I've been wondering how the iPhoneX dot projector looks under NODs, but when testing it out in the past I couldn't see anything and then never thought about it again. Now a few days ago I learned it turns the projector ON only if it recognizes a face with the regular NIR flood + the front NIR camera.

Of course I had to check it again and to my surprise some odd shapes popped out in both of the tubes. I took pics of only one of them because the other is pretty much clean. There's another odd thing about the other tube in the DTNVG that while being almost clean of these shapes, it has them reversed in a way that it has light shapes while the other has dark.

Otherwise both of the tubes are clean, no blems or non-uniform amplification. The tube that shows this more, the one pictured, does seem to have some part of not exactly straight because halos are larger toward one side and considerably smaller at the opposite side. The other tube has uniform halos (and smaller overall).

Edit: forgot to mention the shapes are 100% stationary. Doesn't change if focusing or by changing where the projector is / what it is shining onto. You can't see even a slightest hint of them normally.

The dot projector is pointed to the ground (not in focus) and NOD pointing down. If it makes any difference the projector is a VCSEL type laser. The odd shape is visible also if the dots are in focus though not as much. I don't know the wavelength or if there is some odd polarization going along too. The projector is visible to the naked eye even though it's low power in the 4-6 dots (of 30k, so a fraction of total power) visible when looked directly at with your eye.

What are these?

Here's the same pictures, but the first has the red circle showing the area that has the smallest halos, about the same size (maybe still a tad bigger) than in the tube that is mostly clean of these shapes. Like I mentioned in the first post, the other tube that is almost free of this oddity has very small halos over the whole area. The yellow area shows interesting "streaks" that start as dark from the edge and then turn into lighter ones.

The second picture is just the same, but adjusted to show the shapes clearer.

Forgot to mention the tubes are both thin filmed. The major difference being halo size, otherwise quite close, in age & overall image quality.

What is a dot projector?

It's part of the facial recognition software. The iPhone projects an array of tiny IR dots onto your face in order to read the shapes of your face. I believe it is the reason a mere photograph would not work to trick the facial recognition software.

Yeah, it's a small laser that has some kind of a pattern etched (or so I think) on it so that it projects 30,000 IR dots instead of a single point laser.

Why the shapes pop up when a tube is illuminated by the light from that kind of a laser is a total mystery to me and so are the shapes. It's odd they are both dark and light, one "line" starts as dark but then changes to lighter hue than what's on the areas where you see normally. If there was some object at where I took the pic it would be visible too, along with that shape / mess. The right bottom corner marked with red is a part where the object would be visible pretty much like usual, like it was just illuminated with any IR laser.

I'd get this more easily if I pointed the laser directly at the tube, but there must be some property in the laser that despite being reflected from the ground a tube that sees the reflection sees something that is never otherwise there. Maybe they are old bright lights that have left marks on the tube and maybe for some odd reason they become visible under this specific type of laser light. Though the tubes have seen pretty much the same kind of life and due to the halo size thing I explained I think it might have something to do with this.

Not that this has any practical purpose whatsoever (unless this is a way to check if a tube has been used a lot or not much, though seems it isn't as the other tube is a lot clearer), purely curiosity as to what it is and why it happens.

You normally don't see this when opening your iPhone with NODs on as the dot projector is not enabled then. It only enables when a face (without NODs) is recognized first and then it scans the face more accurately, like a LIDAR.

If any of you reading this have an iPhone X you can (at least on my phone) get the dot projector stuck on by going to Messages, open up a conversation and bring up the keyboard, then tap the camera icon (could be this icon is there only in iOS 12 version), when the camera opens up switch to front camera, and then tap the flowery looking button on left bottom that enables the filters to be added. It starts scanning with the dot projector and keeps doing it no matter if a face is present or not.

Here’s a video capture of the iPhone

I'm going to guess that it is because the laser is polarized, and there is something that has been used on the optics, possibly when cleaning it, that left a film that is polarizing depending on it's thickness.

you could try to get a pair of polarizing sunglasses, put it infront of the nvd, shine the iphone laser, and rotate the sunglasses to see if anything changes as you rotate the plane of polarization in front of the nvd

edit - I may be over complicating things. try rotating the iphone or the nvd and see if the opacity of the shapes changes

My guess is that is a good guess

The video in the previous post did not show nothing in their tube, though my conditions were absolute dark versus their high light where the laser is considerably dimmer. Not much was visible when I first saw this in a same kind of a setting.

Moving / rotating doesn't change the shape / opacity in any way, so my thinking goes that it's not linearly polarized then. I have some circular polarizing filters somewhere I could try.

Circular polarizers did nothing. Also noticed that in light levels similar to in the previously linked video the shapes can't be seen - they pop up the best when it's the only illumination.

Though now noticed something different, it's not only the dot projector, but also the proximity sensor IR led that is very dim and has a narrow throw. The iPhone has 3 IR lights, the dot laser, a bright flood for good illumination for the NIR camera, and then the proximity sensor. the flood doesn't show the shapes, but the dim proximity led does.

Will need to try linearly polarized glasses / filters next.

could be that the exact frequency of the laser matches the sensitivity some of the deposited GaAs if they deposit slightly different chemical combinations to cover more frequencies or mixes on the photocathode , or maybe its just showing the thicknesses of the deposit - thats all i can think of so far- is the tube clean and even in normal use ?

Yes, both are clean in regular user or under other illuminators. Good guesses, interesting stuff if true.

Image viewed in tube rotates with tube being rotated while light source stationary? or image moves as light source is rotated and tube is stationary?

Image seems "imprinted" onto the tube input. Does not change when moving/rotating the tube - the image rotates with the tube, just like a blem would. Also does not change in any way if light source is moved/rotated or if objective lens is focused (rotated). If the projected dots are brought to focus (NOD focus set to wherever the dots are reflecting from) then the shape is only marginally visible due to it showing only on the portions that are illuminated by the dots. The projector is rather dim so the test picture was taken at distance of about 40cm from the ground where the light was shining onto (NOD focused to infinity, so the illuminated area seems uniform as it's very blurry).

Edit: the shape does change "in any way" if the light source is moved, but only in a similar way that a normal illuminator would. Bring the illuminator closer, making the illuminated area brighter -> the shapes become brighter accordingly. If the area that is illuminated is only partially covering the image seen though the tube then only that portion shows the shapes.

So in other words, it's just like any other illuminator, but wherever the light is seen, along with the brightness of that area going up also the shapes become visible. I could try taking a video.

Not sure if it’s a bonding agent for fiber optic inverter. Does any other light source cause this?

Does turning eyepiece focus slightly change the image you see?

I tried to reproduce any kind of pattern similar to what was pictured, but couldn't.

could you post a picture of what you were doing, so I can see if I tried to reproduce your images correctly?

also, does your device have a gain? if so, what happens when the gain is changed?

thanks

No had not seen under any other illuminator. I am sure you replicated it just fine, but doesn't show in your tube. The setup is just as simple as you'd think, a NOD, iPhone and a dark place. Anywhere where the dot projector is seen bright enough shows the shapes. No manual gain, F9800 series tubes.

Eyepiece focus doesn't affect the shapes.

But, seems cnoct has either by coincidence uploaded a video describing this or he's read/heard and decided to upload a related video: https://www.youtube.com/watch?v=ic8EBmRJoU0

At 0:40 and onwards you can see the exact same patterns. My tube that shows this the most is from mid 2000's and a ITT Pinnacle (OMNI VI F9800RG). Maybe newer tubes aren't as prone.

Edit: am I understanding this right then, that part of the illumination goes through the photocathode, bounces back from the MCP, and then has another chance to get absorbed into the PC? And in between, something odd happens that I don't fully understand. Or then exactly what johnelot said and some parts of the PC do absorb it and others don't, and it shows as an image of parts that did and didn't absorb.

So it'd seem the reason why I haven't seen this before is I haven't used long enough wavelength illuminators.

It appears many kinds of imperfections in the PC are possible that show under >910nm (or so?) light.

Interesting observations.

Gen 3 tubes start behaving in odd ways when the PC stops being opaque (around 890nm for room temperature GaAs I think). The PC thickness is a few wavelengths thick at ~900nm and that's always a recipe for observing odd optical effects. Reflection off the MCP is also a thing but I don't think that's what you're seeing. Tends to look different. Looking into a Gen 3 tube under say 940nm illumination makes it look like a Gen 2 tube, with the MCP producing the familiar diffraction pattern.

Indeed interesting!

Got a reply from cnoct/Stan:
"Can't say it's specific to a manufacturer or time period but I've only noticed the wafer defects, as you've noted in your F9800RG, in ITT commercial tubes from approximately 2004 to 2008. The dislocation defects (cross hatch pattern) I've seen in both ITT and L3 tubes. The same can be said for interference rings but those seem to be much more pronounced in ITT tubes. The earliest tube I've seen the interference rings is a tube from 1992."

hmmm... so you need to beam the laser towards the photocathode? is he adjusting the focus or something to make the various defects appear?

are there any references for this? I tried seaching, and didn't see anything directly related

thanks in advance for the info

I'm not sure if his illuminator is variable power but that would be the simplest way for his kind of demonstration where the shapes come on gradually.

You don't need to shine the laser toward the tube, a reflection works fine. In case of iPhone I see it best when in a light proof room and shining the laser onto any surface from a rather close distance. The example image was taken when both the illuminator & NOD were about 30-40cm from the surface directly facing it.

The angle of the reflection / angle & distance between light & tube doesn't seem to matter. As long as the area being illuminated looks bright through the tube it will show (with this tube at least). This tube is indeed  from the time period cnoct mentioned and is a non-contract tube.

Edit: oh I got you wrong. I think he has a bunch of different tubes and thus the different effects.

okay. that there are several tubes and he is showing various defects from different ones make sense...

thanks!