scholarly journals Central-Obscuration Removal Plates for Focal-Plane Phase-Mask Coronagraphs with a Centrally-Obscured Telescope

2014 ◽  
Vol 126 (937) ◽  
pp. 270-279 ◽  
Author(s):  
Fumika Oshiyama ◽  
Naoshi Murakami ◽  
Olivier Guyon ◽  
Frantz Martinache ◽  
Naoshi Baba ◽  
...  
Keyword(s):  
Focal Plane ◽  
Phase Mask ◽  
Central Obscuration

scholarly journals Calibration of quasi-static aberrations in exoplanet direct-imaging instruments with a Zernike phase-mask sensor

2019 ◽  
Vol 629 ◽  
pp. A11 ◽  
Author(s):  
A. Vigan ◽  
M. N’Diaye ◽  
K. Dohlen ◽  
J.-F. Sauvage ◽  
J. Milli ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Near Infrared ◽  
Angular Separation ◽  
Phase Mask ◽  
Internal Source ◽  
Detailed Model ◽  
Circumstellar Environments ◽  
The Difference ◽  
The Impact ◽  
Central Obscuration

Second-generation exoplanet imagers using extreme adaptive optics (ExAO) and coronagraphy have demonstrated their great potential for studying close circumstellar environments and for detecting new companions and helping to understand their physical properties. However, at very small angular separation, their performance in contrast is limited by several factors: diffraction by the complex telescope pupil (central obscuration and spiders) not perfectly canceled by the coronagraph, residual dynamic wavefront errors, chromatic wavefront errors, and wavefront errors resulting from noncommon path aberrations (NCPAs). These latter are differential aberrations between the visible wavefront sensing path of the ExAO system and the near-infrared science path in which the coronagraph is located. In a previous work, we demonstrated the use of a Zernike wavefront sensor called ZELDA for sensing NCPAs in the VLT/SPHERE exoplanet imager and their compensation with the high-order deformable mirror of the instrument. These early tests on the internal light source led to encouraging results for the attenuation of the quasi-static speckles at very small separation. In the present work, we move to the next step with the on-sky validation of NCPA compensation with ZELDA. With an improved procedure for the compensation of NCPAs, we start by reproducing previous results on the internal source. We show that the amount of aberration integrated between 1 and 15 cycles/pupil (c/p) is decreased by a factor of approximately five, which translates into a gain in raw contrast of between 2 and 3 at separations below 300 mas. On sky, we demonstrate that NCPA compensation works in closed loop, leading to an attenuation of the amount of aberration by a factor of approximately two. However, we identify a loss of sensitivity for the sensor that is only partly explained by the difference in Strehl ratio between the internal and on-sky measurements. Our simulations show that the impact of ExAO residuals on ZELDA measurements is negligible for integration times beyond a few tenths of a second. Coronagraphic imaging on sky is improved in raw contrast by a factor of 2.5 at most in the ExAO-corrected region. We use coronagraphic image reconstruction based on a detailed model of the instrument to demonstrate that both internal and on-sky raw contrasts can be precisely explained, and we establish that the observed performance after NCPA compensation is no longer limited by an improper compensation for aberration but by the current apodized-pupil Lyot coronagraph design. We finally conclude that a coronagraph upgrade combined to a proper NCPA compensation scheme could easily bring a gain in raw contrast of a factor of two to three below 200 mas.

scholarly journals On-Sky Demonstration of Low-Order Wavefront Sensing and Control with Focal Plane Phase Mask Coronagraphs

2015 ◽  
Vol 127 (955) ◽  
pp. 857-869 ◽  
Author(s):  
Garima Singh ◽  
Julien Lozi ◽  
Olivier Guyon ◽  
Pierre Baudoz ◽  
Nemanja Jovanovic ◽  
...  
Keyword(s):  
Focal Plane ◽  
Phase Mask ◽  
Wavefront Sensing ◽  
And Control ◽  
Low Order

scholarly journals The Single-mode Complex Amplitude Refinement (SCAR) coronagraph

2020 ◽  
Vol 635 ◽  
pp. A56 ◽  
Author(s):  
S. Y. Haffert ◽  
E. H. Por ◽  
C. U. Keller ◽  
M. A. Kenworthy ◽  
D. S. Doelman ◽  
...  
Keyword(s):  
Focal Plane ◽  
Single Mode ◽  
Single Mode Fiber ◽  
Solar Neighborhood ◽  
Phase Plate ◽  
Promising Technique ◽  
Fiber Array ◽  
Dark Region ◽  
Tilt Stability ◽  
Central Obscuration

We present the monochromatic lab verification of the newly developed SCAR coronagraph that combines a phase plate (PP) in the pupil with a microlens-fed single-mode fiber array in the focal plane. The two SCAR designs that have been measured, create respectively a 360 degree and 180 degree dark region from 0.8–2.4λ∕D around the star. The 360 SCAR has been designed for a clear aperture and the 180 SCAR has been designed for a realistic aperture with central obscuration and spiders. The 360 SCAR creates a measured stellar null of 2–3 × 10−4, and the 180 SCAR reaches a null of 1 × 10−4. Their monochromatic contrast is maintained within a range of ±0.16λ∕D peak-to-valley tip-tilt, which shows the robustness against tip-tilt errors. The small inner working angle and tip-tilt stability makes the SCAR coronagraph a very promising technique for an upgrade of current high-contrast instruments to characterize and detect exoplanets in the solar neighborhood.

Tandem scanning reflected light microscopy: How it works and applications

1986 ◽  
Vol 44 ◽  
pp. 84-87
Author(s):  
Alan Boyde ◽  
Milan Hadravský ◽  
Mojmír Petran ◽  
Timothy F. Watson ◽  
Sheila J. Jones ◽  
...  
Keyword(s):  
Light Microscopy ◽  
Focal Plane ◽  
Central Symmetry ◽  
Single Line ◽  
Scanning Microscope ◽  
Reflected Light ◽  
Illuminating Light ◽  
Illuminating Beam

The principles of tandem scanning reflected light microscopy and the design of recent instruments are fully described elsewhere and here only briefly. The illuminating light is intercepted by a rotating aperture disc which lies in the intermediate focal plane of a standard LM objective. This device provides an array of separate scanning beams which light up corresponding patches in the plane of focus more intensely than out of focus layers. Reflected light from these patches is imaged on to a matching array of apertures on the opposite side of the same aperture disc and which are scanning in the focal plane of the eyepiece. An arrangement of mirrors converts the central symmetry of the disc into congruency, so that the array of apertures which chop the illuminating beam is identical with the array on the observation side. Thus both illumination and “detection” are scanned in tandem, giving rise to the name Tandem Scanning Microscope (TSM). The apertures are arranged on Archimedean spirals: each opposed pair scans a single line in the image.

Imaging sub-micron objects with light microscopy: Visualization of the T-4 bacteriophage

1989 ◽  
Vol 47 ◽  
pp. 834-835
Author(s):  
Malcolm Brown ◽  
Reynolds M. Delgado ◽  
Michael J. Fink
Keyword(s):  
Electron Microscopy ◽  
Light Microscopy ◽  
Focal Plane ◽  
Phase Contrast ◽  
Dark Field ◽  
E Coli ◽  
Polystyrene Beads ◽  
Television Camera ◽  
Transmission Electron ◽  
Universal Microscope

While light microscopy has been used to image sub-micron objects, numerous problems with diffraction-limitations often preclude extraction of useful information. Using conventional dark-field and phase contrast light microscopy coupled with image processing, we have studied the following objects: (a) polystyrene beads (88nm, 264nm, and 557mn); (b) frustules of the diatom, Pleurosigma angulatum, and the T-4 bacteriophage attached to its host, E. coli or free in the medium. Equivalent images of the same areas of polystyrene beads and T-4 bacteriophages were produced using transmission electron microscopy.For light microscopy, we used a Zeiss universal microscope. For phase contrast observations a 100X Neofluar objective (N.A.=1.3) was applied. With dark-field, a 100X planachromat objective (N.A.=1.25) in combination with an ultra-condenser (N.A.=1.25) was employed. An intermediate magnifier (Optivar) was available to conveniently give magnification settings of 1.25, 1.6, and 2.0. The image was projected onto the back focal plane of a film or television camera with a Carl Zeiss Jena 18X Compens ocular.

Microspectroscopy Using a Solid Immersion Lens

2001 ◽  
Vol 7 (S2) ◽  
pp. 148-149
Author(s):  
C.D. Poweleit ◽  
J Menéndez
Keyword(s):  
Spatial Resolution ◽  
Focal Plane ◽  
Numerical Aperture ◽  
Normal Incidence ◽  
Spot Size ◽  
Index Of Refraction ◽  
Objective Lens ◽  
Improvement Factor ◽  
Oil Immersion ◽  
Long Time

Oil immersion lenses have been used in optical microscopy for a long time. The light’s wavelength is decreased by the oil’s index of refraction n and this reduces the minimum spot size. Additionally, the oil medium allows a larger collection angle, thereby increasing the numerical aperture. The SIL is based on the same principle, but offers more flexibility because the higher index material is solid. in particular, SILs can be deployed in cryogenic environments. Using a hemispherical glass the spatial resolution is improved by a factor n with respect to the resolution obtained with the microscope’s objective lens alone. The improvement factor is equal to n2 for truncated spheres.As shown in Fig. 1, the hemisphere SIL is in contact with the sample and does not affect the position of the focal plane. The focused rays from the objective strike the lens at normal incidence, so that no refraction takes place.

SILICON READOUT INTEGRATED CIRCUITS FOR INFRARED FOCAL PLANE ARRAYS BASED ON MERCURY-CADMIUM-TELLURIDE SOLID SOLUTIONS

2019 ◽  
pp. 88-102
Author(s):  
Bazovkin V. M. ◽  
◽  
Dvoretsky S. A. ◽  
Zverev A. V. ◽  
Kovchavtsev A. P. ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
Cadmium Telluride ◽  
Solid Solutions ◽  
Focal Plane ◽  
Mercury Cadmium Telluride ◽  
Focal Plane Arrays ◽  
Infrared Focal Plane Arrays

Fabrication of two-layer integrated phase mask and single-beam, single exposure fabrication of 3D photonic crystal template using the mask

2008 ◽  
Author(s):  
Yuankun Lin ◽  
Ahmad Harb ◽  
Daniel Rodriguez ◽  
Karen Lozano ◽  
Di Xu ◽  
...  
Keyword(s):  
Photonic Crystal ◽  
Phase Mask ◽  
Single Exposure ◽  
Single Beam

Focal plane considerations for fiber laser wide field processing

2010 ◽  
Author(s):  
Mark Brodsky ◽  
Jack Gabzdyl
Keyword(s):  
Fiber Laser ◽  
Focal Plane ◽  
Wide Field
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