There are cameras that can see infrared and ultraviolet, what about microwaves and other wavelengths?
If we had a camera that only images microwaves for example, could we see wi-fi and Bluetooth as they reflect off surfaces?
What are the main limitations of building something like this? Is it the size difference between wavelength and sensor size?
In: Physics
kinda? we just call them microwave wavelength radar.
We definitely have sensors that can detect microwaves in detail however displaying them on a screen like you would a video or photograph would require a heavily processed image. Just like many of the images we have of planets, stars, and galaxies are not actually what they look like if you were to see them up close with a human eye. This is because the data that represents those non-visible wavelengths is processed so that we can see it. You might configure the software that processes it to represent any data that is 2.6 to 2.7 Ghz is colored blue and 2.8 to 3.0 Ghz is purple.
Yes, we call them weather radars. The standard 2400 MHz frequency used by a microwave oven is chosen because it is absorbed and reflected by water.
If you send out signals with a very directional antenna, and have a similar setup to receive the pulses, you have a camera (actually more of a scanner) that creates a picture of where water is ahead of you.
There are array antennas but I don’t think they really act like a camera, just a means of focusing the signals from one very specific direction.
You have. It isn’t a camera but a X-Y table with probe and spectral analyser. By scanning you can create image of different frequencies
Yes and no…
it’s not a camera as such, but still an RF visualizer
https://hackaday.com/2023/03/04/inspect-the-rf-realm-with-augmented-reality/
here’s another AR visualizer for RF
https://hackaday.com/2019/01/09/smartphone-app-uses-ar-to-visualize-the-rf-spectrum/
Yes absolutely, but the resolution will be on the order of centimeters, whereas visible light has resolution on the order of a micrometer, so 10,000x smaller. There are absolutely far infrared cameras, basically thermal optics. The amount of microwaves emitted by typical materials at typical temperatures is so miniscule I can’t think of an application we’re you would want to build an imaging system for a human sized object. Cell towers have a sort of microwave imaging so they can determine the direction of a target and do beam steering. In that case the “image” the whole space around the tower within range.
Microwaves are defined as the part of the electromagnetic spectrum with wavelength between one millimeter and one meter. Radar in the millimeter wave range is used for fire control on the [Longbow variant of the AH-64](https://www.northropgrumman.com/what-we-do/an-apg-78-longbow-fire-control-radar) We know that it produces images, but information is not available as to how much resolution it has. We do know that it can track 256 separate moving targets.
Milimeter wave radar can see a human through a wall, but [the image is more of a point cloud than a “picture”](https://ksp-windmill-itn.eu/research/fmcw-mmwave-radars-can-see-through-walls/) [There is a company using AI to interpret those point clouds, and they claim to be able to see human outlines using only a consumer WiFi router as the emitter.](https://www.sify.com/technology/this-neural-network-uses-wifi-to-see-through-walls/) This is about as close as it comes to a camera. WiFi is 6 or 12cm wavelength, well within the microwave range.
I have taken pictures of microwaves with my iphone. I just go to the kitchen with my phone and voila
We can’t use normal camera sensors because of physics, i.e. the physical properties and the nature of light and electromagnetism.
In order to detect a photon, we use a CCD or CMOS sensor. They are designed to detect photons, and has to do with how photons travel and interact with things.
To detect radio wavelengths, we use antennas. They “couple” to the EM field and so any changes local to the antenna are induced as current changes in the antenna itself.
Compared to a photon, microwave wavelengths are huge.
So to take a “snapshot” of the EM field you would need an array of antennas.
Airport Security Scanners (the booths you stand in with your arms up) use *millimeter* radar to image the person and detect things under clothes. They have enough resolution to require blurring of genital regions. But they also have a large rotating antenna to capture that image. Microwaves in the centimeter range would capture significantly less detail and need larger antenna due to the longer wavelength.
Using multiple antenna to monitor wifi signals, you can detect changes in signal patterns as people move around a room (i.e. static environment), but at very low resolution.
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