Positioning device comprising a light beam

Position measurement system for determining 2D displacement or position of a mobile element with respect to a reference frame, comprising:

• a point light source fixed on a reference frame, said point light source being arranged to emit a light beam;
• an optical mask, comprising transparent and opaque areas on at least one side of its surfaces, said areas defining a repetitive pattern;
• an imager, fixed to a mobile element, comprising integrated electronic circuits allowing detection, computing and analyzing of a shadow projected by the optical mask,
• said position measurement system comprising an optical diffuser plate positioned between said point light source and the optical mask and wherein the imager, the optical mask and the optical diffuser plate form an assembly, said light beam producing a light spot created by the scattering of an incident light beam emitted by the point light source on said optical diffuser plate, and wherein said optical mask, positioned in between said optical diffuser plate and said imager, produces a shadow on said imager, said imager being arranged to compute and provide 2D position of the mobile element relative to the fixed reference frame.