Smartphone camera turn into radiation dose meter

US government researchers at the Idaho National Laboratory have written an Android app that lets your phone’s camera act as a gamma radiation detector. We’re not talking about the same quality of detection as a commercial detector or dosimeter, but if you spend a lot of time in planes, or you live in an area with high levels of natural background radiation (granite, limestone, high altitude), you might soon use your smartphone as a cheap, fairly accurate gamma radiation detector. Such a smartphone app could be a huge boon for emergency services who are first on the scene and aren’t equipped with the correct radiation gear, too, Extreme Tech reported. Believe it or not, but detecting gamma radiation with the standard CMOS sensor in your smartphone is fairly simple. When a single CMOS pixel is hit by a photon of light, it generates an electric charge (a flow of electrons) that can be measured by the sensor’s controller. Gamma rays are very-high-energy photons (tens of thousands of times more powerful), and so it stands to reason that they can also interact with those CMOS pixels. If the gamma rays have just the right trajectory, they draw straight lines on the sensor, which can then be converted into a radiation reading. It isn’t quite that simple, of course, otherwise Samsung would’ve already made some kind of banal and immature ad about how its phones can detect the noxious radiation given off by Apple’s iSheep. The telltale lines drawn by gamma rays can only be seen when there’s very little noise — and CMOS camera sensors are notoriously noisy. First, you have to cover the lens, so that visible light can’t strike the sensor (gamma rays are sparse and would be easily drowned out by the visible light rays). Second, there is a lot of background noise caused by heat and current leakage. A number of mathematical methods are used to remove this noise — the simplest of which is taking a black image with the shutter closed and away from any gamma radiation, to create a “noise map,” and then subtract that noise map when the phone’s being used as a radiation sensor. Any lines that remain after the various noise reduction methods are gamma rays. Oddly enough, while this technique won’t turn your phone into a professional-grade radiation meter, it is surprisingly effective. The researchers loaded the app onto three different Android phones — the Nexus S, Nexus Galaxy, and Nexus 4 — and found that they could all be used to calculate the radiation dose caused by a nearby source of gamma radiation. It wasn’t exact, but it was more than good enough to tell you when you’re being bombarded with more radiation than you should be. The researchers note that, by using both the smartphone’s front and rear camera in concert, it may be possible to detect where the gamma rays are coming from, too — but they haven’t attempted that yet. [Research paper: arXiv:1401.0766 - "Using CMOS Sensors in a Cellphone for Gamma Detection and Classification"] By analyzing the length and brightness of the lines, the researchers also found that they could also work out the type of radiation source (every radioactive source gives off gamma rays of a certain energy level). Again, this could be very useful for the first few people arriving at the scene of a radiation leak — an EMT arriving in an ambulance probably won’t have a professional radiation meter, but would almost certainly have a smartphone that they could use. Really, that’s the point here: The best radiation meter by far is the one that you have with you, even if it isn’t very good. (Read: Smartphone Add-Ons Grow up at CES 2014: Thermal Imaging Cases, Stun Gun Battery Packs, Tricorders.) Sadly the app developed by the Idaho National Laboratory — called CellRad — isn’t available to download. The research paper notes that other people have written similar apps in the past, but we couldn’t find them. Hopefully, as it was developed on the government’s dime, the app will eventually be released to the public for free. It would be very useful if regular fliers and those living in areas of high background radiation could actually see how much radiation they’re being exposed to, and whether they’re at risk or not.