Simple and Efficient Method to Eliminate Spike Noise from Spectra Recorded on Charge-Coupled Device Detectors
Simple and Efficient Method to Eliminate Spike Noise from Spectra Recorded on Charge-Coupled Device Detectors
复制标题
消除电荷耦合器件探测器记录光谱中尖峰噪声的简单有效方法
DOI：
10.1366/0003702934048578
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发表时间：
1993
影响因子：
3.5
通讯作者：
I. Harada
中科院分区：
文献类型：
--
作者：
H. Takeuchi;S. Hashimoto;I. Harada
电荷耦合器件 (CCD) 探测器具有多种适合在极低光照水平下进行光谱测量的特性。 CCD 的量子效率在很宽的波长范围内都很高，并且通过冷却探测器可以大大降低暗计数率。通过将像素合并框设置为实际照亮的检测器区域，可以进一步减少暗计数。如果探测器充分冷却并且在适当的合并后执行信号读出，则除了不可避免的光子散粒噪声之外，唯一重要的噪声源是信号读出过程中产生的噪声。由于读出噪声与曝光时间无关，因此原则上，较长的曝光时间可提供更好的信噪比 (S/N)。然而，曝光时间的实际限制是由尖峰噪声决定的，尖峰噪声是由宇宙射线以及探测器芯片周围的材料发射的可能的 γ 射线和 α 射线产生的。这种高能射线的每一量子撞击 CCD 芯片通常会在像素中产生数千个电子，而探测器吸收的单个光子平均产生不到一个电子。因此，尖峰噪声有时会掩盖非常低的光级光谱。为了进一步延长曝光时间并实现更好的信噪比，需要区分尖峰噪声与真实光子信号并可靠地消除尖峰。有时，采用中值滤波器进行数据处理，以消除 CCD 探测器记录的光谱中的尖峰。然而，这种滤波方法是一种平滑，并且有可能使光谱失真，特别是当光谱线宽与尖峰的线宽相当或小于尖峰的线宽时。我们开发了一种简单有效的方法来消除尖峰噪声而不丢失原始光谱信息。在这里，我们描述了该方法并证明了其在拉曼和原子发射光谱中的有效性。
Charge-coupled device (CCD) detectors have several characteristics which are suitable for spectroscopic measurements at very low light levels. The quantum efficiency of a CCD is high over a wide wavelength range, and the dark count rate is greatly reduced by cooling the detector. Further reduction of the dark count can be made by setting the pixel binning frame to the detector area that is actually illuminated. If the detector is sufficiently cooled and the signal readout is performed after appropriate binning, the only significant noise source, aside from inevitable photon shot noise, is the noise produced in the signal readout process. Since the readout noise is independent of the duration of exposure, longer exposure provides a better signal-to-noise (S/N) ratio, in principle. However, the practical limit to exposure time is set by spike noise, which is generated by cosmic rays as well as possible γ- and α-rays emitted from materials around the detector chip. Each quantum of such high-energy rays striking the CCD chip usually generates thousands of electrons in a pixel, while a single photon absorbed by the detector produces less than one electron on the average. Thus the spike noise sometimes obscures the very low light level spectrum. Distinction of spike noise from the true photon signals and reliable elimination of the spikes are required in order to further elongate the exposure time and to achieve a better S/N ratio. Occasionally, data processing with median filters is employed to remove the spikes from spectra recorded on CCD detectors. However, this filtering method is a kind of smoothing and has a possibility of distorting the spectrum, particularly when spectral linewidths are comparable to or less than those of spikes. We have developed a simple and efficient method to eliminate the spike noise without losing the original spectral information. Here, we describe the method and demonstrate its effectiveness in Raman and atomic emission spectroscopy.