阅读说明：本技术 超短脉冲激光烧蚀物体的超快连续三维成像系统及方法 (Ultrafast continuous three-dimensional imaging system and method for ablating object by ultrashort pulse laser ) 是由 姜澜 郭宝山 张天勇 于 2021-01-21 设计创作，主要内容包括：本发明涉及一种超短脉冲激光烧蚀物体的超快连续三维成像系统及方法,属于超快成像领域。本发明可以实现超高时间分辨率的物体表面三维轮廓信息的获取与复原。系统具体包括超短脉冲激光光源、超连续谱发生器、脉冲分离延时器、多频脉冲干涉条纹发生器、起偏器、时间延迟平台、样品、图像获取装置、计算机、分束-合束镜、反射镜及图像三维轮廓提取方法。本发明可实现超短脉冲激光烧蚀物体材料过程中的超快连续三维观测,时间分辨率达飞秒-皮秒量级,可呈现物体被加工过程中表面三维形貌,增强实验过程中的连续可观性,为超短脉冲激光烧蚀加工物体的机理研究提供重要辅助作用。(The invention relates to an ultrafast continuous three-dimensional imaging system and method for ablating an object by ultrashort pulse laser, and belongs to the field of ultrafast imaging. The method can realize the acquisition and restoration of the three-dimensional contour information of the object surface with ultrahigh time resolution. The system specifically comprises an ultrashort pulse laser source, a supercontinuum generator, a pulse separation delayer, a multi-frequency pulse interference fringe generator, a polarizer, a time delay platform, a sample, an image acquisition device, a computer, a beam splitting-combining mirror, a reflector and an image three-dimensional contour extraction method. The invention can realize the ultrafast continuous three-dimensional observation in the process of ablating object materials by the ultrashort pulse laser, the time resolution reaches the femtosecond-picosecond magnitude, the surface three-dimensional appearance of the object in the process of being processed can be presented, the continuous observability in the experimental process is enhanced, and the invention provides an important auxiliary function for the mechanism research of ablating the object by the ultrashort pulse laser.)

1. The ultrafast continuous three-dimensional imaging method for the ultrashort pulse laser ablation object is characterized in that: time separation is carried out on the frequency spectrums of different wave bands in the super-continuum spectrum to generate pulse sequences, then the pulse sequences are equally divided, so that the frequency spectrums in the same wave band range generate interference fringes in a one-to-one correspondence mode on a time axis, then a plurality of interference fringe patterns with ultra-short time intervals irradiate a sample, finally the interference fringes are captured by different CCDs respectively, the three-dimensional appearance of the sample is obtained after the interference fringes are processed by a computer, and ultra-fast continuous three-dimensional observation is achieved.

2. The ultrafast continuous three-dimensional imaging method for the ultrashort pulse laser ablation object is characterized in that: after the ultrashort pulse laser light source emits ultrashort pulse laser light beams, the ultrashort pulse laser light beams are divided into pump light beams and detection light beams through a beam splitting-combining mirror, wherein the pump light beams are focused on the surface of a sample through a lens and are ablated, and the detection light beams irradiate the surface of the sample and are reflected to an image acquisition device for imaging; the pump beam is adjusted to a polarization state different from that of the detection beam by a polarizer, and then reaches a sample through a time delay platform for ablation processing; the detection light beam generates a super-continuum spectrum with a plurality of frequency doubling layers and extremely wide frequency spectrum after passing through a super-continuum spectrum generator, then generates continuous sub-pulse strings with specific intervals and different wavelengths in time after passing through the pulse separation delayer, and is further equally divided into two pulse strings by a beam splitting and combining mirror, wherein one pulse string is divided into pulses with different wavelength ranges by dichroic mirrors with different cut-off wave bands, and the pulses are correspondingly overlapped with pulse strings which are not divided one by one on wave bands, namely, the pulses correspond to one another in time, and interference fringes with different wavelengths are generated; thus, a plurality of pulse interference fringe patterns with different wavelengths and with time intervals irradiate a sample in sequence, the interference fringe patterns carrying object surface profile information are reflected by a beam splitting-combining mirror, then reflected by a dichroscope with the same cut-off frequency, reach a corresponding CCD and are captured, and then the three-dimensional profile of the object surface is extracted and recovered on a computer by an image three-dimensional profile extraction method, and is drawn into a three-dimensional graph.

3. An apparatus for implementing the method of claim 1 or 2, characterized in that: the system comprises an ultrashort pulse laser source, a supercontinuum generator, a pulse separation delayer, a multi-frequency pulse interference fringe generator, a polarizer, a time delay platform, a sample, an image acquisition device and a computer;

after the ultrashort pulse laser light source (1) sends out an ultrashort pulse laser beam, the ultrashort pulse laser beam is divided into a pump beam and a detection beam through the I beam splitting-combining mirror (2); after the direction of the pump beam is changed by the first reflector (6), the pump beam is adjusted to a polarization state different from that of the detection beam by the polarizer (7), and then is focused on the surface of a sample (9) by a lens after passing through the time delay platform (8) to be ablated; the detection light beam generates a super-continuum spectrum lambda with a plurality of frequency doubling layers and extremely wide frequency spectrum after passing through a super-continuum spectrum generator (3)_nThen generating continuous sub-pulse trains with different wavelengths and time intervals in time after passing through the pulse separation delayer (4); and then the sample enters the multi-frequency pulse interference fringe generator (5) to generate multi-frequency interference fringe patterns with specific time intervals and different wavelength ranges, the multi-frequency interference fringe patterns irradiate the sample ablated by the pump light, then the multi-frequency interference fringe patterns carrying the surface information of the sample are respectively captured by different CCDs in the image acquisition device (10), and are stored in the computer (11), and finally the structural information of the surface of the sample is restored by an image three-dimensional contour extraction method.

4. The apparatus of claim 3, wherein: and the pump light beam passes through the time delay platform (8), then passes through the V-th reflecting mirror (20) and the VI-th reflecting mirror (21), and is focused on the surface of the sample (9) by a lens.

5. The apparatus of claim 3, wherein: the detection light beam is further equally divided into two pulse trains I and II by a II beam splitting-combining mirror (12) after passing through a pulse separation delayer (4), wherein the pulse train I respectively generates three sub-pulses lambda with different wavelength ranges after passing through an I dichroscope (13), an II dichroscope (14) and an II reflector (15)₁、λ₂、λ₃The pulse train II reflected by the third reflector (16) is converged at the third beam splitting-combining mirror (17), the fourth beam splitting-combining mirror (18) and the fifth beam splitting-combining mirror (19) to form a one-to-one corresponding coincidence relation on time and wave bands, so that the frequency spectrums in different wave band ranges form interference fringes separated from each other on time, and then the interference fringes are transmitted through the VI beam splitting-combining mirrorThe surface of a sample (9) is irradiated by a beam mirror (22), after the surface is reflected by the sample (9) and is reflected by a VI beam splitting-combining mirror (22), the surface enters a first CCD (26), a second CCD (27) and a third CCD (28) respectively after passing through a III dichroscope (23), an IV dichroscope (24) and a VI reflecting mirror (25), and finally the three-dimensional profile of the surface of an object is extracted and recovered by an image three-dimensional profile extraction method on a computer to be drawn into a three-dimensional graph.

6. The apparatus of claim 3, wherein: the ultrashort pulse laser light source is pulse laser with single wavelength and emitted by a nanosecond, picosecond or femtosecond laser, and the pulse duration time is respectively nanosecond, picosecond or femtosecond;

the supercontinuum generator is a combination of a focusing objective lens, a photonic crystal fiber and a focusing objective lens;

the pulse separation delayer is dispersive glass or an optical fiber;

the multi-frequency pulse interference fringe generator is composed of a beam splitting-combining mirror, a dichroscope and a reflecting mirror, reference light with time-separated multi-frequency pulse sequences is equally divided into two pulse sequences with the same energy through the beam splitting-combining mirror, wherein one pulse sequence is reflected and transmitted by the binomial mirrors with different cut-off frequencies to generate sub-pulses with mutually separated space and different wavelength ranges, the sub-pulses and the other pulse sequence generate one-to-one correspondence in time and wave bands to generate interference fringes with different wavelength ranges, and the multi-frequency pulses originally have intervals in time, so the interference fringes also have the same time intervals;

the polarizer is used for adjusting the polarization state of the pump light, so that the interference with the probe light is avoided, the imaging is influenced, and unnecessary interference fringe patterns are generated;

the sample is any object material which can be processed by ultrashort pulse laser;

the image acquisition devices are CCD cameras which are placed at different positions and respectively receive image signals, and the received information is an interference fringe pattern which is reflected by the sample and has sample contour information;

the image three-dimensional contour extraction method is a digital image three-dimensional contour extraction technology based on a computer programming language.

Technical Field

The invention relates to an ultrafast continuous three-dimensional imaging system and method for ablating an object by ultrashort pulse laser, and belongs to the field of ultrafast imaging.

Background

Ultrashort pulse laser has very short time scale (ns-ps-fs) and ultrahigh energy density (>10¹⁴W/cm²) Can be used for processing a material on the surface or in the materialFine and complicated micro-nano structure. However, the interaction between the ultrashort pulse laser and the material is a transient process, and the mechanism phenomenon is very difficult to observe. The method comprises laser shock wave front propagation in picosecond time scale, material molecule relaxation vibration and the like; although people explain the processing mechanism of the material through the surface or the internal appearance of the processed material, the mechanism of the intermediate reaction process is very complex and is not easy to explain clearly.

At present, a relatively mature ultrafast observation means is a pumping detection technology, femtosecond-magnitude time-delay photography can be realized at the fastest speed, but the method can only realize single-frame imaging, is not applicable to processes which are difficult to copy or non-repeated, and cannot carry out more detailed observation on the continuous reaction process of ultrafast laser and materials, and in view of the defects, an ultrashort time interval is required on the imaging means, namely imaging time resolution; it is also desirable to be able to observe the progress of the sustained reaction, i.e., the depth of imaging.

In addition, the imaging means is only two-dimensional imaging, including other ultrafast imaging observation technologies, but in order to more intuitively show the morphology change of the material after the ultrashort pulse laser ablation, the three-dimensional imaging technology is indispensable, and although there is a more perfect three-dimensional imaging technology in the field, most of the imaging means is in the macroscopic visual field, and few researches are made on ultrafast imaging and micro-nano imaging, especially on how to observe the continuous three-dimensional imaging with ultrahigh time resolution when the ultrashort pulse laser ablation object is observed. Therefore, a technology which can realize ultrafast multi-frame continuous imaging and show the three-dimensional shape change of the material is urgently needed to further explain the action mechanism of the ultrashort pulse laser and the material.

Disclosure of Invention

The invention aims to solve the technical problems that the surface appearance characteristics of an object are difficult to obtain and the interaction mechanism phenomenon of the object material and laser cannot be subjected to ultrafast continuous effective observation in the continuous action process of the ultrashort pulse laser for ablating the object, provides an ultrafast continuous three-dimensional imaging system and method for ablating the object by the ultrashort pulse laser, and can realize the acquisition and restoration of the three-dimensional profile information of the surface of the object with ultrahigh time resolution.

The purpose of the invention is realized by the following technical scheme.

An ultrafast continuous three-dimensional imaging method for ablating an object by ultrashort pulse laser includes the steps of separating the frequency spectrums of different wave bands in a supercontinuum in time to generate pulse sequences, dividing the pulse sequences equally to enable the frequency spectrums in the same wave band range to generate interference fringes in a one-to-one correspondence mode on a time axis, irradiating a sample by a plurality of interference fringe patterns with ultrashort time intervals, finally respectively capturing the interference fringes by different CCDs, processing the interference fringes by a computer to obtain the three-dimensional appearance of the sample, and achieving ultrafast continuous three-dimensional observation.

An ultrafast continuous three-dimensional imaging method for ablating an object by ultrashort pulse laser comprises the steps that after the ultrashort pulse laser light source emits ultrashort pulse laser light beams, the ultrashort pulse laser light beams are divided into pump light beams and detection light beams by a beam splitting-combining mirror, wherein the pump light beams are focused on the surface of a sample through a lens to ablate the sample, and the detection light beams irradiate the surface of the sample and then are reflected to an image acquisition device for imaging; the pump beam is adjusted to a polarization state different from that of the detection beam by the polarizer, and then reaches the sample through the time delay platform for ablation processing. The detection light beam generates a super-continuum spectrum with a plurality of frequency doubling layers and extremely wide frequency spectrum after passing through a super-continuum spectrum generator, then generates continuous sub-pulse strings with specific intervals and different wavelengths in time after passing through the pulse separation delayer, and is further equally divided into two pulse strings by a beam splitting and combining mirror, wherein one pulse string is divided into pulses with different wavelength ranges by dichroic mirrors with different cut-off wave bands, and the pulses are correspondingly overlapped with pulse strings which are not divided one by one on wave bands, namely, the pulses correspond to one another in time, and interference fringes with different wavelengths are generated; thus, a plurality of pulse interference fringe patterns with different wavelengths and with time intervals irradiate a sample in sequence, the interference fringe patterns carrying object surface profile information are reflected by a beam splitting-combining mirror, then reflected by a dichroscope with the same cut-off frequency, reach a corresponding CCD and are captured, and then the three-dimensional profile of the object surface is extracted and recovered on a computer by an image three-dimensional profile extraction method, and is drawn into a three-dimensional graph.

The device for realizing the method comprises an ultra-short pulse laser light source, a super-continuum spectrum generator, a pulse separation delayer, a multi-frequency pulse interference fringe generator, a polarizer, a time delay platform, a sample, an image acquisition device, a computer, a beam splitting-combining mirror and a reflector.

The ultrashort pulse laser light source is pulse laser with single wavelength and emitted by a nanosecond, picosecond or femtosecond laser, and the pulse duration time is respectively nanosecond, picosecond or femtosecond.

The supercontinuum generator is a combination of a focusing objective lens, a photonic crystal fiber and a focusing objective lens.

The pulse separation delayer is dispersive glass or optical fiber.

The multi-frequency pulse interference fringe generator is composed of a beam splitting-combining mirror, a dichroscope and a reflecting mirror, reference light with time-separated multi-frequency pulse sequences is equally divided into two pulse sequences with the same energy through the beam splitting-combining mirror, one pulse sequence is reflected and transmitted by the two dichroscope with different cut-off frequencies to generate sub-pulses with mutually separated space and different wavelength ranges, the sub-pulses and the other pulse sequence generate one-to-one correspondence in time and wave bands to generate interference fringes with different wavelength ranges, and the multi-frequency pulses originally have intervals in time, so the interference fringes also have the same time intervals.

The polarizer is used for adjusting the polarization state of the pump light, so that the interference with the probe light is avoided, the imaging is not influenced, and unnecessary interference fringe patterns are generated.

The sample is any object material capable of being processed by ultrashort pulse laser.

The image acquisition devices are CCD cameras which are placed at different positions and respectively receive image signals, and the received information is interference fringe patterns which are reflected by the sample and have sample contour information.

The image three-dimensional contour extraction method is a digital image three-dimensional contour extraction technology based on a computer programming language.

Advantageous effects

Compared with other ultrafast continuous imaging technologies, the ultrafast continuous three-dimensional imaging system and the ultrafast continuous three-dimensional imaging method for the object ablated by the ultrashort pulse laser can realize ultrafast continuous three-dimensional observation in the process of ablating the object material by the ultrashort pulse laser, the time resolution reaches the femtosecond-picosecond magnitude, the surface three-dimensional appearance of the object in the process of being processed can be presented, the continuous observability in the experimental process is enhanced, and an important auxiliary effect is provided for the mechanism research of the object ablated by the ultrashort pulse laser.

Drawings

FIG. 1 is a schematic diagram of an ultrafast continuous three-dimensional imaging system for ablating an object with ultrashort pulsed laser;

FIG. 2 is a schematic diagram of an ultrafast continuous three-dimensional imaging optical path;

FIG. 3 is a flow chart of an ultrafast continuous three-dimensional imaging method for ablating an object with ultrashort pulse laser.

Shown in the figure: 1 is an ultrashort pulse laser light source; 2 is the first beam splitting-combining mirror; 3 is a supercontinuum generator; 4 is a pulse separation delayer; 5 is a multi-frequency pulse interference fringe generator; 6 is the first reflector; 7 is a polarizer; 8 is a time delay platform; 9 is a sample; 10, an image acquisition device; 11 is a computer; 12 is the second beam splitting-combining mirror; 13 the second-item color mirror I; 14 is a second-term color mirror; 15 a second mirror; 16 is a III mirror; 17 is a third beam splitting-combining mirror; 18 is the IV beam splitting-combining mirror; 19 is a Vth beam splitting-combining mirror; 20 is a IV reflector; 21 is a Vth reflecting mirror; 22 is a VI beam splitting-combining mirror; 23 is a III second-item color mirror; 24 is a fourth dichroscope; 25 is a VI reflector; 26 is a first CCD; 27 is a second CCD; and 28 is a third CCD.

Detailed Description

The invention will be further explained and explained with reference to the drawings and the detailed working mode, which will facilitate the understanding of the skilled person.

The invention discloses an ultrafast continuous three-dimensional imaging system and method for ablating an object by ultrashort pulse laser, which comprises an ultrashort pulse laser light source 1, a supercontinuum generator 3, a pulse separation delayer 4, a multi-frequency pulse interference fringe generator 5, a polarizer 7, a time delay platform 8, a sample 9, an image acquisition device 10, a computer 11, a beam splitting-combining mirror, a reflecting mirror and an image three-dimensional contour extraction method.

The ultrashort pulse laser light source 1 is an ultrashort pulse laser which is emitted by a nanosecond, picosecond or femtosecond laser and has a single wavelength and nanosecond, picosecond or femtosecond pulse duration, has the characteristics of ultrastrong energy and ultrashort time scale, and can be used for ablation processing of any material; the supercontinuum generator 3 consists of a pair of focusing objective lenses and a photonic crystal fiber and can generate a supercontinuum with a plurality of frequency doubling layers and extremely wide frequency spectrum; the pulse separation delayer 4 is made of dispersive glass or optical fiber, and can control the delay time of multiple pulses according to different thicknesses; the multi-frequency pulse interference fringe generator 5 consists of a second beam splitting-combining mirror 12, a third beam splitting-combining mirror 17, a fourth beam splitting-combining mirror 18, a fifth beam splitting-combining mirror 19, a first second chromatic mirror 13, a second chromatic mirror 14, a second reflecting mirror 15 and a third reflecting mirror 16, and can generate interference fringe patterns with different wavelengths at specific time intervals; the polarizer 7 changes the polarization state of the pump light to avoid interference with the imaged detection light; the time delay platform 8 is used for adjusting the time delay between the pump light and the probe light, more precisely, adjusting the time interval between the pump light and the interference fringes generated by the multi-frequency pulse interference fringe generator 5 reaching the sample; the image acquisition device 10 is 3 CCD cameras with the same specification parameters and is used for acquiring interference fringe patterns reflected back by the sample; the image three-dimensional contour extraction method is an image three-dimensional contour extraction method based on computer languages, and can be used for extracting and restoring a three-dimensional contour in a graph acquired by a CCD.

An ultrafast continuous three-dimensional imaging system and method for ablating objects by ultrashort pulse laser comprises the specific process that after an ultrashort pulse laser light source 1 emits ultrashort pulse laser light beams, the ultrashort pulse laser light beams are divided into pump light beams and detection light beams by an I-th beam splitting-combining mirror 2. The pumping beam is changed in direction by the first reflector 6, adjusted to a polarization state different from that of the detection beam by the polarizer 7, passes through the time delay platform 8, and then passes through the V-th reflector 20 and the V-th reflectorA VI reflecting mirror 21 which is focused on the surface of the sample 9 by a lens and is ablated; the detection beam generates a super-continuum spectrum lambda with a plurality of frequency doubling layers and extremely wide frequency spectrum after passing through a super-continuum generator 3_nThen, the pulse separation delay 4 generates continuous sub-pulse trains with specific intervals in time and different wavelengths, and the continuous sub-pulse trains are further equally divided into two pulse trains I and II by a second beam splitting-combining mirror 12, wherein the pulse train I generates three sub-pulses lambda with different wavelength ranges after passing through a first dichroscope 13, a second dichroscope 14 and a second reflector 15 respectively₁、λ₂、λ₃And the pulse train II reflected by the third reflector 16 is converged at the third beam splitting and combining mirror 17, the fourth beam splitting and combining mirror 18 and the fifth beam splitting and combining mirror 19 to form a one-to-one corresponding coincidence relation on time and wave bands, so that frequency spectrums in different wave band ranges form interference fringes separated from each other in time, then the interference fringes irradiate the surface of the sample 9 through the sixth beam splitting and combining mirror 22, are reflected by the sample 9 and reflected again by the sixth beam splitting and combining mirror 22, then enter the first CCD26, the second CCD27 and the third CCD28 respectively through the third dichroscope 23, the fourth dichroscope 24 and the sixth reflector 25, and finally the three-dimensional profile of the surface of the object is extracted and recovered by an image three-dimensional profile extraction method on a computer to be drawn into a three-dimensional graph.

Example 1:

the ultra-short pulse laser light source 1 emits pulse laser with 50fs pulse width and horizontal polarization, and the pulse laser is reflected into a pump beam by the I beam splitting-combining mirror 2 and is transmitted into a detection beam. Wherein, the pumping beam is converted into vertical polarized light through the polarizer 7 after the direction of the pumping beam is adjusted by the first reflector 6, and then passes through the time delay platform 8, the V-th reflector 20 and the VI-th reflector 21 and is focused on the surface of the sample 9 by a lens for ablation; in the process of pump beam propagation, a probe beam firstly enters a super-continuum spectrum generator 3 consisting of an objective lens, a photonic crystal fiber and the objective lens to generate a super-continuum spectrum with a spectrum of 350nm-1100nm, then the spectrum is separated in time through a pulse separator 4, and a time interval of several femtoseconds can be realized among the spectrums; pulse sequence lambda with a multi-frequency spectrum_n(350nm-1100nm) into a multi-pulse dryThe fringe generator 5 is first equally divided into λ by the second beam splitting/combining mirror 12_n1And λ_n2One beam of lambda_n1Three sub-pulses lambda with different wavelength ranges are respectively generated through an I second-term color mirror 13 (with the cut-off wavelength of 640nm), an II second-term color mirror 14 (with the cut-off wavelength of 875nm) and an II reflecting mirror 15₁(350nm-640nm)、λ₂(640nm-875nm)、λ₃(875nm-1100nm), wherein₁At the III beam splitting-combining mirror 17 with lambda_n2Combined at λ_n2Interference, lambda, is formed in the corresponding wave band range₂And λ₃As well as so. Finally, λ₁、λ₂、λ₃And λ_n2The time and the wave bands form a one-to-one correspondence coincidence relation, the frequency spectrums in different wave band ranges form interference fringes which are separated from each other in time, then the interference fringes irradiate the surface of the sample 9 through the VI beam splitting-combining mirror 22, the interference fringes carrying the appearance of the surface of the sample 9 at different moments are reflected back to the VI beam splitting-combining mirror 22, then the interference fringes are reflected again, then the interference fringes pass through the III second-item chromatic mirror 23, the IV second-item chromatic mirror 24 and the VI reflecting mirror 25 and then respectively enter the first CCD26, the second CCD27 and the third CCD28, and finally the three-dimensional contour of the surface of the object is extracted and recovered through an image three-dimensional contour extraction method on a computer, and a continuous three-dimensional graph is drawn. Thus, the three-dimensional contour information of the object surface with ultrahigh time resolution is completed, the time resolution among images is several femtoseconds, and the maximum space resolution is 1.22 um.

The above detailed description is intended to illustrate the objects, aspects and advantages of the present invention, and it should be understood that the above detailed description is only exemplary of the present invention and is not intended to limit the scope of the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.