超弱发光成像的分水岭法光子信息提取

Photonic information extraction of utraweak emission imaging based on watershed algorithm

对电子倍增CCD(EMCCD)超弱光子成像图像灰度的特性分析发现,一个像素的灰度值与相邻的8个像素的灰度值有强相关性。这一特征说明,简单地使用阈值法对其进行光子信号的数量和位置信息提取和图像处理,将会有较大的失真性。在超弱发光的条件下(如生物超弱发光),一幅图像中的光子信号数远小于像素数,光子信号在图像中呈现散粒状态。据此,在阈值法的基础上引入数学形态学分水岭法,将处理后光子灰度图像中孤立的峰值区作为光子信号响应。新算法克服阈值法只能对单个像素进行判断的局限,考虑到局部像素群的整体特征。结果表明,新算法的处理结果更加真实可靠,稳定性更好。通过绿豆芽的超弱自发光成像实验,验证了新算法的灵敏度和可靠性。

Electron multiplier CCD （EMCCD） can potentially count a single photon because of the very low detection noise. But the gray values of adjacent pixels are highly correlated with each other in photon grayscale images obtained by EMCCD （coorelation coefficients are larger than 0.72）. This feature shows that the number and location of photon signals will have a greater distortion if the images are processed based on the threshold algorithm. In addition,the number of photon signals isolated from each other in an image is much smaller than that of pixels under the situation of ultraweak luminescence, e. g. Therefore, a new algorithm was developed based on watershed algorithm by treating one isolated high-value region as the response of one photon. This new algorithm gives baseline estimation synchronously, and takes the characteristics of group pixels into account rather than a single pixel. The results show that the new al gorithm is more reliable and stable due to reducing the influence of unsureness of optimal threshold value and protecting the location information of photons better. The sensitivity and reliability of this new algorithm are also tested and confirmed with EMCCD imaging of mung bean sprouts, even the signals are as weak as 146 photons/image.