A non-contact method of inspecting the topography of an area of an object via analysis of the phase of a pattern projected on the object. The method includes taking a first image of the object, obtained from a first perspective, on which an optical pattern is projected, and taking a second image of the object, obtained from a second perspective, on which an optical pattern is projected but in which the optical pattern, as it falls on the object, in the second image differs to that in the first image. The method further includes determining data describing the topography of at least a region of the object based on phase data relating to the phase of at least a region of the optical pattern as imaged in the first image. Phase data obtained from a corresponding region of the object as imaged in the second image is used to resolve any ambiguity in the phase or topography data obtained from the first image.