Time-Resolved Fluorescence Wiki

pile-up_effect

Anonymous (anonymous@undisclosed.example.com) — 2015-06-03T15:09:55+00:00

2015/06/03 17:09		current
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-	{{tag>pile-up TCSPC pile-up dead_time}}	+	{{tag> TCSPC pile-up dead_time}}
	~~TOC~~		~~TOC~~

bifl

Anonymous (anonymous@undisclosed.example.com) — 2015-02-10T16:34:08+00:00

2014/04/09 22:38		current
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	BIFL stands for Burst Integrated Fluorescence Lifetime: The photon events of a complete burst are accumulated into a [[TCSPC]] histogram which is used for lifetime analysis methods afterwards. Usually a burst is defined as a time interval for which the intensity of a time trace or [[MCS]] measurement is above a chosen threshold. Evaluation of all bursts present in an [[MCS]] trace, for example, results in a lifetime histogram.		BIFL stands for Burst Integrated Fluorescence Lifetime: The photon events of a complete burst are accumulated into a [[TCSPC]] histogram which is used for lifetime analysis methods afterwards. Usually a burst is defined as a time interval for which the intensity of a time trace or [[MCS]] measurement is above a chosen threshold. Evaluation of all bursts present in an [[MCS]] trace, for example, results in a lifetime histogram.

-	BIFL is supported by the [[products:SymPhoTime]] software, alongside with a variety of burst related techniques.	+	BIFL is supported by the [[software:SymPhoTime]] software, alongside with a variety of burst related techniques.

dead_time

Anonymous (anonymous@undisclosed.example.com) — 2015-06-03T15:04:41+00:00

2015/06/03 17:04		current
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	In TCSPC the term dead time refers to the time the TCSPC system needs armed again after detecting an event. During the dead time the TCSPC system is blind.		In TCSPC the term dead time refers to the time the TCSPC system needs armed again after detecting an event. During the dead time the TCSPC system is blind.

-	If for example two photons are detected with the dead time of the TCSPC device the second photon will be lost. This leads to the so called [[glossary:Pile Up Effect]].	+	If for example two photons are detected with the dead time of the TCSPC device the second photon will be lost. This leads to the so called [[glossary:Pile-up Effect]].

	Note that not only TCSPC devices but also photon counting devices exhibit dead times.		Note that not only TCSPC devices but also photon counting devices exhibit dead times.

deconvolution

Anonymous (anonymous@undisclosed.example.com) — 2013-08-06T14:41:19+00:00

2013/08/06 16:13		current
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	====== Deconvolution ======		====== Deconvolution ======
-
-	===== What is "Deconvolution"? =====

	Deconvolution is used in time domain data analysis for removal of broadening effects due to instrumental resolution. In this context deconvolution is mainly concerned with the [[IRF]] (or lamp function) including the finite light source pulse width and other broadening effects (e.g. electronics). The effects caused by the [[IRF]] are dominant in the onset of a decay curve.		Deconvolution is used in time domain data analysis for removal of broadening effects due to instrumental resolution. In this context deconvolution is mainly concerned with the [[IRF]] (or lamp function) including the finite light source pulse width and other broadening effects (e.g. electronics). The effects caused by the [[IRF]] are dominant in the onset of a decay curve.
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	===== How deconvolution should be done =====		===== How deconvolution should be done =====

-	Best, not at all ;-). At PQ we use [[reconvolution]] instead, for a variety of good reasons (see [[IRF]]). If one cannot resist applying deconvolution, the best way of doing it (at least for time domain data) would be via Fourier transform. Fourier transform is a slow process (even with [[FFT]]) and it has to be done twice, since the deconvoultion itself is performed on the transformed data set, which has to be retransformed afterwards.	+	Best, not at all ;-). At PicoQuant, for a variety of good reasons (see [[IRF]]) we use [[reconvolution]] instead. If one cannot resist applying deconvolution, the best way of doing it (at least for time domain data) would be via Fourier transform. Fourier transform is a slow process (even with [[FFT]]) and it has to be done twice, since the deconvoultion itself is performed on the transformed data set, which has to be retransformed afterwards.


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	The most prominent application of deconvolution techniques is imaging. Usually one tries to remove blurring by deconvolution (or deconvolution-like) techniques. What holds for time domain data, also holds for imaging: Deconvolution has a disturbingly high potential for producing artefacts - and there is no way of telling apart artefacts and effects. The images may look nicer (which undoubtedly is valuable especially for publication purposes), but the content of information has not necessarily improved.		The most prominent application of deconvolution techniques is imaging. Usually one tries to remove blurring by deconvolution (or deconvolution-like) techniques. What holds for time domain data, also holds for imaging: Deconvolution has a disturbingly high potential for producing artefacts - and there is no way of telling apart artefacts and effects. The images may look nicer (which undoubtedly is valuable especially for publication purposes), but the content of information has not necessarily improved.
-

differential_count_rate

Anonymous (anonymous@undisclosed.example.com) — 2017-09-26T11:46:03+00:00

2017/09/24 05:34		current
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	Not really. In case of pulsed signals the average count rate is a misleading quantity. An average count rate value does not take into account when and how those photons are emitted and detected. Interpreting a 100 kcps intensity as a constant emission rate (Poisson mean rate, in math terms) is a misconception. The physics of the measurement is completely different. These photons are obviously not emitted evenly, one by one over the whole one second period. They arrive to the detector bunched, as flashes. These are short time intervals with huge photon density (rate), separated by long "dark", quiet periods.		Not really. In case of pulsed signals the average count rate is a misleading quantity. An average count rate value does not take into account when and how those photons are emitted and detected. Interpreting a 100 kcps intensity as a constant emission rate (Poisson mean rate, in math terms) is a misconception. The physics of the measurement is completely different. These photons are obviously not emitted evenly, one by one over the whole one second period. They arrive to the detector bunched, as flashes. These are short time intervals with huge photon density (rate), separated by long "dark", quiet periods.

-	Getting a final count at "1% of SYNC rate" is a result of **low sampling rate of a high rate signal**.	+	In yet another words, achieving a final count rate at "1% of SYNC rate" is a result of **sparse sampling with dead time**. The sampled signal features much higher photon density, but lasts only for a short time.

	In mathematical terms, "average count rate of 1..2% of SYNC rate" means the overall detection probability, integrated over the whole duration of a measurement. The concept of //differential count rate// is related to the //probability density function//. The detected signal in TCSPC has a very inhomogeneous time distribution.		In mathematical terms, "average count rate of 1..2% of SYNC rate" means the overall detection probability, integrated over the whole duration of a measurement. The concept of //differential count rate// is related to the //probability density function//. The detected signal in TCSPC has a very inhomogeneous time distribution.

	Note: for detectors that exhibit count rate dependent shifting of the IRF, extra care has to be taken when measuring the IRF and directly using it for decay analysis. ((Takuhiro Otosu, Kunihiko Ishii and Tahei Tahara, Note: Simple calibration of the counting-rate dependence of the timing shift of single photon avalanche diodes by photon interval analysis, Rev. Sci. Instrum. 84, 036105 (2013); [[http://dx.doi.org/10.1063/1.4794769]]))		Note: for detectors that exhibit count rate dependent shifting of the IRF, extra care has to be taken when measuring the IRF and directly using it for decay analysis. ((Takuhiro Otosu, Kunihiko Ishii and Tahei Tahara, Note: Simple calibration of the counting-rate dependence of the timing shift of single photon avalanche diodes by photon interval analysis, Rev. Sci. Instrum. 84, 036105 (2013); [[http://dx.doi.org/10.1063/1.4794769]]))