Optoelectronic sensor for measuring the shape of two-dimensional objects

Abstract With the described analogue optoelectronic sensor, the edge of transparent and non-transparent two-dimensional objects, wafers for example, can be scanned on a rotating stage with an incremental encoder. After one revolution of the stage, the polar coordinates of the object's shape are stored as digitalized values. The displacement of the object or the deviation from the ideal shape can be calculated with special algorithms. The measuring resolution is 20 μm and the achieved accuracy is 0.5% of the measurement range.