# Plate Origin

As is the case with checkerboard plates, the tool supports the use of fiducial marks on grid-of-dots plates to define the plate origin and handedness. The tool also supports the use of fiducial marks to indicate the dot spacing.

If the plate includes a single row and colum of dots where the dots appear at twice the normal density, the tool will use the center of the dot that lies at the intersection of the double-density row and column as the plate origin. If the plate includes this double-density row and column, then it must also include a pair of mark spaces (missing dots) to indicate the identity of the x-axis and y-axis and to specify the handedness of the coordinate system. A mark space at the first position from the intersection of the double-density row and column indicates the positive Y-axis while a mark space at the third position indicates the positive X-axis.

The following figure illustrates the use of these fiducial marks:

Note: If the plate includes these fiducials, they must meet the following requirements:

- One row and one column of double-density dots must be present.
- The mark spaces at position 1 and 3 must be present.

Note: Grid-of-dots plates supplied by Cognex that include these fiducials specify a right-handed coordinate space, while Cognex-supplied checkerboard plates specify a left-handed coordinate space.