We present the development and investigation of a holography-based head mounted display (HMD) that uses the proprietary Viewing-Window (VW) technology of SeeReal Technologies to generate a holographic scene. Considering various specification requirements, such as field of view (FOV) and resolution, the development of the HMD system was implemented by means of the optical design software Zemax. A prototypical HMD was set up in the laboratory and several tests were conducted e.g. resolution limit, field of view, and spatial resolution of the holographic reconstruction to investigate the performance. The HMD system reaches a resolution limit of 2.2 cycles/mm at a distance of 1500 mm between observer and image plane. The FOV is 4.1° in the horizontal and 2.3° in the vertical direction. By tuning the focus of a camera it was demonstrated that the holographic reconstruction is spatially resolved in three dimensions. Taking into account all technical specifications and restrictions, the image quality of the HMD was evaluated as good. Using holographic imaging technique has been demonstrated to be suitable to avoid the conflict between accommodation and convergence of the eye and is a promising way in future HMD technology.
SeeReal’s concept of real-time holography is based on Sub-Hologram encoding and tracked Viewing Windows. This solution leads to significant reduction of pixel count and computation effort compared to conventional holography concepts. Since the first presentation of the concept, improved full-color holographic displays were built with dedicated components. The hologram is encoded on a spatial light modulator that is a sandwich of a phase-modulating and an amplitude-modulating liquid-crystal display and that modulates amplitude and phase of light. Further components are based on holographic optical elements for light collimation and focusing which are exposed in photopolymer films. Camera photographs show that only the depth region on which the focus of the camera lens is set is in focus while the other depth regions are out of focus. These photographs demonstrate that the 3D scene is reconstructed in depth and that accommodation of the eye lenses is supported. Hence, the display is a solution to overcome the accommodationconvergence conflict that is inherent for stereoscopic 3D displays. The main components, progress and results of the holographic display with 300 mm x 200 mm active area are described. Furthermore, photographs of holographic reconstructed 3D scenes are shown.
Over the last decade, various technologies for visualizing
three-dimensional (3D) scenes on displays have been
technologically demonstrated and refined, among them such of stereoscopic, multi-view, integral imaging, volumetric,
or holographic type. Most of the current approaches utilize the conventional stereoscopic principle.
But they all lack of their inherent conflict between vergence and accommodation since scene depth cannot be
physically realized but only feigned by displaying two views of different perspective on a flat screen and delivering
them to the corresponding left and right eye. This mismatch requires the viewer to override the physiologically
coupled oculomotor processes of vergence and eye focus that may cause visual discomfort and fatigue.
This paper discusses the depth cues in the human visual perception for both image quality and visual comfort
of direct-view 3D displays. We concentrate our analysis especially on near-range depth cues, compare visual
performance and depth-range capabilities of stereoscopic and holographic displays, and evaluate potential depth
limitations of 3D displays from a physiological point of view.
Large real-time holographic displays with full color are feasible with SeeReal's new approach to holography and today's
technology. The display provides the information about the 3D scene in a viewing window at each observer eye. A
tracking system always locates the viewing windows at the observer eyes. This combination of diffractive and refractive
optics leads to a significant reduction of required display resolution and computation effort and enables holographic
displays for wide-spread consumer applications. We tested our approach with two 20 inch prototypes that use two
alternatives to achieve full color. One prototype uses color filters and interlaced holograms to generate the colors
simultaneously. The other prototype generates the colors sequentially. In this paper we review our technology briefly,
explain the two alternatives to full color and discuss the next steps toward a consumer product.
3D displays comprise stereoscopic displays and holographic displays. Eye convergence and accommodation are
important depth cues for human vision. Stereoscopic displays provide only convergence information whereas
holographic displays also provide accommodation information. Due to the inherently better 3D quality we consider
holographic displays as the preferred alternative to stereoscopic displays. Our new approach to holographic displays
omits unnecessary wavefront information and significantly reduces the requirements on the resolution of the spatial light
modulator and the computation effort compared to conventional holographic displays. We verified our concept with
holographic display prototypes and measurements. SeeReal's approach makes holographic displays feasible as a
consumer product for mass-market applications.
Holography is generally accepted as the ultimate approach to display three-dimensional scenes or objects. Principally,
the reconstruction of an object from a perfect hologram would appear indistinguishable from viewing the corresponding
real-world object. Up to now two main obstacles have prevented large-screen Computer-Generated Holograms (CGH)
from achieving a satisfactory laboratory prototype not to mention a marketable one. The reason is a small cell pitch CGH
resulting in a huge number of hologram cells and a very high computational load for encoding the CGH. These
seemingly inevitable technological hurdles for a long time have not been cleared limiting the use of holography to
special applications, such as optical filtering, interference, beam forming, digital holography for capturing the 3-D shape
of objects, and others. SeeReal Technologies has developed a new approach for real-time capable CGH using the socalled
Tracked Viewing Windows technology to overcome these problems. The paper will show that today's state of the
art reconfigurable Spatial Light Modulators (SLM), especially today's feasible LCD panels are suited for reconstructing
large 3-D scenes which can be observed from large viewing angles. For this to achieve the original holographic concept
of containing information from the entire scene in each part of the CGH has been abandoned. This substantially reduces
the hologram resolution and thus the computational load by several orders of magnitude making thus real-time
computation possible. A monochrome real-time prototype measuring 20 inches has been built and demonstrated at last
year's SID conference and exhibition 2007 and at several other events.