Fringes 2.1.0

Phase shifting algorithms for encoding and decoding sinusoidal fringe patterns.

Fringes

Easily configure, encode and decode sinusoidal fringe patterns using phase shifting algorithms.

Features

• Configure the phase shifting algorithm
• Encode and decode fringe patterns
• Spatial Phase Unwrapping
• Generalized Temporal Phase Unwrapping
• Multiplexing fringe patterns
• Filtering methods

Installation

You can install fringes directly from PyPi via pip:

pip install fringes

Usage

You instantiate, parameterize and deploy the Fringes class:

from fringes import Fringes  # import the Fringes class

f = Fringes()                # instantiate Fringes object

All parameters are accessible as class properties (managed attributes) of the Fringes instance.

f.X = 1920                   # set width of the fringe patterns
f.Y = 1080                   # set height of the fringe patterns
f.N = 4                      # set number of shifts
f.v = [9, 10]                # set spatial frequencies

print(f.T)                   # get number of frames

To encode the fringe pattern sequence I, use the method encode(). It returns a NumPy array in video-shape (frames, height, width, color channels).

I = f.encode()               # encode fringe patterns

Now display each frame of the fringe pattern sequence on a screen and capture the scene with a camera according to the following pseudocode (a minimal working example is depicted here):

# allocate image stack
Irec = []

for t in range(f.T):
    # display frame of pattern sequence on screen
    frame = I[t]
    ...

    # capture scene with camera
    image = ...
    
    # append to image stack
    Irec.append(image)

To decode (recorded) fringe patterns, use the method decode(). It returns the Numpy arrays brightness a, modulation b and (screen) coordinate x.

a, b, x = f.decode(Irec)     # decode fringe patterns

Note:
For the computationally expensive decode()-function we make use of the just-in-time compiler Numba. During the first execution, an initial compilation is executed. This can take several tens of seconds up to single digit minutes, depending on your CPU and energy settings. However, for any subsequent execution, the compiled code is cached and the code of the function runs much faster, approaching the speeds of code written in C.

More complete code examples can be found in the examples directory.

Support

I was looking for a user-friendly tool for phase shifting. Since I couldn't find any, I started developing one myself. It is intended for non-commercial, academic and educational use.

However, I do this entirely in my free time. If you like this package and can make use of it, I would be happy about a donation. It will help me keep it up-to-date and add more features in the future.

Thank you!