Imaging spectrograph

An imaging device (500) comprises: a first telecentric system (SYS1) to form a first image (IMG1) of an object (OBJ1),5 a second telecentric system (SYS2) to provide a bundle of output beams (LB5a,LB5b) for forming a second image (IMG2) such that the output beams (LB5a,LB5b) are formed from light received from the first image (IMG1), and a first dispersive element (G1) positioned between the first telecentric system (SYS1) and the second telecentric system (SYS2) to provide a bundle of deflected light beams (LB3a,LB3b) such that the direction of the deflected light beams (LB3a,LB3b) depends on the wavelength (?), wherein the second telecentric system (SYS2) is arranged to form the output beams (LB5a,LB5b) from light of the deflected light beams (LB3a,LB3b), and the second telecentric system (SYS2) comprises an aperture stop (AP2) to reject light which is outside a selected spectral range (PB1)