一款基于新型Field Programmable Gate Array芯片的投影仪梯形校正系统研究与实现

Realization of Keystone Correction based on a New Field Programmable Gate Array Chip

投影设备配备的梯形校正普遍存在校正范围小,画面的一些线条和字符边缘会出现毛刺和不平滑现象,矫正效果不理想.如果采用通用的图像处理芯片和复杂的算法,可以解决上述问题,但又会导致成本急剧上升.为了解决上述矛盾,提出一种基于FPGA(Field Programmable Gate Array)芯片的新型梯形校正实现方案,解决了校正范围与锯齿失真的矛盾问题,并为进一步成为芯片级产品铺平了道路.图像处理采用kaiser窗函数和sinc函数相结合的方法进行插值,这样的滤波器改善了旁瓣抑制,具有较好的通带性能.介绍了梯形失真的产生和校正原理,提出了利用FPGA芯片XC3S400作为核心图像处理单元的梯形校正系统的硬件和软件实现,说明了该芯片结构、功能及特性,最后提供了校正的效果图.

Nowadays the keystone correction has become the basic function of a projector. But there are several ubiquitous problems, such as small rectification scope as well as unsmoothed edge of some lines and characters on the screen. Sometimes the calibration result is unacceptable. The above problems can be resolved by adopting universal image processing DSP and a complicated algorithm, the price of which will rise dramatically. In order to avoid this conflict and reduce the cost of the projector, this paper provides a new keystone correction solution based on the FPGA （Field Programmable Gate Array） chip. It solves the problem of rectification scope and jaggy distortion and provides the building block for being a chip-class product. The image data is processed by the combination of Kaiser window function and Sinc function. Kaiser window has an adjustable parameter. The parameter controls how steeply it approaches zero at the edges. This kind of filters can relieve side-lobe suppression and has better pass-band capability. This paper introduces the theory about how the keystone distortion comes about and how it can be corrected. It puts forward a method to implement the hardware and software of keystone correction system by using FPGA chip XC3S400 as a kernel of image processing unit. It explains the architecture, function and characteristics of the chip and finally gives the image samples of the correction effect.