JPS62147344A - Multiwavelength spectrophotometer - Google Patents

Abstract

PURPOSE:To make it possible to remove a measuring error due to stray light trouble in an ultraviolet region by performing measurement from the ultraviolet region to a visible region at a high speed, by mounting a first beam source and a second beam source and alternately outputting beams from both beam sources to the same beam path by a photosynthesizer. CONSTITUTION:Ultraviolet rays from a D2 lamp 1 being a first beam source are made intermittent by a first beam chopper 2 and transmitted through a beam splitter 3 to be condensed by a condensing lens 4 and incident to a specimen cell 5. The beam from a Xe lamp 6 being a second beam source passes through a heat ray cutting filter 7 to be converted to beam containing only a visible part and is made intermittent by a second beam chopper 8 and, thereafter, reflected by the splitter 3 and condensed by the lens 4 to be incident to the cell 5. These beams pass through the cell 5 and are subsequently condensed by a condensing lens 9 and passed through a multiwavelength spectrometer slit 10 to be dispersed by a concave diffraction lattice 11. A photodiode array 12 is arranged to the image forming surface of said dispersed beams and beam with each wavelength is received by the beam receiving element provided so as to be opposed to said array 12. By this method, a measuring error can be removed.

Description

[Detailed Description of the Invention] Technical Field of the Invention) The present invention relates to a multi-wavelength spectrophotometer that measures the spectral transmittance, absorption spectrum, absorption intensity, etc. of a sample, and in particular uses a diffraction grating as a light dispersion means. , relates to a multi-wavelength spectrophotometer that can measure data at multiple wavelengths at high speed and with high precision.

[Technical background of the invention and its problems]

In general, the wavelength band in the ultraviolet and visible regions that spectrophotometers measure is from 2o○ to 800nm, but most wavelength scanning types use a D2 lamp (deuterium discharge tube) as a light source in the ultraviolet region from 200 to 400nm. ), and 350 to 800n
W lamps (tungsten light bulbs) are used in the visible range of m, and these are used by switching. In the scanning type, a slit is provided just in front of a single photodetector, and the light dispersed from the light source via the diffraction grating is guided to the photodetector via the slit, and the measurement wavelength is adjusted by rotating the diffraction grating. I'm trying to do a scan. Then, these light sources are switched at the boundary between the ultraviolet region and the visible region, and each data is combined. However, since this method uses a single light-receiving element, it takes several minutes to measure the entire wavelength range, making high-speed measurement difficult.

On the other hand, various types of spectrophotometers that use solid-state imaging devices such as photodiode arrays and CODs for simultaneous photometry of multiple wavelengths have been proposed on the spectral imaging plane of the spectrograph. These features are different from the scanning type, which changes the measurement wavelength on the order of minutes, in that high-speed scanning on the order of milliseconds or simultaneous measurement is possible. This method requires a light source that can cover the entire wavelength range. For this purpose, methods such as using Xe (xenon discharge tube) as a light source, or using a mixed beam of a D2 lamp and a W lamp as a light source, as seen in JP-A-59-135332, have been adopted. There is.

However, solid-state light-receiving elements such as photodiode arrays and CODs have a dark 1! The influence of flow cannot be ignored. Furthermore, since these have a sensitivity in the red region that is 100 times or more higher than in the ultraviolet region, when a diffraction grating is used as a dispersion element, measurement problems due to stray light from the diffraction grating occur in the ultraviolet region. In other words, if an amplifier circuit is used to obtain a constant signal strength over the entire ultraviolet and visible range, the signal gain of the photodetector corresponding to the ultraviolet region will increase, so even if a small amount of red stray light enters, A large stray light signal is observed. When there is no absorption in the sample, in a spectrophotometer experiment using a Xe lamp, Table 1 Therefore, to overcome this stray light obstacle, a prism spectrometer is used instead of a diffraction grating spectrometer. Compared to a spectrophotometer, it has the disadvantage that wavelength calibration is8 more difficult.

In addition, methods are being considered to suppress stray light signals by using filters to cut out the harmful infrared and near-infrared light, but it is currently difficult to manufacture filters that can effectively transmit ultraviolet light of 250 nm or less. It is.

Furthermore, when measuring the entire range of 200 nm to 800 nm using a diffraction grating, for example, 400 to 800 nm is possible. J
! In a certain range, second-order diffracted light of ultraviolet light of 200 to 400 nm enters and lowers the measured IIj[. Therefore, it is necessary to insert a cut filter or the like to remove this second-order diffracted light. For this, the total length number c1
A fine filter had to be inserted only into the visible light incident part of the approximately 11 solid-state light-receiving element array, and a fine and complicated optical system or processing of the light-receiving elements was required.

[Purpose of the invention]

The present invention has been made to solve these various problems, and its purpose is to.

[Summary of the invention]

, the present invention measures the intensity of light transmitted through the sample at each wavelength by uniformly dispersing the light that has passed through the sample using a diffraction grating, and receiving this dispersed light with a plurality of light-receiving elements arranged on the spectral imaging plane. This multi-wavelength spectrophotometer is characterized by having the following means.

That is, it includes a first light source that emits light with a short wavelength and a second light source that emits long wavelength light, and the light from these two light sources is alternately output to the same optical path by a light combiner. At this time, the combined light from the light combiner becomes time-division combined light in which the light from the two light sources is alternately arranged via the optical WA. This combined light is applied to the sample, and the transmitted light is dispersed by a diffraction grating and received by a plurality of light receiving elements. The output signal of the light receiving element during the period when light from the first and second light sources was received is corrected by the output signal of the light receiving element during the light blocking period to obtain the sample transmitted light intensity. It is characterized by

〔Effect of the invention〕

According to the present invention, since measurement can be performed by dividing the ultraviolet region and the visible region, it is possible to overcome the obstacle of stray light in the ultraviolet region, and
During the pA filling measurement, ultraviolet light that causes secondary light does not enter. Moreover, in this invention, since photometry is performed simultaneously in the ultraviolet region and the visible region, high-speed measurement is possible.

0. 'Furthermore, according to the present invention, there is a light blocking period in the combined light, and the signal obtained during this period is used to correct the signal at the time of light reception. Offset errors etc. can be removed and highly accurate measurements can be performed.

Generally speaking, in this invention, since a diffraction grating is used as a dispersion element, the actual length of the dispersed light on the imaging plane and the wavelength have a linear relationship, which facilitates wavelength calibration, which also improves measurement accuracy. I can do it.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail based on examples.

The multi-wavelength spectrophotometer of the present invention can be applied, for example, as a detector for liquid chromatography. Examples of light sources used include D2 lamps, W lamps, and Xe lamps. Figure 6 shows the radiation intensity spectrum of each of these lamps.The light from the X and E lamps can be filtered out by using heat ray cut filters, etc. to remove ultraviolet light of around 300 nm or less and near-infrared light of around 800 nm or more. It can be removed to provide a light source with a band of 300x800 nm.

Here, an example will be described in which a D2 lamp is used as the first light source for short wavelengths and a Xe lamp is used as the second light source for long wavelengths.

FIG. 1 is a diagram showing the configuration of a multiwavelength spectrophotometer according to this embodiment. That is, D, which is the first light source for short wavelengths,
The ultraviolet light from the second lamp 1 is interrupted by a first optical chopper 2, transmitted through a beam splitter 3 made of a synthetic quartz plate, and then condensed by a condensing lens 4 and incident on a sample cell 5. On the other hand, the light including the ultraviolet, visible and near-infrared regions from the Xe lamp 6, which is the second light source for long wavelengths, becomes light including only the visible region by passing through the heat ray cut filter 7, and becomes the second light. After being interrupted by the chopper 8, it is reflected by the beam splitter 3, condensed by the condensing lens 4, and incident on the sample cell 5. After passing through the sample cell 5, these lights are condensed by a condenser lens 9,
It passes through a multi-wavelength spectrometer slit 10. The light passing through the slit 10 is dispersed by the concave diffraction grating 11.

The phytodiode array 12 is disposed on the imaging plane of this dispersed light, and receives light of each wavelength by a corresponding light receiving element.

The same optical choppers 2 and 8 are used, and their rotating disks 13 rotate in synchronization with each other. This rotating disk 1
3, windows 14 for light transmission are formed at a constant pitch in the circumferential direction. As shown in FIG. 2, this window 14 is set so that the ratio with the light shielding portion is 1:3. When the rotating disk 13 of the first chopper 2 and the rotating disk 13 of the second chopper 8 are rotated with a 1/2 pitch shift, as shown in FIG. 3, ultraviolet light→total light cutoff→ Synthetic light whose properties change periodically such as visible light → total light cut → ultraviolet light → etc. is obtained. In other words, the optical choppers 2 and 8 and the beam splitter 3 constitute a light combining means. This combined light is absorbed in accordance with its absorption characteristics while passing through the sample cell 5, and enters the concave diffraction grating 11 via the condenser lens 9 and the slit 10.

The light dispersed by the concave diffraction grating 11 is received by the photodiode array 12 on its imaging plane. Hereinafter, signal processing after the photodiode array 12 will be explained based on FIG.

The output signal from each photodiode 21 constituting the photodiode array 12 is current-voltage converted and amplified by an amplifier 22 provided one-to-one for each photodiode 21, and an amplifier 22 provided one-to-one for each m-width amplifier 22. The sample bold circuit 23 samples and holds the signal. The signals from these sample and hold circuits 23 are converted from parallel to serial by a multiplexer 24,
After being AD converted by the AD converter 25, CP[J26
is imported into the memory of the computer as data. The CPU 26 provides the pulse motor controller 27 with setting data regarding the rotation speed of the optical chopper 2.8 and the like. Further, the pulse motor controller 27 controls the rotation of the optical chopper 2.8 and outputs a signal informing the CPU 26 of the light transmission period and the shutoff period. Sampling in the sample/hold circuit 23 is performed at the following timing.

First, the CPU 26 receives an ultraviolet light ON signal from the ultraviolet light chopper 2 from the pulse motor controller 27, and samples only the signal from the photodiode 21 disposed on the ultraviolet light imaging plane. Therefore, a sample and hold signal is output to the corresponding sample and hold circuit 23. Then, the CPU 26 sequentially reads the data after a certain period of time has elapsed.

Second, the CPU 26 controls the pulse motor controller °=
.

A similar measurement is performed by receiving an ultraviolet light Off signal from photo 4. . . . The output of the diode 21 is taken into the memory as data for dark heel flow correction.

Thirdly, the CPU 26 receives the visible light 0Nfi signal from the visible light chopper 8 from the pulse controller 27 and samples and holds the output of the photodiode 21 arranged on the visible light imaging plane. A sample and hold signal is output to a sample and hold circuit 23 provided correspondingly. As a result, similar signal processing is performed on the phytodiode 21 corresponding to visible light, and visible light data is taken into memory.

Fourth, the CPU 26 controls the pulse motor controller 27
When a visible light OFF signal is received from
The output is taken into memory as "dark current correction" data.

By performing the first to fourth operations as described above, measurements in the non-ultraviolet region and measurements in the visible region can be alternately performed at high speed for each optical data. According to experiments conducted by the inventor, as shown in Table 2, when using the D2 lamp alone, stray light in the ultraviolet region below 400 nm is less than 1%, and the influence of stray light is significantly greater than in the case of Table 1. In addition, in the visible range of 400 nm or longer, as shown in Tables 3 and 4, stray light can be suppressed to 5% or less regardless of whether a W lamp or a Xe lamp is used. can.

An ultraviolet-only square type that measures 200 to 40 Qnm using a conventional method was common. For this reason, to measure the visible part at the same time, a combined D2 and W lamp is used, but this method has a practical b-wave range of 250 to 250 nm due to stray light.
800nm, and the frequently used 200-250nm
It was not possible to measure nm. However, according to this embodiment, the measurement range can be expanded to the short wavelength side, increasing the detectable chemical species in the multi-wavelength detector, increasing the detection sensitivity,
An improvement in accuracy can be expected. Furthermore, compared to measurement at a single wavelength, it is also possible to improve the resolution of a chromatograph by using a spectral arithmetic processing method to measure changes in the absorption spectrum.

In addition, from the point of view of manufacturing the device, the D2 lamp, which is normally used as an ultraviolet light source, has a sharp i-line at 656 nm, so when a combined D2 and W lamp is used, each wavelength In order to equalize the signal level of 656nm
It is characterized in that it requires a filter having fine spectral characteristics as seen in Japanese Patent Application Laid-Open No. 135332/1983 to remove IS.

It should be noted that the present invention is not limited to the embodiments described above.

For example, as a photosynthesis means, first and second
If the light from the light source can be supplied in a time-division manner, a configuration as shown in FIG. 5 may be considered. This device intermittents the output light of the D2 lamp 1 and the Xe lamp 6 by one optical chopper 31, and the light from the D2 lamp 1 is transmitted to the reflecting mirror 3.
After being reflected by the beam splitter 2, the light is transmitted through the beam splitter 33 and guided to the sample, and the light from the Xe lamp 6 is reflected by the beam splitter 33 and guided to the sample.

According to this 61, since there is only one optical chopper 31, the rotation control of the motor is also simplified.

In addition, the present invention is also applicable to those using other light sources such as a W lamp as a light source for ultraviolet light and a light source for visible light. Furthermore, an acousto-optic modulator or a rotating mirror may be used as the photosynthetic year Q.

If a high reflectance throat splitter is available,
A W lamp may be used instead of the lamp. Furthermore, in order to further improve measurement accuracy, special filters and spectroscopic optical means are used to remove visible and near-infrared light from ultraviolet light sources, remove ultraviolet and near-infrared light from visible light sources, and remove visible light from visible light sources. Ultraviolet light and near-infrared light may be removed from the light source.

In addition, the time series of the incidence of ultraviolet light, the incidence of visible light, and the total light cut-off are performed at equal intervals in the above example, but it is also possible to perform them at irregular intervals. Various methods can be considered, such as measuring the visible part at the same time and utilizing only the ultraviolet data, as well as methods of synchronizing the measurement system and data processing.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a multi-wavelength spectrophotometer according to an embodiment of the present invention, FIG. 2 is a plan view showing a part of the optical chopper in the photometer, and FIG. Figure 4 is a block diagram showing the signal processing system of the photometer, Figure 5 is a waveform diagram of the combined light produced by Mizumoto, Z, 5, sample cell, 6, and so on.
Xe lamp, 7... Heat-ray force retrofilter, 10...
Slit, 11... concave diffraction grating, 12... photo 1
-Diode array, 32...Reflector. Applicant: Director of the Agency of Industrial Science and Technology

Claims (4)

[Claims] (1) Multiple wavelengths that measure the intensity of light transmitted through the sample at each wavelength by dispersing the light that has passed through the sample with a diffraction grating and receiving this dispersed light with multiple light-receiving elements placed on the spectral imaging plane. In a spectrophotometer, a first light source that emits short wavelength light, a second light source that emits long wavelength light, and a first light source that emits short wavelength light;
and a photosynthesis means for alternately outputting the light from the second light source onto the optical path on which the sample and the diffraction grating are arranged through a blocking period, and receiving the light from the first and second light sources. A multi-wavelength spectrophotometer comprising: means for correcting the output signal of the light receiving element during the period with the output signal of the light receiving element during the light-blocking period to obtain the intensity of the sample transmitted light. (2) A patent claim characterized in that the light combining means comprises two light choppers that cut off the light from the first and second light sources, respectively, and a beam splitter that combines the light from these light choppers. The multi-wavelength spectrophotometer according to item 1. (3) The multi-wavelength spectrophotometer according to claim 1, wherein the light synthesis means is an acousto-optic modulator. (4) The multi-wavelength spectrophotometer according to claim 1, wherein the light source switching means is a rotating mirror.