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Usual cameras can capture the visible spectrum, and some others the infra-red spectrum. But the world is so much than that, isn't it? I wonder why cameras that could see a larger electro-magnetic spectrum does not exist, let's say from gamma to radio waves. And I am talking about an image representation, not just about detecting intensity.

Let's imagine. Select a specific spectrum and the camera could show you what it sees in false colours. That could be very interesting to see heat losses, Wifi or cellular emissions, astronomy etc.

I suppose it is a technical problem, that it would be needed to have lenses and sensors for each sub-spectrum. But I believe it is possible for some ones, and that some telescopes do it. Am I wrong?

For what spectrum cannot we build lenses and sensors for the moment? How hard would it be to have only one device that could capture all that?

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    $\begingroup$ "Whole spectrum" is a absurd concept. $\endgroup$ – Olin Lathrop Nov 25 '15 at 12:42
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    $\begingroup$ Separate cameras that "see" different parts of the spectrum are already in use especially in astronomy. See: Hubble, Chandra x-ray observatory, James Webb space telescope, and then entire field of radio astronomy. $\endgroup$ – hazzey♦ Nov 25 '15 at 13:21
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Look at it this way:

A simple compass will detect from zero to about 0.1 Hz

your AM radio detects around a MHz

your cellphone around a few GHz or so

Radar systems anywhere from 100kHz to 1 THz

Special materials can handle parts of the range from 10 microns to 0.1 micron (which includes the visible)

Special crystals & other things can detect hard X-rays, gamma rays, etc.

Image "fusion" is a hot and growing field, which involves combining images from different wavelength ranges to provide more information/discrimination about objects.

THere's no reason, or possibility, of having a single tool respond to all those wavelength ranges.

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    $\begingroup$ AM radio and the compass can be used to make point observations; you can think of them as single pixels on a CCD matrix. But how would you even go about creating some kind of camera-like image from waves of kilometer length? $\endgroup$ – SF. Nov 26 '15 at 12:12
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    $\begingroup$ @SF guess you'd need a big canvas :-) $\endgroup$ – Carl Witthoft Nov 26 '15 at 15:26
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Would it be hard to create a camera that could see the whole electro-magnetic spectrum?

Yes.

There is no one technology that can "see" all wavelengths, and then the concept of "whole spectrum" is totally silly anyway since its bounds are infinite.

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  • $\begingroup$ Indeed, consider "the largest pectrum" we can do instead of "the whole spectrum". $\endgroup$ – azmeuk Nov 25 '15 at 15:33
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    $\begingroup$ @azm: First, that's not what you asked, and second, it's still no spec at all. How long are you willing to wait for the result? That's just one limitation on the lower bounds of the spectrum. $\endgroup$ – Olin Lathrop Nov 25 '15 at 17:27
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First, I like your question. You might ponder what you imply when you want to "see" the common parts of the electromagnetic spectrum (e.g. visible light, radio waves, x-rays etc.)

If you want a camera that can "see" a broader spectrum, you are asking for a camera that can transform a broad spectrum of wavelengths into visible light (since we can only use visible light to interpret what the camera is picking up).

Think of this logic: I create a camera that is sensative to visible and infrared radiation. The camera transforms this combined spectrum range into visible light. Problem: if I am seeing the full visible light spectrum, where do I have any unique wavelengths of visible light left to represent infrared wavelengths? Therefore, you have some limitation on overlapping spectrum ranges with visible light. Maybe you'd see greater intensity or brightness in some colors.

Of course, there are other ways to analyze electromagnetic radiation, like in terms of a spectrogram, we can tell which frequencies are more "present" in a signal. But analyzing electramag radiation in this manner for a large spectrum has some harsh limitations: 1) you'd need a lot of different antennas (one size does not fit all) 2) an insanely fast sampling frequency for higher frequency radiation 3) a large bottle of aspirin for the headache you'd get trying to process all that information.

I suppose it would be possible for a hypothetical biological eyeball to have sensitivity to a larger band of the spectrum. You'd need a brain that could process the information. It is possible, since some creatures like Butterflies can make good use of ultraviolet radiation.

Unfortunately I think most engineers on this website have less experience designing eyeballs (excluding some ninja bio-engineers if they exist).

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