Detector pixel width

The acquisition mode (detector pixel width, number of projections and scan time) was optimized for CSCT acquisition. Assuming a point source, in CT the spatial resolution is mainly given by the size of the detector pixels, whereas in CSCT it is given by the detector pixel size, the length of the collimator lamellae in front of the detector and the distance between the object and the detector. In the experiment presented here, the combined effects of detector and collimation resulted in an average spatial resolution of 8 mm. Therefore, only a low-resolution image can be expected from the reconstruction, and consequently a low number of projections is sufficient. 

For a 2D detector this is height and width of the detector pixels. For the Kratky camera with zerodimensional counter this is the height and length of the measuring slit. 

It is clear that the spatial resolution (the separation between the two points required for them to be resolved, i.e. 2r) is not merely dividing the number of detector pixels by the width of the image. The spatial resolution in transmission FTIR imaging should be in the order of 10-30 pm depending on the wavelength of the absorption band used. 

Obviously, such a high-resolution monochromator requires active wavelength stabilization in order to avoid drift problems. This has been accomplished through an internal neon lamp, mounted on an adjustable stand in front of the intermediate slit between the pre- and echelle-monochromator, so that it can be moved into the beam automatically if necessary. The neon lamp emits many relatively narrow lines in the 580-720 nm range, and, in the absence of any pre-selection, these are separated by the echelle grating into various superimposed orders. This means that without pre-dispersion at least two neon lines for every grating position surely fall on the detector, and can be used for stabilization. The precision of this stabilization is only limited by the stepper motor for grating adjustment, and is better than one-tenth of a pixel width (see Welz et al. [10]). 

In this case, dv is the Raman shift increment observable with a slit or pixel of width Wp. However, an array detector has a finite number of pixels, and the flat field of the spectrograph is of finite width, so there is a limit on the range... 

---