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Kern, Brian

Publications and source records attributed to Kern, Brian.

64 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2013

High Contrast Internal and External Coronagraph Masks Produced by Various Techniques

Masks for high contrast internal and external coronagraphic imaging require a variety of masks depending on different architectures to suppress star light. Various fabrication technologies are required to address a wide range of needs including gradient amplitude transmission, tunable phase profiles, ultra-low reflectivity, precise small scale features, and low-chromaticity. We present the approaches employed at JPL to produce pupil plane and image plane coronagraph masks, and lab-scale external occulter type masks by various techniques including electron beam, ion beam, deep reactive ion etching, and black silicon technologies with illustrative examples of each. Further development is in progress to produce circular masks of various kinds for obscured aperture telescopes.

Phase Induced Amplitude Apodization Complex Mask C↗
NASA NTRS2012

Electric Field Reconstruction in the Image Plane of a High-Contrast Coronagraph Using a Set of Pinholes around the Lyot Plane

In a setup similar to the self coherent camera, we have added a set of pinholes in the diffraction ring of the Lyot plane in a high-contrast stellar Lyot coronagraph. We describe a novel complex electric field reconstruction from image plane intensity measurements consisting of light in the coronagraph's dark hole interfering with light from the pinholes. The image plane field is modified by letting light through one pinhole at a time. In addition to estimation of the field at the science camera, this method allows for self-calibration of the probes by letting light through the pinholes in various permutations while blocking the main Lyot opening. We present results of estimation and calibration from the High Contrast Imaging Testbed along with a comparison to the pair-wise deformable mirror diversity based estimation technique. Tests are carried out in narrow-band light and over a composite 10% bandpass.

coronagraphs↗
NASA NTRS2011

Laboratory Testing of a Phased Induced Amplitude Apodization (PIAA) Coronagraph

We present high-contrast images from laboratory testing of a Phase Induced Amplitude Apodization (PIAA) coronagraph at NASA's High Contrast Imaging Testbed (HCIT). Using a deformable mirror and wavefront estimation and control algorithms, we create a 'dark hole' in the monochromatic point-spread function with an inner working angle of (2.05 f lambda/D), with a mean intensity 3.5x10(exp -8). We discuss the contributions to this floor, and the techniques being developed to improve it. We also present simulations that investigate the effect of Lyot stops of various sizes, and conclude that a Lyot stop is necessary for 10(exp -9) performance but that an annular postapodizer is not necessary.

deformable mirror↗
NASA NTRS2011

Studies of the Effects of Optical System Errors on the HCIT Contrast Performance

The High Contrast Imaging Testbed (HCIT) at the Jet Propulsion Laboratory employs a broadband wavefront correction algorithm called Electric Field Conjugation (EFC) to obtain the required 10-10 contrast. This algorithm works with one deformable mirror (DM) to estimate the electric-field to be controlled, and with one or multiple DM's to create a "dark-hole" in a predefined region of the image plane where terrestrial planets would be found. We have investigated the effects of DM actuator errors and the optic position errors on the efficiency of the EFC algorithm in a Lyot coronagraph configuration. The structural design of the optical system as well as the parameters of various optical elements used in the analysis are drawn from those of the HCIT system that have been implemented with one DM. The simulation takes into account the surface errors of various optical elements. Results of some of these studies have been verified by actual measurements.

exoplanetsscopes↗
NASA NTRS2010

Studies of the Effects of Actuator Errors on the HCIT/PIAA Contrast Performance

The High Contrast Imaging Testbed Phase Induced Amplitude Apodization (HCIT/PIAA) coronagraph system at JPL relies on an Electric-Field Conjugation (EFC) wavefront correction algorithm to obtain the required high contrast. This algorithm works with one deformable mirror (DM) to estimate the electric-field to be controlled, and with one or multiple DM's to create a "dark-hole" in the image plane. We have investigated the effects of DM actuator errors on the efficiency of the EFC algorithm. The structural design of the optical system as well as the parameters of various optical elements used in the analysis are drawn from those of the HCIT/PIAA system that have been and will be implemented with one or two DM's. The simulation takes into account the surface errors of various optical elements. In this paper, we report our findings in the case of narrowband wavelength light.

PIAA↗
NASA NTRS2008

Laboratory Demonstrations of High-contrast Imaging for Space Coronagraphy

This slide presentation reviews the use of the High Contrast Imaging Testbed (HCIT) in the design and improvement of space coronagraphs. The objectives of the work are to: (1) Advance the technology readiness of space coronagraph hardware, techniques, algorithms, and predictive models; (2) Provide proof-of-concept demonstrations of coronagraph techniques; and (3) Support collaborations across the exoplanet community in pursuit of the optimal space coronagraph architecture.

High Contrast Imaging Testbed (HCIT)↗