There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Recently, 'Liquid crystal display (LCD) vs. organic light-emitting diode (OLED) display: who wins?' has become a topic of heated debate. In this review, we perform a systematic and comparative study of these two flat panel display technologies. First, we review recent advances in LCDs and OLEDs, including material development, device configuration and system integration. Next we analyze and compare their performances by six key display metrics: response time, contrast ratio, color gamut, lifetime, power efficiency, and panel flexibility. In this section, we focus on two key parameters: motion picture response time (MPRT) and ambient contrast ratio (ACR), which dramatically affect image quality in practical application scenarios. MPRT determines the image blur of a moving picture, and ACR governs the perceived image contrast under ambient lighting conditions. It is intriguing that LCD can achieve comparable or even slightly better MPRT and ACR than OLED, although its response time and contrast ratio are generally perceived to be much inferior to those of OLED. Finally, three future trends are highlighted, including high dynamic range, virtual reality/augmented reality and smart displays with versatile functions.

/pdf/liquid-crystal-display-and-organic-light-emitting-diode-5b9d3ky1k3.pdf

Liquid crystal display and organic light-emitting diode display: present status and future perspectives

The vergence-accommodation conflict (VAC) remains a major problem in head-mounted displays for virtual and augmented reality (VR and AR). In this review, I discuss why this problem is pivotal for nearby tasks in VR and AR, present a comprehensive taxonomy of potential solutions, address advantages and shortfalls of each design, and cover various ways to better evaluate the solutions. The review describes how VAC is addressed in monocular, stereoscopic, and multiscopic HMDs, including retinal scanning and accommodation-free displays. Eye-tracking-based approaches that do not provide natural focal cues—gaze-guided blur and dynamic stereoscopy—are also covered. Promising future research directions in this area are identified.

Resolving the Vergence-Accommodation Conflict in Head-Mounted Displays

Lenses with tunable focal length play important roles in nature by helping species avoid predators and capture prey. Many practical devices mimic lens concept for imaging, sensing, and detection. This review covers fundamental optics of lenses and its extension to lenses made of liquid crystals (LCs). Three main types of LC lenses are described, namely, lenses with curved surfaces, flat gradient-index lenses and composite lenses. The review discusses advantages of LC lenses over their isotropic counterparts, challenges in their fabrication and control, as well as a variety of potential applications. We also discuss the current challenges associated with nematic LC lenses and their solutions. LC lenses are already having significant impacts on optics and optometry, and these impacts will grow with discovering new LC materials and new lens designs.

Liquid crystal lenses with tunable focal length

We analyze the performance of high dynamic range liquid crystal displays (LCDs) using a two-dimensional local dimming mini-LED backlight. The halo effect of such a HDR display system is investigated by both numerical simulation and human visual perception experiment. The halo effect is mainly governed by two factors: intrinsic LCD contrast ratio (CR) and dimming zone number. Based on our results, to suppress the halo effect to indistinguishable level, a LCD with CR≈5000:1 requires about 200 local dimming zones, while for a LCD with CR≈2000:1 the required dimming zone number is over 3000. Our model provides useful guidelines to optimize the mini-LED backlit LCDs for achieving dynamic contrast ratio comparable to organic LED displays.

High dynamic range liquid crystal displays with a mini-LED backlight.

A high dynamic range liquid crystal display (HDR-LCD) can enhance the contrast ratio of images by utilizing locally controlled dynamic backlight. We studied the HDR-LCD as a dual-panel display: a backlight module and a liquid crystal (LC) cell. As the gamma of the LC signal, the backlight module was also endowed with a gamma function to control the contrast ratio of HDR images. The inverse of a mapping function (IMF) method proposed as a dynamic gamma mapping curve for the backlight module, has been demonstrated to further improve in HDR image quality. By implementing the IMF method on a HDR-LCD TV with 88 backlight zones, the image contrast ratio can reach while maintaining high brightness, clear image detail, and an average power reduction of 30%.

https://ir.nctu.edu.tw:443/bitstream/11536/8765/1/000259552500005.pdf

Dynamic Backlight Gamma on High Dynamic Range LCD TVs

— A cylindrical multi-electrically driven liquid-crystal lens (MeD-LC lens) is proposed to extend the range of focusing. The MeD-LC lens could be applied to switching 2-D and 3-D images by supplying a specific operating voltage on each electrode. Therefore, the MeD-LC lens has less cross-talk than that of a conventional LC lens. Furthermore, the simplified structure of a MeD-LC lens with a homogeneous LC layer is much easier for fabrication without a LC-alignment issue.

2‐D/3‐D switchable autostereoscopic display with multi‐electrically driven liquid‐crystal (MeD‐LC) lenses

A high dynamic range liquid crystal display (HDR-LCD) can much enhance the contrast ratio of the image on a locally controlled dynamic backlight. A novel method, inverse of mapping function (IMF), was demonstrated to further improve the HDR image quality from the information of each frame. By using the IMF method, the image contrast ratio in a 37” HDR-LCD TV was successfully improved to ~20,000:1 while maintaining high brightness and clear image details. Besides, for mass production purpose, the backlight of a 37” HDR-LCD TV was divide into 8×8 zones to reduce hardware computation complexity.

39.4: Inverse of Mapping Function (IMF) Method for Image Quality Enhancement of High Dynamic Range LCD TVs

Blur-mask approach (BMA) was developed to simulate the light distribution of locally controlled LED backlight, providing much lower computational complexity which is less than 1% of that of conventional convolution approach and being successfully demonstrated on a 37? high dynamic range (HDR) LCD-TV with real-time modification to perform high quality image (Less image distortion) and high contrast ratio (~ 20,000:1 with test image-Lily).

https://ir.nctu.edu.tw:443/bitstream/11536/5540/1/000275669000001.pdf

Blur-Mask Approach for Real-Time Calculation of Light Spreading Function (LSF) on Spatial Modulated High Dynamic Range LCDs

A new impulse-type display named Local Blinking High Dynamic Range (HDR) LCD System was proposed, which utilized local dimming technology to achieve a local blinking effect that not only suppressed motion blur and reduce Moving Picture Response Time (MPRT) to 3.89 ms but also applied local image compensation to maintain image brightness and details without substituting high power light source. In addition, the intrinsic advantages, such as high dynamic range (high contrast ratio) and low power consumption were also achieved.

/pdf/local-blinking-hdr-lcd-systems-for-fast-mprt-with-high-1b41ltf0mu.pdf

Lin Yao Liao

Papers

Dynamic Backlight Gamma on High Dynamic Range LCD TVs

2‐D/3‐D switchable autostereoscopic display with multi‐electrically driven liquid‐crystal (MeD‐LC) lenses

39.4: Inverse of Mapping Function (IMF) Method for Image Quality Enhancement of High Dynamic Range LCD TVs

Blur-Mask Approach for Real-Time Calculation of Light Spreading Function (LSF) on Spatial Modulated High Dynamic Range LCDs

Local Blinking HDR LCD Systems for Fast MPRT With High Brightness LCDs