# US 11,443,950 B2 · Method for figure control of optical surfaces > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,443,950 B2 - Document ID: US11443950B2 - Status: Granted - Kind: B2 - Application number: 16/800,270 - Filed: 2020-02-25 - Published: 2020-09-03 - Granted: 2022-09-13 - Earliest claimed: 2019-03-01 - Assignees: Zygo Corporation - Applicants: Zygo Corporation - Inventors: Andrew Nelson - Web page: https://patentgrep.com/patent/US11443950B2 ## CPC - C03C 3/06: with more than 90% silica by weight, e.g. quartz {(C03C3/045 takes precedence)} - H10P 50/00: Etching of wafers, substrates or parts of devices - C03C 15/00: Surface treatment of glass, not in the form of fibres or filaments, by etching (etching or surface-brightening compositions, in general C09K13/00) - C03C 15/02: for making a smooth surface - C03C 25/68: by etching - G02B 26/101: {with both horizontal and vertical deflecting means, e.g. raster or XY scanners (colour television using laser beams scanning a display screen H04N9/3129)} - H10P 72/53: {using optical controlling means} - G02B 5/0891: {Ultraviolet [UV] mirrors (apparatus for microlithography exposure G03F7/70; X-ray multilayer structures G21K1/06)} - G02B 5/10: with curved faces - G02B 13/143: {for use with ultraviolet radiation} - G02B 13/18: with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration {(G02B13/002 takes precedence)} - C03C: CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS - H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10 - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract A method for figuring an optical surface of an optical element to achieve a target profile for the optical surface includes: applying a removal process to an extended region of the optical surface extending along a first direction to remove material from the extended region of the optical surface; adjusting a position of the optical surface relative to the removal process along a second direction perpendicular to the first direction to remove material from additional extended regions of the optical surface extending along the first direction at each of different positions of the optical surface along the second direction; and repeating the applying of the removal process and the adjusting of the optical surface relative to the removal process for each of multiple rotational orientations of the optical surface about a third direction perpendicular to the first and second directions to achieve the target profile of the optical surface. ## Claims ### Claim 1 A method for figuring an optical surface of an optical element to achieve a target profile for the optical surface, the method comprising: a. applying a removal process to an extended region of the optical surface extending along a first direction to remove material from the extended region of the optical surface; and b. adjusting a position of the optical surface relative to the removal process along a second direction perpendicular to the first direction to remove material from additional extended regions of the optical surface extending along the first direction at each of different positions of the optical surface along the second direction, c. wherein, during the applying of the removal process and the adjusting of the optical surface relative to the removal process, the optical surface has a first rotational orientation about a third direction perpendicular to the first and second directions, and d. wherein the method further comprises: repeating the applying of the removal process and the adjusting of the optical surface relative to the removal process for each of one or more additional rotational orientations of the optical surface about the third direction to achieve the target profile of the optical surface, wherein the removal process is an etching process wherein at least part of the optical surface is immersed into an etching bath, wherein the adjusting of the optical surface relative to the removal process comprises immersing the optical surface into the etching bath along the second direction, wherein immersing the optical surface into the etching bath along the second direction comprises varying a speed of the immersion of the optical surface into the etching bath along the second direction to cause a rate at which the material at the additional extended regions of the optical surface extending along the first direction are removed at each of the different positions of the optical surface along the second direction to vary nonlinearly with respect to distance along the second direction. ### Claim 2 (depends on 1) The method of claim 1, wherein the extended regions of the optical surface that are immersed in the etching bath have material continuously removed by the etching bath in proportion to a dwell time in the etching bath for each of the extended regions. ### Claim 3 (depends on 1) The method of claim 1, wherein the target profile of the optical surface comprises any of a wedge surface, a spherical surface, an aspherical surface, and a free-form surface. ### Claim 4 A method for figuring an optical surface of an optical element to achieve a target profile for the optical surface, the method comprising: a. applying a removal process to an extended region of the optical surface extending along a first direction to remove material from the extended region of the optical surface; and b. adjusting a position of the optical surface relative to the removal process along a second direction perpendicular to the first direction to remove material from additional extended regions of the optical surface extending along the first direction at each of different positions of the optical surface along the second direction, c. wherein, during the applying of the removal process and the adjusting of the optical surface relative to the removal process, the optical surface has a first rotational orientation about a third direction perpendicular to the first and second directions, and d. wherein the method further comprises: repeating the applying of the removal process and the adjusting of the optical surface relative to the removal process for each of one or more additional rotational orientations of the optical surface about the third direction to achieve the target profile of the optical surface, and further comprising expressing the target profile for the figuring of the optical surface as a superposition of polynomial functions of a coordinate for the second dimension for each of the first rotational orientation and the one or more additional rotational orientations. ### Claim 5 (depends on 4) The method of claim 4, wherein the extended region of the optical surface extending along the first direction from which material is removed by the removal process extends across a full aperture of the optical surface along the first direction. ### Claim 6 (depends on 4) The method of claim 4, wherein the removal process is an etching process wherein at least part of the optical surface is immersed into an etching bath. ### Claim 7 (depends on 6) The method of claim 6, wherein the adjusting of the optical surface relative to the removal process comprises immersing the optical surface into the etching bath along the second direction. ### Claim 8 (depends on 6) The method of claim 6, wherein the method further comprising adjusting a temperature of the etchant bath to adjust an etching rate for the removal process. ### Claim 9 (depends on 4) The method of claim 4, wherein adjusting the position of the optical surface relative to the removal process along the second direction comprises varying a speed of the relative positioning along the second direction to cause a rate at which the material at the additional extended regions of the optical surface extending along the first direction are removed at each of the different positions of the optical surface along the second direction to vary nonlinearly with respect to distance along the second direction. ### Claim 10 (depends on 4) The method of claim 4, further comprising mounting the optical element in a fixture to establish an initial rotational orientation of the optical surface about the third direction prior to an initial application of the removal process to the optical surface. ### Claim 11 (depends on 10) The method of claim 10, further comprising reorienting the optical element in the fixture to establish each of the one or more additional rotational orientations of the optical surface prior to repeating each of the corresponding applications of the removal process and adjustments of the optical surface relative to the removal process. ### Claim 12 (depends on 4) The method of claim 4, wherein the first rotational orientation and the one or more additional rotational orientations collectively comprise at least four different rotational orientations. ### Claim 13 (depends on 12) The method of claim 12, wherein the at least four different rotational orientations comprise eight different rotational orientations. ### Claim 14 (depends on 12) The method of claim 12, wherein the at least four different rotational orientations are selected from rotations corresponding to integer multiples of 45 degrees. ### Claim 15 (depends on 4) The method of claim 4, wherein the adjustment of the optical surface relative to the removal process along the second direction for each of the first rotational orientation and the one or more additional rotational orientations is based on the polynomial function for each corresponding one of the first rotational orientation and the one or more additional rotational orientations. ### Claim 16 (depends on 15) The method of claim 15, wherein a speed of the adjustment of the optical surface relative to the removal process along the second direction for each of the first rotational orientation and the one or more additional rotational orientations corresponds to a derivative of the polynomial function with respect to the coordinate for the second dimension for each corresponding one of the first rotational orientation and the one or more additional rotational orientations. ### Claim 17 (depends on 4) The method of claim 4, wherein a desired profile for the figuring of the optical surface can be expressed in terms of coefficients for a set of Zernike polynomials, and where the method comprises approximating the desired profile with the target profile expressed as the superposition of polynomial functions for each of the first rotational orientation and the one or more additional rotational orientations. ### Claim 18 (depends on 4) The method of claim 4, wherein a full aperture of the optical surface is greater than 25 cm. ### Claim 19 (depends on 4) The method of claim 4, wherein a full aperture of the optical surface is greater than 50 cm. ### Claim 20 (depends on 4) The method of claim 4, wherein a full aperture of the optical surface is greater than 100 cm. ### Claim 21 (depends on 4) The method of claim 4, wherein the removal process is laterally extended along the first direction to simultaneously remove the material from the region of the optical surface extending along the first direction. ### Claim 22 (depends on 4) The method of claim 4, wherein the removal process is laterally extended along the first direction to uniformly remove the material from the region of the optical surface extending along the first direction. ### Claim 23 (depends on 4) The method of claim 4, wherein the removal process is an ion beam etching process. ### Claim 24 (depends on 23) The method of claim 23, wherein a dimension of the ion beam for the ion beam etching process along the first direction is at least ten times greater than a dimension of the ion beam along the second direction.