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08-01-2017, 06:31 AM #1
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Stupid Optics Question - Laser line divergence

I have a stupid question, if using a plano-convex cylinder lens or a glass rod with a laser beam which has been focused to infinity (to produce a thin wide line), what is the divergence of the line?

Some might look at this question as invalid; how is divergence related to a laser line which spreads into a thin plane many degrees wide? I mean in the opposite plane, or the thickness of the line. What determines how much thicker it gets as the line travels forward?

My assumption is the thickness of the line diverges at the same rate as the beam had prior to shooting into the line lens, correct? Yes, no? More info?

EDIT:

One more maybe not so stupid question, I want to bore a hole through a PBS cube, anyone know where I can send a cube to get it done? Needs to be accurate without damaging the cube. This would be to coaxially combine three beams, the beam going through the hole a much smaller diameter beam than the other two going through and being combined, of course. I'd rather have a cube which simply has an absence of a polarised layer in a very small area in the center, but haven't seen anything like that.

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"I regard consciousness as fundamental. I regard matter as derivative from consciousness..." - Max Planck. "Everything we call real is made of things that cannot be regarded as real" - Neils Bohr. "What we call physical things and events do not exist independently of subjective experience..." - Deepak Chopra.

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Last edited by Alaskan; 08-01-2017 at 07:51 AM.

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08-01-2017, 08:04 PM #2
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paul1598419
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Re: Stupid Optics Question - Laser line divergence

If you look at the data sheets of these diodes you'll see divergent full angles for parallel and perpendicular with respect to the diode's band gap. They are independent of each other. Hope that helps.

As for your other question.... I have no idea.
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632.8nm P210 New Laser Tube 0.57mW Melles Griot 05-LMP-827-037 PS
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Last edited by paul1598419; 08-01-2017 at 08:05 PM.

08-01-2017, 09:24 PM #3
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RedCowboy
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Re: Stupid Optics Question - Laser line divergence

Yes, both the vertical and horizontal axis diverge, one just diverges faster than the other, so if using a cylinder lens you only reshape 1 axis, the other axis continues to diverge unaffected.

If you make your beam look square at the aperture it does not mean it will look square in the far field because each axis although at the moment look the same will diverge differently.

Is that what you meant?
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08-01-2017, 09:35 PM #4
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Re: Stupid Optics Question - Laser line divergence

I was trying to determine something else. If you fully collimate a laser diodes output, and then shoot the beam into a laser line lens, a cylinder lens, or a glass rod, what the divergence of the line it produces would be. Is it the same divergence as the collimated beam shot into it? The line produced by such a lens will become thicker and thicker as the beam travels forward, my assumption is the divergence of that line is a function of the original collimated divergence of the beam. That's why it's likely a stupid question, probably a no brainer to assume it would be.
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Sam's Laser FAQ: Sam's Laser FAQ: Welcome Page

RHD's Relative Perceived Brightness Calculator. Compare brightness @nm: http://lsrtools.1apps.com/relativebrightness

To shorten my signature I have moved most of my laser related web links to this forum page, the second post in that thread shows most of my builds... Alaskan's Laser Links: http://laserpointerforums.com/f44/al...ml#post1449395

Sincerely investigate any of these three short quotes as new concepts and you've taken your first step into a larger world:

"I regard consciousness as fundamental. I regard matter as derivative from consciousness..." - Max Planck. "Everything we call real is made of things that cannot be regarded as real" - Neils Bohr. "What we call physical things and events do not exist independently of subjective experience..." - Deepak Chopra.

Each of these three rabbit holes go deep, ending up in the same place.

Useless troll fighting.
.........................
http://imgbb.com

High resolution of my avatar: https://ibb.co/fWOhXF

08-01-2017, 09:52 PM #5
 Class 4 Laser Join Date: Sep 2013 Location: Washington State Posts: 5,435 Rep Power: 51609
paul1598419
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Re: Stupid Optics Question - Laser line divergence

Yes, the uneffected axis will continue to diverge as if nothing had been done. The line is just a line and will continue to diverge very aggressively.
__________________
405nm Laser Pointer 45mW
405nm C11 700mW
405nm Laser Shack Pointer 80mW
Thor H Dual Power 445nm, 438 mW & 1648 mW
445nm 3 watts MS-SSW-II
445nm 2.2 watts Nichia MS Envy

445nm 2 watt SMP Copper Host
477nm 127 mW 501B
488nm Uniphase #2201-20SLAT argon laser head and power supply >40mW
520nm LaserLands pointer Measures 510nm
532nm LSR532H-1W Laser, LSR-PS-N1 Driver, RS-75-5 P.S. 1300 mW
532nm 200mW Thermostatically Controlled Fan Cooled (Besram) >230mW
532nm 189mW pocket lab laser
532nm lasers X6 100mW-200mW
532nm lasers X4 75mW- 140mW
632.8nm P210 New Laser Tube 0.57mW Melles Griot 05-LMP-827-037 PS
632.8nm Spectra- Physics He- Ne #102-2 4mW heads X2 and #236 power supply
632.8nm PMS He-Ne # 201P/ LPS-115 2mW
632.8nm Siemens HeNe LGK7630S 7.6mW
635nm 1 watt Cyprus II
635nm 1 watt SMP Copper host
635nm 5mW pointer
635nm 100mW pointer
650nm 65mW pointer
650nm 380mW 501B
808nm 1+W infrared laser
infrared video camera for collimating IR lasers
Ocean Optics USB2000 Spectrometer
Scientech Vector S310 with AC2500 10 Watt LPM
LaserBee II 3.2 Watt LPM

08-01-2017, 09:54 PM #6
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RedCowboy
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Re: Stupid Optics Question - Laser line divergence

All beams are either diverging or converging by some amount even when perfectly collimated, remember it's 3 dimensional, but you know this.

A perfect beam only exist in our minds, to have a truly perfect beam it would have to be a single string of photons, as in 1 photon wide by 1 photon tall and in a vacuum.
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08-01-2017, 09:55 PM #7
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Re: Stupid Optics Question - Laser line divergence

Thanks, what I need to do next is figure out at what the percentages of original power put into it are at different distances, as viewed or captured by the human eye. As that line spreads out more and more, it's probably .000001 or less a mile away, compared to a 1 mRad laser beam. Maybe it isn't as weak as that, I just don't know through intuition.

Would be cool to have a string of photons without divergence but I suppose that is impossible, or can we fire single photo's in a line without departure from it? Probably not. Is the problem caused by using lenses to collimate the beam? All refraction destined to produce an imperfect collimation? This is where a guru usually steps in to show me the light, which guru this time?
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Sam's Laser FAQ: Sam's Laser FAQ: Welcome Page

RHD's Relative Perceived Brightness Calculator. Compare brightness @nm: http://lsrtools.1apps.com/relativebrightness

To shorten my signature I have moved most of my laser related web links to this forum page, the second post in that thread shows most of my builds... Alaskan's Laser Links: http://laserpointerforums.com/f44/al...ml#post1449395

Sincerely investigate any of these three short quotes as new concepts and you've taken your first step into a larger world:

"I regard consciousness as fundamental. I regard matter as derivative from consciousness..." - Max Planck. "Everything we call real is made of things that cannot be regarded as real" - Neils Bohr. "What we call physical things and events do not exist independently of subjective experience..." - Deepak Chopra.

Each of these three rabbit holes go deep, ending up in the same place.

Useless troll fighting.
.........................
http://imgbb.com

High resolution of my avatar: https://ibb.co/fWOhXF

Last edited by Alaskan; 08-01-2017 at 10:12 PM.

08-01-2017, 10:26 PM #8
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RedCowboy
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Re: Stupid Optics Question - Laser line divergence

Our moisture rich air is also littered with gases and dust, a laser beam catches hell over a long distance, not the 100 feet that I play with but even at 100 feet I see some strange things, like the boarder edge of the spot twitching, now I know when growing the substrate on the silicon wafer they introduce a line of trash at the edge to define it so that could be what I am seeing at distance where I am looking at a exploded view of the emitter.

But through our air a visible wavelength gets influenced my humidity.

What was the best wavelength, microwaves work well but wasn't it in the near IR that travels the best through air?

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You can not put freedom in a bag.
It is in fact an abstract concept.
Yet it is the single most valuable thing anyone has ever had.

Last edited by RedCowboy; 08-01-2017 at 10:32 PM.

08-01-2017, 11:08 PM #9
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Re: Stupid Optics Question - Laser line divergence

Quote:
 Originally Posted by Alaskan I have a stupid question, if using a plano-convex cylinder lens or a glass rod with a laser beam which has been focused to infinity (to produce a thin wide line), what is the divergence of the line? Some might look at this question as invalid; how is divergence related to a laser line which spreads into a thin plane many degrees wide? I mean in the opposite plane, or the thickness of the line. What determines how much thicker it gets as the line travels forward? My assumption is the thickness of the line diverges at the same rate as the beam had prior to shooting into the line lens, correct? Yes, no? More info? EDIT:
It depends on the focal length of the pcx lens.

A rod lens is similar to a ball lens both having very short focal lengths. In the use of a rod if placed perpendicular one axis will expand at a rate independent of its collimation mrd. The other axis is unchanged. If place parallel to the beam the same happens.

08-02-2017, 01:21 AM #10
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Re: Stupid Optics Question - Laser line divergence

I guess is this is where the prism-pair corrective optics come in: Trade a narrow beam with high divergence to a wider one with smaller divergence, but only in one direction.

Something similar could possibly done with half-cylindrincal/rod lenses as well.

It can vastly improve the far-field shape of a laser dot, but in practical use do not expect any miracles. With a multimode dode the 'dot' will be a rectangle regardless of what you do. It may just become more of a rectangle than a line, which could be good enough for some applications.

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