There are two main components in a light pipe design: the LED light source and the light pipe. The design engineer must pay close attention to the pairing of the light pipe and the LED to minimize light loss and ensure best performance.
The LED must be effectively matched to the entrance of the light pipe to allow for proper light capture for maximum light transfer.
The importance of reducing light bleed
Light bleed occurs when light from the LED can be visible around the LED and light pipe area. Light bleed causes false-readings, muted and blended colors, crosstalk between adjacent light pipes, and unwanted glow in the enclosure.
When a rigid light pipe is located over the LED, it allows for a certain amount of light bleed at the base of the light pipe. A flexible light pipe is designed to provide less light bleed with a coated optical fiber and a light resistant black adapter. Rigid and flexible light pipes can also be PCB mounted. To eliminate light bleed, rigid and flexible light pipes are now available with a fully enclosed adapter as well.
Maximum design flexibility occurs when the designer can choose between designing with individual components (LED and light pipe) or using a complete system solution that includes both elements. Bivar offers both options.
LED choices for light pipe pairing
Two types of LEDs are commonly available. Surface mount LEDs, often called SMD (surface mount device) LEDs, are mounted on the surface of the PCB and are smaller and brighter than through hole LEDs. Both types are offered in a wide range of sizes, colors, luminosities, and powers. Through-hole LEDs are mounted by inserting leads through the PCB and soldering to provide a stronger connection between layers; the soldering also increases protection against mechanical stress.