凹面衍射光栅兼具色散分光与光束聚焦功能, 同时具有像差校正、 低杂散光、 无鬼线和高信噪比等优势而受到光谱仪器领域的广泛关注。 衍射效率作为凹面光栅最重要的技术指标之一, 其测量技术水平逐渐成为光谱仪器行业最为关注的课题之一。 传统方法一般采用双单色仪结构实现凹面光栅衍射效率的测量, 该方法主要存在两方面问题, 一是测量标准反射镜和待测光栅的出射光谱带宽不同, 二是光栅叠级、 杂散光的影响; 上述问题的存在降低了高性能凹面光栅衍射效率测量的准确性。 本文提出了一种基于傅里叶光学原理测量凹面光栅衍射效率的新方法; 针对该方法建立了凹面光栅衍射效率测量的数学模型, 并采用光学追迹和傅里叶光学方法相结合对其进行了仿真分析, 从而验证了该方法的正确性; 针对动镜横移误差、 倾斜误差、 光源稳定性、 动镜运动距离误差等因素影响凹面光栅衍射效率测量精度的问题, 提出引入辅助探测器的方法来进一步提高衍射效率测量精度, 并对有无辅助探测器情况下的上述误差对衍射效率的影响进行了数学推导和仿真分析, 分析结果表明引入辅助探测器可以有效抑制了上述误差对凹面光栅衍射效率测量的影响。 对比传统双单色仪测量方法而言, 该方法不仅能够解决传统测量方法存在的问题, 同时还具有多波长同时测量、 高光通量、 高分辨率、 高波数精度等优势, 可以有效提高凹面光栅衍射效率的测量精度和测量效率。

Concave diffraction grating not only possesses the function of dispersion and focusing for the light beam at the same time, but also has the advantages of aberration correction, low stray light, none ghost line existence and high signal-to-noise ratio. It has been received extensive attention in the spectral instrument field. As one of the most important performance properties of concave diffraction grating, the measurement level of the diffraction efficiency for concave grating becomes one of the most concerned topics in the spectral instrument industry. Double monochromatic structure is usually adopted to measure the diffraction efficiency for concave grating in the traditional method, but it involves two major problems: the first one is the differences of output bandwidths during measuring standard mirror and the tested grating, and the second one is the overlapping of diffracted spectra and scatter light in the instrument. Therefore, the traditional method which contains above problems influences the measurement accuracy of diffraction efficiency for high performance concave grating. In this paper, a new measuring method of diffraction efficiency based on Fourier Optics principle is proposed. The mathematical model of diffraction efficiency measurement is firstly deduced and then verified with ray tracing and Fourier optics simulation. Aiming at reducing the influence of the moving cube corners tilt error, lateral shift error, source instability and maximal moving distance error, we put forward to introducing an assistant detector to collect data together with the main detector. The relative mathematical deduction and simulation have been made under the condition of existence and non-existent of the assistant detector, the result shows that we can effectively control the influences of the above errors and can greatly increase the measurement accuracy of diffraction efficiency when the assistant detector is introduced in the light path. Compared with the traditional double monochromatic structure, our method not only solve the problem mentioned above, but also has the advantages of multi-wavelengths measurement in the same time, high luminous flux, high spectral resolution, and high wave-number accuracy.