Requirements for a NI Vision Calibration Grid

Issue Details

Solution

• Minimum Dot Size

The actual size of the dot will vary based on the number of pixels of the camera and field of view selected of the camera. An optimal size is at least 9 pixels (3 x 3), which will ensure the camera will detect the dot accurately and IMAQ Vision will correctly process the dots.

• Minimum Dot Spacing

The individual dots should be at least 4 pixels apart. This will prevent two or more dots from being processed as one dot.

• Quantity of Dots Consideration

• As the number of dots in the field of view increases, the calibration of the image (in software) becomes better. For irregular or curved surfaces, a greater number of dots will insure the contour of the field of view is more accurately represented.

• Grid Layout

The dots need to be in vertical and horizontal lines that are perpendicular to each other to make up the grid:

             

Additional Information

NI Vision ships with 3 calibration examples for LabVIEW that install by default in<labview>\examples\Vision\2. Functions\Calibration

You may use the calibration grid installed with NI Vision by selecting Start»All Programs»National Instruments»Vision»Documentation»Calibration Grid. The dots have radii of 2 mm and center-to-center distances of 1 cm.

See NI Vision Concepts Help and Perspective and Nonlinear Distortion Calibration for more details on calibration grids and the calibration process.