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# -*- coding: utf-8 -*- |
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""" |
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This file contains the Qudi logic for the extraction of laser pulses. |
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Qudi is free software: you can redistribute it and/or modify |
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it under the terms of the GNU General Public License as published by |
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the Free Software Foundation, either version 3 of the License, or |
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(at your option) any later version. |
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Qudi is distributed in the hope that it will be useful, |
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but WITHOUT ANY WARRANTY; without even the implied warranty of |
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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GNU General Public License for more details. |
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You should have received a copy of the GNU General Public License |
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along with Qudi. If not, see <http://www.gnu.org/licenses/>. |
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Copyright (c) the Qudi Developers. See the COPYRIGHT.txt file at the |
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top-level directory of this distribution and at <https://github.com/Ulm-IQO/qudi/> |
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""" |
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import numpy as np |
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from scipy import ndimage |
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from logic.generic_logic import GenericLogic |
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class PulseExtractionLogic(GenericLogic): |
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"""unstable: Nikolas Tomek """ |
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_modclass = 'PulseExtractionLogic' |
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_modtype = 'logic' |
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# declare connectors |
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_out = {'pulseextractionlogic': 'PulseExtractionLogic'} |
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def __init__(self, config, **kwargs): |
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super().__init__(config=config, **kwargs) |
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self.log.info('The following configuration was found.') |
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# checking for the right configuration |
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for key in config.keys(): |
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self.log.info('{0}: {1}'.format(key, config[key])) |
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def on_activate(self, e): |
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""" Initialisation performed during activation of the module. |
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@param object e: Event class object from Fysom. |
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An object created by the state machine module Fysom, |
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which is connected to a specific event (have a look in |
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the Base Class). This object contains the passed event, |
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the state before the event happened and the destination |
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of the state which should be reached after the event |
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had happened. |
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""" |
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self.extraction_method = None # will later on be used to switch between different methods |
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return |
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def on_deactivate(self, e): |
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""" Deinitialisation performed during deactivation of the module. |
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@param object e: Event class object from Fysom. A more detailed |
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explanation can be found in method activation. |
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""" |
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pass |
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def gated_extraction(self, count_data, conv_std_dev): |
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""" Detects the rising flank in the gated timetrace data and extracts |
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just the laser pulses. |
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@param numpy.ndarray count_data: 2D array, the raw timetrace data from a |
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gated fast counter, dimensions: |
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0: gate number, |
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1: time bin) |
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@param float conv_std_dev: standard deviation of the gaussian filter to be |
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applied for smoothing |
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@return numpy.ndarray: The extracted laser pulses of the timetrace |
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dimensions: |
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0: laser number, |
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1: time bin |
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""" |
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# sum up all gated timetraces to ease flank detection |
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timetrace_sum = np.sum(count_data, 0) |
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# apply gaussian filter to remove noise and compute the gradient of the |
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# timetrace sum |
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#FIXME: That option should be stated in the config, or should be |
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# choosable by the GUI, since it is not always desired. |
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# It should also be possible to display the bare laserpulse, |
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# without cutting away something. |
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conv_deriv = self._convolve_derive(timetrace_sum.astype(float), conv_std_dev) |
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# get indices of rising and falling flank |
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rising_ind = conv_deriv.argmax() |
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falling_ind = conv_deriv.argmin() |
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# slice the data array to cut off anything but laser pulses |
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laser_arr = count_data[:, rising_ind:falling_ind] |
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return laser_arr.astype(int) |
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def ungated_extraction(self, count_data, conv_std_dev, num_of_lasers): |
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""" Detects the laser pulses in the ungated timetrace data and extracts |
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them. |
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@param numpy.ndarray count_data: 1D array the raw timetrace data from an |
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ungated fast counter |
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@param int num_of_lasers: The total number of laser pulses inside the |
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pulse sequence |
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@param float conv_std_dev: standard deviation of the gaussian filter to be |
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applied for smoothing |
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@return 2D numpy.ndarray: 2D array, the extracted laser pulses of the |
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timetrace, dimensions: |
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0: laser number, |
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1: time bin |
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Procedure: |
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Edge Detection: |
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--------------- |
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The count_data array with the laser pulses is smoothed with a |
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gaussian filter (convolution), which used a defined standard |
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deviation of 10 entries (bins). Then the derivation of the convolved |
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time trace is taken to obtain the maxima and minima, which |
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corresponds to the rising and falling edge of the pulses. |
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The convolution with a gaussian removes nasty peaks due to count |
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fluctuation within a laser pulse and at the same time ensures a |
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clear distinction of the maxima and minima in the derived convolved |
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trace. |
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The maxima and minima are not found sequentially, pulse by pulse, |
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but are rather globally obtained. I.e. the convolved and derived |
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array is searched iteratively for a maximum and a minimum, and after |
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finding those the array entries within the 4 times |
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self.conv_std_dev (2*self.conv_std_dev to the left and |
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2*self.conv_std_dev) are set to zero. |
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The crucial part is the knowledge of the number of laser pulses and |
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the choice of the appropriate std_dev for the gauss filter. |
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To ensure a good performance of the edge detection, you have to |
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ensure a steep rising and falling edge of the laser pulse! Be also |
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careful in choosing a large conv_std_dev value and using a small |
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laser pulse (rule of thumb: conv_std_dev < laser_length/10). |
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""" |
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# apply gaussian filter to remove noise and compute the gradient of the |
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# timetrace |
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conv_deriv = self._convolve_derive(count_data.astype(float), conv_std_dev) |
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# use a reference for array, because the exact position of the peaks or |
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# dips (i.e. maxima or minima, which are the inflection points in the |
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# pulse) are distorted by a large conv_std_dev value. |
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conv_deriv_ref = self._convolve_derive(count_data, 10) |
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# initialize arrays to contain indices for all rising and falling |
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# flanks, respectively |
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rising_ind = np.empty([num_of_lasers],int) |
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falling_ind = np.empty([num_of_lasers],int) |
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# Find as many rising and falling flanks as there are laser pulses in |
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# the trace: |
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for i in range(num_of_lasers): |
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# save the index of the absolute maximum of the derived time trace |
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# as rising edge position |
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rising_ind[i] = np.argmax(conv_deriv) |
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# refine the rising edge detection, by using a small and fixed |
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# conv_std_dev parameter to find the inflection point more precise |
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start_ind = int(rising_ind[i]-conv_std_dev) |
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if start_ind < 0: |
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start_ind = 0 |
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stop_ind = int(rising_ind[i]+conv_std_dev) |
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if stop_ind > len(conv_deriv): |
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stop_ind = len(conv_deriv) |
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if start_ind == stop_ind: |
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stop_ind = start_ind+1 |
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rising_ind[i] = start_ind + np.argmax(conv_deriv_ref[start_ind:stop_ind]) |
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# set this position and the surrounding of the saved edge to 0 to |
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# avoid a second detection |
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if rising_ind[i] < 2*conv_std_dev: del_ind_start = 0 |
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else: |
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del_ind_start = rising_ind[i] - 2*conv_std_dev |
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if (conv_deriv.size - rising_ind[i]) < 2*conv_std_dev: |
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del_ind_stop = conv_deriv.size-1 |
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else: |
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del_ind_stop = rising_ind[i] + 2*conv_std_dev |
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conv_deriv[del_ind_start:del_ind_stop] = 0 |
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# save the index of the absolute minimum of the derived time trace |
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# as falling edge position |
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falling_ind[i] = np.argmin(conv_deriv) |
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# refine the falling edge detection, by using a small and fixed |
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# conv_std_dev parameter to find the inflection point more precise |
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start_ind = int(falling_ind[i]-conv_std_dev) |
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if start_ind < 0: |
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start_ind = 0 |
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stop_ind = int(falling_ind[i]+conv_std_dev) |
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if stop_ind > len(conv_deriv): |
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stop_ind = len(conv_deriv) |
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if start_ind == stop_ind: |
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stop_ind = start_ind+1 |
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falling_ind[i] = start_ind + np.argmin(conv_deriv_ref[start_ind:stop_ind]) |
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# set this position and the sourrounding of the saved flank to 0 to |
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# avoid a second detection |
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if falling_ind[i] < 2*conv_std_dev: del_ind_start = 0 |
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else: |
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del_ind_start = falling_ind[i] - 2*conv_std_dev |
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if (conv_deriv.size - falling_ind[i]) < 2*conv_std_dev: |
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del_ind_stop = conv_deriv.size-1 |
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else: |
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del_ind_stop = falling_ind[i] + 2*conv_std_dev |
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conv_deriv[del_ind_start:del_ind_stop] = 0 |
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# sort all indices of rising and falling flanks |
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rising_ind.sort() |
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falling_ind.sort() |
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# find the maximum laser length to use as size for the laser array |
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laser_length = np.max(falling_ind-rising_ind) |
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#Todo: Find better method, here the idea is to take a histogram to find |
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# length of pulses |
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#diff = (falling_ind-rising_ind)[np.where( falling_ind-rising_ind > 0)] |
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#self.histo = np.histogram(diff) |
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#laser_length = int(self.histo[1][self.histo[0].argmax()]) |
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# initialize the empty output array |
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laser_arr = np.zeros([num_of_lasers, laser_length],int) |
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# slice the detected laser pulses of the timetrace and save them in the |
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# output array according to the found rising edge |
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for i in range(num_of_lasers): |
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if (rising_ind[i]+laser_length > count_data.size): |
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lenarr = count_data[rising_ind[i]:].size |
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laser_arr[i, 0:lenarr] = count_data[rising_ind[i]:] |
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else: |
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laser_arr[i] = count_data[rising_ind[i]:rising_ind[i]+laser_length] |
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return laser_arr.astype(int) |
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def _convolve_derive(self, data, std_dev): |
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""" Smooth the input data by applying a gaussian filter. |
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@param numpy.ndarray data: 1D array, the raw data to be smoothed |
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and derived |
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@param float std_dev: standard deviation of the gaussian filter to be |
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applied for smoothing |
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View Code Duplication |
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@return numpy.ndarray: 1D array, the smoothed and derived data |
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The convolution is applied with specified standard deviation. The |
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derivative of the smoothed data is computed afterwards and returned. If |
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the input data is some kind of rectangular signal containing high |
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frequency noise, the output data will show sharp peaks corresponding to |
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the rising and falling flanks of the input signal. |
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""" |
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conv = ndimage.filters.gaussian_filter1d(data, std_dev) |
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conv_deriv = np.gradient(conv) |
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return conv_deriv |
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