Image Processing Reference

In-Depth Information

Effects of Turbulence on a Wavefront

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Figure 2.2
Deflection of a non-normal angle of incidence ray of light as it travels

through the atmosphere toward the ground. The deflection of the ray is shown in nor-

malized units and does not include the effects of the earth's curvature.

however, these small variations create significant changes in the propagation path

of light, particularly when it is traveling over long distances.

Combining the information from Fig. 2.1 with Eq. 2.1 yields the static index of

refraction of the atmosphere. Figure 2.2 shows the effect that this modeled atmo-

sphere has on a ray of light. This “flat-earth model” shows a beam entering the up-

per atmosphere at an angle of 10 deg from vertical and the amount that the light is

bent from its linear path.

Of course, this model of the atmosphere is not complete, because it assumes

that air within the various layers does not mix. As such, this model is only good for

a brief instant of time.

2.3 Description of a Wavefront

Geometrical optics describes the path of a ray of light traveling between two points.

The path it travels through the various media is described by Snell's law of reflec-

tion and refraction (Hecht 2002), which was used to generate the results shown in

Fig. 2.2. The breakdown of the simple geometric optics model becomes apparent