1. A method for integrating a synthetic hologram in a directly observable image of a scene, comprising the steps of: defining a first source image of said scene, comprising grayscale pixels; forming first and second pixel matrixes from the first source image, the first matrix comprising pixels of a first and of a second shade according to whether a corresponding pixel of the first source image has a gray level greater than or smaller than a gray level threshold, each element of the second matrix comprising a value equal to a gray level difference between the corresponding pixel of the first source image and a corresponding pixel of the first matrix; forming a third pixel matrix by calculating a phase image of a synthetic hologram obtained by a Fourier transform of an image originating from a second source image of the hologram; forming a fourth pixel matrix, each pixel of the fourth matrix comprising an area internal to the pixel having its surface area determined based on a value of a corresponding pixel of the second matrix and off-centered in the pixel according to a value of a corresponding pixel of the third matrix; and performing a lithography of an opaque layer at the surface of a wafer according to a pattern defined by the fourth pixel matrix, the pattern comprising the value of the corresponding pixel of the second matrix and the value of the corresponding pixel of the third matrix, the lithography being provided to remove, from a pixel, the opaque layer inside of the internal area if the equivalent pixel of the first matrix is of the first shade and to remove the opaque layer outside of the central internal area if the equivalent pixel of the first matrix is of the second shade.