Projection system and contact lens used therefor

A projection system, comprising:

• an optical device, configured to be disposed on an eye and having a substrate and at least two positioning components, wherein the positioning components are respectively disposed on a plurality of different areas of the substrate;
• a positioning device, configured to perform a positioning on the optical device according to the positioning components on the substrate and generate a position signal;
• and
• a projector, configured to project an image light beam to the optical device, wherein the projector receives the position signal and determines a projection direction of the image light beam according to the position signal,
• wherein the positioning device comprises a radar, the radar projects a plurality of sensing signals to the at least two positioning components and receives a plurality of reflection signals, and the positioning device obtains the position signal according to the reflection signals.