A robust photometric calibration framework for projector-camera display system

A novel photometric calibration framework is presented for a projector-camera （ProCam） display system, which is currently under booming development. Firstly, a piecewise bilinear model and five 5-ary color coding images are used to construct the homography between the image planes of a projector and a camera. Secondly, a photometric model is proposed to describe the data flow of the ProCam display system for displaying color images on colored surface in a general way. An efficient self-calibration algorithm is correspondingly put forward to recover the model parameters. Aiming to adapt this algorithm to different types of ProCam display system robustly, a 3× 7 masking coupling matrix and a patches image with 1024 color samples are adopted to fit the complex channel interference function of the display system. Finally, the experimental results demonstrate the validity and superiority of this calibration algorithm for the ProCam display system.     

Color rendering and luminous efficacy analysis in YAG PC-LED by improved Gauss simulation

Gauss simulation is often used to help design new LEDs according to photometric and colorimetric performance requirements. This research investigates an improved Gauss simulation model for simulating YAG-PC LEDs. Three types of PC-LEDs are investigated at commonly used CCT ranges. This research shows that desirable photometric and colorimetric qualities can be achieved. For warm white, pure white and cold white CCT ranges, CRI of 72.1, 79.8 and 84.5 can be achieved, respectively. LEDs with optimal color rendering qualities are designed; packaging and measurement of said LEDs shows that the simulation model is successful.     

小电流LED屏白平衡色温的控制

为了改善小电流LED屏的显示效果,基于新型LED灯珠光学性能测试数据,采用变量控制法,首先,分析了单色RGB色坐标及亮度分别对白平衡色温的影响,接着,从单变量分析中找到影响色温偏差较大的参数进行双偏分析,最后,进行变量分析结论的数据验证。研究结果表明,红光芯片亮度(Lr)、蓝光芯片亮度(Lb)及蓝光芯片坐标(Yb)是影响LED屏白平衡色温的主因,要使白平衡色温偏差控制在±500 K范围内,单偏条件下,要求Lr偏差不超过11%,Lb偏差不超过14%,Yb偏差不超过0.006;同时,也给出了双偏条件下相应的控制指标。该研究有望在LED分光机芯片分选,白光照明及小电流、小间距LED显示屏色偏差调节等方面获得相关的应用。     

超薄前投激光显示系统研制

为了解决光学系统投影厚度过大问题,采用自由曲反射面结合非球面设计方法设计出超短距离、超广角投影显示系统,其屏幕投影距离小于20 cm。为解决激光色域系统转换,建立了激光三基色与荧光粉三基色色域变换与扩展的理论模型并搭建了基于DSP高速图像处理芯片为核心的颜色变化实时硬件处理试验开发系统。通过该系统可以调试不同颜色系统转换算法,验证转换模型的正确性,并为实现专用颜色转模块提供了开发平台。     

辅助脉冲数调制改善彩色等离子体显示器的白平衡

为改善彩色等离子体显示器(PDP)的白平衡,研究了维持期寻址电极辅助脉冲对PDP亮度的影响,提出了辅助脉冲数调制改善PDP白平衡的新方法。通过在各子场对三基色寻址电极分别加幅度、宽度和延时相同,但数目不同的辅助脉冲,从而改变三基色之间的亮度比率,使每个子场和各灰度级的白平衡满足要求,改善了全屏白平衡一致性,而不需要改变现有电路硬件设计,不增加额外电源。实验结果表明,在整个灰度区间,PDP的白平衡平均从0.021改善到0.0025,并且分布在较小的色温区间。     

彩色显示管电子光学系统的计算和分析

为了实现高清晰度显示,大量采用非旋转对称的系统以减小电子束上屏的束点尺寸。考虑到目前电子光学系统的一些新特点,采用一些特殊的模拟方法利用SEU-3D三维程序计算和分析了彩色显示管中电子光学系统     

Development of a PC interface board for true color control using an Ar–Kr white-light laser

For the optimal laser display, it is crucial to select and control color signals of proper wavelengths in order to construct a wide range of laser display colors. In traditional laser display schemes, color control has been achieved through the mechanical manipulation of red, green, and blue (RGB) laser beam intensities using color filters. To maximize the effect of a laser display and its color contents, it is desirable to generate laser beams with wide selection of wavelengths. We present an innovative laser display control technique, which generates six channel laser wavelengths from a white-light laser using a RF-controlled polychromatic acousto optical modulator (PCAOM). This technique enables us not only to control the intensity of individual channels, but also to achieve true color signals for the laser beam display including RGB, yellow, cyan, and violet (YCV), and other intermediate colors. For the optimal control of the PCAOM and galvano-mirror, we designed and fabricated a PC interface board. Using this PC control, we separated the white-light from an Ar–Kr mixed gas laser into various wavelengths and reconstructed them into different color schemes. Also we demonstrated the effective control and simultaneous display of reconstructed true color laser beams on a flat screen.     

一种色度自适应投影标记点的选取方法

近年来,对物体的颜色显现力、光源光谱功率分布和自身表面反射光谱三者的定量关系方面的研究备受大家关注。在三维扫描测量领域,由于颜色特征具有反映物体材料和纹理等丰富信息的优势,提出了一种主要由彩色相机、投点光源和PC机组成的色度自适应投点仪结构,其中数字微镜(DMD)作为投点光源的核心元件用于调制R,G,B 三个LED光源的光谱功率分布。然而主动式标记点的颜色显现力因受未知反射光谱投影接受面的影响,其颜色特征往往难以识别和区分。为了提高投影标记点与不同反射光谱的投影接收面作为背景的分辨力,描述了一种色度自适应投影标记点的选取方法。在高维线性反射光谱建模的基础上,用光谱响应的方法对彩色投点仪设备特征化,以解决三通道彩色相机设备特征化精度低的问题。并通过样本训练为高维线性反射光谱的求解提供条件约束。继而,在CIE1931色度坐标空间下,选取与投影接收面背景色度坐标欧氏矩最大的色度坐标点。根据投点仪设备特征化结果,推导其LED最优设定值。最后,采用24孟塞尔色卡作为被投影对象,主动标记点与色块的色差作为其颜色显现力的评价参数,通过与激光二极管投点仪做对比性实验。实验结果表明对各不同色度的投点接受面,提出的色度自适应投影标记点的选取方法均有较好表现。     

微型投影机光学引擎的研究

设计了一种针对个人用户使用的微型投影机光学引擎,系统为单片式数字光线处理器结构,采用红绿蓝三色大功率高亮度发光二极管作为光源,使用X棱镜作为合色元件,从而实现38.1～50.8 cm的彩色投影显示.对设计结果进行理论分析后可知,设计结果满足投影显示对颜色的要求,光学引擎的理论效率为16.1%.同时利用Light Tools仿真软件对系统进行建模分析,300万条光线追迹仿真的结果表明,光学引擎的效率为14.6%,与理论分析结果基本符合,屏幕上光通量为22.8 lm,其美国国家标准协会规定的九点照度均匀性达到91.55%和-93.36%,满足设计要求.     

Voltage-controlled optical filter based on electrowetting

In this letter, we propose a voltage-controlled optical filter based on electrowetting. The device is made of a transparent cubic cell filled with two immiscible liquids having three indium tin oxide electrodes fabricated on the bottom substrate of the cell. A conductive droplet carrying a color filter is placed on the ITO electrode and the surrounding liquid is density-matched silicone oil. Under zero bias, the droplet is placed in the middle of the substrate and white light passes through the filter and we can see red light on the screen. When a voltage is applied to the device, the filter moves with the liquid based on electrowetting effect, we can see the white light on the screen. Due to the movement of the liquid, our device functions as an optical switcher. The switch time of the device is ~70 ms. The proposed device has a wide application in optical communication, electronic display, and optical switch.     

Fast time-division color electroholography using a multiple-graphics processing unit cluster system with a single spatial light modulator

We demonstrate fast time-division color electroholography using a multiple-graphics-processing-unit(GPU) cluster system with a spatial light modulator and a controller to switch the color of the reconstructing light. The controller comprises a universal serial bus module to drive the liquid crystal optical shutters. By using the controller, the computer-generated hologram(CGH) display node of the multiple-GPU cluster system synchronizes the display of the CGH with the color switching of the reconstructing light. Fast time-division color electroholography at 20 fps is realized for a three-dimensional object comprising 21,000 points per color when 13 GPUs are used in a multiple-GPU cluster system.     

A Color Holographic Reconstruction System by Time Division Multiplexing with Reference Lights of Laser

3D-TV systems by holography technique have been studied in the world. In this paper, we report a color holographic reconstruction system by time division multiplexing method with reference lights of laser. The method can reconstruct a color holographic image by switching reference lights of red, green and blue colors at certain intervals. We can observe a color holographic image using red and green lasers as the reference lights, a high minute liquid crystal display (LCD) panel as a spatial light modulator (SLM) and electro-shutters as the shuttering device of the laser lights in the optical system. This approach has some advantages. Namely, the structure of the optical system can be simple and the number of LCD panels in the optical system can be decreased.     

LED显示屏高光效高画面填充比光学设计与研究

针对传统LED显示屏光能利用率和图像画面填充比低的缺点,基于非成像光学理论,提出了一种提高光能利用率和画面填充比的全彩LED显示模块结构系统和设计方法。利用复合抛物面集光器CPC对LED管芯发出光线的发散角进行变换压缩,从而避免了外表面全反射损耗,大幅度提高了系统的光能利用率。利用积分方腔匀光原理和散射元件对光能的二次分配,提高了显示屏的画面填充比、单位像素均匀度及基色复用面积。作为实例,根据上述方法设计了一个P10 mm全彩LED显示模块,利用光学设计软件LIGHTTOOLS对该显示模块系统进行了仿真建模和光线追迹,并对设计结果进行了分析。结果表明,系统光能利用率大于70%,画面填充比接近100%,单位像素区域内均匀度好于85%。显示模块具有能量利用率高、高画面填充比、显示效果均匀柔和、易于生产和装调的优点。     

Red-enhanced white light-emitting diodes using external AlGaInP epilayers with various aperture ratios

A novel hybrid white light-emitting diode (LED) is proposed to enhance the red color and stability of the chromaticity under various operating currents using an AlGaInP photon-recycling (PR) epilayer. A blue/yellow white InGaN LED sample is covered with an external patterned AlGaInP epilayer. Under an optimum aperture ratio of 30%, the luminous efficiency of the PR-LED lamp can achieve a color coordinate of (x=0.340, y=0.295). When the injection current increases from 50 to 350 mA, the color temperature decreases from 4030 to 3700 K and the color rendering index increases from 81 to 86. These could be due to the fact that the AlGaInP epilayer was not attached onto the LED chip, alleviating the thermal effect on the color coordinate. The present white PR-LED samples have high potential for portable liquid-crystal-display backlight applications.     

数码相机原理与系统设计研究

介绍了数码相机的工作原理 ,分析了数码相机的系统结构 ,提出了设计数码相机的处理流程。典型的数码相机系统有镜头、闪光灯、光学取景器、LCD显示屏、图像数据存储扩展设备接口、图像数据传输接口、供电系统以及核心处理器等八个主要模块。数码相机的数据流向从图像传感器开始 ,止于图像数据的存储和传输。数据流的处理主要包括模数转换、光学黑电平钳位、针对镜头的边缘畸变的运算修正、坏像素处理、白平衡处理、伽马校正、色彩合成处理、边缘检测 (锐度检测 )和伪彩色检测 (伪彩色抑制 )、JPEG压缩和图像存储器等模块     

真实场景的三维视频采集及显示

提出了一种真实场景三维视频采集及彩色显示的方法.设计了一种采用条纹投影的实时三维成像系统及采用液晶空间光调制器的实时全息彩色三维显示系统.在三维成像系统中采用π相移正弦条纹与编码图案结合实现绝对相位测量,从而可以测量孤立物体.同时对采用数字微镜的投影仪进行改造,实现高速投影,并与高速摄像机配合实现三维视频采集.首先利用实时三维成像系统同时获取三维场景的彩色强度像和距离像;然后根据这些三维成像数据, 设计和制作计算菲涅耳全息图;最后在实时全息彩色三维显示系统中再现.三维信息的采集和显示速度达到了60帧每秒.     

360 degree realistic 3D image display and image processing from real objects

A 360-degree realistic 3D image display system based on direct light scanning method, so-called Holo-Table has been introduced in this paper. High-density directional continuous 3D motion images can be displayed easily with only one spatial light modulator. Using the holographic screen as the beam deflector, 360-degree full horizontal viewing angle was achieved. As an accompany part of the system, CMOS camera based image acquisition platform was built to feed the display engine, which can take a full 360-degree continuous imaging of the sample at the center. Customized image processing techniques such as scaling, rotation, format transformation were also developed and embedded into the system control software platform. In the end several samples were imaged to demonstrate the capability of our system.     

Computer Generated Rainbow Hologram

The rainbow hologram is very practical to display 3-D images because it can be reconstructed with white light. We propose a simplified model to calculate the computer generated rainbow hologram quickly. In the proposed method, we can simply generate the final hologram from intermediate data, whose total number of samples can be less than one tenth of the final hologram. This intermediate format makes fast computation and effective storage/transmission possible. Only multiple and additional operation need be used to convert the intermediate data to final data. Therefore, it is possible that hardware can be added to an electro-holographic display or printer. In this paper, we discuss both theory of the simplified model and experimental results of white light reconstructed images. Full color holograms are also discussed.     

Beat pattern selection — Multi-color-grating moiré

It is shown how a specific beat pattern can be extracted from superposed periodic structures. The selection is a accomplished by addition of three spatially shifted versions of a conventional moiré. This displacement is automatically achieved using color component gratings and the beat discrimination by the color sequence within them. For the final display a black and white system is used.     

Theoretical Modeling of Luminous Efficacy for High-Power White Light-Emitting Diodes

The photometric characteristics of high-power white light-emitting diode(LED)devices are investigated.A theoretical model for the luminous efficacy of high-power white LED devices and LED systems is proposed.With the proposed theoretical model,the mechanism of the luminous efficacy decrease is explained.Meanwhile,the model can be used to estimate the luminous efficacy of LEDs under general operation conditions,such as different operation temperatures and injection currents.The wide validity of the luminous efficacy model is experimentally verified through the measurements of different types of LEDs.The experimental results demonstrate a high estimation accuracy.The proposed models not only can be applied to estimate the LED photometric performance,but also is helpful for reliability research of LEDs.