A usually glass or polished metal surface having a large number of very fine parallel grooves or slits cut in the surface and used to produce optical spectra by diffraction of reflected or transmitted light.衍射光栅：一般为玻璃或光亮的金属面，面上刻有很密的很精细且互相平行的沟槽或狭缝，光线通过它或被它反射时就形成光谱