Ion-beam machining of millimeter scale optics

Area of Science:

• Optics and Materials Science
• Precision Engineering
• Surface Metrology

Background:

• Conventional machining of small optics faces challenges like tool wear and edge effects.
• Ion figuring offers a noncontact alternative for precise material removal.
• Accurate control of ion beam dwell time is crucial for achieving desired surface contours.

Purpose of the Study:

• To develop and implement an ion-beam microcontouring process for millimeter-scale optics.
• To establish a deconvolution method for determining ion beam dwell functions.
• To demonstrate the feasibility of ion figuring for high-precision optical surface finishing.

Main Methods:

• A wavelet-based deconvolution algorithm was developed to compute the ion beam dwell function.
• The ion beam dwell function was synthesized from desired removal contours and known beam shapes.
• A duo-plasmatron ion source generated a focused argon ion beam, rastered by electrostatic plates.
• A computer guidance system controlled the ion beam rastering for precise material removal.

Main Results:

• The ion-beam microcontouring process was successfully implemented for millimeter-scale optics.
• A one-dimensional sinusoidal depth profile was machined in silicon with a root-mean-square error of 25 nm in one iteration.
• The wavelet-based algorithm effectively modeled the deconvolution process for determining the dwell function.

Conclusions:

• Ion-beam microcontouring is a viable and precise method for finishing small optical components.
• The developed wavelet-based algorithm provides accurate control over the material removal process.
• This noncontact technique overcomes limitations of conventional machining for micro-optics.