Imaging fiber bundles can relay a curved image surface to a conventional at focal plane, effectively providing the curved image sensor needed for some high performance lenses. If the fiber bundle period or image sensor pitch are very different, the system resolution is determined by the oversampled fiber or sensor feature. But crosstalk imposes an approximately 2µm minimum waveguide pitch, and light collection and fabrication constraints impose a lower limit of 1-2µm for the sensor pitch. Maximizing image information leads to some degree of aliasing, which appears in the form of moiré pattern on the raw image sensed. For example, a 30 Mpixel 120° field of view imager using a 1.75µm Bayer filtered CMOS focal plane with 2.5µm pitch fiber bundle yielded images with visible moiré. Here we present a study of moiré effects in fiber-coupled image sensors, including a method for quantitative analysis of moiré, and experimental characterization of the sensors with 1.1µm pixel pitch, the highest spatial resolution in commercially available focal plane arrays. We investigate the effect of exposure time of the sensor, angle of incidence of collimated light, and imaging lens F/# on the raw moiré pattern strength. This study provides guidelines for optimization and operation of high resolution fiber-coupled imagers.
Monocentric lenses allow high resolution panoramic cameras, where imaging fiber bundles transport the hemispherical image surface to conventional focal planes. Refraction at the curved image surface limits the field of view coupled through a single bundle of straight fibers to less than ±34°, even for NA 1 fibers. Previously we have demonstrated a nearly continuous 128° field of view using a single lens and multiple adjacent straight fiber-coupled image sensors, but this imposes mechanical complexity of fiber bundle shaping and integration. However, a 3D waveguide structure with internally curved optical fiber pathways can couple the full continuous field of view onto a single focal plane. Here, we demonstrate wide-field imaging using a monocentric lens and a single curved fiber bundle, showing that the 3D bundle formed from a tapered fiber bundle can be used for relaying a 128° field of view from a curved input to the planar output face. We numerically show the coupling efficiency of light to the tapered bundle for different field of views depends on the taper ratio of the bundle as well as center of the curvature chosen for polishing of the fiber bundle facet. We characterize a tapered fiber bundle by measuring the angle dependent impulse response, transmission efficiency and the divergence angle of the light propagating from the output end of the fiber.
High resolution, wide field-of-view and large depth-of-focus imaging systems are greatly desired and have received much attention from researchers who seek to extend the capabilities of cameras. Monocentric lenses are superior in performance over other wide field-of-view lenses with the drawback that they form a hemispheric image plane which is incompatible with current sensor technology. Fiber optic bundles can be used to relay the image the lens produces to the sensor's planar surface. This requires image processing to correct for artifacts inherent to fiber bundle image transfer. Using a prototype fiber coupled monocentric lens imager we capture single exposure focal swept images from which we seek to produce extended depth-of-focus images. Point spread functions (PSF) were measured in lab and found to be both angle and depth dependent. This spatial variance enforces the requirement that the inverse problem be treated as such. This synthesis of information allowed us to establish a framework upon which to mitigate fiber bundle artifacts and extend the depth-of-focus of the imaging system.
We present the concept, optical design, and first proof of principle experimental results for a telescopic contact lens
intended to become a visual aid for age-related macular degeneration (AMD), providing magnification to the user
without surgery or external head-mounted optics. Our contact lens optical system can provide a combination of
telescopic and non-magnified vision through two independent optical paths through the contact lens. The magnified
optical path incorporates a telescopic arrangement of positive and negative annular concentric reflectors to achieve 2.8x -
3x magnification on the eye, while light passing through a central clear aperture provides unmagnified vision.
We developed a new type of optical lens device that can change its curvature like crystalline lens in human eye. The
curvature changing capability of the lens allows for a tremendous tuning range in its optical power and subsequently
enables miniaturized imaging systems that can perform autofocus, optical zoom, and other advanced functions. In this
paper, we study the physical properties of bio-inspired fluidic lenses and demonstrate the optical functionality through
miniaturized optical systems constructed with such lenses. We report an auto-focusing optical system that can turn from
a camera to a microscope, and demonstrate more than 4X optical zoom with a very short total track length. Finally, we
demonstrate the benefits of fluidic lens zoom camera through minimally invasive gallbladder removal surgery.