Richardson–Lucy deconvolution

本文深入探讨了Richardson-Lucy去模糊算法的核心原理,包括其数学公式、迭代过程及适用条件,特别关注了算法在解决模糊图像恢复问题时的实际应用。

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Richardson–Lucy deconvolution

From Wikipedia, the free encyclopedia

The Richardson–Lucy algorithm, also known as Lucy–Richardson deconvolution, is an iterative procedure for recovering a latent image that has been blurred by a known point spread function.[1][2]

Pixels in the observed image can be represented in terms of the point spread function and the latent image as

 d_{i} = \sum_{j} p_{ij} u_{j}\,

where p_{ij} is the point spread function (the fraction of light coming from true location j that is observed at position i), u_{j} is the pixel value at location j in the latent image, and d_{i} is the observed value at pixel location i. The statistics are performed under the assumption that u_j are Poisson distributed, which is appropriate for photon noise in the data.

The basic idea is to calculate the most likely u_j given the observed d_i and known p_{ij}. This leads to an equation for u_j which can be solved iteratively according to

u_{j}^{(t+1)} = u_j^{(t)} \sum_{i} \frac{d_{i}}{c_{i}}p_{ij}

where

c_{i} = \sum_{j} p_{ij} u_{j}^{(t)}.

It has been shown empirically that if this iteration converges, it converges to the maximum likelihood solution for u_j.[3]

In problems where the point spread function p_{ij} is dependent on one or more unknown parameters, the Richardson–Lucy algorithm cannot be used. A later and more general class of algorithms, theexpectation-maximization algorithms,[4] have been applied to this type of problem with great success

[edit]References

  1. ^ Richardson, William Hadley (1972). "Bayesian-Based Iterative Method of Image Restoration"JOSA 62 (1): 55–59. doi:10.1364/JOSA.62.000055.
  2. ^ Lucy, L. B. (1974). "An iterative technique for the rectification of observed distributions". Astronomical Journal 79 (6): 745–754. doi:10.1086/111605.
  3. ^ Shepp, L. A.; Vardi, Y. (1982), "Maximum Likelihood Reconstruction for Emission Tomography", IEEE Transactions on Medical Imaging 1: 113, doi:10.1109/TMI.1982.4307558
  4. ^ A.P. Dempster, N.M. Laird, D.B. Rubin, 1977, Maximum likelihood from incomplete data via the EM algorithm, J. Royal Stat. Soc. Ser. B, 39 (1), pp. 1–38
来源:http://en.wikipedia.org/wiki/Richardson%E2%80%93Lucy_deconvolution
### RichardsonLucy去卷积算法实现及其应用 RichardsonLucy (RL) 去卷积算法是一种用于图像恢复的技术,广泛应用于天文学、显微镜成像以及医学影像等领域。该方法基于贝叶斯推断理论,假设观测到的模糊图像是由清晰图像通过某种点扩散函数(PSF, Point Spread Function)产生的[^1]。 #### 理论基础 RL算法的核心在于迭代更新估计值 \( f^{(k)} \),使得它逐渐逼近原始未被模糊化的图像。具体而言,给定一幅模糊图像 \( g(x,y) \) 和已知的 PSF 函数 \( h(x,y) \),可以通过以下公式计算第 k 次迭代的结果: \[ f^{(k+1)}(x,y) = f^{(k)}(x,y) \cdot \frac{g(x,y)}{(h * f^{(k)})} \] 其中,“*”表示卷积操作,\( f^{(0)} \) 是初始猜测值通常设为均匀分布或者全一矩阵[^2]。 #### 实现代码示例 以下是 Python 中利用 NumPy 库实现的一个简单版本 RL 去卷积算法: ```python import numpy as np from scipy.signal import convolve2d def richardson_lucy(image, psf, iterations=30): """ Apply the Richardson-Lucy deconvolution on an image. Parameters: image : ndarray The blurred input image. psf : ndarray The point spread function used during blurring process. iterations : int Number of iterations for the algorithm. Returns: estimate : ndarray Deblurred version of `image`. """ im_deconv = np.ones_like(image, dtype=float) for _ in range(iterations): relative_blur = image / convolve2d(im_deconv, psf, mode='same') error_estimation = convolve2d(relative_blur[::-1, ::-1], psf[::-1, ::-1], mode='same')[::-1, ::-1] im_deconv *= error_estimation return im_deconv ``` 此代码片段定义了一个名为`richardson_lucy()` 的函数来执行 RL 迭代过程,并返回最终估算出来的无噪声图片数据数组形式结果。 #### 应用场景 RL 方法特别适合处理那些由于光学系统缺陷而引起的恒星或其他光源形状失真的情况,在天文摄影中有重要用途;另外还常用来改善电子显微照片质量以及核磁共振扫描仪获取的数据精度等问题上也有良好表现。
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