The paper mentioned in the Description section can be read here: https://www.academia.edu/52566311/_title_Volume_phase_hologr...
My guess is that each of the items in patent diagram labeled 20 and 22 are gratings of this sort, perhaps with the fringes angled at 45 degrees.
Some additional info may be gleaned from the one patent citing this one, invented by one of the co-inventors of the latter: https://patents.google.com/patent/DE102019206354A1/en
The paper mentioned in the Description section can be read here: https://www.academia.edu/52566311/_title_Volume_phase_hologr...
My guess is that each of the items in patent diagram labeled 20 and 22 are gratings of this sort, perhaps with the fringes angled at 45 degrees.
Some additional info may be gleaned from the one patent citing this one, invented by one of the co-inventors of the latter: https://patents.google.com/patent/DE102019206354A1/en