Plasma Jet Machining

Abstract

Plasma Jet Machining (PJM) is a surface figuring technology based on atmospheric plasma assisted chemical etching or deposition, respectively. In both cases a sub‐aperture plasma jet source is used combined with a CNC multi‐axes system for the processing of curved surfaces. It is under development for the surface figuring of a variety of optical materials by IOM for about 15 years. PJM is capable to figure deep aspheric or free‐form substrates with high material removal rate and high spatial resolution. Based on chemical reactions between plasma generated radicals and the surface PJM does not introduce any damage to the processed surface and sub‐surface region in contrast to abrasive techniques. Deterministic deposition of SiOx layers and subsequent proportional transfer using ion beams or polishing is another plasma jet based technique for surface figuring that extends the range of machinable materials. The article gives an overview on the current state of PJM development in IOM and shows examples of its application.

Plasma jet polishing of optical surfaces

“…The IR camera is used to measure temperature profiles for moving PJ and still standing PJ, as shown in Figure 2(a), while the mean temperature of the pyrometer measuring spot is TPyro= 1600°C. Assuming a linear relationship between the temperature readings of the IR camera and the pyrometer within the elliptical area of the pyrometer spot, and scaling the mean of the IR camera temperature to the value of the pyrometer temperature, a scaling function can be obtained which is given in Equation (1). Now, the maximum surface temperature in the contact zone of the PJ to the sample can be obtained using the IR camera and the principle of the closed-loop can be transferred.…”

“…Atmospheric pressure plasma jet (PJ) is an established tool for applications in optical surface manufacturing. The shape generation as well as the figure error correction capabilities have been further improved and adapted to current requirements in recent years, mainly on Fused Silica (FS), but also on other optical materials [1][2][3]. The application as a polishing tool has also moved into focus in recent years, in order to be able to cover the process chain of optics manufacturing with PJ technology.…”

Jet morphology analysis of microwave‐generated plasma for microfabrication of optics

“…As a microscale energy beam with chemical etching capability, it has advantages in fabricating high aspect ratio structures for hard and brittle optical materials. [ 15–17 ] Arnold et al and Adam et al [ 18,19 ] have developed a series of microwave plasma jets used for the etching process. Depending on the size of the plasma jet device and the working parameters (applied power, the composition of the working gas, etc), the series of plasma jets have different morphologies, resulting in that the etching process could have different material removal rates (MRR) ranging from 0.1 to 30 mm 3 /min and the full width at half maximum (FWHM) of the removal profile ranging from 0.2 to 12 mm, meeting different processing requirements.…”

Introducing Full-Aperture FJP (faFJP), a Technique for Manufacturing Sub-Millimetre Aspheres

“…Unfortunately, optics designers have been insisting on using aspherical lenses, due to their better performance in handling optical rays and because the use of one of these types of lenses replaces up to five spherical lenses within the design of an optical system. The fact that aspherical lenses possess line symmetry, rather than point symmetries, forced optical fabrication engineers to invent numerous dedicated polishing techniques, each featuring the generation and application of sub-aperture footprints (local polishing spots within the clear aperture of the optical surface) such as belts [1], bonnets [2], fluid jets [3,4], ion beams [5], plasma jets [6], magnetorheological fluids [7], rotating spheres [8] or polyurethane needles. All these techniques distinguish themselves in the type of aspherical shapes producible, quality generable or dimensions manageable.…”