JP2733040B2 - Ultra-high sensitivity optical rotation measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-high sensitivity optical rotation measuring device for non-invasively measuring the concentration of a rotatory substance in a suspension, in particular, sugar or cholesterol in blood.

[0002]

2. Description of the Related Art Conventionally, as means for measuring the rotation angle of a plane of polarization, that is, the optical rotation generated when linearly polarized light passes through an object to be measured, signal light passing through an analyzer is received by a photodiode. The optical rotation corresponding to the polarization characteristic of the object to be measured is measured based on the photoelectric conversion signal output from the photodiode.

[0003]

In a method for non-invasively measuring the blood glucose level and cholesterol level in a living body from outside the body, if the optical rotation of sugar or cholesterol is to be used, the blood may not be absorbed in the living body. Since the angle of rotation must be measured in the state of coexistence with the tissue, it corresponds to the measurement in the state of low concentration, and furthermore, the light passing through the living body is scattered and is in the same state as the suspension. Therefore, the sensitivity for measuring the blood glucose level and cholesterol level is required to be extremely high. In order to realize such an ultra-high sensitivity, it is necessary to adopt a means capable of increasing the sensitivity in principle, and to have a high degree of amplification and all noises caused by mechanical, electrical and environmental factors. Must be able to be removed. An object of the present invention is to provide an ultra-high-sensitivity optical rotation measurement device capable of realizing ultra-high sensitivity by removing various noise components.

[0004]

A first ultrahigh-sensitivity optical rotation measurement apparatus for solving the above-mentioned problems divides light having temporal coherence emitted from a light source into signal light and reference light. After modulating the signal light at a predetermined frequency by the modulating means, and passing the polarization signal light through the DUT while the polarization planes of the modulated signal light and the reference light are polarized in predetermined directions, respectively. An optical path length for electrically changing a difference in optical path length between the signal light and the reference light in an optical path for photoelectrically converting the combined light of the polarized signal light and the reference light having passed through the measured object by photoelectric conversion means. Variable means and mechanically driven optical path length varying means, and polarization plane rotation means for rotating the polarization plane of the polarization signal light, and the intensity of the optical heterodyne beat electrical signal photoelectrically converted by the photoelectric conversion means. To maximize the mechanical drive An optical rotation angle signal proportional to the first power of a rotation angle of a polarization plane corresponding to the polarization characteristic of the object to be measured, while controlling the optical path length variable means to adjust the path length variable means and to keep the phase constant; In order to obtain the polarization signal light, the polarization plane rotation means is controlled so that the polarization planes of the polarization signal light and the reference light form a certain angle.

A second ultra-high sensitivity optical rotation measurement device for solving the above-mentioned problem divides light having temporal coherence emitted from a light source into a signal light and a reference light, and outputs the signal light and the reference light. And the reference light are respectively modulated by the first and second modulating means at different frequencies, and the polarization signal light is modulated in a state where the polarization planes of the modulation signal light and the modulation reference light are respectively polarized in predetermined directions. The difference between the optical path length of the signal light and the reference light is transmitted to the optical path through which the combined light of the polarized signal light and the polarized reference light passes through the measured object. An optical path length varying means for electrically varying the polarization signal light, and a polarization plane rotating means for rotating the polarization plane of the polarization signal light, driving the optical path length varying means with a signal of a predetermined frequency, and Rotation angle of the polarization plane according to the polarization characteristics of the body The polarization plane of the polarized signal light and the polarization reference beam is configured to control the polarization plane rotating means so as to form a certain angle in order to obtain the optical rotation angle signal proportional to the first power of.

A third ultrasensitive optical rotation measurement device for solving the above-mentioned problem divides light having temporal coherence emitted from a light source into a signal light and a reference light and outputs the signal light. And the reference light are respectively modulated by the first and second modulating means at different frequencies, and the polarization signal light is modulated in a state where the polarization planes of the modulation signal light and the modulation reference light are respectively polarized in predetermined directions. The difference between the optical path length of the signal light and the reference light is transmitted to the optical path through which the combined light of the polarized signal light and the polarized reference light passes through the measured object. An optical path length variable means for electrically varying the polarization signal light, and a polarization plane rotation means for rotating the polarization plane of the polarization signal light, and the polarization signal light and the polarization reference light photoelectrically converted by the photoelectric conversion means. Constant phase of optical heterodyne beat electrical signal The polarization signal light and the polarization reference light in order to obtain the optical rotation angle signal proportional to the first power of the rotation angle of the polarization plane according to the polarization characteristic of the device under test, while controlling the optical path length varying means. The polarization plane rotating means is configured to control the polarization plane rotation means so that the plane of polarization forms a certain angle.

The above-mentioned first, second and third ultra-highly sensitive optical rotation measuring devices are disclosed in Japanese Patent Application No. 7-16063 filed on Feb. 2, 1995 by the present applicant. As described in "Optical Rotation Measurement Apparatus," an optical heterodyne system capable of outputting an angle signal proportional to the first power of the optical rotation angle even if the optical rotation angle corresponding to the polarization characteristic of the measured object becomes minute. Then, the following noise reduction control is performed.

The first ultra-high sensitivity optical rotation measurement device adjusts a mechanically driven optical path length varying means to maximize the intensity of an optical heterodyne beat electric signal photoelectrically converted by the photoelectric conversion means, The optical path length varying means is controlled to make the phase constant, and the polarization plane rotating means is controlled so that the polarization planes of the polarization signal light and the reference light form a constant angle.

A second ultra-high sensitivity optical rotation measurement device is
The optical path length varying means is driven by a signal of a predetermined frequency, and the polarization plane rotating means is controlled so that the polarization planes of the polarization signal light and the polarization reference light form a fixed angle.

Further, a third ultra-high sensitivity optical rotation measurement device is
The optical path length varying means is controlled to make the phase of the optical heterodyne beat electric signal of the polarization signal light and the polarization reference light photoelectrically converted by the photoelectric conversion means constant, and the polarization plane of the polarization signal light and the polarization reference light is controlled. Control the polarization plane rotating means so that.

[0011]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of the ultra-high sensitivity optical rotation measurement device of the first embodiment. Hereinafter, the configuration of the ultrasensitive optical rotation measurement device of the first embodiment will be described together with its operation. As shown in FIG. 1, a light source 1 is provided. The light source 1 is a vertically polarized super luminescent diode (SLD) having low temporal coherence. The light P0 is incident on the beam splitter 2 as substantially vertically polarized light in the process of passing through the photoisolator PI.

Light P emitted from the beam splitter 2
Is the light P1 transmitted and the light P2 reflected at right angles.
And divided into While the light P1 serves as a reference light,
The light P2 becomes signal light. In the process of passing through the half-wave plate 3, the reference light P1 is rotated by 90 degrees in the plane of polarization, and only light having the polarization to be interfered by passing through the polarizer 4 is used as the reference light P1A as the multiplexer 5 Is incident on.

On the other hand, the signal light P2 split by the beam splitter 2 is incident on an acousto-optic modulator (AOM) 6 functioning as a frequency shifter. The signal light P2 incident on the acousto-optic modulator 6 is modulated by the acousto-optic modulator 6 at a frequency of 80.000 MHz by an output signal from the signal oscillator 7. Therefore, the light that has passed through the acousto-optic modulator 6 is the signal light P whose frequency is shifted by 80.000 MHz.
2A. Although the reference light P1 is not modulated, the acousto-optic modulator 6A having the same function as the acousto-optic modulator 6 has
80.455 MHz (indicated by a two-dot chain line in FIG. 1)
It may be modulated by frequency.

After the signal light P2A is reflected at right angles by the reflector 8, it passes through the vertical polarizer 9 and becomes vertically polarized light. Thereafter, the signal light P2A functions as a polarization plane rotating device. The light is incident on a data (FR) 10.
This Faraday rotator 10 is a Faraday rotator.
This is to magnetically change the polarization direction of the signal light P2B passing through the data 10. Therefore, the Faraday rotator 10 is driven to rotate in accordance with a negative feedback signal obtained by adding a signal 25A from a PID circuit 25 to be described later and a reference signal of the lock-in amplifier 23, and the polarization direction of the signal light P2A is magnetic. And the signal light becomes the signal light P2B.

The signal light P2B whose polarization plane has been rotated by the driving of the Faraday rotator 10 passes through the measured object S composed of multiple scatterers containing blood sugar or cholesterol. When the signal light P2B passes through the measured object S, the polarization of the measured object S causes a slight rotation of the polarization plane of the signal light to become the signal light P2C.

The signal light P2C that has passed through the object S to be measured
Is a state in which a minute rotation of the polarization plane based on the minute polarization property of the measured object S occurs, and the reflection mirror PZ driven by the piezoelectric element is used.
After being reflected at right angles by the reflection surface of T and undergoing an optical path length change, the light is incident on a polarizer 11 that passes a horizontal component. Then, by passing through the polarizer 11, it becomes the deflection signal light P <b> 2 </ b> D from which unnecessary vertical components have been removed, and enters the multiplexer 5. Since the piezoelectric element driven reflecting mirror PZT expands and contracts the piezoelectric element in accordance with the applied voltage, the position of the reflecting mirror can be displaced, so that the optical path difference between the reference light and the signal light can be varied. . The mechanically driven mirror (mechanically driven optical path length varying means) MM is controlled so that the intensity of the heterodyne beam is maximized. The reflecting mirror PZT may be driven by a magnetostrictive element instead of driven by a piezoelectric element.

When the reference light P1A and the signal light P2D enter the multiplexer 5, the multiplexer 5 combines the two lights, and the combined light P3 is received by the photodiode 12. The multiplexed light P3 is composed of a reference light P1A polarized in the horizontal direction,
The polarization plane of the light P2A, which is vertically polarized light and modulated at a frequency of 80.000 MHz, is rotated by the Faraday rotator 10, and the rotation of the minute polarization plane based on the polarization property of the measured object S is further increased. Is generated, the signal light P2C in which the horizontal polarization component has been generated is multiplexed with the horizontal polarization P2D component from which the vertical component has been removed by passing through the horizontal polarizer 11.
The photodiode 12 receives the combined light P3, performs photoelectric conversion, and outputs an electric signal corresponding to the combined light P3. An LC resonance circuit 13 that resonates at 80.000 MHz is connected to the terminal of the photodiode 12, and 80.0% of the electric signals output from the photodiode 12 are connected.
Only the 00 MHz component is resonantly output.

The electric signal output from the LC resonance circuit 13 is converted into a double balanced mixer (DBM) 14
Is input to This double balanced mixer-14
Are 80.000 MHz electric signals including a signal of rotation of a minute polarization plane by the measured object S and a rotation of polarization plane by the Faraday rotator 10 output from the LC resonance circuit 13, and 80.455 MHz. A signal from the signal oscillator 15 is input, and a 455 KHz beat signal is output. Since only the beat signal 16A in the precise range of 455 kHz ± 1.2 kHz passes through this beat signal by the band pass filter (BPF) 16, the noise component is almost removed at this stage. The 455 kHz beat signal 16A passed through the band pass filter 16 is input to the double balanced mixer 17.

On the other hand, as described above, the signal oscillator 7
The 0.000 MHz signal is input to the acousto-optic modulator 6 and also to the double balanced mixer 18. In addition, this double balanced mixer-18
80.455 MHz from the aforementioned signal oscillator 15
A signal is also input. Therefore, this double balanced
The mixer 18 generates a signal 18A having a frequency difference between the output signals of the two signal oscillators.

The signal 18A is supplied to the band-pass filter 1
9, only signal components in the range of 455 KHz ± 1.2 KHz are passed. The signal 19A that has passed through the band-pass filter 19 is phase-shifted by the phase shifter 20, and then converted to a double-balanced mixer 20A.
21.

On the other hand, the double balanced mixer
The 455 KHz beat signal output from 14 passes through the above-described band-pass filter 16, and is 455 KHz ± 5.0 KHz by the band-pass filter 22.
Only the signal component 22A in the range of? Passes through and is input to the double balanced mixer 21.

The double balanced mixer 21 inputs a signal 21A having a frequency difference between the signals 20A and 22A to the lock-in amplifier 23. The lock-in amplifier 23 detects the phase of the signal 21A and outputs the signal 23A.
A is output. , PID control circuit 24 outputs the signal 23
After the PID processing of A, the signal 2 is used as a negative feedback signal for keeping the phase of the optical heterodyne beat electric signal constant.
4A is input to the above-described piezoelectric element driven reflecting mirror PZT.

As described above, the 455 KHz beat signal 16A that has passed through the band-pass filter 16 is
The signal is input to the balanced mixer 17. Further, the double balanced mixer 17 has the above-mentioned 455 KHz
And the signal 19A from the band-pass filter 19 are synthesized. After the output signal 17A of the double balanced mixer 17 is subjected to PID processing in the PID control circuit 25, the output signal 17A is supplied from the PID circuit 25 to the Faraday rotator 10 so that the signal 17A becomes zero. And the reference signal of the lock-in amplifier 23 is added to output the negative feedback signal 10A. Then, the signal 25A obtained in this control is used as an output signal proportional to the first power of the optical rotation of the measured object S.

Next, a second embodiment will be described. FIG.
FIG. 3 is a block diagram showing an overall configuration of an ultra-high sensitivity optical rotation measurement device according to a second embodiment. Hereinafter, the configuration of the ultra-high sensitivity optical rotation measurement device of the second embodiment will be described together with its operation. Components similar to those shown in FIG. 1 are denoted by the same reference numerals as those in FIG. As shown in FIG.
Light P emitted from a laser diode light source 1 that emits a single-mode horizontally polarized laser light P with high temporal coherence
Is a photo isolator P. The light enters the beam splitter 2 via I.

The light P incident on the beam splitter 2 is
It is split into transmitted light P1 and light P2 reflected in a right angle direction. The light P1 serves as a reference light while the light P1
2 becomes signal light. The reference light P1 is incident on a first acousto-optic modulator (AOM) 6A. First acousto-optic modulator 6
The reference light P1 incident on A is 80.455M in the acousto-optic modulator 6A according to the output signal of the signal oscillator 15.
It is modulated at a frequency of Hz. Therefore, the light that has passed through the first acousto-optic modulator 6A becomes reference light modulated at a frequency of 80.455 MHz.

On the other hand, the signal light P2 is incident on a second acousto-optic modulator (AOM) 6B. The signal light P2 incident on the second acousto-optic modulator 6B is 80.000M in the acousto-optic modulator 6B according to the output signal of the signal oscillator 7.
It is modulated at a frequency of Hz. Accordingly, the light that has passed through the second acousto-optic modulator 6B becomes signal light modulated at a frequency of 80.000 MHz.

The reference light P 1 having passed through the first acousto-optic modulator 6 A has its polarization plane rotated by 90 degrees in the process of passing through the half-wave plate 3, becomes vertical polarization, and enters the polarizer 4. Then, by passing through the polarizer 4, the reference light P1A is narrowed down to only the direction in which the polarization direction is necessary.
While a part is reflected by the reflection plate 31, most of the reference light P1
A passes through the reflection plate 31 and a reflection mirror PZT driven by a piezoelectric element.
After being reflected in the right-angle direction by the reflection surface, the light passes through the polarizer 11A and is limited to only light having a polarization surface in the vertical direction, and is incident on the multiplexer 5. Reflector 31
The reference light P1A reflected by the light source is incident on the photodiode 33, and after being photoelectrically converted, an output signal thereof is amplified by an amplifier circuit (not shown) to drive a laser diode constituting the light source 1. , The amplitude noise of the emission of the laser diode is canceled, and the measured object S
Optical rotation can be measured with ultra-high sensitivity.

The signal light P2A modulated at a frequency of 80.000 MHz passing through the second acousto-optic modulator 6B
Is reflected by the reflector 8 at right angles, is limited to only horizontally polarized light in the process of passing through the polarizer 9A, and is then subjected to a Faraday rotator (F.
R. ) 10. Faraday rotator 10
The signal from the PID circuit 25 and 1
It is driven by a signal obtained by adding the signal from the 100 Hz oscillator 32.

The signal light P2C whose polarization plane has been rotated by driving the Faraday rotator 10 passes through the measured object S. When the signal light P2C passes through the measurement target S, the polarization of the measurement target S causes the signal light P2C to slightly rotate the plane of polarization. The signal light P2D that has passed through the measured object S is
In a state where a minute vertical polarization component is generated by the rotation of the minute polarization plane based on the polarization property of the measured object S, the polarizer 11
B is incident. Then, the vertically polarized signal light P2E from which most of the horizontally polarized components have been removed through the polarizer 11B is incident on the multiplexer 5.

When the reference light P1A and the signal light P2E enter the multiplexer 5, the multiplexer 5 combines the two lights, and the combined light P3 is received by the photodiode 12. The electric signal photoelectrically converted by the photodiode 12 is 455 KHz ± 1.
It becomes an optical heterodyne beat electric signal in the range of 2 KHz, is full-wave rectified by the full-wave rectifier REC, and is input to the lock-in amplifier 23. This lock-in amplifier 23
The signal from the 00 Hz oscillator 32 is input as a reference signal, and 110 out of the signals output from the full-wave rectifier REC.
Only the 0 Hz component is detected and output.

The signal output from the lock-in amplifier 23 is a signal proportional to the first power of the rotation angle of the minute polarization plane based on the polarization of the object S to be measured. The signal output from the lock-in amplifier 23 is
5 and becomes a more precise signal corresponding to the rotation angle of the polarization plane of the measured object S. This signal is used as a precise output signal proportional to the rotation angle of the plane of polarization.

This output signal is output from the above 1100
In a state where the signal is added to the oscillation signal from the Hz oscillator 32, the signal is negatively fed back to the Faraday rotator 10 described above. The Faraday rotator 10 is operated by the negative feedback signal.
Rotates in the opposite direction to cancel the rotation of the minute polarization plane based on the polarization property of the object S to be measured. The output signal of the PID control circuit 25 is the output signal of this ultra-high sensitivity optical rotation measurement device.

Next, a third embodiment will be described. FIG.
FIG. 9 is a block diagram showing the overall configuration of the ultra-high-sensitivity optical rotation measurement device of the third embodiment. Hereinafter, the configuration of the ultra-high sensitivity optical rotation measurement device of the third embodiment will be described together with its operation. Parts similar to those shown in FIGS. 1 and 2 are denoted by the same reference numerals as those in FIGS. As shown in FIG. 3, light P emitted from a laser diode light source 1 that emits a single-mode horizontally polarized laser light P having high temporal coherence is separated by a photo-isolator P.I. Bee through I
The beam enters the splitter 2.

The light P incident on the beam splitter 2 is
It is split into transmitted light P1 and light P2 reflected in a right angle direction. The light P1 serves as a reference light while the light P1
2 becomes signal light. The reference light P1 is incident on a first acousto-optic modulator (AOM) 6A. First acousto-optic modulator 6
The reference light P1 incident on A is 80.455M in the acousto-optic modulator 6A according to the output signal of the signal oscillator 15.
It is modulated at a frequency of Hz. Therefore, the light that has passed through the first acousto-optic modulator 6A becomes reference light modulated at a frequency of 80.455 MHz.

On the other hand, the signal light P2 is incident on a second acousto-optic modulator (AOM) 6B. The signal light P2 incident on the second acousto-optic modulator 6B is 80.000M in the acousto-optic modulator 6B according to the output signal of the signal oscillator 7.
It is modulated at a frequency of Hz. Accordingly, the light that has passed through the second acousto-optic modulator 6B becomes signal light modulated at a frequency of 80.000 MHz.

The reference light P1 that has passed through the first acousto-optic modulator 6A has its polarization plane rotated 90 degrees to become vertically polarized light in the process of passing through the half-wave plate 3, and is incident on the polarizer 4. . Then, the light passes through the polarizer 4 to become the reference light P1A from which components other than the vertically polarized light have been removed.
1, while most of the reference light P1A passes through the reflecting plate 31, is reflected at right angles by the reflecting surface of the reflecting mirror PZT driven by the piezoelectric element, and then passes through the polarizer 11A. Is input to the multiplexer 5 as vertically polarized reference light P1B having higher purity. The reference light P1A reflected by the reflection plate 31 is incident on a photodiode 33, and after being photoelectrically converted, an output signal thereof is amplified by an amplifier circuit (not shown) to form a laser diode constituting the light source 1. The negative feedback to the drive circuit of the diode cancels out the amplitude noise of the laser diode light emission, so that the optical rotation of the object S can be measured with ultra-high sensitivity.

The signal light P2A modulated at a frequency of 80.000 MHz passing through the second acousto-optic modulator 6B
Is reflected at a right angle by the reflector 8 and then, in the process of passing through the polarizer 9A, light other than horizontal polarized light is removed to become high-purity horizontal polarized light, which is a Faraday rotator functioning as a polarization plane rotating device. (FR) 10. The signal light P2B whose polarization plane has been rotated by the driving of the Faraday rotator 10 passes through the measured object S. When the signal light P2B passes through the measurement target S, the polarization of the measurement target S causes the signal light P2B to slightly rotate the polarization plane. Then, only the vertical polarization component generated based on the rotation of the polarization plane generated by the passage of the Faraday rotator 10 and the measured object S passes through the polarizer 11B, and becomes the signal light P2C. The light enters the multiplexer 5.

When the reference light P1B and the signal light P2C enter the multiplexer 5, the multiplexer 5 multiplexes the two lights, and the combined light P3 is received by the photodiode 12. The electric signal photoelectrically converted by the photodiode 12 is 455 KHz ± 1.
An optical heterodyne beat electric signal in the range of 2 kHz is obtained.

This beat electric signal is precisely 455 KHz ± 1.2 K by a band pass filter (BPF) 16.
Since only the beat signal 16A in the Hz range is passed,
At this stage, the noise component is almost removed. The 455 kHz beat signal 16A passed through the band pass filter 16 is input to the double balanced mixer 17. On the other hand, 80.000 MHz of the aforementioned signal oscillator 7
The signal is also input to the double balanced mixer 18. Also, this double balanced mixer 18 has
The 80.455 MHz signal from the signal oscillator 15 is also input. Therefore, the double balanced mixer 18 generates a signal 18A having a frequency difference between the output signals of the two signal oscillators.

The signal 18A is transmitted to the bandpass filter 1
9, only signal components in the range of 455 KHz ± 1.2 KHz are passed. The signal 19A that has passed through the band-pass filter 19 is phase-shifted by the phase shifter 20, and then converted to a double-balanced mixer 20A.
21.

On the other hand, the electric signal photoelectrically converted by the photodiode 12 passes through the above-mentioned band-pass filter 16 and is further converted to 455 by the band-pass filter 22.
Only the signal component 22A in the range of KHz ± 5.0 KHz is input to the double balanced mixer-21.

The double balanced mixer 21 inputs a signal 21A having a frequency difference between the signals 20A and 22A to the lock-in amplifier 23. The lock-in amplifier 23 detects the phase of the signal 21A, performs PID processing of the signal 23A in the PID control circuit 24, and as a negative feedback signal for keeping the phase of the optical heterodyne beat electric signal constant. The signal 24A is input to the above-described piezoelectric element driven reflecting mirror PZT.

As described above, the 455 KHz beat signal 16A that has passed through the band-pass filter 16 is
The signal is input to the balanced mixer 17. Further, the double balanced mixer 17 has the above-mentioned 455 KHz
And the signal 19A from the band-pass filter 19 are synthesized. After the output signal 17A of the double balanced mixer 17 is subjected to PID processing in the PID control circuit 25, the signal 25A from the PID circuit 25 and the reference signal of the lock-in amplifier 23 are converted so that the signal 17A becomes zero. Negative feedback signal 1 added
0A is input to the Faraday rotator 10 described above. The signal 25A obtained in the negative feedback control is used as an output signal proportional to the first power of the optical rotation of the measured object S.

In the above embodiment, the measurement target S is shown as a general multiple scatterer, but a finger or an ear lobe is used as a measurement target, and polarized signal light is transmitted through the measurement target S to measure the measurement target. By measuring the rotation angle of a minute polarization plane based on the polarization of the body, it is possible to non-invasively measure a blood glucose level or a cholesterol level in a living body including a human body. Further, it is possible to precisely measure the rotation angle of a minute polarization plane based on the polarization of a turbid object as well as a transparent object.

[0045]

As described above, according to the present invention, a signal proportional to the first power of the rotation angle of a minute polarization plane based on the polarization of the measured object is output in a state where noise is sufficiently removed. be able to. Therefore, even if the rotation angle is extremely small, since noise is sufficiently removed, amplification with a high amplification factor is possible, and the optical rotation can be measured with high accuracy. Therefore, using this as a basic technology, blood glucose level or cholesterol level in living body including human body,
It opens up the prospect for highly accurate, non-invasive measurement. In addition, the present invention can measure the rotation angle of a minute polarization plane based on the polarization of the multiple scatterers with ultra-high sensitivity, so not only in the medical field, but also in the biotechnology field,
Applications in the field of engineering, etc. are possible.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing an overall configuration of a second embodiment of the present invention.

FIG. 3 is a block diagram showing an overall configuration of a third embodiment of the present invention.

[Explanation of symbols]

1 light source 6, 6A. 6B Acousto-optic modulator 7 80.000 MHz oscillator 8 Reflector 10 Faraday rotator (polarization plane rotating means) 12,33 Photo diode (photoelectric conversion means) 15 80.455 MHz oscillator 16,19,22 band Pass filter 17, 18, 21 Double balanced mixer 20 Phase shifter 23 Lock-in amplifier 24, 25 PID control circuit PZT Piezoelectric element driven reflecting mirror S DUT

Continuation of the front page (56) References JP-A-4-34337 (JP, A) JP-A-63-44136 (JP, A) JP-A-8-210971 (JP, A) JP-A-4-231848 (JP , A) JP-A-7-114051 (JP, A)

Claims (6)

(57) [Claims] 1. A light having temporal coherence emitted from a light source is divided into a signal light and a reference light, and the signal light is modulated at a predetermined frequency by a modulating means. In a state where the polarization planes are polarized in predetermined directions, the polarization signal light is passed through the object to be measured, and the combined light of the polarization signal light having passed through the object to be measured and the reference light is photoelectrically converted. Optical path length varying means for electrically varying the optical path length difference between the signal light and the reference light, and mechanically driven optical path length varying means, and polarization for rotating the polarization plane of the polarization signal light. Surface rotation means, and
Optical heterodyne beam photoelectrically converted by the photoelectric conversion means
G) adjusting the mechanically driven optical path length varying means to maximize the intensity of the electric signal, and controlling the optical path length varying means to keep the phase constant, and according to the polarization characteristics of the object to be measured. Controlling the polarization plane rotation means so that the polarization planes of the polarization signal light and the reference light form a constant angle in order to obtain an optical rotation angle signal proportional to the first power of the rotation angle of the polarization plane. Ultra-high sensitivity optical rotation measurement device. 2. The ultra-high sensitivity optical rotation measuring device according to claim 1, wherein a modulation means for modulating the reference light at a frequency different from the modulation frequency of the signal light is provided in an optical path of the reference light. 3. Light having temporal coherence emitted from a light source is divided into signal light and reference light, and the signal light and reference light are respectively separated at different frequencies by first and second modulating means. After being modulated, the polarization signal light and the modulation reference light are polarized in predetermined directions, respectively, and the polarized signal light is passed through the measured object, and the polarized signal light passing through the measured object is An optical path for photoelectrically converting the multiplexed light with the polarization reference light by a photoelectric conversion unit, an optical path length variable unit for electrically varying a difference in optical path length between the signal light and the reference light, and a polarization plane of the polarization signal light; And a polarization plane rotating means for rotating the optical path length varying means, the optical path length varying means being driven by a signal of a predetermined frequency, and an optical rotation in proportion to the first power of a rotation angle of a polarization plane corresponding to the polarization characteristic of the measured object. The polarization signal light and the polarization signal light to obtain an angle signal An ultra-high-sensitivity optical rotation measurement apparatus, wherein the polarization plane rotation unit is controlled so that the polarization plane of the polarization reference light forms a predetermined angle. 4. Light having temporal coherence emitted from a light source is divided into signal light and reference light, and the signal light and reference light are respectively separated by first and second modulating means at different frequencies. After being modulated, the polarization signal light and the modulation reference light are polarized in predetermined directions, respectively, and the polarized signal light is passed through the measured object, and the polarized signal light passing through the measured object is An optical path for photoelectrically converting the multiplexed light with the polarization reference light by a photoelectric conversion unit, an optical path length variable unit for electrically varying a difference in optical path length between the signal light and the reference light, and a polarization plane of the polarization signal light; And a polarization plane rotating means for rotating the optical path length. The optical path length is variable so as to keep the phase of the optical heterodyne beat electric signal of the polarization signal light and the polarization reference light photoelectrically converted by the photoelectric conversion means constant. Means for controlling In order to obtain an optical rotation angle signal proportional to the first power of the rotation angle of the polarization plane corresponding to the polarization characteristic of the polarization plane, the polarization plane rotation means so that the polarization plane of the polarization signal light and the polarization reference light form a certain angle. An ultra-high sensitivity optical rotation measurement device characterized by controlling. 5. A light source using a semiconductor light emitting element, an optical path length varying means using a reflecting mirror driven by a piezoelectric element or a magnetostrictive element, and a polarization plane rotating means using a Faraday rotator. The ultra-high-sensitivity optical rotation measurement device according to claim 1, 2, 3, or 4. 6. The method according to claim 1, wherein the light emitted from the light source is detected and photoelectrically converted, and the electric signal is negatively fed back to the light source to eliminate the amplitude noise of the light emitted from the light source. Claim 1, 2, 3, 4 or 5
The ultra-high sensitivity optical rotation measurement device described in the above.