Pinhole Lens Research Articles

Incorrectly Focused Neodymium:Yttrium-Aluminum-Garnet (Nd:YAG) Laser Beam Leads to Massive Destructive Effects in Small-Aperture (Pinhole) Intraocular Lenses.

Pinhole intraocular lenses (IOLs) were developed to improve reading by compensating for loss of accommodative function. The IC-8® Apthera™ is a small-aperture presbyopia-correcting IOL that combines the proven principle of small-aperture optics with an aspheric monofocal lens to deliver a continuous range of vision for patients withcataractsfrom distance to near vision. Posterior capsule opacification is the most common sequela after cataract surgery. It is effectively treated by laser capsulotomy. However, if the laser beam is incorrectly focused, the IOL can be permanently damaged (pits/shots). In this experimental study, yttrium-aluminum-garnet (YAG) pits were purposefully created. Defects were analyzed and compared between the periphery of the ring in the clear area of the hydrophobic acrylic lens and at the carbon black (CB)-polyvinylidene fluoride (PVDF) filtering component (FilterRing™) of the pinhole lens. All defects were made using identical settings/energy levels (2.6mJ). The damage induced to the IC-8® Apthera™ IOL was examined by low-magnification images, light microscopy, scanning electron microscopy, and micro-computed tomography (micro-CT). YAG defects in the carbon black filter ring were much more severe than those in the clear zone due to the high absorption of the carbon black. Massive defects and destruction of the lens with tearing out of fragments and particles were observed. The missing volume calculated from the micro-CT reconstruction was 0.266 mm3, which is 1.6% of the entire IOL volume, or more than 1000 times the volume damaged in the largest shot in the periphery. Based on the results, we highly recommend using the lowest possible energy levels, posterior offset setting, and circular pattern for maximum safety when performing laser capsulotomy with pinhole implants. Care should be taken to avoid creating irreversible iatrogenic defects that may affect overall quality. The safest area for performing capsulotomy seems to be the periphery of the ring segment. Video available for this article.

Comparison Between the Properties of Three New Designs of Pinhole Magnetic Lens

Three different new designs of an objective pinhole lens were compared. Their magnetic and optical properties were studied using Finite Element Method for Calculating Magnetic Field Distribution (FEM-CMFD) and Magnetic Electron Lens Optical Properties (MELOP) software. The focal length (fo), spherical aberration (Cs), chromatic aberration (Cc), and the resolving power (δ) of each lens were compared at a range of relatively corrected acceleration voltages (Vr = 100 V-100 kV) and a constant excitation of (NI = 5280 A-t (where A represents Ampere and t represents turn)) and current density (2 A/mm2) to find the best design. The L1 lens is similar to the Gemini lens. L2 and L3 are the traditional pinhole lens shape. The L1 lens gave the best results in terms of optical and magnetic properties as its optical properties at medium and low acceleration voltages. L2 and L3 Lenses had almost identical magnetic properties, but the difference was apparent in optical properties.

LD-SLAM: A Robust and Accurate GNSS-Aided Multi-Map Method for Long-Distance Visual SLAM

Continuous, robust, and precise localization is pivotal in enabling the autonomous operation of robots and aircraft in intricate environments, particularly in the absence of GNSS (global navigation satellite system) signals. However, commonly employed approaches, such as visual odometry and inertial navigation systems, encounter hindrances in achieving effective navigation and positioning due to issues of error accumulation. Additionally, the challenge of managing extensive map creation and exploration arises when deploying these systems on unmanned aerial vehicle terminals. This study introduces an innovative system capable of conducting long-range and multi-map visual SLAM (simultaneous localization and mapping) using monocular cameras equipped with pinhole and fisheye lens models. We formulate a graph optimization model integrating GNSS data and graphical information through multi-sensor fusion navigation and positioning technology. We propose partitioning SLAM maps based on map health status to augment accuracy and resilience in large-scale map generation. We introduce a multi-map matching and fusion algorithm leveraging geographical positioning and visual data to address excessive discrete mapping, leading to resource wastage and reduced map-switching efficiency. Furthermore, a multi-map-based visual SLAM online localization algorithm is presented, adeptly managing and coordinating distinct geographical maps in different temporal and spatial domains. We employ a quadcopter to establish a testing system and generate an aerial image dataset spanning several kilometers. Our experiments exhibit the framework’s noteworthy robustness and accuracy in long-distance navigation. For instance, our GNSS-assisted multi-map SLAM achieves an average accuracy of 1.5 m within a 20 km range during unmanned aerial vehicle flights.

Sample balancing of curves for lens distortion modeling and decoupled camera calibration

State-of-the-art camera calibration methods usually estimate the pinhole model and lens distortion together by strict point correspondence. However, in many applications, only part of the full calibration result is required. Simpler calibration patterns like straight lines are studied in many works to calibrate only the lens distortion but lack precision compared with conventional methods. In this paper, we study the geometric invariants of line straightness and proposed a method to accurately estimate the normal vector of the original line from the distorted curve. We discovered that unbalanced samples have a significant influence on estimation accuracy. We proposed a sample balancing method and linear COD determination methods based on normal geometry. The proposed method requires little positioning restrictions of the camera or the calibration pattern, and lines are very easily found or established patterns. The proposed method is demonstrated with both synthetic data and real images. We show by experiment that camera calibration can be decoupled, and more flexible calibration patterns can be used for each stage.

ORB-SLAM3: An Accurate Open-Source Library for Visual, Visual–Inertial, and Multimap SLAM

This paper presents ORB-SLAM3, the first system able to perform visual, visual-inertial and multi-map SLAM with monocular, stereo and RGB-D cameras, using pin-hole and fisheye lens models. The first main novelty is a feature-based tightly-integrated visual-inertial SLAM system that fully relies on Maximum-a-Posteriori (MAP) estimation, even during the IMU initialization phase. The result is a system that operates robustly in real-time, in small and large, indoor and outdoor environments, and is 2 to 5 times more accurate than previous approaches. The second main novelty is a multiple map system that relies on a new place recognition method with improved recall. Thanks to it, ORB-SLAM3 is able to survive to long periods of poor visual information: when it gets lost, it starts a new map that will be seamlessly merged with previous maps when revisiting mapped areas. Compared with visual odometry systems that only use information from the last few seconds, ORB-SLAM3 is the first system able to reuse in all the algorithm stages all previous information. This allows to include in bundle adjustment co-visible keyframes, that provide high parallax observations boosting accuracy, even if they are widely separated in time or if they come from a previous mapping session. Our experiments show that, in all sensor configurations, ORB-SLAM3 is as robust as the best systems available in the literature, and significantly more accurate. Notably, our stereo-inertial SLAM achieves an average accuracy of 3.6 cm on the EuRoC drone and 9 mm under quick hand-held motions in the room of TUM-VI dataset, a setting representative of AR/VR scenarios. For the benefit of the community we make public the source code.

Rapid assessment of prevalence of blindness and cataract surgery in Kabul province, Afghanistan

ObjectiveTo estimate prevalence and causes of blindness and vision impairment and assess cataract surgical coverage and quality of cataract surgery in Kabul.Methods and analysisA total of 3751 adults aged 50...

Design of high-definition pinhole lens optical system

安防监控镜头在保护人身及财产安全方面越来越重要，其中针孔镜头因其特殊的结构而被广泛运用。利用ZEMAX软件设计了一款用于公安取证，侦察，反恐及高温炉、工业检测等特殊场合的针孔镜头。针对光阑前置这种失对称的光学系统，通过控制其像散、场曲、畸变等几何像差进行优化设计。设计的镜头<i>F</i>数为2，焦距为6 mm，匹配1/4英寸CCD，工作光谱为可见光波段，空间频率100 lp/mm处全视场MTF≥0.48，畸变≤±3%。该设计结构简单，全部采用标准球面设计，光学总长小于22 mm。

Distorted pinhole camera modeling and calibration.

Camera modeling and calibration are essential tasks in modern optics. Conventionally, the pinhole model is adopted with a further extension for lens distortion. However, pinhole and distortion models are mutually dependent; thus, the standard approach induces systematic camera calibration errors. This research presents a unifying distorted pinhole camera model that includes a telecentric, distortion-free pinhole, and radial lens distortion as particular cases. An iterative calibration method based on the derived distorted pinhole model is proposed, and experimental evaluation by calibrating a camera with high radial distortion is performed. The calibration results are compared with the standard and fisheye models using a well-known commercial camera calibrator software. The proposed method outperforms the standard model and achieves accuracy comparable to the fisheye model, and the proposed approach is a versatile and accurate tool for diverse optical metrology applications.

Handling regular and irregular astigmatism during cataract surgery.

There are several different approaches to handling regular and irregular astigmatism during cataract surgery, but still much debate on which solutions are most effective given unique patient circumstances. In this review, we examine recent literature and studies to highlight some of the most effective ways to plan preoperatively, manage regular and irregular astigmatism during cataract surgery, as well as managing postoperative complications. Recent developments in technology have provided increased courses of action for astigmatism management during cataract surgery. Additional options of toric IOLs with presbyopic platforms, light adjustable lenses, intraocular pinhole lenses, online technological tools and platforms, wavefront or topographic laser technology, and phototherapeutic keratectomy are all effective solutions to managing regular and irregular astigmatism. In this review, we will explore optimal approaches for unique situations. With increased technology, research, and methods, correcting regular and irregular astigmatism during cataract surgery is achievable in most patients. With in-depth preoperative planning, analysis of patient-specific factors, and a tailored approach, surgeons can obtain excellent uncorrected vision for patients.

Current perspectives in the management of keratoconus with contact lenses.

Our aim is to review current and significant articles on contact lens wear in keratoconus patients. A comprehensive literature search of PubMed was performed for the following topics on contact lens wear in keratoconus patients: (1) characteristics of contact lens wearers, (2) safety and efficacy, (3) complications, (4) fitting techniques, (5) contact lens wear after procedures/surgeries, (6) patient satisfaction. A total of 104 studies were finally selected and reviewed. Gas permeable (GP) lens wear provided significantly better vision than glasses. Special cone design lenses had better patient comfort levels though there was no difference in best corrected visual acuity among the GP lenses. Soft lenses showed good efficacy for the treatment of mild-to-moderate keratoconus with newer designs improving visual performance such as customised hydrogel and novel pinhole lenses. Scleral and hybrid lenses provide good visual acuity and comfort for keratoconic patients previously intolerant to RGP lenses. RGP lens wear post-cross linking (CXL) is relatively well-tolerated. Contact lenses may still be required post intrastromal corneal ring procedures and post keratoplasty. Scheimpflug imaging and anterior segment optical coherent tomography (ASOCT) are useful in contact lens fitting. Computerized contact lens fitting techniques could reduce the chair time of lens fitting as well as improve comfort and visual performance. Contact lenses play an important role in the visual rehabilitation of keratoconus patients. New contact lens designs and materials have significantly expanded the available fitting options for keratoconus patients. Imaging technology can be utilized to guide contact lens fitting.

Improvement of the Optical Performance of the Geometrical Parameters of Snorkel Magnetic Lens

Two models of asymmetrical magnetic objective lens geometries have been designed and studied. These two models are called Pinhole and Snorkel lenses. The comparison between these models was realized by the aid of simulation EOD program (Electron Optical Design), using the finite element method to analyze the magnetic flux density and optical properties at constant excitation (NI=2000A-t). The optimal model (Snorkel Lens) gives the best characteristics that were compatible with the research purposes in details, such as the changing of air gap and the axial polepiece bore diameter on the optical performance of the snorkel magnetic lens. This type of lens was used in low energies scanning electron microscope (SEM), which achieved the lowest values of the aberrations coefficient at long working distance.

Clinical Efficacy of Pinhole Soft Contact Lenses for the Correction of Presbyopia

ABSTRACTWe investigated the clinical efficacy of pinhole soft contact lenses for presbyopia correction. Twenty participants with presbyopia wore pinhole soft contact lenses in the non-dominant eye for 2 weeks. Manifest refraction, Goldmann binocular visual field tests, contrast sensitivity tests, and biomicroscopic examinations were performed along with evaluations of questionnaire responses and the binocular corrected distance visual acuity (CDVA), distance-corrected near visual acuity (DCNVA), distance-corrected intermediate visual acuity (DCIVA), and depth of focus, both before and after 2 weeks of lens wear. DCNVA at 33 and 40 cm and DCIVA at 50 and 70 cm showed significant improvements after pinhole lens wear (P-value: <0.001, <0.001, <0.001, and 0.046, respectively), with no changes in the binocular visual field and binocular CDVA. Contrast sensitivities under photopic and mesopic conditions decreased at some frequencies; however, visual function questionnaire scores significantly improved (all P-values <0.001). These findings suggest that pinhole contact lenses effectively correct presbyopia.

Isolating lens effects from source camera identification using sensor pattern noise

ABSTRACTLens aberrations can be used to determine the provenance of camera optics in an image. However, this method does not necessarily identify the camera itself, since lens systems are often interchanged. A method, first published by Lukàš, Fridrich and Goljan, proposed using Fixed Pattern Noise to link a photo to an image sensor using sensor pattern noise. However, their model did not fully account for lens artefacts or temperature. In our work, we have applied standard image processing theory and an understanding of the geometric properties of light and sensor dark current to continue the isolation of artefacts within the sensor pattern noise model. We use three image sensors to take images using six integrated lenses and prepare reference patterns based on the lens for each camera. We then repeat our experiments with a pinhole lens of our design before comparing the correlation energy contained within each. We show that majority of the unique signal power used to correlate an image to a specific camera is related to the photo response non-uniformity noise; however, additional signal power can also be attributed to the optical system of the camera as well as the sensor’s dark current.

Coded pinhole lens imaging

This paper presents a coded pinhole lens imaging system consisting of a pinhole array aperture, followed by a thin convex lens, mounted onto a standard DSLR camera body. The combination of pinhole and lens incurs two questions: (1) Is the new camera based on pinhole or lens imaging principle? (2) Can the lens improve the imaging quality? The study reveals that the camera is based on pinhole imaging, but the lens can improve its optical resolution from 0.44 mm (pinhole size) to 0.042 mm, leading to a significant improvement in imaging quality. The numerous pinholes on the aperture also improve the camera’s light throughput ability over single pinhole camera. The camera could be used for applications where a large depth of field is required while the illumination condition is poor.

Rapid assessment of avoidable blindness in Papua New Guinea: a nationwide survey

ObjectiveTo estimate the prevalence and main causes of blindness and vision impairment in people aged 50 years and older in Papua New Guinea (PNG).DesignNational cross-sectional population-based survey in National Capital...

Gradient lens with a positive image curvature in optical schemes of endoscopic type and Pin Hole lenses

Gradient lens with a positive image curvature in optical schemes of endoscopic type and Pin Hole lenses

Calibration of AOTF-based 3D measurement system using multiplane model based on phase fringe and BP neural network.

A specifically designed imaging system based on an acousto-optic tunable filter (AOTF) can integrate hyperspectral imaging and 3D reconstruction. As a result of the complicated optical structure, the AOTF imaging system deviates from the traditional pinhole model and lens distortion form, causing difficulty to achieve precise camera calibration. The influencing factors leading to the deviation are discussed and a multiplane model (MPM) is proposed with phase fringe to produce dense mark points and a back propagation neural network to obtain subpixel calibration. Experiments show that MPM can reduce the back projection error efficiently compared with the pinhole model. A 3D reconstruction process is conducted based on the calibration result to verify the feasibility of the proposed method.

大视场针孔物镜设计及成像畸变校正

大视场针孔物镜设计及成像畸变校正

One-dimensional searches for finding new lens design solutions efficiently.

A special structure is present in the lens design landscape that makes it different from a general global optimization problem: many local minimums are closely related to minimums of simpler problems and can therefore be found by decomposing the search for them in simple steps. We show here that in the design landscape of a wide-angle pinhole lens and in closely related optimization landscapes, all good local minimums found by other methods can be obtained easily with a succession of one-dimensional searches starting from simpler systems. By replacing high-dimensional searches with a succession of one-dimensional searches, the design efficiency can be increased significantly. By combining this method with conventional design methods, the wide-angle pinhole lens can be designed starting from a single lens.

Depth of field synthesis from sparse views

Computer generated images are most easily generated as pinhole images whereas images obtained with optical lenses exhibit a Depth-of-Field (DOF) effect. This is due to the fact that optical lenses gather light across finite apertures whereas the simulation of a pinhole lens means that the light is gathered through an infinitesimal small aperture, thus producing sharp images at any depth. Simulating the physical process of gathering light across a finite aperture can be done for example with distributed ray tracing, but it is computationally much more expensive than the simulation through an infinitesimal aperture. The usual way of simulating lens effects is therefore to produce a pinhole image and then post processes the image to approximate the DOF. Post processing algorithms are fast but suffer from incorrect visibilities. In this paper, we propose a novel algorithm that tackles the visibility issue with a sparse set of views rendered through the optical center of the lens and several peripheral viewpoints distributed on the lens. All peripheral images are warped towards the central view to create a Layered-Depth-Image (LDI), so that all observed 3D points located on the same central view-ray are stacked on the same pixel of the LDI. Then, each pixel in the LDI is conceptually scattered into a Point-Spread-Function (PSF) and blended in depth order. While the scatter method is very inefficient on a GPU, we propose a selective-gather method for DOF synthesis, which scans the neighborhood of a pixel and blends the colors from the PSFs covering the pixel. Experiments show that the proposed algorithm can synthesize high-quality DOF effects close to the results of distributed ray tracing but at a much higher speed.