CN114326099B - One-dimensional high-speed high-resolution imaging system and real-time molten pool monitoring method based on same - Google Patents
One-dimensional high-speed high-resolution imaging system and real-time molten pool monitoring method based on same Download PDFInfo
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Abstract
The invention discloses a one-dimensional high-speed high-resolution imaging system and a real-time molten pool monitoring method based on the same. The novel molten pool monitoring imaging system comprises: femtosecond laser, optical time domain stretching component, optical path component, focusing component, dichroic mirror, filtering component, signal collecting component, circulator, modulation component, etc. The advantages are as follows: 1. the invention is based on the imaging principle of an optical microscope system, and the imaging frame rate can reach 100MHz magnitude (the frame interval is 10 nanoseconds); 2. the invention can reach the spatial resolution near the diffraction limit; 3. the invention can achieve the time resolution of the order of nano seconds; 4. the invention can realize long-time continuous shooting, thereby completely meeting the requirements of research and online monitoring of the dynamics of a laser processing molten pool; 5. the system light path of the invention is femto-second laser active illumination, and combines grating beam combination and pulse coupling, thereby well inhibiting adverse effect of strong light in a processing area on imaging.
Description
Technical Field
The invention relates to the technical field of high-speed imaging, in particular to a one-dimensional high-speed high-resolution imaging system and a real-time molten pool monitoring method based on the same.
Background
The processing and manufacturing of high-power laser materials are widely applied to various manufacturing fields in recent years, and rapid development is achieved. Real-time online monitoring of molten pool evolution in the laser and material action area during the processing of high-power laser materials has been a concern.
The temperature of the molten pool is higher, the volume is smaller, the applicable online monitoring method is not many, and the current common method is to monitor the molten pool by using devices such as a high-speed camera, a thermal infrared imager, a pyrometer and the like. The molten pool generated in the laser processing process has a fast change process, usually in the order of nanoseconds to milliseconds, and a high-speed camera is difficult to capture a dynamic process. In addition, the molten pool of laser processing has high temperature, strong brightness of a field of view, millimeter level, high cooling speed, and strong interference generated from visible light to infrared wave bands due to the shielding of plasma or steam generated by processing, and great observation difficulty. The current X-ray imaging technology with good molten pool evolution time resolution monitoring effect is only suitable for scientific research due to the fact that the device is complex, the cost is high, the frame rate of continuous shooting is low, and the X-ray imaging technology is difficult to popularize and apply as an online real-time monitoring system in industrial processing. The imaging frame rate of the existing CCD or CMOS-based high-speed camera is 1MHz at most, and high-time resolution observation cannot be carried out on the molten pool change process under 1 microsecond.
Disclosure of Invention
Aiming at the problems, the embodiment of the application realizes the acquisition of the continuous molten pool surface morphology image with high speed, high resolution and long time by providing a high-speed and high-resolution molten pool on-line monitoring technology, and improves the imaging frame rate from 1MHz of a traditional high-speed camera by two orders of magnitude to 100 MHz;
the invention provides a one-dimensional high-speed high-resolution imaging system, which is characterized in that the system is a one-dimensional imaging system based on a transmission principle;
a light source assembly: as an imaging system light source;
one-dimensional dispersive element: the method is used for carrying out space conversion and one-dimensional dispersion Fourier transform on laser;
and a focusing module: for focusing the spatial laser pulses;
and a modulation component: for modulating the laser pulses;
and a filtering component: the filter is used for filtering and separating the space light beam;
a signal collection assembly: the method is used for collecting dynamic detection signals of the laser processing piece in real time, and converting photoelectric and analog electric signals and processing the signals.
In the above one-dimensional high-speed, high-resolution imaging system, the one-dimensional dispersive element comprises: an optical fiber, a diffraction grating; the optical fiber performs dispersion Fourier transform on different component lights in laser signal pulses generated by the light source component in the time domain; the diffraction grating projects different wavelength components of the pulse spectrum to different positions of the space, so that the space information of the molten pool to be detected is mapped onto the frequency spectrum of the pulse; the wavelength parameters of the light source component laser and the wavelength parameters of the laser used for processing are different, and the reflection and refraction of the processing laser can be prevented from interfering or affecting the observation laser pulse by filtering processing through the filtering component.
In the above-mentioned one-dimensional high-speed high-resolution imaging system, characterized in that,
the modulation assembly 1 comprises: an arbitrary waveform generator, modulator 1; in the monitoring light path, random binary codes are generated by using an arbitrary waveform generator, the binary codes are modulated on the time domain signals of the monitoring pulse laser by using a modulator 1, and the laser pulses are coded and modulated.
In the above-mentioned one-dimensional high-speed and high-resolution imaging system, the optical path may be divided into two paths: a monitoring light path and a processing light path; the monitoring light path is emitted by the light source component, passes through the one-dimensional dispersion component 1, the modulation component 2, the one-dimensional dispersion component 2, the focusing module 1, the light-permeable laser processing piece, the focusing module 2 and the filtering component, and finally enters the signal collecting component; the processing light path is emitted by a light source of the laser processing equipment, enters a light-permeable laser workpiece through a focusing module 3, and the residual laser workpiece is transmitted through the focusing module 2 and enters a filtering component to be filtered; in addition, the square wave emitted by the modulation component 1 is converged into the detection light path in the one-dimensional dispersion components 1 and 2.
A one-dimensional high-speed and high-resolution imaging system, which is characterized in that the system is a one-dimensional imaging system based on a reflection principle; comprising the following steps:
a light source assembly: as an imaging system light source;
one-dimensional dispersive element: the method is used for carrying out space conversion and one-dimensional dispersion Fourier transform on laser;
and a focusing module: for focusing the spatial laser pulses;
the circulator is as follows: the system is used for realizing bidirectional optical signal transmission on a single optical fiber in a system optical path;
and a modulation component: for modulating the laser pulses;
and a filtering component: the filter is used for filtering and separating the space light beam;
a signal collection assembly: the method is used for collecting dynamic detection signals of the laser processing piece in real time, and converting photoelectric and analog electric signals and processing the signals.
In the above one-dimensional high-speed, high-resolution imaging system, the one-dimensional dispersive element comprises: an optical fiber, a diffraction grating; the optical fiber performs dispersion Fourier transform on different component lights in laser signal pulses generated by the light source component in the time domain; the diffraction grating projects different wavelength components of the pulse spectrum to different positions of the space, so that the space information of the molten pool to be detected is mapped onto the frequency spectrum of the pulse; the wavelength parameters of the light source component laser and the wavelength parameters of the laser used for processing are different, and the reflection and refraction of the processing laser can be prevented from interfering or affecting the observation laser pulse by filtering processing through the filtering component.
In the above-described one-dimensional high-speed, high-resolution imaging system, the modulation assembly 1 includes: an arbitrary waveform generator, modulator 1; in the monitoring light path, random binary codes are generated by using an arbitrary waveform generator, the binary codes are modulated on the time domain signals of the monitoring pulse laser by using a modulator 1, and the laser pulses are coded and modulated.
In the above-mentioned one-dimensional high-speed and high-resolution imaging system, the optical path may be divided into two paths: a monitoring light path and a processing light path;
the monitoring light path is emitted by the light source component, enters the non-light-permeable laser processing piece through the one-dimensional dispersion component 1, the one-dimensional dispersion component 2, the circulator, the filter component, the focusing module 1, is reflected to the focusing module 1 by the processing piece, passes through the filter component, is converted into the light path direction by the circulator, and finally enters the signal collecting component; the processing light path is emitted by a light source of the laser processing equipment, enters into a non-light-permeable laser workpiece through a focusing module 3, is reflected by a residual laser workpiece, enters into a filtering component through a focusing module 1 and is filtered; in addition, the square wave emitted by the modulation component 2 merges into the detection light path in the one-dimensional dispersion components 1, 2.
The real-time molten pool monitoring method based on the one-dimensional high-speed and high-resolution imaging system is characterized by comprising the following steps of:
step 1, the sequence of starting the light source assembly and the laser in the laser processing equipment is as follows: the detection light path light source assembly is started first, and a laser used for laser processing is started after the light source assembly and the observation system reach a stable state, so that the situation that effective observation cannot be obtained in the early stage of a molten pool phenomenon can be avoided;
step 2, the light source component emits laser pulses as a light source of the monitoring imaging system;
step 3, the laser pulse is incident to the one-dimensional dispersion component 1, and the laser pulse is subjected to time domain stretching;
step 4, the modulating component 1 generates square waves to modulate the laser pulse;
step 5, the modulated laser pulse subjected to time domain stretching is emitted to the modulation component 2;
step 6, the laser pulse is emitted to a one-dimensional dispersion component 2, and different wavelength components of a pulse spectrum are projected to different positions of a space to perform one-dimensional dispersion;
step 7, focusing on a laser workpiece through the focusing module;
step 8, collecting laser pulses carrying molten pool observation information and laser used for laser processing emitted by the light-permeable laser workpiece by the focusing module, injecting the laser pulses into the filtering component, filtering processing laser, and reserving the laser pulses with coding information;
and 9, the space coding pulse is incident to the signal collecting assembly, and the detection signal is collected, converted into digital electric signal and analog electric signal and processed, so that the real-time dynamic change of the laser workpiece is observed.
10. The real-time molten pool monitoring method based on the one-dimensional high-speed and high-resolution imaging system is characterized by comprising the following steps of:
step 1, firstly, starting a light source assembly, and starting a laser for laser processing after the light source assembly and an observation system reach a stable state;
step 2, the light source component emits laser pulse as an imaging system light source;
step 3, the laser pulse is incident to the one-dimensional dispersion component 1, and the laser pulse is subjected to time domain stretching;
step 4, the modulating component 1 generates square waves to modulate the laser pulse;
step 5, the modulated laser pulse subjected to time domain stretching is emitted to the modulation component 2;
step 6, the laser pulse is emitted to a one-dimensional dispersion component 2, and different wavelength components of a pulse spectrum are projected to different positions of a space to perform one-dimensional dispersion;
step 7, focusing on a laser workpiece through the focusing module;
step 8, collecting laser pulses carrying molten pool observation information and laser used for laser processing by the opaque laser workpieces through the focusing module, injecting the laser pulses and the laser used for laser processing into the filtering component, filtering processing laser, and reserving the laser pulses with coded information;
step 9, the space coding pulse is injected into the circulator and is emitted to the signal collecting assembly from the other output port of the circulator;
and step 10, the laser pulse is incident to the signal collecting assembly along an original light path, and the detection signal is collected, converted into digital-to-electric and analog-to-digital signals and processed, so that the real-time dynamic change of a laser workpiece is observed.
Therefore, the invention has the following advantages: 1. the invention is based on the imaging principle of an optical microscope system, and the imaging frame rate can reach 100MHz magnitude (the frame interval is 10 nanoseconds); 2. the invention can reach the spatial resolution near the diffraction limit; 3. the invention can achieve the time resolution of the order of nano seconds; 4. the invention can realize long-time continuous shooting, thereby completely meeting the requirements of research and online monitoring of the dynamics of a laser processing molten pool; 5. the system light path of the invention is femto-second laser active illumination, and combines grating beam combination and pulse coupling, thereby well inhibiting adverse effect of strong light in a processing area on imaging.
The invention provides a high-speed and high-resolution molten pool on-line monitoring technology by utilizing an imaging principle of an optical microscope system; the invention aims to solve the problem that the existing molten pool phenomenon is difficult to obtain a real-time monitoring image. The invention has the advantages that in a transmission type imaging system and a reflection type imaging system, laser processing and real-time detection can be performed simultaneously; the processing laser and the observing laser have different pulse wavelengths, so that the interference or other influences on the observing laser pulse caused by the reflection and refraction of the processing laser can be avoided by filtering the processing laser through a filtering component; different from the traditional molten pool detection technology, the molten pool online detection technology provided by the invention has the characteristics and advantages of spatial resolution near the diffraction limit, time resolution of nanosecond magnitude, long-time continuous shooting and the like; meanwhile, the invention has simple structure and lower cost than the prior art; the invention becomes a general technique for observing a molten pool in a series of laser advanced manufacturing such as laser welding, additive manufacturing, surface cladding, polishing and the like, and has important academic value and practical value in the field of the major science of laser processing mechanism research.
Drawings
FIG. 1 is an overall block diagram of a transmission imaging system in a high-speed, high-resolution melt pool on-line monitoring technique.
FIG. 2 is an overall block diagram of a reflective imaging system in a high-speed, high-resolution melt pool on-line monitoring technique.
FIG. 3 is a schematic diagram of a transmission imaging system in a high-speed and high-resolution molten pool on-line monitoring technique according to an embodiment of the present invention.
FIG. 4 is a schematic diagram of a reflective imaging system in a high-speed, high-resolution molten pool on-line monitoring technique according to an embodiment of the present invention.
Detailed Description
The embodiment of the invention realizes the acquisition of the surface morphology image of the continuous molten pool at high speed and high resolution for a long time by providing a high-speed and high-resolution molten pool on-line monitoring technology, and improves the imaging frame rate from 1MHz of a traditional high-speed camera by two orders of magnitude to 100 MHz;
the embodiment of the application provides a high-speed and high-resolution molten pool on-line monitoring technology, which respectively establishes a transmission imaging optical path system and a reflection imaging optical path system according to different light transmission properties of processing materials.
1. In a transmission imaging system, comprising: femtosecond lasers, optical time domain stretching components, focusing modules, dichroic mirrors, filtering components, modulation components, circulators (only needed by a reflective imaging system), signal collection components; the whole set of monitoring system also comprises laser processing equipment and laser processing parts (light-permeable and light-impermeable);
the optical time domain stretching assembly includes: an optical fiber;
the beam splitter includes: a prism, a diffraction grating;
the light path assembly includes: a collimator;
the focusing modules 1, 2, 3 include: an objective lens;
the filter assembly includes: a filter;
the modulation assembly includes: a waveform generator, modulator;
the signal collection assembly includes: the photoelectric detector, the analog-to-digital converter and the computer;
the whole set of monitoring system also comprises laser processing equipment and laser workpieces (light-permeable and light-impermeable);
the imaging light path system in the monitoring system comprises the following steps:
in a transmission type imaging system, taking a femtosecond laser pulse emitted by the femtosecond laser as detection light; generating a Gaussian or binary signal by adopting an arbitrary waveform generator in the modulation component, and carrying out code modulation on the Gaussian or binary signal by a modulator; stretching different wavelength components of the femtosecond laser ultrashort pulse in a time domain through a roll of optical fiber with a certain length in the optical time domain stretching assembly by utilizing a frequency-time mapping technology; the optical splitter in the optical time domain stretching assembly performs one-dimensional dispersion on the ultrashort pulse by utilizing a frequency-space mapping technology, and different wavelength components in the pulse spectrum are projected to different positions in space to bear the space information of the molten pool phenomenon of the laser workpiece to be detected; when the femtosecond laser pulse is incident to the molten pool area of the laser workpiece, the spatial information of the molten pool to be detected is mapped to the frequency spectrum of the femtosecond laser pulse; the femtosecond laser pulses transmitted through the light-permeable laser work piece melt pool are spatially re-polymerized and combined; receiving and sampling by a photoelectric detector and an analog-to-digital converter; finally, the computer carries out signal processing;
the optical fiber used for stretching in the optical time domain stretching assembly can be selected as a single mode optical fiber, and the advantage of small power loss is achieved;
the filter plate in the filter assembly can be selected as a short-pass filter plate, so that a better filtering effect is achieved;
the optical time domain stretching component comprises an optical time domain stretching component, a diffraction grating and a focusing module, wherein the optical time domain stretching component is used for carrying out one-dimensional dispersion on femtosecond laser pulses, the diffraction grating is used for carrying out spatial dispersion on the femtosecond laser pulses to form linear one-dimensional dispersion pulses, the linear one-dimensional dispersion pulses are focused on an observation object through the focusing module, and surface information of the observation object is encoded on a spectrum of the linear one-dimensional dispersion pulses, so that space encoding pulses are formed;
the trigger signal of the arbitrary waveform generator in the modulation component can be subjected to low-pass filtering through a low-pass filter, and the arbitrary waveform generator is triggered to generate a square wave signal;
the focusing module 1, the focusing module 2 and the focusing module 3 can be long-focus objective lenses;
the focusing module objective lens can be selected as a tele objective lens, so that the placement space of other components can be increased;
the modulator in the modulation component can be an electro-optic modulator;
the analog-to-digital converter in the signal collection assembly can be selected as an oscilloscope;
2. in a reflective imaging system, comprising: femtosecond lasers, optical time domain stretching components, focusing modules, dichroic mirrors, filtering components, modulation components, circulators (only needed by a reflective imaging system), signal collection components; the whole set of monitoring system also comprises laser processing equipment and laser processing parts (light-permeable and light-impermeable);
the optical time domain stretching assembly includes: an optical fiber;
the beam splitter includes: a prism, a diffraction grating;
the light path assembly includes: a collimator;
the focusing modules 1, 2, 3 include: an objective lens;
the filter assembly includes: a filter;
the modulation assembly includes: a waveform generator, modulator;
the signal collection assembly includes: the photoelectric detector, the analog-to-digital converter and the computer;
the whole set of monitoring system also comprises laser processing equipment and laser workpieces (light-permeable and light-impermeable);
the imaging light path system in the monitoring system comprises the following steps:
the step of emitting the laser workpiece from the femtosecond laser is consistent with a transmission imaging system, and is not repeated here; the random waveform generator in the modulation component is adopted to generate Gaussian or binary signals, the modulated pulses are subjected to coded modulation through the modulator and are incident on a molten pool, the pulses reflected by the molten pool return according to an original path and are recompressed in a time domain, and the compressed pulses are received and sampled through the photoelectric detector and the analog-to-digital converter; finally, the computer carries out signal processing; each optical pulse detects the information of one section of the molten pool, and the rear end can acquire a complete two-dimensional image of the appearance of the molten pool by splicing pulse signals through digital signal processing;
in addition, the whole detection system also comprises laser processing equipment and laser processing parts; placing the objective lens for focusing in front of a laser processing head to focus a processing laser beam; focusing a laser beam on the dichroic mirror; reflecting the laser beam by the dichroic mirror for a certain angle to achieve the effect of perpendicular incidence to the laser workpiece; the laser processing piece is placed perpendicular to the direction of the femtosecond laser pulse;
the optical fiber used for stretching in the optical time domain stretching assembly can be selected as a single mode optical fiber, and the advantage of small power loss is achieved;
the filter plate in the filter assembly can be selected as a short-pass filter plate, so that a better filtering effect is achieved;
the optical time domain stretching component comprises an optical time domain stretching component, a diffraction grating and a focusing module, wherein the optical time domain stretching component is used for carrying out one-dimensional dispersion on femtosecond laser pulses, the diffraction grating is used for carrying out spatial dispersion on the femtosecond laser pulses to form linear one-dimensional dispersion pulses, the linear one-dimensional dispersion pulses are focused on an observation object through the focusing module, and surface information of the observation object is encoded on a spectrum of the linear one-dimensional dispersion pulses, so that space encoding pulses are formed;
the trigger signal of the arbitrary waveform generator in the modulation component can be subjected to low-pass filtering through a low-pass filter, and the arbitrary waveform generator is triggered to generate a square wave signal;
the focusing module 1, the focusing module 2 and the focusing module 3 can be long-focus objective lenses;
the focusing module objective lens can be selected as a tele objective lens, so that the placement space of other components can be increased;
the modulator in the modulation component can be an electro-optic modulator;
the analog-to-digital converter in the signal collection assembly can be selected as an oscilloscope;
for a clearer description of the technical solutions in the present embodiment, the drawings that are required to be used in the description of the embodiment will be briefly introduced; it is apparent that the system in the above figures is one embodiment of the present invention, and that other figures can be obtained from these figures without inventive effort for a person of ordinary skill in the art;
the transmission type on-line monitoring technical structure shown in fig. 3 comprises: a 101-femtosecond laser, 102-single mode fiber, 103-arbitrary waveform generator, 104-electro-optic modulator, 105-collimator, 106-diffraction grating, 107-objective lens, 108-dichroic mirror, 109-laser processing equipment, 110-objective lens, 111-laser work piece, 112-filter, 113-objective lens, 114-diffraction grating, 115-collimator, 116-photodetector, 117-high speed oscilloscope;
the reflective on-line monitoring technical structure shown in fig. 4 comprises: 201-femtosecond laser, 202-single mode fiber, 203-arbitrary waveform generator, 204-electro-optic modulator, 205 circulator, 206-collimator, 207-diffraction grating, 208-filter, 209-objective, 210-dichroic mirror, 211-laser processing equipment, 212-objective, 213-laser work piece, 214-collimator, 215-dispersion compensating fiber, 216-photodetector, 217 high-speed oscilloscope;
the transmission type on-line monitoring technical structure is characterized in that the 101 femtosecond laser is connected with the 102 dispersion optical fiber for time stretching; the 102 dispersion optical fiber is connected with the 105 collimator; the 103-arbitrary waveform generator is connected with the 104-electro-optic modulator, and the 102-dispersion optical fiber is connected with the 104-electro-optic modulator; said 104-electro-optic modulator is connected to said 105 collimator; said 106 diffraction grating is located between said 105 collimator and said 107 objective lens; the 108 dichroic mirror is positioned between the 107 objective lens and the 111 laser work piece (light transmissible); the 112 filter is positioned between the 111 laser machined part (light-permeable) and the 113 objective lens; the 109 laser processing equipment laser head is aligned with a processed area of a workpiece, and the shot laser forms a certain angle with the normal line of a processing surface at a processing point; the 110 objective lens is positioned between the 109 laser machining device and the 108 dichroic mirror; the 114 diffraction grating is positioned between the 113 objective lens and the 115 collimator, and the 116 photoelectric detector is connected with the 115 collimator; the 116 photoelectric detector is connected with the 117 high-speed oscilloscope;
the reflective imaging system is characterized in that the 201 femtosecond laser is connected with the 202 single-mode optical fiber for time stretching, the 203 arbitrary waveform generator is connected with the 204 electro-optic modulator, and the 202 dispersive optical fiber is connected with the 204 electro-optic modulator; the 204 electro-optic modulator is connected with one end of the 205 circulator; the 206 collimator is connected with the 205 circulator; the 207 diffraction grating is placed 206 between the collimator and the 208 filter at a distance and angle; the 208 filter is positioned between the 207 diffraction grating and the 209 objective, the dichroic mirror is positioned between the 209 objective, the 213-laser work piece (opaque) and the 212 objective at an angle; the 211 laser processing equipment laser head is aligned 213 with the processed area of the laser processing piece, and the emitted laser forms a certain angle with the normal line of the processing surface at the processing point; the 212 objective is placed between the 213 laser work piece and the 210 dichroic mirror; the 214 collimator is connected with the other end of the 205 circulator; the 215 dispersion compensating fiber is connected with the 214 collimator; the 216 photoelectric detector is connected with the 217 dispersion compensation optical fiber; the 217 high-speed oscilloscope is connected with the 216 photoelectric detector;
the following describes a high-speed and high-resolution online monitoring technique for molten pool provided in this embodiment with reference to fig. 3 and 4, which includes the following steps:
respectively establishing a transmission type imaging light path system and a reflection type imaging light path system according to different light transmission properties of processing materials;
a transmissive imaging system comprising the steps of:
step 1, generating femtosecond laser pulses into the 102-dispersion optical fiber by the 101 femtosecond laser;
step 2, performing time domain stretching on different wavelength components in the laser pulse by the 102 dispersion optical fiber, and incidence the laser pulse to the 103 collimator;
step 3, generating a Gaussian or binary signal by the 103 arbitrary waveform generator and entering the 104 electro-optic modulator;
step 3, laser pulses are incident to the 106 diffraction grating by the 105 collimator, are spatially dispersed to form one-dimensional dispersion pulses, and are incident to the 107 objective lens;
step 4, the 108 dichroic mirror transmits the one-dimensional dispersion femtosecond laser pulse;
step 5, focusing the one-dimensional dispersion pulse on a laser workpiece to be detected by the 107 objective lens, and coding the surface information of the observation object onto the spectrum of the one-dimensional dispersion pulse to form a space coding pulse;
step 6, processing laser beams are emitted by the 109 laser processing equipment, and the beams are focused on the 108 dichroic mirror through the 110 objective lens;
step 7, reflecting the focused laser beam onto the 111 laser machined piece by the 108 dichroic mirror for machining;
step 8, the femtosecond laser pulse and processing beam mixed beam penetrates through the light-permeable workpiece and then is emitted to the 112 filter, the 112 filter filters the processing beam, and the coding pulse carrying information is reserved;
step 9, collecting the space coding pulse by the 113 objective lens;
step 10, re-polymerizing the spatially encoded pulses by the 114 diffraction grating;
step 11, converging the space coding pulse to the 115 collimator and making the space coding pulse incident to the 116 photoelectric detector;
step 12, converting the laser pulse signal into an analog electric signal through the 116 photoelectric detector, and transmitting the analog electric signal to a 117 high-speed oscilloscope;
step 13, the 113 high-speed oscilloscope converts the analog electric signal received by the 112 photoelectric detector into a digital electric signal;
a reflective imaging system comprising the steps of:
step 1, generating femtosecond laser pulses into the 202 dispersion optical fiber by the 201 femtosecond laser;
step 2, the femtosecond laser pulse performs time domain stretching on different wavelength components in the laser pulse by the 202 dispersion optical fiber;
step 3, generating a Gaussian or binary signal by the 203 arbitrary waveform generator to enter the 204 electro-optic modulator;
step 4, the femtosecond laser pulse is emitted to the 204 electro-optic modulator by the 202 dispersion optical fiber for coded modulation;
step 5, the femtosecond laser pulse is incident to a 205 circulator by the 204 electro-optic modulator;
step 6, the 205 circulator irradiates the femtosecond laser pulse to the 206 collimator;
step 7, the laser pulse is incident to 207 a diffraction grating by the 206 collimator; spatially dispersing to form a one-dimensional dispersion pulse, and incident to the 208 filter;
step 8, emitting a processing laser beam by the 211 laser processing device, and focusing the beam on the 210 dichroic mirror through the 212 objective lens;
step 8, reflecting the focused laser beam by the 210 dichroic mirror onto the 213 laser work piece for processing;
step 9, the one-dimensional dispersion pulse is transmitted through the 208 filter and the 210 dichroic mirror, the 209 objective lens focuses the one-dimensional dispersion pulse on a 213 laser workpiece (non-transparent) to be monitored, and the surface information of the observation object is encoded on the spectrum of the one-dimensional dispersion pulse to form a space encoding pulse;
step 10, reflecting the space coding pulse and the processing laser beam onto the 210 dichroic mirror because the laser workpiece is opaque;
step 11, collecting the space coding pulses by the 209 objective lens;
step 12, the space coding pulse is emitted to the 208 filter, the 208 filter filters the residual processing laser beam, and the space coding pulse is reserved;
step 13, re-aggregating the space coding pulse by the 207 diffraction grating;
step 14, the space coding pulse is converged to the 214 collimator after passing through the 205 circulator and is incident to the 215-dispersion compensation optical fiber;
step 15, the space coding pulse passes through the 215 dispersion compensation optical fiber and then enters the 216 photoelectric detector;
step 16, converting the laser pulse signal into an analog electric signal through the 216 photoelectric detector, and transmitting the analog electric signal to the 217 high-speed oscilloscope; the 217 high-speed oscilloscope converts the analog electrical signal received by the photoelectric detector into a digital electrical signal;
specifically, in a transmission imaging system, the 106 diffraction grating is disposed in front of the 105 collimator at a distance (e.g., d1=100 mm) and an angle (e.g., θ1=45°); the laser work piece is placed in parallel in front of the 107 objective lens at a distance (e.g. d2=8mm); the 111 laser work piece is placed in parallel in front of the 108 objective lens at the same distance (e.g. d3=8 mm); the 107 objective lens and the 113 objective lens are coaxially and oppositely arranged; the 107-laser processing device is arranged above the processing surface of the 111-laser processing piece, and the laser emitted by the device forms a certain angle (such as theta 2 = 45 degrees) with the normal line of the processing surface at the processing point; the 114 diffraction grating is placed in front of the 111 collimator at a distance (e.g. d4=100 mm) and an angle (e.g. θ2=45°);
specifically, in a reflective imaging system, the 207 diffraction grating is placed in front of the 206 collimator at a distance (e.g., d5=100 mm) and an angle (e.g., θ3=45°); the 213 laser machined parts are arranged in parallel in front of the 209 objective lens at a certain distance (for example d6=8mm); the 211 laser processing device is arranged in front of the 210 dichroic mirror at a certain distance (for example d7=30mm) according to the processing requirement; the 209 objective lens is arranged above the 213 laser processing piece processing surface at a certain distance (d8=10mm), and the laser emitted by the equipment forms a certain angle (for example, θ4=45°) with the normal line of the processing surface at the processing point;
the 101 femtosecond laser and the 201 femtosecond laser are pulse lasers with a central wavelength of 1550nm, a spectral width of 30nm, a pulse width of 100fs and a repetition frequency of 101.7 MHz; the 102 dispersion optical fiber is a single mode optical fiber with group velocity dispersion of 300 ps/nm; the 105 collimator, the 111 collimator, the 206 collimator and the 210 collimator are F260FC-1550 of Thorlabs; the 106 diffraction grating, the 114 diffraction grating and the 207 diffraction grating are selected to be 600/mm in reticle density; the 107 objective lens, the 108 objective lens, the 209 objective lens and the 212 objective lens are MY50X-825 of Thorlabs, the numerical aperture is 0.42, and the magnification is 50X; the selection of the 112 filter plate and the 208 filter plate is FB1550-12 of Thorlabs; the selection of the 108 dichroic mirrors and 210 dichroic mirrors is DMLP1180T of Thorlabs, and the selection of the 103 arbitrary waveform generator and 203 Arbitrary Waveform Generator (AWG) 103 is M8195A of De technology in the United states; the 104 electro-optic modulator and the 204 electro-optic modulator are 40Gbps Mach-Zehnder modulators with 1550nm wave band; the 116 photoelectric detector and the 216 photoelectric detector are APDs 130C/M of Thorlabs; the 117 high-speed oscilloscope and the 217 high-speed oscilloscope are DSA91304A which is De technology in the United states.
In summary, the components in the monitoring system device and the monitoring method are all common components, so that the monitoring system device and the monitoring method are convenient to realize;
it should be noted that although terms of 101 femtosecond laser, 102 single mode fiber, 103-arbitrary waveform generator, 104 electro-optic modulator, 105 collimator, 106 diffraction grating, 107 objective lens, 108 dichroic mirror, 109 laser processing apparatus, 110 objective lens, 111 laser work piece, 112 filter, 113 objective lens, 114 diffraction grating, 115 collimator, 116 photodetector, 117 high speed oscilloscope, 201 femtosecond laser, 202 single mode fiber, 203 arbitrary waveform generator, 204 electro-optic modulator, 205 circulator, 206 collimator, 207 diffraction grating, 208 filter, 209 objective lens, 210 dichroic mirror, 211 laser processing apparatus, 212 objective lens, 213 laser work piece, 214 collimator, 215 dispersion compensating fiber, 216 photodetector, 217 high speed oscilloscope, etc. are used more herein, the possibility of using other terms is not excluded. These terms are used merely to facilitate a description of the nature of the invention and are to be construed as being without any limitation thereto.
Finally, it should be noted that the above-mentioned embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same, and although the present invention has been described in detail with reference to examples, it should be understood by those skilled in the art that modifications and equivalents may be made to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention, and all such modifications and equivalents are intended to be encompassed in the scope of the claims of the present invention.
Claims (4)
1. A one-dimensional high-speed and high-resolution imaging system is characterized in that the system is a one-dimensional imaging system based on a transmission principle;
a light source assembly: as an imaging system light source;
one-dimensional dispersive element: the method is used for carrying out space conversion and one-dimensional dispersion Fourier transform on laser;
and a focusing module: for focusing the spatial laser pulses;
and a modulation component: for modulating the laser pulses;
and a filtering component: the filter is used for filtering and separating the space light beam;
a signal collection assembly: the device is used for collecting dynamic detection signals of the laser processing piece in real time, and converting photoelectric and analog electric signals and processing the signals;
the one-dimensional dispersive element includes: an optical fiber, a diffraction grating; the optical fiber performs dispersion Fourier transform on different component lights in laser signal pulses generated by the light source component in the time domain; the diffraction grating projects different wavelength components of the pulse spectrum to different positions of the space, so that the space information of the molten pool to be detected is mapped onto the frequency spectrum of the pulse; the wavelength parameters of the light source component laser and the wavelength parameters of the laser used for processing are different, and the reflection and refraction of the processing laser can be prevented from interfering or affecting the observation laser pulse by filtering the processing laser through the filtering component;
the modulation assembly 1 comprises: an arbitrary waveform generator, modulator 1; the modulation assembly 2 includes: a modulator 2; in a monitoring light path, generating random binary codes by using an arbitrary waveform generator, modulating the binary codes on a time domain signal of monitoring pulse laser by using a modulator 1, and performing code modulation on the laser pulse; the modulator 2 changes the propagation direction of the light pulse, so that light spots are focused at different positions of a molten pool of processing materials, and one-dimensional dispersion of the pulse is realized;
in the one-dimensional imaging system, the light path is divided into two paths: a monitoring light path and a processing light path;
the monitoring light path is emitted by the light source component, passes through the one-dimensional dispersion component 1, the modulation component 2, the one-dimensional dispersion component 2, the focusing module 1, the light-permeable laser processing piece, the focusing module 2 and the filtering component, and finally enters the signal collecting component; the processing light path is emitted by a light source of the laser processing equipment, enters a light-permeable laser workpiece through a focusing module 3, and the residual laser workpiece is transmitted through the focusing module 2 and enters a filtering component to be filtered; in addition, the square wave emitted by the modulation component 1 is converged into the detection light path in the one-dimensional dispersion components 1 and 2.
2. A one-dimensional high-speed and high-resolution imaging system is characterized in that the system is a one-dimensional imaging system based on a reflection principle; comprising the following steps:
a light source assembly: as an imaging system light source;
one-dimensional dispersive element: the method is used for carrying out space conversion and one-dimensional dispersion Fourier transform on laser;
and a focusing module: for focusing the spatial laser pulses;
the circulator is as follows: the system is used for realizing bidirectional optical signal transmission on a single optical fiber in a system optical path;
and a modulation component: for modulating the laser pulses;
and a filtering component: the filter is used for filtering and separating the space light beam;
a signal collection assembly: the device is used for collecting dynamic detection signals of the laser processing piece in real time, and converting photoelectric and analog electric signals and processing the signals;
the one-dimensional dispersive element includes: an optical fiber, a diffraction grating; the optical fiber performs dispersion Fourier transform on different component lights in laser signal pulses generated by the light source component in the time domain; the diffraction grating projects different wavelength components of the pulse spectrum to different positions of the space, so that the space information of the molten pool to be detected is mapped onto the frequency spectrum of the pulse; the wavelength parameters of the light source component laser and the wavelength parameters of the laser used for processing are different, and the reflection and refraction of the processing laser can be prevented from interfering or affecting the observation laser pulse by filtering the processing laser through the filtering component;
the modulation assembly 1 comprises: an arbitrary waveform generator, modulator 1; the modulation assembly 2 includes: a modulator 2; in a monitoring light path, generating random binary codes by using an arbitrary waveform generator, modulating the binary codes on a time domain signal of monitoring pulse laser by using a modulator 1, and performing code modulation on the laser pulse; the modulator 2 changes the propagation direction of the light pulse, so that light spots are focused at different positions of a molten pool of processing materials, and one-dimensional dispersion of the pulse is realized;
in the one-dimensional imaging system, the light path is divided into two paths: a monitoring light path and a processing light path;
the monitoring light path is emitted by the light source component, enters the non-light-permeable laser processing piece through the one-dimensional dispersion component 1, the one-dimensional dispersion component 2, the circulator, the filter component, the focusing module 1, is reflected to the focusing module 1 by the processing piece, passes through the filter component, is converted into the light path direction by the circulator, and finally enters the signal collecting component; the processing light path is emitted by a light source of the laser processing equipment, enters into a non-light-permeable laser workpiece through a focusing module 3, is reflected by a residual laser workpiece, enters into a filtering component through a focusing module 1 and is filtered; in addition, the square wave emitted by the modulation component 2 merges into the detection light path in the one-dimensional dispersion components 1, 2.
3. A method of real-time puddle monitoring of a one-dimensional high-speed, high-resolution imaging system of claim 1, comprising the steps of:
step 1, the sequence of starting the light source assembly and the laser in the laser processing equipment is as follows: the detection light path light source assembly is started first, and a laser used for laser processing is started after the light source assembly and the observation system reach a stable state, so that the situation that effective observation cannot be obtained in the early stage of a molten pool phenomenon can be avoided;
step 2, the light source component emits laser pulses as a light source of the monitoring imaging system;
step 3, the laser pulse is incident to the one-dimensional dispersion component 1, and the laser pulse is subjected to time domain stretching;
step 4, the modulating component 1 generates square waves to modulate the laser pulse;
step 5, the modulated laser pulse subjected to time domain stretching is emitted to the modulation component 2;
step 6, the laser pulse is emitted to a one-dimensional dispersion component 2, and different wavelength components of a pulse spectrum are projected to different positions of a space to perform one-dimensional dispersion;
step 7, focusing on a laser workpiece through the focusing module;
step 8, collecting laser pulses carrying molten pool observation information and laser used for laser processing emitted by the light-permeable laser workpiece by the focusing module, injecting the laser pulses into the filtering component, filtering processing laser, and reserving the laser pulses with coding information;
and 9, the space coding pulse is incident to the signal collecting assembly, and the detection signal is collected, converted into digital-electric and analog-electric signals and processed, so that the real-time dynamic change of the laser workpiece is observed.
4. A method of real-time puddle monitoring of a one-dimensional high-speed, high-resolution imaging system of claim 2, comprising the steps of:
step 1, firstly, starting a light source assembly, and starting a laser for laser processing after the light source assembly and an observation system reach a stable state;
step 2, the light source component emits laser pulse as an imaging system light source;
step 3, the laser pulse is incident to the one-dimensional dispersion component 1, and the laser pulse is subjected to time domain stretching;
step 4, the modulating component 1 generates square waves to modulate the laser pulse;
step 5, the modulated laser pulse subjected to time domain stretching is emitted to the modulation component 2;
step 6, the laser pulse is emitted to a one-dimensional dispersion component 2, and different wavelength components of a pulse spectrum are projected to different positions of a space to perform one-dimensional dispersion;
step 7, focusing on a laser workpiece through the focusing module;
step 8, collecting laser pulses carrying molten pool observation information and laser used for laser processing by the opaque laser workpieces through the focusing module, injecting the laser pulses and the laser used for laser processing into the filtering component, filtering processing laser, and reserving the laser pulses with coded information;
step 9, injecting the space coding pulse into the circulator, and injecting the space coding pulse from the other output port of the circulator to the signal collecting assembly;
and step 10, the laser pulse is incident to the signal collecting assembly along an original light path, and the detection signal is collected, converted into digital-to-electric and analog-to-digital signals and processed, so that the real-time dynamic change of a laser workpiece is observed.
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