Interferometric measuring device

A non-transitory computer readable storage medium comprising a computer program comprising instructions, the instructions capable of being executed by a processor associated with an interferometric measuring device that measures a surface or a profile of an optical element having a first surface and a second surface opposite the first surface,

• wherein an interferometric measuring device, upon its processor executing the instructions, carries out the following:
• defines at least a first measurement point, a second measurement point and a third measurement point on a measurement surface of the optical element, the measurement surface being one of the first surface and the second surface;
• measures a first position of the first measurement point by directing a measurement beam from a measurement head onto the first measurement point, by receiving via the measurement head a first measurement beam portion reflected at the first measurement point, and by detecting the first measurement beam portion by a detector optically coupled to the measurement head;
• subsequently measures at least a second position of the second measurement point and a third position of the third measurement point by directing the measurement beam onto the second measurement point and directing the measurement beam onto the third measurement point, by receiving via the measurement head a second measurement beam portion reflected at the second measurement point and a third measurement beam portion reflected at the third measurement point, respectively, and by detecting the second measurement beam portion and the third measurement beam portion by the detector, respectively;
• and
• determines at least one of a decenter and a tilt of the measurement surface relative to a reference axis on the basis of at least the first position, the second position and the third position;
• wherein one of the first surface and the second surface of the optical element facing towards the measurement head and the other one of the first surface and the second surface facing away from the measurement head is the measurement surface, wherein the first position, the second position and the third position is measured by directing the measurement beam onto a first target point, a second target point and a third target point, wherein the first target point, the second target point and the third target point are located on the one of the first surface and the second surface facing towards the measurement head, and wherein the measurement beam propagates through a medium of the optical element, and
• wherein any of the first, second and third measurement beams propagating from the respective first, second and third target points towards the first, second and third measurement points, respectively, hit the measurement surface substantially perpendicularly.

An interferometric measuring device for measuring a surface or a profile of an optical element having a first surface and a second surface opposite the first surface, the measuring device comprising:

• a light source for emitting a measurement beam;
• a mount to fix the optical element;
• a measurement head variably movable relative to the mount and optically coupled to the light source for directing a measurement beam onto a predefined first measurement point, onto a predefined second measurement point and onto a predefined third measurement point of the measurement surface, wherein the measurement head is further configured to receive a first measurement beam portion reflected at the first measurement point, a second measurement beam portion reflected at the second measurement point, and a third measurement beam portion reflected at the third measurement point, respectively;
• a detector optically coupled to the measurement head for detecting the measurement beam portion reflected at least at the first measurement point, the second measurement point and the third measurement point;
• a signal analyzer connected to the detector for determining at least a first position of the first measurement point, a second position of the second measurement point and a third position of the third measurement point, and for determining at least one of a decenter and a tilt of the measurement surface relative to a reference axis on the basis of at least the first position, the second position and the third position;
• wherein the measurement head is positioned relative to the optical element to direct the measurement beam onto at least a first target point, a second target point and a third target point on one of a first surface and a second surface of the optical element opposite to the measurement surface and facing towards the measurement head, wherein each of the first target point, the second target point and the third target point correlates with one of the first measurement point, the second measurement point and the third measurement point, and
• wherein the measurement head is positioned such that the measurement beam entering a medium of the optical element at the first target point, at the second target point and at the third target point hits the measurement surface substantially perpendicularly and is internally retroreflected at the first measurement point, the second measurement point and the third measurement point, respectively.