3DOF(xyθ_z) measurement of a planar stage with one single 1D CCD from a 2D Moiré pattern

Abstract

As technology is advancing, the need for precision stages is increasing. These stages are being used with (electron) microscopes for scientific research and industrial applications. They can be operated manually or by actuators, where the motorized stages are quite expensive in general and the cost increase significantly if better performance is required. The increased cost is mainly due to the used sensors, such as linear encoders for stacked stages and laser interferometers for planar stages. It is a trade-off between the performance and cost. Alternative low-cost sensor systems have already been developed by the MSD group. A recent sensor system uses an 8-megapixel 2D image sensor with QR-like patterns to achieve micrometre precision and a relatively low sample rate of 16 Hz. This sensor system is limited by the sensor and the image-recognition algorithm. By using a cost-effective linear image sensor (2000 pixels) the same precision could be achieved while the sample rate can be significantly higher. This thesis presents a new methodology to measure the 3DOF(xyθ_z) of a planar stage with a single linear charge-coupled device (CCD) from a self-designed pattern. The feasibility of the methodology has been shown with a self-developed line scan simulation tool. A sensor system has been built and implemented in a demonstrator to gain knowledge about the different sensitivities in the sensor system and to demonstrate the possibilities of the sensor system.