Dual harmonization method and system for a head-worn display system for making the display of piloting information of an aircraft conform with the outside real world

A dual harmonization method for a head-worn display system for causing a display of piloting information of an aircraft to conform with an outside real world, the head-worn display system comprising:

• a transparent head-worn display, a head posture detection subsystem having a mobile tracking first element securely attached to the transparent head-worn display, a fixed second element securely linked to a platform of the aircraft, and a means for measuring and determining a relative orientation M12 of the mobile tracking first element relative to a reference frame of the fixed second element linked to the platform of the aircraft, an attitude inertial device for supplying a relative attitude M3t of the platform of the aircraft relative to a terrestrial reference frame linked to Earth, a harmonization subsystem for the head-worn display system for causing the display of the piloting information of the aircraft on the transparent head-worn display to conform with the outside real world, the harmonization subsystem having a dual harmonization computer and a human-system interface for managing and performing the dual harmonization method, the dual harmonization method comprising:
• performing a series of an integer number N of different sightings Vi, wherein N is greater than or equal to 3, and i varying from 1 to N, performed through the transparent head-worn display by aligning a centred sighting visual pattern on any same fixed target of the outside real world, each sighting Vi corresponding to a different fixed position Pi of the centre of the sighting visual pattern on the transparent head-worn display and having a sighting vector {right arrow over (x)}i determined as a function of the position Pi, and for each sighting Vi, acquiring a corresponding measurement {circumflex over (K)}i of a relative angular orientation of the mobile tracking first element relative to a reference direction, that is fixed relative to the platform of the aircraft, then:
• computing a matrix of relative orientation M01 between the transparent head-worn display in a tilted position and the mobile tracking first element as a right matrix {circumflex over (D)}, a solution of a system of equations:
• solution of a system of equations:
• Ĝ·{circumflex over (K)}i·{circumflex over (D)}·{right arrow over (x)}i={right arrow over (y)}0 for i=1 to N, A vector {right arrow over (y)}0 denoting a vector in an inertial reference frame of the platform of the aircraft corresponding to a target point targeted in the outside real world and being unknown;
• and a left matrix Ĝ being a matrix M23 of a relative orientation between the reference frame of the fixed second element, linked to the platform of the aircraft and a reference frame of the attitude inertial device, which is potentially incorrect but assumed constant as a function of time, and which, when it is unknown, requires at least four measurements {circumflex over (K)}i.