Methods to measure properties of slow-scan CCD cameras for electron detection

Abstract

New ways to measure detection properties of slow-scan charge-coupled device (CCD) cameras suitable for electron microscopy, mainly based on the statistics of single-electron events, are discussed. The experiments concentrate on the newly introduced Gatan 679 slow-scan CCD camera. It has been established that for this instrument (if equipped with a thin YAG scintillator) 20% of the true intensity is recorded at the highest detectable spatial frequency (Nyquist frequency), limited mostly by the modulation transfer function of the YAG scintillator. The detection quantum efficiency is 0.45 for single 100-kV electrons and 0.15 for single 400-kV electrons, and is approaching unity for intensities higher than ten electrons. Furthermore, nonlinearity of the response is smaller than deviations in the image intensity due to shot noise. Examples are presented illustrating the detection properties of slow-scan CCD cameras for electron imaging, which also include high dynamic range and negligible geometric distortion.

Electron detection characteristics of a slow-scan CCD camera, imaging plates and film, and electron image restoration

“…At low dose, the noise method fails because the readout noise and dark current of CCD. The MTF of SSC camera does depend on the electron high voltage, contrary to the previous finding the (de Ruijter and Weiss, 1992). The tail of PSF increases significantly at 400 kV.…”

Advantages of CCD detectors for de novo three-dimensional structure determination in single-particle electron microscopy

“…A more routine method to test the performance of a recording device is the determination of the modulation transfer function (MTF) from averages of Fourier-transformed electron-noise images (de Ruijter and Weiss, 1992). The MTF has the value one at the base frequency of the device, whereas for all other spatial frequencies up to the Nyquist frequency the relative signal strength is plotted.…”

Assessing the capabilities of a 4kx4k CCD camera for electron cryo-microscopy at 300 kV

“…There are a wide variety of techniques used to estimate the MTF for a CCD camera, including, the use of knife edges, interferometer and statistical methods (de Ruijter and Weiss, 1992). Typically, MTF curves are normalized to unity at the origin.…”