基于二值化图像叠加的CMOS相机动态范围扩展方法

Method for Enlarging Dynamic Range of CMOS Camera Based on Binary Image Superposition

受动态范围的限制,传统的CMOS相机需要通过曝光时间控制和自动增益控制方式减小像素饱和与溢出的影响,以获得目标场景的清晰信息。若要同时获取目标场景的暗场和亮场图像,必须扩展CMOS图像传感器的动态范围。提出一种基于二值化图像叠加的CMOS相机动态范围扩展方法。该方法利用曝光时间按对数变化的一系列二值化图像进行叠加,拓宽了CMOS相机的图像探测动态范围,即使在亮度变化很大的环境下也能实现强信号和弱信号的同时探测,从而获得目标场景清晰的灰度图像。实验结果表明,与传统CMOS相机成像相比,二值化叠加CMOS相机的相对动态范围最高可拓宽8倍以上。通过图像亮度曲线对比,发现二值化叠加CMOS相机具有有效的对数响应输出。二值化叠加CMOS相机能有效减少图像亮处的饱和溢出和暗处细节信息的丢失,在高亮和背光处均能获得完整清晰、亮度均匀的图像。

Due to the limitation of dynamic range, it needs to control the exposure time and automatic gain for traditional cameras to obtain clear information of the target scene through reducing the influences of pixel saturation and overflow. In order to obtain a clear image simultaneously including dark and bright field information, the dynamic range of the CMOS image sensor must be extended. In this paper, a dynamic range expanding method of CMOS cameras based on binary image superposition is proposed. By superposing a series of binary images with a logarithmic exposure time, the image detection dynamic range of the CMOS camera is improved. As a result, the camera can simultaneously detect strong and weak signals even in the environment with a large brightness variation, and obtain clear gray images of the target scenes. The experimental results show that the relative dynamic range of this binary superposition CMOS camera can be enlarged to more than 8 times that of the traditional counterpart. A comparison of image brightness curves shows that this camera has an effective logarithmic response output. This camera can also effectively reduce the saturation overflow in the bright part and the loss of details in the dark part of the image, and can obtain a complete clear and uniform image in both the highlighted and backlit parts.