psf.mmdft

MMDFT Point Spread Function (PSF) Module

This module provides functionality for simulating and analyzing the Point Spread Function (PSF) of optical systems using the Matrix Multiply Discrete Fourier Transform. It includes capabilities for generating a monochromatic PSF at a desired image size and pixel pitch from given wavefront aberrations and calculating the Strehl ratio. Visualization is handled by the base class.

Scott Paine, 2025

Classes

MMDFTPSF(optic, field, wavelength[, ...])

Class representing the Matrix Multiply Discrete Fourier Transform (MMDFT) PSF.
class MMDFTPSF(optic, field, wavelength: str | float, num_rays=128, image_size=None, pixel_pitch=None, strategy='chief_ray', remove_tilt=False, **kwargs)[source]

Class representing the Matrix Multiply Discrete Fourier Transform (MMDFT) PSF.

This class computes the PSF of an optical system by taking the Fourier Transform of the pupil function. It inherits common visualization and initialization functionalities from BasePSF.

Parameters:

  • optic (Optic) – The optical system object, containing properties like paraxial data and surface information.

  • field (tuple) – The field point (e.g., (Hx, Hy) in normalized field coordinates) at which to compute the PSF.

  • wavelength (str | float) – The wavelength of light in micrometers. Can be ‘primary’ or a float value.

  • num_rays (int, optional) – The number of rays used to sample the pupil plane along one dimension. The pupil will be a grid of num_rays x num_rays. Defaults to 128.

  • image_size (int, optional) – The size of the image plane, in pixels. If not specified, it is calculated based on num_rays.

  • pixel_pitch (float, optional) – The size of the pixels in the image plane. If not specified, it is calculated based on image_size.

  • strategy (str) – The calculation strategy to use. Supported options are “chief_ray”, “centroid_sphere”, and “best_fit_sphere”. Defaults to “chief_ray”.

  • remove_tilt (bool) – If True, removes tilt and piston from the OPD data. Defaults to False.

  • **kwargs – Additional keyword arguments passed to the strategy.

pupil

A complex-valued pupil function based on the wavelength used in the Wavefront parent. The pupil is a 2D array.

Type:

be.ndarray

psf

The computed Point Spread Function. This is a 2D array representing the intensity distribution in the image plane, normalized such that a diffraction-limited system has a peak of 100.

Type:

be.ndarray

image_size

The output size of the image after DFT calculation.

Type:

int

pixel_pitch

The resolution of the image after DFT calculation.

Type:

float

num_rays

The number of rays used to sample the pupil. This is the num_rays passed during initialization and used by Wavefront for generating OPD/intensity data.

Type:

int

static fit_and_remove_tilt(data: WavefrontData, remove_piston: bool = False, ridge: float = 1e-12) → be.ndarray

Removes piston and tilt from OPD data using weighted least squares.

Parameters:

  • data (WavefrontData) – The wavefront data containing pupil coordinates and OPD.

  • remove_piston (bool, optional) – If True, removes piston term as well as tilt. Defaults to False.

  • ridge (float, optional) – Small diagonal regularization for stability. Defaults to 1e-12.

Returns:

OPD with piston and tilt removed, shape (N,).

Return type:

opd_detrended (be.ndarray)

get_data(field: tuple[float, float], wl: float) → WavefrontData

Retrieves precomputed wavefront data for a field and wavelength.

Parameters:

  • field (tuple[float, float]) – The field coordinates, or a FieldPoint.

  • wl (float) – The wavelength in µm, or a WavelengthPoint.

Returns:

A data container with the computed wavefront results.

Return type:

WavefrontData

strehl_ratio()[source]

Computes the Strehl ratio of the PSF.

The Strehl ratio is the ratio of the peak intensity of the aberrated PSF to the peak intensity of the diffraction-limited PSF. Assumes self.psf is normalized such that its peak would be 1.0 (or 100%) for a diffraction-limited system.

Returns:

The Strehl ratio.

Return type:

float

Raises:

RuntimeError – If the PSF has not been computed.

view(fig_to_plot_on: Figure | None = None, projection: str = '2d', log: bool = False, figsize: tuple = (7, 5.5), threshold: float = 0.05, num_points: int = 128) → tuple[Figure, Axes]

Visualizes the PSF.

Parameters:

  • projection (str, optional) – The projection type. Can be ‘2d’ or ‘3d’. Defaults to ‘2d’.

  • log (bool, optional) – Whether to use a logarithmic scale for the intensity. Defaults to False.

  • figsize (tuple, optional) – The figure size. Defaults to (7, 5.5).

  • threshold (float, optional) – The threshold for determining the bounds of the PSF for zoomed view. Defaults to 0.05.

  • num_points (int, optional) – The number of points used for interpolating the PSF for smoother visualization. Defaults to 128.

Returns:

A tuple containing the figure and axes objects.

Return type:

tuple

Raises:

  • RunentimeError – If the PSF has not been computed.

  • ValueError – If the projection is not ‘2d’ or ‘3d’.

  • RuntimeError – If the PSF has not been computed by the subclass.