Systematic characterization and optimization of 3D light field displays

Abstract

One of the key issues in conventional stereoscopic displays is the well-known vergence-accommodation conflict problem due to the lack of the ability to render correct focus cues for 3D scenes. Recently several light field display methods have been explored to reconstruct a true 3D scene by sampling either the projections of the 3D scene at different depths or the directions of the light rays apparently emitted by the 3D scene and viewed from different eye positions. These methods are potentially capable of rendering correct or nearly correct focus cues and addressing the vergence-accommodation conflict problem. In this paper, we describe a generalized framework to model the image formation process of the existing light-field display methods and present a systematic method to simulate and characterize the retinal image and the accommodation response rendered by a light field display. We further employ this framework to investigate the trade-offs and guidelines for an optimal 3D light field display design. Our method is based on quantitatively evaluating the modulation transfer functions of the perceived retinal image of a light field display by accounting for the ocular factors of the human visual system.

High-performance integral-imaging-based light field augmented reality display using freeform optics

“…The key specifications of the prototype system are summarized in Table 1. As discussed in [22], one of the key parameters to determine in our design process is the view density of the system defined as the number of views per unit area on the entrance pupil of the eye in order to characterize the view sampling property of a light field 3D display. The effects of the view density on the retinal image quality, DOF, and the eye accommodative response of a light field display were systematically characterized in [22].…”

“…As discussed in [22], one of the key parameters to determine in our design process is the view density of the system defined as the number of views per unit area on the entrance pupil of the eye in order to characterize the view sampling property of a light field 3D display. The effects of the view density on the retinal image quality, DOF, and the eye accommodative response of a light field display were systematically characterized in [22]. For instance, a light field 3D display constructed with a view density of 0.57mm −2 and a fill factor of 1, which corresponds to a view pitch of 1.5mm at the exit pupil of an HMD, offers a total of 4 elemental views over a 3-mm eye pupil.…”

“…For instance, a light field 3D display constructed with a view density of 0.57mm −2 and a fill factor of 1, which corresponds to a view pitch of 1.5mm at the exit pupil of an HMD, offers a total of 4 elemental views over a 3-mm eye pupil. As suggested in [22], without considering the resolution limit of a microdisplay and eye accommodation error, such a display can yield a DOF of approximately ± 1 diopters to achieve a limiting spatial resolution of 1.2 arc minutes or threshold spatial frequency of 25 cycles/degree. In the meantime, when the reconstruction depth is shifted away from the CDP of the light field 3D display by 1 diopter, the eye accommodation error, which is defined as the axial displacement between the actual eye accommodative distance and the depth dictated by the rendering to characterize the residual VAC conflict in a light field 3D display, can be as large as 0.2 diopters for targets with a spatial frequency of 5 cycles/degree or lower [22].…”

“…As suggested in [22], without considering the resolution limit of a microdisplay and eye accommodation error, such a display can yield a DOF of approximately ± 1 diopters to achieve a limiting spatial resolution of 1.2 arc minutes or threshold spatial frequency of 25 cycles/degree. In the meantime, when the reconstruction depth is shifted away from the CDP of the light field 3D display by 1 diopter, the eye accommodation error, which is defined as the axial displacement between the actual eye accommodative distance and the depth dictated by the rendering to characterize the residual VAC conflict in a light field 3D display, can be as large as 0.2 diopters for targets with a spatial frequency of 5 cycles/degree or lower [22]. Although a larger view density potentially offers a larger DOF and smaller accommodation error, it comes at the cost of a lower image resolution and also lower image contrast due to increasing diffraction effects.…”

“…Although a larger view density potentially offers a larger DOF and smaller accommodation error, it comes at the cost of a lower image resolution and also lower image contrast due to increasing diffraction effects. Based on the trade-off analysis in [22], we firstly set the view density of our light field 3D system to be 0.38mm −2 , which corresponds to a total of 2 by 2 views encircled by a 3.5 mm pupil, to obtain a good balance among the factors of the limiting spatial resolution, DOF, and eye accommodation error. To further allow for the eye movement in viewing the display, a larger viewing window of 6mm by 6mm was created.…”