STimulated emission depletion (STED) nanoscopy has been proposed to extend greatly our capability of using light to study a variety of biological problems with nanometer-scale resolution. However, in practice the unwanted background noise degrades the STED image quality and precludes quantitative analysis. Here, we discuss the underlying sources of the background noise in STED images, and review current approaches to alleviate this problem, such as time-gating, anti-Stokes excitation removal, and off-focus incomplete depletion suppression. Progress in correcting uncorrelated background photons in fluorescence correlation spectroscopy combined with STED (STED-FCS) will also be discussed.

受激发射损耗（STED）纳米显微镜已经提出了大大延长我们利用光来研究各种与纳米级分辨率的生物学问题的能力。然而，在实践中多余的背景噪音降低了STED的图像质量，并且排除了定量分析。在这里，我们讨论STED图像背景噪声的深层根源，并检讨目前的办法来缓解这一问题，如时间选通，反斯托克斯激发去除，并且离焦不完全枯竭抑制。在校正在荧光相关光谱与STED（STED-FCS）结合不相关的背景光子进步也将被讨论。