scholarly journals The Subaru coronagraphic extreme AO (SCExAO) system: wavefront control and detection of exoplanets with coherent light modulation in the focal plane

2010 ◽  
Author(s):  
Olivier Guyon ◽  
Frantz Martinache ◽  
Vincent Garrel ◽  
Frederic Vogt ◽  
Kaito Yokochi ◽  
...  
Keyword(s):  
Focal Plane ◽  
Light Modulation ◽  
Coherent Light ◽  
Wavefront Control

scholarly journals Calibration of the island effect: Experimental validation of closed-loop focal plane wavefront control on Subaru/SCExAO

2018 ◽  
Vol 610 ◽  
pp. A18 ◽  
Author(s):  
M. N’Diaye ◽  
F. Martinache ◽  
N. Jovanovic ◽  
J. Lozi ◽  
O. Guyon ◽  
...  
Keyword(s):  
Image Quality ◽  
Focal Plane ◽  
Closed Loop ◽  
Near Infrared ◽  
Experimental Tests ◽  
Relative Increase ◽  
Visible Range ◽  
Wavefront Control ◽  
Island Effect ◽  
Plane Wavefront

Context. Island effect (IE) aberrations are induced by differential pistons, tips, and tilts between neighboring pupil segments on ground-based telescopes, which severely limit the observations of circumstellar environments on the recently deployed exoplanet imagers (e.g., VLT/SPHERE, Gemini/GPI, Subaru/SCExAO) during the best observing conditions. Caused by air temperature gradients at the level of the telescope spiders, these aberrations were recently diagnosed with success on VLT/SPHERE, but so far no complete calibration has been performed to overcome this issue. Aims. We propose closed-loop focal plane wavefront control based on the asymmetric Fourier pupil wavefront sensor (APF-WFS) to calibrate these aberrations and improve the image quality of exoplanet high-contrast instruments in the presence of the IE. Methods. Assuming the archetypal four-quadrant aperture geometry in 8 m class telescopes, we describe these aberrations as a sum of the independent modes of piston, tip, and tilt that are distributed in each quadrant of the telescope pupil. We calibrate these modes with the APF-WFS before introducing our wavefront control for closed-loop operation. We perform numerical simulations and then experimental tests on a real system using Subaru/SCExAO to validate our control loop in the laboratory and on-sky. Results. Closed-loop operation with the APF-WFS enables the compensation for the IE in simulations and in the laboratory for the small aberration regime. Based on a calibration in the near infrared, we observe an improvement of the image quality in the visible range on the SCExAO/VAMPIRES module with a relative increase in the image Strehl ratio of 37%. Conclusions. Our first IE calibration paves the way for maximizing the science operations of the current exoplanet imagers. Such an approach and its results prove also very promising in light of the Extremely Large Telescopes (ELTs) and the presence of similar artifacts with their complex aperture geometry.

scholarly journals Simulating digital micromirror devices for patterning coherent excitation light in structured illumination microscopy

2020 ◽  
Author(s):  
Mario Lachetta ◽  
Hauke Sandmeyer ◽  
Alice Sandmeyer ◽  
Jan Schulte am Esch ◽  
Thomas Huser ◽  
...  
Keyword(s):  
High Speed ◽  
Consumer Electronics ◽  
Light Sources ◽  
Structured Illumination ◽  
Light Modulation ◽  
Coherent Light ◽  
Structured Illumination Microscopy ◽  
Excitation Light ◽  
Coherent Excitation ◽  
Digital Micromirror Devices

SummaryDigital micromirror devices (DMDs) are spatial light modulators that employ the electro-mechanical movement of miniaturized mirrors to steer and thus modulate the light reflected of a mirror array. Their wide availability, low cost and high speed make them a popular choice both in consumer electronics such as video projectors, and scientific applications such as microscopy.High-end fluorescence microscopy systems typically employ laser light sources, which by their nature provide coherent excitation light. In super-resolution microscopy applications that use light modulation, most notably structured illumination microscopy (SIM), the coherent nature of the excitation light becomes a requirement to achieve optimal interference pattern contrast. The universal combination of DMDs and coherent light sources, especially when working with multiple different wavelengths, is unfortunately not straight forward. The substructure of the tilted micromirror array gives rise to a blazed grating, which has to be understood and which must be taken into account when designing a DMD-based illumination system.Here, we present a set of simulation frameworks that explore the use of DMDs in conjunction with coherent light sources, motivated by their application in SIM, but which are generalizable to other light patterning applications. This framework provides all the tools to explore and compute DMD-based diffraction effects and to simulate possible system alignment configurations computationally, which simplifies the system design process and provides guidance for setting up DMD-based microscopes.

scholarly journals A New Ocular Micrometer for the MAHIS

1995 ◽  
Vol 167 ◽  
pp. 335-336
Author(s):  
T. R. Kirian ◽  
V. S. Korepanov ◽  
V. M. Grozdilov
Keyword(s):  
Focal Plane ◽  
Ccd Camera ◽  
Optical Scheme ◽  
List Type ◽  
Coherent Light ◽  
Working Model ◽  
Ccd Matrix ◽  
Ocular Micrometer ◽  
Flat Mirror ◽  
Laboratory Investigations

A working model of an ocular micrometer has been designed for the MAHIS (Meridian Automated Horizontal Instrument by Sukcharev). An optical scheme of the micrometer includes the following devices: a)Artificial light marks in the focal plane of the objective. The marks have an increased sharpness and have a stable scale factor under defocusing. An amplitude-phase grid illuminated by coherent light from the second main point of the objective is used to make the marks.b)The observed stars and artificial marks are imaged on the CCD chip by means of an additional objective. This objective also corrects chromatic aberations of the main objective.c)A concentric meniscus is used to compensate for the chromatic refraction of the atmosphere. The meniscus center of curvature coincides with the center of the system's pupil image. In this case the compensation is equal at all points of the field of view.d)The possibility of measuring the normal attitude of the flat mirror relative to the main instrumental plane during each observation is discussed. For these purposes there needs to be a holographic grid on the mirror surface, an artificial zenith or nadir horizon and an autocollimated source of light in the focal plane.e)Laboratory investigations of a working model of a CCD camera are being carried out and the basic software is being developed. This work is planned to be finished in the autumn of 1994. The CCD matrix ISD 011A (NPO “Electron”, St. Petersburg, Russia) 512 × 512 pixels, with pixel size of 16 × 16 mkm is used. The noise is 5 electrons/pixel/sec when the temperature is −40° C (thermoelectric cooler).

scholarly journals SCExAO: First Results and On-Sky Performance

2013 ◽  
Vol 8 (S299) ◽  
pp. 34-35 ◽  
Author(s):  
Thayne Currie ◽  
Olivier Guyon ◽  
Frantz Martinache ◽  
Christophe Clergeon ◽  
Michael McElwain ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Focal Plane ◽  
Closed Loop ◽  
Giant Planets ◽  
Wavefront Sensor ◽  
Strehl Ratio ◽  
Wavefront Control ◽  
Contrast Gain ◽  
First Results ◽  
Plane Wavefront

AbstractWe present new on-sky results for the Subaru Coronagraphic Extreme Adaptive Optics imager (SCExAO) verifying and quantifying the contrast gain enabled by key components: the closed-loop coronagraphic low-order wavefront sensor (CLOWFS) and focal plane wavefront control (“speckle nulling”). SCExAO will soon be coupled with a high-order, Pyramid wavefront sensor which will yield > 90% Strehl ratio and enable 106–107 contrast at small angular separations allowing us to image gas giant planets at solar system scales. Upcoming instruments like VAMPIRES, FIRST, and CHARIS will expand SCExAO's science capabilities.

scholarly journals Comparing focal plane wavefront control techniques: Numerical simulations and laboratory experiments

2020 ◽  
Vol 635 ◽  
pp. A192 ◽  
Author(s):  
A. Potier ◽  
P. Baudoz ◽  
R. Galicher ◽  
G. Singh ◽  
A. Boccaletti
Keyword(s):  
Numerical Simulations ◽  
Focal Plane ◽  
Spectral Band ◽  
Wavefront Sensing ◽  
High Contrast ◽  
Contrast Imaging ◽  
Wavefront Control ◽  
Control Techniques ◽  
High Contrast Imaging ◽  
Plane Wavefront

Context. Fewer than 1% of all exoplanets detected to date have been characterized on the basis of spectroscopic observations of their atmosphere. Unlike indirect methods, high-contrast imaging offers access to atmospheric signatures by separating the light of a faint off-axis source from that of its parent star. Forthcoming space facilities, such as WFIRST/LUVOIR/HabEX, are expected to use coronagraphic instruments capable of imaging and spectroscopy in order to understand the physical properties of remote worlds. The primary technological challenge that drives the design of these instruments involves the precision control of wavefront phase and amplitude errors. To suppress the stellar intensity to acceptable levels, it is necessary to reduce phase aberrations to less than several picometers across the pupil of the telescope. Aims. Several focal plane wavefront sensing and control techniques have been proposed and demonstrated in laboratory to achieve the required accuracy. However, these techniques have never been tested and compared under the same laboratory conditions. This paper compares two of these techniques in a closed loop in visible light: the pair-wise (PW) associated with electric field conjugation (EFC) and self-coherent camera (SCC). Methods. We first ran numerical simulations to optimize PW wavefront sensing and to predict the performance of a coronagraphic instrument with PW associated to EFC wavefront control, assuming modeling errors for both PW and EFC. Then we implemented the techniques on a laboratory testbed. We introduced known aberrations into the system and compared the wavefront sensing using both PW and SCC. The speckle intensity in the coronagraphic image was then minimized using PW+EFC and SCC independently. Results. We demonstrate that both techniques – SCC, based on spatial modulation of the speckle intensity using an empirical model of the instrument, and PW, based on temporal modulation using a synthetic model – can estimate the wavefront errors with the same precision. We also demonstrate that both SCC and PW+EFC can generate a dark hole in space-like conditions in a few iterations. Both techniques reach the current limitation of our laboratory bench and provide coronagraphic contrast levels of ∼5 × 10−9 in a narrow spectral band (< 0.25% bandwidth). Conclusions. Our results indicate that both techniques are mature enough to be implemented in future space telescopes equipped with deformable mirrors for high-contrast imaging of exoplanets.

Phase analysis for partially coherent light propagating through an optimized aperture in a synchrotron beamline

2020 ◽  
Vol 27 (6) ◽  
pp. 1485-1493
Author(s):  
Junchao Ren ◽  
Xiangyu Meng ◽  
Yong Wang ◽  
Jiefeng Cao ◽  
Junqin Li ◽  
...  
Keyword(s):  
Focal Plane ◽  
Phase Distribution ◽  
Spot Size ◽  
Distribution Area ◽  
Aperture Size ◽  
Optical Intensity ◽  
Coherent Light ◽  
Incoherent Light ◽  
Partially Coherent ◽  
Partially Coherent Light

The mutual optical intensity propagation of partially coherent light through a beamline is calculated for different aperture sizes and positions. The coherence, intensity and phase distribution can be extracted from the mutual optical intensity. The phase distribution depends on the aperture size and position. The results show that the widest flat phase distribution is obtained at the optimized aperture size and position. The aperture plays a more important role for partially coherent light than for incoherent light. The influence of the aperture size and position on the intensity and spot size at the focal plane is also analyzed. A way to obtain a balance between the flat phase distribution area, spot size and intensity for partially coherent light in the beamline is demonstrated.

scholarly journals Broadband focal plane wavefront control of amplitude and phase aberrations

2012 ◽  
Author(s):  
Tyler D. Groff ◽  
N. Jeremy Kasdin ◽  
Alexis Carlotti ◽  
A. J. Eldorado Riggs
Keyword(s):  
Focal Plane ◽  
Wavefront Control ◽  
Plane Wavefront ◽  
Phase Aberrations

Binary wavefront control in the focal plane for improved fiber coupling in air-to-air laser communication

2007 ◽  
Author(s):  
Peter Crabtree ◽  
Charles Woods ◽  
Jed Khoury ◽  
Matthew Goda ◽  
Michael Temple ◽  
...  
Keyword(s):  
Focal Plane ◽  
Laser Communication ◽  
Wavefront Control ◽  
Fiber Coupling
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