JP2001255306A - Laser ultrasonic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser ultrasonic apparatus capable of detecting a weak luminous intensity signal with high sensitivity and capable of observing minute frequency shift contained therein in magnitude of a noise level or more. SOLUTION: The laser ultrasonic apparatus is equipped with a resonator length control means 15 for allowing the output signal level of a light detection means 12 or a part of measuring laser beam to be incident on a Fabry-Perot resonator 10 through a light path avoiding a material to be inspected and controlling the resonance length of the Fabry-Perot resonator 10 from the output signal level of a separate light detection means 20 for detecting the intensity of the output light of the resonator, and a sensitivity adjusting means 31 for adjusting the sensitivity of the light detection means 12 on the basis of predetermined time delay and predetermined time width in the modulation timing of a first laser beam source 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noncontact and nondestructive method for inspecting a crack or a defect or evaluating a material on a measurement object which is difficult to contact or approach, such as a small-sized, high-temperature, narrow part or a moving part. The present invention relates to a laser ultrasonic apparatus that performs high-precision laser irradiation.

[0002]

2. Description of the Related Art For example, a laser ultrasonic method has recently been proposed as a means for inspecting cracks in equipment and structural materials of a power plant. For an overview of this technique, see, for example, “Yamawaki:“ Laser Ultrasonic and Non-Contact Material Evaluation ”, Journal of the Japan Welding Society, Vol. 64, No. 2, P. 104-108 (199)
5 years)), the ultrasonic wave is transmitted to the material to be inspected using thermal stress generated by irradiating a pulse laser beam in many cases, or a vaporization reaction force. On the other hand, in many cases, this technique is to irradiate a receiving point with another laser beam that continuously oscillates, and to receive displacement induced by ultrasonic waves by using the straightness and coherence. It is a well-known technique that it is possible to detect cracks and intrinsic defects in a material using ultrasonic waves, or to evaluate material properties.According to the laser ultrasonic method, these can be performed in a non-contact manner.
Application to various material evaluation fields is expected.

Several different optical systems have been proposed as means for transmitting and receiving ultrasonic waves in the laser ultrasonic method.
Generation of ultrasonic waves by pulsed laser beam irradiation,
For the reception of ultrasonic waves using the Perot resonator, see FIG.
There are the following. FIG. 34 is a block diagram showing a conventional laser ultrasonic apparatus.

As shown in FIG. 34, a laser beam EL oscillated from a laser light source 1 for generating an ultrasonic wave is reflected by mirrors 2a and 2a.
A predetermined position on the surface of the inspection target material 4 is irradiated with a predetermined beam shape via the lens b and the lens 3. As the laser light source 1, a Q-switched YAG laser or the like is often used.
Therefore, in the conventional laser ultrasonic device, the material to be inspected 4
The ultrasonic wave of various modes such as a longitudinal wave, a transverse wave, and a surface wave is generated in the material 4 to be inspected due to the interaction between the laser beam EL and the irradiation laser light EL. Phenomena such as reflection, scattering, and change in the speed of sound occur due to the material characteristics of the material 4 to be inspected, and a detailed description thereof will be omitted here. In any case, when the ultrasonic wave propagated based on a certain propagation process reaches an arbitrary measurement point on the inspection target material 4, a displacement occurs at the site.

On the other hand, in FIG. 34, a laser beam ML oscillated from a laser light source 5 for detecting an ultrasonic wave is controlled by a half-wave plate 6, and then subjected to a polarization beam splitter and a lens 8. The measurement point on the inspection material 4 is irradiated. As the laser light source 5, a continuous wave laser light source such as a frequency stabilized He—Ne laser, an argon laser, and a YAG laser is often used.

When the measuring point is displaced by the arrival of the ultrasonic wave, the frequency of the laser beam ML irradiated and reflected at the point shifts by an amount proportional to the vibration speed by the Doppler effect, and follows the same path as the irradiation. The light is returned to the polarization beam splitter 7 via Here, if the surface of the inspection object 4 is optically rough, the deflection of the reflected light is random, so that half of the light is reflected by the polarization beam splitter 7 and the Fabry-Perot resonator (FP)
It is led to 10. If the inspection target material 4 has an optically good surface, if the quarter-wave plate is inserted closer to the inspection target material 4 than the polarizing beam splitter 7, the measurement light PL can be more efficiently transmitted. Light can be collected. A part of the light component PL guided to the Fabry-Perot resonator 10 is
After passing through the Perot resonator 10, the light is guided to a photodetector 12 such as a photodiode via a lens 11. In the photodetector 12, the intensity of light transmitted through the Fabry-Perot resonator 10 is converted into an electric signal, and the electric signal is amplified to a predetermined signal by the signal processing device 13, filtered, and processed by the display device 14. Displayed and recorded.

Next, the operation of the Fabry-Perot resonator 10 will be described.

The Fabry-Perot resonator 10 is an optical resonator composed of two opposing mirrors 10a and 10b each having a reflectance of less than 100% as shown in FIG. 34, and these mirrors 10a and 10b Is an integer n times the wavelength λ of the incident light, the light resonates between the mirrors 10a and 10b, and the transmitted light amount I becomes the maximum.

FIG. 35 shows a change in the amount of transmitted light I of the Fabry-Perot resonator 10 when the resonator length r is artificially scanned by a distance equal to or longer than the wavelength λ. As shown in FIG. 35, it can be seen that the amount of transmitted light I becomes maximum at the time when the resonator length r becomes an integer n times the wavelength λ, and thereafter, the behavior of rapidly attenuating is repeated for each wavelength.

On the other hand, the cavity length r is fixed at the point A where the rate of change of the amount of transmitted light per unit length change is maximum in the curve shown in FIG. 35, and the optical frequency ν (= c / λc: speed of light) is scanned. FIG. 36 shows a change in the transmitted light amount I in the case. This is relatively fixed at the optical frequency ν (or wavelength λ) and the cavity length r
Is changed, the behavior becomes the same as that of (ν ₀ + Δν) =
The curve has a peak at r / n.

A case where the light PL reflected from the material 4 to be inspected is incident on the Fabry-Perot resonator 10 thus adjusted will be described. In a normal case, since the surface of the inspection object 4 is stationary, the frequency of the light PL reflected on the inspection object 4 surface remains ν ₀ , and the transmitted light amount I of the Fabry-Perot resonator 10 is It is constant at I _0.

However, when the ultrasonic wave reaches the measurement point, the frequency of the measurement light PL changes by ± ν _D due to the Doppler shift as described above, and as shown schematically in FIG. 36, the Fabry-Perot resonator The amount of transmitted light I at 10 also changes by ± _ID accordingly.

That is, the Fabry-Perot resonator 10 can detect the arrival of the ultrasonic wave as a change in the intensity of the transmitted light. This change in light intensity is determined by an avalanche photodiode (hereinafter referred to as APD), PIN
Since it can be converted into an electric signal using a photodetector 12 such as a photodiode (hereinafter referred to as PIN-PD), a photodiode (hereinafter referred to as PD), a photomultiplier tube (hereinafter referred to as PM), an oscilloscope. If you display the time on the horizontal axis and the electric signal strength on the vertical axis using
The ultrasonic signal can be displayed and recorded on the display device 14 for observation.

On the other hand, as described above, the distance r between the opposing mirrors 10a and 10b in the Fabry-Perot resonator 10 is sufficiently shorter than the wavelength of incident light (for example, about 633 nm in the case of He-Ne laser light). The adjustment must be made by the spatial length, and the adjustment may be easily shifted due to thermal expansion of parts due to a change in ambient temperature or mechanical vibration around the part.

Therefore, there is a conventional laser ultrasonic apparatus provided with a resonance length control system as shown in FIG. Note that FIG.
In FIG. 7, the same portions as those of the laser ultrasonic apparatus shown in FIG. 34 are denoted by the same reference numerals, and redundant description will be omitted. The same applies to other conventional examples.

In this laser ultrasonic apparatus, as shown in FIG. 37, the laser beam ML oscillated from the laser light source 5 is 1 /
After the polarization plane is controlled by the two-wavelength plate 6, a part thereof is branched in advance by the polarization beam splitter 17, and passes through the polarization beam splitter 18 as the reference light RL without passing through the test object 4, and passes through the Fabry-Perot resonator 10. Incident on The transmitted light transmitted through the Fabry-Perot resonator 10 and the reflected light PL from the test object 4 are separated by a polarization beam splitter 19,
The light is detected by the light detector 20.

Here, since the reference light RL does not undergo any frequency shift on the optical path, the output signal level of the photodetector 20 should normally be always constant. If the signal level of the photodetector 20 changes,
Since this means that the resonator length r has changed for some reason, the output signal level of the photodetector 20 is input to a driving mechanism 16 such as a piezo element for driving the mirror 10b via the controller 15. The resonator length r is always controlled to an optimum value by driving the mirror 10b so that the output signal level of the photodetector 20 becomes constant.

With this configuration, the photodetector 12 is a high-speed detector in the MHz band for ultrasonic measurement, and the photodetector 20 is a low-speed detector in the at most kHz band for detecting disturbance vibration and temperature change. Can be used, and a signal in a specific band can be detected with high sensitivity.
In this case, the measurement light PL is placed on the optical path of the measurement light PL.
Beam splitter 1 for superimposing light and reference light RL
It is necessary to install a half-wave plate 6b so as to allow the transmission of light through the wavelength plate 8.

On the other hand, as a simplified type of the conventional laser ultrasonic apparatus shown in FIG. 37, an apparatus as shown in FIG. 38 has also been proposed. In this case, the photodetector 12 is required to have a wide band capable of detecting both a high-frequency signal due to ultrasonic waves and a low-frequency signal due to disturbance. The high-frequency component of the signal detected by the photodetector 12 due to the ultrasonic signal is transmitted to the control device 1
If the frequency characteristics of the driving mechanism 5 and the driving mechanism 16 are sufficiently low, the operation of the resonator is not affected. Therefore, substantially the same effect as the apparatus shown in FIG. 37 can be obtained without the reference light RL.

Conversely, when measurement is performed while scanning the measurement points on the material 4 to be inspected, when the transmitted light intensity changes for each measurement point, is it due to the change in the state of the resonator? Alternatively, it cannot be distinguished whether the difference is due to a difference in the surface reflectance of the material 4 to be inspected. In addition, since the shot noise generated in the photodetector 12 is proportional to the square root of the measurement band, there is a problem that an increase in noise due to the broadening of the photodetector 12 cannot be avoided in principle.

[0021]

In the conventional laser ultrasonic apparatus, the surface of the material to be inspected 4 has a relatively uniform and good reflection characteristic, and the displacement induced by the ultrasonic wave, that is, the frequency shift. The amount is large enough and the resonator length r
Good measurement is possible when the influence of the surrounding environment on the change in is relatively mild.

However, for example, when inspecting structural materials and equipment of a plant during operation, the surface of the inspected material 4 is non-uniform and has different reflection characteristics, so that the light intensity that can be guided to the Fabry-Perot resonator 10 is low. Expected to be small. Since ultrasonic waves are attenuated during propagation due to deterioration of the surface properties and internal characteristics of the material to be inspected, it is expected that the displacement of the ultrasonic waves to be detected, that is, the amount of frequency change of the optical signal is also small.

Further, as described above, the control of the Fabry-Perot resonator 10 needs to be driven and controlled in an order sufficiently shorter than the wavelength, and there is a limitation in driving a relatively heavy mirror using a high-speed piezoelectric element. There is a problem that there is. Further, since the drive of the Fabry-Perot resonator 10 needs to be controlled in an order sufficiently shorter than the wavelength, assuming the use in the field, the initial adjustment can be automated or facilitated, and Need to show the health of Furthermore, when the influence of the surrounding environment is great, it is no longer possible to stably control the Fabry-Perot resonator 10 from the observed signal level.

As described above, the photodetector 12 in the conventional example mainly includes APD, PIN-PD, P
M are used, but in the normal case they are
It has an internal configuration as shown in FIG. That is, when light is incident on the light detection element 22, a current i _sig proportional to the light amount is generated by the photoelectric conversion effect as shown in FIG. 40, and the current _isig is electrically processed by the electric load 24. . Here, the keep applying a reverse bias voltage V _B to the light-detecting element 22 by the DC power source 23, it is possible to improve the photoelectric conversion efficiency, i.e., the sensitivity of the light detecting element 22 in accordance with the voltage that is applied.

However, if light of relatively high intensity is continuously detected while a high bias voltage is constantly applied to the light detecting element 22, the generated current _isig heats the light detecting element 22 and the thermal noise is remarkably increased. In addition to the increase, if the current value is excessive, the element may burn out.

Therefore, the limiting resistor 25 is connected in series with the light detecting element 22, and in a situation where an excessive signal current flows, a voltage drop is caused by the limiting resistor 25 and applied to the light detecting element 22. The voltage is reduced.

On the other hand, in a conventional laser ultrasonic device,
The detector 12 always operates as described with reference to FIG.
Constant light intensity I₀The ultrasonic signal that arrives at a certain time
No. U _sigThat is, the change in the frequency of the incident light is detected.
Is I₀± I_DWith the phenomenon that only changes
It is premised on the usage of detecting. At this time, super sound
Wave detection sensitivity, i.e. transmitted light per unit frequency change
In order to maximize the quantity change, the operating point I₀Figure 3
It is necessary to select the vicinity of the inflection point of the curve shown in FIG.
The higher the peak of the curve, the higher the sensitivity
I understand.

However, this means that the light intensity I₀Absolute
Value also increases, as shown in FIG.
In such a conventional photodetector 12, light that is always incident
Quantity I ₀The voltage at the limiting resistor 25 at a constant current flowing by
And the photoelectric conversion efficiency of the photodetector 22 is low.
The measurement must be performed in a stable state (see FIG. 40).
See). In FIG. 40, I_PIs the peak power, τ
_MIs the time to observe the arrival of the ultrasonic wave, τ_PIs the pulse width,
τ_RIs the repetition period. On the other hand, the limiting resistor 25 is removed
Then, the amount of light I that is always incident₀Constant flowing by
Thermal noise increases or current burns due to current
It is inevitable.

Therefore, the present invention has been made in view of the above circumstances, and a first object is to detect a weak light intensity signal with high sensitivity and to detect a minute frequency signal contained therein. It is an object of the present invention to provide a laser ultrasonic apparatus capable of observing a shift with a magnitude equal to or larger than a noise level.

A second object of the present invention is to provide a laser ultrasonic apparatus capable of following and controlling high-speed peripheral disturbances, for example.

A third object of the present invention is to provide a laser ultrasonic apparatus which can be used in, for example, a continuous vibration environment or an environment having a temperature change and does not require control of a Fabry-Perot resonator. To provide.

A fourth object of the present invention is to make it possible to immediately adjust the Fabry-Perot resonator when an apparatus is installed at an inspection / measurement site, and to maintain the state of the state during operation. An object of the present invention is to provide a laser ultrasonic device capable of confirming the performance.

[0033]

According to the first aspect of the present invention, there is provided a first laser for emitting an excitation laser beam modulated to generate an ultrasonic wave on a material to be inspected. A light source, a second laser light source that emits a measurement laser beam for observing an ultrasonic wave that has propagated through the inspection target material, and irradiates the excitation laser beam to a predetermined position of the inspection target material under predetermined conditions. First optical means for irradiating the measurement laser beam to a predetermined position of the inspection target material under predetermined conditions and guiding reflected light from the inspection target material. A Fabry-Perot resonator for receiving the reflected light guided by the second optical means, at least one light detecting means for detecting the intensity of the output light of the Fabry-Perot resonator, Means output signal A level or a part of the measuring laser beam is incident on the Fabry-Perot resonator through an optical path avoiding the material to be inspected, and the Fabry-Perot resonator is detected from the output signal level of another light detecting means for detecting the intensity of the output light.・
Resonator length control means for controlling the resonance length of the Perot resonator, and adjusting the sensitivity of the light detection means with a predetermined time delay and a predetermined time width based on the modulation timing of the first laser light source. And a sensitivity adjusting means.

According to the first aspect of the present invention, there is provided a sensitivity adjusting means for adjusting the sensitivity of the light detecting means with a predetermined time delay and a predetermined time width based on the modulation timing of the first laser light source. As a result, a weak light intensity signal can be detected with high sensitivity, and a minute frequency shift contained therein can be observed with a magnitude greater than the noise level.

According to the second aspect of the present invention, the first laser light source that emits an excitation laser beam modulated to generate an ultrasonic wave on the material to be inspected, and the ultrasonic wave that has propagated through the material to be inspected are observed. Emitting a measurement laser beam for the second
A laser light source, a first optical unit for irradiating the excitation laser beam to a predetermined position of the inspection target material under predetermined conditions, and the measurement laser beam to a predetermined position of the inspection target material. A second optical means for irradiating under predetermined conditions and guiding reflected light from the material to be inspected; a Fabry-Perot resonator for receiving reflected light guided by the second optical means; At least one light detecting means for detecting the intensity of the output light of the Fabry-Perot resonator;
One of the output signal levels of the light detecting means or a part of the measuring laser beam is incident on the Fabry-Perot resonator through an optical path avoiding the material to be inspected, and the intensity of the output light is detected. Resonator length control means for controlling the resonance length of the Fabry-Perot resonator from the output signal level of the light detection means, and adjusting the amount of light incident on the Fabry-Perot resonator from the output signal level of the light detection means And a light amount adjusting means disposed on an optical path of oscillation light of the second laser light source.

According to the second aspect of the present invention, the light amount adjusting means for adjusting the amount of light incident on the Fabry-Perot resonator based on the output signal level of one of the light detecting means is oscillated from the second laser light source. By arranging them on the optical path of light, the same operations and effects as those of the first aspect can be obtained.

According to the third aspect of the present invention, a first laser light source for emitting an excitation laser beam modulated to generate an ultrasonic wave on a material to be inspected, and the ultrasonic wave transmitted through the material to be inspected are observed. Emitting a measurement laser beam for the second
A laser light source, first optical means for irradiating a predetermined position of the material to be inspected with the excitation laser beam under predetermined conditions, and for splitting the measurement laser beam into at least two laser beams. A first light splitting means, an optical modulation means for shifting an optical frequency of at least one laser beam split by the first splitting means by a predetermined amount, and a first light splitting means split by the first splitting means. While irradiating the other laser beam to a predetermined position of the inspection target material under predetermined conditions, guiding the reflected light from the inspection target material, and further combining the laser beam modulated by the light modulation means on the same optical path. Optical means, a Fabry-Perot resonator for receiving the light beam synthesized by the second optical means, and the output light of the Fabry-Perot resonator A second light splitting means for splitting the reflected light from the material into a laser beam modulated by the light modulation means, and at least two light detecting means for detecting the intensity of each optical signal split by the second light splitting means; A light detecting means, and a resonator for controlling a resonance length of the Fabry-Perot resonator from an output signal level of the light detecting means which receives the laser beam modulated by the light modulating means among the light detecting means. Length control means.

According to the third aspect of the present invention, there is provided an optical modulation means for shifting the optical frequency of at least one laser beam split by the first splitting means by a predetermined amount. The same operation and effect as those described above can be obtained.

According to the fourth aspect of the present invention, the first laser light source that emits a laser beam for excitation modulated to generate ultrasonic waves on the material to be inspected, and the ultrasonic waves that have propagated through the material to be inspected are observed. Emitting a measurement laser beam for the second
A laser light source, a first optical unit for irradiating the excitation laser beam to a predetermined position of the inspection target material under predetermined conditions, and the measurement laser beam to a predetermined position of the inspection target material. A second optical means for irradiating under predetermined conditions and guiding reflected light from the material to be inspected; a Fabry-Perot resonator for receiving reflected light guided by the second optical means; At least one light detecting means for detecting the intensity of the output light of the Fabry-Perot resonator;
The output signal level of one of the light detecting means or a part of the laser beam for measurement is incident on the Fabry-Perot resonator, and the output signal level of another light detecting means detecting the intensity of the output light is used as the output signal level. Resonator length control means for controlling the resonance length of the Fabry-Perot resonator,
This resonator length control means is a laser beam transmitting member which is inserted between two mirrors of the Fabry-Perot resonator and whose transmission length can be adjusted.

According to the fourth aspect of the present invention, the resonator length control means is a laser beam transmitting member which is inserted between the two mirrors of the Fabry-Perot resonator and whose transmission length can be adjusted. This makes it possible to follow a high-speed peripheral disturbance.

According to the fifth aspect of the present invention, a first laser light source that emits an excitation laser beam modulated to generate an ultrasonic wave on a material to be inspected, and an ultrasonic wave transmitted through the material to be inspected are observed. A second laser light source that emits a laser beam for measurement, a first optical unit for irradiating the laser beam for excitation on a predetermined position of the inspection target material under predetermined conditions, and the measurement laser beam. A second optical unit for irradiating a predetermined position of the inspection target material under predetermined conditions and guiding reflected light from the inspection target material, and receives reflected light guided by the second optical unit. Fabry
A Perot resonator, at least one light detecting means for detecting the intensity of the output light of the Fabry-Perot resonator, and an output signal level of one of the light detecting means or a part of the measuring laser beam. The Fabry-Perot resonator for controlling the resonance length of the Fabry-Perot resonator from the output signal level of another light detecting means which is incident on the Fabry-Perot resonator on the optical path avoiding the inspected material and detects the intensity of the output light. Resonator control means, the resonator control means being sealing means for spatially sealing the Fabry-Perot resonator, and pressure adjusting means for adjusting the internal pressure of the sealing means. Features.

According to the fifth aspect of the present invention, the resonator control means is a sealing means for spatially sealing the Fabry-Perot resonator, and a pressure adjusting means for adjusting the internal pressure of the sealing means. Thereby, the same operation and effect as those of the fourth aspect can be obtained.

According to the sixth aspect of the present invention, the first laser light source for emitting a laser beam for excitation modulated to generate ultrasonic waves on the material to be inspected, and the ultrasonic waves propagated through the material to be inspected are observed. Emitting a measurement laser beam for the second
A laser light source, a first optical unit for irradiating the excitation laser beam to a predetermined position of the inspection target material under predetermined conditions, and the measurement laser beam to a predetermined position of the inspection target material. A second optical means for irradiating under predetermined conditions and guiding reflected light from the material to be inspected; a Fabry-Perot resonator for receiving reflected light guided by the second optical means; At least one light detecting means for detecting the intensity of the output light of the Fabry-Perot resonator;
One of the output signal levels of the light detecting means or a part of the measuring laser beam is incident on the Fabry-Perot resonator through an optical path avoiding the material to be inspected, and the intensity of the output light is detected. Resonator length control means for controlling the resonance length of the Fabry-Perot resonator from the output signal level of the light detection means, wherein the Fabry-Perot resonator has a surface facing in the optical axis direction as a focal point A laser beam transmitting member having a curved surface and a reflecting surface having a predetermined reflectance in an optical path, wherein the resonator length control means adjusts a tilt of the laser beam transmitting member with respect to an optical axis; It is characterized by controlling the mechanism.

According to the sixth aspect of the present invention, Fabry
A laser beam transmitting member having a curved surface shape whose focal point is a surface opposed in the optical axis direction and having a reflection surface having an appropriate reflectance in an optical path; By controlling the drive mechanism for adjusting the inclination of the member with respect to the optical axis, the same operation and effect as in the fourth aspect can be obtained.

According to the seventh aspect of the present invention, a first laser light source for emitting an excitation laser beam modulated to generate an ultrasonic wave on a material to be inspected, and the ultrasonic wave propagating through the material to be inspected are observed. Emitting a measurement laser beam for the second
A laser light source, a first optical unit for irradiating the excitation laser beam to a predetermined position of the inspection target material under predetermined conditions, and the measurement laser beam to a predetermined position of the inspection target material. A second optical means for irradiating under predetermined conditions and guiding reflected light from the material to be inspected; a Fabry-Perot resonator for receiving reflected light guided by the second optical means; At least one light detecting means for detecting the intensity of the output light of the Fabry-Perot resonator;
Another light detecting means for inputting the output signal level of this light detecting means or a part of the measuring laser beam to the Fabry-Perot resonator through an optical path avoiding the material to be inspected, and detecting the intensity of the output light. Resonator length control means for controlling the resonance length of the Fabry-Perot resonator from the output signal level of the second laser light source, the second laser light source is a tunable laser light source, and one of the light detection means The oscillation wavelength of the tunable laser light source is controlled from an output signal level.

According to the seventh aspect of the present invention, the second laser light source is a wavelength variable laser light source, and the light detecting means receives the other laser beam split by the first light splitting means among the light detecting means. By controlling the oscillation wavelength of the wavelength tunable laser light source from the output signal level of the means, the same operation and effect as in claim 4 can be obtained.

According to the eighth aspect of the present invention, the first laser light source that emits an excitation laser beam modulated to generate an ultrasonic wave on the material to be inspected, and the ultrasonic wave that has propagated through the material to be inspected are observed. Emitting a measurement laser beam for the second
A laser light source, a first optical unit for irradiating the excitation laser beam to a predetermined position of the inspection target material under predetermined conditions, and the measurement laser beam to a predetermined position of the inspection target material. A second optical means for irradiating under predetermined conditions and guiding reflected light from the material to be inspected; a Fabry-Perot resonator for receiving reflected light guided by the second optical means; At least one light detecting means for detecting the intensity of the output light of the Fabry-Perot resonator;
Another light detecting means for inputting the output signal level of this light detecting means or a part of the measuring laser beam to the Fabry-Perot resonator through an optical path avoiding the material to be inspected, and detecting the intensity of the output light. Resonator length control means for controlling the resonance length of the Fabry-Perot resonator from the output signal level of the second laser, wherein the second laser is controlled so that the output signal level of one of the light detection means is constant. A variable frequency shifter for shifting the frequency of the oscillation light of the light source is provided.

According to the eighth aspect of the present invention, the output signal level of the light detecting means, which receives the other laser beam split by the first light splitting means among the light detecting means, becomes constant. By providing a variable frequency shifter for shifting the frequency on the optical path of the oscillation light of the second laser light source, the same operation and effect as in claim 4 can be obtained.

According to the ninth aspect of the present invention, the first laser light source that emits an excitation laser beam modulated to generate an ultrasonic wave on the material to be inspected, and the ultrasonic wave that has propagated through the material to be inspected are observed. Emitting a measurement laser beam for the second
A laser light source, a first optical unit for irradiating the excitation laser beam to a predetermined position of the inspection target material under predetermined conditions, and the measurement laser beam to a predetermined position of the inspection target material. A second optical means for irradiating under predetermined conditions and guiding reflected light from the material to be inspected; a Fabry-Perot resonator for receiving reflected light guided by the second optical means; At least one light detecting means for detecting the intensity of the output light of the Fabry-Perot resonator;
Signal oscillating means for oscillating a periodic signal, and at least one mirror of the Fabry-Perot resonator for at least one wavelength of the second laser light source in accordance with an output signal of the signal oscillating means And a driving unit for operating the first laser light source linearly in parallel with the optical axis, wherein the first laser light source oscillates in synchronization with an output signal of the signal oscillation unit.

According to the ninth aspect of the present invention, the first laser light source 1 is a pulse oscillation light source, and a signal oscillation means for oscillating a periodic signal, and the first laser light source 1 responds to an output signal of the signal oscillation means. Drive means for operating at least one mirror of the Fabry-Perot resonator linearly in parallel with the optical axis for at least one wavelength of the second laser light source, and an output of the signal oscillating means. By oscillating the first laser light source in synchronization with a signal, the first laser light source can be used in a continuous vibration environment or an environment having a temperature change, and the control of the resonator becomes unnecessary.

According to a tenth aspect of the present invention, in the laser ultrasonic apparatus according to the ninth aspect, the output signal level of the light detecting means or a part of the measuring laser beam is transmitted along the optical path avoiding the inspection object. When the signal level of one of the other light detection means that has entered the Fabry-Perot resonator and detected the intensity of the output light is in a predetermined state, the first
Oscillation control means for causing the laser light source to oscillate.

According to the tenth aspect of the present invention, the output signal level of the light detecting means or a part of the measuring laser beam is incident on the Fabry-Perot resonator through the optical path avoiding the material to be inspected, and the output thereof is output. 10. The same operation as in claim 9, further comprising an oscillation control unit for oscillating the first laser light source when one signal level of another light detection unit that has detected the light intensity is in a predetermined state. And effects are obtained.

According to an eleventh aspect of the present invention, in the laser ultrasonic apparatus according to the ninth or tenth aspect, the first laser light source is a pulse oscillation light source, and is disposed on an optical path of the second laser light source and is intermittent. Optical amplification means that operates
Another light detecting means for inputting the output signal level of the light detecting means or a part of the measuring laser beam to the Fabry-Perot resonator through an optical path avoiding the material to be inspected, and detecting the intensity of the output light. When one of the signal levels is in a predetermined state, the first laser light source is oscillated, and the oscillation for operating the optical amplifying means is delayed by a predetermined time from the time when the first laser light source oscillates. Control means.

According to the eleventh aspect of the present invention, the first laser light source is a pulse oscillation light source, and is disposed on the optical path of the second laser light source and operates intermittently. The output signal level or a part of the measuring laser beam is incident on the Fabry-Perot resonator through the optical path avoiding the material to be inspected, and the signal level of one of the other light detecting means for detecting the intensity of the output light is a predetermined level. When in the state, the first laser light source oscillates, and oscillation control means for operating the optical amplification means with a predetermined time delay from the time when the first laser light source oscillates is provided. The same operation and effect as the ninth aspect are obtained.

According to a twelfth aspect of the present invention, in the laser ultrasonic apparatus according to the ninth or tenth aspect, the light detection is performed with a predetermined time delay and a predetermined time width based on the oscillation time of the first laser light source. A sensitivity adjusting means for adjusting the sensitivity of the means.

According to the twelfth aspect of the invention, there is provided a sensitivity adjusting means for adjusting the sensitivity of the light detecting means with a predetermined time delay and a predetermined time width based on the oscillation time of the first laser light source. Thereby, the same operation and effect as the ninth aspect are obtained.

According to the thirteenth aspect of the present invention, the first laser light source that emits an excitation laser beam modulated to generate an ultrasonic wave on the material to be inspected, and the ultrasonic wave transmitted through the material to be inspected are observed. A second laser light source for emitting a laser beam for measurement, a first optical means for irradiating a predetermined position of the material to be inspected with a predetermined condition on the material to be inspected, and the laser beam for measurement Is irradiated on a predetermined position of the inspection target material under predetermined conditions, and second optical means for guiding reflected light from the inspection target material, and reflected light guided by the second optical means An incident Fabry-Perot resonator; and at least one photodetector for detecting the intensity of the output light of the Fabry-Perot resonator, wherein the second laser light source periodically scans the wavelength within a certain range. Wave A tunable laser light source, the Fabry-part of the output signal level or the measurement laser beam of said light detecting means in the optical path that avoids the inspection member
Oscillation control means for oscillating the first laser light source is provided when one signal level of another light detection means that is incident on the Perot resonator and detects the intensity of the output light is in a predetermined state. It is characterized by the following.

According to the thirteenth aspect of the present invention, the second laser light source is a wavelength-variable laser light source whose wavelength is periodically scanned in a certain range, and the output signal level of the light detecting means or the measuring laser beam Is incident on the Fabry-Perot resonator through an optical path avoiding the material to be inspected, and when one signal level of another light detecting means that detects the intensity of the output light is in a predetermined state, the first 10. An oscillation control means for oscillating the laser light source according to claim 9 is provided.
The same operation and effect as those described above can be obtained.

According to a fourteenth aspect of the present invention, in the laser ultrasonic apparatus according to any one of the ninth to twelfth aspects,
A driving mechanism operated by a signal oscillating means for oscillating a periodic signal is inserted between two mirrors of the Fabry-Perot resonator, and a transmission length of the oscillation wavelength of the second laser light source. A laser beam transmitting member having a regular 2n polygonal shape (where n is an integer of 2 or more) that can be adjusted by a distance equal to or longer than the length.

According to the fourteenth aspect of the present invention, the driving mechanism operated by the signal oscillating means for oscillating a periodic signal is inserted between the two mirrors of the Fabry-Perot resonator and transmitted. 10. A laser beam transmitting member having a regular 2n polygonal shape (where n is an integer of 2 or more) whose length can be adjusted by a distance equal to or longer than the oscillation wavelength of the second laser light source. Similar functions and effects can be obtained.

According to a fifteenth aspect of the present invention, in the laser ultrasonic device according to any one of the ninth to fourteenth aspects,
Signal monitoring means for extracting a characteristic amount of one output signal of the light detection means; comparing means for comparing the characteristic amount extracted by the signal monitoring means with a preset reference value; And display means for displaying the result.

According to the fifteenth aspect of the present invention, the signal monitoring means for extracting the characteristic amount of one output signal of the light detecting means, and the characteristic amount extracted by the signal monitoring means and a preset reference value By providing a comparison means for comparing the value with the display and a display means for displaying the result of the comparison means, the resonator can be adjusted immediately when the device is installed at the inspection / measurement site, and furthermore, during operation. Can confirm the soundness of the state.

According to a sixteenth aspect of the present invention, in the laser ultrasonic apparatus according to any one of the ninth to fourteenth aspects, signal monitoring means for extracting a characteristic amount of one output signal of the light detection means, and the fabric An adjusting mechanism for adjusting the length of the Perot resonator and the two-dimensional inclination of the mirror thereof, and the adjusting mechanism such that the characteristic amount extracted by the signal monitoring means becomes a preset reference value. And an adjustment control means for driving the motor.

According to the sixteenth aspect of the present invention, the signal monitoring means for extracting the characteristic amount of one output signal of the light detecting means, and the length of the Fabry-Perot resonator and the two-dimensional inclination of the mirror are determined. 16. An image forming apparatus comprising: an adjusting mechanism for adjusting; and an adjusting control means for driving the adjusting mechanism such that the characteristic amount extracted by the signal monitoring means has a preset reference value. The same operation and effect as those described above can be obtained.

[0065]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a laser ultrasonic apparatus according to the present invention will be described below with reference to the drawings.

[First Embodiment] FIG. 1 is a block diagram showing a first embodiment of the laser ultrasonic apparatus according to the present invention. In addition, the same or corresponding parts as the conventional configuration include:
Description will be made using the same reference numerals as those in FIGS.

As shown in FIG. 1, a laser light source 1 for generating an ultrasonic wave as a first laser light source is modulated so as to generate an ultrasonic wave on a material 4 to be inspected. The laser beam EL is applied to a predetermined position on the surface of the inspection target material 4 in a predetermined beam shape (predetermined conditions) via mirrors 2a and 2b and a lens 3 constituting the first optical unit.

A laser light source 5 for detecting an ultrasonic wave as a second laser light source emits a measuring laser beam for observing the ultrasonic wave transmitted through the material 4 to be inspected. After the polarization plane is controlled by the １ ／ wavelength plate 6 a, the light is radiated to a measurement point on the inspection target material 4 via the polarization beam splitter 17, the polarization beam splitter (first light splitting means) 7, and the lens 8. You. That is, the laser light ML oscillated from the laser light source 5 is controlled in its polarization plane by the half-wave plate 6 a, and a part thereof is branched in advance by the polarization beam splitter 17, and is referred to without passing through the inspection target material 4. Light RL
And then enter the Fabry-Perot resonator 10 via the polarizing beam splitter 18. On the other hand, the reflected light (hereinafter, also referred to as measurement light) PL from the inspection target material 4 passes through the lens 8, the polarizing beam splitter 7, the mirror 9, the half-wave plate 6b, and the polarizing beam splitter 18 to generate Fabry-Perot resonance. Incident on the vessel 10. Here, the half-wave plate 6a, the polarization beam splitters 17 and 7, the lens 8, the mirror 9, the half-wave plate 6b, and the polarization beam splitter 18
Constitutes a second optical unit.

The reference light RL transmitted through the Fabry-Perot resonator 10 is separated from the reflected light PL from the test object 4 via a lens 11 by a polarization beam splitter 19 as a second light splitting means. , Are detected by a photodetector 20 as another light detecting means.

Here, since the reference light RL does not undergo any frequency shift on the optical path, the output signal level of the photodetector 20 should normally be always constant. If the signal level of the photodetector 20 changes,
Since it means that the resonator length r is changed for some reason, the output signal level of the photodetector 20 is controlled by a mirror 15b via a controller 15 as a resonator length control means. And the mirror 10b is driven by the drive mechanism 16 so that the output signal level of the photodetector 20 becomes constant, so that the resonator length r is always controlled to an optimum value. .

On the other hand, the reflected light PL transmitted from the material to be inspected 4 through the Fabry-Perot resonator 10 is split by the polarization beam splitter 19 through the lens 11 and guided to the light detector 12 as light detecting means. The photodetector 12 converts the transmission intensity of the Fabry-Perot resonator 10 into an electric signal,
After the electric signal is amplified and filtered by the signal processing device 13, it is displayed and recorded on the display device 14.

In this embodiment, the photodetector 12
Is changed, and the operation of the photodetector 12 is controlled by the sensitivity adjusting means 31 for adjusting the reverse bias voltage applied to the photodetector 12. As described above, the photodetector 12 mainly includes an APD and a PIN.
-PD and PM are used.

[0073] Light detector 12, when light enters the light detection element 22, as shown in FIG. 2, the current i _sig proportional to the quantity by photoelectric conversion effect is generated, the current i _sig is electrical load 24 Is processed electrically. here,
If you leave applying a reverse bias voltage V _B to the light-detecting element 22 by the DC power source 23, it is possible to improve the photoelectric conversion efficiency, i.e., the sensitivity of the light detecting element 22 in response to the applied voltage. However, if light of relatively high intensity is continuously detected while a high bias voltage is continuously applied, the generated current _isig heats the photodetector element 22, significantly increases thermal noise, and causes an excessive current value. In this case, the element may be burned out.

Therefore, in the present embodiment, the light detecting element 22
The operation of the switch 26 is controlled by the sensitivity adjusting means 31. That is, in the present embodiment, the laser light source 1
The sensitivity adjusting means 31 adjusts the sensitivity of the photodetector 12 with a predetermined time delay and a predetermined time width based on the modulation timing.

The operation of the sensitivity adjusting means 31 will be described with reference to FIG.

The specifications of the laser light source 1 to be used are as follows: peak power I _P , pulse width τ _P = 10 nsec, and repetition frequency 50 Hz (repetition period τ _R = 20 msec). Here, the duration of the ultrasonic wave propagation phenomenon to be observed can be roughly estimated as follows. For example, when the material to be inspected 4 is carbon steel, the sound velocity is about 2,900 m / s even if the surface wave has the lowest sound velocity among longitudinal waves, transverse waves, and surface waves.
ec.

Even if the range to be observed is a distance of 1 m, the propagation time, that is, the time τ _M to observe the arrival of the ultrasonic wave, is only about 330 μsec. That is, it is understood that the measurement system needs to be kept in a highly sensitive state in order to detect the ultrasonic wave at most about 330 μsec for the ultrasonic wave transmitted every 20 msec.

Therefore, the oscillation timing of the laser light source 1
Is detected by the sensitivity adjusting means 31, and then an appropriate time
Τ_DTo turn on the switch 26 and turn on the light detecting element 22
Reverse bias voltage V at which maximum sensitivity is obtained_BAnd apply
After the observation time is over, the sensitivity adjustment means 21 switches quickly.
26 is turned off, the ultrasonic signal U
_sigAt the timing to observe the sensitivity of the photodetector 12
Is the maximum, and the observation time τ within 20 msec_M
About 19.7 msec other than the current i_sigAlmost flow
Can be kept in the undetected state.
Thermal noise and burnout caused by temperature rise of element 22 can be avoided
It works.

The time delay τ _D is provided in order to prevent extremely high-intensity pulsed light oscillated from the laser light source 1 from entering the measurement system, and has a pulse width τ _P = 10
nsec, and the observation time τ _M = 33
It is sufficient if the time is sufficiently shorter than 0 μsec, for example, about 1 μsec. Alternatively, it may be 0 if the wavelength filtering in the measurement system is sufficient.

[0080] Further, when the rise of the reverse bias voltage V _B is delayed like the time constant of the circuit, the anticipation time tau _F with respect to the optical pulse signal shown in an ON signal shown in FIG. 4 (B) (A) It may be generated only in advance.

As described above, according to the present embodiment, the sensitivity of the photodetector 12 is adjusted by the sensitivity adjusting means 31 with a predetermined time delay and a predetermined time width based on the modulation timing of the laser light source 1. , A weak light intensity signal can be detected with high sensitivity, and a minute frequency shift contained therein can be observed with a magnitude equal to or higher than the noise level.

[Modification of First Embodiment] FIG. 5 is a block diagram showing a modification of the first embodiment of the laser ultrasonic apparatus according to the present invention. The same or corresponding parts as those in the first embodiment will be described with the same reference numerals. The same applies to the following embodiments and modified examples.

This modification is different from the first embodiment in FIG.
The configuration and operation of the sensitivity adjusting means 31 and the photodetector 12 are the same as those of the first embodiment, but the photodetector 12
Is also used for controlling the Fabry-Perot resonator 10, so that the output signal of
so that the effect of changing the sensitivity by c does not affect the control,
It is necessary to set the time constant of the controller 15 or the drive mechanism 16 sufficiently later. Therefore, the same effect as that of the first embodiment can be obtained in this modified example.

As a simpler configuration having substantially the same effect as the device configuration of this modification, a configuration in which a shutter for opening and closing the optical path is provided on the optical path immediately before the photodetector 12 as sensitivity adjusting means is also available. Conceivable. As this shutter, a liquid crystal shutter or the like can be considered in addition to a shutter that operates an opaque substance to mechanically block an optical path.
However, these elements can be realized when the operation time of the sensitivity adjusting means is relatively slow because the operation time is relatively slow. However, the detection sensitivity of the photodetector 12 is controlled on the order of μsec as described above. Sometimes unsuitable.

[Second Embodiment] FIG. 6 is a block diagram showing a second embodiment of the laser ultrasonic apparatus according to the present invention.

As shown in FIG. 6, in the present embodiment, the ultrasonic wave excited by the laser beam EL is applied to the Fabry-Perot resonator 10 which is stably controlled by using the laser beam RL.
The operation of measuring by inputting the measurement light PL that is the reflected light from the measurement point on the inspection target material 4 is the same as in the first embodiment.

In this embodiment, for example, the half-wave plate 6b is installed on the optical path of the measurement light PL by using the light amount adjusting means 37 based on the characteristic amount of the output signal of the photodetector 12, and
The wavelength plate 6b is rotated so that the amount of light incident on the Fabry-Perot resonator 10 is controlled to an optimum value.

As described above with reference to FIGS. 1 and 2, in the photodetector 12 of the ordinary laser ultrasonic device, in principle, the larger the amount of incident light, the more sensitive the ultrasonic signal can be detected. However, due to the limitations of the detection device, it is estimated that the sensitivity of the light detection element 22 decreases when the amount of light equal to or more than a certain value enters, and the overall detection sensitivity decreases.

[0089] Therefore, it is believed that optimal incident light intensity I _C is present in the intermediate region as schematically shown in FIG.
Therefore, in the case of using the optical detector 12 is a sensitivity on expedient to leave adjusted to the light amount of the I _C is obtained an amount of light incident on the advance Fabry-Perot resonator 10 by the optical detector 12 .

However, since the surface of the structural material of the plant during operation has various reflectances and reflection directivities, it is impossible to always maintain a constant amount of reflected light. Therefore, the laser light M from the laser light source 5 is such that a slightly excessive amount of reflected light can be obtained under the reflection characteristics assumed in advance.
L is oscillated, and from the output signal level of the photodetector 12, the 光 量 wavelength plate 6b is rotated using the light amount adjusting means 37 so that I ₀ = I _C, and the polarization beam splitter 1
By adjusting the amount of measurement light PL that passes through the light source 8, that is, the amount of light incident on the Fabry-Perot resonator 10, the ultrasonic signal can always be detected with the optimum detection sensitivity even when the ordinary photodetector 12 is used. It becomes possible.

However, in this case, the light quantity adjusting means 37 is sufficiently slower than the controller 15 and the driving mechanism 16 and is placed on the material 4 to be inspected so that the light quantity adjusting means 37 does not follow the light quantity change due to the change in the resonator length. It is necessary to set a time constant earlier than the change of the measurement point in.

The characteristic amount of the output signal of the photodetector 12 may be the DC level of the signal or the maximum amplitude value of the ultrasonic signal (AC component). Furthermore, an optical attenuator is installed on the optical path of the measurement light PL instead of the wave plate,
The same effect can be obtained by adjusting the optical attenuator.

As described above, according to the present embodiment, the Fabry-Perot resonator 10 is determined based on the output signal level of the photodetector 12.
The half-wave plate 6b rotated by using the light-amount adjusting means 37 is arranged on the optical path of the measurement light PL from the laser light source 5 in order to adjust the amount of light incident on the laser light source. , A weak light intensity signal can be detected with high sensitivity, and a minute frequency shift contained therein can be observed with a magnitude equal to or higher than the noise level.

[Modification of Second Embodiment] FIG. 8 is a block diagram showing a modification of the second embodiment of the laser ultrasonic apparatus according to the present invention.

This modification is different from the second embodiment in that FIG.
And is configured to drive an optical attenuator 38 installed on the measurement light PL by a light amount adjusting means 37 as shown in FIG. Are the same as those of the second embodiment.

When the oscillation output of the laser light source 5 can be controlled, the same effect can be obtained even if the oscillation output of the laser light source 5 is controlled based on the output signal level of the photodetector 12. No drive mechanism or optical attenuator is required,
The structure can be simplified. However, in this case, since the light amount of the reference light RL changes accordingly, care must be taken in controlling the Fabry-Perot resonator 10.

[Third Embodiment] FIG. 9 is a block diagram showing a third embodiment of the laser ultrasonic apparatus according to the present invention.

As shown in FIG. 9, also in the present embodiment, the ultrasonic wave excited by the laser beam EL is used to convert the measurement light PL, which is the reflected light from the measurement point on the test object 4, to the Fabry-Perot resonator 10. The basic operation of measuring by entering the light beam is the same as in the first embodiment.

In the present embodiment, the frequency of the reference light RL branched by the polarization beam splitter 17 as the first light branching means is shifted by using the light modulator 40 as the light modulation means driven by the oscillator 39, The Fabry-Perot resonator 10 is controlled using laser light having a frequency (that is, a wavelength) slightly different from the measurement light PL.

In order to detect the vibration of an object, that is, the Doppler shift component of light, with the maximum sensitivity using the Fabry-Perot resonator 10, the resonator must have an inflection of the transmitted light amount curve as described with reference to FIGS. It is necessary to control the point, that is, the point A in the figure.

However, when the inspection material is a structural material of the plant during operation, the amount of the reflected light PL from the target surface depends on the surface state, and the peak of the transmitted light curve changes. Therefore, it is difficult to find the point A in the monotonically increasing signal change, and the control must be performed at a constant level assumed in many cases.

[0102] Therefore, in the present embodiment, by using the optical modulator 30 leave half the frequency of only the reference beam RL bandwidth f _B are previously shifted as shown in FIG. 10, the peak (in the drawing point B) , The Fabry-Perot resonator 10 can be more easily controlled at the point of maximum sensitivity.

As described above, according to the present embodiment, the frequency of the reference light RL branched by the polarization beam splitter 17 is shifted by using the optical modulator 40 driven by the oscillator 39, whereby the first embodiment differs from the first embodiment. Similar effects can be obtained.

[Fourth Embodiment] FIG. 11 is a block diagram showing a fourth embodiment of the laser ultrasonic apparatus according to the present invention.

As shown in FIG. 11, also in this embodiment, the ultrasonic wave excited by the laser beam EL is used to convert the measurement light PL, which is the reflected light from the measurement point on the material 4 to be inspected, into the Fabry-Perot resonator 10. The basic operation of measuring by entering the light beam is the same as in the first embodiment.

In the present embodiment, the Fabry-Perot resonator 1 is used.
Rotation stage 4 between mirrors 10a, 10b
Transmission plate 4 which is a laser beam transmission member installed on 1
2 is arranged, and the rotary stage 41 is driven by the controller 15 as resonator control means based on the output signal of the photodetector 20 that has detected the signal level of the reference light RL.

As shown in FIG. 37, in the ordinary laser ultrasonic device, the adjustment of the resonator length r is performed by using one of the mirrors 10a and 10b (the mirror 10b in FIG. 37) constituting the Fabry-Perot resonator 10. A driving mechanism 16 such as a piezo element is installed, and the driving mechanism 16
Is finely moved in parallel with the optical axis so that the resonator length r is n
It is adjusted so as to be point A at the peak of λ. However, the piezo element has a problem that it is impossible to operate a relatively heavy optical mirror at high speed.

Therefore, in the laser ultrasonic apparatus of the present embodiment, the control of the resonator length r is replaced by a rotary drive by the rotary stage 41 instead of a linear drive by a piezo element or the like. The means for controlling the resonator length by the rotary stage 41 will be described with reference to FIG.

As shown in FIG.
For the optical path L _org in the Perot resonator 10, the thickness d,
When the transmitting plate 42 of refractive index n ₂ is inserted vertically, the change in optical path length is not, cavity length and the mirror 10a 1
0b. Here, FIG.
As shown in (B), the transmission plate 4 is
Rotation 2 by the angle theta _1, the light is refracted by the difference between the refractive index n ₁ of the peripheral medium (e.g., air, etc.) and the refractive index n ₂ of the transparent plate 42, the optical path is as l _org. At this time, in the optical path l _var and the optical path lorg, the length is

(Equation 1) However,

(Equation 2) Only the optical path length difference occurs. In this way, the optical path length can be controlled relatively easily by the rotating operation of the rotary stage 41, and the optical path length can be adjusted at high speed by appropriately selecting the thickness d of the transmission plate 42. Becomes

As described above, according to the present embodiment, the transmission plate 42 as the resonance length adjusting means is disposed between the mirrors 10a and 10b constituting the Fabry-Perot resonator 10, and the rotary stage for rotating the transmission plate 42 is provided. The drive control of the Fabry-Perot resonator 10 can be performed in an order sufficiently shorter than the wavelength by controlling the drive of the controller 41 as the resonator control means. be able to.

[Modification of Fourth Embodiment] FIG. 13 is a block diagram showing a modification of the fourth embodiment of the laser ultrasonic apparatus according to the present invention.

This modification is different from the fourth embodiment in FIG.
The operation and effect of the fourth embodiment are the same as those of the fourth embodiment except that the output signal of the photodetector 12 is also used to control the Fabry-Perot resonator 10. is there.

[Fifth Embodiment] FIG. 14 is a block diagram showing a fifth embodiment of the laser ultrasonic apparatus according to the present invention.

As shown in FIG. 14, also in the present embodiment, the ultrasonic wave excited by the laser light EL is used to convert the measurement light PL, which is the reflected light from the measurement point on the test object 4, to the Fabry-Perot resonator 10. The basic operation of measuring by entering the light beam is the same as in the first embodiment.

In this embodiment, the Fabry-Perot resonator 10 is covered with a pressure-controlled hermetic container 44.

By the way, as shown in FIG. 37, in the ordinary laser ultrasonic device, the resonator length r
The driving means 16 such as a piezo element is installed on one of the mirrors 10a and 10b (10b in the figure) constituting the Fabry-Perot resonator 10, and the driving means 16 moves the mirror 10b in parallel with the optical axis. Was compensated for by fine movement by the distance to cancel out. However, it is originally desired that the deviation to be compensated is small.

Therefore, in the laser ultrasonic apparatus according to the present embodiment, the Fabry-Perot resonator 10 is completely sealed by a sealed container 44 as sealing means, and the inside of the sealed container 44 is substantially evacuated by pressure adjusting means (not shown). By controlling the pressure to the state, an atmosphere with little change in thermal and pressure is created, so that the original deviation amount is suppressed to a small value.

The reflectance of the two mirrors 10a and 10b constituting the Fabry-Perot resonator 10 is
Since the transmission performance of the Perot resonator 10 is greatly affected, it is possible to prevent the reflection surface from being damaged due to dust adhesion or foreign matter by blocking the air from the outside with the closed container 44, and to reduce the change of the reflectance from the design value. It becomes possible.

As described above, according to the present embodiment, the Fabry-Perot resonator 10 is completely sealed by the closed container 44, and the pressure inside the closed container 44 is controlled to a substantially vacuum state by pressure adjusting means (not shown). Accordingly, the drive of the Fabry-Perot resonator 10 can be controlled in an order sufficiently shorter than the wavelength, and the control can be performed to follow a high-speed peripheral disturbance.

[Sixth Embodiment] FIG. 15 is a block diagram showing a sixth embodiment of the laser ultrasonic apparatus according to the present invention.

As shown in FIG. 15, also in this embodiment, the ultrasonic wave excited by the laser beam EL is used to convert the measurement light PL, which is the reflected light from the measurement point on the test object 4, to the Fabry-Perot resonator 10. The basic operation of measuring by entering the light beam is the same as in the first embodiment.

In the present embodiment, the Fabry-Perot resonator is not composed of two opposing mirrors, but has a confocal shape with the opposing surface as the focal point in the optical axis direction and a predetermined surface. It is provided with a Fabry-Perot resonator 10A having a reflecting surface having a reflectance, being thermally stable, and including a laser beam transmitting member that can be considered transparent to the measurement light PL.

By the way, as shown in FIG. 37, in the ordinary laser ultrasonic device, the resonator length r
The driving means 16 such as a piezo element is installed on one of the mirrors 10a and 10b (10b in the figure) constituting the Fabry-Perot resonator 10, and the driving means 16 moves the mirror 10b in parallel with the optical axis. Was compensated for by fine movement by the distance to cancel out. However, it is originally desired that the deviation to be compensated is small.

Therefore, in the laser ultrasonic apparatus according to the present embodiment, by using a bulk material, for example, a reflection film formed on the periphery of quartz glass, etc., in the Fabry-Perot resonator 10A, thermal and pressure By creating a Fabry-Perot resonator with little change, the original deviation amount is suppressed to a small value.

The reflectances of the two mirrors constituting the Fabry-Perot resonator 10 are also different from those of the Fabry-Perot resonator 1.
0 greatly affects the transmission performance, but in the Fabry-Perot resonator 10A of the present embodiment, since the resonance surface is cut off from the outside, damage to the reflection surface due to dust adhesion or foreign matter is prevented, and the design value of the reflectance is reduced. Can be reduced.

In this case, the structure is hardly affected by disturbance such as mechanical vibration. However, in order to correct a change in resonance length due to a slight influence of other factors, the Fabry-Perot resonator 10A is driven by a rotary stage as a driving mechanism. 45 on,
The rotary stage 45 may be controlled and driven by the controller 15 so as to keep the output signal level of the photodetector 20 constant. That is, the controller 15 controls the rotary stage 45 to adjust the inclination of the Fabry-Perot resonator 10A with respect to the optical axis.

As described above, according to the present embodiment, the Fabry-Perot resonator 10A has a confocal shape and a reflecting surface having a predetermined reflectance on the opposing surface, is thermally stable, and The same effect as in the fourth embodiment can be obtained by using a medium that can be considered transparent to the measurement light PL.

[Seventh Embodiment] FIG. 16 is a block diagram showing a seventh embodiment of the laser ultrasonic apparatus according to the present invention.

As shown in FIG. 16, in the present embodiment, the ultrasonic wave excited by the laser beam EL is applied to the laser beam RL.
Fabry-Perot resonator 10 controlled stably by using
The measurement light P, which is the reflected light from the measurement point on the material 4 to be inspected,
The basic operation of measuring by making L incident is the same as in the first embodiment.

In the present embodiment, the laser light source 45 as the second laser light source that oscillates the laser light ML is a tunable laser light source, and is based on the output signal of the photodetector 20 that has detected the signal level of the reference light RL. The control unit 46 controls the oscillation wavelength of the laser light source 45.

By the way, as shown in FIG. 37, in the ordinary laser ultrasonic device, a change in the resonator length r due to mechanical vibration or a change in the surrounding temperature is measured by the mirrors 10a and 10b constituting the Fabry-Perot resonator 10. Driving means 16 such as a piezo element is installed on one side (10b in the figure), and the mirror length of the mirror 10b is finely moved by the driving means 16 in parallel with the optical axis by a distance to cancel the change, so that the resonator length r is constant. It is adjusted so that it becomes. However, there is a problem that the mechanical adjustment means such as a piezo element may be prevented from being driven by the durability of the device or the bite of dust mixed from the surrounding environment.

Therefore, in the laser ultrasonic apparatus of the present embodiment, the fluctuation of the resonator is optically compensated by directly adjusting the oscillation wavelength of the measuring laser beam ML to the change of the resonator length r. I have.

FIG. 35 shows the amount of transmitted light when the resonator length of the Fabry-Perot resonator 10 is scanned, and FIG. 35 shows the amount of transmitted light when the wavelength of the measurement light incident on the Fabry-Perot resonator 10 is scanned. As is clear from the comparison of the curves shown in FIG. 36, mechanical adjustment of the resonator length r and adjustment of the wavelength (frequency) of the incident light have an equivalent meaning.

Therefore, in the present embodiment, the transmitted light level of the reference light RL is monitored by the photodetector 20, and the oscillation wavelength of the tunable laser light source 45 is controlled by the control means 46 so as to cancel the level change. If it is changed, it becomes possible to measure an ultrasonic signal without mechanically controlling the resonator length of the Fabry-Perot resonator 10. In addition, as the wavelength variable laser light source 45, a wavelength variable laser diode or the like can be used.

As described above, according to the present embodiment, the laser light source is the tunable laser light source 45 and the photodetector 20 is used.
By controlling the oscillation wavelength of the laser light source 45 from the output signal level of the laser light source 45 by the control means 46, the same effect as in the fourth embodiment can be obtained.

[Modification of Seventh Embodiment] FIG. 17 is a block diagram showing a modification of the seventh embodiment of the laser ultrasonic apparatus according to the present invention.

This modification differs from the seventh embodiment in FIG.
In this modification, the control means 4 controls the wavelength control so that the wavelength control does not follow a high-speed signal level change due to the reception of the ultrasonic signal.
The time constant of 6 needs to be set sufficiently slower than the frequency and duration of the ultrasonic signal.

[Eighth Embodiment] FIG. 18 is a block diagram showing an eighth embodiment of the laser ultrasonic apparatus according to the present invention.

As shown in FIG. 18, in the present embodiment, the operation of the laser ultrasonic apparatus is not controlled by the wavelength-variable laser light source 45 whose oscillation wavelength is controlled by the control means 46 but by the control means 46.
The wavelength of the oscillation light ML of the laser light source 5 may be controlled by an optical frequency shifter (variable frequency shifter) 48 driven by an oscillator 47. Here, the oscillation frequency of the oscillator 47 is controlled by the control unit 49 so as to cancel the level change of the output signal of the photodetector 20 that monitors the transmitted light level of the reference light RL.

As described above, according to the present embodiment, the laser light source 5 is controlled so that the output signal level of the photodetector 20 becomes constant.
By arranging the optical frequency shifter 48 for shifting the frequency on the optical path of the oscillating light, the same effect as in the fourth embodiment can be obtained.

[Modification of Eighth Embodiment] FIG. 19 is a block diagram showing a modification of the eighth embodiment of the laser ultrasonic apparatus according to the present invention.

This modification is different from the eighth embodiment in FIG.
In this modification, the control means 4 controls the wavelength control so that the wavelength control does not follow a high-speed signal level change due to the reception of the ultrasonic signal.
The time constant of 6 needs to be set sufficiently slower than the frequency and duration of the ultrasonic signal.

[Ninth Embodiment] FIG. 20 is a block diagram showing a ninth embodiment of the laser ultrasonic apparatus according to the present invention.

As shown in FIG. 20, in this embodiment, the ultrasonic wave excited by the laser beam EL is applied to the laser beam RL.
Fabry-Perot resonator 10 controlled stably by using
The measurement light P, which is the reflected light from the measurement point on the material 4 to be inspected,
The operation of measuring by making L incident is the same as in the first embodiment.

In the present embodiment, the resonator length of the Fabry-Perot resonator 10 is forcibly set to a distance of at least one wavelength of the laser beam ML by the driving means 16 attached to one of the mirrors 10b using the signal oscillator 50. In this case, the ultrasonic signal is measured at the timing of the maximum sensitivity at which the vibration is always passed.

By the way, as shown in FIG. 37, in the ordinary laser ultrasonic device, a change in the resonator length r due to a mechanical vibration or a change in ambient temperature is measured by the mirrors 10a and 10b constituting the Fabry-Perot resonator 10. A driving unit 16 such as a piezo element is installed on one side (10b in the figure), and the mirror 10b is finely moved by this driving unit 16 in parallel with the optical axis by a distance to offset the change, so that the resonator length r is constant. It is adjusted so that However, this control is a control having a length sufficiently shorter than the wavelength of the measurement light PL, and the control is not stabilized depending on a disturbance situation, and once it deviates from the operating point, it may automatically return. There are problems such as difficulties.

Therefore, in the laser ultrasonic apparatus of the present embodiment, the cavity length r is forcibly scanned by using a piezo element.
By performing oscillation of the pulse laser light for ultrasonic transmission and detection of the ultrasonic signal in the maximum sensitivity region that always passes along with this scanning, without fine control of the resonator length,
This makes it possible to perform measurement.

Next, the operation of the laser ultrasonic apparatus according to the present embodiment will be described with reference to FIG.

First, from the signal oscillator 50, FIG.
A signal V having a sinusoidal shape as shown in FIG. _oscOscillated
To drive the driving mechanism 16 such as a piezo element.
Let it. At this time, the period of the signal is the maximum of the pulse laser light source 1.
Large repetition period and duration of ultrasonic phenomenon to be observed
It is necessary to set it sufficiently longer than this.

The amplitude of the driving mechanism 16 is controlled by the mirror 1.
0b should be a voltage necessary for operating along the optical axis over a distance corresponding to one wavelength of the laser beam ML. Here, for simplicity, the operating range of the drive mechanism 16 is one wavelength or more and two
Consider the case of less than the wavelength. At this time, if the response time of the driving mechanism 16 is sufficiently earlier than the cycle of V _osc , the interval r between the resonators changes following V _osc as shown in FIG. At this time, as apparent from the description of FIG. 35, if there is no ultrasonic signal, the output signal i
_none indicates that the resonator length r is nλ as shown in FIG.
The curve has a peak at the following time, and repeats it according to the operation of the resonator.

Therefore, the ultrasonic signal U _sig is previously set in the resonator.
At which measurement can be performed, that is, τ _{M in the} figure.
If a oscillating voltage value within the range of (1) is obtained and a trigger signal Trg for oscillating the pulse laser light source 1 is supplied from the signal oscillator 50 to the laser light source 1 immediately before reaching the voltage value, the resonator always emits ultrasonic waves. An ultrasonic signal can be measured at a timing at which the signal U _sig can be measured.

In this case, the output signal I of the photodetector 12
_sig is a waveform as ultrasonic signals U _sig to a direct current component due to the scanning of the cavity length is superimposed as shown in FIG. 21 (E), is sufficiently slow as compared with the observation time period of V _osc, the The DC component can be almost neglected. If the DC component cannot be neglected, a normal signal can be obtained by passing the DC component through an appropriate high-pass filter.

As described above, according to the present embodiment, the laser light source 1 is a pulse oscillation light source, and the signal oscillator 50 for oscillating a periodic signal, and the laser light source according to the output signal of the signal oscillator 50 5, the mirror 10b of the Fabry-Perot resonator 10 is operated linearly in parallel with the optical axis for at least one wavelength, and the laser light source 1 is oscillated in synchronization with the output signal of the signal oscillator 50. Thereby, the control of the Fabry-Perot resonator 10 is not required, and the device can be used in a continuous vibration environment or an environment having a temperature change.

[Tenth Embodiment] FIG. 22 is a block diagram showing a tenth embodiment of the laser ultrasonic apparatus according to the present invention.

In the ninth embodiment, when the disturbance is extremely severe, the operation of the output value V _osc of the signal oscillator and the operation of the resonator length r may not be uniquely determined.

Therefore, in the laser ultrasonic device of the present embodiment, as shown in FIG. 22, the basic configuration of the laser ultrasonic device is the same as the configuration using the reference light RL shown in FIG.
The forcible scanning of the resonator length by the driving mechanism 16 driven by the signal oscillator 51 is the same as that of the ninth embodiment. In this way, the photodetector 20 can always detect the signal i _ref as shown in FIG.

[0157] Therefore, instead of the appropriate level of the signal V _osc of the signal oscillator 51, and set the trigger level to a suitable value of the signal i _{re f,} the laser light source 1 and the signal at the signal oscillator 52 as an oscillation control means be supplied, it is possible to measure an ultrasonic signal in a more reliable timing resonator is ready measure an ultrasonic signal U _{si g.}

In this case, in the configuration of the ninth embodiment,
Also it is possible to set the measurement time tau _M optimal timing of the down slope of hard signal V _osc to set measurement timing, it is also possible to increase the frequency of detection of ultrasound. In this case, the output signal i of the photodetector 12
_sig is a waveform as ultrasonic signal U _sig is superimposed on the low frequency components by scanning the resonator length as shown in FIG. 23 (E), the period of the signal V _{o sc} is sufficiently slow as compared with the observation time For example, the component can be almost ignored, and if it cannot be ignored, a normal signal can be obtained by passing the component through an appropriate high-pass filter in the signal processing device 13. Furthermore, by electrically dividing the signals i _sig appropriate gain signal was amplified, attenuated i _ref, not only this effect, it is possible to cancel the influence of such as the output fluctuation of the example source.

As described above, according to this embodiment, the driving mechanism 16 driven by the signal oscillator 51 forcibly scans the resonator length, and sets the trigger level to an appropriate value of the output signal i _ref of the photodetector 20. And sets the signal to the signal oscillator 52
By supplying the laser light to the laser light source 1, the same effect as in the ninth embodiment can be obtained.

[Eleventh Embodiment] FIG. 24 is a block diagram showing an eleventh embodiment of the laser ultrasonic apparatus according to the present invention.

The laser ultrasonic device of the eleventh embodiment is for performing a measurement with higher sensitivity based on the device configuration of the tenth embodiment, and the basic configuration is the same as that of the reference light shown in FIG. The configuration is the same as that using the RL,
The driving mechanism 16 driven by the signal oscillator 51 forcibly scans the resonator length, sets a trigger level to an appropriate value of the output signal i _ref of the photodetector 20, and outputs the signal to the laser light source 1 by the signal oscillator 53. The configuration that enables the resonator to measure the ultrasonic signal at a timing at which the resonator can measure the ultrasonic signal U _sig more reliably is the same as the device of the tenth embodiment. is there.

In this embodiment, the laser light source 54 oscillates.
The divided laser light ML is divided into a reference light RL and a measurement light PL.
After branching, the light enters the optical amplifier 55, and the light amount I of the measurement light PL
_MIs the measurement time τ_MOnly to increase the output. here
The operation timing of the optical amplifier 55 as shown in FIG.
Output signal i_refOr the oscillation tie of the laser light source 1
Synchronization with an appropriate delay from
The ultrasonic signal U _sigCan be measured
Ultrasonic signal is measured with a large amount of light at timing
can do. Also in this case, the output signal of the photodetector 12
i_sigIs used to scan the length of the resonator as shown in FIG.
The ultrasonic signal U_sigAs superimposed
Signal V_oscPeriod is longer than the observation time
If it is slow enough, its components can be almost ignored,
If it cannot be seen, an appropriate high-pass
Normal signal can be obtained by passing through the filter
You. Further, the output signal i_sigWith appropriate gain
Attenuated output signal i_refElectrically dividing by
In addition to this effect, for example, the output fluctuation of the light source
The effects can also be offset.

In the present embodiment, the optical amplifier 55
If the optical element 56 for harmonic generation is inserted in the subsequent stage, the wavelength of the reference light RL for controlling the resonator length of the Fabry-Perot resonator 10, for example, the fundamental wavelength of a YAG laser of 1,064 nm, The wavelength of the measuring light PL, for example, YAG
It is possible to stably control while setting the second harmonic wavelength 532 nm of the laser to another wavelength, and to prevent the leaked transmitted light from being mixed into the photodetector 12 when the reference light RL is reflected by the polarization beam splitter 19. Can be prevented by a wavelength filter (not shown).

As described above, according to the present embodiment, when one appropriate signal level of the photodetector 12 that has detected the intensity of the output light is in a predetermined state, the laser light source 1 is oscillated, and By operating the optical amplifier 55 with a predetermined time delay from the time at which the oscillation occurs, the same effect as in the ninth embodiment can be obtained.

[Twelfth Embodiment] FIG. 26 is a block diagram showing a twelfth embodiment of the laser ultrasonic apparatus according to the present invention.

The twelfth embodiment is for performing higher-sensitivity measurement based on the device configuration of the tenth embodiment, and a signal serving as a sensitivity adjusting means is adjusted in accordance with the oscillation timing of the laser light source 1. are those by the oscillator 52 to adjust the control to the sensitivity to show the reverse bias voltage V _B in FIG. 27 (F) to be applied to the photodetector 12, as described in the first embodiment, in this manner, The ultrasonic signal can be measured in the maximum sensitivity state of the photodetector 12 at the timing when the resonator can always measure the ultrasonic signal U _sig .

Also in this case, the output signal i of the photodetector 12
_{The sig} has a waveform as shown in FIG. 27 (E) in which the ultrasonic signal U _sig is superimposed on the low frequency component due to the scanning of the resonator length, but if the cycle of the signal V _osc is sufficiently slower than the observation time The component can be almost ignored, and if it cannot be ignored, a normal signal can be obtained by passing the component through an appropriate high-pass filter in the signal processing device 13.

Further, _isig is amplified with an appropriate gain.
By electrically dividing by the attenuated i _ref , it is possible to cancel not only this effect but also the effect such as the output fluctuation of the light source. As described above, according to the present embodiment, the same effects as in the ninth embodiment can be obtained.

[Thirteenth Embodiment] FIG. 28 is a block diagram showing a thirteenth embodiment of the laser ultrasonic apparatus according to the present invention.

As shown in FIG. 28, in this embodiment, the ultrasonic wave excited by the laser beam EL is applied to the laser beam RL.
Fabry-Perot resonator 10 controlled stably by using
The measurement light P, which is the reflected light from the measurement point on the material 4 to be inspected,
The operation of measuring by making L incident is the same as in the first embodiment.

In the present embodiment, the Fabry-Perot resonator 1 is used.
Instead of controlling the resonator length of 0, the oscillation wavelength from the tunable laser light source 57 is swept, and the ultrasonic signal is measured at the timing of the maximum sensitivity that always passes.

By the way, as shown in FIG. 37, in the ordinary laser ultrasonic device, the change of the resonator length r due to the mechanical vibration and the change of the surrounding temperature is measured by the mirrors 10a and 10b constituting the Fabry-Perot resonator 10. A driving unit 16 such as a piezo element is installed on one side (10b in the figure), and the mirror 10b is finely moved by this driving unit 16 in parallel with the optical axis by a distance to offset the change, so that the resonator length r is constant. It is adjusted so that However, this control is a control having a length sufficiently shorter than the wavelength of the measurement light PL, and the control is not stabilized depending on a disturbance situation, and once it deviates from the operating point, it may automatically return. There are problems such as difficulties.

Therefore, in the laser ultrasonic apparatus of this embodiment, the resonator length r is fixed, the oscillation wavelength of the wavelength-variable laser light source 57 is swept over time, and the maximum sensitivity that always passes through the sweeping. By performing the oscillation of the pulse laser light for transmitting the ultrasonic wave from the signal oscillator 53 as the oscillation control means and the detection of the ultrasonic signal in the region, the measurement can be performed without performing the delicate control of the resonator length. Is what makes it possible.

Next, the operation of the laser ultrasonic apparatus according to the present embodiment will be described with reference to FIG.

First, the oscillation wavelength λ of the tunable laser light source 57 is swept in a sine wave shape as shown in FIG.
At this time, the sweep cycle needs to be set sufficiently longer than the maximum repetition cycle of the pulse laser light source 1 and the duration of the ultrasonic phenomenon to be observed. Since the wavelength sweep and the scanning of the resonator length have relatively the same effect, the same effect as that described with reference to FIG. 23 appears in the output signal i _ref of the photodetector 20.

[0176] Therefore, oscillating the laser light source 1 a trigger level set to the appropriate level of the output signal i _ref, by looking at the output signal i _sig photodetector 12, it is always matching the measurement wavelength and the resonator In this state, the ultrasonic signal U _sig can be observed.

In this case, the output signal i of the photodetector 12
_{The sig} has a waveform in which the ultrasonic signal U _sig is superimposed on a low frequency component due to the sweep of the oscillation wavelength as shown in FIG. 29 (E). If the sweep cycle of λ is sufficiently slower than the observation time, the waveform becomes larger. The components can be almost neglected, and if they cannot be neglected, a normal signal can be obtained by passing the signal through an appropriate high-pass filter in the signal processing device 13. Furthermore, by electrically dividing the signals i _sig appropriate gain signal was amplified, attenuated i _ref, can this effect as well, for example, the influence of the output fluctuation of the light source is also canceled.

As described above, according to the present embodiment, the resonator length r is fixed, the oscillation wavelength of the wavelength-variable laser light source 57 is swept temporally, and in the maximum sensitivity region that always passes along with the sweep. By oscillating the pulse laser beam for ultrasonic transmission and detecting the ultrasonic signal, the same effect as in the ninth embodiment can be obtained.

[Fourteenth Embodiment] FIG. 30 is a block diagram showing a fourteenth embodiment of the laser ultrasonic apparatus according to the present invention.

As shown in FIG. 30, in the present embodiment, the ultrasonic wave excited by the laser beam EL, the measuring light PL which is the reflected light from the measuring point on the material 4 to be inspected is scanned by the resonator length. The operation of making the light incident on the Fabry-Perot resonator 10 and measuring at a timing at which high detection sensitivity is obtained is the same as that of the laser ultrasonic apparatus according to the ninth to twelfth embodiments.

In the present embodiment, the control of the Fabry-Perot resonator 10 is not performed by scanning the length of the resonator, but the two mirrors 10a,
This is performed by rotating a laser beam transmitting member 58 of a regular 2n polygonal shape (where n is an integer of 2 or more) inserted between 10b by a rotation driving mechanism 59. Since the regular 2n polygonal shape of the laser beam transmitting member 58 always has parallel opposing surfaces, the laser beam transmitting member 58 is rotated by the rotation drive mechanism 59 to rotate the laser beam transmitting member 58 between the optical axis and the surface according to the same principle as that described in FIG. If the angle is changed, the same effect as scanning the length of the resonator can be obtained.

In the present embodiment, the same effect can be obtained by the rotation operation as compared with the case where a relatively heavy mirror is linearly vibrated by the driving mechanism 16 such as a piezo element. It is effective for such as.

As described above, according to the present embodiment, the Fabry-Perot resonator 10 is controlled by rotating the laser beam transmitting member 58 by the rotation driving mechanism 59 to change the angle between the optical axis and the surface. , The resonator length can be scanned at high speed.

[Fifteenth Embodiment] FIG. 31 is a block diagram showing a fifteenth embodiment of the laser ultrasonic apparatus according to the present invention.

As shown in FIG. 31, in the present embodiment, the resonator excited by the laser beam EL is used to scan the ultrasonic wave excited by the laser beam EL and the measurement light PL which is the reflected light from the measurement point on the test object 4. The operation of making the light incident on the Fabry-Perot resonator 10 and measuring at a timing at which high detection sensitivity is obtained is the same as that of the laser ultrasonic apparatus according to the ninth to twelfth embodiments.

In this embodiment, the signal monitoring means 60 for extracting the characteristic amount of the output signal i _ref of the photodetector 20 observed with the scanning of the resonator length, and the signal monitoring means 60 extracts the characteristic quantity. And a display means 62 for displaying the result of the comparison means 61. The Fabry-Perot resonator 10 is provided according to the state of the display means 62. Alternatively, the soundness of the entire device is detected.

Next, the operation of the laser ultrasonic apparatus according to the present embodiment will be described with reference to FIG.

As described in the operation of the laser ultrasonic apparatus according to the ninth to twelfth embodiments, for example, the mirrors 10a and 10b of the Fabry-Perot resonator 10 are scanned as shown in FIG. Then, the output signal level of the photodetector 20 changes as shown in FIG.

However, for example, when the reflectance of the material to be inspected 4 is extremely low, or when some optical elements on the laser ultrasonic device are displaced, adhere with dust, or are damaged, the light detector The output signal level of No. 20 is as shown in FIG.

Therefore, in a sound state, the characteristic amount of the output signal required for measurement, in this case, the peak height i _peak is set, and if the peak height does not reach it, an LED lamp or the like is used. If the display means 62 is turned on, it becomes possible to know whether or not the laser ultrasonic device or the measurement conditions are sufficient for the measurement during the measurement.

[0191] Another unsoundness of the laser ultrasonic device or the measurement conditions includes the Fabry-Perot resonator 10
Misalignment. This is mirror 10a and 10
b is not facing normally or the mirror 10
This is the case where the interval between a and 10b does not coincide with their focal lengths. In this case, the output signal of the photodetector 20 has a peak height as shown in FIG. In addition to the decrease, the waveform may be asymmetric as shown in FIG.

In order to detect such a phenomenon, as other characteristic amounts, for example, a waveform distortion amount, a frequency, a time interval crossing a trigger level, a rise / fall time deviation, an integral value of the entire waveform, and the like. What is necessary is just to select suitably.

As described above, according to the present embodiment, the output signal i of the photodetector 20 observed with the scanning of the resonator length is obtained.
The characteristic amount of _ref is extracted by the signal monitoring unit 60, the extracted characteristic amount is compared with a preset reference value by the comparing unit 61, and the comparison result is displayed on the display unit 62. , The integrity of the Fabry-Perot resonator 10 or the entire device.

[Sixteenth Embodiment] FIG. 33 is a block diagram showing a sixteenth embodiment of the laser ultrasonic apparatus according to the present invention.

As shown in FIG. 33, in the present embodiment, the ultrasonic wave excited by the laser beam EL is used to scan the measuring light PL, which is the reflected light from the measuring point on the material 4 to be inspected, and the resonator length is scanned. The operation of making the light incident on the Fabry-Perot resonator 10 and measuring at a timing at which high detection sensitivity is obtained is the same as that of the laser ultrasonic apparatus according to the ninth to twelfth embodiments.

In this embodiment, the signal monitoring means 60 for extracting the characteristic amount of the output signal i _ref of the photodetector 20 observed with the scanning of the resonator length, and the Fabry-Perot resonator 10 are constituted. Adjusting mechanism 63 for adjusting the two-dimensional inclination of the mirror (in this case, 10a)
And an adjustment control unit 64 for inputting a drive signal to the adjustment mechanism 63 so as to compare the feature value extracted at 0 with a preset reference value and correct the deviation. When the soundness of the Fabry-Perot resonator 10 deteriorates, the coarse adjustment is automatically performed.

Next, the operation of the laser ultrasonic apparatus according to the present embodiment will be described.

As described in the operation of the laser ultrasonic apparatus of the fifteenth embodiment, when the state of the Fabry-Perot resonator 10 is deteriorated, the output signal i _ref of the photodetector 20 has a reduced peak height or a reduced waveform. There is a tendency such as distortion. For example, in the case of minute mechanical vibration or thermal distortion, this is automatically compensated by the drive mechanism 16, but a large displacement such as deviating from the operation range of the drive means 16 occurs, or When a positional deviation in the torsional direction occurs, it is impossible to compensate for it by the driving means 16.

Therefore, in the present embodiment, the adjustment control means 64 compares the characteristic amount of the output signal i _ref of the photodetector 20 with its normal value, and uses a suitable control algorithm to eliminate the deviation. By operating the adjusting mechanism 63 installed on the mirror 10a where the mirror 16 is not installed,
It is possible to compensate for a large misalignment that has occurred unexpectedly.

In the present embodiment, the output signal i _ref
The mirror position of the Fabry-Perot resonator 10 or other optical elements may be appropriately adjusted manually based on the result of the comparison between the characteristic amount and the normal value thereof by the adjustment control means 42.

[0201]

As described above, according to the laser ultrasonic apparatus of the present invention, the sensitivity of the light detecting means is determined with a predetermined time delay and a predetermined time width with reference to the modulation timing of the first laser light source. By providing sensitivity adjustment means for adjusting the sensitivity, a weak light intensity signal can be detected with high sensitivity, and a minute frequency shift contained therein can be observed with a magnitude equal to or higher than the noise level. A laser ultrasonic device can be provided.

Further, for example, it is possible to provide a laser ultrasonic apparatus capable of following and controlling a high-speed peripheral disturbance. Further, it is possible to provide a laser ultrasonic apparatus which can be used in, for example, a continuous vibration environment or an environment having a temperature change and does not require resonator control. Then, for example, when the device is installed at an inspection / measurement site, it is possible to provide a laser ultrasonic device capable of immediately adjusting the resonator and confirming the soundness of the state during operation. Thus, for example, a laser ultrasonic apparatus that can be used for inspection of structural materials and equipment of a plant during operation can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a laser ultrasonic apparatus according to the present invention.

FIG. 2 is a circuit diagram showing a photodetector used in the laser ultrasonic device of FIG.

FIG. 3 is a timing chart showing the operation of the laser ultrasonic device according to the first embodiment.

FIG. 4 is a timing chart showing another operation of the laser ultrasonic apparatus according to the first embodiment.

FIG. 5 is a block diagram showing a modified example of the first embodiment of the laser ultrasonic apparatus according to the present invention.

FIG. 6 is a block diagram showing a second embodiment of the laser ultrasonic apparatus according to the present invention.

FIG. 7 is a characteristic diagram of a photodetector.

FIG. 8 is a block diagram showing a modified example of the second embodiment of the laser ultrasonic apparatus according to the present invention.

FIG. 9 is a block diagram showing a third embodiment of the laser ultrasonic apparatus according to the present invention.

FIG. 10 is an explanatory diagram showing the operation of the laser ultrasonic device according to the third embodiment.

FIG. 11 is a block diagram showing a fourth embodiment of the laser ultrasonic apparatus according to the present invention.

FIGS. 12A and 12B are explanatory diagrams illustrating an optical path length difference due to a rotation operation of a transmission plate according to a fourth embodiment.

FIG. 13 is a block diagram showing a modified example of the fourth embodiment of the laser ultrasonic apparatus according to the present invention.

FIG. 14 is a block diagram showing a fifth embodiment of the laser ultrasonic apparatus according to the present invention.

FIG. 15 is a block diagram showing a sixth embodiment of the laser ultrasonic apparatus according to the present invention.

FIG. 16 is a block diagram showing a seventh embodiment of the laser ultrasonic apparatus according to the present invention.

FIG. 17 is a block diagram showing a modified example of the seventh embodiment of the laser ultrasonic apparatus according to the present invention.

FIG. 18 is a block diagram showing an eighth embodiment of the laser ultrasonic apparatus according to the present invention.

FIG. 19 is a block diagram showing a modified example of the eighth embodiment of the laser ultrasonic apparatus according to the present invention.

FIG. 20 is a block diagram showing a ninth embodiment of the laser ultrasonic apparatus according to the present invention.

FIG. 21 is a timing chart showing the operation of the laser ultrasonic device according to the ninth embodiment.

FIG. 22 is a block diagram showing a tenth embodiment of the laser ultrasonic apparatus according to the present invention.

FIG. 23 is a timing chart showing the operation of the laser ultrasonic device according to the tenth embodiment.

FIG. 24 is a block diagram showing an eleventh embodiment of the laser ultrasonic apparatus according to the present invention.

FIG. 25 is a timing chart showing the operation of the laser ultrasonic device according to the eleventh embodiment.

FIG. 26 is a block diagram showing a twelfth embodiment of the laser ultrasonic apparatus according to the present invention.

FIG. 27 is a timing chart showing the operation of the laser ultrasonic device according to the twelfth embodiment.

FIG. 28 is a block diagram showing a thirteenth embodiment of the laser ultrasonic apparatus according to the present invention.

FIG. 29 is a timing chart showing the operation of the laser ultrasonic device according to the thirteenth embodiment.

FIG. 30 is a block diagram showing a fourteenth embodiment of the laser ultrasonic apparatus according to the present invention.

FIG. 31 is a block diagram showing a fifteenth embodiment of the laser ultrasonic apparatus according to the present invention.

FIG. 32 is a timing chart showing the operation of the laser ultrasonic apparatus according to the fifteenth embodiment.

FIG. 33 is a block diagram showing a sixteenth embodiment of the laser ultrasonic apparatus according to the present invention.

FIG. 34 is a block diagram showing a laser ultrasonic apparatus according to a first conventional example.

FIG. 35 is an explanatory view showing the operation of the Fabry-Perot resonator.

FIG. 36 is an explanatory view showing the operation of the Fabry-Perot resonator.

FIG. 37 is a block diagram showing a laser ultrasonic apparatus according to a second conventional example.

FIG. 38 is a block diagram showing a laser ultrasonic apparatus according to a third conventional example.

FIG. 39 is a circuit diagram showing a photodetector used in each conventional laser ultrasonic device.

FIG. 40 is a timing chart showing the operation of a conventional laser ultrasonic device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser light source (1st laser light source) 2a, 2b Mirror 3 Lens 4 Inspection material 5 Laser light source (2nd laser light source) 6a, 6b 1/2 wavelength plate 7 Polarization beam splitter (1st light splitting means) Reference Signs List 8 lens 9 mirror 10 Fabry-Perot resonator 10A Fabry-Perot resonator 10a, 10b mirror 11 lens 12 photodetector (light detection means) 13 signal processing device 14 display device 15 controller (resonator length control means) 16 drive Mechanism 17 Polarization beam splitter 18 Polarization beam splitter 19 Polarization beam splitter (second light branching unit) 20 Photodetector (another photodetection unit) 22 Photodetection element 23 DC power supply 24 Load 26 Switch 31 Sensitivity adjustment unit 37 Light intensity adjustment Means 38 Optical attenuator 39 Oscillator 40 Optical modulator 41 Rotation stage 42 Transmission plate Length adjusting means) 44 Airtight container 45 Laser light source (second laser light source) 46 Control means 47 Oscillator 48 Optical frequency shifter (variable frequency shifter) 49 Control means 50 Signal oscillator 51 Signal oscillator 52 Signal oscillator 53 Signal oscillator 54 Laser light source 55 Optical amplifier 56 optical element 57 laser light source 58 laser beam transmitting member 59 rotation drive mechanism 60 signal monitoring means 61 comparison means 62 display means 63 adjustment means 64 adjustment control means

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shigehiko Mukai 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Inside the Toshiba Yokohama Office (72) Inventor Yuji Sano 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa (72) Inventor Shigeru Kanemoto 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture In-house Toshiba Yokohama Office (72) Inventor Hidetoshi Nakano 1-4-1 Umezono, Tsumeba, Tsukuba-city, Ibaraki Pref. 2G047 BC00 BC07 CA04 GD01 5F072 AA01 AB01 KK06 KK15 KK30 YY20

Claims (16)

[Claims] 1. A first laser light source for emitting a laser beam for excitation modulated to generate an ultrasonic wave on a material to be inspected, and a laser beam for measurement for observing the ultrasonic wave propagated through the material to be inspected A second laser light source that emits light, first optical means for irradiating the excitation laser beam to a predetermined position of the inspection target material under predetermined conditions, and the measurement laser beam A second optical unit for irradiating a predetermined position with predetermined conditions and guiding reflected light from the material to be inspected; and a Fabry-Perot resonance for entering reflected light guided by the second optical unit. Detector, at least one light detecting means for detecting the intensity of the output light of the Fabry-Perot resonator, and a part of the output signal level of the light detecting means or the measuring laser beam to avoid the material to be inspected. did A resonator length control means for controlling the resonance length of the Fabry-Perot resonator from the output signal level of another light detecting means which is incident on the Fabry-Perot resonator by an optical path and detects the intensity of the output light; And a sensitivity adjusting means for adjusting the sensitivity of the light detecting means with a predetermined time delay and a predetermined time width with reference to the modulation timing of the first laser light source. 2. A first laser light source for emitting an excitation laser beam modulated to generate an ultrasonic wave on a material to be inspected, and a measurement laser beam for observing the ultrasonic wave propagated through the material to be inspected. A second laser light source that emits light, first optical means for irradiating the excitation laser beam to a predetermined position of the inspection target material under predetermined conditions, and the measurement laser beam A second optical unit for irradiating a predetermined position with predetermined conditions and guiding reflected light from the material to be inspected; and a Fabry-Perot resonance for entering reflected light guided by the second optical unit. Detector, at least one light detecting means for detecting the intensity of the output light of the Fabry-Perot resonator, and one of the light detecting means.
One output signal level or a part of the measurement laser beam is incident on the Fabry-Perot resonator in an optical path avoiding the test object, and the output signal level of another light detecting means for detecting the intensity of the output light. Resonator length control means for controlling the resonance length of the Fabry-Perot resonator from
The amount of light incident on the Fabry-Perot resonator is adjusted based on the output signal level of the light detection means, and the second
And a light amount adjusting means disposed on an optical path of oscillation light of the laser light source. 3. A first laser light source for emitting an excitation laser beam modulated to generate an ultrasonic wave on a material to be inspected, and a measuring laser beam for observing the ultrasonic wave transmitted through the material to be inspected. A second laser light source that emits light, first optical means for applying the excitation laser beam to a predetermined position of the test object under predetermined conditions, and at least two laser beams for the measurement laser beam. First optical splitting means for splitting the laser beam into a plurality of laser beams, optical modulation means for shifting the optical frequency of at least one laser beam split by the first splitting means by a predetermined amount,
Irradiating the other laser beam branched by the branching means to a predetermined position of the inspection target material under predetermined conditions, guiding reflected light from the inspection target material, and further modulating the laser beam modulated by the light modulation means. A second optical unit for combining the beam with the same optical path, a Fabry-Perot resonator for receiving the light beam combined by the second optical unit,
Second light splitting means for splitting the output light of the Fabry-Perot resonator into reflected light from the material to be inspected and a laser beam modulated by the light modulation means, and separated by the second light splitting means At least two light detecting means for detecting the respective optical signal intensities, and the Fabry / Frequency detection means based on the output signal level of the light detecting means which receives the laser beam modulated by the light modulating means among the light detecting means.
A laser ultrasonic apparatus, comprising: resonator length control means for controlling the resonance length of a Perot resonator. 4. A first laser light source for emitting an excitation laser beam modulated to generate an ultrasonic wave on a material to be inspected, and a measurement laser beam for observing the ultrasonic wave propagated through the material to be inspected. A second laser light source that emits light, first optical means for irradiating the excitation laser beam to a predetermined position of the inspection target material under predetermined conditions, and the measurement laser beam A second optical unit for irradiating a predetermined position with predetermined conditions and guiding reflected light from the material to be inspected; and a Fabry-Perot resonance for entering reflected light guided by the second optical unit. Detector, at least one light detecting means for detecting the intensity of the output light of the Fabry-Perot resonator, and one of the light detecting means.
One output signal level or a part of the measurement laser beam is incident on the Fabry-Perot resonator, and the resonance of the Fabry-Perot resonator is determined based on the output signal level of another light detection unit that detects the intensity of the output light. Resonator length control means for controlling the length, wherein the resonator length control means is inserted between two mirrors of the Fabry-Perot resonator and has a transmission length adjustable. A laser ultrasonic device, which is a transmission member. 5. A first laser light source for emitting an excitation laser beam modulated to generate an ultrasonic wave on a material to be inspected, and a measuring laser beam for observing the ultrasonic wave propagated through the material to be inspected. A second laser light source that emits light, first optical means for irradiating the excitation laser beam to a predetermined position of the inspection target material under predetermined conditions, and the measurement laser beam A second optical unit for irradiating a predetermined position with predetermined conditions and guiding reflected light from the material to be inspected; and a Fabry-Perot resonance for entering reflected light guided by the second optical unit. Detector, at least one light detecting means for detecting the intensity of the output light of the Fabry-Perot resonator, and one of the light detecting means.
One output signal level or a part of the measurement laser beam is incident on the Fabry-Perot resonator in an optical path avoiding the test object, and the output signal level of another light detecting means for detecting the intensity of the output light. Resonator length control means for controlling the resonance length of the Fabry-Perot resonator, the resonator control means comprising: a sealing means for spatially sealing the Fabry-Perot resonator; and a sealing means. A laser adjusting device for adjusting the internal pressure of the laser ultrasonic wave. 6. A first laser light source for emitting an excitation laser beam modulated to generate an ultrasonic wave on a material to be inspected, and a measurement laser beam for observing the ultrasonic wave propagated through the material to be inspected. A second laser light source that emits light, first optical means for irradiating the excitation laser beam to a predetermined position of the inspection target material under predetermined conditions, and the measurement laser beam A second optical unit for irradiating a predetermined position with predetermined conditions and guiding reflected light from the material to be inspected; and a Fabry-Perot resonance for entering reflected light guided by the second optical unit. Detector, at least one light detecting means for detecting the intensity of the output light of the Fabry-Perot resonator, and one of the light detecting means.
One output signal level or a part of the measurement laser beam is incident on the Fabry-Perot resonator in an optical path avoiding the test object, and the output signal level of another light detecting means for detecting the intensity of the output light. And a resonator length control means for controlling the resonance length of the Fabry-Perot resonator, wherein the Fabry-Perot resonator is formed into a curved surface having a surface facing the optical axis direction as a focal point, and A laser beam transmitting member having a reflection surface having a predetermined reflectance in an optical path, wherein the resonator length control means controls a driving mechanism for adjusting a tilt of the laser beam transmitting member with respect to an optical axis. Laser ultrasonic device. 7. A first laser light source for emitting an excitation laser beam modulated to generate an ultrasonic wave on a material to be inspected, and a measuring laser beam for observing the ultrasonic wave propagated through the material to be inspected. A second laser light source that emits light, first optical means for irradiating the excitation laser beam to a predetermined position of the inspection target material under predetermined conditions, and the measurement laser beam A second optical unit for irradiating a predetermined position with predetermined conditions and guiding reflected light from the material to be inspected; and a Fabry-Perot resonance for entering reflected light guided by the second optical unit. Detector, at least one light detecting means for detecting the intensity of the output light of the Fabry-Perot resonator, and a part of the output signal level of the light detecting means or the measuring laser beam to avoid the material to be inspected. did A resonator length control means for controlling the resonance length of the Fabry-Perot resonator from the output signal level of another light detecting means which is incident on the Fabry-Perot resonator by an optical path and detects the intensity of the output light; Wherein the second laser light source is a tunable laser light source, and the oscillation wavelength of the tunable laser light source is controlled from an output signal level of one of the photodetectors. 8. A first laser light source for emitting an excitation laser beam modulated to generate an ultrasonic wave on a material to be inspected, and a measurement laser beam for observing the ultrasonic wave propagated through the material to be inspected. A second laser light source that emits light, first optical means for irradiating the excitation laser beam to a predetermined position of the inspection target material under predetermined conditions, and the measurement laser beam A second optical unit for irradiating a predetermined position with predetermined conditions and guiding reflected light from the material to be inspected; and a Fabry-Perot resonance for entering reflected light guided by the second optical unit. Detector, at least one light detecting means for detecting the intensity of the output light of the Fabry-Perot resonator, and a part of the output signal level of the light detecting means or the measuring laser beam to avoid the material to be inspected. did A resonator length control means for controlling the resonance length of the Fabry-Perot resonator from the output signal level of another light detecting means which is incident on the Fabry-Perot resonator by an optical path and detects the intensity of the output light; And a variable frequency shifter for shifting the frequency of the oscillation light of the second laser light source so that the output signal level of one of the light detection means is constant. apparatus. 9. A first laser light source for emitting an excitation laser beam modulated to generate an ultrasonic wave on a material to be inspected, and a measurement laser beam for observing the ultrasonic wave propagated through the material to be inspected. A second laser light source that emits light, first optical means for irradiating the excitation laser beam to a predetermined position of the inspection target material under predetermined conditions, and the measurement laser beam A second optical unit for irradiating a predetermined position with predetermined conditions and guiding reflected light from the material to be inspected; and a Fabry-Perot resonance for entering reflected light guided by the second optical unit. Detector, at least one light detecting means for detecting the intensity of the output light of the Fabry-Perot resonator, a signal oscillating means for oscillating a periodic signal, and an output signal of the signal oscillating means. The second record Driving means for linearly operating at least one mirror of the Fabry-Perot resonator for at least one wavelength of a laser light source in parallel to an optical axis, and providing an output signal of the signal oscillating means. A laser ultrasonic device, wherein the first laser light source oscillates in synchronization. 10. The laser ultrasonic apparatus according to claim 9, wherein an output signal level of said light detecting means or a part of said measuring laser beam is transmitted to said Fabry-Perot resonator through an optical path avoiding said material to be inspected. Incident, and when one signal level of another light detecting means that has detected the intensity of the output light thereof is in a predetermined state, oscillation control means for oscillating the first laser light source is provided. Laser ultrasonic device. 11. The laser ultrasonic apparatus according to claim 9, wherein said first laser light source is a pulse oscillation light source, and is arranged on an optical path of said second laser light source and operates intermittently. Means, a part of the output signal level of the light detection means or a part of the laser beam for measurement is incident on the Fabry-Perot resonator in an optical path avoiding the material to be inspected, and another intensity of the output light is detected. When one signal level of the light detecting means is in a predetermined state, the first
A laser control unit for oscillating the laser light source and operating the optical amplifying unit with a predetermined time delay from the time when the first laser light source oscillates. 12. The laser ultrasonic apparatus according to claim 9, wherein the sensitivity of said light detecting means is adjusted with a predetermined time delay and a predetermined time width with reference to an oscillation time of said first laser light source. A laser ultrasonic device comprising a sensitivity adjusting means. 13. A first laser light source for emitting an excitation laser beam modulated to generate an ultrasonic wave on a material to be inspected, and a measuring laser beam for observing the ultrasonic wave propagated through the material to be inspected. A second laser light source that emits light, first optical means for irradiating the excitation laser beam to a predetermined position of the inspection target material under predetermined conditions, and the measurement laser beam A second optical unit for irradiating a predetermined position with predetermined conditions and guiding reflected light from the material to be inspected; and a Fabry-Perot resonance for entering reflected light guided by the second optical unit. Vessels,
A wavelength tunable laser light source comprising at least one light detecting means for detecting the intensity of the output light of the Fabry-Perot resonator, wherein the second laser light source periodically scans a wavelength within a certain range; A part of the output signal level of the light detection means or the measurement laser beam is incident on the Fabry-Perot resonator in an optical path avoiding the inspection object,
An oscillation control means for oscillating the first laser light source when one signal level of another light detection means which has detected the intensity of the output light is in a predetermined state. Sonic device. 14. The laser ultrasonic apparatus according to claim 9, wherein the driving mechanism operated by the signal oscillating means for oscillating a periodic signal comprises two Fabry-Perot resonators. A regular 2n polygonal shape (where the transmission length can be adjusted by a distance equal to or greater than the oscillation wavelength of the second laser light source)
(n is an integer of 2 or more) a laser beam transmitting member. 15. The laser ultrasonic apparatus according to claim 9, wherein a signal monitoring unit for extracting a characteristic amount of one output signal of the light detection unit, and the signal monitoring unit extracts the characteristic amount of the output signal. A laser ultrasonic apparatus, comprising: comparison means for comparing a characteristic amount with a preset reference value; and display means for displaying a result of the comparison means. 16. The laser ultrasonic apparatus according to claim 9, wherein a signal monitoring means for extracting a characteristic amount of one output signal of said light detecting means, and a length of said Fabry-Perot resonator. And an adjustment mechanism for adjusting the two-dimensional inclination of the mirror, and an adjustment mechanism for driving the adjustment mechanism so that the characteristic amount extracted by the signal monitoring means becomes a preset reference value. A laser ultrasonic device comprising a control unit.