Case History #3: Side view Mirrors With Turn Signals

Polaroid Corp. initiated a program for a client to develop turn signal lights that are incorporated into the side view mirror assemblies of vehicles. The objectives were as follows.

Lights must be bright enough to be seen in bright sunlight. The viewing angle must be wide enough so the lights are visible from positions both beside the vehicle and behind the vehicle. Light must emerge from the visible surface of the mirror yet not create glare at night. The system must fit into existing mirror housings.

Surveying the available technology and its trends

The planned system was intended to use Polaroid's proprietary holographic optical elements in an unspecified way and TIG, acting as a subcontractor, was to locate and/or design a suitable light source. We surveyed the available sources and selected new high output LEDs.

Carrying out design, prototype fabrication and testing

After choosing a source TIG designed the optical system a combination of non imaging, total internal reflecting optics, holographic optical elements and the mirror coating.

The result was a monolithic system comprising the mirror glass, the optical elements and the light source. This eliminated any bare surfaces except the outer surface of the mirror. Because of this feature scattered light was reduced to the point where it was not objectionable at night even without a dimming feature which a competitive design required.

We fabricated the light sources and non-imaging optics and Polaroid fabricated the holographic optical elements. TIG carried out proprietary image-based photometric measurements to characterize the performance.

Working with standards setting organizations

TIG also developed a basis for standards for the proposed system.