Projection imaging system

Figure 12.2 Projection imaging system. (Reprinted with permission from Taylor Francis Group LLC. )...

To describe the X-ray imaging system the projection of 3D object points onto the 2D image plane, and nonlinear distortions inherent in the image detector system have to, be modelled. A parametric camera model based on a simple pinhole model to describe the projection in combination with a polynomal model of the nonlinear distortions is used to describe the X-ray imaging system. The parameters of the model are estimated using a two step approach. First the distortion parameters for fixed source and detector positions are calculated without any knowledge of the projection parameters. In a second step, the projection parameters are calculated for each image taken with the same source and detector positions but with different sample positions. 

From (1) it is clear that the phase contrast can be interpreted simply in terms of tbe variation (second order derivative) of the projected image density, and increases with improving resolution of the system, in agreement with the findings of [3]. 

In case of some samples besides the cross sectional CT-slice also a projectional image is of interest. In these cases the test mode Digital Radiography (DR) is applied. In the DR-mode the object is not turned, but scanned horizontally and vertically. Again the very high dynamic of the detector and the mechanical accuracy of the complete system are of large benefit to the image quality. 

The system uses a remote controlled manipulator system whieh scans the volume of interest. It also positions the x-ray source and x-ray camera at different angles relative the crack and create projection images of the craek. By using a tomographic reconstruction of these images a 3-D representation of the crack can be used for analysis and sizing. 

Fig. 2.2.15 Desktop MR microscope system overview (top left) yokeless permanent magnet (top right) and maximum intensity projection image of a blue berry (bottom).

Fig. 9. Cylindrical imaging system prototype (top) and 24-40 GHz laboratory cylindrical imaging results. Lower left image is a single 90° arc segment reconstruction of a mannequin with no concealed weapons. Lower right image is a combined 360° cylindrical reconstruction projected into an individual image showing...

This is possible because the projection lens system, which for clarity was not shown in Figure 4.7, is normally included behind the objective lens and below the source image plane. This lens system allows the projection of both the diffraction pattern and the specimen image on the observation screen. In Figure 4.8, [50] the electron diffraction pattern of a Fe thin film is shown. In Figure 4.9, the transmission electron micrograph of the mordenite included in the sample CMT-C (see Table 4.1), where fiber-like crystals of mordenite are seen, is shown [51],... 

Projection imaging with DUV (193 nm) and VUV (157 nm) excimer laser radiation was demonstrated by Ehrlich et al. (215). The optical system makes... 

In an FT-IRI experiment, no physical apertures are used to limit the illumination area of the IR beam. Instead, an array of IR detector elements is used to collect the projected image of the unmasked IR beam on the sample. While FPA systems dramatically improve the rate at which IR images can be collected, the spatial resolution is poorer than that of a confocal FT-IRM microscope because an FT-IRI instrument cannot operate in a confocal arrangement. 

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