基于空间光调制的确定性相位恢复研究

发布时间：2018-02-09 15:16

本文关键词： 相位恢复强度传输方程空间光调制相位调制振幅调制　出处：《安徽大学》2017年硕士论文　论文类型：学位论文

【摘要】：光波场的性质可以从三个方面来完全描述:振幅(亮度)、波长(颜色)和相位(一个波长内相位等同于深度)。统计表明80%以上的信息保存在相位项中,由此可见,相对于强度等其他信息,相位信息显得尤为重要。然而,光波场的振荡频率(约为1015Hz)远高于现有最高速的光探测器帧频(108Hz),探测器只能测量出光波场的强度变化,而无法直接探测到光波场的相位信息。因此,需要利用测量的强度分布来计算相位信息,即为相位恢复问题。目前,相位恢复已经应用到光学测量、天文学成像、电子显微学、自适应光学、光学相位显微等众多领域。基于强度传输方程的相位恢复是一种典型的非干涉确定性相位恢复方法。该方程建立了光强度的轴向变化量与相位之间的定量关系,只需要测量物面的强度分布,就可以通过求解该方程直接计算出相位信息。相较于干涉相位恢复方法,基于强度传输方程的相位恢复不需要复杂的光学系统,对于实验环境要求不苛刻。另外,求解过程不需要迭代,且求解出的相位不需要解缠。然而,基于强度传输方程求解的结果存在分辨率低以及采集图像时需要机械地移动成像器件CCD等缺点,易受到强度差分高阶近似的非线性误差和测量噪声的影响,因而,限制了恢复结果的精度。空间光调制器本质上是一个适应性光学装置,它能在波阵面上施加空间和时间变化调制,改变波阵面的振幅、相位和偏振。本文利用空间光调制器对光场调制的特性,将其应用到相位恢复的相关计算中,提出了新的相位恢复算法,搭建了相应的实验平台,获得了具有高质量的相位恢复结果。主要研究工作和创新点如下:(1)基于空间域相位调制的相位恢复,研究了基于倾斜光照合成的相位恢复算法。将空间光调制器放置在空间域中,加载不同角度的倾斜光栅对入射光场进行相位调制,并通过合成孔径技术计算出相位,提高了恢复图像的分辨率,获得了具有高质量的恢复结果。(2)基于空间域振幅调制的相位恢复,提出了基于余弦光栅调制和强度传输方程的相位恢复算法。将空间光调制器放置在空间域中,加载余弦光栅对入射光场进行振幅调制,利用获取的强度图像求解强度传输方程计算出相位偏导数,进一步地由相位偏导数恢复出相位信息。并通过实验验证了该算法的有效性,实验结果表明该算法可有效地抑制噪声对恢复结果的影响。(3)基于频率域振幅调制的相位恢复,提出了基于正弦光栅调制的相位恢复算法。将空间光调制器放置在频率域中,加载正弦光栅对光场的振幅进行调制,通过强度与相位偏导数之间的关系计算出相位偏导数,从而进一步获得相位信息。设计了光学实验平台,可快速采集到强度图像,避免了传统方法中机械地移动成像器件造成的误差,并利用采集的真实图像计算出相位分布。模拟实验与真实实验结果验证了该算法的正确性和有效性。
[Abstract]:The properties of the optical wave field can be described in three aspects: amplitude (luminance), wavelength (color) and phase (the phase within a wavelength is equal to depth). Statistics show that more than 80% information is stored in the phase term. Compared with other information, such as intensity, the phase information is particularly important. However, the oscillation frequency of the optical wave field (about 1015Hz) is much higher than the frame rate of the most high-speed photodetector (108Hz), and the detector can only measure the intensity change of the optical wave field. But the phase information of light wave field can not be detected directly. Therefore, it is necessary to use the intensity distribution of measurement to calculate the phase information, that is, phase recovery problem. At present, phase recovery has been applied to optical measurement, astronomical imaging, electron microscopy. Adaptive optics, optical phase microscopy and so on. The phase recovery based on the intensity transfer equation is a typical non-interference deterministic phase recovery method. The equation establishes the quantitative relationship between the axial variation of optical intensity and the phase. The phase information can be directly calculated by solving the equation by measuring the intensity distribution of the object surface. Compared with the interferometric phase recovery method, the phase recovery based on the intensity transmission equation does not require complex optical systems. The requirements for the experimental environment are not harsh. In addition, the solution process does not require iteration, and the phase of the solution does not require unwrapping. However, The results based on the intensity transfer equation have the disadvantages of low resolution and the need to move the imaging device CCD mechanically when collecting images, which are easily affected by the nonlinear error of high-order approximation of intensity difference and measurement noise. The spatial light modulator is essentially an adaptive optical device that can apply spatial and temporal modulation on the wavefront to change the amplitude of the wavefront. Based on the characteristics of spatial light modulator for light field modulation, this paper applies it to the calculation of phase recovery, proposes a new phase recovery algorithm, and builds a corresponding experimental platform. The results of phase recovery with high quality are obtained. The main work and innovations are as follows: 1) Phase recovery based on spatial phase modulation. The phase recovery algorithm based on tilted light synthesis is studied. The spatial light modulator is placed in the spatial domain, and the incident light field is modulated by a tilted grating with different angles, and the phase is calculated by the synthetic aperture technique. The resolution of the restored image is improved, and the phase recovery based on amplitude modulation in spatial domain is obtained. A phase recovery algorithm based on cosine grating modulation and intensity transfer equation is proposed. The spatial light modulator is placed in the spatial domain and cosine grating is loaded to modulate the incident light field. Using the obtained intensity image to solve the intensity transfer equation, the phase partial derivative is calculated, and the phase information is further recovered from the phase partial derivative. The validity of the algorithm is verified by experiments. Experimental results show that the proposed algorithm can effectively suppress the effect of noise on the recovery results. The phase recovery algorithm based on amplitude modulation in frequency domain is proposed. A phase recovery algorithm based on sinusoidal grating modulation is proposed. The spatial light modulator is placed in the frequency domain. The amplitude of light field is modulated by loading sinusoidal grating, the phase partial derivative is calculated by the relation between intensity and phase partial derivative, and the phase information is further obtained. The error caused by mechanical moving imaging device in the traditional method is avoided, and the phase distribution is calculated by using the collected real image. The correctness and validity of the algorithm are verified by the simulation and real experiment results.
【学位授予单位】：安徽大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN761;TP391.41

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