Have you ever seen the hairs on an ant’s face?

Since the invention of the optic or photonic microscope in 1590, humanity has marvelled at discovering the microscopic-scale details of everyday elements of our day-to-day life. This instrument was key in the discovery of microorganisms, and in a multitude of medical, scientific and technological advances.

Optical microscopes are instruments that allow us to see tiny objects thanks to the use of precision lenses. Current manufacturing techniques allow us to insert dozens of these lenses into objectives just a few centimetres long, and combine them with the aim of magnifying hundreds of times, and even thousands, the apparent size of the objects observed.

Detail photo of the stamens of a flower. Source:

How many times can an image be magnified with an optical microscope?

So why not making objectives, or groups of objectives, with more lenses to magnify objects tens of thousands of times? Or even hundreds of thousands? Sure, they would be expensive objectives, but they would certainly be worth using in the field of nanotechnology, right? Well, I’m sorry, but I have to tell you that, no matter how well manufactured those lenses and objectives were, you would not be able to see sharp images at more than 2000x magnification, so these mega lenses would only be a very expensive way to see diffuse spots with a greatly expanded size.

And why is this happening? The problem is that optical microscopes use visible light as a signal. This means that we apply light on the sample that we are observing, and it is this same light that our eye, which is the receiver, collects and is able to interpret. Well, what we call visible light is composed of waves with lengths of hundreds of nanometers, which are not small enough to give us information about elements with nanometric sizes.

Electromagnetic spectrum. Source:

Looking for an analogy, it is as if visible light, affected by the phenomenon of diffraction, was capable of showing us reality with a “pixel size” of about 200 nm. This is the shortest distance that must exist between two objects to be viewed separately, and is called the resolution limit or resolving capability. No matter how much zoom we want to do thanks to optical lenses, the resolution capacity of light has a definite value, and we can do nothing about it. Therefore, in most cases it is useless to use optical systems with more than 1000x magnification, and the megapixels of digital cameras in microscopes are unable to obtain images with high resolution if the objectives and lenses have already magnified the image by hundreds.

Resolution concept. Source:

These concepts, and many more complex ones, were studied by physicists and researchers such as Abbe, Airy or Rayleigh, whose contributions I will try to explain you in future posts. Meanwhile, I will continue to battle against the resolution limit of light to obtain my artworks.