Method and system for calibrating a spatial optical modulator in an optical microscope

A method for the calibration of an optical device having a spatial optical modulator (6), said device comprising a light source point (1), an optical objective (8) of large numerical aperture adapted to receive an incident beam and/or to collect an optical beam reflected by a sample, a camera (14) placed in a plane that is optically conjugate to the focal plane of the objective (8) and a spatial optical modulator placed on the optical beam upstream of the camera (14), said method comprises the following steps:

• a) placement of a reflective planar sample (10) in the vicinity of the focal plane of the objective (8);
• b) application of a command of amplitude Rij on an element Pi of the spatial optical modulator (6), in such a manner to modulate the optical beam incident and/or reflected on the sample (10);
• c) acquisition of an image of the intensity PSF in a plane conjugate to the focal plane of the objective (8);
• d) modification of the relative axial distance between the objective (8) and the reflecting sample (10) by a known quantity Z;
• e) iteration of the steps c) and d) for a plurality of relative axial distances between the sample (10) and the focal plane of the objective (8);
• f) reconstruction of the amplitude and/or phase profile of the beam in a plane conjugate to the focal plane of the objective by a phase diversity algorithm for a value Rij of an element Pi;
• g) iteration of the steps b) to f) for a plurality of amplitude values Rij for an element Pi of the spatial optical modulator (6);
• h) determination of the influence function Ei of an element Pi on the amplitude profile A and/or phase profile φ of the beam;
• i) iteration of the steps b) to h) for the different elements Pi i=1, . . . , N of the spatial optical modulator (6);
• j) determination of the influence functions (E1, . . . EN) of all the elements P1, . . . PN of the spatial optical modulator (6) on the amplitude profile A and/or phase profile φ of the beam.