WaveScan - A new method to measure extremely complex wavefronts
MEMS wavefront sensor for characterization of optical components - WaveScan
Brief project description:
The characterization of lenses used in ophthalmology constitutes increasingly higher demands on metrology. The present project aims for the development of a wavefront sensor based upon state-of-the-art MEMS technolgy that features high dynamic range that meets the increased requirements.
Wavefront sensors are used for detailed characterization of optical components. They can measure optics even if they are part of a lens system and cannot form real optical images themselves. Such sensors are commonly available as Shack-Hartmann sensors. A Shack-Hartmann sensor consists of a plane array of microlenses, which focus the incoming light onto a CCD- or CMOS-chip where they form a characteristic spot pattern. By image post-processing, the wavefront can be reconstructed from the spot pattern and can be compared to the theoretical design of the optics.
In principle, Shack-Hartmann sensors are subject to restrictions regarding spatial resolution and dynamic range, so that steep gradients and strong curvatures of a wavefront can only be measured up to a certain limit. Although the dynamic range of present Shack-Hartmann sensors is capable of measuring wavefronts with several hundreds to thousands wavelengths of form height, an increase in dynamic range is interesting for extreme test samples. For the characterization of complex ophthalmologic lenses an increase of lateral resolution would be beneficial. In order to bypass the previously mentioned restrictions, Trioptics is currently developing a new wavefront sensor with funding of the “European Fund for Regional Development (ERFE)”. The new sensor incorporates MEMS mirrors, which scan the wavefront with high spatial resolution. By successive determination of local wavefront tilt, the commitment to a rigid lens array and the related physical restrictions of a Shack-Hartmann sensor can be overcome. By means of a special detection concept an increase of dynamic range will be pursued, which does not lower spatial resolution.