1. A process for digitizing closed books without having to open them, printed documents or manuscripts, bound or in batches, without having to separate them, using an imaging system of a three-dimensional object by Terahertz (THz) waves comprising: acquiring by an THz acquisition subsystem a set of low-resolution three-dimensional images representative of said object, said low-resolution three-dimensional images being obtained by application of orthogonal shifts in three-dimensional translation according to which the object and the THz acquisition subsystem are relatively shifted relative to each other, wherein during said three-dimensional shifts, the amplitude of the relative shift in each of said three dimensions is less than the spatial resolution of said THz acquisition subsystem in each of said three dimensions; and performing a three-dimensional super-resolution processing step, capable of generating a super-resolved three-dimensional image from a linear combination of said low-resolution three-dimensional images and an image-restoration step capable of generating a restored super-resolved three-dimensional image from deconvolution by a point spread function of said super-resolved three-dimensional image, wherein said linear combination of said three-dimensional images is determined by the following equation: I SR ( ⁢ i + ⁢ a , ⁢ j + ⁢ b , ⁢ k + ⁢ c ) = ⁢ ⁢ 1 FSR X * FSR Y * FSR Z ⁢ [ ⁢ ∑ u = 0 a ⁢ ∑ v = 0 b ⁢ ∑ w = 0 c ⁢ A uvw ⁡ ( p , q , r ) + ∑ u = a + 1 FSR X - 1 ⁢ ∑ v = 0 b ⁢ ∑ w = 0 c ⁢ A uvw ⁢ ( p - 1 , q , r ) + ∑ u = 0 a ⁢ ∑ v = b + 1 FSR Y - 1 ⁢ ∑ w = 0 c ⁢ A uvw ⁡ ( p , q - 1 , r ) + ∑ u = a + 1 FSR X - 1 ⁢ ∑ v = b + 1 FSR Y - 1 ⁢ ∑ w = 0 c ⁢ A uvw ⁢ ( p - 1 , q - 1 , r ) + ∑ u = 0 a ⁢ ∑ v = 0 b ⁢ ∑ w = c + 1 FSR Z - 1 ⁢ A uvw ⁡ ( p , q , r - 1 ) + ∑ u = a + 1 FSR X - 1 ⁢ ∑ v = 0 b ⁢ ∑ w = c + 1 FSR Z - 1 ⁢ A uvw ⁢ ( p - 1 , q , r - 1 ) + ∑ u = 0 a ⁢ ∑ v = b + 1 FSR Y - 1 ⁢ ∑ w = c + 1 FSR Z - 1 ⁢ A uvw ⁡ ( p , q - 1 , r - 1 ) + ∑ u = a + 1 FSR X - 1 ⁢ ∑ v = b + 1 FSR Y - 1 ⁢ ∑ w = c + 1 FSR Z - 1 ⁢ A uvw ⁡ ( p - 1 , q - 1 , r - 1 ) ⁢ ] where: I SR designates the super-resolved image of dimension N X , N Y , Nz; FSR X , FSR Y , FSR Z designate the factors of super-resolution according to X, Y and Z in a orthonormal marker (O; X, Y, Z), whereof the values are natural whole numbers greater than or equal to 1; I SR (i+a, j+b, k+c) designates the voxel of the image I SR located at the coordinate i+a of the dimension X, the coordinate j+b of the dimension Y and the coordinate k+c of the dimension Z of the matrix I SR , with i a multiple of FSR X such as 0≦i<N X , j a multiple of FSR Y such as 0≦j<N Y , k a multiple of FSR Z such as 0≦k<N Z , and with a, b, c whole variables such that they take their values in the set 0, 1, 2,. .. , FSR X −1 (respectively FSR Y −1, FSR Z −1); {A uvw , with 0≦u<FSR X ; 0≦v<FSR Y 0≦w<FSR Z } is the set of 3D low-resolution images, where u, v, w represent the index of the position of the image in respectively the dimensions X, Y and Z; A uvw (p, q, r) designates the voxel of the image A uvw located at the coordinate p of the dimension X, the coordinate q of the dimension Y and the coordinate r of the dimension Z of the matrix A uvw , with p = i FSR X ; q = j FSR Y ; r = k FSR Z .