Video rate widefield sensitive polarized light microscopy by spectrally structured illumination

In this Letter, we propose a setup to realize quantitative and sensitive widefield microscopy of optical retardation and azimuth of a birefringent specimen at video rate. The originality of the technique lies in the spectral structuration of the microscope illumination using spectral coding of polarization. The optical retardation and azimuth map of the specimen are obtained from a combination of three intensity images captured after successive illumination of the microscope by three phase-shifted spectrally structured spectra from light-emitting diodes (LEDs). The high commutation speed of the LEDs and the passive nature of all optical elements allow the acquisition at video rate and potentially more.