Pair Of Lenses Research Articles

Orthokeratology for high myopia

Purpose. With an increasing proportion of children with myopia especially in Asia, efforts have been made to reduce chances of preventable sight loss related to high myopia in the future. Orthokeratology lens has been used as one of the modalities not just to correct myopia, but also to slow down myopic progression and axial elongation. This case report reviews a patient with clinically significantly high myopia, whose refractive errors was partially corrected with orthokeratology lens and spectacle lenses. Material and Methods. A now 14-year-old patient with a history of fast progressing myopia, was prescribed and commended orthokeratology to manage myopia, while regularly monitoring her refractive errors, axial length, binocular vision status, corneal topography, and anterior eye health was monitored regularly at the author’s practice. Results. Over a two year follow up period, a partial correction of high myopia with orthokeratology lenses and residual refractive errors with additional spectacle lenses was effective in managing this patient’s myopia, as well as slowing of axial elongation. An updated pair of orthokeratology lens with a steeper back optic zone radii were prescribed to reduce superficial corneal staining and to maintain corneal health. Conclusion. Patient commitment and adherence to close monitoring of eyes in terms refractive errors, axial length, and anterior eye health, are vital in achieving a successful orthokeratology lens wear for high myopia. A dual fitting strategy consisting of orthokeratology lens and spectacle wear can be a safe management strategy that is acceptable for patients with high myopia. It would be helpful for practitioners to be able to rely on robust evidence-based guidance when determining whether lens wear can be ceased, i.e. when further axial elongation and myopic progression are no longer likely.

A Long-Range Lidar Optical Collimation System Based on a Shaped Laser Source

Semiconductor near-infrared lasers have been widely used in lidar systems. However, various source types have different shapes and divergence angles, causing more difficulties for long-distance detection. In this paper, an optical collimation system is designed for a long-range lidar system with a shaped laser source (the wavelength is 905 nm, the emitted spot size is 50 µm long by 10 µm wide, and the divergence angles are 33°and 15°, respectively, which are unconventional). On the basis of the traditional method of aspheric lens setting, a pair of asymmetric aspherical lenses were designed using an extended polynomial. The simulation results show that the spot shapes are all close to circular from 100 mm to 30 m and the spot size always remains the same value. The corrected optical system is put into the designed lidar system for verification. It results show that the average divergence angles in the long and short axis directions are 0.06°and 0.07°, which satisfy the project requirements. This optical system designed provides a collimation scheme and expands the application of vehicle-mounted lidar in the field of long-range detection.

NO2 gas-sensing enhancement by selective laser surface treatment of SnO2 nanorods

A new surface engineering technology has been introduced that can dramatically change the morphology and composition of existing SnO2 nanorods (NRs) to SnOx nanobeads (NBs) + NRs with the addition of a 1–6s laser + convex lens pair (LCP) process. Unlike the existing flame chemical vapour deposition (FCVD) method, which has a two-dimensional effect on a sample, LCP can control a relatively local area with a radius of several microns, making it a more sophisticated and advanced process. Notably, the LCP process at each second was directly linked to the change in the composition of the surface of the SnO2 NRs, and the response to NO2 gas in the SnO2 NBs + NRs with 1second LCP process was improved by approximately three times compared to that of bare SnO2 NRs. Therefore, a new gas-sensing mechanism was proposed through comparing the types of oxygen defect on the SnO2 NRs surface during a slight morphological transition and thermodynamic data of the composition before and after gas sensing.

Line-field dynamic optical coherence tomography platform for volumetric assessment of biological tissues.

Dynamic optical coherence tomography (dOCT) utilizes time-dependent signal intensity fluctuations to enhance contrast in OCT images and indirectly probe physiological processes in cells. Majority of the dOCT studies published so far are based on acquisition of 2D images (B-scans or C-scans) by utilizing point-scanning Fourier domain (spectral or swept-source) OCT or full-field OCT respectively, primarily due to limitations in the image acquisition rate. Here we introduce a novel, high-speed spectral domain line-field dOCT (SD-LF-dOCT) system and image acquisition protocols designed for fast, volumetric dOCT imaging of biological tissues. The imaging probe is based on an exchangeable afocal lens pair that enables selection of combinations of transverse resolution (from 1.1 µm to 6.4 µm) and FOV (from 250 × 250 µm2 to 1.4 × 1.4 mm2), suitable for different biomedical applications. The system offers axial resolution of ∼ 1.9 µm in biological tissue, assuming an average refractive index of 1.38. Maximum sensitivity of 90.5 dB is achieved for 3.5 mW optical imaging power at the tissue surface and maximum camera acquisition rate of 2,000 fps. Volumetric dOCT images acquired with the SD-LF-dOCT system from plant tissue (cucumber), animal tissue (mouse liver) and human prostate carcinoma spheroids allow for volumetric visualization of the tissues' cellular and sub-cellular structures and assessment of cellular motility.

Tomographic waveguide-based augmented reality display

A tomographic waveguide-based augmented reality display technique is proposed for near-eye three-dimensional (3D) display with accurate depth reconstructions. A pair of tunable lenses with complementary focuses is utilized to project tomographic virtual 3D images while maintaining the correct perception of the real scene. This approach reconstructs virtual 3D images with physical depth cues, thereby addressing the vergence-accommodation conflict inherent in waveguide augmented reality systems. A prototype has been constructed and optical experiments have been conducted, demonstrating the system’s capability in delivering high-quality 3D scenes for waveguide-based augmented reality display.

Experimental Verification of a Modified Cylindrical Focused Laser Differential Interferometer

A modification to cylindrical focused laser differential interferometry (CFLDI) that, without beam intersection, can achieve smaller stand-off distances from flat geometries than conventional FLDI is presented. The modified system uses a cylindrical lens pair to expand and collimate the beam in a single direction, parallel to the model surface, forming a long, flat, elliptical profile. Subsequently, a spherical lens focuses the beam. Mach 7.3 hypersonic flow, produced by the T4 Stalker Reflected Shock Tunnel, was used for an experimental comparison between the responses of the modified CFLDI and a similar FLDI system in the freestream and just above the boundary-layer edge. Good agreement between the modified CFLDI and FLDI among all measured frequencies was observed when probing near the boundary-layer edge. The comparison in the freestream had good agreement up to 1500 kHz, and higher frequencies saw the modified CFLDI response attenuated at a shallower angle than the FLDI. A combination of different system parameters and base noise levels between the experiments is believed to account for this difference. The modified CFLDI system was used to probe inside the boundary layer, achieving a y/δ of approximately 0.4, where broadband turbulence is detected.

Design of a dual hollow beam optical antenna based on a Fresnel lens-conical lens combination

To improve the transmission efficiency of Cassegrain antennas and enable the simultaneous transmission of signals with different wavelengths in the antenna system, this study introduces Fresnel lenses and conical lenses in front of the Cassegrain antenna at the transmitting end. Reflective mirrors and focusing lenses are introduced at the receiving end. A detailed description is provided of the design process for the Fresnel lens, as well as the impact of various parameters on the hollow radius when combined with the conical lens. Based on the laws of vector reflection and refraction, simulations are performed to track the propagation of light through the entire communication system and lens pairs, providing transmission efficiency plots of the antenna system under deflection and off-axis conditions. Taking into account practical factors such as lens chamfer, transmittance, Cassegrain antenna reflectance, and material dispersion, the transmission efficiency of the antenna system at 1550 nm wavelength can still reach 93.45%. The proposed method not only improves the transmission efficiency of Cassegrain antennas, but also enables the transmission of different information through the inner and outer layers of the antenna system.

Varifocal occlusion in an optical see-through near-eye display with a single phase-only liquid crystal on silicon

We propose a near-eye display optics system that supports three-dimensional mutual occlusion. By exploiting the polarization-control properties of a phase-only liquid crystal on silicon (LCoS), we achieve real see-through scene masking as well as virtual digital scene imaging using a single LCoS. Dynamic depth control of the real scene mask and virtual digital image is also achieved by using a focus tunable lens (FTL) pair of opposite curvatures. The proposed configuration using a single LCoS and opposite curvature FTL pair enables the self-alignment of the mask and image at an arbitrary depth without distorting the see-through view of the real scene. We verified the feasibility of the proposed optics using two optical benchtop setups: one with two off-the-shelf FTLs for continuous depth control, and the other with a single Pancharatnam–Berry phase-type FTL for the improved form factor.

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.

Ion trap with in-vacuum high numerical aperture imaging for a dual-species modular quantum computer.

Photonic interconnects between quantum systems will play a central role in both scalable quantum computing and quantum networking. Entanglement of remote qubits via photons has been demonstrated in many platforms; however, improving the rate of entanglement generation will be instrumental for integrating photonic links into modular quantum computers. We present an ion trap system that has the highest reported free-space photon collection efficiency for quantum networking. We use a pair of in-vacuum aspheric lenses, each with a numerical aperture of 0.8, to couple 10(1)% of the 493nm photons emitted from a 138Ba+ ion into single-mode fibers. We also demonstrate that proximal effects of the lenses on the ion position and motion can be mitigated.

Switching and control mechanism between p-type and n-type in SnO2 nanorods using laser with added convex lens to control oxygen concentrations

In a significant advancement, a novel technology has been developed to precisely control the electronic sensitization of SnO2 nanorods. This control is accomplished in a matter of seconds through the external injection of energy via laser and convex lens pairs (LCP). Utilizing LCP, selective redox reactions can be induced on the surface of SnO2 nanorods. The study focused on the contrasting effects of NO2, an oxidizing gas, and H2, a reducing gas. In the presence of NO2, the electronic sensitization caused by LCP outweighs the chemical sensitization due to NO2, thereby resulting in both n-type and p-type behaviors. In contrast, when exposed to H2, the nanorods exhibit only n-type behavior, as the chemical sensitization effect of H2 is more significant than the electronic sensitization effect of LCP. The observed variations in electronic properties can be systematically accounted for by the differential bonding energies between oxidizing and reducing gases.

Association of Alpha-Crystallin with Human Cortical and Nuclear Lens Lipid Membrane Increases with the Grade of Cortical and Nuclear Cataract.

Eye lens α-crystallin has been shown to become increasingly membrane-bound with age and cataract formation; however, to our knowledge, no studies have investigated the membrane interactions of α-crystallin throughout the development of cataracts in separated cortical membrane (CM) and nuclear membrane (NM) from single human lenses. In this study, four pairs of human lenses from age-matched male and female donors and one pair of male lenses ranging in age from 64 to 73 years old (yo) were obtained to investigate the interactions of α-crystallin with the NM and CM throughout the progression of cortical cataract (CC) and nuclear cataract (NC) using the electron paramagnetic resonance spin-labeling method. Donor health history information (diabetes, smoker, hypertension, radiation treatment), sex, and race were included in the data analysis. The right eye lenses CM and NM investigated were 64 yo male (CC: 0), 68 yo male (CC: 3, NC: 2), 73 yo male (CC: 1, NC: 2), 68 yo female (CC: 3, NC: 2), and 73 yo female (CC: 1, NC: 3). Similarly, left eye lenses CM and NM investigated were 64 yo male (CC: 0), 68 yo male (CC: 3, NC: 2), 73 yo male (CC: 2, NC: 3), 68 yo female (CC: 3, NC: 2), and 73 yo female (CC: 1, NC: 3). Analysis of α-crystallin binding to male and female eye lens CM and NM revealed that the percentage of membrane surface occupied (MSO) by α-crystallin increases with increasing grade of CC and NC. The binding of α-crystallin resulted in decreased mobility, increased order, and increased hydrophobicity on the membrane surface in male and female eye lens CM and NM. CM mobility decreased with an increase in cataracts for both males and females, whereas the male lens NM mobility showed no significant change, while female lens NM showed increased mobility with an increase in cataract grade. Our data shows that a 68 yo female donor (long-term smoker, pre-diabetic, and hypertension; grade 3 CC) showed the largest MSO by α-crystallin in CM from both the left and right lens and had the most pronounced mobility changes relative to all other analyzed samples. The variation in cholesterol (Chol) content, size and amount of cholesterol bilayer domains (CBDs), and lipid composition in the CM and NM with age and cataract might result in a variation of membrane surface mobility, membrane surface hydrophobicity, and the interactions of α-crystallin at the surface of each CM and NM. These findings provide insight into the effect of decreased Chol content and the reduced size and amount of CBDs in the cataractous CM and NM with an increased binding of α-crystallin with increased CC and NC grade, which suggests that Chol and CBDs might be a key component in maintaining lens transparency.

Design and characterization of a hyperbolic-elliptical lens pair in a rapid beam steering system for single-pixel terahertz spectral imaging of the cornea.

Terahertz (THz) time-domain spectroscopy has been investigated for assessment of the hydration levels in the cornea, intraocular pressure, and changes in corneal topography. Previous efforts at THz imaging of the cornea have employed off-axis parabolic mirrors to achieve normal incidence along the spherical surface. However, this comes at the cost of an asymmetric field-of-view (FOV) and a long scan time because it requires raster-scanning of the collimated beam across the large mirror diameter. This paper proposes a solution by designing a pair of aspheric lenses that can provide a larger symmetric spherical FOV (9.6 mm) and reduce the scan time by two orders of magnitude using a novel beam-steering approach. A hyperbolic-elliptical lens was designed and optimized to achieve normal incidence and phase-front matching between the focused THz beam and the target curvature. The lenses were machined from a slab of high-density polyethylene and characterized in comparison to ray-tracing simulations by imaging several targets of similar sizes to the cornea. Our experimental results showed excellent agreement in the increased symmetric FOV and confirmed the reduction in scan time to about 3-4 seconds. In the future, this lens design process can be extended for imaging the sclera of the eye and other curved biological surfaces, such as the nose and fingers.

23.1-Gb/s 135-GHz Wireless Transmission Over 4.6-Km and Effect of Rain Attenuation

In this article, we have experimentally demonstrated a fiber-wireless-integration <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D$</tex-math> </inline-formula> -band (110–170 GHz) transmission system. To extend the wireless transmission distance while maintaining the wireless bit rate as high as possible, we designed high-gain lens horn antenna modules consisting of a pair of dielectric plano-convex lenses and horn antennas for long-haul wireless links. In addition, we employ the Volterra nonlinear equalization (VNE) algorithm based on the multiple-input–multiple-output (MIMO) structure to precisely compensate for the in-phase/quadrature (I/Q) imbalance and nonlinear impairment of quadrature amplitude modulation (QAM) signals mainly caused by photoelectric (O-E) conversion and electric-photo (E-O) conversion. Meanwhile, one of the methods adopted in our experiment to decrease the influence of nonlinearity on high-order QAM signals is coupling the high-order modulation format with the probabilistic shaping (PS) technology. As a result of outdoor field experimental verification, the demonstration at 135 GHz carrier with a net rate of 23.1 Gb/s over 10 km optic-fiber and 4.6 km wireless transmission distance has been successfully carried out. It is, as we know, the first time that a record-breaking product of net bit rate and wireless transmission distance, i.e., 23.1 Gb/s <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 4.6 km <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$=$</tex-math> </inline-formula> 106.3 Gb/s <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot$</tex-math> </inline-formula> km, has been accomplished based on a fiber-wireless-integration system. Also, for the first time, we have measured the effect of rain attenuation for the 135 GHz millimeter-wave (mm-wave) wireless link and established more accurate rainfall models for the Shanghai region of China by comparing them with multiple rainfall models. This work can be used as a complement to the International Telecommunication Union-Radiocommunication sector (ITU-R) recommendations.

The contribution of image minification to discomfort experienced in wearable optics.

Wearable optics have a broad range of uses, for example, in refractive spectacles and augmented/virtual reality devices. Despite the long-standing and widespread use of wearable optics in vision care and technology, user discomfort remains an enduring mystery. Some of this discomfort is thought to derive from optical image minification and magnification. However, there is limited scientific data characterizing the full range of physical and perceptual symptoms caused by minification or magnification during daily life. In this study, we aimed to evaluate sensitivity to changes in retinal image size introduced by wearable optics. Forty participants wore 0%, 2%, and 4% radially symmetric optical minifying lenses binocularly (over both eyes) and monocularly (over just one eye). Physical and perceptual symptoms were measured during tasks that required head movement, visual search, and judgment of world motion. All lens pairs except the controls (0% binocular) were consistently associated with increased discomfort along some dimension. Greater minification tended to be associated with greater discomfort, and monocular minification was often-but not always-associated with greater symptoms than binocular minification. Furthermore, our results suggest that dizziness and visual motion were the most reported physical and perceptual symptoms during naturalistic tasks. This work establishes preliminary guidelines for tolerances to binocular and monocular image size distortion in wearable optics.

Unobtrusive Refractive Power Monitoring: Using EOG to Detect Blurred Vision.

The rise in population and aging has led to a significant increase in the number of individuals affected by common causes of vision loss. Early diagnosis and treatment are crucial to avoid the consequences of visual impairment. However, in early stages, many visual problems are making it difficult to detect. Visual adaptation can compensate for several visual deficits with adaptive eye movements. These adaptive eye movements may serve as indicators of vision loss. In this work, we investigate the association between eye movement and blurred vision. By using Electrooculography (EOG) to record eye movements, we propose a new tracking model to identify the deterioration of refractive power. We verify the technical feasibility of this method by designing a blurred vision simulation experiment. Six sets of prescription lenses and a pair of flat lenses were used to create different levels of blurring effects. We analyzed binocular movements through EOG signals and performed a seven-class classification using the ResNet18 architecture. The results revealed an average classification accuracy of 94.7% in the subject-dependent model. However, the subject-independent model presented poor performance, with the highest accuracy reaching only 34.5%. Therefore, the potential of an EOG-based visual quality monitoring system is proven. Furthermore, our experimental design provides a novel approach to assessing blurred vision.

Low-loss tunable beam collimator and expander assembly with no moving parts using anengineered diffuser and varifocal lenses.

In this paper, we present a novel design for a tunable beam collimator. A variable collimator assists in achieving an adaptive size of an output collimated beam. Alternatively, it can also provide an adjustable output beam divergence angle for a noncollimated beam output. Tunable collimators are highly desirable for various applications in testing, engineering, and measurements. Such devices are also useful in providing tunable illumination of samples or targets in microscopes and emulating different target distances for characterizing the performance of camera systems in laboratory settings. The proposed collimator has two distinct advantages: it is light-efficient compared with pinhole-based collimator designs, and it delivers a large range of output beam sizes without involving the mechanical motion of bulk components. These attributes are achieved via the use of an engineered diffuser (in the place of a pinhole) and a pair of large aperture tunable focus lenses, which deliver a tunable magnification to the output collimated beam. In laboratory experiments, we achieve an optical transmission efficiency of 90% for the proposed tunable collimator.

High-Content Screening Discovers Microplastics Released by Contact Lenses under Sunlight.

The widespread use of plastic products leads to the ubiquity of microplastics in daily life, while the release of microplastics from long-used contact lenses has not been reported due to the limitations of conventional detection methods. Here, we established a new and rapid method to capture and count microplastics by using a high-content screening system. This method can simultaneously measure the diameter, area, and shape of each plastic particle, and the reliability and applicability of this method were verified with commercial microplastics. It is estimated that 90,698 particles of microplastics could be released from a pair of contact lenses during a year of wearing. The microplastics in the leachates were confirmed to be released from the contact lenses by scanning electron microscopy and Fourier transform infrared spectroscopy fingerprint analysis. Our study reveals an undiscovered pathway of microplastic direct exposure to humans, highlighting the urgent need to assess the potential health risks caused by eye exposure to microplastics.

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.

True optical spatial derivatives for direct phase gradient measurements

This paper shows analytically and numerically that a vortex plate coupled to a neutral density filter can deliver a true optical spatial derivative when placed at the focal plane of a 2f lens pair. This technique turns any intensity or phase variations of coherent light into an intensity that is proportional to the square of the norm of the initial variation gradient. Since the optical derivative removes the uniform background, it is possible to measure the mode numbers of spatial phase gradients or fluctuations optically, without using any interferometer.