Holographic HUD

A holographic head-up display (HUD), comprising:

• a picture generation unit (PGU) including at least one laser light source to generate an optical image to be projected on a HUD;
• a first mirror to reflect the optical image from the PGU;
• a second mirror to reflect the optical image reflected by the first mirror;
• a holographic optical element (HOE) to diffract the optical image reflected by the second mirror at a first diffraction angle to provide an output optical image in a target direction;
• and
• a transmissive compensatory HOE disposed between the PGU and the first mirror to diffract the optical image from the PGU at a second diffraction angle,
• wherein, in response to change of a wavelength of the optical image from the PGU, the transmissive compensatory HOE is configured to diffract the optical image from the PGU at a third diffraction angle different from the second diffraction angle such that the HOE provides the output optical image in the target direction based on the following equation:
• λ=2Λ sin(θi+θtilt),
• where λ is a wavelength of light incident to the transmissive compensatory HOE, Λ is a period of a volume grating of an interference pattern formed in the transmissive compensatory HOE, θi is an incident angle of the light incident to the transmissive compensatory HOE, and θtilt is a diffraction angle of the transmissive compensatory HOE.