Optical Mouse Navigation

[Alan Anderson]

Originally Posted by phrontist

I'm sorry, I don't know that much about optics, please explain how this is not a focus problem. Logically, if you move the mouse up and down it will be tracking larger and smaller patches of carpet. Why would a sudden jump in registered distance occur if it were getting a clear image?

The "larger and smaller patches of carpet" will appear to be moving by "smaller and larger distances" as seen by the sensor. If you travel three feet, the mouse will record a certain number of counts. If you then raise the mouse and travel the same distance, the mouse will record fewer counts.

An optical mouse works by tracking offsets in the image at the sensor. The image at the sensor is a scaled representation of the carpet being viewed. The scale factor varies with distance from the carpet. If the distance is not kept perfectly consistent, the resulting measurements are likewise not consistent.