Let's think, we have a detector array (128x1 and each cmos detector responds 400 to 1000 nm TSL1401CL that way, each detector has 4.6875 nm interval). Then, basically in a spectrometer a prism reflect the waves(visible and near-ir) after that, these reflected waves come to the detector array. I understand that. But I dont understand that how each reflected waves comes to the always same detector.(for instance 400 nm is on 1st one than 405 nm on 2nd one...). What kind of optical system assure it?