o/t tank night vision sights question

[dog of war]

have a question i hope some one can answer not relating to the game

it concerns tank night vision sights

reading through a couple of different books giving specs on various tanks the night vision section has me confused .russian tanks and early us/nato had active infra red .fine

modern us/nato have passive imaging or thermal imaging .is passive and thermal the same thing .if not what is the difference.how they work

[gibsonm]

No.

By “Passive” I think you mean Image Intensifier. These harness the existing light and amplify it to create an image. This is how starlight scopes and most current night vision goggles work.

These only work at night as during the day the light is bright enough.

“Thermal” relates Thermal Imagery. This uses the heat signature of a given object compared to the background. TI sights can be used during the day or night as they can see say a running tank engine through fog or mist or rain or whatever.

Both are passive systems in that they don’t project a beam as the old active Infra Red systems did.

[flamingknives]

There are two commonly used night visions systems.

Image Intensification

This amplifies the light available. The output is usually green since the human eye can resolve more shades of green than any other colour, but it is almost always monochrome.

Thermal imageing

This 'sees' in the infra-red frequency range and so can pick up emitted heat

Both systems are passive (i.e. do not need an output like a radar to see)

Systems described as active infrared are very similar to image intensifiers (change light that you can't see into a display that you can) but they are also sensitive to near infra-red as well. When used in conjunction with an infra-red spotlight they can be used see the otherwise invisible light that the spotlight throws out. Civilian first generation night vision on video cameras and the like also use this technolgy and will have an IR illuminator built in.

Unfortunately, anyone else with image intensifiers can see your searchlight. It's similar with some lasers and image intensifiers used in night vision goggles. With the goggles on you can see the laser, without and you can't.

[SgtMuhammed]

Active IR means they shine an IR spotlight and look at the reflected light. The recievers are not as sensitive as later generation vision devices and so don't work well without the added illumination of the IR spot.

Passive IR sensors use more sensative IR recievers and are more aptly called light amplification. They can intensify any light source to allow you to see in extremely low light. They do, however, require some sort of light. In a perfectly dark room you can't see anything. This is why most NODs (Night Optical Devices) come with a small IR spotlight build in.

Thermal imaging is based off of temperature differences. Originally they could detect 1 degree of temperature difference and produce an image, and they have only gotten better. Thermal sights can get an image even if the room is perfectly dark because all materials absorb and radiate heat differently. The only way to effectively hide from a thermal device is to either achieve the same temperature as the air around you or get behind something.

[SgtMuhammed]

I knew you guys were posting as I was writing. I could feel your presence.

[M1A1TC]

The hottest things on a vehicle in your thermal sights are usually the engine compartment and the track. We, as tankers, fight mostly using thermals, so we have to learn thermal signitures of many vehicles, friendly or enemy

[gibsonm]

Originally posted by SgtMuhammed:

I knew you guys were posting as I was writing. I could feel your presence.

Well at least we all said basically the same thing.

Could have been untidy if they had been radically different.

[Flanker15]

Couple of corrections:

Passive IR is the same thing as thermal imaging, which visualizes radiant heat given off from objects.

Active IR is as described above, the visualization of reflected IR off objects from a spotlight.

Image intensifiers don't use IR and simply boost the available light coming in, they're commonly what are called night visions goggles. They work by taking the available photons transferring them to electrons, boosting the amount then emitting them back out as photons to your eye.

[gibsonm]

You can have II on vehicles too.

The British Scorpion CVRT had II as a night vision aid for the gunner. This is mounted into the mantlet and requires the gunner to switch from the day to night sight to use it.

[flamingknives]

The thing is that image intensifiers are not limited to the visual spectrum, and they will pick up photons in the near infra-red band an re-emit them as visible light.

Since early image intensifiers did not have sufficient amplification to work to any useful distance with naturally occuring visible light, the active IR searchlight was often added, since this was still invisible to the unaided eye. This lack of amplification is also why the "starlight scopes" had such enormous objective lenses.

[SgtMuhammed]

Strong IR sources will show up with II devices as well. We could see the hot parts of a camp stove even after the glow was no longe visible to the naked eye. IR chemlights are also invisible to the Mk1 eyeball but bright as day under NODs. Things like vehicle exhaust pipes are also brighter.

And you should see what a pair of PVS7's do for a comet. Awesome.

[FAI]

So, in a low-light condition firefight, soldiers using active IR would at a great disadvantage over opponents using passive?

[SgtMuhammed]

Unless they had some sort of light or IR source. Then again it would be easier to blind more sensative optics than the older ones although both will go blind if something like an illum round goes off.

[flamingknives]

Even if they had an IR light source, the "active IR" chaps would be at a serious disadvantage, as later generation II would see their lights, and thus them, at a far greater distance than they'd see the passive guys.

It becomes more equal if you have an IR illuminating flare or something.

Versus someone with no II or TI equipment, active IR would fare better than plain II.

[SgtMuhammed]

Right. It's like walking around with a flashlight. If you are the only one who can see the flashlight then you are golden. If everyone can see it then you have made yourself a rather large target.

[SpitfireXI]

On a related note, why can't my Abrams see targets in or through smoke screens? I was under the impression that they could.

[gibsonm]

Who has fired the smoke?

If it is “multi spectral” smoke (as opposed to just WP) then it is designed to defeat TI, in either direction.

So if the multi spectral smoke lands between say an M1 and a TI equipped T-72, then the M1 can’t see the T-72 and nor can the T-72 see the M1.

Its impossible to make this stuff like a one way mirror.

[SgtMuhammed]

This is the product of much debate. All US combat vehicles use multispectral smoke. While this might not be the case in Iraq where there is no real threat from sophisticated ATGMs. In Syria, where we KNOW they have the latest Russian gear it was decided that vehicles would be loaded with multispectral smoke because the enemy would have Thermal Imaging sights.

So the short of it is, the Abrams can't see through its own smoke because it is designed to defeat thermal sights.

[SpitfireXI]

Ah! Very interesting now that makes sense. However, I often have seen my Abrams not be able to see through smoke caused by its use of its weapons on a building or when a building collapses, should'nt the sites be able to see through that?

[gibsonm]

“see” or “target”?

If you are “targeting” then this also includes the laser range finder giving a range and confirming LOS.

Lasers tend to “back scatter“ when fired through large amounts of dust and debris like a collapsing building and give multiple readings to the target.

Perhaps that is what you are observing?

[M1A1TC]

Dont forget that Abrams has an axillary Mk1 Eyeball sight that looks exactly at the same spot where the main gun is aiming at. So possibly you could get a glimpse of your target using that through the smoke, versus thermals.

Also, the M1A1 driver's night periscope is image intensification, not thermals. They might have changed that in M1A2

[gibsonm]

Sure, but that’s why I’m asking what is he doing when he is talking about “seeing”.

If by that he means “I select target but the line doesn’t go through the smoke” then the driver or the GAS has nothing to do with it.

AFAIK “Target” means using the GPS to provide LOS and the range info.

[SpitfireXI]

Thanks for the reply, what I often like doing is firing at a building to make it collapse. After a few shots the Abrams stops and I order them to keep firing but the los tool says it cannot 'see' the building because of the smoke created by the previous rounds.

[MikeyD]

A collapsed building is not 'smoke' per se, its debris. You're trying to see through asbestos particles and powered wall board and bits of teddy bear innards floating above the wreckage. And that debris could very well be giving off its own thermal signature. After that 'smoke' settles you'd need a shovel to dispose of it.

[SpitfireXI]

That's true, never thought of it that way. Teddy bear innards!