TY - JOUR

T1 - Lensless projection of automotive light distributions using an advanced printer for volume holographic optical elements

AU - Hiller, Lukas T.

AU - Wallaschek, Jörg

N1 - Publisher Copyright: © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 International License.

PY - 2024/6/14

Y1 - 2024/6/14

N2 - Volume holographic optical elements (vHOEs) are currently used in various applications, such as augmented reality displays or wearables. Yet, the use of vHOEs as illumination optics has not found its way into products. In automotive exterior lighting, vHOEs could enable unique styling, reduction of installation space, weight, and material. However, in headlamps, rear lamps, or signal lamps, several technical and conceptional challenges must be addressed. One of these challenges is to replace lasers, which are expensive and have high safety demands, by light emitting diodes (LEDs), which are widely used in the field of automotive lighting. The reconstruction of volume holograms with LEDs is straightforward for graphical holograms showing a three-dimensional scene. For automotive exterior lighting, however, the hologram is not just a design element, but in addition must feature a light distribution fulfilling all the legal requirements. The vHOE thus becomes the most important functional element of the lighting system projecting the light distribution without an additional lens. For instance, the low beam distribution must provide a sharp, asymmetric cutoff line and white color, which turns out to be difficult. We have developed an improved manufacturing technique of such vHOEs, using two spatial light modulators. We present the design, the holographic printer setup, and first experimental results of vHOE samples.

AB - Volume holographic optical elements (vHOEs) are currently used in various applications, such as augmented reality displays or wearables. Yet, the use of vHOEs as illumination optics has not found its way into products. In automotive exterior lighting, vHOEs could enable unique styling, reduction of installation space, weight, and material. However, in headlamps, rear lamps, or signal lamps, several technical and conceptional challenges must be addressed. One of these challenges is to replace lasers, which are expensive and have high safety demands, by light emitting diodes (LEDs), which are widely used in the field of automotive lighting. The reconstruction of volume holograms with LEDs is straightforward for graphical holograms showing a three-dimensional scene. For automotive exterior lighting, however, the hologram is not just a design element, but in addition must feature a light distribution fulfilling all the legal requirements. The vHOE thus becomes the most important functional element of the lighting system projecting the light distribution without an additional lens. For instance, the low beam distribution must provide a sharp, asymmetric cutoff line and white color, which turns out to be difficult. We have developed an improved manufacturing technique of such vHOEs, using two spatial light modulators. We present the design, the holographic printer setup, and first experimental results of vHOE samples.

KW - automotive lighting

KW - hologram printer

KW - holographic optical element

KW - lensless projection

KW - light emitting diode

UR - http://www.scopus.com/inward/record.url?scp=85211075561&partnerID=8YFLogxK

U2 - 10.1117/1.OE.63.11.111803

DO - 10.1117/1.OE.63.11.111803

M3 - Article

AN - SCOPUS:85211075561

VL - 63

SP - 111803

JO - Optical engineering

JF - Optical engineering

SN - 0091-3286

IS - 11

ER -