South Korean researchers say they have used a series of light diffusers to vastly improve the quality of holograms, creating a 3D holographic display that performs 2,600 times better than existing displays, according to a new paper in Nature Photonics.
The technique is expected to improve the limited size and viewing angle of 3D images -- a serious problem in current holographic displays.
In their study, YongKeun Park, PhD, and colleagues from the Korea Advanced Institute of Science and Technology (KAIST) aimed for a solution that overcame the limitations of current wavefront modulator technology, which can produce only the smallest 3D holographic images (Nature Photonics, January 23, 2017).
The 3D holograms of movie fame are created with computer graphics, while methods for creating true 3D holograms are still being studied in the laboratory, according to a release from KAIST. Owing to the difficulty of generating real 3D images, for example, recent virtual reality (VR) and augmented reality (AR) devices project two different 2D images onto a viewer to induce optical illusions.
Creating 3D holograms that can be viewed without special equipment such as 3D glasses requires control of a wavefront of light using a wavefront modulator, an optical manipulation device that can control the direction of light propagation. These include spatial light modulators and deformable mirrors.
But these modulators have a big limitation in the number of pixels they can contain -- to date, only enough to create a 2D image or a tiny 3D image. The largest image that can be made with existing wavefront modulator technology is 1 cm in size with a viewing angle of just 3°, which is too small to be practical.
As an alternative, the researchers used a deformable mirror and added two successive holographic diffusers to scatter light. Scattering light in many directions allows for a wider viewing angle and a larger image, but it creates volume speckle fields due to the interference of the scattered light.
The researchers fixed the problem by using a wavefront-shaping technique to control the fields. They succeeded in producing an enhanced 3D holographic image with a viewing angle of 35° in a volume of 2 cm in length, width, and height. The result was approximately 2,600 times stronger than the original image definition generated without a diffuser.
