NCPA¶

Overview¶

The NCPA (Non-Common Path Aberrations) class creates a static OPD offset to simulate aberrations that are seen by the science camera but not by the wavefront sensor. It generates the OPD as a linear combination of modal basis functions (KL modes, Zernike polynomials, or a user-supplied M2C matrix), optionally following a 1/f² power law distribution over modes.

Quick start¶

from OOPAO.NCPA import NCPA

# Blank NCPA (can assign OPD map manually)
ncpa = NCPA(tel, dm, atm)
ncpa.OPD = my_opd_map

# NCPA from specific KL mode coefficients
ncpa = NCPA(tel, dm, atm, coefficients=[0, 0, 50e-9, 100e-9])

# 1/f² NCPA: 200 nm RMS, modes 5–25, cutoff frequency 1
ncpa = NCPA(tel, dm, atm, f2=[200e-9, 5, 25, 1])

# Propagate
src * tel * ncpa * wfs

API reference¶

class OOPAO.NCPA.NCPA(tel, dm, atm, modal_basis='KL', coefficients=None, f2=None, seed=5, M2C=None)[source]¶

Static non-common-path aberration map.

Parameters:

tel (Telescope) – Telescope object.
dm (DeformableMirror) – Deformable mirror object (used to compute the modal basis).
atm (Atmosphere) – Atmosphere object (used to compute the KL basis).
modal_basis (str) – Basis used to generate the OPD. 'KL' (default), 'Zernike', or 'M2C'.
coefficients (list[float] or None) – List of modal coefficients in metres. Length determines how many modes are used. Default None (blank OPD).
f2 (list or None) – Four-element list [amplitude_m, start_mode, end_mode, cutoff_freq] for a 1/f² power-law NCPA. Default None.
seed (int) – Random seed for reproducible 1/f² generation. Default 5.
M2C (numpy.ndarray or None) – Mode-to-command matrix for the 'M2C' basis option. Default None.

Key properties

OPD: numpy.ndarray¶: 2-D OPD map in metres. Can be set directly to an arbitrary map.

tag: str¶: Always 'NCPA'.

Operator summary

Expression	Effect
`src * tel * ncpa * wfs`	Add NCPA OPD to telescope OPD before WFS sensing