JP2829966B2 - Laser Doppler speedometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in the following order.

A Industrial application field B Outline of the invention C Conventional technology (Fig. 6) D Problems to be solved by the invention (Fig. 6) E Means for solving the problems (Figs. 1 to 3) F action (FIG. 1) G embodiment (G1) First embodiment (FIG. 1) (G2) Second embodiment (FIG. 2) (G3) Third embodiment (FIG. 3 and FIG. (Fig. 4) (G4) Fourth embodiment (Fig. 5) (G5) Other embodiments H Effect of the invention A Industrial application field The present invention relates to a laser Doppler velocimeter, and in particular, reflected light from an object to be measured. This utilizes the Doppler effect generated in the beam.

B. Outline of the Invention According to the present invention, in a laser Doppler speedometer, a measurement result can be obtained with high accuracy by modulating an optical modulator with a sine wave modulation signal.

C Conventional Art Conventionally, in this type of laser Doppler velocimeter, the speed of a measurement object such as a moving body, a vibrating body, a fluid, and the like (that is, a moving speed of the moving body, a vibration speed of the vibrating body, a flow velocity of the fluid ) Is measured (IEICE Research Report OQE85)
-160, pages 25-30).

That is, when the object to be measured is irradiated with a light beam obtained from the laser light source, a reflected light beam having a frequency shifted according to the speed of the object to be measured can be obtained.

Therefore, by measuring the frequency shift amount of the reflected light beam with respect to the light beam irradiated on the measured object, the speed of the measured object can be measured.

The laser Doppler velocimeter forms a reference light beam that is frequency-shifted by a predetermined amount with respect to a light beam obtained from a laser light source based on such a measurement principle, and the frequency of the reflected light beam with respect to the reference light beam. The speed of the object to be measured is measured by measuring the amount of deviation.

That is, in a laser Doppler velocimeter, a reference light beam is obtained by entering a light beam emitted from a laser light source into an optical modulator in which an electrode is formed on a dielectric substrate with a waveguide interposed therebetween. At the same time, the object to be measured is irradiated with a light beam to obtain a reflected light beam.

In the optical modulator, since the refractive index of the waveguide changes according to the applied voltage between the electrodes, it is possible to obtain an emission light beam whose phase has changed in proportion to the applied voltage with respect to the incident light beam.

As represented by the equation of the slave connexion the applied voltage the following equation V ₁ = at ...... the V _{1 (1),} if such increases monotonically with voltage increase rate a, the angular frequency of the incident light beam L ₁ the value ω ₁ Distant, value E ₁ the amplitude value, a proportional constant at a value k, the following equation _{a 1 (t) = E 1} cos (ω 1t + kat) = E 1 cos (ω 1 + ka) t ...... (2) Electric field strength whose frequency is shifted by the value ka expressed by the relational expression
A _{1 (t)} reference light beam can be obtained.

Therefore, as shown in FIG. 6, the sawtooth signal S _{1 is} applied between the electrodes.
The applied is set so that the phase difference between the reference light beam to the incident light beam between the maximum potential difference V _max and the minimum potential V _min of the sawtooth wave signal S ₁ is changed 360 °, serrated The repetition frequency of the wave signal S ₁ is represented by an angular frequency ω ₂ , and the amplitude value is a value E _2, and the following expression A _{2 (t)} = E ₂ cos (ω ₁ + ω ₂ ) t (3) A reference light beam having an electric field intensity A _{2 (t)} whose frequency is shifted by the angular frequency ω ₂ represented by the following _equation can be obtained.

On the other hand, the reflected light beam is shifted in frequency according to the speed of the object to be measured, so that if the measurement light beam and the reference light beam are made incident on the photodetector, the photodetector can be used. By using the frequency of the sawtooth signal used for forming the reference light beam as the center frequency, a frequency modulation signal that shifts in frequency according to the speed of the measured object can be obtained.

Thus, the output signal of the photodetector is set to the frequency (FM) using the frequency of the sawtooth signal as the center frequency.
n) By demodulating, the speed of the measured object can be measured.

D Problems to be Solved by the Invention However, in this type of laser Doppler velocimeter, it is necessary to form a saw-tooth wave signal having a very small waveform distortion and an extremely high signal level maintained at a predetermined signal level. is there.

That is, if waveform distortion occurs in the sawtooth signal or the signal level changes, the frequency characteristics of the reference light beam deteriorate, and the reference light beam contains many harmonic components.

Since the frequency modulation signal obtained via the photodetector is a frequency modulation signal whose frequency shifts in accordance with the speed of the measured object with the sawtooth signal as the center frequency, such a harmonic component occurs, The generation of many harmonic signal components with respect to the center frequency results in deterioration of the accuracy of the measurement result.

In practice, when the object to be measured is a moving object having a moving speed of about 3 [m / sec], a frequency of 10
It is necessary to apply a sawtooth signal having a peak value of about several tens of volts at about [MHz].

However, when a sawtooth signal is applied to the electrode of the optical modulator, it is practically difficult to apply such a sawtooth signal having a large frequency and signal level without causing waveform distortion. Inevitable.

Furthermore, since the frequency modulation signal obtained through the photodetector is a frequency modulation signal having the center frequency of the sawtooth wave signal as a center frequency, when measuring an object to be measured at a high speed, the sawtooth waveform is added. It is necessary to increase the frequency of the wave signal, and in such a case, the waveform distortion is further increased and the accuracy of the measurement result is reduced. Therefore, in practical use, this type of laser Doppler velocimeter has a problem that it is difficult to measure the speed of the object to be measured at a high speed.

The present invention has been made in consideration of the above points, and a laser Doppler velocimeter capable of obtaining a measurement result with high accuracy and capable of reliably measuring the speed even in the case of a fast measurement target. It is something to propose.

In the present invention for solving means above problems to solve E problems, the source light beam LA ₁ emitted from the laser light source 4, an optical path formed on the dielectric substrate 5 (6,7 , the obtaining by connexion measuring light beam LA ₄ to the reflected light generated by irradiating the object to be measured 3 through 8, 9, 10), the light source beam LA ₁
The through optical path (6,7,9,11) to give the reference light beam LA ₃ had it occurred modulated reference signal S _C by entering the light modulator 12 which is formed on the dielectric substrate 5, Reference light beam L
A ₃ and the measurement light beam LA ₄ give the combined light by combining the optical path (6-11), and light detecting means 21 the combined beam
, A light detection signal S ₀ including a Doppler signal component representing the moving speed of the measured object 3 is obtained, and the light detection signal S ₀
It shall apply in Rezadotsupura speedometer which measures the speed of motion of the object to be measured 3 on the basis of the sinusoidal modulation signal of angular frequency ω as the reference signal S _C by supplying to the optical modulator 12, an optical detection signal S ₀ sinusoidal modulated signal, with the sinusoidal modulation signal of the harmonic signal and Dotsupura signal components to generate a corresponding frequency-modulated signal component measuring optical system DEV1, reference signal S _C
, A frequency signal having an angular frequency that is an odd or even multiple of the angular frequency ω of the sine wave modulation signal or M / 2 (M is an integer) is generated, and the frequency signal and the light detection signal S ₀ are generated.
And a measurement signal forming circuit DEV2 that obtains a measurement output corresponding to the movement speed of the measured object 3 by demodulating the Doppler signal component after mixing the frequency modulation signal component with the frequency modulation signal component.

By that the F acts light modulator 12 so as to by connexion modulation operation to a sine wave modulation signal S _2, effectively prevent the risk such as by connexion measurement accuracy that harmonic components as in the prior art is caused to deteriorate can do.

G Example Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

(G1) First Embodiment In FIG. 1, DEV indicates a laser Doppler velocimeter as a whole, and includes a measurement optical system DEV1 and a measurement signal forming circuit DEV2.
And measures the vibration speed of the vibration surface of the speaker 3 driven by the drive circuit 2 as an object to be measured.

Laser light source 4 source light beam LA ₁ emitted from led dielectric material waveguide 6 formed on a substrate 5 made of, bifurcation 7, the waveguide 8 in passing connexion bifurcation 9, the waveguide 10 as well as
The light is branched by 11 and enters the optical modulator 12.

The optical modulator 12 has a pair of electrodes 14 facing each other with a waveguide 13 formed on the substrate 5 therebetween. One end of the waveguide 13 is connected to the waveguide 11 and the other end is connected to the substrate 5. Is connected to the mirror section 15 formed on the end face of.

Thus, the light beam split by the splitter 9 and made incident on the optical modulator 12 is reflected by the mirror unit 15 and then passes through the optical modulator 12 and is emitted toward the splitter 9 again. In this way, while the light source light beam LA ₁ passes between the electrodes 14,
The optical modulator 12 forms a reference light beam LA ₃ by shift the phase, which waveguide 11, the branch 9, to return to the branch unit 7 through the waveguide 8, via the waveguide 20 The light is emitted to the photodetector 21 composed of a PIN photodiode.

Electrode 14 of the optical modulator 12 is connected to a drive circuit 22, based on the reference signal S _C that is supplied to the drive circuit 22, the following equation _{V (t) = Vsinω 3 t} ...... (4), Signal level V _(t) having amplitude V and angular frequency ω ₃
By sinusoidal modulated signal S ₂ of is applied, the optical modulator
12 performs the modulation operation.

The resulting reference light beam LA via the light modulator 12
₃ has a complex amplitude E _{3 (t)} , the wavelength of the light source light beam LA ₁ is a value λ, and the interval and length of the electrode 14 are values d and L, respectively.
When the refractive index of the substrate 5 is a value n and the electro-optic constant is a value r, In conjunction with use of the value B ₁ represented, the initial phase value phi _3, when placed with the amplitude value E _3, the following formula _{E 3 (t) = E 3} exp {j · (ω 1 t + B 1 sinω 3 t + φ 3) ｝ Changes as shown by (6).

On the other hand, the light beam LA ₁ for the light source guided to the waveguide 10
Is irradiated to the vibration surface of the speaker 3 through the self-O poke microlens 23 attached to the end face of the substrate 5, the self-OH poke microlens 23 and the reflected light as measurement light beam LA _4, waveguide 10, the branch portion 9 after was Modotsu bifurcation 7 through the waveguide 8, the waveguide 20 is combined with passing connexion reference light beam LA ₃ is incident on the light detecting element 21.

Accordance connexion, values the amplitude values for vibrating surface of the speaker 3 A, the displacement A _(t) when the angular frequency is a value omega _4, the following equation _{A (t) = Asinω 4 t} = Asin2πf 4 t ...... (7) expressed in relationship, the complex amplitude E of the measuring light beam LA _{4
4 (t)} can be expressed as the following equation, where E ₄ is the amplitude value, and E _{4 (t)} = E ₄ exp {j · (ω ₁ t + A ₁ sinω ₄ t + φ ₄ )} (8) .

Here, based on the displacement A _(t) of the vibrating surface, the measurement light beam LA
Signal components produced in _4, since a value corresponding to the displacement velocity of the displacement A _(t) of the I connexion plane of vibration in Dotsupura effect (i.e. the differential value of the displacement A _(t)), the initial phase phi ₄ the signal component Along with A ₁ sinω ₄ t. However, 2πf ₄ = ω ₄ (10)

Accordingly, the reference light beam LA ₃
And similar light detection signal S ₀ is obtained and the squared detection combined light of the measuring light beam LA _4, which is based on (6) and (8), the following expression S _{0 (t)} = | E _{3 (t) + E 4 (} t) | 2 = {E 3 cos (ω 1 t + B 1 sinω 3 t + φ 3) + E 4 cos (ω 1 t + A 1 sinω 4 t + φ 4)} 2 + {E 3 sin (ω 1 t + B ₁ sinω ₃ t + φ ₃ ) + E ₄ sin (ω ₁ t + A ₁ sinω ₄ t + φ ₄ )｝ ² = E ₃₂ ｛cos ² (ω ₁ t + B ₁ sinω ₃ t + φ ₃ ) + sin ² (ω ₁ t + B ₁ sinω ₃ t + φ ₃ )｝ + E ₄₂ ｛cos ² (ω ₁ t + A ₁ sin ω ₄ t + φ ₄ ) + sin ² (ω ₁ t + A ₁ sin ω ₄ t + φ ₄ )｝ + 2E ₃ · E ₄ cos (ω ₁ t + B ₁ sin ω ₃ t + φ ₃ ) · cos (ω ₁ t + A ₁ sinω ₄ t + φ ₄ ) + 2E ₃ · E ₄ sin (ω ₁ t + B ₁ sinω ₃ t + φ ₃ ) · sin (ω ₁ t + A ₁ sinω ₄ t + φ ₄ ) = E ₃₂ + E ₄₂ + 2E ₃ · E ₄ cos (B ₁ sinω ₃ t−A ₁ sinω ₄ t + Δφ (11) However, the signal level S _{0 (t)} represented by the relational expression of Δφ = φ ₂ −φ ₁ (12 ₎ Having.

As described above, the light detection signal S ₀ has a DC component of a signal level proportional to the sum of squares of the amplitude values E ₃ and E ₄ (that is, the first component on the right side).
Term and the second term) are superimposed with the signal component of the AC component of the third term on the right side.

Then, only the cosine function part is extracted for the third term on the right side of the equation (11), and the following equation ω ₄ <ω ₃ (13) is obtained. Then, the following equation cos (B ₁ sinω ₃ t−A ₁ sinω _{4 t + Δφ) = cos (} B 1 sinω 3 t) · cos (a 1 sinω 4 t-Δφ) + sin (B 1 sinω 3 t) · sin (a 1 sinω 4 t-Δφ) as ... (14) Can be expanded. Therefore, equation (14) can be expanded based on Neumann's formula. As a result, the cosine function part of the third term on the right side of equation (11) is Can be expanded as follows.

In this manner, the light detection signal S ₀ obtained from the photodetecting element 21, the angular frequency omega ₃ of sinusoidal modulated signal S ₂ which is applied to the electrode 14 in the fundamental frequency, the harmonic components thereof is obtained It can be seen that the side band of the harmonic component includes the vibration speed information of the vibration surface of the speaker 3.

In this example, extract from such an optical detection signal S ₀ and the fundamental frequency component and frequency component twice that is adapted to measure the vibration velocity.

That is, the bandpass filter circuit 30 is
The center frequency receiving the light detection signal S ₀ of the sine wave modulation signal S ₂
And a bandpass filter circuit with an angular frequency of ω ₃
As a result, the signal level S _{3 (t)} of the output signal S ₃ obtained from the band-pass filter circuit 30 is given by the following equations (11) and (14): S _{3 (t)} = 2J ₁ (B ₁ ) E ₃・ E ₄ sinω ₃ t ・ sin (A ₁ sinω ₄ t−Δφ) = J ₁ (B ₁ ) E ₃・ E ₄・ [cos ｛ω ₃ t− (A ₁ sinω ₄ t−Δφ)｝ −cos ｛ ω ₃ t + (A ₁ sin ω ₄ t−Δφ)｝] (16)

Bandpass filter circuit hand 31, the light detecting element 21 of the light detection signal S ₀ and receive center frequency bandpass angular frequency 2 [omega ₃ of 2 times the angular frequency omega ₃ of sinusoidal modulated signal S ₂ The signal level S of the output signal S ₄ which is constituted by a filter circuit and is obtained from the band-pass filter circuit 31 as a result.
_{4 (t)} is (11) and (14) from the _{equation, S 4 (t) = 2J} 2 (B 1) E 3 · E 4 cos2ω 3 t · cos (A 1 sinω 4 t-Δφ) = J ₂ (B ₁ ) E ₃ · E ₄ · [cos ｛2ω ₃ t- (A ₁ sinω ₄ t-Δφ)｝ + cos ｛2ω ₃ t + (A ₁ sinω ₄ t-Δφ)｝] Become.

The output signal S ₄ is multiplied by the reference signal S _C in the multiplier circuit 32, output via a bandpass filter circuit 33 that multiplies the output signal center frequency is set to the angular frequency omega ₃ of sinusoidal modulated signal S ₂ and outputs it as the signal S _5.

Thus the output signal S ₅ obtained in the same manner as is as if the center frequency and low frequency converted twice the angular frequency 2ω comprising _three signal components of the sinusoidal modulated signal S ₂ ((17) formula) to the angular frequency omega ₃ , The following equation Has a signal level S5 _(t) represented by

Amplifier circuit 35, phase circuit 36 and amplifier circuit 37, phase circuit 38
, As the signal level of the output signal S ₃ and S ₅ of the band-pass filter circuit 30 and 33 are equal, respectively, after amplifying the output signal S ₃ and S _5, summed phase matching circuit 39
Output to

As a result, the constants C and C ₁ (C ₁ = 2)
With C), (16) and equation (18) from the equation, the following equation _{S 6 (t) = C ·} E 3 · E 4 · [cos {t- ω 3 (A 1 sinω 4 t-Δφ)} −cos ｛ω ₃ t + (A ₁ sinω ₄ t−Aφ)｝] + C · E ₃ · E ₄ · [cos ｛ω ₃ t− (A ₁ sinω ₄ t−Δφ)｝ + cos ｛ω ₃ t + (A ₁ sinω ₄ t−Δφ)｝] = C ₁ · E ₃ · E ₄ · cos {ω ₃ t− (A ₁ sinω ₄ t−Δφ)} (19) The signal level S _{6 (t)} it is possible to obtain the output signal S ₆ of.

From thus (19), in the output signal S _6, and the angular frequency omega ₃ of sinusoidal modulated signal S ₂ to the center frequency, the frequency-modulated signal whose frequency is shifted in accordance with the displacement of the speaker 3 is obtained I understand.

The output signal S ₆ is by connexion demodulation processing to the FM demodulation circuit 40, thereby the measurement output corresponding to the vibration speed of the vibration surface of the speaker 3 can be output from the FM demodulation circuit 40.

In the above configuration, the light source beam LA ₁ emitted from the laser light source 4 is converted by the optical modulator 12 into a sine wave modulated signal S ₂
It is connexion modulation processing on, thereby the reference light beam LA ₃ whose frequency is shifted sinusoidally is formed.

In contrast, the source light beam LA ₁ measuring light beam LA ₄ obtained by irradiating the vibrating surface of the speaker 3, the conductive to the light detecting element 21 with the reference light beam LA _3, as a result the light detector From 21 measure light beam LA ₄ and reference beam LA ₃ are 2
Light detection signal S ₀ was detected ride is obtained.

Of the light detection signal S _0, a sinusoidal modulation signal S ₂ of the angular frequency omega ₃ signal components with a center frequency of the bandpass filter circuit 30, the amplifier circuit 35, adding via the phase circuit 36 circuit
Is input to 39, this signal component centered frequency twice the angular frequency 2 [omega ₃ against the angular frequency omega ₃ of sinusoidal modulated signal S ₂ is extracted at the band-pass filter circuit 31 with respect to the multiplication circuit 32 After being converted to an angular frequency ω ₃ at low frequency, the signal is input to an addition circuit 39 via a band-pass filter circuit 33, an amplification circuit 37 and a phase circuit 38.

As a result, the output signal S ₆ , which is a frequency modulation signal whose frequency shifts according to the displacement of the vibration surface of the speaker 3, with the angular frequency ω ₃ of the sine wave modulation signal S ₂ as the center frequency via the addition circuit 39. Is obtained and demodulated in the FM demodulation circuit 40, whereby a measurement output corresponding to the vibration speed of the vibration surface of the speaker 3 can be obtained.

According to the above configuration, by the place of the sawtooth signal by modulating operated by connexion light modulator 12 to a sine-modulated signal S ₂ to measure the velocity of the object to be measured, has failed inevitable conventional It is possible to effectively avoid deterioration of measurement accuracy caused by waveform distortion of the sawtooth signal.

By further using a sinusoidal modulated signal S _2, since in the sinusoidal modulated signal S ₂ can be effectively avoid the occurrence of waveform distortion even by increasing the frequency, if the speed of the object to be measured is high In this method, the speed can be measured without deteriorating the measurement accuracy simply by increasing the frequency.

Further, in the case of the sawtooth signal, in order to maintain the signal level with no waveform distortion and with high accuracy, it is necessary to apply a light modulator 12 having a complicated drive circuit configuration, as described above. According to the arrangement, by which to use a sinusoidal modulated signal S _2, may further simplify the configuration of the signal processing circuit of the output signal obtained from the drive circuit and the light detecting element.

(G2) is the second view showing parts corresponding to those in the second embodiment Figure 1 shows a second embodiment of the present invention, the light detection signal S ₀ of the bandpass filter circuit 50 by providing the, the signal component of the angular frequency omega ₃ of sinusoidal modulated signal S _2, which was then extracted signal component at twice the angular frequency 2 [omega ₃ of the angular frequency omega ₃ so as to signal processing is there.

Based on the signal components S3 _(t) and S4 _(t) obtained by the above equations (16) and (17), the output of the bandpass filter circuit 50 is given by the following equation. S _{7 (t)} = S _{3 (t)} + S _{4 (t)} = J ₁ (B ₁ ) E ₃ · E ₄ · [cos ｛ω ₃ t- (A ₁ sinω ₄ t-Δφ)｝ -cos ｛ω _{3 t + (A 1 sinω 4} t-Δφ)}] + J 2 (B 1) E 3 · E 4 · [cos {2ω 3 t- (A 1 sinω 4 t-Δφ)} + cos {2ω 3 t + (A 1 sinω ₄ t−Δφ)｝] An output signal S ₇ having a signal level S _{7 (t)} represented by the following equation (20) can be obtained.

In this case the amplifier circuit 51 and the phase circuit 52, by adjusting the phase amplifies the reference signal S _C, the amplitude value
With A ₅ and a phase difference phi _5, the following expression _{S 8 (t) = A 5} cos (ω 3 t + φ 5) output signal ...... signal level S ₈ represented by the relational expression _{(21) (t)} to form an S _8.

The multiplier circuit 53, the amplifier circuit 54 and the phase circuit 55, after the reference signal S _C was doubled, by adjusting the phase amplifies, by using the amplitude values A ₆ and a phase difference phi _6, the following equation S _{9 (t)} = A ₆ cos (2ω ₃ t + φ _{6 )} An output signal S ₉ having a signal level S _{9 (t)} represented by the following equation (22) is formed.

Multiplication circuit 56 multiplies the output signal S ₇ of the band-pass filter circuit 50 combines the output signal S ₈ and S ₉ output from the phase circuit 52 and 55, the band-pass filter circuit 33 that multiplies the output signal Output to the FM demodulation circuit 40 via the

Of the product output signal that results from the multiplication circuit 56, the signal component of a center frequency equal angular frequency omega ₃ of sinusoidal modulated signal S ₂ is input is extracted into the FM demodulation circuit 40.

That is, at the output terminal of the bandpass filter circuit 33,
(20) the center frequency of the signal component of the angular frequency omega ₃ to the right side is represented by the first term and the (22) resulting signal component obtained by multiplying the angular frequency omega ₃ of the signal component represented by the formula of Formula omega _{3 and} the angular frequency ω expressed by the second term on the right side of equation (20)
_Third signal component (21) the sum signal S ₁₀ of the center frequency omega _third signal component of the angular frequency omega ₃ resulting signal component obtained by multiplying the signal component of the formula is obtained.

As the output signal S ₁₀ of the sub connexion bandpass filter circuit 33, It is possible to obtain an output signal S ₁₀ of the signal level S ₁₀ represented by the equation _(t).

The gain of the slave connexion amplifying circuit 51 and 54 is set to a predetermined gain, the following relational expression _{A 5 · J 2 (B 1} ) = A 6 · J 1 (B 1) ...... (24) is obtained The signal levels S _{8 (t)} and S _{9 (t)} of the output signals S ₈ and S ₉ are set to predetermined values and the phase circuit
52 and by adjusting the amount of phase shift of 55, the following equation _{-φ 5 = φ 6 = φ 56} ...... (25) of a predetermined value the phase difference relationship output signal as to obtain S ₈ and S ₉ by installing the from (23), the following formula _{S 10 (t) = a 5} · J 2 (B 1) E 3 · E 4 · cos (ω 3 t + a 1 sinω 4 t + φ 56 -Δφ) ...... it is possible to obtain an output signal S ₁₀ of the signal level S ₁₀ represented by the equation of _{(26) (t).}

Thus, it is possible to obtain a frequency modulation signal to shift the frequency in accordance with the displacement of the sine wave modulation signal S angular frequency omega ₃ in the center frequency vibration surface _2, by demodulating via the FM demodulation circuit 40 The vibration speed of the transmission surface can be measured.

According to the configuration of FIG. 2, in the first embodiment and can obtain the same effect, the signal components per and a center frequency angular frequency omega ₃ of sinusoidal modulated signal S ₂ to write, twice the angular frequency 2 [omega ₃ may min without separated into a signal component having a of the can simplify the structure as a whole.

(G3) Third Embodiment FIG. 3 shows a third embodiment of the present invention in which parts corresponding to those in FIG. In this case, the multiplication circuit 56
The reference signal S _C 1/2 step-down circuit 61, the amplifier circuit 62, an output signal S ₁₁ obtained via the phase circuit 63, the output obtained from the band-pass filter circuit 50 the signal S ₇ ((20) Expression).

Here 1/2 step-down circuit 61 by step down the angular frequency of the reference signal S _C to 1/2, the following equation as the output signal S ₁₁ Angular frequency obtaining omega _3/2, the output signal S ₁₁ of the amplitude A ₇ and a phase difference phi ₇ as.

As a result, the following expression is provided at the output end of the multiplication circuit 56. As in, 3/2 with respect to the angular frequency omega ₃ of sinusoidal modulated signal S ₂
Output signal S comprising a multiple of the angular frequency 3 [omega] _3/2 of the signal component
₁₂ is obtained.

Following formula of the output signal S _12, signal components of angular frequency 3 [omega] _3/2 is extracted at the band-pass filter circuit 64 having a center frequency of the angular frequency, thereby to the output terminal of the band-pass filter circuit 64 Obtain the output signal S ₁₃ which is represented in.

Here, regarding the parameters, J ₁ (B ₁ ) = J ₂ (B ₁ ) and
By selecting φ ₇ = 0, π, 2π, 3π..., (2
9) The formula is It can be expressed by a simplified mathematical formula as shown below.

By the way, it is understood that the condition of J ₁ (B ₁ ) = J ₂ (B ₁ ) is satisfied at B ₁ = 2.6, as is apparent from FIG.

But the value of B ₁ represents that with the way, by connexion determined such relationship to the voltage amplitude V of the sinusoidal modulation signal S ₂ is represented by the equation (5).

By adjusting the Yotsute B ₁ = 2.6 (sub connexion _{J 1 (B 1) = J} 2 (B 1)) so as to become the driving circuit 22 to adjust the amplitude V of the slave connexion sinusoidal modulated signal S ₂ , as represented Te cowpea to (30), can be the center frequency to obtain the output signal of the frequency modulation signal format 3 [omega] _3/2 from the band-pass filter circuit 64, thereby the FM demodulation circuit 40, a speaker The measurement signal indicating the vibration speed of the vibration surface of No. 3 can be easily demodulated.

Incidentally, per obtain the output signal S _13, the phase difference phi ₇ phi
Instead of selecting ₇ = 0, π, 2π, 3π,..., The equation (30) can be obtained by selecting φ ₇ = π / 2, 3π / 2, 5π / 2,. it is possible to obtain an output signal S ₁₃ of the same frequency modulation signal format and the.

(G5) Other Embodiments (1) In the embodiment of FIG.
A signal component having an angular frequency omega ₃ of sinusoidal modulated signal S ₂ from the 21 of the optical detection signal has dealt with the case of the signal processing to extract a signal component having an angular frequency 2 [omega ₃ twice that,
The present invention is not limited to this, for example, a signal component at twice the angular frequency 2 [omega _3, may be extracted by the signal processing and the signal component of three times the angular frequency 3 [omega] _3, short sinusoidal modulated signal S for _two of the angular frequency ω _3, an odd multiple of the angular frequency ω _3, 3ω _3, 5ω ₃
, And even multiples of angular frequencies 2ω ₃ , 4ω ₃
The signal processing may be performed together with the signal component having.

(2) In the embodiment of FIG. 1-FIG. 3, a single substrate incident light on the 5 obtained from the laser light source 4 beam LA ₁ bifurcation 7, 9 and the waveguide 6, 10 branches and synthesizing, 11, 20
And the case where the optical modulator 12 and the optical modulator 12 are integrally configured, but the present invention is not limited to this, and may be configured separately.

(3) In the embodiment shown in FIGS. 1 to 3, an optical modulator 12 having a pair of electrodes 14 opposed to each other with a waveguide interposed therebetween is used. In the embodiment shown in FIG. , Vibrator 72
Has dealt with the case of using as an optical modulator, the present invention is not limited thereto, to obtain a modulated light as frequency deviates sinusoidally accordingly by short applying a sine-wave modulated signal S ₂ Such optical modulators can be widely applied.

(4) In the above description, the embodiment in which the present invention is applied to the case where the vibration speed of the vibration surface of the speaker 3 is measured has been described. However, the present invention is not limited to this, and the present invention is not limited to this. The present invention can be widely applied to a laser Doppler velocimeter adapted to measure a velocity by utilizing the effect.

(5) In the embodiment shown in FIG. 2 and FIG.
The per inputting the output signal S ₇ including a signal component of the angular frequency omega ₃ and omega _4, has been adapted to remove signal components due connexion other angular frequency bandpass filter circuit 50, instead of this, The bandpass filter circuit 50 is omitted and the detection signal S ₀ is omitted.
Is directly input to the multiplication circuit 56, the same effect as in the above case can be obtained.

H Effects of the Invention As described above, according to the present invention, on a dielectric substrate, a combined light of a reference beam and a measurement light beam obtained from an optical modulator is obtained, and a sinusoidal signal is obtained from a light detection signal obtained from the combined light. A frequency modulation signal component corresponding to the wave modulation signal, its harmonic signal, and a Doppler signal component representing the motion speed of the object to be measured is obtained, and this is odd or even multiple of the angular frequency ω of the sine modulation signal, or M / After mixing with a frequency signal having an angular frequency twice (M is an integer), the Doppler signal component is demodulated, so that the speed of the object to be measured can be measured with a simple configuration and with high accuracy. In addition to this, it is possible to reliably measure the movement speed of a measurement target having a high movement speed.

[Brief description of the drawings]

1, 2, and 3 are schematic diagrams showing first, second, and third embodiments of the laser Doppler velocimeter according to the present invention, and FIG. 4 is a setting in the embodiment of FIG. FIG. 5 is a signal waveform chart for explaining the conventional technology, and FIG. 5 is a signal waveform chart for explaining the prior art. 3 ... speaker, 4 ... laser light source, 5 ... board, 6,
8, 10, 11, 13, 20 ... waveguide, 7, 9 ... branch part, 12
…… optical modulator, 21 …… photodetector, 30, 31, 33, 50 ……
Bandpass filter circuit, 32, 56 ... Multiplier circuit, 35, 3
7, 51, 54, 62 ... amplifier circuit, 36, 38, 52, 55, 63 ...
Phase circuit, 40 ... FM demodulation circuit, 53 ... Multiplier circuit, 61 ...
Down converter, DEV ... Laser Doppler speedometer.

Claims (2)

(57) [Claims] 1. A measuring light beam is obtained by reflected light generated by irradiating an object to be measured with a light source light beam emitted from a laser light source via an optical path formed on a dielectric substrate. Irradiating the light beam for the light source to the optical modulator formed on the dielectric substrate via the optical path to obtain a reference light beam modulated by a reference signal, and obtaining the reference light beam and the measurement. The light beam is combined in the optical path to obtain a combined light, and the combined light is incident on light detection means to obtain a light detection signal including a Doppler signal component representing the movement speed of the object to be measured, and the light detection is performed. A laser Doppler velocimeter for measuring the movement speed of the object to be measured based on a signal, wherein a sine wave modulation signal having an angular frequency ω is supplied to the optical modulator as the reference signal. A measurement optical system for generating the sine wave modulation signal as a light detection signal, a harmonic signal of the sine wave modulation signal, and a frequency modulation signal component corresponding to the Doppler signal component; and the sine wave modulation signal based on the reference signal. By generating a frequency signal having an odd frequency or an even multiple of the angular frequency ω of the frequency signal, demodulating the Doppler signal component after mixing the frequency signal and the frequency modulation signal component of the photodetection signal. And a measurement signal forming circuit for obtaining a measurement output corresponding to the movement speed of the object to be measured. 2. A measuring light beam is obtained by reflected light generated by irradiating a light source light beam emitted from a laser light source onto an object to be measured via an optical path formed on a dielectric substrate. Irradiating the light beam for the light source to the optical modulator formed on the dielectric substrate via the optical path to obtain a reference light beam modulated by a reference signal, and obtaining the reference light beam and the measurement. The light beam is combined in the optical path to obtain a combined light, and the combined light is incident on light detection means to obtain a light detection signal including a Doppler signal component representing the movement speed of the object to be measured, and the light detection is performed. A laser Doppler velocimeter for measuring the movement speed of the object to be measured based on a signal, wherein a sine wave modulation signal having an angular frequency ω is supplied to the optical modulator as the reference signal. A measurement optical system for generating the sine wave modulation signal as a light detection signal, a harmonic signal of the sine wave modulation signal, and a frequency modulation signal component corresponding to the Doppler signal component; and the sine wave modulation signal based on the reference signal. A frequency signal having an angular frequency of M / 2 times (M is an integer) of the angular frequency ω is generated, and the frequency signal is mixed with the frequency modulation signal component of the photodetection signal. A measurement signal forming circuit for obtaining a measurement output corresponding to the movement speed of the measured object by demodulation.