For those who wonder how to mount a diffraction grating on a Reflex or a compact camera, the company Cokin offers two solutions.
The first one can be used with most of reflex (SLR) cameras, but special attention must be paid to the adaptation ring diameter. There is just to screw the adaptor ring onto the lens, for permanent mounting (it does not prevent installing the lens hood).
The other solution is designed to be used on compact cameras. Here, a small Canon camera. Beware when selecting the holder model, as some compacts have a telescopic lens which may come up against the filter.
Notice that Cokin also provides a diffraction filter (visible here) which seems to be a 240 lines/mm. The first-order mode efficiency seems to be around 5%. Some tests are undertaken with this type of diffraction grating.