红外图像实时显示增强系统设计

为了解决红外实时图像处理系统中热像仪输出大动态范围和监视器显示输出小动态范围之间的矛盾，满足信息处理系统大数据量高实时性的要求，设计了一种新的基于FPGA实现的红外实时图像增强算法。首先采用均值滤波的思想统计图像的局部极值，然后使用多级均值法计算图像灰度变换区间分界点，最后对图像作分段线性灰度变换，整个算法通过FPGA实现。实验结果表明，该方法不仅解决了非制冷红外焦平面阵列探测器输出值随其工作时间变化的问题，而且消除了图像中探测器盲元的干扰，丰富了图像背景细节，增强了图像显示效果。与直方图变换等传统图像增强算法相比，该算法计算时间缩短了1.38ms，占用存储资源减少了42倍。在工程应用上，该方案简单可靠，成本较低，易于FPGA实现，可为其他红外实时图像处理系统的设计提供参考。

Design of real-time infrared image enhancing system

There is a severe contradiction between the 14bits output data of the infrared thermal imager and the 8bits input data of the monitor in a real-time infrared image processing system. A novel algorithm for real-time infrared image enhancement based on FPGA is proposed not only to solve this problem but also satisfy the real-time and mass data need of the system. First, an image mean filter is used to compute the local limit values for each frame dynamically. Next, a multi-level average statistics method is designed to calculate the values of segment points for each gray normalization partition. Finally, the means of different linear normalization on different gray level segments is taken to enhance the infrared image. The whole algorithm is developed on the FPGA hardware with Verilog language. Experimental result shows that this algorithm settles the problem that the output values of un-cooled focal plane array detector are varied with its working duration. Moreover, the algorithm could reduce the impact from little bad pixels with very large values, and enhance the details of an image which has some objects of high and low temperature simultaneously in a scene. Compared with histogram projection, one of the most traditional image enhancement methods, this algorithm shortens the computation time about 1.38ms and consumes only 1/42 memory resource than histogram does. Therefore, it could be implemented by FPGA easier and perform better in a real-time infrared image enhancement system. In terms of engineering application, the proposed scheme with simple architecture, high reliability and low cost characters could provide a valuable reference for other design of a real-time infrared image processing system.