Time-Resolved Fluorescence Wiki

support_plane_analysis

Anonymous (anonymous@undisclosed.example.com) — 2014-01-21T16:46:58+00:00

2014/01/21 17:46		current
Line 13:		Line 13:
	===== References =====		===== References =====

-	Lakowicz JR (1999)// Principles of Fluorescence Spectroscopy//, 2nd edn. Kluver Academic/Plenum Publishers, New York (available in room C202)*	+	*Lakowicz JR (1999)// Principles of Fluorescence Spectroscopy//, 2nd edn. Kluver Academic/Plenum Publishers, New York

asymptotic_standard_errors

Anonymous (anonymous@undisclosed.example.com) — 2015-02-10T16:33:41+00:00

2014/04/09 22:41		current
Line 5:		Line 5:
	The asymptotic standard errors (ASE) are used for analyzing fitting parameter error intervals. For illustration let's start at the best fit parameter set, which can be regarded as a single point in the parameter space. Now we remove the parameter for which we want to calculate the error intervals from this location, that is, we take a single step parallel to its parameter axis. We then calculate the reduced X<sup>2</sup> for this new paramter set. By iterating this procedure we get X<sup>2</sup> as a function of the parameter of interest. The intersection points of this function with a given X<sup>2</sup> confidence limit define the boundaries of the confidence interval of the parameter.		The asymptotic standard errors (ASE) are used for analyzing fitting parameter error intervals. For illustration let's start at the best fit parameter set, which can be regarded as a single point in the parameter space. Now we remove the parameter for which we want to calculate the error intervals from this location, that is, we take a single step parallel to its parameter axis. We then calculate the reduced X<sup>2</sup> for this new paramter set. By iterating this procedure we get X<sup>2</sup> as a function of the parameter of interest. The intersection points of this function with a given X<sup>2</sup> confidence limit define the boundaries of the confidence interval of the parameter.

-	At PQ the asymptotic standard errors are supported by [[products:FluoFit]] and the [[products:SymPhoTime]] software.	+	At PQ the asymptotic standard errors are supported by [[software:FluoFit]] and the [[software:SymPhoTime]] software.

pile-up_effect

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

2015/06/03 17:09		current
Line 1:		Line 1:
-	{{tag>pile-up TCSPC pile-up dead_time}}	+	{{tag> TCSPC pile-up dead_time}}
	~~TOC~~		~~TOC~~

differential_count_rate

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

2017/09/24 05:34		current
Line 17:		Line 17:
	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]]))

fast_lifetime

Anonymous (anonymous@undisclosed.example.com) — 2013-08-06T14:43:32+00:00

2013/08/06 16:43		current
Line 3:		Line 3:
	A method for estimating the average lifetime, calculated non-distinctive on different exponentials in a simple single path calculation, compared to a complete fitting operation against a more complex, non-linear model. Often used with [[FLIM]] go get a first idea of the lifetime distribution in the image.		A method for estimating the average lifetime, calculated non-distinctive on different exponentials in a simple single path calculation, compared to a complete fitting operation against a more complex, non-linear model. Often used with [[FLIM]] go get a first idea of the lifetime distribution in the image.

-	In detail, FastLT is calculating the barycentre of the (pseudo–)pixel's decay. The time span from the barycentre of the IRF to the barycentre of the decay equals the average lifetime. This estimate is very fast and does not suffer as much from low statistics. If an [[IRF]] is not available, the "time zero" $t_0_$ has to be estimated differently, for example by using the rising flank of the decay or the entrance of the [[FWHM]] interval. However, this may introduce a systematic shift in the estimated average lifetimes.	+	In detail, FastLT is calculating the barycentre of the (pseudo–)pixel's decay. The time span from the barycentre of the IRF to the barycentre of the decay equals the average lifetime. This estimate is very fast and does not suffer as much from low statistics. If an [[IRF]] is not available, the "time zero" $t_\theta$ has to be estimated differently, for example by using the rising flank of the decay or the entrance of the [[FWHM]] interval. However, this may introduce a systematic shift in the estimated average lifetimes.

hybrid_pmt

Anonymous (anonymous@undisclosed.example.com) — 2015-11-03T15:00:37+00:00

2015/11/03 15:59		current
Line 3:		Line 3:
	"The hybrid photodetector's structure is similar yet different from a conventional PMT. Like PMTs, the HPD is a vacuum tube with a photocathode that detects light, an electron multiplier that multiplies electrons, and an output terminal that outputs an electrical signal. But unlike PMTs which use multiple dynodes as electron multipliers, the HPD uses a silicon avalanche diode (AD) instead"((continue reading on the [[http://www.hamamatsu.com/us/en/community/optical_sensors/tutorials/what_is_hpd/index.html\|Hamamatsu]] website.))		"The hybrid photodetector's structure is similar yet different from a conventional PMT. Like PMTs, the HPD is a vacuum tube with a photocathode that detects light, an electron multiplier that multiplies electrons, and an output terminal that outputs an electrical signal. But unlike PMTs which use multiple dynodes as electron multipliers, the HPD uses a silicon avalanche diode (AD) instead"((continue reading on the [[http://www.hamamatsu.com/us/en/community/optical_sensors/tutorials/what_is_hpd/index.html\|Hamamatsu]] website.))

-	PicoQuant integrates various Hybrid PMT tubes into a convenient assembly called [[https://www.picoquant.com/products/category/photon-counting-detectors/pma-hybrid-series-hybrid-photomultiplier-detector-assembly\|PMA Hybrid]].	+	PicoQuant integrates Hybrid PMT tubes into a convenient assembly called [[https://www.picoquant.com/products/category/photon-counting-detectors/pma-hybrid-series-hybrid-photomultiplier-detector-assembly\|PMA Hybrid]].

	The PMA Hybrid is a compact single photon sensitive detector based on a fast hybrid photomultiplier tube with peltier cooler to reduce the dark count rate. The detector includes a high voltage power supply and pre-amplifier with overload protection and emergency shut down procedure if the detector count rate reaches a critical limit.		The PMA Hybrid is a compact single photon sensitive detector based on a fast hybrid photomultiplier tube with peltier cooler to reduce the dark count rate. The detector includes a high voltage power supply and pre-amplifier with overload protection and emergency shut down procedure if the detector count rate reaches a critical limit.

mcs

Anonymous (anonymous@undisclosed.example.com) — 2014-01-21T16:39:04+00:00

2014/01/21 17:38		current
Line 1:		Line 1:
	====== MCS ======		====== MCS ======

-	MCS stands for Multi Channel Scaler. At PQ this term is used in the following context: Single photon events, as originating from a [[TTTR]] measurement are sorted by means of their macroscopic time into equally spaced time bins. What immediately results is a time trace of the fluorescence intensity. In a subsequent analysis the binned ensemble of photons can be used to form [[TCSPC]] histograms, which in turn can be used for lifetime analysis, time-gated analysis etc.	+	MCS stands for Multi Channel Scaler. At PicoQuant this term is used in the following context: Single photon events, as originating from a [[TTTR]] measurement are sorted by means of their macroscopic time into equally spaced time bins. What immediately results is a time trace of the fluorescence intensity. In a subsequent analysis the binned ensemble of photons can be used to form [[TCSPC]] histograms, which in turn can be used for lifetime analysis, time-gated analysis etc.

tcspc

Anonymous (anonymous@undisclosed.example.com) — 2014-01-28T13:06:31+00:00

2014/01/28 14:06		current
Line 1:		Line 1:
	====== TCSPC ======		====== TCSPC ======

-	TCSPC stands for Time Correlated Single Photon Counting: A stream of photons is recorded, each photon with respect to a (often periodical) signal, e.g. a repeated laser pulse. The single photon events are sorted into histogram channels that correspond to the time that elapsed since the last excitation pulse. It is a time domain method of investigating time resolved fluorescence.	+	TCSPC stands for Time Correlated Single Photon Counting: A stream of photons is recorded, each photon with respect to a (often periodical) signal, e.g. a repeated laser pulse. The single photon events are sorted into histogram channels that correspond to the time that elapsed since the last excitation pulse. It is a time domain method for investigating time resolved fluorescence.