Method and device for measuring freeform surfaces
First Claim
1. An optical measuring instrument for measuring aspheric surfaces, the optical measuring instrument comprising:
- an optical measuring arm including a detector that captures information regarding wavefront shape, and imaging optics incorporating a variable focusing optic that images subapertures of an aspheric surface onto the detector; and
a multi-axis drive platform including first and second rotational axes that relatively moves the optical measuring arm with respect to the aspheric surface through a plurality of subaperture measurement positions, a first translational axis along which are maintained different centers of curvature associated with a predetermined local shape of the aspheric surface at a crossing point of the first and second rotational axes through the plurality of subaperture measurement positions, and a second translational axis along which are maintained the subapertures of the aspheric surface conjugate to the detector through the plurality of subaperture measurement positions,wherein the variable focusing optic maintains a focus of the focusing optic at the crossing point of the first and second rotational axes through the plurality of subaperture measurement positions.
1 Assignment
0 Petitions
Accused Products
Abstract
An optical measuring instrument for measuring aspheric surfaces includes an optical measuring arm and a multi-axis drive platform. The optical measuring arm provides for illuminating and imaging the aspheric surfaces. The multi-axis drive platform relatively moves the optical measuring arm with respect to the aspheric surfaces through a plurality of subaperture measurement positions. A focus of adjustable focusing optic is maintained at a nominal center of curvature of the aspheric surfaces. A variable optical aberrator adds aberration to an illumination wavefront to match the illumination wavefront to the intended local shape of the aspheric surface. Fitted low-frequency shape information is distinguished from a remainder of the local shape information yielding mid-frequency topographic measurements of the subapertures, which can be assembled to construct a profile measurement of the aspheric surface.
12 Citations
26 Claims
-
1. An optical measuring instrument for measuring aspheric surfaces, the optical measuring instrument comprising:
-
an optical measuring arm including a detector that captures information regarding wavefront shape, and imaging optics incorporating a variable focusing optic that images subapertures of an aspheric surface onto the detector; and a multi-axis drive platform including first and second rotational axes that relatively moves the optical measuring arm with respect to the aspheric surface through a plurality of subaperture measurement positions, a first translational axis along which are maintained different centers of curvature associated with a predetermined local shape of the aspheric surface at a crossing point of the first and second rotational axes through the plurality of subaperture measurement positions, and a second translational axis along which are maintained the subapertures of the aspheric surface conjugate to the detector through the plurality of subaperture measurement positions, wherein the variable focusing optic maintains a focus of the focusing optic at the crossing point of the first and second rotational axes through the plurality of subaperture measurement positions. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
-
-
9. A method of measuring aspheric surfaces, the method comprising:
-
mounting a test object having an aspheric surface on a multi-axis drive platform having drive axes that relatively moves an optical measuring arm, including a detector and imaging optics incorporating a variable focusing optic, with respect to the aspheric surface; relatively rotating the measuring arm with respect to the aspheric surface about two rotational axes to illuminate a succession of subapertures of the aspheric surface and imaging the succession of subapertures onto the detector; relatively moving the aspheric surface with respect to a crossing point of the two rotational axes to maintain different local centers of curvature associated with the predetermined shape of the aspheric surface at the crossing point through the succession of subapertures; relatively moving the measuring arm with respect to the crossing point to maintain the subapertures of the aspheric surface conjugate to the detector; and adjusting the adjustable focusing optic to maintain a focus of the focusing optic at the crossing point through the succession of subapertures. - View Dependent Claims (10, 11, 12, 13, 14)
-
-
15. An optical measuring instrument for measuring freeform surfaces, the optical measuring instrument comprising:
-
an optical measuring arm including a wavefront detector and optics that shape an illumination wavefront and imaging subapertures of a freeform surface onto the wavefront detector as a test wavefront, wherein the optics include a variable focusing optic and a variable optical aberrator that adds aberration to the illumination wavefront to substantially match the illumination wavefront to a predetermined local shape of the aspheric surface within subapertures of the freeform surface; a multi-axis drive platform that relatively moves the optical measuring arm with respect to the freeform surface through a succession of measurement positions to illuminate the subapertures of the freeform surface and to image the illuminated subapertures onto the detector; and a processor that (a) extracts local shape information from the imaged subapertures of the freeform surface, (b) distinguishes fitted low-frequency shape information having an order corresponding to an order of aberration that defines the predetermined local shape of the freeform surface from the local shape information yielding mid-frequency profile measurements of the subapertures and (c) assembles the mid-frequency profile measurements of the subapertures to construct a profile measurement of the freeform surface. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22)
-
-
23. A method of measuring freeform surfaces of test objects, the method comprising:
-
mounting a test object having a freeform surface on a multi-axis drive platform that relatively moves an optical measuring arm with respect to the freeform surface through a succession of measurement positions; adjustably focusing an illumination wavefront through an adjustable focusing optic to illuminate subapertures of the freeform surface at the succession of measurement positions; imaging the illuminated subapertures of the freeform surface onto a wavefront detector in the form of test wavefronts reflected from the freeform surface at the succession of measurement positions; capturing shape information from the test wavefronts that are imaged onto the wavefront detector at the succession of measurement positions; fitting low-frequency shape information having an order corresponding to an order of aberration that defines the predetermined shape of the freeform surface at the succession of measurement positions distinguishing the low-frequency shape information from the captured shape information yielding mid-frequency profile measurements of the subapertures; and assembling the mid-frequency profile measurements of the subapertures to construct a profile measurement of the freeform surface. - View Dependent Claims (24, 25, 26)
-
Specification