The main objectives of the activity are the following:1) to define design tools for optical instruments using free-form optical elements. These tools shall be directly implementable in the available optical design software (e.g. macros or dynamic link libraries in Zemax and/or CodeV).2) to identify adequate alignment procedures for optical systems with free-form surfaces.

Current optical design of optical instruments is based on conic or aspheric surfaces of revolution (both on-axis and off-axis). Free-form surfaces (surfaces with no axis of symmetry) can now be manufactured thanks to recent advances in Single Point Diamond Turning. Despite this technological breakthrough the theory is unfortunately not at the same level. Free-form surfaces cannot be represented properly in an optical design software and cannot be used for efficient optimisation algorithms. Therefore the use of free-forms in the optical design of instruments for space missions is very limited despite the advantages this could bring in terms of compactness and improvement of image quality. For rotationally symmetric optical surfaces the metrology and alignment is well developed and state-of-the-art in the production of precision optics. However when free-form optics will become more common, the challenging requirements regarding the precise shape and alignment of the optical elements require the elaboration of adequate advanced concepts for alignment and metrology to reduce the efforts in the time-consuming alignment of free-form optical elements.The aim of the study is twofold: - First aim is to investigate design tools for the definition and optimisation of optical instruments using free-form surfaces. The main objective is to develop tools that can be directly employed in the commercially available optical design software (e.g. macros or dynamic link libraries in Zemax or CodeV). - Second aim is to identify alignment concepts for free-form surfaces for optical instruments in space applications (e.g. high-resolution telescopes or new types of spectrometers). For example, one of the possible strategies could be precise diamond turning of the optical surface along with the alignment features in the same fabrication run, resulting thus in an efficient and easy "snap-together" alignment. In addition to alignment, figure metrology of these surfaces also presents some unique challenges. Although CGH (computer generated hologram) masks and 3D profilometer can be used for metrology, the process involved is very complex and time-consuming. One of the aims of this activity will be to simplify this task using fiducials on the metrology tools and/or the optical element itself.