Standard digital cameras can register images of narrow range of spectra. Normally this is visible light and some of IR area. If you need more specific characteristics, then price of such cameras grows exponentially. Hobbyists always try to find cheap solutions in order to get desired results. One of them is to use single pixel camera which simply scans through all image and then combines it in to picture. Single pixel is nothing more than photo-diode which can be sensitive to different wavelengths. Artyom have built a simple prototype of single pixel camera where sensitive photodiode is moved to scan all image.
The idea lies in to building dark box with tiny hole in it. Image passing through that hole can be projected on the opposite plane. In order to get better image resolution he had to test various photodiodes. They have to be small size to give more resolution, but bigger sensors give less noise. This single pixel camera is universal tool. For instance if you need to register images in infrared spectra, then use IR photo diode. Visible light sensor is great for taking BW images. And if you need other properties, then put a sensor of your choice. The only downside is speed – process is really slow.