NALUX NANO OPTICAL, INC.
65 E.State Street, Suit2000
Columbus, Ohio 43215
c/o Schneider Downs
"Lighting a path to the future with nano-optics."
Single point diamond turning (SPDT) is a well known method for fabricating micro optics. The easiest way to think of SPDT is to imagine a standard lathe in your average machine shop because this is basically what a single point diamond turning machine is. The big difference between a standard lathe and a single point diamond turning machine is that the SPDT machine uses a diamond tipped bit for it's machining and it is able to machine surface finishes of a few nano meters in roughness and features that are down to about 1 micron in size. In keeping with the lathe analogy, single point diamond turning is used for radially symmetrical optics including aspherical shapes such as parabolas and for optics such as Fresnel lenses.
Single point diamond turning is mainly used with metals, crystals, and plastics. Glasses are much too hard and abrasive and don't yield a good surface finish so unfortunately diamond turning glass optics is really not an option.
When diamond turning metals, the main products made are metal mirrors and the molds for molding either plastic or glass optics. When creating mirrors, some materials used are copper, brass, and even gold. When creating a mold by diamond turning, usually the mold base and the bulk of the cavity insert is a type of stainless steel. The mold base will be machined by normal machine shop lathes and milling machines. The cavity insert, where the part is actually formed, will also be rough cut using a standard milling machine or lathe. However, when creating a cavity insert for optics, once the rough cut is completed, then the surface of the insert is coated with a thin (usually no more than 0.25mm) material that is hard enough to withstand the rigors of the molding process but still accepts machining. The diamond turning equipment then cuts the final shape into this thin coating to create the final cavity insert that is used in the production mold.
When diamond turning plastics, there are many plastics (acrylic, COP, polystyrene) that will accept the SPDT process but there is a catch. This catch is that some plastics, notably polycarbonate, haze over after they are diamond turned. This means that you can start with a block of water clear polycarbonate but after the diamond turning process is complete the polycarbonate is opaque. Because of this, it is important to consider the plastic to be used in production and if a lens is being made and the plastic for production is polycarbonate, then if you want to machine a prototype you may need to switch the material for the prototype to acrylic (a very good material for diamond turning) which may also necessitate a change in the curvature.
Optics created by this method are used in all kinds of applications. They can be used in astronomy, industry, and medical applications. One of the advantages of using single point diamond turning is the ability to make lens shapes very accurately without expensive tooling. Lead times can also be as short as a week since a mold isn't required. The only tooling required for the process is a diamond bit. One of the disadvantages of single point diamond turning is the fact that there can be a high reject rate because the surface finishes and accuracy requirements are so demanding and plastics tend to be less stable when subjected to machining operations than do metals. Additionally, the process isn't really suited for mass production because it takes much more time to machine an optic as opposed to molding an optic so diamond turned optics are often 100 to 1000 times more costly than a molded optic.
So, like any other process, single point diamond turning has it's strengths and it's weaknesses and Nalux has the equipment and the expertise in using the process to provide some of the finest optics possible.