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基于朗奇(Ronchi)检验法和同步相位探测技术,在点光源离轴情况下提出一种检验非球面反射镜的方法。该方法利用透射液晶显示器(LCD)显示垂直和水平两个方向的正弦光栅,由摄像机记录经被测镜面反射产生的光栅变形条纹图,通过四步相移法获得条纹图的相位分布。由变形条纹和光栅的同名相位点确定被测镜面每一点的横向像差,对应理想镜面的横向像差由几何关系算出,通过两镜面对应点的横向像差之差获得待测点面形偏差的梯度信息,对其积分恢复面形偏差,最后重建被测面形。检测中光栅由计算机产生,可实现精确的相移,使垂直和水平光栅严格达到90°。采用预设标记点来引导相位展开,有效地解决了变形条纹和光栅的相位对应问题。模拟和实验初步验证了这一方法的可行性。
Based on the Ronchi test and the synchronous phase detection technique, a method of testing aspheric mirrors is proposed in the case of off-axis point sources. In this method, a vertical and horizontal sinusoidal grating is displayed by a transmissive liquid crystal display (LCD). A grating deformation fringe pattern recorded by the mirror is recorded by the camera. The phase distribution of the fringe pattern is obtained by a four-step phase shift method. The transverse aberration of each point of the mirror to be measured is determined by the deformed stripe and the point of the same name of the grating. The lateral aberration corresponding to the ideal mirror is calculated from the geometric relationship. The deviation of the measured point from the difference of the transverse aberrations of the corresponding points of the two mirrors is obtained Of the gradient information, the integral recovery of surface shape deviation, and finally reconstruct the measured surface shape. Detection of the grating generated by the computer, can achieve accurate phase shift, so that vertical and horizontal grating strictly up to 90 °. Predetermined points are used to guide the phase unwrapping, which effectively solves the problem of deformation fringes and grating phase correspondence. Simulation and experiment preliminary verify the feasibility of this method.