Yaron Rachlin

Design architectures for optically multiplexed imaging.

Optically multiplexed imaging is the process by which multiple images are overlaid on a single image surface. Uniquely encoding the discrete images allows scene reconstruction from multiplexed images via post processing. We describe a class of optical systems that can achieve high density image multiplexing through a novel division of aperture technique. Fundamental design considerations and performance attributes for this sensor architecture are discussed. A number of spatial and temporal encoding methods are presented including point spread function engineering, amplitude modulation, and image shifting. Results from a prototype five-channel sensor are presented using three different encoding methods in sparse-scene star tracking demonstration. A six-channel optically multiplexed prototype sensor is used to reconstruct imagery from information rich dense scenes through dynamic image shifting.

Compressed Sensing Techniques for Image Reconstruction in Optical Interferometry

We develop a novel method of image reconstruction from bispectrum and magnitude observables of an optical interferometer using Compressed-Sensing techniques.We validate our method in simulation and with actual measurements from a Fizeau interferometer.

Dynamic Optically Multiplexed Imaging

Optically multiplexed imagers overcome the tradeoff between field of view and resolution by superimposing images from multiple fields of view onto a single focal plane. In this paper, we consider the implications of independently shifting each field of view at a rate exceeding the frame rate of the focal plane array and with a precision that can exceed the pixel pitch. A sequence of shifts enables the reconstruction of the underlying scene, with the number of frames required growing inversely with the number of multiplexed images. As a result, measurements from a sufficiently fast sampling sensor can be processed to yield a low distortion image with more pixels than the original focal plane array, a wider field of view than the original optical design, and an aspect ratio different than the original lens. This technique can also enable the collection of low-distortion, wide field of view videos. A sequence of sub-pixel spatial shifts extends this capability to allow the recovery of a wide field of view scene at sub-pixel resolution. To realize this sensor concept, a novel and compact divided aperture multiplexed sensor, capable of rapidly and precisely shifting its fields of view, was prototyped. Using this sensor, we recover twenty-four megapixel images from a four-megapixel focal plane and show the feasibility of simultaneous de-multiplexing and super-resolution.

Refractive optically multiplexed LWIR imaging system

Using a novel computational imaging architecture, we double the field of view of a long-wave infrared microbolometer camera while maintaining resolution. Due to the compact designs enabled by this architecture and the critical impact of resolution on classification performance, this approach is compelling for surveillance applications where low size, weight, power and cost (SWaP-C) systems are desired. We detail the optical design, characterization, and performance of a compact, refractive, optically multiplexed imaging system for use in the long-wave infrared (8-12 μm). A pair of prisms are used to divide the aperture and expose the uncooled microbolometer focal plane to two fields of view simultaneously, doubling the number of output pixels and the horizontal field of view. The image is reconstructed by rotating the prisms about the optical axis, inducing opposing vertical shifts in the two channels. Focal length, field of view, MTF, and NEDT are used to compare performance to a conventional camera. Shifting methods for proper demultiplexing are discussed, and reconstructed images are offered as a demonstration of system performance.

Computational reconfigurable imaging spectrometer

We demonstrate a novel hyperspectral imaging spectrometer based on computational imaging that enables sensitive measurements from smaller, noisier, and less-expensive components (e.g. uncooled microbolometers), making it useful for applications such as small space and air platforms with strict size, weight, and power requirements. The computational reconfigurable imaging spectrometer (CRISP) system exploits platform motion and a spectrally coded focal-plane mask to temporally modulate the optical spectrum, enabling simultaneous measurement of multiple spectral bins. Demodulation of this coded pattern returns an optical spectrum in each pixel.

Design and calibration of a wide field of view MWIR optically multiplexed imaging system

We describe the optical design and characterization testing of an optically multiplexed imaging system operating in the 3.4 to 5 micron waveband. The optical design uses a division of aperture method to overlay six images on a single focal plane and produce a 90 by 15 degree 6-megapixel field of view. Image disambiguation is achieved through image shifting enabled by piezo-actuated mirrors in the multiplexing assembly. This paper provides an overview of the optical design including focal plane selection, image resolution and distortion, pupil imaging, and aperture division geometry. A method of applying one and two-point non-uniformity correction using radiometric test data is suggested. Sensor-level per-channel image quality and sensitivity tests including MTF, 3D-noise and NEDT are shown to validate the design assumptions.