Detector types scanner

Collecting optics, radiation detectors and some form of indicator are the basic elements of an industrial infrared instrument. The optical system collects radiant energy and focuses it upon a detector, which converts it into an electrical signal. The instrument s electronics amplifies the output signal and process it into a form which can be displayed. There are three general types of instruments that can be used for predictive maintenance infrared thermometers or spot radiometers line scanners and imaging systems. 

Two types of ultrasonic systems are available that can be used for predictive maintenance structural and airborne. Both provide fast, accurate diagnosis of abnormal operation and leaks. Airborne ultrasonic detectors can be used in either a scanning or contact mode. As scanners, they are most often used to detect gas pressure leaks. Because these instruments are sensitive only to ultrasound, they are not limited to specific gases as are most other gas leak detectors. In addition, they are often used to locate various forms of vacuum leaks. 

X-ray CT uses a high intensity X-ray beam and a series of detectors that rotate around the subject. Modern CT scanners use multiple sets of X-ray sources and detectors to simultaneously acquire multiple slices (currently, up to 64) to speed acquisition. This allows full brain coverage at high spatial resolution in a matter of seconds. High doses of X-ray (about 5 rads) are typical exposures for this type of exam. 

Industrial CT scanners are fundamentally different from clinical scanners. Although both types of scanners need to take X-ray projections from several angulations as discussed above, in industrial CT scanners the object is rotated in the beam path produced by a stationary X-ray source, while in clinical CT the X-ray unit (source and detector) rotates around a stationary patient. In addition, since the radiation exposure of the object being scanned is normally not a problem in industrial... 

Series/Parallel Scan with time delay and integration remains the principal approach to advanced thermal imaging systems. However, for applications where only a small number of resolution elements are needed, two-dimensional staring detector arrays with CCD or CID readout are being considered [8.106]. This does away with the scanner and a focal optics used with conventional systems. However, to compensate for nonuniformities, both dc offset and gain correction must be made on a pixel by pixel basis. Detector responsivity and readout nonlinearities will increase the number of computations needed for sufficient correction and only experience with the stability of different types of arrays will determine how often the correction algorithms must be calibrated [8.107,108]. 

There are three types of WDXRF instruments sequential spectrometers, which use a goniometer and sequentially measure the elements by scanning the wavelength simultaneous spectrometers, which use multiple channels, with each channel having its own crystal/detector combination optimized for a specific element or background measurement and hybrid spectrometers, which combine sequential goniometers or scanners with fixed channels as well as XRD channels and goniometers. Hybrid instruments will be discussed in Section 8.4 with XRD instruments. 

The CT parameters will also impact the quality of the 2D, multiplanar and 3D reconstructed images. The details of scanner type, collimation, pitch, detector array for volume scanner, gantry rotation... 

The 16-slice CT systems have adaptive array detectors in general. A representative example for this scanner type, the Siemens SOMATOM Sensation 16 scan-... 

Fig. 1.5a,b. Schematic illustration of a dual-source CT (DSCT) system using two tubes and two corresponding detectors offset by 90°. A scanner of this type provides temporal resolution equivalent to a qiuirter of the gantry rotation time, independent of the patient s heart rate. In a technical realization, one detector (a) covers the entire scan field of view with a diameter of 50 cm, while the other detector (b) is restricted to a smaller, central field of view... 

When CT scanners with less than 40 detector rings are used, the collimation may have to be adapted to values around 1.25-2 mm in order to reduce the acquisition time to less than 25-30 s. Since protocols of data acquisition are dependent on type and brand of the CT scanner, only some examples can be given here (Table 23.1). Further details are accessible on the Internet (e.g., http //www.CTisus.com, http //www.multide-tector-row-ct.com). 

To be able to perform the same types of studies that are currently performed on humans (average adult weight of 70 kg), small animal imaging devices must have a spatial resolution scaled appropriately to the object of interest. Typical human clinical scanners have a spatial resolution of 5-10 mm. Because the typical human chest has a diameter of 30-50 cm, spatial resolution in the mouse, with a chest diameter of 2-3 cm, must improve by a factor of at least 10, that is < 1 mm. Spatial resolution demands of this sort have required new and improved technologies of both detector and overall camera design. 

Photodetector (photon detector) - A type of infrared detector that has fast response, (on the order of microseconds) limited spectral response and usually requires cooled operation photodetectors are used in infrared radiation thermometers, scanners and imagers. 

Image plates have a spatial resolution comparable to film with a much larger dynamic range. However, they still suffer from the need for scanning which, even with ingenious online carousels and dedicated scanners, still makes it impossible to conduct genuinely real-time interactive experiments. The examples of diffraction data included in this review illustrate the use of the various types of detector. 

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