Measurement of spatial coherence through diffraction from a transparent mask with a phase discontinuity

Cho, Seong-Keun; Alonso, Miguel A.; Brown, Thomas G.

doi:10.1364/ol.37.002724

Cited by 30 publications

(8 citation statements)

References 10 publications

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“…A generalized source as in (11) satisfying Eqs. (12,13) is situated at the plane z = 0. At the detection plane z = d, the coherence G d (y 1 , y 2 ) is well approximated by…”

Section: Propagation Of Fields Produced By a Generalized Sourcementioning

confidence: 99%

“…The coherence function G relating two points x 1 , x 2 in a quasi-monochromatic scalar field is given by G(x 1 , x 2 ) = U (x 1 )U * (x 2 ) , where • represents an ensemble average, and U (x) is one realization from the ensemble [1]. This coherence function can be obtained by various measurement strategies, e.g., through the use of double slits [2][3][4][5][6], non-redundant arrays of apertures [7,8], lateral-shearing Sagnac and reversed-wavefront Young interferometers [9][10][11], microlens arrays [12], and phase-space methods [13][14][15]. The intensity of the field I is subsumed in the coherence function and lies along its diagonal I(x) = G(x, x).…”

Section: Introductionmentioning

confidence: 99%

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Spatial coherence of fields from generalized sources in the Fresnel regime

et al. 2017

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Analytic expressions of the spatial coherence of partially coherent fields propagating in the Fresnel regime in all but the simplest of scenarios are largely lacking, and calculation of the Fresnel transform typically entails tedious numerical integration. Here, we provide a closed-form approximation formula for the case of a generalized source obtained by modulating the field produced by a Gauss-Shell source model with a piecewise constant transmission function, which may be used to model the field's interaction with objects and apertures. The formula characterizes the coherence function in terms of the coherence of the Gauss-Schell beam propagated in free space and a multiplicative term capturing the interaction with the transmission function. This approximation holds in the regime where the intensity width of the beam is much larger than the coherence width under mild assumptions on the modulating transmission function. The formula derived for generalized sources lays the foundation for the study of the inverse problem of scene reconstruction from coherence measurements.

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“…A generalized source as in (11) satisfying Eqs. (12,13) is situated at the plane z = 0. At the detection plane z = d, the coherence G d (y 1 , y 2 ) is well approximated by…”

Section: Propagation Of Fields Produced By a Generalized Sourcementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Spatial coherence of fields from generalized sources in the Fresnel regime

et al. 2017

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“…Furthermore, it was found that one can reduce turbulence-induced scintillation (i.e., intensity fluctuation) through manipulating the correlation functions of partially coherent beams [29,30], which makes partially coherent beams with prescribed correlation functions attractive for free-space optical communications. Various methods have been developed to generate partially coherent beams with prescribed correlation functions and measure their correlation functions [17,28,[30][31][32][33][34][35][36][37].…”

Section: Introductionmentioning

confidence: 99%

Overcoming the classical Rayleigh diffraction limit by controlling two-point correlations of partially coherent light sources

Liang¹,

Wu²,

Wang³

et al. 2017

Opt. Express

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In classical optical imaging, the Rayleigh diffraction limit d R is defined as the minimum resolvable separation between two points under incoherent light illumination. In this paper, we analyze the minimum resolvable separation between two points under partially coherent beam illumination. We find that the image resolution of two points can overcome the classic Rayleigh diffraction limit through manipulating the correlation function of a partially coherent source, and the image resolution, which independent of the specified positions of two points in the object plane, can in principle reach the value of 0.17d R. Furthermore, we carry out an experimental demonstration of sub-Rayleigh imaging of a 1951 USAF resolution target via engineering the correlation function of the illuminating beam. Our experimental results are in agreement with our theoretical predictions.

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“…Other approaches make use of non-redundant arrays of apertures to multiplex interferograms [24,25], a pair of non-parallel slits for multiplexing one-dimensional interferograms [26,27], or exploit wavefront sensors [28]. Another strategy for acquiring the spatial coherence function relies on phase-space methods that exploit the connection between spatial coherence and the Wigner distribution associated with the field [29][30][31].…”

Section: Introductionmentioning

confidence: 99%

Coherence measurements of scattered incoherent light for lensless identification of an object’s location and size

et al. 2017

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In the absence of a lens to form an image, incoherent or partially coherent light scattering off an obstructive or reflective object forms a broad intensity distribution in the far field with only feeble spatial features. We show here that measuring the complex spatial coherence function can help in the identification of the size and location of a one-dimensional object placed in the path of a partially coherent light source. The complex coherence function is measured in the far field through wavefront sampling, which is performed via dynamically reconfigurable slits implemented on a digital micromirror device (DMD). The impact of an object - parameterized by size and location - that either intercepts or reflects incoherent light is studied. The experimental results show that measuring the spatial coherence function as a function of the separation between two slits located symmetrically around the optical axis can identify the object transverse location and angle subtended from the detection plane (the ratio of the object width to the axial distance from the detector). The measurements are in good agreement with numerical simulations of a forward model based on Fresnel propagators. The rapid refresh rate of DMDs may enable real-time operation of such a lensless coherency imaging scheme.

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Measurement of spatial coherence through diffraction from a transparent mask with a phase discontinuity

Cited by 30 publications

References 10 publications

Spatial coherence of fields from generalized sources in the Fresnel regime

Spatial coherence of fields from generalized sources in the Fresnel regime

Overcoming the classical Rayleigh diffraction limit by controlling two-point correlations of partially coherent light sources

Coherence measurements of scattered incoherent light for lensless identification of an object’s location and size

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