Optical, Laser and Darkfield Mice – What’s the Diff?

Before you get any ideas, I’m not talking about mice with laser beams on their heads a la Dr Evil.

If you have been using computers for a while you might remember those wretched mice with the little ball inside them that would always misbehave just when you had a deadline or wanted any sort of precision. They would also get all sorts of dirt and gunk inside which would need to be cleaned out (my cleaning instrument of choice was a toothpick).

We’ve come some way since then in terms of mouse technology (not to mention ditching the old serial and PS2 connectors for more ubiquitous USB plugs). However, you might be thinking that all mice with a little light inside are all the same.

That thought would be quite wrong.

First to hit the market were the original optical mice (the ones with the little red LED in them). After the novelty of accidentally blinding siblings, co-workers or even yourself had worn off these mice broke ground by removing the need for the trackball and moving parts inside a mouse. By today’s standards they were primitive in that their sensors were limited in the resolution they could track (both size and colour depth). This subsequently restricted optical mice to mouse pads or other coarsely textured surfaces (glass or glossy surfaces were an absolute no-go).

The introduction of laser mice that use infra-red light (which is outside of the visible spectrum of light for humans) increased the resolution and precision of mice that employ such technology. Lasers allow greater levels of detail to be exposed to a mouse sensor compared to that of LEDs. As a result, laser mice are less fussy on the surfaces they are used upon compared to optical mice as they can detect finer irregularities upon the surface they are being used but mileage on highly transparent or translucent surfaces does vary across the various brands.

More recently, there have been proprietary technology developed by Logitech called “Darkfield”. Two mice currently sport this technology, specifically the Logitech Anywhere Mouse MX and the Logitech Performance Mouse MX (which I use at work). Darkfield technology works by using two lasers on glass or similar surfaces and treating the glass itself as a black surface and tracking residue on the glass (be it dust particles, fingerprint smudges, etc). Instead of the sensor detecting everything placed underneath it only allows light to enter the sensor that comes in at a particular angle. Light emitted by the lasers will be scattered by objects on the glass which will be detected by the sensor whilst all other laser emitted light simply passes through the glass.

It’s interesting to note that Darkfield was inspired by the same technology used in laboratory microscopes used to detect tiny and otherwise poorly contrasted objects called “dark field illumination”.

This is a very rudimentary explanation of the technology and physics behind modern mice but I hope it gives you some appreciation for the advances that have been developed over the years.