The effects of source resolution on resolution enhancement through shifted superimposition projection

Resolution in a projected display is traditionally defined by the number of pixels in the projector's spatial light modulator (SLM). In recent years, different techniques that increase the resolution on the screen above the number of SLM pixels have gained popularity. In one such technique, called pixel‐shifting or shifted‐superimposition, the display physically shifts every n^th frame on the projected screen, and the overlapping pixel grids forms a finer subpixel grid with a higher pixel count. There is still an open question how much this method increases the resolution and how to quantify it. The resolution on the screen also depends upon the resolution of the input image fed to the projector. In this work, we experimentally investigate how the projector performs with resolution enhancement through pixel‐shifting and how this method relates to the source resolution. We also investigate some known methods of resolution measurement and evaluate how these methods perform for the shifted‐superimposition case. We find that the resolution enhancement through shifted‐superimposition enhances the resolution to about 40% over native resolution, and we also find two different measurement methods (grille contrast and least resolvable line pair method) that is relevant for effectively measuring resolution within such systems.     

A YC‐separation‐type projector: High dynamic range with double modulation

Abstract— An experimental projector that features double modulation to obtain high‐resolution (4096 × 2160 pixels) and high‐dynamic‐range images has been developed. Although a conventional projector contains three modulators for red, green, and blue and outputs light after combining the modulated light from these three sources, our projector has an additional modulator for luminance that modulates the combined RGB modulated light. It can display high‐resolution color images by combining three low‐resolution panels for chrominance modulation and one high‐resolution panel for luminance modulation. In addition, the dynamic range is dramatically improved because the double‐modulation scheme minimizes black levels in projected images. The projector demonstrates an extremely high dynamic range of 1.1 million to 1 and 10‐bit tone reproduction.     

Non‐planar projection performance evaluation and projector pose optimization

In projector applications, the actual display effect is primarily dependent on two aspects: projector performance parameters (intrinsic properties), and projector placement (extrinsic properties). Many studies have been conducted on the impact of the original resolution, illumination, and contrast ratio on projection performance. However, few studies have focused on the influence of extrinsic properties, including the position and orientation of the projector on the projection effect. In this paper, three projection performance evaluation criteria—projection resolution, resolution difference, and projection distance difference—are proposed in terms of extrinsic properties. Based on these evaluation criteria, a projection performance evaluation function was constructed. Through this function, as well as optimization employing the multi‐start and Monte Carlo methods, projector pose parameters corresponding to optimal projection effects can be obtained. Evaluations demonstrated that the proposed projection performance evaluation criteria could correctly describe the impacts of projector placement on projection effects. Projection systems arranged according to the projector pose optimization methods achieved good performance on screens in difference shapes with different numbers of projectors, where the resolution and display improved with no change of projector hardware parameters. The optimal projector poses calculated using these optimization methods can provide theoretical guidance for practical projector placement.     

Seamless ultrathin rear projection display

A new architecture for a thin (2‐cm depth) rear projection display is described. In order to achieve this small depth, a very high density of rear projectors is used. Three prototype displays using rear projectors on both 5‐ and 2‐cm pitch arrays are described. The displays can achieve an effective screen pixel pitch of as small as 0.5 mm, which makes this technology competitive in terms of resolution with fine pitch LED displays; however, orders of magnitude fewer LEDs are required: Each rear projector requires only one white LED and a color liquid crystal light modulator. In the three prototypes, the projector light modulators utilize 101‐cm (40 in.), 80‐cm (31.5 in.), and 60‐cm (24 in.) diagonal liquid crystal display glass. To minimize cost, no lenses are utilized for the rear projectors. An RGB LED array may augment the projector array, which provides a low resolution component of the image onto which the high resolution component is superimposed by the projector array. Edge gaps between active areas on adjacent LCD glass units are completely eliminated by the rear projection approach enabling low profile wall‐size seamless displays. Display contrast depends on rear projection screen design.     

An efficient projection defocus algorithm based on multi-scale convolution kernel templates

The focal problems of projection include out-of-focus projection images from the projector caused by incomplete mechanical focus and screen-door effects produced by projection pixilation. To eliminate these defects and enhance the imaging quality and clarity of projectors, a novel adaptive projection defocus algorithm is proposed based on multi-scale convolution kernel templates. This algorithm applies the improved Sobel-Tenengrad focus evaluation function to calculate the sharpness degree of intensity equalization and then constructs multi-scale defocus convolution kernels to remap and render the defocus projection image. The resulting projection defocus corrected images can eliminate out-of-focus effects and improve the sharpness of uncorrected images. Experiments show that the algorithm works quickly and robustly and that it not only effectively eliminates visual artifacts and can run on a self-designed smart projection system in real time but also significantly improves the resolution and clarity of the observer＇s visual perception.     

New Products

The Aydin Controls Model 8063 large-screen projector is a direct-writing CRT/lens assembly for projection of random stroke-generated data. The unit features a resolution of 1024 X 1024 elements, full-scale vector writing time of 50 msecs, and a light output of 10 foot-lamberts. It has a display size of 6 X 6 feet and a throw distance of 14 feet. The projector and drive electronics are packaged as two individual units which may be separated by up to 6 feet.     

Spatially uniform colors for projectors and tiled displays

Abstract— A major issue when setting up multi‐projector tiled displays is the spatial non‐uniformity of the color throughout the display's area. Indeed, the chromatic properties do not only vary between two different projectors, but also between different spatial locations inside the displaying area of one single projector. A new method for calibrating the colors of a tiled display is presented. An iterative algorithm to construct a correction table which makes the luminance uniform over the projected area of one single projector is presented first. This so‐called intra‐projector calibration uses a standard camera as a luminance measuring device and can be processed in parallel for all projectors. Once the color inside each projector is spatially uniform, the set of displayable colors — the color gamut — of each projector is measured. On the basis of these measurements, the goal of the inter‐projector calibration is to find an optimal gamut shared by all the projectors. Finding the optimal color gamut displayable by n projectors in time O(n) is shown, and the color conversion from one specific color gamut to the common global gamut is derived. The method of testing it on a tiled display consisting of 48 projectors with large chrominance shifts was experimentally validated.     

服务机器人智能空间中顶棚投影器建模与外参数标定

研究服务机器人智能空间中顶棚投影器的运动学建模和外参数标定问题.首先,利用D-H方法对投影器进行运动学建模;然后,给出一种全新的求解一类关于旋转矩阵方程组的非线性迭代优化算法,以完成投影器的外参数标定;最后进行了实验验证.实验结果表明,所提出的投影器建模方法和外参数标定算法具有很高的精度,经过标定后的投影器能够在地面上投射出完全按期望路径引导机器人运动的激光斑点,从而实现低成本服务机器人高效和精确地导航.     

多媒体教室投影仪的科学维护

针对目前国内各高等院校为了大力发展现代化教育,建设了大量的多媒体教室,其中多媒体教室中的投影仪这一重要的教学设备,在教学过程中经常会突然出现故障,这些都严重影响到了正常的教学工作,为了提高投影仪的正常工作时间,降低投影仪的故障率,科学维护投影仪的工作至关重要,根据投影仪的工作原理,强调了对多媒体教室投影仪进行科学维护的重要性以及方法。     

面向识别的雷达舰船目标低分辨回波仿真技术

雷达目标回波的高精度仿真是目标识别系统训练和测试的重要手段.针对低分辨雷达舰船目标自动识别的应用背景,提出了基于模板和模型的低分辨回波仿真技术.根据舰船目标的CAD三维模型,利用电磁计算方法得到全姿态的一维距离像模板.在凝视状态下,利用目标距离像模板和雷达发射信号模拟目标低分辨回波;在扫描状态下,利用全姿态一维距离像重构不同角区中目标的散射中心模型,并结合雷达波束的扫描方式获得了目标的仿真回波.结果表明,所提出的基于模板和模型的回波仿真技术对雷达舰船目标具有良好的低分辨回波仿真能力.     

Automatic Registration of Multi‐Projector Domes Using a Single Uncalibrated Camera

In this paper we present a novel technique for easily calibrating multiple casually aligned projectors on spherical domes using a single uncalibrated camera. Using the prior knowledge of the display surface being a dome, we can estimate the camera intrinsic and extrinsic parameters and the projector to display surface correspondences automatically using a set of images. These images include the image of the dome itself and a projected pattern from each projector. Using these correspondences we can register images from the multiple projectors on the dome. Further, we can register displays which are not entirely visible in a single camera view using multiple pan and tilted views of an uncalibrated camera making our method suitable for displays of different size and resolution. We can register images from any arbitrary viewpoint making it appropriate for a single head‐tracked user in a 3D visualization system. Also, we can use several cartographic mapping techniques to register images in a manner that is appropriate for multi‐user visualization. Domes are known to produce a tremendous sense of immersion and presence in visualization systems. Yet, till date, there exists no easy way to register multiple projectors on a dome to create a high‐resolution realistic visualizations. To the best of our knowledge, this is the first method that can achieve accurate geometric registration of multiple projectors on a dome simply and automatically using a single uncalibrated camera.     

结构光三维测量系统的建模与标定

改进了结构光三维测量系统的数学模型,将投影仪的内外部参数引入其中,并在该模型的基础上采用了一种投影仪标定的新方法.为了提高黑白摄像机在暗区的对比度用红/蓝棋盘代替了黑/白棋盘.将投影仪看作是摄像机的倒置,统一了标定摄像机和投影仪的方法.在3dMA×仿真环境下分别标定了摄像机和投影仪,标定实验的相对误差小于0.32%.利用已经标定的结构光三维测量系统进行重构仿真实验,测量误差小于0.136mm.     

Metric classifier using multilevel network of templates

A new approach is proposed to constructing a classifier of two-dimensional (2D) objects in a space of multiresolution object representations. The approach is based on constructing tree-structured covers (TSCs) of clusters of a training set by spheres in the space of the object representations taken at the maximum resolution level. The covering spheres and their projections of all resolution levels generate a multilevel network of templates in which the sphere centers yield the templates, while the spheres themselves form the influence regions of the templates at the corresponding resolution levels. Using the multilevel structure of the template network, a hierarchical search algorithm is proposed for making a decision group of the templates by a given voting criterion. A computational complexity of this algorithm is evaluated. An efficiency of the proposed TSC classifier is demonstrated by estimates of error rates in experiments on signature, hand gesture and face recognition, as well as by the comparative error rates obtained for these sources using the known SVM classifier.     

基于投影二维平面靶标的投影仪现场标定方法研究

投影仪的标定是结构光三维视觉测量系统应用的基础。提出了一种利用投影二维平面靶标对投影仪进行现场标定的新方法。与传统的投影仪标定相比,该方法不需要精密的标定设备,提高了标定精度,简化了标定过程,能够满足现场不断变换的要求。实验证明:该标定方法获得的结果较准确,方法简便易行,能够满足现场不断变化的测量需求。     

A high‐resolution autostereoscopic display system with a wide viewing angle using an LCOS projector array

Abstract— This study develops an autostereoscopic display based on a multiple miniature projector array to provide a scalable solution for a high‐resolution 3‐D display with large viewing freedom. To minimize distortion and dispersion, and to maximize the modulation transfer function (MTF) of the projection image to optimize 3‐D image quality, a dedicated projection lens and an accurate six‐axis adjusting platform for the miniature projector were designed and fabricated. Image‐blending technology based on a lookup table was adopted to combine images from 30 miniature projectors into a seamless single image. The result was a 35‐in. autostereoscopic display with 60 views ata 30° viewing angle, 90° FOV, and large range of viewing distance. The proposed system exhibits very smooth motion parallax when viewers move around in front of it.     

Aqueous droplet manipulation by optically induced Marangoni circulation

The manipulation of picoliter droplets is demonstrated using optically induced microscale circulatory flows. The circulation results from Marangoni effects induced by optical heating from light patterns created by a computer projector. Manipulation of single droplets and parallel manipulation of multiple droplets are achieved with induced forces of up to 1 nN and an average resolution of 146.5 μm.     

投影仪曲面投影校正技术

当投影仪将图像投影到曲面时,为使观察者看到不失真图像,采用两步校正法对图像进行预变形处理．该方法将投影仪假设为针孔模型,并获取投影系统的相关几何参数,通过对观察者所需的理想图像进行变换获得投影仪所需预变形图像．利用纹理投影技术并采用OpenGL编程实现该校正方法．实际投影结果表明该方法可以取得较好效果．     

结构光测量系统的投影仪标定方法研究

传统单目视觉结构光测量系统通过解相位间接计算被测物的高度信息,系统约束性过强、不易操作、且标定精度较低.将双目立体视觉原理引入单目结构光视觉测量系统,根据投影仪图像坐标和摄像机图像坐标的对应关系,将投影仪当作一个逆向的相机,建立了投影仪模型,使用成熟的相机标定算法对投影仪进行标定.再配合四步相移法和基于多频外差原理的时域相位展开法,实现条纹图像的快速精确解相位.相对于传统的单目视觉结构光测量系统,本方法具有单目视觉系统操作简单、鲁棒性强的特点,同时也可以达到双目视觉测量的精度.实验结果表明,这种方法的投影仪标定精度达到了实际应用的要求.     

Flexible calibration of structured-light systems projecting point patterns

Structured-light systems (SLSs) are widely used in active stereo vision to perform 3D modelling of a surface of interest. We propose a flexible method to calibrate SLSs projecting point patterns. The method is flexible in two respects. First, the calibration is independent of the number of points and their spatial distribution inside the pattern. Second, no positioning device is required since the projector geometry is determined in the camera coordinate system based on unknown positions of the calibration board. The projector optical center is estimated together with the 3D rays originating from the projector using a numerical optimization procedure. We study the 3D point reconstruction accuracy for two SLSs involving a laser based projector and a pico-projector, respectively, and for three point patterns. We finally illustrate the potential of our active vision system for a medical endoscopy application where a 3D cartography of the inspected organ (a large field of view surface also including image textures) can be reconstructed from a video acquisition using the laser based SLS.     

针对多投影仪显示墙画面校正的图像对准技术

针对多投影仪显示墙画面校正问题中相机与投影仪间图像对准问题,提出一种基于自适应细分网格的稀疏对应点加密方法,可以得到任意光滑屏幕上投影图像与相机图像间的像素级对应关系。该方法利用改进的自适应4点插值细分曲线思想构造细分网格方法,可以将投影仪图像与相机图像间稀疏对应点网格加密到任意精度,从而建立从相机到投影仪图像间的像素级一一映射关系,为多投影仪显示墙系统的几何和色彩校正提供精确的图像对准基础。与现有算法的对比分析和虚拟机场塔台仿真系统中的实际应用表明,该方法具有较高的图像对准精度,并且无显式的需求投影仪、投影屏幕和相机的内部参数。