Method of measuring a deviation of an optical surface from a target shape

The method according to claim 1,nwherein the tilt between said surface normals of said diffractive measurement structures is at least 1°.

The method according to claim 1,nwherein the tilt between said surface normals of said diffractive measurement structures is between 20° and 90°.

The method according to claim 1,nwherein said surface normals are tilted such that said diffractive measurement structures form a roof-shaped structure, which is adapted such that said optical surface having a convex shape can be inserted at least partly into the roof-shaped structure.

The method according to claim 1,nwherein said incoming light comprises two separate light beams, each of which propagates along a respective surface normal of said diffractive measurement structures.

The method according to claim 1,nwherein said diffractive measurement structures are part of respective wave shaping elements and said method further comprises aligning said wave shaping elements by:providing a first one of said wave shaping elements with a diffractive alignment structure, andaligning said first wave shaping element and a second one of said wave shaping elements relative to each other by evaluating alignment light having consecutively interacted with said diffractive alignment structure and with said second wave shaping element.

The method according to claim 1, further comprising:nilluminating a first area of said optical surface with said incoming light having traversed said diffractive measurement structures and thereby generating first measuring light having interacted with said first area,generating second measuring light having interacted with at least a second area of said optical surface and determining the wave front of said second measuring light, designated as a second wave front, by performing a second interferometric measurement, anddetermining said deviation of said optical surface from said target shape based on said first and said second interferometric measurements.

The method according to claim 1,nwherein each diffractive measurement structure illuminates a separate area of said optical surface, and said method further comprises:illuminating a first area of said optical surface with said incoming light having traversed said diffractive measurement structures, thereby generating first measuring light having interacted with said first area,determining the wave front of said first measuring light, designated as a first wave front, by performing a first interferometric measurement,generating second measuring light having interacted with at least a second area of said optical surface and determining the wave front of said second measuring light, designated as a second wave front, by performing a second interferometric measurement, anddetermining a deviation of said optical surface from said target shape using a stitching algorithm, which stitching algorithm includes determining misalignment components of said at least two diffractive measurement structures based on said first wave front and said second wave front.