CDA is a recognized specialist for the manufacture of complex, microfunctional and cost-effective optical microstructures in plastic, both for optical and optofluidic applications. CDA has now released collimator surfaces for diffraction-limited and general illumination applications.
The most recent addition to CDA's extended plastic optical element portfolio is a set of collimator surfaces. Different collimator surfaces (arrays) can be generated for a spectral range covering the near UV/violet to NIR, and comprising either a refractive (continuous or segmented) and/or a diffractive surface.
Continuous refractive elements are diffraction-limited and are intrinsically broadband (and dispersive, depending on the plastic used). A maximum sag limits NA, depending on the diameter of the lens, with values as high as 0.75 for small microlenses. Alternatively, segmented (Fresnel-like) lenses can be generated with a higher NA, although this type of optic is not diffraction-limited.
Instead, a diffractive optical element (DOE) can be generated, also providing diffraction-limited performance at the design wavelength, albeit with less efficiency. This type of structure is more wavelength-sensitive, although a relatively good broadband behavior can be designed into the diffractive at the expense of diffraction-limited performance. For minimally apodizing structures, the NA can be as high as 0.5.
Either type of optic can be tailored to provide specific collimation properties dependent on the application, including improving the light capture from LEDs and bundling light into camera pixels. For more exacting applications, either continuous refractive or diffractive surfaces are required -- for optic diameters above 2mm, the space savings provided by a diffractive surface can be dramatic. Arbitrary aspheres are also relatively easy to realize using a diffractive surface, and by combining refractive and diffractive optical surfaces, small bandwidth achromats and athermalized lenses can be realized.
Lastly, in all cases, CDA's replication technology ensures exceptionally high repeatability for arrays of elements forming an extended surface.
These new structures can additionally be incorporated in a further recent development at CDA, i.e. in the manufacture of double-sided structures and stacks in plastic. Such structures can comprise any combination of functionality from CDA's two principal micro-technology platforms, namely refractive micro-optical elements and arrays, diffractive structures (DOEs) and optical diffusors for optics, and microfluidic structures and surface structuring for analytical lab-on-a-chip applications.
Photo and caption: A regular refractive lens array with high reproducibility and high NA.
CDA GmbH - Dr. Nicolaus Hettler
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