JPH0829248A - Laser doppler vibration meter - Google Patents

Abstract

PURPOSE:To provide a laser Doppler vibration meter which can optimize the intensity of laser beams discharged from the vibration meter and at the same time prevent measurement data from deteriorating by detecting the reduction in signal component of input scattered light or self vibration. CONSTITUTION:In a laser Doppler vibration meter with a signal processing device 13 which performs light heterodyne detection of a scattered light 3e of laser beams reflected from a vibration object 10 and the above laser beams by an optical interference system 4 and converts the output light to an electrical signal by a photodetector 12 and then extracting the vibration information of the vibration object 10 from the electrical signal, a signal strength shortage detection means consisting of a constant-voltage generator 15a for generating a signal strength lower-limit value which can be processed by the signal processing device 13 and a comparator 16a for comparing the output signal of a photodetector 12 and the generation signal of the constant-voltage generator 15a is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibrometer for measuring the vibration of structures such as pipes and equipment in a non-contact manner. It relates to the excluded laser Doppler type vibrometer.

[0002]

2. Description of the Related Art A vibrometer which measures the vibration of a vibrating object in a non-contact manner when pipes, equipment, structures, etc. are vibrated. Then, there is a laser Doppler vibrometer which measures vibration from the Doppler shift amount.

As shown in the block diagram of FIG. 9, in this laser Doppler vibrometer 1, a laser beam 3a continuously output from a laser light source 2 at a specific frequency f ₀ and a wavelength λ ₀ is used for optical heterodyne. The beam splitter 5a of the optical interference system 4 splits the laser beam 3a into a laser beam 3b having an optical axis direction orthogonal to the laser beam 3a and an emitted light 3c having the same optical axis direction.

The laser beam 3b among them is reflected by the mirror 6
The reference light 3 that is incident on the frequency shifter 8 driven by the frequency shifter driver 7 via a, undergoes a frequency shift by a constant frequency f _s , and has a frequency of f ₀ + f _s.
It becomes d and is incident on the beam splitter 5b through the mirror 6b. On the other hand, the emitted light 3c goes straight, passes through the beam splitter 5b, and is irradiated onto the surface of the vibrating object 10 by the condensing optical system 9.

Now, the vibrating object 10 has a frequency f _m and a maximum velocity V.
_Assuming that it oscillates sinusoidally in the vibration direction 11 at ₀ , its vibration velocity v is expressed by the following equation (1) as a function of time t.

V = v ₀ sin (2πf _m t) (1)

Further, the vibrating object 10 vibrating in this way
The emitted light 3c which is radiated at right angles to the surface of is subjected to the Doppler shift f _d represented by the following equation (2) and the frequency f ₀ + f
It becomes _d scattered light 3e.

F _d = 2v / λ ₀ (2)

The scattered light 3e is condensed on the beam splitter 5b by the condensing optical system 9 and is superposed on the reference light 3d guided from the mirror 6b as described above by the beam splitter 5b and is then detected by the photodetector. Guided to 12.

The photodetector 12 converts the input light into an electric signal. This electric signal has a beat signal frequency f _B represented by the following equation (3), which is generated by the interference of the reference light 3d and the scattered light 3e. The signal has such an AC component.

F _B = f _s + f _d = f _s + 2v / λ ₀ (3)

When this is detected by the signal processing device 13 as an FM signal having a carrier frequency f _s , an analog signal having a frequency equal to the vibration frequency f _m of the vibrating object 10 and a peak value proportional to the vibration speed v can be obtained. it can.

The above is known as a technique for detecting the vibration velocity using the optical interference system 4 for optical heterodyne, from the literature and catalogs of laser Doppler vibrometers that have been commercialized in the past.

[0014]

In the conventional laser Doppler vibrometer 1, depending on the state of the emitted light 3c, the positional relationship between the condensing optical system 9 and the vibrating object 10, and the surface condition of the vibrating object 10, The intensity of the scattered light 3e that can be collected by the optical system 9 for light may be significantly reduced. In such a case, the signal processing device 13 has a problem in that the vibration signal component and the noise component cannot be discriminated from each other and incorrect data is output.

Further, even when the laser Doppler vibrometer 1 itself vibrates for some reason, it is impossible to distinguish the detected vibration of the vibrating object 10 from the self-vibration, and both are erroneously overlapped. There was also the problem of outputting vibration information.

An object of the present invention is to detect a decrease in signal component of input scattered light or self-vibration,
An object of the present invention is to provide a laser Doppler vibrometer in which the intensity of laser light emitted from the vibrometer is optimized and deterioration of measurement information is prevented.

[0017]

In order to achieve the above object, a laser Doppler vibrometer according to a first aspect of the present invention is a laser light emitted from a laser light source, the scattered light reflected from a vibrating object, and the laser light source. The laser light from the laser is detected by an optical interference system by optical heterodyne detection, and the output light is converted into an electric signal by a photodetector, and information on the Doppler shift amount of the laser light generated by the vibrating object is extracted from the electric signal. In a laser Doppler type vibrometer equipped with a signal processing device, the output signal of the reference signal generator and the photodetector and the generated signal of the reference signal generator that generate a signal intensity lower limit value that can be processed by the signal processing device. It is characterized in that a signal strength deficiency detection means including a comparator for comparison is provided.

According to a second aspect of the present invention, there is provided a laser Doppler vibrometer in which an optical heterodyne detection is performed by an optical interference system between scattered light reflected from a vibrating object of laser light emitted from a laser light source and laser light from the laser light source. In addition, in the laser Doppler system vibrometer equipped with a signal processing device for converting the output light into an electric signal by a photodetector and extracting information regarding the Doppler shift amount of the laser light generated by the vibrating object from the electric signal, It comprises a distortion extractor for extracting a waveform distortion component from the output signal of the signal processing device, a reference signal generator for outputting a distortion detection value larger than the distortion output signal, and a comparator for comparing the distortion output signal and the distortion detection value. It is characterized in that a signal strength shortage detecting means is provided.

According to a third aspect of the present invention, in a laser Doppler vibrometer, the laser light emitted from a laser light source is scattered by light reflected from a vibrating object and the laser light from the laser light source is detected by an optical interferometer. In addition, in the laser Doppler system vibrometer equipped with a signal processing device for converting the output light into an electric signal by a photodetector and extracting information regarding the Doppler shift amount of the laser light generated by the vibrating object from the electric signal, Distortion extractor for extracting a waveform distortion component from the output signal of the signal processing device, signal strength shortage detection means comprising a waveform monitoring device for observing the waveform of the output signal, and removal of the waveform distortion component from the output signal of the signal processing device Vibration frequency detecting means including a distortion eliminator and a frequency counter, and a peak value of an output signal of the signal processing device is detected. Characterized in that a vibration speed detection means consisting of a high detector and a voltmeter.

According to a fourth aspect of the present invention, there is provided a laser Doppler vibrometer in which an optical interferometer detects optical heterodyne of scattered light of a laser beam emitted from a laser light source, which is reflected from a vibrating object, and the laser beam from the laser light source. In the laser Doppler vibrometer equipped with a signal processing device that converts the output light into an electric signal by a photodetector and extracts information regarding the Doppler shift amount of the laser light generated by the vibrating object from the electric signal, the signal Signal strength shortage detection means for detecting a signal strength shortage in the processing device, an optical system drive device for driving an optical system for irradiating the vibrating object with laser light to collect scattered light, and outputs of the signal strength shortage detection means A control device for controlling the optical system driving device is provided so that the amount of condensed light becomes appropriate according to a signal.

According to a fifth aspect of the present invention, there is provided a laser Doppler vibrometer in which an optical interferometer is used for optical heterodyne detection of scattered light of a laser beam emitted from a laser light source, which is reflected from a vibrating object, and laser light from the laser light source. In addition, in the laser Doppler system vibrometer equipped with a signal processing device for converting the output light into an electric signal by a photodetector and extracting information regarding the Doppler shift amount of the laser light generated by the vibrating object from the electric signal, A signal strength shortage detecting means for detecting a signal strength shortage in the signal processing device is provided.

Further, the optical interference system for performing the optical heterodyne detection outputs the first polarization angle adjusting means for adjusting the polarization angle of the laser light emitted from the laser light source and the transmitted light for each polarization component thereof. Beam splitting means for splitting the emitted light and the reference light, a light amount adjusting means for adjusting the intensity of the split reference light, and a second polarization angle adjustment for making the reference light incident on the photodetector. And a third polarization angle adjusting means for allowing the scattered light collected by the optical system to enter the photodetector.

Further, a beam combining means for combining the reference light and the scattered light, an analyzer for interfering the reference light and the scattered light combined by the beam combining means, and the first The polarization angle adjusting means is provided with a first drive mechanism, and the light amount adjusting means is provided with a second drive mechanism, and the first and second drive mechanisms are controlled by the output signal of the signal strength insufficient detection means. And a control device for

According to a sixth aspect of the present invention, there is provided a laser Doppler vibrometer in which optical laser heterodyne detection of scattered light of a laser beam emitted from a laser light source, which is reflected from a vibrating object, and laser light from the laser light source is performed by an optical interference system. In addition, a laser Doppler system vibrometer equipped with a signal processing device that converts this output light into an electric signal with a photodetector and extracts information about the Doppler shift amount of the laser light generated by the vibrating object from the electric signal At least one or more acceleration measuring means installed on the outer surface or inside of the vibrometer, a converter for converting a measurement signal by the acceleration measuring means into a speed signal, and the speed signal detected by the signal processing device. A gain adjuster for normalizing the vibration signal, an output signal of the gain adjuster, and an output of the signal processing device Characterized by providing a differentiator for obtaining the difference between the No..

[0025]

According to the first aspect of the present invention, the output signal of the photodetector is output from the reference signal generator in the signal strength shortage detecting means, and the preset detection lower limit voltage of the signal processing device is used as the set voltage value and the comparator. Compare with.

When the output signal of the photodetector falls below the set voltage value of the reference signal generator, the comparator outputs the detection lower limit signal, and this detection lower limit signal informs the signal strength insufficiency in the signal processing device.

According to the second aspect of the invention, when the output signal of the signal processing device for extracting the vibration information from the output signal of the photodetector is passed through the distortion extractor in the signal strength shortage detecting means, a waveform distortion component is generated. While obtaining the extracted distortion output signal, the distortion output signal is compared with the output of the reference signal generator having a distortion detection value larger than the distortion output signal in advance by the comparator.

When the signal strength input in the signal processing device is insufficient, a distortion component is generated in the output signal. Therefore, when this distortion output signal exceeds the distortion detection value of the reference signal generator, the comparator is Since the detection lower limit signal is output, the detection lower limit signal notifies the signal strength insufficiency in the signal processing device.

According to a third aspect of the present invention, the output signal of the signal processing device for extracting the vibration information from the output signal of the photodetector is passed through the distortion extractor for extracting the waveform distortion component of the signal strength insufficient detection means. Then, the waveform of the distorted output signal is observed by the waveform monitoring device, and if there are many distorted waveforms, it is determined that the signal strength input to the signal processing device is insufficient. Further, when the output signal of the signal processing device passes through the distortion remover of the vibration frequency detecting means, the waveform distortion component is removed and the frequency counter can detect the accurate vibration frequency.

Further, the output signal of the signal processing device is
By passing through the full-wave rectifier circuit that detects the peak value of the vibration speed detection means, only the vibration component is extracted and the correct peak value is given to the vibration speed. It is possible to know various vibration speeds.

According to a fourth aspect of the present invention, when the output signal of the signal processing device for extracting the vibration information from the output signal of the photodetector is input to the signal strength shortage detection means and the signal strength shortage is detected. The focal length of the optical system is adjusted via the control device and the optical system drive device by the detection lower limit signal output from the insufficient signal strength detection means, and the amount of light collected from the vibrating object is automatically controlled appropriately.

According to a fifth aspect of the present invention, when the output signal of the signal processing device for extracting the vibration information from the output signal of the photodetector is input to the signal strength shortage detecting means and the signal strength shortage is detected. By the detection lower limit signal output from the signal strength shortage detection means, via the control device and the first drive mechanism,
The first polarization angle adjusting means is driven to adjust the polarization angle of the laser light.

As a result, the intensity division ratio of the emitted light and the reference light is changed, and the intensity of the reference light is adjusted by driving the light quantity adjusting means through the control device and the second drive mechanism. The amount of light collected from the vibrating object is automatically controlled appropriately.

According to a sixth aspect of the present invention, when vibration occurs in the laser Doppler vibrometer itself, the acceleration measuring means detects the vibration and outputs a measurement signal. This measurement signal is converted into a velocity signal by the converter, and after gain adjustment by the gain adjuster, the output of the signal processing device that extracts the vibration information from this output signal and the output signal of the photodetector by the differentiator By obtaining the difference from the signal, the vibration information of only the vibrating object from which the self-vibration component is removed can be obtained.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. It should be noted that the same components as those in the above-described conventional technique are designated by the same reference numerals, and detailed description thereof will be omitted. In the first embodiment, as shown in the block diagram of FIG. 1, it is possible to detect a shortage of the detection signal strength during vibration measurement.

In this laser Doppler type vibrometer 14, the laser light source 2, the optical interferometer for optical heterodyne 4, the focusing optical system 9, the photodetector 12 and the vibration measuring portion of the signal processing device 13 are shown in FIG. The configuration is similar to that of the conventional technology.

In addition to this, on the output side of the photodetector 12,
A constant voltage generator 15a of a reference signal generator that constantly outputs the detection lower limit voltage of the signal processing device 13 measured in advance as a signal strength shortage detecting means as a set voltage value, the set voltage value and the photodetector 12 A comparator 16a, which is a comparator for comparing the output voltage signals from, is provided and configured. further,
O is output by the output of the comparator 16a as an alarm means.
For example, a speaker driving device 17 and a speaker 18 that are N / OFF controlled are installed.

Next, the operation of the above configuration will be described. The laser beam 3a continuously output from the laser light source 2 is generated by the optical heterodyne optical interference system 4 as described in the prior art with reference to FIG.
Is divided into a laser beam 3b having an optical axis direction orthogonal to and an emitted light 3c having the same optical axis direction. The split laser beam 3b is incident on the frequency shifter 8 and undergoes a constant frequency shift to become reference light 3d, which is then incident on the beam splitter 5b.

On the other hand, the emitted light 3c goes straight, is irradiated onto the surface of the vibrating object 10 by the condensing optical system 9, and enters the condensing optical system 9 as scattered light 3e. The scattered light 3e is detected by the photodetector 12 by the optical heterodyne method, transmitted from the photodetector 12 to the signal processing device 13 as an electric signal,
Information about vibration is extracted.

Here, the output voltage signal from the photodetector 12 is also input to the comparator 16a of the signal strength shortage detecting means, and in this comparator 16a, the constant voltage generator 15a.
Is compared with the set voltage value that occurs.

Here, if the intensity of the scattered light 3e condensed by the condensing optical system 9 is remarkably reduced due to the positional relationship between the condensing optical system 9 and the vibrating object 10 and the surface state of the vibrating object 10. Since the output signal voltage of the photodetector 12 is insufficient and the signal component and the noise component are insufficiently discriminated when the vibration information is processed by the signal processing device 13, accurate vibration information extraction is hindered. It will be.

However, the output signal voltage of the photodetector 12 at this time is compared with the lower detection limit voltage generated by the constant voltage generator 15a in the comparator 16a, and the output signal voltage is lower than the set voltage value. 16a outputs a detection lower limit signal.

By the detection lower limit signal, the speaker driving device 17 of the alarm means causes the speaker 18 to sound, and the measuring condition is abnormal for the measurer. Therefore, the detection signal strength is insufficient and the signal processing device Notify that there is a possibility of error in the information on vibration in 13.

Upon receiving this alarm, the measurer can determine the positional relationship between the focusing optical system 9 and the vibrating object 10, the surface condition of the vibrating object 10 or the state of the light 3c emitted from the focusing optical system 9. By knowing that the measurement condition is not appropriate and immediately improving the above-mentioned trouble to bring it into a normal state, and then performing the vibration measurement again, it is possible to perform the vibration measurement with high accuracy and reliability.

That is, if the cause of insufficient detection signal strength is eliminated, a sufficiently high output signal voltage is output from the photodetector 12 to the signal processing device 13 and the comparator 16a, and the signal processing device 13 outputs a signal component and a noise component. Therefore, accurate vibration information extraction processing is performed.

Further, since the output signal voltage to be compared in the comparator 16a is higher than the voltage value set by the constant voltage generator 15a, the output of the detection lower limit signal is stopped. No play is performed.

In the second embodiment, similarly to the first embodiment described above, it is possible to detect a shortage of the detection signal strength during vibration measurement. As shown in the block configuration diagram of FIG. 2, the laser Doppler type vibrometer 19 includes a laser light source 2, an optical interference system 4 for optical heterodyne, a condensing optical system 9, a photodetector 12, and a vibration measuring portion in the signal processing device 13. Is the same as the first embodiment.

In addition to this, on the output side of the signal processing device 13, a high-pass filter 20 of a distortion extractor, a constant voltage generator 15b as a reference signal generator, and a comparator comparator.
16b is provided to provide a signal strength shortage detection means.

The high-pass filter 20 of the strain extractor is set to a value which is higher than the vibration frequency to be measured in advance and is as low as possible (for example, the vibration frequency of structures such as pipes and equipment is several hundred Hz at most, so that it is 1 kHz. The cutoff frequency is defined as the cutoff frequency.

The constant voltage generator 15b always outputs the distortion detection set value L which is a value sufficiently higher than the noise level of the output signal of the high pass filter 20.

Further, the comparator 16b compares the distortion detection setting value L from the constant voltage generator 15b with the output of the high pass filter 20, and when the output of the high pass filter 20 exceeds the distortion detection setting value L. The detection lower limit signal is output to. Further, an alarm means, for example, a lamp driving device 21 and a lamp 22, which are ON / OFF controlled by the detection lower limit signal output from the comparator 16b, is installed.

Next, the operation of the above configuration will be described. The emitted outgoing light 3c is reflected from the surface of the vibrating object 10, and the scattered light 3e is detected by the condensing optical system 9 and vibrates in the signal processing device 13 via the heterodyne optical interference system 4 and the like. That information is measured is the first
It is similar to the embodiment.

As shown in the output signal waveform characteristic diagram of FIG. 3, the signal processing device 13 has a sinusoidal vibration velocity waveform shown in FIG. A sinusoidal output signal as shown in (b) is obtained. On the other hand, when the input signal strength due to the output signal of the photodetector 12 decreases below the limit, the output waveform of the signal processing device 13 is distorted as shown in FIG.

Therefore, in the signal strength shortage detecting means,
When the output signal of the signal processing device 13 is filtered by the high-pass filter 20 of the distortion extracting means having the cut-off frequency set to a value as low as possible that is higher than the vibration frequency to be measured in advance, it is shown in FIG. Thus, a distortion output signal in which only the distortion component is emphasized is obtained.

Therefore, the distortion output signal and the distortion detection set value L output from the constant voltage generator 15b are compared by the comparator 16b, and when the distortion output signal exceeds the distortion detection set value L, The comparator 16b outputs a detection lower limit signal.

That is, when the output signal voltage of the photodetector 12 becomes insufficient, and the accurate extraction of vibration information in the signal processing device 13 is hindered, the distorted portion in the output signal of the signal processing device 13 becomes large. Since the distortion output signal exceeds the distortion detection set value L, the comparator 16b outputs the detection lower limit signal to the lamp driving device 21 of the alarm means.

As a result, the lamp driving device 21 is operated by the lamp 22.
Is lit to inform the measurer that the measurement condition is abnormal, the detection signal strength is insufficient for this reason, and there is a possibility of error in the extraction of the information regarding the vibration in the signal processing device 13.

Upon receipt of this alarm, the measurer knows that the positional relationship between the condensing optical system 9 and the vibrating object 10 and the measurement conditions such as the surface condition of the vibrating object 10 are not appropriate, and immediately the above-mentioned defect relationship. By performing the above-mentioned improvement to bring it to a normal state and then performing the vibration measurement again, the vibration information with high accuracy and reliability can be obtained from the signal processing device 13.

If the cause of insufficient detection signal strength is eliminated, the photodetector 12 outputs a sufficiently high output signal voltage to the signal processing device 13 and the comparator 16b. Since it is easy to discriminate between the noise component and the noise component, accurate vibration information extraction processing can be performed.

At this time, in the comparator 16b, since the distortion output signal from the signal processing device 13 to be compared is higher than the distortion detection set value L output from the constant voltage generator 15b, the detection lower limit signal is not output. Therefore, the lamp 22 does not light.

In the second embodiment, the alarm means has been described as being constituted by the lamp driving device 21 and the lamp 22, but the alarm means is the same as in the first embodiment.
The speaker driving device 17 and the speaker 18 may be used. Further, the alarm means by the lamp driving device 21 and the lamp 22 shown in the second embodiment may be adopted in the first embodiment, or the speaker 18 and the lamp 22 may be used together.

In the third embodiment, similarly to the second embodiment, the waveform distortion can be removed during the detection as well as the detection of the insufficient detection signal strength during the vibration measurement. As shown in the block diagram of FIG. 4, the laser Doppler vibrometer 23
The vibration measuring portion in the laser light source 2, the optical interference system 4 for optical heterodyne, the condensing optical system 9, the photodetector 12, and the signal processing device 13 are the same as those in the first embodiment.

In addition to this, on the output side of the signal processing device 13, a high-pass filter 20 of a distortion extractor for obtaining a distortion output signal in which only the distortion component is emphasized is provided as a signal strength insufficient detection means, and this distortion output. An oscilloscope 24 of a waveform monitoring device for observing a waveform is provided.

Further, as a vibration frequency means for detecting a correct vibration frequency, a frequency counter 26 through a low-pass filter 25 of a distortion remover having a cutoff frequency higher than the vibration frequency to be measured, and similarly to know an accurate vibration speed of,
As the vibration velocity detecting means, for example, a voltmeter 28 via a full-wave rectifier circuit 27, which is a peak value detector shown in the connection diagram of FIG. 5, is provided.

Next, as a function of the above-described structure, the emitted light 3c that has been irradiated is reflected from the surface of the vibrating object 10, and this scattered light 3e is detected by the converging optical system 9, and the heterodyne optical interference system 4 is detected. The vibration information is measured in the signal processing device 13 via the same as in the first embodiment.

In the vibration information output from the signal processing device 13, if the signal intensity of the photodetector 12 is insufficient, as shown in FIG. 3 (c), a distortion component is present in the signal waveform. Will be included.

When this is filtered by the high-pass filter 20 and observed by the oscilloscope 24, the distortion output signal in which only the distortion component is emphasized can be directly observed as shown in FIG. The details such as the degree can be easily known. If you make a vibration measurement again after improving the measurement conditions, the result will be immediately
It can be confirmed by 24.

When the low-pass filter 25 of the distortion remover, which is the vibration frequency means, is passed through, the distortion component in FIG. 3C is removed. The frequency of the signal output from the low-pass filter 25 is the vibration frequency. Since the same value is obtained, the correct vibration frequency is displayed on the frequency counter 26 which has input this value.

Further, regarding the peak value corresponding to the vibration speed in the output from the signal processing device 13, a full-wave rectification circuit composed of the diodes 27a to 27d and the capacitor 29 of the peak value detector.
By passing through 27, only the vibration component is extracted from the signal waveform, and the correct peak value is given to the vibration velocity.

Therefore, by reading the output voltage of the full-wave rectifier circuit 27 with the voltmeter 28, the accurate vibration speed can be known. As a result, even when the detection signal strength is insufficient, the frequency counter 26 and the voltmeter 28 can accurately know the vibration frequency and the vibration speed, respectively.

In the fourth embodiment, when insufficient detection signal strength is detected, the measurement conditions are automatically optimized to increase the amount of detected light. As shown in the block diagram of FIG. 6, the laser Doppler vibration meter 30 includes a laser light source 2, an optical interference system 4 for optical heterodyne, a focusing optical system 9, a photodetector 12, and a vibration measurement part in the signal processing device 13. Is
This is similar to the first embodiment.

In addition to this, on the output side of the signal processing device 13, a distortion extractor having a cut-off frequency set to a value as low as possible, which is a vibration frequency to be measured in advance, which is a signal strength shortage detection means, is provided. The comparator 16b of the comparator connected through the high-pass filter 20 and the constant voltage generator 15b of the reference signal generator that constantly outputs the distortion detection setting value L connected to one of the comparators 16b are provided.

Further, the condensing optical system 9 is provided with a motor 31a of an optical driving device for adjusting the focal length of the optical system 9 for light, and the motor 31a is used as an output signal of the comparator 16b. A controller 32a and a driver 33a of a control device controlled by the above are installed and configured.

Next, the operation of the above configuration will be described. It should be noted that the emitted emitted light 3c is reflected from the surface of the vibrating object 10, and the scattered light 3e is detected by the condensing optical system 9 and passes through the heterodyne optical interference system 4 and the like and the signal processing device 13 The vibration information is measured in the same way as in the first embodiment.

The vibration information output from the signal processing device 13 is filtered by the high pass filter 20 and input to the comparator 16b as a distortion output signal. Note that the comparator
The distortion detection set value L from the constant voltage generator 15b is input to one of 16b and compared.

At this time, if the distortion output signal in the signal processing device 13 exceeds the distortion detection set value L due to the insufficient detection signal strength by the photodetector 12 and the insufficient detection signal strength is detected in the comparator 16b, , The comparator 16b outputs a detection lower limit signal.

This detection lower limit signal is input to the controller 32a, and the controller 32a drives the motor 31a of the optical driving device via the driver 33a.
The drive of the condensing optical system 9 by 31a is performed by a comparator.
At the position where the signal output by 16b does not indicate a lack of detection signal intensity, the focal length of the condensing optical system 9 is adjusted until the intensity of the scattered light 3e to be condensed becomes sufficiently large.

As a result, if the cause of insufficient detection signal strength is eliminated, the photodetector 12 outputs a sufficiently high output signal voltage to the signal processing device 13, and the signal processing device 13 produces a signal component and a noise component. Since it is easy to determine, accurate measurement can be performed.

When the extraction of the vibration information obtained by the signal processing device 13 returns to normal, the distortion output signal included in the output waveform decreases and falls below the distortion detection set value L, so that the output from the comparator 16b is It disappears, and the condensing optical system 9
Since the driving of is stopped at the optimum position, the vibration information can always be automatically extracted under the optimum conditions.

In the fifth embodiment, similarly to the fourth embodiment, when insufficient detection signal strength is detected, the measurement conditions are automatically optimized to increase the detected light amount. As shown in the block diagram of FIG. 7, the laser Doppler vibration meter 34
The vibration measurement part for extracting information on vibration from the electric signal detected by the photodetector 12 by the optical heterodyne method using the signal processing device 13 is the same as that of the first embodiment.

Here, as the optical interference system for performing optical heterodyne detection, a 1/2 wavelength plate 35a which is a first polarization angle adjusting means for adjusting the polarization angle of the laser beam 3a emitted from the laser light source 2 is used. , The reference light 3f in which the transmitted light is polarized for each polarization component and the outgoing light 3 in which the polarized light is polarized.
A polarizing beam splitter 36a, which is a beam splitting means for splitting the beam into a g beam, is provided.

Further, the intensity ratio of the polarized reference light 3f and the polarized output light 3g can be adjusted, and the mirror 6a and the frequency shifter are provided on the optical path of the polarized reference light 3f. A frequency shifter 8 driven by a driver 7 is provided.

Furthermore, the mirror 6b that changes the direction of the reference light 3h that has received the polarized light that has passed through the frequency shifter 8, the variable light attenuator 37 that is the light quantity adjusting means for adjusting the intensity, and the second polarization angle adjusting means. 1/2 wave plate 35b is installed.

Further, on the optical path of the polarized outgoing light 3g, there is provided a polarization beam splitter 36b as a beam synthesizing means for combining the polarized reference light 3h and scattered light 3e with each other.
The quarter-wave plate 38 as the polarization angle adjusting means and the condensing optical system 9 are provided.

On the other hand, the scattered light 3e reflected from the surface of the vibrating object 10 and condensed by the condensing optical system 9 and the polarized reference light 3h are combined by the polarization beam splitter 36b, An analyzer provided in the optical path interferes with 39 and guides it to the photodetector 12. A signal processing device 13 is connected to the output side of the photodetector 12.

Further, the half-wave plate 35a and the variable optical attenuator 37 are provided with a motor 31b as a first drive mechanism and a motor 31c as a second drive mechanism for rotating each. ing.

These motors 31b and 31c are composed of a high-pass filter 20 of a distortion extractor connected to the output side of the signal processing device 13, a constant voltage generator 15b of a reference signal generator, and a comparator 16b of a comparator. It is configured to be driven by the following signal strength shortage detection means, a controller 32b that is a control device that controls the output signal of the comparator 16b that is the output, and drivers 33b and 33c connected to the controller 32b.

Next, the operation of the above configuration will be described. The polarization beam splitters 36a and 36b provided on the optical paths of the polarized outgoing light 3g and scattered light 3e transmit the horizontal polarization component (P wave) of the incident wave and the vertical polarization component (S wave).
Since it has a characteristic of reflecting light, it is possible to easily adjust the intensity of the emitted light 3g polarized by the combination of these positions.

Therefore, the condensing optical system 9 and the vibrating object 10
And the state of the surface of the vibrating object 10 changes the state of the scattered light 3e taken in by the condensing optical system 9, and the intensity of the detection signal input to the signal processing device 13 becomes insufficient. If the measurement process of 1 cannot be performed accurately, the emitted light 3g that is polarized automatically is strengthened according to the detection result of the signal strength shortage detection means.

As a result, the amount of scattered light 3e that can be condensed by the condensing optical system 9 is increased, and it is sufficiently high to enable accurate measurement of vibration information from the photodetector 12 to the signal processing device 13. Allow the output signal voltage to be applied.

That is, since the polarization angle of the laser beam 3a emitted from the laser light source 2 can be controlled by rotating the ½ wavelength plate 35a, it can be operated by the driving motor 31b. The intensity division ratio of the polarized reference light 3h and the similarly polarized output light 3g can be arbitrarily selected.

The motor 31b controls the rotational position of the half-wave plate 35a via the controller 32b and the driver 33b by the output signal of the comparator 16b. This control is a state in which the output of the comparator 16b does not indicate the lack of detection signal strength. By adjusting the light amount of the emitted light 3g that has been polarized in a state where the intensity of the scattered light 3e that can be collected is sufficiently large, an error in the signal processing device 13 due to the insufficient detection signal intensity in the photodetector 12 is caused. Data output is prevented.

If the intensity of the polarized reference light 3h becomes excessive and the output of the photodetector 12 is saturated, the controller 32b and the driver 33c are driven by the output signal of the comparator 16b. Since the motor 31c is driven through the control of the variable optical attenuator 37 to reduce the intensity of the polarized reference light 3h, the output saturation of the photodetector 12 can be automatically prevented.

The sixth embodiment prevents deterioration of measurement information due to vibration of the vibrometer itself. As shown in the block diagram of FIG. 8, the laser Doppler vibrometer 40 includes a laser light source 2, an optical interference system 4 for optical heterodyne, a condensing optical system 9, a photodetector 12, and a vibration measuring portion in the signal processing device 13. Is similar to the first embodiment.

In addition to this, an accelerometer 41 as an acceleration measuring means is installed inside the laser Doppler vibrometer 40 or on the outer surface of the case, and a charge amplifier 42 for amplifying the output signal of the accelerometer 41. And an integrator 43 which is a converter for converting the output of the charge amplifier 42 into a speed signal.
Is provided.

Further, a gain adjuster 44 for normalizing the speed signal voltage value output from the integrator 43 and the speed signal voltage value output from the signal processing device 13, and the speed signal of the signal processing device 13. A differential amplifier 45, which is a difference device for obtaining the difference between the output and the self-speed signal of the laser Doppler vibration meter 40 after gain adjustment, is provided.

Next, the operation of the above configuration will be described. It should be noted that the emitted emitted light 3c is reflected from the surface of the vibrating object 10, and the scattered light 3e is detected by the condensing optical system 9 and passes through the heterodyne optical interference system 4 and the like and the signal processing device 13 The vibration information is measured in the same way as in the first embodiment.

When a vibration occurs in the laser Doppler vibrometer 40 itself when measuring the vibration of the vibrating object 10, this vibration is detected by the accelerometer 41, and the self-vibration signal is amplified by the charge amplifier 42. The integrator 43 converts the speed signal.

Further, the speed signal output of this self-vibration is
After being adjusted by the gain adjuster 44 that normalizes the speed signal voltage value of the signal processing device 13, it is input to the differential amplifier 45,
Similarly, the difference from the speed signal output of the signal processing device 13 is obtained.

Thus, the vibration of the laser Doppler vibrometer 40 itself can be removed from the vibration information measured by the signal processing device 13, and only the vibration signal of the vibrating object 10 alone can be accurately extracted.

In the sixth embodiment, the detection of self-vibration in the laser Doppler vibrometer and the prevention of deterioration of the vibration information of the vibrating object 10 obtained separately have been described, but the sixth embodiment is the same as the first embodiment. It can be applied to any of the examples to the sixth embodiment.

Further, the signal strength shortage detecting means in the above-mentioned first to third embodiments are different from each other in construction and operation, but both the first and third embodiments are the same as the above-mentioned fourth embodiment. Alternatively, it goes without saying that the present invention can also be applied to the fifth embodiment.

[0103]

As described above, according to the present invention, when measuring the vibration by the laser Doppler vibrometer, due to the insufficient intensity of the scattered light from the vibrating object, it is possible to surely and easily confirm the poor accuracy in the measured vibration information. It will be possible. In addition, optimum measurement conditions can be automatically and quickly obtained.

Furthermore, by removing the self-vibration of the vibrometer from the measured vibration information of the vibrating object, it is possible to prevent the deterioration of the vibration information due to the self-vibration.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of a laser Doppler vibrometer according to a first embodiment of the present invention.

FIG. 2 is a block configuration diagram of a laser Doppler vibration meter according to a second embodiment of the present invention.

FIG. 3 is an output signal waveform characteristic diagram of the second embodiment according to the present invention. (A) is a vibration velocity waveform, (b) is a signal waveform when the output is sufficient, and (c) is insufficient output. Time signal waveform,
(D) shows an extracted distortion waveform.

FIG. 4 is a block configuration diagram of a laser Doppler vibration meter according to a third embodiment of the present invention.

FIG. 5 is a connection diagram of a full-wave rectifier circuit according to a third embodiment of the present invention.

FIG. 6 is a block configuration diagram of a laser Doppler vibrometer according to a fourth embodiment of the present invention.

FIG. 7 is a block configuration diagram of a laser Doppler vibrometer according to a fifth embodiment of the present invention.

FIG. 8 is a block diagram of a laser Doppler vibrometer according to a sixth embodiment of the present invention.

FIG. 9 is a block diagram of a conventional laser Doppler vibrometer.

[Explanation of symbols]

1, 14, 19, 23, 30, 34, 40 ... Laser Doppler vibrometer, 2 ... Laser light source, 3a, 3b ... Laser beam, 3c
... outgoing light, 3d ... reference light, 3e ... scattered light, 4 ... optical heterodyne optical interference system, 5a, 5b ... beam splitter,
6a, 6b ... Mirror, 7 ... Frequency shifter driver, 8 ...
Frequency shifter, 9 ... Focusing optical system, 10 ... Vibrating object, 11 ...
Vibration direction, 12 ... Photodetector, 13 ... Signal processing device, 15a, 15
b ... Constant voltage generator, 16a, 16b ... Comparator, 17 ... Speaker drive device, 18 ... Speaker, 20 ... High pass filter, 21 ... Lamp drive device, 22 ... Lamp, 24 ... Oscilloscope, 25 ... Low pass filter, 26 ... Frequency Counter, 27
... Full wave rectifier circuit, 27a to 27d ... Diode, 28 ... Voltage type, 29 ... Capacitor, 31a to 31c ... Motor, 32a, 32b
... controller, 33a-33c ... driver, 35a, 35b ...
Half-wave plate, 36a, 36b ... Polarizing beam splitter, 37
... Variable optical attenuator, 38 ... Quarter wave plate, 39 ... Analyzer,
41 ... Accelerometer, 42 ... Charge amplifier, 43 ... Integrator, 44 ...
Gain adjuster, 45 ... Differential amplifier.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazumi Watanabe 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Prefecture Toshiba Research and Development Center (72) Inventor Seiki Soramoto Komukai, Kouki-ku, Kawasaki-shi, Kanagawa Toshiba Town No. 1 Inside Toshiba Research and Development Center

Claims (6)

[Claims] 1. A laser light emitted from a laser light source is subjected to optical heterodyne detection of scattered light reflected from a vibrating object and laser light from the laser light source, and the output light is electrically detected by a photodetector. In a laser Doppler system vibrometer equipped with a signal processing device that converts information into a signal and extracts information related to the Doppler shift amount of laser light generated by a vibrating object from this electric signal, a signal intensity lower limit value that can be processed by the signal processing device is set. 2. A laser Doppler vibrometer, comprising: a signal strength shortage detection means comprising a reference signal generator that is generated and a comparator that compares the output signal of the photodetector with the signal generated by the reference signal generator. 2. A laser light emitted from a laser light source is subjected to optical heterodyne detection of scattered light reflected from a vibrating object and the laser light from the laser light source, and the output light is electrically detected by a photodetector. In a laser Doppler vibrometer equipped with a signal processing device for converting into a signal and extracting information on the Doppler shift amount of laser light generated by a vibrating object from this electric signal, a waveform distortion component is extracted from the output signal of the signal processing device. A signal strength deficiency detection means comprising a distortion extractor, a reference signal generator for outputting a distortion detection value larger than the distortion output signal, and a comparator for comparing the distortion output signal with the distortion detection value is provided. Laser Doppler vibration meter. 3. A laser light emitted from a laser light source is subjected to optical heterodyne detection of scattered light reflected from a vibrating object and the laser light from the laser light source, and the output light is electrically detected by a photodetector. In a laser Doppler vibrometer equipped with a signal processing device for converting into a signal and extracting information on the Doppler shift amount of laser light generated by a vibrating object from this electric signal, a waveform distortion component is extracted from the output signal of the signal processing device. Vibration frequency detection including a signal strength shortage detecting means including a distortion extractor and a waveform monitoring device for observing the waveform of the output signal, a distortion remover for removing a waveform distortion component from the output signal of the signal processing device, and a frequency counter. And a vibration velocity detecting means including a peak value detector for detecting the peak value of the output signal of the signal processing device and a voltmeter. Laser Doppler vibrometer characterized by 4. Optical heterodyne detection of the scattered light of the laser light emitted from the laser light source, which is reflected from the vibrating object, and the laser light from the laser light source, and the output light is electrically detected by a photodetector. In a laser Doppler vibrometer equipped with a signal processing device for converting into a signal and extracting information regarding the Doppler shift amount of laser light generated by a vibrating object from this electric signal, a signal strength shortage for detecting a signal strength shortage in the signal processing device Detection means,
An optical system driving device that drives an optical system that irradiates the vibrating object with laser light and collects scattered light, and the optical system driving device that adjusts the amount of light condensing appropriately by the output signal of the signal strength insufficient detection means. A laser Doppler vibration meter, which is provided with a control device for controlling the laser. 5. Optical heterodyne detection of the scattered light of the laser light emitted from the laser light source, which is reflected from the vibrating object, and the laser light from the laser light source is performed by an optical interference system, and the output light is electrically detected by a photodetector. In a laser Doppler vibrometer equipped with a signal processing device for converting into a signal and extracting information regarding the Doppler shift amount of laser light generated by a vibrating object from this electric signal, a signal strength shortage for detecting a signal strength shortage in the signal processing device An optical interference system for performing the optical heterodyne detection is provided with a detecting means, and a first polarization angle adjusting means for adjusting the polarization angle of the laser light emitted from the laser light source and the transmitted light for each polarization component thereof. Beam splitting means for splitting the outgoing light and the reference light, a light amount adjusting means for adjusting the intensity of the split reference light, and Second polarization angle adjusting means for making the reference light of the above-mentioned incident on the photodetector, and a third means for making the scattered light condensed by the optical system enter the photodetector.
Polarization angle adjusting means, beam combining means for combining the reference light and scattered light, an analyzer for interfering the reference light and scattered light combined by the beam combining means, and The first polarization angle adjusting means is provided with a first drive mechanism, and the light amount adjusting means is provided with a second drive mechanism, and the first and second drive mechanisms are provided by an output signal of the signal strength insufficient detection means. And a control device for controlling the laser Doppler vibrometer. 6. A laser light emitted from a laser light source is subjected to optical heterodyne detection of scattered light reflected from a vibrating object and the laser light from the laser light source, and the output light is electrically detected by a photodetector. A laser Doppler vibrometer equipped with a signal processing device that converts the signal to extract the information related to the Doppler shift amount of the laser light generated by the vibrating object from this electrical signal. Also, at least one acceleration measuring means, a converter for converting a measurement signal by the acceleration measuring means into a speed signal, and a gain adjuster for normalizing the speed signal with the vibration signal detected by the signal processing device. And a differencer for obtaining the difference between the output signal of the gain adjuster and the output signal of the signal processing device. -The Doppler vibration meter.