Imaging Lens Research Articles

Design and 3D printing of the Powell lens for sub-terahertz imaging.

The aim behind this work is to design and manufacture a beam shaping lens for active terahertz imaging systems that boosts their performance in terms of sensitivity and image quality. The proposed beam shaper is based on an adaptation of the original optical Powell lens, where a collimated Gaussian beam is converted into a uniform flattop intensity beam. The design model for such a lens was introduced, and its parameters were optimized by a simulation study conducted using COMSOL Multiphysics software. The lens was then fabricated using a carefully chosen material [polylactic acid (PLA)] through a 3D printing process. The manufactured lens was implemented in an experimental setup to validate its performance using a continuous-wave sub-terahertz source around 100GHz. Experimental results demonstrated a high-quality flattop beam maintained along the propagation path, which is highly recommended for terahertz and millimeter-wave active imaging systems to produce high-quality images.

Optical design of vertical edge Thomson scattering on HL-2M tokamak

A vertical edge Thomson scattering (ETS) diagnostic system on HL-2M tokamak has been designed. The ETS system collects the scattered light from Nd:YAG laser (1064 nm, 2 J, 30 Hz, 15 ns). The laser beam propagates vertically through the plasma region and the polarization is parallel to the toroidal magnetic field. A special designed Galileo-type telescope with long Rayleigh length is applied to focus the laser size and ensure collimation. A group of double-Gaussian collection lenses image the 600 mm vertical scattered region onto rectangular fiber arrays with a spatial resolution of 10 mm. The 2.20 mm × 2.86 mm fiber optic bundle consists of 130 low hydroxyl (OH) 200/220 μm (core/cladding) diameter fibers with numerical aperture NA = 0.22, carrying the light to remotely located multi-channel polychromators. Effect of oblique incidence on narrow band filter has been analyzed. The designed electron temperatures range from 5 to 1000 eV and electron densities from 5 × 1018 to 1 × 1020 m−3.

P‐12.9: Self‐powered Large Aperture Liquid Crystal Lens for Light Field Imaging Based on Fur Triboelectric Nanogenerators

Liquid crystal (LC) is an intermediate state compound between liquid and crystal, which has the anisotropy of crystal molecules while having the fluidity of liquid. It is a cutting‐edge technology in optoelectronics. LC lens is an electrically controlled focusable gradient refractive index lens. In light field displays, LC lenses with diameters in the millimetre range can cover more areas. Therefore, we propose a large aperture (LA) liquid crystal (LC) lens with an electrically controlled focal length of 4 mm in diameter. LC lenses with large apertures require large voltages and there are certain safety issues and equipment requirements. We have therefore utilised a triboelectric nanogenerator (TENG) that can harvest energy from the environment and convert it into usable electrical energy. TENG has the advantages of being small and portable and enables the use of renewable energy. In this paper, we propose a new type of feather TENG (F‐TENG) with a positive friction electrode of feathers and a negative electrode of polytetrafluoroethylene (PTFE) mixed with graphene, which enables the use of F‐TENG to power LC lens systems, thus providing a new application idea for the display field.

50.2: Invited Paper: A Closer Look: Advancements in Near‐Eye Display Testing and Metrology

This paper discusses the importance of optical testing metrology for near‐eye displays (NED) used in virtual reality (VR) and augmented reality (AR) environments. The accuracy of parameters such as resolution, contrast, field of view, and color accuracy is critical to the effectiveness of NED. However, existing testing methods for these parameters may not consider the visual characteristics of NED. The paper proposes innovative testing methods for evaluating contrast, pupil swim, and pixel per degree (PPD) in NED. The proposed ANSI contrast test method is found to be more suitable for evaluating the contrast of VR headsets than traditional methods. The paper also proposes two advanced PPD testing methods that take into account lens design and image rendering, providing a more accurate and comprehensive evaluation of pixel distribution on screens at different viewing angles. These testing methods have the potential to improve the development of high‐resolution displays and advance our understanding of the perception of visual stimuli.

Novel diffraction limit implied geometric lens imaging model based on a finite number of pixels for integral imaging display

We propose a novel diffraction limit implied geometric lens imaging (DLI-GLI) model considering diffraction effect on a finite number of pixels in elemental image (EI)and 3D depth priority-oriented integral imaging (DPO-II) showing variations of the lateral resolution (LR) within enhanced depth of focus (DoF) range graphically. We assigned 3 representative gaps between lens array and display panel including gap at conventional DPII to find the optimized DoF and enhanced LR. We show that the number of pixels in an elemental lens (EL), and focal length and width of the lens determine practical LR and DoF at the focal plane, and the numerically induced DOP-II with two specified DPO-gaps which are larger than focal length have the enhanced LR and DoF comparing with those of the conventional DPII presenting the optimized LR and DoF near to two DPO-gaps. We show that one of the DPO-gaps has largest DoF and another has largest resolution within some part of DoF in the on-axial DPO-spot size diagram (DPO-SD). Though this DPO-SD, it is expected that the various 3D geometric imaging configurations according to the application fields of 3D imaging could be designed as well. Finally, we verified that the numerically induced 3 geometrical structures based on the proposed model show the similar results with measurements of the optical experiments on the built-up DPO-asymmetric II (DPO-AII) system.

High Refractive Index GRIN Lens for IR Optics

Infrared gradient refractive index (GRIN) material lenses have attracted much attention due to their continuously varying refractive index as a function of spatial coordinates in the medium. Herein, a glass accumulation thermal diffusion method was used to fabricate a high refractive index GRIN lens. Six Ge17.2As17.2SexTe(65-x) (x = 10.5-16) glasses with good thermal stability and high refractive index (n@10 μm > 3.1) were selected for thermal diffusion. The refractive index span (∆n) of 0.12 was achieved in this GRIN lens. After thermal diffusion, the lens still had good transmittance (45%) in the range of 8-12 μm. Thermal imaging confirmed that this lens can be molded into the designed shape. The refractive index profile was indirectly characterized by the structure and composition changes. The structure and composition variation became linear with the increase in temperature from 260 °C to 270 °C for 12 h, indicating that the refractive index changed linearly along the axis. The GRIN lens with a high refractive index could find applications in infrared optical systems and infrared lenses for thermal imaging.

JWST’s PEARLS: Dust Attenuation and Gravitational Lensing in the Backlit-galaxy System VV 191

We derive the spatial and wavelength behavior of dust attenuation in the multiple-armed spiral galaxy VV 191b using backlighting by the superimposed elliptical system VV 191a in a pair with an exceptionally favorable geometry for this measurement. Imaging using the James Webb Space Telescope and Hubble Space Telescope spans the wavelength range 0.3–4.5 μm with high angular resolution, tracing the dust in detail from 0.6–1.5 μm. Distinct dust lanes continue well beyond the bright spiral arms, and trace a complex web, with a very sharp radial cutoff near 1.7 Petrosian radii. We present attenuation profiles and coverage statistics in each band at radii 14–21 kpc. We derive the attenuation law with wavelength; the data both within and between the dust lanes clearly favor a stronger reddening behavior (R = A V /E B−V ≈ 2.0 between 0.6 and 0.9 μm, approaching unity by 1.5 μm) than found for starbursts and star-forming regions of galaxies. Power-law extinction behavior ∝λ −β gives β = 2.1 from 0.6–0.9 μm. R decreases at increasing wavelengths (R ≈ 1.1 between 0.9 and 1.5 μm), while β steepens to 2.5. Mixing regions of different column density flattens the wavelength behavior, so these results suggest a different grain population than in our vicinity. The NIRCam images reveal a lens arc and counterimage from a background galaxy at z ≈ 1, spanning 90° azimuthally at 2.″8 from the foreground elliptical-galaxy nucleus, and an additional weakly lensed galaxy. The lens model and imaging data give a mass/light ratio M/L B = 7.6 in solar units within the Einstein radius 2.0 kpc.

Compound super-oscillation lens for reflective confocal imaging

The super-oscillation lens (SOL) can achieve super-resolution focusing but have to trade-off with weaker hotspots and higher sidebands. We propose a single compound SOL to achieve reflective confocal imaging in principle without additional lenses. The designed SOL consists of an outer lens and an inner lens which play the role of focusing lens and collective lens respectively. As a result, focusing and collecting functions can be simultaneously realized. The improved system can achieve excellent imaging performance with an ultra-high resolution (<0.314λ/NA, NA stands for numerical aperture), and almost negligible side lobe ratio and no side bands, which proved superior to conventional laser scanning confocal microscopy and single SOL. This technology can be attractive for a variety of applications in super-resolution imaging and biomedical sciences.

Structural, thermal and optical studies of Eu3+ ion doped Ge22As20Se58 glass

The effect of Eu3+ doping on improving the amorphous nature of commercial chalcogenide glass/ChG (Ge22As20Se58), which is typically used as a molded lens for mid-infrared imaging, has been investigated. The observed absence of bright spots in Transmission Electron Microscope-Selected area (electron) diffraction (TEM-SAED) pattern confirmed the doping-induced amorphous nature of Eu-Ge22As20Se58 glass. The thermal studies over glass transition temperature (Tg) using DSC technique also revealed that Eu doping has increased the amorphous nature along with the thermal stability of Ge22As20Se58 glass. The optical analysis using UV–vis absorption spectroscopy showed that the activity of Eu-doped ChG has been extended across the UV-visible region. Tauc plot derived band gap energy of Eu-doped and undoped ChG is found to be 2.2 and 2.6 eV, respectively.

EFFECT OF DEVIATION FROM AN ASPHERICAL SURFACE ON THE MODULATION TRANSFER FUNCTION OF A THERMAL IMAGING LENS IN CONTRAST ESTIMATION ON A COLLIMATION INSTALLATION

This article discusses the Chinese lens with a focal length of F50 and its analogue, developed by me at the production enterprise LLC “Doksard” for the overall dimensions of the body already delivered to the stream, with high-precision manufacture of aspherical surfaces: with a deviation accuracy of up to 0.1 microns and with an accuracy of up to 1 mm. The quality of the obtained image from the lens is analyzed. The purpose of the work was to determine the necessary error. The TAS-7T software, CDT15120HR collimation unit and the World TCB 4.5 kit are used. The worlds are located in a revolver mechanism, the lens is assembled, installed in a collimation installation, after which an image from the sight is displayed on the computer and the picture is fixed when observing different worlds. As a result of the conducted research, it is possible to draw conclusions about the dependence of the manufacturing accuracy and how well the quality of modern thermal imaging lenses can be determined using collimation installations. The data proposed in this paper on the results of the quality of optical sights: the dependence of the modulation transfer function on the accuracy of the manufacture of aspherical surfaces. The results of these studies will help to form the basic technical requirements for the design of thermal imaging sights during the transition of the Russian market to radiation receivers of the next generation of 14 and 12 mkm.

HOLISMOKES

Modeling of strong gravitational lenses is a necessity for further applications in astrophysics and cosmology. With the large number of detections in current and upcoming surveys, such as the Rubin Legacy Survey of Space and Time (LSST), it is pertinent to investigate automated and fast analysis techniques beyond the traditional and time-consuming Markov chain Monte Carlo sampling methods. Building upon our (simple) convolutional neural network (CNN), we present here another CNN, specifically a residual neural network (ResNet), that predicts the five mass parameters of a singular isothermal ellipsoid (SIE) profile (lens center x and y, ellipticity ex and ey, Einstein radius θE) and the external shear (γext, 1, γext, 2) from ground-based imaging data. In contrast to our previous CNN, this ResNet further predicts the 1σ uncertainty for each parameter. To train our network, we use our improved pipeline to simulate lens images using real images of galaxies from the Hyper Suprime-Cam Survey (HSC) and from the Hubble Ultra Deep Field as lens galaxies and background sources, respectively. We find very good recoveries overall for the SIE parameters, especially for the lens center in comparison to our previous CNN, while significant differences remain in predicting the external shear. From our multiple tests, it appears that most likely the low ground-based image resolution is the limiting factor in predicting the external shear. Given the run time of milli-seconds per system, our network is perfectly suited to quickly predict the next appearing image and time delays of lensed transients. Therefore, we use the network-predicted mass model to estimate these quantities and compare to those values obtained from our simulations. Unfortunately, the achieved precision allows only a first-order estimate of time delays on real lens systems and requires further refinement through follow-up modeling. Nonetheless, our ResNet is able to predict the SIE and shear parameter values in fractions of a second on a single CPU, meaning that we are able to efficiently process the huge amount of galaxy-scale lenses expected in the near future.

Milky translucent haze of a large-scale topological defect array in nematic liquid crystal

ABSTRACTA large two-dimensional (2D) topological defect array in nematic liquid crystal (NLC) shows a translucent watery hazy texture. The haze is a composition of three optical phenomena: scattering of light, lens imaging and diffraction. The scattering of light causes the milky haze. Vertically aligned NLC cells with pixel electrodes were fabricated to produce the crowded irregular defects. The key parameters are the electrode shape (pad or annulus), the array structure (square or hexagonal) and the pixel size (from 15μm×15μm to 200μm×200μm). Location and topological charge of the defects are identified under a polarised optical microscope. 2D Fourier transform of the defect distribution gives the spatial frequency spectrum, which is the diffraction pattern of light through the defects. Large pad electrodes produce ordered defects and significant diffraction. Crowded irregular defects render the milky translucent haze and a continuous spatial spectrum. The traditional haze measurement is not able to distinguish the scattered and diffracted light. The spatial spectrum can accurately describe the appearance perceived by the viewers. Small annulus electrodes in a hexagonal array produce the messiest defects, the haziest texture and the most comfortable visual experience among the others.

Development of an upgraded motional Stark effect diagnostic system on EAST tokamak

A new multi-channel motional Stark effect (MSE) diagnostic system has been developed on the upgraded EAST tokamak, which was installed on the port C to observe a tangential neutral beam. A telecentric imaging lens was deployed to ensure uniform illumination from the core to the boundary. A square fiber head which contained 23 fiber bundles was mounted to this imaging lens; each fiber bundle contained 19 fibers and two of them were assigned to CXRS and BES spectrometer, respectively. The angle tuning method was used for matching the Doppler shift of the σ component’s wavelength which was caused by the beam voltage. At the present stage, the MSE system only contains ten channels that would be extended to 23 channels in the future, covering a measurement range from R = 1.8 to R = 2.27 m with a temporal resolution of 10 ms and a spatial resolution of 3 cm. The polarization angle-constrained q profiles and current density profiles were reconstructed with EFIT equilibrium reconstructions. In the sawtooth discharges, the q = 1 surface position was validated by the ECE signals, which further verified the rationality of the MSE measurement.

Electrically Tunable Lenses for Imaging and Light Manipulation

Optofluidics seamlessly combines optics and microfluidics together to construct novel devices for microsystems, providing flexible reconfigurability and high compatibility. By taking advantage of mature electronic fabrication techniques and flexible regulation of microfluidics, electrically actuated optofluidics has achieved fantastic optical functions. Generally, the optical function is achieved by electrically modulating the interfaces or movements of microdroplets inside a small chamber. The high refractive index difference (~0.5) at the interfaces between liquid/air or liquid/liquid makes unprecedented optical tunability a reality. They are suitable for optical imaging devices, such as microscope and portable electronic. This paper will review the working principle and recent development of electrical optofluidic devices by electrowetting and dielectrophoresis, including optical lens/microscope, beam steering and in-plane light manipulation. Some methods to improve the lens performance are reviewed. In addition, the applications of electrical microfluidics are also discussed. In order to stimulate the development of electrically controlled liquid lens, two novel designs derived from electrowetting and dielectrophoresis are introduced in this paper.

Adaptive lens for foveal vision, imaging, and projection over large clear apertures.

We report an electrically tunable liquid crystal device that enables the generation of lenses the diameters of which may be dynamically changed from sub-millimeter to multiple millimeter sizes. These lenses can be created in different regions of interest over very large (above 50 mm) optical clear apertures. The approach is based on the activation of periodically spaced contacts on a single serpentine-shaped electrode with phase-shifted electrical signals. It enables a highly reconfigurable operation of locally created lenses with variable position, diameter, optical power (OP) and aberrations. The preliminary demonstration of the capabilities of the proposed device is presented here by creating a local lens, moving its center over an area of 25 mm x 25 mm, gradually changing its diameter from 1.3 mm to 4.55 mm as well as by tuning its OP value from zero up to, respectively, ≈ 40 and ≈3.5 diopters. Typical driving signals are at the order of 3.5 V. We think that such lenses can be used for ophthalmic or augmented reality applications as well as in microscopy, adaptive panoramic cameras with large distorted field of view, dynamic projection, etc.

Dual-resonant scanning multiphoton microscope with ultrasound lens and resonant mirror for rapid volumetric imaging

A dual-resonant scanning multiphoton (DRSM) microscope incorporating a tunable acoustic gradient index of refraction lens with a resonant mirror is developed for high-speed volumetric imaging. In the proposed microscope, the pulse train signal of a femtosecond laser is used to trigger an embedded field programmable gate array to sample the multiphoton excited fluorescence signal at the rate of one pixel per laser pulse. It is shown that a frame rate of around 8000 Hz can be obtained in the x–z plane for an image region with a size of 256 × 80 pixels. Moreover, a volumetric imaging rate of over 30 Hz can be obtained for a large image volume of 343 × 343 × 120 μm3 with an image size of 256 × 256 × 80 voxels. Moreover, a volumetric imaging rate of over 30 Hz can be obtained for a large image volume of 256 × 256 × 80 voxels, which represents 343 × 343 × 120 μm3 in field-of-view. The rapid volumetric imaging rate eliminates the aliasing effect for observed temporal frequencies lower than 15 Hz. The practical feasibility of the DRSM microscope is demonstrated by observing the mushroom bodies of a drosophila brain and performing 3D dynamic observations of moving 10-μm fluorescent beads.

Real-time wavefront correction using diffractive optical networks.

Real-time wavefront correction is a challenging problem to present for conventional adaptive optics systems. Here, we present an all-optical system to realize real-time wavefront correction. Using deep learning, the system, which contains only multiple transmissive diffractive layers, is trained to realize high-quality imaging for unknown, random, distorted wavefronts. Once physically fabricated, this passive optical system is physically positioned between the imaging lens and the image plane to all-optically correct unknown, new wavefronts whose wavefront errors are within the training range. Simulated experiments showed that the system designed for the on-axis field of view increases the average imaging Strehl Ratio from 0.32 to 0.94, and the other system intended for multiple fields of view increases the resolvable probability of binary stars from 30.5% to 69.5%. Results suggested that DAOS performed well when performing wavefront correction at the speed of light. The solution of real-time wavefront correction can be applied to other wavelengths and has great application potential in astronomical observation, laser communication, and other fields.

A broadband picometer resolution visible CCD spectrometer based on virtually imaged phased array technology.

Coincidental realization of broadband spectral coverage and high resolution in one spectrometer system has always been a challenge. Here, we report the development of a high-resolution visible CCD spectrometer based on the virtually imaged phase array (VIPA) technique. By using a thin glass plate and a reflective grating, a two-dimensional cross-dispersion was realized. A broadband coverage of ∼14.94 THz and a high resolution of ∼1 GHz at 632.996 nm were achieved with a simple structure. The effects of the surface quality of VIPA etalon, the pixel size of the CCD camera, the pinhole size of the input beam, and the focal length of the imaging lens on the resolution of the spectrometer and the transverse spot size on the detector plane were considered. A comparison between the experimental results by changing the imaging lens and the theoretical calculation results proved a better simulation of these two parameters, which is a helpful contribution to the design and construction of a VIPA spectrometer. The developed spectrometer will provide a useful tool for the study of high-resolution spectroscopy and for simultaneous multi-species trace detection.

Compound Super-Oscillation Lens for Reflective Confocal Imaging

Compound Super-Oscillation Lens for Reflective Confocal Imaging

Ultramicroscopic imaging of biological cell lenses based on a dual fiber optic tweezer system

Ultramicroscopic imaging of biological cell lenses based on a dual fiber optic tweezer system