# Optical Film with Microstructures to Regulate Viewing Angle of HUDs

## TL;DR

This paper introduces an optical film with microstructures to independently control horizontal and vertical viewing angles in head-up displays, improving visibility for drivers.

## Contribution

A novel method to independently regulate horizontal and vertical viewing angles using ellipsoid-shaped microstructures in an optical film.

## Key findings

- The horizontal viewing angle increased from 2° to 23° at 85% maximum luminance with the film.
- The vertical viewing angle increased from 2° to 10° at 85% maximum luminance with the film.
- Practical measurements confirmed significant differentiation between horizontal and vertical viewing angles.

## Abstract

Head-up displays (HUDs) can effectively enhance driving safety by projecting information—such as speed and maps—onto the windshield, thereby reducing blind spots caused by drivers looking down. As drivers need to observe road conditions within a wider horizontal viewing field, and considering that the observed angle in a vertical direction is relatively small, it becomes reasonable for an HUD to present a larger horizontal viewing angle than vertical viewing angle. This paper proposes a method to independently regulate the horizontal and vertical viewing angles. The original microstructure morphology is modeled as an ellipsoid, and the curvatures of the ellipsoid’s major and minor axes are calculated according to the required viewing angles. The simulation results show that the horizontal viewing angle corresponding to 85% of the maximum luminance increases from 2° without the film to 20° with the film, while the vertical viewing angle increases from 2° to 8°. The optical film with the designed microstructures is prepared and measured. The practical measurement results indicate that the tested horizontal and vertical viewing angles exhibit significant differentiation. At 85% of the maximum luminance, the horizontal viewing angle increases from 2° without the film to 23° with the film, while the vertical viewing angle increases from 2° to 10°. These results meet the requirements for independently regulating horizontal and vertical viewing angles and widening the horizontal viewing angle.