Light charge coupled device

An x-ray area detector can be used to collect the intensities of many reflections at a time. The crystal must be oriented in many different settings with respect to the incident beam but the detector needs to be positioned at only a few positions to collect all of the data. A charge coupled device (CCD) is used as the area detector on the Siemens SMART single crystal diffractometer system. The SMART detector consists of a flat 6-cm circular phosphorescent screen that converts x-ray photons to visible light photons. The screen is coupled to a tapered fiber optics bundle which is then coupled to a one inch by one inch square CCD chip. The CCD chip has 1024 x 1024 pixels each of which stores an electrical charge proportional to the number of... 

Sihcon charge coupled devices (CCDs), commonly used in soHd-state video cameras and in research appHcations, are being appHed to low light level spectroscopy appHcations. The main advantage of area array CCDs over linear photodiode detectors is the two-dimensional format, which provides simultaneous measurements of spatial and spectral data. 

Figure 4.2 Schematic diagram of a charge-coupled device (CCD) imaging sensor. It consists of a semiconducting substrate (silicon), topped by a conducting material (doped polysilicon), separated by an insulating layer of silicon dioxide. By applying charge to the polysilicon electrodes, a localized potential well is formed, which traps the charge created by the incident light as it enters the silicon substrate.

An improvement to this technique will be to use a continuous blue/UV light source and replacing the PMT by a compact spectrometer coupled to a CCD (charge-coupled device) for readout, thus accelerating the data acquisition. In the latter case, the scanning and evaluation takes a few milliseconds. 

P. G. LeComber and W. E. Spear, The Development of the a-Si H Field-Effect Transistor and Its Possible Applications D. G. Ast, a-Si H FET-Addressed LCD Panel S. Kaneko, Solid-State Image Sensor M. Matsumura, Charge-Coupled Devices M. A. Bosch, Optical Recording A. D Amico and G. Fortmato, Ambient Sensors H. Kukimoto, Amorphous Light-Emitting Devices R. J. Phelan, Jr., Fast Detectors and Modulators J. I. Pankove, Hybrid Structures... 

The minimum detectable signal for visible light in Table 20-2 is 17 photons/s. The sensitivity of the charge coupled device is derived from its high quantum efficiency (electrons generated per incident photon), low background electrical noise (thermally generated free... 

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