JPH09184800A - Time resolved optical measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform measurement at a plurality of wavelengths and measuring points without any time deviation and using a single detector and a single TAC. SOLUTION: An oscillation signal from an oscillator 4 is simultaneously supplied to semiconductor lasers 2-1 and 2-2 with different oscillation wavelengths but one coaxial cable 5-2 is longer and has a delay element 30. Laser pulse beams oscillated from both semiconductor lasers 2-1 and 2-2 are guided to a specimen 8 by optical fibers 3-1 and 3-2, respectively, pulse beams through the specimen 8 are detected by a detector 10, and time until photo is detected by the detector 10 is outputted as a voltage and integrated by a TAC 14. The obtained integral waveform by the semiconductor laser 2-1 and that by the semiconductor laser 2-2 are separated as shown in (a) and waveforms for a plurality of light sources can be measured without any time deviation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring a time change of a light phenomenon that changes at high speed, such as a biological oxygen monitor or optical CT, and an optical constant measuring apparatus for a scatterer, and in particular, TAC (Time-to-Amplitude Co
nverter; time-voltage converter) and a device for performing measurement by the time correlation single photon counting method.

[0002]

2. Description of the Related Art In the time-correlated single photon counting method, when it is attempted to detect a time-resolved waveform of light incident on a subject from a plurality of light sources with a single detector, the oscillation of the light sources is switched or a plurality of light sources are switched. It is necessary to switch the light oscillated from the optical switch by an optical switch. FIG. 1A shows a method for switching the oscillation of the light source. The signal from the oscillator 4 is switched by the switch 6 and given to the two semiconductor lasers 2-1 and 2-2 having different wavelengths, and one of the semiconductor lasers is pulse-oscillated to be incident on the subject 8. The pulsed light scattered and transmitted through the subject is detected by the detector 10.
In the TAC 14, the photon detection signal from the detector 10 is CF
After going through D (Constant Fraction Discriminater) 12, T
AC14 is given as a start signal, the oscillation signal from the oscillator 4 is given as a stop signal to the TAC14 via the CFD 16 and the delay circuit 15 having an appropriate delay,
The time difference between the start signal and the stop signal from the detector 10 is output as a voltage. The output voltage of TAC14 is A
It is converted into a digital signal by the / D converter 18, and MCA (Ma
The signal from the semiconductor laser is instructed by the ltichannel analyzer) 20 and stored in the respective memory devices 22-1 and 22-2. The stored waveform is a measurement of the time difference between the detection signal and the delayed oscillation signal, but the time difference waveform between the irradiation time and the detection time that should be originally obtained is merely different in the direction of the time axis. This relationship is generally called reverse connection. The waveforms shown as a1 and a2 in FIG. 1 are shown with their time axes reversed.

The operation time of the TAC 14 is the time from the output of the oscillation signal from the oscillator 4 to the completion of the photon detection by the detector 10, and is an extremely short time such as several nanoseconds. Therefore, laser irradiation is performed in a cycle with a time interval as short as possible (for example, 200 nanoseconds), and the oscillation of the semiconductor lasers 2-1 and 2-2 is switched by the switch 6 within such a short irradiation interval. It is not possible.

Further, in the TAC measurement, the intensity distribution is obtained by integrating the photon detection probability distribution of one time many times. Therefore, when one of the semiconductor lasers, for example, 2-1 is oscillated, the semiconductor laser 2-1 is repeatedly oscillated and the operation by the TAC 14 is repeated, and the outputs thereof are integrated, as shown in (a1). The waveform obtained by the semiconductor laser 2-1 is obtained. The time required to obtain this waveform is (oscillation interval time of semiconductor laser x number of times of integration). Then, switch 6
Therefore, the oscillation of the semiconductor laser is caused on the other side, for example, 2-2.
The same measurement is performed after switching to the side.

Instead of switching the oscillation signal, the semiconductor lasers 2-1 and 2-2 are driven by the oscillator 4 as shown in FIG.
It is also possible to oscillate 2 simultaneously and switch the laser pulse light guided to the subject 8 by the optical switch 24.
In this case as well, switching by the optical switch 24 is performed in units of (oscillation interval time of semiconductor laser × number of times of integration).

[0006]

As shown in FIG. 1, in the method of switching the oscillation signal or switching the oscillated pulsed light, a time lag (time shift) corresponding to the integration time of TAC occurs. Especially, in biometrics, the optical constant is calculated by comparing the waveform at a certain wavelength or a certain measurement point with other waveforms or waveforms at other measurement points. As a result, the measurement accuracy is lowered. In order to reduce such a time shift, it is necessary to shorten the integration time, that is, to increase the irradiation cycle without reducing the irradiation light amount for one irradiation. To this end, it is necessary to increase the output power of the semiconductor laser. However, there are technical limitations.

In the measurement by the time correlation single counting method, it is an absolute condition that the detected light is in a single photon state (one photon or less is detected for one irradiation). Therefore, the probability of detecting a photon is 1/20 (or 1/50 or 1/100) with respect to the cycle of the applied light.
It is necessary to measure as follows.

[0008] Usually, in photobiological measurement, the light scattered and transmitted through the subject is very weak due to the limit of the light source for irradiation, and it is not uncommon for this light to greatly fall below this single-photon condition. That is, when viewed from the detector side, the waiting time is large and the operating rate during the integration time is extremely low.

Therefore, the present invention intends to perform measurement by another light source (wavelength or another measurement point) in this time gap. However, when irradiation or detection is performed at two or more wavelengths or measurement points at the same time, the detectors cannot select each wavelength or each measurement point, and thus the observed waveforms overlap. In order to avoid such problems, it is necessary to shift the irradiation time or the detection time for each wavelength or point so that the integrated waveforms do not overlap.

An object of the present invention is to enable measurement at a plurality of wavelengths or measurement points without a long time lag of an integration time as in the conventional case, and to perform measurement with one detector and one TAC. That is.

[0011]

According to the present invention, at least one of a light incident side to a subject and a light emitting side from the subject has a plurality of channels, and a photodetector detects photons of each channel. A delay element was provided so that the times did not overlap each other and photon detection by the photodetectors of all channels was completed within the single operating time region of the TAC.

The delay elements include the following. (1) A coaxial cable or the like for guiding a light source trigger signal (= oscillation signal) for turning on the light source to the light source is lengthened, and thereby electrically delayed. (2) A light guide path such as an optical fiber for guiding the light that has been turned on to the subject is lengthened, whereby the optical path from the light source to the subject is optically delayed. (3) A light guide path such as a light-receiving side optical fiber that guides the scattered transmitted light emitted from the subject to the detector is lengthened, whereby the optical path from the subject to the detector is optically delayed. If the delay element is a coaxial cable or optical fiber, approximately 2
With a length of 0 cm, a delay amount of about 1 nanosecond can be obtained.

[0013]

EXAMPLE FIG. 2A shows a first example. The same parts as those in the embodiment of FIG. 1 are designated by the same reference numerals. The oscillation signals from the oscillator 4 are semiconductor lasers 2-1 and 2-having different oscillation wavelengths.
2 are simultaneously supplied via coaxial cables 5-1 and 5-2, respectively, but the coaxial cable 5-2 is longer than the coaxial cable 5-1 and the extended coaxial cable is the delay element. It is 30. Laser pulse lights emitted from the two semiconductor lasers 2-1 and 2-2 are guided to the same position or different positions of the subject 8 by the optical fibers 3-1 and 3-2, respectively. The pulsed light scattered and transmitted through the subject 8 is detected by the detector 10. In the TAC 14, the photon detection signal from the detector 10 passes through the CFD 12 and becomes TAC.
14 is provided as a start signal to the oscillator 14, and the oscillation signal from the oscillator 4 is a CFD 16 and a delay circuit 15 having an appropriate delay.
After that, it is given to the TAC 14 as a stop signal, and the time difference between the start signal and the stop signal is output as a voltage. The output voltage of the TAC 14 is converted into a digital signal by the A / D converter 18, and is passed through the MCA 20 to the memory device 22.
Are stored in and accumulated.

The detector 10 detects both the photons of the pulsed light from the semiconductor lasers 2-1 and 2-2 within the operation time of the TAC 14, but the semiconductor laser 2-2 is detected by the delay element 30.
Since the pulsed light of 1 is supplied to the subject 8 later than the pulsed light of the semiconductor laser 2-1, the detector 10 shifts the photons by the pulsed light from both semiconductor lasers 2-1 and 2-2 in time. Detect by status. The integrated waveform thus obtained is as shown in (a), and the data by the semiconductor laser 2-1 and that by the semiconductor laser 2-2 are separated in data processing, and the waveforms for a plurality of light sources are measured with almost no time lag. Will be able to.

The light that is scattered and transmitted is relatively strong,
When it deviates from the complete single-photon state, waveform distortion occurs. In this case, the power of the irradiation light may be weakened. Even in that case, there is no time lag, there is an advantage that a complicated element such as a switch is not required, and there is no problem that the integration time becomes long.

In FIG. 2B, an optical fiber 3 for oscillating two semiconductor lasers 2-1 and 2-2 at the same time by an oscillator 4 and guiding a laser pulse from both semiconductor lasers 2-1 and 2-2 to a subject 8. It shows an embodiment in which the delay is made by making the lengths of -1 and 3-2 different from each other. In this case, the optical fiber 3- is better than the optical fiber 3-1.
2 is made longer, and the lengthened portion 32 becomes a delay element. Other configurations and operations are the same as those in (A).

FIG. 3 shows still another embodiment. (A) shows one semiconductor laser 2 with an oscillator 4.
Is pulse-oscillated, the pulsed light is demultiplexed into two optical paths by the optical demultiplexer 34, and the pulsed light of each optical path is incident on different positions of the subject 8 via the optical fibers 36-1 and 36-2. It is a thing. In this case, the length of one optical fiber 36-2 is made longer than the length of the other optical fiber 36-1, and the lengthened portion 38 serves as a delay element. The other structure is the same as that of the embodiment of FIG.

FIG. 3B shows still another embodiment, in which one semiconductor laser 2 is provided for the subject 8.
Pulse light from the optical fiber 36 to the subject 8 is received, the pulse light scattered and transmitted through the subject 8 is received at different positions, and each received pulse light is received by the optical fiber 40-.
1, 40-2 are guided to the optical multiplexer 44, and the pulsed lights guided from the two optical fibers by the optical multiplexer 44 are combined into one optical path and guided to the detector 10. Here, the subject 8
To optical multiplexers 40 to 40-2
Are different from each other, the length of the optical fiber 40-2 is longer than that of the optical fiber 40-1, and the lengthened portion 42 serves as a delay element. In this case, information at two positions of the subject 8 can be obtained at the same time.

Instead of the optical demultiplexer 34 and the optical multiplexer 44,
A branched optical fiber 48 as shown in FIG. 3C may be used. In this case, the two branched optical paths 50-1
And 50-2, one optical path 50-2 becomes longer,
The lengthened portion 52 serves as a delay element.

FIG. 4 shows still another embodiment, in which four phenomena are superposed on one TAC. 2 wavelengths 760nm and 800n as light source
m and semiconductor lasers 2-1 and 2-2, and the subject 8
For optical fiber 56-1,56-
The pulsed light is made incident by 2 and is received by the optical fiber 60 from one position of the subject 8 and guided to the photomultiplier tube of the detector 10. The pulsed lights from the two semiconductor lasers 2-1 and 2-2 are mixed by the optical fiber 54 to form one optical path, and then are branched into two optical paths by the optical fibers 56-1 and 56-2 to be different. The subject is irradiated at the position.
The distance between the light incident point by one optical fiber 56-1 and the light receiving point by the optical fiber 60 is 25 mm, and the distance between the light incident point by the other optical fiber 56-2 and the light receiving point by the optical fiber 60 is 40 mm.

In the coaxial cables 5-1 and 5-2 to which the oscillation signals are supplied to the semiconductor lasers 2-1 and 2-2, respectively, the coaxial cable 5-2 is longer, and the longer portion 30 is provided. Becomes a delay element
This causes a delay of about 4 nanoseconds in the oscillation signal on the second side. The optical pulses from the two semiconductor lasers 2-1 and 2-2 are mixed by the optical fiber 54 and then split again, and the optical fibers 56-1 and 56-2 for guiding the split optical pulses are the optical fibers 56-2. Is longer, and the lengthened portion 58 causes a delay of about 6 nanoseconds. As a result, the optical fibers 56-1 and 56-2 are both 76
Optical pulses having wavelengths of 0 nm and 800 nm are incident on the subject 8, but the pulsed light of 800 nm has a delay of about 4 nanoseconds at the time of oscillation, and the optical pulse incident on the subject 8 from the optical fiber 56-2 is It has a delay of about 6 nanoseconds with respect to the light pulse entering the subject 8 from the optical fiber 56-1.

The operation of this embodiment is shown collectively in FIG.
If there is no delay, as shown in the column of the original time-resolved waveform in the table (A), there is a change in the waveform according to the distance between transmitting and receiving, but no time difference appears. However, as a result of the provision of the delay, the 760 nm optical pulse a incident from the optical fiber 56-1 is detected without delay, and the next 800n incident from the optical fiber 56-1 is detected.
A light pulse b of m is detected with a delay of about 4 nanoseconds. Next, the optical pulse c of 760 nm incident from the optical fiber 56-2 is detected with a delay of about 6 nanoseconds, and the optical pulse d of 800 nm incident from the optical fiber 56-2 is detected with a delay of about 10 nanoseconds. . By overlapping the four signals a to d and inputting them into one TAC and integrating them, the waveform shown in (B) is obtained.

FIG. 6A shows still another embodiment. The pulsed light from the semiconductor laser 2 is split into two optical paths by the optical demultiplexer 62, and one optical path passes through the optical fiber 64-1 and the dimmer 65 for dimming to a single-photon state, and is optically combined. Incident on the optical instrument 70, the other optical path enters the subject 8 via the optical fiber 64-2, and the photons scattered and transmitted through the subject 8 enter the optical multiplexer 70 via the optical fiber 68. The optical fiber 64-2 is provided with a delay element 66 by lengthening the optical fiber. The two optical pulses merged into a single optical path by the optical multiplexer 70 are detected by the detector 1
It is detected at 0 and is guided to the TAC 14 via the CFD 12. The other structure is the same as that shown in FIG.

In this embodiment, as shown in (B), pulsed light that does not pass through the subject 8 is first detected as reference light, and then pulsed light that has passed through the subject 8 is set by the delay element 66. It is detected with a delay of time. The sum of the detection results by the TAC 14 is shown in (B), which is stored in the memory as data.

FIG. 7A shows still another embodiment, in which two semiconductor lasers 2-1 and 2 having different wavelengths are used.
-2 is 2 by each optical demultiplexer 62-1 and 62-2.
The optical pulse is divided into two optical paths, and the optical pulse of each one optical path is guided to the optical multiplexer 70 as the reference light via the dimmers 65-1, 65-2, respectively, and the optical pulse of each other optical path is observed light. Is irradiated to the subject 8. The optical fibers that guide the observation light to the subject 8 are provided with delay elements 66-1 and 66-2, which are long optical fibers. Further, the coaxial cable that guides the oscillation signal to the semiconductor laser 2-2 is made longer than the coaxial cable that guides the oscillation signal to the semiconductor laser 2-1, so that the delay element 30 having a delay time longer than that of the delay element 66-1 is provided. Has been.

In this embodiment, as shown in (B), first, the reference light by the optical pulse from the semiconductor laser 2-1 is detected, and then the observation light by the optical pulse from the semiconductor laser 2-1 is delayed. Detected with a delay due to element 66-1. After that, the reference light by the optical pulse from the semiconductor laser 2-2 having the delay by the delay element 30 is detected, and then the observation light by the optical pulse from the semiconductor laser 2-2 is detected by the delay by the delay element 66-2. To be done.

The present invention includes the following aspects in addition to the invention described in the claims. (1) Each channel has a different wavelength of pulsed light from the light source. This allows the time response waveforms of a plurality of wavelengths to be measured simultaneously or almost simultaneously with one TAC. (2) Each channel has a different distance between the incident position of the pulsed light on the subject and the light receiving position of the scattered transmitted light from the subject. This allows the time response waveforms at a plurality of measurement points to be measured simultaneously or almost simultaneously with one TAC. (3) Each channel is a combination of different wavelengths of the pulsed light from the light source and different distances between the incident position of the pulsed light on the subject and the receiving position of the scattered transmitted light from the subject. It is a thing. Thereby, for example, four phenomena in which two wavelengths and two measurement points are combined can be simultaneously or almost simultaneously measured by one TAC. (4) At least one channel is further provided in which the pulsed light from the light source does not pass through the subject and is directly received by the detector to serve as reference light. This makes it possible to observe changes in the measuring device, such as changes in the light source and changes in the sensitivity of the detector, without time lag from the measurement light and without wasting time. Then, by dividing the data of the detection signal by the measurement light transmitted through the subject by the data of the detection signal by the reference light, it is possible to eliminate the error due to the temporal fluctuation of the light source and the detector, which is stable. Measurement becomes possible.

[0028]

According to the present invention, at least one of the light incident side to the subject and the light emitting side from the subject has a plurality of channels, and the time until the photon detection of each channel by the photodetector overlaps each other. In addition, since a delay element is provided so that photon detection by the photodetectors of all channels is completed within one operation time region of the TAC, time response waveforms of multiple wavelengths and time at multiple measurement points are provided. It makes it possible to measure the response waveform with one TAC simultaneously or almost simultaneously. Since only one detector and one TAC are required, the device configuration becomes simple and can be realized at low cost. In addition, it is possible to collect data efficiently without increasing the power of irradiation light.

[Brief description of the drawings]

1A and 1B are block diagrams showing a configuration of a conventional measuring apparatus, respectively.

2A and 2B are block diagrams showing a configuration of an embodiment, respectively.

3A and 3B are block diagrams showing configurations of other embodiments, and FIG. 3C is a perspective view showing a branch optical fiber which replaces the optical demultiplexer and the optical combiner in those embodiments. It is a figure.

FIG. 4 is a schematic diagram showing a configuration of still another embodiment.

5 is a waveform chart showing the operation of the embodiment of FIG.

FIG. 6A is a block diagram showing the configuration of still another embodiment, and FIG. 6B is a waveform diagram showing the operation thereof.

FIG. 7A is a block diagram showing the configuration of still another embodiment, and FIG. 7B is a waveform diagram showing the operation thereof.

[Explanation of symbols]

2,2-1,2-2 Semiconductor laser 4 Oscillator 8 Subject 10 Detector 14 TAC 30, 32, 38, 42, 58, 66, 66-1, 66
-2 delay element

Claims (1)

[Claims] 1. A light source for making pulsed light incident on a subject, a photodetector for receiving transmitted scattered light at the subject, and from the time when pulsed light is generated at the light source to the photon detection by the photodetector. An apparatus for measuring a time change of a fast-changing light phenomenon, which is provided with at least one time-voltage converter that outputs time as a voltage, wherein at least one of a light incident side to a subject and a light emitting side from the subject is measured. In a plurality of channels, the time until the photon detection of each channel by the photodetector does not overlap with each other, and the photon detection by the photodetectors of all the channels is performed by one operation of the time-voltage converter. A time-resolved optical measuring device, characterized in that a delay element is provided so as to be completed within a time domain.