JPH0448185B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a device for measuring the transient waveform of light emission of a sample excited by pulsed light, that is, the temporal change in the light emission intensity, and particularly relates to a measuring device using a multi-time-voltage converter. . <Prior art> Time to voltage converter (time to amplitude)
converter) converts the time from the reference time of light emission to the generation of photoelectrons into an analog voltage, and can be used up to the picosecond (10 ^-12 seconds) region, and from nanoseconds (10 ^-9 seconds) to microseconds (10 ^-6 seconds) is one of the effective means of measuring the luminescence lifetime in the region. The principle of this measurement is as follows. That is, the capacitor is charged with a constant current using the start pulse of the reference time of light emission, and the charging is stopped using the stop pulse described later. Furthermore, if this voltage is used as an input signal to a multichannel pulse height analyzer, a histogram of the stop pulse occurrence frequency with the voltage on the horizontal axis can be obtained. Since voltage is ∝ time at this time, this histogram represents a temporal change in luminescence intensity, that is, a luminescence transient waveform, and the luminescence lifetime of the sample can be calculated from this transient waveform analysis. In a measuring device equipped with only one time-voltage conversion device, the number of photoelectron pulses that can be used in one light emission is limited to one at most, and therefore the efficiency of using photoelectron pulses is poor. Therefore, in order to increase this efficiency, an application has been filed for an apparatus for measuring the luminescence lifetime of a sample having the configuration shown in FIG. 2 (Japanese Patent Application Laid-open No. 137843/1983). An overview of this conventional technology will be explained based on the same figure. Reference numeral 31 is a pulsed light source that emits pulsed light;
When the light flashes twice, the light is detected by the start photodetector 32, and the start pulse R _K (see FIG. (referred to as TAC) 33. This multi TAC33
A plurality of constant current charging circuits each consisting of a capacitor are provided, and the charging circuits simultaneously start charging in response to the start pulse _PK . on the other hand,
34 is excited by the flash, and when the sample 34 emits light, it is detected by the stop photodetector 35, which emits a stop pulse P _T (see FIG. 3B), and the multi-TAC 33 is input. Charging of the capacitors is sequentially stopped each time the stop pulse _PT is input. In addition, in the same figure, 36 is an optical aperture, and 37 is an optical aperture.
38 and 39 are pulse shaping circuits, 40 is a changeover switch, 41 is an AD converter, and 42 is a multichannel pulse height analyzer. However, since the device has a finite response speed, there is a lower limit to the time interval valve in which two stop pulses P _T that are input close to each other can not be individually recognized. The time is called ΔT. That is, as shown in FIG. 3B, if the pulse separation T _PS between the previously input stop pulse P _T1 and the subsequently input stop pulse P _T2 is smaller than the pulse pair resolution time ΔT, the subsequent Stop pulse P _T2 is not recognized. Therefore, even if multi-TAC is used as described above,
For example, if the optical diaphragm 36 is opened too much and the photon counting rate is increased too much, 2
The frequency with which more than one photoelectron pulse (stop pulse) occurs increases, causing waveform distortion in the measurement results. That is, in FIG. 3D, the solid line shows the measurement result with waveform distortion when two or more photoelectron pulses occur frequently within the pulse pair resolution time ΔT, and the broken line shows the measurement result when the pulse pair resolution time ΔT=0. It shows the true emission transient waveform measurement results that should be obtained. <Problems to be Solved by the Invention> The present invention provides the ability to obtain true pulse counts in each measurement channel even if two or more photoelectron pulses frequently occur within the pulse pair resolution time ΔT. The purpose is to obtain light emission transient waveform measurement results without waveform distortion. As a result of various studies, the present inventors found that it is possible to correct the waveform distortion used in the pulse-to-resolution time ΔT by calculation. By fixing the pulse-to-resolution time ΔT to a constant value and correcting it through calculations after the measurement, it was possible to obtain the true pulse count value. <Means for Solving the Problems> The apparatus for measuring the luminescence lifetime of a sample according to the present invention comprises: a light emission source of pulsed light; a start pulse generating means for generating a start pulse upon receiving the pulsed light; A multi-time-voltage converter comprising a stop pulse generating means for generating a stop pulse in response to light emitted from a received sample, and a plurality of constant current charging circuits that start operating in response to the start pulse and sequentially stop operating in response to the stop pulse. In the apparatus for measuring the luminescence lifetime of a sample, a pulse-to-resolution time fixing means for setting the pulse-to-resolution time to an integral multiple of the measurement channel is provided between the stop pulse generation means and the multi-time-voltage converter, and the number of stop pulses is set to an integral multiple of the measurement channel. The gist is that the true number is determined by correcting it based on the following formula. N ^c ₁ = N ₁ 2≦i≦N

[Formula] When i>N

[Formula] However, Ni: Measured value of stop pulses in the i-th measurement channel N ^c/i : True number of stop pulses in the i-th measurement channel N: The value when the pulse-to-resolution time is set to an integral multiple of the measurement channel. Integer Ne: integrated value of start pulses (number of flashes) <Example> An example of the present invention will be described below with reference to FIG. In FIG. 1, 1 is a light emitting source of pulsed light P, 2
A start pulse generating means receives the pulsed light P and generates a start pulse P _K , and is composed of, for example, a photo multiplier 2a and a pulse shaping circuit 2b. 3 is the sample, 4 is the pulsed light P
The stop pulse generating means generates a stop pulse P _T in response to the light emitted from the sample 3, and is composed of, for example, a photo multiplier 4a and a pulse shaping circuit 4b. 5 is an optical aperture, and 6 is a spectroscopic means such as a spectrometer. 7 starts operation by the start pulse P _K and the stop pulse
This is a known multi-TAC having a plurality of constant current charging circuits whose operation is sequentially stopped by P _T (see, for example, FIG. 2 of the above-mentioned Japanese Patent Laid-Open No. 57-137843). 8 is a changeover switch for selectively taking out the output of the multi-TAC 7 for each TAC, and is, for example, a multiplexer. 9 is an AD converter, and 10 is a multichannel pulse height analyzer. The components 1 to 10 above are the same as the conventional device. 11 is a stop pulse generating means 4 and a multi
A pulse-to-resolution time fixing means interposed between the TAC 7 and the TAC 7, which is composed of, for example, a mono-multivibrator, sets the pulse-to-resolution time ΔT (hereinafter simply expressed as ΔT) to an integral multiple of the measurement channel. Here, the measurement channel means the minimum unit of the measurement range on the time axis of the measurement device, and is shown in Fig. 3D.
is the horizontal axis, that is, one division (one unit) representing time. For example, if the minimum unit of measurement range is
At 0.1nS/channel, the above ΔT is N×
It is expressed as 0.1 nS (N is an integer). By artificially fixing ΔT in this way, only the first stop pulse P _T1 is considered effective within a certain ΔT, and the subsequent stop pulse P _T2
...is ignored. That is, when one stop pulse P T1 is output from the stop pulse generating means 4, the third stop pulse P _T1 is output from the pulse pair resolution time fixing means 11.
A TAC input stop signal (ie, a stop pulse output through the pulse pair resolution time fixing means 11) P _S having a pulse width ΔT as shown in FIG. C is output. Therefore _, even if another stop pulse P _T2 . 12 is a pulse counter that counts the number of generated start pulses _PK , that is, the number of times the light emitting source 1 flashes. Reference numeral 13 denotes an arithmetic processing unit which receives data from the multi-channel pulse height analyzer 10 and the integrated value of the start pulse P _K obtained by the pulse counter 12 and performs a calculation based on a formula described later. In the above configuration, when the light emitting source 1 emits the pulsed light P by one flash, the start pulse generating means 2 detects, for example, the rising edge of the pulsed light P and emits the start pulse _PK . This start pulse
Due to P _K , all constant current charging circuits in the multi-TAC 7 start charging at the same time. On the other hand, the sample 3 is excited by the pulsed light P and emits light. The stop pulse generating means 4 generates stop pulses P _T1 , P _{T2 ,} . . . every time light emission from the sample 3 is detected. When each of the stop pulses P _T1 , _{P T2} . Stop charging operation. The multi-TACs 7 operate simultaneously in response to the start pulse _PK and output analog voltages proportional to the time from when each stop signal P _S . . . is input. These output signals are sequentially switched by a changeover switch 8, input to a multichannel pulse height analyzer 10 via an AD converter 9, and stored in its memory. In this way, the light emitting source 1 is caused to emit light repeatedly, and the output signal from the multi-TAC 7 is sent to each TAC each time.
If the signal is taken out every time and inputted into the multichannel pulse height analyzer 10 after AD conversion, a histogram of the frequency of stop pulse occurrence with time (voltage) plotted on the horizontal axis is obtained. In FIG. 1, when the opening degree of the optical diaphragm 5 is large, the photon counting rate becomes large. However, if this photon counting rate is too large, as mentioned above, in the conventional device, as shown by the solid line in FIG. 3D, Additionally, waveform distortion occurs in the measurement results. Therefore, in the present invention, the arithmetic processing section 13 is provided at the subsequent stage of the multichannel pulse height analyzer 10,
The number of stop pulses is corrected. Next, the operation in the arithmetic processing section 13 will be explained in detail. Pulse-to-resolution time ΔT (hereinafter simply referred to as ΔT)
The sample where two or more stop pulses are output within a period can be calculated as follows. P _i ^c : Probability (true probability) that a stop pulse will enter the i-th measurement channel when ΔT = 0 (ideal state) Pi: A stop pulse will enter the i-th measurement channel of a device where ΔT has a certain finite value other than 0 Probability that N: Integer when expressing ΔT as the number of measurement channels (for example, if the minimum unit of measurement range is 1nS/
channel, if ΔT=5nS,
(N = 5), all stop pulses that come in the first measurement channel are counted without being affected by ΔT, so P ₁ = P ^c/1 ...(1) The measurement channel is If 2≦i≦N, the stop pulse that comes to the i-th channel is the probability that the stop pulse will come to the i-th channel under the condition that the stop pulse is completed by the i-1th channel, so Pi=Pi ^c _i-1 π ^j=1 (1-P ^c/j ) ...(2) When the measurement channel is i>N, Pi=Pi ^c _i-1 π ^j=i-(N-1) (1-P ^c/j ) ... ...(3) Here, in the above equations (1) to (3), each is multiplied by the number of flashes of the light source (which is also the integrated value of the start pulse _PK ) Ne. Rough NeP ₁ = NeP ^c/1 ∴N ₁ = N ^c/1 ……(1)′ NePi=NeP ^c/i _i-1 π ^j=1 (1−P ^c/j ) ∴Ni=N ^c/i _i-1 π ^j=1 (1−P ^c/j ) ……(2)′ NePi=NeP ^c/i _i-1 π ^j=1-(N-1) (1−P ^c/j ) ∴ _i Ni=N ^c/i _i-1 π ^j=1(N-1) (1-P ^c/j ) ...(3)′ However, when N ^c/i = NeP ^c/i :ΔT=0, Number of stop pulses to be loaded on the i-th measurement channel Ni = NePi: Number of stop pulses loaded on the i-th measurement channel of a device where ΔT has a certain value other than 0 (1)', (2)', (3) From ', the measured value (output of the multi-channel pulse height analyzer 10 and counter 12)
From this, the true number of stop pulses in each measurement channel can be calculated. N ^c/1 = N ₁ ...(1)'' The data of the first measurement channel can be used as is as the number of true stop pulses. Using the data of the first measurement channel, the true number of stop pulses of the second measurement channel can be calculated. Then, using the true number of stop pulses of the second measurement channel, the number of true stop pulses of the third measurement channel can be calculated. The following calculations can be made in the same manner. Similarly to the above, for each measurement channel,
The number of true stop pulses can be calculated in sequence. Next, an example of calculation when N=3 will be shown. this is,
Measurement range is 1nS/measurement channel, ΔT=3nS
This is the case. In the first measurement channel, N1 ^c = N ₁ In the second measurement channel, N2 ^c = N ₂ /1 - N1 ^c /Ne In the third measurement channel, N3 ^c = N ₃ / (1 - N2 ^c /Ne ) (1-N1 ^c /Ne) In the fourth measurement channel, N ^c ₄ = N ₄ / (1-N3 ^c /Ne) (1-N2 ^c /Ne) Similarly, the true value in each measurement channel is The number of stop pulses can be calculated. As described above, the number of stop pulses in each measurement channel is corrected and the true number of stop pulses is obtained, thereby eliminating waveform distortion in measurement results, which has been a problem in the past. In the embodiments described above, a monomultivibrator is used to set ΔT, but instead of this, a constant fraction discriminator whose pulse pair resolution time is known may be used. Further, a computer may be used to perform the processing in the multi-channel pulse height analyzer 12 and the arithmetic processing unit 13 according to a program. <Effects of the Invention> As detailed above, according to the present invention, the pulse pair resolution time is artificially fixed, and the distortion of the output waveform caused by the pulse pair resolution time is corrected by calculation. , it becomes possible to increase the average number of photometers, and therefore measurement can be performed accurately and in a short time.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of the structure of a sample according to the present invention, FIG. 2 is a block diagram showing a conventional apparatus, and FIGS. 3 A, B, C, and D are explanatory diagrams of operations. DESCRIPTION OF SYMBOLS 1... Light emitting source, 2... Start pulse generation means, 3... Sample, 4... Stop pulse generation means, 7... Multi time-voltage converter (multi
TAC), 11...Pulse pair resolution time fixing means, P
...Pulse light, P _K ...Start pulse, P _T ...
Stop pulse.

Claims (1)

[Scope of Claims] 1. A light emitting source of pulsed light, a start pulse generating means that generates a start pulse upon receiving the pulsed light, and a stop pulse generator that generates a stop pulse upon receiving light emitted from a sample that has received the pulsed light. and a multi-time-voltage converter having a plurality of constant current charging circuits that start operating in response to the start pulse and sequentially stop operating in response to the stop pulse, Time-
A pulse-to-resolution time fixing means is provided between the voltage converter and the pulse-to-resolution time to set it to an integral multiple of the measurement channel, and the number of stop pulses is corrected based on the formula below to find the true number. A luminescence lifetime measuring device for a sample, characterized in that: N ^c ₁ = N ₁ When 2≦i≦N [Formula] When i>N [Formula] However, Ni: Measured value of the stop pulse in the i-th measurement channel N ^c _i : True value of the stop pulse in the i-th measurement channel Number of pieces N: An integer when the pulse-to-resolution time is set to an integer multiple of the measurement channel Ne: Accumulated value of start pulses (number of flashes)