Minimally invasive surgery system

A minimally invasive surgery system comprising

• a robot comprising at least one movable robot arm,
• a cannula assembly detachably mounted to the robot arm and comprising a cannula and a pattern generating member, the cannula having a distal end, a proximal end with a flange portion having a port formed thereon for insufflating a body cavity, an elongate cannula shaft portion extending from the proximal end to the distal end along a longitudinal axis extending therebetween, and an access port through the elongate cannula shaft portion, the pattern generating member comprising a pattern light source and a projector temporarily or permanently fixed to the elongate cannula shaft portion, the pattern light source operatively connected to the projector for projecting a light pattern, and
• a computer system configured for receiving image data, in real time, representing light pattern reflections from a surgical surface and for determining a real-time spatial position of the cannula assembly relative to the surgical surface based on the image data, for determining a real-time spatial position of a distal end of a surgical tool of a surgical instrument disposed in the access port of the cannula relative to the cannula assembly based on motion data received from a motion sensor, and for determining a distance of the distal end of the surgical tool from the surgical surface based on the determined real-time spatial positions of each of the cannula assembly and the distal end of the surgical tool and an orientation of the distal end of the surgical tool relative to the longitudinal axis.