1,720,968 research outputs found
Advanced optical systems for imaging and fabrication
No full textAdvanced optical systems for imaging and fabricatio
Enhanced volumetric imaging in 2-photon microscopy via acoustic lens beam shaping
No full textThree-dimensional imaging at high-spatiotemporal resolutions and over large penetration depths is key for unmasking the dynamics and structural organization of complex biological systems. However, the need to axially shift the focus, with consequent limitations in imaging speed, and signal degradation at large depths due to scattering effects, makes this task challenging. Here, we present a novel approach in 2-photon excitation microscopy that allows fast volumetric imaging and enhanced signal-to-background (S/B) in thick tissue. Our technique is based on ultrafast beam shaping at each pixel by means of an acoustic optofluidic lens. Shaping the excitation beam with different phase profiles enables both high-speed axial focus shifting, for continuous volumetric imaging, and controlled aberrated imaging, advantageous for out-of-focus background removal. We provide a theoretical description of our approach, and demonstrate volumetric imaging of neuronal cells from a mouse brain slice with enhancements in S/B up to a factor of 10 over a depth of 600Î1⁄4m
Inside Front Cover: Enhanced volumetric imaging in 2-photon microscopy via acoustic lens beam shaping (J. Biophotonics 2/2018)
No full textAbstract image Two-photon microscopy is the tool of choice for fluorescence imaging of deep tissues with high resolution, but can be limited in three-dimensional acquisition speed and penetration depth. In this work, these issues are addressed by using an acoustic
optofluidic lens capable of ultrafast beam shaping on a pixel basis. Driving the lens with different phase profiles enables high-speed volumetric imaging, or enhanced signal-to-background for deeper penetration. Further details can be found in the article by Simonluca
Piazza et al.(e201700050
Towards nanopatterning by femtosecond laser ablation of pre-stretched elastomers
No full textDiffraction limits the focusing capabilities of an optical system seriously constraining the use of lasers for nanopatterning. In this work, we present a novel and simple approach to reduce the minimum feature size of a laser-direct write system by ablating a pre-stretched material. In particular, by focusing and scanning a femtosecond laser beam on the surface of a uniaxially pre-stretched elastomeric membrane we are able to obtain microstructures according to a desired pattern. After removing the stress applied to the elastomer, the membrane relaxes to its original size and the ablated patterns shrink while preserving their shape. In this way, the minimum feature size that is typically determined by the optical properties of the focusing system can be now controlled by the strain applied to the elastomer during the ablation process. We demonstrate this approach by ablating lines on a stretchable polymeric membrane at different strain conditions. Experimental results are in good agreement with theoretical predictions. The proposed method opens up new interesting possibilities for the rapid prototyping of micro- and nano-structures suitable for a wide range of applications such as soft-lithography, micro-/nano-fluidics and lab-on-chip
Fast Volumetric Imaging in Two-Photon Microscopy and Enhanced Background Rejection using an Acoustic Lens
No full text
Optical-Quality Assessment of a Miniaturized Intraocular Telescope
No full textAge-related macular degeneration (AMD) causes severe vision impairments, including blindness. An option to improve vision in AMD patients is through intraocular lenses and optics. Among others, implantable miniaturized telescopes, which direct light to healthy lateral regions of the retina, can be highly effective in improving vision in AMD patients. Yet, the quality of the restored vision might be sensitive to the optical transmission and aberrations of the telescope. To shed light on these points, we studied the in vitro optical performance of an implantable miniaturized telescope, namely, the SING IMT™ (Samsara Vision Ltd., Far Hills, NJ, USA) designed to improve vision in patients affected by late-stage AMD. Specifically, we measured the optical transmission in the spectral range 350–750 nm of the implantable telescope with a fiber-optic spectrometer. Wavefront aberrations were studied by measuring the wavefront of a laser beam after passing through the telescope and expanding the measured wavefront into a Zernike polynomial basis. Wavefront concavity indicated that the SING IMT™ behaves as a diverging lens with a focal length of −111 mm. The device exhibited even optical transmission in the whole visible spectrum and effective curvature suitable for retinal images magnification with negligible geometrical aberrations. Optical spectrometry and in vitro wavefront analysis provide evidence supporting the feasibility of miniaturized telescopes as high-quality optical elements and a favorable option for AMD visual impairment treatments
Direct Laser Printing of Tailored Polymeric Microlenses
No full textWe
report a laser-based approach for the fast fabrication of high-optical-quality
polymeric microlenses and microlens arrays with controllable geometry
and size. Our strategy consists of the direct laser printing of microdroplets
of a highly viscous UV prepolymer at targeted positions, followed
by photocuring. We study the morphological characteristics and imaging
performance of the microlenses as a function of the substrate and
laser parameters and investigate optimal printing conditions and printing
mechanisms. We show that the microlens size and focusing properties
can be easily tuned by the laser pulse energy, with minimum volumes
below 20 fL and focal lengths ranging from 7 to 50 μm
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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