Axial scanning in confocal microscopy employing adaptive lenses (CAL)

Abstract

In this paper we analyze the capability of adaptive lenses to replace mechanical axial scanning in confocal microscopy. The adaptive approach promises to achieve high scan rates in a rather simple implementation. This may open up new applications in biomedical imaging or surface analysis in micro- and nanoelectronics, where currently the axial scan rates and the flexibility at the scan process are the limiting factors. The results show that fast and adaptive axial scanning is possible using electrically tunable lenses but the performance degrades during the scan. This is due to defocus and spherical aberrations introduced to the system by tuning of the adaptive lens. These detune the observation plane away from the best focus which strongly deteriorates the axial resolution by a factor of ~2.4. Introducing balancing aberrations allows addressing these influences. The presented approach is based on the employment of a second adaptive lens, located in the detection path. It enables shifting the observation plane back to the best focus position and thus creating axial scans with homogeneous axial resolution. We present simulated and experimental proof-of-principle results.

On the Complexity Reduction of Laser Fault Injection Campaigns Using OBIC Measurements

“…1) Setup 1 (Laser Scanning Microscope): Setup 1 is a modified self-built laser scanning confocal microscope [23], [24], which is used for OBIC and reflective mode imaging with high resolution and precision. A temperature stabilized, fiber coupled laser diode module from Lumics at 1064 nm was used as light source.…”

Volumetric HiLo microscopy employing an electrically tunable lens

“…Moving the objective is slow for heavy objectives due to inertia and might lead to motion artifacts. Recently, a variety of microscopes such as confocal microscopy [16,17,18], wide field microscopy [19], structured illumination microscopy [20] and light sheet microscopy [21] benefited from using electrically or acoustically tunable lenses for axial scanning. However, as shown in [16] for confocal microscopy, the axial resolution degrades with increasing actuation voltages due to increasing aberrations of the tunable lens.…”

“…Recently, a variety of microscopes such as confocal microscopy [16,17,18], wide field microscopy [19], structured illumination microscopy [20] and light sheet microscopy [21] benefited from using electrically or acoustically tunable lenses for axial scanning. However, as shown in [16] for confocal microscopy, the axial resolution degrades with increasing actuation voltages due to increasing aberrations of the tunable lens. In contrast, HiLo microscopy is expected to be robust against a degradation of the axial resolution due to aberrations, since the speckles that are used for the optical sectioning in the HiLo algorithm are invariant to aberrations and scattering in the sample (as long as the speckles are fully developed [10,11]).…”

Miniaturized fiber-coupled confocal fluorescence microscope with an electrowetting variable focus lens using no moving parts

“…Variable focus lenses have been shown to allow axial scanning with no mechanical actuation for various microscopy applications [19–22]. Variable focus lenses for endoscopes have also been demonstrated, including a shape-changing polymer lens [20] and a pressure-driven liquid lens [16].…”