When I worked for an imaging company, we used to have diffraction grating spectrographic plates (the DVD is a great idea) embedded in 35mm slide mounts.

We’d stick a standard CCD (like in any DSLR) behind them, and voila! You have a spectrometer! This would also give you a good optical path, for focusing light.

You’d still need to calibrate the driver, but that’s just paperwork.