Single Lens Research Articles

Fast tool servo-based ultra-precision diamond sculpturing for fabricating micro-structured surfaces

To eliminate differences in surface quality and improve the machining flexibility of micro-structured surfaces, this paper proposes a novel ultra-precision diamond sculpturing method based on a triaxial fast tool servo (FTS). In this method, the diamond tool is directly driven by the FTS rather than the ultra-precision lathe to fabricate the micro-structure surfaces. The corresponding toolpath generation algorithm is established to take full advantage of the triaxial FTS. The toolpath is first generated through traditional calculating the shortest tool edge projection on the desired surface and the curve interpolation. The overshoot around the path corner is predicted by simulating the tracking path. Then an extended path is added to the original toolpath to stabilize the overshoot before removing the material. The simulation indicates that the hexagonal lens array can be favorably fabricated by the proposed ultra-precision diamond sculpturing method, and the developed toolpath reduces the form error from 20 to 5nm. The sculpturing experiments of sinusoidal micro-structure array and micro-lens array surfaces suggest that their actual peak-to-valley (PV) form errors are 70nm and 50nm, respectively. The single lens with the surface roughness Sa 3.44nm can be precisely fabricated in 0.1s, demonstrating the high machining efficiency and high machining quality of the proposed ultra-precision diamond sculpturing method.

Modernistic Perspective on Kafka's Metamorphosis

This study explores Kafka's "Metamorphosis" using a modernistic lens. The study employs a qualitative method, analyzing textual lines through the ideas of modernism presented by Berry (1995). Findings reveal that Kafka employed experimental writing techniques of symbolism and stream of consciousness to depict elements of hope and the human connection with himself. Moreover, "Metamorphosis" contains modernistic themes of dehumanization, existential crisis, fear, violence, and absurdity. All these themes signify the degradation of Samsa to the extent that he ultimately meets his death. This study paves the way for academia to perceive literature in a broader sense rather than confining it to a single lens of interpretation.

Much ado about no offset – characterizing the anomalous multiple-image configuration and the model-driven displacement between light and mass in the multiplane strong lens Abell 3827

ABSTRACT Abell 3827 is a unique galaxy cluster with a dry merger in its core causing a highly resolved multiple-image configuration of a blue spiral galaxy at zs = 1.24. The surface brightness profiles of four merging galaxies around zd = 0.099 complicate a clear identification of the number of images and finding corresponding small-scale features across them. The entailed controversies about offsets between luminous and dark matter have never been settled and dark matter characteristics in tension with bounds from complementary probes and simulations seemed necessary to explain this multiple-image configuration. We resolve these issues with a systematic study of possible feature matchings across all images and their impact on the reconstructed mass density distribution. From the local lens properties directly constrained by these feature matchings without imposing any global lens model, we conclude that none of them are consistent with expected local characteristics from standard single-lens-plane lensing, nor can they be motivated by the light distribution in the cluster. Inspecting complementary spectroscopic data, we show that all these results originate from an insufficient constraining power of the data and seem to hint at a thick lens and not at exotic forms of dark matter or modified gravity. If the thick-lens hypothesis can be corroborated with follow-up multiplane lens modelling, A3827 suffers from a full three-dimensional degeneracy in the distribution of dark matter because combinations of shearings and scalings in a single lens plane can also be represented by an effective shearing and a rotation caused by multiple lens planes.

Novel developments of refractive power measurement techniques in the automotive world

Refractive power measurements serve as the primary quality standard in the automotive glazing industry. In the light of autonomous driving new optical metrics are becoming more and more popular for specifying optical quality requirements for the windshield. Nevertheless, the link between those quantities and the refractive power needs to be established in order to ensure a holistic requirement profile for the windshield. As a consequence, traceable high-resolution refractive power measurements are still required for the glass quality assessment. Standard measurement systems using Moiré patterns for refractive power monitoring in the automotive industry are highly resolution limited, wherefore they are insufficient for evaluating the camera window area. Consequently, there is a need for more sophisticated refractive power measurement systems that provide a higher spatial resolution. In addition, a calibration procedure has to be developed in order to guarantee for the comparability of the measurement results. For increasing the resolution, a measurement setup based on an auto-correlation algorithm is tested in this paper. In order to benchmark the proposed high-resolution refractive power measurement technique, a novel laser-based setup has been realized in the Volkswagen Laser Laboratory as a reference method tuned for high-accuracy measurements. Furthermore, a calibration procedure is established by using a single reference lens with a nominal refractive power of . For the calibration of the entire measurement range of the system, the lens is tilted by an inclination angle orthogonal to the optical axis. The effective refractive power is then given by the Kerkhof model. By adopting the measurement and calibration procedure presented in this paper, glass suppliers in the automotive industry will be able to detect relevant manufacturing defects within the camera window area more accurately paving the way for a holistic quality assurance of the windshield for future advanced driver-assistance system (ADAS) functionalities. Concurrently, the traceability of the measurement results is ensured by establishing a calibration chain based on a single reference lens, which is traced back to international standards.

Optical levitation in high vacuum using a 0.9-numerical-aperture lens

Nanoparticles levitated in high vacuum are isolated from the surrounding environment and thus can be used in various applications, including quantum physics research. We demonstrated optical levitation of a nanoparticle, which was trapped without cooling at a pressure of 4.5 × 10−3 Pa, using a single aspheric lens with a large numerical aperture (= 0.9) and 1030-nm laser. We also activated parametric feedback cooling to trap the particle at a pressure of 5.8 × 10−4 Pa. This experimental system will be useful for studying nanoparticles in ultrahigh vacuum and for building a mixed system with laser-cooled atoms.

Correlation between the scan strategy, residing spatter distribution, and parts quality in laser powder bed fusion

Spattering may cause defects in the Laser Powder Bed Fusion (LPBF) process, and the inert gas flow has been identified as an effective method for removing/mitigating the negative effects and preventing vapor interference in the melting process. Given the variability of scan strategies in LPBF, optimizing the scan strategy to minimize residing spatters on powder bed is challenging but important. This study focuses on the correlation between the distribution of residing spatters, parts quality, and scan strategies (particularly scan direction and scan sequence here) under the influence of inert gas flow. A single lens reflex camera and image processing are employed to detect the distribution of spatters residing on the powder bed, providng unprecedented insight and valuable guidance for the design of scan strategy. The results reveal that the scan sequence against the gas flow induces fewer spatters residing on the powder bed. The large size residing spatters, with the diameter ranging from 80 μm to 210 μm, are concentrated along the scan direction in close proximity to the melting area. Scan sequence along the gas flow leads to rougher surface of the part, and more defects are formed between layers caused by spatter inclusions, which deteriorates the tensile properties obviously. It is recommended to employ orthogonal S-scanning strategy (S-45° with 90° layerwise rotation, scan sequence against gas flow) during the LPBF process. The selection of scanning parallel or perpendicular to the gas flow is dependent on the distribution of the surrounding processing areas, to ensure consistency of the parts quality.

Detecting Multiplanetary Systems with Gravitational Microlensing and the Roman Space Telescope

It is plausible that most of the Stars in the Milky Way Galaxy, like the Sun, consist of planetary systems, instead of a single planet. Out of the estimately discovered 3980 planet-hosting stars, about 860 of them are known to be multiplanetary systems (as of 2023 June). Gravitational microlensing, which is the magnification in the light of a source star, due to a single or several lenses, has proven to be one of the most useful astrophysical phenomena with many applications. Until now, many extrasolar planets (exoplanets) have been discovered through binary microlensing, where the lens system consists of a star with one planet. In this paper, we discuss and explore the detection of multiplanetary systems that host two exoplanets via microlensing. This is done through the analysis and modeling of possible triple-lens configurations (one star and two planets) of a microlensing event. Furthermore, we examine different magnifications and caustic areas of the second planet, by comparing the magnification maps of triple and binary models in different settings. We also discuss the possibility of detecting the corresponding light curves of such planetary systems with the future implementation of the Nancy Grace Roman (Roman) Space Telescope and its Galactic Time Domain survey.

A Perceptual Measure for Deep Single Image Camera and Lens Calibration.

Image editing and compositing have become ubiquitous in entertainment, from digital art to AR and VR experiences. To produce beautiful composites, the camera needs to be geometrically calibrated, which can be tedious and requires a physical calibration target. In place of the traditional multi-image calibration process, we propose to infer the camera calibration parameters such as pitch, roll, field of view, and lens distortion directly from a single image using a deep convolutional neural network. We train this network using automatically generated samples from a large-scale panorama dataset, yielding competitive accuracy in terms of standard l2 error. However, we argue that minimizing such standard error metrics might not be optimal for many applications. In this work, we investigate human sensitivity to inaccuracies in geometric camera calibration. To this end, we conduct a large-scale human perception study where we ask participants to judge the realism of 3D objects composited with correct and biased camera calibration parameters. Based on this study, we develop a new perceptual measure for camera calibration and demonstrate that our deep calibration network outperforms previous single-image based calibration methods both on standard metrics as well as on this novel perceptual measure. Finally, we demonstrate the use of our calibration network for several applications, including virtual object insertion, image retrieval, and compositing.

Fabrication and characterization of a two-dimensional individually addressable electrowetting microlens array.

We demonstrate a two-dimensional, individually tunable electrowetting microlens array fabricated using standard microfabrication techniques. Each lens in our array has a large range of focal tunability from -1.7 mm to -∞ in the diverging regime, which we verify experimentally from 0 to 75 V for a device coated in Parylene C. Additionally, each lens can be actuated to within 1% of their steady-state value within 1.5 ms. To justify the use of our device in a phase-sensitive optical system, we measure the wavefront of a beam passing through the center of a single lens in our device over the actuation range and show that these devices have a surface quality comparable to static microlens arrays. The large range of tunability, fast response time, and excellent surface quality of these devices open the door to potential applications in compact optical imaging systems, transmissive wavefront shaping, and beam steering.

Quality of life after wearing multifocal contact lenses for myopia control for 2 weeks in the BLINK Study.

To validate Pediatric Refractive Error Profile 2 (PREP2) subscales that can be used to evaluate contact lens wearers and compare vision-specific quality of life measurements between children wearing multifocal and single vision contact lenses for 2 weeks. Two hundred and ninety-four myopic children aged 7-11 years (inclusive) were enrolled in the 3-year, double-masked Bifocal Lenses In Nearsighted Kids (BLINK) Study. Participants completed the PREP2 survey after having worn contact lenses for 2 weeks. The Vision, Symptoms, Activities and Overall PREP2 subscales were used to compare participants' subjective assessment while wearing +1.50 or +2.50 D add multifocal or single vision contact lenses. Rasch analysis was used to validate each subscale and to compare participants' subjective assessment of contact lens wear. Item fit to the Rasch model was good for all scales, with no individual items having infit mean square statistics outside the recommended range (0.7-1.3). Response category function was acceptable for all subscales, with ordered category thresholds. Measurement precision, assessed by the Rasch person reliability statistic, was less than ideal (≥0.8) for three of the subscales, but met the minimum acceptable standard of 0.5. Scores for the Vision subscale differed by treatment assignment (p = 0.03), indicating that participants with the highest add power reported statistically worse quality of vision, although the difference was only 3.9 units on a scale of 1-100. Girls reported fewer symptoms than boys (p = 0.006), but there were no other differences between boys and girls. Rasch analysis demonstrates that the PREP2 survey is a valid instrument for assessing refractive error-specific quality of life. These results suggest that vision-related quality of life is not meaningfully affected by 2 weeks of soft multifocal contact lens wear for myopia control.

Wavelength-actuated varifocal and polarization-insensitive metalenses assisted by monolayer single-celled phase-change metasurfaces

Varifocal metalenses with tunable focal lengths allowing for transforming the complex and bulky tunable lens kit into a single flat lens, show great potential applications in tomography techniques, 3D displays, multi-imaging processing, among others. However, varifocal metalenses that integrate key properties, such as modest efficiency, large numerical aperture (NA) as well as polarization insensitivity into one remain elusive. Here, we present and numerically demonstrate a wavelength-actuated varifocal and polarization-insensitive metalens. This metalens is based on a novel generic design principle that relies on independently tailoring two sets of Ge2Sb2Se4Te1 (GSST) anisotropic nanofins corresponding to two resonant wavelengths of λ 1 and λ 2, respectively. Via intelligently integrating two sets of anisotropic nanofins into a monolayer single-celled phase-change metasurface in the form of ‘cross’ or ‘straight’ composite, the metalens design not only enables the crosstalks between two wavelength channels minimized, but also is endowed with polarization-insensitive and varifocal performance, while maintaining high focusing efficiency and diffraction-limited performance. Due to the noninterleaved arrangement making the meta-structure more compact, another prototype of wavelength-actuated varifocal metalens with ultrahigh-NAs (0.89 and 0.95, respectively corresponding to the target wavelengths of λ 1 and λ 2) are also implemented with a field of view of 4° based on this principle. We also demonstrate the versatility of our approach by successfully implementing the generation of the polarization-insensitive varifocal focusing optical vortex. Additionally, the phase transition of GSST enables the proposed meta-devices to switch between ON and OFF states for spot focusing. Our design can be easily extended to visible or THz wavebands and will enable enormous applications ranging from switchable optical scanners, dynamic optical tweezers and spanners, to miniaturized polarization-insensitive imaging devices.

Repeated Low-Level Red Light Therapy for the Control of Myopia in Children: A Meta-Analysis of Randomized Controlled Trials.

Repeated low-level red light (RLRL) therapy has been suggested to be effective in children with myopia. However, evidence from randomized controlled trials (RCTs) is still limited. We performed a meta-analysis of RCTs to systematically evaluate the efficacy of RLRL on changes of axial length (AL) and cycloplegic spherical equivalent refraction (SER) in children with myopia. Relevant RCTs were obtained through a search of electronic databases including PubMed, Embase, Cochrane Library, Wanfang, and China National Knowledge Infrastructure from inception to September 15, 2022. A random-effects model was used to pool the results after incorporating the influence of potential heterogeneity. Subgroup analyses were performed according to the control treatment and follow-up duration. A total of seven RCTs involving 1,031 children with myopia, aged 6 to 16 years, were included in the meta-analysis. Compared with control treatment without RLRL, treatment with RLRL was associated with a significantly reduced AL (mean difference [MD]: -0.25 mm, 95% confidence interval [CI]: -0.32 to -0.17, P<0.001; I2=13%) and a significantly increased cycloplegic SER (MD: 0.60 D, 95% CI: 0.44-0.76, P<0.001; I2=20%). Further subgroup analyses showed consistent results in studies comparing children wearing single vision lenses and those receiving active treatment including orthokeratology or low-dose atropine eye drops, as well as studies of treatment duration of 6 and 12 months. Results of the meta-analysis suggested that RLRL treatment is effective for slowing down the progression of myopia in children aged 6 to 16 years.

One time only

Single use contact lenses are well suited to outdoor, summer lifestyles. Optician showcases some of the best products in the category

Interferometric visibility of single-lens models: The thin-arcs approximation

Long baseline interferometry of microlensing events can resolve the individual images of the source produced by the lens, which combined with the modelling of the microlensing light curve, leads to the exact lens mass and distance. Interferometric observations thus offer a unique opportunity to constrain the mass of exoplanets detected by microlensing, and to precisely measure the mass of distant isolated objects such as stars and brown dwarfs, and of stellar remnants such as white dwarfs, neutron stars, and stellar black holes. Having accurate models and reliable numerical methods is of particular importance as the number of targets is expected to increase significantly in the near future. In this work we discuss the different approaches to calculating the fringe complex visibility for the important case of a single lens. We propose a robust integration scheme to calculate the exact visibility, and introduce a novel approximation, which we call the ‘thin-arcs approximation’, which can be applied over a wide range of lens-source separations. We find that this approximation runs six to ten times faster than the exact calculation, depending of the characteristics of the event and the required accuracy. This approximation provides accurate results for microlensing events of medium to high magnification observed around the peak (i.e. a large fraction of potential observational targets).

Lens File: Myopia done the MyCon way

Andrew Copley explains why single vision lenses are not the answer for myopia management and how Rodenstock's MyCon offers a solution

Ball Lens‐Assisted Cellphone Imaging with Submicron Resolution

AbstractOne of the most significant developments in life sciences—the discovery of bacteria and protists—was accomplished by Antoni van Leeuwenhoek in the 17th century using a single ball lens microscope. It is shown that the full potential of single lens designs can be realized in a contact mode of imaging by ball lenses with a refractive index of n ≈ 2, suitable for developing compact cellphone‐based microscopes. The quality of imaging is comparable to basic compound microscopes, but with a narrower field‐of‐view, and is demonstrated for various biomedical samples. The maximal magnification (M &gt; 50) with the highest resolution (≈0.66 µm at λ = 589 nm) is achieved for imaging of nanoplasmonic structures by ball lenses made from LASFN35 glass, the index of which is tuned near n = 2 using chromatic dispersion. Due to limitations of geometrical optics, the imaging theory is developed based on an exact numerical solution of the Maxwell equations, including spherical aberration and the nearfield coupling of a point source. The modeling is performed using multiscale analysis: from the field propagation inside ball lenses with diameters 30 &lt; D/λ &lt; 4000 to the formation of the diffracted field at distances of ≈105 λ. It is shown that such imaging enables the transition from pixel‐ to diffraction‐limited resolution in cellphone microscopy.

De‐noising method of aquatic product image with foreign matters based on improved wavelet transform and bilateral filter

AbstractAiming at the strong spot noise caused by the reflection of meat slices in fish image with foreign matters that collected by ordinary camera or Single Lens Reflex (SLR) camera, we proposed an improved wavelet transform and bilateral filtering algorithm to reduce the noise of image. In this paper, our algorithm absorbed the advantages of wavelet threshold de‐noising algorithm and bilateral filtering algorithm, the wavelet threshold de‐noising algorithm being used for high frequency components and bilateral filtering being used for low frequency components, which not only achieved the effect of eliminating noise and weakening light spot, but also protected the details of the image. In the experiment, in order to verify the effectiveness of the proposed algorithm, we used the traditional bilateral filtering, Gaussian filtering and median filtering algorithms to process 500 salmon fish images which had residual fishbone, respectively. Since the original image itself was a noisy image, it was impossible to evaluate the noise reduction effect by using an algorithm that requires a noiseless image as a reference image, so we used five methods to evaluate the quality of the image processed by each algorithm, which were Blind/Referenceless Image Spatial QUality Evaluator (BRISQE), Cumulative Probability of Blur Detection (CPBD), variance, image entropy, and operation speed. Among them, BRISQE and CPBD could quantitatively reflect the overall quality of the image, the lower the BRISQE score or the higher the CPBD score, the better the quality of the image. Compared with other algorithms, the BRISQE score and CPBD score of the image processed by our algorithm were the best, with the average scores reaching 20.65 and .8421, respectively. Experimental results showed that the improved algorithm in this paper can effectively eliminate this kind of strong spot noise. The processed image has achieved better visual effect in both subjective and objective level.

Blickrichtungsabhängige Visusbestimmung bei korrekt und falsch zentrierten asphärischen Einstärkenbrillengläsern

Purpose. To investigate the effect on visual acuity of dis- regarding the centre of rotation requirement when using single vision aspheric lenses for correction of moderate to high hyperopes. Material and Methods. Two aspheric single vision lenses are fitted in each eye of 15 hyperopic subjects. One lens is exactly centred, the other lens is horizontally decentrated five milli- metres temporally. The interpolated LogMAR is then deter- mined in five different directions of gaze. The extent to which the LogMAR achieved differs between the lens with the observed centre of rotation requirement and the disregarded centre of rotation requirement in the individual directions of gaze is then examined. In addition, the influence of age is investigated. The results of the sub-samples “Age &lt; 50 years” and “Age ≥ 50 years” are analysed descriptively. A clinically significant difference is defined as half a visual acuity level (corresponds to 0.05 LogMAR). Results. Significant differences in LogMAR between exact and incorrect centring could be determined for 30° nasal gaze (-0.09 LogMAR) and for 0° gaze through the lens (-0.07 LogMAR). Visual acuity was better with the precisely centred lens in each case. When testing for differences in LogMAR between the defined age-dependent subsamples, no signif- icant differences could be determined. Conclusion. The results show that the aberrations astigma- tism of oblique bundles and the image field curvature with the resulting deviation from refractive accuracy have less influence on visual acuity than previously assumed. Keywords spectacle lens centration, aspheric single vision lenses, centre of rotation requirement, astigmatism of oblique incidence, refractive accuracy

Design of non-imaging receiving system for large field of view lidar

Lidar has been widely used in many fields due to its high precision. The system must also have a corresponding large field of view receiving capability in order to achieve effective detection of targets when imaging lidar realizes large-angle scanning. For the InGaAs-APD detector component, there is a contradiction between the high-frequency response bandwidth and the size of the photosensitive surface. This paper proposes a large surface four-quadrant InGaAs-APD detector with 2 × 2 area array structure design, which based on a small photosensitive panel detector with a unit diameter of 0.5 mm. On the basis of ensuring the cut-off frequency bandwidth of 100 MHz, it also realizes signal reception with large field of view and high sensitivity. For the receiving lens of the system, the relationship between the bin size of the detector and the receiving field of view in the non-imaging optical receiving system is studied. Under the condition that the parameters such as the size of the detector facet have been determined, the best position of the detector is optimally designed to maximize the receiving field of view. Based on theoretical foundations such as radiation angle coefficient and etendue, the non-imaging optical system lidar distance equation is established to evaluate the light-gathering ability of receiving lenses with different effective apertures and focal lengths, and to optimize optical structural parameters such as the best effective aperture and focal length of the receiving lens. Finally, the aspheric lens with the best parameters is selected as the basic receiving optical lens of the system, and an array type large field of view direct detection technology is proposed. The receiving optical system is composed of 6 aspheric single lenses, and the structure is in the form of 2 × 3 array, which finally realizes the efficient detection of echo signals with a large field of view of 48° × 26°.

TDCOSMO

Time-delay distance measurements of strongly lensed quasars have provided a powerful and independent probe of the current expansion rate of the Universe (H0). However, in light of the discrepancies between early- and late-time cosmological studies, current efforts revolve around the characterisation of systematic uncertainties in the methods. In this work we focus on the mass-sheet degeneracy (MSD), which is commonly considered a significant source of systematics in time-delay strong lensing studies, and aim to assess the constraining power provided by integral field unit (IFU) stellar kinematics. To this end, we approximated the MSD with a cored, two-parameter extension to the adopted lensing mass profiles (with core radius rc and mass-sheet parameter λint), which introduces a full degeneracy between λint and H0 from lensing data alone. In addition, we utilised spatially resolved mock IFU stellar kinematics of time-delay strong lenses, given the prospects of obtaining such high-quality data with the James Webb Space Telescope (JWST) in the near future. We constructed joint strong lensing and generalised two-integral axisymmetric Jeans models, where the time delays, mock imaging, and IFU observations are used as input to constrain the mass profile of lens galaxies at the individual galaxy level and consequently yield joint constraints on the time-delay distance (DΔt) and the angular diameter distance (Dd) to the lens. We find that mock JWST-like stellar kinematics constrain the amount of internal mass sheet that is physically associated with the lens galaxy and limit its contribution to the uncertainties of DΔt and Dd, each at the ≤4% level, without assumptions on the background cosmological model. Incorporating additional uncertainties due to external mass sheets associated with mass structures along the lens line of sight, these distance constraints would translate to a ≲4% precision measurement on H0 in flat Λ cold dark matter cosmology for a single lens. Our study shows that future IFU stellar kinematics of time-delay lenses will be key in lifting the MSD on a per lens basis, assuming reasonable and physically motivated core sizes. However, even in the limit of infinite rc, where DΔt is fully degenerate with λint and is thus not constrained, stellar kinematics of the deflector, time delays, and imaging data will provide powerful constraints on Dd, which becomes the dominant source of information in the cosmological inference.