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Detective quantum efficiency of electron area detectors in electron microscopy.

McMullan G, Chen S, Henderson R, Faruqi AR - Ultramicroscopy (2009)

Bottom Line: Recent progress in detector design has created the need for a careful side-by-side comparison of the modulation transfer function (MTF) and resolution-dependent detective quantum efficiency (DQE) of existing electron detectors with those of detectors based on new technology.In the case of film, the effects of electron backscattering from both the holder and the plastic support have been investigated.We also show that part of the response of the emulsion in film comes from light generated in the plastic support.

View Article: PubMed Central - PubMed

Affiliation: MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB20QH, UK. gm2@mrc-lmb.cam.ac.uk

ABSTRACT
Recent progress in detector design has created the need for a careful side-by-side comparison of the modulation transfer function (MTF) and resolution-dependent detective quantum efficiency (DQE) of existing electron detectors with those of detectors based on new technology. We present MTF and DQE measurements for four types of detector: Kodak SO-163 film, TVIPS 224 charge coupled device (CCD) detector, the Medipix2 hybrid pixel detector, and an experimental direct electron monolithic active pixel sensor (MAPS) detector. Film and CCD performance was measured at 120 and 300 keV, while results are presented for the Medipix2 at 120 keV and for the MAPS detector at 300 keV. In the case of film, the effects of electron backscattering from both the holder and the plastic support have been investigated. We also show that part of the response of the emulsion in film comes from light generated in the plastic support. Computer simulations of film and the MAPS detector have been carried out and show good agreement with experiment. The agreement enables us to conclude that the DQE of a backthinned direct electron MAPS detector is likely to be equal to, or better than, that of film at 300 keV.

No MeSH data available.


(a) The measured MTF at 300 keV for SO-163 film showing the effects of electron backscattering from the metal holder and light generated in the plastic backing: dashed line is the MTF obtained with an unmodified holder; the dotted line is with the metal backing removed; the solid line is with both the metal backing removed and ink applied to suppress light reflection off the bottom of the film. The inset in (a) shows the measured ESF used in calculating the solid line. (b) The measured DQE for SO-163 film as a function of spatial frequency with (grey) and without (black) the metal holder.
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fig10: (a) The measured MTF at 300 keV for SO-163 film showing the effects of electron backscattering from the metal holder and light generated in the plastic backing: dashed line is the MTF obtained with an unmodified holder; the dotted line is with the metal backing removed; the solid line is with both the metal backing removed and ink applied to suppress light reflection off the bottom of the film. The inset in (a) shows the measured ESF used in calculating the solid line. (b) The measured DQE for SO-163 film as a function of spatial frequency with (grey) and without (black) the metal holder.

Mentions: Both the reflected light and the electron backscatter contribute to a long range tail in the PSF of film and consequent rapid drop in the MTF at low spatial frequencies. The stochastic nature of the scattering of light and electron backscatter means that, unlike deterministic blur, the reduction in the MTF is not reflected in the NPS, and both effects will reduce for . This is illustrated in Fig. 10a which shows the measured MTF results at 300 keV obtained with a normal film holder, over a cut-away section, and over a cut-away section with black ink. The corresponding results for a normal film holder and over a cut-away section are shown in Fig. 10b. The films used to calculate the DQE and MTF were taken with an OD of approximately 1 and digitised using steps on the MRC-LMB KZA scanner [32].


Detective quantum efficiency of electron area detectors in electron microscopy.

McMullan G, Chen S, Henderson R, Faruqi AR - Ultramicroscopy (2009)

(a) The measured MTF at 300 keV for SO-163 film showing the effects of electron backscattering from the metal holder and light generated in the plastic backing: dashed line is the MTF obtained with an unmodified holder; the dotted line is with the metal backing removed; the solid line is with both the metal backing removed and ink applied to suppress light reflection off the bottom of the film. The inset in (a) shows the measured ESF used in calculating the solid line. (b) The measured DQE for SO-163 film as a function of spatial frequency with (grey) and without (black) the metal holder.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2864625&req=5

fig10: (a) The measured MTF at 300 keV for SO-163 film showing the effects of electron backscattering from the metal holder and light generated in the plastic backing: dashed line is the MTF obtained with an unmodified holder; the dotted line is with the metal backing removed; the solid line is with both the metal backing removed and ink applied to suppress light reflection off the bottom of the film. The inset in (a) shows the measured ESF used in calculating the solid line. (b) The measured DQE for SO-163 film as a function of spatial frequency with (grey) and without (black) the metal holder.
Mentions: Both the reflected light and the electron backscatter contribute to a long range tail in the PSF of film and consequent rapid drop in the MTF at low spatial frequencies. The stochastic nature of the scattering of light and electron backscatter means that, unlike deterministic blur, the reduction in the MTF is not reflected in the NPS, and both effects will reduce for . This is illustrated in Fig. 10a which shows the measured MTF results at 300 keV obtained with a normal film holder, over a cut-away section, and over a cut-away section with black ink. The corresponding results for a normal film holder and over a cut-away section are shown in Fig. 10b. The films used to calculate the DQE and MTF were taken with an OD of approximately 1 and digitised using steps on the MRC-LMB KZA scanner [32].

Bottom Line: Recent progress in detector design has created the need for a careful side-by-side comparison of the modulation transfer function (MTF) and resolution-dependent detective quantum efficiency (DQE) of existing electron detectors with those of detectors based on new technology.In the case of film, the effects of electron backscattering from both the holder and the plastic support have been investigated.We also show that part of the response of the emulsion in film comes from light generated in the plastic support.

View Article: PubMed Central - PubMed

Affiliation: MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB20QH, UK. gm2@mrc-lmb.cam.ac.uk

ABSTRACT
Recent progress in detector design has created the need for a careful side-by-side comparison of the modulation transfer function (MTF) and resolution-dependent detective quantum efficiency (DQE) of existing electron detectors with those of detectors based on new technology. We present MTF and DQE measurements for four types of detector: Kodak SO-163 film, TVIPS 224 charge coupled device (CCD) detector, the Medipix2 hybrid pixel detector, and an experimental direct electron monolithic active pixel sensor (MAPS) detector. Film and CCD performance was measured at 120 and 300 keV, while results are presented for the Medipix2 at 120 keV and for the MAPS detector at 300 keV. In the case of film, the effects of electron backscattering from both the holder and the plastic support have been investigated. We also show that part of the response of the emulsion in film comes from light generated in the plastic support. Computer simulations of film and the MAPS detector have been carried out and show good agreement with experiment. The agreement enables us to conclude that the DQE of a backthinned direct electron MAPS detector is likely to be equal to, or better than, that of film at 300 keV.

No MeSH data available.