JPS58178227A - Multiple wavelength spectroscope device - Google Patents

Abstract

PURPOSE:To enhance light measuring accuracy by a simple improvement, by providing a light shielding plate, which shields the straight input of dispersed light, for at least one light receiving element in an image forming region of the dispersed light, detecting the amount of stray light, and correcting the amount of the stray light with respect to the measured values of the light from other light emitting elements. CONSTITUTION:The light, which is inputted to an incident slit 1 from a light source, is dispersed on a photodiode array 4 and an image is formed. The photodiode array 4 is arranged on a Rowland circle, and the light is dispersed sequentially from a short wavelength side between l0 and ln. When diffracted light in the range of l1-ln is inputted to the photodiode array 4, the light is reflected and scattered on the surface of each of photodiodes 61-6n. The light is further reflected by a light receiving window 7 and inputted again. At this time, the scattered and astrayed light is distributed to the photodiode 60 on the short wavelength side, and the largest effect is received. Since the direct propgressing light is not inputted to the photodiode 60, only the astray light is detected. The same amount of the astray light is inputted to the neighboring photodiode 6a. When the detected astray signal of the photodiode 60 is subtracted from the detected signal of the photodiode 6a, the effect of the astray light of the photodiode 6a is mostly eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multi-wavelength spectrophotometric device, and more particularly to a multi-wavelength spectrophotometric device using a play-deaf photodetector as a light receiving element.

Multi-wavelength spectrophotometry is excellent for measuring the spectral absorption characteristics of unknown samples in terms of tMi time. In this method, white light transmitted through a sample is dispersed into wavelength components by a dispersor such as a diffraction grating, and detected by light receiving elements corresponding to a plurality of desired wavelength light convergence positions. The photoelectric output of these 71 light-receiving elements is related to m degrees of sample components at a desired wavelength, and information on a plurality of components can now be determined at once.

The above method does not require a mechanical system for wavelength scanning, and the apparatus can be made compact and simple, and wavelength scanning can be performed at a speed of 1°. However, on the other hand, it had the disadvantage of a lot of stray light and poor photometry accuracy. In other words, light dispersed by a dispersion element is imaged as a JAM spectrum on a photo-auto array in which a plurality of light-receiving elements are arranged.
These lights are split or scattered between the light receiving surface and the transparent light receiving window covering the light receiving surface of the photodiode array. These lights re-enter the light receiving element on the shorter wavelength side as stray light and are detected together with the measurement signal light.

Generally used as a light source with a wide wavelength range, the light beam has a long wavelength and large energy, so
When stray light containing a large amount of long wavelength light mixes with short-wavelength light with little energy, the photometry accuracy deteriorates dramatically. In order to improve this problem, conventional methods have been to improve the spatial separation of incident light by using a full-wave mask that matches each light-receiving element, or by providing side walls between adjacent elements.

However, since this method also cuts the signal light itself to some extent, the S/N ratio of the measurement system is not improved much. Furthermore, this method uses a photodiode array in which the spacing between the photodetectors is very close (usually 0.1 to 0.025
When mm spacing is used, it becomes difficult to provide masks and side walls as described above, and in particular, even if they are made, they are extremely expensive.

Another method is to arrange all the light-receiving elements for detecting stray light outside the imaging area, detect the signal light, and subtract their output from each output of the light-receiving element group. In this method, the location where the light-receiving element for stray light detection (hereinafter referred to as stray light monitor) is installed is different from the location where the light-receiving element group is installed, so the amount of stray light is also different, and measurement errors cannot be fully eliminated. .

The present invention is a multi-wavelength spectrophotometric device suitable for eliminating the drawbacks of the prior art and improving photometric accuracy! The purpose of the IJt is to provide IJt, and its feature is that a light transmitting plate is installed on at least four of the light receiving elements in the imaging area of the dispersed light to prevent the direct incidence of the dispersed light, so that all stray light can be detected. There is a VC that is configured without performing correction regarding the amount of stray light with respect to the photometric values of other light-receiving elements.

FIG. 1 shows a device equipped with a light receiving element group which is an embodiment of the present invention.
4 is an optical system diagram of a spectrophotometric device. Light that enters the entrance slit 1 from the light source is diffracted by the concave diffraction grating 2, reflected by the plane mirror 3, and formed into a dispersed image on the photodiode array 4.

This photodiode array 4 is arranged on a Rowland circle formed by the entrance slit 1 and the concave diffraction grating 2, and is sequentially dispersed between VC1o ``'' tI and from the short wavelength side.

FIG. 2 is a front view of the photodiode array shown in FIG. 1, and FIG. 3 is a sectional view taken along the line AB in FIG. Inside the rectangular container 5 are photodiodes 6° to 6. are arranged in an array and sealed with a light receiving window 7 made of a quartz plate that transmits light of all wavelengths well. A light-shielding plate 8 is attached to a part of the surface of the light-receiving window 7, and a light-shielding plate 8 is passed through to prevent straight light to from entering the photodiode 6o located inside the light-shielding plate 8. When the diffracted light at t, -t1 enters the photodiode array 4, each photodiode 61-6. reflected and scattered on the surface of
Furthermore, it is reflected by the light receiving window 7 and enters again. At this time, these scattered stray lights are also scattered to the photodiode 6° on the short wavelength side, so the frog is also greatly affected. This is because the sensitivity of the photodiode 6 is low at short wavelengths and high at long wavelengths. Further, when a tungsten metal plate is used as a light source, the energy increases rapidly especially as the wavelength of the light increases.

Now, stray light also enters the photodiode 6°, but
Since no straight light is incident on this photodiode 6°, only stray light is detected. Also, since the same amount of stray light is incident on the adjacent photodiode 6, if the stray light detection signal of the photodiode 6° is subtracted from the detection signal of the photodiode 6, the influence of the stray light of the photodiode 61 is almost eliminated. It will be removed. According to experiments by the inventors, the amount of stray light of the photodiode is 6 degrees, and the positional relationship with the cover light-shielding plate 8 indicates that the photodiode is actually fi.

Since the outputs appear slightly lower than the output values, it is necessary to calibrate the outputs in advance so that they are approximately equal.

For example, if the calibration coefficient α for the photodiode 6G is determined so that the outputs of the photodiodes 6 and 6o are equal, then the absorbance (Abs) can be determined by the following equation.

However, Dr is the output Ds of the photodiode 6° when receiving the reference light, and the output S of the photodiode 6G when receiving the sample light is the output R of the other photodiode 6 when receiving the sample light. Output Note that the calculation of this equation is performed by a microcomputer included in the spectrophotometer.

If other wavelengths of light are calculated by the same device, the measured WA difference due to stray light will be corrected, but the amount of stray light will differ as the distance from the photodiode, which is 6° as expected by the stray light monitor, increases.

However, when a tungsten lamp is used as a light source, the amount of incident light increases rapidly as the wavelength becomes longer, so the content of stray light decreases and the merit of removing stray light decreases. That is,
As mentioned above, it can be said that it is most effective to provide a stray light monitor on the short wavelength side where the amount of incident light is small.

In the above example, the distance between each photodiode in the photodiode array 4 is α12 mm, and the linear dispersion when an iodine tungsten lamp is used as a light source is 25 nm.
This is done using a 7mm photometric needle. Also, 340n
The stray light content rate at m is O, S. The gap between the light receiving surface of the stray light monitor and the light shielding plate 8 is 1.5 mrn.

Figure 4 shows the NAD measurement using the multi-wavelength spectrophotometer of this example.
Calibration of alkaline diluted solution of
The measurement is performed at 3 4 Q nm, which is the absorption band of DH (dephosphopyridine-nucleotide 2-Na). The horizontal axis shows the dilution (concentration) of the NADH alkaline bath solution, and the vertical axis shows the absorbance (Abs). In the conventional method shown by the broken line, the absorbance is curved from around 0.65, but when the stray light calibration means of this example is used, the solid line is a straight line until the absorbance is around 2.5, and the linearity is significantly improved. It's improving.

The multi-wavelength spectrophotometer of this embodiment uses a photodiode array as a photodetector, and a light-shielding plate is installed in front of the photodiode element to detect only stray light. Second, automatically performing and displaying the calculation of subtracting the difference by 1 to the photometric value with the addition of positional correction has the effect that the measured ff1l can be greatly improved.

The multi-wavelength spectrophotometric device of the present invention is expected to have the effect of improving photometric accuracy through relatively simple improvements.

[Brief explanation of the drawing]

Figure 1 shows a multi-wavelength spectrophotometry mto, which is an embodiment of the present invention.
Part 2 IQ is a front view of the photodiode play in the 11th Q4D embodiment, FIG. 3 is a cross-sectional view of MuB in FIG. 2, and No. 4!11 is a diagram comparing calibration curves.

Claims (1)

[Claims] 1. In a multi-wavelength spectrophotometer that measures spectral characteristics by arranging a plurality of light-receiving elements within an imaging region of nine wavelength components of light dispersed by a dispersion element, at least one of the light-receiving elements has dispersed light. A continuous light plate is installed to prevent the direct incidence of the light, and the amount of stray light is detected, and the photometric values of the other light-receiving elements are corrected for the amount of stray light.t4
Multi-wavelength spectrophotometer called IglL.