Polychromatic polarization microscope: bringing colors to a colorless world.

Michael Shribak

doi:10.1038/srep17340

Abstract

Interference of two combined white light beams produces Newton colors if one of the beams is retarded relative to the other by from 400 nm to 2000 nm. In this case the corresponding interfering spectral components are added as two scalars at the beam combination. If the retardance is below 400 nm the two-beam interference produces grey shades only. The interference colors are widely used for analyzing birefringent samples in mineralogy. However, many of biological structures have retardance <100 nm. Therefore, cells and tissues under a regular polarization microscope are seen as grey image, which contrast disappears at certain orientations. Here we are proposing for the first time using vector interference of polarized light in which the full spectrum colors are created at retardance of several nanometers, with the hue determined by orientation of the birefringent structure. The previously colorless birefringent images of organelles, cells, and tissues become vividly colored. This approach can open up new possibilities for the study of biological specimens with weak birefringent structures, diagnosing various diseases, imaging low birefringent crystals, and creating new methods for controlling colors of the light beam.

Highlights

We developed a new polychromatic polarized light microscope that produces interference colors at retardance of several nm
Traditional Newton colors require that the interfering beams with the same polarization states, and the beam amplitudes are added as two scalars
The optical design of polychromatic polscope is based on a standard polarized light microscope equipped with special spectral polarization state generator and analyzer

Summary

Introduction

We developed a new polychromatic polarized light microscope (polychromatic polscope) that produces interference colors at retardance of several nm. Traditional Newton colors require that the interfering beams with the same polarization states, and the beam amplitudes are added as two scalars. In our approach of generating interference colors we utilize the beam polarization and amplitudes of the interfering beams, which are added as two vectors. In polychromatic polscope the hue is determined by the orientation of the birefringent structure, not by its retardance. The polychromatic polscope shows the orientation-independent birefringence image without requiring any digital computation. An eye or camera can directly see the colored polarization image in real time through the ocular with brightness corresponding to retardance and color corresponding to the slow axis orientation. Colorless organelles, cells, and tissues birefringent images become vividly colored

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