We present techniques and results of optical simulations of microstructured surfaces using BSDF measurements.

Wide field-of-view gigapixel imaging systems capable of diffraction-limited resolution and video-rate acquisition have a broad range of applications, including sports event broadcasting, security surveillance, astronomical observation, and bioimaging. The complexity of the system integration of such devices demands precision optical components that are fully characterized and qualified before being integrated into the final system. In this work, we present component and assembly level characterizations of microcameras in our first gigapixel camera, the AWARE-2. Based on the results of these measurements, we revised the optical design and assembly procedures to construct the second generation system, the AWARE-2 Retrofit, which shows significant improvement in image quality.

We investigate ray trace simulations of isotropic and anisotropic diffusers. Such diffusers require large data sets of highly accurate BSDF measurements that cover the range of illumination angles incident on the diffuser in the simulation.

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.

Multiscale parallel imaging-based on a monocentric optical design-promises revolutionary advances in diverse imaging applications by enabling high resolution, real-time image capture over a wide field-of-view (FOV), including sport broadcast, wide-field microscopy, astronomy, and security surveillance. Recently demonstrated AWARE-2(1) is a gigapixel camera consisting of an objective lens and 98 microcameras spherically arranged to capture an image over FOV of 120 degrees by 50 degrees, using computational image processing to form a composite image of 0.96 gigapixels. Since microcameras are capable of individually adjusting exposure, gain, and focus, true parallel imaging is achieved with a high dynamic range. From the integration perspective, manufacturing and verifying consistent quality of microcameras is a key to successful realization of AWARE cameras. We have developed an efficient testing methodology that utilizes a precisely fabricated dot grid chart as a calibration target to extract critical optical properties such as optical distortion, veiling glare index, and modulation transfer function to validate imaging performance of microcameras. This approach utilizes an AWARE objective lens simulator which mimics the actual objective lens but operates with a short object distance, suitable for a laboratory environment. Here we describe the principles of the methodologies developed for AWARE microcameras and discuss the experimental results with our prototype microcameras.

In multiscale imagers a single objective lens is shared by multiple secondary optical systems, so that a high-resolution wide-angle image is acquired in overlapping fields sensed by multiple conventional focal planes. In the "AWARE2" 2 Gigapixel imager, F/2.4 optics cover a 120 degree field of view using a monocentric glass primary lens shared by 221 molded plastic subimagers, each with a 14 Megapixel focal plane. Such imagers can independently focus parts of the image field, allowing wide-angle imaging over relatively close and deep image fields. However, providing hundreds of independent mechanical focus adjustments has a significant system impact in terms of complexity, bulk, and cost. In this paper we explore the use of an electronically controlled liquid crystal lens for focus of multiscale imagers in general, and demonstrate use with the AWARE2 imager optics. The Lens Vector Auto Focus (LVAF) liquid crystal lens provides up to 5 diopters of optical power over a 2.2mm aperture diameter, the maximum currently available aperture. However, a custom lens using the same materials and basic structure can provide the 5 diopters power and 6.4 mm aperture required to obtain full resolution overlapping image fields in the AWARE2 imager. We characterize the LVAF lens and the optical performance of the LVAF lens in the current AWARE2 prototype, comparing the measured and optically modeled resolution, and demonstrating software control of focus from infinity to an 2m object distance.

Gigapixel camera economics favors reutilization of design components including optics, optomechanics, and electronics. We show microcamera designs for multiscale architectures that only change optical surface profiles that span orders of magnitude of gigapixels.

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 have developed an interactive tolerancing capability for our optical design program, using the optimization error function as the performance criterion. The implementation was carried out using the program's built-in command language, and allows evaluation based on either the error function used during the actual design phase or a standard criterion (magnification, distortion, rms spotsize or wavefront error, etc.). This approach is more flexible than schemes that permit only pre-defined criteria.

We have used the gaussian-integration techniques described by Forbes to build a default error function for our optical design program. To make the function suitable for practical design, we have added ad-hoc extensions that account for vignetting and allow for a variety of user-defined weights. We have now acquired about a year's experience in using the function to design several different systems. Our results have been generally good, and we have recently extended the function to provide additional control over astigmatic aberrations.

In recent years, the application area of gradient-index has extended to optical communication1), photocopy machine, endoscope, facsimile, printer, optical disk system2) and so on.

An axial gradient index singlet collimator lens for use in the compact disk system has been designed and successfully fabricated. Cost and manufacturing constraints have led to a plano-convex design with the axial gradient index profile symmetric about the plane, perpendicular to the optical axis, passing through the center of the lens. Diffraction limited performance has been obtained in the collimator singlet.