30 Oct LED Light Pipes
LEDs are nearly ubiquitous in modern products. However, as devices continue to shrink in size and increase in complexity, it can often be impossible to locate an LED exactly where you want it in a device. This is where light pipes come into play: they provide a path for light to travel from a light source (typically an LED) to another location some distance away.
Light pipes operate under the principle of total internal reflection (or TIR). The basic idea of TIR is that if all light traveling through an object maintains a certain critical angle as it contacts the outer surface of that material, then it is entirely reflected and none is transmitted (and lost) to ambient. Through careful choice of a light pipe’s material, surface finish, and geometry, it’s possible to redirect nearly 100% of a LEDs output from one location to another.
An important distinction should be made between light “pipes” and light “diffusers”. Although these terms are often used interchangeably, they are actually different things and require very different design considerations. Where light pipes are great at moving light from one place to another, light diffusers are used to blend light sources together to create a smooth, uniform illuminated surface. A common example of a light diffuser is the light ring on the popular Amazon Alexa speakers – several discrete LEDs combined with a light diffuser are used to create a nice smooth illuminated ring.
With so many design considerations, prototyping functional light pipes or diffusers may seem like a daunting challenge. Thankfully, due to improvements in modern 3D printing (particularly stereolithography), it’s possible to print functional light pipe prototypes with near-production performance. Although not a complete replacement for true molded light pipes, the ability to 3D print allows for very rapid iterations and can help inform light pipe design early on in the development process.
- LED Light Pipes - October 30, 2020