Apparatus and methods for performing wavefront-based and profile-based measurements of an aspheric surface

1. An apparatus for measuring a shape of an aspheric surface of an aspheric element, comprising:

a support structure;

a moveable stage moveably attached to the support structure;

a rotatable base disposed on the movable stage and adapted to rotatably support the aspheric element along an apparatus axis;

an interferometric wavefront measurement system operably supported by the support structure and adapted to optically interrogate the aspheric surface with a measurement wavefront to collect wavefront-based measurement data of the aspheric surface;

a profile measurement system operably supported by the support structure and adapted to perform at least one non-contact profile-based measurement of the aspheric surface to collect profile-based measurement data of the aspheric surface; and

a controller adapted to receive and process the wavefront-based measurement data and the profile-based measurement data to define a combined measurement of the aspheric surface.

2. The apparatus of claim 1 , wherein the support structure comprises a platform that supports first and second support pillars, and wherein the interferometric wavefront measurement system is supported by the first support pillar and the profile measurement system is supported by the second support pillar.

3. The apparatus of claim 2 , wherein the interferometric wavefront measurement system includes a null optical element that is moveably mounted to the first support pillar.

4. The apparatus of claim 1 , wherein:

the controller includes a processor and a memory, with the memory including ideal aspheric-surface-shape data;

the wavefront-based measurement data includes a non-rotationally symmetric data component and a mid-spatial-frequency component, wherein the profile-based measurement data includes a rotationally symmetric data component; and

the controller is operably configured with instructions embodied in a computer-readable medium to cause the processor to process the non-rotationally symmetric data component, the mid-spatial-frequency component, the rotationally symmetric data component and the ideal aspheric-surface-shape data to define the combined measurement of the aspheric surface.

5. The apparatus of claim 1 , wherein the apparatus includes the aspheric element, and wherein the aspheric element has either a generally concave or generally convex surface.

6. The apparatus of claim 1 , wherein the aspheric element comprises a mirror.

7. The apparatus of claim 1 , wherein the aspheric element has an actual manufactured aspheric shape and a target aspheric surface shape, and wherein combined measurement of the aspheric surface includes a difference between the actual manufactured aspheric shape and the target aspheric surface shape.

8. An apparatus for measuring a shape of an aspheric surface of an aspheric element that has an actual manufactured aspheric shape and a target aspheric surface shape, comprising:

a moveable stage that supports a rotatable base, the rotatable base being adapted to rotatably support the aspheric element along an apparatus axis;

an interferometric wavefront measurement system operably arranged relative to the aspheric element and that optically interrogates the aspheric surface with a measurement wavefront to collect wavefront-based measurement data of the aspheric surface;

a profile measurement system operably arranged relative to the aspheric element and that optically interrogates the aspheric surface with probe light to perform at least one non-contact, profile-based measurement of the aspheric surface to collect profile-based measurement data of the aspheric surface; and

a controller adapted to receive and process the wavefront-based measurement data and the profile-based measurement data to define a combined measurement of the aspheric surface.

9. The apparatus of claim 8 , wherein:

the controller includes a processor and a memory, with the memory including data representative of the target aspheric-surface-shape data;

the wavefront-based measurement data includes a non-rotationally symmetric data component and a mid-spatial-frequency component, wherein the profile-based measurement data includes a rotationally symmetric data component; and

the controller is operably configured with instructions embodied in a computer-readable medium to cause the processor to process the non-rotationally symmetric data component, the mid-spatial-frequency component, the rotationally symmetric data component and the target aspheric-surface-shape data to define the combined measurement of the aspheric surface.

10. The apparatus of claim 8 , wherein combined measurement of the aspheric surface includes a difference between the actual manufactured aspheric shape and the target aspheric surface shape.

11. The apparatus of claim 8 , wherein the apparatus includes the aspheric element, and wherein the aspheric element has either a generally concave or generally convex surface.

12. The apparatus of claim 8 , wherein the interferometric wavefront measurement system and the profile measurement system are respectively supported by first and second pillars each supported by a platform, and wherein the moveable stage is moveably supported by the first pillar.

13. A method of characterizing an aspheric surface of an aspheric element that has an actual manufactured aspheric shape and a target aspheric surface shape, comprising:

supporting the aspheric element on a rotatable base;

performing at least one wavefront-based measurement of the aspheric surface to obtain wavefront-based measurement data that includes a non-rotationally symmetric data component and a mid-spatial-frequency data component;

performing at least one profile-based measurement of the aspheric surface to obtain profile-based measurement data that includes a rotationally symmetric data component;

defining, from the non-rotationally symmetric data component, the mid-spatial-frequency data component, the rotationally symmetric data component and the target aspheric surface shape, a deviation of the actual manufactured aspheric shape from the target aspheric surface shape; and

wherein said performing of the at least one wavefront-based measurement and the at least one profile-based measurement are performed without removing the aspheric element from the rotatable base.

14. The method of claim 13 , further comprising:

performing multiple wavefront-based measurements of the aspheric surface at different angular positions of the rotatable base; and

processing the multiple wavefront-based measurements to reduce a measurement error in the non-rotationally symmetric data component.

15. The method of claim 13 , wherein performing at least one profile-based measurement includes performing between 1 and 10 profile-based measurements.

16. The method of claim 13 , wherein the at least one profile-based measurement is performed before the at least one wavefront-based measurement.

17. The method of claim 13 , wherein the at least one wavefront-based measurement is performed by a wavefront interferometer system, the at least one profile-based measurement is performed by a profile measurement system, and the wavefront interferometer system and the profile measurement system are each operably supported by a support frame that also supports the rotatable base on a moveable stage.

18. The method of claim 13 , wherein the aspheric element has either a generally concave or generally convex aspheric surface.

19. The method of claim 13 , further comprising averaging multiple profile-based measurements to establish the profile-based measurement data.

20. The method of claim 13 , further comprising using a controller operably configured with instructions embodied in a computer-readable medium to cause a processor of the controller to process the non-rotationally symmetric data component, the mid-spatial-frequency component, the rotationally symmetric data component and the target aspheric-surface-shape data to determine the deviation of the actual manufactured aspheric shape from the target aspheric surface shape.