JP2004101478A - Simultaneous and optical measurement method using multiple light, and apparatus for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical measurement method and an apparatus for it, which have a simple apparatus constitution, implement spectral-optical measurement in one step and are hardly influenced by external light. <P>SOLUTION: The measurement apparatus radiates lights having different wavelengths λ1, λ2, λ3 from lasers 2-1, 2-2, 2-3, modulates the amplitudes of the emitted lights by frequencies ω1, λω, ω3 different from modulation signal generators 4-1, 4-2, 4-3, provided in a laser drive circuit and simultaneously radiates amplitude modulation lights to a subject T through optical fibers 6-1, 6-2, 6-3. The amplitude modulation lights, pass through the subject T and a plurality of component signals corresponding to the frequencies ω1, λω, ω3 in an electrical signal, obtained by photoelectric conversion of a photodiode 20 so as to be extracted, based on frequency signals obtained from the modulation signal generators 4-1, 4-2, 4-3. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention belongs to the technical field of optical measurement, in particular, by irradiating the subject with a plurality of lights of different wavelengths, and detecting light passing through the subject, the spectroscopic The present invention relates to a method for measuring characteristics and an apparatus used for the method. The measurement of the present invention can be applied to, for example, measurement of a dynamic state change of a subject or atomic absorption analysis.
[0002]
Problems to be solved by the prior art and the invention
Conventionally, when simultaneously irradiating a subject with continuous spectrum light or a plurality of lights having different wavelengths to perform spectroscopic measurement, a spectroscope having a complicated mechanism as a photodetector and complicated adjustment is required. In addition, the spectroscope has a disadvantage that the accuracy is easily deteriorated due to the influence of the thermal expansion, so that maintaining the conditions for maintaining the accuracy is troublesome. In addition, by sequentially irradiating the subject with a plurality of lights having different wavelengths, spectroscopic measurement can be performed without using a spectroscope. However, in this case, since simultaneous measurement cannot be performed, accurate simultaneous measurement cannot be performed in the case of a subject performing a dynamic state change.
[0003]
Further, the conventional optical measurement method as described above has a drawback that when external light including the wavelength involved in the measurement is incident, the measurement result is affected and accurate measurement cannot be performed. There is a disadvantage that it is necessary to perform the measurement in a dark place where light does not enter.
[0004]
SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical measurement method and an optical measurement method which can perform spectroscopic measurement at a time with a simple device configuration and are not easily affected by external light.
[0005]
[Means for Solving the Problems]
According to the present invention, as achieving the above objects,
A plurality of amplitude-modulated lights obtained by modulating the amplitudes of a plurality of lights having different wavelengths at a plurality of different frequencies are simultaneously irradiated on the subject, and the amplitude-modulated light passing through the subject is photoelectrically converted. Extracting a plurality of component signals corresponding to each of the plurality of frequencies in the electrical signal, a simultaneous optical measurement method using a plurality of lights,
Is provided.
[0006]
In one embodiment of the present invention, the plurality of lights are emitted from a plurality of lasers, and a plurality of modulation signal generators provided in a driving circuit of the plurality of lasers cause a plurality of modulation signal generators to change the amplitudes of the plurality of lights from each other. The signal is modulated by a frequency, and the plurality of component signals are extracted based on signals of those frequencies obtained from the plurality of signal generators for modulation. In one embodiment of the present invention, the plurality of lights are emitted from a plurality of lasers, and the amplitudes of the plurality of lights emitted from the plurality of lasers are modulated at a plurality of different frequencies by a plurality of modulation elements. The plurality of component signals are extracted based on the signal of the frequency of the modulation element.
In one embodiment of the present invention, the object is irradiated after the plurality of amplitude-modulated lights are combined.
[0007]
Further, according to the present invention, as achieving the above objects,
A plurality of light sources that emit light of different wavelengths, a plurality of modulation units that modulate the amplitudes of a plurality of light beams emitted from the plurality of light sources at a plurality of different frequencies, and modulation by the plurality of modulation units. A light irradiation optical system that guides the plurality of amplitude-modulated lights to the subject, a photodetector that performs photoelectric conversion by detecting the amplitude-modulated light that has passed through the subject, and outputs an electric signal obtained by the photodetector. Simultaneous optical measurement using a plurality of lights, characterized by comprising: component signal extracting means for extracting a plurality of component signals corresponding to the signals based on a plurality of frequencies obtained from a plurality of modulating means. apparatus,
Is provided.
[0008]
In one embodiment of the present invention, the light source is a laser, and the modulating means is a modulation signal generator provided in a driving circuit of the laser. In one embodiment of the present invention, the light source is a laser, and the modulation unit is a modulation element provided on a passage of light emitted from the laser. In one embodiment of the present invention, the light irradiation optical system includes a plurality of optical fibers each having one end coupled to each of the plurality of light sources, and the other ends of the optical fibers are collectively combined into one light emitting unit. The light irradiation optical system further includes a collimator that guides light emitted from the light emitting unit to the subject. In one embodiment of the present invention, a light guide optical system that guides the amplitude-modulated light that has passed through the subject to the photodetector is provided. In one embodiment of the present invention, the light guiding optical system includes a condensing lens that condenses light from the subject, light that is condensed by the condensing lens is incident from one end, and the other end is An optical fiber coupled to the photodetector.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0010]
FIG. 1 is a schematic diagram for explaining an embodiment of the optical measuring method and the apparatus according to the present invention.
[0011]
In the present embodiment, the first laser 2-1, the second laser 2-2, and the third laser 2-3 are respectively different first wavelength λ1, second wavelength λ2, and third wavelength λ3. Emits light. The drive circuits of the lasers 2-1, 2-2, and 2-3 modulate the amplitude of light emitted from the lasers at a first frequency ω1, a second frequency ω2, and a third frequency ω3 different from each other. It includes a first modulation signal generator 4-1 as a plurality of modulation means, a second modulation signal generator 4-2, and a third modulation signal generator 4-3.
[0012]
Light emitted from the lasers 2-1, 2-2, and 2-3 is amplitude-modulated light that has been subjected to amplitude modulation by the modulation signal generators 4-1, 4-2, and 4-3, respectively. The part is made to enter one end of the first optical fiber 6-1, the second optical fiber 6-2, and the third optical fiber 6-3 which constitute the light irradiation optical system. A part of the light emitted from the lasers 2-1, 2-2, 2-3 is converted into optical fibers 8-1, 8-2, 8-3 which form an output stabilizing feedback circuit which forms a laser driving circuit. At one end of the optical fiber, the light is guided through the optical fiber, and the other end is incident on photodiodes 10-1, 10-2, and 10-3 as photodetectors constituting an output stabilizing feedback circuit. The laser drive circuit performs feedback control such that the amount of light detected by the photodiodes 10-1, 10-2, and 10-3 is stabilized on a time average.
[0013]
The other ends of the first to third optical fibers 6-1 to 6-3 are collectively formed to form one light emitting unit 7, and the light irradiation optical system further includes a light emitting unit 7 for emitting light emitted from the light emitting unit 7. Is provided to the subject T placed on the subject placing part 12. The light emitted from the light emitting unit 7 is converted into substantially parallel light by the collimator lens 14 and irradiates the subject T.
[0014]
Light (reflected light, transmitted light, scattered light, or the like) that has passed through the subject T is condensed by the condenser lens 16, is made incident on one end of the optical fiber 18, is guided in the optical fiber, and is transmitted through the other end. Incident on the photodiode 20 as a photodetector. The condenser lens 16 and the optical fiber 18 constitute a light guiding optical system. It should be noted that a filter 15 or a fiber grating that blocks transmission of light of wavelengths other than λ1, λ2, λ3 and wavelengths near the wavelengths may be arranged between the subject mounting part 12 and the condenser lens 16. Further, the light condensed by the condenser lens 16 may directly enter the photodiode 20 without using the optical fiber 18.
[0015]
The electric signal obtained by the photoelectric conversion in the photodiode 20 is amplified by the amplifier 22, and is input as an amplified signal V (t) to the signal extraction circuit 24 constituting the component signal extraction means. The signal extraction circuit 24 extracts a plurality of component signals corresponding to the three frequency (ω1, ω2, ω3) signals obtained from the modulation signal generators 4-1, 4-2, and 4-3. .
[0016]
Hereinafter, the operation of the optical measurement according to the present embodiment will be described.
[0017]
FIG. 2 shows signals from lasers 2-1, 2-2, and 2-3 that have been amplitude-modulated by three frequencies (ω1, ω2, ω3) of modulation signal generators 4-1, 4-2, and 4-3. It is a figure which shows the time change of intensity | strength P1, P2, P3 of the emitted light (amplitude modulation light). Here, P1 is a constant value P0 with a component proportional to sin ω1 · t superimposed thereon, P2 is a constant value P0 with a component proportional to sin ω2 · t superimposed thereon, and P3 is a constant value P0 Is superimposed with a component proportional to sinω3 · t. The light emitted to the subject T is obtained by combining these three amplitude-modulated lights in the light emitting unit 7. The light applied to the subject T undergoes a change due to the interaction with the subject T. Light that arrives at the condenser lens 16 via the subject T, for example, reflected light, transmitted light, or scattered light undergoes a change due to the above-described interaction for each of the three wavelengths λ1, λ2, and λ3. The same applies to an electric signal obtained by photoelectrically converting light incident on the photodiode 20 via the optical fiber 18 by the photodiode 20 and an amplified signal V (t) obtained by amplifying the electric signal by the amplifier 22.
[0018]
Therefore, the signal extraction circuit 24 performs the following calculation based on the signals of the three frequencies ω1, ω2, ω3 obtained from the modulation signal generators 4-1, 4-2, and 4-3 to obtain 3 Component signals S1, S2, S3
S1 = (1 / T) ∫ 0 T V (t) · sin [ω1 · t] dt
S2 = (1 / T) ∫ 0 T V (t) · sin [ω2 · t] dt
S3 = (1 / T) ∫ 0 T V (t) · sin [ω3 · t] dt
Is extracted. Here, T is a measurement time. These signal components S1, S2, and S3 have undergone changes due to the interaction of the amplitude-modulated light having the wavelengths λ1, λ2, and λ3 with the subject T (the magnitude thereof differs depending on the wavelengths λ1, λ2, and λ3). It also shows the results, and further corresponds to the results when the light of the wavelengths λ1, λ2, λ3 without amplitude modulation undergoes a change due to the interaction with the subject T, respectively.
[0019]
In the present embodiment, the subject T is irradiated with light obtained by performing amplitude modulation on light of a plurality of wavelengths at different frequencies from each other, and from an electric signal obtained by photoelectric conversion by the photodiode 20, the light of each wavelength is converted to the modulation frequency. Since the corresponding components are selected, the presence of external light does not substantially affect the measurement.
[0020]
Further, in the present embodiment, a spectroscope is not required, and only one photodiode 20 serving as a photodetector may be used. Therefore, the device configuration is simplified, and spectroscopic measurement can be performed at a time.
[0021]
In the above embodiment, the modulation signal generator provided in the laser driving circuit such as a semiconductor laser is used as the modulation means. However, in the present invention, the modulation means is provided in the passage of the light emitted from the laser. The provided modulation element can be used. FIG. 3 is a schematic diagram partially showing an embodiment of an external modulation method using such a modulation element. The first modulating element 3-1 is arranged in a passage of continuous light having a wavelength λ1 emitted from the first laser 2-1. By performing the modulation, the intensity P1 of the light passing through the modulation element 3-1 can be made similar to that described with reference to FIG. The light of the wavelengths λ2 and λ3 emitted from the second and third lasers is similarly modulated by the second and third modulation elements. Thereby, a plurality of lights are emitted from a plurality of lasers, and the amplitudes of the plurality of lights emitted from the plurality of lasers are modulated at a plurality of frequencies different from each other by a plurality of modulation elements. The plurality of component signals are extracted based on the signal. In this embodiment, the same operation and effect as those of the above embodiment can be obtained.
[0022]
【The invention's effect】
As described above, according to the present invention, a plurality of amplitude-modulated lights obtained by modulating the amplitudes of a plurality of lights having different wavelengths at a plurality of different frequencies are simultaneously irradiated on a subject, and the subject is irradiated with the plurality of amplitude-modulated lights. Since a plurality of component signals corresponding to each of the plurality of frequencies in the electric signal obtained by photoelectrically converting the passed amplitude modulated light are extracted, spectroscopic measurement can be performed at a time with a simple device configuration, and Optical measurement that is less susceptible to the effects of
[Brief description of the drawings]
FIG. 1 is a schematic diagram for explaining an embodiment of an optical measurement method and an apparatus therefor according to the present invention.
FIG. 2 is a diagram showing a temporal change in intensity of light emitted from a laser (amplitude modulated light) that has been amplitude-modulated by three frequencies ω1, ω2, and ω3 of a modulation signal generator.
FIG. 3 is a schematic diagram partially showing an embodiment of an external modulation scheme.
[Explanation of symbols]
2-1, 2-2, 2-3 Laser 3-1 Modulation element 4-1 4-2, 4-3 Modulation signal generator 6-1, 6-2, 6-3 Optical fiber 7 Light emitting section 8-1, 8-2, 8-3 Optical Fiber 10-1, 10-2, 10-3 Photodiode 12 Subject Placement Section 14 Collimator Lens 15 Filter 16 Condenser Lens 18 Optical Fiber 20 Photodiode 22 Amplifier 24 Signal extraction circuit T Subject

Claims (10)

A plurality of amplitude-modulated lights obtained by modulating the amplitudes of a plurality of lights having different wavelengths at a plurality of different frequencies are simultaneously irradiated on the subject, and the amplitude-modulated light passing through the subject is photoelectrically converted. A simultaneous optical measurement method using a plurality of lights, wherein a plurality of component signals corresponding to each of the plurality of frequencies in the electric signal are extracted. The plurality of lights are emitted from a plurality of lasers, and the amplitudes of the plurality of lights are modulated at a plurality of different frequencies by a plurality of modulation signal generators provided in a driving circuit of the plurality of lasers. 2. The simultaneous optical measurement method using a plurality of lights according to claim 1, wherein the plurality of component signals are extracted based on signals of those frequencies obtained from a modulation signal generator. The plurality of lights are emitted from a plurality of lasers, the amplitudes of the plurality of lights emitted from the plurality of lasers are modulated at a plurality of different frequencies by a plurality of modulation elements, and a signal having a frequency of the plurality of modulation elements is obtained. The simultaneous optical measurement method using a plurality of lights according to claim 1, wherein the plurality of component signals are extracted based on the plurality of component signals. The simultaneous optical measurement method using a plurality of lights according to any one of claims 1 to 3, wherein the object is irradiated after the plurality of the amplitude modulated lights are combined. A plurality of light sources that emit light of different wavelengths, a plurality of modulation units that modulate the amplitudes of a plurality of light beams emitted from the plurality of light sources at a plurality of different frequencies, and modulation by the plurality of modulation units. A light irradiation optical system that guides the plurality of amplitude-modulated lights to the subject, a photodetector that performs photoelectric conversion by detecting the amplitude-modulated light that has passed through the subject, and outputs an electric signal obtained by the photodetector. Simultaneous optical measurement using a plurality of lights, characterized by comprising: component signal extracting means for extracting a plurality of component signals corresponding to the signals based on a plurality of frequencies obtained from a plurality of modulating means. apparatus. The simultaneous optical measurement apparatus using a plurality of lights according to claim 5, wherein the light source is a laser, and the modulation unit is a modulation signal generator provided in a driving circuit of the laser. . The simultaneous optical measurement using a plurality of lights according to claim 5, wherein the light source is a laser, and the modulation means is a modulation element provided in a passage of light emitted from the laser. apparatus. The light irradiation optical system includes a plurality of optical fibers each having one end coupled to each of the plurality of light sources, and the other ends of the optical fibers are collectively formed as one light emitting portion, and the light 8. The simultaneous optical system according to claim 5, wherein the irradiation optical system further includes a collimator that guides light emitted from the light emitting unit to the subject. 9. measuring device. 9. A simultaneous optical measurement using a plurality of wavelengths of light according to claim 5, further comprising a light guiding optical system for guiding the amplitude-modulated light passing through the subject to the photodetector. apparatus. The light guide optical system has a condenser lens for condensing light from the subject, and light condensed by the condenser lens which is incident from one end and the other end of which is coupled to the photodetector. The simultaneous optical measurement device using a plurality of wavelengths of light according to claim 9, further comprising an optical fiber.

Images