1. An imaging method involving a X-rays or infrared light beams to irradiate a body and signal processing to obtain representative images of values associated with each zone of a sectional plane of the body, with the aid of an imaging device comprising a source and a detector, in which, crosswise scannings in the sectional plane of the body are carried out a variation of intensity of the X-ray or infra-red light beams between the source and the detector is measured along scanning profiles, and by means of a programmed computer, i) initial values coefficients of attenuation are calculated for a number of zones of the sectional plane of the body equal to the crosswise scannings, and a low definition initial image of said sectional plane is constructed from an initial matrix of initial values, in order to obtain a high definition image, wherein, a first and a second series of supplementary scannings of the sectional plane of the body are carried out, the scannings of the first series being crossed with respect to the scannings of the second series, a variation of intensity of the X-ray or infrared light beam between the source and the detector is measured along respectively n and m scanning profiles of the first and the second series, and by means of the suitably programmed computer, ii) an expanded rectangular matrix is constructed from the initial matrix, comprising n lines and m columns of values estimated by making an interpolation between the values associated with two zones, or by dividing a zone up into micro-zones and distributing in the micro-zones the value associated with this zone, in which the m values of the n lines correspond to the m interpolated values or to the m micro-zones along n scanning profiles derived from the first scanning series, and in which the n values of the m columns correspond to the n interpolated values or to the n micro-zones along the m scanning profiles derived from the second scanning series, iii) n and m line and column boundary values of the expanded matrix are calculated, representative of the high definition image, in which a line boundary value is the sum of the m terms of a line and in which a column boundary value is the sum of the n terms of a column, and iv) each of the n times m terms of the expanded matrix is adjusted using a least squares method of adjustment, taking into account the line and column constraints relating to the boundaries of the expanded matrix, in which the n line constraints are determined by the variation of intensity of the X-ray or infra-red light beams along the n scanning profiles derived from the first scanning series, and in which the m column constraints are determined by the variation in intensity of the X-ray or infra-red light beams along the m scanning profiles derived from the second scanning series, and by using the following formula: C ij = B ij + 1 n ⁢ ( ρ j - ∑ i = 1 n ⁢ ⁢ B ij ) + 1 m ⁢ ( c i - ∑ j = 1 m ⁢ B ij ) - 1 n ⁢ ⁢ m ⁢ ( ∑ j = 1 m ⁢ ρ j - ∑ i = 1 n ⁢ ⁢ ∑ j = 1 m ⁢ ⁢ B ij ) where, in this formula, Cij is the sought value, Bij is the initially estimated value (n) is the number of lines of the rectangle matrix (m) is the number of columns of the rectangle matrix ∑ i = 1 n ⁢ ⁢ C ij = ρ j for all the values of i, the constraint of the column j ∑ j = 1 m ⁢ ⁢ C ij = c i for all the values of j, the constraint of the line i, so as to obtain the n times m values representative of the high definition image by a number of supplementary scanning profiles limited to n plus m and thereby reduce the exposure of the body to X-rays or infra-red light beams while increasing the definition of the image.