Diffuser optics


Diffuser optics are optical components that have widespread applications. They are mainly used to spread the energy from a laser beam onto a bigger area. At the same time, the effect of diffuser optics is a smoothing operation on the original beam. Thus, any imperfection on the beam is kind of washed out.

There are many types of diffuser optics and the decision to use one or another is highly dependent on the type of input beam that it is going to be used. One type of diffuser optics is the diffractive diffuser. In this type of diffuser optics, the change in radiance is obtained by means of a global interference effect, which is referred to as diffraction. To design a diffractive diffuser, first we start by clearly defining the shape of the desired output beam. Then by means of an iterating process that involves simulating the back and forth propagation of the optical beam from the diffuser to the output plane, the diffractive structure is obtained.

Due to the fact that diffraction is the main effect underpinning the performance of the diffractive diffuser, chromatic dispersion is very strong.  For this reason, diffractive diffusers are often used with monochromatic light, mainly multi-mode lasers .

In those cases where the above conditions are not fully met, other types of diffuser optics can be used. If the incoming beam is polychromatic, such as the light coming from an RGB laser module, for instance, then a more suitable type of diffuser optics is the refractive diffuser. The most common example of a refractive diffuser is the micro lens array.

Unlike the design of diffractive diffusers, which heavily relies on an iterative procedure, the design of a refractive diffuser is analytical. Parameters such as lenses’ radii and pitch can be chosen and their effects calculated.  When more degrees of freedom are needed, which is the case when more control needs to be exerted onto the final radiance pattern, a more sophisticated hybrid refractive-diffractive diffuser can be used which is referred to as the broadband diffuser. Broadband diffusers can be regarded as one of the most powerful types of diffuser optics. They consist of an array of micro lenses,  but with a low frequency modulation in a parameter such as lens height or lens curvature superimposed on the array. Thus, although the design becomes much more complicated, better control is gained over the final radiance distribution .

 


SND Team

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