7,051 research outputs found
SLM-based Digital Adaptive Coronagraphy: Current Status and Capabilities
Active coronagraphy is deemed to play a key role for the next generation of
high-contrast instruments, notably in order to deal with large segmented
mirrors that might exhibit time-dependent pupil merit function, caused by
missing or defective segments. To this purpose, we recently introduced a new
technological framework called digital adaptive coronagraphy (DAC), making use
of liquid-crystal spatial light modulators (SLMs) display panels operating as
active focal-plane phase mask coronagraphs. Here, we first review the latest
contrast performance, measured in laboratory conditions with monochromatic
visible light, and describe a few potential pathways to improve SLM
coronagraphic nulling in the future. We then unveil a few unique capabilities
of SLM-based DAC that were recently, or are currently in the process of being,
demonstrated in our laboratory, including NCPA wavefront sensing,
aperture-matched adaptive phase masks, coronagraphic nulling of multiple star
systems, and coherent differential imaging (CDI).Comment: 14 pages, 9 figures, to appear in Proceedings of the SPIE, paper
10706-9
Optimal Radiometric Calibration for Camera-Display Communication
We present a novel method for communicating between a camera and display by
embedding and recovering hidden and dynamic information within a displayed
image. A handheld camera pointed at the display can receive not only the
display image, but also the underlying message. These active scenes are
fundamentally different from traditional passive scenes like QR codes because
image formation is based on display emittance, not surface reflectance.
Detecting and decoding the message requires careful photometric modeling for
computational message recovery. Unlike standard watermarking and steganography
methods that lie outside the domain of computer vision, our message recovery
algorithm uses illumination to optically communicate hidden messages in real
world scenes. The key innovation of our approach is an algorithm that performs
simultaneous radiometric calibration and message recovery in one convex
optimization problem. By modeling the photometry of the system using a
camera-display transfer function (CDTF), we derive a physics-based kernel
function for support vector machine classification. We demonstrate that our
method of optimal online radiometric calibration (OORC) leads to an efficient
and robust algorithm for computational messaging between nine commercial
cameras and displays.Comment: 10 pages, Submitted to CVPR 201
Aerospace medicine and biology: A continuing bibliography with indexes, supplement 184
This bibliography lists 139 reports, articles, and other documents introduced into the NASA scientific and technical information system in August 1978
TITAN's Digital RFQ Ion Beam Cooler and Buncher, Operation and Performance
We present a description of the Radio Frequency Quadrupole (RFQ) ion trap
built as part of the TITAN facility. It consists of a gas-filled, segmented,
linear Paul trap and is the first stage of the TITAN setup with the purpose of
cooling and bunching radioactive ion beams delivered from ISAC-TRIUMF. This is
the first such device to be driven digitally, i.e., using a high voltage
(), wide bandwidth ()
square-wave as compared to the typical sinusoidal wave form. Results from the
commissioning of the device as well as systematic studies with stable and
radioactive ions are presented including efficiency measurements with stable
Cs and radioactive Cs. A novel and unique mode of
operation of this device is also demonstrated where the cooled ion bunches are
extracted in reverse mode, i.e., in the same direction as previously injected.Comment: 34 pages, 17 figure
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