Developing high resolution imaging techniques based on fluorescence microscopy is a highly topical field of research (Nobel Prize in Chemistry in 2014). Our research focusses on further developing techniques, which provide highest lateral resolution, three dimensional imaging as well as confocal laser scanning microscopy.
In structured illumination microscopy (SIM) high spatial frequencies of the sample (finer object structures) are down-modulated into the transfer band of the objective by applying a stripe shaped illumination pattern. Hence structured illumination improves the resolution. The research work, regarding SIM focuses on:
A second approach in order to enhance the resolution is direct stochastic optical reconstruction microscopy (dSTORM). In dSTORM a series of images is recorded. At each image only a small fraction (statistically determined) of all fluorophores is emitting light. Due to the sparse emission pattern, the emission centers can be determined with very high accuracy. The high resolution image is subsequently reconstructed by superposing all frames of the series.
Currently we aim for combining this method with automated multiple staining and image recording steps in order to develop a systematically working high resolution analysis tool.
The third pillar of our research on fluorescence microscopy is laser scanning microscopy (LSM). There we focus on two approaches for enhancing the resolution provided by typical confocal techniques:
We work on different approaches in order to develop alternative microscopic methods. On the one hand they complement the methods from fluorescence microscopy. On the other hand they aim for extending known as well as developing new techniques.
Particularly high resolution microscopy requires a complex post record image processing. Thus our research also focusses on new and further development of theoretical approaches for image processing as well as their implementation:
The main issue is the detection of light absorption in optical materials and coatings with sub-ppm sensitivity. In order to achieve this high sensitivity, we have developed the LID technique (LID… laser induced deflection, patent-registered), which is based on the photo thermal effect. The LID possesses an independent absolute calibration, which is superior compared to other photo thermal methods. Combining the LID technique with laser induced fluorescence (LIF) helps to investigate a multitude of questions in material science, such as investigating the interaction between laser irradiation and optical materials, as well as dielectric optical coatings.
We apply the Cavity Ring-Down (CRD) technique in order to determine smallest optical losses. This enables for instance the precise determination of highest mirror reflectance (R>> 99.9%). In combination with the LID method we are also able to assign the losses to their particular origin (scattering, absorption).
Apart from scientific projects, our multitude of available laser sources/wavelengths allows offering a broad range of measurement services for optical material and coating characterization.
Following the institute’s guiding idea "From Ideas To Instruments", both, the LID - as well as the CRD technique have been transferred recently into commercial prototypes/systems – partially based on an external partner.