imaging plate

An integration-type two-dimensional detector that utilizes fluorescence emission generated by a beam of X-rays, electrons, or neutrons. The "imaging plate" is made of a plastic film coated with microcrystlas of photostimulable phosphor (BaFX:Eu2+ (X = Cl, Br, I)). The imaging plate has excellent linear sensitivity. The plate possesses a large recording area of about 80 mm × 100 mm and a large dynamic range of 5 to 6 digits. The exposed imaging plate is irradiated with He-Ne laser light, and then blue light emitted from the plate is converted into electric signals by a photomultiplier tube (PMT). By scanning the laser light on an imaging plate, a microscope image is obtained from the recorded signals. One PMT covers a dynamic range of only 5 digits but a recent reading device which combines a PMT and a semiconductor detector covers a 6-digit dynamic range. Whether a large dynamic range can be effectively used or not is dependent on the performance of a reading device. Also, the positional resolution (pixel size) changes from 15 μm to 50 μm depending on the performance of the reading device. The maximum gray level of the imaging plate is 20 bits. The imaging plate is advantageous for both recording a low-magnification TEM image that needs to cover a large area and a diffraction pattern that has a wide dynamic range. Compared to CCD, the disadvantage of the imaging plate is that its use is limited to offline.

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