Know About Broadband Hybrid Diffusers

Broadband hybrid diffusers are optical elements that can perform beam shaping transformations in optical beams without suffering from excessive chromatic dispersion. This stems from the fact that a broadband hybrid diffuser is a broadband diffuser with some diffractive structure embossed on top to provide fine control over the high spatial frequencies.

A normal broadband diffuser is very similar to a microlens array. The main difference, and one which provides a considerable extra capability, is the ability to vary the radius of curvature among the lenslets on the array. This crucial feature permits the broadband diffuser to alter the shape of an incoming beam according to the requirements of whatever application is at hand. And because works under the same principle as a microlens array, the output beam does not vary its dimensions or characteristics with wavelength. Thus, it is said to be an achromatic component.  

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There are some applications in which greater control is needed over the output beam in terms of beam shaping. Diffractive beam shapers are known for the greater capability they can provide in this regard. A broadband hybrid diffuser is then a merge between a diffractive beam shaper and a broadband diffuser. The overall structure of the beam is obtained first from the action of the broadband diffuser structure onto the input beam. Then, the fine beam shaping is accomplished by the effect of the diffractive structure that is written on top.

A broadband hybrid diffuse can have many applications in which the output beam has to work on a wide spectral range. In microscopy, for instance, in which there is white illumination of the sample, a broadband hybrid diffuser will provide much better control than a normal broadband diffuser and with much less chromatic dispersion. Another useful application for hybrid broadband diffusers is in modern digital cinemas. In this application, an imager, such as a digital light processor or liquid crystal device, is illuminated with three different high-power LEDs (red, green, and blue). The plane at which the imager device is located has to be uniformly illuminated as any variation will be noticeable at the final projection screen. With a broadband hybrid diffuser, this uniformity requirement can be met with a single element for all three light sources. This entails a considerable reduction of volume and mass for the device as a whole.

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