Polarization Microscopy - Biomedical Optical Phase Microscopy and Nanoscopy - page 311

acquisition and processing algorithms relate measured image intensities and compensator
settings to optical characteristics of the specimen (e.g., [18] ). Here we discuss in more
detail the LC-PolScope, a birefringence imaging system that was first developed at the
Marine Biological Laboratory (MBL) and is commercially available from CRi Inc. (Now
part of Caliper Life Sciences and PerkinElmer, http://www.caliperls.com/ ) .
The optical design of the LC-PolScope builds on the traditional polarized light microscope,
introducing two essential modifications: the specimen is illuminated with nearly circularly
polarized light and the traditional compensator is replaced by a liquid crystal-based universal
compensator. The LC-PolScope also requires the use of narrow bandwidth ( # 40 nm) or
monochromatic light. In Figure 15.6 , the schematic of the optical train shows the universal
Figure 15.6
LC-PolScope. The optical design (left) builds on the traditional polarized light microscope with
the conventional compensator replaced by two variable retarders LC-A and LC-B. The polarization
analyzer passes circularly polarized light and is typically built from a linear polarizer and a quarter
wave plate. Images of the specimen (top row, aster isolated from surf clam egg) are captured at
five predetermined retarder settings, which cause the specimen to be illuminated with circularly
polarized light (first, left-most image) and with elliptically polarized light of different axis
orientations (second to fifth image). Based on the raw PolScope images, the computer calculates
the retardance image and the slow axis orientation or azimuth image using specific algorithms
[18] . The false-color image on the right was created by combining the retardance and slow axis
orientation data, with the orientation encoded as hue and the retardance as brightness.
(For interpretation of the references to color in this figure legend, the reader is referred to the
web version of this topic.)