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Post by deltav on Mar 19, 2017 9:09:30 GMT
The foundation of this thread (as I understand it) is... 1. Weak lasers with Watts of power are instantly taking out much stronger lasers. 2. The sun at midday is at best 1000 W/m^2 and if that doesn't hurt anything, then lasers at that power shouldn't. 3. Our laser mirrors are so tough and can take so much intensity, they should be able to handle just as much coming "in". --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- 1. I'm doubting weak lasers (sub 400kW) instantly popping much stronger ones. I'll be posting a video with tests, but I just wonder about this. 2. The sun at midday analogy could work but don't we need to make sure it is a fair comparison? We need to compare optics looking straight at the sun + at midday + at the equator + in a cloudless sky + in the summer + for extended periods. That would be pretty intense. The sun is enough to damage cameras and other optical equipment if their shutter speed isn't fast enough. www.digital-photo-secrets.com/tip/1797/can-i-damage-my-camera-by-pointing-it-at-the-sun/ forums.creativecow.net/archivethread/35/628678Enough to damage a laser? Don't know. 3. Our lasers use "adaptive optics" which are very fragile. They are a bunch of tiny mirrors (or a flexible mirror) on a kind of movable lattice. It wouldn't take much heat to destroy the tiny parts that allow the mirror to focus properly. The more powerful the laser (larger the laser aperture), the more delicate and vulnerable the focusing mirror and its components are.Also they never directly handle the full intensity of the focused laser beam, which does not happen until it reaches the target up to 1000 km away. It would be like Johnny with the magnifying glass focusing the beam on an ant. If Johnny puts his hand close up to the glass before the beam is focused, it wouldn't do much of anything. If this is true, then this is why the beam expander and the struts that hold it never are damaged despite always being in the path of the laser. It is unfocused. Lastly the optics of our lasers are essentially telescopes in reverse, they would magnify and intensify any laser beam that hit at the right angle, far above anything the optics are designed to handle. I don't know if the way lasers depicted in game is realistic, but I know some of the assumptions deserve much deeper investigation.I know I had my assumptions questioned when we first started playing COADE. "Isn't one nuke enough?" "Why do we need 100?" I don't plan to argue this much, I'm hoping someone who has real world knowledge of lasers will step in and speak up, these are just my thoughts. Note: I edited this comment dozens of times to make sure the language was as diplomatic as possible. My intentions were/are completely honorable.
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Post by samchiu2000 on Mar 19, 2017 10:38:47 GMT
Oh i am surprised that the sun CAN do some optical damage deltav
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Post by deltav on Mar 19, 2017 10:51:26 GMT
I was gonna add this too but I don't want to edit if someone has already responded... More examples of how Adaptive mirrors work... Damage to cameras shooting directly looking into the sun? Sure, at least that's what those on the links say. I've never tried it. I found another link that showed that even special effects/ concert lasers (non weaponized) can easily damage camera sensors and optics. Posted it earlier on the thread.
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Post by Enderminion on Mar 19, 2017 15:50:56 GMT
Oh i am surprised that the sun CAN do some optical damage deltav The Human Eye is optical in nature, staring at the sun cause eye damage.
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Post by gedzilla on Mar 19, 2017 16:14:47 GMT
What im getting out of this is that optics are actually pretty vulnerable, and the sun can cuase optics damage irl, so although the almost instant death of lasers to basically flashlights is bugged, its only bugged a little bit, not a ton
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Post by bigbombr on Mar 19, 2017 16:39:40 GMT
Oh i am surprised that the sun CAN do some optical damage deltav The Human Eye is optical in nature, staring at the sun cause eye damage. Blindness by staring at the sun is caused by the overheating of vital proteins in your retina, which happens at less than 333 K. Aluminium mirrors are 1) more temperature tolerant and 2) actively cooled. Furthermore, eyes aren't designed to shoot GW-range lasers. And comparing the human eye to military tech is naive at best.
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Post by lawson on Mar 19, 2017 19:00:34 GMT
The foundation of this thread (as I understand it) is... 1. Weak lasers with Watts of power are instantly taking out much stronger lasers. 2. The sun at midday is at best 1000 W/m^2 and if that doesn't hurt anything, then lasers at that power shouldn't. 3. Our laser mirrors are so tough and can take so much intensity, they should be able to handle just as much coming "in". --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- 1. I'm doubting weak lasers (sub 400kW) instantly popping much stronger ones. I'll be posting a video with tests, but I just wonder about this. 2. The sun at midday analogy could work but don't we need to make sure it is a fair comparison? We need to compare optics looking straight at the sun + at midday + at the equator + in a cloudless sky + in the summer + for extended periods. That would be pretty intense. The sun is enough to damage cameras and other optical equipment if their shutter speed isn't fast enough. www.digital-photo-secrets.com/tip/1797/can-i-damage-my-camera-by-pointing-it-at-the-sun/ forums.creativecow.net/archivethread/35/628678Enough to damage a laser? Don't know. 3. Our lasers use "adaptive optics" which are very fragile. They are a bunch of tiny mirrors (or a flexible mirror) on a kind of movable lattice. It wouldn't take much heat to destroy the tiny parts that allow the mirror to focus properly. The more powerful the laser (larger the laser aperture), the more delicate and vulnerable the focusing mirror and its components are.Also they never directly handle the full intensity of the focused laser beam, which does not happen until it reaches the target up to 1000 km away. It would be like Johnny with the magnifying glass focusing the beam on an ant. If Johnny puts his hand close up to the glass before the beam is focused, it wouldn't do much of anything. If this is true, then this is why the beam expander and the struts that hold it never are damaged despite always being in the path of the laser. It is unfocused. Lastly the optics of our lasers are essentially telescopes in reverse, they would magnify and intensify any laser beam that hit at the right angle, far above anything the optics are designed to handle. I don't know if the way lasers depicted in game is realistic, but I know some of the assumptions deserve much deeper investigation.I know I had my assumptions questioned when we first started playing COADE. "Isn't one nuke enough?" "Why do we need 100?" I don't plan to argue this much, I'm hoping someone who has real world knowledge of lasers will step in and speak up, these are just my thoughts. Note: I edited this comment dozens of times to make sure the language was as diplomatic as possible. My intentions were/are completely honorable. Just to add a data-point. I work with LIDAR systems for looking at clouds. Our lidars have a 40cm diameter main mirror and the secondary mirror is only ~5cm below the focus of the main mirror. The lidar doesn't scan, but it has stared at or near the sun several times. Putting ~400W in a 2cm diameter spot heats things up a lot, but aluminum tape is enough to shield most parts. (the aluminum secondary mount has gotten above 100C several times, and different fiber-glass mount started slowly smoking ) So what happens if the sun is perfectly aligned with our lidar aperture? By design, all that happens to our system is that the background noise swamps our signal. None of the mirrors or surrounding structure overheat. None of the receiver filters overheat. Even the 100um diameter field stop is fine. Now if the sun was replaced by an equally bright laser at 532nm tuned to the 1109 line of Iodine, we'd probably burn our LIDAR detectors looking at the new green laser sun. Even then, the damage wouldn't be instant and a suitable shutter could be added to block incoming light when it gets too bright. A military laser in a similar situation has it much easier because the attacking beam is going the opposite direction from the normal output. In that case a Faraday Isolator and beam-dump is all that's needed. TLDR, damage to military laser optics due to counter-lasers is an engineering problem with simple solutions, especially when the counter-laser has power/intensity similar to the outgoing laser beam.
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Post by Durandal on Mar 19, 2017 20:24:02 GMT
The foundation of this thread (as I understand it) is... 1. Weak lasers with Watts of power are instantly taking out much stronger lasers. 2. The sun at midday is at best 1000 W/m^2 and if that doesn't hurt anything, then lasers at that power shouldn't. 3. Our laser mirrors are so tough and can take so much intensity, they should be able to handle just as much coming "in". --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- 1. I'm doubting weak lasers (sub 400kW) instantly popping much stronger ones. I'll be posting a video with tests, but I just wonder about this. 2. The sun at midday analogy could work but don't we need to make sure it is a fair comparison? We need to compare optics looking straight at the sun + at midday + at the equator + in a cloudless sky + in the summer + for extended periods. That would be pretty intense. The sun is enough to damage cameras and other optical equipment if their shutter speed isn't fast enough. www.digital-photo-secrets.com/tip/1797/can-i-damage-my-camera-by-pointing-it-at-the-sun/ forums.creativecow.net/archivethread/35/628678Enough to damage a laser? Don't know. 3. Our lasers use "adaptive optics" which are very fragile. They are a bunch of tiny mirrors (or a flexible mirror) on a kind of movable lattice. It wouldn't take much heat to destroy the tiny parts that allow the mirror to focus properly. The more powerful the laser (larger the laser aperture), the more delicate and vulnerable the focusing mirror and its components are.Also they never directly handle the full intensity of the focused laser beam, which does not happen until it reaches the target up to 1000 km away. It would be like Johnny with the magnifying glass focusing the beam on an ant. If Johnny puts his hand close up to the glass before the beam is focused, it wouldn't do much of anything. If this is true, then this is why the beam expander and the struts that hold it never are damaged despite always being in the path of the laser. It is unfocused. Lastly the optics of our lasers are essentially telescopes in reverse, they would magnify and intensify any laser beam that hit at the right angle, far above anything the optics are designed to handle. I don't know if the way lasers depicted in game is realistic, but I know some of the assumptions deserve much deeper investigation.I know I had my assumptions questioned when we first started playing COADE. "Isn't one nuke enough?" "Why do we need 100?" I don't plan to argue this much, I'm hoping someone who has real world knowledge of lasers will step in and speak up, these are just my thoughts. Note: I edited this comment dozens of times to make sure the language was as diplomatic as possible. My intentions were/are completely honorable. Just to add a data-point. I work with LIDAR systems for looking at clouds. Our lidars have a 40cm diameter main mirror and the secondary mirror is only ~5cm below the focus of the main mirror. The lidar doesn't scan, but it has stared at or near the sun several times. Putting ~400W in a 2cm diameter spot heats things up a lot, but aluminum tape is enough to shield most parts. (the aluminum secondary mount has gotten above 100C several times, and different fiber-glass mount started slowly smoking ) So what happens if the sun is perfectly aligned with our lidar aperture? By design, all that happens to our system is that the background noise swamps our signal. None of the mirrors or surrounding structure overheat. None of the receiver filters overheat. Even the 100um diameter field stop is fine. Now if the sun was replaced by an equally bright laser at 532nm tuned to the 1109 line of Iodine, we'd probably burn our LIDAR detectors looking at the new green laser sun. Even then, the damage wouldn't be instant and a suitable shutter could be added to block incoming light when it gets too bright. A military laser in a similar situation has it much easier because the attacking beam is going the opposite direction from the normal output. In that case a Faraday Isolator and beam-dump is all that's needed. TLDR, damage to military laser optics due to counter-lasers is an engineering problem with simple solutions, especially when the counter-laser has power/intensity similar to the outgoing laser beam. Very good to know, thank you. What about if the incoming beam were at a different power/intensity value? Or there were several beams at different intensities/wave lengths?
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Post by deltav on Mar 19, 2017 20:28:46 GMT
The lidar doesn't scan, but it has stared at or near the sun several times.... So what happens if the sun is perfectly aligned with our lidar aperture? By design, all that happens to our system is that the background noise swamps our signal. None of the mirrors or surrounding structure overheat. None of the receiver filters overheat. Even the 100um diameter field stop is fine. Now if the sun was replaced by an equally bright laser at 532nm tuned to the 1109 line of Iodine, we'd probably burn our LIDAR detectors looking at the new green laser sun. Even then, the damage wouldn't be instant and a suitable shutter could be added to block incoming light when it gets too bright. A military laser in a similar situation has it much easier because the attacking beam is going the opposite direction from the normal output. In that case a Faraday Isolator and beam-dump is all that's needed. TLDR, damage to military laser optics due to counter-lasers is an engineering problem with simple solutions, especially when the counter-laser has power/intensity similar to the outgoing laser beam. Thanks for sharing that.
Well it's great you had practical experience with lasers. You are just the man to talk to. I think for this discussion we have to have some boundaries or we won't ever get anywhere with our main problem. Mainly that we stick to unshuttered lasers firing at one another or something very similar. Speaking of one LIDAR firing at another, this guy on the internet is pretty upset at what happened to his LIDAR. About weak sunlight on day with clouds, I'm guessing far from the equator, and Lidar well that's not exactly sun at optimum power. IF we want to talk about what 1000/m^2 sunlight, it has to be focused, or at least at the equator, on a clear day, in the summer, etc to be a fair comparison.Shuttering, beam dumping and faraday isolators may have some effectiveness, it would be countermeasures to counter lasers, and that is another discussion. We here are talking about to what extent real life behavior of 2 lasers firing at one another would resemble behavior in COADE. To that end to agree on anything or get anywhere we need to stick exclusively to a situation not addressed anywhere here, real life data or research on what would happen if 2 lasers were aimed directly at one another shooting at one another for an extended period.
So first we have to establish just what the behavior in COADE is. Almost done with a video that deals with the very issue. I'll just say that things are not as they appear.
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Post by lawson on Mar 19, 2017 21:11:49 GMT
That link is two Lidar speed guns taking each other out. So I assume a linear mode APD reciver and the whole device is cheaper than most optical isolators. (APD's are biased to 100-300V and internal gain to make 100-1000 electrons for each photon. They're also tiny. Makes them easy to burn out.) Good point that we need to confirm the effectiveness of kilo-watt scale counter lasers. Anybody have a YouTube video? Durandal, it's all going to depend on the details of the scenario being tested. It's a wild guess, but setting the counter-laser damage threshold the same as the intensity at the output aperture is a good start.
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Post by vegemeister on Mar 19, 2017 21:33:31 GMT
I'm working on a Liberty Assault Cutter, and my current design has a 100 kw counter-laser feeding 10 turrets with 5 cm mirrors. Intensity at 100 km is 4.5 kW/m2, so a few times brighter than the sun. 3 LACs working together disable enemy lasers as fast as I can re-target the currently-active one.
No video, I'm afraid.
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Post by deltav on Mar 19, 2017 22:00:33 GMT
I'm working on a Liberty Assault Cutter, and my current design has a 100 kw counter-laser feeding 10 turrets with 5 cm mirrors. Intensity at 100 km is 4.5 kW/m2, so a few times brighter than the sun. 3 LACs working together disable enemy lasers as fast as I can re-target the currently-active one. No video, I'm afraid. Making a Laser Sniper video, editing it now, will have it up soon.Features many lasers all basically stock for easy reproduction, but one custom 100 kw laser that can fit in your hand. Will post it here... hopefully in the next half hour. Something else that bothers me. Where did this "GW/M^2 damage threshold" figure come from regarding aluminum optics?Real world sources complain that aluminum optics are very fragile and easy to damage...www.thorlabs.com/NewGroupPage9_PF.cfm?Guide=10&Category_ID=138&ObjectGroup_ID=264Aluminum optics rely on thin coatings, and if that coating goes, the whole laser goes. Here is according to the link, a laser supply company, the best way to calculate laser damage threshold. Our lasers are CW lasers, but I'm not sure how to calculate these numbers just yet. --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- "In order to use the specified CW damage threshold of an optic, it is necessary to know the following: Wavelength of your laser Linear power density of your beam (total power divided by 1/e2 beam diameter) Beam diameter of your beam (1/e2) Approximate intensity profile of your beam (e.g., Gaussian)"
"The power density of your beam should be calculated in terms of W/cm. The graph to the right shows why expressing the LIDT as a linear power density provides the best metric for long pulse and CW sources. In this regime, the LIDT given as a linear power density can be applied to any beam diameter; one does not need to compute an adjusted LIDT to adjust for changes in spot size. This calculation assumes a uniform beam intensity profile. You must now consider hotspots in the beam or other non-uniform intensity profiles and roughly calculate a maximum power density. For reference, a Gaussian beam typically has a maximum power density that is twice that of the uniform beam (see lower right).
Now compare the maximum power density to that which is specified as the LIDT for the optic. If the optic was tested at a wavelength other than your operating wavelength, the damage threshold must be scaled appropriately. A good rule of thumb is that the damage threshold has a linear relationship with wavelength such that as you move to shorter wavelengths, the damage threshold decreases (i.e., a LIDT of 10 W/cm at 1310 nm scales to 5 W/cm at 655 nm):
CW Wavelength Scaling
While this rule of thumb provides a general trend, it is not a quantitative analysis of LIDT vs wavelength. In CW applications, for instance, damage scales more strongly with absorption in the coating and substrate, which does not necessarily scale well with wavelength. While the above procedure provides a good rule of thumb for LIDT values, please contact Tech Support if your wavelength is different from the specified LIDT wavelength. If your power density is less than the adjusted LIDT of the optic, then the optic should work for your application.
Please note that we have a buffer built in between the specified damage thresholds online and the tests which we have done, which accommodates variation between batches. Upon request, we can provide individual test information and a testing certificate. The damage analysis will be carried out on a similar optic (customer's optic will not be damaged). Testing may result in additional costs or lead times. Contact Tech Support for more information."
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Post by deltav on Mar 20, 2017 1:08:49 GMT
Video done, check it out
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Post by bigbombr on Mar 20, 2017 5:33:02 GMT
I'm working on a Liberty Assault Cutter, and my current design has a 100 kw counter-laser feeding 10 turrets with 5 cm mirrors. Intensity at 100 km is 4.5 kW/m2, so a few times brighter than the sun. 3 LACs working together disable enemy lasers as fast as I can re-target the currently-active one. No video, I'm afraid. Making a Laser Sniper video, editing it now, will have it up soon.Features many lasers all basically stock for easy reproduction, but one custom 100 kw laser that can fit in your hand. Will post it here... hopefully in the next half hour. Something else that bothers me. Where did this "GW/M^2 damage threshold" figure come from regarding aluminum optics?Real world sources complain that aluminum optics are very fragile and easy to damage...www.thorlabs.com/NewGroupPage9_PF.cfm?Guide=10&Category_ID=138&ObjectGroup_ID=264Aluminum optics rely on thin coatings, and if that coating goes, the whole laser goes. Here is according to the link, a laser supply company, the best way to calculate laser damage threshold. Our lasers are CW lasers, but I'm not sure how to calculate these numbers just yet. --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- "In order to use the specified CW damage threshold of an optic, it is necessary to know the following: Wavelength of your laser Linear power density of your beam (total power divided by 1/e2 beam diameter) Beam diameter of your beam (1/e2) Approximate intensity profile of your beam (e.g., Gaussian)"
"The power density of your beam should be calculated in terms of W/cm. The graph to the right shows why expressing the LIDT as a linear power density provides the best metric for long pulse and CW sources. In this regime, the LIDT given as a linear power density can be applied to any beam diameter; one does not need to compute an adjusted LIDT to adjust for changes in spot size. This calculation assumes a uniform beam intensity profile. You must now consider hotspots in the beam or other non-uniform intensity profiles and roughly calculate a maximum power density. For reference, a Gaussian beam typically has a maximum power density that is twice that of the uniform beam (see lower right).
Now compare the maximum power density to that which is specified as the LIDT for the optic. If the optic was tested at a wavelength other than your operating wavelength, the damage threshold must be scaled appropriately. A good rule of thumb is that the damage threshold has a linear relationship with wavelength such that as you move to shorter wavelengths, the damage threshold decreases (i.e., a LIDT of 10 W/cm at 1310 nm scales to 5 W/cm at 655 nm):
CW Wavelength Scaling
While this rule of thumb provides a general trend, it is not a quantitative analysis of LIDT vs wavelength. In CW applications, for instance, damage scales more strongly with absorption in the coating and substrate, which does not necessarily scale well with wavelength. While the above procedure provides a good rule of thumb for LIDT values, please contact Tech Support if your wavelength is different from the specified LIDT wavelength. If your power density is less than the adjusted LIDT of the optic, then the optic should work for your application.
Please note that we have a buffer built in between the specified damage thresholds online and the tests which we have done, which accommodates variation between batches. Upon request, we can provide individual test information and a testing certificate. The damage analysis will be carried out on a similar optic (customer's optic will not be damaged). Testing may result in additional costs or lead times. Contact Tech Support for more information."
They're very fragile against scratching, not lasing.
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Post by deltav on Mar 20, 2017 6:55:15 GMT
I ran the tests again. All I can tell is turret speed is very important. More turret speed seems to = better accuracy.Also it only takes a brief direct hit on the optics w/ enough laser intensity to disable a laser. [Turret speed (time on target) x intensity x total power of all detached laser modules]/aperture of enemy laser turret = time to laser disabling? Plus they must have those faraday modules lawson you were speaking of. Why is only the turret disabled but not the detached laser module? Also the beam spreader and struts are coated in the same material as the rest of the turret. It must be that the focusing mirror itself is being attacked by our counter lasers. Still looking for some real world data on laser vs laser sniping. www.thenakedscientists.com/articles/questions/if-you-shone-two-lasers-directly-each-other-what-would-happen------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Edit: So I was thinking. Take the stock 300 MW laser with attached turret.Assuming counter lasers are "focused" on the focusing mirror of the laser they are attacking.The Aluminum focusing mirror is 94.7% efficient, which means 5.3% of the laser light is not reflected, and is absorbed into the focusing mirror as heat. The turbopump is able to handle cooling the focusing mirror normally, but only to a point above abnormal heating (like from a counter laser). If the ambient temp at the focusing mirror goes from 1223 K to 1238 K the mirror melts.How much output energy from a counter laser would it take to heat the mirror 15 K?
I don't know how the fact that the mirror is reflective to a certain wavelength etc comes into it. Watts = 0.018 x Lbs of Aluminum x ΔT (in °F) / Heat-Up Time (in hrs) farnam-custom.com/resources/engineer-talk/how-much-wattage-do-i-need/Not an engineer or a scientist but is this a logical way to go about this? We don't know how much our focusing mirror mass, but we can guess using the aperture and data from real world lasers. Let's say it is a disk w/ a 65 cm radius, which is a diameter of 130 cm. www.loptics.com/faq.htmlI was looking for deforming mirrors that use adaptive optics, but the only thing I could find was for telescopes. So using a round approximation, let's say 51 kg of aluminum. 0.018 x 113 lbs x 27 = 54.918 / Heat-Up Time (in hrs) = Watts Let's say 1 minute = 0.0166667 329 Watts to melt the mirror in question. Am I on the right track with this? Any ideas? Mirror is 13273.228961417 cm^2 which is 1.32732289614170007 m^2 So we would need about 437 Watt/m^2 of laser intensity for 1 minute to melt this mirror. The 400 kW counter laser would reach this intensity somewhere early on, maybe 950 kM out from the 300 MW laser provided the accuracy (turret speed) of the 400 kW is high enough to stay locked on long enough, and the 300 MW laser's turret speed and accuracy is low enough not to take out the 400 kW laser beforehand. If we say 20 secs, 0.005 hrs, that's about 11 kw, 14.5 kw/m^2. Just throwing out some math which is far from my strong suit. Please anyone chime in with suggestions or better math. In counter laser situations, the targeted laser is unshuttered and also firing, we would calculate how much counter laser output is needed to overheat the focusing mirror enough to deform it or melt it (which is usually only a few Kelvin).
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