Armory Sponsor
Posted: 3/9/2015 12:19:11 PM EDT
|
For some days I have been wondering if the autogating function of today's tubes would be fast enough for range gating applications. Then when searching for existing solutions from the net, I bumped into Katod NV's site where they show their NV scope with exactly this function. http://katodnv.com/en/catalog/nigh-vision-sights/
Would be great to have this functionality added to every autogated tube, so that you could control the gating and a laser illuminator at the same time. If the gating is already fast enough I wonder why there isn't more of these. I hate when the bushes and branches blind me when using illumination when where I would like to see is tens of meters into the front. Front illuminated --------------------------------------------------- Middle ------------------------------------------- Back   
|
|
Does anyone know the speed of the autogate function? Does it have a persistence of some kind or is it an instant shutoff and then instant on again? If this is something that can't be discussed here then no problem, ITAR is what it is.
Manual gain tubes already have an interface for changing the gain, it just sounds it would be almost equally easy to expose the gating interval or even to control the gating from external electronics. From the Katod pictures you can see that the furthest areas are always somewhat illuminated, so it seems they keep the gate open longer than they have it closed. In theory you could just illuminate a certain range, like from 20 meters to 25 meters if the gating was fast enough. I doubt it is and maybe that explains the Katod's route of implementation. Obviously this has almost zero use in tactical situations where IR discipline is critical, but for hunting it would be perfect. You could see critters hiding behind a bush by just adjusting the range to illuminate only the backside of the bush. |
|
I think I understand what you are getting at.....maybe.
Sort of like those future weapons shows where you program a 40mm grenade at a certain range to detonate just over the top of the enemy cover targeting only that area. Looking at it from a physics perspective, I don't think its possible. For the same reasons we don't have light sabers, you can't terminate light at a definitive range. I also don't think its possible to control the gating of a tube for a specific distance either. The pictures look like there is artificial light in the background as well, not necessarily "watching" how fast the autogating works. Im sure the autogate response time of the tube is closely guarded by ITAR as you mention but I think the best solution for the result you mention are different power illuminations. Then again I'm no PHD either. CJ may have some better info on this. |
|
You're right, that's pretty much what I was going after.
The point is not to terminate light at a definitive range, but to block that which sees the light (I^2 tube) when necessary. In other words, first you have your tube gated OFF, a laser illuminator flashes a short pulse, the IR light will propagate 1 meter per 3.3 nanoseconds, so if you want only to illuminate objects further than 10 meters, you wait 2 * 10m / (1m / 3.3ns) = 66 nanoseconds before you open the tube gate. This way all the illumination that has bounced back before the 10 meter limit will not be seen by the tube, because it was powered off. Then if you want to limit the range from 10 meters to 20 meters and not beyond, you close the gate again when light has had the time to travel the 20meters * 2 distance. The IR illuminator must not be on during the time the tube gate is open as it would ruin the whole thing. The idea is to send a quick flash and then begin waiting until that flash begins to reflect back from the desired distance. Then rinse and repeat and it will look like you have constant illumination when in reality it's modulated very rapidly. I'm sure there is limits to how fast you can do it, but the two main requirements are that the IR illuminator must be able to shut off fast and the tube gate must open real fast. Here's a pretty drawing of the situation: 
You mention different power illuminators and that works for the most part, but has the big problem of shutting an autogated tube to it's dimmest if you have anything close by reflecting the light back at you. Also the benefits of being able to limit the range of your illumination would be obviously handy. You could look behind bushes with ease, assuming there is holes in the bush that allow even some light to go through. |
|
I would think that in order to determine the range to a light source that is illuminating a pixel, you'd need stereo tubes. That, or a laser rangefinder that does a raster scan in parallel with the pixels of the tube. If you had either of those, then I'd think it wouldn't be difficult to auto-gate on a per pixel basis. But I don't know nuthin'! |
|
Quoted:
I would think that in order to determine the range to a light source that is illuminating a pixel, you'd need stereo tubes. That, or a laser rangefinder that does a raster scan in parallel with the pixels of the tube. If you had either of those, then I'd think it wouldn't be difficult to auto-gate on a per pixel basis. But I don't know nuthin'! I don't mean that you should determine a range to a source, but have the source attached to your night vision scope and slaved to the tube gating frequency in a way. You would need to limit when the illuminator is on & off and when the tube gate is on & off. Light propagates with a known speed, so you can just wait "eyes" closed until your clock shows it's time to open them to begin seeing the light that is bouncing back from a distance further than the bush directly in front of you. The light that bounced from the bush has gone already, it's nowhere to be seen (except from behind you, but that doesn't matter). And the range would be dialed in by you, a knob that controls the time how long the tube gate is closed after the IR pulse is sent. Thus no real range in meters is known or needed, you will be able to tune it by seeing. The IR illuminator would not be on the whole time, it would only send quick pulses when the tube gate is closed. I'm not sure about if my terminology is correct. The term "range" might throw you off, because the idea is not to range in the sense of figuring out a distance like laser range finders do. With range gating I mean opening and closing the tube's gate per a time light uses to travel a certain distance. Also the illuminator doesn't need to be laser, I just figured it might be the fastest one to shut off, and I have no real basis for that assumption, it just sounds cool 
|
|
Quoted: I don't mean that you should determine a range to a source, but have the source attached to your night vision scope and slaved to the tube gating frequency in a way. You would need to limit when the illuminator is on & off and when the tube gate is on & off. Light propagates with a known speed, so you can just wait "eyes" closed until your clock shows it's time to open them to begin seeing the light that is bouncing back from a distance further than the bush directly in front of you. The light that bounced from the bush has gone already, it's nowhere to be seen (except from behind you, but that doesn't matter). And the range would be dialed in by you, a knob that controls the time how long the tube gate is closed after the IR pulse is sent. Thus no real range in meters is known or needed, you will be able to tune it by seeing. The IR illuminator would not be on the whole time, it would only send quick pulses when the tube gate is closed. I'm not sure about if my terminology is correct. The term "range" might throw you off, because the idea is not to range in the sense of figuring out a distance like laser range finders do. With range gating I mean opening and closing the tube's gate per a time light uses to travel a certain distance. Also the illuminator doesn't need to be laser, I just figured it might be the fastest one to shut off, and I have no real basis for that assumption, it just sounds cool Quoted: Quoted: I would think that in order to determine the range to a light source that is illuminating a pixel, you'd need stereo tubes. That, or a laser rangefinder that does a raster scan in parallel with the pixels of the tube. If you had either of those, then I'd think it wouldn't be difficult to auto-gate on a per pixel basis. But I don't know nuthin'! I don't mean that you should determine a range to a source, but have the source attached to your night vision scope and slaved to the tube gating frequency in a way. You would need to limit when the illuminator is on & off and when the tube gate is on & off. Light propagates with a known speed, so you can just wait "eyes" closed until your clock shows it's time to open them to begin seeing the light that is bouncing back from a distance further than the bush directly in front of you. The light that bounced from the bush has gone already, it's nowhere to be seen (except from behind you, but that doesn't matter). And the range would be dialed in by you, a knob that controls the time how long the tube gate is closed after the IR pulse is sent. Thus no real range in meters is known or needed, you will be able to tune it by seeing. The IR illuminator would not be on the whole time, it would only send quick pulses when the tube gate is closed. I'm not sure about if my terminology is correct. The term "range" might throw you off, because the idea is not to range in the sense of figuring out a distance like laser range finders do. With range gating I mean opening and closing the tube's gate per a time light uses to travel a certain distance. Also the illuminator doesn't need to be laser, I just figured it might be the fastest one to shut off, and I have no real basis for that assumption, it just sounds cool I'm approaching it from the standpoint that illuminating nearby objects causes gating, which obscures distant objects that are being hit with less light. I think I see what you're getting at, but since the bush is being illuminated before the distant objects, would the distant objects ever get illuminated? Let's say light takes 1 second to hit a bush 20 yards away, and 5 seconds to hit an object 100 yards away. You want to see the object at 100 yards, but the system is shutting the tube and the illuminator down every 2 seconds, so as to prevent the bush from being illuminated. |
|
Quoted:
I think I see what you're getting at, but since the bush is being illuminated before the distant objects, would the distant objects ever get illuminated? Let's say light takes 1 second to hit a bush 20 yards away, and 5 seconds to hit an object 100 yards away. You want to see the object at 100 yards, but the system is shutting the tube and the illuminator down every 2 seconds, so as to prevent the bush from being illuminated. Yes exactly like that. If you would like to see the object at 100 yards, the sequence would be: at 0 seconds: send the quick & bright IR pulse. Tube is gated off at 1 second: bush at 20 yards gets illuminated, and the IR light bounces back. The tube is powered / gated off at this time. at 2 seconds: the reflection from the bush at 20 yards arrives back, but the tube is still gated off, so no overillumination & autogating happens here at 5 seconds: bush at 100 yards gets light. Tube is still gated off. at 10 seconds: the reflection from the bush at 100 yards arrives back and the tube gate is opened (because we dialed in a 10 second delay by hand), thus you see the scene as if only the bush at 100 yards was illuminated and anything between you and that bush is as dark as it would be without any IR assistance Then after a while close the tube gate again and start the process from the beginning. Obviously these things happen in nanoseconds, so the tube would not be gated off for long periods that could be seen as flickering. This probably should be an alternative to autogating. If the light levels exceed a certain threshold when autogating should kick in, perhaps it should to prevent damage. Then you would lose the ranging function, but that's something you probably can't do anything about. |
|
Quoted: Yes exactly like that. If you would like to see the object at 100 yards, the sequence would be: at 0 seconds: send the quick & bright IR pulse at 1 second: bush at 20 yards gets illuminated, and the IR light bounces back. The tube is powered / gated off at this time at 5 seconds: bush at 100 yards gets light. Tube is still gated off. at 10 seconds: the reflection from the bush at 100 yards arrives back and the tube gate is opened (because we dialed in a 10 second delay by hand), thus you see the scene as if only the bush at 100 yards was illuminated and anything between you and that bush is as dark as it would be without any IR assistance Then after a while close the tube gate again and start the process from the beginning. Quoted: Quoted: I think I see what you're getting at, but since the bush is being illuminated before the distant objects, would the distant objects ever get illuminated? Let's say light takes 1 second to hit a bush 20 yards away, and 5 seconds to hit an object 100 yards away. You want to see the object at 100 yards, but the system is shutting the tube and the illuminator down every 2 seconds, so as to prevent the bush from being illuminated. Yes exactly like that. If you would like to see the object at 100 yards, the sequence would be: at 0 seconds: send the quick & bright IR pulse at 1 second: bush at 20 yards gets illuminated, and the IR light bounces back. The tube is powered / gated off at this time at 5 seconds: bush at 100 yards gets light. Tube is still gated off. at 10 seconds: the reflection from the bush at 100 yards arrives back and the tube gate is opened (because we dialed in a 10 second delay by hand), thus you see the scene as if only the bush at 100 yards was illuminated and anything between you and that bush is as dark as it would be without any IR assistance Then after a while close the tube gate again and start the process from the beginning. But the light bouncing back from the bush is gated every 2 seconds. Thus, it would be gated at 2, 4, 6, 8, 10 seconds, etc. And you're not waiting 1 second to send out a new 'pulse' of light, so the gating would take place every 0.000000537 seconds (assuming you use a laser.) |
|
Quoted:
But the light bouncing back from the bush is gated every 2 seconds. Thus, it would be gated at 2, 4, 6, 8, 10 seconds, etc. And you're not waiting 1 second to send out a new 'pulse' of light, so the gating would take place every 0.000000537 seconds (assuming you use a laser.) Does it have to gate every two seconds? If the gate time was adjustable and you could dial in it to gate for longer periods, keep the gate closed for 10 seconds (while the IR light propagates to the object and back), open the gate for some period and close again. It would not be automatic gating for adjusting brightness, but periodic depending on which ranges you would like to see illuminated. With seconds I mean only to illustrate some times, like you said it's nanoseconds in reality |
|
While it seems the topic is not particularly interesting to other than me, I have to update that Hamamatsu website had the information for gating speeds. Their I^2's gate rises in 5 nanoseconds from off to on. That means the gate time is in the ballpark for range gating applications as light will only travel 1.5 meters in that time. That kind of timing would provide a pretty sharp cutoff for the illumination, you would see the scene illumination begin gradually withing 1.5m of the desired range. If their gate closes in the same time, then limiting the far end of the illumination range would be no problem either.
From that information I can draw the conclusion that Katod might actually have a scope that does this. Hamamatsu probably has higher quality tubes than what Katod has, but the gating tech could be similar in speed. |
|
Quoted:
Isn't the phosphor decay time longer than that? How would you be able to see the effect if the phosphor remains illuminated in the off period? From what I think it should not matter how the phosphor behaves, only what comes into the intensifier. The phosphor screen won't show anything that doesn't come through the MCP, thus if the voltage is cut off during periods when unwanted illumination is being "received" / reflected back, you won't see it. So even if the phosphor is slow, it only means the image updates slower. I might be missing something, but I can't figure why it couldn't work. With continuous illumination from an IR torch it doesn't, but the IR torch must be pulsed so that it's cut off before the MCP voltage is turned back on, and only turned briefly back on when MCP is cut off. |
|
Here's an example with a digital NV. I don't know how they do the actual gating, might be it's just the sensor that is fast enough. If you think you would replace the digital screen with an analog phosphor screen, it would make no difference. In I^2 the "sensor" is gated and the display is pretty much continuously on, updating the image when electrons hit it. It wouldn't still show anything that isn't coming into the MCP, but wouldn't flicker either because of the persistence.
Range gated digital NV video |
|
Quoted:
Active range gating has been around since at least the 1970s (gen 1 devices). Problem is the electronics for syncing the laser and image intensifier gates is larger than handheld. Used for accurate range-finding and "seeing" through fog and smoke. Should the case still be that the electronics would be that large? The gating stuff is embedded into the PSU of the I^2 already, you would only need a control signal from outside to tell the PSU when to do it. With the same signal turn the laser on and off, just reversed of course. Crystal oscillators can be really fast so the problem shouldn't be that of accuracy at that point. I bet it can be put into a small microchip, but I have no first hand experience obviously, so there might be more to it. Interesting to hear it's been around that long. The gating times are so unbelievably fast that my guess was it was a newer thing. |
|
Quoted:
Active range gating has been around since at least the 1970s (gen 1 devices). Problem is the electronics for syncing the laser and image intensifier gates is larger than handheld. Used for accurate range-finding and "seeing" through fog and smoke. |
|
Quoted:
Have you tried it in fog and smoke? Quoted:
Quoted:
Active range gating has been around since at least the 1970s (gen 1 devices). Problem is the electronics for syncing the laser and image intensifier gates is larger than handheld. Used for accurate range-finding and "seeing" through fog and smoke. Here's a PDF from some company that makes digital range gating systems. There's a picture of fog with and without range gating, plus a few other examples. Really bad low res pics, but it gives some clues how it might work. http://www.laseroptronix.se/gated/Rangegatedcameras.pdf |
|
All Gen2 and Gen3 tubes can be gated - Note that Autogating and Gating are related, but different. If you could control the gating pulse of an autogated system, then all you need is an illuminator with a variable pulse width frequency modulator and connect this to the PSU of the tube such that it gates at a variable delay in sync with the illuminator - Such devices can see underwater quite well- if you looked into a lake with that scope you'd see fish swimming around, sunken boats, etc. They also see through fog very well due to elimination of near-field backscatter. Ultimately, they are pretty neat and perfect for hunting too. Even to the point that you will see things behind bushes and trees that would normally be obscured by leaves. Anyway... PSU. The tube PSU is the problem - You need one with a gating input. As for how fast the tubes are? You could probably light up a target's nose and leave his ears in the dark... They are that accurate - Picoseconds for Gen2/Gen3 tubes. ( Except inverters of the old MX9644 type - they are a little slower to gate because of the voltages involved and the capacitance of the tubes ). Picoseconds is the simple answer... These tubes can all gate in the picosecond region. Also, you can variably gate based on range - this makes the illuminator appear brighter the further you get away - it's just another mode of operation, but would be very useful if using a very high powered illuminator - eg, one that would go for kilometers - in an area with a lot of scrub or bush. Also, because you're using an illuminator, you can get away with a lower spec tube :) Nice to see someone has made good use of it - I imagine this may increase in popularity. It would make target identification a lot easier. These devices have specific military uses for search and locate applications and are covered by their own specific section of ITAR. Russia is well ahead of the US in development of these systems - Regards David |
|
cj7hawks comment makes me wonder two things:
Do any manufacturers use gating-capable power supplies, but tie the gating pin to a total current demand sensor, and merely fail to bring an extra lead out from that gating pin for customer applications? And, Do the the manual gain control-capable scopes use the gating pin to induce a steady-state, but variable bias to the gating pin - and could the pulse-modulated, timed gating pulses merely be applied between two of those leads to accomplish the same result? |
|
Quoted:
cj7hawks comment makes me wonder two things: Do any manufacturers use gating-capable power supplies, but tie the gating pin to a total current demand sensor, and merely fail to bring an extra lead out from that gating pin for customer applications? And, Do the the manual gain control-capable scopes use the gating pin to induce a steady-state, but variable bias to the gating pin - and could the pulse-modulated, timed gating pulses merely be applied between two of those leads to accomplish the same result? Good questions. I have a feeling that to your second question the answer is no, because there was manual gain tubes before Autogating came into the PSU's. I doubt they would've changed it to that. Though makes you wonder has Katod made a custom tube for their scope, or do they actually use a gating pin for the manual gain already and just took advantage of it? The device seems to have four knobs in the control box. I assume one is the gate pulse width, one is delay, one might be manual gain and is the last one just a ON/OFF switch. |
Found and interesting piece of info from a YouTube video of an ICCD camera which apparently uses Gen3 tubes. It says like this, look at the gate time and the (3) at the bottom:
It says it can be externally gated, so some tubes do expose the interface. Edit: I'm guessing this is a Hamamatsu Gen3 tube they are using, because the numbers are the same and cj7hawk talked about gating being picoseconds with US made tubes. But anyway, at least someone (besides Katod) does make tubes with exposed controls. |
|
The gating function as defined in that brochure is based on the PSU specs - the tube itself will gate as fast as you can move the power, so is based on the speed and power of the transistors that do the gating - All tubes are pretty quick to gate - Here's an article that explains some of the electronics/technical aspects of the process - http://www.researchgate.net/publication/252497252_Self-tuning_flexible_output_nanosecond_gate_unit_for_image_intensifiers_and_photomultipliers This one talks about nanoseconds and picoseconds in a way that will demonstrate context. Regards David |
|
Quoted:
The gating function as defined in that brochure is based on the PSU specs - the tube itself will gate as fast as you can move the power, so is based on the speed and power of the transistors that do the gating - All tubes are pretty quick to gate - Here's an article that explains some of the electronics/technical aspects of the process - http://www.researchgate.net/publication/252497252_Self-tuning_flexible_output_nanosecond_gate_unit_for_image_intensifiers_and_photomultipliers This one talks about nanoseconds and picoseconds in a way that will demonstrate context. Regards David Thanks, that makes it a lot clearer. The next question I have is how digital (non-photocathoded-CCD's) can be gated this fast. Not saying thanks cj7hawk, please do the research for me and paste the good bits, just interested why there isn't cheap range gating scopes. My guess would be the lack of an photocathode makes it harder as you have nothing to shut off so fast. But let's see what the Internet can teach me. |
|
Quoted: Thanks, that makes it a lot clearer. The next question I have is how digital (non-photocathoded-CCD's) can be gated this fast. Not saying thanks cj7hawk, please do the research for me and paste the good bits, just interested why there isn't cheap range gating scopes. My guess would be the lack of an photocathode makes it harder as you have nothing to shut off so fast. But let's see what the Internet can teach me. Quoted: Quoted: The gating function as defined in that brochure is based on the PSU specs - the tube itself will gate as fast as you can move the power, so is based on the speed and power of the transistors that do the gating - All tubes are pretty quick to gate - Here's an article that explains some of the electronics/technical aspects of the process - http://www.researchgate.net/publication/252497252_Self-tuning_flexible_output_nanosecond_gate_unit_for_image_intensifiers_and_photomultipliers This one talks about nanoseconds and picoseconds in a way that will demonstrate context. Regards David Thanks, that makes it a lot clearer. The next question I have is how digital (non-photocathoded-CCD's) can be gated this fast. Not saying thanks cj7hawk, please do the research for me and paste the good bits, just interested why there isn't cheap range gating scopes. My guess would be the lack of an photocathode makes it harder as you have nothing to shut off so fast. But let's see what the Internet can teach me. Eh? There are cheap range-gated scopes - The Russian companies sell them - :) They are great for searching lakes. I saw some nearly 20 years ago. Anyway, the fastest shutters in the world are photocathodes - Nothing else comes close - The digital solution is an array of cameras timed to go off one after another - You see this used a lot in special effects - but it's very different from photocathode like speeds - They use image tubes for all that kind of work - Streak tubes are another similar product - a steerable image intensifier - Good for taking high speed pictures of bullets in flight and the likes - Regards David |
|
Quoted:
Eh? There are cheap range-gated scopes - The Russian companies sell them - :) They are great for searching lakes. I saw some nearly 20 years ago. Anyway, the fastest shutters in the world are photocathodes - Nothing else comes close - The digital solution is an array of cameras timed to go off one after another - You see this used a lot in special effects - but it's very different from photocathode like speeds - They use image tubes for all that kind of work - Streak tubes are another similar product - a steerable image intensifier - Good for taking high speed pictures of bullets in flight and the likes - Regards David Right ok, so there are them =) Now that you say, there's no reason why they couldn't be Gen1 with very powerful IR torches. All my searching results to either military, research or other kind of ranging stuff, haven't seen those old ones come up in Google. |
|
I thought this German system that was range gated was neat:
http://www.optoprecision.de/en/security-systems/our-products/video-surveillance-systems/range-gated-camera-systems/ It even did coloring to show the various ranges in the field of view. |
| Couldn't you range gate in multiple stages so that you get a complete picture with the benefit of range gating, like that German optic? Say you are always range gating, but are constantly adjusting the gating time, so you start close and pulse further and further away. If we are in picoseconds or even nano seconds I would think you could get images from multiple distances while still holding a 60hz or better refresh rate. It would seem you could get the detail from all the different distances and "blend" them into one image that still is smooth to motion. |
|
Quoted:
Couldn't you range gate in multiple stages so that you get a complete picture with the benefit of range gating, like that German optic? Say you are always range gating, but are constantly adjusting the gating time, so you start close and pulse further and further away. If we are in picoseconds or even nano seconds I would think you could get images from multiple distances while still holding a 60hz or better refresh rate. It would seem you could get the detail from all the different distances and "blend" them into one image that still is smooth to motion. I think what you are describing is what cj7hawk proposed a while back, a varying gate time for the "sweep" from close to far away, so that the illuminator would seem to be dim at close and get brighter and brighter the further it shines. Short gate times right after the IR pulse and longer and longer gate times until a given time has gone after which you close the gate and send the IR pulse away again. That way you could still see through objects without them blinding the view. |
|
If you had a range-gated system and I had a non-gated system and was observing you, would it appear from my perspective that you're having a laser-light party rave under NVG's?
How could a group of people utilize this technology together without each persons sequence tripping up the other peoples images? in a very small group, you could have a series of wavelengths assigned, and each NVD has a slightly different notched filter to allow ONLY the ir wavelength of your unit through, but that would become logistically challenging for large institutions. Alternately you could synchronise them all beforehand, this would require EXTREMELY accurate clocks and when we are talking nano-seconds and pico-seconds, honest to god time dilation will become an issue if one group of troops were moving at ground speeds and another travelling on transport aircraft. You could battle network them all via bluetooth or wifi, and with some accelerometers so they are spatially aware, that way when I am looking in your direction the range gating feature cuts way back so our "force" doesn't constantly blind itself. |
|
Yep that's certainly an issue =)
The Katod NV scope does the IR pulses at 30Khz so it wouldn't show as a rave party, but I doubt anyone is willing to build man portable range gating systems that sync with each other, quite an ordeal I guess too. On the other hand, if you have a close group, only one of them could have the illuminator pulsing at a known frequency and the rest could tune their gate times accordingly. Not sure how convenient that would be, but at least it would work to some extent. I'm personally not that interested in this other than having an convenient illumination system when I'm alone in the woods (usually). My thinking is this is quite simple to implement if the gate interface would just be exposed. Would not many pennies extra to expose it and a few hundred bucks for someone to take advantage of it. |
Armory Sponsor