JPS631220Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a spectrophotometer capable of short-time spectroscopic measurements.

When using a spectrometer as a detection device in liquid chromatography to analyze chromatographic peaks over time, the time for one analysis operation is required to be several seconds or less, so a spectrometer such as a wavelength scanning spectrometer is used. Analysis is difficult with devices that have mechanically moving parts. For this reason, a spectroscopic device that does not have mechanically moving parts forms a spectral image on a photoelectric conversion element that has at least one-dimensional resolution, such as a photodiode array, and performs spectroscopic measurements by electrical scanning. A device can be considered. When using a diffraction grating as a dispersive element, the spectral image on the photoelectric conversion element is first-order diffracted light,
Since the second-order diffracted light and the like partially overlap, the wavelength range that can be spectrally measured becomes very narrow.

Therefore, the present invention provides a spectroscopic device using the photodiode array described above, which eliminates the overlap between the first-order diffracted light and the second-order diffracted light of the spectral image produced by the diffraction grating, thereby making it possible to perform spectroscopic measurements over a wide range. It was made for the purpose of

First, the concept of the present invention will be explained using a simple example. In FIG. 1, G is a flat diffraction grating, and when a parallel light beam is incident at an angle of −θ with respect to the normal N thereof, specularly reflected light, that is, 0th-order diffraction light, is directed in the direction of +θ. Consider light diffracted in a direction between this 0th order diffracted light and the incident light. Let the angle between the diffracted light and the normal N be φ. φ assumes that the right side of N is positive. The wavelength λ of this diffracted light is nλ=d(sinθ−sinφ) where d is a lattice constant and n is the order of diffraction. The relationship between this wavelength and φ is illustrated as a solid line in FIG. 2. Normal N with the direction of incidence of the incident light reversed
When the incident angle is +θ (in principle, +θ
It doesn't have to be. The relationship between the wavelength of the diffracted light and the diffraction angle φ (which only needs to be on the opposite side of −θ with respect to the normal N) can be illustrated in the same way as described above. The shape will be flipped horizontally. Here, let λ ₀ be the limit on the short wavelength side of the incident light. Then, the diffraction angle b of the incident light from the -θ direction is
The diffracted light in the range from a to a is only the first-order diffracted light and does not include the second-order diffracted light. Therefore, if a photometric element with a one-dimensional resolution such as a photodiode array is placed in the range of the horizontal line P in the range of diffraction angles b to _a in Fig. It is possible to measure light up to the vicinity beyond the limit. Next, when the incident direction of the light is changed and the light is made incident from the +θ direction, the light incident on the array element P ranges from the wavelength of the first-order diffracted light around dsinθ to λa and the wavelength of the second-order diffracted light from λ ₀ to λ′ (λ′>λ ) is the range of light. Therefore, if the light with a wavelength shorter than the wavelength dsinθ is removed by a filter on the incident light side, only the first-order diffracted light will be incident on the array element, and the range of wavelengths from dsinθ to λa can be photometered, and the incident light can be divided into -θ and +θ. By switching to , it is possible to perform spectrophotometry in the range of approximately 2λo wavelength difference from λ ₀ to λa in two operations, and the spectrum formed on the array element can be measured at once without wavelength scanning, reducing the time required for spectroscopic analysis. This will shorten the time considerably. Here, the position of a can be brought up to the +θ position as seen from FIG. In Fig. 1, the right end of P can be extended to the position of the 0th order diffracted light as shown by the dotted line.

Alternatively, as shown in Fig. 1, a photodiode array is placed with its center on the normal line N, and a high-pass filter is used to measure the second-order diffracted light in the short wavelength range for light incident from -θ. Alternatively, a low-pass filter may be used for the light incident from the source to photometer the first-order diffracted light in the long wavelength range. In other words, in Figure 2, if we use a photodiode array covering the range of ±a and use a high-pass filter to remove light with wavelengths longer than λ' from the diffracted light of the incident light from -θ (shown by the solid line), we can obtain from _λ0 to The range up to λ' is spectrophotometered using second-order diffracted light, and when light with a wavelength of λ' or more is input through a low-pass filter for the incident light from +θ, only the first-order diffracted light shown by the dotted line is received, and from λ ₀ to dsinθ+λ ₀ range is spectrophotometrically measured.

The present invention will be explained below with reference to Examples. FIG. 3 shows an embodiment of the present invention. 3 is a concave diffraction grating with a grating constant of 600 lines/mm, and R is a Rowland circle with a diameter of 150 mm. Input slits 1 and 2 are placed on the Rowland circle at an angle of 10.37 degrees on both sides of the normal N set at the center of the grid 3, and the slits 1 and 2 are placed near the intersection with the normal N on the Rowland circle. and install photodiode array 4. In this case, the required length of the array is 18 mm and can cover wavelengths from 200 nm to 800 nm. 5 is a light source, 6 is a concave mirror, 7 is a sample cell, the light from the light source 5 is converged on the sample cell by the mirror 6, the light transmitted through the sample cell 7 becomes a parallel light beam by the concave mirror 8, and in this light beam, with luminous flux
A sector mirror 9 is arranged at an angle of 45, concave mirrors 10 and 11 are arranged symmetrically with respect to the sector mirror 9, and the parallel light beam reflected by the mirror 8 passes through the sector mirror 9 and reaches the mirror 10. The light enters or is reflected by the sector mirror 9 and enters the mirror 11. Mirrors 10 and 11 focus the incident light onto slit 1 or 2. Thus, the sample cells 7 are placed alternately in the slits 1 and 2 in a time-division manner.
The light that has passed through is incident. A filter 12 is arranged in front of the slit 1. This slit is
This is a low-pass filter that cuts out light with wavelengths shorter than 400nm. The photodiode array 4 has a wavelength of 400nm to 800nm due to the light incident from the slit 1.
The first-order diffracted light and the second-order diffracted light of 200 nm to 400 nm are made incident. The light from the light source does not include light with wavelengths shorter than 200 nm. Here, because of the filter 12, there is actually no second-order diffracted light from 200 nm to 400 nm, and only first-order diffracted light from 400 nm to 800 nm is projected onto the photodiode array 4. Furthermore, the light incident from the slit 2 includes only the first-order diffracted light from 200 nm to 400 nm. In this way, by making the light enter the slits 1 and 2 alternately,
Photodiode array 4 starts from wavelength 200nm
Capable of spectrophotometry up to 800nm.

In this embodiment, the photodiode array 3 may be placed exactly between slits 1 and 2, and a high pass filter may be placed in front of slit 1 and a low pass filter may be placed in front of slit 2. Furthermore, instead of arranging the photodiode array asymmetrically with respect to the normal line N, the slits 1 and 2 may be made asymmetrically with respect to the normal line N, and a low-pass filter may be used only in one of the slits.

FIG. 4 shows another embodiment of the present invention. This embodiment is an example in which the present invention is applied to two-beam spectrophotometry. 5 and 5' are light sources, and one of the two is D ₂
The lamp emits light in the short wavelength range, and the tungsten lamp 5' handles light in the long wavelength range. A low-pass filter 12' is placed in front of the tungsten lamp 5'.
The wavelength range is made so that it does not overlap with the D ₂ lamp.
13 is a sector mirror, making it a double-sided mirror.
The mode in which the light from the _D2 lamp 5 is sent to the optical path A and the light from the tungsten lamp 5' is sent to the optical path B, and the mode in which the light from the _D2 lamp is sent to the optical path B and the light from the tungsten lamp to the optical path A are alternately repeated. It will be done. On the two beams A and B, 14 is a sample cell and 14' is a control cell. Two beams A and B are sent to slits 1 and 2 by a sector mirror 9'. The sector mirror 9' is synchronized with the sector mirror 13, and during one mode of the sector mirror 13 where the light from one lamp 5 is on the A optical path and the light from the other lamp 5' is on the B optical path, the A In the mode in which the light on the optical path is first sent to slit 1, and then the light on the B optical path is sent to slit 2, and in the other mode of the sector mirror 13, the light on the A optical path is first sent to slit 2, and then the light on the B optical path is sent to slit 2. The two modes, the one sent to the first one, are alternated. This is illustrated in FIG. 5. That is, in the first mode of the sector mirror 13, the light from the _D2 lamp becomes A.
When the light from the tungsten lamp is on the B optical path, (1) the sector mirror 9' first sends the light in the short wavelength range from the A optical path, that is, the _D2 lamp, to the slit 2;
Next, (2) the light from the tungsten lamp in the long wavelength region of optical path B is sent to slit 1; The first-order diffracted light of the light entering from slit 2 is in the short wavelength range, and then passes through slit 1.
The first-order diffracted light of the light that enters is in the long wavelength range. In the second mode of sector mirror 13, first
(1) The light from the tungsten lamp in optical path A enters the first slit, and the first-order diffracted light in the long wavelength range is measured.
Next, the light from the _D2 lamp in the (2)'B optical path enters the second slit, and the first-order diffracted light in the short wavelength range is measured. In this way, the short wavelength region,
Transmitted light in the long wavelength range is measured.

The spectrometer of the present invention has the above-mentioned configuration, and can perform order separation of diffracted light by using only one photodiode array, and can perform spectral images simultaneously (within the scanning time range of the photodiode array) without performing wavelength scanning. ), so spectrophotometry can be done in an extremely short time.

[Brief explanation of the drawing]

Fig. 1 is a diagram explaining the principle of the present invention, Fig. 2 is a diagram showing the relationship between the diffraction angle and wavelength, Figs. 3 and 4 are plan views of different embodiments of the device of the present invention, and Fig. 5 5 is a diagram showing the operation mode of the sector mirror in the embodiment shown in FIG. 4. FIG. 1, 2...Incidence slit, 3...Diffraction grating, 4
...Photodiode array, 5...Light source, 7...
...Sample cell, 9...Sector mirror, 12...Filter.

Claims (1)

[Scope of utility model registration request] Input slits are provided approximately symmetrically on both sides of the normal line erected at the center of the diffraction grating, and a photoelectric conversion element with one-dimensional resolution is placed near the extension of the normal line along the spectral image plane. A spectroscopic device comprising: an optical system for alternately making light incident on the slits; and means for removing short-wavelength or long-wavelength components of the light beam incident on at least one of the slits.