Light Diffuser for Automotive Indicator

Introduction: Custom PRNDL Backlighting Diffuser   

When a tier-one automotive supplier was designing the backlighting module for a new gear shift indicator (otherwise known as a PRNDL), they came to Boyd to develop a custom light diffuser. The light diffuser would be a die-cut polycarbonate screen printed with inks of varying opacity and density levels. This variance allows differing amounts of light to come through the PRNDL, illuminating each icon with specific brightness and color.

Project Details

Tier-one Automotive Supplier

Gear Shift Indicator

Die-Cut Backlighting Diffuser


United States


PRNDL Backlighting Challenges

Boyd realized that there would be a few challenges to perfecting the customer’s requested appearance upon further investigation into the backlighting diffusion requirements. The PRNDL was set to be featured in a new line of premium vehicles, so the lighting had to meet strict visual standards for color, brightness, and opacity in all lighting conditions. Since there were multiple LEDs operating within the compact lighting fixture, it was also important to eliminate any hotspots or light leaks.


 PRNDL Diffuser Project Goals

  • Create a custom light diffuser that achieves uniform backlighting through the PRNDL
  • Ensure the backlighting met the visual specifications in all lighting conditions
  • Eliminate any hot spots or light leaks from the PRNDL
Boyd’s Printed PRNDL Diffuser Solution

Boyd was supplied with the PRNDL and an LED light fixture that was identical to the actual model used in the vehicle. The customer also provided target values for brightness and color for each character on the gear shift indicator.

Work began in Boyd’s state-of-the-art light lab. First, Boyd’s engineers used a spectroradiometer to get a reading on all five individual LEDs in the light fixture. This provided a luminance value in footlamberts, which became a reference point while creating the diffuser. To ensure uniformity across the iconography on the PRNDL, multiple spectroradiometer readings were taken across each character and subsequently averaged together. Various lighting scenarios were then tested in the lab to ensure the diffused backlighting accurately matched the desired look, regardless of external lighting conditions.

With these reference luminance values, it was possible to begin mixing colors for screen-printing the inks on the diffuser. The colors were mixed based on the spectroradiometer readings and the X/Y stimulus values provided by the customer. Each ink had to closely match the specified reference color, so several inks were created for different areas of the diffuser. The inks were screen printed on the polycarbonate sheet in three separate passes. On the fourth pass, an adhesive was printed onto the back of the diffuser for its easy adhesion to the PRNDL.

The PRNDL printing project also needed to reconcile the specified values with the actual look of the part. Based on several variables such as external lighting and different spectroradiometer readings, colors can match specifications but still look off on the PRNDL itself. To prevent this, densitometers and spectroradiometers were used to frequently spot-check different parts throughout production runs to ensure they met the correct values.

With five bright LEDs installed within the compact lighting fixture, it was also crucial that the PRNDL didn’t have hot spots or emanate light from undesired areas. The ink densities were monitored and adjusted throughout production to prevent bright spots and excessive light escaping through the edges of the PRNDL.

PRNDL Backlighting Diffuser Project Results

Ultimately, the light diffuser made its way to PRNDLs in two separate car models. Boyd was able to leverage its backlighting experience, printing expertise, and die-cutting capabilities to create a custom PRNDL diffuser solution that met all the project requirements.

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