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Dual-frame decentralized fusion scanning for digital drive on-silicon microdisplays
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摘要:
当microLED处于正向工作区时，难以精确调节它们的电压来获得不同的发光亮度；且当microLED/OLED工作时，会较长时间处于闭合状态，导致人眼观察到的图像显示亮度变差。为解决以上问题，本文提出一种双帧分权融合扫描策略，通过调节microLED/OLED导通时间来获得不同亮度。该方法先对数据位重新分权，使导通时间分散插入到闭合时间内，然后将分权后的各数据位权值进行双帧融合，最后重新定义数据位的扫描顺序。并根据所提出的扫描策略设计了一款面向数字驱动式硅基微显示器的扫描控制器。结果表明：本文提出的双帧分权融合扫描策略可以精确调节microLED/OLED的发光亮度，提高人眼观察到图像显示亮度。该扫描策略与其它扫描策略相比，扫描效率提升至93.75%，场频提升至2040 Hz，扫描时钟频率为102.36 MHz，且同时减小了扫描数据带宽。最后通过测试证明了扫描控制器的可行性。
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关键词:
- 发光亮度 /
- 双帧分权融合 /
- 数字驱动式硅基微显示器 /
- 扫描控制器 /
- 扫描效率
Abstract:When the microLED is in the forward working direction, it is difficult to precisely adjust its voltage to obtain different brightness. Moreover, when the microLED/OLED is turned on, they will be in a closed state for a long time, causing the image display brightness to be deteriorated by the human eye. In order to solve these problems, this paper proposes a dual-frame decentralized fusion scanning strategy to achieve different brightness by adjusting the microLED/OLED on-time. Firstly, the method de-weights the data bits and inserts their on-times into the closed time. Then the data bit weights are double-frame fused after decentralization. Finally, the scanning order of the data bits is redefined. According to the proposed scanning strategy, we designed a scanning controller to drive digital on-silicon microdisplay. The results show that the dual-frame decentralized fusion scan proposed in this paper can accurately adjust the luminance of microLED/OLED and improve the brightness of the image observed by human eyes. Compared with other scanning strategies, the scanning strategy improves the scanning efficiency to 93.75%, the field frequency is increased to 2040 Hz, the scanning clock frequency is 102.36 MHz, and the scanning data bandwidth is reduced. The feasibility of the scan controller is proved by testing at last.
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Overview: MicroLEDs and OLEDs are the two leading edge display technologies. Compared to conventional LED technology, microLED has higher luminance and luminous efficiency, and lower power consumption at the same brightness. Both microLED and OLED luminescent materials can be grown on a silicon substrate to form an on-silicon microdisplay. When the microLED is in the forward working direction, it is difficult to precisely adjust its voltage to obtain different brightness. Moreover, the microLED/OLED will be in a closed state for a long time during working, resulting in deterioration of the brightness of the image observed by the human eye. In order to solve these problems, this paper proposes a dual-frame decentralized fusion scanning strategy to achieve different brightness by adjusting the microLED/OLED on-time. Firstly, the method de-weights the data bits and inserts their on-times into the closed time. Then the data bit weights are double-frame fused after decentralization. Finally, the scanning order of the data bits is redefined. According to the proposed scanning strategy, we designed a scanning controller to drive digital on-silicon microdisplay. The results show that the dual-frame decentralized fusion scan proposed in this paper can accurately adjust the luminance of microLED/OLED and improve the brightness of the image observed by human eyes. Compared with other scanning strategies, the scanning strategy improves the scanning efficiency to 93.75%, the field frequency is increased to 2040 Hz, the scanning clock frequency is 102.36 MHz, and the scanning data bandwidth is reduced. The digital drive on-silicon microdisplay system used in this paper is mainly divided into two parts. The first part is the microdisplay driver chip, which mainly includes row, column and pixel driver circuits. The second part is the scan controller, which will process the data signal from the video source and generate the control signal to control the operation of the microdisplay. When the video source data is entered, we need to process it in a certain way, such as image scaling, gamma correction, etc., and then transfer the data to the RAM module. The RAM module functions as a buffered data before data storage. When the cached data input to the RAM satisfies the burst length of the SDRAM, the data is input to the SDRAM module. The SDRAM module acts as an external memory for the frame buffer and rearrange the data according to the scanning policy. The scan control module receives the data transmitted by the SDRAM module and generates the timing required to control the microdisplay. Both RAM module and SDRAM are operated by ping-pong operation. Finally, the output module is used to configure the LVDS interface on the FPGA and the chip, and then transmit the control signal generated by the controller and the processed data signal to the microdisplay through the interface to display the image. The scan controller proved to be feasible by testing at last.
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图 4 数字式硅基微显示器整体系统结构
Figure 4. The overall structure of digital on-silicon microdisplay system
图 5 (a) 硅基OLED芯片；(b)硅基microLED芯片
Figure 5. (a) OLED on-silicon chip; (b) MicroLED on-silicon chip
图 8 (a) 控制器实物图；(b)硅基微显示器点亮图；(c)列驱动测试图；(d)行驱动测试图
Figure 8. (a) The photo of the controller; (b) On-silicon microdisplay lighting; (c) Column drive test; (d) Line drive test
表 1 数字式硅基微显示器各性能参数
Table 1. The parameters of digital on-silicon microdisplay system
发光材料 灰度等级 分辨率 尺寸/inch 像素密度/PPI OLED(RGB) 256 1600×(3)×1600 1.15 1968 OLED(单色) 256 1280×1024 0.64 2561 MicroLED(单色) 256 1280×720 2.89 5000 
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表 2 各算法性能参数
Table 2. Algorithm performance parameters
扫描算法 线性度/% 扫描效率/% 场频/Hz 传统线性PWM 100 3.52 15360 12子场 100 66.41 720 19子场 100 83.88 1140 “Z”字形扫描 25 100 480 双帧分权融合 100 93.75 2040
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