A spectral imaging device (12) for generating an image (13A) of a sample (10) includes (i) an image sensor (30); (ii) a tunable light source (14) that generates an illumination beam (16) that is directed at the sample (10); (iii) an optical assembly (22) that collects light from the sample (10) and forms an image of the sample (10) on the image sensor (30); and (iv) a control system (32) that controls the tunable light source (14) and the image sensor (30). During a time segment, the control system (32) (i) controls the tunable light source (14) so that the illumination beam (16) has a center wavenumber that is modulated through a first target wavenumber with a first modulation rate; and (ii) controls the image sensor (30) to capture at least one first image at a first frame rate. Further, the first modulation rate is equal to or greater than the first frame rate.