JPH063400B2 - Spectrophotometer - Google Patents

Description

The present invention relates to a spectrophotometer, and more particularly to a two-beam two-wavelength spectrophotometer.

(B) Prior art The main drawback of the two-wavelength side light method is that a so-called two-wavelength spectrum curve obtained by fixing one wavelength and scanning the other wavelength is due to a light source, a spectroscope, a detector, etc. Since the instrumental function appears as it is, the bending of the baseline becomes very large, and the light value on the two-wavelength side is obtained as the ratio of the two wavelength intensities, so the integrated value of the light source intensity over all wavelengths is constant. Also, when the two light wavelengths are extracted, when the light source shows a so-called color temperature change in which the intensity changes between the two wavelengths, the side light value considerably changes accordingly.

(C) Objective The present invention has been made in view of the above-mentioned drawbacks, and is a two-wavelength spectrophotometer capable of stably obtaining a two-wavelength spectrum with a flat baseline. The purpose is to provide means for dividing by.

(D) Structure The present invention divides a light flux of two different wavelengths into four light fluxes of a control light and a measurement light, respectively, guides each light flux to a sample on the control side and a sample to be measured, and a sample optical signal by light of one wavelength. A spectrophotometer that obtains a two-wavelength two-wavelength signal by taking the ratio of the ratio of the contrast light signal to the ratio of the sample light signal due to the light of the other wavelength to the ratio of the contrast light signal. Is composed of a sector mirror having a reflection effect on both front and back surfaces, and a pair of choppers arranged with the sector mirror sandwiched therebetween and rotating in synchronization with the sector mirror, and further between the sector mirror and the pair of choppers. This is a spectrophotometer in which a phase is shifted and a dark current correction period during which a light beam does not enter the control side and the sample side is provided during one rotation of a sector mirror and a pair of choppers.

(E) Example Hereinafter, the present invention will be described based on an example of the drawings.

FIG. 1 is a block diagram showing the configuration of a two-beam two-wavelength spectrophotometer, which is the premise of the present invention. White light emitted from a light source 1 is split into two lights of different wavelengths by spectroscopes 2 and 3. It is guided to the same position of the light beam splitting mechanism 4. The two light fluxes having different wavelengths are each split into two light fluxes by the splitting mechanism 4, and are absorbed by the control sample 5 and the measured sample 6 and guided to the detector 7. The signal discriminating circuit 8 includes the two light beam splitting mechanism 4
The signal from the detector 7 is discriminated into four signals, namely, the sample optical signal S1 of one wavelength light and the same reference optical signal R1, and the sample optical signal S2 of the other wavelength light and the same reference optical signal R2. Play a role. This signal discrimination circuit 8 divides the dark signal. The four signals thus discriminated are subjected to the calculation of (S1 / R1) / (S2 / R2) ... (1) by the processing device 9, and the result is displayed on the display device 10. In addition, although the case where a single detector is used is shown in FIG. 1, basically the same is true even if two different detectors are used on the sample side and the control side. Moreover, although two wavelengths of light from the same light source are taken out by different spectroscopes, the same is true even when two different light sources are used. Further, regarding a spectroscope, one spectroscope has two wavelengths of light. The same applies to a duochrometer that takes out. (S1 / R1) in equation (1)
And (S2 / R2) are used to correct the baseline flattening effect and light source luminance change in each wavelength light, and obtain the two-wavelength effect by taking the ratio of their divisors. In the case of absorbance display, Eq. (1) can be replaced by the following equation by the relational expression of A = -ogT ………………………… (2).

ogR1-ogS1 + ogS2-ogR2 (3) FIG. 2 is a more specific optical system diagram of FIG. First
The same parts as those in the figure are designated by the same reference numerals. The detector 7 is a photomultiplier tube, and the sum of the output signals S1 + R1 + S2 + R2 has a constant value for the purpose of setting a sufficient multiplication factor in the detector 7 within the range where the signal is not saturated. Adder 11
And a DC / DC converter 12 to form a dynode feedback circuit. The signal discrimination circuit 8 is S1, R1,
It is for separating the four signals of S2 and R2.
This is done by performing synchronous rectification on the signal from the synchronous signal by the synchronous signal output from the dividing mechanism 4. FIG. 3 shows an enlarged perspective view of the dividing mechanism 4. This dividing mechanism 4
A sector mirror 13 formed on both front and back sides as a surface having a reflection effect by silver plating, choppers 14 and 15 for blocking an optical path, a disc 16 for generating a synchronization signal,
Similarly, a photo coupler 17 for generating a synchronizing signal, a sector mirror 13, choppers 14 and 15, and a disc 16 and a photo coupler 17 including a motor 18 for rotating the disc 16 in synchronization with each other provide phase information of the sector mirror 13 and the choppers 14 and 15. It is for taking out, and it is necessary to have the number of pairs according to the number of phases per rotation,
Only one set is shown in FIG. The synchronizing signal output from the photocoupler 17 is sent to the signal discriminating circuit 8 in FIG. 2 and used for synchronous rectification. The optical path is the sector mirror 13 and the chopper 1 as shown by the arrow in FIG.
The light beams passing through the upper half of the mirrors 4 and 15 and incident from the directions a and b are c. It is divided in the d direction. FIG. 4 shows the state of the luminous flux at each phase when the sector mirror 13 and the choppers 14 and 15 make one rotation. (A) is the chopper on the spectrometer 2 side, (B) is the sector mirror, and (C). Shows the situation in which the choppers on the spectroscope 3 side are viewed from the front, and the state of the (D) F light flux is seen from directly above. In FIG. 3D, the solid line shows the state where the choppers 14 and 15 or the sector mirror 13 are inserted in the optical path, and the dotted line shows the state where they are not inserted in the optical path. Also, the black circles in the figures (A) to (C) are the portions where the optical path intersects the choppers 14, 15 or the sector mirror 13. As is apparent from FIG. 4, the incident light from the spectroscopes 2 and 3 is R1, S1, S2, and R2 at each phase of I to IV that occurs when the sector mirror 13 and the choppers 14 and 15 make one rotation. It is divided into light beams and guided to the sample 6 to be measured and the control sample 5, respectively. The light flux absorbed in each sample is guided to the same detector 7 and detected, and a signal including each signal component of S1, R1, S2, and R2 is generated in time division. The subsequent signal processing is as described above.

On the other hand, in general, a constant output signal is generated in the detector even when the signal is not incident on the detector. In the case of a photomultiplier tube, this output signal is called dark current. In order to correct this dark current, it is necessary to hold the output signal of the detector during the period when the light beam is not incident on the detector and subtract it from the output signal when the light beam is incident. It is necessary to provide a dark current correction period during which the luminous flux does not enter the detector.

As a method for providing a general dark current correction period when a sector mirror is used as the light beam splitting means, FIG.
As shown in (B), there is a method of providing "black blades 19" on both sides of the sector mirror to block light. However, according to this method, the dark current correction period can be set in the intermediate phase of each phase of the sector mirror and the chopper in FIG. 4, but the price is increased because the “black blade 19” needs to be attached, and Since the black blade 19 "and the mirror surface of the sector mirror are almost in the same plane, a very small amount of reflected light on the surface of the" black blade 19 "wraps around the measurement light beam, and a value higher than the original dark current value is set. There is a drawback that The present invention solves this drawback.

That is, the sector mirror 1 in FIG. 3 and FIG.
Phase between 3 and 2 choppers 14 and 15 is 22.5 °
A dark current correction period can be provided by tilting and setting the central angle θ of the sector mirror 13 to 45 °. This is shown in FIG. The phase indicated by “D” in FIG. 6 (D) is the dark current correction period, which corresponds to the IV phase and the VIII phase. Others are the same as in FIG. In general, the dark current does not change much compared to the original signal, so it is not a good idea in terms of signal utilization efficiency to have a large proportion of the dark current correction period in the signal. In the embodiment shown in FIG.
1/4 is allocated to the dark current correction period, and the efficiency is quite good. In addition, the planes of the chopper and the sector mirror are not on the same plane, and the reflected light does not wrap around during the dark current correction period, so a good effect can be expected. Needless to say, the price is low.

(F) Effect As described above, according to the present invention, a dual-wavelength spectrophotometer capable of stably obtaining a flat two-wavelength spectrum of a baseline, and effective dark current correction by an inexpensive configuration. It has the effect that it can be achieved.

[Brief description of drawings]

FIG. 1 is a block diagram showing the structure of a two-wavelength spectrophotometer which is the premise of the present invention, FIG. 2 is an optical system diagram showing a concrete example of FIG. 1, and FIG. 3 is a sector mirror and a chopper. Fig. 4 is a perspective view of the light beam splitting mechanism, and Fig. 4 is a diagram showing the relative relationship between the sector mirror and the chopper and the optical path. Fig. 5 is a diagram when the "black blade" is attached to the sector mirror. It is a figure which shows the relationship between the dark current correction | amendment period, and the relative relationship of a chopper and an optical path. In the figure, 1 ... Light source, 2, 3 ... Spectrometer, 4 ... Light beam splitting mechanism,
5 ... Control sample, 6 ... Measured sample, 7 ... Detector, 8 ... Signal discrimination circuit, 9 ... Signal processing device, 10 ... Display device, 11 ... Adder, 12 ... DC / DC converter, 13 ... Sector mirror ， 14,15 ，…
Chopper, 16 ... Disc, 17 ... Photo coupler, 18 ... Motor, 19 ... Black blade, S1, S2, R1, R2, D ... Signals.

Claims (1)

[Claims] 1. A means for extracting light of two different wavelengths, a means for intersecting the light of two different wavelengths with each other, and a light beam of two different wavelengths at the intersecting position for a reference light beam and a sample light beam, respectively. A light beam splitting means for splitting into a light source, and a means for guiding the control light beam and the sample light beam split by this splitting means to the control side sample and the sample to be measured, respectively.
Means for detecting the light flux absorbed by each sample, and means for discriminating and extracting a signal component corresponding to light of two different wavelengths from each of the detected signal corresponding to the reference light flux and the signal corresponding to the sample light flux And a ratio of the sample optical signal to the reference optical signal by the light of one wavelength and the ratio of the sample optical signal to the control optical signal by the light of the other wavelength from these signal components In the spectrophotometer for obtaining the above, the light beam splitting means is disposed on both front and back surfaces with a sector mirror having a reflection effect, and is sandwiched between the sector mirror and rotates in synchronization with the sector mirror.
It is composed of a pair of choppers, and the phase between the sector mirror and a pair of choppers is further shifted so that a dark current correction period in which the luminous flux does not enter either the control side or the sample side is set to a pair with the sector mirror. The spectrophotometer, which is provided during one rotation of the chopper.