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Brief Introduction of Diffraction Grating Element
As the name suggests, diffractive optics work by 'diffraction' of light rather than refraction or reflection as in conventional lenses and mirrors. It can be made to perform functions that are impossible using lenses and mirrors.
The diffractive lens consists of a flat window which has a 2-dimensional pattern etched onto one face. The surface is divided-up into a large number of square 'cells', each of which is etched to a pre-determined (calculated) depth.
When a concentrated bright spot of light passes through the etched pattern, each cell modifies the phase of the related portion of the beam wavefront.
The beam propagated onwards to the image plane, where the phase- modified wavefront results in the desired pattern (intensity distribution).
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