Design, analysis, and testing of a microdot apodizer for the apodized pupil Lyot coronagraph

Imaging planets requires instruments capable of dealing with extreme contrast ratios and that have a high resolution. Coronagraphs that can reach a contrast ratio in a neighborhood of 10 9 will be capable of observing Jupiter-like planets, while those with a contrast greater than a benchmark number of 10 10 to within a few λ/D of an on-axis star will render possible imaging of Earth-like planets. Plans for achieving this feat have been developed for use on telescopes with unobscured, circularly symmetric apertures. However; given that the next generation of large telescopes are on-axis designs with support structures in the telescope aperture and a central obstruction due to the secondary mirror, it has proven necessary to develop coronagraphic techniques that compensate for obstructions. Pueyo & Norman (2012) present a possible solution to the problem of the support structures using ACAD. In this paper, we present a coronagraphic design that uses a vector vortex and pupil apodization to compensate for the secondary mirror that could possibly be used in conjunction with a wavefront control system and/or ACAD. This coronagraph is capable of achieving a contrast ratio of at least 10 10 in a working angle of (1.5 − 30) λ/D in conjunction with an on-axis telescope. We can construct our pupil using a classical transmissive apodizer or pupil remapping. We find that the mirror shapes required are relatively simple (requiring ≤ 40 degrees of freedom to describe) and we expect they will be feasible to manufacture, and potentially even to implement with deformable mirrors. By combining existing high-contrast imaging techniques, we demonstrate that a relatively simple design may be used to image exo-Earths.

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“…[15][16][17] Unfortunately, the parameter space of performance vs. manufacturability is big and a lot reamins to be explored.…”

Section: 4mentioning

confidence: 99%

Optimal apodizations for on-axis vector vortex coronagraphs

Fogarty

Pueyo

Mawet³

2014

SPIE Proceedings

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“…Examples include antenna array synthesis (see, e.g., [12,13,16]), FIR filter design (see, e.g., [4,23,24]), and coronagraph design (see, e.g., [8,19,11,10,17,20,7,9,14]). If the design function f can be constrained to vanish outside a compact interval C = (−a, a) of the real line centered at the origin, then we can write the Fourier transform as f (ξ) = c(x)f (x)dx subject to −ε ≤ f (ξ) ≤ ε,…”

Section: Fourier Transforms In Engineeringmentioning

confidence: 99%

Fast Fourier optimization

Vanderbei

2012

Math. Prog. Comp.

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Many interesting and fundamentally practical optimization problems, ranging from optics, to signal processing, to radar and acoustics, involve constraints on the Fourier transform of a function. It is well-known that the fast Fourier transform (fft) is a recursive algorithm that can dramatically improve the efficiency for computing the discrete Fourier transform. However, because it is recursive, it is difficult to embed into a linear optimization problem. In this paper, we explain the main idea behind the fast Fourier transform and show how to adapt it in such a manner as to make it encodable as constraints in an optimization problem. We demonstrate a real-world problem from the field of high-contrast imaging. On this problem, dramatic improvements are translated to an ability to solve problems with a much finer grid of discretized points. As we shall show, in general, the "fast Fourier" version of the optimization constraints produces a larger but sparser constraint matrix and therefore one can think of the fast Fourier transform as a method of sparsifying the constraints in an optimization problem, which is usually a good thing.

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“…In such conditions and assuming a VLT-like entrance pupil, the APLC demonstrates the ability to reduce the on-axis starlight by a factor of 700 on the peak, and to reach a contrast of 5 10 −5 and 10 −6 at 3 and 20 /D (0.12 and 0.8 for a 8-m telescope) respectively (see Figure 5). More détails can be found in [2].…”

Section: Performance Obtained With the Aplc And Blcs In The Near-irmentioning

confidence: 99%

“…Diffraction stray-light analysis and guidelines for the design of pupilapodized coronagraphs (e.g. apodized pupil Lyot coronagraph, dual zone coronagraph, conventional pupil-apodization concepts) are available in [1,2], while the specific case of focal-plane mask with a …”

mentioning

confidence: 99%

Halftoning for high-contrast imaging

Martínez

Dorrer

Carpentier

et al. 2011

EPJ Web of Conferences

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Abstract. High-contrast instruments, such as SPHERE (upcoming planet finder instrument for the ESO-VLT), or EPICS (planet hunter project for the future E-ELT), will require customized components with spatially varying transmission (e.g. coronagraphs, optical components that reduce the contrast between a companion and its parent star). The goal of these sub-systems is to control the spatial transmission, either in a pupil plane (pupil apodization), or in a focal plane of the instrument (occulting mask, i.e. lowfrequency filter). Reliably producing components with spatially varying transmission is not trivial, and different techniques have been already investigated for application to astronomy (e.g. metal deposition with spatially-varying thickness, or high-energy beam sensitive glass using e-beam lithography). We present some results related to the recent development of components with spatially varying transmission using a relatively simple technique analogous to the digital halftoning process used for printing applications. HALFTONE DOT PROCESS PRINCIPLEHalftoning has been used for hundreds of years in the printing industry as a solution for generating continuous-tone images with only black or white dots. The so-called halftone image, seen from a distance, should resemble the original continuous-tone image as much as possible, based on human vision perception. Following this idea, the continuous transmission of an optical filter can be generated with a specific implementation of opaque and transparent pixels as presented in Figure 1.The resulting microdot filter is an array of dots (i.e. pixels) that are either opaque (0% transmission) or transparent (100% transmission). It is fabricated by lithography of a light-blocking metal layer deposited on a transparent glass substrate. The technique has several advantages: relative ease of manufacturing, achromaticity, reproducibility, and ability to generate continuous and rapidly varying transmission functions, without introducing wavefront errors.Several application-dependent parameters must be carefully defined. Microdot filters are arrays of pixels with binary transmission, and light propagating through them has a continuously varying intensity after free-space propagation, or after filtering in the far field. Therefore, these filters have a power spectrum different from the power spectrum of an ideal continuous filter. The way dots are distributed, the size of the dots, and the density of the dots in the pattern directly impact the power spectrum of the filter, and these parameters must be carefully studied accordingly with the application. Several studies have been carried out to quantify diffraction effects induced by the pixellation and binary transmission of the pixels. Diffraction stray-light analysis and guidelines for the design of pupilapodized coronagraphs (e.g. apodized pupil Lyot coronagraph, dual zone coronagraph, conventional pupil-apodization concepts) are available in [1,2], while the specific case of focal-plane mask with a

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Design, analysis, and testing of a microdot apodizer for the apodized pupil Lyot coronagraph

Cited by 34 publications

References 13 publications

Optimal apodizations for on-axis vector vortex coronagraphs

Optimal apodizations for on-axis vector vortex coronagraphs

Fast Fourier optimization

Halftoning for high-contrast imaging

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