Incorporating constraints into the design of locally identifiable calibration patterns

Camera calibration requires the identification of points in an image that correspond to known locations in the scene. These are typically determined through the use of a calibration pattern designed to facilitate feature localisation. We present in this paper a novel method of generating patterns such that each subregion is individually identifiable by its cross ratio. The method aims to minimise the probability of misidentifying a subregion. A key advantage of the method is the ability to place constraints on the size of the elements constituting the pattern. This allows a calibration object to be used in a wider variety of viewing conditions, increasing the flexibility of the calibration process.