Improvements to holographic exhibits are ready to enhance virtual and augmented reality

Researchers have developed a new approach that improves the image quality and contrast for holographic exhibits. The new technology can help improve near-eye displays used for virtual and augmented reality applications.

“Augmented and virtual reality systems intend to have a transformative impact on our society by providing a seamless interface between the user and the digital world,” said Jonghyun Kim, research team member at technology company NVIDIA and Stanford University. . “Holographic displays can overcome some of the biggest remaining challenges for these systems by enhancing the user experience and enabling more compact devices.”

In Optics, The Optical Society (OSA) journal, the researchers describe their new holographic display technology called Michelson holography. The approach combines a new optical setup inspired by Michelson interferometry with a recent software development. The setup generates the interference patterns needed to make digital holograms.

“Although we have recently seen tremendous progress with computer-generated holography through machine learning, these algorithms are fundamentally limited by the underlying hardware,” Kim said. “Together we have designed a new hardware configuration and a new algorithm to overcome some of these limitations and show modern results.”

Improving quality Holographic displays can outperform other 3D display technologies used for virtual and augmented reality by enabling more compact screens, enhancing the user’s ability to focus their eyes at different distances, and providing the opportunity to suitable for users wearing corrective lenses. However, the technology has not yet reached the image quality of more conventional technologies.

For holographic displays, the image quality is limited by an optical component known as a phase-only spatial light modulator (SLM). SLMs create the differentiated light that creates the interference pattern needed to form visible 3-D images. However, the phase-only SLMs commonly used for holography exhibit low degradation efficiency that significantly degrades the perceived image quality, especially image contrast.

Because it is difficult to dramatically increase the diffraction efficiency of SLMs, the researchers designed a completely new optical architecture to create holographic images. Instead of using a single-phase SLM like most setups, their Michelson holographic approach uses two SLMs for phase only.

“The core idea of ​​Michelson holography is to destructively blend the derived light from one SLM using the uninterrupted light of the other,” Kim said. “It allows the uninterrupted light to shape the image rather than create stains and other artifacts.”

Image Optimization The researchers combined this new hardware setup with a camera-in-the-loop (CITL) optimization procedure that they adapted for their optical setup. CITL optimization is a computer approach that can be used to directly optimize a hologram or to train a computer model based on a neural network.

CITL allowed the researchers to use a camera to capture a series of displayed images. This meant that they could correct minor misalignments of the optical system without using precise measuring devices.

“Once the computer model is trained, it can be used to figure out exactly what a captured image would look like without physically capturing it,” Kim said. “This means that the entire optical setup in the cloud can be simulated to perform real-time derivation of computer problems with parallel calculations. It can be useful, for example, to calculate a computer-generated hologram for a complex 3D scene.”

The researchers tested their new Michelson holographic architecture using an optical setup on the table in their laboratory. They used it to display several 2-D and 3-D holographic images, which were recorded with a regular camera. The demonstration showed that the dual SLM holographic display with CITL calibration provides significantly better image quality than existing computer-generated hologram approaches.

To make the new system practical, the layout of the table must be translated to a system small enough to be incorporated into a portable supplement or virtual reality system. The researchers point out that their approach to hardware and software design can be useful for improving other applications of computer screens and computer imaging in general.