Automotive intelligence is an unstoppable process, and as a key display system in the intelligent cockpit, augmented reality head-up display (AR-HUD) is becoming more and more important. AR-HUD presents the vehicle's sensor information, driving speed information, navigation information, and other enhanced image information integrated with the real environment to the driver, thus improving the driving experience and safety. Large field of view and eye box are very important for AR-HUD. However, for an AR-HUD system based on traditional geometric imaging methods, AR-HUD systems with a large field of view and large eye box require a larger-scale volume of the optical system, which is determined by the Rach invariant of the imaging system. The only display method that can break the limitation of Rach invariant is optical waveguide display technology, including relief grating optical waveguide, geometric optical waveguide, and volume holographic optical waveguide. The relief grating optical waveguide has high production cost and is difficult to be used for large-scale volume optical waveguide displays, while the geometric optical waveguide has low production efficiency and is not suitable for large-scale volume optical waveguide displays. Volume holographic optical waveguides are manufactured by laser exposure, which has the potential advantage to realize the display of large-scale volume waveguides. However, the preparation of traditional volume holographic optical waveguides requires the use of coupling prisms. Filling refractive index matching solution between the holographic photosensitive material and the coupling prisms will lead to troublesome manufacturing problems and is not conducive to automatic manufacturing.

In this paper, a complete theoretical derivation method of exposure volume holographic grating under the condition of non-total reflection is realized. Starting from the exposure parameters of holographic optical waveguides, this paper gives the parameter design method of large-scale volume holographic optical waveguide exposure under non-total reflection conditions based on grating degeneracy theory in the vector sphere. It is concluded that the transmitted-volume holographic grating and the transition grating used for two-dimensional pupil expansion are not valid to be exposed under the condition of non-total reflection, and the reflective volume holographic grating waveguides can only be manufactured under the condition of non-total reflection. Based on the theoretical derivation, a fully automatic splicing and exposure system of volume holographic optical waveguides is designed and built, which successfully realizes the manufacturing of large-scale volume holographic optical waveguides.

Based on the exposure angle parameters obtained by theoretical calculation, a large-scale volume holographic optical waveguide splicing exposure system is built, and a large-scale volume holographic optical waveguide with a size of 130 mm×270 mm is fabricated through 18 splicing. The projector is used as the image source for display, and the AR display results are obtained. Although we realize monochrome display, the exposure angle parameters are wavelength independent, which means that this set of parameters can be used to make three primary color waveguides using three color lasers for color display. In addition, a two-dimensional pupil expansion waveguide can be composed of two one-dimensional pupil expansion waveguides, so the method in this paper can be applied to the development of a two-dimensional pupil expansion waveguide for AR-HUD applications.

Starting from the exposure parameters of holographic optical waveguides, this paper gives the parameter design method of large-scale volume holographic optical waveguide exposure under non-total reflection conditions based on grating degeneracy theory in the vector sphere. A large-scale volume holographic optical waveguide automatic exposure system is designed and built. The large-scale volume holographic optical waveguide with a size of 130 mm×270 mm is demonstrated, and the AR display results are obtained. The successful breakthrough of this technology has laid a solid foundation for the mass production and wide application of large-scale volume holographic optical waveguide AR-HUD.