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 degrees, even for NA 1 fibers. Previously we have demonstrated a nearly continuous 128 degrees 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 degrees 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.

We demonstrate an extremely compact 127° field of view F/1.35 imager using a 12mm focal length monocentric lens coupled to a 25 Megapixel full-frame color CMOS sensor by the curved fibers from a 2.9μm pitch tapered fiber bundle.

System requirements for many military electro-optic and IR camera systems reflect the need for both wide-field-of-view situational awareness as well as high-resolution imaging for target identification. In this work we present a new imaging system architecture designed to perform both functions simultaneously and the AWARE 10 camera as an example at visible wavelengths. We first describe the basic system architecture and user interface followed by a laboratory characterization of the system optical performance. We then describe a field experiment in which the camera was used to identify several maritime targets at varying range. The experimental results indicate that users of the system are able to correctly identify ~10 m targets at between 4 and 6 km with 70% accuracy.

Fiber-coupled imaging provides new opportunities for optomechanical system design and layout, and also new challenges when achieving high pixel counts and wide fields of view using multiple sensors in monocentric imaging systems with integrated focus.

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.

We characterize the spatially variant transfer function of a fiber coupled monocentric lens imager, and show image processing techniques to reduce defects caused by the fiber bundle, improve image uniformity and increase spatial resolution.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text A. R. Johnson, R. E. Tennill, H. S. Son, J. Kim, D. L. Marks, S. D. Feller, D. J. Brady, and R. A. Stack, "System Design Considerations for Gigapixel Imaging Systems," in Classical Optics 2014, OSA Technical Digest (online) (Optica Publishing Group, 2014), paper CTh1C.4. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

Recent developments in multiscale imaging systems have opened up the possibility for commercially viable wide-field gigapixel cameras. While multiscale design principles allow tremendous simplification of the optical design, they place increased emphasis on optomechanics and system level integration of the camera as a whole. In this paper we present the optomechanical design of a prototype two-gigapixel system (AWARE-2) that has been constructed and tested.

The AWARE-2 camera uses a parallel array of microcameras to capture one-gigapixel images at three frames per minute.

Gigapixel cameras have been confined to specialized applications such as aerial photography and astronomical observatories. A simplified architecture would better suit terrestrial imaging and reduce instrument cost and complexity. Our gigapixel AWARE camera is based on monocentric multiscale optical design principles that produce high-resolution images with a field of view (FOV) limited only by vignetting. This design allows resolution to approach the theoretical diffraction limits for a given entrance pupil size and FOV.

Recent investigations into high pixel count imaging using multiscale optics have led to a novel optical design for a wide field, gigapixel camera. We review the mechanical design and optical performance of this imager.

Testing a 2-Gigapixel 8 arcsec IFOV, 120° FOV camera requires integration of precision mechanical automation, optical instrumentation, image diagnostics, electronics and networking hardware. We detail the ongoing AWARE Wide Field Camera efforts.

We present an unconventional coaxial architecture for simultaneous acquisition of images in two discrete spectral bands. The approach is realized by taking advantage of a novel annular-folded lens design previously developed under the DARPA/MONTAGE program.

We present the design and experimental demonstration of an ultrathin four-reflection imager. The F/1.15 prototype imager achieves a focal length of 18.6 mm in a track length of just 5.5 mm, providing a 17 degrees field of view over 1.92 megapixels of a color image sensor with 3 microm pixels. We also present the design and experimental results of pupil-phase encoding and postprocessing, which were applied to extend the depth of field and compensate a small amount of axial chromatic aberration present in the four-reflection imager prototype.

We describe an approach to polarimetric imaging based on a unique folded imaging system with an annular aperture. The novelty of this approach lies in the system's collection architecture, which segments the pupil plane to measure the individual polarimetric components contributing to the Stokes vectors. Conventional approaches rely on time sequential measurements (time-multiplexed) using a conventional imaging architecture with a reconfigurable polarization filter, or measurements that segment the focal plane array (spatial multiplexing) by super-imposing an array of polarizers. Our approach achieves spatial multiplexing within the aperture in a compact, lightweight design. The aperture can be configured for sequential collection of the four polarization components required for Stokes vector calculation or in any linear combination of those components on a common focal plane array. Errors in calculating the degree of polarization caused by the manner in which the aperture is partitioned are analyzed, and approaches for reducing that error are investigated. It is shown that reconstructing individual polarization filtered images prior to calculating the Stokes parameters can reduce the error significantly.

With smaller, slimmer and lighter cameras in high demand for consumer portable devices and military applications, optics is challenged with the questionhow can we make optics smaller without giving up the functionality associated with larger cameras? A big part of the problem is simply scalability. As conventional imaging systems are scaled down, the focal length (i.e. magnification) scales down with the allowed optical thickness. Being additionally limited by the size of the smallest available image sensors, we find that these cameras are usually limited to short focal length, small aperture lenseswhat you find in the majority of cell phones. While fine for many applications, there are others, such as surveillance and high-end portable device cameras that could benefit dramatically from larger magnification and better light collection with minimal added bulk or thickness.

Annular folded imagers can be up to 10x thinner than corresponding full-aperture imagers, but have tight fabrication tolerances and relatively shallow depth of focus. Wavefront coding, the use of specialized optics with postdetection signal processing, has been used to improve the depth of focus in full-aperture imaging systems. Here we explore the application of wavefront coding to annular folded optics. We compare the design and experimental results for an imaging system with a 38 mm focal length and just 5 mm total track.

We present the design and implementation of annular 8-fold and 4-fold imagers with both full and arc-section reduced apertures. The advantages and trade-offs of arc-section apertures are discussed and shown experimentally compared to their full-aperture counterparts.

We present a reflective multiple-fold approach to visible imaging for high-resolution, large aperture cameras of significantly reduced thickness. This approach allows for reduced bulk and weight compared with large high-quality camera systems and improved resolution and light collection compared with miniature conventional cameras. An analysis of the properties of multiple-fold imagers is presented along with the design, fabrication, and testing of an eightfold prototype camera. This demonstration camera has a 35 mm effective focal length, 0.7 NA, and 27 mm effective aperture folded into a 5 mm total thickness.

We present an arc-section eight-fold imager with depth of field increased 4x and volume reduced 5x compared to its symmetric counterpart. We also present the design of a pupil-phase encoded four-fold imager.