Camera Calibration

Camera Calibration#

Calibration is the crucial step that establishes the exact geometric relationship between the real world, coordinates in millimeters, and the image acquired by the camera, coordinates in pixels. Without accurate calibration, the precision of the picking system is compromised, making the entire application unreliable.

Warning

Fundamental prerequisite

Before proceeding with calibration, make sure that all hardware setup steps have been completed correctly:

Calibration must be repeated every time the position of the camera and or the robot is changed.

Tip

It is not necessary to recalibrate if only the position of the FlexiBowl is changed.

Why calibration is necessary#

Calibration is necessary because every sensor and lens combination introduces specific alterations into the image. Its main goal is to correct these distortions.

Types of optical distortion#

Types of optical distortion

Examples of optical distortion: no distortion, left, barrel distortion, center, and pincushion distortion, right#

Step 1: Calibration grid#

Error

Make sure that:

  • The backlight is on, SETUP > FlexiBowl Setup > Config FlexiBowl > Light ON

  • The TopLight is off

The dedicated ARS calibration grid must be positioned on the FlexiBowl:

0

If present, remove the diverters mounted on the FlexiBowl.

1

Loosen the four screws of the central FlexiBowl flange

2

Rotate the central flange slightly counterclockwise and remove it

3

Carefully lift and remove the surface

4

Position the ARS grid on the FlexiBowl, aligning the positioning pins with the predefined holes
Calibration grid positioning

Correct positioning of the ARS calibration grid on the FlexiBowl#

Attention

The calibration grid must be positioned at the same height as the object used in the application.

For this reason, the grid is supplied with spacers that must be inserted in the grid pins before installation on the FlexiBowl. The spacers are used to raise the grid to the same level as the part height, ensuring accurate calibration.

Spacers

../../../_images/altezzacalibrazione.png

Step 2: Basic adjustments#

5

Open the Camera SETUP section from SETUP

6

Click the Config Camera button for the corresponding camera

7

Click EXPERT in the Camera FLB page

8

Set the camera to live display mode Before adjusting the aperture, activate continuous display mode:

  • live image

9

Set the iris aperture

  • Slightly loosen the screw of the upper ring on the camera lens

  • Rotate the ring while observing the live image, until the correct amount of light enters the camera

  • Tighten the screw of the upper ring

../../../_images/Esp_Corretta.png

10

Adjust camera focus manually

  • Slightly loosen the screw of the lower ring on the camera lens

  • Rotate the ring slowly while observing the live image

  • When the pattern appears sharp, focus is correct

  • Tighten the screw of the lower ring

  • Close the screen

../../../_images/Fuoco_Corretto.png

11

Click Back

Warning

Pay attention to depth of field

Focus must guarantee sharpness over the entire FlexiBowl surface, not only in the center.

If the center is sharp but the edges are blurred:

  • Verify that the optics are clean

  • Verify that the working distance is correct

  • Verify that the camera is perfectly parallel to the plate

  • Close the iris slightly to increase depth of field

If the problem persists, the mechanical installation of the camera may need to be reviewed.

Error

If, by clicking RUN multiple times, even once you see a completely blue screen, refer to Camera Calibration Troubleshooting

12

Adjust camera exposure

  • In the Camera FLB x page, locate the Cam Exposure parameter

  • Adjust the Cam Exposure parameter and click TEST, repeating the step until the correct image exposure is found:

    • grid pattern clearly visible, black on white or vice versa

    • high contrast between black and white squares

    • no overexposure, no fully burned white areas

    • no underexposure, no image that is too dark

13

Click NEXT
Example of correct exposure

Example of correct exposure: high contrast, well-defined pattern, no burned areas#

Tip

Exposure optimization

The higher the time, the more light enters the optics

  • Time too short: dark image, pattern poorly visible

  • Time too long: overexposed image, loss of detail

  • Optimal time: maximum contrast without saturation

Step 3: Camera calibration#

14

Verify that the grid is centered, sharp, and fully visible before acquiring the calibration image.

15

Click Grab Image Calib to capture a photo of the calibration grid.

Visually verify that:

  • the entire grid is visible

  • the pattern is sharp

  • there are no shadows or reflections

16

Set both Tile Size X and Tile Size Y to 10

17

Click Calibrate to perform calibration

18

Evaluate calibration quality

The Result Calibration parameter will return a value:

🟢 Excellent, Green: excellent calibration, optimal precision.

🟠 Acceptable, Orange: acceptable calibration, good precision but not optimal.

🔴 Bad, Red: poor calibration, insufficient precision, must be repeated.

Important

Accept only Excellent calibrations. Any other result compromises the behavior of the entire application.

Note

Acceptance criterion

A satisfactory result requires correct aperture setting, correct focus, and the best exposure setting for the application.

Warning

Errors during calculation

If the calibration calculation fails:

Possible causes:

  • Pattern not detected, image too dark or too bright

  • Grid squares partially obscured

  • Excessive distortion, camera too close or too far

  • Wrong Tile Size entered

Solution:

  • Verify and improve acquired image quality

  • Make sure the entire grid is visible and well illuminated

  • Verify the Tile Size value

  • Repeat image acquisition, Grab Image, and try again

When calibration must be repeated#

Recalibrate when:

First system setup, mandatory. After changing the camera position. After moving the robot. If systematic picking errors are detected.

Recalibration is not necessary when:

If the part type changes while FlexiBowl and camera remain the same. If focus or aperture of the lens is adjusted. If only the software recipe changes. If only recognition parameters are adjusted. If robot programs are updated.

Robot Calibration#

Step 4: Laser mounting#

19

Once excellent calibration quality has been achieved, click NEXT.
A window will appear asking for robot calibration before continuing. Do not click Yes yet, and follow the next steps.

20

Mount the Laser Tool with its dedicated support

21

Position the Spacer Bracket (A) under the laser

22

Lower the laser to the level of Spacer (A), so the laser is positioned exactly 3 cm above the calibration grid

../../../_images/spacerbracket.png

23

Remove the Spacer Bracket

24

Turn on the laser

Step 5: Define a 3-point plane#

25

Move the laser to the origin point

26

Move the laser to the end point of the X axis

27

Move the laser to the end point of the Y axis

Step 6: Verify robot trajectory#

28

Bring the laser back to the origin point

29

Move the robot from its teach pendant along the X and Y axes

30

Verify that the correct trajectory is followed: when moving only along X and Y, the robot must correctly follow the grid lines

31

Click YES

Step 7: Save the base recipe#

32

Click Recipes

33

Verify that the recipe containing all setup steps and calibration is selected in the left menu, then click Save Recipe

34

This allows all completed steps to be stored separately, providing a base for all future recipes that will contain the various models for the calibrated system

35

To continue with model creation, duplicate the base recipe, rename it as desired, and click Edit Recipe. A page with the list of available models will open

Common problems during calibration#

Pattern not detected#

Warning

Error: “Unable to detect calibration pattern”

Cause: the software cannot identify the grid pattern.

Solutions:

  • Increase contrast by adjusting exposure or illumination

  • Verify that the entire grid is visible in the image

  • Improve focus

  • Clean the grid surface, dust or fingerprints may interfere

Calibration always “Bad” or “Acceptable”#

Warning

Insufficient calibration quality

If calibration remains below Excellent despite adjustments:

  1. Verify camera-FlexiBowl working distance, it must match the calculated one

  2. Check that the camera is parallel to the FlexiBowl plane and perfectly horizontal

  3. Make sure the camera is stable, no vibrations during acquisition

  4. Verify that the lens is fully screwed in

If the problem persists, there may be a mechanical installation issue. Review Mechanical Installation.


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