Standard glass lens have mediocre power loss and focusing power. They don't have the problem of melting during high power laser output.
What's a "standard" lens by your definition? Usually the lenses that are sold by O-like or whomever are just 3-element lenses coated for certain wavelengths. They're pretty decent as long as you match the AR-coating with your laser.
G1/Gx lens are high quality glass lens that has 30% higher transmissivity than the regular glass lens.They also won't melt at higher power.
G-series lenses are just glass lenses with very short focal lengths and AR-coatings. There's nothing magical about them. They transmit more power only because the short focal length captures more of the output from the emitters, and that they don't have multiple lenses that cause extra per-lens losses. Capturing more of the emitter output means the G-series lenses have uglier beam-spots, as they capture all the beam artifacts present from the emitter.
Acrylic lens at below 500mW have higher transmissivity than the G1/Gx lens (especially for the 630-680nm spectrum). However at higher power, there is a chance of melting so it would be best to focus them to infinity.
No, you should
only use acrylic,
AR-coated lenses with
red wavelengths. For shorter bluish wavelengths, they don't have the correct AR-coating, and worse, will melt even at lower powers < 500mW. For red, the AR-coated acrylic lenses have good transmission because they have good coatings, and they're a single lens like the G-series lenses.
Even for the uncoated acrylic lenses -- which you shouldn't bother with anyway -- I would
never use an acrylic lens with 405nm or 445nm lasers unless they're sub-100mW, and even then the 3-element lenses are so cheap that you shouldn't bother anyway.
Ok... then what about 3 element glass lens?
I read that 3 elements glass lens have a AR outer lens with 20% more transmissivity over acrylic
Get a 3-element lens if you want a nicer spot, but higher losses because of multiple interfaces the light has to go through (versus a G-series lens for blue, AR-coated acrylic for red). Always buy lenses with the correct AR coating.
The 3-element lenses are the "standard" lenses available anyway, so you'll probably be using one if you don't have a more specialty lens.
:beer:
