Fizeau interferometers generate an interference between the surface of a test sample and a reference surface that is brought close to the test sample. The interference image is recorded and analysed by an imaging optics system. The contrast and the shape of the interference signals depend, however, on the reflectivity of the test samples. The time and effort required for measuring and analysing the topographies of differently reflecting test pieces is therefore significantly increased.
The method of separating the wavefronts of the reference surface and the test sample surface in the plane of the reference surface – for which a patent has been applied for – uses a new generation of commercially available beam splitters, also called "on-axis beam splitters", which cause a separation of the polarisation directions of the incident light along the optical axis. In comparison with common Fizeau interferometers, this has various advantages. On the one hand, through the generation of polarised light, the measurement can be traced back to a pure two-beam interference. The analysis of the signal is thus significantly facilitated and improved. Classic Fizeau interferometers, however, are based on the analysis of the multiple-beam interference.
On the other hand, by varying the direction of polarisation, a maximum contrast can be set, independent of the reflectivity of the test sample. In contrast to this, in conventional Fizeau interferometers, different reference surfaces with adapted reflectivity must be held available in case the reflectivity of the test samples varies strongly.
In order to increase the accuracy of analysis of common Fizeau interferometers, a variable phase is generated by varying mechanically the distance between the test sample and the reference surface (phase-shifter interferometry). Another advantage of the new method is that such a phase shifting becomes possible through the use of electro-optical components and thus without using mobile parts. Thanks to the increased measuring dynamics achieved in this way, it is, for example, possible to carry out topographical measurements in environments which are subjected to vibrational strain.
The new method allows a facilitated and improved analysis of the measurement data, requires only one calibrated reference surface instead of several, and opens up new possibilities of application in the field of dynamic interferometry. It is particularly suited for measurements on structured or unstructured surfaces with different reflectivities – especially in the optical and semiconductor industry.
Erika Schow | alfa
First Juno science results supported by University of Leicester's Jupiter 'forecast'
26.05.2017 | University of Leicester
Measured for the first time: Direction of light waves changed by quantum effect
24.05.2017 | Vienna University of Technology
Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.
Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....
Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.
The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
24.05.2017 | Event News
23.05.2017 | Event News
22.05.2017 | Event News
26.05.2017 | Life Sciences
26.05.2017 | Life Sciences
26.05.2017 | Physics and Astronomy