Welcome to Laser Pointer Forums! If you are looking for a laser you may want to check out the database of laser pointer companies. The link will open in a new window for your convenience.

 Laser Pointer Forums - Discuss Laser Pointers Core's divergence? Laser Pointer Company Database     Laser Top Sites List     Lasers by Type     Green Lasers

09-22-2007, 04:47 PM #17
 Class 3R Laser Join Date: Jun 2007 Posts: 1,208 Rep Power: 340
steve001
Class 3R Laser

Join Date: Jun 2007
Posts: 1,208
Rep Power: 340
Re: Core's divergence?

[quote]Laserrod, I always thought this was what a collimator did:

LASER beam&gt;====(]==[)---------TARGET

Doesn't that seem more logical? Wouldn't you want the beam to be more concentrated for burning?[/qoute]
Quote:
 Originally Posted by Gazoo In your diagram the beam would collimate with the first lens and spread with the second one.
To Gazoo
No and yes. the first lens will obviously focus the beam after which the beam will begin to spread. As it passes throught the second lens the beam can be made too focus or diverge or make the beam diverge optimally
This type of collimator using two positive focal length lenses is known as a Keplerian beam expander. If the distance between the lenses is the sum of the focal lengths then the beam is collimated optimally meaning minimal divergence.

09-22-2007, 05:00 PM #18
 Class 3R Laser Join Date: Jun 2007 Posts: 1,208 Rep Power: 340
steve001
Class 3R Laser

Join Date: Jun 2007
Posts: 1,208
Rep Power: 340
Re: Core's divergence?

Quote:
 Originally Posted by Angdvl089 Laserrod, I always thought this was what a collimator did: LASER beam>====(]==[)---------TARGET Doesn't that seem more logical? Wouldn't you want the beam to be more concentrated for burning?

This is what this type of expander does. The resulting beam will be larger at the aperture. Actually this is what all beam expanders can do

Laser&lt;&lt;&lt;&lt;&lt;&lt;(]&gt;&gt;&gt;&lt;&lt;&lt;&lt;&lt;[)=====

09-22-2007, 07:42 PM #19
 Class 1M Laser Join Date: Aug 2007 Posts: 168 Rep Power: 10
Angdvl089
Class 1M Laser

Join Date: Aug 2007
Posts: 168
Rep Power: 10
Re: Core's divergence?

Laserrod that helped me a ton. So basically your taking a smaller beam with a positive divergence and making a bigger beam with negative divergence?

09-22-2007, 08:16 PM #20
 Class 3B Laser Join Date: Sep 2007 Location: Southern California Posts: 3,249 Rep Power: 273
RA_pierce
Class 3B Laser

Join Date: Sep 2007
Location: Southern California
Posts: 3,249
Rep Power: 273
Re: Core's divergence?

My collimator i made works like this:
[LASER]---[)&gt;&lt;[(----------
The first lens is plano-convex so it has a focal point at about 4.5cm.
The second lens is plano-concave and collimates the beam.
(All the diagrams I've seen on here use two plano-convex lenses and that would just make the laser into a flashlight.)
The two lenses in my collimator ate set at the best distance for collimation and the second lens can be adjusted to expand the beam or be removed, so the first lens can be used for focused burning. It works like a 'phony disruptor'- just waaaaay cheaper and isn't used for flash blinding people or stopping cars on a freeway.
Without the collimator my laser has a divergence of about .7mrad. I used the laserglow method to measure it.
__________________
DNA works in mysterious ways.

09-22-2007, 08:16 PM #21
 Class 3B Laser Join Date: Jun 2007 Location: Dallas Tx Posts: 3,204 Rep Power: 179
Gazoo
Class 3B Laser

Join Date: Jun 2007
Location: Dallas Tx
Posts: 3,204
Rep Power: 179
Re: Core's divergence?

Quote:
 Originally Posted by steve001 [quote author=Angdvl089 link=1190270166/0#8 date=1190437099] Laserrod, I always thought this was what a collimator did: LASER beam>====(]==[)---------TARGET Doesn't that seem more logical? Wouldn't you want the beam to be more concentrated for burning?

This is what this type of expander does. The resulting beam will be larger at the aperture.

Laser&lt;&lt;&lt;&lt;&lt;&lt;(]&gt;&gt;&gt;&lt;&lt;&lt;&lt;&lt;[)=====[/quote]

Thanks for that and I understand...a larger beam sounds interesting. I might have to give it a go sometime.

09-22-2007, 09:42 PM #22
 Class 3R Laser Join Date: Jun 2007 Posts: 1,208 Rep Power: 340
steve001
Class 3R Laser

Join Date: Jun 2007
Posts: 1,208
Rep Power: 340
Re: Core's divergence?

Quote:
 Originally Posted by RA_pierce My collimator i made works like this: [LASER]---[)><[(---------- The first lens is plano-convex so it has a focal point at about 4.5cm. The second lens is plano-concave and collimates the beam. (All the diagrams I've seen on here use two plano-convex lenses and that would just make the laser into a flashlight.) The two lenses in my collimator ate set at the best distance for collimation and the second lens can be adjusted to expand the beam or be removed, so the first lens can be used for focused burning. It works like a 'phony disruptor'- just waaaaay cheaper and isn't used for flash blinding people or stopping cars on a freeway. Without the collimator my laser has a divergence of about .7mrad. I used the laserglow method to measure it.
You've your lens setup backwards Did you know that ?

09-22-2007, 11:17 PM #23
 Class 2 Laser Join Date: Sep 2007 Posts: 323 Rep Power: 15
Rasel
Class 2 Laser

Join Date: Sep 2007
Posts: 323
Rep Power: 15
Re: Core's divergence?

.. couldn't it work either way? I mean the first way you diverge the laser then you make it converge again. The second way, you converge the laser and then make it diverge. The second way would be better because you get a smaller beam diameter in the end.

:-?

09-22-2007, 11:51 PM #24
 Class 1M Laser Join Date: May 2007 Posts: 165 Rep Power: 14
Thories
Class 1M Laser

Join Date: May 2007
Posts: 165
Rep Power: 14
Re: Core's divergence?

HAHAHA this is almost the last question of my physics paper. member if it travels through the focal point it comes out parallel. so one lens focusing towards the other lenses focal point should cause it to travel out parallel from lens 2. now if u had really tiny lenses with tiny focal points you could minimize the spread that occurs between the two lenses thus getting a fine parallel beam. not sure what types of lenses ud need to use without doing an annoying ray diagram (i hate those things) but if u used bi concave/convex at the right focal points and distance surely it would work?

09-23-2007, 04:31 AM #25
 likewhat Guest Posts: n/a
likewhat
Guest

Posts: n/a
Re: Core's divergence?

Hey, I also posted this on ************

I hope these pictures will make beam expanders make a little more sense to some people. (if someone could get the to post on here that would be nice)

imagehosting.com/show.php/1170171_beamresizing.bmp.html

If you start with a collimated beam that has a diameter of d and go through the lenses you get a resized beam that will have a diameter of d*f2/f1.

But what if your beam was not collimated when it entered?
You can adjust the spacing between the lenses, and at some point the output of it will be collimated. In fact, if you had two lenses that were of the same focal length and your incoming beam was just slightly not collimated, there would be some spacing (close to the sum of the focal lengths) that would give you a collimated beam.

Hope this helps someone.

09-24-2007, 04:19 PM #26
 Class 3B Laser Join Date: Sep 2007 Location: Southern California Posts: 3,249 Rep Power: 273
RA_pierce
Class 3B Laser

Join Date: Sep 2007
Location: Southern California
Posts: 3,249
Rep Power: 273
Re: Core's divergence?

Quote:
 Originally Posted by steve001 [quote author=RA_pierce link=1190270166/15#19 date=1190492185]My collimator i made works like this: [LASER]---[)><[(---------- The first lens is plano-convex so it has a focal point at about 4.5cm. The second lens is plano-concave and collimates the beam. (All the diagrams I've seen on here use two plano-convex lenses and that would just make the laser into a flashlight.) The two lenses in my collimator ate set at the best distance for collimation and the second lens can be adjusted to expand the beam or be removed, so the first lens can be used for focused burning. It works like a 'phony disruptor'- just waaaaay cheaper and isn't used for flash blinding people or stopping cars on a freeway. Without the collimator my laser has a divergence of about .7mrad. I used the laserglow method to measure it.
You've your lens setup backwards Did you know that ?[/quote]

Yup. And it works perfectly fine.
__________________
DNA works in mysterious ways.

09-24-2007, 04:49 PM #27
 Class 2M Laser Join Date: May 2007 Posts: 534 Rep Power: 12
Aseras
Class 2M Laser

Join Date: May 2007
Posts: 534
Rep Power: 12
Re: Core's divergence?

the point of collimination is to uses lenses to bend the light straight. If you light is expanding ( normally ) your first lense will converge it and you align the second lense to negate it and keep the light as parallel to emission as possible. You can also do the reverse but it's very hard. Upcollimation is easy. down collimintaion is possible but expensive and very hard to do since oyu need tiny lenses that aren't lossy and can handle HUGE power desnities.

so you are going [ch1776]&lt;=[ch8801])=[ch8801]–-(=========

09-24-2007, 07:09 PM #28
 Class 3B Laser Join Date: Sep 2007 Location: Southern California Posts: 3,249 Rep Power: 273
RA_pierce
Class 3B Laser

Join Date: Sep 2007
Location: Southern California
Posts: 3,249
Rep Power: 273
Re: Core's divergence?

Yeah the diameter is slightly larger but the divergence is at less than .3mRad.
__________________
DNA works in mysterious ways.

09-25-2007, 06:20 AM #29
 Class 4 Laser Join Date: May 2007 Location: Queensland, AU Posts: 7,549 Rep Power: 689
Things
Class 4 Laser

Join Date: May 2007
Location: Queensland, AU
Posts: 7,549
Rep Power: 689
Re: Core's divergence?

hmmmm i took a pic of the aperature for some reason.
Attached Thumbnails

09-26-2007, 02:20 PM #30
 Class 3R Laser Join Date: Jun 2007 Posts: 1,208 Rep Power: 340
steve001
Class 3R Laser

Join Date: Jun 2007
Posts: 1,208
Rep Power: 340
Re: Core's divergence?

Quote:
 Originally Posted by RA_pierce [quote author=steve001 link=1190270166/15#21 date=1190497359][quote author=RA_pierce link=1190270166/15#19 date=1190492185]My collimator i made works like this: [LASER]---[)><[(---------- The first lens is plano-convex so it has a focal point at about 4.5cm. The second lens is plano-concave and collimates the beam. (All the diagrams I've seen on here use two plano-convex lenses and that would just make the laser into a flashlight.) The two lenses in my collimator ate set at the best distance for collimation and the second lens can be adjusted to expand the beam or be removed, so the first lens can be used for focused burning. It works like a 'phony disruptor'- just waaaaay cheaper and isn't used for flash blinding people or stopping cars on a freeway. Without the collimator my laser has a divergence of about .7mrad. I used the laserglow method to measure it.
You've your lens setup backwards Did you know that ?[/quote]

Yup. And it works perfectly fine.
[/quote]

Sorry your wrong. You will not be able to collimate a laser beam over any significant distance if the last lens the beam travels through is a negative focal lens. Lenses that have a negative focal length will diverge light. This applet will show you precisely what I mean http://www.lightmachinery.com/gausbeam.php
This applet works best with Internet Explorer

Focal lengths of the lenses can be any length.
First lens separation should be 1mm
First lens focal length 6mm
second lens focal length - 48mm

now start decreasing the distance of the second lens and watch how the rayleigh range changes. Do you notice that this range is less than 1mm and that it has increased just a bit from its original distance.

now repeat this procedure again, but this time the 6mm lens will have a negative focal length and the 48 mm lens a positive focal length. Start the second lens at 48 mm distance. Then start to decrease the distance. Watch how the Rayleigh range increases dramatically. There will be a point where the beam is optimally collimated.

09-26-2007, 04:16 PM #31
 Class 1 Laser Join Date: Jun 2007 Posts: 73 Rep Power: 13
Orr3
Class 1 Laser

Join Date: Jun 2007
Posts: 73
Rep Power: 13
Re: Core's divergence?

When I measured my Core I also got .3 mRad.

09-26-2007, 04:58 PM #32
 Class 1 Laser Join Date: Feb 2007 Posts: 69 Rep Power: 10
BooBoo
Class 1 Laser

Join Date: Feb 2007
Posts: 69
Rep Power: 10
Re: Core's divergence?

Its amazing that anyone would put Any Stock in the claims almost any laser manufacturer make about thier products divergange....Especially WickedLasers and any of thier lasers, including the Core.
As None, I have ever bought, (even counting a small few of my laser, not bought from WickedLasers), were ever Delivered within Specs of such.....and with the experiences of most long time laser-Enthusiasts....many here ought to already know that, you get what you get, and then try and tweak the focus, and such, to get the divergance you wish... or RMA RMA RMA, and pay enough in shipping, to where you could have bought another one or two lasers with....Before getting one that is as advertised and within specs.

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

All times are GMT. The time now is 01:26 PM.

 -- DarkShadows V5 -- Responsive LPF -2562016 -- Default Style Contact Us - Laser Pointer Forums - Archive - Top