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Improved wavefront estimation accuracy in a programmable grating array based wavefront sensor
Journal of Optics ( IF 2.1 ) Pub Date : 2021-04-06 , DOI: 10.1088/2040-8986/abeec4
Biswajit Pathak

Shack–Hartmann wavefront sensor (SHWS) is one of the popular zonal wavefront sensor that typically consists of a two-dimensional (2D) array of lenslets and a camera. Another variant of a zonal wavefront sensor is the programmable grating array based wavefront sensor (PGAWS) that replaces the lenslets array of the SHWS with a 2D array of programmable diffraction gratings and a single focusing lens to result in a 2D array of +1 order spots. The ability of a PGAWS to correctly measure the incident wavefront depends on the accuracy with which each +1 order spot centroid position in the camera plane is calculated. However, in practical applications the intensities of the +1 order spots are usually non-uniform and there is presence of higher order spots that lead to erroneous calculation of the centroid position. In the present work, an improved PGAWS is proposed and by exploiting its programmable facility the transmittance function of the grating array is defined to generate an array of uniform intensity +1 order spots with negligible contribution from unwanted higher order spots by breaking them into noise. We present proof-of-concept simulation results that illustrate the generation of uniform intensity +1 order spots and also quantify its uniformity numerically by defining a quality metric. Furthermore, the working of the proposed PGAWS is substantiated through simulation results which demonstrate its accurate wavefront estimation capability in comparison to the conventional PGAWS, in the presence of non-uniform intensity +1 order spots.



中文翻译:

改进基于可编程光栅阵列的波前传感器的波前估计精度

Shack-Hartmann 波前传感器 (SHWS) 是流行的带状波前传感器之一,通常由二维 (2D) 小透镜阵列和相机组成。带状波前传感器的另一个变体是基于可编程光栅阵列的波前传感器 (PGAWS),它用可编程衍射光栅的二维阵列和单个聚焦透镜代替 SHWS 的小透镜阵列,从而产生 +1 级光斑的二维阵列. PGAWS 正确测量入射波前的能力取决于计算相机平面中每个 +1 级光斑质心位置的精度。然而,在实际应用中,+1 级光点的强度通常是不均匀的,并且存在导致质心位置计算错误的高次光点。在目前的工作中,提出了一种改进的 PGAWS,并通过利用其可编程设施,光栅阵列的透射函数被定义为生成一个强度均匀的 +1 级光斑阵列,通过将不需要的高阶光斑分解为噪声,这些光斑的贡献可忽略不计。我们提出了概念验证模拟结果,该结果说明了均匀强度 +1 级点的生成,并通过定义质量度量以数值方式量化其均匀性。此外,所提出的 PGAWS 的工作通过模拟结果得到证实,模拟结果证明了与传统 PGAWS 相比,在存在非均匀强度 +1 级点的情况下其准确的波前估计能力。

更新日期:2021-04-06
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