Recently, a team led by Prof. YANG Jianfeng from Xi'an Institute of Optics and Precision Mechanics (XIOPM) of the Chinese Academy of Sciences (CAS) proposed high-accuracy twist measurement based on the spherical wave Talbot effect for a bi-grid modulation collimator Their up-to-date result was published on Applied Optics.

The bi-grid modulation collimator is an important way for imaging solar flares in hard x rays. The imaging quality of the bi-grid collimator is sensitive to the relative twist between the rear grid and the front grid. Therefore, how to achieve high-accuracy twist measurement is an essential issue.

To address the above problem, YANG and his team members proposed a novel way to accurately measure twist for a bi-grid modulation collimator, which is based on the spherical wave talbot effect. The whole principle was disassembled into two parts, spherical wave talbot effect and twist angle measurement principle.

According to the experiments results, on the basis of the spherical wave talbot effect, demonstrated the effectiveness of the proposed measurement. In the future, the proposed measurement will be helpful in improving the imaging quality of the bi-grid collimator.

Sketch of the experimental setup. (Image by XIOPM)