Active Matrix Liquid Crystal Displays
A definitive guide to the theory and applications of AMLCDs, this book contains numerous design and applications examples to help illustrate key points and make them relevant to real-world engineering tasks.
TABLE OF CONTENTS Active Matrix Liquid Crystal Displays
Chapter 9: Active Matrix Flat Panel Image Sensors
In this final chapter, flat panel technologies using similar types of active matrix arrays, as in AMLCDs, are described. They underscore the more general application of a-Si TFT arrays in electronic devices. A prominent one is their use in 2D image sensors for X-ray detectors. These detectors are replacing X-ray film and, combined with ultra-high-resolution AMLCDs, provide diagnostic-quality images to radiologists. They eliminate all chemical film processing and allow easy electronic storage and transfer of digital image files.
9.1 Flat Panel Image Sensors
Instead of writing data to an active matrix array, as is done in displays, it is also possible to read data from specialized active matrix arrays that function as large-area image sensors. They have a photo-conversion material and/or photosensitive device added at each pixel. The resulting flat panel sensor is scanned one row at a time, in a similar way as AMLCDs. The data driver ICs are replaced by readout chips which amplify the readout charge from each pixel and multiplex the data signals from the array into a video signal, representing the 2D image. This technology is now increasingly used for flat panel X-ray detectors in medical and industrial imaging and in security applications.
Discovered by R ntgen in 1895, projection radiography is the oldest medical imaging technique; more than 200,000 systems are in use worldwide. Since there are no good optics elements available to focus an X-ray image, the X-ray system uses projection from the X-ray source through the object onto a full-field-size receptor, as shown...
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