JP2007078603A - Spectrophotometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stable and inexpensive measuring device without the use of optical fibers, in a spectrophotometer implementing measurements by moving the position of detector for any measurements, such as for absolute reflectivity. <P>SOLUTION: Since a detector 14 with changeable position is used for measurement only at the sample side and a detector 5 of the main body A of the spectrophotometer is used to a reference side detector, usage of optical fibers becomes unnecessary and also additional costs are suppressed to the minimal. In order to suppress the drift of the detector 14 utilizing a photoelectron-multiplier tube to minimal, a light source 16 of LED is prepared in an external sample chamber to be changed to ON/OFF according to the measured sequence. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ultraviolet / visible spectrophotometer and an ultraviolet / visible / near infrared spectrophotometer used as a general-purpose spectrophotometer.

  The spectrophotometer measures the light intensity transmitted through the sample to be measured or the light intensity reflected from the surface of the sample to be measured, and obtains the absorption spectrum or reflection spectrum of the sample, thereby analyzing the component of the sample or optical of the sample. Analyzes the characteristics.

  In general, there are two types of spectrophotometers, a double beam method and a single beam method. The double beam spectrophotometer performs qualitative and quantitative analysis by measuring the ratio of the light intensity transmitted or reflected through the measurement sample and the light intensity transmitted or reflected through the reference sample. FIG. 2 shows a schematic configuration diagram of a double beam type spectrophotometer. The example of this figure is intended to measure the transmitted light of the sample. The light from the light source 1 is monochromatic by the spectroscope 2 and reaches the sector mirror 4. As illustrated in FIG. 4, the sector mirror 4 is a mirror in which a part of the disk is a mirror, and is rotated by means such as a motor in a plane that forms an angle of 45 ° with the luminous flux.

  By the sector mirror 4 and the plurality of mirrors 3, the light flux from the spectroscope 2 is alternately sent to the sample-side light flux S and the reference-side light flux R, and the sample to be measured or the reference placed in the cell holder 7 in the sample chamber 6. After passing through the sample, the light is incident on the detector 5 typified by a photomultiplier tube by the mirror 3. The detector 5 alternately outputs a signal proportional to the light intensity of the sample-side light beam S and a signal proportional to the light intensity of the reference-side light beam R in synchronization with the rotation of the sector mirror 4. By obtaining the ratio of these two signals, an object is to obtain an accurate measurement in which the spectral characteristics of the light source intensity, the spectral characteristics of the spectroscope, and the influence of temporal variations in the light source intensity are eliminated. (See Patent Document 1)

  In the spectrophotometer, in addition to the measurement of the transmitted light of the sample, it is required to measure the reflectance of the surface of each sample. In particular, when measuring the absolute reflectance of a sample at different incident angles, it is necessary to rotate the detector around the sample. FIG. 3 shows a schematic configuration diagram of an example of a spectrophotometer for performing such absolute reflectance measurement. In the example of this figure, the apparatus is composed of a spectrophotometer main body A having the same configuration as that shown in FIG. 2 and an external sample chamber B attached thereto. A sample table 12 having a rotation center axis perpendicular to the sample table 12 and a detector 14 capable of rotating around the sample table 12 are provided. As the detector, a photomultiplier tube is widely used. The light from the light source 1 of the spectrophotometer main body A is monochromatized by the spectroscope 2 and distributed to the sample side light beam S and the reference side light beam R by the sector mirror 4 and the mirror 3 as in the example of FIG.

  The sample-side light beam S is introduced into the external sample chamber B by the two mirrors 8 and 9 installed in the sample chamber 6 and then enters the surface of the sample 13 held on the sample table 12 by the mirror 15. . The light reflected from the surface of the sample 13 enters the detector 14. One reference-side light beam R is condensed and introduced into the incident end of the optical fiber 11 by the mirror 10. The other end (outgoing end) of the optical fiber 11 is held immediately before the detector 14 in the external sample chamber B, and the light emitted from the optical fiber 11 enters the light receiving portion of the detector 14. Since the optical fiber 11 is sufficiently flexible, the detector 14 is moved as indicated by the broken arrow line without interfering with the sample-side light beam S while maintaining the relative positional relationship between the detector 14 and the output end of the optical fiber 11. Is possible. Further, in this measurement method, the detector (5 in FIG. 2) originally included in the spectrophotometer main body A is not used at all.

In order to measure the absolute reflectance of the sample 13 using the apparatus shown in FIG. 3, the measurement condition such as the wavelength of the spectroscope is set to a predetermined value and then detected before mounting the sample 13 on the sample stage 12. 3 is placed at the position indicated by the broken line in FIG. 3, and the sample-side light beam S from the mirror 15 is directly introduced into the detector 14 so that the intensity of the sample-side light beam S and the reference-side light beam R from the optical fiber 11 are reduced. The ratio I ₀ to the intensity is obtained. Next, the sample 13 is mounted on the sample table 12, the sample table 12 is rotated to adjust the incident angle on the sample 13, and the position of the detector 14 is the position where the reflected light from the sample 13 is incident (see FIG. 3) (fixed line position). Determining the ratio I _R of the reflected light intensity and the reference light intensity at this position. Finally, the ratio of I ₀ and I _R is calculated to obtain the absolute reflectance R = I _R / I ₀ .
JP 2002-156282 A

  A conventional spectrophotometer having a variable position mechanism of the detector has the configuration described above, but this has the following problems.

  As shown in FIG. 3, in the prior art, the optical fiber 11 is used to introduce light from the reference-side light beam R into the detector 14 that moves its position. Since the optical fiber 11 as an optical material has high flexibility and can guide light in a free direction and place, an optical element including the moving detector 14 shown in FIG. It is widely used to realize an optical system that cannot be completely fixed. However, the transmission efficiency of the optical fiber 11 varies depending on the radius of curvature of the deflection. In the example of FIG. 3, by moving the position of the detector 14, the radius of curvature at the intermediate portion of the optical fiber 11 changes, and the transmission efficiency of the optical fiber 11 changes. For this reason, when the incident angle to the sample 13 is changed, there is a complication that the signal must be zero-adjusted.

  In addition to the example shown in FIG. 3, a method of guiding the reference-side light beam to a movable detector using an optical element such as a mirror or a lens without using an optical fiber is also considered, but the optical system is complicated and the manufacturing cost is low. In addition, there is a problem in that the selection of the position of the detector is limited and the measurement method has a low degree of freedom.

An object of the present invention is to solve such problems and to enable stable measurement, and in a double beam spectrophotometer having a position variable mechanism of a detector, each of a sample side beam and a reference side beam. 1 is provided with one independent detector.
In addition to a light source that supplies light used for spectrophotometry, in addition to a light source that irradiates light to a detector provided in the sample-side light beam, a mechanism for blinking the light source is provided for the purpose of further stabilizing the measurement. It is characterized by that.

  By introducing the reference-side light beam into an independent detector, the use of an optical fiber becomes unnecessary, and the stability of the measurement can be improved. Further, since a complicated optical system is not required, the manufacturing cost of the apparatus can be reduced. Furthermore, operability can be improved by turning on and off the light source in the sample chamber in conjunction with the measurement sequence.

  In the present invention, since it is indispensable to move the detector, the apparatus is composed of an external sample chamber including a movable detector and the spectrophotometer body, and is originally included in the spectrophotometer body. The detector is used to measure the intensity of the reference side beam.

  The embodiment will be described below with reference to FIG. As shown in FIG. 1, a spectrophotometer for measuring absolute reflectance according to the present invention includes a spectrophotometer main body A having the same configuration as that shown in FIG. 2, and an external sample chamber attached thereto. 1 is held in the external sample chamber B on the end of a sample stage 12 having a rotation center axis perpendicular to the paper surface of FIG. 1 and an arm 19 that rotates about the same rotation axis as the sample stage 12. A detector 14 is provided. A photomultiplier tube is used as the detector. The light from the light source 1 of the spectrophotometer main body A is monochromatized by the spectroscope 2 and distributed to the sample side light beam S and the reference side light beam R by the sector mirror 4 and the mirror 3 as in the example of FIG.

  The sample-side light beam S is introduced into the external sample chamber B by the two mirrors 8 and 9 installed in the sample chamber 6 and then enters the surface of the sample 13 held on the sample table 12 by the mirror 15. . The light reflected from the surface of the sample 13 enters the detector 14 (photomultiplier tube). On the other hand, the reference-side light beam R enters the detector 5 that the spectrophotometer main body A originally has after the mirror 3. Therefore, a signal proportional to the light intensity of the sample-side light beam S from one detector 14 and a signal proportional to the light intensity of the reference-side light beam R from the other detector 5 are synchronized with the rotation of the sector mirror 4. Are alternately output.

In order to measure the absolute reflectance of the sample 13, after setting the measurement conditions such as the wavelength of the spectroscope 2 to a predetermined value, the arm 19 is first rotated as indicated by an arrow before mounting the sample 13 on the sample stage 12. Then, the position of the detector 14 is placed at the position indicated by the broken line in FIG. 1, the sample-side light beam S from the mirror 15 is directly introduced into the detector 14, and the intensity of the sample-side light beam S output from the detector 14 And the ratio I ₀ between the intensity of the reference-side light beam R output from the detector 5 is obtained. Next, the sample 13 is mounted on the sample table 12, the sample table 12 is rotated to adjust the incident angle to the sample 13, and the arm 19 is rotated in the reverse direction so that the position of the detector 14 is reflected from the sample 13. It moves to the position where light enters (the position of the solid line in FIG. 1) and is fixed. A reflected light intensity output from the detector 14 in this position, the ratio I _R of the reference light intensity output from the detector 5 obtains. Finally, the ratio of I ₀ and I _R is calculated to obtain the absolute reflectance R = I _R / I ₀ .

  According to the spectrophotometer described above, the reference-side light beam R and the sample-side light beam S are measured by two independent detectors 5 and 14, respectively. There is no need. Thus, measurement instability due to the optical fiber is eliminated. In addition, since the detector 5 for measuring the reference side light flux R and the optical system such as the mirror 3 used for introduction use an object originally included in the spectrophotometer main body A, the manufacturing cost for this is as follows. Not added at all.

In this embodiment, two independent photomultiplier tubes are used as the detectors 5 and 14.
Among these, the detector 5 is installed in a stable place where there is no intrusion of outside light other than the measurement light, but the external sample chamber B where the detector 14 is installed is where the sample 13 is taken in and out, and the position of the detector 14. The detector 14 is frequently opened and closed for adjustment or the like, and the detector 14 is exposed to external light each time. A photomultiplier tube placed in such a state may cause unstable drift in the output signal. To prevent this, the photomultiplier tube is kept constant at times other than during measurement. It is known that exposure to intense light is effective. For this reason, in this embodiment, a light source 16 using a light emitting diode is arranged inside the external sample chamber B, and the light source 16 is blinked by a switch 17 controlled by the control unit 18 in the spectrophotometer body A. The

The specific sequence of blinking of the light source 16 during measurement is as follows:
(1) The light source 16 is turned on.
(2) Turn off the light source 16 and perform baseline measurement.
(3) After the baseline measurement, the light source 16 is turned on.
(4) The sample 13 is mounted and the position of the detector 14 is adjusted.
(5) The light source 16 is turned off and measurement is performed.
(6) The light source 16 is turned on after the measurement is completed.
(7) Repeat (4) to (6) for measurement.
This sequence can be automatically advanced by the control unit 18 when necessary. This makes it possible to perform absolute reflectance measurement while minimizing the drift of the detector 14.

  The features of the present invention are as described above. However, the present invention is not limited to the above and illustrated examples, and includes various modifications. For example, the present invention can be widely applied to measurement methods that perform measurement by changing the position of the detector, such as not only absolute reflectance measurement but also variable light reception angle transmission measurement.

  The present invention relates to a spectrophotometer.

It is a schematic block diagram of the spectrophotometer for the absolute reflectance measurement concerning this invention. It is a schematic block diagram of a double beam spectrophotometer. It is a schematic block diagram of the spectrophotometer for the absolute reflectance measurement by a prior art. It is a figure which shows the shape of a sector mirror.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Spectrometer 3 Mirror 4 Sector mirror 5 Detector 6 Sample chamber 7 Cell holder 8 Mirror 9 Mirror 10 Mirror 11 Optical fiber 12 Sample stand 13 Sample 14 Detector 15 Mirror 16 Light source 17 Switch 18 Controller 19 Arm A Spectrophotometer Main unit B External sample chamber R Reference beam S Sample sample beam

Claims (1)

  In a double beam spectrophotometer having a detector position variable mechanism, each of the sample-side light beam and the reference-side light beam is provided with one independent detector, and separately from the light source for spectrophotometry, other than during measurement A spectrophotometer comprising a light source for illuminating a detector provided in the sample-side light beam.

Images