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 Laser Pointer Forums - Discuss Laser Pointers FS: Hi-Power AR Lens Assy- 25-30% Inc. vs. Aixiz

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06-14-2010, 07:33 PM #209
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edison
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Re: FS: Hi-Power AR Lens Assy- 25-30% Inc. vs. Aixiz

Hello guys

I found a document in Word on the internet:

Circularize the laser diode beam using cylindrical lens

Cylindrical lenses focus or expand light in one axis only. They can be used to expand the output of the laser diode into a symmetrical beam. The rectangular cross-section of the laser diode cavity results in a beam shape with a wider angular output from the narrow cavity dimension and a narrower angular output from the wide cavity dimension. Laser diodes have an asymmetric radiation pattern which, when collimated, becomes an elliptical beam pattern. As a result, anamorphic prism pairs are often used to convert the elliptical collimated beam to a circular shape.

One can also use a pair of cylindrical lenses to achieve similar results to the anamorphic prism pairs. One cylindrical lens can be used to collimate the laser diode’s slow axis and a second cylindrical lens can be used to collimate the fast axis. By simply matching the laser diode beam divergence ratio (vertical vs. horizontal) to the ratio of the focal lengths of the two lenses, a nearly symmetrical circular beam can be created.

Since a laser diode is considered as a point source, the two lenses should be placed a distance equal to their respective focal lengths from the laser diode emitter orthogonally to create a collimated beam output. Make sure the beam size at each lens does not exceed the clear aperture of the lens. The output beam width is equal to 2f tan Θ (where Θ is beam divergence).

Below is an example of how to match the laser diode beam divergence ratio with the focal length ratio of two cylindrical lenses to create a nearly circular beam.

Specifications of the Thorlabs HL6320G, 635nm, 10mW Laser Diode
G1 = 11 Divergence x-axis FWHM (deg)
G2 = 37 Divergence y-axis FWHM (deg)
Divergence ratio: 3.364

Specifications of cylindrical lenses
F1 = 50.0mm Thorlabs’ LJ1695L1
F2 = 12.7mm Thorlabs’ LJ1942L1
Focal length ratio: 3.937

Specifications of output beam
d1 = 2f1 tan (G1) = 19.44mm
d2 = 2f2 tan (G2) = 19.14mm

As you can see, the output beam is slightly asymmetric but with a great improvement on the beam shape quality.

Maybe this could be of any help to calculate the cilindrical lens.

You only have to fill in the formule for the x-as (fast axis)

Larry measured 40 degrees.

Who is a wizzkid

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06-23-2010, 09:10 PM #210
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laser_freak
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Re: FS: Hi-Power AR Lens Assy- 25-30% Inc. vs. Aixiz

Quote:
 Originally Posted by edison Hello guys I found a document in Word on the internet: Circularize the laser diode beam using cylindrical lens Cylindrical lenses focus or expand light in one axis only. They can be used to expand the output of the laser diode into a symmetrical beam. The rectangular cross-section of the laser diode cavity results in a beam shape with a wider angular output from the narrow cavity dimension and a narrower angular output from the wide cavity dimension. Laser diodes have an asymmetric radiation pattern which, when collimated, becomes an elliptical beam pattern. As a result, anamorphic prism pairs are often used to convert the elliptical collimated beam to a circular shape. One can also use a pair of cylindrical lenses to achieve similar results to the anamorphic prism pairs. One cylindrical lens can be used to collimate the laser diode’s slow axis and a second cylindrical lens can be used to collimate the fast axis. By simply matching the laser diode beam divergence ratio (vertical vs. horizontal) to the ratio of the focal lengths of the two lenses, a nearly symmetrical circular beam can be created. Since a laser diode is considered as a point source, the two lenses should be placed a distance equal to their respective focal lengths from the laser diode emitter orthogonally to create a collimated beam output. Make sure the beam size at each lens does not exceed the clear aperture of the lens. The output beam width is equal to 2f tan Θ (where Θ is beam divergence). Below is an example of how to match the laser diode beam divergence ratio with the focal length ratio of two cylindrical lenses to create a nearly circular beam. Specifications of the Thorlabs HL6320G, 635nm, 10mW Laser Diode G1 = 11 Divergence x-axis FWHM (deg) G2 = 37 Divergence y-axis FWHM (deg) Divergence ratio: 3.364 Specifications of cylindrical lenses F1 = 50.0mm Thorlabs’ LJ1695L1 F2 = 12.7mm Thorlabs’ LJ1942L1 Focal length ratio: 3.937 Specifications of output beam d1 = 2f1 tan (G1) = 19.44mm d2 = 2f2 tan (G2) = 19.14mm As you can see, the output beam is slightly asymmetric but with a great improvement on the beam shape quality. Maybe this could be of any help to calculate the cilindrical lens. You only have to fill in the formule for the x-as (fast axis) Larry measured 40 degrees. Who is a wizzkid
Or an expensive possible solution: Thorlabs.com - Anamorphic Prism Pairs

07-05-2010, 06:11 AM #211
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LarryDFW
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Re: FS: Hi-Power AR Lens Assy- 25-30% Inc. vs. Aixiz

After talking with a optics specialist, I don't think the anamorphic prisms are a good solution either. He told me that losses would be >25% with the prisms.

I am still playing with cylindrical lenses after the aspherical.
I think it will give the most circular beam and power.

This is the Hi-Power aspherical lens set-up I got the best results & power with.
It has a stainless steel aperture mounted on the lens assembly, right in front of the diode:

It minimizes the fast axis of the 445nm diode creating a slightly better beam pattern.

LarryDFW
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UV LED Lights F/S, 445nm, Blu-Rays, Red 1/2W, Green Focusables,
Link- Blu-Ray/445 Diode Test Current Levels for Long Life

Last edited by LarryDFW; 07-08-2010 at 11:12 PM.

07-05-2010, 08:05 AM #212
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DJNY
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Re: FS: Hi-Power AR Lens Assy- 25-30% Inc. vs. Aixiz

Great Larry
Are you able to show us some 445nm pics with your new lense?

Quote:
 Originally Posted by LarryDFW After talking with a optics specialist, I don't think the anamorphic prisms are a good solution either. He told me that losses would be >25% with the prisms. I am still playing with cylindrical lenses after the aspherical. I think it will give the most circular beam and power. This is the Hi-Power aspherical lens set-up I got the best results & power with. It has a steel aperture mounted on the lens assembly, right in front of the diode: It minimizes the fast axis of the 445nm diode creating a slightly better beam pattern. LarryDFW 445 "Direct-Drive" Member
__________________
405nm >> Wickedlasers SONAR by lazeerer peak@968mW
445nm >> Kryton Smooth by lazeerer peak@2075mW
453nm >> Lipstick by rhd peak@158mW
473nm >> Optotronics RPL-B peak@112mW
515nm >> Skylasers HL peak@41mW
532nm >> Novalasers Alpha HP peak@284mW
589nm >> CNI PGL-III-A peak@89mW
594nm >> Laserglow Rigel peak@4mW
635nm >> MXDL by DTR peak@38mW
642nm >> Saillaser peak@23mW
660nm >> CR2 by lazeerer peak@524mW
685nm >> MXDL by lazereer peak@42mW

Above lasers measured with an Ophir nospin LPM

- - - - - - - - -
- - - - - - - - -

Note that Imageshack is automatically resizing some of my older
pictures back to original full-size after a while.

07-24-2010, 03:36 AM #213
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LarryDFW
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Re: FS: Hi-Power AR Lens Assy- 25-30% Inc. vs. Aixiz

DJNY;

The 445nm beam photo is one the 1st page of this thread.

There is a rectangular area above the dot, but it is fairly dim.

LarryDFW
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UV LED Lights F/S, 445nm, Blu-Rays, Red 1/2W, Green Focusables,
Link- Blu-Ray/445 Diode Test Current Levels for Long Life

08-06-2010, 11:09 PM #214
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planters
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Re: FS: Hi-Power AR Lens Assy- 25-30% Inc. vs. Aixiz

Larry DFW, Reading through this long thread discussing your Hi Power lens was fun. You remained polite as well as helpful. I am interested in purchasing a group of 10 to 20 matched lenses for collimating an array of 445 nm diodes. The array is 30 mm on a side so beam dia. is not important but collimation is. Optima supplies molded aspheric lenses with smaller NA and longer FL than your Hi Power lens. Would they be s better fit for this application or could I go with the Hi Power?

08-08-2010, 05:06 PM #215
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LarryDFW
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Re: FS: Hi-Power AR Lens Assy- 25-30% Inc. vs. Aixiz

Quote:
 Originally Posted by planters I am interested in purchasing a group of 10 to 20 matched lenses for collimating an array of 445 nm diodes. The array is 30 mm on a side so beam dia. is not important but collimation is. Optima supplies molded aspheric lenses with smaller NA and longer FL than your Hi Power lens. Would they be s better fit for this application or could I go with the Hi Power?
The larger NA & shorter FL of the Hi-Power lens collimates more of the LD beam.

If this is important in your application, then these lenses would perform well.

The fast axis remains more divergent, which forms the wings.

The least complex solution is the Hi-Power lens with an aperture to circularize the beam.

Here is my beam analysis from post #204 in this thread:

Beam Characteristics

[Deleted Offer]

Thanks;

Larry
__________________
UV LED Lights F/S, 445nm, Blu-Rays, Red 1/2W, Green Focusables,
Link- Blu-Ray/445 Diode Test Current Levels for Long Life

Last edited by LarryDFW; 11-04-2010 at 05:29 AM.

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