JPH1133017A - Optical heterodyne method spectroscopic analyser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely analyze a light absorption characteristic of an object to be measured by photoelectrically converting modulation signal light and modulation reference light at a plurality of wavelengths so as to provide an optical heterodyne beat electric signal and analyzing a light absorption characteristic of the object to be measured on the basis of the optical heterodyne beat electric signal, which is obtained by differential computing, at each wavelength. SOLUTION: Signal light laser beams emitted from a first and second light sources 1, 12 are modulated by means of acousto-optical modulators 5, 15, while reference light beams are modulated by means of acousto-optical modulators 7, 16. Differential computing for optical heterodyne beat electric signals outputted from photoelectric converters 31, 32 are carried out by means of a differential computing circuit 33 and an amplitude fluctuation constituent is eliminated, the optical heterodyne beat electric signals are separated by means of bandpass filters 34, 35 so as to be converted into direct current signals by means of rectifiers 36, 37, and ratio computing for these direct current signals are carried out by means of a ratio computing circuit 38. On the basis of the ratio between the direct current signals, an analyzer 39 connected to an output terminal of the ratio computing circuit 38 measures an optical absorption rate of the object to be measured in a body to be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for analyzing the light absorption characteristics of an object to be measured, for example, a multiple scatterer of a living body, and measuring the concentration of the object in the object by an optical heterodyne method.

[0002]

2. Description of the Related Art Conventionally, as a means for measuring the light absorption characteristics and the like of an object to be measured composed of multiple scatterers such as a living body, for example, an optical blood sugar level nondestructive measuring method described in Japanese Patent Application Laid-Open No. 5-176917 has been proposed. And equipment. " According to the present invention, near-infrared light selected from a wavelength of 0.78 to 1.32 μm is incident on a human body, the intensity of the transmitted light is detected, and glucose concentration and the like in the human body are determined based on the detection result. Is what you want.

[0003]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 5-176 is disclosed.
According to “Optical blood sugar level non-destructive measuring method and apparatus” described in JP-A-917, wavelength 0.78 to 1.32 μm
The near-infrared light selected from above is incident on the human body, the intensity of the transmitted light is detected, and the glucose concentration or the like in the human body is determined based on the detection result. Since infrared light contains a time-varying amplitude fluctuation component, there is a problem that glucose concentration cannot be measured accurately. Further, the intensity of the transmitted light includes not only the absorption by glucose in the human body but also the scattered light that returns by circumventing a distant place, so that the intensity of the transmitted light greatly depends on the shape of the measured object.

Accordingly, in the present invention, amplitude-varying components that change with time from a plurality of light sources are removed, and only non-scattered light (straight light, ballistic photons) is selectively obtained without depending on the shape of the measured object. An object of the present invention is to provide an optical heterodyne spectroscopic analyzer capable of detecting and accurately analyzing light absorption characteristics of an object to be measured and measuring the concentration of the object in the object to be measured.

[0005]

According to a first aspect of the present invention, there is provided a first light source for emitting light having a first wavelength which is easily absorbed by an object to be measured in the object to be measured; A second light source that emits light of a second wavelength that is hardly absorbed by the measurement object; a signal light that causes the respective light emitted from the first light source and the second light source to pass through the measurement object; and Means for splitting the signal light into reference light that does not pass through the object to be measured, and signal light and reference light of the first wavelength and the second wavelength, respectively, which are modulated at required frequencies to obtain a first wavelength and a second wavelength. Means for generating a modulated signal light and a modulated reference light, means for multiplexing the modulated signal light and the modulated reference light of the first wavelength and the second wavelength, and for dividing and transmitting the divided light at a predetermined ratio; Photoelectrically converting the illuminated modulated signal light and modulated reference light of the first wavelength and the second wavelength. Means for obtaining an optical heterodyne beat electric signal corresponding to the difference between the modulation frequencies of the modulated signal light and the modulated reference light of each wavelength, and differentially operates the optical heterodyne beat electric signal of each wavelength. Means for analyzing the optical absorption characteristics of the object to be measured based on the differentially calculated optical heterodyne beat electric signal and measuring the concentration of the object to be measured.

According to a second aspect of the present invention, in the optical heterodyne spectroscopic analyzer of the first aspect, a plurality of lights having different wavelengths are emitted from the first light source, and the light of each wavelength is converted into a signal light and a reference light. In this case, an optical heterodyne beat electric signal of each wavelength is obtained by dividing and modulating.

According to a third aspect of the present invention, in the optical heterodyne spectroscopic analyzer of the first or second aspect, the means for generating the modulated signal light and the modulated reference light is an acousto-optic modulator that is modulated and driven by an ultrasonic oscillator. Is used.

According to the first aspect of the present invention, the signal light and the reference light obtained by dividing the light of the first wavelength and the light of the second wavelength emitted from the first light source and the second light source, respectively, are converted into the required frequency. To generate a modulated signal light and a modulated reference light of the first wavelength and the second wavelength, respectively, and multiplex the modulated signal light and the modulated reference light of the first wavelength and the second wavelength, and The first light source and the second light source are obtained by performing a differential operation on the optical heterodyne beat electrical signal obtained by photoelectrically converting the modulated signal light and the modulated reference light of each wavelength divided and transmitted at the ratio of , A time-varying amplitude fluctuation component can be removed. Therefore, even if the amplitudes of the light from the first light source and the second light source fluctuate with time, the light absorption characteristics of the device under test are accurately analyzed based on the difference between the optical heterodyne beat electrical signals, and the device under test is measured. The concentration of an object can be measured. Also,
Since the measurement is based on the non-scattered light, the light absorption characteristics of the object can be accurately analyzed without depending on the shape of the object, and the concentration of the object can be measured.

According to a second aspect of the present invention, an object to be measured is obtained from an optical heterodyne beat electric signal corresponding to the difference between the modulation frequencies of the modulation signal light and the modulation reference light of each of a plurality of wavelengths emitted from the first light source. Since the measurement can be performed while distinguishing the absorption characteristics of other components having absorption wavelengths close to that of the object, more accurate light absorption characteristics of the measured object can be measured.

According to the third aspect of the present invention, since the acousto-optic modulator is used to generate the modulated signal light and the modulated reference light, the light necessary for obtaining the optical heterodyne beat electric signal can be easily modulated. it can.

[0011]

Next, an embodiment of the present invention will be described. FIG. 1 is a block diagram illustrating an overall configuration of an optical heterodyne spectroscopic analyzer according to an embodiment.
Hereinafter, the configuration of the optical heterodyne spectrometer will be described together with its operation. As shown in FIG.
The light PA emitted from the first light source 1 is 1 /
The light enters a non-polarization type beam splitter 4 via a two-wavelength plate 2. Note that, when the light PA passes through the object S to be described later, the wavelength of the light having a high absorption rate by the object in the object S, for example, glucose, such as 780,
It has a wavelength of nm.

The light PA incident on the beam splitter 4
Is 50 to the light PA1 going straight and the light PA2 reflected
It is split into pairs 50. The light PA1 is signal light that passes through the object S to be described later, while the light PA2 is reference light that does not pass through the object S. The signal light PA1 enters the acousto-optic modulator (AOM1) 5, and the reference light PA2 enters the acousto-optic modulator (AOM2) 7. The reference light PA1 incident on the acousto-optic modulator 5 is 80.000 MH oscillated from the ultrasonic oscillator 6 in the acousto-optic modulator 5.
It is modulated by the ultrasonic wave of z. Therefore, the light that has passed through the acousto-optic modulator 5 becomes a modulated signal light PA3 modulated at a frequency of 80.000 MHz.

On the other hand, the reference light PA2 input to the acousto-optic modulator 7 is modulated by the acousto-optic modulator 7 with an ultrasonic signal of 80.455 MHz by the output signal of the ultrasonic oscillator 8. Therefore, the light passing through the acousto-optic modulator 7 is 80.4
The modulated reference light PA4 is modulated by the 55 MHz ultrasonic wave. The modulated signal light P that has passed through the acousto-optic modulator 5
A3 is reflected by the mirror 9 at 90 degrees, and then enters the multiplexer 11.

The light PB emitted from the second light source 12 that emits laser light is a non-polarization type beam.
The light PB1 incident on the splitter 14 and traveling straight is split into 50:50 light PB1 and reflected light PB2. The light PB1 becomes signal light passing through the measured object S,
The light PB2 is a reference light that does not pass through the measured object S. The signal light PB1 is incident on an acousto-optic modulator (AOM) 15,
The reference light PB2 is incident on an acousto-optic modulator (AOM) 16. Note that the light PB has a wavelength of 850 nm, which has a low absorption rate by an object to be measured, for example, glucose when transmitted through the object to be measured S, for example, glucose.

The signal light P incident on the acousto-optic modulator 15
B1 is an ultrasonic oscillator 17 in the acousto-optic modulator 15.
Is modulated by the 79.800 MHz ultrasonic wave oscillated from. Therefore, the light passing through the acousto-optic modulator 15 is 79.
The modulated signal light PB3 is modulated at a frequency of 800 MHz. Then, the modulated signal light PB3 that has passed through the acousto-optic modulator 15 is reflected by the mirror 19 at 90 degrees and then enters the multiplexer 11.

On the other hand, the reference light PB2 incident on the acousto-optic modulator 16 is modulated by the acousto-optic modulator 16 with 80.550 MHz ultrasonic waves oscillated from the ultrasonic oscillator 18. Therefore, the light passing through the acousto-optic modulator 16 is 8
The reference light PB4 is modulated by an ultrasonic wave of 0.550 MHz.

The modulated signal light PA3 multiplexed by the multiplexer 11
And the modulated signal light PB3 is the measured object S (for example, a human finger)
, And becomes a multiplexed signal light P1 to be incident on a beam splitter 21 of a non-polarization type.

The modulated reference light PA4 that has passed through the acousto-optic modulator 7 is reflected by the mirror 22 at 90 degrees, and then enters the multiplexer 24. The acousto-optic modulator 1
The modulated reference light PB4 that has passed through No. 6 is 90
After being reflected by the light, the light is incident on the multiplexer 24. The multiplexer 24 multiplexes the modulated reference light PA4 and the modulated reference light PB4, and then enters the beam splitter 21 as a multiplexed reference light P2.

The beam splitter 21 multiplexes the multiplexed signal light P1 and the multiplexed reference light P2 that have passed through the measured object S, divides the multiplexed signal light P1 into 50:50, and divides the multiplexed reference light P2 into photoelectric converters 31, 32. Make it incident. Photoelectric converter 3 composed of a photodiode
The photoelectric conversion signals output from 1, 32 have been subjected to optical heterodyne detection. That is, in the laser light having a wavelength of 780 nm emitted from the first light source 1, the signal light is modulated at 80.000 MHz by the acousto-optic modulator 5 and the reference light is modulated at 80.455 MHz by the acousto-optic modulator 7. Therefore, the photoelectric conversion signals output from the photoelectric converters 31 and 32 become optical heterodyne beat electric signals having a difference of 455 KHz between the modulation frequencies of the signal light and the reference light, and the wavelength emitted from the second light source 12 is In the 850 nm laser light, the signal light is modulated at 79.800 MHz by the acousto-optic modulator 15 and the reference light is 80.550 MH by the acousto-optic modulator 16.
Since the signal is modulated by z, the photoelectric conversion signal output from the photoelectric converters 31 and 32 becomes an optical heterodyne beat electric signal having a difference of 750 KHz in the modulation frequency.

The 45 output from the photoelectric converters 31 and 32
5 KHz optical heterodyne beat electrical signal and 750 KH
The z optical heterodyne beat electric signal is supplied to the differential operation circuit 33.
Is differentially calculated. Therefore, the first light source 1, the second light source 1,
The amplitude fluctuation component of the 455 KHz optical heterodyne beat electric signal and the 750 KHz optical heterodyne beat electric signal output from the differential operation circuit 33 also corresponds to the time-varying amplitude fluctuation component from the light source 12. Is removed.

The output terminal of the differential operation circuit 33 has 455K
Hz band-pass filter 34 and a 750 KHz band-pass filter 35 are connected.
The 455 KHz optical heterodyne beat electric signal and the 750 KHz optical heterodyne beat electric signal output from 3 are separated by passing through band-pass filters 34 and 35.

455 passed through the band-pass filter 34
The KHz signal is converted to a DC signal by the rectifier 36, and the 750 KHz signal passed through the band-pass filter 35 is converted to a DC signal by the rectifier 37. Then, the DC signal output from the rectifier 36 and the DC signal output from the rectifier 37 are ratio-calculated by the ratio calculation circuit 38.

The signal output from the ratio calculation circuit 38 is
DC signal value corresponding to 455KHz signal and 750KH
It is the ratio of the value of the DC signal corresponding to the z signal. The analyzer 39 connected to the output terminal of the ratio calculation circuit 38 measures the light absorptivity of the test object (glucose) in the test object S based on the DC signal ratio. That is, 455 KHz
The DC signal corresponding to the signal corresponds to the light intensity after light having a wavelength absorbed by glucose in the measurement target S has passed through the measurement target S as non-scattered light, and corresponds to a 750 KHz signal. Corresponds to the light intensity after light of a wavelength not absorbed by glucose in the measurement object S has passed through the measurement object S as non-scattered light, so that the analyzer 39 detects the light intensity based on the ratio of both DC signals. From the light absorption rate of the measurement object S, gluco-
The concentration of the solution can be measured.

When the analyzer 39 analyzes the light absorptance of the test object S based on the ratio of the two DC signals and measures the glucose concentration in the test object S as described above, the initial adjustment is performed. The signal output from the ratio calculating circuit 38 when the modulated signal light PA3 and the modulated signal light PB3 multiplexed by the multiplexer 11 are directly incident on the beam splitter 21 without passing through the measured object S. The luminous intensity from the first light source and the luminous intensity from the second light source are adjusted so as to be equal to each other, and then the object to be measured S is set in the optical path.

In the above embodiment, one light source is used for each of the first light source 1 and the second light source 12, but the first light source 1 and the second light source 12 are absorbed by the object in the object S as the first light source. A plurality of light emitters may be used to emit a plurality of lights having wavelengths in the vicinity of the wavelength at which light is easily emitted. In this case, the light emitted from each light emitter is divided into signal light and reference light, and then modulated by an acousto-optic modulator to correspond to the difference between the modulation frequencies of the modulated signal light and the modulated reference light of each wavelength. Since a plurality of optical heterodyne beat electrical signals are obtained and the optical absorption characteristics of components different from the object in the object S can be measured separately, the concentration of the object in the object S can be increased. It can be measured accurately.

[0026]

According to the first aspect of the present invention, even if the light amplitude of each of the first and second light sources fluctuates with time, the light absorption characteristics of the object to be measured are accurately analyzed, and the object to be measured is analyzed. It is possible to measure the concentration of the measured object therein. Further, the concentration of the measured object in the measured object can be measured without depending on the shape of the measured object.

According to the second aspect of the present invention, the measured object is obtained from the optical heterodyne beat electric signal corresponding to the difference between the modulation frequency of the modulation signal light and the modulation frequency of the modulation reference light emitted from the first light source. Since the light absorption characteristic of another component different from that of the object to be measured can be measured, the light absorption characteristic of the object to be measured can be measured more accurately.

According to the third aspect of the present invention, it is possible to easily modulate light necessary for obtaining an optical heterodyne beat electric signal.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of an embodiment of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 first light source 4, 14 beam splitter 5, 7, 15, 16 acousto-optic modulator 6, 8, 17, 18 ultrasonic oscillator 12 second light source 21 multiplexer 31, 32 photoelectric converter 33 difference Dynamic operation circuit 34, 35 Band-pass filter 36, 37 Rectifier 38 Ratio operation circuit 39 Analyzer S Measurement object

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tomonari Kamei 8 Suzuken, Higashi-Katabata-cho, Higashi-ku, Nagoya-shi, Aichi Prefecture (72) Inventor Takeshi Naito 8-Shift, Higashi-Katabata-cho, Higashi-ku, Nagoya-shi, Aichi ( 72) Inventor Yoshihide Naito 52-1 Katasaka-cho, Mizuho-ku, Nagoya-shi, Aichi

Claims (3)

[Claims] 1. A first light source that emits light having a first wavelength that is easily absorbed by an object in a measurement object, and a second light source that emits light of a second wavelength that is hardly absorbed by the measurement object in the measurement object. A second light source that emits light, and splits each light emitted from the first light source and the second light source into a signal light that passes through the object to be measured and a reference light that does not pass through the object to be measured. Means for modulating the signal light and the reference light at the first wavelength and the second wavelength at required frequencies to generate modulated signal light and modulated reference light at the first and second wavelengths, respectively. Means for multiplexing the modulated signal light and the modulated reference light having the first wavelength and the second wavelength and transmitting the divided light at a predetermined ratio; The modulation signal of each wavelength is obtained by photoelectrically converting the modulation signal light and the modulation reference light of the wavelength. Means for obtaining an optical heterodyne beat electric signal corresponding to the difference between the modulation frequencies of the light and the modulated reference light; means for differentially operating the optical heterodyne beat electric signal; and differentially operated optical heterodyne beat Means for analyzing light absorption characteristics of the object to be measured based on the electrical signal and measuring the concentration of the object to be measured. 2. A light heterodyne beat electrical system of each wavelength by emitting a plurality of lights having different wavelengths from the first light source, dividing the light of each wavelength into signal light and reference light, and modulating the light. The optical heterodyne spectroscopic analyzer according to claim 1, wherein a signal is obtained. 3. The optical heterodyne spectroscopic analyzer according to claim 1, wherein the means for generating the modulated signal light and the modulated reference light uses an acousto-optic modulator modulated and driven by an ultrasonic oscillator.