F_VN_CalibrateLinescanCameraExp

Compute the camera parameters (intrinsic + extrinsic) by evaluating images containing a line calibration pattern. The pattern must consist of alternating vertical and diagonal lines, with each diagonal having the same constant slope: |\|\|...\|. The results are only valid for the x-direction of a line scan image. To get accurate x-values for a transformation into world coordinates, the y-coordinate must be set to half the sensor width and so equal to the cy-value of the camera matrix. For other y-values, the results are approximated and can be inaccurate. The extrinsic parameters are computed for the first image in the array. (expert function)
Can use available TwinCAT Job Tasks for executing parallel code regions.

Syntax

Definition:

FUNCTION F_VN_CalibrateLinescanCameraExp : HRESULT
VAR_INPUT
    pSrcImages              : PVOID;
    nSrcArraySize           : UINT;
    ipPatternLineOrigins    : ITcVnContainer;
    fSlopeRad               : LREAL;
END_VAR
VAR_IN_OUT
    aCameraMatrix           : TcVnMatrix3x3_LREAL;
    aDistortionCoefficients : TcVnArray8_LREAL;
    aRotationMatrix         : TcVnMatrix3x3_LREAL;
    aTranslationVector      : TcVnVector3_LREAL;
    fReprojError            : LREAL;
    stCalibrationOptions    : TcVnCameraCalibrationOptions;
END_VAR
VAR_INPUT
    eEdgeDirection          : ETcVnEdgeDirection;
    fMinStrength            : REAL;
    nMaxSearchLines         : UDINT;
    nMaxThickness           : UDINT;
    nSubpixelsIterations    : UDINT;
    fApproxPrecision        : REAL;
    eAlgorithm              : ETcVnEdgeDetectionAlgorithm;
    hrPrev                  : HRESULT;
END_VAR

Inputs

Name	Type	Description
pSrcImages	PVOID	Pointer to an array of 1 or more source images (1 channel). If the images have more than 1 row, each row must contain an image of the same pattern position.
nSrcArraySize	UINT	pSrcImages array size
ipPatternLineOrigins	ITcVnContainer	X position of the pattern line origins (ContainerType_Vector_REAL, usually same origin for vertical and following diagonal line)
fSlopeRad	LREAL	Slope of the diagonal line in rad (> 0, < PI/2), relative to the vertical line (i.e., 0 would be a vertical line, PI/2 a horizontal line)
eEdgeDirection	ETcVnEdgeDirection	Specification of the edge direction to search for
fMinStrength	REAL	Specification of the minimum strength (intensity difference) of the edge to search for
nMaxSearchLines	UDINT	Maximum number of search lines (equally distributed over the image height, at most 1 searchline per image row)
nMaxThickness	UDINT	Specification of the maximum thickness of the edge to search for, which means fMinStrength must be reached within nMaxThickness pixels
nSubpixelsIterations	UDINT	Specifies the number of subpixels (for INTERPOLATION, 10 - 20 usually is sufficient) or maximum number of iterations for optimizing the parameters (for APPROX_ERF and APPROX_GAUSSIAN, 50 - 100 usually is sufficient)
fApproxPrecision	REAL	Specifies the approximation precision for APPROX_ERF and APPROX_GAUSSIAN (0.001 usually is sufficient, unused for INTERPOLATION)
eAlgorithm	ETcVnEdgeDetectionAlgorithm	Selection of the edge detection algorithm
hrPrev	HRESULT	HRESULT indicating the result of previous operations (If SUCCEEDED(hrPrev) equals false, no operation is executed.)

In/Outputs

Name	Type	Description
aCameraMatrix	TcVnMatrix3x3_LREAL	Returns the camera matrix
aDistortionCoefficients	TcVnArray8_LREAL	Returns the lens distortion coefficients [k1, k2, p1, p2, k3, k4, k5, k6]
aRotationMatrix	TcVnMatrix3x3_LREAL	Returns the rotation matrix
aTranslationVector	TcVnVector3_LREAL	Returns the translation vector
fReprojError	LREAL	Returns the reprojection error
stCalibrationOptions	TcVnCameraCalibrationOptions	Calibration options (recommended to set bFixAspectRatio, bFixPrincipalPoint, bZeroTangentDist)

Return value

HRESULT

Required License

TC3 Vision Metrology 2D

System Requirements

Development environment	Target platform	PLC libraries to include
TwinCAT V3.1. 4024.44 or later	PC or CX (x64) with PL50, e.g. Intel 4-core Atom CPU	Tc3_Vision