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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.


Calculation of the Medipix2 DQE at 120 keV using the statistics of individual electron events. (a) shows the total number of events  recorded per frame and the composition in terms of events recorded in a given number of pixels, as a function of the energy threshold. A total of 2100 electrons were expected per frame. For a threshold of one half the incident energy only single pixel events are seen and at 120 keV no events were seen involving six or more pixels even with a very low threshold. (b) shows the DQE calculated using , where  is the number of events in each frame where a single electron is counted in  adjacent pixels. Also shown is the corresponding DQE at Nyquist calculated using Eq. (6).
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fig8: Calculation of the Medipix2 DQE at 120 keV using the statistics of individual electron events. (a) shows the total number of events recorded per frame and the composition in terms of events recorded in a given number of pixels, as a function of the energy threshold. A total of 2100 electrons were expected per frame. For a threshold of one half the incident energy only single pixel events are seen and at 120 keV no events were seen involving six or more pixels even with a very low threshold. (b) shows the DQE calculated using , where is the number of events in each frame where a single electron is counted in adjacent pixels. Also shown is the corresponding DQE at Nyquist calculated using Eq. (6).

Mentions: As the Medipix2 detector counts the events associated with individual electrons it is possible to calculate the DQE from the statistics of individual events [6]. This is illustrated in Fig. 8 where the analysis of images obtained with an average dose of 1 electron per 100 pixels is presented.


Detective quantum efficiency of electron area detectors in electron microscopy.

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

Calculation of the Medipix2 DQE at 120 keV using the statistics of individual electron events. (a) shows the total number of events  recorded per frame and the composition in terms of events recorded in a given number of pixels, as a function of the energy threshold. A total of 2100 electrons were expected per frame. For a threshold of one half the incident energy only single pixel events are seen and at 120 keV no events were seen involving six or more pixels even with a very low threshold. (b) shows the DQE calculated using , where  is the number of events in each frame where a single electron is counted in  adjacent pixels. Also shown is the corresponding DQE at Nyquist calculated using Eq. (6).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
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fig8: Calculation of the Medipix2 DQE at 120 keV using the statistics of individual electron events. (a) shows the total number of events recorded per frame and the composition in terms of events recorded in a given number of pixels, as a function of the energy threshold. A total of 2100 electrons were expected per frame. For a threshold of one half the incident energy only single pixel events are seen and at 120 keV no events were seen involving six or more pixels even with a very low threshold. (b) shows the DQE calculated using , where is the number of events in each frame where a single electron is counted in adjacent pixels. Also shown is the corresponding DQE at Nyquist calculated using Eq. (6).
Mentions: As the Medipix2 detector counts the events associated with individual electrons it is possible to calculate the DQE from the statistics of individual events [6]. This is illustrated in Fig. 8 where the analysis of images obtained with an average dose of 1 electron per 100 pixels is presented.

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.