近些年新出现的层叠相位重建引擎（PIE）是一种能够有效解决相位测量难题的无透镜成像技术，相比于传统的相干衍射成像技术，PIE技术具备更高的重建精度、更好的收敛性。由于理论上具备可无限拓展的视场范围、超高分辨能力和对噪声的强鲁抗性，PIE目前被广泛应用于各种相位成像和相位测量领域。讨论了PIE技术提出的背景和核心原理，同时总结了近些年该类算法的主要技术突破，特别地，讨论了PIE技术在X射线、电子束和可见光波段成像领域的关键节点。此外，还总结了在其他领域中基于PIE技术的变形算法，并对将来可能的技术突破点和所面临的挑战进行了讨论。

激光光束质量因子(M²)是全面表征激光光束质量的一个技术评价指标。提出了一种基于振幅调制的M²测量方法,该方法通过记录单幅激光光斑就可以利用迭代计算重建光束的复振幅;进而根据标量衍射理论,可以得到沿光束传输方向任意截面位置的光束强度分布;最后由二阶矩和双曲线拟合方法计算M²因子。模拟和实验验证了所提方法的有效性,且该实验技术简单、快速,不需要复杂的机械扫描结构,适用于脉冲激光光束质量的测量。

将相干调制成像(CMI)迭代过程等效为梯度搜索算法,建立了CMI收敛模型,从解方程角度提出为保证重建结果的唯一性需要满足的基本条件,即有调制板时光斑非0点数是无调制板时光斑非0点数的2倍,或有调制板时放大λL(λ为波长, L为衍射距离)倍后的调制板频谱截止宽度与无调制板时光斑截止宽度的比值至少为0.414。通过模拟计算进行了很好的验证。该研究为CMI的进一步优化提供了理论依据。

提出一种大倾角照明条件下的高精度PIE(ptychographic iterative engine)迭代重建算法。该算法用小角度照明的透射光代替大角度照明的透射光,通过修正角谱传递函数,得到适应大角度迭代的光场传输公式。在非傍轴条件下,该算法能够避免样品面上相位分布欠采样的问题,同时精确计算衍射面上的衍射光斑,为单次曝光PIE成像的进一步发展和实际应用解决了最为关键的技术难题。

Ptychography是近些年快速发展起来的一种新型相位恢复技术,通过对待测样品以小于照明光直径的步长扫描后,利用迭代计算可以重建出照明光和样品复振幅分布,是一种理论分辨率为衍射极限的非透镜相位成像技术。虽然其提出初期受限于基本假定条件,但近些年随着相关研究的跟进,人们对Ptychography算法特性的理解逐渐深入,算法也日趋成熟,在可见光、X射线和电子束等领域已被广泛应用于相位成像、波前诊断和光学计量,因此针对影响重建过程和精度的关键因素,如模态多样化、扫描误差、光斑误差、距离误差、样品厚度不可忽略等进行了总结,并讨论了针对上述问题的关键技术进展。

As a newly developed lensless imaging technique, PIE (ptychographical iterative engine) does not only maintain the simplicity and convenience of the equipment of traditional coherent diffraction imaging (CDI) methods, but also overcomes the drawbacks such as restricted field of view and slow convergence. With the extensible imaging field, better convergence speed and higher immunization capability to noise, PIE is widely researched and used in optical, X-ray and electron beam imaging fields. PIE is a new method which is possible to replace the current phase imaging methods. The background, development, applications, problems and developing trend of the PIE method are introduced.

Coherent modulation imaging (CMI) based algorithm has been employed for on- shot laser beam diagnostics in high power laser facility and off- line measurement of large- scale optic element. A single- shot intensity measurement is sufficient for wave-front reconstruction after the random phase plate has been accurately pre- characterized, and the iteration process can be finished in 30 seconds with the acceleration of graphics processing unit (GPU) device. Furthermore, a compact structure is also available after combining CCD and phase plate together, which can be placed almost anywhere of high power laser facilities. Series of experiments have been finished for focal-spot prediction, measurement of large-scale continuous phase plate, and on-shot wave-front reconstruction of seed pulse in our high power laser facility with amplifiers turned off. The flexibility of CMI for focal- spot prediction, on- shot wave- front diagnostic and off- line measurement of optic elements has been demonstrated for its characteristic. It has significant influence on the development of high power laser facilities as a new method for wave-front measurement and diagnostics.

When high-power solid laser working in high repetition rate, the laser output wave-front changes due to the thermal distortion, which is caused by the gain medium under the heat deposition. Therefore, the coherent modulation imaging technology is used to realize the measurement of the laser output wave-front from one frame of diffraction intensity recorded. The phases of thermal distortion of the optical element are obtained when the amplifier working in 1, 5, 7 Hz frequency. Experimental results show that thermal distortion effect is significantly increased, the heat is concentrated toward the center region and the phase change increases as the working frequency increases.

高功率固体激光器工作在高重复频率时，增益介质因热量的沉积而发生热畸变，导致激光输出波前发生变化。为此，利用相干调制成像技术通过记录单幅衍射光斑实现输出光场的波前测量，获得了放大器工作在1,5,7 Hz频率时光学元件的热畸变相位。实验结果显示，随着工作频率增大，热量向中心区域集中，热沉积效应明显增加了波前变化。

作为一种新近发展的无透镜成像技术，PIE(ptychographical iterative engine)不但保持了传统相干衍射成像方法装置简单、使用方便等优点，克服了视场受限和收敛速度慢等缺点，还具有成像范围可扩展、收敛速度快、抗噪声能力强等优势，在光学、X射线和电子束等领域得到了广泛关注并开展了大量研究，是一种有可能在大范围内替代现有相位成像技术的新方法。主要介绍了PIE方法的技术背景、技术现状、相关应用及面临的问题和可能的发展方向。