Custom Lenses Research Articles

Novel plenoptic Imager for 3D Particle Tracking Velocimetry for Fluid Structure Interactions

We show a novel plenoptic camera architecture and demonstrate its ability to perform three-dimensional three-component velocimetry using standard multi camera processing techniques. The novel architecture needs only a custom lens assembly with no modification to the camera body. This allows the use of any camera with an appropriate sensor size. The architecture directly creates multiple views of a scene side by side on the camera sensor which can be separated and treated as if they originated from independent cameras. Standard calibration techniques for creating 3D to 2D correspondence on the images can then be implemented to reconstruct 3D scene information. For this case we focus on performing 3D PTV using the commercial software DaVis and the "shake-the-box" algorithm. We look at the flow induced by an oscillating rod and compare the results with the analytical solution to validate the results.

Custom lens design for ultrasonic inspection of immersed anisotropic parts

Inspection of anisotropic parts using immersion ultrasonic waves poses resolution challenges caused by directionally dependent wave properties. Currently, focused lenses with spherical or cylindrical geometries are the standard method for creating convergent, small cross-section, and high amplitude beams within solids. These lenses form a conical beam that uniformly refracts at the fluid-solid interface of the immersed part when the solid is isotropic, producing the desired focusing behavior. However, for anisotropic solids, refraction becomes directionally dependent, which distorts the beam and causes non-uniform focal profiles and, in some cases, multiple foci. In this work, the forward wave propagation for an immersed anisotropic solid is modeled and exploited to develop custom lens geometries. These custom lenses utilize inverted slowness profiles to produce conical beams within the anisotropic solid. By incorporating these lenses, the focused beam behavior is improved and becomes more circular, higher in amplitude, and smaller in the cross-sectional area. These lenses have the potential to improve inspection resolution in anisotropic solids, an effort beneficial to the additive, aerospace, and electronics industries.

The correction of a hyperopic astigmatism with full-toric orthokeratology lenses. Clinical case

Orthokeratology has gained widespread clinical application in the last decade due to accumulated scientifi c data confi rming its effectiveness in inhibiting progressive myopia in children and adolescents. In cases of correction of other refractive errors, such as hypermetropia, mixed astigmatism, specialists inform patients about the possibilities of orthokeratology lenses (OKL) not often. This clinical case demonstrates the possibilities of customized, full-toric OKL to correct complex hyperopic astigmatism in an 11-year-old child. The patient was observed for several years with complex hyperopic astigmatism in ophthalmological clinics and followed the recommendations of specialists to use eyeglass correction. At the stage of transition from preschool to primary school, the child became shy of glasses and refused to wear them. In search of an alternative method of correction, parents sought advice in the special contact lens practice. The patient underwent a complete ophthalmological examination, including corneal topography. Taking into account the features of refraction and the shape of the cornea, the wishes of the child and parents, we have chosen customized orthokeratology lenses (OKL) with a fully toric design (full-toric) as method of correction. The OKL parameters were calculated by using the RGP Designer program. The lenses were made by OKVision Laboratory (Moscow). The fi tting of customized OKL allowed us to solve several tasks at once: the correction of complex hyperopic astigmatism and the freedom from using correction tools in the daytime. Despite the fact that orthokeratology is not the fi rst-line choice for optical correction of hyperopia, in some cases the method may become the only alternative to glasses and soft contact lenses

Etched Silicon Planar CRL Optics for the High-Energy X-ray Diffraction Beamlines 11-ID-B and 11-ID-C at the APS

The focusing of high-energy X-rays is most commonly achieved by commercially available compound refractive lenses (CRL), which are added together in larger structures. There is a need for high-energy X-ray beamlines to enable focusing in only one dimension down to a few micrometers to study layered materials and thin films. High-energy X-rays above 50 keV require often 100 lenses or more, therefore it is more efficient to etch the complete arrays of lenses into a monolithic substrate like a silicon wafer. Custom lens arrays were fabricated for the high-energy x-ray beamlines 11-ID-B, and 11-ID-C at the Argonne National Laboratory. The fabrication required tuning parameters of the Bosch process to optimize the etching of deep vertical sidewalls at a reasonable speed without overheating. The beamline 11-ID-B is equipped with lens arrays of 85-110 lenses for 59 keV and 190-250 lenses for 87 keV photon energy, focusing the beam vertically below 5.0 µm at the sample positions between 1600 mm to 2100 mm. 11-ID-C has received arrays of 435 lenses that focus 106 keV X-rays to a vertical height of 2.0 µm at the sample position. In both cases, the flux density gain in the focal spot is larger than a factor of 20, relative to using slits to cut the beam size. The lens setup is permanently installed and can be moved in and out of the beam during the experiment without further alignment. The lenses have enabled operando diffraction studies on interfaces in batteries and the development of pair distribution function (PDF) analysis using grazing incidence geometry.

A miniaturized, low-cost lens tube based laser-induced fluorescence detection system for automated microfluidic analysis of primary amines.

In situ analyses are essential to ascertain potential past or present habitability in celestial bodies. One technique that provides the sensitivity and miniaturization needed to successfully detect trace organics in the outer Solar System is laser-induced fluorescence (LIF) detection, which, when coupled with microfluidic systems, provides a powerful wet chemistry platform that can meet the size and resource consumption constraints of a remote analysis mission. Herein, a portable LIF detection module (44-mm long, 18-mm wide) was prototyped and utilized to quantify bulk organics in a liquid sample via manual and automated analysis utilizing a programmable microfluidic architecture. The experimental limit of detection (LOD) for primary amines was 11.8μM. A sample (Y31B) collected from the Atacama Desert in Yungay, Chile, was analyzed manually and found to contain 300±50μM of bulk primary amine organics, while the automated microfluidic protocol found the sample to contain 289±4μM of primary amines. Automated analyses showed no statistically significant differences when compared to the manual analyses (t-test, C.I. 95%). Our results demonstrate that the coupling of programmable microfluidic devices with a custom lens tube-based LIF detector enables automated analysis of primary amines using a protocol appropriate for remote analyses. This technique is an invaluable tool for in situ analysis applications in distant, resource-restricted environments.

3D Printing of Customized Aspheric Lenses for Imaging.

A simple and efficient process for fabricating customized aspheric lenses is reported, in which a stereolithographic 3D printer combined with the meniscus equilibrium post-curing technique is employed. Two kinds of UV-curable resins, DentaClear and HEMA, were used for printing aspheric lenses in our experiments. The printed DentaClear lens featured low surface profile deviation of ~74 and showed satisfactory optical imaging resolution of 50.80 lp/mm, i.e., 4.92 . The surface roughness of the printed lens with DentaClear was measured to be around 2 nm with AFM. The surface roughness was improved as a result of post-curing, which reduced the ripples on printed lens surfaces. In contrast, the printed HEMA lens exhibited a significant stair-stepping effect with a large surface profile deviation of ~150 . The ripples were somewhat apparent even if the printed HEMA lens surface was smoothed by means of post-curing. No sharp image can be obtained with the HEMA lens in the resolution testing. The composition of HEMA resin may be the reason for the relatively poor surface quality and optical properties.

Clinical significance of contact lens related changes of ocular surface tissue observed on optical coherence images

PurposeTo investigate the relationship between the real contact lens imprint into the conjunctival tissue, observed by optical coherence tomography (OCT) and conjunctival staining and contact lens wearing comfort. Methods17 participants (mean age = 26.6 SD ± 3.6 years; 7 females) were fitted with three different contact lenses base curves of the same silicone hydrogel custom lens type (Visell 50; Hecht Contactlinsen, Au, Germany) in a randomised order. One lens was optimally fitted according to the manufacturer's recommendation, one fitted 0.4 mm flatter and one fitted 0.4 mm steeper. After 4 h of lens wear the contact lens edge in the area of the conjunctiva was imaged nasally and temporally using OCT (Optovue iVue SD-OCT). To correct the artefact due to optical distortion with OCT, the imprint of all worn lenses was measured on a glass plate afterwards. Conjunctival staining in the limbal region after 4 h of lens wear was classified using the CCLRU Grading Scale. Comfort scoring was based on visual analog scales from 0 (very poor) to 100 (excellent). ResultsThe mean conjunctival imprint of all contact lens edges was 32.0 ± 8.1 μm before and 7.3 ± 6.5 μm after distortion correction of the OCT images. The distortion corrected conjunctival imprint with the 0.4 mm steeper lens (11.5 ± 6.2 μm) was statistically significantly greater compared to the optimally fitted lens (6.5 ± 5.9 μm) (One-way ANOVA followed Tukey-test; p = 0.017) and greater compared to the 0.4 mm flatter lens (3.9 ± 5.3 μm) (p < 0.001). There was no statistically significant difference between the optimally fitted lens and the 0.4 mm flatter lens (p = 0.209). The nasally measured imprint (11.4 ± 9.0 μm) was significantly greater than the temporally measured (3.3 ± 7.6 μm) (p < 0.001). There was no statistically significant correlation between the amount of conjunctival imprint and the graded conjunctival staining (p = 0.346) or the wearer’s comfort (p = 0.735). ConclusionsContact lens edges imaged by OCT exhibited displacement artefacts. The observed conjunctival imprints are a combination of real conjunctival compression and artefacts. A deeper imprint of the contact lens into the conjunctiva caused by a steeper base curve was not related to clinically significant staining or changes in comfort after 4 h of lens wear. The observed differences between nasal and temporal imprint are likely to be caused by variations of conjunctival thickness and the shape of the underlying sclera.

Update on Contact Lens Treatment of Keratoconus

Keratoconus (KC) is a progressive disease that leads to major losses of visual quality and related quality of life. Contact lens (CL) application has a primary place and importance in the correction of the optic problems due to the disease. The corneal changes and increased irregular astigmatism that occur with KC progression necessitate special CL designs and fitting methods. In addition to disease stage, the patient’s lens tolerance also plays a role in the application of CLs in KC patients. With recent advances in materials and design technology, the CLs used in the treatment of KC have developed considerably and there are various types available. In this review, we discuss the wide range of CLs, including rigid and soft lenses, hybrid and scleral lenses, and even custom lens designs, in light of recent scientific advances.

A high magnification UV lens for high temperature optical strain measurements.

Digital Image Correlation (DIC) measures full-field strains by tracking displacements of a specimen using images taken before and after deformation. At high temperatures, materials emit light in the form of blackbody radiation, which can interfere with DIC images. To screen out that light, DIC has been recently adapted by using ultraviolet (UV) range cameras, lenses, and filters. Before now, UV-DIC had been demonstrated at the centimeter scale using commercially available UV lenses and filters. Commercial high-magnification lenses using visible light have also been used for DIC. However, there is currently no commercially available high-magnification lens that will allow images to be taken (a) in the UV range, (b) at a submillimeter scale, and (c) from a relatively long working distance separating a specimen inside a test chamber and a camera outside the chamber. In this work, a custom UV high-magnification lens is demonstrated to perform high-magnification, high-temperature DIC measurements. To demonstrate the capabilities of this lens, a series of thermo-mechanical tests was run on a stainless-steel ring specimen. Two UV cameras performed simultaneous measurements: one at lower magnification using a commercial UV lens, and one with the custom high-magnification UV lens. At room temperature, the custom lens produces sufficiently bright images to perform DIC, while at high temperature (demonstrated to 900 °C) the images retained sufficient contrast while avoiding oversaturation. The lens can detect submillimeter rigid motion and tensile strains from long working distances and high magnification. These tests show that the custom lens is suitable for use in high-magnification UV-DIC measurements.

Telecentric broadband objective lenses for optical coherence tomography (OCT) in the context of low uncertainty metrology of freeform optical components: from design to testing for wavefront and telecentricity.

Freeform optical components enable significant advances for optical systems. A major challenge for freeform optics is the current lack of metrology methods with measurement uncertainty on the order of tens of nanometers or less. Towards addressing this challenge, optical coherence tomography (OCT) is a viable technique. In the context of low uncertainty metrology, the design requirements pertaining to the sample arm of an OCT metrology system are explicitly addressed in this paper. Two telecentric, broadband, diffraction limited, custom objective lens designs are presented with their design strategies. One objective lens was fabricated and experimentally tested for wavefront performance and telecentricity. This lens demonstrates near diffraction limited performance and a maximum deviation from telecentricity of 8.7 arcseconds across the full field of view, correlating to measurement uncertainty of less than 12 nm in simulation. The telecentricity test method developed completes the loop with respect to the design requirements and strategies presented and provides further intuition for telecentric lens designs in general.

Bidirectional evaluation with direct manipulation

We present an evaluation update (or simply, update) algorithm for a full-featured functional programming language, which synthesizes program changes based on output changes. Intuitively, the update algorithm retraces the steps of the original evaluation, rewriting the program as needed to reconcile differences between the original and updated output values. Our approach, furthermore, allows expert users to define custom lenses that augment the update algorithm with more advanced or domain-specific program updates. To demonstrate the utility of evaluation update, we implement the algorithm in Sketch-n-Sketch, a novel direct manipulation programming system for generating HTML documents. In Sketch-n-Sketch, the user writes an ML-style functional program to generate HTML output. When the user directly manipulates the output using a graphical user interface, the update algorithm reconciles the changes. We evaluate bidirectional evaluation in Sketch-n-Sketch by authoring ten examples comprising approximately 1400 lines of code in total. These examples demonstrate how a variety of HTML documents and applications can be developed and edited interactively in Sketch-n-Sketch, mitigating the tedious edit-run-view cycle in traditional programming environments.

Highly curved image sensors: a practical approach for improved optical performance.

The significant optical and size benefits of using a curved focal surface for imaging systems have been well studied yet never brought to market for lack of a high-quality, mass-producible, curved image sensor. In this work we demonstrate that commercial silicon CMOS image sensors can be thinned and formed into accurate, highly curved optical surfaces with undiminished functionality. Our key development is a pneumatic forming process that avoids rigid mechanical constraints and suppresses wrinkling instabilities. A combination of forming-mold design, pressure membrane elastic properties, and controlled friction forces enables us to gradually contact the die at the corners and smoothly press the sensor into a spherical shape. Allowing the die to slide into the concave target shape enables a threefold increase in the spherical curvature over prior approaches having mechanical constraints that resist deformation, and create a high-stress, stretch-dominated state. Our process creates a bridge between the high precision and low-cost but planar CMOS process, and ideal non-planar component shapes such as spherical imagers for improved optical systems. We demonstrate these curved sensors in prototype cameras with custom lenses, measuring exceptional resolution of 3220 line-widths per picture height at an aperture of f/1.2 and nearly 100% relative illumination across the field. Though we use a 1/2.3" format image sensor in this report, we also show this process is generally compatible with many state of the art imaging sensor formats. By example, we report photogrammetry test data for an APS-C sized silicon die formed to a 30° subtended spherical angle. These gains in sharpness and relative illumination enable a new generation of ultra-high performance, manufacturable, digital imaging systems for scientific, industrial, and artistic use.

Tri-modal microscope for head and neck tissue identification.

A novel tri-modal microscope combining optical coherence tomography (OCT), spectrally encoded confocal microscopy (SECM) and fluorescence imaging is presented. This system aims at providing a tool for rapid identification of head and neck tissues during thyroid surgery. The development of a dual-wavelength polygon-based swept laser allows for synchronized, co-registered and simultaneous imaging with all three modalities. Further ameliorations towards miniaturization include a custom lens for optimal compromise between orthogonal imaging geometries as well as a double-clad fiber coupler for increased throughput. Image quality and co-registration is demonstrated on freshly excised swine head and neck tissue samples to illustrate the complementarity of the techniques for identifying signature cellular and structural features.

Vision Stations: Addressing Corrective Vision Needs With Low-cost Technologies.

Eyeglasses, required for functional vision by nearly half the world's population, are still needed by more than a billion people. There are a number of constraints on the provision of eyeglasses: product cost, durability, and appearance; traditional approaches to evaluating refraction; and sustainably scaling potential distribution methods. We offer our experience with an immigrant population in a US urban setting using a “Vision Station.” The station allowed for immediate provision of adjustable glasses using self-refraction, ordering of custom lenses from a low-cost website, and referral to primary and eye care physicians for those with medical eye concerns. As with models in development by other groups, Vision Stations connect people with the life-changing provision of functional vision.

Optimal lens design and use in laser-scanning microscopy

In laser-scanning microscopy often an off-the-shelf achromatic doublet is used as a scan lens which can reduce the available diffraction-limited field-of-view (FOV) by a factor of 3 and introduce chromatic aberrations that are scan angle dependent. Here we present several simple lens designs of superior quality that fully make use of high-NA low-magnification objectives, offering diffraction-limited imaging over a large FOV and wavelength range. We constructed a two-photon laser-scanning microscope with optimized custom lenses which had a near diffraction limit point-spread-function (PSF) with less than 3.6% variation over a 400 µm FOV and less than 0.5 µm lateral color between 750 and 1050 nm.

Progress on Thomson scattering in the Pegasus Toroidal Experiment

A novel Thomson scattering system has been implemented onthe Pegasus Toroidal Experiment where typical densities of 1019 m−3 and electron temperatures of 10 to 500 eV are expected. The systemleverages technological advances in high-energy pulsed lasers, volume phaseholographic (VPH) diffraction gratings, and gated image intensified (ICCD)cameras to provide a relatively low-maintenance, economical, robustdiagnostic system. Scattering is induced by a frequency-doubled, Q-switchedNd:YAG laser (2 J at 532 nm, 7 ns FWHM pulse) directed to the plasma over a7.7 m long beam path, and focused to < 3 mm throughout the collectionregion. Inter-shot beam alignment is adjustable with less than a 0.01 mmspatial resolution in the collection region. A custom lens system collectsscattered photons at radii 15 cm to 85 cm from the machine's center, at ∼ F/6 with 14 mm radial resolution. The initial configuration providesscattering measurements at 12 spatial locations and 12 simultaneousbackground measurements at adjacent locations. If plasma backgroundsubtraction proves to be insignificant, these background channels will beused as viewing channels. Each spectrometer supports 8 spatial channels andcan provide 8 or more spectral bins each. The spectrometers usehigh-efficiency VPH transmission gratings (eff. > 80%) and fast-gatedICCDs (gate > 2 ns, Gen III intensifier) with high-throughput (F/1.8),achromatic lensing. A stray light mitigation facility has been implemented,consisting of a multi-aperture optical baffle system and a simple beam dump.Successful stray light reduction has enabled detection of scattered signal,and Rayleigh scattering has been used to provide a relative calibration.Initial temperature measurements have been made and data analysis algorithmsare under development.

Multispectral Endoscopic Imaging of Colorectal Dysplasia In Vivo

Light provides a broad range of colors in the visible and near-infrared (400–900 nm) spectrum that can be used to transmit information about molecular expression in normal and diseased tissues. The absorbance spectrum of hemoglobin, the primary chromophore in tissue, is shown in Fig. 1A. Genetic changes that occur in cancer transformation can be heterogeneous, and several signaling pathways may be activated concurrently.1 Moreover, molecular activity levels may vary between individual patients, at different time points, and within the tumor. Thus, a single genetic mutation is unlikely to characterize most disease processes over a general population. Unfortunately, most endoscopic imaging methods are sensitive to only one molecular parameter.2 Thus, a methodology that can image multiple molecular targets simultaneously is better suited to address the heterogeneity of cancer and achieve disease detection with high sensitivity and specificity desired for efficient surveillance. In addition, these multiplexed strategies can potentially visualize the interactions between signaling pathways and allow for better understanding of disease pathogenesis on a systems level. Figure 1 A) The visible and near-infrared spectrum of light provides a broad range of colors to generate molecular images from digestive tract mucosa that can be collected with a B) 1.6 mm diameter multispectral scanning fiber endoscope. C) Excitation is delivered ... Recently, significant progress has been made in advancing new methods of endoscopic imaging to target disease in the digestive tract, including the development of novel instruments and specific contrast agents.3 In this video journal, we aim to demonstrate the application of a novel, multispectral endoscope that uses a scanning fiber to image multiple targets at the same time. Fluorescence imaging can be achieved with high target-to-background ratios, and allow us to see the different target expression patterns in an Apc-mutation dependent mouse model of spontaneous colorectal adenomas using multiple peptides as targeting ligands.4

A Thomson scattering diagnostic on the Pegasus Toroidal experiment

By exploiting advances in high-energy pulsed lasers, volume phase holographic diffraction gratings, and image intensified CCD cameras, a new Thomson scattering system has been designed to operate from 532 - 592 nm on the Pegasus Toroidal Experiment. The system uses a frequency-doubled, Q-switched Nd:YAG laser operating with an energy of 2 J at 532 nm and a pulse duration of 7 ns FWHM. The beam path is < 7m, the beam diameter remains ≤ 3 mm throughout the plasma, and the beam dump and optical baffling is located in vacuum but can be removed for maintenance by closing a gate valve. A custom lens system collects scattered photons from 15 cm < R(maj) < 85 cm at ~F∕6 with 14 mm radial resolution. Initial measurements will be made at 12 spatial locations with 12 simultaneous background measurements at corresponding locations. The estimated signal at the machine-side collection optics is ~3.5 × 10(4) photons for plasma densities of 10(19) m(-3). Typical plasmas measured will range from densities of mid-10(18) to mid-10(19) m(-3) with electron temperatures from 10 to 1000 eV.

Comparison of retinal image quality with spherical and customized aspheric intraocular lenses

We hypothesize that an intraocular lens (IOL) with higher-order aspheric surfaces customized for an individual eye provides improved retinal image quality, despite the misalignments that accompany cataract surgery. To test this hypothesis, ray-tracing eye models were used to investigate 10 designs of mono-focal single lens IOLs with rotationally symmetric spherical, aspheric, and customized surfaces. Retinal image quality of pseudo-phakic eyes using these IOLs together with individual variations in ocular and IOL parameters, are evaluated using a Monte Carlo analysis. We conclude that customized lenses should give improved retinal image quality despite the random errors resulting from IOL insertion.

Optical design and imaging performance testing of a 96-mm diameter femtosecond laser microsurgery probe

We present the optical design of a 9.6-mm diameter fiber-coupled probe for combined femtosecond laser microsurgery and nonlinear optical imaging. Towards enabling clinical use, we successfully reduced the dimensions of our earlier 18-mm microsurgery probe by half, while improving optical performance. We use analytical and computational models to optimize the miniaturized lens system for off-axis scanning aberrations. The optimization reveals that the optical system can be aberration-corrected using simple aspheric relay lenses to achieve diffraction-limited imaging resolution over a large field of view. Before moving forward with custom lenses, we have constructed the 9.6-mm probe using off-the-shelf spherical relay lenses and a 0.55 NA aspheric objective lens. In addition to reducing the diameter by nearly 50% and the total volume by 5 times, we also demonstrate improved lateral and axial resolutions of 1.27 µm and 13.5 µm, respectively, compared to 1.64 µm and 16.4 µm in our previous work. Using this probe, we can successfully image various tissue samples, such as rat tail tendon that required 2-3 × lower laser power than the current state-of-the-art. With further development, image-guided, femtosecond laser microsurgical probes such as this one can enable physicians to achieve the highest level of surgical precision anywhere inside the body.