Imaging with photoelastic modulators

Elastic instabilities in planar elongational flow of monodisperse polymer solutions

“…A 5× objective lens is used to focus light from the midplane of the OSCER device onto a 2048 × 2048 pixel, 12-bit CCD array (which provides a field of view ≈ 2 × 2 mm and hence a spatial resolution of ≈ 1 μ m/pixel). A stroboscopic illumination technique 95 96 is used to determine the elements of the 4 × 4 Mueller matrix P necessary to compute the pixelwise sample retardance δ and angle of the high refractive index (i.e. slow) optical axis θ over the full field of view:…”

“…To compute the required elements of the Mueller matrix, the CCD camera records a total of seven frames, each accumulated over ≈1 s, and each with the light source modulated in order to sample specific polarization states achieved within the PEM cycle 96 . The spatially-resolved birefringence of the sample is obtained as follows:…”

Relaxation time of dilute polymer solutions: A microfluidic approach

“…This instrument is based on a dual photoelastic modulator system and can make full-field quantitative birefringence images using a seven-frame image processing algorithm [55,56]. The seven individual images required for the birefringence determination are captured at a rate of 1 frame per second onto a 2048 Â 2048 pixel 16-bit CCD array.…”

Polarized light imaging in biomedicine: emerging Mueller matrix methodologies for bulk tissue assessment

“…60 PEMs can only modulate the retardance in a sinusoidal fashion; however, they have larger clear aperture well suited for imaging over a large field of view. 67,69 Snapshot systems, based on diffractive components, are the fastest, but they use spatial frequency filters, which reduce the amount of imaging information and may be suboptimal for high-resolution imaging over a large field of view. 70 One emerging direction in polarized light imaging is combining the measurement instruments with wide-field depth-resolved techniques.…”

“…Polarization can be modulated electronically by liquid crystals (LCs) or photoelastic modulators (PEMs), mechanically by rotating linear polarizers and quarter waveplates, and by diffraction using polarizing prisms, gratings, or graded index lenses. [59][60][61][62][63][64][65][66][67][68][69][70][71][72] In recent years, the field has witnessed many advanced designs and approaches, and there have been several demonstrations of using these novel systems for imaging biological tissues (Fig. 3).…”