Ni80Cr20 alloy film shows a good neutral transmission in visible light. A large area and high precision neutral density filter with multiple steps made of Ni80Cr20 is presented in this work, which proposes one manufacturing method for controlling film thickness. The quartz crystal sensor in the coating machine has a thickness uncertainty larger than 5%, which leads to the low accuracy of optical density value of the filter. To solve this problem, we bombarded the membrane surface with low energy ion beams when the optical density of the filter was slightly larger than we wanted. The absolute error of optical density could then be controlled within 0.01, and the relative error is ±2%, a result which is much better than those that accompany existing commercial neutral density filters. Finally, a neutral density filters with 18 steps is manufactured, which can used as a component of a spectral sensitivity spectrometer.

Ni80Cr20合金膜在可见光下显示出良好的中性透射。本文提出了一种由Ni80Cr20制成的大面积、高精度的多阶中性密度滤光片，提出了一种控制膜厚的制造方法。镀膜机中石英晶体传感器的厚度不确定度大于5%，导致滤光片光密度值精度不高。为了解决这个问题，当过滤器的光密度比我们想要的略大时，我们用低能离子束轰击膜表面。光密度的绝对误差可以控制在0.01以内，相对误差为±2%，比现有的商用中性密度滤光片要好得多。最后，制造了一个 18 步的中性密度滤光片，