The biggest issue with VR, AR or mixed reality devices such as HoloLens is the Field of View (FOV). It appears that Microsoft has discovered a new way to deal with these issues, according to a patent titled “LENSLET NEAR-EYE DISPLAY DEVICE” filed back in April, 2016 and published on 19 July, 2018.
In the background section of the patent application, Microsoft explains the variety of virtual reality or augmented reality display systems could face limited field of view issues.
“There are a variety of virtual reality or augmented reality display systems that seamlessly blend digital content with the physical world. For example, a head-mounted display (HMD) device can include transparent display elements that enable users wearing the HMD device to see concurrently both the physical world around them and digital content displayed by the HMD device. An HMD device is more generally referred to as a type of near-eye display (NED) device that can enable a mixed reality experience by a user wearing the HMD device,” the patent’s background reads.
Microsoft says that the field of view (FOV) of a typical NED device is limited and a HMD device can only display images in front of the user’s eyes (one for each eye).
“Typical HMD devices fail to create a fully immersive experience for users wearing the HMD devices,” Microsoft explains. While increasing the size of the display is indeed a good solution but it’s impractical as the devices are complex, consume considerable amounts of resources, and are expensive.
The patent applications explains the method below:
“The techniques introduced here include at least one display device. Embodiments of the display device include substantially transparent substrates, a lenslet array including substantially transparent lenslets disposed between the transparent substrates, and light sources disposed between the substantially transparent substrates. The light sources are operable to emit light towards respective lenslets of the lenslet array, and the lenslet array is configured to render a digital image by reflecting the emitted light towards the light sources.
Having a reflective object would normally hinder the see-through performance since a reflective surface would reflect light rays. In this case, a partially reflective surface is employed, i.e., one which still transmits at least some light. Since the partially reflective surface is index matched, distortion from the optical power of the surface is minimized or even eliminated, since in the transmission case there is no effective lens power or index change. Therefore, the reflective lenslets effectively only work in reflection, but light can transmit through the lenslets unaltered“.
It is however worth noting that this is just a patent but it’s likely that Microsoft’s next-generation HoloLens will come with better FOV. The next generation HoloLens is codenamed Sydney and is expected to arrive in early 2019. The rumours claim that the HoloLens 2 will feature significantly improved holographic displays and it would cost significantly less.