A spectral instrument (100,300,400,500) comprising: a light source (102,302) configured to produce a light beam (104,304), the light beam comprising a plurality of wavelengths (106,308), the light beam being about collimated or pseudo-collimated; a spectral dispersion device (108,116,306) in optical communication with the light source, configured to disperse the light beam into a plurality of wavelengths, wherein the plurality of wavelengths include a first beam and a second beam, wherein the first beam represents one wavelength of light and the second beam represents another wavelength of light; a first screen (110,316,502) disposed in an optical path after the spectral dispersion device, the first screen comprising a material configured to be substantially opaque to at least some of the plurality of wavelengths, the first screen sized and dimensioned to at least partially block selected ones of the plurality of wavelengths, the first screen being movable to both rotate, in the optical path, about a first axis of the first screen, the first axis of the first screen being orthogonal to the optical path, and to translate, across the optical path, along a second axis of the first screen, wherein rotation of the first screen changes a width of a notch etched into a spectral output of an output beam; a second screen (114, 504) disposed in the optical path after the spectral dispersion device, the second screen comprising a material configured to be substantially opaque to at least some of the plurality of wavelengths, the second screen sized and dimensioned to at least partially block selected different ones of the plurality of wavelengths, the second screen configured to rotate, in the optical path, about a first axis of the second screen, the first axis of the second screen being orthogonal to the optical path, and to translate, across the optical path, along a second axis of the second screen, wherein rotation of the second screen changes the width of the notch etched into the spectral output of the output beam, wherein the first screen (110,316, 502)is located a first distance from the second screen (114,504), wherein the spectral dispersion device (108,116,306) is configured to separate two wavelengths of the plurality of wavelengths (106,308) such that, after the plurality of wavelengths have traveled a second distance along the optical path, the two wavelengths are separated by a third distance, wherein the first distance is selected to correspond to the third distance; and an imaging lens (112,324) disposed in the optical path and disposed either after the first screen or before the first screen, wherein the imaging lens is configured to converge the plurality of wavelengths separated by the dispersion device back to a focal point. a light source (102,302) configured to produce a light beam (104,304), the light beam comprising a plurality of wavelengths (106,308), the light beam being about collimated or pseudo-collimated; a spectral dispersion device (108,116,306) in optical communication with the light source, configured to disperse the light beam into a plurality of wavelengths, wherein the plurality of wavelengths include a first beam and a second beam, wherein the first beam represents one wavelength of light and the second beam represents another wavelength of light; a first screen (110,316,502) disposed in an optical path after the spectral dispersion device, the first screen comprising a material configured to be substantially opaque to at least some of the plurality of wavelengths, the first screen sized and dimensioned to at least partially block selected ones of the plurality of wavelengths, the first screen being movable to both rotate, in the optical path, about a first axis of the first screen, the first axis of the first screen being orthogonal to the optical path, and to translate, across the optical path, along a second axis of the first screen, wherein rotation of the first screen changes a width of a notch etched into a spectral output of an output beam; a second screen (114, 504) disposed in the optical path after the spectral dispersion device, the second screen comprising a material configured to be substantially opaque to at least some of the plurality of wavelengths, the second screen sized and dimensioned to at least partially block selected different ones of the plurality of wavelengths, the second screen configured to rotate, in the optical path, about a first axis of the second screen, the first axis of the second screen being orthogonal to the optical path, and to translate, across the optical path, along a second axis of the second screen, wherein rotation of the second screen changes the width of the notch etched into the spectral output of the output beam, wherein the first screen (110,316, 502)is located a first distance from the second screen (114,504), wherein the spectral dispersion device (108,116,306) is configured to separate two wavelengths of the plurality of wavelengths (106,308) such that, after the plurality of wavelengths have traveled a second distance along the optical path, the two wavelengths are separated by a third distance, wherein the first distance is selected to correspond to the third distance; and an imaging lens (112,324) disposed in the optical path and disposed either after the first screen or before the first screen, wherein the imaging lens is configured to converge the plurality of wavelengths separated by the dispersion device back to a focal point.