Patent ID: 8488107

Claim:
A combination of a movable substrate support configured to support a substrate and a level sensor configured to determine the height level of a surface of the substrate supported on the movable substrate support, comprising: multiple projection units, each projection unit configured to project a measurement beam on a measurement location on the substrate, multiple detection units, each detection unit arranged to receive the measurement beam after redirection by the substrate, and a processing unit to calculate the height level for each of the measurement locations on the basis of the measurement beams, wherein the level sensor is configured to measure the height levels simultaneously at multiple measurement locations on the substrate, wherein the substrate support is configured to move the substrate in a first direction substantially parallel to the surface of the substrate to measure the height level of the surface at different locations on the substrate, and wherein at least part of the multiple measurement locations are at least spaced in as second direction that is substantially parallel to the surface of the substrate and substantially perpendicular to the first direction.