Method and apparatus for painting objects

1. A method for painting an object, said method comprising the steps of:

arranging a painting head in a predetermined working area, said painting head equipped with at least one spraying nozzle arranged to deliver a flow of paint on a surface of an object;

moving said painting head in said working area, said moving being carried out by moving means having at least two degrees of freedom;

identifying the three-dimensional shape of said surface of said object, said identifying step comprising the steps of:

projecting a grid, or matrix, of infrared points on said surface of said object, obtaining a projected image comprising a plurality of points;

detecting said projected image obtaining a detected projected image comprising a plurality of points, or pixels, having determined spatial coordinates, said detecting step carried out by optical sensor means integral to said painting head;

processing said detected projected image, said processing step arranged to determine said spatial coordinates of each of said points of said detected projected image in order to determine the three-dimensional shape of said object, said spatial coordinates x, y being determined on the basis of the position of each point, or pixel, in the detected projected image, said processing step comprising a step of converting said three-dimensional shape in a two-dimensional geometric shape of said surface of said object, said converting step being carried out computing the grey-level values of said points, or pixels, of said detected projected image;

moving said painting head in said working area on the basis of said spatial coordinates of said points in such a way that during said painting step, said spraying nozzle is arranged at a substantially fixed distance from said surface of said object and can follow its curvature.

2. A method, according to claim 1 , wherein said processing step further comprises the steps of:

comparing said two-dimensional geometric shape with the two-dimensional geometric shapes of a plurality of models contained in a predetermined database, said comparing step being carried out on the basis of the grey-level values of a predetermined group of points of said detected projected image and of a corresponding group of points of said models;

associating to each model of said plurality of a corresponding similarity index i s with said object;

selecting among said plurality of models the model having the highest similarity index, or the similarity index i s that is higher than a predetermined threshold value i s *;

associating said selected model to said two-dimensional geometric shape of said object;

displaying a variety of colours associated to said selected model;

selecting a predetermined colour among said variety of colours.

3. A method, according to claim 1 , wherein said comparing step comprises the steps of:

identifying the contour, or perimeter, of said two-dimensional geometric shape on the basis of said grey-level values of said points, or pixels, of said detected projected image;

said identifying step providing the steps of:

computing the highest grey-level value l max among all the points, or pixels, of said plurality of points of said detected projected image, corresponding to the point, or pixel, that is most distant from said sensor means;

computing the lowest grey-level value l min among all the points, or pixels, of said plurality of points of said detected projected image, corresponding to the point, or pixel, nearest to said sensor means;

associating a first grey-level value, to all the points having a grey-level value set between l max and l min and a second grey-level value to all the points having a different grey-level;

comparing said defined contour, or perimeter, with the contour, or perimeter, of said plurality of models contained in said database.

4. A method, according to claim 3 , wherein said first grey-level value is “255” corresponding to the white and said second grey-level value is “0” corresponding to the black.

5. A method, according to claim 1 , wherein a centering step is provided for centering said sensor means with respect to said surface of said object to be detected, said centering step comprising the steps of:

detecting a position of said optical sensor means with respect to said surface of said object, said detection comprising the steps of:

determination, by said processing means, the spatial coordinates of a centroid of said detected projected image;

creating a geometric figure of reference arranged to approximate said detected projected image;

identifying, by said processing means, the center of said geometric figure of reference;

moving said optical sensor means and said painting head with respect to said object up to cause said center of said geometric figure to coincide substantially with said centroid of said detected projected image and with said position of said optical sensor means.

6. A method, according to claim 1 wherein said spatial coordinates z is determined on the basis of the grey-level value of the corresponding point, or pixel.