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The old fashioned mice worked via two wheels that are turned by a ball:

enter image description here

Found here

One represented the x-axis while the other represtened the y-axis. Turning one, would move the mouse in that specified direction. Moving both resulted in a combined and (somewhat) smooth movement of the mouse.

With the advent of Lasers and optics, we now more commonly use the 'Laser Mouse'. How do they work exactly? How does a laser light and moving of the device translate into those x and y values for movement on the screen?

Detailed explanations are welcomed.

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Why don't you type the question into google? it comes up with lots of answers. – Matt H May 11 '11 at 22:30
@MattH yes I could do that, but then a lot of the question found within SU could be solved with a simple Google search and some reading, and would never be found here. Being able to Google the answer shouldn't prevent us asking such questions on SU. I'm giving my fellow Super Users an opportunity to gain rep answering a legit question. – KronoS May 11 '11 at 22:33
@MattH 12 of my most recent 30 answers are somewhat based on the information contained in Linux/Mac OS X man pages. This question at least requires googling. – Daniel Beck May 26 '11 at 17:46
up vote 8 down vote accepted

Laser and optical mice essentially take hundreds of photos every second. They compare successive images to find a common point between them, and from that common point, calculate x and y offsets to send to the computer. The laser or LED merely act as a light source.

Of course this is a vast over simplification. There are a couple of methods for determining the common point, for instance.

As for moving to laser light from LEDs, that was done to get higher resolution images (finer control), as well as allowing mice to be used reliably on more surfaces.

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Using a laser also dramatically reduces the amount of power the device uses - making wireless mice much less batty dependent. I have a mouse that I use for 6-10 hours a day and it lasts 6 months on 2 AA batteries. – charliehorse55 May 11 '11 at 22:57

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