JP2013011473A - Spectrophotometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spectrophotometer that divides a measuring beam into beams with different modes with a rotating rotation sector mirror, and that enables adjustment of data integration period setting of each mode.SOLUTION: When a control part 20 receives an instruction to integrate a signal of a mode D1 from a change detection part 19, the control part 20 refers to a delay time Td1 corresponding to the mode D1 in a delay time storage part 21. Then, the control part 20 continues to send a data collection signal for a prescribed period to an ADC 18 after a delay time Td1 passed from when receiving the instruction from the change detection part 19. The ADC 18 samples a light intensity signal from a photodetector 17, converts the light intensity signal into digital values while receiving the data collection signal, and sends the digitalized values to an integration processing part 22. The integration processing part 22 integrates data acquired from the ADC 18. The integrated values are sent to the control part 20, and then stored by the control part 20 in a storage region, in an integration value storage part 23, corresponding to the mode D1.

Description

  The present invention relates to a spectrophotometer, and more particularly to a double beam type spectrophotometer that divides measurement light into a sample-side light beam and a reference-side light beam by a rotating sector mirror.

  The spectrophotometer has a double beam method and a single beam method depending on the configuration of the optical path. The double beam method is more advantageous than the single beam method in terms of analysis accuracy because it is possible in principle to cancel the influence of the light amount fluctuation of the light source in the process of calculating the absorbance.

  In a double beam type spectrophotometer, in order to divide monochromatic light extracted by a spectroscope (monochromator) into a sample-side light beam and a reference-side light beam, the light beam is split mainly using a beam splitter, and a rotating sector mirror is used. One of the distribution of the luminous flux is used. The beam splitter method divides monochromatic light into a sample-side light beam and a reference-side light beam at a certain ratio by the beam splitter and irradiates the sample to be measured and the reference sample, and two photodetectors that handle each transmitted light beam. It is something to introduce against.

  On the other hand, the rotating sector mirror method irradiates the sample to be measured and the reference sample by alternately allocating (switching) the monochromatic light to the sample-side light beam and the reference-side light beam by the sector mirror that is driven to rotate at a constant speed. Light is alternately introduced into one photodetector (see Patent Document 1). In this configuration, generally, in order to measure a dark signal in a state where light is not incident on the photodetector, a light-shielding portion that shields light is provided in the rotating sector mirror.

  In a double beam type spectrophotometer, it is common to detect each signal of a sample signal, a reference signal, and a dark signal for each wavelength while performing wavelength scanning. At this time, it is desirable that the frequency of light beam switching be high in order to ensure the simultaneity of the signals. On the other hand, the detection signal at the photodetector greatly changes due to the switching of the light beam, but the change of the detection signal is not instantaneous, and it takes time to completely change. The time required for the detection signal to completely change with the light beam switching is referred to as “light beam switching time”. When the light beam switching frequency is high, the ratio of the light beam switching time included in the unit time increases. This is disadvantageous in ensuring a sufficient S / N ratio for each signal. As described above, a high-speed rotation of about 1500 rpm to 2000 rpm is required for a motor used for rotational driving of the rotating sector mirror in order to balance the simultaneity of each signal and securing the S / N ratio. In such a spectrophotometer, after the apparatus is once operated, the measurement is generally not interrupted even during idling. From the above requirements, a special motor that does not require special control and can rotate at high speed is often used as a drive source for the rotating sector mirror.

  Some spectrophotometers may use a stepping motor as a drive source for the rotating sector mirror. However, stepping motors are not suitable for high-speed rotation that can handle wavelength scanning of spectrophotometers. Since there is a problem that vibration, heat generation, and abnormal noise are generated as the rotational speed is increased, it is rarely used for such applications.

  As described above, a special drive circuit is not required for driving a synchronous motor. However, since a rotational position cannot be directly specified as in a stepping motor, measurement signals, reference signals, It is necessary to grasp the switching timing of the dark signal, that is, the measurement start timing and the measurement end timing in each of the aforementioned signals. For grasping this timing, a rotating sector mirror having a structure as shown in FIG. 5 and a photo interrupter arranged in the vicinity thereof are generally used.

  As shown in the side view of FIG. 5A, the rotating sector mirror 100 has one rotating shaft 100c, and a first sector plate 100a and a second sector plate 100b fixed to the rotating shaft 100c. . The first sector plate 100a has four fan-shaped shielding plates 101 that block the incident light beam to the rotating sector mirror 100 (FIG. 5 (c)), and the second sector plate 100b reflects the incident light beam. The fan-shaped mirror 102 is provided (FIG. 5D). FIG. 5 (b) is a front view of the rotating sector mirror 100 having the two sector plates 100a and 100b. As shown in FIG. 5B, the rotating sector mirror 100 viewed from the front has an opening 103 that does not include the shielding plate 101 and the mirror 102 and through which the incident light beam to the rotating sector mirror 100 can pass. The light that has passed through the opening 103 becomes a sample-side light beam and is irradiated on the sample to be measured. Further, the light reflected by the mirror 102 becomes a reference-side light beam and is irradiated on the reference sample.

  Hereinafter, the opening 103 is referred to as a sample light portion. Further, the shielding plate 101 is referred to as a light shielding portion, and the mirror 102 is referred to as a reference light portion. These parts are collectively referred to as sector parts. In the example of FIG. 5B, the rotating sector mirror 100 has eight sector parts, and there are four light shielding parts 101, two reference light parts 102, and two sample light parts 103, respectively. Become. Each sector section is configured to be 180 ° rotationally symmetric.

  When the incident light beam on the rotating sector mirror 100 is incident on the position L in FIG. 5B and the rotating sector mirror 100 rotates in the direction of arrow D, the position of the incident light beam is rotated while the rotating sector mirror 100 makes one rotation. The light shielding part 101 → the reference light part 102 → the light shielding part 101 → the sample light part 103 → the light shielding part 101 → the reference light part 102 → the light shielding part 101 → the sample light part 103 comes in order in L. Also, the incident light beam distribution mode by the rotating sector mirror 100 is as follows: light shielding (D) → reflection (R) → light shielding (D) → passing (S) → light shielding (D) → reflection (R) → light shielding (D) → It will be switched in the order of passing (S).

Mode switching by the rotating sector mirror 100 is detected as follows.
A light-shielding portion tab 101a is provided on the outer periphery of each shielding plate (light-shielding portion) 101 of the first sector plate 100a, and the light-emitting element and the light-receiving element sandwich the orbit on the rotation orbit of the light-shielding part tab 101a. A first photo interrupter 104 is provided. Further, a reference light portion tab 102a is provided on the outer periphery of each mirror (reference light portion) 102 of the second sector plate 100b, and the second light is placed on the rotation orbit of the reference light portion tab 102a so as to sandwich the orbit. A photo interrupter 105 and a third photo interrupter 106 are provided. The positions at which these three photo interrupters 104, 105, and 106 are arranged vary depending on the configuration of the rotating sector mirror 100. For example, as shown in FIG. Are arranged every 90 ° along the direction of rotation of the rotating sector mirror 100.

  When the rotating sector mirror 100 rotates in the direction of arrow D (counterclockwise), the positional relationship among the sector portions of the rotating sector mirror 100, the incident light beam, and the photointerrupters 104, 105, and 106 is as shown in FIGS. Will change. Here, in the case of the positional relationship as shown in FIG. 6, it is indicated that the light shielding portion tab 101 a blocks the light from the light emitting element of the first photo interrupter 104 and detects the light shielding portion tab 101 a from the first photo interrupter 104. A tab detection signal is output. In the case of FIG. 7, tab detection signals are output from the third photo interrupter 106, in the case of FIG. 8, from the first photo interrupter 104, and in the case of FIG. 9, from the second photo interrupter 105, respectively.

When the tab detection signal is output from the first photo interrupter 104 (that is, in the state shown in FIGS. 6 and 8), the incident light beam to the rotating sector mirror 100 is blocked by the light blocking unit 101. When a tab detection signal is output from the third photo interrupter 106 (in the state shown in FIG. 7), the incident light beam is reflected by the reference light unit 102. When a tab detection signal is output from the second photo interrupter 105 (in the state shown in FIG. 9), the incident light beam passes through the sample light unit 103. In this way, it is possible to grasp in which mode the incident light flux to the rotating sector mirror 100 is distributed depending on which of the photo interrupters 104, 105, and 106 outputs the tab detection signal.
The control unit of the spectrophotometer determines which mode the detection signal from the photodetector is acquired based on which of the photo interrupters 104, 105, and 106 outputs the tab detection signal, A detection signal for each mode is acquired, and integration processing and averaging processing are performed as necessary.

  In the above description, the tabs are arranged over the entire outer periphery of each sector part. However, depending on the light beam state and the required time for the detection signal, the tabs can be provided only on a part of the outer periphery of each sector part. Further, this tab can be arranged at an arbitrary position on the outer periphery of the sector portion.

JP 2001-356049 A

  In a double beam spectrophotometer using a rotating sector mirror, as described above, the detection signal at the photodetector changes greatly by switching the mode (light beam), but it takes some time to change completely. Cost. This is because the light beam incident on the rotating sector mirror has a constant diameter, so that it takes time for the light beam to pass through the boundary of each sector on the rotating sector mirror, and the photodetector and the subsequent amplification circuit. This is because it takes time to stabilize the signal due to the frequency response characteristics of the circuit including the above. As described above, since it is impossible to accurately detect the mode switching time point, in consideration of the time width of the mode switching in the conventional apparatus, the data is not changed after the mode switching is completed. The position of the photo interrupter has been adjusted so as to start acquisition. A conventional method for adjusting the position of the photo interrupter will be described with reference to FIG.

  FIG. 10 is a diagram for explaining the arrangement of photo interrupters with respect to an incident light beam having a predetermined diameter. For example, as shown in FIG. 10A, the first photo interrupter 104 detects the light shielding portion tab 101a in a state where the light shielding portion 101 of the first sector plate 100a is not completely within the range of the incident light beam. Then, at first, the photodetector outputs a detection signal in a mode other than the light shielding mode, but the control unit acquires data as a detection signal for the light shielding mode.

  Therefore, as shown in FIG. 10B, the first photo interrupter 104 is set so that the first photo interrupter 104 detects the light shielding portion tab 101a in a state where the light shielding portion 101 is completely within the range of the incident light beam. Deploy. Thereby, the control unit can acquire only the detection signal for the light shielding mode.

  This is only described with respect to the incident light beam, but in addition to this, there are problems related to microscopic fluctuations (rotation unevenness such as jitter) of the rotational speed (rotation speed) of the rotating sector mirror and the frequency response of the photodetector. There is also. Further, when the incident light to the rotating sector mirror 100 is incident from an oblique direction, the incident position of the light to each sector plate is slightly different from that when viewed from the front. Since these all affect the start time of each mode and thus the measurement accuracy of the spectrophotometer, the setting of the data acquisition start time considering these is an important step in manufacturing the device. .

  In addition, a synchronous motor generally used as a driving source for a rotating sector mirror has a problem that the number of rotations depends on a power supply frequency. For this reason, adjustment corresponding to the power supply frequency in each region where the apparatus is used, and adjustment taking into account minute fluctuations in the power supply frequency are necessary. Further, when the rotational speed of the rotating sector mirror is changed, the integration time of the detection signal is changed accordingly, so that the S / N ratio of the measurement result is changed. Therefore, there is also a problem that the device performance varies from region to region. Originally, it is desirable that the rotational speed of the rotating sector mirror be variable according to the response speed of the photodetector, but it is not easy to change the rotational speed of the synchronous motor.

  The present invention has been made to solve the above-described problems, and a main object thereof is to provide a spectrophotometer that facilitates adjustment related to setting of a data integration period in each mode.

The present invention made to solve the above problems
A rotating sector mirror that has at least two sector portions and distributes measurement light into at least two modes corresponding to each sector portion; and a photodetector that measures the light intensity of each mode and generates a light intensity signal. In the spectrophotometer provided,
A rotational position detector for detecting the rotational position of the rotating sector mirror set for each mode;
A delay time storage unit for storing a delay time for each mode;
A measurement period storage unit for storing a measurement period for each mode;
After receiving the detection signal from the rotational position detector, the light intensity from the photodetector only during the measurement period of the corresponding mode after being delayed by the delay time of the mode corresponding to the detection signal. A measurement control unit for acquiring a signal as a measurement value;
It is characterized by providing.

  The spectrophotometer according to the present invention is characterized in that the measurement timing for each sector can be adjusted by software by setting the delay time and the measurement period for each sector. In the spectrophotometer of the present invention, even if there is a mechanical error in the apparatus, it can be adjusted so that the deviation is absorbed by the setting of the delay time and the measurement period. Significantly reduced. Even when a synchronous motor is used as the drive source for the rotating sector mirror, it can be easily handled by changing the delay time and the measurement period according to the change in the number of rotations in each region.

As a driving source for the rotating sector mirror, a synchronous motor can be used as usual, but a brushless DC motor is more preferable. The brushless DC motor is capable of high-speed rotation and continuous operation, and does not cause a change in the rotational speed due to the power supply frequency. Although there is a problem that the rotation unevenness is larger than that of the synchronous motor, this can be solved by appropriately setting the delay time in consideration of a time lag due to the rotation unevenness. Also, unlike the synchronous motor, it is easy to control the number of rotations, so by incorporating a rotation number control unit that controls the rotation number of the rotating sector mirror into the device, it is possible to set according to the response characteristics of the photodetector. Become. In addition, the adjustment according to the change in the rotation speed of the rotating sector mirror may be performed by setting the delay time appropriately in the present invention.
In addition to the brushless DC motor, any motor may be used as long as it is a motor capable of high-speed rotation, continuous operation, and rotation speed control.

  The rotation position detection unit includes a plurality of tabs provided on the same rotation orbit on the outer periphery of the rotating sector mirror, a photo interrupter provided on the rotation orbit and detecting passage of the tab, and the photo interrupter. And a change detection unit that detects a change in the signal output from.

  In the conventional configuration, the number of mode interrupters is provided. This is for detecting the switching of the mode and for finely adjusting the position of the photo interrupter for each mode. However, in the present invention, it is possible to cope by setting the delay time without performing fine adjustment for each mode. Therefore, if the above configuration is used, only one photo interrupter is required.

  The rotational position detection unit detects a reference point during one rotation period of the rotating sector mirror, generates a reference point signal and transmits the reference point signal to the measurement control unit, and the measurement control unit receives the reference point signal. The time when the delay time for each mode has been added to the standard time until each sector unit reaches the predetermined rotational position from the time when the light intensity signal is acquired for each mode. It can also be set as the structure. Even if this configuration is used, only one photo interrupter is required.

  In the spectrophotometer according to the present invention, since the mechanical error of the apparatus can be adjusted by setting the delay time, the labor of adjustment at the time of manufacture is greatly reduced. In addition, since the problem of rotation unevenness can be solved by setting the delay time, even a motor that cannot detect the rotation position, such as a brushless DC motor, can be used as a drive source for the rotating sector mirror. Variations in device performance from region to region can be eliminated. Furthermore, since it is easy to control the rotational speed of the brushless DC motor, the rotational speed can be set according to the response characteristic of the photodetector. It is also possible to reduce the number of photo interrupters arranged in the rotating sector mirror.

The principal part block diagram which shows one Example of the spectrophotometer which concerns on this invention. The side view (a) of the rotation sector mirror used for the spectrophotometer of a present Example, a front view (b), the front view (c) of a 1st sector plate, and the front view (d) of a 2nd sector plate. In the spectrophotometer of this embodiment, the light intensity signal from the photodetector (a) accompanying the rotation of the rotating sector mirror, the output signal from the photo interrupter (b), the passage of the delay time from the switching timing to each sector part FIG. 5 is a schematic timing chart showing a data collection period (c) and a data collection signal. The front view of the modification of the rotation sector mirror of a present Example. A side view (a), a front view (b), a front view (c) of a first sector plate, and a front view (d) of a second sector plate of a conventional rotating sector mirror. A front view (a) of a conventional rotating sector mirror, a front view (b) of a first sector plate, and a front view (c) of a second sector plate. A front view (a) of a conventional rotating sector mirror, a front view (b) of a first sector plate, and a front view (c) of a second sector plate. A front view (a) of a conventional rotating sector mirror, a front view (b) of a first sector plate, and a front view (c) of a second sector plate. A front view (a) of a conventional rotating sector mirror, a front view (b) of a first sector plate, and a front view (c) of a second sector plate. The front view (a) before adjusting the position of the 1st photo interrupter with respect to a 1st sector board, and the front view (b) after adjusting a position.

  The spectrophotometer which is one Example of this invention is demonstrated with reference to FIGS. FIG. 1 is a block diagram of the main part of a double beam spectrophotometer according to this embodiment.

  In FIG. 1, light emitted from a light source 1 is introduced into a spectroscope 6 including an entrance slit 2, a diffraction grating 3, an exit slit 4, and a stepping motor (M) 5, and monochromatic light having a predetermined wavelength is extracted. The stepping motor 5 changes the wavelength of the monochromatic light extracted through the exit slit 4 by changing the angle of the diffraction grating 3 that is a wavelength dispersion element with respect to the incident light that has passed through the entrance slit 2. The monochromatic light extracted from the spectroscope 6 is distributed to one of the two reflecting mirrors 10 and 11 or shielded from light by a rotating sector mirror 7 that is rotationally driven by a motor (M) 8.

In this embodiment, a three-phase brushless DC motor is used as the motor 8 that is a drive source of the rotating sector mirror 7. The three-phase brushless DC motor is provided with a motor drive controller 9 that controls the number of rotations based on a drive control signal from the controller 20.
The motor drive control unit 9 controls the number of rotations of the motor 8, for example, a closed loop using a signal from a hall element that is often provided in a three-phase brushless DC motor or a signal from a rotary encoder attached to the motor rotation shaft. Can be done by control.

  Next, the rotating sector mirror 7 used in this embodiment is shown in FIG. This rotating sector mirror 7 has two sector plates, a first sector plate 70a and a second sector plate 70b, fixed to a rotating shaft 70c, as in the conventional rotating sector mirror shown in FIG. 4 (FIG. 2). (a)). The first sector plate 70a has four fan-shaped shielding plates (light-shielding portions) 71 (FIG. 2C), and the second sector plate 70b has two sector-shaped mirrors (reference light portions) 72 ( FIG. 2 (d)). The rotating sector mirror 7 viewed from the front has an opening (sample light portion) 73 (FIG. 2B). These sector portions are configured to be 180 ° rotationally symmetric and rotate in the direction of arrow D (counterclockwise).

On the other hand, as a structure different from the conventional rotating sector mirror, in the rotating sector mirror 7 of this embodiment, the tab 74 is provided only on the outer periphery of the light shielding portion 71 of the first sector plate 70a, and the photo interrupter detects the passage of the tab 74. Only one 75 is provided on the rotation path of the tab 74. Further, one of the four tabs 74 provided in each of the four light shielding portions 71 is provided with a slit 76 for distinguishing the sector portion.
Hereinafter, when distinguishing the four tabs 74, the tab 74 provided with the slit 76 is referred to as a first tab 74a, and the other three tabs 74 are arranged in the clockwise order from the first tab 74a, the second tab 74b, and the second tab 74a. A third tab 74c and a fourth tab 74d are used. When distinguishing each of the eight sector parts, the light shielding part 71 provided with the first tab 74a is used as the first light shielding part 71a, and the first reference light parts are arranged in the clockwise order from the first light shielding part 71a. 72a, second light-shielding part 71b, first sample light part 73a, third light-shielding part 71c, second reference light part 72b, fourth light-shielding part 71d, and second sample light part 73b.

  The third tab 74c, which is rotationally symmetric with the first tab 74a, is not provided with a slit, but 180 ° of the slit in the first tab 74a from the end on the adjacent first sample light portion 73a side. The defect 77 is provided up to the rotationally symmetric position. As described later, this means that the sector part switching position from the first sample light part 73a to the third light shielding part 71c is rotated by 180 ° and the sector part switching position from the second sample light part 73b to the first light shielding part 71a is rotated by 180 °. This is because the delay times are aligned in accordance with the symmetrical position.

  The tab detection signal (hereinafter referred to as “PI signal”) output from the photo interrupter 75 is sent to the change detection unit 19. Here, switching of the sector part is detected from the change in the PI signal, and the control unit 20 is notified of the mode to be integrated. A specific detection method of sector part switching by the change detection unit 19 will be described later.

  When the sample light portion 73 comes to the irradiation position L of the monochromatic light coming from the spectroscope 6 as the rotating sector mirror 7 rotates, the monochromatic light passes through the sample light portion 73 and hits the reflecting mirror 11 to cause the sample-side light beam Ls. And the sample 13 to be measured is irradiated. On the other hand, when the reference light unit 72 comes to the irradiation position L of the monochromatic light, the monochromatic light is reflected by the reference light unit 72 and hits the reflecting mirror 10 to be irradiated to the reference sample 12 as a reference side light beam Lr. Further, when the light-shielding portion 71 comes to the monochromatic light irradiation position L, the sample-side light beam Ls and the reference-side light beam Lr are not present.

  The reference-side light beam Lr that has passed through the reference sample 12 is reflected by the reflecting mirror 14, and the sample-side light beam Ls that has passed through the sample 13 to be measured is reflected by the reflecting mirrors 15 and 16, and both are introduced into the photodetector 17. The sample signal and the reference signal are detected by time division. Further, a dark signal is detected by the photodetector 17 during a period in which neither the sample-side light beam Ls nor the reference-side light beam Lr is present.

  Hereinafter, the period in which the reference signal is detected is referred to as mode R, and the period in which the measurement signal is detected as mode S. Further, the period during which the dark signal is detected depends on whether it is shielded by the first light-shielding part 71a or the third light-shielding part 71c and when it is shielded by the second light-shielding part 71b or the fourth light-shielding part 71d. The former is mode D1, and the latter is mode D2. That is, in this embodiment, it is assumed that there are four modes.

  A detection signal (light intensity signal) from the photodetector 17 is amplified by an amplifier (not shown) and the like and then input to an A / D converter (ADC) 18. On the other hand, when receiving the notification of the mode to be integrated from the change detection unit 19, the control unit 20 refers to the delay time corresponding to the mode from the delay time storage unit 21. Further, the measurement period storage unit 24 refers to the measurement period corresponding to the mode. As described above, in this embodiment, four modes of S, R, D1, and D2 are assumed. The delay time storage unit 21 is provided with delay times Ts, Tr, Td1, Td2 corresponding to each of the S, R, D1, and D2 modes, and the measurement period storage unit 24 is provided with measurement periods Ws, Wr, Wd1,. Wd2 is available. The control unit 20 transmits a data collection signal to the ADC 18 only during the measurement period of the mode after the time corresponding to the delay time of the corresponding mode has elapsed since the notification was received. Note that the delay time and the measurement period can be changed according to conditions such as the number of revolutions of the motor 8.

  When the ADC 18 receives the data collection signal from the control unit 20, the ADC 18 samples the light intensity signal at a predetermined sampling period, converts it to a digital value, and sends it to the integration processing unit 22. The integration processing unit 22 integrates these digital values and sends the integration value to the control unit 20. The control unit 20 stores the integration value in the storage area of the corresponding mode in the integration value storage unit 23. When integration is performed a predetermined number of times for the same mode, for example, the control unit 20 sends a data collection signal to the ADC 18 and simultaneously refers to the integration value of the corresponding mode from the integration value storage unit 23, and A configuration may be used in which the initial value is given to the integration processing unit 22 and the digital value of the light intensity signal sent from the ADC 18 is sequentially integrated with the initial value. Thereafter, the old integrated value data stored in the integrated value storage unit 23 is replaced with new integrated value data.

  In this embodiment, the integration process is always performed on the digital value of the light intensity signal sent from the ADC 18, but the time-division signal from the ADC 18 is directly used as a predetermined storage unit without performing the integration process. It is also possible to adopt a configuration in which each mode is stored.

  Next, the integration processing for each mode, which is characteristic of the spectrophotometer of the present embodiment, will be described with reference to the timing chart of FIG. FIG. 3A shows a change in the light intensity signal accompanying the rotation of the rotating sector mirror 7. As shown in this figure, the light intensity signal output from the photodetector 17 has a period during which the signal is settled and a period during which the signal is in the middle of change. In order to obtain an accurate measurement result, it is necessary to collect data within a period in which the signal is settled in each mode of S, R, D1, and D2.

  FIG. 3B shows changes in the PI signal output from the photo interrupter 75. As shown in this figure, the PI signal has a period in which the signal level continuously changes from strong to weak and from weak to strong at short time intervals. This indicates that the photo interrupter 75 has detected the passage of the slit 76 in the first tab 74a. The change detection unit 19 determines that the sector portion has been switched from the second sample light unit 73b to the first light-shielding unit 71a thereby, and signals change from strong to weak, weak to strong and weak to strong due to the passage of the slit 76. When the change occurs, the control unit 20 is notified that the mode D1 is to be integrated.

  When the control unit 20 receives a notification that the mode D1 is to be integrated from the change detection unit 19, the control unit 20 refers to the delay time Td1 and the measurement period Wd1 corresponding to the mode D1 from the delay time storage unit 21 and the measurement period storage unit 24. Then, after elapse of the delay time Td1 from the time when the notification is received from the change detector 19, the data collection signal is sent to the ADC 18 during the measurement period Wd1 (FIG. 3 (d)).

  FIG. 3 (c) is a timing chart showing the passage of the delay time from the switching timing to each sector and the data collection period in an easy-to-understand manner. The ADC 18 performs sampling of the light intensity signal from the photodetector 17 and conversion into a digital value within a period in which the data collection signal is received, and sends the signal to the integration processing unit 22. In the integration processing unit 22, the data acquired from the ADC 18 is integrated, and the integrated value is sent to the control unit 20, and then stored in the storage area corresponding to the mode D 1 in the integrated value storage unit 23 by the control unit 20. Saved. As described above, the control unit 20 of this embodiment controls each part of the apparatus and also functions as an integration control unit of the present invention.

  On the other hand, when the first tab 74a completely passes between the photo interrupters 75, the PI signal changes from strong to weak. After detecting the passage of the slit 76, the change detection unit 19 changes the signal level of the PI signal from strong to weak, weak to strong, strong to weak, weak to strong, strong to weak, weak to strong, strong to weak. For each sector, the first reference light section 72a, the second light shielding section 71b, the first sample light section 73a, the third light shielding section 71c, the second reference light section 72b, the fourth light shielding section 71d, and the second sample light section 73b. The control unit 20 is notified that the mode to be integrated is changed to R, D2, S, D1, R, D2, and S, respectively. The control unit 20 refers to the delay time storage unit 21 and the measurement period storage unit 24 every time the mode is changed by a notification from the change detection unit 19, and each time when the respective delay time has elapsed from the time when the notification is received. A data collection signal is transmitted to the ADC 18 only during the measurement period. Then, after integrating the digital value of the light intensity signal collected in the integration processing unit 22, the integration value is stored in the storage area of the corresponding mode in the integration value storage unit 23.

  Thus, since one rotation of the rotating sector mirror 7 has been completed, the change detection unit 19 detects the passage of the slit 76 again. As a result, the change detection unit 19 recognizes that the sector unit has been switched from the second sample light unit 73b to the first light-shielding unit 71a, so that the control unit 20 performs each mode in the next one rotation by the same operation as described above. Control the integration. Thus, since the position of the slit 76 can be determined by the continuous change of the PI signal, for example, even when starting a new measurement, the change detection unit 19 does not correspond to which sector part the change of the PI signal corresponds to. Can be determined.

  The sector part switching position from the first sample light part 73a to the third light shielding part 71c is switched at the sector part from the second sample light part 73b to the first light shielding part 71a by the defect 77 provided on the third tab 74c. It is a position that is 180 ° rotationally symmetric with respect to the position. Thereby, although the tab shape differs between the first tab 74a and the third tab 74c, the same Td1 can be used as the delay time of the mode D1. Of course, it is possible to set and refer to independent delay times and measurement periods without providing the defects 77.

FIG. 4 shows a modification of the rotating sector mirror 7 used in the spectrophotometer of this embodiment. In the rotating sector mirror 7 of this modification, only one reference point detecting tab 74e is provided at the end on the second sample light portion 73b side of the outer periphery of the first light shielding portion 71a. When the tab 74e passes between the photo interrupters 75, the photo interrupter 75 outputs a PI signal that changes from weak to strong and from strong to weak in a short period of time. The change detection unit 19 uses the rotation position of the rotating sector mirror 7 when the PI signal changes from weak to strong as a reference point, detects the reference point, and switches from the second sample light unit 73b to the first light shielding unit 71a. Every time when a standard time from the point in time until switching to each sector portion elapses, the controller 20 is notified of the mode to be integrated. In this case, it can be said that each delay time corresponds to the time from the reference point to the measurement start time in each sector.
For example, when the central angles of the sector portions are all 45 ° and the time required for one rotation of the rotating sector mirror 7 is Tw, the sector portions are switched every Tw / 8. The subsequent operation is the same as in the above embodiment.

  The above-described embodiment is an example of the present invention, and it is a matter of course that modifications, corrections, and additions may be appropriately made within the scope of the present invention, and included in the scope of the claims of the present application. For example, the PI signal from the photo interrupter 75 can be used for controlling the rotation speed of the motor drive control unit 9. Conversely, a signal from a hall element or a rotary encoder provided in the motor 8 may be used to detect the rotational position of the rotating sector mirror 7.

DESCRIPTION OF SYMBOLS 1 ... Light source 2 ... Entrance slit 3 ... Diffraction grating 4 ... Exit slit 5 ... Stepping motor 6 ... Spectroscope 7 ... Rotating sector mirror 8 ... Motor 9 ... Motor drive control part 10, 11, 14, 15, 16 ... Reflector mirror 12 Reference sample 13 Sample to be measured 17 Photo detector 18 A / D converter (ADC)
DESCRIPTION OF SYMBOLS 19 ... Change detection part 20 ... Control part 21 ... Delay time memory | storage part 22 ... Integration processing part 23 ... Integration value memory | storage part 24 ... Measurement period memory | storage part 70a ... 1st sector board 70b ... 2nd sector board 70c ... Rotating shaft 71 ... Shading part (shielding plate)
71a ... 1st light shielding part 71b ... 2nd light shielding part 71c ... 3rd light shielding part 71d ... 4th light shielding part 72 ... Reference light part (mirror)
72a ... 1st reference light part 72b ... 2nd reference light part 73a ... 1st sample light part 73b ... 2nd sample light part 74 ... Tab 74a ... 1st tab 74b ... 2nd tab 74c ... 3rd tab 74d ... 4th Tab 74e ... Reference point detection tab 75 ... Photo interrupter 76 ... Slit 77 ... Defect

Claims (9)

A rotating sector mirror that has at least two sector portions and distributes measurement light into at least two modes corresponding to each sector portion; and a photodetector that measures the light intensity of each mode and generates a light intensity signal. In the spectrophotometer provided,
A rotational position detector for detecting the rotational position of the rotating sector mirror set for each mode;
A delay time storage unit for storing a delay time for each mode;
A measurement period storage unit for storing a measurement period for each mode;
After receiving the detection signal from the rotational position detector, the light intensity from the photodetector only during the measurement period of the corresponding mode after being delayed by the delay time of the mode corresponding to the detection signal. A measurement control unit for acquiring a signal as a measurement value;
A spectrophotometer comprising:   The spectrophotometer according to claim 1, wherein the delay time and the measurement period can be changed according to the operation of the rotating sector mirror. further,
An integration processing unit that integrates the light intensity signal acquired by the measurement control unit for each mode;
An integrated value storage unit for storing the integrated value by the integration processing unit for each mode;
The spectrophotometer according to claim 1 or 2, characterized by comprising:   4. The spectrophotometer according to claim 1, wherein a brushless DC motor is used as a driving source of the rotating sector mirror.   The spectrophotometer according to claim 4, further comprising a rotation speed control unit that controls a rotation speed of the brushless DC motor.   The rotational position detection unit includes a plurality of tabs provided on the same rotational trajectory on the outer periphery of the rotating sector mirror, a photo interrupter provided on the rotational trajectory for detecting passage of the tab, and the photo interrupter. The spectrophotometer according to claim 1, further comprising: a change detection unit that detects a change in a signal output from the signal.   The spectrophotometer according to claim 6, wherein the number of the photo interrupters is one. The rotational position detection unit detects a reference point during one rotation period of the rotating sector mirror, generates a reference point signal and transmits the reference point signal to the measurement control unit,
The measurement control unit determines a point in time when a time obtained by adding a delay time for each mode to a standard time from when the reference point signal is received until each sector unit reaches a predetermined rotational position. As the acquisition start time of the light intensity signal for each mode,
The spectrophotometer according to any one of claims 1 to 5.   The spectrophotometer according to claim 8, wherein the reference point is detected by a single photo interrupter.

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