JPH11118709A - Optical heterodyne method spectrophotometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical heterodyne method spectrophotometer capable of analyzing the light absorption characteristics of a plurality of constituents of a body to be measured and measuring concentration. SOLUTION: This spectroscope is provided with a light source 1 to emit light with variable wavelengths, a controller 15 to variably control the wavelength of light P from the light source 1, a beam splitter 2 to divided the light P from the light source 1 into signal light P1 which is passed through a body to be measured S and reference light P2 which is not passed through the body to be measured S, a means to create modulated signal light P3 obtained by modulating the signal light P1 and modulated reference light P4 obtained by modulating the reference light P2 by frequencies which do not change the angles of diffraction of the signal light P1 and reference light P2 at the time when the wavelength of the light P is changed, a beam splitter 9 to obtain light heterodyne beats by combining the waves of modulated signal light PS and the modulated reference light P4, photoelectric converters 10 and 11, and an analyzing device 14 to analyze the light absorption characteristics of the constituents of the body to be measured S and measure the concentration on the basis of a light heterodyne beat electric signal.

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 a light absorption characteristic of a component of an object to be measured by an optical heterodyne method and measuring the concentration of the component.

[0002]

2. Description of the Related Art Conventionally, an optical heterodyne spectroscopic analyzer for analyzing the optical absorption characteristics of components of an object to be measured by an optical heterodyne method and measuring the concentration of the components has been known. An acousto-optic modulator driven by modulation by an ultrasonic wave is used to modulate each of the reference beams not to be passed and to obtain an optical heterodyne beat. When the wavelength of the light emitted from the light source changes, the diffraction angle of the acousto-optic modulator changes greatly with the change in the wavelength, making it difficult to obtain an accurate optical heterodyne beat and making the concentration measurement difficult. Therefore, the wavelength of light emitted from the light source is fixed, and the acousto-optic modulator is driven at a constant driving frequency of the ultrasonic wave corresponding to this wavelength, that is, a constant modulation frequency.

[0003]

Generally, a plurality of components are mixed in an object such as a living body, and the wavelength of light which is most easily absorbed by each component is different. In order to analyze the light absorption characteristics and measure the concentration, the wavelength of the light emitted from the light source is changed for each component, and in order to keep the diffraction angle of the acousto-optic modulator unchanged, It is necessary to change the modulation frequency of the acousto-optic modulator. However, in the conventional optical heterodyne spectroscopic analyzer, since the wavelength of light emitted from the light source and the modulation frequency of the acousto-optic modulator are constant, the optical absorption characteristics of a plurality of components in the measured object are analyzed. The concentration cannot be measured.

Accordingly, an object of the present invention is to provide an optical heterodyne spectroscopic analyzer capable of analyzing the light absorption characteristics of a plurality of components in a measured object and measuring the concentration.

[0005]

According to a first aspect of the present invention, there is provided a light source for emitting light having a variable wavelength, control means for variably controlling the wavelength of the light emitted from the light source, and light emitted from the light source. Means for dividing the light into signal light that passes through the object to be measured and reference light that does not pass through the object to be measured, and when the wavelength of the light is changed by the control unit, the signal light and the reference light, respectively. Means for generating a modulated signal light that modulates the signal light at a frequency that does not change the diffraction angle and a modulated reference light that modulates the reference light, the modulated signal light that has passed through the DUT and the DUT Means for obtaining an optical heterodyne beat by multiplexing the modulated reference light which does not pass through, means for obtaining an optical heterodyne beat electrical signal by photoelectrically converting the optical heterodyne beat, and the control means. Output Wavelength corresponding signal to the optical heterodyne bi - said on the basis of the preparative electric signal by providing the means for measuring the analyzed concentration of light-absorbing properties of the component 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, the control means changes the wavelength of the light of the light source in a stepwise manner, and the signal light corresponds to the wavelength change. And changing the modulation frequency of the reference light.

According to a third aspect of the present invention, there is provided the optical heterodyne spectrometer according to the first or second aspect, wherein the optical heterodyne beat is divided into two equal parts, and each of the two divided optical heterodyne beats is provided. And means for performing a differential operation on each of the optical heterodyne beat electric signals obtained by photoelectrically converting the signals.

According to the first aspect of the present invention, the wavelength of the light from the light source is changed in accordance with the light absorption characteristics of each of the components to be measured in the object to be measured, and the diffraction angles of the signal light and the reference light, respectively. Since the signal light and the reference light can be modulated at a frequency at which the optical signal does not change, the measurement of the DUT is performed based on the optical heterodyne beat electric signal obtained by photoelectrically converting the optical heterodyne beat obtained by the optical heterodyne method. The light absorption characteristics of each component can be analyzed to determine the concentration.

According to the second aspect of the present invention, the wavelength of the light from the light source can be changed in a stepwise manner, so that the light absorption characteristics of each component in the object to be measured for each wavelength are analyzed to measure the concentration. be able to.

According to the third aspect of the invention, even if the amplitude of the light from the light source fluctuates with time, the amplitude component of the light can be removed. It can be analyzed and the concentration can be measured accurately.

[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. 1, the optical heterodyne spectroscopic analyzer is provided with a light source (LD) 1 composed of a wavelength variable laser that emits a spectrum light P having a variable wavelength. The light source (LD) 1 is connected to a controller 15 that controls the entire optical heterodyne spectroscopic analyzer, and emits a spectrum light P having a wavelength based on a wavelength control signal from the controller 15. It is configured as follows. The wavelength control signal output from the controller 15 changes the wavelength of the spectrum light P emitted from the light source 1 continuously or stepwise.

The spectral light P emitted from the light source 1 is
The light is incident on the beam splitter 2 and split into light beams P1 and P2 in the beam splitter 2. The light P1 is signal light that passes through the object S to be described later, and the light P2 is reference light that does not pass through the object S. The signal light P1 is incident on the acousto-optic modulator (AOM1) 3, and the reference light P2 is incident on the acousto-optic modulator (AOM2) 4.

The acousto-optic modulator (AOM1) 3 is connected to an ultrasonic oscillator (OSC1) 5, and the acousto-optic modulator (AOM2) 4 is connected to an ultrasonic oscillator (OSC2) 6
Is connected to The ultrasonic oscillator (OSC1) 5 and the ultrasonic oscillator (OSC2) 6 are connected to the controller 15, and the controller 15 outputs the ultrasonic oscillator (OSC1).
1) The frequencies f1 and f2 based on the oscillation frequency control signals output to 5 and the ultrasonic oscillator (OSC2) 6, respectively.
Oscillates ultrasonic waves.

The signal light P1 incident on the acousto-optic modulator (AOM1) 3 is modulated by ultrasonic waves having a frequency f1 oscillated by an ultrasonic oscillator (OSC1) 5, and the modulated signal light P
It becomes 3. The reference light P2 incident on the acousto-optic modulator (AOM2) 4 is an ultrasonic oscillator (OSC2) 6
Is modulated by the ultrasonic wave of the frequency f2 oscillated at the above, and becomes the modulated reference light P4.

After the modulated signal light P3 is reflected by the mirror 7 at 90 degrees, the modulated signal light P3 is incident on an object to be measured S (for example, a human finger, milk, skim milk, or the like), and is transmitted as a modulated signal light PS to form a non-polarized light. The beam is incident on a beam splitter 9 of a scalable type. The modulated reference light P4 is reflected by the mirror 8 at 90 degrees, and then enters the non-polarization type beam splitter 9.

The modulation signal light PS and the modulation reference light P4 are
After being multiplexed by the splitter 9, based on the principle of optical heterodyne, the spectrum light P has a frequency (f1-f2) which is the difference between the modulation frequencies of the modulation signal light PS and the modulation reference light P4.
Is modulated to generate an optical heterodyne beat. Then, the optical heterodyne beat generated by the beam splitter 9 is equally divided and incident on the photoelectric converters (PD1) 10 and (PD2) 11 composed of photodiodes.

The signals photoelectrically converted by the respective photoelectric converters 10 and 11 become optical heterodyne beat electric signals subjected to optical heterodyne detection. This optical heterodyne beat electric signal is converted into an AC signal having a frequency (f1-f2) which is the difference between the modulation frequencies of the modulation signal light PS and the modulation reference light P4.

Each of the optical heterodyne beat electric signals output from the photoelectric converters 10 and 11 is converted into a differential operation circuit 1
2 and a differential operation is performed. Therefore, even if the amplitude of the spectral light P emitted from the light source 1 fluctuates with time, the amplitude fluctuating component is removed by the differential operation, so that the optical heterodyne signal from which the amplitude fluctuating component of the spectral light P is removed is removed. Only the electrical signal is output from the differential operation circuit 12.

The output side of the differential operation circuit 12 is connected to a lock-in amplifier 13 which uses the difference (f1-f2) of the modulation frequencies as a synchronization signal. Lock-in amplifier 13
Are connected to the controller 15, and when a synchronization signal corresponding to the difference (f1-f2) of the modulation frequencies is output from the controller 15, the optical heterodyne output from the differential operation circuit 12 is output. The beat electric signal is converted by the lock-in amplifier 13 into a DC signal from which noise components have been removed. Note that, instead of the lock-in amplifier 13, a band-pass filter and a rectifier of a variable pass frequency that uses the difference (f1-f2) of the modulation frequencies as a pass frequency can be used.

The DC signal output from the lock-in amplifier 13 is input to the analyzer 14, where the light absorption spectrum of the component of the device S to be measured corresponding to the wavelength of the spectral light P emitted from the light source 1 is stored. The controller 15 is
The wavelength of the spectral light P emitted from the light source 1 is continuously or variably controlled in a required wavelength range, and the oscillation frequencies of the ultrasonic oscillators 5 and 6 for driving the acousto-optic modulators 3 and 4 for modulation. f1 and f2 are inversely proportional to the wavelengths, and control is performed so that the diffraction angles of the modulation signal light P3 and the modulation reference light P4 do not change. When the above control is performed by the controller 15, the analyzer 14 stores the light absorption spectra of the plurality of components of the measured object S in the required wavelength range.

When the wavelength of the spectrum light P from the light source 1 is continuously and variably controlled, the analyzing device 14 is used for measuring the concentration of a plurality of components constituting the object S based on the light absorption spectrum. By measuring the light absorption characteristics of each component while distinguishing the light having the absorption wavelength of the component from the light having the absorption wavelength of the component other than the concentration measurement purpose, the concentration of each component can be measured more accurately. When the wavelength of the spectrum light P from the light source 1 is variably controlled stepwise,
Since the wavelength can be switched instantaneously, the light absorption characteristics of each component for a plurality of wavelengths can be measured in a short time.
Therefore, when measuring the light absorption characteristics of the components of the living body, it is relatively unaffected by the movement of the muscles of the living body and blood flow, which are the main factors of noise.

An optical heterodyne beat signal obtained by the optical heterodyne spectroscopic analyzer configured as described above is
Since it corresponds to the amount of non-scattered light transmitted through the measurement object S, a calibration curve is generally created by applying a mass analysis method or the like generally used in a spectrometer, and the measurement object S is formed based on the calibration curve. By analyzing the light absorption characteristics of a plurality of constituent components, the concentration of each component can be measured.

The optical heterodyne spectroscopic analyzer described above uses one light source 1 to continuously or stepwise change the wavelength of the light emitted from the light source 1 so that the object S can be measured. It has been described that the light absorption characteristics of a plurality of components are measured and the concentration of each component is measured.However, the light source is composed of a plurality of light sources, and the wavelength that is easily absorbed from each light source to each component of the measurement object is used. The light absorption characteristics of a plurality of components of the measured object S are measured by measuring the light absorption characteristics of a plurality of components of the measurement target S by changing the oscillation frequency of the ultrasonic oscillators 5 and 6 in synchronization with the above-described wavelength switching while causing the light to emit light. Can be.

[0024]

According to the first aspect of the present invention, the wavelength of the light from the light source is changed in accordance with the light absorption characteristics of each of the components to be measured in the object to be measured, and the signal light and the reference light are each changed. Since the signal light and the reference light can be modulated at a frequency at which the diffraction angle does not change, measurement is performed based on the optical heterodyne beat electrical signal obtained by photoelectrically converting the optical heterodyne beat obtained by the optical heterodyne method. The light absorption characteristics of each component in the body can be analyzed to determine the concentration.

According to the second aspect of the present invention, since the wavelength of the light from the light source can be changed in a stepwise manner, the concentration is measured by analyzing the light absorption characteristics of each component in the measured object with respect to each wavelength. be able to.

According to the third aspect of the present invention, even if the amplitude of the light from the light source fluctuates with time, the amplitude component of the light can be removed, so that the concentration of each component in the measured object can be accurately determined. Can be measured.

[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 light source 2, 9 beam splitter 3, 4 acousto-optic modulator 5, 6 ultrasonic oscillator 7, 8 mirror 10, 11 photoelectric converter 12 differential operation circuit 13, lock-in amplifier 14 analyzer 15 controller S DUT

 ────────────────────────────────────────────────── ─── 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] A light source that emits light of variable wavelength; control means for variably controlling the wavelength of the light emitted from the light source; and a signal light for passing the light emitted from the light source through an object to be measured. Means for dividing the signal light into reference light that does not pass through the object to be measured, and the signal light at a frequency that does not change the respective diffraction angles of the signal light and the reference light when the wavelength of the light is changed by the control means. Means for generating a modulated modulated signal light and a modulated reference light that modulates the reference light, and multiplexes the modulated signal light passed through the measured object and the modulated reference light not passed through the measured object. Means for obtaining an optical heterodyne beat, means for photoelectrically converting the optical heterodyne beat to obtain an optical heterodyne beat electric signal, and a wavelength corresponding signal output from the control means and the optical heterodyne beat. Means for analyzing the light absorption characteristics of the components of the object to be measured based on the beat electric signal and measuring the concentration. 2. The apparatus according to claim 1, wherein the control means changes the wavelength of the light from the light source in a stepwise manner, and changes the modulation frequencies of the signal light and the reference light in accordance with the wavelength change. 2. The optical heterodyne spectroscopic analyzer according to 1. 3. A means for equally dividing said optical heterodyne beat into two, and a difference between respective optical heterodyne beat electric signals obtained by photoelectrically converting each of the divided optical heterodyne beats. 3. An optical heterodyne spectroscopic analyzer according to claim 1, further comprising means for performing a dynamic operation.