Measurement method and device for thread parameters

A method of measuring thread parameters, in particular for a threaded object, wherein a measurement device is provided incorporating one or more optical sensors adapted to retrieve the shape of the threaded object, having a nose and defining a first spatial reference system comprising first co-ordinate axes the measurement device defining a second spatial reference system comprising second co-ordinate axes providing a computer for storing a preset algorithm to calculate a first matrix that describes the quadratic form representing the threaded object in the second spatial reference system, thus providing the relationship between the first and second spatial reference systems, the method comprising the steps of:

• predefining at least one trajectory of the one or more optical sensors on the threaded object along which one or more predefined measurement points are selected such that the matrix evaluated on these values has a maximum rank;
• performing a first scanning operation by the one or more optical sensors along said at least one trajectory and retrieving data of the one or more predefined measurement points;
• feeding the data to the preset algorithm and calculating an axes transformation matrix relating the first spatial reference system to the second spatial reference system for defining the relative position of the threaded object with respect to the second spatial reference system;
• and
• using the axes transformation matrix to convert all data retrieved from the second spatial reference system to the first spatial reference system.