Flatfield and scale images:

Hi, @mathew and @SimonPyle -

Terrific work! After seeing the demonstration mathew gave at the barnraising in November '16, and then looking at Cambridge's design, a question comes to mind. The Cambridge site says they use a white LED from below to illuminate the object you're viewing. Would a laser LED, rather than white light, give better image quality and get rid of chromatic aberration? As you're viewing it on a screen rather than peering through a lens, then, no worries about retinal damage. It might make visualizing the particles easier. If you're interested in the refractive properties of silica, this paper is useful: https://pdfs.semanticscholar.org/69f6/5aa112dc080f7fd9058cb94c895748e9a278.pdf

That is an interesting question. I think the laser would get rid of chromatic aberration-- its a single frequency of light-- but I'm not sure that would improve image quality.

We are a ways away from silica-specific analysis but thanks for the paper recommendation I'll work it into the bibiliography

Hello, "Cambridge" here (though I've actually moved now). You're right, a laser diode would certainly get rid of the chromatic issues. I suspect aligning the condenser better (v5.16, now in beta, makes it possible to adjust the condenser alignment) would also go a long way to fixing that. The trouble with using a laser is that coherent light imaging comes with other problems - any stray light, or any dirt on the optics, tends to cause "speckle" that makes the image look nasty and causes trouble for a lot of image analysis methods. A single-colour LED (I recommend green) would reduce chromatic aberration without giving you speckle. On the other hand, if you're careful about dirt, and you do the right holographic reconstruction, a laser diode illumination (which amounts to in-line holography of your sample) should give you lots of nice information about your sample, particularly if you know beforehand that it's silica. Better than a laser diode would be a slightly broken (i.e. not entirely coherent) laser diode. These are often called "superluminescent diodes" and sold for ~100x the price of laser diodes, and essentially they are narrow bandwidth (1-10nm spectral width) partially coherent sources. If somebody can work out how to do that cheaply (e.g. by hacking the electronics for a laser diode) it would be an awesome tool for all sorts of microscopy.