The role of the fluorescent dipoles
A fluorescent dipole absorbates and re-emits light of a different wave length
The intensity of re-emitted ligth is proportional to the scalar product of the E-field with the dipole vector.
This relation is visualized in the image above.
The non-trivial field distribution in the confocal microscope leads therefore
to an intensity difference of the re-emitted ligth. You may follow that
after scanning the microscope over the dipole, the pattern for the angles
theta and phi describing the dipole direction is measured.