The spatio-angular resolution of a light field (LF) display is a crucial factor for delivering adequate spatial image quality and eliciting an accommodation response. Previous studies have modelled retinal image formation with an LF display and evaluated whether accommodation would be evoked correctly. The models were mostly based on ray-tracing and a schematic eye model, which pose computational complexity and inaccurately represent the human eye population's behaviour. We propose an efficient wave-optics-based framework to model the human eye and a general LF display. With the model, we simulated the retinal point spread function (PSF) of a point rendered by an LF display at various depths to characterise the retinal image quality. Additionally, accommodation responses to rendered LF images were estimated by computing the visual Strehl ratio based on the optical transfer function (VSOTF) from the PSFs. We assumed an ideal LF display that had an infinite spatial resolution and was free from optical aberrations in the simulation. We tested images rendered at 0-4 dioptres of depths having angular resolutions of up to 4x4 viewpoints within a pupil. The simulation predicted small and constant accommodation errors, which contradict the findings of previous studies. An evaluation of the optical resolution of the rendered retinal image suggested a trade-off between the maximum resolution achievable and the depth range of a rendered image where in-focus resolution is kept high. The proposed framework can be used to evaluate the upper bound of the optical performance of an LF display for realistically aberrated eyes, which may help to find an optimal spatio-angular resolution required to render a high quality 3D scene.
The spatio-angular resolution of a light field (LF) display is a crucial factor for delivering adequate spatial image quality and eliciting an accommodation response. Previous studies have modelled retinal image formation with an LF display and evaluated whether accommodation would be evoked correctly. The models were mostly based on ray-tracing and a schematic eye model, which pose computational complexity and inaccurately represent the human eye population’s behaviour. We propose an efficient wave-optics-based framework to model the human eye and a general LF display. With the model, we simulated the retinal point spread function (PSF) of a point rendered by an LF display at various depths to characterise the retinal image quality. Additionally, accommodation responses to the rendered point were estimated by computing the visual Strehl ratio based on the optical transfer function (VSOTF) from the PSFs. We assumed an ideal LF display that had an infinite spatial resolution and was free from optical aberrations in the simulation. We tested points rendered at 0–4 dioptres of depths having angular resolutions of up to 4x4 viewpoints within a pupil. The simulation predicted small and constant accommodation errors, which contradict the findings of previous studies. An evaluation of the optical resolution on the retina suggested a trade-off between the maximum achievable resolution and the depth range of a rendered point where in-focus resolution is kept high. The proposed framework can be used to evaluate the upper bound of the optical performance of an LF display for realistically aberrated eyes, which may help to find an optimal spatio-angular resolution required to render a high quality 3D scene.
Light field (LF) displays are a promising 3D display technology to mitigate the vergence-accommodation mismatch. In this study, we empirically evaluated the optical resolution of a neareye LF display test bed by capturing rendered test images and compared it to simulation results based on a previously developed computational model. The LF display prototype employs a time-multiplexing technique and achieves a high angular resolution of 6×6 viewpoints in the eyebox of a 2.8-mm square. The test image was rendered at various depths ranging 0-3 diopters, and the displayed images were captured by a camera for analysis of the optical resolution the display achieved at varying focusing depths. Both the simulation and measurement results indicated that the display correctly provides the focusing effects to the camera, although errors up to 0.5 diopters were found in the measurement. The measured responses were much more limited than the simulated responses, and on-and off-axis aberrations did not fully explain that difference, suggesting large effects of potential errors in the optical alignment and the LF image processing pipeline. An additional simulation on a hypothetical model indicated that larger viewpoint subapertures may be important for providing better optical resolution with LF displays.
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