Resolution Of Lens Research Articles

Design and Manufacture of 30-Degree Projection Lens for Augmented Reality Waveguide.

A projection lens with a 30-degree field of view is developed for use in augmented reality (AR) glasses, including a waveguide combiner designed for a 0.35-inch LCoS panel. The entrance pupil diameter of the lens is 14 mm and the lens has an effective focal length of 16.443 mm; an F-number of 1.175. This paper has four key issues: optical projection lens design, lens manufacturing and assembly tolerance analysis, projection lens resolution testing, and AR glasses system resolution testing of panel images projected by the projection lens. After lens manufacture, the lens was tested, achieving a central field image quality of 57 cycles/mm, an angular resolution of 33 pixels per degree (PPD), a 0.7 field image quality of 40.3 cycles/mm, and an angular resolution of 23 pixels per degree (PPD). Imaging performance testing based on a diffraction-type waveguide shows a resolution of 57 cycles/mm in the center area and an angular resolution of 33 PPD.

Exit wave reconstruction of a focal series of images with structural changes in high-resolution transmission electron microscopy.

High-resolution transmission electron microscopy (HRTEM) images can capture the atomic-resolution details of the dynamically changing structure of nanomaterials. Here, we propose a new scheme and an improved reconstruction algorithm to reconstruct the exit wave function for each image in a focal series of HRTEM images to reveal structural changes. In this scheme, the wave reconstructed from the focal series of images is treated as the initial wave in the reconstruction process for each HRTEM image. Additionally, to suppress noise at the frequencies where the signal is weak due to the modulation of the lens transfer function, a weight factor is introduced in the improved reconstruction algorithm. The advantages of the new scheme and algorithms are validated by using the HRTEM images of a natural specimen and a single-layer molybdenum disulphide. This algorithm enables image resolution enhancement and lens aberration removal, while potentially allowing the visualisation of the structural evolution of nanostructures.

Optical lens optimization design and tolerance analysis for a depth camera

This paper describes a depth camera lens design composed of eight glass lenses, where the field of view is 100°, the focal length is 1.88 mm, and the F/# is 2. The lens design requires the lens to be fixed and the object distance to be fixed at −745.964 mm. The depth of focus ranges from −0.0047 mm to 0.0096 mm and can be obtained by selecting a spatial frequency of 60 lp/mm for the Through-focus MTF optimization design. The object distance ranges from negative infinity (-∞) to −250 mm (for the depth of field), the MTF is greater than 0.73 at 60 lp/mm, the lateral color difference is less than 1.58 μm, the optical distortion is less than 1%, and the relative illumination is greater than 64%. When conducting tolerance analysis, we select a spatial frequency requirement of tolerance MTF>0.3. At an object distance of −745.964 mm, the lens resolution can reach 80 lp/mm. The object distance is -∞, and the lens resolution is above 59 lp/mm. The object distance is −250 mm, and the lens resolution can reach over 43 lp/mm. In this work, the depth camera lens is designed to have an object distance shooting range of −6 m to −0.25 m. When the object distance is −6 m, the object depth resolution is 61 mm; while at the object distance of −0.25 m, the object depth resolution is 0.1045 mm.

An energy resolved neutron imaging detector based on boron doped nMCP coupled with a time stamping optical camera

Energy resolved neutron imaging has developed rapidly due to its advantage on testing the inner structure of crystal samples. Neutron detector is one of the key components to determine the imaging results quality. The neutron sensitive microchannel plate (nMCP) has been widely used in energy resolved neutron imaging experiments because of the high spatial and timing resolution. However, the ability to adjust field-of-view (FOV) and spatial resolution has not been realized in the nMCP detector, which is an attractive capability in energy resolved neutron imaging experiments. In this paper, an energy resolved neutron imaging detector was developed by coupling nMCP with a time stamping camera. The neutrons were absorbed by nMCP and converted into light through a phosphor screen. Then the light was focused on the camera by optical lens. A data algorithm was designed to improve the data quality. By changing the magnification of the optical lens, large FOV (46mm diameter) and high spatial resolution (26 μm) were realized in the experiments at CSNS beamline 20. The energy resolved ability was demonstrated by a Bragg-edge transmission imaging experiment for aluminum and stainless-steel samples. The performance of this detector makes it a promising candidate used in energy resolved neutron imaging.

Quantitative characterization of archaic magnifying lenses from Ialysos, Rhodes

Here we report on the initial quantitative characterization of the imaging properties of a set of archaic period lens-shaped artifacts from the temple of Athena at Ialysos, Rhodes. Using a combination of standard lens resolution methods and a test case of resolving micro-printed features on modern currency, we demonstrate that using some of these lens-shaped artifacts, an adult with nominal vision can resolve finer detail in an object compared to an adult that did not use this artifact. The combination of quantitative evidence along with archaeological and physical characteristics of the artifacts provides strong support for the hypothesis that these lens-shaped artifacts are early examples of purpose-made magnifying tools in the ancient Mediterranean world.

Influence of refractive index contrast between microsphere lens and immersion medium on imaging resolution

A microsphere lens could couple the near-field evanescent wave and convert it into propagation wave, which helps microscope to break the diffraction limit and improve its imaging resolution. However, the imaging conditions for microsphere lens is still not clear, and also the conversion process between evanescent wave and propagation wave. Here, we deduced the imaging conditions of microsphere lens through the refractive index contrast between microsphere and immersion medium, and simulated the coupling and scattering process of evanescent wave by microsphere lens. At last, we demonstrated the microsphere assisted super-resolution imaging under different immersion conditions. The experimental results verified that, only within the range predicted by theoretical deduction, the evanescent wave could be converted and the imaging resolution of objective lens could be improved. Our work predicts the super-resolution imaging condition of microsphere lens, and explains its mechanism with evanescent wave conversion, which could guild the design of microsphere lens under different immersion conditions and extend its application in various fields.

The extremely X-ray luminous radio-loud quasar CFHQS J142952 + 544717 at z = 6.18 under Chandra high-angular resolution lens

ABSTRACT We present the first X-ray observation at sub-arcsecond resolution of the high-redshift (z = 6.18) radio-loud quasar CFHQS J142952 + 544717 (J1429). The ∼100 net-count 0.3–7 keV spectrum obtained from ∼30 ks Chandra exposure is best fit by a single power-law model with a photon index Γ = 2.0 ± 0.2 and no indication of an intrinsic absorber, implying a 3.6–72 keV rest-frame luminosity $L_{\rm X}=(2.3^{+0.6}_{-0.5})\times 10^{46}$ erg s−1. We identify a second X-ray source at 30″ distance from J1429 position, with a soft (Γ ≃ 2.8) and absorbed (equivalent hydrogen column density NH < 13.4 × 1020 cm−2) spectrum, which likely contaminated J1429 spectra obtained in lower angular resolution observations. Based on the analysis of the Chandra image, the bulk of the X-ray luminosity is produced within the central ∼3 kpc region, either by the disc/corona system, or by a moderately aligned jet. In this context, we discuss the source properties in comparison with samples of low- and high-redshift quasars. We find indication of a possible excess of counts over the expectations for a point-like source in a 0.5″–1.5″ (∼3−8 kpc) annular region. The corresponding X-ray luminosity at J1429 redshift is 4 × 1045 erg s−1. If confirmed, this emission could be related to either a large-scale X-ray jet, or a separate X-ray source.

High-efficiency focusing and imaging by dielectric kinoform zone plate lenses with soft X-rays.

With fast advances in enhancing the focusing/imaging resolution of Fresnel zone plate lenses toward sub-10 nm, low diffraction efficiency in connection with their rectangular zone shape still remains a big issue in both soft and hard X-ray microscopy. In hard X-ray optics, encouraging progress has recently been reported in our earlier attempts of high focusing efficiency by 3D kinoform shaped metallic zone plates, formed by greyscale electron beam lithography. This paper addresses our efforts towards high focusing/imaging efficiency by developing a novel dielectric kinoform zone plate lens for soft X-rays. The effects of the zone materials and zone shapes on the focusing/imaging quality were first theoretically investigated by a modified thin-grating-approximation method, revealing superior efficiencies of dielectric kinoform zone plates over rectangular ones in metals. Optical characterizations of replicated dielectric kinoform zone plates by greyscale electron beam lithography demonstrate a focusing efficiency of 15.5% with a resolution of 110 nm in the water window of X-rays. Apart from high efficiency, the novel kinoform zone plate lenses developed in this work exhibit significant advantages over conventional zone plates, i.e. simplified process, low cost and no need for a beamstop.

Target-free vision-based approach for modal identification of a simply-supported bridge

Accurate and efficient vibration response measurement is one of the key tasks in structural health monitoring (SHM) of civil engineering structures. Normally, dynamic responses such as displacement responses, are acquired by physical sensors and data acquisition systems installed on the structures. However, the installation of sensors may be time-consuming and costly. In recent decades, computer vision-based methods have been introduced into civil engineering to provide alternatives for traditional displacement measurements. However, the camera specifications, such as limitations on field of view (FOV) and relatively low resolution of economic lens, have prevented the vision-based method from being widely used for vibration displacement measurement on relatively large-scale structures. This paper proposes a target-free vision-based approach for dynamic displacement measurement and modal identification of simply-supported bridges using a single camera. In this study, a series of videos are captured in separate experimental tests using a consumer-class GoPro on a long-span beam subjected to a moving load. The radial distortion of videos caused by the wide-angle lens is offset by distortion adaption, and the scale factor is fitted using a static video shooting experiment. The tracking process consists of three basic steps, namely, region of interest (ROI) selection, natural feature extraction and features tracking. The results are compared with those measured by linear variable differential transducer (LVDT), demonstrating a high accuracy by the proposed approach. Vibration characteristics, including natural frequencies and mode shapes of the bridge, are identified from the measured displacement. The overall mode shapes are obtained by combining the mode shapes identified from different segmental videos of the bridge obtained by roving the single camera along the bridge for measurements. Comparisons of the natural frequencies and mode shapes between the results from the proposed approach and LVDTs demonstrate the effectiveness and accuracy of the proposed approach for displacement measurement and modal identification of long bridges under moving loads.

Analysis of influence of imaging resolution of relay lens on image reconstruction quality in pixel-wise coded exposure imaging technology

Pixel-wise coded exposure (PCE) imaging based on digital micromirror device (DMD) is an advanced high-speed imaging technology, which can realize the high-speed imaging by using a low-frame-rate camera. During exposure time, the multi-frame image information of a dynamic object can be integrated into one encoded image, and then the multi-frame sub-exposure images can be extracted by the post-processing algorithm. Therefore, the accurate pixel-to-pixel alignment between the DMD and the camera is the key step to realize PCE imaging, which has drawn much attention from researchers. So their studies mainly focused on how to achieve accurate pixel matching. However, the resolution of the relay imaging lens, as another important influence factor of PCE imaging, also has a significant influence on the imaging results, but few people have studied and analyzed it. To solve this problem, in this work, we theoretically analyze the influence of the resolution of the relay imaging system on the reconstructed decoded images, and verifies the theoretical analysis through simulation and imaging experiments. On this basis, a PCE imaging system is built, and a point spread function (PSF) estimation method of relay lens based on the fringe phase is proposed. Furthermore, a Richard-Lucy deconvolution algorithm is introduced into the reconstruction process of coded image to effectively improve the quality of PCE imaging, which is of great significance in developing the PCE imaging technology.

A Framework of Maximum Feature Exploration Oriented Remote Sensing Object Detection

Object detection from remote sensing images is an interesting research topic full of theoretical and application values. Compared with generic images, those of remote sensing contain much less distinguishing representation information due to far-away capturing position and limited camera lens resolution, the perpendicular to ground capturing view, almost unacquirable 3-D object structure and serious roof occlusion, and the inherent unimportance of top roof view. Focusing on this intrinsic disadvantage, in this letter, we propose a general framework of accurate remote sensing object localization constructed with the core idea of maximum image feature exploration. This integrated structure is mainly comprised of cascaded tiny patch correlation (CTPC) based feature digging, averaging local patch regression (ALPR) centered coarse location acquisition, and instance segmentation oriented further refinement (ISOFR). All those components are designed to maximize feature digging and usage. We believe this is the first to implement the idea of maximum feature exploration to each corner of object detection architecture. Extensive experiments on challenging aerial image datasets DOTA and NWPU VHR-10 show state-of-the-art performance.

Integrated Image Processing Toolset for Tracking Direction of Metal Grain Deformation

Grain boundaries (GBs), which are among the mechanical properties of a material, are a microstructural aspect that contributes to the overall behavior of metal. A deep understanding of the behavior of the GBs’ deformation, dislocation, and fracture will encourage the rapid development of new materials and lead to the better operation and maintenance of materials during their designed lifetimes. In this study, an integrated image processing toolset is proposed to provide an expeditious approach to extracting GBs, tracking their location, and identifying their internal deformation. This toolset consists of three integrated algorithms: image stitching, grain matching, and boundary extraction. The algorithms are designed to simultaneously integrate high and low spatial resolution images for gathering high-precision boundary coordinates and effectively reconstructing a view of the entire material surface for the tracing of the grain location. This significantly reduces the time needed to acquire the dataset owing to the ability of the low spatial resolution lens to capture wider areas as the base image. The high spatial resolution lens compensates for any weakness of the base image by capturing views of specific sections, thereby increasing the observation flexibility. One application successfully described in this paper is tracking the direction of the metal grain deformation in global coordinates by stacking a specific grain before and after the deformation. This allows observers to calculate the direction of the grain deformation by comparing the overlapping areas after the material experiences a load. Ultimately, this toolset is expected to lead to further applications in terms of observing fascinating phenomena in materials science and engineering.

Directly observed images through the shell-lenses of Onithochiton neglectus (Mollusca: Polyplacophora: Chitonidae)

ABSTRACT The dorsal shell surface of the New Zealand-endemic chitonid Onithochiton neglectus exhibits ocelli (eyes) associated with sensory organs (aesthetes) penetrating the shell. Each ocellus includes a mineral lens which focusses light onto a retina, potentially able to resolve images. In order to discover the spatial resolution of lenses of O. neglectus, we isolated them, examined their mineralogy with X-ray diffractometry, imaged the constituent crystals with scanning electron microscopy, and mounted them onto a camera to directly observe and record images. Lenses of O. neglectus are aragonitic and therefore birefringent, providing two different focal lengths, possibly one for in-air and one for underwater vision. Chitons may be able to image nearby shapes with visual acuity equivalent to 6/24 (m), a VAdec of 0.25. Onithochiton neglectus lenses can focus images in air about as well as a person with low visual acuity, sufficient to discern shapes and shadows in the surrounding environment. Lenses from subtidal O. neglectus were less eroded than those from intertidal environments; chitons in different habitats exhibit different visual acuity. It is unclear why a few lineages of chitons have developed such complex eyes; we speculate that body-orientation and navigation could be among the advantages driving such development.

Cost-Effective Design of a Miniaturized Zoom Lens for a Capsule Endoscope.

This paper presents a miniaturized design of a 2× zoom lens for application to a one-megapixel image sensor in a capsule endoscope. The zoom lens is composed of four lenses, including three plastic aspheric lenses and one glass spherical lens, and adopts a three-lens group design. This capsule endoscope is mainly for observation of the small intestine, which has a radius of about 12.5 mm. The height of the object is thus set to 12.5 mm. The object surface is designed to be curved surface with a radius of curvature of 15 mm. The focal length of the zoom lens ranges from 1.064 mm to 2.039 mm, and the full angle of view ranges from 60° to 143°, the f-number is F/2.8-F/3.5, the zoom lens is 11.6 mm in length, and the maximum effective diameter of the zoom lens is 6 mm. The zoom lens design is divided into six segments, corresponding to the different magnifications from Zoom 1 to Zoom 6. The magnification ratios are -0.0845, -0.0984, -0.1150, -0.1317, -0.1482, and -0.1690, respectively. Comparing the positions from Zoom 1 to Zoom 6, the maximum optical distortion is -14.89% for the Zoom 1 and 1.45% for the Zoom 6. The maximum vertical video distortion is 8.19% for Zoom 1 and 1.00% for Zoom 6. At a 1.0 field of view, the minimum relative illuminance is 71.8% at a magnification of M = -0.1317. Finally, we perform the tolerance analysis and lens resolution analysis at different zooming positions. Our design can obtain high-quality images for capsule endoscope.

A functionally ordered visual feature map in the Drosophila brain

Topographic maps, the systematic spatial ordering of neurons by response tuning, are common across species. In Drosophila, the lobula columnar (LC) neuron types project from the optic lobe to the central brain, where each forms a glomerulus in a distinct position. However, the advantages of this glomerular arrangement are unclear. Here, we examine the functional and spatial relationships of 10 glomeruli using single-neuron calcium imaging. We discover novel detectors for objects smaller than the lens resolution (LC18) and for complex line motion (LC25). We find that glomeruli are spatially clustered by selectivity for looming versus drifting object motion and ordered by size tuning to form a topographic visual feature map. Furthermore, connectome analysis shows that downstream neurons integrate from sparse subsets of possible glomeruli combinations, which are biased for glomeruli encoding similar features. LC neurons are thus an explicit example of distinct feature detectors topographically organized to facilitate downstream circuit integration.

Spectroscopic analysis with tender X-rays: SpAnTeX, a new AP-HAXPES end-station at BESSY II

We present a newly developed end-station at BESSY II dedicated to in situ Spectroscopic Analysis with Tender X-rays (SpAnTeX). The core of the end-station is a new SPECS PHOIBOS 150 HV NAP electron spectrometer. First, we show that the system has successfully achieved high electron transmission and detection efficiency under gas pressures up to 30 mbar and photon energies ranging between 200 eV and 10 keV. Second, using two features of this spectrometer (a new lateral resolution lens and a 3D delay line detector), we show that the endstation enables collection of the photoelectron spatial distribution under realistic working conditions (p ≥ 20 mbar) with a resolution better than 30 μm and the possibility to perform time resolved studies using a continuous tender X-ray source. We conclude by reporting an example of the possible experiments that can be performed using this new endstation using the Dip-and-Pull technique.Although mainly focused on the characterization of solid/liquid interfaces using AP-HAXPES, the end-station can be used at soft X-ray beamlines for more traditional AP-XPS experiments. The Dip-and-Pull module also demonstrates good electrochemical performance. The wide pressure and photon energy range covered by this end-station also enables investigations of solid/solid, solid/gas, liquid/vapor and liquid/liquid interfaces at pressures up to 30 mbar with tender X-rays.

РАСПОЗНАВАНИЕ ШТРИХ-КОДА НА СИЛЬНО ИСКАЖЕННЫХ ИЗОБРАЖЕНИЯХ И ИЗОБРАЖЕНИЯХ С НИЗКИМ РАЗРЕШЕНИЕМ

Almost all products and items that exist on the market today have a unique code or identifier associated with them. We call this special identifier a barcode. Barcode detection is very common and is a necessity today as it makes our job easier. You can simply scan the code and easily get all the product information. Barcodes are still the prevalent machine-readable encoding mechanism for most products and services. At this stage of development, the barcode was quite common. Most items and products present in the household now have their own unique barcodes. They can be scanned and easily get all the necessary information, such as price, product details and description. There are even various apps available to scan the barcode through our phones. This is due to the high-quality pixel cameras that are present in all iPhones, android devices, or windows phones. Today, a wide range of portable devices for general use, such as mobile phones, come with an optical imaging system. Providing these general-purpose portable devices with barcode recognition is a cost-effective alternative to conventional barcode scanners. The equipment is available to billions of people. Combined with new services, this could revolutionize day-to-day shopping, including checking in-store prices, getting product information, accessing product reviews, finding similar products and services, and comparing prices locally. Detecting barcodes in images captured by general-purpose portable devices is particularly challenging due to the limitations of the integrated imaging system and on-device processing capabilities. These devices often have lower quality lens systems and lower resolution imaging circuits when compared to dedicated digital cameras. The optical system is often not designed for shooting close to the lens, resulting in out-of-focus and poorly lit images with rich colors. These limitations often mean that using conventional threshold detection methods cannot create a suitable template for barcode recognition. These limitations need to be considered in an algorithm that can invariably be implemented on a wide variety of portable devices. Barcode reading must be resistant to harsh conditions such as blur, noise, low resolution or low-quality camera lenses, which are very common. Surprisingly, even the most advanced barcode reading algorithms fail when some of these factors come into play. In this article, we present a new approach to barcode image detection. Our algorithm is specially designed to recognize barcodes when an image may be of low resolution, low quality, or suffer from significant blur, defocus, uneven lighting, noise and color saturation. The algorithm is accurate, fast, scalable and can be easily configured to find a valid result within a time constraint. Our algorithm is useful for real-time barcode recognition on handheld devices with limited processing capabilities such as mobile phones.

Limitations and potentials of generalized Veselago-Pendry lenses

We study the imaging performance of anisotropic generalized Veselago–Pendry (GVP) lenses derived via complex transformation optics technique. The derived material tensors of such generalized lenses can be controlled via a complex coordinate transformation parameter resulting in an anisotropic constitutive tensor with loss/gain characteristics. We discuss their limitations and potentials based on the parametric analysis of material properties. We show that, although GVP lenses are not affected by the loss/gain level, akin to conventional VP lenses, their subwavelength imaging performance is also susceptible to material deviations from their original values. We also discuss that the resolution of GVP lenses can be significantly improved by tuning the real part of the transformation parameter. The proposed GVP lenses could be realized using, for instance, a metal-dielectric structure, with improved subwavelength imaging characteristics.

Numerical analysis on high resolution optical measurement method with long working distance objective for in-line inspection of micro-structured surface

For in-line surface inspection of microfluidic devices, optical measurement techniques with sub-micrometer resolution and a long working distance (W.D.) objective lens are needed. Structured illumination microscopy (SIM) is a good candidate to achieve high resolution. In micro-structured surface inspection, however, measurement needs to be carried out through coherent imaging, and thus conventional incoherent SIM cannot be applied directly due to interference of light from a sample. In this study, equations are reformulated by considering amplitude and phase of light waves. As a result, we found that higher spatial frequencies of samples can be derived even through coherent imaging by using multiple interference images. Based on this proposed coherent SIM, an optical measurement method with a long W.D. objective lens and sub-micrometer resolution for in-line surface inspection of sub-micro- and micro-structured surfaces is proposed. We analyzed resolution and performance of the proposed method from a theoretical and numerical perspective based on Fourier optics and imaging theory. The results verified that even with a long W.D. objective lens, the concept of the proposed method allows us to achieve sub-micrometer resolution in spite of non-fluorescence observation. This cannot be achieved by standard microscopy and the conventional incoherent SIM. We also conducted numerical analysis considering external disturbance that can occur in practical in-line inspection. The results revealed that the proposed method is capable to resolve two points with a distance less than half a micrometer with the maximum measurement error of no larger than 5%, under the condition where a maximal phase error of reference light is 2π/20 i.e., 20 nm error in length. These values are practical in in-line inspection.

A study of greyscale electron beam lithography for a 3D round shape Kinoform lens for hard X-ray optics

For high quality imaging of materials in nanoscale by hard X-ray optics, high resolution lenses with high focusing/imaging efficiency are needed. Refraction based conventional Kinoform lenses with 1D linear configuration in Si has been attempted for decades, but there has still been no sign of success due to the enormous difficulty in fabrication. This paper proposes a novel configuration of golden Kinoform lenses with round shape on a plate, in which each zone maintains the typical 3D parabolic profile as seen in the traditional 1D counterpart. The major focus in this work is on the generation of the 3D profile in e-beam resist through greyscale electron beam lithography (EBL) as the template for the golden Kinoform lens. Systematic study of the greyscale lithography conditions, including the comparisons of resists, developers and charge distributions, has been conducted by using Monte Carlo simulation as well as e-beam lithography. Initial results have been achieved for replicating the desired 3D profile of the golden Kinoform lens in the resist. Using the generated profile in resist as templates, the golden Kinoform lens with 200 μm diameter and 3.5 μm height has been successfully fabricated, for the first time, which will hopefully replace the existing Fresnel zone plates for hard X-ray imaging with high resolution and high efficiency.