Method for checking tyres in a tyre production line, the method comprising: - providing a tyre to be checked; - illuminating, with a first grazing light radiation, a surface portion of said tyre and acquiring a first image of said surface portion illuminated by said first light radiation, said first image being two-dimensional; - illuminating substantially said surface portion, at times different from those when the surface portion is illuminated with the first radiation, with a second grazing light radiation and acquiring a second image of substantially said surface portion illuminated by said second light radiation, said second image being two-dimensional; wherein for each point (P, P') of said surface portion, at least 75% of the respective overall light power of said first and second light radiation incident at the point respectively comes from two half-spaces that are opposite with respect to an optical plane passing through the perpendicular to the surface of the tyre at said each point, wherein said first and second grazing light radiation are light radiations in which at least 75% of an overall light power of the light radiation incident on each point of the surface portion forms, with a plane tangent to the surface portion at said each point, a first incidence angle smaller than or equal to 60°; wherein said first and second digital image are composed of a respective plurality of first and second linear images of a succession of respective linear surface portions, contiguous or partially superimposed on each other, said first and second linear images being acquired on each linear surface portion of said respective succession of linear surface portions respectively illuminated by said first and second light radiation in alternated sequence, wherein each pair of first and second linear images show two respective linear surface portions that are spatially shifted from each other by a distance less than a linear size of surface associated with a pixel, and wherein said succession of linear surface portions is obtained by rotation of the tyre around its axis; - processing said first and second image, wherein said first and second image are compared with each other in order to obtain information on an altimetric profile of said surface portion, wherein said comparison between the first and second image comprises calculating a difference image in which each pixel is associated with a value representative of the difference between the values associated with the corresponding pixels in said first and second image. - providing a tyre to be checked; - illuminating, with a first grazing light radiation, a surface portion of said tyre and acquiring a first image of said surface portion illuminated by said first light radiation, said first image being two-dimensional; - illuminating substantially said surface portion, at times different from those when the surface portion is illuminated with the first radiation, with a second grazing light radiation and acquiring a second image of substantially said surface portion illuminated by said second light radiation, said second image being two-dimensional; wherein for each point (P, P') of said surface portion, at least 75% of the respective overall light power of said first and second light radiation incident at the point respectively comes from two half-spaces that are opposite with respect to an optical plane passing through the perpendicular to the surface of the tyre at said each point, wherein said first and second grazing light radiation are light radiations in which at least 75% of an overall light power of the light radiation incident on each point of the surface portion forms, with a plane tangent to the surface portion at said each point, a first incidence angle smaller than or equal to 60°; wherein said first and second digital image are composed of a respective plurality of first and second linear images of a succession of respective linear surface portions, contiguous or partially superimposed on each other, said first and second linear images being acquired on each linear surface portion of said respective succession of linear surface portions respectively illuminated by said first and second light radiation in alternated sequence, wherein each pair of first and second linear images show two respective linear surface portions that are spatially shifted from each other by a distance less than a linear size of surface associated with a pixel, and wherein said succession of linear surface portions is obtained by rotation of the tyre around its axis; - processing said first and second image, wherein said first and second image are compared with each other in order to obtain information on an altimetric profile of said surface portion, wherein said comparison between the first and second image comprises calculating a difference image in which each pixel is associated with a value representative of the difference between the values associated with the corresponding pixels in said first and second image.