Lens Design Process Research Articles

Design and characterization of a hyperbolic-elliptical lens pair in a rapid beam steering system for single-pixel terahertz spectral imaging of the cornea.

Terahertz (THz) time-domain spectroscopy has been investigated for assessment of the hydration levels in the cornea, intraocular pressure, and changes in corneal topography. Previous efforts at THz imaging of the cornea have employed off-axis parabolic mirrors to achieve normal incidence along the spherical surface. However, this comes at the cost of an asymmetric field-of-view (FOV) and a long scan time because it requires raster-scanning of the collimated beam across the large mirror diameter. This paper proposes a solution by designing a pair of aspheric lenses that can provide a larger symmetric spherical FOV (9.6 mm) and reduce the scan time by two orders of magnitude using a novel beam-steering approach. A hyperbolic-elliptical lens was designed and optimized to achieve normal incidence and phase-front matching between the focused THz beam and the target curvature. The lenses were machined from a slab of high-density polyethylene and characterized in comparison to ray-tracing simulations by imaging several targets of similar sizes to the cornea. Our experimental results showed excellent agreement in the increased symmetric FOV and confirmed the reduction in scan time to about 3-4 seconds. In the future, this lens design process can be extended for imaging the sclera of the eye and other curved biological surfaces, such as the nose and fingers.

Inverse design of optical lenses enabled by generative flow-based invertible neural networks

Developing an optical geometric lens system in a conventional way involves substantial effort from designers to devise and assess the lens specifications. An expeditious and effortless acquisition of lens parameters satisfying the desired lens performance requirements can ease the workload by avoiding complex lens design process. In this study, we adopted the Glow, a generative flow model, which utilizes latent Gaussian variables to effectively tackle the issues of one-to-many mapping and information loss caused by dimensional disparities between high-dimensional lens structure parameters and low-dimensional performance metrics. We developed two lenses to tailor the vertical field of view and magnify the horizontal coverage range using two Glow-based invertible neural networks (INNs). By directly inputting the specified lens performance metrics into the proposed INNs, optimal inverse-designed lens specifications can be obtained efficiently with superb precision. The implementation of Glow-assisted INN approach is anticipated to significantly streamline the optical lens design workflows.

Imaging stretching and displacement using gradient-index elements during the lens design process.

In this study, we propose an approach to stretch or translate images using gradient-index (GRIN) elements with a rotationally symmetric shape in lens systems. In this method, the GRIN material, instead of optical surfaces, are utilized to enable a breaking of rotational symmetry for the two image translations. GRIN expression with anamorphic and tilting terms is introduced. A pair of GRIN elements in front of the given system alters the magnification in two orthogonal directions using the anamorphic terms in the expression, which realizes image stretching. A pair of GRIN elements with tilting terms is used after the given system tilts the optical path to achieve a transverse displacement of the image. The structure of the given system remains unchanged when these translations are performed. A design method for the GRIN elements is presented. Additionally, a design example is presented whose image is stretched by 1.33 times in one direction and displaced to one side of its axis to demonstrate the feasibility of the proposed approach. The approach in this study may enable novel imaging GRIN lens system designs with flexible image positions or special optical functions.

Optical Aberrations Correction in Postprocessing Using Imaging Simulation

As the popularity of mobile photography continues to grow, considerable effort is being invested in the reconstruction of degraded images. Due to the spatial variation in optical aberrations, which cannot be avoided during the lens design process, recent commercial cameras have shifted some of these correction tasks from optical design to postprocessing systems. However, without engaging with the optical parameters, these systems only achieve limited correction for aberrations. In this work, we propose a practical method for recovering the degradation caused by optical aberrations. Specifically, we establish an imaging simulation system based on our proposed optical point spread function model. Given the optical parameters of the camera, it generates the imaging results of these specific devices. To perform the restoration, we design a spatial-adaptive network model on synthetic data pairs generated by the imaging simulation system, eliminating the overhead of capturing training data by a large amount of shooting and registration. Moreover, we comprehensively evaluate the proposed method in simulations and experimentally with a customized digital-single-lens-reflex camera lens and HUAWEI HONOR 20, respectively. The experiments demonstrate that our solution successfully removes spatially variant blur and color dispersion. When compared with the state-of-the-art deblur methods, the proposed approach achieves better results with a lower computational overhead. Moreover, the reconstruction technique does not introduce artificial texture and is convenient to transfer to current commercial cameras. Project Page: https://github.com/TanGeeGo/ImagingSimulation .

Developing an optical design pipeline for correcting lens aberrations and vignetting in light field cameras.

Light field cameras have been employed in myriad applications thanks to their 3D imaging capability. By placing a microlens array in front of a conventional camera, one can measure both the spatial and angular information of incoming light rays and reconstruct a depth map. The unique optical architecture of light field cameras poses new challenges on controlling aberrations and vignetting in lens design process. The results of our study show that field curvature can be numerically corrected for by digital refocusing, and vignetting must be minimized because it reduces the depth reconstruction accuracy. To address this unmet need, we herein present an optical design pipeline for light field cameras and demonstrated its implementation in a light field endoscope.

Considerations and Framework for Foveated Imaging Systems †

Foveated sight as observed in some raptor eyes is a motivation for artificial imaging systems requiring both wide fields of view as well as specific embedded regions of higher resolution. These foveated optical imaging systems are applicable to many acquisition and tracking tasks and as such are often required to be relatively portable and operate in real-time. Two approaches to achieve foveation have been explored in the past: optical system design and back-end data processing. In this paper, these previous works are compiled and used to build a framework for analyzing and designing practical foveated imaging systems. While each approach (physical control of optical distortion within the lens design process, and post-processing image re-sampling) has its own pros and cons, it is concluded that a combination of both techniques will further spur the development of more versatile, flexible, and adaptable foveated imaging systems in the future.

Aspherical plastic lens injection molding warpage and opto-mechanical analysis

Abstract The aspherical plastic lens is commonly used in commercial optical products. The injection molding process introduces warpage and stress residue into the aspherical plastic lens. Mold flow software is generally used in injection molding simulation and successfully predicts molding warpage results. This paper attempts to link mold flow and optical design software by opto-mechanical analysis. The lens surface warpage can apply the Zernike polynomial and transform it to the optical aberration. Meanwhile, the injection molding process and the operation parameters also affect the plastic lens warpage value. Thus, according to optical software, the injection molding process parameters will affect lens optical performance. The plastic lens aberration results can evaluate the lens warpage effect and optimize the injection molding process parameters. Further, by reversing lens warpage aberration in the plastic lens model, it can preliminarily compensate for the warpage error in the lens design process.

54.3: Cluster LED Spectral Optimization as Lens Design

AbstractWe proposed a general design procedure included six steps that can be analogous to the conventional lens design process to optimize a LEDs cluster with high color rendering capability and good efficiency for a desired range of color temperature. The concept was illustrated via a cluster composed of red/green/blue/amber/cool‐white (R/G/B/A/CW) LEDs. The result shows the R/G/A/CW cluster can be applied to the range of color temperature from 2600K to 8500K with the color quality scale > 80 points and with the averaged luminous efficiency of 97% cluster's limit.

Spectacle lenses designed for the modified Listing eye rotation

Knowledge of the way the eye rotates when changing gaze direction is important for the lens design process. Listing's law of eye rotation conveniently describes that rotation for distant vision. Here, a recently discovered departure from Listing's law in near vision is examined. Although lens designs that accommodate the modified rotations can be produced, as demonstrated here, the benefits to the wearer are unlikely to be perceptible except perhaps in cases of highly astigmatic vision.

A Flexible Automatic Lens Correction Procedure

Since the advent of high-speed automatic computing machinery, workers in the field of optical design have been intrigued by the idea of automating the lens design process. Various methods have been proposed and tested. Most of these, in the author’s view, do not allow sufficient control to be exercised over the nature of the design solution. Those which do allow such control appear to be inefficient because of slow convergence to a solution. This paper describes a correction procedure which permits a high degree of control over the nature of the design solution and which has shown a reasonably good rate of convergence in a limited number of tests. The operation of a computer program to carry out the procedure is described, and the results of a typical design problem are presented.