Far-field focussing of laser projectors

[weartronics]

I read about far-field focussing of laser projectors in the LMR light show handbook, but I am a bit sketchy on the details. As I understand it, rather than picking a beam diameter/divergence to focus at infinity, you project a converging beam, which should give you a very small spot size on a projection surface which is located at the focal plane.

Who has done this? distances? screens? buildings? clouds? I am interested to hear any comments you have.

Best regards,

weartronics

[Laser Ben]

I know you can do this with a scan lens like the kind found in laser markers.

[weartronics]

Hi Ben, yes without an "f-theta" lens in front of the galvos, the focal plane is actually a spherical surface, not a flat plane. For light show applications, the throw distance is much longer and the focal plane is much less critical, so the expensive "f-theta" lens is not necessary, we can just use a small lens to focus the beam before it goes in to the galvos. Best regards, weartronics