# Grid of Dots Plate Requirement

Note: Cognex recommends the use of checkerboard calibration plates with the CogCalibCheckerboardTool. Support for grid-of-dots plates is provided for compatibility purposes.

The Checkerboard calibration tool can be used with grid-of-dots calibration plates that meet the following specification.

- The plate must contain a regular grid of round dots.
- The rows and columns of dots must be at right angles to each other.
- Both black dots on a white background and white grids on a black background are supported, as long as the difference in grey levels between dots an the background exceeds 8% (20 grey levels in an 8-bit image).
- The dots must be the same size. A single dot may be up to 50% smaller or larger than the average dot size.
- The dot spacing in the X-direction must differ from the Y-direction spacing by no more than 10%.

The following figure shows an example of a grid-of-dots calibration plate: