JP2006275863A - Concentration measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems wherein, when trying acquisition of optical rotation in a wide range, accuracy is lowered, and on the contrary, when trying improvement of the accuracy, the range of the measurable optical rotation is narrowed, since the accuracy is lowered in proportion to largeness of a modulation width when using a method for modulating the optical rotation, in the case where the optical rotation by a rotatory material in a sample is measured. <P>SOLUTION: In this concentration measuring device for measuring the concentration of the rotatory material in the sample by measuring the optical rotation by the rotatory material in the sample, when calculating the concentration of the rotatory material in the sample from a light intensity signal after passing of the sample in a photodetector when the optical rotation of linearly polarized light entering the sample is modulated by an optical rotation modulation means, a modulation range of the optical rotation of the linearly polarized light by the optical rotation modulation means is changed, based on a detection signal by the photodetector, and a detection signal capable of calculating the concentration is acquired, and thereby highly-accurate concentration measurement becomes possible regardless of the intensity of the concentration in the sample. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a concentration measuring apparatus using optical rotation, and more particularly to a technique for measuring the concentration with high accuracy regardless of the concentration of the optical rotatory substance contained in a sample.

As a means of measuring the concentration of the optically rotatory substance in the sample, an optical method in which light is incident on the sample and the concentration is determined by measuring the optical rotation, etc. can be measured without touching the sample directly. Therefore, it is considered useful. The principle of the method for obtaining the concentration of the optically rotatory substance in the sample from the optical rotation is based on Equation 1.
θ (λ) = α (λ) · c · L (Formula 1)
Here, θ (λ) is the optical rotation when the wavelength of the light beam is λ, α (λ) is the specific rotation of the optical rotatory material when the wavelength of the light beam is λ, and c is the optical rotation material in the sample. , L is the optical path length of the sample. In Equation 1, the specific optical rotation α (λ) is a coefficient specific to the optical rotatory substance, and the optical path length L of the sample is also a known value before the concentration measurement. By measuring θ (λ), the concentration c of the optical rotatory substance can be obtained.

  The configuration of a conventional optical rotation measuring device is shown in FIG. A light beam emitted from the light source 501 enters a lens 502 such as a collimator to be a parallel light beam, and then enters a polarizer 503. The light transmitted through the polarizer 503 is linearly polarized light having an optical axis in the transmission axis direction of the polarizer 503. Here, the transmission axis direction of the polarizer 503 is a vertical direction. Next, linearly polarized light enters the optical rotation modulation element. Here, the optical rotation modulation element is an electro-optical element, and examples thereof include a liquid crystal element, a Faraday element, a Pockel cell, and the like. In this configuration, the liquid crystal element 504 is used. When passing through the liquid crystal element 504, the polarization direction of the linearly polarized light changes depending on the voltage applied to the liquid crystal element from the outside. Here, by modulating the voltage applied to the liquid crystal element 504 with a certain frequency f, the polarization direction of the linearly polarized light passing through the liquid crystal element 504 is modulated within a range of an angle ± β with respect to the vertical axis. Next, linearly polarized light whose polarization direction is modulated is incident on the sample 505. Here, it is assumed that the linearly polarized light is rotated by an unknown amount + γ by the optical rotatory substance contained in the sample 505 when passing through the sample 505. Here, as shown in FIG. 6, the polarization direction of the light beam that has passed through the sample 505 is modulated in an angular range from (−β + γ) to (β + γ) with respect to the vertical axis. Here, β is larger than γ.

  Next, the light beam that has passed through the sample 505 is incident on the analyzer 506, so that only the light component in the direction of the transmission axis of the analyzer 506 is transmitted and reaches the light receiving unit of the photodetector 507. The photodetector 507 outputs the intensity change of the received light as a voltage change. Here, if the transmission axis direction of the analyzer 506 is 90 degrees with respect to the vertical axis, the signal detected by the photodetector 507 has two local maxima and minima each in time 1 / f, as shown in FIG. It becomes such a signal.

  Here, the optical rotation + γ by the sample 505 can be obtained by performing calculation based on the detection signal as shown in FIG. 2 in the photodetector 507 and the voltage value applied to the liquid crystal element 504, for example. For example, Patent Document 1 proposes a method for obtaining the optical rotation based on the maximum value and the minimum value in the detection signal in the photodetector 507.

  As a general method for obtaining the optical rotation, there is a method for obtaining the optical rotation by mechanically rotating the analyzer with a motor or the like and searching for an angle at which the detection signal in the photodetector becomes maximum or minimum. Can be mentioned.

In addition, as a means for measuring the concentration of the optically rotatory substance in the sample, an enzyme method using an enzyme can be given. In the enzyme method, an enzyme that reacts with a specific substance is used to measure the concentration by measuring components produced by the reaction. For example, GOD (glucose oxidase) method is known as a method for measuring glucose concentration.

JP-A-9-236542 (FIG. 5)

  However, the above method has the following problems. In the above concentration measuring apparatus using the conventional optical rotation, when the optical rotation is measured from the detection signal in the photodetector, the optical rotation of the sample must be within the modulation region by the optical rotation modulation element. That is, for example, when the modulation width by the optical rotation modulation element is ± 3 °, the measurable optical rotation is within ± 3 °, and no more optical rotation can be measured. Therefore, it is necessary to widen the modulation width when measuring the optical rotation of ± 3 ° or more.

  However, since the resolution at the time of measuring the optical rotation from the detection signal depends on the modulation width by the optical rotation modulation element, the accuracy is lowered by increasing the modulation width. In other words, the smaller the modulation width, the higher the accuracy, but the larger the modulation width, the lower the accuracy, so if you try to find the optical rotation over a wide range, the accuracy will drop, and conversely, try to improve the accuracy. Then, there exists a subject that the range of the optical rotation which can be measured will become narrow.

  In addition, in the method of obtaining the optical rotation by mechanically rotating the analyzer with a motor or the like, a mechanical operation such as rotating the element is required, leading to an increase in the size of the entire apparatus and high power consumption. End up. In addition, a high-performance motor is indispensable for obtaining the optical rotation with high accuracy, leading to complication of the apparatus.

  As for the enzyme method, it is known that the measurement can be performed as it is at a low concentration, but the reaction is saturated when the concentration exceeds a certain value. Therefore, when measuring a high-concentration sample, a pre-measurement process such as diluting the original sample is required, which causes a problem that the number of measurement steps increases. Moreover, since it is an enzyme, the subject that a use period and the frequency | count of use will be limited also arises.

  Therefore, in the present invention, in order to eliminate the above-mentioned problems caused by the prior art, the concentration of the optically rotatory substance in the sample can be set with high accuracy without using mechanical operation or an enzyme, and regardless of the density of the concentration. It is an object of the present invention to provide a concentration measuring apparatus capable of measuring in a short time.

  In order to solve these problems, the concentration measuring apparatus according to the present invention employs the following means. That is, the concentration measuring apparatus of the present invention includes a linearly polarized light output unit that outputs linearly polarized light, an optical rotation modulation unit that modulates the optical rotation of the linearly polarized light, and a linear light beam whose optical rotation is modulated by the optical rotation modulation unit. A concentration measuring device comprising: a detecting means for detecting transmitted light that is irradiated and transmitted through a sample; and a calculating means for calculating the concentration of an optical rotatory substance in the sample from a detection signal in the detecting means, wherein the detection signal is optically rotated. The modulation range of the optical rotation of the linearly polarized light by the optical rotation modulation means is changed by feeding back to the degree modulation means.

  In the concentration measurement apparatus of the present invention, it is preferable that the linearly polarized light output means, the optical rotation modulation means, the detection means, and the calculation means do not require mechanical operation for measurement.

  Moreover, it is preferable that the calculation means in this invention calculates a density | concentration based on the maximum value and minimum value in a detection signal.

  In the present invention, it is preferable that both the modulation width and the central axis of the modulation be variable in the optical rotation modulation range.

  In the present invention, it is preferable that the optical rotation modulation range has a constant modulation width and a variable central axis.

  The optical rotation modulation means in the present invention is preferably a liquid crystal element, a liquid crystal element and a wave plate, a Faraday cell, a photoelastic modulator, or a Pockel cell.

  Moreover, the sample in the present invention is urine, and the optical rotatory substance in the sample is more useful when it is urine glucose.

(Function)
In a concentration measuring device that measures the optical rotation of the optical rotatory substance in the sample to measure the concentration of the optical rotatory substance in the sample, the optical rotation of the linearly polarized light incident on the sample is modulated by the optical rotatory modulation means. When calculating the concentration of the optical rotatory substance in the sample from the detection signal after passing through the sample in the photodetector, the detection signal in the photodetector is fed back to the optical rotation modulation means, and the optical polarization of the linearly polarized light by the optical rotation modulation means By changing the modulation range, the concentration can be measured with high accuracy regardless of the density of the sample.

  As described above, the concentration measuring device of the present invention has the effects described below.

  In a concentration measuring device that measures the optical rotation of the optical rotatory substance in the sample to measure the concentration of the optical rotatory substance in the sample, the optical rotation of the linearly polarized light incident on the sample is modulated by the optical rotatory modulation means. When calculating the concentration of the optical rotatory substance in the sample from the detection signal after passing through the sample in the photodetector, the modulation range of the optical polarization of linearly polarized light by the optical rotation modulation means based on the detection signal in the photodetector, ie, modulation By changing the width and / or the center axis of the modulation and obtaining a detection signal that can calculate the concentration, even if the concentration in the sample is high, the concentration can be measured with the same high level of accuracy as when the concentration is low. It becomes possible.

  Further, in the present invention, since a mechanical operation such as mechanically rotating the analyzer with a motor or the like is unnecessary, the apparatus can be reduced in size and the apparatus configuration can be simplified. Further, when a liquid crystal element is used as the optical rotation modulation element, it is possible to reduce power consumption.

  Furthermore, in the present invention, since no enzyme or the like is used for concentration measurement, pretreatment for measurement such as thinning of the sample is unnecessary, and the method can be used without limitation in terms of period and number of times.

  Hereinafter, an optimum embodiment of a concentration measuring apparatus using the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing a first embodiment of the present invention. In FIG. 1, a light beam emitted from a light source 101 such as a laser diode driven by a drive circuit 108 enters a collimator lens 102. Here, the light source 101 emits a light beam having a certain wavelength, and is not limited to a laser diode. The collimator lens 102 converts incident light into parallel light, and changes the position according to the spread angle of the light from the light source. Next, the light beam that has been collimated by the collimator lens 102 is incident on the polarizer 103. The light beam becomes linearly polarized light having an optical axis in the transmission axis direction of the polarizer 103 by the polarizer 103. Here, the transmission axis direction of the polarizer 103 is a vertical direction. Next, the linearly polarized light transmitted through the polarizer 103 is incident on the optical rotation modulation element. The optical rotation modulation element is an electro-optical element, and the liquid crystal element 104 is used in this embodiment shown in FIG. Here, the liquid crystal element 104 is driven by the liquid crystal drive circuit 109, and the voltage applied to the liquid crystal element 104 is modulated at a certain frequency f, whereby the polarization direction of the linearly polarized light passing through the liquid crystal element 104 is within a certain angle range. Modulate.

  Next, linearly polarized light whose polarization direction is modulated is incident on the sample 105. Here, when the linearly polarized light passes through the sample 105, it is rotated by an unknown amount by the optical rotatory substance contained in the sample 105. Next, the light beam that has passed through the sample 105 enters the analyzer 106, so that only the light component in the direction of the transmission axis of the analyzer 106 is transmitted and reaches the light receiving unit of the photodetector 107. Here, the transmission axis direction of the analyzer 106 is 90 degrees with respect to the vertical axis. The photodetector 107 outputs the intensity change of the received light as a voltage change. The detection signal of the photodetector 107 is amplified by an amplifier or the like and input to a computing unit 110 such as a PC. The arithmetic unit 110 not only performs calculations but also controls the liquid crystal drive circuit 109 as a controller. At this time, a method for obtaining the optical rotation by the sample 105 by performing calculation based on the detection signal in the photodetector 107 and the voltage value applied to the liquid crystal element 104 will be described below.

  First, for example, at the beginning of measurement, the optical rotation modulation range by the liquid crystal element 104 is set to ± 90 ° with respect to the vertical direction. As a result, regardless of the value of the amount of rotation by the sample 105, the signal detected by the photodetector 107 becomes a signal as shown in FIG. 2 having two maxima and minima each in time 1 / f. Alternatively, the modulation amount can be made smaller than ± 90 ° when the amount of rotation of the light from the sample 105 is well known.

  Although it is possible to calculate the optical rotation using the maximum and minimum values, for example, from the detection signal at this time, as described above, the resolution when measuring the optical rotation from the detection signal is modulated by the optical rotation modulation element. Since it depends on the width, the accuracy is low as it is. Therefore, based on the detection signal obtained during the ± 90 ° modulation, the modulation width and the central axis of the modulation are reset, and the modulation is performed in the same manner. For example, when the optical rotation by the sample is calculated to be about + 30 ° at the time of ± 90 ° modulation, the optical rotation can be performed with higher accuracy by setting the modulation central axis to + 30 ° and the modulation width to ± 10 °. Can be calculated. By repeating this process further and reducing the modulation width, the modulation width finally becomes sufficient to obtain sufficient accuracy in optical rotation measurement, and the optical rotation is calculated based on the detection signal obtained at that time. By doing so, the optical rotation can be obtained with very high accuracy. That is, it is possible to measure the concentration with high accuracy regardless of the density of the sample.

  The above method will be described with reference to FIG. In FIG. 3, the horizontal axis represents the voltage V applied to the liquid crystal element 104, and the vertical axis represents the detection signal intensity I in the photodetector 107. In FIG. 3, at the initial stage of measurement, the modulation range is set to a, and based on the detection signal at that time, the modulation width and the central axis of modulation are changed, and the modulation range is reduced to b. Further, based on the detection signal at that time, similarly, the modulation width and the central axis of the modulation are changed, and the modulation range is reduced to c. At this time, even when the modulation range is reduced from a to b and from b to c, the detection signal is always a signal having two maxima and minima in time 1 / f as shown in FIG. To do.

Here, when the modulation range is reduced as described above and the modulation range is wide enough to obtain sufficient accuracy in the optical rotation measurement, pay attention to the detection signal, and the detection signal constructed in advance The concentration is calculated in accordance with the relational expression between the ratio of the two maximum values and the optical rotation, and the optical rotation and the concentration during time 1 / f. Here, the relational expression between the ratio between the two maximum values and the optical rotation during the time 1 / f of the detection signal depends particularly on the type of liquid crystal and the modulation width. By this method, the same high resolution can be obtained regardless of the density of the sample, and highly accurate concentration measurement can be performed.

  Here, the values such as the modulation range in the above-described embodiment are merely examples, and are not limited to these values.

(Second embodiment)
Next, a second embodiment will be described. The optical elements and the like are shown in FIG. 1 as in the first embodiment. Similar to the first embodiment, by modulating the voltage applied to the liquid crystal element 104 at a certain frequency f, the polarization direction of the linearly polarized light passing through the liquid crystal element 104 is modulated within a range of an angle. At this time, the modulation range is fixed to a modulation width d that can provide sufficient accuracy in optical rotation measurement.

  Here, it is assumed that the modulation width d that provides sufficient accuracy in the optical rotation measurement is ± 3 °, and the central axis of the modulation is the vertical direction at the beginning of the measurement. At this time, when the optical rotation by the sample 105 is within ± 3 °, the optical rotation can be measured with high accuracy from the detection signal in the photodetector 107. As a calculation method, for example, as described above, the ratio between the maximum value and the optical rotation, and the relational expression between the optical rotation and the concentration, which are constructed in advance, are determined based on the ratio between the two maximum values during the time 1 / f of the detection signal. For example, a method for calculating the concentration.

  However, in this method, when the optical rotation by the sample 105 is not within ± 3 °, only one maximum value is observed during the time 1 / f of the detection signal, and therefore the optical rotation cannot be calculated. Therefore, with reference to the detection signal, the modulation range is changed when there is only one maximum value in time 1 / f. As a method of change, for example, it is changed to a range of −2 ° to + 4 ° next to ± 3 °, and if there is only one maximum value in time 1 / f of the detection signal even in the modulation range, the modulation range is changed. There is a method of changing from −4 ° to + 2 °, and changing in the same manner. In this manner, when two maximum values are observed during the time 1 / f of the detection signal as shown in FIG. 2, it is possible to calculate the concentration by the calculation method as described above. In this case, since the modulation range is already wide enough to obtain sufficient accuracy in optical rotation measurement, the accuracy is high. Further, since the modulation range is changed to a range suitable for the optical rotation by the sample 105, measurement with high accuracy is always possible without depending on the concentration of the optical rotatory substance in the sample 105.

  FIG. 4 illustrates the above method. As in FIG. 3, in FIG. 4, the horizontal axis represents the voltage V applied to the liquid crystal element 104, and the vertical axis represents the detection signal intensity I in the photodetector 107. In FIG. 4, modulation is performed at the position A at the initial stage of measurement, but the density cannot be calculated from the detection signal at this position. Therefore, the modulation range is changed while feeding back the detection signal, and finally the modulation range is changed to the position B. By calculating the concentration using the detection signal at this time, measurement with high accuracy is always possible without depending on the concentration.

  Here, as in the first embodiment, the values such as the modulation range in the above-described embodiment are merely examples, and are not limited to these values.

  In addition, a liquid crystal element is used as the optical rotation modulation means in the above-described embodiment, but this method is also effective when, for example, a Faraday cell, a photoelastic modulator, a Pockel cell, or the like is used.

It is a figure which shows the structure of the density | concentration measuring apparatus in 1st embodiment of this invention. It is a figure which shows the output waveform of the photodetector in embodiment of this invention. It is a figure which shows the relationship between the voltage applied to the liquid crystal element in embodiment of this invention, and the light intensity in a photodetector. It is a figure which shows the relationship between the voltage applied to the liquid crystal element in embodiment of this invention, and the light intensity in a photodetector. It is the schematic of the optical rotation measuring apparatus in a prior art example. It is a figure which shows the change of the modulation range of the optical rotation by a sample.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Light source 102 Collimating lens 103 Polarizer 104 Liquid crystal element 105 Sample cell 106 Analyzer 107 Photo detector

Claims (7)

A linearly polarized light output means for outputting linearly polarized light; an optical rotation modulation means for modulating the optical rotation of the linearly polarized light; and a linear light beam whose optical rotation is modulated by the optical rotation modulation means is applied to the sample and transmitted through the sample. A concentration measuring device comprising: a detecting means for detecting transmitted light coming in; and a calculating means for calculating the concentration of the optical rotatory substance in the sample from a detection signal in the detecting means, wherein the detection signal is converted into the optical rotation angle. A concentration measuring apparatus that changes a modulation range of optical rotation of linearly polarized light by the optical rotation modulation means by feeding back to the modulation means. The concentration measuring apparatus according to claim 1, wherein the linearly polarized light output unit, the optical rotation modulation unit, the detection unit, and the calculation unit do not require mechanical operation for measurement. The concentration measuring apparatus according to claim 1, wherein the calculating unit calculates the concentration based on a maximum value and a minimum value in the detection signal. 4. The concentration measuring apparatus according to claim 1, wherein the modulation range of the optical rotation is variable in both a modulation width and a central axis of modulation. 5. The concentration measuring apparatus according to any one of claims 1 to 3, wherein the modulation range of the optical rotation has a constant modulation width and a variable central axis. 6. The concentration measuring apparatus according to claim 1, wherein the optical rotation modulation means is a liquid crystal element, a liquid crystal element and a wave plate, a Faraday cell, a photoelastic modulator, or a Pockel cell. The concentration measurement apparatus according to any one of claims 1 to 6, wherein the sample is urine, and the optical rotatory substance in the sample is urine glucose.

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