SAL3D > METRIC CALIBRATION TOOL

The AQSENSE SAL3D Metric Calibration Tool provides a straightforward procedure for obtaining true XYZ metric coordinates from 2.5D rangemaps, permitting the reconstruction of the COP with metric units and removing perspective distortion. Find here how to get Range Maps for Metric

Non calibrated COP		Calibrated COP with Metric Tool

Features • Easy to use (see brouchure for three easy steps) • Accurate conversion 2.5D → 3D  • Removes perspective distortion • Linear and Static calibration

 

Linear Metric Calibration
	This approach involves the acquisition of the RangeMap of a specially designed object
		Accurate In-line measurement for parts with a constant linear movement (conveyors with encoder) Calibration pattern and object dimensions should be similar. The object, or the block camera-laser must have a linear displacement.
Static Metric Calibration
	This approach only requires a single profile to determine the relation between camera pixels and metric units
		A cost effective option when linear displacement is constant. Suited for environments where movement conditions are irregular (vibrations). Suited for calibration in set-ups where movement is not linear (e.g. rotating, robot arm)

Remove Perspective Distortion

For a human observer, closer objects seem to be bigger than the same objects in a farther position (related to the observer). The observer has the impression that a long pipe, as looked at from one of its extremes, seems to be decreasing in diameter as the observer looks farther along the pipe.

This is known as Perspective Effect (see following figure) or in terms of 3D acquisition, Perspective Distortion.

The following pictures show an example of the reconstruction of a tilted cylinder using proportional reconstruction and using SAL3D Metric reconstruction. The proportional reconstruction assumes a constant ratio between pixels and metric units, but, due to perspective distortion, this assumption is not true.

Proportional cylinder reconstruction. a) Range Map; b) COP; c) ZMap

SAL3D Metric cylinder reconstruction. a) Range Map; b) COP; c) ZMap

Observing the cloud of points and also the ZMap obtained in both situations, it is clear that the proportional reconstruction distortes the object, while the SAL3D Metric reconstruction preserves the original shape.

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