Optical component fabrication using metals or ceramic materials involves many grinding and/or machining and polishing steps to achieve the proper form to the tolerances of imaging or photonic focusing instruments. These instruments range from infrared sensors, through visible and ultraviolet, to X-ray and even thermal neutron focusing. Conventional manufacturing methods require many days or even months of precise polishing to improve selected areas of the component.

The objective of this innovation is to provide a method of deterministically controlling the form and finish of an optical or other precision component made of conductive or semi-conductive material by applied electrochemical methods superimposed upon applied mechanical polishing methods. Mechanical polishing is widely used in prior and present art optical fabrication, while electrochemical methods are not commonly used in optical fabrication. The combination of both procedures with the appropriate materials and methods permits overcoming serious deficiencies in the conventional polishing operations.

An electrochemically enhanced mechanical polishing process (EEMP) is provided for deterministically perfecting the form, figure, and surface finish of high-quality optical components in a reduced time and at a lower capital cost. The addition of a small-combination electrode/ polishing pad, and an applied electrical current with the use of a specific electrolyte, in conjunction with a selected polishing medium, provides an improved rate of metal removal and a predictable control of the figure in a precision optical component. The use of a computer-controlled current source and polishing arm permits a fully controlled process.

It is known that an applied electrical current and the use of a suitable electrolyte will etch most conductive materials. By placing an electrode above an “elevated” area of an optical surface and applying an electric current, the process can be used for correcting the figure of the optical surface. The material removal rate can be controllable through the electric current and waveform adjustment, and the material can be removed selectively from only “elevated” areas of the optical surface. The applied current is such that the component is anodically etched deterministically based on the measured surface profile. This measured profile data is the basis for the programmable current power source input and subsequent current output, which tracks the profile and selectively etches more at the elevated disparities on the surface. A combination of electrochemical etching with standard mechanical polishing, i.e., electromechanical polishing with a polishing compound (or abrasive grit) added to the electrolyte, is proposed. The figuring (electrochemical polishing) and the surface finishing (mechanical polishing) can be done simultaneously, and the material removal rate can be much higher compared to conventional polishing methods. This results in a significant reduction of manufacturing time for optical components.

This work was done by Carl Benson, Brian Ramsey, and William (Bill) Jones of Marshall Space Flight Center; Darell Engelhaupt of the University of Alabama Huntsville; and Mikhail Gubarev of Universities Space Research Association (USRA). For more information, contact Ronald C. Darty, Licensing Executive in the MSFC Technology Transfer Office, at This email address is being protected from spambots. You need JavaScript enabled to view it.. Refer to MFS-32588-1.


NASA Tech Briefs Magazine

This article first appeared in the August, 2015 issue of NASA Tech Briefs Magazine.

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