Modeling of light-emitting diode wavefronts for the optimization of transmission holograms

Abstract

The objective of applying transmission holograms in automotive headlamp systems requires the adaptation of holograms to divergent and polychromatic light sources like light-emitting diodes (LEDs). In this paper, four different options to describe the scalar light waves emitted by a typical automotive LED are regarded. This includes a new approach to determine the LED's wavefront from interferometric measurements. Computer-generated holograms are designed considering the different LED approximations and recorded into a photopolymer. The holograms are reconstructed with the LED and the resulting images are analyzed to evaluate the quality of the wave descriptions. In this paper, we show that our presented new approach leads to better results in comparison to other wave descriptions. The enhancement is evaluated by the correlation between reconstructed and ideal images. In contrast to the next best approximation, a spherical wave, the correlation coefficient increased by 0.18% at 532 nm, 1.69% at 590 nm, and 0.75% at 620 nm.

Advanced printer for volume holographic optical elements in automotive exterior lighting

“…Here, k is the hologram with certain exposure properties and i, j encodes the specific subhologram (5). The diffraction efficiency of each hologram is then determined by (6).…”

Enhancement of Luminous Intensity Emission from Incoherent LED Light Sources within the Detection Angle of 10° Using Metalenses

“…Light-emitting diodes (LEDs) are commonly used as practical light sources [ 63 ]. However, the luminous intensity from LEDs dramatically decreases as the light propagates due to the emission of diverging spherical waves [ 64 ]. The intensity of light extraction efficiency of LEDs has been enhanced using microlens arrays [ 65 , 66 , 67 ], surface roughening [ 68 , 69 , 70 , 71 ], photonic crystal patterning [ 72 , 73 ], patterned substrates [ 74 , 75 ], and surface plasmons [ 76 , 77 , 78 ].…”

Manufacturing of volume holographic cell arrays for usage with uncollimated LEDs in automotive applications

“…That means each new illumination system would require a specific manufacturing setup, as the reference beam has to be formed accordingly. But achieving such large divergence angles with lasers is nearly impossible with common lenses and generating point sources by diffraction at small apertures does not give accurate results as the characteristics strongly depend on the lightsource used [9,10].…”