CN102297899B - Acoustic method for judging damage to film and optical element - Google Patents
Acoustic method for judging damage to film and optical element Download PDFInfo
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- CN102297899B CN102297899B CN201010572845.XA CN201010572845A CN102297899B CN 102297899 B CN102297899 B CN 102297899B CN 201010572845 A CN201010572845 A CN 201010572845A CN 102297899 B CN102297899 B CN 102297899B
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Abstract
The invention belongs to the measuring field of judgment of damage to a film and an optical element and particularly relates to an acoustic method for judging damage of the film and the optical element. The prior art for testing a laser damage threshold has the problems that the testing repeatability is difficult to be ensured and the testing accuracy is also difficult to be ensured. In order to overcome the problems of the prior art, the invention provides a technical scheme that a damage judging method based on acoustics comprises the following steps: detecting an acoustic time domain strength signal instantly caused by film damage, so as to perform Fourier transform on the acoustic time domain strength signal; after performing the Fourier transform, extracting a frequency domain feature of the acoustic time domain strength signal, namely showing a specific frequency which uniquely represents if the film is damaged; and comprehensively giving an accurate criterion indicating if the film is damaged according to the acquired acoustic time domain strength signal and the frequency domain feature of the acoustic time domain strength signal, namely indicating if the time domain has a strength peak and if the frequency domain has a feature frequency. The acoustic method provided by the invention has excellent repeatability and high accuracy.
Description
Technical field
The invention belongs to the fields of measurement of a kind of film and optic element damage differentiation, the acoustic method of specifically a kind of film and optic element damage differentiation.
Background technology
The resisting laser damage performance of film and optical element is an important technology index in device application, but to laser damage threshold test existence two subject matters, one is that the repeatability of testing is difficult to ensure; Two is that the accuracy of test is difficult to ensure, and to occur on the method for discrimination that the main cause of the problems referred to above is thin film damage not science, existing defects.At present, the differentiation film adopted in national standard and ISO and the method for optic element damage are phasecontrast microscope manual observation methods, and the method is offline inspection and human factor is comparatively large, different people test result disunity; The scattered light damage method of discrimination also having researcher to grow up in addition, the method is based on the scattered light variable quantity detecting impaired loci, differentiate whether check point damages, can be implemented in line to measure, but due to measuring object difference (such as film system function is different), the amplitude difference of scattered light variable quantity is very far away, is therefore difficult to provide a unified damage discrimination standard; The plasma spark method of discrimination of another report, thinks that the moment of thin film damage produces with plasma spark, can be implemented in line and measures; But the flash of light wave band of different membraneous materials and optical element material is different, be difficult to provide a unified damage discrimination standard equally.The photothermal deflection method thin film damage method of discrimination that development in recent years is got up, the method is actual is a set of laser photothermal spectroscopy Detection Techniques, need corresponding sample moving platform, the photothermal image of film is obtained by scanning, judge whether film damages through identifying, this device is complicated and have difficulties in differentiation in good time.
Summary of the invention
The present invention, in order to solve the problem, propose the acoustic method of a kind of film and optic element damage differentiation, can realize damaging method of discrimination online, accurately.
In order to overcome prior art Problems existing, technical scheme provided by the invention is:
The acoustic method that a kind of film and optic element damage differentiate: the acoustics time domain strength signal produced instantaneously by detection thin film damage, and then the vertical leaf change of pair is carried out to time domain strength signal, stand after leaf change through pair, extract the frequency domain character of time-domain signal, namely there is a certain specific frequency, whether this frequency uniquely characterizes film and damages, from the frequency domain character of the time-domain signal obtained and this signal, comprehensively provide thin film damage whether accurate criterion, namely whether time domain there is intensity peak and whether frequency domain has characteristic frequency.
Compared with prior art, the present invention has the following advantages and beneficial effect:
1, contrast with the phasecontrast microscope manual observation method of existing national regulations, method provided by the invention can be implemented in line ground and differentiates in good time; And damage differentiation process and do not need human intervention, then person can obtain unified result to realize different measuring.
2 with scattering damage method of discrimination with etc. stereo flash damage method of discrimination compare, owing to have employed the technology that frequency domain body characteristics peak and time domain intensity peak are extracted simultaneously, achieve the unification of discrimination standard.
3 compare with photothermal deflection method thin film damage method of discrimination, and the method needs the equipment such as spectrometer, mobile platform, cost intensive, complex structure; And damage method of discrimination structure provided by the invention is simple, relative cost is low.
Accompanying drawing explanation
Fig. 1 the invention provides the structural representation of a device of measuring method;
Fig. 2 collects the time domain collection of illustrative plates of signal when being measurement one thin film damage;
Fig. 3 collects the time domain amplitude variations of signal when being measurement one thin film damage;
Fig. 4 collects the frequency domain collection of illustrative plates of signal when measuring a thin film damage;
Fig. 5 is the Time Domain Spectrum of the acoustic signals that embodiment 2 obtains,
Fig. 6 collects the frequency domain collection of illustrative plates of signal when measuring a thin film damage.
Reference numeral is as follows:
1-damage pulse laser, 2-optical system, 3-sample stage, 4-probe microphone assembly, 5-acoustic signal frequency domain positioning system, 6-Signal transmissions, 7-damages judgement system.
Embodiment
Below in conjunction with accompanying drawing, the present invention is described in detail.
The acoustic method that a kind of film provided by the invention and optic element damage differentiate: the acoustics time domain strength signal produced instantaneously by detection thin film damage, and then the vertical leaf change of pair is carried out to time domain strength signal, determine the frequency domain characteristic of time-domain signal.Generally, the intensity of time-domain signal can with membraneous material, film system function difference, the time-domain signal intensity produced in damage generation moment is different, and the problem therefore brought remains and can not provide a unified standard (namely the intensity of time-domain signal is greater than how much just think that film damages) judging to damage; Stand after leaf change through pair, can extract the frequency domain character of time-domain signal, namely occur a certain specific frequency, whether this frequency uniquely characterizes film and damages.Like this from the frequency domain character of the time-domain signal obtained and this signal, comprehensively provide thin film damage whether accurate criterion, namely whether time domain there is intensity peak and whether frequency domain has characteristic frequency.
In order to realize said method, the invention provides the measurement mechanism that the damage of a kind of acoustics differentiates.See Fig. 1, this device comprises the high power pulse laser 1 of damage, optical system 2, sample stage 3, probe microphone assembly 4, acoustic signal frequency domain positioning system 5, signal transmssion line and damage judgement system 7.Said probe microphone assembly 4 to respond infrasonic wave, audio frequency and hyperacoustic combinations of detectors; Acoustic signal frequency domain positioning system 5 can be extracted the frequency domain information of time-domain signal by various hardware/software algorithm realization; The amplitude of time-domain signal that said damage judgement system 7 can comprehensively obtain and the characteristic frequency of frequency domain are to differentiate whether film or optics unit are damaged.As long as the device that can realize the inventive method all can adopt.
Embodiment 1: utilize the damage of the inventive method to film to test
Fig. 2 provides when being testing film damage, when collecting different pulsed laser energy effect, obtains the Time Domain Spectrum of acoustic signals.A figure is in the less situation of impulse impairments energy, and obtain the time-domain curve of acoustic signal, normalized amplitude intensity is 0.04; And after increasing pulsed laser energy, as shown in b figure, time-domain signal intensity amplitude is increased to 0.6; Further increase energy, time-domain signal intensity amplitude is increased to 0.8(and sees that c schemes).Problem is that sound signal intensity reaches how many on earth, and think that film damages, namely Damage criterion is difficult to determine.General way is to the specific film of one, measures the acoustic signal intensity under different damage pulse energy, makes the curve of intensity peak and damage pulse energy, as shown in Figure 3.Generally choose intensity peak reach or exceed how many times, be defined as the criterion of film deteriorates, then get ready according to this criterion, calculated the damage threshold of film by extrapolation.Dotted line position in such as Fig. 3, namely think that amplitude reaches 50% and thinks that film damages damage, different testers has different standards, and the result of so testing is with regard to disunity; If in addition membraneous material or film system different, damage time-domain signal intensity differ greatly, unified damage discrimination standard can not be provided.
We are by obtaining the frequency domain spectrogram of time-domain signal under three kinds of different-energies to acoustic signal frequency domain positioning system 5 for this reason, as Fig. 4 (a), shown in (b) He (c), the obvious spectral density occurring strengthening successively at about 4500Hz in Fig. 4 (b) and (c), and in Fig. 4 (a) again this frequency range there is no obvious characteristic frequency, although the time-domain signal that Fig. 4 (a) is corresponding has oscillator intensity, can not judge that film damages under pulse energy.Therefore combine in conjunction with time-domain signal intensity and frequency-domain frequency location and judge whether film damages, the i.e. moment of pulsed laser action film, intensity peak (this is the necessary condition judging whether film damages) should be there is in time-domain signal, observe frequency domain character frequency (this is the necessary condition judging whether film damages), the two occurs judging that film damages simultaneously simultaneously.
Embodiment 2: utilize the damage of the inventive method to optical element to test
Fig. 5 gives a kind of optical element when damaging during generation, when collecting different pulsed laser energy effect, obtains the Time Domain Spectrum of acoustic signals.A figure is in the less situation of impulse impairments energy, and obtain the time-domain curve of acoustic signal, normalized amplitude intensity is very weak; And after increasing pulsed laser energy, as shown in b figure, time-domain signal intensity amplitude is increased to 0.8.Still there is the problem how differentiating damage.We are by obtaining the frequency domain spectrogram of time-domain signal under two kinds of different-energies to acoustic signal frequency domain positioning system 5 for this reason, as shown in Fig. 6 (a) He (b), the obvious spectral density occurring strengthening successively at about 4500Hz in Fig. 6 (b), and in Fig. 6 (a) again this frequency range there is no obvious characteristic frequency, although the time-domain signal that Fig. 6 (a) is corresponding has oscillator intensity, can not judge that film damages under pulse energy.Therefore combine in conjunction with time-domain signal intensity and frequency-domain frequency location and judge whether film damages, the i.e. moment of pulsed laser action film, intensity peak (this is the necessary condition judging whether film damages) should be there is in time-domain signal, observe frequency domain character frequency (this is the necessary condition judging whether film damages), the two occurs judging that optical element damages simultaneously simultaneously.
Claims (1)
1. the acoustic method of a film and optic element damage differentiation, it is characterized in that: the acoustics time domain strength signal produced instantaneously by detection thin film damage, and then the vertical leaf change of pair is carried out to time domain strength signal, stand after leaf change through pair, extract the frequency domain character of time-domain signal, namely there is a certain specific frequency, whether this frequency characterizes film and damages, from the frequency domain character of the time-domain signal obtained and this signal, comprehensively provide thin film damage whether accurate criterion, namely whether time domain there is intensity peak and whether frequency domain has characteristic frequency;
When described testing film damage, when collecting different pulsed laser energy effect, obtain the Time Domain Spectrum of acoustic signals;
To the specific film of one, measure the acoustic signal intensity under different damage pulse energy, make the curve of intensity peak and damage pulse energy, choose intensity peak and reach or exceed how many times, be defined as the criterion of film deteriorates;
Combine in conjunction with time-domain signal intensity and frequency-domain frequency location and judge whether film damages, i.e. the moment of pulsed laser action film, time-domain signal should occur intensity peak, observe frequency domain character frequency, the two occurs judging that film damages simultaneously simultaneously.
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| CN101419196A (en) * | 2008-12-08 | 2009-04-29 | 浙江大学 | Thin crack hammering response detection device and method for poultry egg |
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