estimate_b_ratio

This module’s scope is the estimation of the b-ratio (the ratio between the size of the pixels in the CCD and the focal length).

Example:

>>> import tuna
>>> estimate = tuna.tools.estimate_b_ratio ( radii = [ 100, 200 ], orders = [ 800, 801 ] )
>>> estimate
0.00028933783055714126
class tuna.tools.estimate_b_ratio.b_ratio_estimator(radii, orders)[source]

Estimator object for finding the b-ratio.

The b-ratio is the ratio between the pixel size (of the interferometer pixel detector) and the focal length of the interferometers. In the absence of this information, it can be estimated by a geometrical relation between two “consecutive” rings in the same interferogram, which is what this estimator does.

Parameters:

  • radii : list of floats

    Contains the concentric radii, sorted with smallest radius first.

  • orders : list of integers

    Contains the interference orders corresponding to the listed radii.

estimate()[source]

The self.radii list should contain at least two radii. The innermost radii is of order “p”, and the next one is of order “p-1”.

The estimate is calculated as:

b^2 = \dfrac { 2 p_c - 1 } { p_c^2 ( r_{c-1}^2 - r_c^2 ) - 2 p_c r_{c-1}^2 + r_{c-1}^2 }

(Thanks to Mr. Benoît Epinat for this model.)

tuna.tools.estimate_b_ratio.estimate_b_ratio(radii, orders)[source]

From a list of radii, supposing each radius corresponds to the distance from a ring to the center, calculates b.

Parameters:

  • radii : list of floats

    Contains the concentric radii, sorted with smallest radius first.

  • orders : list of integers

    Contains the interference orders corresponding to the listed radii.

Returns:

  • estimate : float

    The value estimated for the b-ratio.