#Y2021 #光学测量 #模型 A double monochromator situates a second single monochromator at the exit of the first.Entering the first monochromator is all the light from the source to be measured; entering the second monochromator is the wavelength selected and a level of stray light, which one desires to reduce. Gratings are usually designated by their groove density, the number of grooves per unit length, usually expressed in grooves per millimeter (g/mm), also equal to the inverse of the groove period. 下图是[bentham](https://www.bentham.co.uk/)公司的Monochromators产品，三角哪里是不同的grating