Light Pipe

Usually made of a clear plastic material, light pipes “pipe” light from a source (usually an LED) inside a hardware device to a visible part on the outside of the hardware. You’ll find these behind indicator lights on hardware. Often, the outside part of your hardware where you need an indicator light is far away from the circuit board where your LED is mounted, and you need to get the light from the board to the viewer outside.

Light pipes can be designed and simulated in optical software to find the optimal shape that brings the most light to the outside. They can be “tested out” in the software before anything is ever prototyped in real life. With this optical engineering you save time and money in HW R&D stages!

At Spire Starter, we get asked by mechanical engineers and industrial designers to simply tell them in a few sentences how to design a light pipe. While there is guidance we can share to give you a design starting point, it’s just that: a starting point!

In general, you want to start with:

  1. gradual slopes to any curves in your geometry,
  2. good LED-to-exit area placement to allow for those gradual slopes,
  3. clear material,
  4. no texture except where you want light to leave the light pipe.

You can do all that, and if you’re doing a legit optical design that’s just Step 1, not the end of the process. You’re not going to have ideal geometry from those steps. So, after that, comes many iterations, dozens, even hundreds, of simulations using millions or billions of ray calculations to optimize the performance.

Could you do those design iterations on a lab bench instead? Sure, you could, but chances are you won’t have the resources in man hours, time remaining in your project, and monetary costs to arrive at an optimized light pipe design.
Still, if you’re just doing a rough, proof-of-concept version, you might get “good enough” with real-life design iterations. If you need something more polished, book a free preliminary consultation with Spire Starter to discuss optical design!

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