JPH06100501B2 - Wavelength selection driving method in spectroscopic device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving method for precisely rotating a spectroscopic element used in a spectrophotometer or other spectroscopic device for wavelength selection.

2. Description of the Related Art As is well known, in a spectroscopic device, it is necessary to disperse white light provided from a light source into monochromatic light in a predetermined wavelength range by a dispersive element (dispersion element), and in that case, it is necessary to perform wavelength scanning. Many. As such a spectroscopic element, a diffraction grating (prism) or a prism is generally used, and in that case, the wavelength scanning is performed by rotating the spectroscopic element in small increments. In order to obtain monochromatic light, it is necessary to precisely control the rotation angle of the spectroscopic element.

In a conventional spectrophotometer, a driving device for rotating a diffraction grating as a spectroscopic element generally uses a so-called sine bar and a feed screw. The 12th example
It is shown schematically in the figure.

In FIG. 12, a feed screw 3 is formed on a drive shaft 2 of a rotary drive source 1 such as a motor, and an advancing / retreating base 4 is screwed onto the feed screw 3 to allow the feed screw 3 to move. The advancing / retreating base 4 is configured to move linearly along the axial direction of the feed screw 3 while being guided by the guide frame 5 by rotation. On the other hand, a bar 8 is extended from the rotating base 7 supporting the diffraction grating 6 toward the advancing / retreating base 4 in a plane orthogonal to the rotating axis of the diffraction grating 6, and the tip of the bar 8 is extended. The roller 9 provided at the position is pressed against the advancing / retreating base 4.
Therefore, the diffraction grating 6 rotates according to the linear movement of the advancing / retreating base 4.

The wavelength λ selected by the diffraction grating is a sine function of the rotation angle θ of the diffraction grating, as will be described later. Therefore, in the drive device using the so-called sine bar system as shown in FIG. And the wavelength have a linear relationship, which is an advantage that drive control for wavelength selection can be performed relatively easily. However, in the drive device as shown in FIG. 12, since the rotary drive is once converted into the linear motion and then converted into the rotary motion again, the number of parts constituting the device must be increased, and The entire device had to grow. Further, there is a problem that backlash occurs in the screwed portion between the feed screw 3 and the advancing / retreating base 4 and the reproducibility of wavelength selection deteriorates. To avoid this, the screwed portion must be finished with extremely high precision. However, in that case, there arises a problem that the processing cost becomes high, and some backlash is unavoidable no matter how highly accurate the finish is. Further, the apparatus shown in FIG. 12 has a problem that the wavelength scanning speed must be slowed down.

Therefore, the present inventors have already filed Japanese Patent Application No. 60-291666 (Japanese Patent Publication No. 5-6
No. 0535), the rotation of the drive shaft of a rotary drive source such as a stepping motor is directly converted to a linear motion by a belt such as a steel belt so that the wavelength can be selected. We have proposed a drive device that does. Specifically, in the drive device of the first invention in the above patent application, the optical element to be rotated, for example, the rotation axis of the diffraction grating, has at least a part of a cylindrical surface centered on the rotation axis. A driven piece having a peripheral surface to be formed is fixed, and a drive shaft rotated by a rotary drive source such as a stepping motor is arranged in parallel with the rotation axis at a position close to the peripheral surface of the driven piece. However, the intermediate portion in the longitudinal direction of the belt made of a steel belt or the like having substantially no elongation and flexibility is provided as a single layer on the peripheral surface of one of the drive shaft and the driven piece. Projection in which the belt is wound twice or more, a part of the wound portion is fixed to a part of the peripheral surface of the one member, and both end sides of the belt are projected on a plane orthogonal to the rotation axis. Both ends of the belt so that they intersect in the figure By extending along the side peripheral surface of the other member opposite directions, it is characterized in that fixed to both end portions at the other of the members. Further, the driving device of the second invention of the above patent application has a peripheral surface forming at least a part of a cylindrical surface centering on the rotation axis of the rotation axis of the optical element to be rotated, for example, the diffraction grating. The driven piece is fixed, and at a position close to the peripheral surface of the driven piece, a drive shaft rotated by a rotary drive source such as a stepping motor is arranged parallel to the rotation axis, and One portion of each of the first belt and the second belt made of a steel belt or the like having substantially no elongation and flexibility is provided on the peripheral surface of one of the driving piece and the driving piece. On a projection view in which the end portions of the first belt and the second belt are wound on each other in a double or double or more manner, and the other ends of the first belt and the second belt are projected on a plane orthogonal to the rotation axis. So that they cross each other at
The other end of each belt is extended in opposite directions along the peripheral surface of the other member, and each end is fixed to the other member.

According to these drive devices, since the rotational movement of the drive shaft is directly transmitted as rotation to the diffraction grating, the rotational movement is once converted into a linear movement like the conventional device using a sine bar and a feed screw. After that, the number of parts is remarkably reduced compared to the method of converting the motion into rotary motion and rotating the diffraction grating. Since one part is fixed to the drive shaft and the other part of the belt is fixed to the driven piece on the diffraction grating side, there is no backlash in principle, and moreover, there is no backlash between the belt, the drive shaft and the driven piece. There is an advantage that slipping does not occur between them, and therefore the wavelength reproducibility is not deteriorated due to backlash or slippage.

However, as described above, the wavelength λ is a sine function of the rotation angle θ of the diffraction grating. Therefore, when the rotation of the drive shaft of the stepping motor is transmitted as it is to the diffraction grating without using the sine bar method. The rotation angle of the drive shaft is a function of sin ⁻¹ of the wavelength λ, as will be described later, and therefore the relationship between the number of pulses for driving the stepping motor and the wavelength λ to be selected is also a special function of sin ⁻¹ . Therefore, the calculation time for calculating the number of pulses to be given to set the wavelength to be selected becomes long, and a large number of memories are required.

The present invention has been made in view of the above circumstances. The first invention of the above patent application, the first invention of the above patent application, without using the sine bar method as described above, that is, without converting the rotary shaft of the stepping motor into a linear motion. In the case where the rotation transmission mechanism having the same configuration as that of the second invention is used to transmit the rotation motion to the rotation axis of the spectroscopic element such as the diffraction grating, the wavelength selection of the spectroscopic element can be performed easily and easily. It is an object of the present invention to provide a wavelength selective driving method as described above.

Means for Solving the Problems The wavelength selection driving method of the first invention is a wavelength selection driving method in a spectroscopic device in which the wavelength of light to be emitted is changed by changing the angle of the spectroscopic element, wherein a: wavelength selection Using a stepping motor as a drive source, b: and as a rotation transmission mechanism for transmitting the rotation of the rotation axis of the stepping motor to the rotation axis of the spectroscopic element; A driven piece having a peripheral surface forming at least a part of a cylindrical surface as a center is fixed, and the rotation axis of the stepping motor is parallel to the rotation axis at a position close to the peripheral surface of the driven piece. And wrapping the intermediate portion in the length direction of the belt, which has substantially no elongation and flexibility, on the peripheral surface of the rotating shaft in a single or double or more manner. part Both end portions of the belt are fixed to a part of the peripheral surface of the rotating shaft, and both end portions of the belt are driven so as to intersect with each other on a projection view projected on a plane orthogonal to the rotation axis. , Which are configured so that both ends are fixed to the driven piece by extending in opposite directions along the peripheral surface of c, and in order to drive the stepping motor with wavelength or / and wave number in advance. The relationship between the number of pulses and the number of pulses is stored as a table, and d: the number of pulses corresponding to the wavelength or wave number to be set is read by referring to the table when selecting a wavelength, and that number of pulses is given to the stepping motor. Is characterized by rotating the spectroscopic element by a required angle to set the wavelength or the wave number.

The wavelength selection driving method of the second invention is a wavelength selection driving method in a spectroscopic device in which the wavelength of light to be emitted is changed by changing the angle of the spectroscopic element, wherein: a stepping motor is used as a wavelength selection driving source. , B: and as a rotation transmission mechanism for transmitting the rotation of the rotation shaft of the stepping motor to the rotation shaft of the spectroscopic element; the rotation shaft of the spectroscopic element has at least a cylindrical surface centered on the rotation axis. A driven piece having a peripheral surface forming a part is fixed, and at a position close to the peripheral surface of the driven piece,
The rotation shaft of the stepping motor is arranged in parallel with the rotation axis, and one end side of each of the first belt and the second belt which is substantially inextensible and has flexibility on the peripheral surface of the rotation shaft. Part is wound in a single layer or in a double layer or more and its tip end is fixed to the rotating shaft, and the other ends of the first belt and the second belt are projected on a plane orthogonal to the rotation axis. The other end side of each belt is extended in the opposite direction along the peripheral surface of the driven piece so that each end is fixed to the driven piece so as to intersect with each other on the projection view. C: Moreover, the relationship between the wavelength or / and the wave number and the pulse number for driving the stepping motor should be tabulated and stored in advance, and d: should be set by referring to the table when selecting the wavelength. Pulse corresponding to wavelength or wave number Reading, the spectral element by giving the number of pulses to the stepping motor is required angle rotated to set the wavelength or wave number, it is characterized in.

First, the rotation transmission mechanism used in the wavelength selection driving method of the first invention will be described. In this rotation transmission mechanism, the intermediate portion of the belt is wound around the peripheral surface of the rotation shaft of the stepping motor. Part of the part is fixed to the peripheral surface of the rotating shaft, and both ends of the belt are fixed to the driven piece side. A part of the belt is fixed at the end of the belt because one end is wound around the rotary shaft and pulled by the length of the circumference of the rotary shaft corresponding to the rotation angle. The driven piece being rotated rotates by an angle corresponding to the circumferential length of the driven piece that is equal to the wound length. At this time, the other end side of the belt is unwound (rewound) from the rotary shaft by a length corresponding to the rotation angle of the rotary shaft, and therefore, the unwound length (= winding length) corresponds to the unwound length. The driven piece is allowed to rotate (that is, the spectroscopic element rotates) by an angle corresponding to the circumference of the driven piece.

In this way, the driven piece rotates in accordance with the rotation of the rotation shaft of the stepping motor, and the spectroscopic element rotates.At this time, the rotation shaft and the driven piece are partially fixed to the belt. Moreover, since the belt does not substantially stretch, the rotation angle of the rotary shaft and the winding length (feeding length) of the belt always have a correspondence relationship of one low. The (feeding length) and the rotation angle of the driven piece (that is, the rotation angle of the spectroscopic element) always have a constant correspondence relationship, and no backlash occurs in principle even when the rotation direction of the rotation shaft is reversed. Moreover, slippage does not occur between the belt and the rotating shaft and between the belt and the driven piece.

On the other hand, in the case of the rotation transmission mechanism used in the wavelength selection driving method of the second invention, if the rotation shaft of the stepping motor rotates by a certain angle, one of the two belts corresponds to the rotation angle. Is wound around the rotary shaft by the length of the circumference of the rotary shaft, and the other belt is unwound from the rotary shaft by the same length, so that the driven piece becomes the unwound length (= unwinding length) of the belt. It will rotate by an angle corresponding to the same circumference of the driven piece. In this case as well, as with the rotation transmitting mechanism used in the method of the first invention, there is no backlash and no slippage.

Next, the overall operation of the wavelength selection driving method using the rotation transmission mechanism as described above will be described.

The relationship between the wavelength λ of the spectroscopic element, for example, a diffraction grating and the rotation angle θ of the diffraction grating is as follows.
If the angle formed by the incident light and the diffracted light is 2γ, it is expressed by the following equation (1).

λ = (2d / m) · cosγ · sinθ (1) As a specific example, if the lattice constant d is 1200 lines / mm, the diffraction order m is 1 (that is, first-order light), and 2γ = 30 ° , (1) can be rewritten as the following expression (2).

λ = 1609.87 × sin θ (2) Therefore, from formula (2), θ = sin ⁻¹ (λ / 1609.87) (3) holds.

In the present invention, the rotation of the stepping motor is transmitted to the rotary shaft of the diffraction grating as a rotary motion without being converted into a linear motion as in the sine bar method. It is proportional to the rotation angle θ of the lattice by a linear function. For example, if the damping ratio of the rotation transmission mechanism is 1 / 10.2, then φ = 10.2 × θ = 10.2 × sin ⁻¹ λ / 1609.87 (4).

In this way, the rotation angle φ of the stepping motor has a special function (sin ⁻¹ ) with respect to the wavelength λ. Therefore, when the wavelength is selected, if the stepping motor feed pulse number corresponding to the wavelength is calculated, The calculation time becomes long and a lot of memory is required. Therefore, in the present invention, the relationship between the wavelength and the stepping motor feed pulse number is stored in advance as a table, and at the time of wavelength selection, the table is referenced to read the pulse number corresponding to the desired wavelength, and the number of pulses is stepped. It is given to the motor to rotate its rotation shaft by a required angle, and the diffraction grating is rotated by a required angle via the rotation transmission mechanism to set a required wavelength.

By thus creating and storing the table in advance, it is possible to shorten the calculation time at the time of wavelength selection and reduce the number of memories.

When it is desired to set a wavelength that is not in the table, interpolation calculation is performed from the wavelengths stored in the table by an approximate expression to obtain the number of pulses, and the stepping motor may be driven by the number of pulses.

Further, instead of or in addition to the wavelength-pulse number table, a wave number-pulse number table may be stored, and in this case, the wave number can be selected.

Embodiments First, mechanical components of an apparatus for carrying out the method of the present invention, particularly a portion for driving a diffraction grating as a spectroscopic element, will be described.

FIG. 1 shows an example in which a belt 15 is used as a rotation transmission mechanism 14 for decelerating the rotation of the rotation shaft 11 of the stepping motor 10 and transmitting it to the rotation shaft 13 of the diffraction grating 12, and FIG.
FIG. 3 shows an example of the belt 15 used in the mechanism shown in FIG.

In FIG. 1, the diffraction grating 12 is attached to a rotary base frame 16, and the rotary base frame 16 is attached to a rotary shaft 13. Further, a driven piece 17 extending in the radial direction is fixed to the rotary shaft 13. The driven piece 17 has an arcuate peripheral surface 17A that constitutes a part of a cylindrical surface centered on the axis of the rotating shaft 13. At a position close to the peripheral surface 17A of the driven piece 17, the rotary shaft 11 of the stepping motor 10 is arranged so as to be parallel to the axis of the rotary shaft 13.

The belt 15 interposed between the rotating shaft 11 and the driven piece 17 is a belt made of a material having substantially no elongation and flexibility, for example, a steel belt made of stainless steel. The development view is shown in FIG. In FIG. 3, the belt 15 has one side 15B with respect to the central portion 15A,
A long hole 18 having a predetermined width is formed along the length direction, and a central portion 15
The other side 15C with respect to A is made narrow so that it can be inserted into the elongated hole 18, and the central portion and one end portion and the other end portion have mounting holes 19A for mounting and fixing. , 19B, 19
C is formed. Such a belt 15 is shown in FIG.
As shown in FIG. 2, the vicinity of the central portion 15A is wound around the outer peripheral surface 11A of the rotary shaft 11 in a single layer, and the narrow portion 15C on the other side is inserted into the elongated hole 18 on one side of the belt 15, respectively. End portions of the driven parts 17 extend in opposite directions along the peripheral surface 17A of the driven piece 17. And the central portion 15A of the belt 15 is the mounting hole 19A
Is fixed to the rotating shaft 11 by the mounting screw 20, and both ends of the belt 15 are fixed to the driven piece 17 by the mounting screw 20 in the mounting holes 19B and 19C, respectively.

In the mechanism shown in FIG. 1, a stepping motor
If the rotary shaft 11 of 10 rotates clockwise by an angle α as shown in FIG. 4, the belt 15 rotates the rotary shaft 11 corresponding to the angle.
One side is wound around the rotating shaft 11 and the other side is paid out by the circumference of. That is, when the radius of the rotating shaft 11 is r, the winding state of the belt 15 with respect to the rotating shaft 11 is displaced by a length of 2πr × α / 360. As a result, the driven piece 17 to which both ends of the belt 15 are fixed is rotated by an angle β corresponding to the circumferential length of the driven piece 17 corresponding to the displacement amount (2πr × α / 360) of the belt 15. . That is, the peripheral surface of the driven piece 17
Assuming that the radius of 17A is R, it rotates by β = α × r / R. Therefore, the rotation angle α of the rotary shaft 11 and the rotation angle β of the driven piece 17 are inversely proportional to the ratio of the respective radii.
By rotating the driven piece 17 by the angle β in this way, the diffraction grating 12 also rotates by the angle β, and the wavelength of the light emitted from the exit slit (not shown) provided at a predetermined position is the angle β. Will be changed by the amount corresponding to.

In FIG. 1, reference numeral 21 is a reference position detector for detecting the reference position of the diffraction grating 12, for example, a photo coupler,
An operating piece 22 for operating the photocoupler 21 is provided at a predetermined position of the driven piece 17.

In the example shown in FIGS. 1 to 3, the belt 15 has a long hole 18 formed on one side 15B thereof, and the narrow portion 15C on the other side is inserted into the long hole 18 so that both ends are cross-shaped. However, it is not always necessary to configure in this way. That is, both end sides of the belt 15 of the driven piece 17 are arranged so that both ends of the belt 15 intersect with each other on a projection view projected on a plane orthogonal to the rotational axis of the driven piece 17 and the rotary shaft 13. It suffices to extend them in opposite directions along the circumferential surface. Therefore, for example, as shown in FIG. 5, a simple belt-shaped belt 15 is used, and the rotation shaft 11 of the stepping motor 10 is spirally wound in a single or double layer or more. Wind it and attach a part of it to the peripheral surface of the rotating shaft 11 with screws.
Even if it is fixed by 20A or the like, both end sides of the belt 15 are extended in opposite directions along the peripheral surface of the driven piece 17, and the tips thereof are fixed to the driven piece 17 by mounting screws 20B and 20C, respectively. good.

However, in the case of the configuration shown in FIG. 5, when the rotating shaft 11 is rotated, a force for twisting the rotating shaft 11 acts. Therefore, in order to avoid this, for example, as shown in FIG. It is desirable to use two belts 15 shown in the figure to balance the twisting forces of the belts 15.

In FIG. 7, two belts 15 ₁ and 15 are provided as the rotation transmission mechanism 14.
An example using ₂ is shown. As the two belts 15 ₁ and 15 ₂ , steel belts or the like having substantially no elongation and flexibility, and simple belt-shaped belts are used as in the example of FIG. Each belt 15 ₁ and 15 ₂ has one end 1
5B ₁ and 15B ₂ are wound around the rotary shaft 11 of the stepping motor 10 in a single or double or more spiral shape, and the tips thereof are fixed to the peripheral surface 11A of the rotary shaft 11 by mounting screws 23A ₁ and 23A ₂ . The other end portions 15C ₁ and 15C ₂ are extended along the peripheral surface 17A of the driven piece 17, and the tips thereof are fixed to the driven piece 17 by mounting screws 23B ₁ and 23B ₂ . However, both belts 15 ₁ ,
15 the other end side 15C ₁ of _2, the extension direction of the 15C ₂ are opposite to each other, thereby being adapted to cross in projection drawing projected on a plane perpendicular to the rotation axis.

In the example of FIG. 7, the belt shown in FIG. 1 or FIG.
It is possible to consider that 15 is divided into two with the part fixed to the rotating shaft 11 as a boundary, and therefore operates in the same manner as described above.

FIG. 8 shows an example of the overall configuration of an apparatus for carrying out the method of the present invention using the rotation transmission mechanism 14 as shown in each of the above examples.

In FIG. 8, a microcomputer or a dedicated
An operation panel 31, a storage unit (memory) 32, and an input / output interface circuit 33 are connected to the control unit 30 including an IC or the like. A stepping motor drive circuit 34 is connected to the input / output interface circuit 33, and the stepping motor drive circuit 34 drives the stepping motor 10. The rotation shaft 11 of the stepping motor 10 has a rotation transmission mechanism 14 as described above.
Is connected to the rotating shaft 13 of the diffraction grating 12 via. The output signal of the reference position detector 21 for detecting the reference position of the diffraction grating 12 is the input / output interface circuit 33.
It is adapted to be added to the control unit 30 via.

The operation panel 31 is for inputting the wavelength or wave number of light to be selected and other information. In addition to the control program 35, the storage unit 31 stores a wavelength-pulse number table 36 in which the relationship between the wavelength and the stepping motor feed pulse number is tabulated. The wavelength-pulse number table 36 is normally stored in the RAM area. In the wavelength-pulse number table 36, the relationship between the function of the rotation angle θ and the wavelength λ of the diffraction grating 12 and the rotation angle of the diffraction grating 12 when the stepping motor 10 rotates by one pulse (hence this) Is also related to the reduction ratio of the rotation transmission mechanism 14), and the relationship between the wavelength and the number of pulses is previously calculated, and the number is tabulated.

It is needless to say that the table 36 may be obtained not only by calculation but also by correcting the numerical values in the table in advance by wavelength calibration by actual spectroscopy.
Alternatively, the correction coefficient for the numerical value in the table is obtained by wavelength calibration by actual spectroscopy, and the correction coefficient is stored in a separate memory and the numerical value in the table is automatically multiplied by the correction coefficient when the normal wavelength is selected. The calibration may be performed automatically or by inputting the correction coefficient from the operation panel.

As the number of pulses to be set in the wavelength-pulse number table 36, the number of pulses from the position of the 0th order light of the diffraction grating 12 and the diffraction grating 12 will be described later.
And the case where the number of pulses from the reference position (usually a position rotated in the direction slightly negative from the 0th-order light position) is set
There is a street. In the former case, it is necessary to separately store the number of pulses corresponding to the angle from the reference position to the 0th-order light position.

Control signal or wavelength-pulse number table from the control unit 30
The information of the stepping motor feed pulse number read from 36 is given to the stepping motor drive circuit 34 via the input / output interface circuit 33, and the stepping motor 10 is driven according to the excitation sequence given from the drive circuit 34 to the stepping motor 10. To be done. A 5-phase motor, for example, is used as the stepping motor 10.
For example, the rotation angle per pulse is 0.18 °. Further, using the rotation transmission mechanism 14 as shown in FIG. 1, for example, the radius of the rotating shaft 11 of the stepping motor 10 is 5 mm, and the driven piece 17 is
If the radius of the peripheral surface 17A is 51 mm, the rotation transmission mechanism 1
The reduction ratio of 4 is 10.2: 1. Therefore, in this case, when the stepping motor 10 rotates by one pulse, the diffraction grating 12
Will rotate 0.18 ° / 10.2 = 0.017647 °.

Next, the procedure for actually performing wavelength selection using the apparatus shown in FIG. 8 will be described with reference to the flowcharts shown in FIGS. Here, it is assumed that the wavelength-pulse number table 36 stores the number of pulses of each wavelength from the 0th-order light position.

At the time of starting the apparatus, first, according to the 0th-order light position detection sequence of FIG. 9, the stepping motor 10 is pulsed one pulse at a time so that the rotation direction of the diffraction grating 12 becomes a negative direction with respect to the initial position (close to the 0th-order light position). Drive in the negative direction. Diffraction grating 12
A reference position detector 21 is provided at a position rotated by a few degrees in the negative direction with respect to the zero-order light position. If this position is detected, the rotation in the negative direction is stopped and the reference position is detected. Is indexed. Then, the stepping motor 10 is driven in the positive direction by the number of pulses from the reference position to the 0th-order light position stored in advance during adjustment. In this state, the diffraction grating 12 is 0
It has been set to the next light position. Subsequently, according to the initial wavelength setting sequence shown in FIG. 10, the number of pulses corresponding to the wavelength to be set is read from the wavelength-pulse number table 36, and the stepping motor 10 is driven in the positive direction by the number of pulses. By doing so, the diffraction grating 12 is rotated from the reference position in the positive direction by a predetermined angle, and the set wavelength is selected.

After that, when changing the selected wavelength, according to the wavelength changing sequence shown in FIG. 11, the number of pulses from the reference position to the new setting wavelength and the number of pulses from the reference position to the current setting wavelength are the wavelengths. Reading from the pulse number table 36, calculating the difference between these pulse numbers and comparing the new set wavelength with the current wavelength (or comparing each pulse number), if the former is larger than the latter the direction of rotation Is set in the positive direction, and in the opposite case, the rotation direction is set in the negative direction, and the stepping motor 10 is driven in that direction by the pulse number of the difference. In this way a new wavelength is selected.

In the above description, after the apparatus starts to rotate, it rotates in the negative direction to detect the reference position, then temporarily rotates in the positive direction by the number of pulses stored in advance up to the 0th light position, and then read from the table 36. It is driven by the number of pulses corresponding to the set wavelength and rotated to the set wavelength position. Of course, when the reference position is detected, it is set from the number of pulses from the reference position to the 0th-order light position and the 0th-order light position according to table 36. It is also possible to add the number of pulses up to the wavelength position and rotate in the positive direction by the added number of pulses to rotate to the set wavelength position.

Further, as already described, the wavelength-pulse number table 36 may be a table in which the relationship between the number of pulses from the reference position to each wavelength position and the wavelength, rather than the 0th-order light position, is tabulated. After the start-up is started, the reference position is detected by rotating from the initial position to the reference position in the same manner as described above, and then it is possible to immediately drive in the positive direction by the number of pulses of the wavelength set by the table.

Further, when it is desired to set a wavelength not included in the wavelength-pulse number table, for example, the wavelength λ in the table 36 shown in FIG.
_When a wavelength λ _P between ₁ and λ ₂ is set, a linear approximation is performed from the number of pulses S ₁ and S ₂ of wavelengths λ ₁ and λ ₂ on both sides of λ _P.
It is sufficient to interpolate the number of pulses in and drive according to the number of pulses as described above. Of course, in order to perform more accurate interpolation calculation, approximation by a quadratic expression or higher order approximation may be performed instead of linear approximation.

Here, as described above, the wavelength λ and the angle (0
The relationship with the angle from the next light position) θ is expressed by the above equation (1). Then, under a specific condition, the equation (3) is established. In equation (3), if the wavelength used is 190 to 700 nm, the change in θ per 1 nm is 0.034 to 0.038 °. Therefore, if θ can be changed with a precision of 0.034 ° or less, the wavelength accuracy is ± 1nm or less will be realized. As described above, the stepping motor used is a motor with a rotation angle of 0.18 ° per pulse, and when the reduction ratio between the rotation axis of the stepping motor and the rotation axis of the diffraction grating is 10.2: 1, the stepping motor is The rotation of one pulse causes the diffraction grating to rotate by 0.017647 °, which is about half of the above-mentioned 0.034 °, which means that in this case, wavelength accuracy of about ± 0.5 nm or less can be realized. Of course, if the reduction ratio between the rotation axis of the stepping motor and the rotation axis of the diffraction grating is further increased, the wavelength accuracy can be further improved, and it is possible to achieve up to ± 0.2 nm or less. Table 1 shows the number of wavelength pulses (0
As an example of the number of pulses sent from the next light position) and the table, a table under the above-mentioned conditions is shown.

In the above description, the relationship between the wavelength and the stepping motor feed pulse number was tabulated, but if you want to set the light of the wavelength to be set with that wave number, you should create a table of the relationship between the wave number and the pulse number. Wave number-
The number of pulses up to the selected wave number position may be read by referring to the pulse number table, and the pulse number may be given to the stepping motor to rotate the diffraction grating to the position of the set wave number. Furthermore, in some cases, the wavelength-pulse number table and wave number-
Both the pulse number table and the pulse number table may be stored and the pulse number may be read from either one of the tables by designating the wavelength setting or the wave number setting during operation. In this case, the same device is used. Both wavelength setting and wave number setting can be performed with. As described above, in the present invention, it is also an important feature that the wavelength setting and the wave number setting can be arbitrarily changed without changing the device configuration.

In addition, although the diffraction grating is used as the spectroscopic element in the above description, it is needless to say that the present invention can be applied to the case where a prism is used as the spectroscopic element. However, in the case of a prism, since the refractive index is related to the relationship between the wavelength and the rotation angle of the spectroscopic element, the wavelength (or wave number) -stepping motor feed pulse number table also includes the value of the refractive index of the prism. Of course, it is necessary to create it from the relational expression.

EFFECTS OF THE INVENTION The wavelength selection driving method of the spectroscopic element of the present invention is a rotation transmission mechanism for directly giving a rotation motion by a stepping motor to the diffraction grating as a rotation motion, and a portion having a belt which is substantially inextensible is provided. Backlash is the principle when the spectroscopic element is driven to rotate, because it is fixed to a part of the peripheral surface of the rotation shaft of the stepping motor, and the other part is fixed to a driven piece that is integrated with the spectroscopic element. Does not occur,
Further, no slippage occurs between the belt and the rotating shaft or between the belt and the driven piece, so that the reproducibility of wavelength selection is good and the wavelength scanning speed is improved. Further, in the case of the present invention, the relationship between the wavelength or / and the wave number and the number of feed pulses of the stepping motor is made into a table in advance, and when the wavelength is set, the table is referred to give the required number of pulses to the stepping motor to set the wavelength. Therefore, there is an advantage that the time required for calculating the number of pulses for wavelength setting is shortened and the number of memories is small. Further, in the method of the present invention, when setting the wavelength of the light to be obtained, even when the setting is changed from the state of setting the wavelength value to the state of setting the wave number value, or vice versa, the apparatus configuration is There is also an advantage that it is possible to change the table only by exchanging the table or designating the table without changing.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of mechanical components of an apparatus used for carrying out the method of the present invention, particularly an example in which a belt is used for a rotation transmission mechanism, and FIG. 2 is an apparatus shown in FIG. FIG. 3 is a perspective view of a belt wound around the belt used in FIG. 3, FIG. 3 is a developed view of the same belt, FIG. 4 is a schematic plan view for explaining the operation of the rotation transmission mechanism shown in FIG. 1, and FIG. 7 to 7 are perspective views showing other examples in which a belt is used for the rotation transmission mechanism, and FIG. 8 shows an example of the overall constitution of the apparatus used for carrying out the method of the present invention. FIG. 9 is a block diagram, FIG. 9 to FIG. 11 are flow charts showing an example of concrete procedures for carrying out the method of the present invention.
FIG. 12 is a schematic plan view showing an example of a diffraction grating driving method in a conventional spectroscopic device. 10 ... Stepping motor, 11 ... Rotation axis, 12 ... Diffraction grating as a spectroscopic element, 13 ... Rotation axis, 14 ... Rotation transmission mechanism, 15 ... Belt, 17 ... Driven piece, 21 ... ... Reference position detector, 30 ... control section, 31 ... operation panel, 32 ... storage section, 34 ... stepping motor drive circuit, 35 ... control program, 36 ... wavelength-pulse number table.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-50-127649 (JP, A) JP-A-60-33019 (JP, A) JP-A-52-20844 (JP, A) JP-A-58- 55723 (JP, A) JP 62-103528 (JP, A) Actually developed 60-41834 (JP, U)

Claims (2)

[Claims] 1. A wavelength selection driving method in a spectroscopic device in which a wavelength of light to be emitted is changed by changing an angle of a spectroscopic element, wherein a: a stepping motor is used as a wavelength selection driving source, and b: and its stepping As a rotation transmission mechanism for transmitting the rotation of the rotation shaft of the motor to the rotation shaft of the spectroscopic element; the circumference of the rotation shaft of the spectroscopic element forming at least a part of a cylindrical surface centered on the rotation axis. A driven piece having a surface is fixed, and a rotation shaft of a stepping motor is arranged parallel to the rotation axis at a position close to the peripheral surface of the driven piece. The belt having no flexibility and flexibility is wound around the intermediate portion in the length direction in a single or double layer, and a part of the wound part is attached to a part of the peripheral surface of the rotating shaft. Fixed and its bell Both end sides of the belt are extended in opposite directions along the peripheral surface of the driven piece so that both end sides of the belt intersect on a projection view projected on a plane orthogonal to the rotation axis. Using a structure in which both ends are fixed to the driven piece, c: In addition, the relationship between the wavelength or / and the wave number and the pulse number for driving the stepping motor is tabulated and stored in advance, d: When selecting a wavelength, refer to the table above to read the number of pulses corresponding to the wavelength or wave number to be set, and apply that number of pulses to the stepping motor to rotate the spectroscopic element a required angle to set the wavelength or wave number. A method for driving a wavelength selection in a spectroscopic device, comprising: 2. A wavelength selection driving method in a spectroscopic device in which a wavelength of light to be emitted is changed by changing an angle of a spectroscopic element, wherein a: a stepping motor is used as a wavelength selection driving source, and b: and its stepping As a rotation transmission mechanism for transmitting the rotation of the rotation shaft of the motor to the rotation shaft of the spectroscopic element; the circumference of the rotation shaft of the spectroscopic element forming at least a part of a cylindrical surface centered on the rotation axis. A driven piece having a surface is fixed, and at a position close to the peripheral surface of the driven piece,
The rotation shaft of the stepping motor is arranged in parallel with the rotation axis, and one end side of each of the first belt and the second belt which is substantially inextensible and has flexibility on the peripheral surface of the rotation shaft. Part is wound in a single layer or in a double layer or more and its tip end is fixed to the rotating shaft, and the other ends of the first belt and the second belt are projected on a plane orthogonal to the rotation axis. The other end side of each belt is extended in opposite directions along the peripheral surface of the driven piece so that each end is fixed to the driven piece so as to intersect with each other on the projection view. C: Moreover, the relationship between the wavelength or / and the wave number and the pulse number for driving the stepping motor is tabulated and stored in advance, and d: set by referring to the table when selecting the wavelength. Corresponds to the desired wavelength or wave number Reads the pulse number, the wavelength selection drive method in the spectral apparatus that number of pulses the spectral element is required angle rotated by providing a stepper motor to set the wavelength or wavenumber, characterized in that.