Optimal precision and accuracy in 4Pi-STORM using dynamic spline PSF models.

Coherent fluorescence imaging with two objective lenses (4Pi detection) enables single-molecule localization microscopy with sub-10 nm spatial resolution in three dimensions. Despite its outstanding sensitivity, wider application of this technique has been hindered by complex instrumentation and the challenging nature of the data analysis. Here we report the development of a 4Pi-STORM microscope, which obtains optimal resolution and accuracy by modeling the 4Pi point spread function (PSF) dynamically while also using a simpler optical design. Dynamic spline PSF models incorporate fluctuations in the modulation phase of the experimentally determined PSF, capturing the temporal evolution of the optical system. Our method reaches the theoretical limits for precision and minimizes phase-wrapping artifacts by making full use of the information content of the data. 4Pi-STORM achieves a near-isotropic three-dimensional localization precision of 2-3 nm, and we demonstrate its capabilities by investigating protein and nucleic acid organization in primary neurons and mammalian mitochondria.

Flexible solid immersion meniscus lens (SIMlens) approach for enhancing biological imaging of cleared samples.

Tissue-clearing techniques have revolutionized the field of biological imaging by rendering biological specimens transparent and enabling inside optical detection. Light-sheet fluorescence microscopy (LSFM) is a powerful tool for three-dimensional imaging of large biological samples. Combining tissue-clearing techniques with LSFM has advanced the efficient 3D visualization of these samples. A crucial challenge with LSFM is the requirement for the objective to operate within the clearing reagent, which can cause aberrations. To address this issue, we introduce a novel, to our knowledge, approach for the flexible design of the solid immersion refractive meniscus lens (SIMlens), facilitating the use of air objectives with cleared samples. Compared to the previous SIMlens, this method not only eliminates aberrations but also offers customized options for enhancing the numerical aperture and working distance of the objective lens, achieving at least a 10% improvement. We have demonstrated the feasibility of this new method using mouse brain samples.

Extended depth-of-field wide-field fluorescence microscopy with a micro-mirror array lens system for versatile cellular examination.

We present a versatile extended depth-of-field (EDOF) wide-field fluorescence microscopy using a new, to the best of our knowledge, active device, micro-mirror array lens system (MALS) for calibration-free and orientation-insensitive EDOF imaging. The MALS changed the focal plane during image acquisition, and the system could be operated in any orientation. Two EDOF imaging modes of high-speed accumulation and low-speed surface sectioning were implemented. The performance was demonstrated in non-contact imaging of conjunctival goblet cells in live mice and depth-resolved cellular examination of ex-vivo human cancer specimens. MALS-based EDOF microscopy has potential for versatile cellular examination.

Upconversion nanoparticles doped optical lens: let's see the near-infrared light.

The human cannot detect light with a wavelength exceeding 700 nm, primarily due to limitations in the physiological structure of the human eye. However, in certain specific scenarios, the ability to detect near-infrared (NIR) light proves to be extremely valuable. To attain this desired capability, NIR up conversion nanoparticles (UCNPs) were prepared and doped in the optical lens materials, aiming to obtain a NIR light "visible" optical lens. It is demonstrated that the doping of UCNPs in the optical lens materials does not significantly impact on their mechanical properties, optical properties, surface properties and it exhibits excellent biocompatibility in cell and animal experiments. More importantly, the UCNPs doping can convert NIR light into visible light within the material effectively and stably. The eyes can "see" the NIR light after wearing such UCNPs doped optical lens. Such NIR light visible optical lens could have great potential in actual applications.

Development of a bio-inspired optical system that mimics accommodation and lighting regulation like the human eye.

Bio-inspired optical systems have recently been developed using polarizers and liquid or rigid lenses. In this work, we propose a bio-inspired opto-mechatronic system that imitates the accommodation and regulation of light intensity as the human eye does. The system uses a polymeric lens as a cornea, an adjustable diaphragm as an iris, a tunable solid elastic lens as a crystalline lens, and a commercial sensor as a retina. We also present the development of the electronic control system to accommodate and regulate the amount of light that enters the system, for which two stepper motors, an Arduino control system, and light and movement sensors are used. The characterization of the system is presented together with the results obtained, where it can be seen that the system works in an acceptable range as the human eye does.

Comparison of proximal and minus lens autorefraction techniques to measure monocular accommodative amplitude.

SIGNIFICANCE: This study provides a faster method for objectively measuring accommodative amplitude with an open-field autorefractor in a research setting. PURPOSE: Objective measures of accommodative amplitude with an autorefractor take time because of the numerous stimulus demands tested. This study compares protocols using different amounts and types of demands to shorten the process. METHODS: One hundred participants were recruited for four age bins (5 to 9, 10 to 14, 15 to 19, and 20 to 24 years) and monocular amplitude measured with an autorefractor using three protocols: proximal, proximal-lens (letter), and proximal-lens (picture). For proximal, measurements were taken as participants viewed a 0.9 mm "E" placed at 13 demands (40 to 3.3 cm = 2.5 to 30 D). The other protocols used a target (either the "E" or a detailed picture) placed at 33 and 12.5 cm followed by 12.5 cm with a series of lenses (-2, -4, and -5.5 D). Adjustments were made for lens effectivity for the three lens conditions, which were thus 9.6, 11.1, and 12.0 D for individuals without additional spectacle lenses. Accommodative amplitude was defined as the greatest response measured with each technique. One-way analysis of variance was used to compare group mean amplitudes across protocols and differences between letter protocols by age bin. RESULTS: Amplitudes were significantly different between protocols (p < 0.001), with proximal having higher amplitudes (mean ± standard deviation, 8.04 ± 1.70 D) compared with both proximal-lens protocols (letter, 7.48 ± 1.42 D; picture, 7.43 ± 1.42 D) by post hoc Tukey analysis. Differences in amplitude between the proximal and proximal-lens (letter) protocol were different by age group (p = 0 .003), with the youngest group having larger differences (1.14 ± 1.58 D) than the oldest groups (0.17 ± 0.58 and 0.29 ± 0.48 D, respectively) by post hoc Tukey analysis. CONCLUSIONS: The proximal-lens protocols took less time and identified the maximum accommodative amplitude in participants aged 15 to 24 years; however, they may underestimate true amplitude in younger children.

Intracapsular accommodation mechanism in terms of lens curvature gradient.

The intracapsular accommodation mechanism (IAM) may be understood as an increase in the lens equivalent refractive index as the eye accommodates. Our goal was to evaluate the existence of an IAM by analysing observed changes in the inner curvature gradient of the lens. To this end, we fitted a gradient index and curvature lens model to published experimental data on external and nucleus geometry changes during accommodation. For each case analysed, we computed the refractive power and equivalent index for each accommodative state using a ray transfer matrix. All data sets showed an increase in the effective refractive index, indicating a positive IAM, which was stronger for older lenses. These results suggest a strong dependence of the lens equivalent refractive index on the inner curvature gradient.

Effects of magnification on restorative dental preparation performance: a scoping review and level of evidence mapping.

OBJECTIVE: This scoping review aimed to identify and describe the available evidence on the effect of magnifying devices (loupe or microscope) on the performance of restorative dental preparations. MATERIALS AND METHODS: This study was conducted according to the PRISMA-ScR guidelines for scoping reviews and registered on the INPLASY database. An electronic search was performed in four databases and Grey literature for articles published until November 2023. Eligibility criteria were determined using the PICOS strategy and comprised studies that evaluated the performance of magnification devices for restorative dental preparations. A bibliographic mapping of the evidence was conducted. RESULTS: Sixteen studies met the inclusion criteria. Most of the studies (n = 12) compared the performance of dental preparations using magnification loupes vs. no magnification. The magnification for loupes and microscopes ranged from 2.5x to 4.0x and 6.4x to 10x, respectively. The use of magnifying loupes improved the performance of restorative preparations in 66.6% of the evaluated studies. However, when the magnifications were compared, the greater magnification provided by microscopes did not improve preparation performance compared to magnification loupes. Regarding the place of publication, the American continent concentrates the most significant number of evidence. CONCLUSIONS: Although evidence for magnification improving the performance of dental preparations has increased over the last decade, basically only in vitro studies (most of which have taken place in the Americas) have been reported in the literature. The evidence suggests that magnification significantly improves restorative preparation performance when compared to non-magnification. However, higher magnifications (e.g., microscopes) do not appear to improve tooth preparation performance compared with lower magnification devices (e.g., magnification loupes). CLINICAL RELEVANCE: Available evidence supports that using magnification can improve the performance of restored tooth preparations. However, high magnifications have no advantages over lower magnifications.

High-Density Polyethylene Custom Focusing Lenses for High-Resolution Transient Terahertz Biomedical Imaging Sensors.

Transient terahertz time-domain spectroscopy (THz-TDS) imaging has emerged as a novel non-ionizing and noninvasive biomedical imaging modality, designed for the detection and characterization of a variety of tissue malignancies due to their high signal-to-noise ratio and submillimeter resolution. We report our design of a pair of aspheric focusing lenses using a commercially available lens-design software that resulted in about 200 × 200-µm2 focal spot size corresponding to the 1-THz frequency. The lenses are made of high-density polyethylene (HDPE) obtained using a lathe fabrication and are integrated into a THz-TDS system that includes low-temperature GaAs photoconductive antennae as both a THz emitter and detector. The system is used to generate high-resolution, two-dimensional (2D) images of formalin-fixed, paraffin-embedded murine pancreas tissue blocks. The performance of these focusing lenses is compared to the older system based on a pair of short-focal-length, hemispherical polytetrafluoroethylene (TeflonTM) lenses and is characterized using THz-domain measurements, resulting in 2D maps of the tissue refractive index and absorption coefficient as imaging markers. For a quantitative evaluation of the lens effect on the image resolution, we formulated a lateral resolution parameter, R2080, defined as the distance required for a 20-80% transition of the imaging marker from the bare paraffin region to the tissue region in the same image frame. The R2080 parameter clearly demonstrates the advantage of the HDPE lenses over TeflonTM lenses. The lens-design approach presented here can be successfully implemented in other THz-TDS setups with known THz emitter and detector specifications.

A new scope warmer/cleaner for laparoscopic surgery: a disposable hot pack.

BACKGROUND: Fogging and staining of a laparoscope lens negatively impact surgical visualization. We hypothesized that the disposable hot pack could not only warm but also clean laparoscopes. Hence, this study verified and developed the disposable hot pack with anti-fogging and cleaning function. MATERIAL AND METHODS: The laparoscope was inserted into a swine abdominal cavity for five minutes. Then, the laparoscopic tip was heated with 65 °C saline or the folded disposable hot pack with nonwoven fabric coated surfactant for ten seconds (n = 15). Also, a laparoscopic tip with dirt was wiped with the prototype or conventional gauze for 10 s (n = 10). The dirt, fogging, and temperature of the laparoscopic tip were respectively evaluated after the laparoscope was inserted into the abdominal cavity. RESULTS: The laparoscopic tip temperature five minutes after insertion into the abdominal cavity was similar (31.1 °C vs 31.2 °C, p = 0.748) and there was no fogging in both methods. The conventional gauze had significantly less temperature of the laparoscopic tip after cleaning and higher fogging occurrence than the prototype (29.5 °C vs 34.0 °C, p < 0.001, 30% vs 0%, p = 0.030, respectively), although there was no dirt left after both methods. CONCLUSION: The disposable hot pack has a strong potential as an anti-fogging and cleaning device for use during laparoscopic surgery.

[Structural and functional features of the eye in Marfan syndrome. Report 2. Changes in the anatomical complex of the lens]. / Strukturno-funktsional'nye osobennosti glaza pri sindrome Marfana. Soobshchenie 2. Izmeneniya anatomicheskogo kompleksa khrustalika.

Analysis of lens changes in Marfan syndrome (MS), in addition to assessing the position of the lens itself, should include the possibility of examining its supporting and accommodative components (ciliary zonule and ciliary body), or what can be called the entire anatomical complex of the lens. Optical methods of studying the structures of the anterior segment of the eye, due to iris opacity, allow only to analyze the state of the lens within the natural or medically enlarged pupil width. Visualization of the structures located behind the iris is possible with the use of radiation diagnostic methods, in particular ultrasound biomicroscopy (UBM). PURPOSE: This study assesses the state of the anatomical complex of the lens in MS using UBM. MATERIAL AND METHODS: The study was carried out on clinical material previously used by us to analyze changes in the fibrous membrane of the eye in MS. At the first stage, the main (19 patients with MS, 38 eyes) and the control (24 patients with myopia, 48 eyes) groups were formed for comparative evaluation. The formed groups were standardized according to the age of the patients and the axial length of the eye. At the second stage, patients with MS were divided into subgroups depending on the absence or presence of biomicroscopic signs of ectopia lentis (22 and 16 eyes, respectively). For UBM, an ultrasound linear sensor with a scanning frequency of 50 MHz was used (Aviso device, Quantel Medical, France). Various biometric UBM indicators were determined: lens thickness, diameter of the lens, lens-axial length factor, iris-lens angle, iris-lens contact distance, posterior chamber depth, length of the fibers of ciliary zonule, thickness of the ciliary body, sclera-ciliary process angle. RESULTS: There are changes in the anatomical complex of the lens as a whole in MS (in the lens itself, the ciliary zonule, and the ciliary body), which are characterized by an increase in lens thickness and a decrease in the diameter of the lens, an increase in the length of the fibers of the ciliary zonule and a decrease in the thickness of the ciliary body. At the same time, the displacement of the lens detected by optical biomicroscopy (ectopia lentis) can be considered as an advanced stage of changes in the anatomical complex of the lens. CONCLUSION: UBM provides the possibility of full-fledged visualization of all components of the anatomical complex of the lens in terms of both diagnostics, and monitoring of changes in MS. The question of the advisability of including this method in the algorithm for diagnosing ocular manifestations in order to verify the MS remains open. Possible obstacles may be, on the one hand, related to the need for special and expensive equipment, and on the other hand, the absence of a generally accepted «normal¼ values of UBM indicators of the anatomical complex of the lens.

Electrically tunable lenses - eliminating mechanical axial movements during high-speed 3D live imaging.

The successful investigation of photosensitive and dynamic biological events, such as those in a proliferating tissue or a dividing cell, requires non-intervening high-speed imaging techniques. Electrically tunable lenses (ETLs) are liquid lenses possessing shape-changing capabilities that enable rapid axial shifts of the focal plane, in turn achieving acquisition speeds within the millisecond regime. These human-eye-inspired liquid lenses can enable fast focusing and have been applied in a variety of cell biology studies. Here, we review the history, opportunities and challenges underpinning the use of cost-effective high-speed ETLs. Although other, more expensive solutions for three-dimensional imaging in the millisecond regime are available, ETLs continue to be a powerful, yet inexpensive, contender for live-cell microscopy.

Ultraportable Flow Cytometer Based on an All-Glass Microfluidic Chip.

The flow cytometer has become a powerful and widely accepted measurement device in both biological studies and clinical diagnostics. The application of the flow cytometer in emerging point-of-care scenarios, such as instant detection in remote areas and emergency diagnosis, requires a significant reduction in physical dimension, cost, and power consumption. This requirement promotes studies to develop portable flow cytometers, mostly based on the utilization of polymer microfluidic chips. However, due to the relatively poor optical performance of polymer materials, existing microfluidic flow cytometers are incapable of accurate blood analysis, such as the four-part leukocyte differential count, which is necessary to monitor the immune system and to assess the risk of allergic inflammation or viral infection. To address this issue, an ultraportable flow cytometer based on an all-glass microfluidic chip (AG-UFCM) has been developed in this study. Compared with that of a typical commercial flow cytometer (BD FACSAria III), the volume of the AG-UFCM was reduced by 90 times (from 720 to 8 L). A two-step laser processing was employed to fabricate an all-glass microfluidic chip with a surface roughness of less than 1 nm, significantly improving the optical performance of on-chip micro-lens. The signal-to-noise ratio was enhanced by 3 dB, compared with that of polymer materials. For the first time, a four-part leukocyte differential count based on single fluorescence staining was realized using a miniaturized flow cytometer, laying a foundation for the point-of-care testing of miniaturized flow cytometers.

Lenz Lenses in a Cryoprobe: Boosting NMR Sensitivity Toward Environmental Monitoring of Mass-Limited Samples.

Nuclear magnetic resonance (NMR) spectroscopy is commonly employed in a wide range of metabolomic research. Unfortunately, due to its relatively low sensitivity, smaller samples become challenging to study by NMR. Cryoprobes can be used to increase sensitivity by cooling the coil and preamplifier, offering sensitivity improvements of ∼3 to 4x. Alternatively, microcoils can be used to increase mass sensitivity by improving sample filling and proximity, along with decreased electrical resistance. Unfortunately, combining the two approaches is not just technically challenging, but as the coil decreases, so does its thermal fingerprint, reducing the advantage of cryogenic cooling. Here, an alternative solution is proposed in the form of a Lenz lens inside a cryoprobe. Rather than replacing the detection coil, Lenz lenses allow the B1 field from a larger coil to be refocused onto a much smaller sample area. In turn, the stronger B1 field at the sample provides strong coupling to the cryocoil, improving the signal. By combining a 530 I.D. Lenz lens with a cryoprobe, sensitivity was further improved by 2.8x and 3.5x for 1H and 13C, respectively, over the cryoprobe alone for small samples. Additionally, the broadband nature of the Lenz lenses allowed multiple nuclei to be studied and heteronuclear two-dimensional (2D) NMR approaches to be employed. The sensitivity improvements and 2D capabilities are demonstrated on 430 nL of hemolymph and eight eggs (∼350 µm O.D.) from the model organismDaphnia magna. In summary, combining Lenz lenses with cryoprobes offers a relatively simple approach to boost sensitivity for tiny samples while retaining cryoprobe advantages.

Mechanically loaded GRIN lens for endoscopy.

Endoscopic techniques are broadly used in medicine. Small diameter endoscopes are either made as fiber bundles or, beneficially, as graded index lenses. Fiber bundles can withstand a mechanical load during their use but the GRIN lens's performance can be affected by its deflection. Here, we analyze the effect of deflection on the image quality and unwanted associated effects with relation to the eye endoscope we designed and built. We also present the result of our effort to make a reliable model of a bent GRIN lens in the OpticStudio software.

Improving flat fluorescence microscopy in scattering tissue through deep learning strategies.

Intravital microscopy in small animals growingly contributes to the visualization of short- and long-term mammalian biological processes. Miniaturized fluorescence microscopy has revolutionized the observation of live animals' neural circuits. The technology's ability to further miniaturize to improve freely moving experimental settings is limited by its standard lens-based layout. Typical miniature microscope designs contain a stack of heavy and bulky optical components adjusted at relatively long distances. Computational lensless microscopy can overcome this limitation by replacing the lenses with a simple thin mask. Among other critical applications, Flat Fluorescence Microscope (FFM) holds promise to allow for real-time brain circuits imaging in freely moving animals, but recent research reports show that the quality needs to be improved, compared with imaging in clear tissue, for instance. Although promising results were reported with mask-based fluorescence microscopes in clear tissues, the impact of light scattering in biological tissue remains a major challenge. The outstanding performance of deep learning (DL) networks in computational flat cameras and imaging through scattering media studies motivates the development of deep learning models for FFMs. Our holistic ray-tracing and Monte Carlo FFM computational model assisted us in evaluating deep scattering medium imaging with DL techniques. We demonstrate that physics-based DL models combined with the classical reconstruction technique of the alternating direction method of multipliers (ADMM) perform a fast and robust image reconstruction, particularly in the scattering medium. The structural similarity indexes of the reconstructed images in scattering media recordings were increased by up to 20% compared with the prevalent iterative models. We also introduce and discuss the challenges of DL approaches for FFMs under physics-informed supervised and unsupervised learning.

Integral imaging reconstruction system based on the human eye viewing mechanism.

For integral stereo imaging systems based on lens arrays, the cross-mixing of erroneous light rays between adjacent lenses seriously affects the quality of the reconstructed light field. In this paper, we proposed a light field reconstruction method based on the human eye viewing mechanism, which incorporates simplified human eye imaging into the integral imaging system. First, the light field model for specified viewpoint is established, and the distribution of the light source for each viewpoint is accurately calculated for the EIA generation algorithm of fixed viewpoint. Second, according to the ray tracing algorithm in this paper, non-overlapping EIA based on the human eye viewing mechanism is designed to suppress the amount of crosstalk rays fundamentally. The actual viewing clarity is improved with the same reconstructed resolution. Experimental results verify the effectiveness of the proposed method. The SSIM value is higher than 0.93, which verifies that the viewing angle range is increased to 62°.

Geometric-phase-based axicon lens for computational achromatic imaging.

Conventional optical imaging systems usually utilize several lenses within a precise assembly to eliminate chromatic aberration, which increases the difficulty of system integration. In recent years, with the rapid development of metasurfaces and liquid crystals (LCs), planar optical elements provide feasible solutions to realize flexible light manipulation and lightweight systems. However, there also exists chromatic aberration, which can be corrected but at the cost of a complex device design. Here, a geometric-phase-based axicon lens is utilized to correct chromatic aberration across a broadband wavelength with the assistance of a post-process algorithm. The axicon lens is fabricated through arranging orientations of liquid-crystal molecules with a standard photoalignment technique, and it produces an approximately invariant point spread function (PSF) at several discrete wavelengths, which is used as the prior information to extract the object in the blurred image. In the experiment, the reconstruction quality is significantly improved after the post-process algorithm. We expect our work to provide further development to reduce the dispersion with both the device design and the computational image technique.

Modified Mach-Zehnder interferometer for spatial coherence measurement.

Spatial coherence of light sources is usually obtained by using the classical Young's interferometer. Although the original experiment was improved upon in successive works, some drawbacks still remain. For example, several pairs of points must be used to obtain the complex coherence degree (normalized first-order correlation function) of the source. In this work, a modified Mach-Zehnder interferometer which includes a pair of lenses and is able to measure the spatial coherence degree is presented. With this modified Mach-Zehnder interferometer, it is possible to measure the full 4D spatial coherence function by displacing the incoming beam laterally. To test it, we have measured only a 2D projection (zero shear) of the 4D spatial coherence, which is enough to characterize some types of sources. The setup has no movable parts, making it robust and portable. To test it, the two-dimensional spatial coherence of a high-speed laser with two cavities was measured for different pulse energy values. We observe from the experimental measurements that the complex degree of coherence changes with the selected output energy. Both laser cavities seem to have similar complex coherence degrees for the maximum energy, although it is not symmetrical. Thus, this analysis will allow us to determine the best configuration of the double-cavity laser for interferometric applications. Furthermore, the proposed approach can be applied to any other light sources.

Optical edge detection with adjustable resolution based on cascaded Pancharatnam-Berry lenses.

We designed a versatile optical edge detection setup with two cascaded Pancharatnam-Berry lenses (PBLs) placed at the Fourier plane of a 4f system. When the two PBLs are parallel and close to each other, owing to the moiré-like effect, one-dimensional edge detection with adjustable resolution is achieved by introducing a transverse displacement of one PBL. Furthermore, two-dimensional edge detection with adjustable resolution can also be realized by tuning the longitudinal distance between the PBLs, and the transverse displacement is exploited to adjust the edge resolution in specified directions. The proposed scheme is verified by a proof-of-principle experiment in which the resolution-adjustable edges of different targets and cells were clearly observed, showing its flexibility and potential application in image processing and high-contrast microscopy.