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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.


MTF (left) and  (right) calculated from the 300 keV images in Fig. 4 for (a) Kodak SO-163 film using a cut-away holder, (b) TVIPS 224 and (c) MAPS detectors. The indicated detectors results are shown in black but to aid comparison the corresponding results for the other detectors are shown in grey.
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fig6: MTF (left) and (right) calculated from the 300 keV images in Fig. 4 for (a) Kodak SO-163 film using a cut-away holder, (b) TVIPS 224 and (c) MAPS detectors. The indicated detectors results are shown in black but to aid comparison the corresponding results for the other detectors are shown in grey.

Mentions: Typical images obtained by digitising the optical density on film are shown in Fig. 4a and b. Similar images after bright and dark field corrections of the three electronic detectors are shown in Fig. 4c and d (TVIPS 224 CCD), Fig. 4e (Medipix2) and Fig. 4f (MAPS). Figs. 5 and 6 show the corresponding MTF and measurements at 120 and 300 keV, respectively. It can be seen that all three detectors are very good at 120 keV. The data shown used pixel sizes of on film, on TVIPS and on Medipix2, but if a larger pixel size is used on film (e.g., 12 or ) and a smaller pixel size on a different phosphor/fibre-optic CCD (e.g., ), then the performance of film exceeds that of the electronic detectors above half Nyquist. The DQE results for the TVIPS CCD and MAPS detector shown in Figs. 5 and 6 were derived using the obtained from the difference between successive frames. If instead, the were obtained from featureless areas of bright and dark field corrected images, even if this flat field correction is carried out immediately before recording an image, the resulting noise levels would be higher and the corresponding DQEs lower. As a result, even at 120 keV with pixels, film is normally the detector of choice for imaging radiation sensitive specimens.


Detective quantum efficiency of electron area detectors in electron microscopy.

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

MTF (left) and  (right) calculated from the 300 keV images in Fig. 4 for (a) Kodak SO-163 film using a cut-away holder, (b) TVIPS 224 and (c) MAPS detectors. The indicated detectors results are shown in black but to aid comparison the corresponding results for the other detectors are shown in grey.
© Copyright Policy
Related In: Results  -  Collection

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

fig6: MTF (left) and (right) calculated from the 300 keV images in Fig. 4 for (a) Kodak SO-163 film using a cut-away holder, (b) TVIPS 224 and (c) MAPS detectors. The indicated detectors results are shown in black but to aid comparison the corresponding results for the other detectors are shown in grey.
Mentions: Typical images obtained by digitising the optical density on film are shown in Fig. 4a and b. Similar images after bright and dark field corrections of the three electronic detectors are shown in Fig. 4c and d (TVIPS 224 CCD), Fig. 4e (Medipix2) and Fig. 4f (MAPS). Figs. 5 and 6 show the corresponding MTF and measurements at 120 and 300 keV, respectively. It can be seen that all three detectors are very good at 120 keV. The data shown used pixel sizes of on film, on TVIPS and on Medipix2, but if a larger pixel size is used on film (e.g., 12 or ) and a smaller pixel size on a different phosphor/fibre-optic CCD (e.g., ), then the performance of film exceeds that of the electronic detectors above half Nyquist. The DQE results for the TVIPS CCD and MAPS detector shown in Figs. 5 and 6 were derived using the obtained from the difference between successive frames. If instead, the were obtained from featureless areas of bright and dark field corrected images, even if this flat field correction is carried out immediately before recording an image, the resulting noise levels would be higher and the corresponding DQEs lower. As a result, even at 120 keV with pixels, film is normally the detector of choice for imaging radiation sensitive specimens.

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.