Apodization

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Apodization literally means "removing the foot". To apodize is the technical term for changing the shape of a mathematical function, an electrical signal, an optical transmission or a mechanical structure to remove or smooth a discontinuity at the edges. An example of apodization is the use of the Hann window in the Fast Fourier transform analyzer to smooth the discontinuities at the beginning and end of the sampled time record.

When stopping your car, if you "remove your foot" to reduce the brake pedal force just as you come to a stop, you will not feel a "jerk" and the car will come to a smooth stop. This is a form of apodization.

In optical sciences, apodization refers to purposely changing the transmission properties of an optical system. It usually refers to non-uniform illumation or transmission, like laser beam profile. This may be a complicated function to tailor the system to certain properties. Apodization is used in telescope optics in order to improve the dynamical range of the image. For example, stars with low intensity in the close vicinity of very bright stars can become visible using this technique. Generally, apodization reduces the resolution of an optical image. The diaphragm of a photo camera is not stricly an example of apodization, since the stop doesn't produce a smooth transition to zero intensity. However, in optical design jargon, any function that describes the intensity distribution across the pupil of a lens is called an Apodization function.

[edit] See also

• Apodization function

[edit] References

Apodization in Optics [1]