Research on a foveated imaging system (FIS) through optical manipulation for super-resolution near-eye display (NED) view

Abstract

The visual performance, in terms of resolution, of a single near-eye display (NED), is often restricted by the pixel density of the display panel. In a NED configuration, displays are often magnified optically to provide a wide field of view (FOV) and to create an image at a certain ideal depth. The magnification of the image, thus, causes the pixels of the display panel to be more visible. On the other hand, displays with a physically dense pixel pitch would otherwise lead to high driving power and therefore put further burden on the device supply. There are plenty of attempts to solve this issue in the research literature, but those solutions would however cause adverse effects on other factors such as device form factor, eyebox size, FOV, etc. In this dissertation, an advanced foveated imaging system (FIS) is proposed with the use of two identical displays and a compound tilting device. The concept of foveation is built on the fact that the Human Visual System (HVS) has limited performance due to the natural distribution of receptors on the retina. With the knowledge on the HVS, the FIS is designed in such a way that the high-resolution foveal region with an angle of about $32^\circ$ is relayed onto the low-resolution peripheral view with a total FOV of $104 ^\circ$. The foveal image of the proposed FIS is optically enhanced by 4.3 times and reaches 52cpd. In any foveated system, an eye-tracking system is necessary to provide information on the focus of the eye so that the foveal image can be translated to the corresponding position. Thus, in the existing foveated system, often additional tilting mechanism like a motor for full directional tilting or phase modulating for restricted tilting are employed. However, motor actuation would lead the system to a bulky form and phase modulation of light normally operates in only two ways (i.e left/right or up/down). In the proposed FIS, the fabricated tilting mirror holds the role in both image resolution enhancement and a steering device. In other words, it can directly integrate with an eye-tracking device in the future without the need of an external actuator. On a separate analysis, the current version of the fabricated steering mirror is a cylindrical device with a diameter of 50mm and a thickness of 15mm. It is experimentally measured to have a tilting range of +/- $10^\circ$ in multiple axes with its actuation governed by push-pull electromagnets. On top of that, the device response time is comparable at 16.6ms. With this, the system latency of the proposed FIS is estimated to be around 50ms. This system design aimed to mimic the perception of a human eye to provide a realistic viewing in a NED has challenged the conventional trade-off issue between resolution and FOV. Besides, high resolution is supported at low driving costs and thus efficient battery power maintenance.