The theory used as a basis for a laser diffraction particle size analyzer (i.e. particle size analyzer that operates based on the laser diffraction/scattering method) is the Mie scattering theory.
And, the relationship between particle size and diffracted/scattered light intensity distribution pattern calculated according to this theory is a fundamental scale for these analyzers. It is this relationship that corresponds to a standard for particle size measurement, and this is stored on each, individual analyzer as a parameter table and used for calculating particle size distribution. In a sense, traceability within each, individual analyzer is already complete.
So, strictly speaking, with the laser diffraction/scattering method, the concept of calibration using reference particles should be non-existent. Note, however, that calibration may sometimes be required to adjust outputs since multiple light sources or complex optical systems are adopted for some models of some manufacturers.
The Shimadzu SALD series does not require calibration since it uses just one light source and one optical system.