平场全息凹面光栅的理想像面应为一平面, 此时子午焦线与弧矢焦线均位于像面内且彼此重合, 形成接近理想像点的光谱像。 但子午焦线总是存在弯曲, 只有弧矢焦线在满足一定条件的情况下可以成为直线。 鉴于此, 提出一种满足平场弧矢焦线条件的平场全息凹面光栅设计方法。 利用光学设计软件ZEMAX研究了运用此方法设计的零像散光栅的成像特性, 并与原有设计方法得到的结果进行比较。 模拟结果显示, 满足平场弧矢焦线条件的光栅能够达到与原有方法所设计光栅相当的光谱分辨率, 而其全波段零像散特性使其拥有更加出色的弧矢方向聚焦性能, 显著提高平场光谱仪的信噪比。

The desirable imaging locations of the flat-field holographic concave gratings should be in a plane. And the object can be imaged perfectly by the grating when the tangential focal curve and sagittal focal curve both superpose the intersection of the image plane and dispersion plane. But actually, the defocus can not be eliminated over the entire wavelength range, while the astigmatism vanishes when the grating parameters satisfy some conditions. An optimization method for broad-band flat-field holographic concave gratings with absolute astigmatism correction was proposed. The ray tracing software ZEMAX was used for investigating the imaging properties of the grating. And we made a comparison between spectral performance of gratings designed by this new method and that by conventional method, respectively. The results indicated that the spectral performance of gratings designed by using the absolute astigmatism correction method can be as good as gratings designed with the conventional method. And the focusing performance in the sagittal direction is much better, so that the S/N ratio can be greatly improved.