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Originally Posted by RGClark
I'm not so sure about that. The reason why they don't have 3 different pixels for each of R, G, B is because that reduces the resolution. If this system made the reduction in resolution a non-issue I'm not so sure imaging scientists wouldn't opt for this. Note that with the current system there are days before you can release a full color image. With simultaneous exposure you could release it as soon as you could release any of the single color image.
The ideal solution though would be a system that could change each and any pixel to any frequency range you chose on command.
Bob Clark
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Actually, I would say using an array with a RGBG filter you would need a CCD array with higher resolution, but that is not the real problem, these arrays are quite common, almost all digital cameras use them. But they introduce artifacts along the edges of objects in the picture, since the sensor for each color will be hit by light coming from a slightly different angle. Also the problem is that you would want more than three frequencies for scientific reasons(it can help you identify minerals, for example), and want to use filters with tight band pass characteristics that is stable over the entire sensor surface, it is much easier to do in a single filter.
Using a digital color camera to take your holiday pictures, for example, is not a problem, you use them to help your memory of it, not to analyze what everything is made of, the loss of information due to the fact that the camera must maintain the relative levels of the red, green and blue channel is not usually an issue. But sending a lander to another planet is not a holiday excursion, you don't do it to make eye candy images, you do it to learn, to study that world, and so you would want as much information packed in to the data as possible, but use the minimal amount of bandwidth possible. Reduced detail due to limited use of the grayscale, can not be undone in software, if you have a dark picture using only 128 levels of 4096, it will only use 128 levels no matter how you try to increase its brightness...
Anyway it does not matter, as the problem with generating color images have nothing to do with taking three simultaneous or three sequential images, both these methods have been used in cameras on earth for decades. The two ways are essentially the same, you get three separate grayscale images the electronics must integrate into one image.
Seeing as you can not use multiple(more than 3, I mean) filters easily with arrays where the filters are on the surface of the sensor, and that using a separate sensor for each channel and using dichroic mirrors to split the light makes the system rather heavy, using a single imager with exchangeable filters is the best trade of, that you can not easily image something moving rapidly across your field of view, is not a big problem.