A NEW QUASI-CONFOCAL IMAGE PLATE SCANNER WITH IMPROVED SPATIAL-RESOLUTION AND IDEAL DETECTION EFFICIENCY

Image plates (IF) can be used for electron detection in the EM like co nventional negative material [N. Mori et al., Ultramicroscopy 25 (1988 ) 195]. The stored information can later be retrieved by a scanning pr ocess in form of a digitized image. Although the physics of the electr on storage process of the IPs in theory predicts electron detection wi th high spatial resolution, high detection efficiency and high dynamic range, in practice the scanning process limits resolution and detecti on efficiency. At present the scanners yield only moderate spatial res olution - about 100 mu m effective pixel size (i.e. about 200 mu m lin e resolution [S. Isoda et al., Ultramicroscopy 41 (1992) 99]. Data on the detection efficiency have not been published so far. Here we repor t a scanner of novel design with an improved optical detection device which gives highly increased spatial resolution (40 mu m effective pix el size) and an optimal detection efficiency with a DQE of about 0.9. These properties are comparable to values published on slow-scan CCD c ameras. Using subsequent scans of the same IP (which could register an image, an electron diffraction pattern or a parallel EELS recording) a linear dynamic detection range of almost 5 orders of magnitude is po ssible. We discuss how these properties of the IP scanner system could be utilized in future applications.