The Importance of Designing For Optical Assembly

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Optical design is the process of design optical devices to meet a set of performance constraints and requirements, including manufacturing and cost limitations. The process involves determining such parameters as surface profile types (diffractive, holographic, aspheric, spherical, and so on), the radius of curvature, material type, decenter (translation in X and Y), angular motion (tip/tilt), axial motion (translation in Z), and distance to next surface. There are several reasons why designing should be done before optical assembly.

 Stray light analysis

 Susceptibility to stray light should be analyzed before the final design. Stray light analysis is important in helping you avoid unwanted light, which can cause such problems as glass failure in laser applications, ghost images, and reduced contrast.

 Factoring environmental effects

 In the lab and using modeling software, it is difficult to simulate environmental effects. Designing for optical assembly takes into account adverse environmental conditions like stress, vibration during operation and shipment, acceleration/shock, underwater use, and temperature fluctuations.

 Application-specific assembly

 Most optical assembly requirements are application specific. This means you cannot rely on what an optical assembly company has been doing for other customers, even those with a similar product. Examples of these are:

  • Optical performance requirements that affect image quality and that are quantified by such metrics as encircled energy, Strehl ratio, modulation transfer fraction, pupil performance, and ghost reflection control.

  • Physical requirements like static volume, weight, dynamic volume, COG, and other configuration requirements.

  • Environmental requirements like temperature, vibration, electromagnetic shielding, and pressure.

  • Design constraints like dispersion and refraction indices, entrance and exit angles, and air-space between lenses

 High Precision

 Optical assembly requires high levels of precision. Coming up with radius of curvature, tilt, and other parameters is computationally intensive. It involves the use of such techniques as ray tracing to model how the optical device behaves (such as how a lens affects light that is passing through it). Failure to be precise leads to unusable products.

 Manufacturing costs and delivery schedule

 Optical design greatly influences manufacturing costs and delivery schedule. In today’s competitive marketplace where every dollar counts, it is important that these costs be as low as possible. Design should come before assembly because once the product has gone into production, then assembly becomes the dominant cost. Designing for optical assembly makes the assembly process simpler and consequently cheaper.

 Consultations/alignment before production

 After the initial proof-of-principle design, the next step in the design process is talking to all stakeholders to align the final system. This alignment and consultation is important because it helps you identify design elements that may be problematic to align, assemble, or fabricate. Failure to align could lead to the manufacture of unusable items, which is very costly.

 Aligning performance and positioning tolerances

 An opto-mechanical engineer should be brought in after the preliminary design to check positioning and performance tolerances. This will help identify mounts that best meet these tolerances. This ensures the size and cost of mounts does not fall outside the system specifications. The cost of the small changes that occur at this point pales in comparison to what it would cost to redo mounts after production.

 Developing alignment procedure

 Once you have a working opto-mechanical design, the assembly technician will come up with an alignment procedure. Paying attention to alignment makes for easier transition from prototype to the final product.

 Is the product designed to be reassembled?

 If you plan to reassemble in the future, then the design needs to consider such things as the adhesive and the mounting to use. Accessibility should also be considered in some components need to be replaced with time.

 At Penn Optical Coatings, we offer specialized and custom solutions over and above our custom solutions. We have the experience, team, and technology necessary to get you exactly what you require.