I'd offer that 3.5 meters isn't all that far for a concentrated IR emitter like a TV remote. Those things emit a pretty powerful signal, even though we can't see it. They have to combat the ambient temperatures in peoples homes, the energy emitted by direct sunlight hitting the receivers (well, in some cases...one of my IR remotes still works when the receiver is bathed in direct sunlight, the others tend to be sketchy), etc. In terms of infrared light, those remote controls send out a pretty "bright" beam...kind of like a bright visible light of a handheld search light vs. the dimmer beam of a flashlight.
You also have to wonder if your little remote control is just emitting IR, or whether it is emitting some visible light as well. I know that I can see a faint yellow light emitted from the IR LED in one of my TV remotes if I look at it while it's emitting. I think I once had a remote that emitted bright red light as well as IR, as it doubled as the indicator light telling the user that the remote was actually indeed sending a signal.
It doesn't have to be that strong because window glass is mostly opaque to near-IR and quite a wide band of IR and UV, all sunlight in homes is diffuse, and IR receivers in TVs and other devices only accept very specific signals (repeating patterns of very specific duration and interval) of an extremely narrow band of IR, namely the wavelength of the remote controller.
Well, first off, you have a few things wrong here. Window glass is mostly opaque to UV, and tends to block around 90% of it. However given the intensity of the sun, a LOT of IR gets through. IR is one of the primary means by which heat is transferred from the sun, and the sun is massively intense. Even if window glass blocks 70% of it, the 30% that gets through is still considerable. Next, NOT all sunlight in homes is diffuse. Sunlight shining directly through a window is not diffuse at all, it's direct. You put your hand under it, and you can feel the heat, which is primarily transferred via IR radiation.
There was no visible light, I've tested the remote controller I used on another person with normal vision, that person could see nothing with the lights on and nothing in complete darkness. I could, but that's beside the point, my eyes aren't normal.
I figured. If you allowed normal light to expose along with the IR beam, you probably wouldn't see much of the IR beam at all. Because of the IR cut filter, the camera is going to receive much more visible light than IR. It isn't a hard cutoff, it gradually falls off from around 630nm or so until maybe 780nm, then it falls off more quickly until around 1100nm. The filter is still blocking the vast majority of IR from around 750nm through 1100nm though.
You should also note that the different types of cones in people can have different spectral sensitivity curves, the cones in some people's eyes can simply have a much wider spectrum they detect than some others. There can be significant variance to spectral sensitivity in the cones, depending on genetic and environmental factors (smoking, retinol intake, betacarotein intake, exposure to UV, genetic sensitivity to UV, physical properties of the lens, refractive index of the lens, cataracts, how easily the lens "clouds" in response to stimuli and so on). Like I said, I'm no scientist, but I know that much from reading and participating in conversations. The 380-750 is by no means a hard limit. In the case of extremely bright IR sources like lasers, there are even military reports of people being able to see the beams of 1064 nm lasers on a moonless night in some cases. Like you already pointed out yourself, sensitivity is different from absolute ability.
There are exceptionally few human individuals on the planet who can see beyond the range of 380nm to 750nm. That would be more of a maximum range, factoring in the weakest sensitivities under stringent testing conditions, which is quite different than normal vision on a normal day to day basis. Realistically, I'd say human vision on the average case is from ~400nm to ~700nm or so.
I used to do extensive research in color theory and how it pertained to human vision. There are some rare genetic aberrations that give some people much more limited sensitivity to light, usually the loss of function in one type of cone (this usually leads to one of the various forms of color blindness). A very small percentage of women seem to have an extra cone color, called the orange cone with an 'orange yellow-orange' color, within the 2° foveal spot. It isn't well understood how this extra cone works with the normal process of vision, although it seems to be sensitive to a narrower band than standard red cones. Some scientists suspect it is simply a differently or malformed red cone, and is therefor treated as a red cone by the brain. Being sensitive to light wavelengths closer to green than standard red cones and not sensitive to blue light at all, it may not significantly change the range of wavelengths these women are sensitive to, if it changes the range at all. I don't know of any human who has even more than the most minimal sensitivity to frequencies around 380nm, although I've read some obscure things about other rare diseases that might enhance sensitivity to blue and purple hues. Some humans are rarely sensitive down to 780nm, however sensitivity levels are extremely low (notice the right-hand shoulder of the green sensitivity curve below, how it tapers off very slowly to the end of the graph...something like that, only with the red sensitivity curve.)
Human vision is a tristimulus, we see three primary bands of light...the reds, the greens, and the blues, however our red cones are also visible to some blue as well (which is what gives us the ability to see magenta.) The spectral response of the cones in the vast majority of human eyes is as follows:
The blue curve produces a narrower peak, with little overlap with green and red sensitivity (although do note that red sensitivity reaches almost to 400nm). You can see how rapidly blue sensitivity falls off after ~420nm, down to nothing by 380nm. Even if that faloff curve was extended or even shifted to 370nm or 360nm, it is not going to greatly enhance our sensitivity to near-uv. Official range measurements for cone sensitivity in humans is as follows:
The widest variations in human vision are primarily caused by defects in the way rods and cones form. This is primarily dominated by color blindness, which basically punches holes in the spectrum of visible light which color blind individuals can see. The various forms of color blindness each affect anywhere from 1% to 5% of the population, depending on the kind. An ultra-rare group of people on earth have monochromatic vision (lack of functioning cones entirely), therefor they see the world in black and white with only their rods. Another exceptionally rare forms of color blindness result in random interpretation of various wavelengths of light (knew someone like this when I was a kid...he would organize crayons into a "rainbow" according to how his brain interpreted each color...it looked completely random and without pattern or sequence to everyone else...weirdest vision impairment I've ever encountered in my life, and his impairment was around one in a billion, so exceptionally rare.)
In all honesty, outside of the orange cones in a very small percentage of women, I don't really know of any regular wild variations in cone type and spectral sensitivity, nor anyone who can really see UV light...even if they had a sensitivity to it, it would be so minimal that it wouldn't affect their vision much in a regular basis. They would probably only learn they had such a sensitivity in a carefully controlled scientific test space and shown deep violet and UV lights of varying frequencies. It certainly isn't common enough to be of concern in the context of photography. Extreme exposures to UV light can and will certainly damage your eyes, and indeed it can cause terrible ailments like cataracts...but that doesn't actually have anything to do with how sensitive our cones are to UV frequencies.
As for people seeing 1064nm lasers...you gotta provide some references to that one! I might be able to understand the use of such a laser to stun someone or temporarily blind them with a short pulse, however that is well
beyond the range of human eyesight. Well beyond. I highly doubt more than a handful of people on earth could see that, if even one person at all could see infrared energy if that frequency.