Optical navigation device having a variable depth of field

1 . A navigation device comprising:

at least one light channel for reflecting from a surface, said reflection being used to facilitate a determination of directional movement of said device with respect to said surface, said surface having a Z dimension as measured from a bottom surface of said device; and

means operable when said device is positioned with respect to a particular surface for adjusting the depth of field of at least one light column of said device to match the Z dimension of said particular surface.

2 . The device of claim 1 wherein said device comprises multiple light channels each light channel having a different depth of field and wherein said adjusting means comprises:

means for selecting which of said light channels to enable for a particular Z dimension.

3 . The device of claim 2 wherein a transparent medium is positioned between said bottom surface of said device and surface, said transparent medium controlling, at least in part, the Z dimension of said surface.

4 . The device of claim 2 wherein said depth of field for each of said light columns is a particular fixed Z dimension.

5 . The device of claim 4 further comprising:

a sensor for receiving light reflected from said surface for at least one of said light columns; and wherein said adjusting means is controlled, at least in part, by the depth of field of a particular light column as said light column reflects from said surface.

6 . The device of claim 2 wherein said depth of field for at least one of said light columns is a variable Z dimension.

7 . The device of claim 6 further comprising:

means for allowing a device user to selectively change said variable Z dimension of said variable depth of field light column.

8 . The device of claim 2 wherein said light columns are contained within a single housing.

9 . A method for determining movement relative to a surface, said method comprising:

positioning a navigation device above said surface, said device containing a plurality of light sources, each light source impacting said surface at a different angle, said angle calculated to yield a depth of field with respect to a base of said navigation device; and

selecting which light source to use for a particular surface, said selection dependant upon the Z dimension between said particular surface and said bottom surface of said navigation device.

10 . The method of claim 9 wherein said particular surface is adjacent said navigation device base.

11 . The method of claim 9 wherein said particular surface is separated from said navigation base device by a transparent medium.

12 . The method of claim 11 wherein said transparent medium has a thickness which yields a Z dimension of approximately 30 mm.

13 . The method of claim 9 wherein said Z dimension is variable depending upon the angle of selected light source.

14 . The method of claim 9 wherein said selecting comprises:

turning off all said light sources that do not reflect light from said surface to a sensor positioned within said device.

15 . The method of claim 9 wherein said selecting comprises:

determining which of said light sources best reflects light from said surface to a sensor positioned within said device.

16 . The method of claim 9 wherein said selecting comprises:

manually selecting one of said light sources based on reflection of light from said surface to a sensor positioned within said device.

17 . A method for determining movement relative to a surface, said method comprising:

positioning a navigation device above said surface, said device containing a plurality of light sources, each light source having a different depth of field as measured from a base of said navigation device; and

selecting which light source to use for a particular surface, said selection dependant upon the Z dimension between said particular surface and said bottom surface of said navigation device.

18 . A method for determining movement relative to a surface, said method comprising:

positioning a navigation device above said surface, said device containing a light source having multiple depth of fields as measured from a base of said navigation device; and

selecting which depth of field to use for a particular surface, said selection dependant upon the Z dimension between said particular surface and said bottom surface of said navigation device.

19 . A navigation system for determining movement relative to a surface, said system comprising:

a light source within a housing, said light source having multiple depths of field with respect to said surface, said depth of field being measured from a base of said navigation device; and

an algorithm for determining which depth of field is to be used for any particular surface having a Z dimension as measured from said housing device base.

20 . The system of claim 19 wherein said light source is a plurality of light sources each having a unique depth of field.

21 . A navigation device for determining movement relative to a surface, said device comprising:

a light source, said light source having multiple depths of field with respect to said surface, said depth of field being measured from a base of said navigation device; and

a sensor positioned to receive light reflected from said surface, said light received based upon the depth of field and the Z dimension of said surface as measured from said base.

22 . The device of claim 21 wherein said light source is a plurality of light sources each having a unique depth of field.