Optics Primer: Manufacturing Shapes

Posted by Steve Rowe on

Like many industries, the manufacture of optics presents different challenges and definitions that must be understood early in the design process. As a result, Esco Optics periodically distributes educational blogs on a specific topic for various audience levels. If you are ‘new’ to the optics industry, the article below is for you. 

Circle, square, or triangle optics all appear to be basic shapes; however, the methods to manufacture each vary greatly which in turn affects cost. This article covers the techniques and processes used to give you insight on how shape impacts cost in precision glass optics. 

speedfam, double sided polisher, 16B, 20B, double sided polishingFor all of the scenarios discussed, we consider a baseline of commercial-grade optics using Corning 7980 fused silica. To maximize manufacturing efficiencies, plano-optics (flat) typically run on a double-sided polisher known as a SpeedFam. The top and bottom plates of the Speedfam have a polishing pad with a pattern of grooves that fill with a polishing medium. The optics are placed within carriers which rotate as they engage grooved teeth on the center and outside perimeter of the unit. Commercial optics typically run through two cycles. The first step, grinding, uses an abrasive pad that removes material to ensure two parallel surfaces. The second cycle, polishing, uses a finer grit pad that improves any surface imperfections from the grind. 

speedfam, double sided polisher, 16B, 20B, double sided polishingSquare optics follow the same process as round parts, but with some added challenges, namely corners. As mentioned above, round parts sit inside carriers and slowly rotate as the top and bottom pads polish the surfaces. For square parts, the corners are susceptible to suction created between the part and the polishing medium which can lead to low spots. When the part is removed it may have some spring and a slight curl that call the potato-chip effect; however, this is mainly a fabrication concern on larger parts with shallow thicknesses.

how are prisms made, optical prisms, right angle prisms, polishing prismsFor prism fabrication, the process changes as there are more steps involved for additional finished surfaces. Starting with a rectangular glass block, the top is finished using a method called blocking. Specifically, the glass is adhered to a flat plate using hot wax for its first grind followed by polishing. This process is repeated until all four sides are polished. Next, the glass is cut into segments that represent two prisms per square. The final face sides are again blocked and polished. Now that all sides of the glass are polished, the angle is cut along the hypotenuse to create two prisms. Lastly, the newly cut surface is ground and polished to its defined angle and specifications. Most of the time, simple prisms are always created in pairs so consider this multiple when ordering.

how are prisms made, optical prisms, right angle prisms, polishing prisms, glass prisms, laser prismsFrom this brief overview, optics of all shapes and sizes can prevent manufacturing challenges. That is why working with a manufacturer early in your design process can lead to insights that will save you time and money. Our sales team is always available to assist with your catalog or custom precision optics. Get started today with our online quote tool or drop us an email on this or other topics.

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