Coherence and fringe visibility Coherence and fringe visibility Coherence and fringe visibility

Coherence Coherence Coherence

Coherence is a measure of the correlation between the phases measured at different (temporal and spatial) points on a wave

Coherence theory is a study of the correlation properties of random light which is also known as the statistical optics.

Coherence and fringe visibility Coherence and fringe visibility Coherence and fringe visibility

Coherence and Fringe Localization, T. D. Milster and N. A. Beaudry,

Statistical Properties of Random Light

Statistical Properties of Random Light

Statistical Properties of Random Light

Coherence

Coherence

Coherence

Degree of Coherence

Degree of Coherence

Degree of Coherence

Temporal Coherence Temporal Coherence Temporal Coherence

See the next example

1 2

r = r ur ur

The temporal autocorrelation means the time average at the same position

Degree of Temporal Coherence

Degree of Temporal Coherence

Degree of Temporal Coherence

Coherence Time and Length Coherence Time and Length Coherence Time and Length

c c

l = c τ

Coherence time

Coherence length

1 τ

= ν

Coherence time Δ

Temporal Coherence Temporal Coherence Temporal Coherence

c ave

1/

τ = τ = Δ ν

/

/

c c

l = c τ = c Δ = ν λ Δ λ

Spatial Coherence: point source

Spatial Coherence: point source

Spatial Coherence: point source

Spatial Coherence: two point source Spatial Coherence: two point source Spatial Coherence: two point source

l

~ λ/θ

Basic properties of Spatial Coherence Basic properties of Spatial Coherence

Fringe visibility

van Cittert-Zernike Theorem :

Degree of Spatial Coherence is

Fourier Transform (or, Fraunhofer Diffraction Pattern) of the source irradiance distribution

of V

Making Light Coherent Making Light Incoherent

Spatial Filter for Spatial Coherence

Wavelenth Filter

for Temporal Coherence

Ground Glass to

Destroy Spatial Coherence

Move it to

Destroy Temporal Coherence

Control of Coherence

Control of Coherence

Control of Coherence