An apparatus for forming a three-dimensional light intensity distribution comprising a spatially limited area of minimum light intensity that is enclosed by areas of higher light intensity, the apparatus comprising:
- two objectives
- which are facing each other on a common optical axis,
- which focus light coming out of opposite directions into a common focal area, and
- which each have a pupil, the common optical axis passing through a center of the pupil,
- at least one light source, and
- a first pair of beam paths each extending from the at least one light source, through one of the objectives and to the common focal area, wherein light intensities of a first pair of coherent light beams each coming from the at least one light source and running along one of the beam paths of the first pair of beam paths extinguish each other in a first partial area of the focal area by destructive interference as the two beam paths of the first pair of beam paths differ from each other in optical length by λ1 (2n+1)/2, wherein λ1 is the wavelength of the light of the first pair of coherent light beams and n is an integer,
- wherein each of the beam paths of the first pair of beam paths pass passes through one of the two objectives in a first pair of partial areas of the pupils of the objectives centered on opposite sides of the common optical axis,
- wherein the apparatus further comprises a second pair of beam paths each extending from the at least one or a second light source, through one of the objectives and to the common focal area, wherein light intensities of a second pair of coherent light beams each coming from the at least one or the second light source and running along one of the beam paths of the second pair of beam paths extinguish each other in a second partial area of the focal area by destructive interference as the two beam paths of the second pair of beam paths differ from each other in optical length by λ2 (2m+1)/2, wherein λ2 is the wavelength of the light of the second pair of coherent light beams and m is an integer,
- wherein each of the beam paths of the second pair of beam paths passes through one of the two objectives in one of a second pair of partial areas of the pupils of the objectives centered on opposite sides of the common optical axis,
- wherein the two partial areas of the second pair of partial areas of the pupils of the objectives are offset in a rotational direction about the common optical axis with regard to the two partial areas of the first pair of partial areas of the pupils of the objectives, and
- wherein the light of the second pair of coherent light beams does not interfere with the light of the first pair of coherent light beams in the common focal area as the light of the second pair of coherent light beams and the light of the first pair of coherent light beams display at least one of the following features:
- they are non-coherent, their wavelengths are not identical, their polarizations are not identical, and they do not coincide in time.