Alors c'est juste pour info et lecture:
Car ca vient d'un site web, peut etre laserfaq ou autre, ils ne faut pas copier coller ces infos sur un autre site, des adresses mails sont inclues etc..
Inexpensive Combining of Argon Ion and HeNe Laser Beams
Also see the section: Combining Light from Multiple Lasers.
(From: John R (
scifind@indy.net).)
White-light color control with a red HeNe and multiline argon ion laser and be done without a PCAOM, but you may not like the answer.
It is much cheaper than the PCAOM method, but still involves lots of work and moderate costs. Of course, if you are a laser hobbyist,
nothing is cheap, especially if you want laser beams other than 632.8 nm red!
For a minimum white light color control system:
You need a multiline argon ion laser with at least the 488 (cyan-blue) and 514.5 (green) lines.
You will need three separate dichroic filters. (Edmund Scientific and others sell these).
One dichro is used to split the multiline Argon beam into a transmitted blue line and a reflected green line at 90 degrees.
This gives you the isolated blue and green beams.
Once you have the separate blue/greens, you need some method of intensity color. Three possibilities are single-channel AOMs,
blanking scanners, or simple beam shutters.
Once you get the blue/green beams through intensity controllers, they must be recombined using another dichro.
Using a third dichro, the Argon beams and then super-imposed onto the red HeNe laser beam.
(Of course, you should have some type of intensity controller for the red HeNe beam as well.)
Thus, the final "white light" beam is made up resultant actions of three dichros and three intensity controllers.
If you have some type of analog controller for each R/G/B color, you can blend them produce an incredible amount of colors.
I once built one of these "RGB color boxes" using an argon and HeNe laser.
It worked quite well, but there was the major hassle of alignment of multiple dichros, other mirrors, and three AOMS.
A significant portion of the Argon power may be lost because it has to pass through three dichros.
As for costs, if you can get surplus AOMs, dichros, and make your own mirror mounts, maybe $200 to $400 - if you're lucky!
Unfortunately, there is no simple or cheap way of doing it.
And, if you are thinking about mixing yellow and orange HeNe's with argons and red HeNe's,
I seriously doubt you will achieve the performance (and ultimate cost) of even a used PCAOM.
Why?
Both yellow and orange HeNe's only give a few milliwatts. They will easily be over-powered by the argon laser not only
in terms of actual milliwatts, but in apparent visual brightness to your eyes.
Unless you are just shining the independent laser beams onto the same spot on the wall,
accurate near- and far-field collimation of a multiline argon with three yellow, orange, and red HeNe's is almost impossible.
You will need some lots of custom dichros to combine the beams and numerous beam leveling mirrors to achieve it.
Lots of dichros and lots of mirrors translates into "lots of losses" and a [censor] to establish and maintain collimation.
Three dichro color systems are still lots of work. In this case, you would have a FIVE-color dichro system.
You may also run into problems as each independent laser has its one beam diameter, divergence, and spatial TEM characteristics.
So if you could collimate them, the resultant "white light" beam will have lots of color fringes.
Of course, it is your time, money, and effort, therefore, I wish you good success.
But using a higher power red HeNe and then blending it with the multiline argon is still the better approach.
For more information, try Laser FX. Their Website author also has an excellent handbook on lasers and laser shows.
There are a couple of chapters devoted to RGB color control in lasers, including HeNe/Argon methods.
If you are serious about making white light beams (and learning about lasers and shows), this is the book to have!
Also, other ideas. Neos Technology has a 4-channel PCAOM crystal for $680 and driver for $600.
If you are a hobbyist, this is not cheap. However, if you can get a PCAOM system, it is vastly superior to the RGB/dichro color method.
(From: L. Michael Roberts (
NewsMail@LaserFX.com).)
To combine the two lasers your best and lowest cost solution would be a dichotic.
Firstly you need to have a set of two FS mirrors on optics mounts [E.G. Newport MMI or RMSM OM3/4] to level and steer the beam.
Purchase a cyan or red dichro [from Edmund or PPS]; mount it on another optics mount.
With a cyan dichro, you shine the argon through the dichro [which transmits green/blue wavelengths]
. Set the dichro in the beam at 45 degrees at the point where the ar and HeNe beams are made to cross at a right angle.
Careful adjustment of the steering mirror pair on each laser will allow you to produce two beams that are level relative to each other
[and the baseplate of your projector] and cross at right angles.
Set the dichro in the position where the beams cross at a 45 degree angle relative to the Ar beam
[with the 45 degree angle such that the HeNe beam is reflected away from the Ar source].
Adjust the beams until the HeNe and argon beams overlay each other on the dichro [near field adjustment].
Now look at the resultant beam at some distance or on the projection surface. Adjust the dichro so that the two spots overlap [far field adjustment].
Adjusting the dichro will cause some change in the position of the Ar and HeNe beams so you then re-adjust the near field
[laser steering mirrors to overlap the beams on the dichro]; then the far field [dichro to overlap beams on the screen].
2-4 adjustments going back and forth form near to far field may be required, but in the end you will have the two beams exactly overlaid on each other.
To the eye, the beam will appear a pinkish white - colour balance can be adjusted by varying the brightness of the Ar laser.
A cyan dichro is recommended as it reflects red and you want to conserve red photons.
You will note that some of the argon beam is deflected in the direction the HeNe would have been going if not reflected.
This is due to beam splitting at the surface of the dichro. If you use a red dichro, those would be red photons you would be throwing away.
You can now place a PCAOM [from NEOS or MVM] in the combined beam. Make sure the polarization of the HeNe is vertical
[check the ar while you are at it - they are usually polarized vertically but poor alignment could have you a bit off]
and that the PCAOM cell is correctly oriented. Varying the control voltages to the PCAOM will allow you to have additive [RGB] colour control.
You can get 16.7 million colours or more depending on the PCAOM and the system used to control it.
Dichroic Mirrors for Separating Multiline Beams
Dichroic (dielectric) mirrors can be used to split a multiline laser beam into two or more sets of separate lines.
They enable the construction of simpler, smaller, and more efficient systems compared to dispersive techniques like prisms or gratings.
But good quality dichros are not cheap.
(From: Steve Roberts" (
osteven@akrobiz.com).)
There are 3 quality sources of laser show dichros that I have used:
New Method Lasers. Ask for Bob Ash.
Lighting Systems Design, Inc.. Ask for Greg Makhov.
Precision Projection Systems. These are more or less optimized for white light krypton. Ask for Jim.
For pricing, you're looking at $20 to $50 a square inch, depending on quality, and whether a precut size is available.
Some may charge a cutting fee or a little more for the AR coated units.
Keep in mind you need to know if you want CMY or RGB and 0 or 45 degree incidence, as most folks will stock the whole set of combinations.
Be clear - specify that you want "transmit blue reflect green at normal incidence" Or "pass blue/green combine red at 45 degrees".
Most people don't think about it, but "pass deep blue and violet" for a argon laser turns out to be a nice dichro to have.
Prisms are generally only useful for separating one line, and for laser display purposes, you need all the power you can get,
so you want all the blue or all the green lines, etc. They are also a pain in the neck as dispersion versus angle is constant,
and a dichro can be tilted off axis quite a bit and still have throughput. Many traditional laser projectors for planetariums did just that,
have a prism and a color selection galvo,
but this takes up several feet of space to do and is difficult to support from a control systems point of view and to align.
With a prism, you're wasting from 60 to 85% of your light at any one time, as you're only using one line.
Also beware that Edmund Scientific's dichros are more or less coated for TV/spotlight applications and thus leak some blue or green that a laser show dichro wouldn't. This spoils the effect of clean contrasting colors, so you need a dichro designed for laser display. Edmund's dichros are great with a tungsten source however.
When you order, ask for backside AR coats on your dichros if available.
Otherwise you'd have 8 to 10% Losses from the Fresnel losses.
Visibility of High Power Laser Beams
The following applies to the visibility of the beam itself (i.e., Star Wars Light Saber style), not to its appearance then it strikes a surface.
(From: L. Michael Roberts (
newsmail@LaserFX.com).)
To create visible beams in *total* darkness you can get away with as little as 100 mW. For beam effects in a club or other venue with some ambient lighting, 1 watt is about the minimum you need to make visible beam effects. Outdoors you will need 5-6 watts to make visible beams [again depending n ambient lighting conditions].
In all cases, a scattering medium (smoke or dust) is required to deflect the light towards the observer's eyes. In clean, clear air in winter, I have seen the beams from a 20 watt argon look lamer than the beams from a 1 watt indoors with a good haze.
(From: Steve Roberts (
osteven@akrobiz.com).)
In a dark room with average dust levels and high humidity you can start to see the forward scattering of an HeNe beam at about 1 mW! 30 to 40 mW of argon makes an OK side view beam in a dim room, but its not exactly a Star Trek photon torpedo kind of glow. It helps if the argon is configured multiline and is doing more green then blue, as the eye peaks in the green. To see the beam in a well lit room requires smoke of some form.
Most laser light show types don't like the common aquafog, it irritates your lungs after constant exposure, so we use hazers indoors. A hazer works by making very tiny particles of medical grade oil. These are small enough to be flushed out of your lungs by normal breathing and if properly set up, are odorless and OSHA approved. Fog machines for the most part are crackers, they work by incomplete combustion of glycols (aquafog) or burning of oil in air. Hazers fragment the oil in CO2 and thus are almost odorless. Plans for a homemade hazer of sorts that uses air are at LaserFX on the "Backstage" pages. It has a slight odor but is not that bad to be around, and mind you I have asthma! I have done indoor shows for 1,200 people using 60 mW and a cracker. I have also done shows indoors for 100 people with a 5 mW hene, it depends on ambient lighting and air circulation/humidity.
It is a minimum of about 5 watts of argon light for a decent outdoor smokeless beam show, with 20 watts being more typical.
(From: Steve Quest (
Squest@cris.com).)
Visible wavelength lasers are more visible in 'plain air' if the angle of incidence is low (you're close to the same angle of the beam) and if the power is greater than about 5 watts. I perform an outdoor laser show using a 30 to 57 (max) watt YAG (frequency doubled to 532 nm) which is plainly visible in mostly clear air (no need to smoke, or fog the air). When I want to do beam effects with a 5 watt argon/krypton white-light laser, I have to fog the air up.
Plain outdoor air has enough particulate matter to scatter a laser beam so long as it is above 25 or so watts, thus making the beam visible. Of course, the more power, the brighter the beam looks, but CDRH has limits, and that limit is .9725 mw/cm2 at 750 feet, so the days of power beam shows going all the way to outer space and beyond is over
.
I use a Laserscope laser, which is FDA (Food and Drug Administration) approved, and am following CDRH (Center for Devices and Radiological Health) guidelines, receive FAA (Federal Aviation Administration) approval and air clearance before every show, and make sure that NOTAM (NOtice To AirMen) are issued to pilots flying in the area of my shows, giving exact details as to what is going on. Pilots love the shows, and air traffic routes planes WAY out of their flightpaths to fly near the beam shows to get the best seats in the house.
However, I have to beam-off when they get too close, then they return to their flightpath, and I can resume the show.
I used to be able to sparkle off the new moon with my YAG at full power and full convergence. It takes some doing but you can see the sparkle from the Sea of Tranquillity with the naked eye off the corner cube reflector, aka: retroreflector left there in 1969 by the astronauts.
(From: Sam.)
WARNING: Shooting a laser into the sky is irresponsible and highly illegal without prior approval from the proper agencies. Airline pilots do not appreciate being blinded!
Here are some additional comments on the effects of viewing direction on apparent brightness:
(From: Johannes Swartling (
Johannes.Swartling@fysik.lth.se).)
What you see is light that has been scattered by the small particles in the fog or smoke. This kind of scattering is called Mie scattering, and occurs when the size of the particles is comparable to or a little smaller than the wavelength of the light. In Mie theory, there is something called a scattering profile - i.e., the probability that the light will scatter in a certain direction.
Now, in the case of very small particles, such as molecules, this scattering profile is isotropic. That means that the light will scatter in all directions with equal probability. This special case is called Rayleigh scattering, and can be seen from pure air if you have a strong enough laser, such as an Ar-ion laser. When the particles get larger, however, the light will tend to scatter more and more in the forward direction. That is what you see from the smoke. When you look along the beam in the direction where it comes from, you see a lot of light that has been scattered just a little bit off the direction of the beam. When you look along the beam away from the laser, there's a lot less light that has been scattered backwards.
(From: Pissavin (
pissavin@aol.com).)
One interesting phenomenon; Depending on whether dust or smoke is used, there is an asymmetry: With smoke, if you put your head near the laser and look down the beam, you see almost nothing. Now, look toward the laser (BUT NOT DIRECTLY INTO THE BEAM!) and you see a clear beam. Then replace the smoke with dust and the effect will be reversed.
(From: NeoLASE (
neolase@lasers.org).)
Large particles like dust have more back scattering centers while small particles like smoke and haze have more forward scattering centers. Mie scattering effects, and all that stuff, I've heard/read of but I haven't studied in detail. Used a lot in laser particle size analysis.
mais elles font toutes deux 100mW donc bien que le vert reste nettement plus visible que le rouge (650nm) je suppose que j'aurait tout de même un mélange de couleur.
