GB1594725A - Method and apparatus for analysing small amounts of fluorescent substance - Google Patents
Method and apparatus for analysing small amounts of fluorescent substance Download PDFInfo
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- GB1594725A GB1594725A GB44093/77A GB4409377A GB1594725A GB 1594725 A GB1594725 A GB 1594725A GB 44093/77 A GB44093/77 A GB 44093/77A GB 4409377 A GB4409377 A GB 4409377A GB 1594725 A GB1594725 A GB 1594725A
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- radiation
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/64—Fluorescence; Phosphorescence
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- Health & Medical Sciences (AREA)
- Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
- Physics & Mathematics (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)
Description
(54)METHOD AND APPARATUS FOR ANALYSING SMALL
AMOUNTS OF FLUORESCENT SUBSTANCE
(71) We, PETER ENEROTH, a
Swedish Subject, of Framnasbacken 22, S-171 42 Solna, Sweden, and WLADIMIR
WLADIMIROFF, a Dutch Subject, of St.
Olofsgatan 43B, S-753 30 Uppsala,
Sweden, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to oe performed, to be particularly described in and by the following statement:- The wavelength position and structure of the fluorescence emission spectrum of a fluorescent sample in the gaseous phase or in liquid or solid solution is typical of the chemical composition of the sample and is also typical of the sample phase. Fluorescence emission has a nanosecond duration and upon excitation of the fluorescence of a sample by a subnanosecond radiation pulse the fluorescence emission intensity decay curve can be recorded as a function of time. This decay curve is again typical of the chemical composition and the phase of the sample.
The fluorescence emission intensity originating from a fluorescent substance is linearly proportional to the concentration of the substance and in known apparatus the fluorescence emission intensity is measured in order to determine the fluorescent substance concentration in the sample.
Often, in cases where the nature of an unknown substance has to be determined, the fluorescence wavelength spectrum is recorded. Such measurements usually are carried out by illuminating the sample with light from a continuous light source, such as a high-pressure xenon arc, or a pulsed light source, such as a flashing lamp, the excitation radiation being passed through a monochromator (A) selecting the excitation wavelength prior to falling onto the sample and the resulting fluorescence emission being passed through a monochromator (B) prior to falling onto a fluorescence radiation detector.The wavelength settings of the two monochromators are ideally such that the light passing through monochromator (A) cannot pass through monochromator (B), in this way avoiding that the radiation detector measuring the fluorescence emission intensity will also be irradiated with light originating from the excitation light source.
However, even the best monochromators have a finite transmission for other wavelengths but the central setting wavelength in the form of stray light and the sensitivity of known fluorescence spectrophotometric apparatus is primarily limited by the circumstance that all fluorescent samples, apart from absorbing the excitation radiation causing the sample fluorescence, will scatter part of the excitation radiation and as monochromator (B) will transmit part of this scattered excitation radiation independently of its central wavelength setting, scattered radiation will be able to reach the fluorescence radiation detector. When the concentration of the fluorescent substance in the sample is so low that its fluorescence intensity is less than the intensity of the scattered excitation radiation reaching the detector, the fluorescence emission cannot be detected in known apparatus.
The light scattering ability of molecules increases with increasing molecular size and consequently the study of the fluorescence emission from biological systems, such as proteins and living tissues, is seriously hampered by light scattering. However, fluorescence studies of such systems are of central importance in the elucidation of biochemical aspects of human diseases and the object of the present invention is to provide a method and apparatus which overcome the sensitivity limitations of known fluorescence spectro-photometers and thus provide a means of analysing hitherto undetectable low levels of fluorescence intensity.
According to one aspect the present invention consists in a method of analysing a fluorescent substance in a gaseous, liquid or solid state sample, the method comprising the steps of:
(i) irradiating the sample with a sub-nanosecond excitation radiation pulse from an excitation source;
(11) detecting a radiation component from said source with a reference detector positioned nearer to the source than is said sample;
(iii) detecting fluorescent radiation emitted by said substance with a fluorescence detector positioned on the opposite side of a filter from said sample;
(iv) gating the output of the fluorescene detector to a store at the end of the time that the excitation pulse takes to reach the sample and subsequently decay by utilizing the output of the reference detector; and
(v) analysing the content of the store thereby to determine the intensity and duration of said fluorescent radiation and yield information relating to said substance.
According to another aspect the invention consists in apparatus for analysing a fluorescent substance in a gaseous, liquid or solid state sample by measuring the fluorescence emission intensity during a gating period that commences immediately after each excitation of said substance by a pulse of a train of sub-nanosecond radiation pulses to cause fluorescence, said apparatus comprising an excitation radiation pulse source generating said sub-nanosecond pulses, deflection means deflecting a component of the radiation of each said excitation radiation pulse to a reference detector, a triggering circuit driven by the output of said reference detector and generating a corresponding electrical trigger signal arranged to render a gating circuit conductive, a sample holder positioned in the path of said radiation pulses at a distance from said source greater than that of said reference detector a fluorescence detector receiving via a filter any fluorescence caused by said excitation to produce an electrical output signal proportional to the intensity of the filtered fluorescence radiation after the gating circuit has become conductive at the end of excitation of said substance by each said pulse, and storage means to store said fluorescence output signal for subsequent analysis.
Thus, the present invention provides a method and apparatus for the analysis of small amounts of fluorescent substance by measuring the fluorescence emission intensity and wavelength spectrum. The signal induced into a fast fluorescence radiation detector by the scattered radiation from a sub-nanosecond excitation pulse is allowed to decay until it has reached a level such that the signal caused by the fluorescence emission from a fluorescent sample excited by said excitation pulse is distinctly larger than the scattered radiation signal.Then the actual detection process is made to start by gating the fluorescence radiation detector signal current to flow into a signal storage capacitor from the moment the scattered radiation signal is negligible until the moment when the fluorescence intensity has decayed to a level causing a fluorescence radiation detector signal comparable to the electrical noise level of the detection electronics. This signal gating sequence is started by an electrical trigger pulse orginating from a reference radiation detector which receives a fraction of each excitation radiation pulse reflected from a beam-splitter which is positioned at such a distance from the excitation radiation source that said fraction arrives at the reference radiation detector substantially before the excitation radiation pulse hits the sample.The reference radiation detector is simultaneously used to monitor the excitation radiation pulse intensity. This is accomplished by gating the reference radiation detector signal current to flow into a reference storage capacitor during a time period of the same duration as the duration of the excitation radiation pulse. Thus a sample signal and a reference signal are made available which after division give the relative fluorescence intensity of the sample. By maintaining an excitation radiation pulse repetition rate of up to 100
Hz an apparatus according to the principles of the present invention can analyse subpicogram amounts of fluorescent substance in microliter sample volumes.
Figure 1 shows the spectral wavelength distribution of the absorption (A) and of the fluorescence emission (B) of a typical fluorescent compound F.
Figure 2 shows the fluorescence intensity decay curves as a function of time for some typical fluorescent compounds F, G, H, and
I, excited with radiation pulses having a decay time of 0.3 ns.
Figures 3a and 3b give the start t1 and the end t2 of the gating sequence for the fluorescence radiation detector signal relative to the time of occurrence of the excitation radiation pulse. In 3a the fluorescence emission peak intensity is of the same order of magnitude as the scattered excitation radiation pulse peak intensity. In 3b the fluorescence emission peak intensity is considerably smaller than the scattered excitation radiation pulse peak intensity.
Figure 4 is a function description of the principles of a measuring system according to the invention.
Figure 5 illustrates the time evolution of a typical laser radiation pulse used to excite the fluorescence emission of samples according to the method of the present invention.
We consider a fluorescent sample F with a radiation absorption spectrum in wavelength region A and a fluorescence emission spectrum in wavelength region B, as illustrated in Figure 1. Exciting the sample with a radiation pulse of central wavelength AeX and with a decay time much shorter than the fluorescence decay time of the sample, the decay curve of the fluorescence emission intensity at a central wavelength A,i can be recorded. Figure 2 gives some typical fluorescence decay curves of different samples as recorded in our laboratory with a nitrogen laser - dye laser combination generating excitation pulses with a decay time of 0.3 ns.
The excitation radiation scattered by the sample has a decay time which is identical and isochronous with the excitation radiation pulse decay. It therefore follows (compare Figure 3) that when detection of the fluorescence emission at e.g. Af from the sample F is started at a time t1, when the excitation radiation pulse intensity has decayed to a level much lower than the fluorescence emission intensity, only a minute fraction of the scattered radiation of wavelength ReX still can be seen by the fluorescence radiation detector and that as time proceeds this fraction rapidly becomes negligible.At time t2 the fluorescence emission intensity at Afl has decayed to a level causing a fluorescence radiation detector signal level comparable to the electrical noise level of the detection electronics, and at that instant the detection is ceased.
Gating the fluorescence emission intensity detection in this manner has two advantages: firstly, scattered excitation radiation is not interfering with the measurement of the fluorescence emission intensity and secondly, only a minimum of electrical noise is incorporated in the measurement.
An example of an apparatus to measure sample fluorescence according to the described method is arranged as illustrated in
Figure 4. The pulsed laser radiation source exciting the sample 4 preferably consists of a radio-frequency interference-free nitrogen laser 1--- dye laser 2 combination from which radiation pulses 3 with a peak power of at least'l kW and a decay time of 0.5 ns or less are obtained in a wavelength region of variable width and wavelength position. Figure 5 illustrates the shape of typical laser radiation pulses from such a combination 1 - 2.Other pulsed laser systems from which equivalent excitation radiation pulses can be obtained may be applied, but it is desirable the condition of radio-frequency interference-free operation be fulfilled in such other systems, as the detection electronics can be disturbed by external noise. The repetition rate of the excitation radiation pulses is typically in the range 20 -- 100 Hz but can be made higher.
The wavelength tunability is typically over at least the spectral region 350 -- 700 nm, while the spectral width of the excitation radiation pulses, measured as full width at half maximum, is variable from at lest 1--20 nm. The radiation pulses excite the sample 4 contained in the sample cell 5. The fluorescence emission from the sample passes through monochromator 6, which corresponds to the earlier mentioned monochromator (B). The monochromator (A) mention earlier is not needed in an apparatus according to the present invention, as the laser radiation source can be made to emit radiation of continuously variable wavelength.
Monochromator 6 may consist of an arrangement of fixed central wavelength interference transmission filters, and is either set at a fixed wavelength, such as , or is made to scan through the fluorescence emission spectrum of the sample, being continuously variable from 350 to 1000 nm.
Thus the apparatus is capable of being used in three ways:- firstly, recording the fluorescence excitation spectrum of the sample, keeping monochromator 6 at a fixed wavelength and having the laser excitation radiation wavelength scan through the absorption spectrum of the sample,
secondly, recording the fluorescence emission spectrum of the sample keeping the laser excitation radiation wavelength
fixed at e.g. Re and having monochromator 6 scan through the fluorescence emission spectrum of the sample,
and thirdly, only determining the concentration of the sample by measuring the fluorescence emission intensity for a given excitation frequency, keeping both leX and Ad1 fixed.
Having passed through monochromator 6 the fluorescence radiation falls onto the fast fluorescence radiation detector 7 which has
a response time of the order of the excitation radiation pulse decay time, and may be a fast multiplier or a fast vacuum diode. The signal coming from the fluorescence radiation detector 7, each time an excitation radiation pulse has hit the sample, is fed into the small signal storage capacitor 8 via the fast switch 9 which is closed and opened by gating unit 12 at times t1 and t2 respectively, as illustrated in Figure 3. The voltage built up over signal storage capacitor 8 is transfered to the larger signal hold capacitor 8 is transfered to the larger signal hold capacitor
10 via switch 11 which is also closed and opened by gating unit 12.The gating unit receives an electrical trigger pulse 13, starting the gating sequence for switch 9, from a fast reference radiation detector 14 which is irradiated by some fraction of the excitation radiation pulse being reflected from beam-splitter 15. The beam-splitter is positioned so that said fraction is made to arrive at the reference radiation detector 14 before the actual excitation radiation pulse 3 arrives at the sample, thus introducing a time difference needed to activate in gating unit 12 the appropriate gating sequence for switch 9.
As the intensity of the excitation radiation pulses coming from the laser radiation source is a function of wavelength and as the excitation radiation wavelength must be changeable in order to be able to excite the maximum fluorescence emission intensity of different samples, the intensity of the excitation radiation pulses is monitored with a fast reference radiation detector 14 by closing and opening switch 16 and charging the reference storage capacitor 17. The electrical trigger signal 18 for the gating sequence of switch 16 comes from the laser radiation source 1 and is routed to gating unit 12 prior to the appearance of the excitation radiation pulse 3. The voltage built up over reference storage capacitor 17 is transferred to the larger reference hold capacitor 19 via switch 20.Both switches 11 and 20 are actuated simultaneously by gating unit 12 once the voltage build-up over storage capacitors 8 and 17 is complete.
The signal from amplifier 22, representing the fluorescence intensity of the sample and the signal from amplifier 21, representing the excitation radiation pulse intensity, are fed into a divider unit 23, the output of which is a signal representing the relative fluorescence intensity from the sample. This signal is independent of the intensity of the excitation radiation pulses. From the divider unit 23 the signal is fed into an analog/digital convertor 24 from which the result of a measurement is available in digital form for further computation, presentation and appropriate administrative handling and storage by a computer unit.
The wavelength positioning mechanisms in both the laser radiation source and in the monochromator 6 can be driven by a stepper motor so that the wavelength setting and control of both apex and A,, can be taken car of by the computer unit.
The laser combination I - 2, the sampler holder 4, the monochromator 6 and both radiation detectors 7 and 14 are contained in a light-tight casing 25 to exclude foreign light from the measurement and to facilitate operg ,on of the appartus under normal laboratory itions.
WHAT WE CLAIM IS:
1. A method of analysing a fluorescent substance in a gaseous, liquid or solid state sample, the method comprising the steps of:
(i) irradiating the sample with a subnanosecond excitation radiation pulse from an excitation source;
(ii) detecting a radiation component from said source with a reference detector positioned nearer to the source than is said sample;
(iii) detecting fluorescent radiation emitted by said substance with a fluorescence detector positioned on the opposite side of a filter from said sample;
(iv) gating the output of the fluorescence detector to a store at the end of the time that the excitation pulse takes to reach the sample and subsequently decay by utilizing the output of the reference detector; and
(v) analysing the content of the store thereby to determine the intensity and duration of said fluorescent radiation and yield information relating to said substance.
2. A method as claimed in Claim 1, wherein the step of sample irradiation is performed using a tunable nitrogen laser dye laser combination.
3. A method as claimed in Claim 1 or
Claim 2, in which said component of said radiation is fed to said reference detector via a beam splitter positioned in the path of the' radiation from said source to said sample.
4. Apparatus for analysing a fluorescent substance in a gaseous, liquid or solid state sample by measuring the fluorescence emission intensity during a gating period that commences immediately after each excitation of said substance by a pulse of a train of sub-nanosecond radiation pulses to cause fluorescence, said apparatus comprising an excitation radiation pulse source generating said sub-nanosecond pulses, deflection means deflecting a component of the radiation of each said excitation radiation pulse to a reference detector, a triggering circuit driven by the output of said reference detector and generating a corresponding electrical trigger signal arranged to render a gating circuit conductive, a sample holder positioned in the path of said radiation pulses at a distance from said source greater than that of said reference detector, a fluorescence detector receiving via a filter any fluorescence caused by said excitation to produce an electrical output signal proportional to the intensity of the filtered fluorescence radiation after the gating circuit has become conductive at the end of excitation of said substance by each said pulse, and storage means to store said fluorescence output signal for subsequent analysis.
5. Apparatus as claimed in Claim 4, in
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (20)
1. A method of analysing a fluorescent substance in a gaseous, liquid or solid state sample, the method comprising the steps of:
(i) irradiating the sample with a subnanosecond excitation radiation pulse from an excitation source;
(ii) detecting a radiation component from said source with a reference detector positioned nearer to the source than is said sample;
(iii) detecting fluorescent radiation emitted by said substance with a fluorescence detector positioned on the opposite side of a filter from said sample;
(iv) gating the output of the fluorescence detector to a store at the end of the time that the excitation pulse takes to reach the sample and subsequently decay by utilizing the output of the reference detector; and
(v) analysing the content of the store thereby to determine the intensity and duration of said fluorescent radiation and yield information relating to said substance.
2. A method as claimed in Claim 1, wherein the step of sample irradiation is performed using a tunable nitrogen laser dye laser combination.
3. A method as claimed in Claim 1 or
Claim 2, in which said component of said radiation is fed to said reference detector via a beam splitter positioned in the path of the' radiation from said source to said sample.
4. Apparatus for analysing a fluorescent substance in a gaseous, liquid or solid state sample by measuring the fluorescence emission intensity during a gating period that commences immediately after each excitation of said substance by a pulse of a train of sub-nanosecond radiation pulses to cause fluorescence, said apparatus comprising an excitation radiation pulse source generating said sub-nanosecond pulses, deflection means deflecting a component of the radiation of each said excitation radiation pulse to a reference detector, a triggering circuit driven by the output of said reference detector and generating a corresponding electrical trigger signal arranged to render a gating circuit conductive, a sample holder positioned in the path of said radiation pulses at a distance from said source greater than that of said reference detector, a fluorescence detector receiving via a filter any fluorescence caused by said excitation to produce an electrical output signal proportional to the intensity of the filtered fluorescence radiation after the gating circuit has become conductive at the end of excitation of said substance by each said pulse, and storage means to store said fluorescence output signal for subsequent analysis.
5. Apparatus as claimed in Claim 4, in
which said radiation source is a nitrogen laser -- dye laser combination.
6. Apparatus as claimed in Claim 5 in which the laser radiation pulses have a continuously variable spectral wavelength in the region from 350 to 700nm.
7. Apparatus as claimed in Claim 5, in which the laser radiation pulses have a continuously variable spectral width of from 1 to 20 nm.
8. Apparatus as claimed in Claim 6, in which said laser includes a spectral wavelength variation mechanism that is driven by a stepper motor.
9. Apparatus as claimed in Claim 4, in which said filter is a monochromator having an arrangement of fixed central wavelength interference transmission filters.
10. Apparatus as claimed in Claim 9, in which the monochromator transmission wavelength is continuously variable over the spectral region from 350 to 1000 nm.
11. Apparatus as claimed in Claim 10, in which the monochromator includes a wavelength variation mechanism that is driven by a stepper motor.
12. Apparatus as claimed in Claim 4, in which said fluorescence detector is a fast photomultiplier having a rise time in the order of magnitude of the fall time of the excitation radiation pulses.
13. Apparatus as claimed in Claim 4, in which said reference detector is a fast vacuum photodiode having a rise time in the order of magnitude of the fall time of the excitation radiation pulses.
14. Apparatus as claimed in Claim 4, in which means are provided for generating an analog signal proportional to the ratio of the stored fluorescence output signal and a stored output from said reference detector.
15. Apparatus as claimed in Claim 14, in which means are provided for converting said analog signal into a digital signal.
16. Apparatus as claimed in Claim 4, in which a light-tight casing is provided for holding said excitation radiation pulse source, said filter, said fluorescence detector, said deflection means and said reference detector, and for excluding ambient light from disturbing the measurements whilst preventing the excitation radiation from irradiating surfaces having no relation to the purpose of the measurements.
17. Apparatus as claimed in Claim 4, in which means are provided for maintaining said gating circuit conducting to pass said fluorescence signal to said storage means for as long as the level of intensity of said fluorescence radiation is greater than the level of intensity of associated electrical noise.
18. Apparatus as claimed in Claim 4, in which said deflection means is a beam splitter positioned with respect to said fluorescent substance to define an optical delay substantially equal to the activation time of said gating circuit plus the duration of any one excitation radiation pulse.
19. A method of analysing a fluorescent substance in a gaseous, liquid or solid state sample, substantially as hereinbefore described with reference to Figures 1 to 5.
20. Apparatus for analysing a fluorescent substance in a gaseous, liquid or solid state sample, substantially as hereinbefore described with reference to Figure 4.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE7611787A SE409623B (en) | 1976-10-22 | 1976-10-22 | PROCEDURE AND DEVICE FOR ANALYSIS OF A FLUORESCENTING SUBJECT |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB1594725A true GB1594725A (en) | 1981-08-05 |
Family
ID=20329230
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB44093/77A Expired GB1594725A (en) | 1976-10-22 | 1977-10-24 | Method and apparatus for analysing small amounts of fluorescent substance |
Country Status (4)
| Country | Link |
|---|---|
| DE (1) | DE2747409A1 (en) |
| FR (1) | FR2368710A1 (en) |
| GB (1) | GB1594725A (en) |
| SE (1) | SE409623B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2215838A (en) * | 1988-02-12 | 1989-09-27 | Nat Res Dev | Fluorimeters |
| US7170069B2 (en) | 2003-08-02 | 2007-01-30 | Schott Ag | Method for quantitative determination of the suitability of crystals for optical components exposed to high energy densities, crystals graded in this way and uses thereof |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4178512A (en) * | 1978-07-21 | 1979-12-11 | Impulsphysik Gmbh | Deepwater in-situ fluorometer |
| DK178879A (en) * | 1979-05-01 | 1980-11-02 | Bioteknisk Inst | PROCEDURE FOR DIRECT PROPHYLACTIC SUPPLY REGISTRATION OF FOODSTUFFS NECESSARY DETERMINATION OF PHOMA AND / OR FUSARIUS ATTACKS AND APPLIANCES FOR THE EXERCISE OF PROMOTION |
| US4259574A (en) * | 1979-11-06 | 1981-03-31 | International Business Machines Corporation | Microanalysis by pulse laser emission spectroscopy |
| DE3206407A1 (en) * | 1982-02-23 | 1983-09-01 | Gesellschaft für Strahlen- und Umweltforschung mbH, 8000 München | Apparatus for the quantitative detection of biochemical reactions |
| GB8401672D0 (en) * | 1984-01-21 | 1984-02-22 | Univ Strathclyde | Measuring fluorescence decay characteristics of materials |
| DE3605598A1 (en) * | 1986-02-21 | 1987-08-27 | Degussa | Method and device for measuring the fluorescence decay time (afterglow time) of a fluorescing substance |
| DE4401351C2 (en) * | 1994-01-14 | 1997-08-21 | Werec Gmbh Berlin Wertstoff Re | Process for the optical identification of luminescent coatings in lamps, in particular in discharge lamps, in a recycling process and device for carrying out the process |
| DE10038080A1 (en) * | 2000-08-04 | 2002-02-21 | Giesing Michael | Registering the presence of immobilized substances on a bio-chip carrier, comprises using a fluorescence scanner, where a pulsed laser excites fluorescent markings to be detected between the pulses with local resolution |
| WO2004027395A2 (en) | 2002-09-16 | 2004-04-01 | Schott Ag | Determining the suitability of an optical material for the production of optical elements, corresponding device, and use of said material |
| DE102011105181A1 (en) * | 2011-06-17 | 2012-12-20 | Leica Microsystems Cms Gmbh | Microscope and method for imaging fluorescence microscopy |
-
1976
- 1976-10-22 SE SE7611787A patent/SE409623B/en unknown
-
1977
- 1977-10-21 DE DE19772747409 patent/DE2747409A1/en not_active Ceased
- 1977-10-21 FR FR7731763A patent/FR2368710A1/en active Granted
- 1977-10-24 GB GB44093/77A patent/GB1594725A/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2215838A (en) * | 1988-02-12 | 1989-09-27 | Nat Res Dev | Fluorimeters |
| GB2215838B (en) * | 1988-02-12 | 1992-10-21 | Nat Res Dev | Fluorimeters |
| US7170069B2 (en) | 2003-08-02 | 2007-01-30 | Schott Ag | Method for quantitative determination of the suitability of crystals for optical components exposed to high energy densities, crystals graded in this way and uses thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2368710B1 (en) | 1983-05-06 |
| SE7611787L (en) | 1978-04-23 |
| DE2747409A1 (en) | 1978-04-27 |
| FR2368710A1 (en) | 1978-05-19 |
| SE409623B (en) | 1979-08-27 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PS | Patent sealed [section 19, patents act 1949] | ||
| PCNP | Patent ceased through non-payment of renewal fee |