New imaging breakthrough: A lensless CCD-based microscope

I was just listening to NPR's Science Friday the other day and there was a really interesting story about the latest breakthrough in microscope technology. Its a tiny "on-chip" microscope, about the size of a dime, consisting of simply a CCD and an aperture, or array of apertures. No lenses at all, which is why it can be so small. The mini-scope can be easily linked to an LCD (either iPod size or a computer screen) or a digital camera to view or capture the image.

The resolution capability on these first on-chip scopes is about equivalent to a mid-power objective, with a maximum resolution of about 0.8 µm. (None of the popular articles, and oddly, not even the original journal article, refer to the functional NA of the on-chip scope. Based on my calculations, and assuming predominance of "mid" visible light wavelengths of around 500-550 nm, the spatial resolution would be equivalent to an NA of about 0.4 – that's the resolving power of a typical 20x achromat lens.) Another restriction is that the objects viewed must be in the same fluid medium as the on-chip scope, and I believe the working distance is quite small.

The CalTech lab that invented this technology is now working on higher resolutions and believe they will actually be able to not only match, but surpass the present limits of light microscope resolution.

Interestingly, the inspiration for this new scope came from looking at the nature of "floaters" in our visual field. These are caused by small proteinaceous particles in the eye's vitreous humor that float right above the retina (our own organic CCD). Floaters, of course, are a familiar annoyance to any microscopist, particularly nearsighted ones like myself. What's particularly cool about this new research finding is how it starts with a visual problem and turns it into a solution – this is scientific creativity at its finest.

Another cool thing about this technology is that its cheap – Changhuei Yang, one of the CalTech scientists who discovered this technology, estimates the on-chip scope itself will only cost around $10 to manufacture, though, of course, it will still need to be attached to other LCD-based viewers to actually see the image. There are all kinds of applications for this new microscope technology – this kind of highly portable microscope can revolutionize medicine and public health in the developing world, not to mention make technology for things like routine blood screening more widely available, and, in combination with imaging software, may even be able to automate some of these tests. For people like myself who are very into field biology, having a portable high-resolution microscope would be an enormous boon – I could only imagine how much easier it would be to identify cryptic mushrooms right out in the field if I could see the spores and other microscopic features right then and there.

If you want to learn more, the Science Friday program can be found here. (The podcast is on the upper left side of the page, and there are also links to other articles on the scope.) The original abstract and journal article can be found here.