3_-_Optics - 3 - Optics The Plan Three ways to follow the...

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3 - Optics I. Newton Newton and his reflecting telescope. ~1672 2 The Plan • Three ways to follow the track of light: – Ray tracing (optical systems) – Diffusion (in stars) – Gravitational lensing (distant galaxies) • Snell’s Law • Paraxial rays • Ray tracing • Aberrations – Spherical Aberration –Coma 3 Image quality • The atmosphere distorts the incoming wave front even further degrading the image. • Because light is a wave it is not possible to form a perfect image. (diffraction) • Bad optics further degrade the images. • How do you trace a ray through a lens and what are the aberrations? • Given a solution how is it improved. (Sorry, not this time!) 4 Diffraction θ 1.2 λ f where f = focal length/diameter and [ θ ] = [ λ ]
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5 ~1.2 λ /D The Diffraction part of the Point Spread Function 6 Tradeoffs • The spot size (the diameter of a point source) is a combination of: – Diffraction – Geometric aberrations – Atmospheric seeing • In general the objective is to have the above contributions to the total image size to be about the same size. • Pick your battles carefully! 7 Apodization (taking the feet off) 8 It Really Works…
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9 Snell’s Law n 1 sin( ϕ 1 ) = n 2 sin( ϕ 2 ) The limit of small ϕ, n 1 ϕ 1 = n 2 ϕ 2 , is called the Paraxial Limit.
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This note was uploaded on 04/05/2009 for the course ASTRO 3332 taught by Professor Houck,j during the Spring '09 term at Cornell University (Engineering School).

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3_-_Optics - 3 - Optics The Plan Three ways to follow the...

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