| 摘要 |
<p>A method and apparatus for aligning a diffraction grating, as, for example, one used in tuning the output of a laser. The total angular misalignment ε between the incident and diffracted beams is a function of three angles: the tuning angle $(u) (16), the angle of tilt β between the plane of the grating (15) and the tuning rotational axis, and the angle α between the grating lines and the projection of the tuning rotational axis in the plane of the grating (15). The present invention provides a method of aligning the diffraction grating so that the residual alignment error is very small over the desired range of tuning angle υ (16), by adjusting only α or only β to zero at two reference tuning angles υ0 and υ1. Knowledge of the value of either α or β is not necessary. For a CO2 laser tuned over the wavelength range 9.11 to 10.88 νm, calculations show that the present method of grating alignment results in a residual angular misalignment error ε of less than 60 νrads, when α is close to 12,000 νrads and β is equal to 10,000 νrads. Since adjustment of only α or β is necessary in minimizing the total misalignment, an apparatus for aligning diffraction gratings consists of providing means for adjusting only one of the two angles α and β in addition to the tuning angle υ.</p> |
