Guidelines for Performing Infield Correction

Quick Tips and Advice

  • For correction over multiple distances, cover at least 500 mm in Z-depth to get the best results.

  • If the board is positioned farther than 3000 mm, it may fail detection or result in inaccurate measurements.

  • Take three or more images to provide multiple data points for the best correction.

  • Take measurements at multiple distances to get a better correction.

  • Try to align the board as much as possible in the X, Y, and Z axis, so the checkerboard surface appears as a flat plane to the camera. The rotation tolerance for the infield correction tool is 15 degrees.

  • Be mindful of ambient lighting conditions if used at long distances.

  • Mount the board on a robot for optimal stability and repeatability.

  • The infield correction should be performed once the camera is mounted where it will be used in production. For example, if the camera is imaging a pallet from above, then the infield correction should be performed on-site with the camera facing downward.

Orienting the Correction Board

When using the infield correction tool, it is important to find the best position for the Zivid calibration target. For the tool to work, the target must be oriented with the checkerboard facing towards the camera.

Image which shows multiple Zivid calibration boards in both valid and invalid orientations.

  • The entire board must be in the field of view of the camera, including the fiducial marker.

  • The board should be aligned approximately perpendicular (flat) to the camera depth axis.

  • The board can be oriented 0, 90, 180 or 270 degrees (+/- 15 degrees) from the perspective of the camera (one edge of the board approximately horizontal in the image).

Note

Support for different orientations of the calibration board added in 2.6 SDK.

Covering Distances for Correction

When applying infield correction, it is important to cover the entire working distance within which objects will be imaged. If possible, it is even better to cover more distance above and below this threshold, as shown in the image below.

Image which shows how calibration boards should be positioned relative to the camera.

Camera Model

Minimum Distance

Maximum Distance

Zivid 2 M70

450 mm

1300 mm

Zivid 2 L100

600 mm

1600 mm

Zivid 2+ M130

800 mm

2000 mm

Zivid 2+ L110

700 mm

1700 mm

Zivid 2+ M60

400 mm

1100 mm

Note

The 600 mm distance is the closest that the Zivid calibration board is within Zivid 2+ camera’s full view. For Zivid 2, that distance is 450 mm.

Correcting for larger FOV

If objects are being picked at the edges of the frame, it is important to cover the center and the edges with the infield correction. Multiple captures at the same distance can provide a better correction metric.

Nine different images which shows how calibration boards can cover larger field-of-views.

If the application has a short working range (e.g., 1000 mm to 1200 mm in Z), then use the method with multiple captures at each of the distances. This can provide a better correction for this range.

Warm-up

It is recommended to Warm-up the camera before running infield correction. For optimized performance, use the same capture cycle during warmup and infield correction as in your application. To further reduce the impact of temperature dependent performance factors, enable Thermal Stabilization.