Frequency domain fluorometry using coherent sampling

Claim 2

Apparatus as claimed in claim 1 wherein said sampling means is operative to sample said response signal so that: T s = T e N w + T e /N p where N w is a positive integer and N p is a rational number having an absolute value greater than one

Claim 3

Apparatus as claimed in claim 1 wherein said excitation means includes means for providing repetitive pulses of light at a pulse repetition frequency equal to said fundamental frequency Fe.

Claim 4

Apparatus as claimed in claim 3 wherein said excitation means includes means for controlling said excitation light pulses so that said excitation light pulses have a duty cycle less than or equal to 1/N p .

Claim 5

Apparatus as claimed in claim 2, wherein said sampling means is operative at a sampling rate F s such that N p is an integer.

Claim 6

Apparatus as claimed in claim 2 wherein said sampling means includes detector means for providing a continuous electrical signal directly related to the amplitude of said emitted light, means for providing a repetitive triggering signal at said sampling frequency F s and analog to digital conversion means for digitizing the instantaneous value of said continuous electrical signal upon each repetition of said triggering signal.

Claim 7

Apparatus as claimed in claim 6 further comprising anti aliasing means for excluding from said sampled response signal components having a frequency greater than F h wherein F h =(N w N p +1)F s /2 , said anti aliasing means including means for low pass filtering said continuous electrical signal.

Claim 8

Apparatus as claimed in claim 7 further comprising anti aliasing means for excluding from said frequency-shifted response signal components having a frequency higher than F h wherein

Claim 9

Apparatus as claimed in claim 1 further comprising means for providing a reference signal having at least one characteristic representing a corresponding characteristic of said excitation light, said means for determining at least one characteristic of said sampled response signal including means for comparing said at least one characteristic of said sampled response signal with a corresponding characteristic of said reference signal.

Claim 10

Apparatus as claimed in claim 9 wherein said means for providing a reference signal includes means for sampling said excitation light at said sampling frequency F s to thereby provide an excitation series of sample values, whereby said excitation series of sample values will represent a sampled excitation signal corresponding to the variations in amplitude of said excitation light.

Claim 11

Apparatus as claimed in claim 10 wherein said means for comparing includes means for determining the degree of modulation for components at each of a plurality of frequencies in each of said sampled response signal and said sampled excitation signal and comparing the degree of modulation for each component in said sampled response signal with the degree of modulation for a corresponding component at the same frequency in said sampled excitation signal.

Claim 12

Apparatus as claimed in claim 10 wherein said means for comparing includes means for determining the phase relationship between each component in said sampled response signal and a corresponding component in said sampled excitation signal at the same component frequency.

Claim 13

Apparatus as claimed in Claim 10, wherein said means for comparing at least one characteristic of said sampled response signal with a corresponding characteristic of said reference signal includes means for transforming said response signal into a frequency domain representation including values of at least one characteristic of each of a plurality of response components at plural frequencies, means for transforming said sampled excitation signal into a frequency domain representation thereof including values of at least one characteristic for each of a plurality of excitation components at plural frequencies and means for comparing the value of each such characteristic for each such response component with the value of the corresponding characteristic for the corresponding excitation component at the same frequency.

Claim 14

Apparatus as claimed in Claim 13, wherein said means for transforming said sampled response signal and said means for transforming said sampled excitation signal include means for providing modulation and phase values for each said response component and for each said excitation component respectively.

Claim 15

Apparatus as claimed in Claim 13, wherein means for transforming said sampled response signal includes means for applying a digital transformation to said response series of values and said means for transforming said sampled excitation signal includes means for applying a digital transformation to said excitation series of values.

Claim 16

Apparatus as claimed in claim 9 wherein said means for providing a reference signal includes means for directing said excitation light through a light path of predetermined characteristics and providing said reference signal representing said excitation light after such passage.

Claim 17

Apparatus as claimed in claim 2 wherein said sampling means includes means for averaging said sampled response signal over a plurality of cycles of the fundamental component therein.

Claim 18

Apparatus as claimed in claim 2 wherein said excitation means includes means for providing excitation light including a plurality of fundamental components varying at a plurality of fundamental frequencies F e and fundamental repetition periods T e , and further including harmonics of each such fundamental frequency and wherein said sampling means includes means for sampling the amplitude of light emitted by said composition separately at each of a plurality of sampling frequencies F s and sampling periods T s , each said sampling frequency F s and sampling period T s being associated with one of said fundamental frequencies and fundamental repetition periods, the relationship between each said sampling period T s and the associated fundamental repetition period being in accordance with said relationship T s = T e N w + T e /N p where N w and N p for the various fundamental frequencies F e and sampling frequencies F s may be the same or different, said sampling means including means for providing plural separate series of sample values each including the sample values obtained by sampling at one said sampling frequency, whereby each said separate series of sample values will represent a separate sampled excitation signal corresponding to variations in said emitted light within a separate range of frequencies incorporating one said fundamental frequency and a preselected number of harmonics of that fundamental frequency.

Claim 19

Apparatus as claimed in claim 18 wherein said excitation means includes means for providing said excitation light including all of said fundamental components and all of said harmonics simultaneously.

Claim 20

Apparatus as claimed in claim 19 wherein said sampling means includes means for detecting the emitted light and generating a composite analog signal representing variations in said emitted light in all of said ranges of frequencies simultaneously, a plurality of sampling devices and bandpass filter means for separating components of said composite analog signal and directing components of said signal in different ones of said ranges of frequencies to different ones of said sampling devices.

Claim 21

Apparatus for determining the response of a chemical composition to light comprising: (a) excitation means for producing excitation light varying repetitively in amplitude, including a fundamental component varying at a fundamental frequency F e and fundamental repetition period T e and also including harmonic components varying at frequencies which are integral multiples of F e and applying said excitation light pulses to said composition whereby said composition will emit light varying repetitively in amplitude at frequencies corresponding to F e and to said frequencies of said harmonic components; (b) sampling means for sampling the amplitude of light emitted by said composition to thereby provide a response series of samples representing said amplitude, whereby said response series of samples will represent a sampled response signal corresponding to the variations in amplitude of said emitted light; (c) means for transforming said response series of sample values into a frequency domain representation thereof including values for at least one characteristic of each of plural response components at plural frequencies by applying a digital transformation to said response series of values; and (d) means for determining a luminescence function of said chemical composition from said characteristics of said response components.

Claim 22

Apparatus as claimed in Claim 21, wherein said means for transforming said sampled response signal includes means for providing a value of modulation and a value of phase for each said response component.

Claim 23

Apparatus as claimed in Claim 21, further comprising means for sampling said excitation light at said sampling frequency F s to thereby provide an excitation series of sample values constituting a sampled excitation signal corresponding to the variations in amplitude of said excitation light and means for transforming said sampled excitation signal into a frequency domain representation thereof including at least one characteristic of each of a plurality of excitation components at plural frequencies, said means for determining at least one characteristic of each said response component including means for comparing each characteristic of each said response component with the corresponding characteristic of a corresponding one of said excitation components at the same frequency.

Claim 25

A method as claimed in claim 24 wherein said sampling step is conducted so that: T s =T e N w +T e /N p where N w is a positive integer and N p is a rational number having absolute value greater than 1.

Claim 26

A method as claimed in claim 25, wherein said sampling step is conducted at a sampling frequency F s such that N p is an integer.

Claim 27

A method as claimed in claim 25 wherein said sampling step includes the steps of detecting said emitted light and providing a continuous electrical signal directly related to the amplitude of said emitted light, providing a repetitive triggering signal at said sampling frequency F s and digitizing the instantaneous value of said continuous electrical signal upon each repetition of said triggering signal.

Claim 28

A method as claimed in claim 27 wherein said sampling step further includes the step of excluding from said sampled response signal components having a frequency greater than F h wherein by low pass filtering said continuous electrical signal.

Claim 29

A method as claimed in claim 24 further comprising the step of providing a reference signal having at least one characteristic representing a corresponding characteristic of said excitation light, said step of determining at least one characteristic of said sampled response signal including the step of comparing said at least one characteristic of said sampled response signal with a corresponding characteristic of said reference signal.

Claim 30

A method as claimed in claim 29 wherein said step of providing a reference signal includes the step of sampling said excitation light at said sampling frequency F s to thereby provide an excitation series of sample values, whereby said excitation series of sample values will represent a sampled excitation signal corresponding to the variations in amplitude of said excitation light.

Claim 31

A method as claimed in claim 30, wherein said step of comparing at least one characteristic of said sampled response signal with a corresponding characteristic of said reference signal includes the steps of transforming said response signal into a frequency domain representation including values of at least one characteristic of each of a plurality of response components at plural frequencies, transforming said sampled excitation signal into a frequency domain representation thereof including values of at least one characteristic for each of a plurality of excitation components at plural frequencies and comparing the value of each such characteristic for each such response component with the value of the corresponding characteristic for the corresponding excitation component at the same frequency.

Claim 32

A method as claimed in Claim 25, wherein said exciting step includes the step of providing excitation light including a plurality of fundamental components varying at a plurality of fundamental frequencies F e and fundamental repetition periods T e , and further including harmonics of each such fundamental frequency and wherein said sampling step includes the step of sampling the amplitude of light emitted by said composition separately at each of a plurality of sampling frequencies F s and sampling periods T s , each said sampling frequency F s and sampling period T s being associated with one of said fundamental frequencies and fundamental repetition period, the relationship between each said sampling period T s and the associated fundamental repetition period being in accordance with said relationship T s = T e N w + T e /N p said sampling step further including the step of providing plural separate series of sample values each including the sample values obtained by sampling at one said sampling frequency, whereby each said separate series of sample values will represent a separate sampled excitation signal corresponding to variations in said emitted light within a separate range of frequencies incorporating one of said fundamental frequencies and a preselected set of harmonics of that fundamental frequency.

Claim 33

A method as claimed in claim 30, wherein said exciting step includes the step of providing said excitation light including all of said fundamental components and all of said harmonics simultaneously.

Claim 34

A method as claimed in claim 33 wherein said sampling step includes the step of detecting the emitted light and generating a composite analog signal representing variations in said emitted light in all of said ranges of frequencies simultaneously, separating components of said composite analog signal and directing components of said signal in different ones of said ranges of frequencies to different sampling devices.

Claim 36

A method as claimed in Claim 35, wherein said step of transforming said sampled response signal is performed by applying a digital transform to said sampled response values.