Multi-Projector Display System

With the rapid expansion of information and the fast improvement of storage or transmission, people are becoming more and more interested in higher resolution display devices. Traditional single projector, which is either cheap and of low resolution, or expansive and of high resolution, can not meet users'daily demand. Multi-projector technique, which is aimed to solve this problem, uses several low-level projectors to display a whole high-resolution image or video.Multi-projector technique, comes with two new issues:the first is, the edge of abutting projectors is not matched; the second is the color-changing of each projector is not the same. The methods to solve the two issues, are named "geometric calibration" and "photometric calibration", which are motivated to build a seamless large-area high-resolution display wall.This article will introduce our multi-projector display system (MPDS). It contains a graphics-rendering cluster with 18-node high performance PC, a high-resolution display wall with 15 ordinary projectors and a large curtain. Besides, we develop a function-consummate software including client and server parts, which is able to automatically accomplish the geometry and photometric calibrations and control the cluster and projectors to carry associated tasks.First, we introduce the process of building the MPDS'hardware environment and the problems we are facing:what kind of configuration the cluster we will use, how to choose the optimal projecting-mode and equipments to realize perfect display-effect, and so on.Next, in this article we introduce how we built MPDS hardware environment to visually achieve the seamless multi-projector splicing-logically as one projector. We improve the methods both in geometry and photometric calibration, and gain good results. In geometric calibration, we pre-calibrate the digital camera to get its distortion coefficient, which we apply to traditional linear geometric calibration method and achieve geometry seamlessness with high precision. In photometric calibration, we use the method combining edge-blending and piecewise linear brightness compensation, without knowing the optical properties of each projector, and also gain good photometric seamlessness results. After that, we use two different devices-photometer and camera to get projector's intensity transfer function, and compare the difference.Then, this article introduces the MPDS'software architecture which contains one client part and two server parts. The basic functions of the software are divided into five parts:progress control, projector control, projector setting, calibration and display, so the UI is designed as a property page. Here, each button's specific function and usual operational process will be explain in detail.In the end, we make a conclusion of this article and give some ideas about our future work.