PGL-III-A Beam Divergence comparison request

Okay, so CNI said that for the next shipment, they can try to get the models to under 1.5mrad. But my observations (1" dot from 30') is pretty close to 1.5mrad. All their AAA laser datasheets also state 1.5mrad.

So, can anyone with a PGL-III-A and a typical greenie do some testing, seeing how big the beam grows? How about taping both switches down outside at night, placing the lasers on a steady surface, and see how big the dots are at 100'? I'd like to know if the PGL-III-A truly has a worse divergence, since I haven't had access to a regular greenie in forever.

1.5mRad is pretty much standard for green laser pointers. Some will have better then 1.5mRad divergence others will be close but not quite 1.5mRad. They are all adjusted by hand, thus depending on how much effort was put into it, each one will probably not be exactly the same. I know certain lasers, such as the Wickelasers units have improved to <1.2mRad divergence on average and the RPL at optotrinics is rated 1.2mRad as well.

However even those with 1.2mRad rating will not all be 1.2mRad. To illustrate the differences between units, I have 7 lasers(of the same model) that are rated 1.2mRad but a couple have closer to 1.5-1.6mRad, yet on one other laser of the same model it's about 0.9-1.0mRad. The rest fall between ~1.2-1.3mRad.

This won't mean a whole lot for lighting matches though, as the difference between 1.2 and 1.5 will not mean much in the first few inches from the aperture. Honestly the PGL-IIIA's are an excellent price and I'd not worry about the 1.5mRad divergence. If one really wanted to improve it, they could replace the lens with that of a leadlight(they have quite good quality lenses).

I will try to post dot shots at 50 feet, but I can tell you the dot is alot larger on the PGL 80 then my 50mw leadlight. I have focused it the best I could, its alot better then it was, but the problem with it is the light coming out of the laser is in a rectangler circle shap, and with a dark line in middle ( and no not the line from the fence crack in the pic below) sorry , its only seen at distance and beam actuly splits in two. Instead of circle like on the lead light. But anyways its not to bad right now and I still love it alot. I can get it to light the free gastation matches with black marker on the tip from more than 4 inchs away in like 5 or less seconds. The thing about it, is the beam may get grow abit at distance but coming right out the laser the beam is alot smaller then on the leadlight. Sorry there phone pics




Heres the PGL at probley alittle over 200 feet

Who would be the best person to speak to about replacing the lenses? I am new to the laser forum so i am not really up on who the main modders are. I am in the new group buy for a pgl-iii-a and i want it to be as good as possible.
marc

Anyone know why it looks like that?

Weird, I set my PGL outside last night, and from 460ft away (google earth accuracy!), it made a PERFECTLY circular circle, about 1ft in diameter. I'll take pics tonight.

Also whitelitee, how did you focus it? Did you alter the distance from the diode to the focusing lens by cutting down on the aluminum barrel? I just cut my barrel down a millimeter or so and haven't noticed any improvement.

Ya its been like that since I got it. I just figured there was nothing I could do since it was a group buy. When I take all the lenses out and look at the laser diode I see some kind of rectanglur metal peice inside the laser dont think I could get to it and wouldnt want to touch the lens.

for mine when I unscrewed the aluminum barrel , a bit the dot got smaller. And put some thread seal tape around the cylinder for it wouldnt rattle. I can get the rectangle dot alittle bit smaller then in the pics I just didnt feel like messing with it more.


edit: What you can do is use somthing to screw the lenses down a bit in the aluminum barrel, it may make a little rattle sound tho....

I have a spreadsheet on my website to calculate divergence as well as irradiance or better know as power density. Power density is what gives a laser it's burning power.
Go to my site and follow the divergence link. You can then click on the sample chart on the webpage to down the excel spreadsheet to play with it and enter your own numbers.

I did just that for the numbers that FNinjaP90 gave and the results for a 1 inch spot at 30ft is 2.63mrad and a 12" spot at 460ft is 2.17mrad.
I would send this one back and have them bring it into spec. After all that's what specs are for...A promise of what the buyer is getting.

The way I test my lasers for this is; I have a black sheet of construction paper taped on my basement wall. I then set the laser on the carpeted stairs at the same level on the opposite side of the basement (25ft). If the laser spot is 1 cm or less or less I call it good, if not, it goes back for adjustment or replacement before it is sold. Of all the units I've gotten, tested and sold; only 2 have had divergence of greater than 1.2 and both of those produced spots of ~1.5cm at the same distance (1.78mrad). Most of them produce a spot size of 8.5 to 9mm at this distance (~1.0mrad).

Jack

If there was a easy way to send it back I would. But I cant think of any praticle way of doing this without spending 40 to ship and having to contact and trouble cni, and then waiting two months to get it back. Thats if they would even do anything about it.

Edit: oh I just relized you where talking about Fnijap90s

Im affraid to do the beam divergence test, I dont want to know how far off / bad it really is.

As Jack mentioned you need to measure the dot diameter over a long distance to get an accurate reading. I myself prefer to use a distance of at leat 20-30 meters, so that you are sure the lens is not focusing but is indeed collimating the beam. 25 feet should be ok though, this is strictly my preference. The other thing you need to do is make sure you are not including any spillage from the intense light at the poi. I find using high OD safety goggles illiminates all glare save for the actual dot at these distances.

Whitelitee > are you saying that the dot from your laser looks like two dots? That is an indication that the laser is operating out of mode tem00, and is either tem01 or tem10 depending on which axis the second dot is appearing. This would greatly reduce the lasers burning capability and also why the beam is spreading so much wider then your leadlight.

Whitelitee said:

Anyone know why it looks like that?

Click to expand...

this link will explain. For lasers like the one you own this is not desirable

http://forum.wickedlasers.com/viewtopic.php?t=4449

Is there a way to fix or adjust the tem mode, does anyone know how to or done this? Thanx

Athoul said:

As Jack mentioned you need to measure the dot diameter over a long distance to get an accurate reading. I myself prefer to use a distance of at leat 20-30 meters, so that you are sure the lens is not focusing but is indeed collimating the beam. 25 feet should be ok though, this is strictly my preference. The other thing you need to do is make sure you are not including any spillage from the intense light at the poi. I find using high OD safety goggles illiminates all glare save for the actual dot at these distances.

Whitelitee > are you saying that the dot from your laser looks like two dots? That is an indication that the laser is operating out of mode tem00, and is either tem01 or tem10 depending on which axis the second dot is appearing. This would greatly reduce the lasers burning capability and also why the beam is spreading so much wider then your leadlight.

Click to expand...

yes, I agree Athoul. The longer the distance the better and you also need a sheet of black paper to help reduce the light spillage, and or a filter of some type to cut down the brightness as the eye can oversaturate and make the spot look bigger than it really is.

I use the 25ft distance in my basement because it's quick and is enough to tell if there's a problem or not. I don't think I would want to take a rather large and heavy case of lasers outdoors for this as, like we all know, anything over 5mW used outdoors in or pointed towards a public place is illegal without having the proper variances. Not only could your laser get permanently confiscated, but you could end up in jail as well.

Jack

seems to that if any purchase of a green laser pointer or any cni lasers should come with an application for a variance! some pointers can be >5mw!
i seriously doubt the teachers and professionals that have these green pointers are even aware a variance is required, nor do i believe the local police are even aware, and if they are i doubt they'll even arrest you unless you point the laser at somebody maliciously!

where can i apply for a variance?

senecaripple said:

seems to that if any purchase of a green laser pointer or any cni lasers should come with an application for a variance! some pointers can be >5mw!
i seriously doubt the teachers and professionals that have these green pointers are even aware a variance is required, nor do i believe the local police are even aware, and if they are i doubt they'll even arrest you unless you point the laser at somebody maliciously!

where can i apply for a variance?

Click to expand...

Your right about one thing local police don't care if you shine a laser up into the air unless there is a state or local law that makes it unlawful. In every state I've looked into all states are concerned with harrassment nothing more. On another site dedicated to laser show companies I asked this question: Is there a federal law that states specifically it is against the law to shine a 5mw plus laser into the sky ?
The only reply I recieved as I recall said: Not that I know of.
To the best of my knowledge there is no federal law specifically in this regard. The only geographical area where trouble could be caused is near airports.
I think this ongoing confusion occurs when people read what is required by the CDRH in regards to commercial venues[ laser light shows] and apply that to the average hobbiest. Filling out a variance is not practical for the hobbiest nor is it practical for the people that work at the CDRH to take time to review it, they would be inundated with paperwork. Nearly everytime you wanted to shine your laser into the sky it would require you 10 hours to do the paperwork. It is the responsibility of the person that owns the laser to acquire the variance which can be found at the CDRH site.

If anyone is interested in reducing divergence I have some modules specially made for me from Leadlight with <0.6 Mr. They are basically the APC module from a 110 with a lens assembly about 3/8" longer in length.

Abeland1,

Is there reason to think that your lens module would fit properly in these lasers, without machine work?

I'd be very interested if that were the case.

Pertinax

I would likewise be interested in one of these if they fit easily.
marc

Mr. CNI guy just said that the laser changes modes when left on continuously for a long time

I don't think it's much of an issue compared to the divergence though. Even if it's rectangular, it'll be a smaller rectangle when it's focused better. CNI said that the next shipment will be <1.5mrad though, so we'll see. Of course, those lens modules do seem interesting if they can work.