The DeSa Monochromator
The patented double-grating monochromator by Richard J. DeSa has stationary optics during scanning. In its unique rapid-scanning mode, only the intermediate slit moves. Conventional scanning by moving the gratings is possible, too.

All early models have an aperture of 4.5 and a focal length of 250 mm. As a subtractive double monochromator, the DeSa model features exceedingly low stray light, high light throughput, a homogeneous output beam, and bandwidth determined by the moving intermediate slit. The DeSa monochromator has all reflective optics, making it usable throughout the UV/Vis/NIR range. One RSM can have almost arbitrary wavelength range(s), wavelength span(s), and spectral resolution(s), as determined by the gratings and ScanDisk.

The diagram and the photo in the right-hand column show the optical path of the DeSa monochromator. The mirror- image optics make it possible to reverse the optical path as the experimental situation requires, making the monochromator equally useful for excitation/ low-light use.