Purpose of diffuser

The purpose of diffuser in a lamp is to soften light output for soft viewing, which is especially important for LED light. LED is a point light source that can emit a lot of light. Fluorescent light tube in this area is a lot of better since its light come out from a long, although narrow area. In some cases fluorescent tube can be view with naked eye.
LED light, on the other hand is another story. Even a LED tube with 300~400 small LED doesn't look very comfortable by eyes. Direct view into our 5Watt LED can hurt our eyes. Unless the lamp is a reflectional design, a diffuser of some kind is needed.

The work of diffuser is to break down intensive output light into random directions, of course much less intense. A point light source would look like light is coming from all directions, hence, looks like from entire area.

There are two type of diffuser design, one use translucent type, the material itself is not complete clear. Its particle absorb light and emit light at all directions. 
The other one is clear type, use its shape to redirect light. the finer its shape, the better it diffuses.

Diffuser panel at 2'x4' size can be found at Home Depot or other home improvement store, these panels can be used as direct drop in for a 2'x4' Troffer lamp.
Our LED module has optional integrated thin film diffuser.  The film is about 0.7mm thick, basically clear film with micro structure at surface.

Click to see how to install thin film diffuser.