JPH0215807B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a time-resolved spectrometer for observing time-resolved spectra of rapidly changing phenomena, and particularly to a time-resolved spectrometer that enables high-speed photometry using a two-dimensional image detector. Regarding.

Traditionally, mechanical high-speed scanning methods, such as scanning dispersive elements such as diffraction gratings at high speed, have been used as spectroscopic means to investigate instantaneous phenomena, but in recent years, high-speed detectors and electronics have been used. As advances have been made, electrical high-speed scanning methods have been used to further improve high-speed performance. Therefore, it is possible to capture moment-to-moment changes in the spectrum of rapidly changing light emission or light absorption phenomena, and it is also possible to obtain a series of time-resolved spectra even for phenomena that occur only once. High-speed scanning detectors used for this purpose include:
One-dimensional detectors such as photodiode arrays,
Two-dimensional image detectors such as a videocon, an image dasector, and a two-dimensional photodiode array are often used.

Such an image detector is placed at an imaging position of light dispersed by a diffraction grating, and the detector is oriented so that each photodiode is lined up on the dispersion plane of the diffraction grating. Therefore, light of different wavelengths is incident on each photodiode element that makes up the image detector.
Detected. To extract a signal from the image detector, a scanner applies a clock pulse to the image detector, and charges accumulated in each element proportional to the amount of incident light are sequentially extracted to the outside by a method such as charge transfer or switching.

With such a high-speed scanning spectrometer, one spectrum can only be obtained within several tens of milliseconds at most, making it virtually impossible to observe even faster phenomena. For example, if we take a photodiode array as an image detector, the operating frequency is practically several tens to hundreds of kHz.
The maximum speed of the element itself is 1MHz. Even if it operates at 500kHz, considering a photodiode array with 512 channels of elements, it will take 1.024msec to extract the charge proportional to the amount of light accumulated on the detector from all elements. Therefore, after obtaining one spectrum, it takes at least 1.024 msec to obtain the next spectrum, and the time resolution is approximately 1 m.
sec is the limit. In order to obtain spectra faster than this, we have to look forward to the emergence of detectors that can scan at higher speeds, but when the scanning speed reaches 1MHz or higher, a sample hold that holds the signal from the image detector is required. The circuit and A-D converter that converts analog signals to digital signals also need to operate in a time shorter than 1 μsec.

As a method for solving the above problems, the inventor of the present application has recently attempted the following method. In other words, two-dimensional photodiode arrays and silicon (Si) videcon are used as image detectors.
Using a dimensional image detector, a high-speed time-resolved image is created on the detector by scanning the dispersed light at high speed in the height direction of the entrance slit against the dispersion surface on the detector. The extraction of screen information is carried out for a relatively long period of time after the high-speed phenomenon ends.

According to this method, the time resolution does not directly depend on the high-speed scanning performance of the detector or the performance of extraction circuits such as sample hold and A-D conversion, but is determined by the optical scanning speed of the dispersed light incident on the detector. For,
It is possible to obtain a time-resolved spectrometer capable of faster scanning.

However, the problem with this method is that
It is extremely difficult to measure high-speed phenomena to be observed while aligning the phase with the phenomenon start time. That is, if we consider the time required to extract screen information by electrical scanning after one screen of optical scanning, image observation by optical scanning on a two-dimensional image detector is limited to the time period of one screen of scanning. Therefore, it is difficult to match the phase of the start of this one-screen scan and the high-speed phenomenon start time. Furthermore, it is more difficult to perform this phase matching with an accuracy of 1 μsec.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide a time-resolved spectrometer that can perform measurements by matching the photometric timing of high-speed phenomena to be observed.

Hereinafter, the present invention will be described in further detail according to embodiments shown in the drawings.

FIG. 1 is a block diagram showing an embodiment of a time-resolved spectrometer according to the present invention, in which a photodiode array is used as a high-speed scanning spectrometer.

In this example, the light from the light source 1 is transmitted to the sample 11.
After passing through the light beam, it passes through the light passage slot 42 of the light scanning disk 43 and reaches the entrance slit 21 of the spectrometer 2. Analysis sample 11 illustrates an example of absorption measurement, but when observing a luminescence phenomenon, sample 11
The light source itself is a light emitter, and the light source 1 is not necessary. In the case of reflection measurement, the principle is exactly the same as in the embodiment shown in FIG. 1, except that the optical system is configured so that the reflected light reaches the entrance slit 21 instead of the transmitted light from the sample 11. .

The optical scanning disk 43 is a disk that is rotated at high speed by a motor 41, as shown in FIG. 2 when viewed from the light source 1 side, and the center of rotation of this disk is approximately on the dispersion plane. Entrance slit 2 of spectrometer 2
1 and is located at a distance r. The optical passage slot 42 of the optical scanning disc 43 is also located on the circumference at a distance r from the rotation center of the optical scanning disc 43. Furthermore, the light passage slot 42
A plurality of are provided at equal angles. Then, the distance H between the light passing slots on the radius r is:
It is made equal to the height of the entrance slit 21 of the spectrometer. If such an optical scanning disk 43 is used,
One of the light passage slots is always passing in front of the entrance slit of the spectrometer, and the light from the light source always enters the spectrometer, and the light from the light source always enters the spectrometer at any position in the height direction of the two-dimensional image detector 3. The spectrum is always observable. Therefore, no matter what time a high-speed phenomenon to be observed starts, the time-resolved spectrum can be observed without missing the phenomenon. Even if the distance H on the radius r of the light passing slot 42 is slightly smaller than the height of the entrance slit of the spectrometer, the purpose of the invention will not be impaired, since the light will always be guided into the spectrometer.

In addition to the above-mentioned entrance slit 21, the spectrometer 2 has a flat reflecting mirror 22 that reflects the light incident through the entrance slit 21, a concave reflecting mirror 23 that reflects the reflected light from the flat reflecting mirror 22, and a concave reflecting mirror 23 that reflects the reflected light from the flat reflecting mirror 22. A diffraction grating 24 that is a dispersion element that disperses the reflected light from the concave reflecting mirror 23, a concave reflecting mirror 25 that reflects the dispersed light from this diffraction grating 24, and this concave reflecting mirror 2.
A plane reflecting mirror 26 that reflects the reflected and dispersed light from 5.
It is made up of.

An image detector 3 is placed at a position where the light dispersed by the diffraction grating 24 is focused. The image detector 3 is a two-dimensional image detector composed of a two-dimensional photodiode array, and can also be composed of, for example, a silicon videcon. This image detector 3 is installed so that each photodiode is lined up on the dispersion plane (in a direction parallel to the plane of the paper) formed by the diffraction grating 24, so each photodiode element constituting the image detector 3 has a different wavelength. λ ₁ …λ _o
of light is incident and detected.

Circuits for extracting signals from the image detector 3 to the outside include an amplifier 4, a scanner 5, a sampling hold circuit 6, an A-D converter 7, a memory circuit 8, a digital computer 9, and a data monitor 10. is used.

The scanner 5 applies a clock pulse to the image detector 3, and sequentially extracts charges proportional to the amount of incident light accumulated in each element to the outside by a method such as charge transfer or switching. In this way, the electric signal taken out to the outside is held by the sampling and holding circuit 6 synchronized with the scanner 5 through the amplifier 4, and is then held by the A-D converter 7.
is converted into a digital signal. The light amount signal converted into a digital signal is stored in the storage circuit 8 directly or via a digital computer 9 or the like. Since the obtained spectrum is stored in the memory circuit 8, after the phenomenon is completed, it is subjected to absorbance conversion and various data processing by calculations on a digital computer, and then displayed on the data monitor 10 or displayed on a recorder (not shown). It is possible to make a hard copy.

Next, the operation of this embodiment will be further explained.

After passing through the analysis sample 11, the white light from the light source 1 reaches the entrance slit 21 of the spectrometer 2 via the optical scanning disk 43. The white light exiting the entrance slit 21 is dispersed by a diffraction grating 24 in the spectrometer 2 depending on the wavelength, and light having wavelengths λ ₁ to _{λ o} is lined up on the detector screen of the image detector 3 . The wavelength dispersion plane is a plane parallel to the plane of the paper, and light of the same wavelength is incident on the detector screen in a direction perpendicular to the plane of the paper (corresponding to the height direction of the entrance slit). In this embodiment, an optical scanning disk 43 having a light passing slot 42 is disposed immediately before (or immediately after) the entrance slit 21, so that the light that has passed through the sample 11 passes through this light passing slot 42. The light enters the entrance slit 21 of the spectrometer 2. Therefore, the light that reaches the entrance slit 21 due to the high-speed rotation of the optical scanning disk 43 flows from the top to the bottom above the entrance slit 21 from the time when the light passage slot 42 reaches the uppermost end of the entrance slit 21 in the height direction. Move at high speed. Therefore, as the incident light moves, the image detector 3
As shown in Fig. 3, the upper spectrum is, from the top to the bottom of the detector screen, spectrum S ₁ at time t ₀ , spectrum S ₂ at time t ₁ , ... spectrum S at time t _o . _o are formed sequentially. That is, the x direction of the detector 3 is the wavelength axis, and the y direction is the time axis. The image detector 3 uses the S ₁ to _{S o} formed in this way.
Since the spectra of S 1 to S o are held as charges, information on the time-resolved spectra S ₁ to _{S o} can be extracted from the image detector 3 over a period of time longer than the photometry time t _o -t ₀ . FIG. 4 illustrates the relationship between the time-resolved spectra measured in this manner with respect to the time axis t, the wavelength axis λ, and the spectral intensity axis I. Number of measurable spectra n
is determined by the number of pixels in the y direction of the two-dimensional image detector 3, and is usually 512ch (x) × which is commercially available.
A 512ch (y) image detector can measure 512 spectra at once. The time resolution depends on the rotational speed of the optical scanning disk 40 and the distance r. The height of the entrance slit 21 is the same as the height of the image detector 3 (the y-direction dimension of the screen), which is 10 mm,
If the number of pixels in the y direction is 512 channels, r = 100 mm, and the rotation speed is 60,000 rpm, the incident light to the entrance slit 21 will move approximately from top to bottom on the entrance slit 21.
It moves during 17μsec, and the time resolution t _i −t _i-1 is approximately
Obtain 0.3μsec. That is, spectra can be observed sequentially every approximately 0.3 μsec. This value is approximately 3,000 times faster than that of a high-speed scanning spectrometer according to the prior art, and by increasing r and further increasing the rotation speed of the optical scanning disk 43,
It is possible to understand faster phenomena.

By using the optical scanning disk as described above, the light from the light source always illuminates any position in the height direction of the two-dimensional image detector. Therefore, no matter when a high-speed phenomenon starts, measurements can always be made with the phase of the phenomenon aligned.

In the embodiment of the present invention described above, in cases where light is always incident on the spectrometer such as in absorption measurement, the two-dimensional image detector 31 does not display the object to be observed even after the phenomenon to be observed has finished. In some cases, the spectrum that is not specified continues to be incident, resulting in multiple exposures. In such cases, after the symptoms start,
Multiple exposure can be prevented by operating the detector for a time corresponding to one optical scanning disk crossing the slit height direction and leaving the detector in a blind state for the rest of the time. FIG. 5 shows an example of flash photolysis in which the phenomenon to be observed is initiated by irradiation of the sample with excitation light. The two-dimensional image detector uses an image tube 31, such as a SIT (silicon intensified target) detector, whose photosensitive state can be controlled by a high-voltage gate pulse. Excitation light from an excitation light source (such as a pulsed laser) 51 is applied to the sample 1.
Upon irradiation with 1, photochemical phenomena within the sample begin. At the same time, the excitation light is split by a beam splitter 52 and detected by a monitor detector 53. The output of the monitor detector triggers a high voltage controller 55 after passing through an amplifier 54. After being triggered, the high voltage controller 55 applies a high voltage pulse to the image tube 31 for a time corresponding to the time when the slot of one optical scanning disk mentioned above crosses the slit, thereby bringing the image tube 31 into a photosensitive state. In this way, multiple exposures can be prevented.

Another embodiment of the present invention will be described using FIG. 6. In the figure, the same symbols as in FIG. 5 represent the same parts. In this embodiment, instead of controlling the photosensitive state of the image tube in FIG.
optically controls the incidence of light on the That is,
On the side of the light source from the entrance slit 21 of the spectrometer 2, an electrically controlled high-speed optical shutter 57 such as a Pockels cell is arranged. The optical shutter 57 may be placed between the optical scanning disk 43 and the entrance slit 21, for example, as long as it is closer to the light source than the spectroscope. This optical shutter 57 is controlled by a controller 56.
Transmission and blocking of light is controlled by control signals from. In response to the trigger signal from the monitor detector 53, the controller 56 applies a signal to the optical shutter 57 to transmit light only for a period of time corresponding to the time when the slot of the optical scanning disk crosses the slit.

In this example, as a two-dimensional image detector,
Multiple exposure can also be prevented for detectors other than those that can control the exposure state, such as SIT detectors.

With the above method, no matter when the phenomenon to be observed starts, it is possible to detect the phenomenon without missing it. cannot be determined. For this reason, even if the signal from the image detector is extracted after photometry and a series of spectra S as shown in Fig. 4 are obtained, it is not possible to identify which spectrum among S ₁ to _{S o} is the first spectrum at the onset of the phenomenon. is possible depending on the nature of the observed object. In order to prevent this, it is possible to take the above-mentioned multiple exposure prevention measures and to make the distance H between the light passage slots 42 on the radius r slightly larger than the height of the entrance slit. If this is done, there will be a short period in which no light enters the spectroscope, and one of the spectra from S ₁ to _{S o} will have a light intensity of 0. Therefore, it can be easily identified that the spectrum S _i+1 following the spectrum S _i with the light intensity of 0 is the spectrum immediately after the phenomenon starts, and that S _i-1 is the spectrum observed last. The same effect can also be obtained by making the exposure time of the image detector or the opening time of the high-speed optical shutter slightly shorter than the time it takes for one light passage slot to cross the slit. Particularly in the case of flash photolysis as shown in Figure 5, if the light from the excitation light source is detected by the detector, accurate absorption measurements (or the same applies to luminescence measurements such as fluorescence) cannot be performed, so as mentioned above, Methods such as opening a high-speed optical shutter to guide the measurement light into the spectrometer after irradiation with excitation light, or making the detector sensitive to light after irradiation with excitation light can improve measurement accuracy. can. If the timing of excitation light irradiation can be accurately controlled, use an optical scanning disk in which the interval between the light passage slots is slightly larger than the height of the entrance slit as described above, and use a photo interrupter or the like to control the optical scanning disk. By detecting the phase and controlling the emission timing of the excitation light source so that excitation light is irradiated in the phase where the incident light is blocked by the optical scanning disk, undesirable excitation light is prevented from entering the spectrometer. , photometry accuracy can be improved.

FIG. 7 is an optical system diagram showing another embodiment of the time-resolved spectrometer according to the present invention. In this example,
A fixed mirror 61 and a rotating mirror 60 are provided in place of the optical scanning disk 43 provided immediately in front of the entrance slit 21. The light from the light source 1 is focused by the fixed mirror 61, and the curvature of the fixed mirror 61 is selected so that the light is focused on at least one point in the height direction of the entrance slit 21. On the other hand, the rotating mirror 60 is rotated at high speed by a motor 41, and its rotation axis is perpendicular to the height direction of the entrance slit 21. It forms an optical deflector that scans downward. FIG. 8 shows the optical deflector in the seventh
This is a view seen from the direction of arrow A in the figure, and a plurality of plane mirrors are arranged around a cylinder. With the above-described configuration, a time-resolved image can be created on the two-dimensional image detector 3 by moving the light beam incident on the spectrometer 2 from the top to the bottom of the entrance slit 21 at high speed. In this embodiment, in FIG. 8, the rotational angular velocity of the rotating mirror 60 is
It is well known that the angle formed by the reflected light, that is, the polarization angle θ, changes at twice the speed, and it is possible to obtain a time-resolved spectrum even faster than in the above embodiment. As shown in FIG. 8, if the aperture angle for one mirror is δ, the deflection angle of the light is 2δ. Therefore, by making the scanning width in the height direction of the image detector 3 due to the deflection angle 2δ of one mirror slightly smaller than the height of the image detector 3, and providing a non-reflective portion 62 when switching each mirror, , the starting point of spectrum measurement can be easily determined.

According to the present invention, time-resolved measurements can be performed in accordance with the photometric timing of a high-speed phenomenon to be observed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a time-resolved spectrometer according to the present invention, FIG. 2 is a side view of an optical scanning disk that is one of its components, and FIG. FIG. 4 is a spectral diagram showing the relative relationship of time-resolved spectra obtained by the present invention. FIG. 5 is an optical diagram showing another embodiment of the present invention. System diagram, FIG. 6 is an optical system diagram showing another embodiment of the present invention, FIG. 7 is an optical system diagram showing still another embodiment of the present invention, and FIG. 8 is a diagram of a rotating mirror which is a component thereof. FIG.

Claims (1)

[Claims] 1. An entrance slit, a dispersion element that disperses light incident from the entrance slit according to wavelength, and a two-dimensional image detector disposed on an imaging plane of the light dispersed by the dispersion element. The light entering the entrance slit is always made to enter at least one position in the height direction of the entrance slit, and
A time-resolved spectrometer comprising an incident light scanning means whose incident position periodically moves along the height direction of the incident slit. 2. In the time-resolved spectrometer according to claim 1, the incident light scanning means is arranged near the incident slit, and a plurality of openings are provided at equal intervals on the circumference thereof. A time-resolved spectrometer, characterized in that it is a rotating disk, and the interval between the openings at the position of the entrance slit is equal to the height of the entrance slit. 3. An entrance slit, a dispersion element that disperses the light incident from the entrance slit according to its wavelength, a two-dimensional image detector placed on the imaging plane of the light dispersed by the dispersion element, and a two-dimensional image detector that disperses the light that enters the entrance slit. The light is always incident on at least one position in the height direction of the entrance slit, and
An incident light scanning means whose incident position periodically moves along the height direction of the entrance slit is used, and the light is transmitted to the two-dimensional image detector only for a period of time shorter than one cycle of the periodic movement by this incident light scanning means. A time-resolved spectrometer characterized by comprising: a control means for acquiring a signal. 4. In the time-resolved spectrometer according to claim 3, the two-dimensional image detector is a detector whose photosensitive state can be controlled, and the control means:
A time-resolved spectrometer, characterized in that it outputs a control signal that enables the two-dimensional image detector to be exposed to light at a predetermined time. 5. In the time-resolved spectrometer according to claim 3, the control means is a light shutter placed near the entrance slit, and controls the incidence of light into the spectrometer for a predetermined period of time. Characteristic time-resolved spectrometer.