Flexible Adaptive Phase Contrast Methods Using a Spatial Light Modulator

Imaging biological objects often is a challenge as most of biological specimens are mainly phase objects. This leads to a reduced contrast. To overcome this problem without using dyes, different phase contrast imaging methods were developed. The most established methods in conventional microscopy are the so-called Zernike phase contrast and Nomarski differential interference contrast (DIC) [1]. To realize those methods in conventional microscopy, different microscopic equipment like special microscope objectives or filters are needed. Each of these methods with their static elements represents a trade-off, as ideal phase contrast imaging depends strongly on the object. A variation of different methods is difficult and expensive. Therefore, we use a phase–only spatial light modulator (SLM) in the pupil plane to realize different phase contrast methods. The filter, which is displayed by the SLM, can be changed and varied pixelwise and, therefore, offers a high flexibility. Additionally, it is possible to adapt the filter to the object and even to vary different methods and their parameters in real time. As there are no mechanical vibrations, it is possible to easily combine those images digitally to benefit from the advantages of different methods.