As an important trend in future display technology, Micro-LED has significant advantages in brightness and contrast, as well as better color performance and response speed. Micro-LED and related display technologies have attracted increasing attention from the academic community in recent years. However, Micro-LEDs with Lambertian emission patterns cannot be directly used in projection displays. Therefore, complex relay optics are often required to collimate the emission light, increasing the system complexity. This paper proposes a novel Micro-LED structure that combines with meta surfaces on top of the Micro-LED. This structure can optically control the light field of Micro-LED into a highly collimating one from the originally Lambertian distribution. Compared with the initial Micro-LED structure, this configuration has good light emission characteristics with primary light concentration between 10 degree intervals. The designed structure has the light distribution with the full width at half maximum (FWHM) angle ±5.48°. At the same time, compared with the traditional Micro-LED structure, its center light intensity is increased to 21.98 times the original. This structure optimizes and improves the performance of Micro-LED in the field of projection display.
In recent years, Mini-LED has been widely used in direct-lit backlight for Liquid Crystal Display (LCD) widely due to its advantages of miniaturization and low power consumption. Typical Mini-LED direct-lit backlights mainly rely on the diffuser plate to convert point-like light sources into uniform surface light sources. However, the diffuser plate cannot achieve high uniformity at a very low optical distance (OD). In this paper, we introduced the pyramidal microstructure and the semi-cylindrical microstructure to both sides of the optical film, respectively. The mechanism of influence of the pyramidal microstructure and the semi-cylindrical microstructure on light was analyzed. We clarified the relationship between the parameters of the microstructure (the pyramid angle, the pyramid dimension) and the illuminance uniformity by simulation. Moreover, two layers of microstructure optical films are discussed and simulated. Through the simulation, the optical effects are evaluated and analyzed from the point of illuminance uniformity. Simulation results maintain that when the OD is 5mm, the illuminance uniformity reaches 93.07%. Compared with the diffuser plate with a thickness of 1.5mm, the thickness is reduced by 0.9mm, and the illuminance uniformity is increased by 11.77%. This work fully demonstrates the advantages of the microstructure optical film to improve the illuminance uniformity.
Micro light-emitting diode (Micro-LED) has the advantages of high brightness, low power consumption, and long life. It has great potential and broad application prospects. Using micro-LED as the light source and image source of the projection system can greatly reduce the size and power consumption of the system. However, the electrical module and the optical module of the micro-LED pico-projection system cannot be separated. This paper uses image fiber to effectively separate the electrical module and optical module in the optical engine, and designs a micro-LED pico-projection optical engine based on an image fiber. This optical engine is composed of a projection lens group, an image fiber and a micro-LED. The projection lens group is composed of 5 spherical lenses, with the total length of 6.752mm and the focal length of 2.8mm. The modulation transfer function (MTF) is higher than 0.8@32lp/mm, and the distortion is below 2%. The image fiber adopts a multi-core fiber with a diameter of 2mm and a resolution of 32lp/mm. Finally, the overall simulation model of the optical engine is built to prove its feasibility.
The key to developing a new type of liquid crystal display (LCD) lighting is to balance light quality with high light efficiency, and the light diffusion plate is an indispensable part of LCD to achieve different light extraction efficiency and light uniformity. In addition, the addition of quantum-dots (QDs) further improves the light transmittance and optical conversion efficiency of the light diffusion plate. In this paper, the surface engineering method was used to prepare QDs composites to improve the stability of QDs diffusion plate under high temperature and humidity. This paper briefly introduced the light diffusion plate, and then discusses the preparation of the QDs composites and the injection molding process of the QDs diffusion plate. Finally, the QDs diffusion plate was assembled into a backlight module, and its stability was tested at 60℃ and 85% relative humidity (RH). The experimental results show that the spectra and external quantum efficiency (EQE) of the QDs diffusion plate do not change significantly after long time storage at high temperature and humidity. This experiment improved the stability of QDs diffusion plate and lays a foundation for the subsequent large-scale production.
The surface modification strategy is widely used to solve the problems of low stability, agglomeration, surface oxidation and photoluminescence quenching of quantum dots (QDs) in practical applications. However this method can easily destroys the surface ligands of QDs, increases defects even leads to a huge loss of fluorescence. In order to improve the stability of QDs, a new synthesis method of QD-silica hybrid nanospheres was proposed in this study. These QD-silica hybrid nanospheres are characterized by using mesoporous silica spheres (MSSs) as template, adsorbing QDs as one shell, and then coating a silica layer as another shell (named SQS). The template MSSs were functionalized by (3-mercaptopropyl) trimethoxysilane (MPTMS) in order to connect MSSs and QDs. After that, the QD-adsorbed silica spheres were coated with silica as the encapsulation layer by Stober method. The structure and morphology of SQS were analyzed by TEM. The effects of different contents of MPTMS and tetraethoxysilane(TEOS) were experimentally compared. Finally, it was found that the optimal contents of MPTMS and TEOS was 250μL and 1.5mL, respectively. The luminescence intensity of SQS samples could reach 2 times higher than that of pure QD solution. Meanwhile, SQS hybrid nanospheres could avoid the tiny spots inside the microstructure caused by QD aggregation and play a better role in dispersion.
This work proposes a research scheme to speed up the design of metasurface skin cloak through low-complexity phase monitoring model and deep learning. This skin cloak conceals a three-dimensional arbitrarily shaped object by complete restoration of the phase of the reflected light at specific wavelength. And the possibility of realizing spectral prediction by deep learning is analyzed. During the study, a phase monitoring system was designed in which the detector, the light source and the monitored nano-antenna were sequentially distributed at equal distances from the emitted wavelength of the light source, so that the monitored phase amount was exactly equal to the phase change before the reflected wave, thus eliminating the need for multiple monitors to measure and calculate the phase change before and after the reflection. The traditional metasurface design is usually constructed by manual library construction based on the phase distribution and the relationship between phase variation and dimensional variation of the cell structure, so this work combines the aforementioned monitoring model with deep learning to generate the database required for modeling. The two variable parameters of device length and width were first defined, and the reflected wavefront phase change used as the optical response, and we reprocessed the original data and finally build and trained an artificial neural network model for forward prediction of optical response. This network can obtain its MSE below 0.001 for the test set after the training is completed. Thus the scheme can replace the role of simulation software to some extent, and its prediction process can be completed in a few milliseconds, improving the efficiency of the design metasurface process.
Quantum dots (QDs) exhibit exceptional optical qualities, including wide excitation wavelength, small full width at half maximum (FWHM), and photobleaching resistance. It had been used to make color-converting diffusers for backlight modules. In this study, the QDs were added into masterbatches to prepare composite components with the functions of diffusion and color conversion. Using a coextrusion approach, masterbatches were made by adding suitable ratio of red and green QDs as color conversion materials in polystyrene (PS), silicone difussion powder as the light diffusing agent, and adding antioxidants to improve the service life of the masterbatch. After that, the QD color masterbatch with uniform dispersion, controllable concentration and good luminescence performance was obtained. A spectrometer was used to examine the photoluminescence performance of the created masterbatches in order to validate their luminescence performance. As a result, the use of QDs masterbatches is a viable option for the application of high performance QD display device.
Mini-LED backlight and quantum-dot color conversion (QDCC) technology are the research hotspots of emerging display technology. When they are combined together, the luminance uniformity issue may occur because of traditional QDCC film (QDCCF) with uniform thickness. This paper designs and optimizes QDCCFs with non-uniform thickness of cone and circular truncated cone, respectively. The illuminance uniformity is analyzed by simulation. Results show that the illuminance uniformity of the optimized cone and circular truncated cone with a single structure can reach 73.97% and 74.72%, respectively. The single structure with uniform thickness is only 35.84%. After that, the single structure with nonuniform thickness is arrayed with a basic substrate added at the bottom, which is matched with the mini-LED backlight. By optimizing the array configuration and the basic substrate, the illuminance uniformity of the backlight reaches 73.55% and 79.25%, respectively. This QDCCF with non-uniform thickness distribution can effectively improve the illuminance uniformity when mini-LED is combined with QDCCF. This work proposes a new strategy for uniform color conversion of mini-LED display backlights.
A majority of electroluminescence spectroscopy inspection systems for LED epitaxial wafers are currently focused on conductive probe contact methods. However, the huge number of bead chips and the difficulty in performing point contact due to the microsize largely limit its application in the field of Micro-LED epitaxial wafers. In order to improve the efficiency of electroluminescence spectroscopy inspection of Micro-LED epitaxial wafers, this study proposed a practical method for contactless electroluminescence of Micro-LEDs, which can achieve contactless electroluminescence while ensuring the characteristics of nondestructive inspection. The basic element of the method is the generation of an induced electric potential by a conducting probe under a high frequency alternating electromagnetic field. The high frequency skin effect of the conductor causes a corona discharge arc at the tip of the probe. The electrical and optical properties of the contactless electroluminescence were analyzed by experiments. The results show that the error in the measured value of the spectral distribution is less than 2%. The system has an ultra-high dynamic inspection range, demonstrating the capability of efficient scanning and inspection.
The polarization emission has many applications in the field of display, and the key to perovskite polarization emission is large-scale orientation. In this paper, we reported the electric field oriented perovskite nanowires method. The perovskite nanowires with average length of 60nm, radius of 5nm and central wavelength of 509nm were synthesized. Then aligned by alternating electric field, and the polarization was finally measured at 0.33, which was three times better than without the alternating electric field.
Micro-LED will probably become the next epochal display technology, which has combined the advantages of liquid crystal display (LCD) and organic light-emitting diode (OLED). Its self-luminous characteristic will greatly compress the volume of the projection optical engine into truly pico-projection level. However, the relevant design and research are still insufficient. In this paper, we design a four-piece sphere lens group with a 5 mm focal length for micro-LED pico-projection, and then a simulation model of self-luminous projection optical engine is built for demonstration. The total length of the projection lens group is only 8.2mm, the modulation transfer function (MTF) is higher than 0.5@66lp/mm, and the distortion is below 1%. The irradiance distribution shows that the light efficiency is 44.9 % and the uniformity reaches 81.3% when the light divergence angle of micro-LEDs is set to 30°. Then, we explore the influence on light efficiency with different light source divergence angles and determine the optimal range of divergence angles. Finally, a R/G/B integrated micro-LED source with blue light and the above red/green quantum-dot color conversion (QDCC) layer is built, proving the feasibility of a full-color pico-projection optical engine with a single-integrated micro-LED chip.
In order to improve high efficiency for light-color conversion, this paper studies a high-efficiency light recycled structure for quantum dot color conversion (QDCC) based on a distributed Bragg reflector (DBR). The difference of optical performance is discussed between the QDCC structure employing a DBR and an absorptive color filter (ACF). Traditional quantum dot color conversion layer (QDCCL) has inherent limitations of blue light leakage and low light utilization rate. To solve this, an optical structure of QDCCL is proposed and discussed in detail, which uses a DBR instead of the traditional color filter and realizes efficient light-color conversion. Different structures are compared via experimental preparation and measurement, such as light-emitting intensity, color gamut, and light utilization rate. Results show that the structure of QDCCL combining a DBR can not only achieve a high color gamut of 124 NTSC%, but also increase the light utilization rate over twice than the traditional ACF structure. More importantly, the light emission intensity of red and green sub-pixels is increased by 2.2 and 2.3 times, respectively. In general, the structure proposed in this paper is of great significance to the development of the display industry.
Light guide plate (LGP) plays an irreplaceable role in backlight module of liquid crystal display (LCD) systems. Based on interactive design of Gtools and Tracepro, we propose an effective design method of scattering dots array for LCD backlight in this paper. This method first initializes the scale of the scattering dots in Gtools, then evaluates illumination distribution in Tracepro, and finally determines the array layout of the scattering dots from the interactive optimization between Gtools and Tracepro. This method can flexibly adjust the light emission in each sub-area of the LGP, which has scientific significance and practical value in some ways.
Light Guide Plate (LGP) plays an irreplaceable role in Liquid Crystal Display (LCD) backlight. LGP with quantum-dot (QD) shows promise in the development of next-generation displays because of QDs’ beneficial characteristics. In this paper, we present a novel QD LGP for LCD backlight based on QD scattering microstructure array (SMA), in which the QD net dots are located discretely and arranged in arrays on the bottom surface of LGP. The paper first introduces the QD backlight briefly, then discusses the preparation and fabrication process of the proposed prototype, and finally presents a systematic photometric approach to reveal the remarkable advantages of QD backlight. The white-balance is achieved by adjusting the proportion of the QDs in the mixture and optimizing the R-QD / G-QD ratio. The apparent morphology of QD SMA is characterized by OLYMPUS laser microscope, while the optical properties of QD backlight are investigated by F-4600 fluorescence spectrophotometer and SRC-200M spectrum color luminance meter, respectively. Experimental results show that the white balance can be achieved when the QDs account for a certain proportion about 7% within the mixture, and the ratio of R-QD / G-QD is optimized to about 1:12. The proposed system offers an alternative and feasible method for fabricating QD backlight, which may have great application prospects in the future.
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