Diffraction-limited Imaging With Large and Moderate Telescopes

Diffraction-limited Imaging With Large and Moderate Telescopes

Swapan K. Saha

Language: English

Pages: 634


Format: PDF / Kindle (mobi) / ePub

This book deals with the fundamentals of wave optics, polarization, interference, diffraction, imaging, and the origin, properties, and optical effects of turbulence in the Earth's atmosphere. Techniques developed during the last few decades to overcome atmospheric image degradation (including passive methods, speckle interferometry in particular, and active methods such as adaptive optics), are highlighted. Also discussed are high resolution sensors, image processing, and the astronomical results obtained with these techniques.

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Length the imaging aspects of the same. Turbulence and the concomitant development of thermal convection in the atmosphere distort the phase and amplitude of the incoming wavefront of the starlight; longer the path, more the degradation that the image suffers. Environment parameters, such as fluctuations in the refractive index of the atmosphere along the light beam, which, in turn, are due to density variations associated with thermal gradients, variation in the partial pressure of water vapour,.

V = V (r · s, t) represents a plane wave in the direction given by the unit vector, s, since at each instant of time, V is constant over each of the planes, r · s = constant, which are perpendicular to s. V (r, t) = V (r · s − v t), (2.10) where V is an arbitrary function of its arguments, which can be differentiated twice, V (r · s − v t) describes a disturbance propagating along the s direction at a constant velocity v , with shape unchanged. The velocity is defined to be the distance.

Light. April 20, 2007 16:31 WSPC/Book Trim Size for 9in x 6in Wave optics and polarization Thus the Mueller matrix of a rotator is expressed as,   1 0 0 0  0 cos 2φ sin 2φ 0   R(φ) =   0 − sin 2φ cos 2φ 0  . 0 0 0 1 lec 73 (2.181) From the equations (2.149) and (2.166), the form of Mueller matrix of an ideal linear polarizer oriented at angle φ is expressed as (Collett, 1993),   1 cos 2φ sin 2φ 0 1  cos 2φ cos2 2φ 21 sin 4φ 0   P (φ) =  (2.182) 2  sin 2φ 21 sin 4φ sin2 2φ.

Perpendicular. Light striking the surface of incidence at right angles is refracted in the first prism into an ordinary (o) and an extra-ordinary (e) ray. The angular splitting α is given by the relation, α = 2(ne − no ) tan θ, where θ April 20, 2007 80 16:31 WSPC/Book Trim Size for 9in x 6in Diffraction-limited imaging with large and moderate telescopes lens. Light passing through such a prism gets split into two orthogonal components parallel (ordinary ray) and perpendicular.

Term |K1 |2 I(r1 , t) is the intensity observed at P(r) when the pinhole at P1 (r1 ) alone is opened (K2 = 0) and the term |K2 |2 I(r2 , t) has similar interpretation. The intensities at I1 (r, t) and I2 (r, t) respectively are: 2 2 2 2 I1 (r, t) = |K1 | I(r1 , t) = |K1 | Γ(r1 , r1 , 0), I2 (r, t) = |K2 | I(r2 , t) = |K2 | Γ(r2 , r2 , 0). (3.56) The normalized complex degree of (mutual) coherence, γ(r1 , r2 , τ ), is defined as, Γ(r1 , r2 , τ ) γ(r1 , r2 , τ ) = Γ(r1 , r1 , 0) Γ(r2 , r2 ,.

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