Zoom Lens Calibration

  • calculates all parameters of the virtual camera model precisely, including field of view and distortion data
  • makes an individual lens calibration of your employed lens possible; for the best matching precision of real and virtual objects
  • automated process based on image processing generates user independent results with a constant high quality
  • optional calibration of the focal distance for physically correct blur in virtual images

 

Besides the exact position and orientation of your broadcast camera, you need to have a precise knowledge about the optical properties of your employed lens. Especially for Augmented Reality, when you like to combine real and virtual objects, it is extremely important that virtual objects do not shift against the real environment while the camera or the lens are moving. Otherwise the illusion of one combined world gets lost.
Here the virtual camera needs to render the virtual image from exactly the same perspective as the real broadcast lens. Besides the pose of the camera, the perspective is mainly build by the optical properties of the lens, which you have to describe carefully over the full range of zoom and focus.  Therefore a lens calibration is employed. During the calibration process you first measure the physical parameters of the real lens. Then you build your virtual camera model out of these interior parameters.

Even if you compare the optical properties of two separate lenses of the same type, you might find large differences. E.g. the field of view may vary by one degree, which changes the size of the virtual scene and objects significantly. The virtual objects will not match the real world conditions. 
For the best possible matching precision we recommend to employ an individual lens calibration. Here exactly your individual lens with it's unique optical properties is calibrated by our zoom lens calibration software.

For the usage with all our camera tracking systems we developed a unique method to calibrate all relevant optical parameters of any zoom lens. In opposite to other tools on the market, this method is completely based on image processing. Here we analyze  the image of the broadcast camera lens by smart algorithms, not by a human trial and error process which quality depends on the experience of the operator.
Our software controls the zoom and focus of the lens remotely. It runs automatically through the full range of zoom and focus and determines all interior parameters of the virtual camera like the field of view and the distortion of the lens. The full parameter set is stored in a lens calibration file for the real-time usage with any of our camera tracking systems. Changing the lens of your camera just means you can simply exchange the pre-calibrated lens file which is dedicated to your current lens.

In addition, we can calibrate the position of the focus plane. When changing the focus of your employed lens, you receive the distance of the plane in relation to your camera which is in focus. This information is used by the render engine to calculate the depth of field and to blur virtual objects in front or behind the focal plane.