Vanishing point and Z-tranform image center calibration techniques are reported for a prototype “compound-eye” camera system which can contain up to 25 “eyelets”. One application of this system is to track a fast-moving object, such as a tennis ball, over a wide field of view. Each eyelet comprises a coherent fiber bundle with a small imaging lens at one end. The other ends of the fiber bundles are aligned on a plane, which is re-imaged onto a commercial CMOS camera. The design and implementation of the Dragonfleye prototype is briefly described. Calibration of the image centers of the eyelet lenses is performed using a vanishing point technique, achieving an error of approximately ±0.2 pixels. An alternative technique, the Z-transform, is shown to be able to achieve similar results. By restricting the application to a two-dimensional surface, it is shown that similar accuracies can be achieved using a simple homography transformation without the need for calibrating individual eyelets. Preliminary results for object tracking between eyelets are presented, showing an error between actual and measured positions of around 3.5 mrad.
Compound eyes are a highly successful natural solution to the issue of wide field of view and high update rate for vision systems. Applications for an electronic implementation of a compound eye sensor include high-speed object tracking and depth perception. In this paper we demonstrate the construction and operation of a prototype compound eye sensor which currently consists of up to 20 eyelets, each of which forms an image of approximately 150 pixels in diameter on a single CMOS image sensor. Post-fabrication calibration of such a sensor is discussed in detail with reference to experimental measurements of accuracy and repeatability.