Centre for Sensors, Instruments and Systems Development

Universitat Politècnica de Catalunya

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Optical metrology


Active optical metrology for applications in the nanometric scale.

Principal investigator

Santiago Royo Royo [+info]


Active and adaptive optics have already proven their capabilities in the field of optical metrology, as a complementary tool which enables the development of novel products and applications, because of a flexibility that passive optical systems deny. The project's aim is to expand the line of research that already exists in this area in the CD6 of UPC in order to develop novel metrological applications. In a former project within the 'Plan Nacional' the combination of optical metrology and adaptive optics techniques was successfully applied to the development of novel
applications of the Shack-Hartmann sensor and of confocal profilometry. The present project will deal with using adaptive optics techniques to enhance the performance of interferometric profilometry techniques.

With this purpose, a thorough analysis of the control techniques of the active elements will be carried out, in order to optimize its behavior in nanometric scale applications. A detailed model of the measuring system will be built, including B-spline polynomials models of the wavefront shape and of the active element. The classical Zernike fitting techniques will also be implemented for comparison purposes. From these system models, we will analyze the implementation of local control techniques in order to enhance the precision in wavefront reconstruction, and the stability and speed of convergence of the control loop. Performance will be compared with that of classical modal control techniques. The active elements modelled will include a PAL-LCOS unit and a micromachined deformable mirror with continuous surface. This set of analysis should provide information on the decision of the final experimental setup and optimal control loop for nano-scale applications. This part of the project is carried out in collaboration with the Applied Optics Group in the National University of Ireland at Galway, lead by Prof.Chris Dainty.

This process of modelling and testing the behavior and control of the active element will be applied to the development of a novel application on interferometric profilometry of devices behind layered media (devices which are sealed or placed behind glass covers), and equivalently
to surfaces embedded within refractive media. This is a non-solved metrological application of the utmost importance for the microelectronics industry, in quality control of embedded systems or, for instance, in quality control of multilevel optical data storage disks. With this purpose we will design, build and set at work an interferometric Linnik-type microscope objective with magnifications around 50x and 100x, which will include an active optical element for compensation of the aberrations induced by the intervening refractive media.



CD6 Centre for Sensors, Instruments and Systems Development
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