An apparatus and method employing principles of stereo vision for determining
one or more orientation parameters and especially the second and third Euler angles
, of an elongate object whose tip is contacting a surface at a contact
point. The apparatus has a projector mounted on the elongate object for illuminating
the surface with a probe radiation in a known pattern from a first point of view
and a detector mounted on the elongate object for detecting a scattered portion
of the probe radiation returning from the surface to the elongate object from a
second point of view. The orientation parameters are determined from a difference
between the projected and detected probe radiation such as the difference between
the shape of the feature produced by the projected probe radiation and the shape
of the feature detected by the detector. The pattern of probe radiation is chosen
to provide information for determination of the one or more orientation parameters
and can include asymmetric patterns such as lines, ellipses, rectangles, polygons
or the symmetric cases including circles, squares and regular polygons. To produce
the patterns the projector can use a scanning arrangement or a structured light
optic such as a holographic, diffractive, refractive or reflective element and
any combinations thereof. The apparatus is suitable for determining the orientation
of a jotting implement such as a pen, pencil or stylus.