JPH10104069A - Spectrophotometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify angular phase regulation between a diffraction grating and an angle detection means by coupling the diffraction grating intermittently with the angle detection means. SOLUTION: A light to be analyzed from a light source A enters through an inlet slit 1 and a first concave reflector 2 into a diffraction grating 3 where it is reflected at every reflection angle corresponding to the wavelength thereof. The reflected light to be analyzed is condensed at an outlet slit 5 through a second concave reflector 4 and then detected at a detecting section 6. The diffraction grating 3 is rotary driven through a drive motor 7 coupled therewith. An electromagnetic clutch 8 couples the drive motor 7 intermittently with the diffraction grating 3. A rotary encoder 9 detects the rotational angle of the diffraction grating 3 through the drive motor 7. Furthermore, a coupling control means 10 is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spectroscopic analyzer for analyzing analysis light by a diffraction grating.

[0002]

2. Description of the Related Art In general, there is a so-called Czerny-Turner type shown in FIG. 3 as a spectroscopic analysis optical system for separating an analysis light by a diffraction grating. A spectrometer using this optical system analyzes the analysis light as follows. That is, the analysis light entered from the light source A such as an ICP via the entrance slit 50 is made incident on the diffraction grating 52 via the first concave reflecting mirror 51, and the analysis light is converted into an angle corresponding to the wavelength. To reflect. Of the reflected light, light of a specific wavelength is the second
Is focused on the exit slit 54 via the concave reflecting mirror 53 of
The light passes therethrough and is detected by a detection unit (for example, a photomultiplier tube) 55.

In this type of spectroscopic analyzer, the angle position of the diffraction grating is finely adjusted in accordance with the wavelength of the analysis light to be analyzed, so that the analysis light is condensed at the exit slit 54 and separated. For this purpose, the diffraction grating 52 is provided with a rotating means 56 such as a sine bar mechanism for rotating the diffraction grating 52.

[0004] The rotation means 56 is configured to estimate the rotation angle of the diffraction grating 52 from the driving amount thereof, but it is sufficiently high to estimate the rotation angle from the driving amount of the rotation means 56. It was difficult to obtain the angular position adjustment accuracy. Therefore, by moving the opening position of the exit slit 54 to the condensing position of the second concave reflecting mirror 53, the angular position adjustment error has been corrected.

However, if the exit slit 54 is slid to correct the angle detection error, the angle adjustment operation requires time and lacks the speed of analysis.

[0006] Therefore, it has been considered to directly detect the rotation angle using a rotary encoder. However, the diffraction grating 52 requires very high angle detection control.
Obtaining such a high angle detection accuracy with a rotary encoder has the disadvantage that the costs are not balanced. This will be described below.

Generally, an inexpensive rotary encoder is
A number of slits are provided along the circumferential direction on a rotating plate that rotates integrally with the detection target (diffraction grating 52), the amount of light passing through the slits is converted into an electric signal, and the wave number is formed after the electric signal is shaped into a waveform. The rotation angle of the diffraction grating 52 is detected based on the counted number. In an inexpensive rotary encoder having such a configuration, the angle detection accuracy and resolution depend on the slit forming accuracy and the slit interval, and a highly accurate angle detection cannot be performed by a normal use method. In order to accurately detect the rotation angle of the diffraction grating 52, an expensive rotary encoder with high detection accuracy must be used, and the spectral analyzer cannot be configured at low cost.

On the other hand, attempts have been made to devise a highly accurate angle detection using an inexpensive incremental type rotary encoder. This is to detect in advance the signal level of an electric signal obtained by converting the amount of light passing through the slit with a light-receiving element such as a photodiode using an inexpensive rotary encoder in correspondence with an angle smaller than one cycle in each cycle of the signal waveform Then, the correspondence between the signal level and the rotation angle is stored with data obtained by simply calibrating the angle sensor with higher accuracy, thereby improving the accuracy and resolution.

In order to detect an angle with high accuracy using an inexpensive rotary encoder in this way, the angle of the detection target corresponding to the signal level of the electric signal before waveform shaping is detected with high accuracy in advance. It is necessary to store the correspondence information in the memory. For example, this is achieved by connecting an expensive rotary encoder with high detection accuracy to an inexpensive rotary encoder, and rotating both in this state to obtain an inexpensive rotary encoder. The period of the electric signal (after waveform shaping) of the rotary encoder and the signal level of the electric signal (before waveform shaping) are measured. Then, the information on the measured cycle and the information on the signal level are stored in the memory in correspondence with the highly accurate angle information detected by the expensive rotary encoder. When the storage operation of such angle information is completed, the expensive rotary encoder is removed from the cheap rotary encoder. Therefore, a single expensive rotary encoder can perform the calibration data collection operation of many inexpensive rotary encoders.

By performing such a calibration data collection operation, the rotation angle of the detection target (diffraction grating 52) can be detected with higher accuracy even with an inexpensive rotary encoder. The data sampling operation must be performed for each inexpensive rotary encoder, and the calibration data sampling requires an enormous number of measurement points as the angular resolution is increased, requiring an enormous data storage area. In addition, the measurement requires a long time. Therefore, it has been considered to shorten the time for collecting calibration data as follows.

That is, in the spectroscopic analyzer, since the emission wavelength or the absorption wavelength corresponding to the number of elements to be analyzed is limited, it is not necessary to disperse light in a wide range of wavelengths. Has a limited angle range, such as an angle near a center corresponding to some specific wavelengths.

Therefore, it is not necessary to collect the calibration data of the rotary encoder for the entire angular range of the rotation range of the diffraction grating 52. The calibration data is obtained only for some rotation angles of the diffraction grating 52 and the angle range in the vicinity thereof. The sampling range of the calibration data can be shortened by limiting the sampling range of the calibration data in this way.

[0013]

However, there are the following problems. That is, a reference angle position of the diffraction grating 52 (for example, an angle position for dispersing zero-order light that is total reflection light) and a reference angle position of the rotary encoder (for example,
(The reference pulse waveform generation angle position), it is necessary to match the angular phase within the accuracy corresponding to the width of the calibration data centered on the angle corresponding to one wavelength collected at the time of calibration, and to connect them. The task is to reduce the width of the calibration data,
It becomes more difficult as the calibration time is reduced.

[0014]

The present invention achieves the above-mentioned object by the following means.

According to the first aspect of the present invention, a diffraction grating for dispersing the incident analysis light, a rotating means for rotating the diffraction grating, and a diffraction grating or a rotation of the diffraction grating connected to the rotating means. In a spectroscopic analyzer provided with angle detecting means for detecting a moving angle, an intermittent means for intermittently connecting a diffraction grating or a rotating means and the angle detecting means is provided.

According to a second aspect of the present invention, there is provided the spectroscopic analyzer according to the first aspect, further comprising a connection control means, wherein the connection control means maintains the connection operation of the intermittent means and the diffraction grating. Or, the rotating means is rotated until one of the angle detecting means reaches the reference angle position, and in this state, the connecting operation of the intermittent means is released, and the other of the diffraction grating or the angle detecting means is returned to the reference angle position. The turning means is turned again until it reaches, and then the connecting operation of the intermittent means is restarted.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing an overall configuration of a spectroscopic analyzer according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing a configuration of a main part thereof.

This spectroscopic analyzer has a Czerni-Turner type optical system, and its configuration is basically the same as that of the conventional one. That is, the analysis light entered from the light source A such as an ICP via the entrance slit 1 is incident on the diffraction grating 3 via the first concave reflecting mirror 2, and the analysis light is changed according to the wavelength. Reflect at each reflection angle. The reflected analysis light is condensed on the exit slit 5 via the second concave reflecting mirror 4, passes therethrough, and is detected by the detection unit (for example, a photomultiplier tube) 6. A drive motor 7 is connected to the diffraction grating 3, and the diffraction grating 3 is driven to rotate by the drive motor 7. Between the drive motor 7 and the diffraction grating 3, there is provided an electromagnetic clutch 8 for intermittently connecting the drive motor 7 and the diffraction grating 3. The drive motor 7 includes a rotary encoder 9.
Are connected. The rotary encoder 9 detects the rotation angle of the diffraction grating 3 via the drive motor 7.
Further, the spectrometer is provided with a connection control means 10. The connection control means 10 includes, for example, a part of a control unit that controls the entire spectroscopic analyzer.

The connection state of the diffraction grating 3, drive motor 7, and rotary encoder 9 will be described with reference to FIG. That is, the support shaft 11 of the diffraction grating 3 is connected to the frame 12 of the spectroscopic analyzer.
Is rotatably mounted via a bearing 13. The tip of the support shaft 11 is connected to the drive motor 7 via an electromagnetic clutch 8.
Of the driving shaft 14. The support shaft 11 is connected to one end 14 a of the drive shaft 14. Drive motor 7
Are supported by a support frame 15 attached to the frame 12. The other end 14 b of the drive shaft 14 protrudes from the drive motor 7, and the other end 14 b is connected to the rotary encoder 9 via a coupling 16. The rotary encoder 9 is supported by a support frame 17 attached to the drive motor 7. The rotary encoder 9 is an inexpensive rotary encoder, that is, a rotary plate that rotates integrally with the detection target (diffraction grating 3) is provided with a number of slits along its circumferential direction, and converts the amount of light passing through these slits into an electric signal. Convert.

For this rotary encoder 9,
The following calibration operation has been performed in advance. That is, an expensive rotary encoder with high detection accuracy (not shown)
Is further connected to the rotary encoder 9, and in this state, the drive motor 7 is moved from the reference angular position of the rotary encoder.
To measure the period of the electric signal of the rotary encoder 9 and the signal level of the electric signal. Then, information on the measured count number of the cycle and information on the signal level are stored in a memory (not shown) in association with highly accurate angle information detected by an expensive rotary encoder. The signal level is stored together with the peak level of the adjacent periodic waveform, and the ratio between the two is used as the calibration value, thereby reducing the influence of the characteristic fluctuation of the light emitting element and the light receiving element. The calibration data is based on the rotation angle (α) of the diffraction grating 3 according to the element to be analyzed.
°, β °, γ °, ...) and the angle range in the vicinity thereof, and no calibration data was collected for the other angle ranges. It is simplified.

After simplifying the operation of collecting the calibration data, when the rotary encoder is mounted on the analyzer, the reference angle position of the diffraction grating 3 (for example, the zero-order light, which is the total reflection light, is not detected). It is necessary to match the angular phase between the angular position for splitting the light and the reference angular position of the rotary encoder 9 (for example, the reference pulse wave generation angular position) with sufficient accuracy. Hereinafter, this angle phase adjustment operation will be described.

First, a connection command signal S1 is transmitted from the connection control means 10 to the electromagnetic clutch 8. The electromagnetic clutch 8 that has received the connection command signal S1 connects the drive motor 7 and the diffraction grating 3. When the drive motor 7 and the diffraction grating 3 are connected, the connection control means 10 transmits a drive command signal S2 to the drive motor 7. The drive motor 7 receiving the drive command signal S2 starts the rotation drive, and slowly rotates the diffraction grating 3 in an arbitrary direction. At this time, the detection unit 6 simultaneously performs a spectrum detection operation of the analysis light separated by the diffraction grating 3 and transmits the detection signal L to the connection control unit 1.
Output to 0.

In this manner, the operation of taking in the detection signal L is performed while the rotation operation of the diffraction grating 3 is continued. When the connection control means 10 detects that the spectral peak is condensed on the exit slit 5 (this can be understood by analyzing the increase or decrease of the detection signal L), the connection control means 10 sets the diffraction grating 3 to the reference angle. When it is determined that the position has been reached, the drive stop signal S3 is transmitted to the drive motor 7. The drive motor 7 receiving the drive stop signal S3 stops the rotation operation of the diffraction grating 3. When the drive operation of the diffraction grating 3 by the drive motor 7 stops, the connection control means 10 transmits a connection release signal S4 to the electromagnetic clutch 8. The electromagnetic clutch 8 that has received the connection release signal S4 releases the connection between the drive motor 7 and the diffraction grating 3.

At this time, the rotational angle position of the diffraction grating 3 may be displaced from the reference angle position due to the impact of the disconnection operation of the electromagnetic clutch 8. In order to detect such a displacement change, the detection unit 6 continues the spectrum detection operation of the analysis light and outputs the detection signal L to the connection control unit 10 even during the operation of releasing the connection of the electromagnetic clutch 8. Then, the connection control means 10 detects whether or not the diffraction grating 3 has rotated based on whether or not the detection signal L has changed during the operation of releasing the connection of the electromagnetic clutch 8. When it is determined that the electromagnetic clutch 8
After the diffraction grating 3 and the drive motor 7 are connected to each other, the operation of adjusting the reference angular position of the diffraction grating 3 described above is repeated.

On the other hand, if the diffraction grating 3 is not displaced from the reference angle position even if the connection of the electromagnetic clutch 8 is released,
When the connection control unit 10 determines, the connection control unit 10 transmits the drive command signal S2 to the drive motor 7 again. The drive motor 7 that has received the drive start command signal S2 restarts the rotational drive. When the drive motor 7 resumes the rotation drive, the connection control means 10 takes in the angle detection signal K of the rotary encoder 9. At this time, the electromagnetic clutch 8 has released the coupling operation, and the diffraction grating 3 does not rotate.
The reference angle position is maintained. When the connection control means 10 detects that the angle position of the rotary encoder 9 has reached the reference pulse waveform generation angle position which is the reference angle position (this can be understood by analyzing the angle detection signal K), the connection control is performed. The means 10 transmits a drive stop signal S3 to the drive motor 7. The drive motor 7 receiving the drive stop signal S3 stops driving. When the drive motor 7 stops driving, the connection control means 10 transmits a connection command signal S1 to the electromagnetic clutch 8. The electromagnetic clutch 8 that has received the connection command signal S1 restarts the connection operation, and connects the diffraction grating 3 and the drive motor 7 in an interlocked manner.

At this time, the rotational angle position of the diffraction grating 3 may deviate from the reference angle position, or the rotary encoder 9 may deviate from the reference angle position, due to the impact of the coupling operation of the electromagnetic clutch 8. . In order to detect such an angle change, the detection unit 6 continues the analysis light spectrum detection operation to output the detection signal L to the connection control means 10 even during the connection restart operation of the electromagnetic clutch 8, while the connection control means 10 Is the angle detection signal K of the rotary encoder 9
Continue the import operation. And the connection control means 10
Then, from the presence or absence of the fluctuation of the detection signal L or the fluctuation of the angle detection signal K during the connection restart operation of the electromagnetic clutch 8,
When the misalignment of the diffraction grating 3 and the rotary encoder 9 is detected, and it is determined that the misalignment of the diffraction grating 3 and the rotary encoder 9 is caused by the operation of restarting the connection of the electromagnetic clutch 8,
Perform the following operations.

That is, the diffraction grating 3 or the diffraction grating 3
When it is determined that both the rotary encoder 9 and the rotary encoder 9 are displaced, the connection between the diffraction grating 3 and the drive motor 7 by the electromagnetic clutch 8 is maintained, and the process returns to the above-described reference angle position angle adjustment operation of the diffraction grating 3. Repeat the operation. On the other hand, if it is determined that the diffraction grating 3 has not been displaced and only the rotary encoder 9 has been displaced, the coupling between the diffraction grating 3 and the drive motor 7 by the electromagnetic clutch 8 is released, and the reference of the rotary encoder 9 is determined. Return to the angle position adjustment operation and repeat the operation. By repeating such a displacement adjustment operation until the diffraction grating 3 and the rotary encoder 9 no longer displace, the angular phase between the diffraction grating 3 and the rotary encoder 9 is accurately adjusted.

In the above embodiment, the electromagnetic clutch 8 is arranged between the drive motor 7 and the diffraction grating 3, but the present invention is not limited to such an embodiment. That is, while the drive motor 7 and the diffraction grating 3 are directly and interlocked, the drive motor 7 and the rotary encoder 9 are connected.
The electromagnetic clutch 8 may be arranged between the two. In this case, a reference angle position adjustment operation of the rotary encoder 9 in a state where the electromagnetic clutch 8 is interlocked, an operation of adjusting the reference angle position of the diffraction grating 3 in a state where the electromagnetic clutch 8 is released, The angle phase adjustment operation may be performed in the order of reconnection.

[0029]

As described above, according to the present invention, the following effects can be obtained. The angle phase adjustment between the reference angle position of the diffraction grating and the reference angle position of the angle detecting means, which is performed to simplify the operation of collecting the calibration data, can be easily performed.

Further, even when the diffraction grating and the angle detecting means are damaged and need to be replaced, the user can easily determine the reference angle position of the diffraction grating and the reference angle position of the angle detecting means. Can be adjusted in phase. Therefore, it is possible to maintain highly accurate angle detection even when the diffraction grating and the angle detecting means are replaced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of a spectroscopic analyzer according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a main part of the spectroscopic analyzer according to one embodiment of the present invention.

FIG. 3 is a diagram showing an overall configuration of a conventional spectroscopic analyzer.

[Explanation of symbols]

 A light source 3 diffraction grating 6 detection unit 7 drive motor 8 electromagnetic clutch 9 rotary encoder 10 connection control means

Claims (2)

[Claims] 1. A diffraction grating for dispersing incident analysis light, a rotation unit for rotating the diffraction grating, and an angle detection coupled to the diffraction grating or the rotation unit to detect a rotation angle of the diffraction grating. A spectroscopic analyzer comprising: means for interrupting the connection between the diffraction grating or the rotating means and the angle detecting means. 2. The spectroscopic analyzer according to claim 1, wherein
Further comprising a connection control means, the connection control means, while maintaining the connection operation of the intermittent means, to rotate the rotation means until one of the diffraction grating or the angle detection means reaches its reference angular position, In this state, the connecting operation of the interrupting means is released, and the rotating means is rotated again until the other of the diffraction grating or the angle detecting means reaches the reference angle position, and then the connecting operation of the interrupting means is restarted. A spectroscopic analyzer characterized by the following.