[CAD_CAM_EDM_DRO] Digitizer, Optical mouse hacking

The new optical mice on the market look like an ideal sensor with which to
construct a 3D digitizer probe. Currently the Microsoft brand sell for under
$40 and seem to have amazingly high resolution for the detection of
movement. The principal of the optical mouse design is that it replaces the
mechanical ball and friction wheels with a laser led and sensor. The laser
led operates automatically in two power modes. After a few seconds of no
movement, the led intensity drops. As soon as there is movement of any kind,
the led steps up into high power for what I guess is to do with resoloution.
These mice will operate on any surface in and oritentation. Now my testing
shows it is not possible to move the mouse even .001 without the led
stepping up in power, but it is possible to get the led to step up without
the cursor on the screen moving. This shows the sensing resoloution is
greater than mouse resoloution. For the probe design, the top of the probe
would have a patterened surface directly under the mouse led and sensor. The
lower down on the probe that the pivot point is, the greater the
resoloution. For example a three inch probe pivioted at one inch from the
bottom would multiply and movement by two. With the mouse static, any
movement of the probe sideways could be detected as mouse movement. For the
software, it would monitor the mouse port and any activity would cause the
M-code trigger, the XYZ encoder positions to be logged and optionally the XY
of the mouse movement recorded for any post processing of the data. For the
vertical trigger one of the mouse buttons could be adapted so that the probe
activates a mouse click which is also processed by the software.

Graham