Spatial coherence mapping of structured sources: a flexible instrument for solar studies

Tiago E. C. Magalhães; José M. Rebordão

doi:10.1364/AO.58.008840

Applied Optics
Vol. 58,
Issue 32,
pp. 8840-8851
(2019)
•https://doi.org/10.1364/AO.58.008840

Spatial coherence mapping of structured sources: a flexible instrument for solar studies

Tiago E. C. Magalhães and José M. Rebordão

Not Accessible

Your library or personal account may give you access

Get PDF
Email
Share
Get Citation
Copy Citation Text
Tiago E. C. Magalhães and José M. Rebordão, "Spatial coherence mapping of structured sources: a flexible instrument for solar studies," Appl. Opt. 58, 8840-8851 (2019)

Export Citation
- BibTex
- Endnote (RIS)
- HTML
- Plain Text
Citation alert
Save article

Check for updates

Abstract

We conceptually describe and design, to first order, an instrument to locally map the spatial coherence of extended and structured sources, such as fiber bundles or the Sun, considered as a mosaic of individual solar cells, which is our main motivation. Our solar coherence instrument (SCI) is an instrument for an afocal solar space telescope; the light from its exit pupil dynamically selects one individual solar cell at a time and performs a series of Young-like experiments with different baselines in order to measure the spectral degree of coherence and therefore the effective correlation length that can be assigned for that solar cell. SCI needs flexibility in terms of selective imaging and Young experiments, which is provided by two digital micromirror devices (DMDs), a technology currently under space qualification. SCI is a compact instrument based on retroreflections, and it generates all data required to image the source, to select the cells, and to implement sequentially a series of Young apertures on a re-imaged pupil. It was designed using the (already launched) Hinode solar optical telescope as a baseline, and the first estimation of the SNR, using commercial DMDs and array sensors, while measuring the modulation of Young interference fringes validates our first-order design.

Full Article | PDF Article

More Like This

Ground-testing method of a zero gravity wavefront for space telescopes

Yongwei Guo, Zhichao Dong, Shen Wang, and Y. Sophia Dai
Appl. Opt. 58(12) 3042-3052 (2019)

Characterization of cyclical spatial heterodyne spectrometers for astrophysical and planetary studies

Sona Hosseini
Appl. Opt. 58(9) 2311-2319 (2019)

Eclipse Instrumentation for the Solar Corona

D. H. Menzel and J. M. Pasachoff
Appl. Opt. 9(12) 2626-2630 (1970)

Previous Article Next Article

Cited By

You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access Optica Member Subscription

Figures (9)

You do not have subscription access to this journal. Figure files are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access Optica Member Subscription

Tables (5)

You do not have subscription access to this journal. Article tables are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access Optica Member Subscription

Equations (65)

You do not have subscription access to this journal. Equations are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access Optica Member Subscription

#	Parameter	Requirement
1	Signal-to-noise ratio	$10^{2}$
2	Central wavelength and bandwidth	$λ_{0} = 430 n m$ $F W H M = 10 n m$
3	Min. number of mirrors per granule ( $n_{g}$ ) in DMD1	$10^{3}$
4	Min. effective correlation length $σ_{μ, e x}$ at the exit pupil of the OTA	1 mm
5	Maximum exposure time	3 s

	Symbol	Description
Lenses	$f_{j}$	Focal length of lens $L_{j} (j = 1, 4)$
Lenses	$β_{S}$	Angular magnification between exit pupils of OTA and SCI
Selective imaging	$A_{F 1}$	Image area at plane $B$
	$N_{g}$	Total no. of granules in L1 image
	$N_{g, e f f}$	Eff. no. of granules within DMD1
	$n_{g}$	No. of DMD1 mirrors per granule
Young apertures	$a$	Apertures size in DMD2
	$b$	Distance between apertures
	$n_{b}$	No. of mirrors to implement $b$
DMD	$N_{x, i}$	No. of mirrors in row (DMD $i$ )
	$N_{y, i}$	No. of mirrors in column (DMD $i$ )
	$Δ_{i}$	DMD’s micromirror size of DMD $i$
	$w_{i}$	Width of DMD $i$
	$h_{i}$	Height of DMD $i$
CCD2	$h_{c}$	Height of CCD2

${F O V}_{o}$	$400^{''}$	Field of view of the OTA
$r_{o}$	250 mm	Entrance pupil outer radius
$r_{i}$	86 mm	Entrance pupil inner radius
$r_{o}^{'}$	15 mm	Exit pupil outer radius
$β_{o}$	16.67	Angular magnification between pupils

	Symbol	Value	Description
Input	$λ_{0}$	430 nm	Central wavelength
	$Δ$	5.4 µm	Micromirror size
	${F O V}_{g}$		FOV of one granule
	$N_{x}$	1528	No. of active mirrors along $x$
	$N_{y}$	2716	No. of active mirrors along $y$
	$N_{c, min}$	3	No. of cycles
	$n_{g}$	1000	No. of mirrors per granule
	$h_{c}$	4.1 cm	Height of CCD2
	$h_{2}$	2.048 cm	Height of DMD2
Output	$f_{1}$	1.596 m	Focal length of lens L1
	$f_{2}$	0.6557 m	Focal length of lens L2
	$f_{3}$	$0.2425 m$	Focal length of lens L3

$λ_{0}$	430 nm	Central wavelength
$Δ λ_{0}$	5 nm	Bandwidth
$r_{s u n}$	$6.96 \times 10^{8} m$	Radius of the Sun
$d_{H}$	$1.496 \times 10^{11} m$	Distance Sun-Hinode
$T_{S}$	5780 K	Temperature of the Sun
$T_{H}$	0.8	Transmission of the OTA
$T_{B S}$	0.95	Transmission of BS
$T_{P}$	0.95	Transmission of P
$T_{1}$	0.9	Transmission of PBS1 and PBS2
$T_{2}$	0.9	Transmission of QWP1 and QWP2
$T_{L i}$	0.9	Transmission of lens $L i (i = 1, 2, 3)$
$R_{D}$	0.95	Reflectance of DMD1 mirrors
$η_{e}$	0.85	Quantum efficiency
$Δ t$	1 s	Integration time
$P$	$2.373 \times 10^{24} W$	Flux from the Sun for central wavelength $λ_{0}$ and bandwidth $Δ λ$
$Φ_{B}$	$100 e^{-} / s$	Background photon flux
$n_{D}$	$8 e^{-} / s$	Dark current
$s_{N}$	$10 e^{-}$	Read noise
$Δ_{c}$	10 µm	Pixel size of CCD2

Tiago E. C. Magalhães	https://orcid.org/0000-0001-8056-003X
José M. Rebordão	https://orcid.org/0000-0002-7418-0345

Abstract

Cited By

Figures (9)

Tables (5)

Equations (65)

Applied Optics