CN111983032B - Online monitoring method and system for damage of optical element - Google Patents
Online monitoring method and system for damage of optical element Download PDFInfo
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- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
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- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/1702—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/1702—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids
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Abstract
The invention discloses an on-line monitoring method and system for damage of an optical element, wherein the method comprises the following steps: collecting ultrasonic signals generated when the preset position of the surface of the optical element is irradiated; converting the ultrasonic signal into a digital signal; and calculating the damage position according to the digital signal, the propagation speed of the ultrasonic signal in the optical element, the damage diameter, the preset position of the surface of the optical element and the emergent position of the ultrasonic signal. By implementing the invention, the real-time on-line monitoring of the damage condition of the optical element by the laser under the normal working condition is realized by adopting the photo-induced sound field effect; meanwhile, the damage position and the size of the optical element can be calculated by acquiring the propagation parameters of the ultrasonic signals, so that the damage condition of the optical element can be known in detail. Therefore, the lens position can be moved in time under the normal working condition of the laser, the damage area is avoided, and the service life of the laser is prolonged.
Description
Technical Field
The invention relates to the technical field of laser damage testing, in particular to an on-line monitoring method and system for damage of an optical element.
Background
High power laser drivers are required to operate stably over a long period of time or the performance of the system is not significantly degraded. However, the optical element in the system is easily damaged after being irradiated by high-power laser. The damage can continue to develop under the action of the subsequent laser pulse, the beam output quality of the high-power laser driver is affected, meanwhile, the modulated laser pulse can cause the damage of the subsequent optical element, and the whole system is paralyzed when serious. The laser damage resistance of the optical element directly affects the design of the whole system and the performance of the system operation, so the problem of laser damage of the optical element is always a bottleneck for the laser to develop towards the high energy and high power direction, and is one of the decisive factors affecting the service life of the whole laser driver system. Therefore, studies on the damage characteristics of optical elements have been a subject of public health for the development of high-power laser systems.
Most of the existing detection methods detect the intrinsic defects of the optical elements in the selection stage, and cannot monitor the conditions of the optical elements on line in the working process of a laser, so that the method is not beneficial to the practical use of a large-scale precise optical system.
Disclosure of Invention
In view of the above, the embodiments of the present invention provide an on-line monitoring method and system for damage of an optical element, so as to solve the technical problem that the damage of the optical element in a laser system cannot be timely monitored on line in the prior art.
The technical scheme provided by the invention is as follows:
an embodiment of the present invention provides an on-line monitoring method for damage to an optical element, where the monitoring method includes: collecting ultrasonic signals generated when the preset position of the surface of the optical element is irradiated; converting the ultrasonic signal into a digital signal; and calculating the damage position according to the digital signal, the propagation speed of the ultrasonic signal in the optical element, the damage diameter, the preset position of the surface of the optical element and the emergent position of the ultrasonic signal.
Further, the method for on-line monitoring of damage to the optical element further comprises: changing the irradiated position of the surface of the optical element, and repeating the on-line monitoring method for the damage of the optical element according to the first aspect of the embodiment of the invention to calculate the damage position.
Further, calculating the damage position according to the propagation speed of the digital signal and the ultrasonic signal in the optical element, the damage diameter, the preset position of the surface of the optical element and the emergent position of the ultrasonic signal, including: determining the propagation time length along the upper boundary of the damage and the propagation time length along the lower boundary of the damage according to the digital signal; calculating the distance between the upper boundary of the damage and the preset position on the surface of the optical element according to the propagation speed of the ultrasonic signal in the optical element and the propagation time length along the upper boundary of the damage; calculating the vertical distance between the upper damage boundary and the surface of the optical element according to the distance between the upper damage boundary and the preset position of the surface of the optical element, the preset position of the surface of the optical element and the emergent position of the ultrasonic signal; calculating the damage diameter according to the vertical distance between the upper damage boundary and the surface of the optical element, the propagation speed of the ultrasonic signal in the optical element, the propagation time length along the lower damage boundary, the preset position of the surface of the optical element and the emergent position of the ultrasonic signal; and calculating the damage position according to the distance between the damage upper boundary and the preset position of the surface of the optical element, the damage diameter, the preset position of the surface of the optical element and the emergent position of the ultrasonic signal.
Further, when the irradiated position of the optical element surface is changed, the horizontal distance between the irradiated position of the optical element surface and the exit position of the ultrasonic signal is unchanged.
A second aspect of an embodiment of the present invention provides an on-line monitoring system for damage to an optical element, the system including: the laser ultrasonic excitation unit comprises a light source, wherein light emitted by the light source is incident to a preset position on the surface of the optical element to generate an ultrasonic signal; the laser ultrasonic detection unit receives the ultrasonic signal, converts the ultrasonic signal into an electric signal and outputs the electric signal to the ultrasonic data processing unit; the ultrasonic data processing unit comprises a signal conversion module and a position calculation module, wherein the signal conversion module converts the electric signal into a digital signal and analyzes and processes the digital signal; the position calculation module calculates the damage position according to the processed digital signal, the propagation speed of the ultrasonic signal in the optical element, the damage diameter, the preset position of the surface of the optical element and the emergent position of the ultrasonic signal.
Further, the position calculation module includes: the time length determining module is used for determining the propagation time length along the upper boundary of the damage and the propagation time length along the lower boundary of the damage according to the processed digital signals; the first distance calculation module is used for calculating the distance between the upper boundary of the damage and the preset position of the surface of the optical element according to the propagation speed of the ultrasonic signal in the optical element and the propagation time length along the upper boundary of the damage; the second distance calculation module is used for calculating the vertical distance between the upper damage boundary and the surface of the optical element according to the distance between the upper damage boundary and the preset position of the surface of the optical element, the preset position of the surface of the optical element and the emergent position of the ultrasonic signal; the damage diameter calculation module is used for calculating the damage diameter according to the vertical distance between the upper damage boundary and the surface of the optical element, the propagation speed of the ultrasonic signal in the optical element, the propagation time length along the lower damage boundary, the preset position of the surface of the optical element and the emergent position of the ultrasonic signal; the position calculation sub-module is used for calculating the damage position according to the distance between the damage upper boundary and the preset position of the surface of the optical element, the damage diameter, the preset position of the surface of the optical element and the emergent position of the ultrasonic signal.
Further, the laser ultrasonic excitation unit further includes: and the galvanometer scanning module is controlled to scan along the surface of the optical element after receiving the electric signal of the preset position of the surface of the optical element by the ultrasonic data processing unit, so as to change the irradiated position of the surface of the optical element.
Further, the laser ultrasonic detection unit includes: the detection probe is arranged on the same side of the light incidence surface of the optical element and is used for acquiring the generated ultrasonic signals; the signal amplification module is used for amplifying the ultrasonic signal and outputting the amplified ultrasonic signal to the ultrasonic data processing unit.
Further, when the irradiation position of the surface of the optical element changes, the ultrasonic data processing unit controls the detection probe to move, and the horizontal distance between the detection probe and the irradiation position of the surface of the optical element is kept unchanged.
Further, the signal amplifying module comprises a three-stage amplifying circuit, the front-stage amplifying circuit comprises a dual-operational-amplifier front-stage amplifier, the middle-stage amplifying circuit comprises a common-mode sampling driving circuit and a capacitance-resistance coupling circuit, and the rear-stage amplifying circuit comprises a phase-locked amplifier.
The technical scheme of the invention has the following advantages:
the on-line monitoring method and the on-line monitoring system for the damage of the optical element provided by the embodiment of the invention judge the damage condition of the optical element by using the photoinduced sound field effect through the ultrasonic signal generated by the irradiation of the optical element by the light source, thereby realizing the real-time on-line monitoring of the damage condition of the optical element under the normal working condition of the laser; meanwhile, the damage position and the size of the optical element can be calculated by acquiring the propagation parameters of the ultrasonic signals, so that the damage condition of the optical element can be known in detail. Therefore, the lens position can be moved in time under the normal working condition of the laser, the damage area is avoided, and the service life of the laser is prolonged. In addition, the online monitoring method not only can detect damage conditions of the subsurface of the surface of the optical element, but also can detect internal damage which is in the order of cm away from the surface of the optical element.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a block diagram of an on-line monitoring system for optical component damage in an embodiment of the invention;
FIG. 2 is a schematic diagram illustrating damage to an optical element according to an embodiment of the invention;
FIG. 3 is a flow chart of an on-line monitoring system for damage to an optical element according to an embodiment of the present invention;
FIG. 4 is a block diagram of an on-line monitoring system for damage to optical elements according to another embodiment of the invention
Fig. 5 is a flowchart of an on-line monitoring method for damage to an optical element according to an embodiment of the invention.
Detailed Description
The following description of the embodiments of the present invention will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; the two components can be directly connected or indirectly connected through an intermediate medium, or can be communicated inside the two components, or can be connected wirelessly or in a wired way. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
An embodiment of the present invention provides an on-line monitoring system for damage to an optical element, as shown in fig. 1, the system includes: the laser ultrasonic excitation unit 10, the laser ultrasonic detection unit 20 and the ultrasonic data processing unit 30, wherein the laser ultrasonic excitation unit 10 comprises a light source, and light emitted by the light source is incident on a preset position on the surface of the optical element to generate an ultrasonic signal; the laser ultrasonic detection unit 20 receives the ultrasonic signal, converts the ultrasonic signal into an electric signal, and outputs the electric signal to the ultrasonic data processing unit 30; the ultrasonic data processing unit 30 comprises a signal conversion module and a position calculation module, wherein the signal conversion module converts an electric signal into a digital signal and analyzes and processes the digital signal; the position calculation module calculates the damage position according to the processed digital signal, the propagation speed of the ultrasonic signal in the optical element, the damage diameter, the preset position of the surface of the optical element and the emergent position of the ultrasonic signal.
In one embodiment, the light source may be a pulsed infrared laser that emits pulsed laser light that is incident on the optical element to generate ultrasound. When the optical element is irradiated with a laser, the acoustic wave can be radiated because its absorption of light changes its internal temperature, causing a volume expansion and contraction thereof. Specifically, parameters such as laser light wave wavelength, pulse energy, pulse width, laser spot diameter, pulse repetition frequency and the like influence the excitation efficiency of laser ultrasound, and can be selected according to imaging depth and imaging resolution requirements. In the practice of the present invention, to achieve an imaging depth of 1cm and an imaging resolution of 10 μm, yttrium aluminum garnet crystal ND: YAG pulse infrared laser, laser wave length is 1064, laser single pulse energy maximum is 20mJ (continuously adjustable), and repetition frequency is 1kHz. The optical element to be inspected may be an element commonly used in laser systems, such as a lens or the like.
In one embodiment, when the optical element is damaged, the damage shape is considered to be spherical in ideal condition, as shown in FIG. 2, the damage diameter of the optical element is represented by phi, and the transmission speed of ultrasonic waves in the optical element is C b The laser ultrasonic detection unit is provided with a detection probe for receiving ultrasonic signals, the distance between the detection probe and the light incidence position is a certain value W, the time length for transmitting the surface wave to the detection probe is unchanged, the fact that the sound path of the bulk wave is shortest when the damaged position of the optical element is positioned at the light incidence position and the midpoint position of the detection probe is known according to the geometric relation, and the corresponding time interval is minimum. Recording the time difference from the laser excited ultrasonic signal to the detected ultrasonic signal to be t 1 The optical element damage position can be calculated by formula (1).
Wherein, as shown in fig. 2, a represents the distance between the upper boundary of the damage and the preset position of the surface of the optical element.
In one embodiment, as shown in FIG. 2, the ultrasonic wave reaches the lesion boundary and then propagates through the lesion lower boundary and is finally detected by the same detection probe, and the corresponding path is C 1 、C 2 、C 3 The time difference from excitation to detection of the ultrasonic wave is denoted as t 2 The lesion diameter may be calculated according to equation (2).
Where β represents the perpendicular distance between the upper boundary of the lesion and the surface of the optical element.
According to the on-line monitoring system for damage of the optical element, provided by the embodiment of the invention, by arranging the laser ultrasonic detection unit and the ultrasonic data processing unit and adopting the photoinduced sound field effect, the real-time on-line monitoring of the damage condition of the optical element under the normal working condition of the laser is realized; meanwhile, the damage position and the size of the optical element can be calculated by acquiring the propagation parameters of the ultrasonic signals, so that the damage condition of the optical element can be known in detail. Therefore, the lens position can be moved in time under the normal working condition of the laser, the damage area is avoided, and the service life of the laser is prolonged. In addition, the online monitoring system not only can detect damage conditions of the subsurface of the optical element surface, but also can detect internal damage on the order of cm away from the optical element surface.
In an embodiment, the laser ultrasonic excitation unit 10 further comprises: and the galvanometer scanning module is controlled to scan along the surface of the optical element after the ultrasonic data processing unit receives the electric signal of the preset position of the surface of the optical element, so as to change the irradiated position of the surface of the optical element. Specifically, when the galvanometer scanning module scans along the surface of the optical element to change the irradiated position of the surface of the optical element, the ultrasonic data processing unit 30 controls the detection probe to move, and the horizontal distance between the detection probe and the irradiated position of the surface of the optical element is kept unchanged.
In one embodiment, the detection probe may be a piezoelectric probe, i.e., a transducer, disposed on the same side of the optical element as the light incident surface, and may collect the generated ultrasonic signal and convert the ultrasonic signal into an electrical signal. Specifically, the detection probe is connected with the optical element by using a couplant, the other end of the detection probe is connected with the ultrasonic data processing unit through the signal amplification module, and the detection frequency of the detection probe is related to the thickness and the size of the piezoelectric material. For example, piezoelectric ceramics (PZT) may be used as the probe, the center frequency of which, the probe diameter, affects image quality. Therefore, a piezoelectric probe with small diameter, bandwidth of 2kHz and center frequency of 10kHz is selected to form the detection probe.
In one embodiment, the signal amplifying module includes a three-stage amplifying circuit, the front-stage amplifying circuit includes a dual operational amplifier front-stage amplifier, the middle-stage amplifying circuit includes a common-mode sampling driving circuit and a capacitance-resistance coupling circuit, and the back-stage amplifying circuit includes a phase-locked amplifier. Specifically, the signal amplification module is used for matching the output impedance of the detection probe with the input impedance of the ultrasonic data processing unit, so that the output signal of the detection probe is collected by a subsequent receiving device as much as possible, the signal to noise ratio of the output photoacoustic piezoelectric signal can be improved, and the output can be amplified.
Alternatively, the amplification factor of the signal amplification module may be set to 1000 times, the bandwidth is 2kHz, and three-stage amplification is adopted, and each stage of amplification is 10 times. In order to improve input impedance and common mode rejection performance, a pre-stage amplifying circuit adopts parallel dual operational amplifiers; the intermediate-stage amplifying circuit adopts a common-mode sampling driving circuit and a capacitance-resistance coupling circuit, so that the rear-end differential amplifying circuit obtains high differential-mode gain and common-mode rejection ratio, and meanwhile, a polarization voltage regulating circuit is also arranged in the intermediate-stage amplifying circuit to eliminate direct-current voltage offset; the post-stage amplifying circuit selects a phase-locked amplifier and can process weak photoacoustic piezoelectric signals. The weak photoacoustic piezoelectric signal can be picked up from the background noise by a phase-locked amplifier, the reference signal of which is provided by the operation trigger signal of the laser.
In one embodiment, the ultrasound data processing unit 30 may be composed of two parts, a hardware platform and a software interface control plane; the hardware platform comprises an NI acquisition card, an NI PXIe machine box, an NI PXIe embedded controller and the like. The acquisition card uses an NI PXI-5152 oscilloscope card; the PXIe chassis uses the NI PXIe-1082 chassis. The PXIe embedded controller uses a PXIe-8133 controller which integrates a CPU, a memory, a hard disk, a main board and the like, and can be provided with an XP and win7 system, and a software control interface is written by using a LabWindows/CVI tool.
Specifically, the ultrasonic data processing unit 30 may receive the electrical signal by the acquisition card, convert the electrical signal into a digital signal, and analyze the digital signal by using wavelet transformation, so as to effectively solve the contradiction between time and frequency resolution, and improve the signal-to-noise ratio.
In an embodiment, as shown in fig. 3 and 4, the working flow of the online monitoring system is that the laser 1 emits laser, and the laser is incident to the optical element 4 after passing through the beam expanding module, the galvanometer scanning module 2 and the focusing module 3 inside the laser ultrasonic excitation unit; the ultrasonic signal generated by the optical element 4 is received by the transducer 5, amplified by the signal amplifying module 6 and then input into the acquisition card 7, the acquisition card 7 finishes the acquisition of data at a certain position and then inputs into the controller 8, a trigger signal is generated, the galvanometer scanning module 2 is controlled by the stepping motor to scan along the X, Y direction, and then the light spot on the surface of the optical element 4 is controlled to move. After completing one round of sampling, the ultrasonic data processing unit 30 analyzes the acquired data to give information of the damage position of the optical element.
Specifically, laser excites ultrasonic wave at the incidence position of the surface of the optical element, the ultrasonic wave propagates in the detected optical element and is reflected at the internal damage position, the reflected ultrasonic wave is detected by the detection probe, the sound path is marked by a and b in fig. 3, the linear distance from the incidence position of the laser to the detection probe is W, an incidence light spot is firstly remained at a preset position, scanning is carried out by moving at a fixed step distance under the action of the galvanometer scanning module, and meanwhile, the detection probe moves along with the light spot at the same direction synchronous distance so as to keep W unchanged. In the light spot moving process, the detection probe records the current ultrasonic signal in real time, and the ultrasonic signal is associated with the position of the light spot. After the scanning is finished, judging the damage condition by analyzing the digital signals obtained by the ultrasonic data processing unit, and marking the damage position.
The embodiment of the invention also provides an on-line monitoring method for the damage of the optical element, as shown in fig. 5, comprising the following steps:
step S101: acquiring an ultrasonic signal generated when a preset position of the surface of the optical element is irradiated; specifically, a pulse infrared laser can be selected to emit pulse laser light to be incident on a preset position on the surface of the optical element to generate ultrasound. Parameters such as laser light wave wavelength, pulse energy, pulse width, laser spot diameter, pulse repetition frequency and the like influence the excitation efficiency of laser ultrasound, and can be selected according to imaging depth and imaging resolution requirements. In the practice of the present invention, to achieve an imaging depth of 1cm and an imaging resolution of 10 μm, yttrium aluminum garnet crystal ND: YAG pulse infrared laser, laser wave length is 1064nm, laser single pulse energy maximum is 20mJ (continuously adjustable), and repetition frequency is 1kHz. Alternatively, the optical element may be an element commonly used in a laser system, such as a lens or the like.
Step S102: converting the ultrasonic signal into a digital signal; specifically, a detection probe can be arranged on the same side of the laser incidence on the surface of the optical element to receive ultrasonic signals, and meanwhile, the received ultrasonic signals are converted into electric signals; the electrical signal received by the acquisition card can be converted into a digital signal, and the converted digital signal can be processed by wavelet analysis.
Step S103: and calculating the damage position according to the digital signal, the propagation speed of the ultrasonic signal in the optical element, the damage diameter, the preset position of the surface of the optical element and the emergent position of the ultrasonic signal. Specifically, when the optical element is damaged, the shape of the damage is considered to be spherical in the ideal case, the damage size diameter of the optical element is represented by phi, and the transmission speed of ultrasonic waves in the optical element is C b A detection probe is arranged in the laser ultrasonic detection unit to receive ultrasonic signals, and the distance between the detection probe and the light incidence position is a certain distanceThe time length of the surface wave transmitted to the detection probe is unchanged, and according to the geometric relationship, it can be known that the acoustic path of the bulk wave is shortest when the damaged position of the optical element is positioned at the light incidence position and the midpoint position of the detection probe, and the corresponding time interval is smallest, as shown in fig. 2. Recording the time difference from the laser excited ultrasonic signal to the detected ultrasonic signal to be t 1 The optical element damage position can be calculated by formula (1).
Wherein, as shown in fig. 2, a represents the distance between the upper boundary of the damage and the preset position of the surface of the optical element.
In one embodiment, as shown in FIG. 2, the ultrasonic wave reaches the lesion boundary and then propagates through the lesion lower boundary and is finally detected by the same detection probe, and the corresponding path is C 1 、C 2 、C 3 The time difference from excitation to detection of the ultrasonic wave is denoted as t 2 The lesion diameter may be calculated according to equation (2).
Where β represents the perpendicular distance between the upper boundary of the lesion and the surface of the optical element.
According to the method for monitoring the damage of the optical element on line, provided by the embodiment of the invention, the damage condition of the optical element is judged by using the photoinduced sound field effect through the ultrasonic signal generated by the irradiation of the optical element by the light source, so that the real-time on-line monitoring of the damage condition of the optical element under the normal working condition of the laser is realized; meanwhile, the damage position and the size of the optical element can be calculated by acquiring the propagation parameters of the ultrasonic signals, so that the damage condition of the optical element can be known in detail. Therefore, the lens position can be moved in time under the normal working condition of the laser, the damage area is avoided, and the service life of the laser is prolonged. In addition, the online monitoring method not only can detect damage conditions of the subsurface of the surface of the optical element, but also can detect internal damage which is in the order of cm away from the surface of the optical element.
In an embodiment, the method for on-line monitoring of damage to an optical element further includes: changing the irradiated position of the surface of the optical element, and repeatedly calculating the damaged position again by the online monitoring method of the damage of the optical element; specifically, after the digital signal converted from the ultrasonic signal at the preset position of the surface of the optical element is obtained, the irradiated position of the surface of the optical element can be changed, for example, a galvanometer scanning module can be arranged between the light source and the optical element, and the galvanometer scanning module is controlled to scan along the surface of the optical element, so that the optical element is sampled. Specifically, when the galvanometer scanning module scans along the surface of the optical element to change the irradiated position of the surface of the optical element, the detection probe can be synchronously controlled to move at the same time, so that the horizontal distance between the detection probe and the irradiated position of the surface of the optical element is kept unchanged.
In addition, the technical features of the different embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
Although the exemplary embodiments and their advantages have been described in detail, those skilled in the art may make various changes, substitutions and alterations to these embodiments without departing from the spirit of the invention and the scope of protection as defined by the appended claims. For other examples, one of ordinary skill in the art will readily appreciate that the order of the process steps may be varied while remaining within the scope of the present invention.
Furthermore, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. From the present disclosure, it will be readily understood by those of ordinary skill in the art that processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present disclosure. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
Claims (8)
1. An on-line monitoring method for damage to an optical element, comprising:
collecting ultrasonic signals generated when the preset position of the surface of the optical element is irradiated;
converting the ultrasonic signal into a digital signal;
calculating a damage position according to the digital signal, the propagation speed of the ultrasonic signal in the optical element, the damage diameter, the preset position of the surface of the optical element and the emergent position of the ultrasonic signal;
calculating the damage position according to the propagation speed of the digital signal and the ultrasonic signal in the optical element, the damage diameter, the preset position of the surface of the optical element and the emergent position of the ultrasonic signal, wherein the method comprises the following steps:
determining the propagation time length along the upper boundary of the damage and the propagation time length along the lower boundary of the damage according to the digital signal;
calculating the distance between the upper boundary of the damage and the preset position on the surface of the optical element according to the propagation speed of the ultrasonic signal in the optical element and the propagation time length along the upper boundary of the damage;
calculating the vertical distance between the upper damage boundary and the surface of the optical element according to the distance between the upper damage boundary and the preset position of the surface of the optical element, the preset position of the surface of the optical element and the emergent position of the ultrasonic signal;
calculating the damage diameter according to the vertical distance between the upper damage boundary and the surface of the optical element, the propagation speed of the ultrasonic signal in the optical element, the propagation time length along the lower damage boundary, the preset position of the surface of the optical element and the emergent position of the ultrasonic signal;
and calculating the damage position according to the distance between the damage upper boundary and the preset position of the surface of the optical element, the damage diameter, the preset position of the surface of the optical element and the emergent position of the ultrasonic signal.
2. The method for on-line monitoring of damage to an optical element of claim 1, further comprising: changing the irradiated position of the surface of the optical element, and repeating the on-line monitoring method for the damage of the optical element according to claim 1 to calculate the damage position.
3. The method for on-line monitoring of damage to an optical element according to claim 2, wherein the probe for detecting an ultrasonic signal is moved synchronously while changing the irradiated position of the surface of the optical element, and the horizontal distance between the irradiated position of the surface of the optical element and the exit position of the ultrasonic signal is unchanged.
4. An on-line monitoring system for damage to an optical element, comprising: a laser ultrasonic excitation unit, a laser ultrasonic detection unit and an ultrasonic data processing unit,
the laser ultrasonic excitation unit comprises a light source, wherein light emitted by the light source is incident to a preset position on the surface of the optical element to generate an ultrasonic signal;
the laser ultrasonic detection unit receives the ultrasonic signal, converts the ultrasonic signal into an electric signal and outputs the electric signal to the ultrasonic data processing unit;
the ultrasonic data processing unit comprises a signal conversion module and a position calculation module,
the signal conversion module converts the electric signal into a digital signal and analyzes and processes the digital signal;
the position calculation module calculates the damage position according to the processed digital signal, the propagation speed of the ultrasonic signal in the optical element, the damage diameter, the preset position of the surface of the optical element and the emergent position of the ultrasonic signal;
the position calculation module includes:
the time length determining module is used for determining the propagation time length along the upper boundary of the damage and the propagation time length along the lower boundary of the damage according to the processed digital signals;
the first distance calculation module is used for calculating the distance between the upper boundary of the damage and the preset position of the surface of the optical element according to the propagation speed of the ultrasonic signal in the optical element and the propagation time length along the upper boundary of the damage;
the second distance calculation module is used for calculating the vertical distance between the upper damage boundary and the surface of the optical element according to the distance between the upper damage boundary and the preset position of the surface of the optical element, the preset position of the surface of the optical element and the emergent position of the ultrasonic signal;
the damage diameter calculation module is used for calculating the damage diameter according to the vertical distance between the upper damage boundary and the surface of the optical element, the propagation speed of the ultrasonic signal in the optical element, the propagation time length along the lower damage boundary, the preset position of the surface of the optical element and the emergent position of the ultrasonic signal;
the position calculation sub-module is used for calculating the damage position according to the distance between the damage upper boundary and the preset position of the surface of the optical element, the damage diameter, the preset position of the surface of the optical element and the emergent position of the ultrasonic signal.
5. The on-line monitoring system for optical element damage of claim 4, wherein the laser ultrasonic excitation unit further comprises: and the galvanometer scanning module is controlled to scan along the surface of the optical element after receiving the electric signal of the preset position of the surface of the optical element by the ultrasonic data processing unit, so as to change the irradiated position of the surface of the optical element.
6. The on-line monitoring system for optical element damage of claim 5, wherein the laser ultrasonic detection unit comprises: the detection probe and the signal amplifying module are connected with each other,
the detection probes are arranged on the same side of the light incidence surface of the optical element and are used for acquiring the generated ultrasonic signals;
the signal amplification module is used for amplifying the ultrasonic signal and outputting the amplified ultrasonic signal to the ultrasonic data processing unit.
7. The on-line monitoring system for damage to an optical element according to claim 6, wherein the ultrasonic data processing unit controls the movement of the inspection probe when the irradiation position of the surface of the optical element is changed, and keeps the horizontal distance between the inspection probe and the irradiation position of the surface of the optical element unchanged.
8. The system of claim 6, wherein the signal amplification module comprises a three-stage amplification circuit, the pre-stage amplification circuit comprises a dual op-amp pre-stage amplifier, the intermediate stage amplification circuit comprises a common mode sampling driving circuit and a capacitive-resistive coupling circuit, and the post-stage amplification circuit comprises a lock-in amplifier.
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