Zygo Corporation

Other

Michael K&uuml;chel

Christopher James Evans

Carl A Zanoni

An optical sphere of nominal radius is positioned and supported within an assembly so that is can be activated with a predetermined motion with respect to an incoming converging spherical wavefront from an interferometer to calibrate the interferometer by determining the differences between the converging spherical wavefront and the reflected wavefront from portions of the area of the optical sphere as sampled thereover. The nominal optical sphere supported and sampled in this way mimics a &ldquo;perfect&rdquo; comparison sphere from which the systematic error of the interferometer wavefront may be determined. The optical sphere is preferably hollow and composed of Zerodur&reg;. Internal magnets in conjunction with external induction coils provide motion control while the optical sphere is mounted on an air bearing for freedom of rotation and safety in transportation.

Apparatus and method for calibrating an interferometer using a selectively rotatable sphere

Interferometric scanning method(s) and apparatus for measuring rotationally and non-rotationally symmetric test optics either having aspherical surfaces or that produce aspherical wavefronts by comparing known and unknown spherical and aspherical shapes. Preferably, a spherical or partial spherical wavefront or reflecting surface is defined with respect to a known origin along a scanning axis. The test optic is aligned with respect the scanning axis and selectively moved along it relative to the known origin so that the spherical shape intersects the test optic at the apex of the aspherical shape and at radial positions where the spherical shape and the aspheric shape intersect at points of common tangency. An axial distance, v, and optical path length, p, are interferometrically measured as the test optic is axially scanned by the spherical shape where v is the distance by which the test optic is moved with respect to the origin and p is the optical path length difference between the apex of an aspherical shape associated with the test optic and the apex of the circles of curvature that intersect the aspherical shape at the common points of tangency. Coordinates of the aspherical surface are calculated wherever the circles of curvature have intersected the aspherical shape and in correspondence with the interferometrically measured distances, v and p. Afterwards, the aspheric shape is calculated. Where the test optic comprises a refracting optic a known spherical reflecting surface is provided upstream of the refracting optic for movement along the optical axis and a known wavefront is made to transit the refracting optic, reflects from the known spherical surface, again transits the refracting optic traveling towards the known origin after which the interferogram is formed.

Scanning interferometer for aspheric surfaces and wavefronts

A method with a traceable calibration for reducing the uncertainty in the precision measurement of aspheric surfaces and wavefronts. A transmission sphere is mounted in an interferometer and its emergent wavefront is calibrated by comparing it to an optical sphere that is moved and sampled in a predetermined manner to make it act like a substantially &ldquo;perfect&rdquo; sphere mounted on a slideway. Afterwards, the calibrated wavefront from the transmission sphere is used to measure a spherical artifact mounted on the slideway to calibrate its surface. A transmission asphere is then mounted in the interferometer, and its emergent wavefront is calibrated by comparing it to the calibrated spherical artifact mounted on the slideway. The calibrated aspheric wavefront from the interferometer is then used to measure an aspherical artifact mounted on the slideway to determine is surface shape. The calibration of the wavefront emerging from the transmission asphere is periodically updated to provide historical data that is used as the basis for quality improvement and assurance.

Rapid in situ mastering of an aspheric Fizeau with residual error compensation

Interferometric method and apparatus for measuring aspheric surfaces and wavefronts by directing a spherical wavefront of known design at a wavelength &lgr; at a reference sphere with known measured surface properties to generate a first electronic signal containing information about the optical path differences between the reference and measurement wavefronts generated an interferometer and directing an aspherical wavefront of known design at a wavelength &lgr; at an aspherical surface or wavefront to be tested to generate a second electronic signal containing information about the optical path differences between the reference and measurement wavefronts generated by the interferometer. The first and second electronic signals are analyzed and calculated therefrom are wavefront error maps W &equals;W (&lgr; ) and W &equals;W (&lgr; ), both of which contain wavelength dependent known design and measured errors and unknown errors due to the manufacture, material composition of components in the interferometer, and systematic errors. Optical path length errors caused by shape errors in the aspherical surface or wavefront are determined while accounting for substantially all error sources present in the electronic signals to provide for enhanced precision.

Dispersive null-optics for aspheric surface and wavefront metrology

Interferometric apparatus and methods by which aspheric surfaces and wavefronts may be precisely measured. The apparatus is provided with two modes of operation. In one mode, the apparatus is configured generally as a Fizeau interferometer in which an aspheric reference surface is used to permit the rapid, robust measurement of the difference between the aspheric reference surface and an aspheric test optic or wavefront. In another mode of operation, the aspheric test surface itself is completely characterized through in-situ use of an interferometric scanning technique using a spherical reference surface.

Growing community of inventors

Oberkochen, Germany

Michael Küchel

Growing community of inventors

Oberkochen, Germany

Michael K&uuml;chel

Michael Küchel