# Plate Origin

By default, the Checkerboard calibration tool uses a Cognex-defined fiducial mark in the input image to establish the origin of raw calibrated space. Fiducial marks have the following requirements:

Note: All Cognex-supplied calibration plates include the fiducial mark.

- The mark must be made of two bars, one 1x5 tiles in size, the other 1x3 tiles in size.
- The short edge of the short bar must touch the long edge of the long bar one tile from the end of the long bar.
- Each bar must be white with a black border one quarter tile thick.
- The bars must be arranged as follows with respect to the polarity of the tiles on the plate: the long bar must lie between two white tiles and the end of the short bar must be adjacent to a white tile.
- The origin is defined as the intersection of two lines drawn perpendicular to the ends of the two bars furthest from their intersection point.
- The positive x-axis is aligned with the long bar in the direction from the bars' intersection to the end of the long bar.
- The positive y-axis is aligned with the short bar in the direction from the bars' intersection to the end of the short bar.

The following figure illustrates the requirements for this fiducial mark (black tiles are shown in grey to help illustrate the fiducial mark):

Keep in mind that the origin specified by the calibration plate origin is for raw calibrated space. You specify the final orientation, handedness, and origin of calibrated space by supplying an optional rigid origin adjustment.

Note: If you supply a calibration image where the fiducial mark indicates a right-handed coordinate space, the tool will swap the handedness of both the calibration and the run-time image during warping. The tool always assumes that the raw calibrated coordinate space is a rotated left-handed coordinate space.