Laser safety of standard laser pointer diode I am thinking about designing vector display with standard pointer laser diodes. I would make display be diffuser of some sort like milky glass or paper, but I want to make it see through, rather than seeing dot on paper. Would that be okay or is it possible to mess up somehow?
 A: It is absolutely possible to mess up, but you can take measures to understand the consequences.
The most useful thing is to understand the classes of lasers.  I'm a fan of this image from Laser Safety Facts.

I would recommend taking the second most conservative approach, and assuming that your diffuser fails completely.  Laser safety isn't all about what happens when things go well, its about how things go when stuff breaks too!  Your laser should be classified as one of these levels (although beware: cheap products may be more powerful than they are supposed to be.  This table will show what happens if the laser diode's output directly hits someone's eyes at various distances.
I mentioned this was the second most conservative approach.  When dealing with Class 2 lasers, its good to make sure that none of the failure mechanisms can create a lens.  The safety of this cannot be easily captured in a table.  There are professionals who do this (which is why the table has so many "Consult an LSO" entries).
I am not a lawyer nor a professional that deals with laser safety, but in general this table should provide you the information you need to make an educated decision about how safe your laser is.
