Abstract: The invention relates to a method for determining a distance between charged particle beamlets in a multi-beamlet exposure apparatus. The apparatus is provided with a sensor comprising a converter element for converting charged particle energy into light and a light sensitive detector provided with a two-dimensional pattern of beamlet blocking and non-blocking regions. The method comprises scanning a first beamlet over the pattern, receiving light generated by the converter element, and converting the received light into a first signal. Then the two-dimensional pattern and the first beamlet are moved relatively with respect to each other over a predetermined distance. Subsequently, the method comprises scanning a second beamlet over the pattern, receiving light generated by the converter element, and converting the received light into a second signal. Finally, the distance between the first beamlet and second beamlet is determined based on the first signal, the second signal and the predetermined distance.

Abstract: A structured light sensor system for measuring contour of a surface includes a control module that coordinates control of both a projection system and an imaging system to operate the structured light sensor system in three different modes. The imaging system is configured to selectively capture an image of light reflected off of the surface. In point mode, the imaging system is on for a first period during which the projection system projects a point of light onto the surface. In line mode, the imaging system is on for a second period during which the projection system projects onto the surface a first plurality of points of light forming a line of light. In area mode, the imaging system is on for a third period during which the projection system projects onto the surface a second plurality of points of light forming a plurality of lines of light.