Tsai's Calibration App

Overview

This software provides a graphical user interface (GUI) for the CMU's implementation of Tsai's calibration algorithm. The application is built using Borland C++ Builder 4.0. Below is the main window of the application.

The main application window has three major panels (by function):

calibration data (left): displays and manages the calibration data
image (top right): displays calibration image and participates in point matching
calibration status (bottom right): displays camera parameters and calibration status

Some additional features of the application main window are

pull-down menu (top) provides application's main functionality
status line (bottom) has two panes:
- (x,y) position of the mouse pointer over the image area
- menu item hint/prompt area

Process

Calibration is done one camera at a time. The complete calibration process consists of

loading the calibration data (menu Points | Import rows...)
indicating if 3D points are co-planar or not (menu Points | Coplanar or Points | Non-coplanar)
loading the calibration image (menu Image | Load...)
loading the camera parameters (menu Camera | Load...)
matching 3D world points to 2D points by Shift-drag&drop from the grid to the image
clearing unmatched points (menu Points | Clear Unmatched)
choosing the calibration strategy (menu Camera | Calibrate | Standard or Camera | Calibrate | Full Optimization)
inspecting the calibration results in Calibration Status panel
saving calibration data (menu Camera | Save...)

The software comes with a set of sample input and output files.

Options and features

Most of application functionality is accessed via the main menu. While most of the menu options are explained in the status line, there are some extra features that the user needs to be aware of.

world points are in mm, while image points are in pixels
the point list control behaves as a normal text grid allowing to enter arbitrary text in its cells, but the application will work only with real numbers
while in the collinear mode (menu Points | Collinear Mode) and as the user starts matching points, the application will attempt to find collinear 3D points and automatically match the corresponding 2D points; this feature does not take into account lens distortions and thus is unable to match the 2D points exactly in the regions where distortions are noticeable; if this happens, it can be turned off from the menu.

Note: this software is an intellectual property of the Keck Lab, University of Maryland. It cannot be used outside the Keck Lab without a prior consent of the person in-charge of the Keck Lab. Users of the software are welcome to report noticed problems with the program or its documentation to the author.