Obvious things are not patentable in the first place, so it doesn't matter what the "with a X" refers to. That the patent office continues to patent things that are obvious to a normal practitioner is a serious problem. I think part of the problem is that the field of technology is so wide right now that most patent examiners aren't good at judging whether something is obvious or not -- so they don't generally attempt it. If it's novel, then it's not obvious, is what I think they are doing.
Having said all that "with a laser diode" is categorically different than "with a computer". In the latter case, you can do any general purpose computation you like. So if you have a machine driven by a computer, you should not be able to patent it if you would not ordinarily be able to patent the machine. In other words, the driving of the machine by a computer should not be patentable, IMHO. Of course it gets complicated as you add more and more machinery to the machine -- should "computer driving a car be patentable"? Probably it should as it is not just software, even though it requires software. I think it's tricky.
If a laser diode allows you to do things you wouldn't otherwise be able to do and that use of the diode is not obvious, then it probably should be patentable. However, generally if "machine with a laser" is not patentable, then "machine with a laser diode" should also not be patentable. There's got to be something special and non-obvious about the use of the laser diode.
Patent offices are patently not doing the job of rejecting obvious modifications. Of course lawyer mangling of the documents does not help with discerning whether something is new or not.
Rotating prisms for scanning lasers are old technology, they were used extensively in photo imagers used to produce film artwork for the printing industry, the most famous of which was the Lasercomp. I was working with these devices in the early 80's. I suspect there is a lot of precident patents and prior art.
