WHAT MATERIALS CAN BE IMAGED?
Low atomic number and density materials such as organic and
biological materials, polymers, and many ceramics can be imaged. As
the density and the atomic number increases, the x-ray absorption
also increases. For such specimens, a small cross section is
required to assure adequate transmission. As a rule of thumb
plastics, and organic materials with a effective transmission
thickness of 2-5 centimeters, ceramics of 1-2 cm, low density
metals of 2-5 mm. See examples here for previously
WHAT SIZE SPECIMEN CAN FIT IN THE MACHINE?
Specimens must fit in a volume of about 6.5 cm height by 6.5 cm
diameter. For optimum performance the cross sections to be
evaluation should be less than the field of view (see below). If
this is not possible the specimen may still be imaged but there may
be some restrictions on the shape of the component.
WHAT RESOLUTION CAN BE ACHIEVED?
Nominally, strong contrast images can be resolved down to 1
micron. If the contrast between features is not strong then the
resolution is of the order of few microns (2-5 microns). Geometric
features need to be few times larger than the resolution limit in
order to be clearly observable. Note that when a very high
resolution is sought there there may be a limit on the diameter of
the specimen as the camera comes very close to the specimen.
WHAT IS THE MAXIMUM FIELD OF VIEW?
There are 3 camera settings:
- Coarse 1000 x 500 pixels - (rapid test - few minutes)
- Medium 2000 x 1000 pixels - (medium duration test - 0.5-2
- Fine 4000 x 2000 pixels - (several hours 2-10 hours)
The first and second numbers denote the diameter and the height
of the field of view. The camera settings and the desired
resolution determine the size of the field of view. For example at
medium camera settings (2K x 1K) and 5 micron resolution a volume
of 10 mm diameter and 5 millimeter height can be imaged. Large
volumes can be scanned at the same resolution and camera setting
- wide scan: can double the diameter of the space that can be
imaged (and doubles the scanning time/price)
- oversize scan: can image sequentially and "stitch" together
multiple views along the height of the specimen (the specimen is
raised or lowered with respect to the camera). The scanning time
(and price) is proportional to the number of views
In some cases the same sample an be scanned at different camera
settings but at the same resolution. Fine camera pixels will give a
larger field of view at the expense of scanning time.