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Radio Camera

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  1. Jul 7, 2015 #1
    Radio is usually used as RADAR blips but has anyone tried to make a visual DSLR type camera and producing images? I'm not talking about a waveform showing the frequency placement but a real image of objects the radio bounced off of?

    We have tons of radio stations as the 'light' source here in my town where the pixels could measure the intensity of energy received. Near infrared is common in hobby cameras and it's very long wave doesn't seem to have a problem getting captured. Heck a creative camera could maybe even have it's own low powered radio source it spewed out. RADAR satellites are cranking out some killer images from space and I'm just wondering if anyone has seen something like this in compact form?

    Thanks
    ~ Tracy
     
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  3. Jul 7, 2015 #2
    They have sonor cameras that do underwater imaging.
     
  4. Jul 7, 2015 #3

    berkeman

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    Welcome to the PF.

    What do you mean by "long wave" IR? Do you know what the actual wavelengths are for IR?

    The resolution of an image is limited by the wavelength of the EM radiation, and the size of the pickup antenna is on the order of the wavelength as well. You could probably make a 2-D array of microwave receive antennas and amplifiers to try to "image" in the microwave bands...
     
  5. Jul 7, 2015 #4
    Thank you! I agree on the many little antennas thing. The satellite's hardware is called synthetic aperture for just that reason. I was curious if anyone had seen this in compact camera form. Sonar is definitely the idea (with baby ultrasounds looking amazing now) but sound is a whole other thing of course. Heck in my mind at least, if one could choose the many radio stations or a few radio stations the power of the radio bouncing off buildings could be one interesting image. But since its intensity and not time like RADAR I'm not sure the whole thing would work.

    ~ T
     
  6. Jul 7, 2015 #5

    e.bar.goum

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    Forgive me if I'm misunderstanding what you're going for, but I'm pretty sure we've done this more than a few times, in fact - it's called a radio telescope.
    VLA2001-116w.JPG
    M87 as seen by the Very Large Array, and the centre, as seen by the Very Large Baseline Array (image credit: wiki)

    M87_VLA_VLBA_radio_astronomy.jpg

    As berkeman points out: you need an antenna of the order of the wavelength of what you're wanting to image.
     
  7. Jul 7, 2015 #6

    Drakkith

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    The wavelength of radiation in the radio band is much too large to get anything close to a decent image (unless you want to image large scale terrain features). Plus the array of antennas would be many meters across for even a small array. One reason RADAR is usually used by 'sweeping' the beam across the target using a single transmitter and receiver antenna is that you only need one of them!

    The microwave range could conceivably get some decent images, but a detector with a 1,000 x 1,000 pixel array would be several feet across. Even then, the resolution of your image would still be much, much less than a visible light camera.
     
  8. Jul 7, 2015 #7
    I'm fairly certain the large array in any country is not "this in compact camera form". But yes indeed that type image is what I'm talking about minus the nebula clusters and more buildings from the local neighborhood. :D

    ~ T
     
  9. Jul 7, 2015 #8
    You probably nailed the answer here. While these satellites are sometimes getting good features on lets say a small automobile, the array is huge. So any hand held camera would not have enough width to get the large waves into a cohesive detailed image.
     
  10. Jul 7, 2015 #9

    e.bar.goum

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    Yes, that's exactly the problem with a "compact camera form" - a fourier transform means that to look at small things, you need to put your detectors far apart - this is why the VLBA looks at finer detail in the above image than the VLA. Ditto your compact camera- you need to put your antennas far enough apart (the wavelength will determine what "far enough" means) to see anything - which means it's not going to be compact.
     
  11. Jul 7, 2015 #10

    Drakkith

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    I don't think satellites use arrays. Not with radar at least. Any high-resolution on the scale of a few meters or less is probably optical/infrared. Not sure though.
     
  12. Jul 8, 2015 #11

    marcusl

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    As mentioned, synthetic aperture radar imaging is highly successful, though not compact. There are also experimental microwave imagers, using array antennas, for imaging parts of the human body. Because the dielectric constant of tissue (water) is about 81, there is a nine-fold reduction in the wavelength, permitting imaging with sub-mm resolution. The skin effect prevents deep penetration, however, which is pretty much a showstopper. Most of these efforts have therefore focused on the detection of small breast cancer tumors. (Breast tissue is fatty and far less conductive, so RF penetration is better. The tradeoff is lower dielectric constant and poorer resolution.) Again, results have not been very impressive. Still, it is definitely possible to image with RF.
     
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