About stereo and spherical calibration (.cal) files.

Last Revision Date: 5/17/2014

This article provides basic information about the calibration files used by our stereo and spherical vision cameras, and discusses our policy on publishing calibration details. 

The calibration file format is not published. The purpose of the file is to provide information to the Triclops or Ladybug SDKs regarding camera calibration. Customers should access the camera parameters via the SDK, so it is not necessary to understand the calibration file format.

The Triclops and Ladybug SDKs rectify input images to form pinhole camera images with aligned coordinate systems. This way, users do not need to worry about lens distortion and misalignment. The rectified images have no rotation between them and are offset in the X axis by the baseline.

In the Triclops SDK, the functions to obtain all the information you need to describe this system are:

triclopsSetResolution()
triclopsGetFocalLength()
triclopsGetImageCenter()
triclopsGetBaseline()

In the Ladybug SDK, the corresponding functions are:

ladybugSetOffScreenImageSize()
ladybugGetCameraUnitFocalLength()
ladybugGetCameraUnitImageCenter()
ladybugGetCameraUnitExtrinsics()

Note: the focal length and image center (principal points) are the same for all stereo cameras. For spherical cameras, these measurements differ slightly for each camera on the system due to correction for fisheye lens distortion. Focal length is supplied in pixels, so you must make sure you set the stereo or spherical resolution first (using triclopsSetResolution or ladybugSetOffScreenImageSize) before you get the focal length and image center.