A large variety of optical concepts for imaging spectrometers with high geometrical and spatial resolution have been studied at Dasa/Ottobrunn in various projects, which were funded by national agencies (DLR) and the European Space Agency (ESA). The imaging spectrometers emphasized herein measure spatial images of the upwelling spectral radiance from 400 to 2400 nm at 5 to 15 nm spectral intervals. All concepts are prism/grating designs based on pushbroom imaging, and are designed to fulfill stringent requirements on spatial and spectral registration accuracy. Such imaging spectrometers comprise several critical and challenging subunits such as frontend calibration, pointing, baffling, telescope and spectrometer optics, focal plane assembly, etc. Of these subunits, the paper emphasizes the driving requirements and constraints of the optics. In particular, methods to control and optimize the most critical parameters like polarization, spatial and spectral purity/accuracy, transmission, and image quality are presented. The achieved performances and design inherent properties of all concepts are given.