2D Pupil Expansion in Plastic Curved Holographic Waveguide Combiner for AR/HUD

Abstract

Waveguide combiners for head up display (HUD) and augmented reality (AR) have the unique advantage to decouple the field of view from the eye box size thanks to pupil replication. However, in order for the image to propagate without aberration in the waveguide, its surfaces have been kept flat and parallel. Here we are presenting a curved waveguide with 2D pupil replication that takes advantage of holographic optical elements for light injection, redirection, and extraction. These HOEs have been designed to compensate for any propagation aberration, so that the extracted image is clear to the viewer. Both ray tracing model and early experimental demonstrator are discussed.

Manufacturing holographic optical elements for automotive industry needs

“…Head-up displays (HUDs) are nowadays widely applied in vehicles and airplanes to illustrate information, for example speed, temperature, navigation and pedestrians and bicycles warning symbol. The field-of-view (FOV) of a HUD with the displayed information is overlayed onto the street view through a transparent glass, e.g., windshield or another combiner [8,9,11,12,13,14,15,16,17]. It is not necessary for the driver to move their heads and look up and down to read the information from separate screens anymore.…”

“…The conventional technologies, based only on mirrors and lenses, cannot provide full colors AR functions within a small and lightweight device, which is very important for automotive and consumer industries. Such AR-HUD devices can be produced only by introducing HOEs into AR domain [8,9,11,13,15,16,17] Two important factors for an implementation of AR-HUDs in a vehicle are the location and the size of the setup. Normally, in a vehicle the eye-box is at a fixed position, sometimes with limited possibilities to adjust it.…”

“…Waveguide systems, with only HOEs and exploiting TIR in lightguides made out of glass or polymer, allow to produce large 2D pupil expanders thus significantly enlarging the eye-box [15,16,17]. The light, which is coupled in with an HOE from the PGU into the glass substrate, is distributed with multiple TIR in the substrate and coupled out from different positions on the glass substrate again with an HOE, as it is shown above in section 2.1 Figure 2.…”

“…The HOE structure can also be one dimensional, which diffracts the light from one direction only to one other direction. In this case, a 2D pupil expansion normally needs three HOEs [16]. The HOE structure could also be multi-dimensional, which could diffract the light from one direction to multiple directions.…”

Advanced multilayer holographic technology for the realization of compact AR-HUDs

“…The usage of HUDs is for the information illustration such as speed, temperature, navigation, and safety warning. It is widely applied in the automotive area and airplanes but also not limited in those areas [1][2][3][4][5][6][7][8][9][10]. With the development of the headup displays, larger FOV, large projection distances, and larger eyebox (aperture) are required for a better using and experience of this application.…”