SPIE presentation addresses micromobility reflectors

Joe Naiman

Special to the Village News

SPIE, the international scientific society dedicated to optical science, returned to the San Diego Convention Center for the Aug. 1-5 Optics and Photonics conference, and an Aug. 4 presentation addressed the issue of providing adequate illumination for electric scooter, electric bicycle, and other micromobility vehicle users without creating light interference for oncoming vehicles or pedestrians.

Rubing Wu of the Rose-Hulman Institute of Technology was the presenter for Iterative and Inverse Design of a Segmented Reflector for Uniform Illumination on the Road. Hossein Alisafaee of Rose-Hulman, which is in the Indiana town of Terre Haute, contributed to the research.

Scooters and other micromobility users have lighting available, but the current designs are not only inefficient in terms of energy output but inconvenient for other road users. "Micromobility users can see the road clearly, but too much light blinds the oncoming traffic," Wu said.

A macrofocal reflector system is the proposed solution to keeping light away from the eyes of oncoming motorists and pedestrians. "Doing this will allow us to extend the light horizontally and vertically," Wu said.

The reflector in the Rose-Hulman research is 50 millimeters by 40 millimeters. It has an illumination range of approximately 20 meters. The maximum brightness is 1,460 candela, which is five times the brightness of a conventional electric scooter or bicycle headlamp.

"For the macrofocal reflector we actually design a single facet," Wu said.

The reflector has a thin aluminum coating, and the housing structure prevents the reflector and the light-emitting diode system from breaking if the vehicle falls. The wires and joints are reinforced to ensure stability. A rechargeable battery powers the illumination system; the power is 4.6 watts and the target voltage regulation is 3.2 volts although the voltage is adjustable.

The cutoff angle is adjusted so that the illumination system does not interfere with oncoming traffic. That cutoff angle limits height to approximately 1 1/2 meters, so any height over that will not be affected by the oncoming light.

"The light is uniform on the computer simulation, but the light pattern is not quite uniform on the prototype," Wu said.

The proposed inverse design of the reflector sought to obtain consistency in manufacturing, although Wu acknowledges that manufacturing defects are inevitable. "There is always going to be some error," he said.

The design is based on meeting the German road regulation standard since no international standard for micromobility device illumination currently exists. "The last thing will be to check the final design with the corresponding regulations," Wu said.