It seems like economist uses Javascript to create the "You've reached your article limit" dialogue. Simple press ESC key to stop JS from executing on Chrome so that you can read the article.
Also here is my TL:DR summary of it if you're still trying to fight through the pay wall:
There is a thing called grating coupler that works like little high frequency antennas that receives light signals. When you put a whole array of them you will be able to do various scans of light signals to simulate the camera pointing at different direction, or fisheye, telephoto effects without the need of tilting or moving the surface of the array. The underlying computation relies on the ability to calculate and control the timing of signal travelled from each antennas, plus some classic signal interference and phasing issues. An 1cm x 1cm array will contain 1 million such couplers which would create a similar sized image as an iPhone 7 rear camera, but since there is no lens involved, the camera can be made a lot thinner.
Also here is my TL:DR summary of it if you're still trying to fight through the pay wall:
There is a thing called grating coupler that works like little high frequency antennas that receives light signals. When you put a whole array of them you will be able to do various scans of light signals to simulate the camera pointing at different direction, or fisheye, telephoto effects without the need of tilting or moving the surface of the array. The underlying computation relies on the ability to calculate and control the timing of signal travelled from each antennas, plus some classic signal interference and phasing issues. An 1cm x 1cm array will contain 1 million such couplers which would create a similar sized image as an iPhone 7 rear camera, but since there is no lens involved, the camera can be made a lot thinner.