The only true way to focus a diode laser is to visually focus it. You activate the laser at its lowest possible setting and then adjust height and lens for the clearest visual on the laser spot/square.
Learned that:
There are 4 common types of diode laser lenses:
3 element
G2
G7
G8
The G8 has these specs:
Optimal focal range: 30-100 mm
EFL: 8mm
NA: .2
Best focal range 70-75 mm
Smallest laser beam spot: 77 x 130 microns (0.0030315 x 0.00511811")
Mistake in the manual???
If you assume the VG-L7X manual had the wrong units for focus, i.e CM vs MM.
Then I have a G8 lens in my unit? Is this a coincidence?
The smallest beam spot also explains why the dot looks rectangular ( laser diodes do not operate in TEM00).