Patent ID: 8619235

Claim:
A level sensor configured to measure a height level of a substrate arranged in a measurement position, the level sensor comprising: a projection unit to project multiple measurement beams on multiple measurement locations on the substrate; a detection unit to receive the measurement beams after reflection on the substrate; a processing unit to calculate a height level on the basis of the reflected measurement beams received by the detection unit; a first reflection bar arranged to receive the measurement beams from the projection unit, and to direct the measurement beams to the substrate, the first reflection bar comprising an oblique first reflective surface onto which the measurement beams are incident and to reflect the measurement beams towards the substrate; and a second reflection bar arranged to receive the reflected measurement beams from the substrate, and to direct the reflected measurement beams to the detection unit, the second reflection bar comprising an oblique second reflective surface onto which the reflected measurement beams are incident and to reflect the reflected measurement beams towards the detection unit, wherein the first and second reflective surfaces face toward each other and toward the substrate.