Method and apparatus for calibrating an electro-optical mouse

DETAILED DESCRIPTION OF THE DRAWINGS The optical mouse of the present invention will be described in detail with reference to the following drawings: FIG.
1 is a side sectional view of one preferred embodiment of the electro-optical mouse in which the present invention is incorporated.
FIG.
2 is a side sectional view of another preferred embodiment of a mouse in which the invention is incorporated, showing an alternative arrangement of the optical elements.
FIGS.
3a to 3c are views of portions of possible grid patterns for use with the present invention.
FIG.
4 is a view of the grid pattern of FIG.
3a as seen by the photodetectors of the optical mouse when degraded optical components are used.
FIG.
5 is a diagram of the circuitry used in the mouse calibration system of the present invention.
FIGS.
6a to 6q are diagrammatic views of a portion of the grid of FIG.
3a, showing 16 positions of the photodetectors relative to the grid pattern, these positions corresponding to the 16 pre-stored combinations of X and Y codes.
FIG.
7 is a graphical representation of the intensity values of a single quadrant of the four-quad photodetector during "non-riding" unidirectional movement.
FIG.
8 is a diagram showing the measured intensity levels of light impinging on a quadrant during calibration in accordance with the invention in relation to the ascending and descending stepped ramps respectively.
FIG.
9 is a diagram showing hypothetical measured intensity levels detected by a quadrant when the initial intensity level of the light-emitting means is too low.
FIG.
10 is a diagram showing the measured intensity levels of light imaging on a quadrant during calibration in accordance with another embodiment of the invention in relation to the ascending stepped ramps.
FIG.
11 is a diagram of light-emitting circuitry similar to that depicted in FIG.
5.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG.
1 shows the preferred embodiment of a position control system 1, movable over surface 3, in which the calibration arrangement of the invention is incorporated