Imaging Spectrometers for Fluorescence and Raman Microscopy: Acousto-Optic and Liquid Crystal Tunable Filters

Abstract

Acousto-optic tunable filters (AOTF) and liquid crystal tunable filters (LCTF) are evaluated for their suitability as fluorescence microscopy imaging spectrometers. AOTFs are solid-state birefringent crystals that provide an electronically tunable spectral notch passband in response to an applied acoustic field. LCTFs also provide a notch passband that can be controlled by incorporating liquid crystal waveplate retarders within a Lyot birefringent filter. In this paper, spectroscopic performance and imaging quality are contrasted by evaluation of model systems. Studies include transmission imaging of standard resolution targets, multispectral fluorescence emission imaging of tagged polystyrene microspheres, and immunofluorescence imaging of neurotransmitters within rat-brainstem thin sections. In addition, the first use of LCTFs for Raman microscopy is demonstrated. Raman microscopy is a noninvasive spectral imaging technique that can provide chemically significant image contrast complementary to fluorescence microscopy without the use of stains or tags.

High Throughput AOTF Hyperspectral Imager for Randomly Polarized Light

“…Both have been studied previously for a number of applications, including fluorescence and Raman microscopy [31], as well as laser-induced breakdown spectroscopy [32]. In this study, we report the comparison between both filters for hyperspectral imaging in (1) spectral resolution; (2) spectral selectivity; (3) reliability and image quality; and (4) spatial resolution [33].…”

Hyperspectral Raman imaging using Bragg tunable filters of graphene and other low‐dimensional materials

“…They generate, however, low to medium throughput because of the characteristics of these filters, which include poor transmission, low polarization sensitivity, and limited spectral dynamic range. [25] Fiber-array spectral translation, dimension reduction arrays or any other technology based on an array of optical fibers have been designed to improve on those hurdles and for acquiring at very high speed wide-field Raman images over the entire region of interest. [22] The local signal acquired in parallel by all the fibers is diffracted by a grating onto a CCD detector.…”

Real-time hyperspectral fluorescence imaging of pancreatic β-cell dynamics with the image mapping spectrometer (IMS)

“…hyperspectral confocal microscope (Sinclair et al, 2006) or in the spectral domain, e.g. liquid-crystal tunable filter or acoustic-optic tunable filter (Morris et al, 1994). The scanning mechanism causes a serious trade-off problem between image acquisition rate and signal throughput -the faster the imager scans, the fewer photons it can collect from each spatial sampling pixel or spectral sampling layer.…”