A standard, brightfield image of an optical fibre consisting of two layers of cladding and two cores.

A QPI phase image of the fibre. Lighter areas are optically thicker, meaning that light has taken longer to travel through those areas. In the case of this fibre this will be because of changes in both physical thickness and refractive index. Looking at the image you can see that the outer cladding has a lower refractive index than the surrounding medium (because it is darker), whilst the inner cladding and cores have a higher refractive index.

Here the phase image has been filtered using the regularisation filter built into the algorithm. The filter has removed the bulk of the thickness information highlighting smaller changes. We can now clearly see the thin inner core, and can determine that it has a higher refractive index than the outer core surrounding it. The image has been coloured to further improve contrast.

By using only the QPI phase image we can emulate the effects of DIC optics as though the sample were perfectly transparent, removing any intensity effects from the image leaving only the remaining phase components. This is impossible with an optical system, but straightforward with Iatia's computational phase imaging approach.

The phase information can also be used to emulate other conventional methods of visualising phase changes, such as darkfield optics.

We can also use the phase information to make measurement of the sample. In this case we have plotted a graph of the optical thickness through the sample. We can see that the graph is made of five distinct sections: (a) is the background medium outside the fibre; (b) is the outer cladding; (c) is the inner cladding; (d) is the outer core and (e) is the inner core. A magnified section of the graph more clearly shows the inner core.