IR Laser pointer spot is not dot

[buyucu]

Hi I am trying to make 500mW IR laser pointer. I ordered LCU80E041A diodes. and 9-18-21mm lenses.
I believe I successfully drive the diode. But when I focus the beam to a 30m target the spot that I get is not a dot. It is a line (1/8 rectangle). I think that it is the image of the radiating junction.
When I illuminate a 3-4 km distant building I get huge 2-3m long spot (line)

How can I get smaller and more circular or near square spot?

I have ordered this anamorphic lens . It's on the way ... but I'm not sure that it will be a solution.

Any suggestions?


Regards,

Buyucu

 

[Cel]

Well, that is normal as it is a multimode diode, like high-power 445nm and 638nm.
They all have rectangle beams and dots...

There are optics to correct that, but you lose some power, and they are expensive and hard to set-up.

You should leave it as it is (IMO)...

 

[hakzaw1]

please make an intro thread before asking for free help here- we also need you to fill in your profile page.

My first question was why even build an IR laser??

just what were you expecting from a non visable wavelength.

also where did you get the idea that all lasers make a round spot/dot?

most do not

we need your location please.

 

[The Lightning Stalker]

I just love these "Yeah, so I was trying to light a match at 3-4km" threads.

 

[scumbagatheist]

Sounds like another person who likes to illegally hunt at night w/ an IR designator. I could be wrong...but 30 meters? IR dot? I doubt I am.

 

[The Lightning Stalker]

Bingo. They think nobody will ever know they're there, but put on a cheap IR scope and it's like Christmas.

 

[zyxwv99]

Over at other forums devoted to things like candle power and night vision, people often discuss the visibility of 808nm. Although some may be involved in illegal hunting, it seems that many of them are survivalists. Not the kind who honestly think Armageddon is coming soon, but the kind who pursue it as a hobbie. They buy high-tech toys, then go out into the wilderness at night to play with them. It's a bit like orienteering (geochaching with a compass instead of GPS).

The biggest complaint I hear is that you can see 808nm a mile away. Then people move up to 940nm, only to discovered that you can see 940nm a hundred yards away. 980nm would probably work, but not 940nm.

I have a 940nm LED flashlight with 5W output and can definitely see the light. Even though there has been some speculation that what is being seen is just spillover into the 800s, the color perfectly matches was 940nm should look like: the same as 645nm, with an R/G ratio of 5.5. (Above 700nm sensitivity of the green cones tapers off more slowly than that of the red cones. At 645nm and 940nm the red cones are 5.5 times as stimulated as the green cones.)

 

[Spooky]

"Yeah, so I was trying to light a match at 3-4km" threads

<starts trying to phase stack all the spare tubes I have>

PASS THE DUCT TAPE I got dis down man

cheers

Dave

 

[jaybeez]

Sounds like another person who likes to illegally hunt at night w/ an IR designator. I could be wrong...but 30 meters? IR dot? I doubt I am.

people pay thousands of dollars to travel to your state to hunt LEGALLY at night. In many states its completely legal. In Texas its an entire tourism industry.

Do you have any suggestions for the op?