Optics manufacturing has long been more an art than a science due to the complex nature of the abrasion processes used, the cocktails of slurries, differential weighting etc. Sub-aperture polishing was introduced to bring a degree of determinism to the optics manufacturing process, and succeeded for the most part. As requirements on optics get tighter (requirements on areal density for mirrors, increased laser damage thresholds, reduced/nil birefringence), abrasion based approaches fail due to their fundamental need to strain the surface to effect material removal.

The basic issue with abrasive based processes is that they form an iterative technique to impart less sub-surface damage (SSD) to the substrate while removing most of the residual SSD from a previous iteration. RAPT Industries, Inc. has recast this manufacturing paradigm as illustrated on the right. A non-contact, damage-free chemical figuring step is used to remove the material. For polycrystalline substrates, an iterative buffing step may be needed due to differences in surface energies at grain boundaries. For most glass materials, this iterative buffing step is not required and RAP^TM can be used as the final figuring step. Material removal rates are typically several cubic millimeters per minute, and are exponentially dependent on temperature. Surface roughness for amorphous materials is seen to increase initially (until the recast layer from an earlier loose abrasive polishing step is completely removed - this is usually 5-10 microns thick), and then decreases. For well-prepared glass surfaces, RMS surface roughness aorund 3-5 Angstroms can be obtained without any intermediate polishing/buffing.

Fundamental improvements to torch stability have resulted in figure errors less than 42nm P-V, or 8nm RMS. An illustration of a five axis figuring is shown below:

RAPT Industries has introduced two product platforms to serve the optics manufacturing market. Both platforms have been demonstrated to provide an excellent return on investment to the customer. RAPT Industries, Inc. provides complete solutions in integrating the RAP^TM process into your manufacturing line. This includes the installation and configuring gas handling, effluent handling/scrubbing systems.

The first platform called the HELIOS is primarily meant for the custom large optics market segment. RAPT Industries works with the customer to develop the ideal machine configuration for their requirements. The customer specifies the number of plasma modules and their kinematic arrangement. Machine software might be configured to provide various modes of operation when multiple plasma modules are used. A commercial CNC controller is used to coordinate the various axes. For detailed specifications on the HELIOS platform, please click on the image.

RAPT Industries has a standard 5-axis configuration for making f/0.3 optics upto 500mm in clear aperture. The EOS platform has a single plasma torch that is positioned in five-axes with respect to the substrate to figure very fast aspheres. The EOS platform can also be outfitted with a VirtuRAP^TM module to provide additional capabilities for localized phase correction on fast aspheres. For detailed specifications on the EOS platform, please click on the image.

RAPT^TM Industries is currently accepting orders for the EOS and Helios tools. For more information on implementing these product platforms for your optics manufacturing needs, please contact sales@raptindustries.com.