The Calibration Model¶

The calibration model is described by the calibration mode, expressed as a combination of options. Use EWorldShape::GetCalibrationModes ^.NET ^Python to access it.

The different calibration models are:

A field-of-view calibration model used when the calibration mode is the combination of the options ECalibrationMode_Scaled ^.NET ^Python, ECalibrationMode_Anisotropic ^.NET ^Python, ECalibrationMode_Skewed ^.NET ^Python, ECalibrationMode_Tilted ^.NET ^Python and/or ECalibrationMode_Radial ^.NET ^Python.
An advanced calibration model using a more complex distortion model capable of better calibrating wide-angle lens.
- This model does not expose its parameters.
- This model is used when the calibration mode is ECalibrationMode_Advanced ^.NET ^Python
Empirical models based either on a quadratic model (ECalibrationMode_Quadratic ^.NET ^Python) or a bilinear model (ECalibrationMode_Bilinear ^.NET ^Python).
- These models do not expose their parameters.

Hint

When using EWorldShape::AutoCalibrateDotGrid ^.NET ^Python, pass the combination of options that you want to test. The method selects the model that has the best precision on the calibration image.

Parameters¶

To tune the field-of-view calibration model, use these parameters:

Sensor Width and Height¶

The sensor width ^.NET ^Python and sensor height ^.NET ^Python give the logical image size, in pixels (always integers).

Field-of-View Width and Height¶

The field-of-view (f-o-v) field width ^.NET ^Python and field height ^.NET ^Python give the actual image size, in length units, i.e. the size of the rectangle corresponding to the image edges in the world space. These values are related to the pixel resolution by the following equations:

\[\begin{split} \begin{aligned} \mathit{f\textrm{-}o\textrm{-}v\ width} &= \mathit{pixel\ width} * \mathit{sensor\ width} \\ \mathit{f\textrm{-}o\textrm{-}v\ height} &= \mathit{pixel\ height} * \mathit{sensor\ height} \end{aligned} \end{split}\]

\[\begin{split} \begin{aligned} \mathit{sensor\ width} &= \mathit{f\textrm{-}o\textrm{-}v\ width} * \mathit{horizontal\ resolution} \\ \mathit{sensor\ height} &= \mathit{f\textrm{-}o\textrm{-}v\ height} * \mathit{vertical\ resolution} \end{aligned} \end{split}\]

By default pixel height is not specified, the pixels are assumed to be square (pixel width = pixel height).

Ratio¶

Center Abscissa and Ordinate¶

The center abscissa ^.NET ^Python (x) and ordinate ^.NET ^Python (y) indicate the image origin point (world coordinates (0,0)). Default is the image center.

Skew Angle¶

The skew angle ^.NET ^Python is the angle formed by the real-world reference frame (X-axis) and the image edge (horizontal). The default is no skew.

../../../../_images/calibrationangle.webp — Skew angle¶

Note

When the pixels are not square, the EWorldShape ^.NET ^Python object can convert the angle between the world and sensor spaces.

X and Y Tilt Angles¶

The X ^.NET ^Python and Y ^.NET ^Python tilt angles describe the viewing plane direction. They correspond to the required rotations around X and Y axis that bring the Z axis parallel to the optical axis.

Perspective Strength¶

The perspective strength ^.NET ^Python gives a relative measure of the perspective effect. The shorter the focal length, the larger the value.

Distortion Strength¶

Distortion strength ^.NET ^Python gives a relative measure of radial distortion in the image corners, that is the ratio of image diagonal length with and without distortion.

Calibration modes ^.NET ^Python, expressed as a combination of options, can be accessed via EWorldShape::GetCalibrationModes ^.NET ^Python.