Laser manufacturing of microstructures using a single focus is a well known technology. Multi-spot optics are applied
for process parallelizing if the demand on throughput in mass production rises or large areas of material have to be
processed. Diffractive optical elements (DOEs) are used for parallel laser processing of a repetitive structure. These
elements split the beam into a periodic spot pattern, where each spot shows the same shape and energy. This allows
simultaneous manufacturing of several equal shaped structures at the same time. For patterning a surface this is state of
the art and the appropriate technique to reduce processing time while maintaining a high lateral resolution as well as a
good relative positioning of the structure due to the DOE.
We investigate the usage of microlens arrays as multifunctional elements for forming an arbitrary shaped laser beam into
a spot-, a ring-spot- or a line-array pattern. It can be shown that the intensity distribution of each spot is equal to the
intensity distribution of all other spots in the whole pattern. The shape of the spots is defined by the angular distribution
of the incident beam. We demonstrate that besides other optical properties the output beam profile strongly depends on
the Fresnel-Number and is influenced by diffraction and interference effects. We present important design rules which
consider geometrical and physical optics. The properties of the spot arrays, like spot diameter, Rayleigh length and beam
divergence in dependency of beam and system properties are investigated. Finally we will show some laser micro
structuring and micro drilling results in different materials.
A quite simple numerical model for the wave-optical simulation of the interference in a grating lateral shearing
interferometer with a periodic light source and a large lateral shear is presented. Aberrations of the collimating lens will
generate a spatially varying modulation in the interference pattern. The model assumes that the light source itself is
completely spatially incoherent so that only the light from each point of the light source has to be propagated wave-optically
through the optical system. Then, the intensity distributions of all light source points in the detector plane can
just be added. The simulations are compared to theoretical calculations of partial coherence theory and also to
Mostly, the typical light distribution of a light source, as a LED or an excimer laser, is not suitable for the application. The excimer laser beam for example shows a distinct elliptical Gaussian profile. As another example the layout of the light emitting chip and the reflector of a LED form an extremely inhomogeneous luminescent area. To achieve a better adapted beam profile a homogenizing setup with beam shaping qualities can be used. In this talk two setups for homogenization with the help of refractive micro lens arrays are shown and compared. The main attention is turned on the influence of the numerical aperture of the micro lenses, the limitations due to the spatial coherence degree and the difficulties of the alignment of the systems. In addition, a diffractive solution of homogenization for spatial partially coherence is presented.