Common optical-path testing of high-numerical-aperture wavefronts

1. An interferometric measurement device for characterizing an input wavefront comprising a polarizing point-diffraction plate positioned along an optical axis of the device, wherein the plate includes two regions and one of the regions includes a first polarizing element adapted to split the input wavefront into a reference wavefront and a test wavefront with mutually orthogonal polarizations; and wherein the other of said two regions includes a second polarizing element perpendicular to the first polarizing element.

2. The interferometric measurement device of claim 1 , further comprising an optical coating to modify an optical property of the plate.

3. The interferometric measurement device of claim 1 , further comprising a means for changing a relative position between a source of said input wavefront and the plate to modify a power ratio of the test and reference beams.

4. The interferometric measurement device of claim 1 , further comprising a phase-shifting interferometer that includes a spatial phase-shifting section to impart different relative spatial phase shifts between said reference and test wavefronts, an interference section to combine the spatially phase-shifted reference and test wavefronts to produce a corresponding interferogram, and a detector section to spatially sample the interferogram.

5. The interferometric measurement device of claim 4 , wherein the splitting section includes an optical splitter and the phase-shifting and interference sections consists of a phase interference plate.

6. The interferometric measurement device of claim 1 , further comprising a phase-shifting interferometer that includes a temporal phase-shifting section to impart different relative temporal phase shifts between the reference and test wavefronts, an interference section to combine the temporally phase-shifted reference and test wavefronts to produce corresponding interferograms, and a detector section to temporally sample the interferograms.

7. The interferometric measurement device of claim 1 , further comprising a phase-shifting interferometer that includes a splitting section to produce a plurality of copies of the reference and test wavefronts, a spatial phase-shifting section to impart different relative spatial phase shifts between said copies of the reference and test wavefronts, an interference section to combine phase-shifted copies of the reference and test wavefronts to produce corresponding interferograms, and a detector section to spatially sample the interferograms.

8. The interferometric measurement device of claim 1 , further comprising a field stop incorporated within an entrance region of the interferometric measurement device, said field stop being conjugate with an input pupil image plane and with a plane of a detector in the device.

9. The interferometric measurement device of claim 1 , further comprising means for changing a relative position between a source of said input wavefront and said polarizing point-diffraction plate.

10. The interferometric measurement device of claim 1 , wherein said first polarizing element includes a grating.

11. The interferometric measurement device of claim 1 , wherein said first and second polarizing elements include a grating.

12. The interferometric measurement device of claim 1 , wherein the polarizing point-diffraction plate is a cover glass for the interferometric measurement device.

13. An interferometric measurement device for characterizing an input wavefront comprising a polarizing point-diffraction plate positioned along an optical axis of the device, wherein the plate includes two regions and one of the regions includes a first polarizing element adapted to split the input wavefront into a reference wavefront and a test wavefront with mutually orthogonal polarizations; and wherein said one region is circumscribed by the other of said two regions of the plate.

14. The interferometric measurement device of claim 13 , further comprising an optical coating to modify an optical property of the plate.

15. The interferometric measurement device of claim 13 , further comprising a means for changing a relative position between a source of said input wavefront and the plate to modify a power ratio of the test and reference beams.

16. The interferometric measurement device of claim 13 , further comprising a phase-shifting interferometer that includes a spatial phase-shifting section to impart different relative spatial phase shifts between said reference and test wavefronts, an interference section to combine the spatially phase-shifted reference and test wavefronts to produce a corresponding interferogram, and a detector section to spatially sample the interferograms.

17. The interferometric measurement device of claim 13 , further comprising a phase-shifting interferometer that includes a splitting section to produce a plurality of copies of the reference and test wavefronts, a spatial phase-shifting section to impart different relative spatial phase shifts between said copies of the reference and test wavefronts, an interference section to combine phase-shifted copies of the reference and test wavefronts to produce corresponding interferograms, and a detector section to spatially sample the interferograms.

18. The interferometric measurement device of claim 17 , wherein the splitting section includes an optical splitter and the phase-shifting and interference sections consists of a phase interference plate.

19. The interferometric measurement device of claim 13 , further comprising a phase-shifting interferometer that includes a temporal phase-shifting section to impart different relative temporal phase shifts between the reference and test wavefronts, an interference section to combine the temporally phase-shifted reference and test wavefronts to produce corresponding interferograms, and a detector section to temporally sample the interferograms.

20. The interferometric measurement device of claim 13 , further comprising a field stop incorporated within an entrance region of the interferometric measurement device, said field stop being conjugate with an input pupil image plane and with a plane of a detector in the device.

21. The interferometric measurement device of claim 13 , further comprising means for changing a relative position between a source of said input wavefront and said polarizing point-diffraction plate.

22. The interferometric measurement device of claim 13 , wherein said first polarizing element includes a grating.

23. The interferometric measurement device of claim 13 , wherein said first and second polarizing elements include a grating.

24. The interferometric measurement device of claim 13 , wherein the polarizing point-diffraction plate is a cover glass for the interferometric measurement device.

25. An interferometric measurement device for characterizing an input wavefront comprising:

a polarizing point-diffraction plate positioned along an optical axis of the device, wherein the plate includes two regions and one of the regions includes a first polarizing element adapted to split the input wavefront into a reference wavefront and a test wavefront with mutually orthogonal polarizations;

a spatial phase-shifting interferometer that includes a splitting section to produce a plurality of copies of the reference and test wavefronts, a phase-shifting section to impart different relative phase shifts between said copies of the reference and test wavefronts, an interference section to combine phase-shifted copies of the reference and test wavefronts to produce corresponding interferograms, and a detector section to spatially sample the interferograms;

wherein the splitting section and the phase-shifting section of the interferometer consists of a polarization beamsplitter, and the interference section consists of a polarizer.

26. The interferometric measurement device of claim 25 , wherein the polarization beamsplitter is a birefringent crystal.

27. An interferometric measurement device for characterizing an input wavefront comprising a polarizing point-diffraction plate positioned along an optical axis of the device, wherein the plate includes two regions for splitting the input wavefront into a first polarized wavefront and a second polarized wavefront with mutually orthogonal polarizations, wherein one of the regions includes a means for rotating said first polarized wavefront to produce said second polarized wavefront;

wherein said means for rotating the first polarized wavefront includes a rotation polarization layer and an output thin-film polarization layer.

28. The interferometric measurement device of claim 27 , further including an input polarizing layer over said two regions to convert the input wavefront into said first polarized wavefront.

29. The interferometric measurement device of claim 27 , further including a metallic layer adjacent to said rotation polarization layer.

30. An interferometric measurement method for characterizing an input wavefront comprising the following steps:

passing the input wavefront through a polarizing point-diffraction plate that includes two regions, one of the regions including a first polarizing element adapted to split the input wavefront into a reference wavefront and a test wavefront having a common optical path and mutually orthogonal polarizations;

passing the reference and test wavefronts through a phase-shifting interferometer maintaining said common optical path;

imaging an interferogram produced by the interferometer onto a detector; and

analyzing the interferogram to characterize the input wavefront;

wherein the other of said two regions includes a second polarizing element perpendicular to the first polarizing element.

31. The interferometric measurement method of claim 30 , further comprising the step of coating the plate to modify an optical property of the plate.

32. The interferometric measurement method of claim 30 , further comprising the step of changing a relative position between a source of said input wavefront and the plate to modify a power ratio of the test and reference beams.

33. The interferometric measurement method of claim 30 , wherein said phase-shifting interferometer includes a splitting section to produce a plurality of copies of the reference and test wavefronts, a phase-shifting section to impart different relative phase shifts between said copies of the reference and test wavefronts, and an interference section to combine phase-shifted copies of the reference and test wavefronts to produce corresponding interferograms.

34. The interferometric measurement method of claim 30 , wherein said phase-shifting interferometer is a temporal phase-shifting interferometer.

35. The interferometric measurement method of claim 30 , wherein said phase-shifting interferometer is a spatial phase-shifting interferometer.

36. The interferometric measurement method of claim 35 , wherein the splitting section includes an optical splitter and the phase-shifting and interference sections consists of a phase interference plate.

37. An interferometric measurement method for characterizing an input wavefront comprising the following steps:

passing the input wavefront through a polarizing point-diffraction plate that includes two regions, one of the regions including a first polarizing element adapted to split the input wavefront into a reference wavefront and a test wavefront having a common optical path and mutually orthogonal polarizations;

passing the reference and test wavefronts through a phase-shifting interferometer maintaining said common optical path;

imaging an interferogram produced by the interferometer onto a detector; and

analyzing the interferogram to characterize the input wavefront;

wherein said one region is circumscribed by the other of said two regions of the plate.

38. The interferometric measurement method of claim 37 , further comprising the step of coating the plate to modify an optical property of the plate.

39. The interferometric measurement method of claim 37 , further comprising the step of changing a relative position between a source of said input wavefront and the plate to modify a power ratio of the test and reference beams.

40. The interferometric measurement method of claim 37 , wherein said phase-shifting interferometer includes a splitting section to produce a plurality of copies of the reference and test wavefronts, a phase-shifting section to impart different relative phase shifts between said copies of the reference and test wavefronts, and an interference section to combine phase-shifted copies of the reference and test wavefronts to produce corresponding interferograms.

41. The interferometric measurement method of claim 37 , wherein said phase-shifting interferometer is a temporal phase-shifting interferometer.

42. The interferometric measurement method of claim 37 , wherein said phase-shifting interferometer is a spatial phase-shifting interferometer.

43. The interferometric measurement method of claim 42 , wherein the splitting section includes an optical splitter and the phase-shifting and interference sections consists of a phase interference plate.

44. An interferometric measurement method for characterizing an input wavefront comprising the following steps:

passing the input wavefront through a polarizing point-diffraction plate that includes two regions, one of the regions including a first polarizing element adapted to split the input wavefront into a reference wavefront and a test wavefront having a common optical path and mutually orthogonal polarizations;

passing the reference and test wavefronts through a phase-shifting interferometer maintaining said common optical path;

imaging an interferogram produced by the interferometer onto a detector; and

analyzing the interferogram to characterize the input wavefront;

wherein said phase-shifting interferometer is a spatial phase-shifting interferometer that includes a splitting section to produce a plurality of copies of the reference and test wavefronts, a phase-shifting section to impart different relative phase shifts between said copies of the reference and test wavefronts, and an interference section to combine phase-shifted copies of the reference and test wavefronts to produce corresponding interferograms; and the splitting section and the phase-shifting section consists of a polarization beamsplitter, and the interference section consists of a polarizer.

45. The interferometric measurement method of claim 44 , wherein the polarization beamsplitter is a birefringent crystal.

46. An interferometric measurement method for characterizing an input wavefront comprising the following steps:

passing the input wavefront through a polarizing point-diffraction plate that includes two regions, one of the regions including a first polarizing element adapted to split the input wavefront into a reference wavefront and a test wavefront having a common optical path and mutually orthogonal polarizations;

passing the reference and test wavefronts through a phase-shifting interferometer maintaining said common optical path;

imaging an interferogram produced by the interferometer onto a detector;

analyzing the interferogram to characterize the input wavefront; and

providing a field step conjugate with an input pupil image plane and with a plane of the detector.

47. The interferometric measurement method of claim 46 , further comprising the step of changing a relative position between a source of said input wavefront and said polarizing point-diffraction plate.