Wink-controlled polarization-switched telescopic contact lenses.

We describe a wink-controlled hands-free switching system for eye-borne telescopic vision, based on a previously tested fixed-magnification telescope embedded within scleral contact lenses. Here we integrate orthogonal polarizers into the contact lens covering the F/9.1 refractive 1× and F/9.6 catadioptric 2.8× vision paths, to allow switching via external liquid crystal shutters. We provide hands-free control by an infrared wink/blink monitor, using passive retroreflectors embedded within the contact lenses. We demonstrate system operation of the self-contained switching eyewear and the modified contact lenses with a life-size human eye model with mechanical "eyelids."

Wearable telescopic contact lens.

We describe the design, fabrication, and testing of a 1.6 mm thick scleral contact lens providing both 1× and 2.8× magnified vision paths, intended for use as a switchable eye-borne telescopic low-vision aid. The F/9.7 telescopic vision path uses an 8.2 mm diameter annular entrance pupil and 4 internal reflections in a polymethyl methacrylate precision optic. This gas-impermeable insert is contained inside a smooth outer casing of rigid gas-permeable polymer, which also provides achromatic correction for refraction at the curved lens face. The unmagnified F/4.1 vision path is through the central aperture of the lens, with additional transmission between the annular telescope rings to enable peripheral vision. We discuss potential solutions for providing oxygenation for an extended wear version of the lens. The prototype lenses were characterized using a scale-model human eye, and telescope functionality was confirmed in a small-scale clinical (nondispensed) demonstration.

Quantitative analysis and temperature-induced variations of moiré pattern in fiber-coupled imaging sensors.

Imaging fiber bundles can map the curved image surface formed by some high-performance lenses onto flat focal plane detectors. The relative alignment between the focal plane array pixels and the quasi-periodic fiber-bundle cores can impose an undesirable space variant moiré pattern, but this effect may be greatly reduced by flat-field calibration, provided that the local responsivity is known. Here we demonstrate a stable metric for spatial analysis of the moiré pattern strength, and use it to quantify the effect of relative sensor and fiber-bundle pitch, and that of the Bayer color filter. We measure the thermal dependence of the moiré pattern, and the achievable improvement by flat-field calibration at different operating temperatures. We show that a flat-field calibration image at a desired operating temperature can be generated using linear interpolation between white images at several fixed temperatures, comparing the final image quality with an experimentally acquired image at the same temperature.

Image processing for cameras with fiber bundle image relay.

Some high-performance imaging systems generate a curved focal surface and so are incompatible with focal plane arrays fabricated by conventional silicon processing. One example is a monocentric lens, which forms a wide field-of-view high-resolution spherical image with a radius equal to the focal length. Optical fiber bundles have been used to couple between this focal surface and planar image sensors. However, such fiber-coupled imaging systems suffer from artifacts due to image sampling and incoherent light transfer by the fiber bundle as well as resampling by the focal plane, resulting in a fixed obscuration pattern. Here, we describe digital image processing techniques to improve image quality in a compact 126° field-of-view, 30 megapixel panoramic imager, where a 12 mm focal length F/1.35 lens made of concentric glass surfaces forms a spherical image surface, which is fiber-coupled to six discrete CMOS focal planes. We characterize the locally space-variant system impulse response at various stages: monocentric lens image formation onto the 2.5 µm pitch fiber bundle, image transfer by the fiber bundle, and sensing by a 1.75 µm pitch backside illuminated color focal plane. We demonstrate methods to mitigate moiré artifacts and local obscuration, correct for sphere to plane mapping distortion and vignetting, and stitch together the image data from discrete sensors into a single panorama. We compare processed images from the prototype to those taken with a 10× larger commercial camera with comparable field-of-view and light collection.

Enhanced signal coupling in wide-field fiber-coupled imagers.

Some high-performance imaging systems, including wide angle "monocentric" lenses made of concentric spherical shells, form a deeply curved image surface coupled to focal plane sensors by optical fiber bundles with a curved input and flat output face. However, refraction at the angled input facet limits the range of input angles, even for fiber bundles with numerical aperture 1. Here we investigate using a curved beam deflector near the focal surface to increase the field of view and improve spatial resolution at the edges of the field of view. We show the field of view of such an imager can be increased from approximately 60° (full width at half maximum intensity) to over 90° using an embossed refractive microprism array, where the prism angle varies across the aperture to maintain coupling. We describe a proof-of-principle experiment using a f = 17.8mm fiber-coupled monocentric singlet lens, and show that a local region of microprisms embossed into a thin layer of SU-8 photopolymer can increase the field of view by 50%.

Panoramic monocentric imaging using fiber-coupled focal planes.

Monocentric lenses provide high-resolution wide field of view imaging onto a hemispherical image surface, which can be coupled to conventional focal planes using fiber-bundle image transfer. We show the design and characterization of a 2-glass concentric F/1.0 lens, and describe integration of 5 Mpixel 1.75µm pitch back-side illuminated color CMOS sensors with 2.5µm pitch fiber bundles, then show the fiber-coupled lens compares favorably in both resolution and light collection to a 10x larger conventional F/4 wide angle photographic lens. We describe assembly of the monocentric lens and 6 adjacent sensors with focus optomechanics into an extremely compact 30Mpixel panoramic imager with a 126° "letterbox" format field of view.

Switchable telescopic contact lens.

We present design and first demonstration of optics for a telescopic contact lens with independent optical paths for switching between normal and magnified vision. The magnified optical path incorporates a telescopic arrangement of positive and negative annular concentric reflectors to achieve 2.8 x magnification on the eye, while light passing through a central clear aperture provides unmagnified vision. We present an experimental demonstration of the contact lens mounted on a life-sized optomechanical model eye and, using a pair of modified commercial 3D television glasses, demonstrate electrically operated polarization switching between normal and magnified vision.

An optomechanical model eye for ophthalmological refractive studies.

PURPOSE: To create an accurate, low-cost optomechanical model eye for investigation of refractive errors in clinical and basic research studies. METHODS: An optomechanical fluid-filled eye model with dimensions consistent with the human eye was designed and fabricated. Optical simulations were performed on the optomechanical eye model, and the quantified resolution and refractive errors were compared with the widely used Navarro eye model using the ray-tracing software ZEMAX (Radiant Zemax, Redmond, WA). The resolution of the physical optomechanical eye model was then quantified with a complementary metal-oxide semiconductor imager using the image resolution software SFR Plus (Imatest, Boulder, CO). Refractive, manufacturing, and assembling errors were also assessed. A refractive intraocular lens (IOL) and a diffractive IOL were added to the optomechanical eye model for tests and analyses of a 1951 U.S. Air Force target chart. RESULTS: Resolution and aberrations of the optomechanical eye model and the Navarro eye model were qualitatively similar in ZEMAX simulations. Experimental testing found that the optomechanical eye model reproduced properties pertinent to human eyes, including resolution better than 20/20 visual acuity and a decrease in resolution as the field of view increased in size. The IOLs were also integrated into the optomechanical eye model to image objects at distances of 15, 10, and 3 feet, and they indicated a resolution of 22.8 cycles per degree at 15 feet. CONCLUSIONS: A life-sized optomechanical eye model with the flexibility to be patient-specific was designed and constructed. The model had the resolution of a healthy human eye and recreated normal refractive errors. This model may be useful in the evaluation of IOLs for cataract surgery.

An optical-coding method to measure particle distribution in microfluidic devices.

We demonstrated an optical coding method to measure the position of each particle in a microfluidic channel. The technique utilizes a specially designed pattern as a spatial mask to encode the forward scattering signal of each particle. From the waveform of the forward scattering signal, one can obtain the information about the particle position and velocity. The technique enables us to experimentally investigate the complex relations between particle positions within the microfluidic channel and flow conditions and particle sizes. The method also produces insight for important phenomenon in microfluidic and lab-on-a-chip devices such as inertial focusing, Dean flow, flow confinement, etc.

Fluidic lens laparoscopic zoom camera for minimally invasive surgery.

This work reports a miniaturized laparoscopic zoom camera that can significantly improve vision for minimally invasive surgery (MIS), also known as laparoscopic surgery. The laparoscopic zoom camera contains bioinspired fluidic lenses that can change curvature and focal length in a manner similar to the crystalline lenses in human eyes. The traditional laparoscope is long, rigid, and made of fixed glass lenses with a fixed field of view. The constricted vision of a laparoscope is often an inconvenience and plays a role in many surgical injuries. To further advance MIS technology, we developed a new type of laparoscopic camera that has a total length of less than 17 mm, greater than 4x optical zoom, and 100 times higher sensitivity than today's laparoscope allowing it to work under illumination as low as 300 lux. All these unique features are enabled by the technology of bioinspired fluidic lenses having a dynamic range over 100 diopters and being convertible between a convex and concave shape.

Bio-inspired fluidic lens surgical camera for MIS.

We report a new type of surgical camera that will greatly improve minimally invasive surgery (MIS). The key enabling technology for this camera is a unique type of lens-bio-inspired fluidic lens, which is a bio-mimetic lens that can change its curvature, just like the way human crystalline lens can accommodate. Because of its curvature changing capability, it is now possible to design a new regime of optical systems where auto-focusing and optical zoom can be performed without moving the lens positions, as is done in typical cameras. Hence, miniaturized imaging system with high functionality can be achieved with such technology. MIS is a surgical technique where small incisions are made on the abdominal wall as opposed to a large cut in open surgery. This type of surgery ensures faster patient recovery. The key tool for MIS is its surgical camera, or laparoscope. Traditional laparoscope is long and rigid and limits the field of view. To further advance MIS technology, we utilized bio-inspired fluidic lens to design a highly versatile imager that is small, can change its field of view or zoom optically, works in low light conditions, and varies the viewing angles. The surgical camera prototype is small (total track<17 mm), possesses 3X optical zoom, operates with light emitting diode (LED) lighting, among many other unique features.