Zoom Lens Research Articles

Metasurface meta-atoms design based on DNN and LightGBM algorithms

Metasurfaces is one of the research hotspots in the field of micro/nanometer technologies during the last decade. Whereas, it remains challenging to inverse design optics devices according to desired physical response. Here we demonstrate an attempt to design a metasurface meta-atoms with machine learning approach. We use the metasurface structure parameters, nanofin material, phase, and transmission as model data of the deep neural networks (DNN) and light gradient boosting machine (LighGBM), and the mapping relationship between geometric parameters and phase and transmission is established. The two models are highly accurate in forward design, achieving the best regression coefficient of 0.969, while for the inverse design the best regression coefficient is 0.918. Using the trained inverse design network, the structural parameters and nanofin composition of the metasurface meta-atoms can be obtained for a given phase and transmittance, and the two models show strong generalization ability. This method may facilitate the viability of complex metasurface design and it can be also potentially applied in optical zoom imaging, perfect absorbers, metasurface filters, and other nanophysics fields.

Evaluation of Mobile and Digital Single-Lens Reflex Photography for Facial Surgical Analysis.

High-quality perioperative photography is imperative to good surgical planning in facial reconstructive and aesthetic surgery. We explore the utility of an add-on smartphone telephoto lens to avoid the distortions noted in prior studies using smartphone cameras. Standard perioperative photographs of the same subject were taken with three distinct cameras using a dual-ring light setup. The three camera setups iPhone 11 alone, iPhone 11 with the 58 Moment telephoto lens attachment, and a D3300 Nikon DSLR APS-C sensor camera with a 60 mm NIKKOR F2.8G ED macro lens were compared using a 47-question online survey consisting of demographic and image-specific questions sent to plastic surgeons. Forty-nine facial plastic surgeons completed the survey. The iPhone 11 alone was identified as having the lowest quality for central/peripheral distortion (83%), columella/caudal septum/alar anatomy (58.3%), and skin quality (38.3%). With the addition of the telephoto lens, the ability to assess all categories was significantly improved. 53.1% (n= 26) of respondents found the iPhone 11 + 58 mm telephoto lens setup to be the most useful for perioperative surgical planning. Smartphone photography with the addition of a telephoto lens can offer a comparable option to the DSLR with regard to photo quality and detail. A telephoto add-on lens is an effective solution to overcome the central distortion seen in images taken by the iPhone for perioperative photography. This photo quality was found to be comparable to that of traditional DSLR cameras in our survey study. 3 Laryngoscope, 133:2590-2596, 2023.

A zoom lens for networks

A zoom lens for networks

Practical zoom camera calibration method for close-range photogrammetry.

Compared to a conventional fixed focus lens, a zoom lens is more flexible and adaptable. However, the challenges involved in precise calibration for a zoom camera prevent its widespread use in close-range photogrammetry. A practical calibration method for a zoom camera is proposed. The zoom-focus model is established through dimension reduction of the setting variables, which is represented as a set of functions of the zoom setting. The zoom and focus settings are updated in real time for objects at different measurement depths. The calibration process only requires the zoom camera to observe the control points distributed in the designed calibration field with several combinations of zoom and focus settings. All the coefficients of the zoom-focus model can be solved by a nonlinear joint optimization. Experimental results have proved that the proposed method is effective for close-range photogrammetry.

A large-scale image database for benchmarking mobile camera quality and NR-IQA algorithms

Camera-oriented quality assessment (CQA) differs from traditional image quality assessment (IQA) in that “distorted” images are straight out of real devices instead of various types and levels of artificial operations. However, despite its value for both customers and manufacturers, academic and industrial fields, there are few CQA databases created years ago. To reflect recent mobile imaging advancements, we present a new massive Phone Camera Benchmarking database (PCB2021) in this paper. In PCB2021, 40 modern phone units featuring photography are simultaneously compared in 182 scenes for a total of 7280 images, which can be classified into six categories (sub-datasets) based on different focal lengths and user cases: main camera (107), ultra-wide (20), 2×, 3×, 5× zoom lenses (26, 8, 10) and night-mode (11). The shooting process begins from 7:00 am to 11:00 pm and lasts more than a month. In the subjective study, to overcome the high-resolution-induced overall quality evaluation difficulty, five image attributes: exposure/contrast, color, sharpness, graininess, artifacts are assessed separately on each dataset. To reduce ranking complexity for large-scale cameras, a dynamic anchor ruler method is proposed to obtain quality orders efficiently. With the constructed PCB2021, we further evaluate 15 mainstream no-reference (NR) IQA algorithms. The finding is that for zoomed images, sharpness metrics can achieve Spearman correlation coefficients above 0.8, while for the subtle main camera and night-mode images, performances of all fifteen algorithms drop down quickly, i.e. 0.1-0.2 for the former and ∼0.5 for the latter. The entire database, expert rankings and algorithm performance reports will be freely available on request.

Optical System Design of MWIR Continuous Zoom Lens with High Zoom Ratio

Optical System Design of MWIR Continuous Zoom Lens with High Zoom Ratio

Computer vision with smartphone microphotography for detection of carious lesions

ObjectivesTo evaluate the similarities in microphotographic images across different smartphones and to establish whether computer vision can use microphotographs to successfully classify dental caries. MethodA universal clip-type microscope with 60x optical zoom was selected to perform in vitro microphotography of extracted teeth. For the first objective, areas of cariogenic interest were physically labelled by dentists and eight smartphones were used to capture images of tooth decays with the microscope fitted over the primary camera lens. For the second objective, 233 microphotography images were acquired and virtually augmented to produce 1631 images that were categorized digitally by an international caries classification system for computer vision-based object detection (YOLO.v4). Five practitioners independently labelled randomly selected images from the test dataset following the caries classification system which were subsequently used to evaluate the diagnostic test accuracy of the YOLO model. ResultA significant overall mean square error [F (df) = 4.03 (6); P < 0.05] was observed while Bhattacharya's distance evaluation produced no significant differences [F (df) = 1.60 (6); P > 0.05] across all eight smartphone derived datasets. Index and reference test comparisons determined an overall sensitivity of 0.99 and specificity of 0.94 for the trained YOLO.v4 and highly significant correlations (r > 0.9, P < 0.001) to the classifications labelled by the dental practitioners. ConclusionNon-standardized images of tooth caries captured by different smartphones generated an accurate diagnostic model for classifying carious lesions that was similar to the visual assessments performed by experienced dental practitioners.

Kombinasi Penerapan Metode WASPAS dan Rank Order Centroid (ROC) dalam Keputusan Pemilihan Teknologi Kamera Ponsel Terbaik

Smartphone camera technology is currently growing rapidly so that it has specifications that support it so that the results obtained are almost on par with the quality of digital cameras. Supported cellphone cameras can be used in learning photography, not necessarily with a digital camera. The increasing number of cellphone choices makes users who want to study photography confused in choosing a cellphone that has the best cellphone camera technology. So that a Decision Support System was applied in this study as a system for obtaining the best cellphone camera technology decisions. In making the right decision on selecting the best cellphone camera technology, it must meet the criteria for Number of Camera Features, Number of Main Cameras, Number of Front Cameras, Main Camera Resolution, Front camera Resolution, Optical Zoom and Quality of Video Recording. Therefore a Decision Support System is needed to solve the problem by applying the ROC (Rank Order Centroid) and WASPAS (Weighted Aggregated Sum Product Assessment) methods which can produce weight and preference values from the first ranking alternative. So that the selection of the best mobile camera technology for the best mobile camera technology can be found in table 7, namely the Samsung Galaxy S22 Ultra which is in the A5 alternative with the highest score of 3.8354 as the first rank

DEVELOPMENT OF OPTICAL SYSTEMS OF 16-LENS ORTHOSCOPIC TELEPHOTO LENSES

In this work, the possibilities of creating multi-lens optical systems of telephoto lenses with a fixed focal length and high image quality with the help of a computer have been experimentally investigated. The effectiveness of the automated procedure for creating new optical systems of orthoscopic telephoto lenses was repeatedly examined. The design procedure utilizes a modified version of the modern stochastic global optimization algorithm. In particular, we carried out the aberration synthesis of several optical systems of 16-lens orthoscopic telephoto lenses having the effective focal length of 300 mm and a F-number equal to 2.8, and designed to work in the visible spectral range with 35-mm full-frame image matrix detectors. Multiple computer simulations of the design process have shown that the global optimization procedure with a total number of variables of around 90 requires significant computing power. Specifically, when running on the Intel Core i9-9900K processor in multi-threaded mode and optimizing the values of the modulation transfer functions, the design procedure can exceed 50 hours. The maximum value of the relative distortion of synthesized variants of telephoto lenses does not exceed 0.017%. In all considered cases, the values of polychromatic modulation transfer functions for a spatial frequency of 30 lines/mm are not smaller than 0.5 over the entire image field. The design results obtained for the specified telephoto lenses confirm the effectiveness of the proposed approach and the practical possibility of achieving high-quality correction of aberrations in the above-mentioned multi-lens telephoto systems even without the use of fluorite (calcium fluoride).

Zoom liquid lens with switchable aperture

A zoom liquid lens with switchable aperture is demonstrated in this paper, which consists of a lens chamber, a circular truncated cone, a limit ring and two immiscible liquids. Different from conventional zoom liquid lenses, the curvature of the liquid-liquid (L-L) interface, the position of the L-L interface and the aperture size of the proposed liquid lens can be tuned by only one actuator. Then, two problems can be solved: a larger range of optical power is realized by the switchable size of the aperture, and the zoom function can be achieved by switchable position of the aperture. Thus, the proposed zoom lens has characteristics of large optical power tunable range and excellent zoom ability with only one actuator. However, due to a single actuator, the curvature, position and aperture of the proposed lens cannot be controlled arbitrarily and individually. With a large aperture of 10 mm and a small aperture of 5 mm, the range of optical power is -43 m−1 ∼ +43 m−1, the zoom ratio reaches ∼2 × and the angular resolution is 27"7. It is promising to promote the development of a new generation of miniaturized optofluidic imaging systems.

A New Method for Surveying the World’s Smallest Class of Dragonfly in Wetlands Using Unoccupied Aerial Vehicles

Field surveys in wetlands are limited by the difficulty in accessing the site, hazards during surveys, and the risk of disturbing the ecosystem. Thus, the use of unoccupied aerial vehicles (UAVs) can overcome these limiting factors and can assist in monitoring small organisms, such as plants and insects, that are unique to wetlands, aiding in wetland management and conservation. This study aimed to demonstrate the effectiveness of a survey method that uses a small drone equipped with a telephoto lens to monitor dragonflies, which are unique to wetlands and have been difficult to survey quantitatively, especially in large wetlands. In this study, the main target species of dragonflies was Nannophya pygmaea, which is the world’s smallest dragonfly (about 20 mm long). The study area was Mizorogaike wetland (Kita Ward, Kyoto City, Japan). The UAV was flown at a low speed at an altitude of 4 m to 5 m, and images were taken using 7× telephoto lens on Mavic 3 (7× optical and 4× digital). A total of 107 dragonflies of seven species were identified from the photographs taken by the drone. N. pygmaea, about 20 mm long, was clearly identified. Eighty-five dragonflies belonging to N. pygmaea were identified from the images. Thus, by using a small drone equipped with a telephoto lens, the images of N. pygmaea were captured, and the effects of downwash and noise were reduced. The proposed research method can be applied to large wetlands that are difficult to survey in the field, and can thus provide new and important information pertaining to wetland management and conservation. This research method is highly useful for monitoring wetlands as it is non-invasive, does not require the surveyor to enter the wetland, requires little research effort, and can be repeated.

Image blurring and spectral drift in imaging spectrometer system with an acousto-optic tunable filter and its application in UAV remote sensing

ABSTRACT In the design and research of an unmanned aerial vehicle-borne hyperspectral imager with an acousto-optic tunable filter (AOTF), the depth of the field range of the imaging objective lens is fixed, the spectral range of 400–1000nm is wide, and the AOTF crystal has different deflection angles for diffracted light of different wavelengths. These features all cause problems such as image blurring and spectral drifts. Therefore, we propose a solution using a tunable zoom lens and multi-modal spectrum registration to solve these problems. We also propose an improved image definition evaluation function using the zoom lens to obtain clear horizontal lines and blurred vertical lines and, thereby, hope to overcome image blurring in an AOTF spectrometer. The zoom parameters corresponding to the clear image in each spectral segment of the AOTF spectrometer can be determined rapidly and accurately. However, it is difficult to establish a mathematical model of the drift, using wavelength as a variable, to compensate the drift due to the clear image of each spectrum obtained using the zoom lens. The calibration method completes the registration of the spectral data cube composed of clear images, solving the problem of spectral band drift. Moreover, it has been verified through UAV-borne hyperspectral imaging that image blurring and spectral drift of the AOTF imaging spectrometer were significantly reduced, providing opportunities for the application and research of AOTF-based hyperspectral imagers in more fields, such as remote sensing.

Design and fabrication of a focus-tunable liquid cylindrical lens based on electrowetting.

In this study, a focus-tunable liquid cylindrical lens based on electrowetting was designed and fabricated. The cylindrical cavity usually used in common electrowetting zoom spherical lenses was replaced by a 20 mm × 10 mm × 8 mm cuboid cavity, in which the interface of two liquids formed a toroid owing to the electrowetting effect. The proposed liquid cylindrical lens can serve as either a converging or diverging lens with the response time under 110 ms by changing the supplied voltage. The zoom lens we fabricated worked stably under 0-110 V voltage for a long time, guaranteeing that the focal length of the liquid cylindrical lens can range within (-∞, -148.36 mm) ∪ (697.21 mm, +∞). By combining the liquid lens that we designed with a simple fixed cylindrical lens, a cylindrical lens system with an arbitrary focal length suitable for various tasks in beam manipulation can be realized.

Design of an achromatic zoom metalens doublet in the visible.

Zoom metalens doublets, featuring ultra-compactness, strong zoom capability, and CMOS compatibility, exhibit unprecedented advantages over the traditional refractive zoom lens. However, the huge chromatic aberration narrows the working bandwidth, which limits their potential applications in broadband systems. Here, by globally optimizing the phase profiles in the visible, we designed and numerically demonstrated a moiré lens based zoom metalens doublet that can achromatically work in the band of 440-640 nm. Such a doublet can achieve a continuous zoom range from 1× to 10×, while also maintaining a high focusing efficiency up to 86.5% and polarization insensitivity.

The interaction of internal and external attention.

The internal/external framework of attention characterizes attention focused to perceptual stimuli and internal representations as highly similar processes. While much research on external attention examines how attention may be broadened or narrowed (attentional zoom lens), it is unclear if internal attention functions in a similar way. In the present study, we manipulate both internal and external attentions to be either broad or narrow. Participants first encoded either a broad or narrow working memory array containing three differently colored items. This array was maintained as they performed an Eriksen flanker task that was either distributed broadly or narrowly, followed by a memory test for a random memory item. We found that regardless of whether the flanker fell inside or outside of the internal breadth of attention, flanker congruency effects did not change. The exception to this was when internal breadth was manipulated with retrocuing, which resulted in greater congruency effects when flankers aligned with the span of internal breadth rather than falling outside of it. Overall, this study shows that internal breadth information is unlikely to alter processing of external distractors until some of the information is cued internally after encoding, suggesting limitations in the internal/external attention framework.

Paraxial design of four-component zoom lens system with fixed distance between focal points by matrix optics

In this paper, we propose a systematic approach to design a four-component zoom system with fixed spacing between focal points based on matrix optics to achieve a relatively high zoom ratio. In the method, the zoom trajectory under each chosen paraxial design is determined through matrix method, which is challenging but meaningful to achieve a globally optimized design for the complex zoom system. The elements of the system matrix imply the working state of the optical system, and axial displacement equation for the desired zoom system are derived by restricting specific matrix elements. Properly selected trajectory of the particular component described by means of a parametric function can make the model become solvable explicitly. Then the paraxial design problem is transformed into the optimization of these parameters with regard to the merit functions encompassing the primary aberration terms, compactness, smoothness of the trajectories. We adopt Particle Swarm Optimization (PSO) algorithm to globally optimize the parameters to retrieve the optimum zoom trajectory in specific design criteria. The proposed method is demonstrated through two specific examples under different configurations, both of which have acquired a final zoom ratio of 8X. The simulation results demonstrate that our proposed method can be a practical and powerful tool for paraxial design of complex multi-group zoom optical systems.

Movable and Focus-Tunable Lens Based on Electrically Controllable Liquid: A Lattice Boltzmann Study.

Adjusting the focal length by changing the liquid interface of the liquid lens has become a potential method. In this paper, the lattice-Boltzmann-electrodynamic (LB-ED) method is used to numerically investigate the zooming process of a movable and focus-tunable electrowetting-on-dielectrics (EWOD) liquid lens by combining the LBM chemical potential model and the electrodynamic model. The LB method is used to solve the Navier-Stokes equation, and the Poisson-Boltzmann (PB) equation is introduced to solve the electric field distribution. The experimental results are consistent with the theoretical results of the Lippmann-Young equation. Through the simulation of a liquid lens zoom driven by EWOD, it is found that the lens changes from a convex lens to a concave lens with the voltage increases. The focal length change rate in the convex lens stage gradually increases with voltage. In the concave lens stage, the focal length change rate is opposite to that in the convex lens stage. During the zooming process, the low-viscosity liquid exhibits oscillation, and the high-viscosity liquid appears as overdamping. Additionally, methods were proposed to accelerate lens stabilization at low and high viscosities, achieving speed improvements of about 30% and 50%, respectively. Simulations of lens motion at different viscosities demonstrate that higher-viscosity liquids require higher voltages to achieve the same movement speed.

Dynamic Characteristic Monitoring of Wind Turbine Structure Using Smartphone and Optical Flow Method

The dynamic characteristics of existing wind turbine structures are usually monitored using contact sensors, which is not only expensive but also time-consuming and laborious to install. Recently, computer vision technology has developed rapidly, and monitoring methods based on cameras and UAVs (unmanned aerial vehicles) have been widely used. However, the high cost of UAVs and cameras make it difficult to widely use them. To address this problem, a target-free dynamic characteristic monitoring method for wind turbine structures using portable smartphone and optical flow method is proposed by combining optical flow method with robust corner feature extraction in ROI (region of interest). Firstly, the ROI region clipping technology is introduced after the structural vibration video shooting, and the threshold value is set in the ROI to obtain robust corner features. The sub-pixel displacement monitoring is realized by combining the optical flow method. Secondly, through three common smartphone shooting state to monitor the structural displacement, the method of high pass filtering combined with adaptive scaling factor is used to effectively eliminate the displacement drift caused by the two shooting states of standing and slightly walking, which can meet the requirements of structural dynamic characteristics monitoring. After that, the structural displacement is monitored by assembling the telephoto lens on the smartphone. The accuracy of displacement monitored by assembling the telephoto lens on the smartphone is investigated. Finally, the proposed monitoring method is verified by the shaking table test of the wind turbine structure. The results show that the optical flow method, combined with smartphones, can accurately identify the dynamic characteristics of the wind turbine structure, and the smartphone equipped with a telephoto lens is more conducive to achieving low-cost wind turbine structure dynamic characteristics monitoring. This research can provide a reference for evaluating the condition of wind turbine structures.

A Novel Fuzzy Controller for Visible-Light Camera Using RBF-ANN: Enhanced Positioning and Autofocusing.

To obtain high-precision for focal length fitting and improve the visible-light camera autofocusing speed, simultaneously, the backlash caused by gear gaps is eliminated. We propose an improved RBF (Radical Basis Function) adaptive neural network (ANN) FUZZY PID (Proportional Integral Derivative) position closed-loop control algorithm to achieve the precise positioning of zoom and focus lens groups. Thus, the Levenberg-Marquardt iterative algorithm is used to fit the focal length, and the improved area search algorithm is applied to achieve autofocusing and eliminate backlash. In this paper, we initially adopt an improved RBF ANN fuzzy PID control algorithm in the position closed-loop in the visible-light camera position and velocity double closed-loop control system. Second, a similar triangle method is used to calibrate the focal length of the visible-light camera system, and the Levenberg-Marquardt iterative algorithm is used to fit the relation of the zoom potentiometer code values and the focal length to achieve the zoom position closed-loop control. Finally, the improved area search algorithm is used to achieve fast autofocusing and acquire clear images. The experimental results show that the ITAE (integrated time and absolute error) performance index of the improved RBF ANN fuzzy PID control algorithm is improved by more than two orders of magnitude as compared with the traditional fuzzy PID control algorithm, and the settling time is 6.4 s faster than that of the traditional fuzzy PID control. Then, the Levenberg-Marquardt iterative algorithm has a fast convergence speed, and the fitting precision is high. The quintic polynomial fitting results are basically consistent with the sixth-degree polynomial. The fitting accuracy is much better than that of the quadratic polynomial and exponential. Autofocusing requires less than 2 s and is improved by more than double that of the traditional method. The improved area search algorithm can quickly obtain clear images and solve the backlash problem.

A dual-view multi-resolution laparoscope for safer and more efficient minimally invasive surgery

Minimally invasive surgery (MIS) is limited in safety and efficiency by the hand-held nature and narrow fields of view of traditional laparoscopes. A multi-resolution foveated laparoscope (MRFL) was invented to address these concerns. The MRFL is a stationary dual-view imaging device with optical panning and zooming capabilities. It is designed to simultaneously capture and display a zoomed view and supplemental wide view of the surgical field. Optical zooming and panning capabilities facilitate repositioning of the zoomed view without physically moving the system. Additional MRFL features designed to improve safety and efficiency include its snub-nosed endoscope, tool-tip auto tracking, programmable focus profiles, unique selectable display modalities, foot pedal controls, and independently controlled surgeon and assistant displays. An MRFL prototype was constructed to demonstrate and test these features. Testing of the prototype validates its design architecture and confirms the functionality of its features. The current MRFL prototype functions adequately as a proof of concept, but the system features and performance require further improvement to be practical for clinical use.