Kato M, Maeda S, Yamagishi F, Ikeda H, Inagaki T
Appl Opt. 1989 Feb 15;28(4):682-6. doi: 10.1364/AO.28.000682.
Grating lenses are small, light, and easily mass-produced. However, wavelength variation in the light source causes aberration and changes the focal length of the grating lens. Therefore, it has been difficult to use grating lenses in high-precision focusing optical systems that use a light source with wavelength variations (e.g., a diode laser). To solve this problem, we designed a grating lens system of two grating lenses, which substantially suppresses aberration and keeps the focal length constant at several tens of nanometers of variation. Each grating is made as a concentric circle. These lenses are arranged so that their centers are collinear. Diffraction angle changes due to wavlength variations are compensated for by the second grating. Our calculations confirmed that the allowable wavelength range was +/-15 nm or more for a numerical aperture (N.A.) of 0.5. We made a prototype of this grating lens system by electron beam lithography and confirmed that this lens system was not affected by limited wavelength variations.
光栅透镜体积小、重量轻且易于大规模生产。然而，光源中的波长变化会导致像差并改变光栅透镜的焦距。因此，在使用具有波长变化的光源（例如二极管激光器）的高精度聚焦光学系统中很难使用光栅透镜。为了解决这个问题，我们设计了一种由两个光栅透镜组成的光栅透镜系统，该系统可大幅抑制像差，并使焦距在几十纳米的变化范围内保持恒定。每个光栅都制成同心圆形状。这些透镜的排列方式使它们的中心共线。第二个光栅可补偿因波长变化而产生的衍射角变化。我们的计算证实，对于数值孔径（N.A.）为0.5的情况，允许的波长范围为+/-15 nm或更大。我们通过电子束光刻制作了这个光栅透镜系统的原型，并证实该透镜系统不受有限波长变化的影响。
