Positioning

Positioning a camera serves two purposes: to aid in placing a camera to its correct position and to calculate the exact position of the camera with respect to a world coordinate system. Sometimes, the parameters defining the position of a camera are called the extrinsic parameters of a camera.

Positioning view

Before calculating the camera position parameters, the previously saved Calibration parameter set must be associated with the camera. Otherwise, a warning is shown in the Positioning view:

Associated calibration parameters missing.

Associated calibration parameters missing.

In this case, you should go back to the Calibration view and associate the calibration parameters by editing the Associated parameters setting value. Note that the same setting in Positioning view means associating the position parameters.

The positioning procedure starts with selecting the correct value in the Camera type setting. For an Area scan camera, the required input parameters are explained in Position camera and for a Line scan camera, in Position line-scan camera.

Exactly one image of the standard calibration target is needed for positioning. It can be either a live image or a recorded image, which can be toggled with the corresponding buttons.

Many matrix cameras can be positioned to the same world coordinate system. In such a case, one of the corners or the center of the calibration target must be visible in every image.

Buttons to switch between live and recorded images.

Buttons to switch between live and recorded images.

With the live image option, the positioning procedure is done for each image captured using either the single shot () button or the continuous capture () button. With the recorded image option, you need to select an image from the list of the recorded images shown at the bottom of the view. If multiple recorded images are selected, the one being shown in the image display is used.

The Positioning view applies the calibration parameters associated with the camera when the images are displayed in the image display on the right side of the view. This means the image pixels can be mapped to the world coordinates. To see the image in world coordinate frame, change Coordinate frame to World in the context menu of the image display. Note that displaying a camera image in the world coordinate frame is possible only in the Positioning view. In the other views, images will always look the same in Image and World coordinate frames. The image display also shows the calculated center position with a frame widget. That should be at the center of the center marker of the calibration plate.

Successful camera positioning.

Successful camera positioning.

You can have a closer look on the exact position by placing the cursor on top of the widget and then zooming closer by holding down the Ctrl key and scrolling up with the mouse's middle button.

Successful camera positioning - center zoomed in.

Successful camera positioning - center zoomed in.

The errorMeasure value shows how successful the positioning procedure was. The smaller the value, the better. The scale is the same as in the Calibration view.

Once you are satisfied with the positioning results, they can be saved as a position parameter set and associated with the camera by editing the Associated parameters setting in the Positioning view.

That's all! Now an Image Source using the camera can be configured to use the associated parameter sets.