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farhadnkm / Fringe.Py

A Python implementation of diffraction and coherent field propagation by angular spectrum method.
MIT License
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angular-spectrum coherent-propagation diffraction holography python

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Fringe.Py

GitHub version PyPI version DOI MIT License

A coherent propagation and diffraction simulation tool, all written in Python.

In this package, a set of utilities are provided to simulate coherent signal propagation. It is particularly made for free-space optical propagation, diffraction, and holography. However, the tools are compatible with 1D and 2D data structures and can be potentially used for any sort of spatially-coherent signals.

## What's inside? A set of modules are provided to solve the scalar diffraction problem. The codes are GPU-friendly, compatible with well-known computation libraries (Numpy, TensorFlow) and they support batch processing. Using the TensorFlow backend, computations become autograd-compatible and could be mounted on machine learning models. Angular spectrum algorithm is the primary work horse for field propagation though other custom solvers could be used. Aside the built-in Numpy and TensorFlow backends, any computational means could be employed to process tensor operations. It also includes: - a simple yet useful data pipeline to load and standardize data. For now, it only supports images. - Gerchberg-Saxton multi-distance phase recovery algorithm. It can be easily tweaked to support other variations of signal e.g. by wavelength. ## Installation To install the package, run: ``` python -m pip install fringe ``` Fringe requires ```numpy```, ```tensorflow 2.x```, and ```scikit_image```. The example files are not included in the package and should be downloaded separately. Also they require ```matplotlib``` to show plots. ## How to Use 1. Import or create data For images: ```python import numpy as np from fringe.utils.io import import_image from fringe.utils.modifiers import ImageToArray, Normalize, MakeComplex ``` Images need to be standardized, normalized, and casted to complex data type. *Modifiers* are tools made for this purpose which apply these operations on import. ```python p1 = ImageToArray(bit_depth=16, channel='gray', crop_window=None, dtype='float32') p2 = Normalize(background=np.ones((512, 512))) p3 = MakeComplex(set_as='amplitude', phase=0) obj = import_image("images/squares.png", preprocessor=[p1, p2, p3]) ``` 2. Propagate *Solvers* contain propagation algorithms and can be called by *solver.solve*. In particular, angular Spectrum algorithm convolves the input field with a free-space propagtor function which depends on *wavelength λ* (or *wavenumber k=2π/λ*) and distance *z*. ```python from numpy import pi, abs, angle from fringe.solvers.AngularSpectrum import AngularSpectrumSolver as AsSolver solver = AsSolver(shape=obj.shape, dr=1, is_batched=False, padding="same", pad_fill_value=0, backend="Numpy") rec = solver.solve(hologram, k=2*pi/500e-3, z=-1000) amp, phase = abs(rec), angle(rec) ax = pyplot.sublots(2, 1, 1) ax[0].imshow(abs(obj)) ax[1].imshow(amp) pyplot.show() ```

Example notebooks provide further details with 1D and 2D diffraction, GPU acceleration, batch processing, and phase recovery. ## License Fringe is released under the MIT license. See LICENSE for details.