Robust optical design of high-contrast vehicle headlamps with cylindrical lens array and inverted triangular beam pattern.

Headlamps are essential for safe night driving, as they must provide sufficient brightness to illuminate the road while minimizing glare for other drivers. Designing low-beam optics is more complex than general lighting optics due to the need for a high-contrast cutoff line, with the brightest point positioned near its edge. This challenge becomes even greater when working with compact optical systems. In this paper, we propose a robust optical design to address this issue effectively. We develop low-beam optics for bicycle headlamps using a cylindrical lens array (CLA) combined with reflective optics to create a specialized light pattern. The CLA spreads the optical pattern horizontally to form the cutoff line; however, this alone does not ensure optimal performance. To overcome this limitation, we introduce a novel design principle: the light pattern generated by the reflector, before passing through the CLA, should be inverse-triangular or trapezoidal. This approach enables the CLA to shift the brightest point upward and closer to the cutoff line, solving a key challenge in previous designs.