Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers



Laser Pointer Store

Powell lens and power reduction?

Niko1987

New member
Joined
Aug 3, 2018
Messages
10
Likes
0
Points
0
Hi everybody, i ve been thinking in a very low cost PIV system for analyzing the hydrodynamic of flocs particles in cloudy water. I bought: dsrl camera @60 fps 1080p( to record the sludge) , a macro lens 1:1 ,a 200mw green module diode laser(i chose the potency from suggestions from other users )and an acrylic transparent tube of 8 inchs of diameter and 10feet of height.

The piv 's trial demands a vertical laser sheet to illuminate the flocs. The laser has nt arrived yet, but i believe it has a 1mm of laser s diameter. The cameras sensor s height is 15mm , there i should buy some system s lens to magnify the diameter of laser light. The expander beam i thinl could be a great option but the camera will capture many particles in the horizontal plane and the analysis will fail. Other posibility is to use a powell lens of 10° aperture to get the a laser sheet of 15mm of height.

My quests are:

How much power will be reduce due the lense? (1/15 x nominal power)?

And, the planar width will keep the width with the lense?
 

paul1598419

Well-known member
Joined
Sep 20, 2013
Messages
13,232
Likes
1,734
Points
113
I now see why you were talking about a line laser to use for this experiment. Though it will produce a plane of light through your sample, that plane will not be polarized. It can only be polarized in the plane around the beam's travel path. That was why I recommended a beam expander.
 

Niko1987

New member
Joined
Aug 3, 2018
Messages
10
Likes
0
Points
0
I now see why you were talking about a line laser to use for this experiment. Though it will produce a plane of light through your sample, that plane will not be polarized. It can only be polarized in the plane around the beam's travel path. That was why I recommended a beam expander.
Hi paul, why is ig important the polarization? Is it related with brighter of alignment? Google is not very clear.

Greattings.
 

paul1598419

Well-known member
Joined
Sep 20, 2013
Messages
13,232
Likes
1,734
Points
113
I thought you posted a comment about beam polarization in the other thread. If you are simply using the laser as a light source, this is not the case. But, then, why use a laser at all? Any light source would do for this experiment, would it not? Even if you just want a monochromatic light source an LED would suffice.
 

Niko1987

New member
Joined
Aug 3, 2018
Messages
10
Likes
0
Points
0
I thought you posted a comment about beam polarization in the other thread. If you are simply using the laser as a light source, this is not the case. But, then, why use a laser at all? Any light source would do for this experiment, would it not? Even if you just want a monochromatic light source an LED would suffice.
I read on a scienti$t paper that lasers are better than led panel for these trials, because his deeper penetration in cloudy waters ans more efficiency (lowe dispersion). Buth i will review more papers linked to that technique.
 

paul1598419

Well-known member
Joined
Sep 20, 2013
Messages
13,232
Likes
1,734
Points
113
It really depends on how much turbidity you are talking about. At a certain point, no light will make it through at an intensity that will allow you to see individual particles. But, if it is just slightly cloudy and your LEDs are bright enough, you should be able to get by with either one. You can certainly get bright LEDs as they are used in some projectors. You can even get UV ones that will cause fluorescence with certain particulate matter.
 

Niko1987

New member
Joined
Aug 3, 2018
Messages
10
Likes
0
Points
0
It really depends on how much turbidity you are talking about. At a certain point, no light will make it through at an intensity that will allow you to see individual particles. But, if it is just slightly cloudy and your LEDs are bright enough, you should be able to get by with either one. You can certainly get bright LEDs as they are used in some projectors. You can even get UV ones that will cause fluorescence with certain particulate matter.
Hi paul, well i am confused about leds. My first impression is its convinence for larger areas

Could i get a vertical light led sheet of 2 x 1 inchs height and 2 mm width?

Thak you very much again.
 

paul1598419

Well-known member
Joined
Sep 20, 2013
Messages
13,232
Likes
1,734
Points
113
I suppose you could get one focused to those parameters. Not exactly sure what you would need to do it, but it would have to be close to the sample you are trying to illuminate. It might be easier to use a laser to get something that specific as it is collimated and will be easier to work with.
 

Niko1987

New member
Joined
Aug 3, 2018
Messages
10
Likes
0
Points
0
I suppose you could get one focused to those parameters. Not exactly sure what you would need to do it, but it would have to be close to the sample you are trying to illuminate. It might be easier to use a laser to get something that specific as it is collimated and will be easier to work with.
I think is good idea too make a comparative between laser and LED. I would consider it in my thesis plan. In my faculty there is a power led panel used in previous thesis ( i don t remember well but was linked to alga studies).

Last question:
What lens do you suggest me to collimate the laser sheet ? Aliexpress has many publications for CO2 lasers ... But i believw is no my case. Ib this forum also i read about the use of fresnel lens. Are them fine?
 

paul1598419

Well-known member
Joined
Sep 20, 2013
Messages
13,232
Likes
1,734
Points
113
Since polarization is not an issue, if your beam diameter is what you want already, a lens to make a line would work fine. You can get them in sizes that would work with whichever laser you want to use. If it is a green 532nm diode pumped solid state laser, you will need to find a lens in a housing that is threaded to be used with that laser.

As an example, if you were using a direct diode laser in a 12 mm module tapped for an M9X0.5M lens, you would want a line lens with M9X0.5M threads. I would search eBay for the one that will fit the laser you will be using. These can be had very inexpensively as an acrylic lens since your power will be ~200 mW. You might be able to find a green 532nmlaser already setup as a line laser. At 200 mW in a lab host with a driver I would expect to pay ~$60 to $70. You should be able to find one like that for that amount of money or even less money. Otherwise, you will have to find the line lens in a housing threaded to go into the laser you are using.
 
Joined
Jan 5, 2011
Messages
402
Likes
61
Points
28
Could i get a vertical light led sheet of 2 x 1 inchs height and 2 mm width
:whistle:
I might imagine the cube of light of those dimensions but it would be good to see a picture what you really need.

Do you really need a collimated sheet?
Would a cylindrical lens be enough instead of the Powell lens?
 




Top