Abstract: A metrology system for measuring aspheric test objects by subaperture stitching. A wavefront-measuring gauge having a limited capture range of wavefront shapes collects partially overlapping subaperture measurements over the test object. A variable optical aberrator reshapes the measurement wavefront with between a limited number of the measurements to maintain the measurement wavefront within the capture range of the wavefront-measuring gauge. Various error compensators are incorporated into a stitching operation to manage residual errors associated with the use of the variable optical aberrator.

Abstract: A metrology system for measuring aspheric test objects by subaperture stitching. A wavefront-measuring gauge having a limited capture range of wavefront shapes collects partially overlapping subaperture measurements over the test object. A variable optical aberrator reshapes the measurement wavefront with between a limited number of the measurements to maintain the measurement wavefront within the capture range of the wavefront-measuring gauge. Various error compensators are incorporated into a stitching operation to manage residual errors associated with the use of the variable optical aberrator.

Abstract: A method for calibrating and aligning a metrology system comprising a machine including multi-axis part-positioning means and a wavefront-measuring gauge embedded in the machine. The gauge is used in determining spatial relationships among the translational and rotational axes, between part surface coordinates and machine coordinates, and between machine coordinates embedded gauge coordinates; in calibrating various components of the machine and the embedded gauge; and in aligning itself to the machine. A complete method comprises the steps of coarsely aligning the machine rotary axes with their respective translational axes and setting nominal zero points for the rotary axes; aligning the embedded gauge mainframe to the machine axes; aligning the embedded gauge focal point onto a spindle axis; determining the spatial offsets between the rotary axes when so aligned; precisely aligning the machine rotary axes with their respective translational axes; and setting precise zero points for the rotary axes.

Abstract: A system comprising a plurality of methods for measuring surfaces or wavefronts from a test part with greatly improved accuracy, particularly the higher spatial frequencies on aspheres. These methods involve multiple measurements of a test part. One of the methods involves calibration and control of the focusing components of a metrology gauge in order to avoid loss of resolution and accuracy when the test part is repositioned with respect to the gauge. Other methods extend conventional averaging methods for suppressing the higher spatial-frequency structure in the gauge's inherent slope-dependent inhomogeneous bias. One of these methods involve averages that suppress the part's higher spatial-frequency structure so that the gauge's bias can be disambiguated; another method directly suppresses the gauge's bias within the measurements. All of the methods can be used in conjunction in a variety of configurations that are tailored to specific geometries and tasks.

Abstract: A method for accurately synthesizing a full-aperture data map from a series of overlapped sub-aperture data maps. In addition to conventional alignment uncertainties, a generalized compensation framework corrects a variety of errors, including compensators that are independent in each sub-aperture. Another class of compensators (interlocked) include coefficients that are the same across all the sub-apertures. A constrained least-squares optimization routine maximizes data consistency in sub-aperture overlap regions. The stitching algorithm includes constraints representative of the accuracies of the hardware to ensure that the results are within meaningful bounds. The constraints also enable the computation of estimates of uncertainties in the final results. The method therefore automatically calibrates the system, provides a full-aperture surface map, and an estimate of residual uncertainties.

Abstract: A method for calibrating and aligning a metrology system comprising a machine including multi-axis part-positioning means and a wavefront-measuring gauge embedded in the machine. The gauge is used in determining spatial relationships among the translational and rotational axes, between part surface coordinates and machine coordinates, and between machine coordinates embedded gauge coordinates; in calibrating various components of the machine and the embedded gauge; and in aligning itself to the machine. A complete method comprises the steps of coarsely aligning the machine rotary axes with their respective translational axes and setting nominal zero points for the rotary axes; aligning the embedded gauge mainframe to the machine axes; aligning the embedded gauge focal point onto a spindle axis; determining the spatial offsets between the rotary axes when so aligned; precisely aligning the machine rotary axes with their respective translational axes; and setting precise zero points for the rotary axes.

Abstract: A method for accurately synthesizing a full-aperture data map from a series of overlapped sub-aperture data maps. In addition to conventional alignment uncertainties, a generalized compensation framework corrects a variety of errors, including compensators that are independent in each sub-aperture. Another class of compensators (interlocked) include coefficients that are the same across all the sub-apertures. A constrained least-squares optimization routine maximizes data consistency in sub-aperture overlap regions. The stitching algorithm includes constraints representative of the accuracies of the hardware to ensure that the results are within meaningful bounds. The constraints also enable the computation of estimates of uncertainties in the final results. The method therefore automatically calibrates the system, provides a full-aperture surface map, and an estimate of residual uncertainties.