Re: 405nm AR glass lenses - fit AixiZ FEELER
robjdixon said:
i might have missed something here, but why do you need 650nm coatings specially built at a much higher cost when aixiz make them?
As far as i know, AixiZ does not make single element glass lenses with or without any coating. They only have a triple element lens.
The triple element lens is not a lens made for power, but for lower beam distortions. It's three lenses, each of them completelly different, and the result is a very parallel beam, with hardly any beams going off to the side - similar results to the much more expensive aspheric lenses, but at the cost of some power.
Due to the three lenses, the losses in such optics are high, so AR coatings are important. All three lenses are AR coated for 650nm, and yet, when i measure that lens on a red, the power is not any higher, than with a clear plastic lens. An AR coated plastic lens (from Dilda) is actually MUCH better when it comes to power, but it has some distortions.
The Meredith glass lens on the other hand increases the power of reds by 20%. That's because of it's larger numerical aperture, and because it is a single element lens AR coated for 650nm..
The idea with the 650nm AR coated custom lenses is to get a similar or same increase in power for red lasers, as with the Meredith lens, but at a much lower price, and hopefully with slightly better fousing properties (for burning).
When the lenses are in, i will test the 405nm ones with blu rays, and the multilayer ones with reds.
But i will also test the multilayer ones with blu rays, to find out the difference in power between a wavelength specific coating and a multilayer coating. That's because the 650nm AR coated lens could have a slightly better transmittance for reds, than the multilayer one, and this experiment will show how much. I will also request transmittance graphs from the manufacturer.
Since the multilayer lenses would only be used in reds anyway, it's better to go for a wavelength specific coating, because of the slightly lower price and a little more power..
P.S. Here is a simulation of a triple element glass lens, that Phenol made a while ago..
The first "square" lens is a Grin lens, that diffracts light by the material properties changing (diffractive index increasing from the center outwards), instead of with shape.