Applying wide field of view retroreflector technology to free space optical robotic communications

This dissertation deals with research into the design and implementation of a new wide field of view retroreflector device for autonomous mobile robot communication. In order to demonstrate effective and efficient optical communication for robots, the research had first to address the problem of expanding the field of view of retroreflectors. Experimentation shows that the device is beneficial for robotics navigation and localization, and for underwater optical communication. The retroreflector is similar to other conventional cat's-eye retroreflector designs, but the use of a fisheye lens and compensating lens to collimates the light before it enters a spherical retroreflector was found facilitate a wider field of view. Using this approach the retroreflector FOV was increased to 180 degrees although at the expense of divergence angle due to spherical aberration. The combination of both a laser transceiver unit and the retroreflector formed a very useful device for several short-range wireless optical communication scenarios including robot to robot communication in situations whereby navigation and localization was executed for collaborating robots and potentially underwater optical communication in turbid water. For ease in testing and implementation visible and near infrared wavelengths were used with a relatively low speed, polarization independent, liquid crystal modulator. While the data rate and range of the tested system are limited, the results of the project indicate that with high speed optical modulators and a suitable pointing and tracking system that collaborative robot activities and robot to robot communications can be substantially advance by using free space optical communications with wide field of view retroreflectors.