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Quantum dots (QDs) have become the most valuable luminescent materials due to their excellent optical properties, such as high color purity, high photoluminescence quantum yield (PLQY), and tunable luminescence spectra. QDs‐based display devices have been used commercially and have shown outstanding advantages such as wide color gamut, high brightness, etc. However, for high‐end displays such as micro‐light‐emitting diodes (Micro‐LED), fine precise patterning of QDs is still a prerequisite and key challenge. Recently, direct photolithography, a method based on photochemical reactions of QDs photoresist (QDPR), has been considered as the most potential patterning technology to achieve high resolution and high‐throughput. This review focuses on the recent progress of QDPR from the point of view of different photochemical reaction mechanisms: starting the monomer polymerization, followed by the ligand crosslinking or decomposition, and eventually introducing crosslinking additives. Furthermore, a comprehensive overview of the current applications of QDPR in displays is provided based on the different types of LED devices. Finally, existing problems in QDs direct photolithography are discussed, along with possible reasons and solutions. This review is expected to accelerate the development of direct photolithography patterning method and provide general guidance for the further design of QDPR for high‐end displays. [ABSTRACT FROM AUTHOR]

Three‐dimensional display has been a widely researched technology, offering an abundance of depth cues to enhance the overall visual experience. The volumetric display system has significant advantages due to its ability to be viewed from any angle and without the need for auxiliary devices. However, the issue of deviation between the rotating axis and the display plane was not taken into consideration in the previous systems. Therefore, we innovatively propose an axis‐shift slicing algorithm for volumetric display systems, leading to improved accuracy and reliability of the image slices data. Moreover, a prototype based on a novel collaborative control scheme as well as a creative software simulator is designed and implemented, laying the foundation for further development and refinement. Finally, the results from both simulations and experiments have demonstrated the effectiveness of the proposed axis‐shift algorithm and the designed volumetric display system. [ABSTRACT FROM AUTHOR]

We are investigating the use of LED panels for ultra‐large glasse‐free 3D applications. For the first stage of our work, parallax barriers are used as these provide a lightweight and inexpensive view‐directing component for a multiview display; ultimately, these will be replaced by lenticular screens as these have a much greater light throughput. This work addresses the two major potential problems with the approach, namely; LED panel positional accuracy, and the effect of the high crosstalk levels encountered when providing sufficient luminance for outdoor environments. In this paper we will describe the mapping of the images and report on the use of 3D illusions to enhance the limited depth of field (DOF) provided by this first version of our display. [ABSTRACT FROM AUTHOR]

The use of high‐power circuit devices puts forward high heat dissipation requirements for LED display. Several heat dissipation methods are studied in this paper to provide a reasonable idea of high power consumption LED display. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Liquid Crystal & Displays is the property of Chinese Journal of Liquid Crystal & Displays and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

LED displays can be used to realize the dual functions of display and communication simultaneously. However, existing LED display-based visible light communication (VLC) systems suffer due to their short transmission distance and are not practical. A long-distance, real-time display-camera communication (DCC) system is proposed in this paper. First, a LED-DCC point clustering scheme is proposed to increase the transmission distance by clustering multiple adjacent LED display points for improving the quality of the VLC signal captured by an image sensor. Then, a lightweight, back-forth, fast image processing algorithm is proposed to reduce the introduced additional computational complexity caused by point clustering and enhance the reliability of information extraction from the real-time captured images/video frames. The experimental system was implemented with a 2.2-inch 16 × 16 point LED display and the CMOS camera on the smartphone. Experimental results show that the proposed system can achieve a maximum data transmission distance of 7 m under a bit error rate (BER) of 0.5, which is about 9 times that of the previous LED-DCC system, and can achieve a data transmission distance of 175 cm under the 7% forward error correction (FEC) limit, which is about 12 times that of the previous LED-DCC system. Additionally, the decoding latency for extracting information from each video frame is only 13.26 ms, which guarantees real-time data reception. [ABSTRACT FROM AUTHOR]

AIRR (Aerial imaging by retro-reflection) can form a large aerial image in mid-air for digital signage. Resolution of the aerial image formed with AIRR is determined mainly by the retro-reflector, which is one of its components. However, increasing the resolution of aerial images by increasing the density of retro-reflective elements poses physical limitations and cost increases. The purpose of this study is to improve the apparent resolution of aerial images by utilizing subjective super-resolution display method. Subjective super-resolution display method is a display method in which spatially coded images are alternately shown on a display panel in a time-shared manner to give the illusion of higher resolution than the number of pixels on the display panel. We validate the effectiveness of the proposed method by evaluating it through subject experiments. In the experiment, the normal display method and the proposed method are evaluated by Scheffe's paired comparison method. As a result of the experiment, it was found that at the 5% level of significance, the display by the proposed method appeared to have higher resolution than the normal display method. [ABSTRACT FROM AUTHOR]

In this article, a pulsewidth modulation (PWM) LED driver is proposed to overcome the challenges of time-multiplexed driving and to enhance the quality of displays sufficient for signage applications. First, adaptive duty cycle restoration (ADCR) compensates for the brightness degradation in low grayscale, where a simple analog timer circuit measures the limited charging time and compensates its effect to ensure the desired emission time. Second, amplitude-segmented PWM (ASPWM) improves the grayscale resolution without increasing the grayscale clock frequency; thus, the electromagnetic interference performance is not sacrificed. The proposed LED driver is fabricated in a 0.18-μm Bipolar-CMOS-DMOS (BCD) process. The measurement results show that the driver Integrated Circuit (IC) achieves a duty cycle restoration factor (DCRF) greater than 0.95 out of ten samples, whereas the DCRF is limited to 0.67 on average when the ADCR scheme is disabled. Resolution enhancement with the proposed ASPWM is verified, achieving 16-b grayscale resolution. The prototype driver IC occupies 3.56 × 3.00 mm of chip area, operated from a 4.5 V supply voltage. [ABSTRACT FROM AUTHOR]

Taking advantage of the photoelectric characteristics of LED other than the light‐emitting function, this paper proposes a light sensing detection method and system without adding additional sensors to the LED screen. A two‐pole detection structure with a function of detecting positive and negative voltage is introduced to the LED drive circuit, which ensures the high‐speed characteristics during detection. What's more, the LED is controlled to work in photoconductive mode to obtain high voltage sensitivity when the intensity of incident light changes. The proposed module can reach an optical signal response rate of 19.1 μs with a detection rate of 23.5 Hz without affecting the original display function. The optical signal detection can reach a voltage sensitivity of 3.02 mV per lx. To verify the photoelectric detection capability of the method presented in this paper, a brand‐new screen object recognition system is built and tested. An 8 × 8 LED display module is used in experiment, and the scale of LED screen can be expanded easily and flexibly. In an ideal environment, a recognition accuracy of 99.25% can be achieved, while the recognition accuracy can still reach over 96.5% in a complex light environment. Therefore, this work has further application possibilities for light interaction and fast object recognition in large screens. [ABSTRACT FROM AUTHOR]

Gallium Nitride (GaN) based light-emitting diodes (LEDs) suffer from the persistent issue of high resistivity of the p-type layer, due to inefficient dopant activation at room temperature. Here, a novel Electrostatic Field Effect LED (EFELED) is demonstrated to solve this issue by introducing significantly more holes into the LED active region for the first time. An increase in drive current is observed through application of positive biases to a capacitor layer on top of a 436 nm InGaN/GaN LED. With a positive bias of 5 V applied to the capacitor, the EFELED showed more than a two-fold increase in optical output from electroluminescence (EL) measurements, as well as over 115% enhanced external quantum efficiency (EQE). Modulation of holes can also be achieved through the novel capacitor integration in the EFELED, which leads to light output control. This proposed EFELED provides an alternative method to efficiently improve hole injection for the active region through energy band bending, which addresses the fundamental p-type doping issue for LED devices.

The potential of ultraviolet (UV) AlGaN quantum well (QW) light-emitting diodes (LEDs) is stunted due to the lack of efficient p-type doping for this ultra wide bandgap material. In this work, a novel device - UV electrostatic field effect LED (EFELED) is demonstrated to address this issue by significantly improving hole injection into the QW active region which leads to a relative increase of external quantum efficiency (EQE) up to 42%. The UV EFELED is realized by integrating a capacitor layer on top of a conventional 267 nm AlGaN QW LED, which introduces band bending to assist hole injection under a forward bias. A 10x increase in injection current is achieved through the application of a positive bias to the integrated capacitor layer. With 20 V applied to the capacitor, a 42% increase of EQE is achieved. Photon intensity modulation is demonstrated with the application of varying capacitor biases, which presents a novel brightness control at UV wavelength. Thus, the proposed UV EFELED provides significantly improved hole injection through a capacitor integration, which leads to high-efficiency UV LEDs for important applications such as sterilization and purification.

LED displays can be used to realize the dual functions of display and communication simultaneously. However, existing LED display-based visible light communication (VLC) systems suffer due to their short transmission distance and are not practical. A long-distance, real-time display-camera communication (DCC) system is proposed in this paper. First, a LED-DCC point clustering scheme is proposed to increase the transmission distance by clustering multiple adjacent LED display points for improving the quality of the VLC signal captured by an image sensor. Then, a lightweight, back-forth, fast image processing algorithm is proposed to reduce the introduced additional computational complexity caused by point clustering and enhance the reliability of information extraction from the real-time captured images/video frames. The experimental system was implemented with a 2.2-inch 16 × 16 point LED display and the CMOS camera on the smartphone. Experimental results show that the proposed system can achieve a maximum data transmission distance of 7 m under a bit error rate (BER) of 0.5, which is about 9 times that of the previous LED-DCC system, and can achieve a data transmission distance of 175 cm under the 7% forward error correction (FEC) limit, which is about 12 times that of the previous LED-DCC system. Additionally, the decoding latency for extracting information from each video frame is only 13.26 ms, which guarantees real-time data reception.

We have developed a new high-speed driving circuit of a multi-color LED panel by the use of FPGA for subjective super-resolution display. In the subjective super-resolution display, the coded display image is switched and displayed at high speed. The viewer makes an unconscious correction by fixational eye movement and perceives the resolution higher than the physical number of pixels of the LED panel. Our developed LED display drive circuit shows multi-color images at a sufficiently high frame rate enough to perform the subjective super-resolution effect. The maximum frequency is 8.5 kHz for 8 multi-color representations. We have designed spatiotemporal coding to show nine adjacent subpixel information for 9 multi-color subframes. The coded 9 subframes are alternately shown on the LED panel by the use of our developed FPGA circuit. We have verified that the image was updated at high speed. The unconscious correction by the fixational eye movement allows the viewer to perceive a higher resolution than the actual number of LED lamps. Through an evaluation experiment, we have verified that the subjective super-resolution effect was induced in a multi-color image, that is, the displayed image in the proposed method looked smoother than that in the normal display method. [ABSTRACT FROM AUTHOR]

The potential of ultraviolet (UV) AlGaN quantum well (QW) light-emitting diodes (LEDs) is stunted due to the lack of efficient p-type doping for this ultra wide bandgap material. In this work, a novel device - UV electrostatic field effect LED (EFELED) is demonstrated to address this issue by significantly improving hole injection into the QW active region which leads to a relative increase of external quantum efficiency (EQE) up to 42%. The UV EFELED is realized by integrating a capacitor layer on top of a conventional 267 nm AlGaN QW LED, which introduces band bending to assist hole injection under a forward bias. A 10x increase in injection current is achieved through the application of a positive bias to the integrated capacitor layer. With 20 V applied to the capacitor, a 42% increase of EQE is achieved. Photon intensity modulation is demonstrated with the application of varying capacitor biases, which presents a novel brightness control at UV wavelength. Thus, the proposed UV EFELED provides significantly improved hole injection through a capacitor integration, which leads to high-efficiency UV LEDs for important applications such as sterilization and purification. [ABSTRACT FROM AUTHOR]

Gallium Nitride (GaN) based light-emitting diodes (LEDs) suffer from the persistent issue of high resistivity of the p-type layer, due to inefficient dopant activation at room temperature. Here, a novel Electrostatic Field Effect LED (EFELED) is demonstrated to solve this issue by introducing significantly more holes into the LED active region for the first time. An increase in drive current is observed through application of positive biases to a capacitor layer on top of a 436 nm InGaN/GaN LED. With a positive bias of 5 V applied to the capacitor, the EFELED showed more than a two-fold increase in optical output from electroluminescence (EL) measurements, as well as over 115% enhanced external quantum efficiency (EQE). Modulation of holes can also be achieved through the novel capacitor integration in the EFELED, which leads to light output control. This proposed EFELED provides an alternative method to efficiently improve hole injection for the active region through energy band bending, which addresses the fundamental p-type doping issue for LED devices. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Liquid Crystal & Displays is the property of Chinese Journal of Liquid Crystal & Displays and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Gallium nitride (GaN)-based light-emitting diodes (LEDs) are being investigated for the next generation display technology. The persistent issue, however, has been the lack of ability to integrate transistors with LEDs for control. Here, a novel vertical integration scheme is utilized to fabricate nanowire LEDs with nanowire field effect transistors (FETs) for the first time. This approach utilizes the unintentionally doped GaN template layer which is common to LED growth for the fabrication of nanowire FETs. The demonstrated voltage-controlled light-emitting unit provides area savings, scaling, and easier fabrication due to the vertical integration. For these initial nanowire devices, light modulation is demonstrated with LED turn OFF at −10 V. Due to the nanowire approach, these devices show over two times improvement in the $I_{ \mathrm{\scriptscriptstyle ON}}$ to $I_{ \mathrm{\scriptscriptstyle OFF}}$ ratio compared with the alternative integration schemes. [ABSTRACT FROM AUTHOR]

Currently, head mounted displays are the most widely used variant of Virtual Reality (VR) systems. While offering reasonable quality at moderate prices, their inherent limitation is that they isolate users from their surroundings, especially other persons in the room. Immersive VR systems with large fixed screens, such as CAVEs and Powerwalls, remain the preferable technology when maximum quality and unencumbered interpersonal communication is required. However, the state‐of‐the‐art of this technology is limited to a single users' view, with the others only seeing a more or less distorted image. Moreover, they are mostly using on rear projection, with its inherent drawbacks on brightness, contrast, and space requirements. In this paper we propose a novel multi‐viewer immersive VR system based on LED display technology, which will overcome these limitations, leading to a new quality of co‐located collaborative VR. [ABSTRACT FROM AUTHOR]

Copyright of Computer Measurement & Control is the property of Magazine Agency of Computer Measurement & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)