Partial beam splitter, stack comprising two or more such partial beam splitters and method of manufacturing such a partial beam splitter

A stack, comprising:

• two or more partial beam splitters, each of the partial beam splitters comprising:
• a substrate made of a substrate material;
• and
• at least one coating arranged on at least one main surface of the substrate, wherein along a first direction which is parallel to a normal vector of the main surface, the substrate and all coatings having a total thickness, and wherein for a specific light beam having a specific wavelength within a range of 450 nm and 650 nm which is incident on the partial beam splitter along a second direction with an angle of 32° enclosed between a vector pointing in the first direction and a vector pointing in said second direction, the specific light beam after transmitting through the partial beam splitter has a phase difference with an absolute value that is smaller than or equal to 30° compared to the case in which another light beam having the specific wavelength is incident on a reference substrate along another second direction with another angle of 32°, the other angle being enclosed between a vector pointing in a first direction that is parallel to a normal vector of a main surface of the reference substrate and a vector pointing in the other second direction, the reference substrate being made of the substrate material and having a thickness identical to the total thickness of the partial beam splitter.