3D hologram adopts SLM, DM for hi-res displays

Article By : KAIST

Adding diffusers or frosted glasses to wavefront modulators in 3D holographic display improves the size and viewing angle by more than 2,600 times.

Creating full-sized organs for 3D analysis remains a challenge due to the limitations of hologram-generation techniques. At the Korea Advanced Institute of Science and Technology (KAIST), a research team has developed a 3D holographic display that performs more than 2,600 times better than existing holographic displays.

The study is expected to improve the limited size and viewing angle of 3D images, which were a major problem of the current holographic displays, according to the researchers.

Contesting constraints

3D holograms in films are created with computer graphic effects. Methods for creating true 3D holograms are still being studied. Due to the difficulty of generating real 3D images, recent VR and AR devices project two different 2D images onto a viewer to induce optical illusions.

To create a 3D hologram that can be viewed without special equipment such as 3D glasses, the wavefront of light must be controlled using wavefront modulators such as spatial light modulators (SLMs) and deformable mirrors (DMs). A wavefront modulator is an optical manipulation device that can control the direction of light propagation.

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Figure 1: The size and viewing angle of 3D holograms can be simultaneously increased using a scattering medium (diffuser), controlling the wavefront impinging on the diffuser.

The biggest limitation with these modulators as 3D displays is the large number of pixels suitable for 2D images that cannot produce 3D images. For this reason, a 3D image that can be made with existing wavefront modulator technology is 1cm in size with a narrow viewing angle of 3°, which is far from practicable.

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Figure 2: The optical set-up consists of a deformable mirror and the scattering medium with two holographic diffusers. A high-numerical-aperture imaging unit mounted on a three-axis motorised translational system is used for wavefront optimisation and imaging.

Practical, dynamic model

KAIST research shows scattered light interferes with the recognition of objects, and 3D displays can be improved significantly with an increased viewing angle and image size by properly controlling the scattered light.

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Figure 3: Picture shows 3D images in a volume of 2cm × 2cm × 2cm with a viewing angle of 35° using one of the wavefront modulators-a digital micromirror device (DMD).

As a result, the research team succeeded in producing an enhanced 3D holographic image with a viewing angle of 35° in a volume of 2cm in length, width and height. This yielded a performance that was about 2,600 times stronger than the original image definition generated when they used a DM without a diffuser.

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Figure 4: A high-resolution 3D hologram rendition of a face.

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