Title: Hybrid low power computer mouse
Type: Issued patent
Patent number: 7,154,477
Issue date: December 26, 2006
Filing date: September 3, 2003
Link to PDF: 
AIPW Summary: This is a low-powered optical mouse with an accelerometer. One problem with existing wireless optical mice is that they rapidly consume batteries; the patent estimates a 2 month battery life for an average wireless optical mouse. (I’m not sure the last time I changed the batteries in my mouse, but I think it’s been more than 2 months.) Another problem is that typical low-powered accelerometers lack sufficient resolution to keep up with the range of possible fast hand movements. To address these problems, this mouse uses the accelerometer all the time (for “dead reckoning tracking”), and uses the optical generator only part of the time, to verify the accelerometer’s readings. An error value is kept for the dead reckoning tracking, and if the error value exceeds a threshold, the optical generator is kept on. See column 3, line 54 to column 4, line 6.