A method of estimating the position of the field of view of an imaging
device, such as a camera, relative to a board involves designating
markings on the board as references and detecting the shift in these
reference markings within the field of view of the camera compared to a
known position therein. The reference markings are selected such that
detection thereof involves analysis of only a subset of the image
produced by the imaging device. The selection of a group of one or more
markings to serve as a reference involves determination of the image
region (error window) in which the reference marking(s) may appear, given
the maximal positional error of the imaging device. It is also checked
(step T4) that the entire error window will be within the useable field
of view of the imaging device and that, within the error window, no other
group of markings will appear that could be confused with the selected
group of markings (step T5). Detection of the reference group of markings
involves generation of an image profile along a line crossing the center
of the error window and finding the best match between the markings along
this profile and the markings in the reference group.