An on-line detection and regulation device and method for laser processing

Abstract

The application discloses an online detection regulation and control device and method for laser processing, and aims at solving the technical problem of low laser processing precision caused by large volume and low expansion capacity of the existing laser regulation and control device. Specifically, the device comprises a light source, a first grating assembly, a second grating assembly, a beam splitter assembly, a laser detector and a control unit. The light source emits incident laser. The first grating assembly and the second grating assembly are arranged on the light path of the incident laser in sequence, and are used for adjusting the pulse width of the incident laser in real time and forming first outgoing light. The beam splitter assembly is arranged on the light path of the first outgoing light, and is used for splitting the first outgoing light into processing laser and detection laser. The laser detector is arranged on the light path of the detection laser, and is used for detecting the pulse width of the detection laser in real time. The control unit is connected with the first grating assembly, the second grating assembly, the beam splitter assembly and the laser detector, and is used for adjusting the first grating assembly, the second grating assembly and the beam splitter assembly in real time.

Description

TECHNICAL FIELD

[0001] The present application relates to a pulse on-line detection device and method, in particular to an on-line detection and regulation device and method for laser processing. BACKGROUND

[0002] In the process of ultrafast laser processing, the pulse width of the emitted laser itself will be broadened or compressed due to the thermal effect of the internal pulse width control components of the laser, the thermal gradient of cooling, mechanical vibration, etc. In addition, the pulse width will be broadened by dispersion effect and nonlinear effect caused by many transmission optical elements and air during the transmission of the laser, for example, 1 cm of glass will broaden the pulse dispersion of 100 fs by about 200 fs; 3 m of air will broaden the pulse dispersion of 5 fs to about 15 fs; this will seriously reduce the roughness, heat affected zone, and consistency of the structure size of the laser processing, thereby reducing the quality of the laser processing. Therefore, it is extremely necessary to study the on-line detection and correction technology of ultrafast laser pulse width.

[0003] In the field of laser processing, there is no device or method related to on-line detection and regulation of laser pulse width reported. However, in the laser technology, the correction of pulse width fluctuation will use the broadening and compression technology of laser pulse width. This technology is mainly used in laser technology, which can be divided into three categories in principle:

[0004] First, prism pair, by designing the distance between the prism pair and adjusting the insertion position to change the size of the positive and negative second-order dispersion, the control range is 100 fs, which is suitable for compensating the dispersion of 1 cm of material and femtosecond pulse laser greater than 20 fs, commonly used in femtosecond laser resonator, has the advantages of high light energy utilization rate, can correct second-order dispersion and third-order dispersion, but when the broadening ratio reaches 10 4 When the broadening ratio reaches 10, for a wide-spectrum femtosecond laser pulse, the size of the prism will exceed the acceptable range, resulting in a very large device, and the large material insertion amount at the second prism will introduce a large amount of positive dispersion, thereby reducing the broadening capacity of the prism.

[0005] Second, grating pair, by designing the distance between the grating pair and the incident angle to achieve the broadening or compression of the pulse width, has the advantages of providing high value of group velocity dispersion and large pulse width control range, but it cannot completely compensate the high-order dispersion introduced by the material in the amplification process, so the compressed pulse cannot reach the Fourier transform limit, and the low transmission efficiency of the compressor grating will lose a lot of energy.

[0006] Third, GTI mirror, chirped mirror, etc., which can be used for precise control of small dispersion, but the dispersion compensation amount is difficult to achieve continuous adjustment within a certain range, and is only suitable for dispersion control of periodic pulse (<10 fs). SUMMARY

[0007] The application aims to provide an online detection regulation device and method for laser processing, so as to solve the technical problem of low laser processing precision caused by large volume and low expansion ability of the existing laser regulation device.

[0008] In order to achieve the above-mentioned purpose, the application provides an online detection regulation device for laser processing, which is characterized in that it comprises a light source, a first grating assembly, a second grating assembly, a beam splitter assembly, a laser detector and a control unit.

[0009] The light source emits incident laser.

[0010] The first grating assembly and the second grating assembly are arranged in sequence on the light path of the incident laser, for adjusting the pulse width of the incident laser in real time, and forming first outgoing light.

[0011] The beam splitter assembly is arranged on the light path of the first outgoing light, for splitting the first outgoing light into processing laser and detection laser.

[0012] The laser detector is arranged on the light path of the detection laser, for detecting the pulse width of the detection laser in real time.

[0013] The control unit is connected with the first grating assembly, the second grating assembly, the beam splitter assembly and the laser detector, for adjusting the first grating assembly, the second grating assembly and the beam splitter assembly in real time according to the detection result of the laser detector.

[0014] Further, the first grating assembly comprises a first spatial light modulator loaded with a grating hologram, a second displacement platform, a first dispersion prism and a third displacement platform.

[0015] The first spatial light modulator is arranged on the second displacement platform and located on the light path of the incident laser; the second displacement platform is used for adjusting the position and angle of the first spatial light modulator.

[0016] The first dispersion prism is arranged on the third displacement platform; the third displacement platform is used for moving the first dispersion prism to / from the light path of the incident laser; the first dispersion prism is used for causing the incident laser to disperse and be incident to the first spatial light modulator, receiving the light modulated by the first spatial light modulator and refracting it to form refracted light of the incident laser.

[0017] The first spatial light modulator, the second displacement platform and the third displacement platform are connected with the control unit respectively.

[0018] The second grating assembly is arranged on the light path of the refracted light.

[0019] Further, the second grating assembly comprises a second spatial light modulator carrying a grating hologram, and a fourth displacement platform, a second dispersion prism and a fifth displacement platform;

[0020] The second spatial light modulator is arranged on the fourth displacement platform and located on the light path of the refracted light; the fourth displacement platform is used to adjust the position and angle of the second spatial light modulator;

[0021] The second dispersion prism is arranged on the fifth displacement platform; the fifth displacement platform is used to move the second dispersion prism to / from the light path of the refracted light; the second dispersion prism is used to receive the refracted light and make it incident on the second spatial light modulator, and receive the light modulated by the second spatial light modulator and reflect it into the first exit light;

[0022] The second spatial light modulator, the fourth displacement platform and the fifth displacement platform are respectively connected with the control unit.

[0023] Further, an isosceles prism assembly is arranged between the first grating assembly and the second grating assembly and located on the light path of the refracted light;

[0024] The isosceles prism assembly comprises a reflective isosceles prism and a sixth displacement platform;

[0025] The reflective isosceles prism is arranged on the sixth displacement platform; the sixth displacement platform is connected with the control unit and used to move the reflective isosceles prism to change the distance between the reflective isosceles prism and the first grating assembly and the second grating assembly, or move the reflective isosceles prism to / from the light path of the refracted light; the reflective isosceles prism is used to receive the refracted light after the first grating assembly and make it exit to the second grating assembly.

[0026] Further, a first mirror, a first displacement platform and a mirror assembly are further included;

[0027] The first mirror is arranged on the first displacement platform; the first displacement platform is used to move the first mirror to / from the light path of the incident laser; the first mirror is used to reflect the incident laser into the first reflected light;

[0028] The mirror assembly is arranged on the light path of the first reflected light and used to reflect the first reflected light into the second exit light;

[0029] The light path of the second exit light intersects with the light path of the first exit light at a variable intersection point;

[0030] The beam splitter assembly corresponds to the variable intersection point; the beam splitter assembly is further used to split the second exit light into the machining laser and the detection laser;

[0031] The control unit is connected with the first displacement platform.

[0032] Further, the beam splitter assembly comprises a beam splitter and a seventh displacement platform;

[0033] The beam splitter is arranged on the seventh displacement platform; the seventh displacement platform is connected with the control unit, and is used for adjusting the position of the beam splitter along the light path of the second emergent light, so that the beam splitter is always located at the variable intersection point.

[0034] Further, the first dispersion prism is an equilateral dispersion prism, and the side length of the equilateral dispersion prism is s.

[0035] The second dispersion prism is an equilateral dispersion prism, and the side length of the equilateral dispersion prism is 2s.

[0036] Further, the first dispersion prism and the second dispersion prism are both made of BK7 glass.

[0037] The grating constant of the first spatial light modulator and the second spatial light modulator is 1200 lines / mm.

[0038] Further, the mirror assembly comprises a second mirror and a third mirror arranged in sequence on the light path of the first reflected light.

[0039] The laser detector is a two-photon detector.

[0040] Meanwhile, the application also provides an online detection and regulation method for laser processing, which is based on the online detection and regulation device for laser processing, and the speciality thereof lies in comprising the following steps:

[0041] Step 1, calibration

[0042] 1.1) start the light source to emit incident laser, and start the laser detector to detect the pulse width of the detection laser; change the optical path between the first grating assembly and the second grating assembly and the detection voltage of the laser detector, and establish a first mapping relationship among the optical path, the detection voltage and the pulse width;

[0043] 1.2) move the first dispersion prism in the first grating assembly and the second dispersion prism in the second grating assembly out of the light path of the incident laser, so that the second spatial light modulator in the second grating assembly and the first spatial light modulator in the first grating assembly are sequentially located on the light path of the incident laser; meanwhile, change the angle between the second spatial light modulator and the incident laser, the distance between the first spatial light modulator and the second spatial light modulator and the detection voltage of the laser detector, and establish a second mapping relationship among the angle, the distance, the detection voltage and the pulse width; when adjusting the second spatial light modulator, the first spatial light modulator also needs to be adjusted, so that the first spatial light modulator is always parallel to the second spatial light modulator;

[0044] Step 2, zeroing

[0045] Moving the first dispersion prism and the second dispersion prism to the light path of the incident laser, and adjusting the positions of the first dispersion prism, the second dispersion prism, the first spatial light modulator and the second spatial light modulator according to the first mapping relationship, so that the pulse width of the incident laser returns to the preset initial value;

[0046] Step 3, laser processing and real-time monitoring

[0047] Performing laser processing by the processing laser, and simultaneously receiving the detection laser by the laser detector to obtain the pulse width of the processing laser;

[0048] If the pulse width of the detection laser is detected to be within the preset range, the laser processing is continued;

[0049] If the pulse width of the detection laser is detected to be positively dispersed, the current pulse width is obtained and step 4 is performed;

[0050] If the pulse width of the detection laser is detected to be negatively dispersed, the current pulse width is obtained and step 5 is performed;

[0051] Step 4, pulse width expansion compensation

[0052] The control unit adjusts the optical path between the first grating assembly and the second grating assembly and the detection voltage of the laser detector according to the current pulse width and the first mapping relationship, respectively, to perform pulse width expansion compensation, until the pulse width of the detection laser is within the preset range, and then the laser processing is continued;

[0053] Step 5, pulse width compression compensation

[0054] 5.1) Moving the first dispersion prism and the second dispersion prism out of the light path of the incident laser, so that the second spatial light modulator and the first spatial light modulator are sequentially located on the light path of the incident laser;

[0055] 5.2) Loading the same positively dispersed blazed grating hologram into the first spatial light modulator and the second spatial light modulator;

[0056] 5.3) Adjusting the angle between the second spatial light modulator and the incident laser, the distance between the first spatial light modulator and the second spatial light modulator, and the detection voltage of the laser detector according to the current pulse width and the second mapping relationship, respectively, to perform pulse width compression compensation, until the pulse width of the detection laser is within the preset range, and then the laser processing is continued.

[0057] Advantages of the present application:

[0058] 1. The application combines the first mirror with the first displacement platform to change the path of the incident laser, and combines the beam splitter assembly and the laser detector to detect the processing laser pulse width in real time. When the pulse width is normal, the first mirror is cut in for normal laser processing. When the pulse width has positive dispersion or negative dispersion, the first mirror is withdrawn and the first echelle assembly and the second echelle assembly are used for pulse width regulation, so that the online detection and regulation of the processing laser are achieved. The structure is compact and small in size, realizes flexible online compensation of pulse width expansion or compression (positive or negative dispersion), has high compensation precision, can improve the laser processing quality, and ensures the size consistency of the laser processing structure.

[0059] 2. The first echelle assembly and the second echelle assembly of the application respectively use a dispersion prism and a spatial light modulator carrying a grating hologram, effectively combining the dispersion compensation advantages of the dispersion prism and the grating, i.e. combining the advantages of large range, high energy utilization rate and high precision dispersion compensation, and further improving the laser regulation precision.

[0060] 3. The application sets an isosceles prism assembly between the first echelle assembly and the second echelle assembly, i.e. increases the optical path adjustable range between the first echelle assembly and the second echelle assembly, and also reduces the size of the entire online detection and regulation device, so that the structure of the entire device is more compact.

[0061] 4. The online detection and regulation device of the application can be placed at the end of the processing laser, i.e. can adopt rear-end detection and compensation, so that the pulse width stability of the processing laser is ensured to the greatest extent, and the laser processing quality is further improved.

[0062] 5. The online detection and regulation device and method of the application can effectively control the thermal effects such as recasting, cracking and recrystallization caused by pulse width expansion in the laser processing process, and reduce the roughness of the surface of the processed material. BRIEF DESCRIPTION OF DRAWINGS

[0063] Figure 1 is a structural schematic view of an embodiment of an online detection and regulation device for laser processing of the application (the first to seventh displacement platforms are not shown in the figure);

[0064] Figure 2 is a structural schematic view of the online detection and regulation device for laser processing of the application when pulse width compression compensation is performed;

[0065] Figure 3 is a principle diagram of regulating pulse width in the embodiment of the application.

[0066] REFERENCE NUMERALS:

[0067] 01-Incident laser, 011-refracted light, 02-first reflected light, 03-second exit light, 04-first exit light, 05-variable intersection, 06-processing laser, 07-detection laser;

[0068] 1-first mirror, 2-first grating assembly, 21-first spatial light modulator, 22-first dispersion prism, 3-second grating assembly, 31-second spatial light modulator, 32-second dispersion prism, 4-laser detector, 5-reflective isosceles prism, 6-splitting mirror, 7-second mirror, 8-third mirror. DETAILED DESCRIPTION

[0069] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0070] The principle of laser pulse width expansion and compression is from the perspective of laser technology. Different laser types and dispersion correction requirements are different. Different expansion and compression schemes can be derived through three major principles of prism pairs, grating pairs and GTI mirrors (or chirped mirrors). The specific optical element quantity, technical index and design layout are very different.

[0071] The embodiment of the present application provides a kind of online detection regulation and control device for laser processing with more compact structure, higher machining precision, greater energy utilization rate and can be continuously adjusted, as shown in Figure 1 As shown, the online detection regulation and control device includes light source, first mirror 1, first displacement platform, mirror assembly, first grating assembly 2, second grating assembly 3, splitting mirror assembly, laser detector 4, isosceles prism assembly and control unit.

[0072] The light source emits incident laser 01.

[0073] The first mirror 1 is arranged on the first displacement platform; the first displacement platform is used to move the first mirror 1 to / from the light path where the incident laser 01 is located; the first mirror 1 is used to reflect the incident laser 01 as the first reflected light 02; that is, when the first displacement platform moves the first mirror 1 to the light path where the incident laser 01 is located, the first mirror 1 reflects the incident laser 01 as the first reflected light 02.

[0074] The mirror assembly is arranged on the light path of the first reflected light 02, and is used for reflecting the first reflected light 02 into the second emitted light 03; specifically, in the embodiment of the application, the mirror assembly comprises a second mirror 7 and a third mirror 8 arranged in sequence on the light path of the first reflected light 02; the second mirror 7 and the third mirror 8 reflect the first reflected light 02 in sequence to form the second emitted light 03; the arrangement of the second mirror 7 and the third mirror 8 enables the first reflected light 02 to reach the spectroscope assembly successfully around the periphery of the first grating assembly 2, the second grating assembly 3 and the isosceles prism assembly, and at the same time, the volume of the entire online detection and regulation device is compressed, and the structure is more compact. Of course, the number of mirrors in the mirror assembly can be more or less, depending on the specific structure.

[0075] The first grating assembly 2, the isosceles prism assembly and the second grating assembly 3 are arranged in sequence on the light path of the incident laser 01; the first grating assembly 2, the isosceles prism assembly and the second grating assembly 3 are used for adjusting the pulse width of the incident laser 01 in real time, and forming the first emitted light 04, and the specific structures of the three are as follows:

[0076] The first grating assembly 2 comprises a first spatial light modulator 21 carrying a grating hologram, a second displacement platform, a first dispersion prism 22 and a third displacement platform; the first spatial light modulator 21 is arranged on the second displacement platform and located on the light path of the incident laser 01; the second displacement platform is used for adjusting the position and angle of the first spatial light modulator 21; the first dispersion prism 22 is arranged on the third displacement platform; the third displacement platform is used for moving the first dispersion prism 22 to / from the light path of the incident laser 01; the first dispersion prism 22 is used for dispersing the incident laser 01 and making it incident to the first spatial light modulator 21, and at the same time, receiving the light rays modulated by the first spatial light modulator 21 and refracting them to form the refracted light rays 011 of the incident laser 01; the first dispersion prism 22 is an equilateral dispersion prism, and its side length is s.

[0077] The isosceles prism assembly is arranged between the first grating assembly 2 and the second grating assembly 3 and is located on the light path of the refracted light 011 of the incident laser 01; the isosceles prism assembly comprises a reflective isosceles prism 5 and a sixth displacement platform; the reflective isosceles prism 5 is arranged on the sixth displacement platform; the sixth displacement platform is used to move the reflective isosceles prism 5 to change the distance between the reflective isosceles prism 5 and the first grating assembly 2 and the second grating assembly 3, or to move the reflective isosceles prism 5 to / from the light path of the refracted light 011 of the incident laser 01; the reflective isosceles prism 5 is used to receive the incident laser 01 after the first grating assembly 2 and emit it to the second grating assembly 3. The arrangement of the isosceles prism assembly increases the adjustable optical path distance between the first grating assembly 2 and the second grating assembly 3, that is, increases the adjustable range of the pulse width of the incident laser, thereby increasing the control precision, and on the other hand, it also compresses the spatial distance between the first grating assembly 2 and the second grating assembly 3, so that the structure of the entire online detection and control device is more compact, smaller in size and occupies less space.

[0078] The second grating assembly 3 comprises a second spatial light modulator 31 carrying a grating hologram, a fourth displacement platform, a second dispersion prism 32 and a fifth displacement platform; the second spatial light modulator 31 is arranged on the fourth displacement platform and is located on the light path of the refracted light 011 after the reflective isosceles prism 5; the fourth displacement platform is used to adjust the position and angle of the second spatial light modulator 31; the second dispersion prism 32 is arranged on the fifth displacement platform; the fifth displacement platform is used to move the second dispersion prism 32 to / from the light path of the refracted light 011; the second dispersion prism 32 is used to receive the refracted light 011 and make it incident to the second spatial light modulator 31, and then receive the light after being modulated by the second spatial light modulator 31 and reflect it into the first emitted light 04. The second dispersion prism 32 is an equilateral dispersion prism, and its side length is 2s.

[0079] The first dispersion prism 22 and the second dispersion prism 32 are both made of BK7 glass. The grating constant of the first spatial light modulator 21 and the second spatial light modulator 22 is 1200 lines / mm.

[0080] The light path of the first exit light 04 converged by the second dispersion prism 32 intersects with the light path of the second exit light 03 at a variable intersection point 05; the beamsplitter assembly corresponds to the variable intersection point 05, and specifically includes a beamsplitter 6 and a seventh displacement platform; the beamsplitter 6 is arranged on the seventh displacement platform; the seventh displacement platform is used to adjust the position of the beamsplitter 6 along the light path of the second exit light 03, so that the beamsplitter 6 is always located at the variable intersection point 05; the beamsplitter 6 is used to split the first exit light 04 or the second exit light 03 into a machining laser 06 and a detection laser 07; the machining laser 06 is used to machine products or materials; and the detection laser 07 is incident to the laser detector 4. The beamsplitter 6 can be a 1:1 beamsplitter.

[0081] The laser detector 4 is arranged on the light path of the detection laser 07 and is used to detect the pulse width of the detection laser 07 in real time; at this time, the detected pulse width of the detection laser 07 is the pulse width of the machining laser 06. The laser detector 4 in the embodiment of the present application is preferably a two-photon detector.

[0082] The control unit is connected with the first spatial light modulator 21, the second spatial light modulator 31, the laser detector 4, the first displacement platform, the second displacement platform, the third displacement platform, the fourth displacement platform, the fifth displacement platform, the sixth displacement platform and the seventh displacement platform, and is used to adjust the first spatial light modulator 21, the second spatial light modulator 31, the laser detector 4, the first displacement platform, the second displacement platform, the third displacement platform, the fourth displacement platform, the fifth displacement platform, the sixth displacement platform and the seventh displacement platform in real time according to the detection result of the laser detector 4.

[0083] The above-mentioned online detection and regulation device introduces a spatial light modulator and combines the position switching of various optical elements, so as to realize flexible online compensation of pulse width expansion or compression (positive or negative dispersion); and effectively combines the advantages of the prism and the grating, that is, combines the advantages of large range, high energy utilization rate, high precision (high-order dispersion compensation) and compact structure; in order to maximize the stability of the machining laser pulse width, a rear-end detection and compensation structure is adopted, and the entire device is preferably placed at the end of the laser machining light path.

[0084] It should be noted that the second order dispersion provided by the first and second grating assemblies at the center wavelength is negative, and the positive and negative of the third order dispersion value is determined by the incident angle. The size of the ratio of the third order dispersion to the second order dispersion can be precisely adjusted by changing the vertical distance between the first and second dispersion prisms and the vertical distance between the first and second spatial light modulators. The spatial light modulator loaded with the grating hologram provides negative second order dispersion and positive third order dispersion to the pulse; the second order dispersion and the third order dispersion provided by the first and second dispersion prisms are both negative, which is in the grating pair pulse width compression pulse width (the first and second grating assemblies provide negative second order dispersion and third order dispersion).

[0085] The method for online regulation by using the above online detection and regulation device for laser processing includes the following steps:

[0086] Step 1, calibration

[0087] 1.1) Start the light source, the light source emits incident laser 01, the control unit controls the first displacement platform to move the first mirror 1 out of the light path of the incident laser 01, and starts the laser detector 4 to detect the pulse width of the detection laser 07; change the optical path between the first and second grating assemblies 2 and 3 and the detection voltage of the laser detector 4, establish the first mapping relationship among the optical path, the detection voltage and the pulse width;

[0088] 1.2) The control unit controls the third, fifth and sixth displacement platforms to move the first dispersion prism 22, the second dispersion prism 32 and the reflective isosceles prism 5 out of the light path of the incident laser 01, and controls the fourth and second displacement platforms to adjust the positions and angles of the second spatial light modulator 31 and the first spatial light modulator 21 respectively, so that the second spatial light modulator 31 and the first spatial light modulator 21 are sequentially located in the light path of the incident laser 01; then change the angle between the second spatial light modulator 31 and the incident laser 01, the distance between the first spatial light modulator 21 and the second spatial light modulator 31 and the detection voltage of the laser detector 4 at the same time, so as to establish the second mapping relationship among the angle, the distance, the detection voltage and the pulse width; It should be noted that when adjusting the position and angle of the second spatial light modulator 31, the position and angle of the first spatial light modulator 21 also need to be adjusted at the same time, so that the first spatial light modulator 21 is always parallel to the second spatial light modulator 31;

[0089] In the calibration, a standard autocorrelator can be used as an auxiliary instrument to provide a calibration target to the laser detector 4; it can be understood that the calibration process can obtain the difference between the actual pulse width and the ideal pulse width, so as to confirm the direction and amount of compensation.

[0090] Step 2, zeroing

[0091] Move the first dispersion prism 22 and the second dispersion prism 32 to the light path of the incident laser 01, and adjust the positions of the first dispersion prism 22, the second dispersion prism 32, the first spatial light modulator 21 and the second spatial light modulator 31 according to the first mapping relationship, so that the pulse width of the incident laser 01 returns to the preset initial value required by the machining laser, and then move the first mirror 1 to the light path of the incident laser 01, so that the incident laser 01 enters the beam splitter 6 in the beam splitter assembly in turn after the first mirror 1, the second mirror 7 and the third mirror 8, and the beam splitter 6 divides the light into machining laser 06 and detection laser 07; the machining laser 06 is used for machining materials or products, and the detection laser 07 is directly incident to the laser detector 4;

[0092] Step 3, laser machining and real-time monitoring

[0093] The machining laser 06 is used for laser machining, and the laser detector 4 receives the detection laser 07 in real time to obtain the pulse width of the machining laser 06; in this embodiment, the laser detector 4 measures once per minute; in the monitoring:

[0094] If the pulse width of the detection laser 07 detected by the two-photon detector does not jitter, that is, within the preset range, the laser machining is continued;

[0095] If the two-photon detector detects that the pulse width of the detection laser 07 is widened, that is, positive dispersion occurs, the current pulse width is obtained and step 4 is performed;

[0096] If the two-photon detector detects that the pulse width of the detection laser 07 is shortened, that is, negative dispersion occurs, the current pulse width is obtained and step 5 is performed;

[0097] Step 4, pulse width compensation

[0098] 4.1) The control unit receives the current pulse width, controls the first displacement platform, and moves the first mirror 1 out of the light path of the incident laser 01, so that the incident laser 01 passes through the first grating assembly 2, the isosceles prism assembly and the second grating assembly 3 in turn to reach the beam splitter 6;

[0099] 4.2) The same grating hologram is loaded into the first spatial light modulator 21 and the second spatial light modulator 31, and the incident laser 01 passes through the refraction and reflection of the first dispersion prism 22 to reach the first spatial light modulator 21, is diffracted by the grating surface in a direction close to the Littrow angle, and then is refracted by the first dispersion prism 22 to enter the reflective isosceles prism 5 and then enter the second grating assembly 3, and finally forms the first outgoing light 04 in the second grating assembly 3 which experiences a path opposite to that of the first grating assembly 2;

[0100] 4.3) According to the current pulse width and the first mapping relationship, respectively adjust the optical path between the first grating assembly 2 and the second grating assembly 3 and the detection voltage of the laser detector 4 to carry out pulse width expansion compensation; that is, change the dispersion compensation amount to realize accurate adjustment of the pulse width, until the pulse width of the detection laser 07 is within the preset range, and then continue to carry out laser processing, which can be expressed as:

[0101] Phase difference brought by optical path difference: ΔΦtotal=2π / λ(C+D+F+I+L+M)+2πn1 / λ(A+B+E+K+N+T)+2πn2 / λ(2G+H)

[0102] Group dispersion delay: GD(λ)=λ 2 ×d(△Φtotal) / 2πc×dλ

[0103] Second-order dispersion: GDD(λ)=λ 4 ×d 2 (△Φtotal) / 4π 2 c 2 / dλ 2 +λ 3 ×d(△Φtotal) / 2π 2 c 2 / dλ

[0104] Third-order dispersion: TOD(λ)=-λ 6 ×d 3 (△Φtotal) / 8π 3 c 3 / dλ 3 3λ 5 ×d 2 (△Φtotal) / 4π 3 c 3 / dλ 2 -3λ 4 ×d(△Φtotal) / 4π 3 c 3 / dλ

[0105] Where λ is the wavelength of the incident laser, n1 is the refractive index of the first dispersion prism and the second dispersion prism, n2 is the refractive index of the reflective isosceles prism, as shown in Figure 1 , A-N and T are respectively the distances between the intersection positions of the laser incident to the surfaces of each prism; d is the first derivative, d 2 is the second derivative, d 3 is the third derivative, and c is the speed of light.

[0106] Step 5, pulse width compression compensation

[0107] 5.1) As Figure 2As shown, the first mirror 1, the first dispersion prism 22, the reflective paper isosceles prism 5 and the second dispersion prism 32 are moved out of the light path of the incident laser 01, and the second spatial light modulator 31 and the first spatial light modulator 21 are sequentially located on the light path of the incident laser 01; that is, the second spatial light modulator 31 and the first spatial light modulator 21 are adjusted to Figure 2 As shown in the position, the incident laser 01 enters the beam splitter 6 after sequentially passing through the second spatial light modulator 31 and the first spatial light modulator 21; specifically, the first spatial light modulator 21 can move along the -X axis through the second displacement platform and change its angle through the rotation shaft, and the second spatial light modulator 31 moves along the Y axis through the fourth displacement platform and changes its angle through the rotation shaft;

[0108] 5.2) The same positive dispersion blazed grating hologram is loaded into the first spatial light modulator 21 and the second spatial light modulator 31 to produce positive dispersion to expand the pulse width;

[0109] 5.3) The angle between the second spatial light modulator 31 and the incident laser 01, the distance between the first spatial light modulator 21 and the second spatial light modulator 31 and the detection voltage of the laser detector are adjusted according to the current pulse width and the second mapping relationship to compensate for pulse compression, so as to accurately adjust and stabilize the pulse until the pulse width of the detection laser 07 is within the preset range, and then laser processing is continued; it is worth noting that the first spatial light modulator 21 is also adjusted while the second spatial light modulator 31 is adjusted, so that it is always parallel to the second spatial light modulator 31. The position of the beam splitter can be adjusted along the light path of the second outgoing light to ensure that the first outgoing light after the first spatial light modulator 21 can be split by the beam splitter 6; which can be expressed as:

[0110] △Φtotal = 2π / λ(d0secθn[1+cos(θn-θm)]

[0111] In the formula, λ is the wavelength of the incident laser, θ is the diffraction angle, θn is the angle between the incident and outgoing light of the first spatial light modulator hologram, θm is the angle between the incident and normal of the first spatial light modulator hologram, d is the number of grating lines, d0 is the vertical distance between the two grating holograms; other parameters are as shown in the figure. Figure 3

[0112] This method can simultaneously realize flexible compensation of positive and negative dispersion of pulse width. In addition, in order to maximize the utilization rate of optical energy in laser processing, after correction is completed before laser processing, the laser first does not pass through the correction and compensation light path, but only monitors and detects it, and if there is fluctuation, it is switched to the correction and compensation light path. Of course, this invention can also directly use the correction and compensation light path, and only needs to set the positions of the elements to zero. ​

[0113] The above merely provides the specific implementation of the present application, but the protection scope of the present application is not limited thereto, any change or replacement within the technical range disclosed by the present application should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An online detection regulation method for laser processing, using an online detection regulation device for laser processing, characterized in that: the online detection regulation device for laser processing comprises a light source, a first grating assembly (2), a second grating assembly (3), a beam splitter assembly, a laser detector (4) and a control unit; the light source emits incident laser (01); the first grating assembly (2) and the second grating assembly (3) are sequentially arranged on the light path of the incident laser (01), for real-time adjustment of the pulse width of the incident laser (01), and form the first exit light (04); the beam splitter assembly is arranged on the light path of the first exit light (04), for splitting the first exit light (04) into processing laser (06) and detection laser (07); the laser detector (4) is arranged on the light path of the detection laser (07), for real-time detection of the pulse width of the detection laser (07); the control unit is connected with the first grating assembly (2), the second grating assembly (3), the beam splitter assembly and the laser detector (4), for real-time adjustment of the first grating assembly (2), the second grating assembly (3) and the beam splitter assembly according to the detection result of the laser detector (4); the online detection regulation method for laser processing comprises the following steps: step 1, calibration; 1.1) start the light source to emit the incident laser (01), and start the laser detector (4) to detect the pulse width of the detection laser (07); change the optical path between the first grating assembly (2) and the second grating assembly (3) and the detection voltage of the laser detector (4), to establish a first mapping relationship among the optical path, the detection voltage and the pulse width; 1.2) move the first dispersion prism (22) in the first grating assembly (2) and the second dispersion prism (32) in the second grating assembly (3) out of the light path of the incident laser (01), so that the second spatial light modulator (31) in the second grating assembly (3) and the first spatial light modulator (21) in the first grating assembly (2) are sequentially located on the light path of the incident laser (01); at the same time, change the angle between the second spatial light modulator (31) and the incident laser (01), the distance between the first spatial light modulator (21) and the second spatial light modulator (31), and the detection voltage of the laser detector (4), to establish a second mapping relationship among the angle, the distance, the detection voltage and the pulse width; while adjusting the second spatial light modulator (31), the first spatial light modulator (21) also needs to be adjusted, so that it is always parallel to the second spatial light modulator (31); step 2, zeroing; move the first dispersion prism (22) and the second dispersion prism (32) to the light path of the incident laser (01), and adjust the positions of the first dispersion prism (22), the second dispersion prism (32), the first spatial light modulator (21) and the second spatial light modulator (31) according to the first mapping relationship, so that the pulse width of the incident laser (01) returns to the preset initial value; step 3, laser processing and real-time monitoring. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The laser processing is performed by processing laser (06), and the laser detector (4) receives the detection laser (07) in real time to obtain the pulse width of the processing laser (06); If the pulse width of the detection laser (07) is detected within the preset range, the laser processing is continued; If the pulse width of the detection laser (07) is detected to occur positive dispersion, the current pulse width is obtained and step 4 is performed; If the pulse width of the detection laser (07) is detected to occur negative dispersion, the current pulse width is obtained and step 5 is performed; Step 4, pulse width expansion compensation The control unit adjusts the optical path between the first grating assembly (2) and the second grating assembly (3) and the detection voltage of the laser detector (4) according to the current pulse width and the first mapping relationship to perform pulse width expansion compensation until the pulse width of the detection laser (07) is within the preset range, and then the laser processing is continued; Step 5, pulse width compression compensation 5.1) Move the first dispersion prism (22) and the second dispersion prism (32) out of the light path of the incident laser (01), so that the second spatial light modulator (31) and the first spatial light modulator (21) are sequentially located in the light path of the incident laser (01); 5.2) Load the same positive dispersion blazed grating hologram into the first spatial light modulator (21) and the second spatial light modulator (31); 5.3) Adjust the angle between the second spatial light modulator (31) and the incident laser (01), the distance between the first spatial light modulator (21) and the second spatial light modulator (31), and the detection voltage of the laser detector according to the current pulse width and the second mapping relationship to perform pulse width compression compensation; while adjusting the second spatial light modulator (31), the first spatial light modulator (21) is also adjusted until the pulse width of the detection laser (07) is within the preset range, and then the laser processing is continued.

2. The online detection and regulation method for laser processing according to claim 1, characterized in that: The first grating assembly (2) comprises a first spatial light modulator (21) carrying a grating hologram, a second displacement platform, a first dispersion prism (22) and a third displacement platform; The first spatial light modulator (21) is arranged on the second displacement platform and located in the light path of the incident laser (01); the second displacement platform is used to adjust the position and angle of the first spatial light modulator (21); The first dispersion prism (22) is arranged on the third displacement platform; the third displacement platform is used to move the first dispersion prism (22) to / from the light path of the incident laser (01); the first dispersion prism (22) is used to disperse the incident laser (01) and make it incident on the first spatial light modulator (21), and at the same time receive and refract the light modulated by the first spatial light modulator (21) to form refracted light (011) of the incident laser (01); The first spatial light modulator (21), the second displacement platform and the third displacement platform are respectively connected with the control unit; The second grating assembly (3) is arranged in the light path of the refracted light (011).

3. The online detection and regulation method for laser processing according to claim 2, characterized in that: The second grating assembly (3) comprises a second spatial light modulator (31) carrying a grating hologram, a fourth displacement platform, a second dispersion prism (32) and a fifth displacement platform; The second spatial light modulator (31) is arranged on the fourth displacement platform and located on the light path of the refracted light (011); The fourth displacement platform is used to adjust the position and angle of the second spatial light modulator (31); The second dispersion prism (32) is arranged on the fifth displacement platform; the fifth displacement platform is used to move the second dispersion prism (32) to / from the light path of the refracted light (011); the second dispersion prism (32) is used to receive the refracted light (011) and make it incident on the second spatial light modulator (31), and then receive the light modulated by the second spatial light modulator (31) and reflect it into the first exit light (04); The second spatial light modulator (31), the fourth displacement platform and the fifth displacement platform are connected with the control unit respectively.

4. The online detection and regulation method for laser processing according to claim 3, characterized in that: Further comprising an isosceles prism assembly arranged between the first grating assembly (2) and the second grating assembly (3) and located on the light path of the refracted light (011) of the incident laser (01); The isosceles prism assembly comprises a reflective isosceles prism (5) and a sixth displacement platform; The reflective isosceles prism (5) is arranged on the sixth displacement platform; the sixth displacement platform is connected with the control unit and is used to move the reflective isosceles prism (5) to change the distance between the reflective isosceles prism (5) and the first grating assembly (2) and the second grating assembly (3), or move the reflective isosceles prism (5) to / from the light path of the refracted light (011); the reflective isosceles prism (5) is used to receive the refracted light (011) after the first grating assembly (2) and make it exit to the second grating assembly (3).

5. The online detection and regulation method for laser processing according to claim 4, characterized in that: Further comprising a first mirror (1), a first displacement platform and a mirror assembly; The first mirror (1) is arranged on the first displacement platform; the first displacement platform is used to move the first mirror (1) to / from the light path of the incident laser (01); the first mirror (1) is used to reflect the incident laser (01) into the first reflected light (02); The mirror assembly is arranged on the light path of the first reflected light (02) and is used to reflect the first reflected light (02) into the second exit light (03); The light path of the second exit light (03) intersects with the light path of the first exit light (04) at a variable intersection point (05); The beam splitter assembly corresponds to the variable intersection point (05); the beam splitter assembly is also used to split the second exit light (03) into the machining laser (06) and the detection laser (07); The control unit is connected with the first displacement platform.

6. The online detection and regulation method for laser processing according to claim 5, wherein: The beam splitter assembly comprises a beam splitter (6) and a seventh displacement platform; The beam splitter (6) is arranged on the seventh displacement platform; the seventh displacement platform is connected with the control unit and is used to adjust the position of the beam splitter (6) along the light path of the second exit light (03) so that the beam splitter (6) is always located at the variable intersection point (05).

7. The online detection and regulation method for laser processing according to claim 6, characterized in that: The first dispersion prism (22) is an equilateral dispersion prism with a side length of s; The second dispersion prism (32) is an equilateral dispersion prism with a side length of 2s.

8. The online detection and regulation method for laser processing according to claim 7, characterized in that: The first dispersion prism (22) and the second dispersion prism (32) are both made of BK7 glass. The grating constant of the first spatial light modulator (21) and the second spatial light modulator (22) is 1200 lines / mm.

9. The online detection and regulation method for laser processing according to claim 8, wherein: The mirror assembly comprises a second mirror (7) and a third mirror (8) arranged in sequence on the light path of the first reflected light (02). The laser detector (4) is a two-photon detector.

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