Stemmer Imaging offers two main calibration methods:

Precise intrinsic calibration using the ZigZag target: This approach provides highly accurate intrinsic calibration, correcting perspective distortion, lense distortion and laser line deformation.
Intrinsic and extrinsic calibration using the AQS12 target: This method is primarily used for correcting inlined laser planes and estimating an extrinsic calibration. However, it also provides a basic intrinsic calibration estimating only the homography.

Note: Please note that both calibration methods are fully compatible with setups where a Scheimpflug adapter is mounted.

Which calibration method do I need for my laser triangulation setup?

The appropriate calibration method depends on your setup and the level of accuracy required. The following table summarizes the calibration methods and the corrections that can be estimated using each:

Calibration Correction	Calibration Method	Link to Calibration Theory
Basic intrinsic calibration - homography	ZigZag/AQS12	Transformation of Range Map Coordinates to Metric Coordinates
Precise intrinsic calibration - homography - lense distortion - laser line distortion	ZigZag
Encoder step	AQS12
Correction of inclined laser plane	AQS12	Correction of an Inclined Laser Plane and Extrinsic Calibration
Rigid-body transformation	AQS12

Note: If you require precise intrinsic calibration as well as correction for the inclined laser plane or extrinsic calibration, you can combine the ZigZag and AQS12 calibration methods.

As the necessary calibration method depends on your laser triangulation setup, three common use cases are described below:

Use Case 1: Modular Setup

Modular Setup

For a modular setup, you will always need an intrinsic calibration to obtain metric x, y and z coordinates. Depending on the required accuracy, you can either perform the ZigZag calibration for high precision or the AQS12 calibration.

An AQS12 calibration is necessary, if any of the following apply:

The encoder step is not (precisely) known.
The laser plane is not perfectly vertical to the direction of movement (inclined about the X- or Z-axis).
You have multiple sensors that need to be transformed into a superordinate coordinate system.

In these cases, you can either perform the AQS12 calibration alone or combine it with the ZigZag calibration if a higher level of accuracy is required.

Use Case 2: Compact Sensors with Intrinsic Calibration

Compact Sensor

If you are using compact sensors with a factory calibration (e.g. the AT CS series), a precise intrinsic calibration is already available. If the encoder step is known and the laser is mounted such that the laser plane is perfectly vertical to the direction of movement, no further calibration is needed. You can simply apply the factory calibration. Section Creating a Calibrated Point Cloud with CVB - Intrinsic Calibration details how to create a calibrated point cloud with CVB.

However, if any of the following conditions apply, an additional AQS12 calibration is required:

The encoder step is not (precisely) known.
The laser plane is not perfectly vertical to the direction of movement (inclined about the X- or Z-axis).
You have multiple sensors that need to be transformed into a superordinate coordinate system.

Use Case 3: Area 3D Compact Sensors

Area 3D Compact Sensor

Area-based 3D sensors typically provide height maps along with resolution value for the x, y, and z dimensions or even pre-calibrated point clouds. The resolution factors can be applied in CVB as described in the section Static Factors for ZMaps.

Use Case 4: Aligning Multiple Sensors to a Superordinate Coordinate System

To align multiple sensors within a shared superordinate coordinate system, a rigid-body transformation using the AQS12 target can be determined. This requires the encoder step to be accurately known and the laser plane to be precisely aligned perpendicular to the direction of movement. If these prerequisites are not met, the encoder step, shear and scale must also be estimated using the AQS12 target.