The optical mouse has numerous advantages. Since it has no mechanical parts, it is almost impervious to wear and needs no maintenance. There's no longer the need to clean the inaccessible wheels with Q-tips and rubbing alcohol. Furthermore, since its movement no longer depends on good contact, the mouse pad has become obsolete. The optical mouse illuminates the surface on which it moves, and an infrared optical sensor takes snapshots at regular intervals. A processor then compares these pictures with each other to determine the coordinates. Agilent Technologies, a spin off of HP, originally developed the process.
The thing about mice is that they have to react immediately, especially for gamers, and especially for those addicted to Quake. If there is the slightest delay between mouse movement and the moment at which this movement is retransmitted to the screen, gamers will start complaining. The time lag is partly determined by the image correlation processing speed, which is expressed by the number of shots per second. This parameter also determines the ability of the mouse to follow very rapid movements without lagging behind or making mistakes in the coordinates.
If the first generations of optical mice were content with 1500 snapshots a second, this figure has improved drastically, although Saitek is still using the original Agilent process. Logitech has increased the speed to 2000 shots a second, and Microsoft has chosen to go even further, by offering a refresh rate of 6000 shots a second. They claim that this is the price to be paid for the ability to be able to move the mouse at top speed without any time lag or position error. It remains to be seen whether this really translates into better performance or whether it is just a marketing ploy.