Three Opto-Mechanical Design Challenges



Opto-mechanics refers to the mechanical design of optical systems. Opto-mechanical design is sometimes dismissed as little more than "wrapping metal" around the optics, but that perspective is detrimental to building the best operating optical instrument.

Opto-mechanical design is a specialized field. An optical system's performance relies on the precise position and orientation of each optical element. Recognizing the challenges associated with opto-mechanics gives insight into how to design an optical system for superior performance. Three major challenges for opto-mechanical designers are explored in this article.

1. Translating between mechanical and optical tolerances

Optical engineers and mechanical engineers use different design software. Optics software treats the objects as floating in free space. Optical tolerances are based on how misalignment of those optical elements affects optical performance tolerances. Mechanical software, by contrast, considers the space around the optical elements. Mechanical tolerances are based on manufacturability. Matching the optical tolerances to the mechanical tolerances is a complex balancing act.

Takeaway: Work with optics suppliers who have the skills to review and collaborate on opto-mechanical design.

2. Surface-finishing mechanical parts correctly for optical systems

Optical systems are designed with the intention that the non-optical elements do not affect the optical performance. The primary concern is scattering from mechanical parts, which redirects unwanted light back into the optical system. For this reason, the interior of the mechanical parts needs to have a high-quality matte black surface so that stray light is absorbed rather than scattered. Creating such a coating is not as simple as painting the interior surface. Conventional paint releases chemicals and colorants that can contaminate the optical elements. Mechanical components, therefore, must be designed with the understanding that the interiors of all the parts require a precise interior pre-finishing to make the surface accept a matte black anodized coating. That requirement limits the allowable size and shape of the mechanical components. It is critical that the opto-mechanical design recognizes those limitations.

Takeaway: Work with optics vendors who can assist in finding optics-compatible machinists.

3. Designing for assembly

Just because the components of an opto-mechanical design fit together does not mean that the system is manufacturable. An opto-mechanical design must consider the methods by which the system will be assembled. An optical system should be straightforward to assemble, and the assembly process should place the optical elements with precision and consistency to minimize the need for "tweaking." (See our previous post on the importance of designing for optical assembly.)

Takeaway: Work with optics vendors who understand optical assembly or that can offer assembly services.

By working with vendors who understand the specialized nature of opto-mechanical design, you can ensure that your system assembly enhances optical performance rather than harming it. At Ross, we have a long track record of helping our customers balance out their optical and mechanical designs to get the best overall system performance. Give us a call and talk to one of our engineers to learn how we can help with your project.

Our free guide includes cost considerations for mechanical design, as well as optical systems and coating design, and designing with specialty optics. Download it now!

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