| ▲ | mikewarot 2 days ago | |
This is a combination of things that almost breaks my brain, but it works, and it's brilliant! First, you need to understand coded masks[1,2]. This is a way to use an LCD or other array to mask off parts of a scene so that very specific parts of it are sampled, but the rest aren't, to get a single, high resolution analog value. Then you switch to other masks, and get more values. You can then work backwards in the math through the known mask shapes, to get the original image with far fewer samples that would be required one at a time. Think of the above as a 2d visual version of the Fourier transform[3,4]. This transform is used heavily to compress images throwing away most of the bits in an image without losing it's essence. The analysis they're talking about uses a very specially printed card. It isn't just something generated with a standard 4 ink printer, each "dot" is a separate unique ink with tightly controlled spectral curves, these form a virtual version of the above masks. When you view these through a sample, it can then give an idea of the spectral response of the camera, and the liquid, by using the many different known response curves of the "dots" to work backwards, and generate the 1 dimensional very tight response curve of a hyperspectral imager, by figuring out where each "dot" is in the scene, then averaging that dot's intensity across the RGB values of the picture taken by the camera. Today's cameras have sufficient resolution and bit depth that you get the original bit depth (usually 8 bits) and an additional bit for each doubling of the number of pixels in a given "dot". This is degraded by Bayer pattern filters[5,6], and the nature of cameras, but it's not unrecoverable. Like with Coded Masks, and Fourier transforms, you then take your high resolution analog values, and work backwards to get the things you want to measure. [1] https://www.youtube.com/watch?v=_ezhdhHNku0 [2] https://en.wikipedia.org/wiki/Coded_aperture [3] https://en.wikipedia.org/wiki/Fourier_transform [4] https://www.youtube.com/watch?v=spUNpyF58BY&pp=ygURZm91cmllc... [5] https://www.youtube.com/watch?v=LWxu4rkZBLw&pp=ygUMYmF5ZXIgZ... | ||