Microlenses have been implemented in confocal systems successfully as components of aperture arrays and as arrays of objective lenses. The use of the novel technology of variable focal length (VFL) microlenses in the confocal system has also shown potential. The properties of the VFL microlenses are controlled by the physical and chemical parameters of the microlenses. Arrays of microlenses with varying parameters are fabricated and their characteristics tuned to meet the demands of confocal microscopy.
We present the investigation of integration of Variable Focal Length (VFL) microlenses into the confocal system. VFL microlenses acting as an array of objective lenses is examined with a novel method for scanning in the axial direction presented. By variation of the focal length of the lenses the focal plane can be scanned through the sample without the mechanical movement of the sample or the objective lens, we have named this 'focal scanning'. Some of the issues related to this experiment are noted and discussed, in particular with reference to the low Numerical Aperture (NA) of the VFL microlenses available. Proposed solutions to these issues deal with the design of higher NA microlenses.
In this paper, we experimentally studied both the bright-field and fluorescence images of microspheres by conventional and confocal scanning polarization microscopes. A qualitative analysis have been given to show a physical picture on the imaging of the microspheres. Emission spectra from melamine formaldehyde microspheres stained with Ethidium Bromide or covered by thin shell of CdTe nanocrystals have been experimentally studied. We adopted analytical expressions describing the resonance spacing in order to determine the size of the microspheres.
Microlenses have been implemented in confocal systems successfully as components of aperture arrays and as arrays of objective lenses. The use of the novel technology of variable focal length (VFL) microlenses in the confocal system is investigated. The use of VFL microlenses as an aperture array in conjunction with an optical fiber as a pinhole array is examined. Axial responses of the system where measured and the Full-Width Half Maximum (FWHM) found to be ~16μm.
VFL microlenses as an array of objective lenses is investigated with a novel method for scanning in the axial direction presented. By variation of the focal length of the lenses the focal plane can be scanned through the sample without the mechanical movement of the sample or the objective lens, we have named this 'focal scanning'. It is shown that the limiting factor with this type of scanning is the low numerical aperture (NA) of the microlenses available. Both focal scanning and conventional scanning are examined for this experimental set-up.
Confocal microscopy has a unique optical sectioning property which allows three-dimensional images at different depths. Use of a microlens array is a potential alternative to the Nipkow disk for parallel imaging with high throughput in real-time confocal microscopy. The use of variable-focal-length microlenses can provide a way to axially scan the foci electronically avoiding the inflexible mechanical movement of the lens or the sample. Here we demonstrate a combination of a variable-focal-length microlens array and a fiber optic bundle as a way to create a high throughput aperture array that would be potentially applied as confocal imaging in vivo biological specimens. Variable focal length microlenses that we use consist of a liquid crystal film sandwiched between a pair of conductive substrates with patterned electrodes. The incident side of the microlens array was determined by examining the focus distribution in the axial direction. The variation of the focal length obtained by changing the voltage and corresponding focus intensity were measured through a conventional microscope. Meanwhile, the fiber bundle was characterized by coupling with either coherent or incoherent light source. We use the fiber bundle as both a multiple aperture and an image-carrying element and combine it with a microlens array to built up a confocal system. Axial responses are measured in two optical arrangements as a route to investigate endoscope potential.