JPH11258154A - Optical rotation measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a small-sized power saving apparatus removing the effect of the stray light incident on a light detection element without utilizing Faraday effect in relation to an optical rotation measuring apparatus measuring the concn. or optical rotation of an optical rotation substance in a soln. SOLUTION: An optical rotation measuring apparatus is constituted so that the laser beam from a laser 1 is linearly deflected by a deflection element 3, thereafter, an optical rotation substance 4 to be measured is passed and the passed beam is separated into polarized beam components mutually different by 90 deg., the separated polarized beam components are respectively detected by two beam detection elements 7a, 7b, and the difference between the output levels of both beam detection elements 7a, 7b is set to a differential optical rotation detection signal to measure an optical rotation. In this case, the laser 1 is allowed to light or put out lights, and optical rotation is calculated on the basis of the difference signal between the above mentioned differential optical rotation detecting signal at a time of lighting and the differential optical rotation detectingg signal at a time of lights-out to remove the effect of stray beam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical rotation measuring device for measuring the concentration of a rotatory substance in a solution, such as the concentration of sugar in urine, and the influence of external incident light or stray light during the measurement. Is to be reduced.

[0002]

2. Description of the Related Art Conventionally, optical rotation measuring apparatuses are disclosed in Japanese Patent Application Laid-Open Nos. 9-138231 and 9-145605. FIG. 3 shows the configuration diagram. Light emitted from the semiconductor laser 1 driven by the laser drive circuit 12 is converted into parallel light by the collimator lens 2, and only light having a polarization component parallel to the paper is transmitted by the polarizer 3. Reference numeral 4 denotes a cylindrical transparent sample cell for holding a test sample, around which a solenoid coil 5 is wound, and a magnetic field is applied to the test sample held by the solenoid coil. This magnetic field is applied substantially uniformly in the light propagation direction, and is proportional to the current flowing through the solenoid coil 5.

Light is rotated with respect to the plane of polarization by the Faraday effect caused by the magnetic field. The analyzer 6 is disposed so as to transmit only light of a polarization component perpendicular to the paper surface, that is, only light of a polarization component perpendicular to the polarization component by the polarizer 3. The light receiving element 7 detects the light transmitted through the analyzer 6 and applies an output corresponding to the intensity to the computer 8. The computer 8 issues a command signal to the current source 9 to control a current value flowing through the solenoid coil 5 and record and analyze the current value. Since the relative angle between the polarizer 3 and the analyzer 6 is 90 degrees, when pure water is measured as a test sample, the light receiving element 7
Is the extinction point of zero. Therefore, in order to measure the optical rotation angle of the test sample, the deviation of the extinction point when the current of the solenoid coil 5 is swept is read by the current of the solenoid coil 5, and is converted into the optical rotation angle by the following equation.

ΘOR = α × C × L (Equation 1) θF = V × H × L (Equation 2) where θOR: rotation of polarized light due to optical rotation α: specific rotation of optically rotating substance C: optical rotation of optically rotating substance Concentration L: Optical path length θF: Rotation of polarized light by Faraday effect V: Verdet constant of solution H: Magnetic field The optical rotation angle and concentration of the test sample can be converted from (Equation 1) and (Equation 2).

[0005]

However, in the above-mentioned conventional configuration, there is a problem that incident light or stray light from the outside enters the light receiving element 7 and affects the measured value of the optical rotation. So we eliminate the effects of external incident light and stray light,
It is required to measure the optical rotation with high accuracy. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide an optical rotation measuring device in which the influence of external incident light and stray light is removed.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is to polarize a laser beam from a laser into linearly polarized light by a polarizing element and then pass the optically rotating substance to be measured, Optical rotation for separating polarization components separated by 90 degrees from each other, receiving the separated polarization components with two light receiving elements, and measuring the optical rotation using a difference between output levels of the two light receiving elements as a differential optical rotation detection signal. In the measuring apparatus, the laser light is turned on and off, and the optical rotation is obtained from a difference signal between a differential optical rotation detection signal when the laser light is turned on and a differential optical rotation detection signal when the laser light is turned off.

[0007] According to this configuration, by taking the difference signal between the differential rotation detection signal at the time of lighting and the differential rotation detection signal at the time of turning off, the light incident on the two light receiving elements from the outside can be obtained. Since the stray light is removed, the influence of external incident light and stray light during measurement can be reduced and removed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention described in claim 1 of the present invention will be described below with reference to FIGS. 1, the same components as those of the conventional example shown in FIG. 3 are denoted by the same reference numerals. Semiconductor laser 1
The light emitted from the light source is collimated by a collimator lens 2, further converted into linearly polarized light by passing through a polarizer 3, and then transmitted through a transparent sample cell 4 in which a test sample solution to be measured is enclosed. I do. The lights transmitted through the sample cell 4 are separated from each other by the polarizing beam splitter 10.
Light receiving elements 7a, 7
b. A subtraction circuit 18 obtains a difference between the output signals of the two light receiving elements 7a and 7b to obtain a differential rotation detection signal.

On the other hand, the laser drive circuit 12 turns on and off the semiconductor laser 1, and the sample and hold circuit 1
5a sample-holds the differential rotation detection signal at the time of lighting, and sample-holds the differential rotation detection signal at the time of light-off by the sample hold circuit 15b. The subtraction circuit 19 calculates the difference between the sampled and held differential optical rotation detection signals at the time of turning on and off, takes in the computer 8, records, and analyzes, thereby calculating the optical rotation and the concentration of the test sample. .

When the semiconductor laser is turned on, if the amount of light transmitted from the sample cell 4 fluctuates due to the transmittance of the test sample or contamination of the sample cell 4, the fluctuation of the amount of light due to the optical rotation cannot be measured accurately, so that the optical rotation measurement is very large. Generate errors.
Therefore, by comparing the sum signal of both outputs of the light receiving elements 7a and 7b with the reference potential 11, an error signal corresponding to the difference is obtained. Using this error signal, the laser driving circuit 1
By performing feedback control of the emission light amount of the semiconductor laser 1 at 2, the light amount emitted from the sample cell 4 when the semiconductor laser is turned on is kept constant.

If the sample cell 4 is extremely contaminated, an overcurrent may flow through the semiconductor laser 1 and destroy it. Therefore, an output signal from the back monitor 13 of the laser and a predetermined reference potential are compared. By making a comparison in the computer 8, the laser drive circuit 12 is stopped, and the “cleaning” of the sample cell 4 is further displayed on the display device 14.
Display an error message such as

However, even if the emitted light amount of the semiconductor laser is controlled so as to keep the sum signal of the two outputs of the light receiving elements 7a and 7b constant, incident light from outside and stray light entering the sample cell 4 and the optical system are not affected. Light may be incident on the light receiving elements 7a and 7b, and may not necessarily be uniformly incident on the light receiving elements 7a and 7b. FIG. 2 is a diagram illustrating the operation of the optical rotation measuring device according to one embodiment of the present invention. In FIG. 2, even when the semiconductor laser is turned off, fluctuations occur in the differential rotation detection signal due to incident light or stray light from the outside as shown by a broken line. Since the optical rotation of the test sample is expressed by the difference between the differential optical rotation detection signal when the semiconductor laser is turned off and when the semiconductor laser is turned on, even if the differential optical rotation detection signal fluctuates, the differential optical rotation detection signal By taking the difference between the time when the light is turned off and the time when the light is turned on instead of the absolute value of the above, it is possible to eliminate the influence of external incident light or stray light.

Here, the sample and hold circuit 15a,
15b and a subtraction circuit 19 are provided to detect the difference between the differential optical rotation detection signals when the semiconductor laser is turned off and when it is turned on.
The differential optical rotation detection signal is directly input to the A / D converter of the computer 8 to A / D-convert the differential optical rotation detection signal when the semiconductor laser is turned off and when it is turned on, and the difference between when the semiconductor laser is turned off and when it is turned on. Can also be realized by a method of digitally performing subtraction.

The differential optical rotation detection signal may be detected once each when the semiconductor laser is turned off and when the semiconductor laser is turned on. May be detected, and the average value thereof may be obtained. Alternatively, the difference may be obtained by performing A / D conversion only once when the light is turned off, and performing A / D conversion only once when the light is turned on, or performing A / D conversion a plurality of times for each.
It is also possible to perform the / D conversion to obtain the average value at the time of turning off and the average value at the time of turning on, and then subtract the average value.

[0015]

As described above, according to the present invention, the influence of external incident light and stray light can be removed, so that the optical rotation can be measured with high accuracy, and a small and power-saving optical rotation can be achieved. A degree measuring device can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram of an optical rotation measuring device according to an embodiment of the present invention.

FIG. 2 is a waveform chart for explaining the operation of the homorotation measurement device.

FIG. 3 is a block diagram of a conventional optical rotation measuring device.

[Explanation of symbols]

 Reference Signs List 1 semiconductor laser 2 collimator lens 3 polarizer 4 sample cell 5 solenoid 6 analyzer 7 light receiving element 7a light receiving element 7b light receiving element 8 computer 9 current source 10 polarization beam splitter 11 reference potential 12 laser drive circuit 13 laser back monitor 14 display device 15a sample hold circuit 15b sample hold circuit 16 addition circuit 17 subtraction circuit 18 subtraction circuit 19 subtraction circuit

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Masahiro Agawa 1 at 8 Koshinmachi, Takamatsu City, Kagawa Prefecture Matsushita Hisashi Denshi Kogyo Co., Ltd.

Claims (1)

[Claims] 1. A laser beam from a laser is polarized into linearly polarized light by a polarizing element and then passed through an optically rotating substance to be measured, and the transmitted light is separated into polarization components different from each other by 90 degrees, and the separated polarization components are separated. Are respectively received by the two light receiving elements, and the difference between the output levels of the two light receiving elements is measured as the differential rotation detection signal, and the optical rotation is measured. An optical rotation measuring device, wherein the optical rotation is obtained from a difference signal between the differential optical rotation detection signal and the differential optical rotation detection signal when the light is turned off.