.
Correspondingly we present simulation techniques to include fabrication specific diffraction efficiencies and stray light
into the optimization and evaluation process.
Many laser applications, for example material processing or fluorescence imaging, require intense and uniform
illumination over a rectangular, slit shaped area with extreme aspect ratio: The short dimension of the illumination field
typically requires diffraction limited imaging, respectively focusing, on a micrometer scale. In contrast the extension in
the long dimension can be hundreds of millimeters. This class of systems requires a highly anamorphic system design for
the homogenization as well as for the projection of the illumination pattern. Aberrations within the projection optical
system, as for example induced by cylindrical optical components, need to be analyzed and controlled. In some cases the
application additionally requires the substrate to be illuminated under some tilted angle, which requires specific solutions
within the optical design. We will illustrate corresponding design examples and solutions for this class of illumination systems.
Optical metrology has shown to be a versatile tool for the solution of many inspection problems. The main advantages of
optical methods are the noncontact nature, the non-destructive and fieldwise working principle, the fast response, high
sensitivity, resolution and accuracy. Consequently, optical principles are increasingly being considered in all steps of the
evolution of modern products. However, the step out of the laboratory into the harsh environment of the factory floor
was and is a big challenge for optical metrology. The advantages mentioned above must be paid often with strict
requirements concerning the measurement conditions and the object under test. For instance, the request for
interferometric precision in general needs an environment where high stability is guaranteed. If this cannot be satisfied to
a great extent special measures have to be taken or compromises have to be accepted. But the rapid technological
development of the components that are used for creating modern optical measurement systems, the unrestrained growth
of the computing power and the implementation of new measurement and inspection strategies give cause for optimism
and show that the high potential of optical metrology is far from being fully utilized. In this article current challenges to
optical metrology are discussed and new technical improvements that help to overcome existing restrictions are treated.
On example of selected applications the progress in bringing optical metrology to the real world is shown.
Time-resolved observation of the fuel/air mixing process prior to ignition is crucial for the development of modern internal combustion engine concepts. The presented fiber optic sensor is designed for the acquisition of in-cylinder data in the area close to the ignition spark, based on UV-laser-induced fluorescence of organic fuel compounds. Excitation and fluorescence light are separately guided through silica fibers. The detection volume is defined by the optical design of the sensor head. Since the related components are completely integrated into a modified spark plug, the sensor can be applied to unmodified production line engines. We present the fundamental spectroscopic concept, the solution for the minimal invasive access through the spark plug and tracer spectra measured with a prototype.