Calculate exposure time, update docstring, documentation added
This commit is contained in:
parent
751d9bd9d3
commit
8845e60654
@ -3,7 +3,7 @@ from .ASensor import ASensor
|
||||
from ..IRadiant import IRadiant
|
||||
from ..Entry import Entry
|
||||
import numpy as np
|
||||
from typing import Union
|
||||
from typing import Union, Tuple
|
||||
from ..psf.Airy import Airy
|
||||
from ..psf.Zemax import Zemax
|
||||
from ..SpectralQty import SpectralQty
|
||||
@ -92,7 +92,7 @@ class Imager(ASensor):
|
||||
common_conf.psf.osf, pixel_size)
|
||||
|
||||
@u.quantity_input(exp_time="time")
|
||||
def getSNR(self, exp_time: u.Quantity):
|
||||
def getSNR(self, exp_time: u.Quantity) -> u.Quantity:
|
||||
"""
|
||||
Calculate the signal to background ratio (SNR) for the given exposure time using the CCD-equation.
|
||||
|
||||
@ -103,91 +103,158 @@ class Imager(ASensor):
|
||||
|
||||
Returns
|
||||
-------
|
||||
snr : float
|
||||
The calculated SNR
|
||||
snr : Quantity
|
||||
The calculated SNR as dimensionless quantity
|
||||
"""
|
||||
# Calculate the electron currents
|
||||
signal_current, background_current, read_noise, dark_current = self.__exposePixels()
|
||||
# Calculate the number of collected electrons
|
||||
signal = signal_current * exp_time
|
||||
background = background_current * exp_time
|
||||
dark = dark_current * exp_time
|
||||
return self.__calcSNR(signal, background, read_noise, dark)
|
||||
|
||||
snr = self.__calcSNR(*self.__exposePixels(), exp_time)
|
||||
return snr.value
|
||||
|
||||
def getExpTime(self, snr: float) -> u.Quantity:
|
||||
def getExpTime(self, snr: u.Quantity) -> u.Quantity:
|
||||
"""
|
||||
Calculate the necessary exposure time in order to achieve the given SNR.
|
||||
|
||||
Parameters
|
||||
----------
|
||||
snr : float
|
||||
The SNR for which the necessary exposure time shall be calculated.
|
||||
snr : Quantity
|
||||
The SNR for which the necessary exposure time shall be calculated as dimensionless quantity.
|
||||
|
||||
Returns
|
||||
-------
|
||||
exp_time : Quantity
|
||||
The necessary exposure time in seconds.
|
||||
"""
|
||||
# # Calculate the number of exposed pixels which will be used for calculating the noise
|
||||
# n_pix_exposed = self.__calcExposedPixels()
|
||||
# # Calculate the electron current from the target and the background
|
||||
# signal_current, background_current = self.__calcElectronCurrent(n_pix_exposed)
|
||||
# # Fix the physical units of the SNR
|
||||
# snr = snr * u.electron**0.5
|
||||
#
|
||||
# # Calculate the ratio of the background- and dark-current to the signal current as auxiliary variable
|
||||
# current_ratio = (background_current + n_pix_exposed * self.__dark_current) / signal_current
|
||||
# # Calculate the necessary exposure time as inverse of the CCD-equation
|
||||
# exp_time = snr ** 2 * (1 + current_ratio + np.sqrt(
|
||||
# (1 + current_ratio) ** 2 + 4 * (self.__read_noise * n_pix_exposed) ** 2 / snr ** 2)) /\
|
||||
# (2 * signal_current)
|
||||
# return exp_time
|
||||
# Calculate the electron currents
|
||||
signal_current, background_current, read_noise, dark_current = self.__exposePixels()
|
||||
# Calculate the electron currents for all pixels
|
||||
signal_current_tot = signal_current.sum()
|
||||
background_current_tot = background_current.sum()
|
||||
read_noise_tot = read_noise.sum()
|
||||
dark_current_tot = dark_current.sum()
|
||||
# Fix the physical units of the SNR
|
||||
snr = snr * u.electron**0.5
|
||||
|
||||
@u.quantity_input(signal_current=u.electron / u.s, background_current=u.electron / u.s,
|
||||
read_noise=u.electron ** 0.5, dark_current=u.electron / u.s, exp_time="time")
|
||||
def __calcSNR(self, signal_current: u.Quantity, background_current: u.Quantity, read_noise: u.Quantity,
|
||||
dark_current: u.Quantity, exp_time: u.Quantity) -> u.dimensionless_unscaled:
|
||||
# Calculate the SNR using the CCD-equation
|
||||
signal = signal_current * exp_time
|
||||
background = background_current * exp_time
|
||||
dark = dark_current * exp_time
|
||||
# Calculate the ratio of the background- and dark-current to the signal current as auxiliary variable
|
||||
current_ratio = (background_current_tot + dark_current_tot) / signal_current_tot
|
||||
# Calculate the necessary exposure time as inverse of the CCD-equation
|
||||
exp_time = snr ** 2 * (1 + current_ratio + np.sqrt(
|
||||
(1 + current_ratio) ** 2 + 4 * read_noise_tot ** 2 / snr ** 2)) /\
|
||||
(2 * signal_current_tot)
|
||||
# Calculate the SNR in order to check for overexposed pixels
|
||||
self.__calcSNR(signal_current * exp_time, background_current * exp_time, read_noise, dark_current * exp_time)
|
||||
return exp_time
|
||||
|
||||
@u.quantity_input(signal=u.electron, background=u.electron, read_noise=u.electron ** 0.5, dark=u.electron)
|
||||
def __calcSNR(self, signal: u.Quantity, background: u.Quantity, read_noise: u.Quantity,
|
||||
dark: u.Quantity) -> u.dimensionless_unscaled:
|
||||
"""
|
||||
Calculate the signal to noise ratio (SNR) of the given electron counts.
|
||||
|
||||
Parameters
|
||||
----------
|
||||
signal : Quantity
|
||||
The collected electrons from the target in electrons.
|
||||
background : Quantity
|
||||
The collected electrons from the background in electrons.
|
||||
read_noise : Quantity
|
||||
The read noise in electrons.
|
||||
dark : Quantity
|
||||
The electrons from the dark current in electrons.
|
||||
|
||||
Returns
|
||||
-------
|
||||
snr : Quantity
|
||||
The signal to noise ration as dimensionless quantity
|
||||
"""
|
||||
# Calculate the total collected electrons per pixel
|
||||
total = signal + background + dark
|
||||
# Check for overexposed pixels
|
||||
overexposed = total > self.__well_capacity
|
||||
if np.any(overexposed):
|
||||
# Show a warning for the overexposed pixels
|
||||
warning(str(np.count_nonzero(overexposed)) + " pixels are overexposed.")
|
||||
info("Collected electrons from target: %1.2e electrons" % signal.sum().value)
|
||||
info("Collected electrons from background: %1.2e electrons" % background.sum().value)
|
||||
info("Electrons from dark current: %1.2e electrons" % dark.sum().value)
|
||||
info("Read noise: %1.2e electrons" % (read_noise ** 2).sum().value)
|
||||
info("Total collected electrons: %1.2e electrons" % total.sum().value)
|
||||
# Calculate the SNR using the CCD-equation
|
||||
snr = signal.sum() / np.sqrt(total.sum() + (read_noise ** 2).sum())
|
||||
# Return the value of the SNR, ignoring the physical units (electrons^0.5)
|
||||
return snr.value * u.dimensionless_unscaled
|
||||
|
||||
def __exposePixels(self) -> (u.electron / u.s, u.electron / u.s, u.electron, u.electron / u.s):
|
||||
signal_current, size, obstruction, background_current = self.__calcPixelElectronCurrent()
|
||||
def __exposePixels(self) -> Tuple[u.Quantity, u.Quantity, u.Quantity, u.Quantity]:
|
||||
"""
|
||||
Expose the pixels and calculate the signal and noise electron currents per pixel.
|
||||
|
||||
Returns
|
||||
-------
|
||||
signal_current : Quantity
|
||||
The electron current from the target as PixelMask in electrons / s
|
||||
background_current : Quantity
|
||||
The electron current from the background as PixelMask in electrons / s
|
||||
read_noise : Quantity
|
||||
The read noise per pixel in electrons
|
||||
dark_current : Quantity
|
||||
The electron current from the dark noise as PixelMask in electrons / s
|
||||
"""
|
||||
# Calculate the total incoming electron current
|
||||
signal_current, size, obstruction, background_current = self.__calcIncomingElectronCurrent()
|
||||
# Initialize a new PixelMask
|
||||
mask = PixelMask(self.__pixel_geometry, self.__pixel_size, self.__center_offset)
|
||||
if size.lower() == "extended":
|
||||
# Target is extended, a diameter of 0 pixels results in a mask with one pixel marked
|
||||
d_photometric_ap = 0 * u.pix
|
||||
# Mask the pixels to be exposed
|
||||
mask.createPhotometricAperture("circle", d_photometric_ap / 2, np.array([0, 0]) << u.pix)
|
||||
else:
|
||||
# Target is a point source
|
||||
if self.__contained_pixels is not None:
|
||||
# Calculate the diameter of the photometric aperture as square root of the contained pixels
|
||||
d_photometric_ap = np.sqrt(self.__contained_pixels.value) * u.pix
|
||||
# Mask the pixels to be exposed
|
||||
mask.createPhotometricAperture("square", d_photometric_ap / 2, np.array([0, 0]) << u.pix)
|
||||
else:
|
||||
# Calculate the diameter of the photometric aperture from the given contained energy
|
||||
d_photometric_ap = self.__calcPhotometricAperture(obstruction)
|
||||
# Mask the pixels to be exposed
|
||||
mask.createPhotometricAperture(self.__shape, d_photometric_ap / 2)
|
||||
background = mask * background_current * u.pix
|
||||
# Calculate the background current PixelMask
|
||||
background_current = mask * background_current * u.pix
|
||||
# Calculate the read noise PixelMask
|
||||
read_noise = mask * self.__read_noise * u.pix
|
||||
# Calculate the dark current PixelMask
|
||||
dark_current = mask * self.__dark_current * u.pix
|
||||
info("The radius of the photometric aperture is %.2f pixels." % (d_photometric_ap.value / 2))
|
||||
info("The photometric aperture contains " + str(np.count_nonzero(mask)) + " pixels.")
|
||||
if size.lower() != "extended":
|
||||
# Map the PSF onto the pixel mask in order to get the relative irradiance of each pixel
|
||||
mask = self.__psf.mapToPixelMask(mask,
|
||||
getattr(getattr(self.__common_conf, "jitter_sigma", None), "val", None),
|
||||
obstruction)
|
||||
signal = mask * signal_current
|
||||
return signal, background, read_noise, dark_current
|
||||
# Calculate the signal current PixelMask
|
||||
signal_current = mask * signal_current
|
||||
return signal_current, background_current, read_noise, dark_current
|
||||
|
||||
def __calcPhotometricAperture(self, obstruction: float) -> u.Quantity:
|
||||
"""
|
||||
Calculate the diameter of the photometric aperture
|
||||
|
||||
Parameters
|
||||
----------
|
||||
obstruction : float
|
||||
The obstruction factor as A_ob / A_ap.
|
||||
|
||||
Returns
|
||||
-------
|
||||
d_photometric_ap : Quantity
|
||||
The diameter of the photometric aperture in pixels.
|
||||
"""
|
||||
# Calculate the reduced observation angle
|
||||
# jitter_sigma = self.__common_conf.jitter_sigma() if hasattr(self.__common_conf, "jitter_sigma") else None
|
||||
jitter_sigma = getattr(getattr(self.__common_conf, "jitter_sigma", None), "val", None)
|
||||
reduced_observation_angle = self.__psf.calcReducedObservationAngle(self.__contained_energy, jitter_sigma,
|
||||
obstruction)
|
||||
@ -202,7 +269,7 @@ class Imager(ASensor):
|
||||
d_photometric_ap = observation_angle / pixel_fov
|
||||
return d_photometric_ap * u.pix
|
||||
|
||||
def __calcPixelElectronCurrent(self) -> (u.electron / u.s, str, float, u.electron / (u.pix * u.s)):
|
||||
def __calcIncomingElectronCurrent(self) -> Tuple[u.Quantity, str, float, u.Quantity]:
|
||||
"""
|
||||
Calculate the detected electron current of the signal and the background.
|
||||
|
||||
@ -213,7 +280,7 @@ class Imager(ASensor):
|
||||
size : str
|
||||
The size of the target.
|
||||
obstruction : float
|
||||
The obstruction factor.
|
||||
The obstruction factor as A_ob / A_ap.
|
||||
background_current : Quantity
|
||||
The electron current on the detector caused by the background in electrons / (s * pix).
|
||||
"""
|
||||
|
||||
Loading…
Reference in New Issue
Block a user