In augmented reality systems, a view of the physical, real world is made visible through a see-through display or is captured by a camera and displayed to a user on a display, along with computer generated images. Thus, the real world and the computer generated images are concurrently visible to the user. In some applications, the position, size, orientation, etc. of the computer generated images may change based on objects in the field of view of the camera. Thus, to display the computer generated images in a manner that is appropriate, it is useful to properly determine the location of the camera in the physical world, a process that is referred to as “registering” the camera.
To aid in accurately registering the camera, prior augmented reality systems have used markers that contain optical codes. The markers are placed at precise, known locations within a physical space. Image processing techniques are used to identify the optical codes in the markers in the captured images of the physical space. From the location of the markers in the images, and the known location of the markers in the physical space, the position of the camera is determined.
In such an approach, the accuracy of the camera registration depends on how much care is taken to place the markers at the proper locations in the physical space. In practice, to register the camera with an acceptable degree of accuracy for most augmented reality applications takes a significant amount of time, labor, and care, which detracts from the user experience. Further, the physical space in which such augmented reality systems may be used is limited to the space in which markers have been placed at the known locations. The system will not be able to properly display computer generated images to a user who wanders off outside of a carefully constructed augmented reality space, since there are no markers outside of the space by which the camera can be properly registered by the system.