# How to Move Calibration Target

AlignPlus can generate applications where the application generates the poses during hand-eye calibration. The poses contain the recommended translation only poses and rotation only poses. The poses are determined by the following parameters:

• The maximum and minimum limits for the X axis, and the number of samples when moving between the two limits

• The maximum and minimum limits for the Y axis, and the number of samples when moving between the two limits

• The maximum and minimum limits for the Theta axis, and the number of samples when moving between the two limits

The table that is shown below shows the default values for the above parameters

| Minimum | Maximum | Steps
X | -2 mm | 2 mm | 3
Y | -2 mm | 2 mm | 3
Theta | -1 degree | 1 degree | 3

The figure below shows the path that will be taken by the motion device for default motion parameters.

All Points:

Calibration Point | X | Y | Theta
--- | --- | --- | ---
1 | -2 | -2 | 0
2 | 0 | -2 | 0
3 | 2 | -2 | 0
4 | 2 | 0 | 0
5 | 0 | 0 | 0
6 | -2 | 0 | 0
7 | -2 | 2 | 0
8 | 0 | 2 | 0
9 | 2 | 2 | 0
10 | 0 | 0 | -1
11 | 0 | 0 | 1

Note: The second point of rotation only pose (0,0,0) overlapped with translation only pose 5, so this point is skipped for rotation only poses.

The figure below shows the path what will be taken by motion device for the default limits and increased number of samples.

Calibration Point | X | Y | Theta
--- | --- | --- | ---
1 | -2 | -2 | 0
2 | -0.667 | -2 | 0
3 | 0.667 | -2 | 0
4 | 2 | -2 | 0
5 | 2 | -0.667 | 0
6 | 0.667 | -0.667 | 0
7 | -0.667 | -0.667 | 0
8 | -2 | -0.667 | 0
9 | -2 | 0.667 | 0
10 | -0.667 | 0.667 | 0
11 | 0.667 | 0.667 | 0
12 | 2 | 0.667 | 0
13 | 2 | 2 | 0
14 | 0.667 | 2 | 0
15 | -0.667 | 2 | 0
16 | -2 | 2 | 0
17 | 0 | 0 | -1
18 | 0 | 0 | -0.333
19 | 0 | 0 | 0.333
20 | 0 | 0 | 1

The poses suggested above are all relative poses to the center point (0,0,0) of the moving path. If the center point is not (0,0,0) , all poses' coordinates should be offset based on the center point(x,y,Ө) to obtain the absolute target pose for motion stage to move to. After move is done at each pose, stage' current absolute pose should be sent back to the vision system in return for it to accumulate stage poses which later will be used for hand-eye calibration computation.

If the customer chooses to supply the poses, they should move the motion device as explained above. If this is not feasible, they should generate poses that contain at-least two positions for each degree of freedom for the motion device. That is, two positions for the X, Y and Theta degrees of freedom.

## Motion Capability Limitations

After defining the moving path, user need to check whether motion moving range can cover all points on moving path. Note that stage's rotation limit varies when its rotation center changes. For example, stage can rotate between -1 degree to 1 degree when stage x, y coordinates are (0,0), but when stage moves to (0,4), the rotation range might be reduced to -0.8 to 0.6 degrees. Therefore, to check whether all the points are within motion's limits, the best way is to command motion move step by step to each point and see whether the reported actual positions are same as required.

### Settling time

During hand-eye calibration, care should be taken to ensure that the motion device has completed motion and has come to a complete rest so that the camera is stationary relative to the calibration target. Failing to do so will affect the quality of the captured image, which in turn affects the hand-eye calibration results. To avoid this situation, a suitable settling time should be added following motion before an image of the target is acquired.

If the customer is responsible for moving the motion device, they should ensure that the target has come to a rest before they send a command to AlignPlus to acquire an image. If the vision application is responsible for moving the motion device, the vision application engineer should apply the settling time in the application.