Time measurement device, fluorescence lifetime measurement device, and time measurement method

Abstract

To improve measurement efficiency by reducing dead time, and to realize high time resolution and long-term measurement. [Solution] The time measurement device 10 comprises a digital counter 20 that outputs a count signal in response to a clock signal, a plurality of TAC circuits 12 (TAC circuits 12a to 12j) that receive the detection signal detected by the detector 4 and the clock signal and output a measurement signal in response to the time between the detection signal and the clock signal, a control unit 14 that derives and outputs time information related to the detection signal based on the count signal output from the digital counter 20 and the measurement signal output from the TAC circuit 12, and a measurement gate 11 that switches the TAC circuit 12 to which the detection signal is input, taking into account the dead time of the TAC circuit 12.

Description

[Technical field]

[0001] The present invention relates to a time measurement device, a fluorescence lifetime measurement device, and a time measurement method. [Background technology]

[0002] In a fluorescence lifetime measuring device that measures the lifetime of fluorescence when a sample is irradiated with excitation light, a time measuring device that outputs information related to the time difference between a start pulse signal and a stop pulse signal is used. As such a time measuring device, a time measuring device that uses a TAC (Time-Analog-Converter) method that outputs the time difference as an analog signal is known (see, for example, Patent Document 1). The TAC method is advantageous in that it has a higher time resolution than the TDC (Time-Digital-Converter) method that measures time by outputting the time difference as a digital signal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2003-522946 Summary of the Invention [Problem to be solved by the invention]

[0004] In the time measurement device described above, when time is measured in a TAC circuit (time-to-amplitude converter), there is a dead time during which time cannot be measured again. The occurrence of such dead time makes it difficult to improve measurement efficiency sufficiently. As described above, the TAC method has the advantage of high time resolution, but it is difficult to perform time measurements on long-term phenomena (long-term measurements).

[0005] The present invention has been made in consideration of the above-mentioned situation, and aims to provide a time measurement device, a fluorescence lifetime measurement device, and a time measurement method that are capable of reducing dead time to improve measurement efficiency and achieving high time resolution and long-term measurement. [Means for solving the problem]

[0006] A time measurement device according to one embodiment of the present invention includes a counter that outputs a count signal in response to a clock signal, a plurality of first time-amplitude converters that receive a detection signal detected in a detector and the clock signal and output a measurement signal in response to the time between the detection signal and the clock signal, a control unit that derives and outputs time information related to the detection signal based on the count signal output from the counter and the measurement signal output from the first time-amplitude converter, and a first switching unit that switches the first time-amplitude converter to which the detection signal is input, taking into account the dead time of the first time-amplitude converter.

[0007] In a time measurement device according to an aspect of the present invention, a plurality of first time amplitude converters are provided, each of which outputs a measurement signal corresponding to the time between a detection signal and a clock signal. In this time measurement device, the first time amplitude converter to which the detection signal is input is switched, taking into consideration the dead time of the first time amplitude converter. For example, when time is measured using only one time amplitude converter, a dead time occurs during which the time amplitude converter cannot measure again after measurement. In this regard, the time amplitude converter is multi-staged and the dead time of the time amplitude converter is taken into consideration when switching the time amplitude converter, so that the time amplitude converter can be switched from a time amplitude converter that cannot measure again after measurement to a time amplitude converter that can measure, thereby significantly reducing the above-mentioned dead time. In addition, in a time measurement device according to an aspect of the present invention, a counter that operates in synchronization with a clock signal outputs a count signal to perform rough time measurement (low time resolution and long time measurement) that depends on the frequency of the clock, and the first time amplitude converter outputs a measurement signal corresponding to the time between the detection signal and the clock signal to perform fine time measurement (high time resolution and short time measurement) that compensates for the roughness of the measurement by the counter. By combining these time measurement results to derive final time information, it is possible to realize high time resolution and long-term measurement. As described above, the time measurement device according to one aspect of the present invention can reduce dead time to improve measurement efficiency, and can realize high time resolution and long-term measurement.

[0008] The first switching unit may switch the first time-to-amplitude converter based on switching information that is set in advance taking into account the dead time. With this configuration, the time-to-amplitude converter can be easily and appropriately switched based on the preset information (switching information that takes into account the dead time).

[0009] The control unit may derive time information indicating the time until the detection signal is input by subtracting the time indicated by the measurement signal from the time corresponding to the count value indicated by the count signal. This makes it possible to derive the time until the detection signal is input with high accuracy based on the count signal and the measurement signal.

[0010] The first switching unit may switch the first time-to-amplitude converter so that the detection signal is input to the first time-to-amplitude converter that is not in the dead time. This makes it possible to appropriately avoid a deterioration in measurement efficiency due to the effect of the dead time of the first time-to-amplitude converter.

[0011] The number of the first time-to-amplitude converters may correspond to the dead time, so that the influence of the dead time can be appropriately avoided by switching the first time-to-amplitude converters.

[0012] The number of the first time-to-amplitude converters may correspond to the amount of signals detected by the detector, and the number of the first time-to-amplitude converters corresponds to the amount of signals detected by the detector, so that the influence of the dead time can be appropriately avoided by switching the first time-to-amplitude converters.

[0013] The above-mentioned time measurement device may further include a second time-amplitude converter that outputs a signal corresponding to a synchronization signal of a phenomenon related to the detection signal detected by the detector, and the control unit may derive the time information by further taking into account the signal corresponding to the synchronization signal. This makes it possible to derive the time information related to the detection signal with higher accuracy by taking into account the actual timing of the phenomenon related to the detection signal.

[0014] The above-mentioned time measurement device may include a plurality of second time-to-amplitude converters, and may further include a second switching unit that switches the second time-to-amplitude converter to which the synchronization signal is input, taking into account the dead time of the second time-to-amplitude converters. This makes it possible to appropriately avoid a deterioration in measurement efficiency due to the effect of the dead time in the second time-to-amplitude converter.

[0015] A fluorescence lifetime measurement device according to one aspect of the present invention is a fluorescence lifetime measurement device that measures the lifetime of fluorescence emitted from a measurement object, and includes the above-mentioned time measurement device, a light source that irradiates the measurement object with generated light, a detector that detects the fluorescence from the measurement object irradiated with the light from the light source and outputs a detection signal, and a signal generation unit that controls the output of light from the light source and outputs a synchronization signal that is synchronized with the light source and the time measurement device. Such a fluorescence lifetime measurement device can efficiently measure the fluorescence lifetime using the above-mentioned time measurement device, and can achieve high time resolution and long-term measurement of the fluorescence lifetime.

[0016] A time measurement method according to one aspect of the present invention is a time measurement method implemented by a time measurement device that measures time while switching between multiple time-to-amplitude converters, and includes the steps of: selecting one time-to-amplitude converter to which a detection signal detected by a detector is input based on the dead time of each of the multiple time-to-amplitude converters; inputting the detection signal and a clock signal to the selected one time-to-amplitude converter to obtain a measurement signal corresponding to the time between the detection signal and the clock signal; and deriving and outputting time information related to the detection signal based on a count signal corresponding to the clock signal and the measurement signal. Such a time measurement method can reduce the dead time to improve measurement efficiency, and can achieve high time resolution and long-term measurement.

[0017] In the above-described time measurement method, the selecting step may select a time-to-amplitude converter that is not in a dead time, thereby making it possible to appropriately avoid a deterioration in measurement efficiency due to the influence of the dead time. Effect of the Invention

[0018] According to the present invention, it is possible to reduce the dead time to improve the measurement efficiency, and to realize high time resolution and long-term measurement. [Brief description of the drawings]

[0019] [Figure 1]1 is a diagram illustrating a schematic diagram of a fluorescence lifetime measurement device according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a diagram for explaining multi-TAC measurement. [Diagram 3] FIG. 1 is a diagram for explaining multi-TAC measurement. [Figure 4] FIG. 13 is a diagram for explaining derivation of time information. [Diagram 5] FIG. 13 is a diagram for explaining derivation of time information. [Figure 6] FIG. 13 is a diagram for explaining derivation of time information. [Figure 7] FIG. 13 is a diagram illustrating an example of a time measurement device according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a time measurement device, a time measurement method, and a fluorescence lifetime measurement device according to one aspect of the present invention will be described in detail with reference to the drawings.

[0021] 1 is a diagram illustrating a schematic diagram of a fluorescence lifetime measurement apparatus 1 according to this embodiment. The fluorescence lifetime measurement apparatus 1 is an apparatus that measures the lifetime of fluorescence emitted from a sample S (measurement object).

[0022] The fluorescence spectrum of an organic material or a fluorescent probe, such as a peak wavelength or fluorescence intensity, is an important parameter for controlling and evaluating the function and characteristics of a sample. However, since the fluorescence spectrum acquires information integrated over time, when a sample contains a plurality of substances or reaction systems, only the information integrated by them can be obtained. In such a case, as a means for evaluating the function and characteristics of a sample, a fluorescence lifetime measurement that measures the time it takes for a sample to return to the ground state after being excited by pulsed light in the subnanosecond to millisecond time domain is effective. In the fluorescence lifetime measurement device 1 according to this embodiment, the detection timing of the fluorescence is derived by a time measurement device 10 described later, and a frequency distribution of the detection timing is obtained by detecting the fluorescence multiple times, and the fluorescence lifetime of the sample S is estimated based on the frequency distribution.

[0023] As shown in Fig. 1, the fluorescence lifetime measurement device 1 includes a pulse generator 2 (signal generation unit), a light source 3, a detector 4, a computer 5, a display device 6, an input device 7, and a time measurement device 10. Note that, among the components of the fluorescence lifetime measurement device 1, a clock generation circuit 9 (see Fig. 3), which will be described later, is not shown in Fig. 1.

[0024] The pulse generator 2 outputs synchronous (e.g., identical timing) pulse signals to the light source 3 and a reference gate 15 (details to be described later) of the time measurement device 10 based on instructions from the computer 5. The pulse generator 2 controls the light output by the light source 3 and outputs the control signal as a pulse signal. The reference gate 15 outputs a synchronization signal to the TAC circuit 16a or TAC circuit 16b based on the pulse signal (details to be described later). Since pulse signals with the same timing are input to the light source 3 and the reference gate 15, the synchronization signal output from the reference gate 15 is a signal that corresponds to (is synchronized with) the irradiation of light (excitation light) from the light source 3.

[0025] The light source 3 outputs excitation light to be irradiated onto the sample S based on the pulse signal output from the pulse generator 2. As the light source 3, an LED (Light Emitting Diode) light source, a laser light source, an SLD (Super Luminescent Diode) light source, a lamp-type light source, or the like can be used. The intensity of the excitation light may be set, for example, such that one photon is emitted when the excitation light is irradiated onto the sample S. Fluorescence corresponding to the excitation light is output from the sample S irradiated with the excitation light.

[0026] The detector 4 detects the fluorescence from the sample S and outputs a detection signal to a measurement gate 11 (described in detail later) of the time measurement device 10. As the detector 4, a photomultiplier tube, an avalanche photodiode, a PIN photodiode, or the like can be used.

[0027] The computer 5 derives the fluorescence lifetime based on the measurement results output from the time measurement device 10 (more specifically, the control unit 14). Specifically, the computer 5 derives a frequency distribution of the fluorescence detection timing from the fluorescence time information (fluorescence detection timing) included in the measurement results, and obtains the fluorescence lifetime of the sample S from the frequency distribution. The computer 5 is composed of a calculation unit such as a CPU, and a storage unit such as a RAM or flash memory. The computer 5 may also perform the function of the control unit 14 of the time measurement device 10.

[0028] The display device 6 is a display electrically connected to the computer 5, and displays the above-mentioned fluorescence lifetime analysis results of the sample S. The input device 7 is a keyboard, a mouse, or the like, and allows the input and setting of analysis conditions and measurement conditions for the fluorescence lifetime.

[0029] The time measurement device 10 is a time measurement device that calculates the time from when a first trigger signal is input to when a second trigger signal is input as a measured time. The time measurement device 10 can be applied to various devices and systems that derive the difference in input timing of two signals (a first trigger signal and a second trigger signal) that are input at different timings. In this embodiment, as described above, the time measurement device 10 is applied to the fluorescence lifetime measurement device 1 that measures the lifetime of fluorescence emitted from a sample S.

[0030] As shown in FIG. 1, the time measurement device 10 includes a measurement gate 11 (first switching unit), a TAC (Time-Analog-Converter) circuit 12 (first time amplitude converter), a TAC control unit 13, a control unit 14, a reference gate 15 (second switching unit), and a TAC circuit 16 (second time amplitude converter). More specifically, the time measurement device 10 includes a plurality of TAC circuits 12a to 12j as the TAC circuit 12, a plurality of TAC control units 13a to 13f as the TAC control unit 13, and a plurality of TAC circuits 16a and 16b as the TAC circuit 16. The plurality of TAC circuits 12a to 12j are connected in parallel to the measurement gate 11, and the plurality of TAC circuits 16a and 16b are connected in parallel to the reference gate 15. Note that in FIG. 1, a digital counter 20 (see FIG. 3), which will be described later, is omitted from the configuration of the time measurement device 10. The digital counter 20 may be provided in the TAC control unit 13 or may be provided separately from the TAC control unit 13.

[0031] The TAC circuit 12 is a time-amplitude converter circuit that outputs the time difference between when a first trigger signal is input and when a second trigger signal is input as an analog signal (amplitude). The TAC circuit 12 is configured to be able to measure a time of, for example, 10 ns. Specifically, the TAC circuit 12 outputs an analog signal (amplitude) according to the time between the detection signal and the clock signal as a measurement signal to the TAC control unit 13, using the detection signal detected in the detector 4 as a first trigger signal and the clock signal output from the clock generation circuit 9 (see FIG. 3) as a second trigger signal. That is, the TAC circuit 12 receives the detection signal detected in the detector 4 and the clock signal, and outputs a measurement signal according to the time between the detection signal and the clock signal. The TAC circuit 12 receives the detection signal input via the measurement gate 11.

[0032] The TAC control unit 13 is an AD converter that converts an analog signal (amplitude) that is a measurement signal input from the TAC circuit 12 into a digital signal. The TAC control unit 13 outputs the digital signal after AD conversion to the control unit 14 as a measurement signal. As described above, the time measurement device 10 has a plurality of TAC control units 13a to 13f as the TAC control unit 13. As shown in FIG. 1, the TAC control unit 13a receives an input of a measurement signal from the TAC circuits 12a and 12b, the TAC control unit 13b receives an input of a measurement signal from the TAC circuits 12c and 12d, the TAC control unit 13c receives an input of a measurement signal from the TAC circuits 12e and 16a, the TAC control unit 13d receives an input of a measurement signal from the TAC circuits 12f and 12g, the TAC control unit 13e receives an input of a measurement signal from the TAC circuits 12h and 12i, and the TAC control unit 13f receives an input of a measurement signal from the TAC circuits 12j and 16b.

[0033] The measurement gate 11 receives a detection signal, which is a first trigger signal, from the detector 4 and outputs the detection signal to the TAC circuit 12. In detail, the measurement gate 11 outputs the detection signal input from the detector 4 to only one TAC circuit 12 among the multiple TAC circuits 12a to 12j. Figures 2 and 3 are diagrams for explaining multi-TAC measurement. Here, multi-TAC measurement refers to a measurement technique in which multiple TAC circuits 12a to 12j are used while being switched.

[0034] 2, the measurement gate 11 has a plurality of gate circuits 11a-11j provided in front of the TAC circuits 12a-12j in one-to-one correspondence with the TAC circuits 12a-12j. Only one of the gate circuits 11a-11j of the measurement gate 11 is enabled (in a state in which the input of a detection signal is accepted). The gate circuits 11a-11j that are not enabled are in a standby state (in a state in which the input of a detection signal is not accepted). The measurement gate 11 switches the enabled gate circuits 11a-11j so that the detection signal is input to only one of the TAC circuits 12a-12j.

[0035] The measurement gate 11 switches the TAC circuits 12a to 12j to which the detection signal is input, taking into consideration the dead time of the multiple TAC circuits 12a to 12j. The dead time here refers to a period of time during which the TAC circuit 12 is unable to measure time again for a certain period of time after the time has been measured. The TAC circuits 12a to 12j have the same performance and the same dead time. The dead times of the TAC circuits 12a to 12j may be different from each other. For example, in the example shown in FIG. 2, the measurement gate 11 first enables the gate circuit 11a and puts the other gate circuits 11b to 11j in a standby state. In this state, when a detection signal is input from the detector 4 to the measurement gate 11, the detection signal is input only to the gate circuit 11a, and the detection signal is input to the TAC circuit 12a via the gate circuit 11a. The TAC circuit 12a outputs a measurement signal according to the time between the detection signal and the clock signal. For a certain period of time after the process of outputting the measurement signal, the TAC circuit 12a cannot measure time again, which is a dead time. Therefore, the measurement gate 11 enables the second gate circuit 11b and puts the other gate circuits 11a, 11c to 11j in a standby state. In this state, when a detection signal is input from the detector 4 to the measurement gate 11, the detection signal is input only to the gate circuit 11b, and the detection signal is input to the TAC circuit 12b via the gate circuit 11b. Then, as in the TAC circuit 12a, the TAC circuit 12b also enters a dead time, so the measurement gate 11 then enables the third gate circuit 11c and puts the other gate circuits 11a, 11b, 11d to 11j in a standby state. In this way, the measurement gate 11 sequentially switches the TAC circuits 12a to 12j to which the detection signal is input by sequentially enabling only one of the gate circuits 11a to 11j corresponding to each of the TAC circuits 12a to 12j. According to this method, the dead time that causes photons to be missed is only the switching time of the gate circuits 11a to 11j, not the dead time (dead time during TAC processing) of the TAC circuit 12. The dead time during TAC processing is, for example, 150 ns, and the switching time of the gate circuits is, for example, 1 ns, so that this method can significantly shorten the dead time that causes photons to be missed.

[0036] The measurement gate 11 switches the TAC circuits 12a to 12j to which the detection signal is input based on switching information that is preset in consideration of the dead time. The switching information is information that specifies the switching order of the TAC circuits 12a to 12j (the order in which the gate circuits 11a to 11j are enabled) so that the detection signal is not input to the TAC circuits 12a to 12j during the dead time. That is, the measurement gate 11 switches the TAC circuits 12a to 12j so that the input destination of the detection signal becomes the TAC circuit 12a to 12j that is not in the dead time. As a prerequisite for such switching, the number of the multiple TAC circuits 12a to 12j is provided according to the dead time of the TAC circuits 12. The number according to the dead time is the number of TAC circuits 12 that will not receive the detection signal during the dead time when the TAC circuits 12 are switched so that the detection signal is input to each TAC circuit 12 in order. Further, the multiple TAC circuits 12a to 12j are provided in a number corresponding to the amount of signal detected by the detector 4. The number corresponding to the amount of signal detected by the detector 4 is a number that prevents a detection signal from being input to the TAC circuit 12 during dead time when the TAC circuits 12 are switched so that the detection signals are input to each TAC circuit 12 in order, even if a detection signal is input with the maximum expected signal amount.

[0037] The control unit 14 derives and outputs time information related to the detection signal detected by the detector 4 based on the count signal output from the digital counter 20 (see FIG. 3) and the measurement signal output from the TAC circuit 12 and converted into a digital signal by the TAC control unit 13. As shown in FIG. 3, the digital counter 20 is a counter to which the detection signal from the detector 4 and the clock signal from the clock generation circuit 9 are input. The digital counter 20 operates in synchronization with the clock signal and outputs a count signal to the control unit 14 in response to the clock signal (by counting the clock signals). Although such a digital counter 20 can perform long-term measurement of the detection signal, it is difficult to increase the time resolution. The control unit 14 realizes high time resolution and long-term measurement of the time information related to the detection signal by combining the time measurement result by the digital counter 20 and the time measurement result by the TAC circuit 12, which has high time resolution.

[0038] 4 to 6 are diagrams for explaining the derivation of the time information described above. In FIG. 4 to FIG. 6, the horizontal axis indicates the time axis. As shown in FIG. 4, the digital counter 20 counts the clock signals and outputs a count signal. FIG. 4 shows an example in which the digital counter 20 outputs count signals indicating 23, 24, 25, 26, 27, and 28. As described above, the digital counter 20 operates in synchronization with the clock signal. As shown in FIG. 4, it is assumed that the TAC circuit 12 measures the time difference T from when the detection signal TRG1 is input from the detector 4 to when the clock signal TRG2 immediately after the detection signal TRG1 is input. In the measurement signal output by the TAC circuit 12, as shown in FIG. 5, the voltage (amplitude) starts to increase according to the detection signal TRG1 from the timing (time t1) when the detection signal TRG1 is input, and the voltage (amplitude) becomes constant according to the clock signal TRG2 from the timing (time t2) when the clock signal TRG2 is input.

[0039] The control unit 14 subtracts the time indicated by the measurement signal from the time corresponding to the count value indicated by the count signal to derive time information indicating the time until the detection signal is input to the TAC circuit 12. That is, in the example shown in Fig. 4, the control unit 14 subtracts the time difference T, which is the time information indicated by the measurement signal, from 23, which is the time corresponding to the count value indicated by the count signal, to derive time information (23-T) indicating the time until the detection signal TRG1 is input to the TAC circuit 12. The derivation of such time information is possible because the clock signal input to the digital counter 20 corresponds to the clock signal input to the TAC circuit 12 (the count value indicated by the clock signal input to the TAC circuit 12 is uniquely determined).

[0040] In a configuration in which a plurality of TAC circuits 12 are switched, the control unit 14 can appropriately perform time measurement even in the case of multi-photons by deriving time information based on information from each TAC circuit 12. In the example shown in Fig. 6, after deriving time information of the TAC circuit 12 (referred to as TAC1 in Fig. 6) to which a detection signal is input first, the control unit 14 derives time information of the TAC circuit 12 (referred to as TAC2 in Fig. 6) to which a detection signal is input second, and further derives time information of the TAC circuit 12 (referred to as TAC3 in Fig. 6) to which a detection signal is input third. 6, the control unit 14 derives time information relating to the measurement result of TAC1 by subtracting time information indicated by the measurement signal output by TAC1 from 23, which is the time corresponding to the count value indicated by the count signal, derives time information relating to the measurement result of TAC2 by subtracting time information indicated by the measurement signal output by TAC2 from 24, which is the time corresponding to the count value indicated by the count signal, and derives time information relating to the measurement result of TAC3 by subtracting time information indicated by the measurement signal output by TAC3 from 27, which is the time corresponding to the count value indicated by the count signal. The control unit 14 outputs the derived time information (measurement results) to the computer 5.

[0041] The TAC circuit 16 is a time-amplitude converter circuit that outputs the time difference between when the first trigger signal is input and when the second trigger signal is input as an analog signal (amplitude). The TAC circuit 16 outputs a signal corresponding to a synchronization signal of a phenomenon related to the detection signal detected in the detector 4. The phenomenon related to the detection signal detected in the detector 4 is the fluorescence from the sample S detected in the detector 4. The synchronization signal of the phenomenon is a synchronization signal output by the reference gate 15 to the TAC circuit 16 based on a pulse signal output by the pulse generator 2 at a timing synchronized (for example, identical) with the light source 3 and the reference gate 15. That is, the synchronization signal here is a signal synchronized with the excitation light irradiated from the light source 3 to the sample S with respect to the detection of the fluorescence. Specifically, the TAC circuit 16 uses the synchronization signal input from the reference gate 15 as a first trigger signal and the clock signal output from the clock generation circuit 9 as a second trigger signal, and outputs an analog signal (amplitude) corresponding to the time difference between the synchronization signal and the clock signal to the TAC control unit 13 as a signal corresponding to the above-mentioned synchronization signal. The time measurement device 10 has two TAC circuits 16a and 16b as the TAC circuit 16. The TAC circuit 16a outputs a signal corresponding to the above-mentioned synchronization signal to the TAC control unit 13c. The TAC circuit 16b outputs a signal corresponding to the above-mentioned synchronization signal to the TAC control unit 13f. The TAC control units 13c and 13f convert the signals input from the TAC circuits 16a and 16b into digital signals and output them to the control unit 14. The control unit 14 may derive time information by further considering the signal corresponding to the above-mentioned synchronization signal. That is, the control unit 14 may specify the start timing (start point) of the phenomenon from the signal corresponding to the above-mentioned synchronization signal and derive time information related to the detection signal detected by the detector 4 with higher accuracy.

[0042] The reference gate 15 switches between the TAC circuits 16a and 16b to which the above-mentioned synchronization signal is input, taking into account the dead time of the TAC circuit 16. The reference gate 15 receives a pulse signal from the pulse generator 2 and outputs a synchronization signal corresponding to the pulse signal to only one of the TAC circuits 16a and 16b. The reference gate 15 switches between the TAC circuits 16a and 16b to which the synchronization signal is input, based on switching information that is preset taking into account the dead time. The switching information is specified so that the synchronization signal is not input to the TAC circuits 16a and 16b during the dead time.

[0043] Next, the actions and effects of the time measurement device 10 according to this embodiment and the fluorescence lifetime measurement device 1 including the time measurement device 10 will be described.

[0044] The time measurement device 10 of this embodiment comprises a digital counter 20 that outputs a count signal in response to a clock signal, a plurality of TAC circuits 12 (TAC circuits 12a to 12j) that receive a detection signal detected by a detector 4 and a clock signal and output a measurement signal in response to the time between the detection signal and the clock signal, a control unit 14 that derives and outputs time information related to the detection signal based on the count signal output from the digital counter 20 and the measurement signal output from the TAC circuit 12, and a measurement gate 11 that switches the TAC circuit 12 to which the detection signal is input, taking into account the dead time of the TAC circuit 12.

[0045] In such a time measurement device 10, a plurality of TAC circuits 12 are provided, which output a measurement signal corresponding to the time between the detection signal and the clock signal. In the present time measurement device 10, the dead time of the TAC circuit 12 is taken into consideration when switching the TAC circuit 12 to which the detection signal is input. For example, when time is measured using only one TAC circuit 12, a dead time occurs during which the TAC circuit 12 is unable to perform measurement again after measurement. In this regard, by providing multiple TAC circuits 12 and switching the TAC circuit 12 while taking into consideration the dead time of the TAC circuit 12, the TAC circuit 12 is switched from the TAC circuit 12 that is unable to perform measurement again after measurement to the TAC circuit 12 that is able to perform measurement, and the dead time described above can be significantly reduced. In addition, in the TAC circuit 12 according to this embodiment, the digital counter 20, which operates in synchronization with the clock signal, outputs a count signal to perform rough time measurement (low time resolution and long-term measurement) depending on the frequency of the clock, and the TAC circuit 12 outputs a measurement signal corresponding to the time between the detection signal and the clock signal to perform fine time measurement (high time resolution and short-term measurement) that compensates for the measurement roughness of the digital counter 20. These time measurement results are combined to derive final time information, thereby realizing high time resolution and long-term measurement. As described above, according to the time measurement device 10 according to this embodiment, it is possible to reduce dead time to improve measurement efficiency and to realize high time resolution and long-term measurement. An example of the time resolution of the time measurement device 10 is 0.25 ps, and an example of long-term measurement is 24 hours or more. Note that the time resolution here is a measurement unit and does not indicate the time resolution of the entire measurement system.

[0046] For example, when an organic EL light-emitting material such as TADF is photoexcited, ns-order light emission and ms-order light emission may occur. When light emission having a decay characteristic with a very large time unit difference occurs, a measurement device capable of performing long-term measurement while maintaining high time resolution is required to efficiently perform fluorescence lifetime measurement. In such fluorescence lifetime measurement, the time measurement device 10 according to the present embodiment, which realizes high time resolution and long-term measurement, can be effectively used. Note that the measurement target of the time measurement device 10 is not limited to the above-mentioned TADF, and may include other phosphors and targets of various phenomena other than the light emission phenomenon.

[0047] Furthermore, the above-described time measurement device 10 can perform time measurement with a higher light intensity (for example, about 10 times the light intensity) than before, for example, in fluorescence lifetime measurement, by switching between the multiple TAC circuits 12 to perform time measurement. When the sample has a strong luminescence intensity, conventionally, measurements are performed by greatly attenuating the luminescence using a filter, and time measurement is performed in a state in which there is a lot of signal loss, but the time measurement device 10 can perform time measurement with high accuracy while suppressing the signal loss.

[0048] The measurement gate 11 may switch the TAC circuit 12 based on switching information that is set in advance taking into account the dead time. With this configuration, the TAC circuit 12 can be easily and appropriately switched based on the preset information (switching information that takes into account the dead time).

[0049] The control unit 14 may derive time information indicating the time until the detection signal is input by subtracting the time indicated by the measurement signal from the time corresponding to the count value indicated by the count signal. This makes it possible to derive the time until the detection signal is input with high accuracy based on the count signal and the measurement signal.

[0050] The measurement gate 11 may switch the TAC circuit 12 so that the detection signal is input to the TAC circuit 12 that is not in the dead time. This makes it possible to appropriately avoid the measurement efficiency from being deteriorated due to the influence of the dead time of the TAC circuit 12.

[0051] A number of TAC circuits 12 may be provided according to the dead time, which makes it possible to appropriately avoid the influence of the dead time by switching the TAC circuits 12.

[0052] The number of TAC circuits 12 may be set according to the amount of signals detected by the detector 4. In this way, the number of TAC circuits 12 set according to the amount of signals is set, and the influence of dead time can be appropriately avoided by switching the TAC circuits 12.

[0053] The time measurement device 10 further includes a plurality of TAC circuits 16 (TAC circuits 16a, 16b) that output a signal corresponding to a synchronization signal of a phenomenon related to the detection signal detected by the detector 4, and the control unit 14 may derive the time information by further taking into account the signal corresponding to the synchronization signal. This makes it possible to derive the time information related to the detection signal with higher accuracy by taking into account the actual timing of the phenomenon related to the detection signal.

[0054] The time measurement device 10 may further include a reference gate 15 that switches the TAC circuit 16 to which the synchronization signal is input, taking into account the dead time of the TAC circuit 16. This makes it possible to appropriately prevent the measurement efficiency of the reference signal from deteriorating due to the influence of the dead time in the TAC circuit 16.

[0055] The fluorescence lifetime measurement device 1 according to this embodiment is a fluorescence lifetime measurement device that measures the lifetime of fluorescence emitted from a sample S, and includes the above-mentioned time measurement device 10, a light source 3 that irradiates the sample S with generated light, a detector 4 that detects fluorescence from the sample S irradiated with light from the light source 3 and outputs a detection signal, and a pulse generator 2 that controls the output of light from the light source 3 and outputs a synchronization signal that is synchronized with the light source 3 and the time measurement device 10. Such a fluorescence lifetime measurement device 1 can use the above-mentioned time measurement device 10 to efficiently measure the fluorescence lifetime and achieve high time resolution and long-term measurement of the fluorescence lifetime.

[0056] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, the time measurement device 10 has been described as including the TAC circuit 16 and the reference gate 15 related to the synchronization signal, but if the timing (repetition timing, etc.) of the phenomenon to be timed can be grasped, a configuration not including the TAC circuit 16 and the reference gate 15 may be adopted as shown in FIG. 7.

[0057] Furthermore, the number of TAC circuits 12 is not limited to the number (8) described in the embodiment, and may be, for example, six TAC circuits 12 (TAC circuits 12a to 12f) as shown in Fig. 7, or another number. The appropriate number of such TAC circuits 12 is preferably changed according to the fluorescence lifetime value to be measured, for example, in the case of fluorescence lifetime measurement. For example, when the fluorescence lifetime value to be measured is 5 μs or less, the number of TAC circuits 12 is set to eight (or less), and when the fluorescence lifetime value to be measured is longer than 5 μs, nine or more TAC circuits 12 may be provided. [Explanation of symbols]

[0058] 1...fluorescence lifetime measuring device, 2...pulse generator (signal generating section), 3...light source, 4...detector, 10...time measuring device, 11...measurement gate (first switching section), 12...TAC circuit (first time amplitude converter), 14...control section, 15...reference gate (second switching section), 16...TAC circuit (second time amplitude converter), 20...digital counter (counter), S...sample (object to be measured).

Claims

1. a counter that outputs a count signal in response to a clock signal; a plurality of first time-to-amplitude converters each receiving a detection signal detected by a detector and the clock signal and outputting a measurement signal corresponding to a time between the detection signal and the clock signal; a control unit that derives and outputs time information related to the detection signal based on the count signal output from the counter and the measurement signal output from the first time-to-amplitude converter; a first switching unit that switches the first time-to-amplitude converter so that the detection signal is input to the first time-to-amplitude converter that is not in a dead time; a second time-to-amplitude converter that outputs a signal corresponding to a synchronization signal of a phenomenon related to the detection signal detected by the detector; The control unit derives the time information by further taking into account a signal corresponding to the synchronization signal.

2. The time measurement device according to claim 1 , wherein the first switching section switches the first time-to-amplitude converter based on preset switching information.

3. 3. The time measurement device according to claim 1, wherein the control unit derives the time information indicating the time until the detection signal is input by subtracting the time indicated by the measurement signal from the time corresponding to the count value indicated by the count signal.

4. 4. The time measurement device according to claim 1, wherein the number of the first time-to-amplitude converters provided corresponds to the dead time.

5. 5. The time measurement device according to claim 1, wherein the number of the first time-to-amplitude converters provided corresponds to an amount of a signal detected by the detector.

6. A fluorescence lifetime measurement device that measures the lifetime of fluorescence emitted from a measurement object, The time measurement device according to any one of claims 1 to 5, A light source that irradiates the generated light onto the measurement object; a detector that detects the fluorescence from the measurement object irradiated with light from the light source and outputs the detection signal; a signal generating unit that controls the output of light from the light source and outputs a synchronization signal to the light source and the time measuring device that are synchronized with each other.

7. A time measurement method implemented by a time measurement device that measures time while switching between a plurality of time-to-amplitude converters, comprising: selecting a time-to-amplitude converter that is not in a dead time as one time-to-amplitude converter to which a detection signal detected by a detector is input; inputting the detection signal and a clock signal into the selected one of the time-to-amplitude converters to obtain a measurement signal corresponding to a time between the detection signal and the clock signal; and deriving and outputting time information related to the detection signal based on a count signal corresponding to the clock signal and the measurement signal, A time measurement method in which, in the step of deriving and outputting the time information, the time information is derived by further taking into consideration a signal corresponding to a synchronization signal output from a time amplitude modulator that outputs a signal corresponding to a synchronization signal of a phenomenon related to the detection signal detected by the detector.

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