JP2003185499A - Spectrophotometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce costs in a switching mechanism and a wavelength-scanning mechanism in a monochrome meter for switching a plurality of diffraction gratings. <P>SOLUTION: A second rotary shaft 16 is rotated from a first rotary shaft 14 that is directly connected to a shaft 13 of a motor 12 via gears 15 and 17, and a base 2 where two diffraction gratings 25 and 27 are provided is fixed to the second rotary shaft 16. The rotary shafts 14 and 16 are supported rotatably to a substrate 20 together, and the substrate 20 is raised and supported while no external force is operated by the balance of two springs 21 and 22. Within a specific rotary angle range of the shaft 13, the substrate 20 is maintained to be raised and at the same time the base 23 is rotated, and a diffraction grating at the rotary center of the first rotary shaft 14 is switched. When the above rotary angle range is exceeded, stoppers 28 and 29 that are provided at the base 23 come into contact with the substrate 20, and the base 23 and the substrate 20 are rotated around the first rotary shaft 14 in one piece. As a result, the diffraction gratings 25 and 27 are rotated while maintaining the position of the center, and wavelength setting is achieved. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spectrophotometer provided with a monochromator for extracting monochromatic light having a specific wavelength, and more particularly to a spectrophotometer for extracting monochromatic light to be extracted. The present invention relates to a spectrophotometer including a monochromator that switches a plurality of wavelength dispersion elements according to a wavelength range. 2. Description of the Related Art In a spectrophotometer such as an ultraviolet-visible light spectrophotometer and an atomic absorption spectrophotometer, a monochromator is used to obtain monochromatic light having a predetermined wavelength. In general, a monochromator includes a wavelength dispersion element such as a diffraction grating or a prism, and a rotation driving mechanism for changing an angle of the wavelength dispersion element with respect to incident light. The wavelength dispersion element is rotated to a predetermined position, and monochromatic light that has passed through the exit slit is extracted from the dispersed light at that time. In recent years, as a wavelength dispersion element,
Since a diffraction grating is widely used, a case where the diffraction grating is used will be described below. However, the same configuration can be applied to another wavelength dispersion element such as a prism. In general, for example, when performing spectral measurement in a wide wavelength range from the near-infrared region to the ultraviolet region, it is difficult for one kind of diffraction grating to cover the entire wavelength range. . Therefore, in this type of conventional spectrophotometer, a switching drive mechanism for switching a plurality of diffraction gratings having different wavelength ranges (actually, changing the positions of the diffraction gratings) and a switching drive mechanism for changing the diffraction grating wavelength range are provided. A rotation driving mechanism for rotating the diffraction grating to scan the wavelength, and firstly setting the diffraction grating at a predetermined position by a switching driving function so as to select a diffraction grating suitable for a desired wavelength, By rotating the diffraction grating, light of a desired wavelength is extracted. The rotation drive mechanism is based on conversion from linear motion to rotary motion by a sine bar mechanism, by open loop control combining a stepping motor and a reduction gear mechanism, or by closed loop control using a DC servo motor. Things are being put to practical use. As described above, this type of conventional spectrophotometer has a drawback that the cost is increased because it has a switching drive mechanism and a rotation drive mechanism for the diffraction grating. Further, in recent years, a double monochromator type spectrophotometer in which two monochromators are optically connected in series has also been used. In such a spectrophotometer, a switching drive mechanism and a rotation mechanism are provided for the front and rear monochromators, respectively. Since it is necessary to provide a driving mechanism, the cost is further increased. SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a spectrophotometer which covers a wide wavelength range by switching a plurality of wavelength dispersion elements as described above. An object of the present invention is to provide a spectrophotometer capable of reducing the cost of a mechanism of a monochromator. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. According to the present invention, there is provided a spectrophotometer including a monochromator for extracting monochromatic light having a predetermined wavelength, wherein the monochromator comprises: a. A) a motor that drives the first rotating shaft to rotate within a predetermined angle range; and b) a second rotating shaft that extends substantially parallel to the first rotating shaft and is rotated by a rotational driving force from the first rotating shaft. C) a base for rotatably supporting the first and second rotating shafts; d) rotating integrally with the second rotating shaft and passing through the first rotating shaft about the second rotating shaft. A plurality of wavelength dispersing elements provided such that their centers are located on the circumference; ande) a rotation restricting portion that rotates integrally with the second rotation shaft and abuts on the base at a predetermined rotation position. In the angle range in which the rotation restricting portion does not contact the base, The switching operation of the wavelength dispersion element is performed by rotating the plurality of wavelength dispersion elements around the second rotation axis. Rotating the plurality of wavelength dispersion elements around the first rotation axis integrally with the base by pressing by a part,
The wavelength is set in the wavelength dispersion element whose center is located near the rotation center of the first rotation axis. An embodiment of the spectrophotometer according to the present invention has two wavelength dispersion elements, and a first rotation axis corresponding to the two wavelength dispersion elements. Rotation restricting portions are provided at predetermined rotation positions on both sides of the rotation range of the second rotation shaft associated with the rotation of. In the rotation range of the first rotation shaft, in a predetermined angle range near the center where neither of the two rotation restricting portions comes into contact with the base, the second rotation is performed along with the rotation of the first rotation shaft. When the shaft rotates, the plurality of wavelength dispersion elements rotate integrally with the second rotation axis, and the wavelength dispersion elements that come near the rotation center of the first rotation axis alternate. That is, switching of the wavelength dispersion element can be achieved. Then, when one of the rotation restricting portions passes through the angular position in contact with the base and further rotates the first rotating shaft, the rotation restricting portion presses the base, whereby both are integrally formed on the first rotating shaft. From the wavelength dispersive element existing near the rotation center of the first rotation axis at that time, the first position is maintained while the position of the center is substantially fixed.
Rotate around a rotation axis. Therefore, since the incident angle of the irradiation light to the wavelength dispersion element changes, the wavelength of the monochromatic light that can be extracted from the wavelength dispersion element changes. That is, wavelength setting or wavelength scanning can be achieved. As described above, in the spectrophotometer according to the present invention, the switching operation of a plurality of wavelength dispersion elements by one motor and the wavelength change by changing the angle of one wavelength dispersion element are performed. Setting and scanning can be performed together. Therefore, the cost of a monochromator having a plurality of wavelength dispersive elements that can be switched can be reduced. In particular, in a double monochromator type spectrophotometer having a plurality of monochromators, the cost is greatly reduced and an inexpensive device is used. Can be provided to the user. An embodiment of the spectrophotometer according to the present invention will be described below with reference to the drawings. FIG. 10 is a schematic configuration diagram of the spectrophotometer according to the present embodiment. Although the light emitted from the light source 1 includes various wavelengths, only the monochromatic light having a specific wavelength is taken out of the monochromator 2 and irradiated on the sample 3. The light passing through the sample 3 or reflected by the sample 3 is a light detector 4
And an intensity signal of the received light is sent to the signal processing unit 5. The signal processing unit 5 calculates the absorbance and the reflectance of the sample 3 and executes qualitative analysis and quantitative analysis of the sample 3. Here, the monochromator 2 switches a plurality of (specifically, two) diffraction grating groups 2A and a plurality of diffraction gratings according to the wavelength to be extracted, and sets the wavelength (or sets the wavelength). (Scanning) diffraction grating switching / rotating unit 2B. The spectrophotometer according to the present embodiment has a feature in the configuration of the monochromator, and therefore, this point will be described in detail below. FIGS. 1 and 2 are structural views of a monochromator in a spectrophotometer according to the present embodiment. FIG. 1 is a front view, and FIG. 2 is a sectional view taken along the line AA 'in FIG. . 3 to 8 are state diagrams for explaining the operation of the monochromator, and FIG. 9 is a conceptual diagram for explaining the operation. First, the configuration of the monochromator 2 will be described with reference to FIGS. A motor 12 as a rotation drive source is fixed to a support 11 fixed to a pedestal or the like (not shown). The motor 12 is, for example, a pulse motor or a geared motor with a harmonic gear. By driving a motor shaft 13 that reduces the rotational power of the motor and outputs the motor to the outside, a high torque is secured in a relatively narrow rotation angle range. I have. A first rotating shaft 14 is directly connected to a motor shaft 13 of the motor 12. A first gear 15 fixed to the first rotating shaft 14 allows the other second rotating shaft 1 to rotate.
The rotational driving force is transmitted to the second gear 17 fixed to the sixth gear 6. The first rotating shaft 14 and the second rotating shaft 16 are rotatably supported by a first bearing 18 and a second bearing 19 provided on a base 20, respectively. Between the lower part of the base body 20 and the support body 11, two coil springs 21 and 22 are provided in a C-shape, and when no force is applied to the base body 20 from outside, two coil springs 21 and 22 are provided. Due to the balance of the tensile forces of the springs 21 and 22, the base 20 stands almost straight as shown in FIG. A base 23 is fixed to the tip of the second rotating shaft 16, and when the second rotating shaft 16 is driven to rotate,
The base 23 rotates around the second rotation shaft 16 as a rotation center. At a predetermined position on the base 23, two first and second diffraction gratings 25 and 27 are attached to the holders 24 and 26, respectively. Holders 24, 26
Also has a function of finely adjusting the positions of the diffraction gratings 25 and 27. Further, the base 23 is provided with first and second two stoppers 28 and 29 each having an adjusting mechanism so as to protrude rearward. The first diffraction grating 25 rotates around the second rotation axis 16, and the center 25C of the diffraction grating 25
When reaching the position of the center of rotation of the rotating shaft 14 (the state shown in FIGS. 1 and 3), the position of the first stopper 28 is adjusted so that the first stopper 28 contacts the right wall surface of the base 20. Keep it. When the second diffraction grating 27 rotates around the second rotation axis 16 and the center 27C of the diffraction grating 25 reaches the position of the rotation center of the first rotation shaft 14 (the state shown in FIG. 5). The position of the second stopper 29 is adjusted so that the second stopper 29 contacts the left wall surface of the base 20. The light incident on the diffraction gratings 25 and 27 comes from directly below in FIG. 1, and impinges on the grating surface of the diffraction grating 25 or 27 located near the rotation center of the first rotating shaft 14 and is reflected while being wavelength-dispersed. Out through a slit provided at a predetermined position (not shown). Therefore, by changing the angle of the grating surface of the diffraction grating 25 or 27 with respect to the incident light, the wavelength of the extracted light changes. Next, the monochromator 2 having the above configuration will be described.
Will be described. The operation of the monochromator 2 is divided into two stages: a switching operation of the two diffraction gratings 25 and 27 corresponding to the measurement wavelength range, and a wavelength scanning operation of each of the diffraction gratings 25 and 27 within the measurement wavelength range. be able to. (1) Switching Operation of Diffraction Grating Now, it is assumed that the positions of the base 23 and the base 20 are in the state shown in FIG. 3 (the same as FIG. 1). That is, at this time, the center 25C of the first diffraction grating 25 is located at the center of the first rotation axis 14, that is, the irradiation center position of the incident light.
When the switching operation from this state to the second diffraction grating 27 is performed, the motor shaft 13, that is, the first rotation shaft 14 is rotated clockwise in FIG. 3 (here, the rotation direction of the motor 12 is Forward direction). Thereby, the first
The gear 15 rotates clockwise and the second gear 17 rotates counterclockwise, and the base 23 rotates counterclockwise around the rotation center of the second rotation shaft 16 as shown in FIG. Therefore, instead of the first diffraction grating 25 moving away from the light irradiation center, the second diffraction grating 27 comes closer to the light irradiation center. Then, as shown in FIG. 5, when the center 27 </ b> C of the second diffraction grating 27 reaches the rotation center of the first rotation shaft 14, the second stopper 29 just contacts the left wall surface of the base 20. Thereby, the switching operation from the first diffraction grating 25 to the second diffraction grating 27 is completed. When the first rotating shaft 14 rotates, the first
A force for rotating the base body 20 acts due to friction with the bearing 18, but this force is much smaller than the urging force of the two coil springs 21 and 22.
While the base 3 rotates, the base body 20 maintains a substantially upright state. (2) Wavelength Scanning Operation of Diffraction Grating As described above, after the second stopper 29 abuts on the left side wall surface of the base 20, if the motor 12 is further driven to rotate in the normal rotation direction, the second stopper 29 Base 23 and base 2
0 is fixed, the rotational driving force of the second rotating shaft 16 is transmitted to the base 20 via the base 23 and the second stopper 29, and the position of the base 20 with respect to the support 11 is changed. It starts to rotate clockwise around the fixed first rotation shaft 14 integrally with the base 23. Thereby, as shown in FIG. 6, the second diffraction grating 27 has its center 2
7C rotates clockwise while being maintained near the rotation center of the first rotation shaft 14. Therefore, wavelength scanning within the wavelength range of the second diffraction grating 27 is achieved. When the base 20 rotates clockwise as described above, the coil spring 22 applies an urging force to rotate the base 20 counterclockwise. As a result, the base body 20 is strongly pressed against the second stopper 29 to secure the integral movement of the two, and the gears 15, 1
7 is no longer affected by the backlash. This also serves to eliminate backlash of the reduction gear in the motor 12, which is a harmonic drive or geared motor. The rotation of the base 20 as described above is possible up to a predetermined angle, and is controlled so as to stop at that angle. After reaching this angular position, the motor 23 is driven to rotate in the reverse direction, so that the base 23
6 rotates counterclockwise about the center of rotation, and the coil spring 2
The base 20 follows the second urging force and rotates counterclockwise about the first rotating shaft 14 as the center of rotation. Therefore, the second diffraction grating 27 also rotates counterclockwise with its center 27C maintained near the rotation center of the first rotation shaft 14. When the position returns to the position shown in FIG. 5, the pressing of the base 20 by the second stopper 29 is released. Therefore, when the motor 12 is further rotated in the reverse direction, the switching operation from the second diffraction grating 27 is performed in the reverse direction. First diffraction grating 25
Is performed. As shown in FIG. 7, the first stopper 28 reaches a position where it comes into contact with the right side wall of the base 20, and the center 25C of the first diffraction grating 25 is the rotation center of the first rotating shaft 14, that is, the irradiation of incident light. When the motor 12 is further driven to rotate in the reverse direction after reaching the center, the base 23 and the base 20 are integrally formed with the first rotating shaft 14 as shown in FIG. It rotates around counterclockwise. Thereby, the first diffraction grating 25 has its center 25C
Is rotated in the counterclockwise direction while being maintained near the rotation center of the first rotation shaft 14. Therefore, the first diffraction grating 2
The wavelength scanning within the wavelength range carried by 5 is achieved. FIG. 9 shows the relationship between the rotation position of the motor shaft 13, that is, the first rotation shaft 14 and the operation. That is, the switching operation of the two diffraction gratings 25 and 27 is performed in the predetermined angle range θ1 sandwiching the center of the rotation angle range of the first rotation shaft 14, and the first diffraction grating is respectively performed in the outer angle ranges θ2 and θ3. The wavelength scanning operation of the grating 25 and the wavelength scanning operation of the second diffraction grating 27 are performed. So, for example,
When the motor 12 is continuously driven to rotate from one end B to the other end B 'of the rotation angle range, first, wavelength scanning within the wavelength range of the first diffraction grating 25 is performed, and then the first diffraction grating 25 is scanned. Switching from the diffraction grating 25 to the second diffraction grating 27 is performed, and thereafter, wavelength scanning within the wavelength range of the second diffraction grating 25 is performed. Of course, the motor 12 may be continuously driven to rotate from the end B ′ to the end B in the rotation angle range. As described above, according to the spectrophotometer of the present embodiment, the switching operation of the plurality of diffraction gratings 25 and 27 and the rotation of one diffraction grating 25 or 27 are performed by rotating and driving one motor 12. And a wavelength scanning (or setting of a predetermined wavelength) operation. It should be noted that the above embodiment is merely an example, and it is apparent that modifications and modifications can be made as appropriate within the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view showing a mechanical system configuration of a monochromator in a spectrophotometer according to the present embodiment. FIG. 2 is a cross-sectional view taken along the line AA ′ in FIG. 1, showing a mechanical system configuration of the monochromator in the spectrophotometer according to the present embodiment. FIG. 3 is a state diagram for explaining the operation of the monochromator in the spectrophotometer according to the embodiment. FIG. 4 is a state diagram for explaining the operation of the monochromator in the spectrophotometer according to the embodiment. FIG. 5 is a state diagram for explaining the operation of the monochromator in the spectrophotometer according to the embodiment. FIG. 6 is a state diagram for explaining the operation of the monochromator in the spectrophotometer according to the embodiment. FIG. 7 is a state diagram for explaining the operation of the monochromator in the spectrophotometer according to the embodiment. FIG. 8 is a state diagram for explaining the operation of the monochromator in the spectrophotometer according to the present embodiment. FIG. 9 is a conceptual diagram for explaining the operation of the monochromator in the spectrophotometer according to the present embodiment. FIG. 10 is a schematic configuration diagram of a spectrophotometer according to the present embodiment. [Description of Signs] 11 ... Support 12 ... Motor 13 ... Motor shaft 14 ... First rotating shaft 15 ... First gear 16 ... Second rotating shaft 17 ... Second gear 18 ... First bearing 19 ... Second bearing 20 ... Bases 21, 22 Coil spring 23 Bases 24, 26 Holder 25 First diffraction grating 27 Second diffraction grating 28 First stopper 29 Second stopper

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Mira Hatao             26 Shimonazue, Nishinokyo Shimoaicho, Nakagyo-ku, Kyoto             Engineering Co., Ltd. F-term (reference) 2G020 CA02 CB04 CC04 CC07 CC55                       CD12 CD13 CD22                 2H049 AA03 AA07 AA13 AA50 AA58                       AA63 AA69

Claims (1)

Claims: 1. A spectrophotometer comprising a monochromator for extracting monochromatic light having a predetermined wavelength, the monochromator comprising: a) a motor for rotating a first rotation axis in a predetermined angle range; B) a second rotating shaft that extends substantially parallel to the first rotating shaft and is rotated by a rotational driving force from the first rotating shaft; and c) the first and second rotating shafts are rotatable. A) a base to be supported; and d) a base that rotates integrally with the second rotation axis and is located on a circumference passing through the first rotation axis about the second rotation axis. A plurality of wavelength dispersion elements, and e) a rotation restricting portion that rotates integrally with the second rotation shaft and abuts on the base at a predetermined rotation position, wherein the rotation restricting portion does not abut on the base. Rotating the plurality of wavelength dispersion elements around the second rotation axis in an angular range; By performing the switching operation of the wavelength dispersion element, when the rotation restricting portion is in an angle range where the rotation restricting portion contacts the base, the plurality of wavelength dispersion elements are integrally formed with the base by pressing by the rotation restricting portion. A spectrophotometer characterized in that the spectrophotometer is rotated around a first rotation axis, and the wavelength of the wavelength dispersion element whose center is located near the rotation center of the first rotation axis is set.