Semi-derivative real filter for quality measurement of microlenses array

We proposed a new kind of setup for the automatic control of the quality of micro lens array, which is based on semiderivative real filter. With the use of the 4f correlator setup with a semiderivative filter placed in the Fourier plane and connected with the camera, it is possible to examine phase objects. Such a setup is shift invariant, so it enables us to simultaneously examine a set of identical elements, such as a micro lens array. Additionally, the same setup allows for a simultaneous measurement of both thin and thick phase objects. It is also possible to measure a wide range of phase gradients. The article presents the results of simulations where the semiderivative filter was used to measure phase objects such as cylindrical and spherical lenses. A special emphasis was placed upon checking how the proposed setup works for a number of similar phase optical elements, such as microlens arrays. The article also presents an analysis of how various technological limitations can influence the quality and the precision of the results obtained. Further on, it shows the initial results of the use of 3D lithography to produce semiderivative filters.