The effect of detector size on the extinction coefficient in confocal polarization microscopes

Abstract

SummaryWe consider the effect of detector size on the polarization extinction coefficient in three geometries of confocal microscopes. We find that a single mode optical fibre-based reciprocal system employing circularly polarized light offers great ease of alignment together with an extremely high extinction coefficient.

Focus-engineered coherent anti-Stokes Raman scattering microscopy: a numerical investigation

“…At this juncture, we consider two detection schemes-the coherent and the incoherent. 33,34 The coherent detection scheme involves integrating the far-field radiation amplitude over the acceptance angle of the detection system. It can be realized experimentally by using a single-mode optical fiber for detecting the far-field radiation.…”

Femtosecond Dynamics of Intracellular Water Probed with Nonlinear Optical Kerr Effect Microspectroscopy

“…In conjunction with the collinear geometry, a spectral shift between pump and probe pulses is introduced that allows us to suppress the pumping radiation at the detector stage by means of a spectral filter. Finally, a coherent detection scheme is adopted to compensate for the polarization changes that are inherently induced by the high-numerical-aperture microscope objectives (Higdon et al, 1997).…”

The effect of detector size on the signal‐to‐noise ratio in confocal polarized light microscopy

“…In practice, of course, a finite‐sized pinhole must be used and we would expect the value of extinction coefficient to fall as the pinhole size increases ( Wilson & Tan, 1996). This prediction is borne out in practice and the extinction coefficient falls smoothly between the confocal and conventional limit as the pinhole size is increased ( Higdon et al ., 1997 ). This raises the question of how to choose the optimum pinhole size in confocal polarized light microscopy.…”

“…The confocal microscope is particularly suitable for polarised light studies since it possesses an infinite extinction coefficient if perfect polars and a vanishingly small pinhole are used ( Wilson & Juškaitis, 1995). The extinction coefficient, which is defined as the ratio of the intensity of the light transmitted between parallel polars to that transmitted when the polars are crossed ( Pluta, 1993), is typically restricted to 10 3 in a conventional microscope whereas values as high at 1.4 × 10 5 have been obtained in confocal systems ( Higdon et al ., 1997 ). The reason for the improved performance of the ideal confocal system with vanishingly small pinhole is that the confocal microscope essentially measures the field amplitude in the back focal plane whereas the wide‐field instrument measures the average intensity.…”