Manufacturing and Measurement of Freeform Optics

What is a Freeform optic?

When creating freeform optics, unlike standard flat or curved shapes, these mirrors incorporate multiple planes and shapes into one solid optic. They must have one surface that “…has no translational or rotational symmetry about axes normal to the mean plane.” This is the toroidal surface that makes freeform optics useful and different from all other types of optics.  With a traditional optic the surface shapes are either spherical or aspherical. A freeform optic will always have an asymmetrical optical surface. 

A freeform optic designed to include spherical, aspherical and toroidal surfaces into a single part, making them complex to design correctly and challenging to manufacture from both a shaping and coating perspective.

Toroidal surfaces can either be positive or negative and in some cases, an optic may have both types of surfaces and focal points depending on its intended design. Meaning, with either an ellipse or parabola focal point. CMM Optic is able to create freeform optics that include both surface types, or a cylinder lens or cylinder mirror that uses one surface design or the other. 

Since freeform optics can be created in multiple ways, but with a wide range of accuracy levels, single point diamond turning can be leveraged to create a polished surface with pinpoint accuracy while removing aluminum or other metal.

By using our proven SPDT processes, CMM Optics is especially suited for creating many forms of custom metal anamorphic optic designs. In addition, CMM is able to create precision versions of made-to-order optics. With several different multi-axis diamond turning machines on our floor, we are able to create those harder to source, larger-sized optics (0.5 mm to 500 mm). 

As access to advanced metrology is also a key to creating high-quality freeform optics, we provide not only significantly experienced milling operation skills, but also verification of performance design with our proven interferometric methodology. After every batch of optics made, we thoroughly measure and verify each part to ensure the ordered performance when installed

Applications for freeform optics are growing, and are commonly used in LED illumination and laser beam shaping, in biomedical engineering and aerospace and are allowing for developments in optical system optimization. For uses that require a high aspect ratio, freeform optics allow for a much improved imaging performance. When anamorphic mirrors are used in a more mundane application, auto mirrors, a driver can enjoy safer driving with the elimination of the blind spot.

For more information, we recommend reading these articles.

http://centerfreeformoptics.org/what-is-freeform-optics/
https://spie.org/news/designing-with-toroids?SSO=1
https://wp.optics.arizona.edu/optomech/wp-content/uploads/sites/53/2016/10/1-s2.0-S0007850613001935-main.pdf