User interface systems for sterile fields and other working environments

A user interface system, comprising:

• a camera configured to capture images of a working environment in which a substrate and a patient are disposed, the camera being positioned remotely from a user;
• a controller that determines, from the captured images, a position and orientation of the substrate within the working environment and changes in said position and orientation;
• and
• a projector that projects a projected image onto the substrate, the projected image or the location of the projected image being adjusted by the controller in response to changes in the determined position or orientation of the substrate;
• wherein the controller further determines, from the captured images, whether and how the user is positioned relative to the substrate, and a perspective view of the projected image being adjusted based on the relative positions of the substrate, the patient and the user, with the perspective view being configured to change based on a change of position of the user relative to the substrate.