Diode Laser ---Under the Hood 07
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- Опубликовано: 6 апр 2024
- My trusted helper, clear acrylic, was the key material that helped me decode the workings of CO2 laser technology. With thousands of people several years ahead of me using blue diode lasers , the accepted truth was that clear acrylic was transparent at 455nm wavelength. From the intial engraving experiments I conducted using clear acrylic, I seemed to verify that thousands of people were correct and that clear acrylic was not going to aid my quest decoding 455nm technology.
The closed nature of the head design and the fixed focus means that there is little left to explore except parameters and materials. There are hundreds of videos out there that demonstrate the limits of the technology if you play by the rules. The aim of my videos is to subvert the rules and explore parts of the technology that are virgin terrirtory. Accepted truths are not always THE truth. My old "lab assistant " (clear acrylic) and I have teamed up again to explore the world of diode lasers. 
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FYI, there a several different scientific instruments that use the the interaction you describe around the 11 minute mark to identify the elements in a sample. The two I've used before are energy dispersive spectroscopy (EDS) and wavelength dispersive spectroscopy (WDS). They look at x-rays, but the quantum mechanics are identical. Also, the inner shell electrons are often knocked completely out of the atom, making it unstable, causing an outer shell electron to fall into the inner shell's hole. This is what people mean when they say "ionizing radiation", an electron gets knocked out of the atom making it an ion.
Russ, fascinating series and I don't even own a diode laser.
A thought for your experimentation (that you’ve probably already thought of): With strong enough neutral density filters (they make ND 10 ones, which is what you’d probably need) and a good long-focal length macro lens you’d be able to directly photograph, measure and characterize the beam spot, and perhaps even observe what’s happening at the surface of the acrylic in real time as the laser is acting on it.
You’ll want a long focal length lens though, to keep the front of the lens out of the way of the laser head and not get fouled by the vaporized material.
(You could do it cheaply by putting an old manual-focus SLR lens on a cheap mirrorless camera (plenty of used ones also) with an adapter. I think Nikon or maybe Canon had 200mm macro lenses that might give you a reasonable stand-off distance.)
Hi Dave
There are some intersting ideas in your comment and I always am grateful to folks who really engage with the subject. You made me stop and rationalize what advantages if any would accrue form seeing what is happening at the contact spot? without any comlications just burning with a focused beam and ldecoding the damsge done tells me all about the intensity distriibution within the spot. The material damage is absolute and records in detail the intensity profilethat caused it in a way that no visible technique can ever match. I have spent many years decoding how a CO2 laser beams cause damage and then reverse engineering the conditions conditons that must have existed to cause the damage. You will see in this next video..
No idea is discarded ,so thanks for some novel thoughts that will be put on one of my many "mind shelves" for use or adaption.
I noticed that Ortur has a 2-diode 22W model they say punches above its weight because the way they combine and focus the beams (they mention polarization, suggesting that’s important) produces a spot that’s square vs rectangular and “40% smaller” (40% or 60% relative size?) compared to others.
Hi Dave
The 5 watt diode I am using heere should have an eliptical beam. Have you seen any evidence of that in my videos so far.? I went into this diode journey expecting super small but starnge spot shapes. So far I havv seen neither despite searching. What is a spot size? In pratice I see it as a set of small numbers for the marketing department to be creative with the truth. No brand states the conditions attached to discovering or proving it's existance.. If I fire the laser at a material for 0.1sec and measure the damage, is that the spot size ? If I now repeat the same test with a different material I guarantee the data will be different. If I use either material and burn a 2 or 3 second spot, in both cases it will be bigger. If you doubt me test it on your own machine. There are only a few specialist sorce companies that produce the precision optical diode modules that exist within the many branded products that are in this market place Novel design features or price are the only two real factors that set machines apart The laser modules and lenses are bits of bolt on specialist kit. You say that Ortur are using 2 diodes to create 22 watts of optical power. That would be amazing bcause up to now the most powerful commercial laser diode has been 6 watts .. Hmmm ....I have just visited the Ortur website and the only unit I can find close to your description is this 4 diode 20watt unit
ortur.net/products/ortur-laser-master-3-engraver-cutter-machine?variant=44969743253737&I&gad_source=1&gclid=Cj0KCQjwiMmwBhDmARIsABeQ7xT3eoMQ3BVcwdd7hSLUdmDSaMC0afO_9O89p2RFqibVRAG3BfLO57oaAgjYEALw_wcB
On the AlgoLaser website they show exactly the same product as a 22watt laser but it still uses 4 x 6 watt diodes.. Watch the cutting video on both sites Interesting? The same technical descrption and square spot size claims.
algolaser.com/products/algolaser-alpha-22w-10w-diode-laser-engraver?gad_source=1&gclid=Cj0KCQjwiMmwBhDmARIsABeQ7xQ2FMihKAahzp_PkCOS8b5SfLK6QsW699VKWS32VkiwF3yx26ISahcaAiwfEALw_wcB&
You will note that the optical paths are diiferent but it appears that the same head design is dressed up in different ways to seemingly make it unique to that brand.
I must stress ther is no criticism of your comment because you have made me do some research that has advance my knowledge in some areas but confirmed my mistrust of Chinese product advertising. Thankyou.
ps I will eventually be testing such a 20 watt uint but I have much to learn about the singlr diode before I pollute the clarity of my research with a 2 or 4 diode system. It seems that they are just adding more photons to increase the intensity of the same spot ie more damage capability.
@@SarbarMultimedia Oh, I’m so sorry to have sent you on a wild goose chase; that must have cost you a lot of time!
I saw the machine after visiting a link to a sales site for a unit another YT channel was using. I browsed around the site and found what was indeed the AlgoLaser. I unfortunately didn’t didn’t realize that the original link had put me on a reseller’s site and so was just thinking it was Ortur, with the AlgoLaser being some extended branding. Apologies again!
I’m not sure where I might have come up with the idea of two diodes, I certainly don’t find it now :-/
And yes, the laser modules are made by some very small number of manufacturers and then sold to all manner of outfits that just slap them on X/Y mechanisms.
I hear and entirely agree with what you’re saying about spot size: What matters is obviously how the beam interacts with the material, and a longer dwell time will clearly leave a bigger area of damage. I also do realize that there’s an energy profile to the beam that falls off with some kind of slope, vs the popular image of lasers as some optical equivalent of a steel rod, going from nothing to 100% in no space at all 😄 The marketing guys could just decide that “spot size” was the width for the beam to go from 100% to 90%, and voila, the smallest spot in the industry!
I’ll take a look at the two sites, I wouldn’t be the least surprised they’re both using the identical head, or if anything, AlgoLaser might be (a) fudging on the specs, (b) just running it harder without regard to life, (c) buying slightly higher-spec modules with first-bin laser chips that can handle more current or (d) doing something else 🤔
AlgoLaser does make the sales point that they’re concentrating the energy into a smaller area, however you define spot size. Whether their claims are true is another question, and as you so rightly point out, it’s all down to how it interacts with the material. If there’s some optical cleverness that could confine the laser energy to a smaller area, I’d think it would hold promise for faster cutting, all else being equal. (It’s tempting to waste a chunk of time looking up what it might be about. I don’t offhand know how polarization would affect the spot size, but optics wasn’t my area.)
(There’s also the question which you’re so thoroughly exploring of how the beam converges and diverges within the medium. - Or the possibility/theory that I think I remember you talking about a year or more back with CO2 lasers, of some of the peripheral beam energy in some situations being deflected back into the center by the walls of the cut as it gets deeper. - And of course, all manner of possibilities for how the optics are set up.)
All in all, the only solution for sorting it all out that I can see is for you to get _two_ 20 watt lasers and spend a couple of months characterizing their beams for is all 😉👍😄
@@DaveEtchells
Visiting new websites is never a waste of time so no apology required. I often spot things that stimulate content for a video or need expolring/debunking.. I alredy have a 20 watt head but will not pollute my research with multi lasers until I understan dthe single one. It will just nbe more photons crammed into the same beam using the same lens to get higher intensity and faster penetration.
@@SarbarMultimedia Kudos for keeping it simple with a single diode until you have a solid grasp on what’s going on; very sensible. 👍
I hope that you do not forget that the focal length depends on the density of the medium in which the rays pass. Please keep this in mind when showing this video.
Thanks for the comment. Yes I am aware that every material has a refracrive index even those like wood and steel that are not transparent. However it matters not in this case because this is a RELATIVE way of examinng the focal point for different lens configurations and not an absolote measurement. When I get to setting the focal point for different materials and lens configurations I do it objectively. I have no idea why manufacturers of these machine think that autofocus is a good idea. In the little I have seen so far ,this is exactly the same as CO2 technology and INTENSITY focus changes with speed and material but less so with power As I progress with this series and start cutting as well as engraving I think this will begin to be obvious.