Updated: Feb 14, 2018
Microscope images of coffee are not only fascinating to look at, but also give us important information about coffee properties. I would like to introduce three microscopes that each give us a different new insight into what goes on inside the bean and the grinder. This time it’s all about a small, easy-to-use microscope that connects straight to your laptop. It’s not just great for playing around at home, but it's suitable for some real experimentation too!
The Dino-Lite Hand-Held USB Microscope
I compared two versions of this fun little microscope with drastically different results.
The very different ways two similar digital microscopes see coffee grinds. Top: Dino-Lite version AM411T5X, bottom: version AM4111T
On the top is a 400x magnified image of ground coffee, taken with Dino-Lite version AM4113T5X. The plastic tip of the microscope is sitting right on top of the coffee. This means the microscope looks at the object from a very short focusing distance. The field of view is small, only a few grind particles fit into the picture, you can’t “zoom out”.
This setup allows for good resolution, allowing us to look at the grinds from really close up, in lots of detail. At the same time, due to the short focusing distance, it has a very shallow depth of field. The top is very clear, but the particles just behind are already out of focus.
Sounds similar to playing with a digital camera?
Indeed, it is exactly the same idea. The achieve a deeper depth of field, the focusing distance needs to be longer, just like when photographing a landscape. The only difference is that a camera also allows you to adjust the aperture, which we can’t control on this microscope.
This photo was taken using the same aperture but a longer focal length on the left.
Photo credit: www.polygon.vn
Back to coffee, the second microscope image was taken with Dino-Lite AM4111T. The magnification is around 50x this time, the field of view is much bigger, the image is more zoomed out. We can see less detail, but a bigger array of particles. The grid under the particles also shows up quite clearly, the depth of field is deeper than before.
Why do we need a grid to look at coffee grinds?
I placed a pretty specialised 200 mesh copper grid under the coffee grinds, that is normally used in transmission electron microscopy. A 200 mesh means that it has exactly 200 threads per inch, or, that one square in the grid represents 127 micrometers (0.127 mm). 7.87 squares then always equal 1mm, regardless of cropping or zooming.
Microscope image of coffee grinds with scale bar added. Now we know this must be a fairly coarse grind.
In other words, we have added a scale bar! This helps us measure the size of the ground coffee particles. Without a known distance in a picture, we cannot calculate the size of any object. This way now we can tell that the grind must have been quite coarse, some particles are nearly 1mm long. Once we have a scale bar, we could take many representative images of a coffee sample and measure the size of the grinds manually (slow, painful, but accurate) or automatically using a program such as Fiji ImageJ (quick, but fairly inaccurate for coffee).
In the next post, I will talk more about grind sizing using microscopy and the ImageJ software.
In the meantime, here are some more pretty coffee-related images taken using one of the Dino-Lite microscopes. Can you guess which version?