It is a best practice to create a target placement strategy before you begin your imaging project. This is especially true when scanning larger objects.
Plan for minimum of three common targets that are randomly spaced in a each sequential image. The common targets must be within the focal field of both the left and right Cobalt cameras, successfully captured by the Cobalt, and identified in Measure. Consider placing targets on the part in all three coordinate system axes to restrict the degrees of freedom and eliminate compounding inaccuracies.
TIP: To be most efficient, plan for more than three common targets, as some may not be visible by both Cobalt cameras, captured by the Cobalt as you might expect, or correctly identified by Measure. Six common targets in each sequential image pair is a safer plan. Your strategy ultimately depends on how your Cobalt 3D Imager(s) are set up: in an array, on robotic arms, with a turntable, or on a tripod.
In this example, we use three targets to illustrate how a placement strategy looks when the last scan overlaps the first, creating a loop.
- Image 1 has 4 targets--A, B, C, H
- Image 2 has 5 targets--A, C, F, G, H
- Image 3 has 4 targets--A, C, H
Notice that targets A, C, and H are common within all three images of the loop. This eliminates compounding errors.
If instead your strategy looks like a serial chain, then you run the risk of introducing inaccuracies between each image pair in the chain.
- Image 1 has 3 targets--A, B, C
- Image 2 has 5 targets--A, B, C, F, G, H
- Image 3 has 4 targets--F, G, H