See-through Holographic Display Research Articles

See-through holographic display with randomly distributed partial computer generated holograms.

Holographic displays have the feature to show images out of the plane of the device itself, which is especially favored for augmented reality (AR) applications where the images need to be merged with the real world. In existing cases of AR holographic display, a combiner is used to converge the light path of the display image and surrounding scene toward the viewer's eye. In this paper, the idea of combining the holographic device and the combiner has been proposed, resulting in a see-through holographic display. In order to maintain the see-through quality of the device, the concept of partial hologram has been introduced, which means only a part of the area on the device has the holographic fringe pattern while leaving the rest fully transparent. Experiment and theoretical investigation shows that an evenly yet randomly distributed partial hologram provides the best holographic image quality assuming a fixed percentage of the holographic area on the device. A passive computer generated hologram (CGH) with two phase levels has been designed and fabricated for the verification. With partial hologram sharing 25% of the whole area, the CGH exhibits 90.9% of total transmission and 72.2% of parallel transmission. The demonstration shows a high see-through quality while providing a clear holographic image.

Viewing angle enlargement in holographic augmented reality using an off-axis holographic lens

In this paper, a viewing angle enlargement method of holographic display using an off-axis holographic lens is proposed, and verification experiment of viewing angle enlargement is developed by using a single spatial light modulator (SLM) and an off-axis holographic lens fabricated by the holographic recording. The experimental results indicate that the viewing angle of holographic reconstructed image is increased to 11.2°, which is about 3.8 times as wide as the original viewing angle formed by the single SLM only. Furthermore, a see-through holographic display system for augmented reality (AR) is constructed, where virtual image is generated by holographic projection. The real scene and the virtual image will fuse together by using the off-axis holographic lens as the image combiner. The results prove that the proposed system can reconstruct virtual three-dimensional (3D) image with correct depth cues, solve the accommodation-vergence conflict problem effectively, and achieve the holographic AR 3D display effect without visual fatigue.