Hyper-Realistic Display

 [Creating the biggest screen with the smallest display]

The widespread adoption of personal computers (PCs), also known as computers, slowed down significantly due to the proliferation of smartphones. While the sluggish growth in the PC market could be partly attributed to the unique circumstances during the COVID-19 pandemic, the smartphone market is also experiencing a notable deceleration in global sales growth compared to its explosive expansion in the past.

Just as the transition from PCs to the era of smartphones occurred, it is anticipated that the AR and VR market will grow in the future.

This is evident from Facebook, which ranks among the top 10 companies in terms of market capitalization, changing its name to Meta by making a significant payment. Mark Zuckerberg, the founder of Facebook, emphasized the concept of the "metaverse." In this context, the term "metaverse" refers to a digital space that combines virtual reality and augmented reality, reflecting the company's future-oriented intention to expand into virtual reality (VR) and augmented reality (AR) technologies.

Currently, the game market utilizing VR (virtual reality) and the smart glasses industry using AR (augmented reality) are experiencing significant advancements. However, in the future, these industries are likely to expand beyond their current boundaries. For instance, we may see automobiles with augmented displays replacing traditional windshields, school lessons integrating augmented reality and virtual reality, and smart glasses potentially replacing smartphones. There is a possibility that the VR and AR industries will extend into everyday spaces, bringing about innovations such as these.

Facebook, which changed its name to Meta

[Focus control for AR VR]

Almost everyone has different visual acuity in their left and right eyes. Additionally, when looking at a specific object, the distances seen by the left and right eyes would differ. Our brain naturally adjusts for these differences in distance and direction to help us perceive images. When displaying images to our eyes through AR or VR devices, the angles at which each eye sees the image must be considered, and the time it takes for the image to reach each eye should also be taken into account. In essence, AR and VR devices require technology that can seamlessly focus for both eyes without any time delay.

The process of achieving focus can be classified into two or four methods, as shown in the diagram below: Power-based/Distance-based or Space-multiplexing/Time-multiplexing/Polarization-multiplexing/Wavelength-multiplexing. For more detailed information, you can refer to the review paper from the source provided below.

Referenence : Zhan, T., Xiong, J., Zou, J. et al. Multifocal displays: review and prospect. PhotoniX 1, 10 (2020). 

"It is also possible to adjust focus by placing liquid crystal molecules within a transparent ITO cell and aligning them. However, a drawback of this method is the need for an additional electrical signaling device to manipulate the liquid crystal molecules."


"Some cases involve using curved substrates like PET or PMMA. However, the process of inserting dielectric materials inside the cell may lead to excessive thickness."


"Mechanically using a rotator to rotate a polarization plate and induce changes in focus. This approach is more commonly chosen by companies due to its practicality compared to the first method."


"Utilizing Blue phase liquid crystal. This method involves stacking multiple layers of polarization and modulation layers and applying voltage as needed. Although it offers a significantly adjustable focus range, it requires a high-voltage system. Additionally, due to the stacking of multiple layers, its thickness is substantial, which limits the response speed."

I've listed a few methods among many. Ultimately, the chosen approach can lead to increased thickness and weight, or issues such as color aberration. In the industry, attempts are being made to develop new processes, such as adjusting the doping ratio or using new materials. Another approach involves introducing patterning methods outside the lens.

[Standard of AR VR]

Reference is being made to the standards set by the IEC (International Electrotechnical Commission) to establish standards. However, even the IEC's standards are continually being revised and improved, and they have not yet been fully established. For instance, there are many aspects that the industry and academia need to define and decide upon, such as whether to express numerical values defining the eyebox in spherical coordinates or whether to measure from the ocular surface or from the center of the eye. Currently, there is no domestic institution in existence that measures and sets standards for the performance of VR and AR devices.

[AR VR headset]

Common Point:

1. High resolution is required due to close proximity to the eyes.

When using a tablet up close compared to a monitor, do you notice that individual pixels are more visible? Even with 4K resolution, there are consumer reviews mentioning the visibility of pixels, which suggests the need to implement 8K. However, implementing 8K could pose challenges for content production companies, as creating high-resolution videos might become problematic. Additionally, there's also the issue of whether devices can transmit the enormous amount of data in 8K without any latency.


2. Viewer fatigue due to subtle latency:

In the past, the U.S. military invested a significant amount in attempting simulated training using AR and VR equipment. When the screen was rapidly moved, subtle latency occurred in forming accurate focus between both eyes. Although the latency was difficult to notice, users experienced no issues when using the equipment for around 10 to 30 minutes. However, during extended usage of 2 to 4 hours, users reported headaches and dizziness.

3. Advancements in battery technology, optical engine software, and more are required.

AR 

- Using LCOS (Liquid Crystal on Silicon):


- Utilizing a transparent display that allows viewing both the real world and augmented graphics through the display.


- Maintaining high brightness compared to VR is crucial when used during the day.


- Relative short focal distance.


- Small-sized lenses.

VR 

- Using OLEDoS (OLED on silicon):

- Displays virtual graphics without showing the external real world.

- Allows immersion on the screen regardless of the external environment due to its enclosed form.

"If micro LED displays were introduced instead of LCOS or OLED?"

"Liquid crystal on Si shares similar advantages with LCD. It boasts superior resolution, brightness, and lifespan.

OLED on Si shares similar advantages with OLED. It offers high contrast ratio, fast response time, low power consumption, and being self-emissive, it has a simple structure.

If micro LED displays were introduced, they would surpass conventional LED-backlit LCD displays, namely liquid crystal on Si, in nearly all aspects such as contrast ratio, response time, color reproduction, viewing angle, brightness, maximum resolution, and lifespan. Furthermore, it does not suffer from burn-in issues like OLED."