Optical Phased Array Axial Focus Regulation Method and System

Abstract

The present invention provides an optical phased array axial focal point regulation method and system. First, the phase difference and phase noise between the unit beams of the array laser are compensated to make the phase control between the unit beams consistent; the focal depth of the array laser on the workpiece to be processed is determined; the expected array distribution of the array laser is calculated according to the expected equivalent focal length; and finally, the expected array distribution is applied to the array laser to change the position where the array laser is focused on the workpiece to be processed. The present invention has no mechanical moving parts, can be applicable to high-power output, improve the focal depth regulation speed, and can improve the processing efficiency of high-power lasers in application scenarios such as industrial cutting.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of fiber laser coherent combination, and in particular to an optical phased array axial focus regulation method and system. Background Art

[0002] Fiber lasers have been widely used in fields such as laser cutting, welding, medical treatment, and laser three-dimensional printing. In certain specific application scenarios, such as biomedical imaging, three-dimensional volume imaging, and laser processing, the axial focus position of the laser needs to be quickly adjustable. For example, in the application of biomedical imaging, a quickly adjustable focusing depth can disperse the optical power along the optical axis to different foci, thereby avoiding phototoxicity. In advanced manufacturing, when using high-power lasers to cut thick metals, an adjustable focusing depth can make the cutting surface smoother and improve processing efficiency.

[0003] Zoom optical elements are usually based on principles such as mechanical movement, electromechanics, refractive index gradient, and Bragg diffraction. Traditional methods use mechanical devices to move the position of the lens to change the focus, which will reduce the dynamic response of the optical system. Axial focus regulation methods for non-mechanical or microelectromechanical systems make it possible to shorten the response time, including liquid crystal lenses, tunable acoustic gradient index lenses, deformable mirrors, etc. The speed of these devices can reach the order of sub-milliseconds and microseconds. Although these methods have excellent performance, they still have limitations in actual applications such as component size, high-power heat absorption, and alignment accuracy. In addition, due to non-linear effects and mode instabilities, the output power of a single-chip fiber laser is limited, while laser processing has increasingly high requirements for the output power and flexibility of fiber lasers.

[0004] Therefore, a regulation method with quickly adjustable axial focus, applicable to high power, good thermal performance, and convenient and precise adjustment is needed. Summary of the Invention

[0005] In view of the defects existing in the prior art, the present invention proposes an optical phased array axial focus regulation method and system.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] On the one hand, the present invention provides an optical phased array axial focus regulation method, including:

[0008] Compensating the phase difference and phase noise between each path of unit beams in the array laser to control the phase between each path of unit beams to be consistent;

[0009] Determining the focus depth of the array laser on the workpiece;

[0010] Calculating the expected array distribution of the array laser according to the expected equivalent focal length;

[0011] Apply the desired array distribution to the array laser, and change the position where the array laser is focused on the workpiece to be processed.

[0012] Further, the array laser in the present invention is focused on the workpiece to be processed after passing through the focusing lens. The distance between the focal point and the focusing lens is f. Assume that the axial step distance of the focal point each time is dz. Then the desired equivalent focal length corresponding to the nth step is f equ = f + n·dz, n = 0, 1, 2…

[0013] Further, in a preferred embodiment of the present invention: calculating the desired array distribution of the array laser according to the desired equivalent focal length includes:

[0014] The array laser and the focusing lens are equivalently regarded as a lens combination composed of two lenses. The phase of the equivalent lens in the lens combination corresponds to the phase of the array laser, and the focal length of the equivalent lens is f 2 , the focal length of the focusing lens is f, and the distance between the equivalent lens and the focusing lens is s;

[0015] Calculate the focal length f of the equivalent lens according to the desired equivalent focal length and the equivalent focal length of the lens combination 2 ;

[0016] According to the focal length f of the equivalent lens 2 Obtain the desired laser array phase distribution.

[0017] Further, in a preferred embodiment of the present invention: the focal length f of the equivalent lens 2 Is determined by the following formula:

[0018]

[0019] Further, in a preferred embodiment of the present invention, the desired laser array phase distribution is:

[0020]

[0021] Where x and y respectively represent the spatial coordinates of the laser distribution in the x direction and the y direction, k = 2π / λ is the wave number, and λ is the wavelength of the array laser.

[0022] On the other hand, the present invention provides an optical phased array axial focal point regulation system, including:

[0023] An array laser coherent synthesis optical path for realizing coherent synthesis and output of multiple unit beams;

[0024] A high reflector is arranged on the output path of the array laser coherent synthesis optical path. Most of the laser output by the array laser coherent synthesis optical path is reflected by the high reflector, and a small part is transmitted through the high reflector;

[0025] Focusing lens, the array laser reflected from the high - reflection mirror is focused on the workpiece to be processed after passing through the focusing lens;

[0026] Signal acquisition module, which is used to collect the optical signal transmitted from the high - reflection mirror and convert it into an electrical signal;

[0027] Data processing module. On the one hand, based on the electrical signal output by the signal acquisition module, it compensates the phase difference and phase noise between the unit beams in the array laser, so that the phases of the unit beams are controlled to be consistent; after the phases of the unit beams are controlled to be consistent, it determines the focal depth of the array laser on the workpiece to be processed; calculates the expected array distribution of the array laser according to the expected equivalent focal length; applies the expected array distribution to the array laser to change the position where the array laser is focused on the workpiece to be processed.

[0028] Furthermore, in a preferred embodiment of the present invention: the coherent combination optical path of the array laser includes a seed laser, a 1×N beam splitter, N phase modulators, N fiber amplifiers, and a laser beam combining device; the laser output by the seed laser is divided into N unit beams by the 1×N beam splitter, and each unit beam is respectively phase - modulated and amplified by the corresponding phase modulator and fiber amplifier, and the N unit beams after phase - modulation and amplification are combined and output by the laser beam combining device.

[0029] Furthermore, in a preferred embodiment of the present invention: the data processing module is connected to the phase modulators of each unit beam for control.

[0030] Furthermore, in a preferred embodiment of the present invention: the array laser reflected from the high - reflection mirror is focused on the workpiece to be processed after passing through the focusing lens, the distance between the focus and the focusing lens is f, assuming the axial step distance of the focus each time is dz, then the expected equivalent focal length corresponding to the nth step is f equ = f + n·dz, n = 0, 1, 2…;

[0031] The array laser and the focusing lens are equivalently regarded as a lens combination composed of two lenses. The phase of the equivalent lens in the lens combination corresponds to the phase of the array laser, and the focal length of the equivalent lens is f 2 , the focal length of the focusing lens is f, and the distance between the equivalent lens and the focusing lens is s;

[0032] According to the expected equivalent focal length and the equivalent focal length of the lens combination, calculate the focal length f of the equivalent lens 2 ;

[0033] According to the focal length f of the equivalent lens 2 Obtain the expected laser array phase distribution.

[0034] The present invention utilizes the phase distribution of an array laser to simulate the phase distribution of a lens, and combines it with a focusing lens of a long focal length to achieve an equivalent variable focal length lens combination, causing the focal depth after the interference of the array laser to shift on the workpiece to be processed, thereby improving the processing efficiency of processes such as laser cutting.

[0035] The present invention uses multiple high-power fiber lasers to form an array, and realizes fast, accurate, and rapid laser focus adjustment by rapidly regulating the piston phase of the laser array. Compared with the prior art, the method of the present invention has no mechanical moving parts, can be applied to high-power output, improves the speed of focal depth adjustment, and can improve the processing efficiency of high-power lasers in industrial cutting and other application scenarios. Brief Description of the Drawings

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0037] Figure 1 It is a flowchart of an embodiment;

[0038] Figure 2 It is a schematic diagram of the principle of an equivalent lens combination in an embodiment;

[0039] Figure 3 It is a schematic structural diagram of an embodiment;

[0040] Figure 4 It is a result diagram of numerical simulation obtained in an embodiment, where (a) is the phase distribution diagram of the equivalent lens; (b) is the sampled array phase distribution diagram;

[0041] Figure 5 It is a comparison diagram of the energy distribution in the optical axis direction before and after the axial focus adjustment of the optical phased array in an embodiment, where (a) shows the energy distribution on the optical axis before the focus adjustment, (b) shows the energy distribution on the optical axis after the focus adjustment, and (c) shows the cross-sectional diagram comparison of the two.

[0042] The realization of the object, functional characteristics, and advantages of the present invention will be further described with reference to the embodiments and the drawings. Detailed Embodiments

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer and more understandable, the spirit of the content disclosed by the present invention will be clearly described below with reference to the accompanying drawings and detailed descriptions. After any person skilled in the relevant technical field understands the embodiments of the content of the present invention, they can make changes and modifications based on the techniques taught by the content of the present invention, which do not depart from the spirit and scope of the content of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but do not limit the present invention.

[0044] Referring to Figure 1 , in one embodiment, an optical phased array axial focus control method is provided, including:

[0045] Compensating the phase difference and phase noise between the unit beams of the array laser to control the phases of the unit beams to be consistent;

[0046] Determining the focal depth of the array laser on the workpiece to be processed;

[0047] Calculating the expected array distribution of the array laser according to the expected equivalent focal length;

[0048] Applying the expected array distribution to the array laser to change the position where the array laser is focused on the workpiece to be processed.

[0049] It can be understood that in the present invention, the phase difference and phase noise between the unit beams of the array laser are compensated. The phase compensation method can be any one of the commonly used or conventional array laser coherent synthesis phase control algorithms in the prior art, such as near-field interference fringe extraction, heterodyne method, and various optimization algorithms. Through phase control, the purpose is to control the phases of the unit beams to be consistent.

[0050] Without loss of generality, taking the optimization algorithm as an example, a photodetector is used to collect the main lobe energy of the far-field interference fringes of the array laser and convert it into an electrical signal. Based on this electrical signal, by executing optimization algorithms such as the stochastic parallel gradient descent method and the dithering method, the phase error between the unit beams is calculated and the corresponding control voltage u is output to the phase modulator corresponding to each unit beam (u = {u 1 , u 2 , …, u N}, where N is the total number of unit beams), so that the main lobe energy of the interference of the array beams detected by the photodetector reaches the maximum value. At this time, the phases between the unit beams will be controlled to be consistent.

[0051] The offset speed of the depth of focus is related to the phase modulation device, and different devices are selected according to requirements. The offset range of the depth of focus is related to the focal length of the focusing lens and the size of a single unit beam. The larger the focal length of the focusing lens and the smaller the size of a single beam, the larger the offset range of the depth of focus. The specific offset range of the depth of focus should be designed according to the application requirements for the size of the unit beam and the focal length of the focusing lens.

[0052] In one embodiment, the array laser is focused on the workpiece after passing through the focusing lens. Through phase compensation control, the phases of the unit beams in the array laser are consistent, the distance between the focus and the focusing lens is f, and the focus falls on the workpiece. Let the axial step distance of the focus each time be dz, then the expected equivalent focal length corresponding to the nth step is f equ = f + n·dz, n = 0, 1, 2….

[0053] In one embodiment, taking laser cutting as an example, the array laser is focused on the upper surface of the workpiece after passing through the focusing lens, and laser cutting operation is performed on the workpiece. After completing the cutting of the workpiece surface, it is desired to move the depth of focus downward to achieve the focusing of the laser energy inside the workpiece and improve the processing efficiency. First, through phase compensation control, the phases of the unit beams in the array laser are consistent. The array laser is focused on the upper surface of the workpiece after passing through the focusing lens, and the distance between the focus and the focusing lens is f, that is, the focus falls on the upper surface of the workpiece. Let the axial step distance of the focus each time be dz, then the expected equivalent focal length corresponding to the nth step is f equ = f + n·dz, n = 0, 1, 2….

[0054] In a preferred embodiment: Calculate the expected array distribution of the array laser according to the expected equivalent focal length, including:

[0055] Refer to Figure 2 , and the array laser and the focusing lens are equivalently regarded as a lens combination composed of two lenses. The equivalent lens combination includes a focusing lens and an equivalent lens. The phase of the equivalent lens in the lens combination corresponds to the phase of the array laser, and the focal length of the equivalent lens is f 2 , the focal length of the focusing lens is f, and the distance between the equivalent lens and the focusing lens is s.

[0056] Calculate the focal length f of the equivalent lens according to the expected equivalent focal length and the equivalent focal length of the lens combination 2 ;

[0057]

[0058] According to the focal length f of the equivalent lens 2 Obtain the expected laser array phase distribution.

[0059]

[0060] Where x and y respectively represent the spatial coordinates of the laser distribution in the x-direction and y-direction, k = 2π / λ is the wave number, and λ is the wavelength of the laser array.

[0061] Referring to Figure 3 , an embodiment of the present invention provides an optical phased array axial focus control system, including:

[0062] An array laser coherent combination optical path for realizing coherent combination and output of multiple unit beams;

[0063] A high-reflection mirror 106 is arranged on the output path of the array laser coherent combination optical path. Most of the laser output by the array laser coherent combination optical path is reflected by the high-reflection mirror and a small part is transmitted through the high-reflection mirror;

[0064] A long-focus focusing lens 107 focuses the array laser reflected from the high-reflection mirror on the workpiece to be processed;

[0065] A signal acquisition module for acquiring the optical signal transmitted from the high-reflection mirror and converting it into an electrical signal;

[0066] A data processing module, on the one hand, compensates for the phase difference and phase noise between the unit beams in the array laser based on the electrical signal output by the signal acquisition module, so that the phases of the unit beams are controlled to be consistent; after the phases of the unit beams are controlled to be consistent, determine the focal depth of the array laser on the workpiece to be processed; calculate the expected array distribution of the array laser according to the expected equivalent focal length; apply the expected array distribution to the array laser to change the position where the array laser is focused on the workpiece to be processed.

[0067] Referring to Figure 3 , the array laser coherent combination optical path includes a seed laser 101, a 1×N beam splitter 102, N phase modulators 103, N fiber amplifiers 104, and a laser beam combining device 105.

[0068] The output of the seed laser 101 is connected to the input of the 1×N beam splitter 102.

[0069] The 1×N beam splitter 102 has one input port and N output ports for splitting a beam of laser into N beams of laser.

[0070] The N output ports of the 1×N beam splitter 102 are respectively connected to N phase modulators 103.

[0071] The N phase modulators 103 have one input port and one output port for applying phase modulation to the laser. The working principle of the phase modulation device is not limited and can be a piezoelectric ceramic device, a crystal device, etc., and is specifically selected according to the device bandwidth requirements.

[0072] The outputs of the N phase modulators 103 are connected to the N fiber optic amplifiers 104.

[0073] The N fiber optic amplifiers 104 are used to amplify the power of the input laser signal.

[0074] The N fiber optic amplifiers 104 are connected to the laser beam combining device 5.

[0075] The laser beam combining device 105 is a collimator array arranged in a two-dimensional pattern and has the function of collimating and outputting the laser. The arrangement of the collimator array in the beam combining device 105 is not limited. The shape of the laser array is not restricted and can be a rectangular distribution, circular distribution, regular hexagon distribution, spiral distribution, etc. Preferably, the photosynthetic beam combining device 105 is selected to be arranged in a regular hexagon.

[0076] The laser output by the seed laser 101 is split into N unit light beams by a 1×N beam splitter 102. Each unit light beam is phase-modulated and amplified by the corresponding phase modulator 103 and fiber optic amplifier 104 respectively. The N unit light beams after phase modulation and amplification are combined and output by the laser beam combining device 105.

[0077] The collimated array laser is emitted from the laser beam combining device 105 into free space and sampled by the high reflector 106. Most of the laser is reflected and a small part of the laser is transmitted.

[0078] The high reflector 106 is a coated optical device with no material limitation and can reflect most of the incident laser and transmit a small part of the incident laser. The high reflector has a high reflectivity such that the ratio of the reflected laser to the transmitted laser is greater than 99.

[0079] In the present invention, the materials of the sampling lenses are not limited and can be optical crystal materials such as K9 and fused silica. The focal length of the lens should be about 1 m. The array laser interferes after being focused by the lens, generating interference fringes with a central main lobe.

[0080] The reflected laser is focused by the long focal length focusing lens 107, and the focused laser reaches the surface of the workpiece 108.

[0081] The long focal length focusing lens 107 has a focal length of f. Without loss of generality, the focal length is selected to be 1 m. The selection of the focal length of the long focal length focusing lens 107 is related to the control range of the focal depth. The longer the focal length, the larger the control range, and the long focal length focusing lens 107 with different focal lengths can be selected according to requirements.

[0082] The laser transmitted by the high reflector is split into two beams of laser by a 50:50 beam splitter 109. The two beams of laser are respectively focused by focusing lenses 110. One beam of laser is input into a photodetector 111 after focusing, which is used to detect the phase of the array laser; the other beam of laser is input into a camera 112 after focusing, which is used to detect the spot shape.

[0083] The 50:50 beam splitter 109 is a coated optical device, which can split the input laser into two beams of laser with the same power.

[0084] The focal length of the focusing lens 110 is not limited.

[0085] The photodetector 111 is used to convert the optical signal into an electrical signal.

[0086] The camera 112 is used to observe the shape of the array laser after focusing.

[0087] After the photodetector 111 converts the optical signal into an electrical signal, the electrical signal is sent to a data processing unit 113. The output of the data processing unit is connected to N phase modulators.

[0088] The data processing unit 113 is pre-loaded with a phase compensation algorithm. On the one hand, it has the ability to compensate for the system phase noise. On the other hand, the data processing unit 113 can apply a given phase distribution to the array laser on the basis of compensating for the phase noise. After the phases of each beam of laser are controlled to be consistent, by changing the phase distribution of the array laser, the position where the final array laser focuses on the workpiece can be changed.

[0089] Specifically, the realization of the focal position regulation of the data processing unit is divided into the following four steps:

[0090] Step 1: Compensate for the phase difference and phase noise between the unit beams in the system. The compensation method can be any array laser coherent combination phase control algorithm, such as near-field interference fringe extraction, heterodyne method, optimization algorithm, etc. Taking the optimization algorithm as an example, Figure 3 In it, the main lobe energy of the far-field interference fringe is converted into an electrical signal by the photodetector 111 and sent to the data processing unit 113. The data processing unit 113 calculates the phase error between each unit beam through an optimization algorithm such as the stochastic parallel gradient descent and outputs the corresponding control voltage u to the phase modulator (u = {u 1 ,u 2 ,…,u N}, N is the number of sub-beams), so that the main lobe energy of the array beam interference detected by the photodetector reaches the maximum value. At this time, the phases between each unit beam will be controlled to be consistent.

[0091] Step 2: Determine the focal depth of the array laser on the workpiece.

[0092] Place the upper surface of the workpiece to be processed at a position f away from the focusing lens 107. When the laser phases of the individual unit beams are consistent, the distance between the focal point and the focusing lens 107 is f, that is, the focal point falls on the upper surface of the workpiece to be processed. Taking laser cutting as an example, when performing a laser cutting operation on the workpiece to be processed, after completing the cutting of the surface of the workpiece to be processed, it is desired to move the focal depth downward to achieve the focusing of the laser energy inside the workpiece to be processed and improve the processing efficiency. Let the focal point step distance be dz, and at this time, the desired system equivalent focal length is f equ = f + n·dz, n = 0, 1, 2….

[0093] Step 3: Calculate the desired array distribution of the array laser according to the desired system equivalent focal length.

[0094] Figure 2 A schematic diagram of the equivalence principle is provided. The equivalent lens combination includes a focusing lens 201 and an equivalent lens 202. The focal length of the focusing lens 201 is f, corresponding to Figure 3 the long-focus focusing lens 107 in the shown structural schematic diagram. The phase of the equivalent lens 202 corresponds to Figure 3 the phase of the array laser emitted from the laser beam combining device 105 in the shown structural schematic diagram, and the focal length is f 2 . It is known from Step 2 that the desired system equivalent focal length is f equ . According to the equivalent focal length calculation formula for the combination of two lenses in formula (1), the focal length f of the equivalent lens 202 can be deduced 2 .

[0095]

[0096] In formula (1), s is the distance between the two lenses.

[0097] From the deduced focal length f of the equivalent lens 202 2 it can be further obtained that the desired laser array phase distribution should satisfy formula (2)

[0098]

[0099] In formula (2), x and y are spatial coordinates, and k = 2π / λ is the wave number.

[0100] Since the controlled phase of the unit beam is the piston phase and cannot fully simulate the phase of the equivalent lens, the center of the unit beam of the array laser is used to sample the phase of the equivalent lens. Figure 4The figure shows a schematic diagram of an array laser phase generation method consisting of 37 unit beams in an embodiment. Assume that the aperture diameter of a single unit beam is 3 mm, the distance between unit beams is 3.16 mm, the array duty cycle is approximately 95%, the focal length of the focusing lens is 1 m, the system focus step value is 1 mm, the array beam is transmitted parallel to the focusing lens, and the distance s between the array laser and the long - focal - length focusing lens is ignored. If the focus position is moved to the 1.001 m position, the equivalent lens focal length f is calculated according to formula (1). 2 =-101 m, and the phase distribution of the equivalent lens can be calculated according to formula (2) as shown in Figure 4 (a). Sampling the phase distribution of the equivalent lens using the central positions of the sub - beams of the array laser composed of 37 unit beams, the corresponding array phase distribution in Figure 4 (b) can be obtained That is, the array phase distribution required to move the system equivalent focus by 1 mm, and the corresponding control voltage offset is Δu = {Δu 1 , Δu 2 , …, Δu 37}.

[0101] Step Four: Apply the generated phase distribution to the array laser.

[0102] In Step One, the phase error existing in the system has been compensated by the applied control voltage u. Adding the required control voltage offset to the control voltage u can obtain the control voltage output u + Δu required for focal depth regulation. To ensure the accuracy of the required phase distribution, it is necessary to periodically compensate and update the control voltage u for the system phase noise. During the process of updating the control voltage u, the focus position is temporarily restored to the upper surface of the workpiece to be processed. Since the time required for phase noise compensation is short, the system can still move the focus to the desired position for most of the time. The optimization algorithm is just one embodiment of the method proposed in the present invention. By using direct phase methods such as near - field interference fringe extraction and heterodyne method, the required phase distribution Δu can be applied while updating the control voltage u, and it is no longer necessary to temporarily move the focus back to the initial position for phase noise correction.

[0103] Figure 5 The figure shows Figure 4 Based on the parameters, before and after focal regulation, the schematic diagram of the energy distribution in the optical axis direction. Figure 5 (a) shows the energy distribution on the optical axis before focal regulation. Figure 5 (b) shows the energy distribution on the optical axis after focal regulation. Figure 5(c) shows a comparison of their cross-sectional views. It can be seen from this that the method provided by the present invention can rapidly change the energy distribution of the focus in the optical axis direction. Taking 80% of the energy as the evaluation criterion, compared with the processing method with a fixed focus, the method provided by the present invention can provide a focal depth of about 3 times, has more advantages in processing thick materials, and can improve the processing efficiency.

[0104] In summary, the present invention outputs by using an array composed of multiple fiber lasers, and changes the focusing position of the output laser by regulating the phase distribution of the array, thereby providing a non-mechanical, high-speed, precise and high-output-power axial focus regulation method. The present invention solves the problems of low output power and long response time of the existing axial focus regulation methods, and improves the accuracy of axial focus regulation.

[0105] Matters not covered by the present invention are well-known technologies.

[0106] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0107] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. Optical phased array axial focus regulation method, Characterized in that, Comprising: Compensating the phase difference and phase noise between the unit beams in the array laser, so that the phase control between the unit beams is consistent; Determine the focal depth of the array laser on the workpiece to be processed. The array laser is focused on the workpiece to be processed after passing through the focusing lens. The distance between the focal point and the focusing lens is f. Let the axial step distance of the focal point each time be dz. Then the expected equivalent focal length corresponding to the nth step is f equ = f + n·dz, n = 0, 1, 2…; Calculating the expected array distribution of the array laser according to the expected equivalent focal length, including: The array laser and the focusing lens are equivalent to a lens combination composed of two lenses. The phase of the equivalent lens in the lens combination corresponds to the phase of the array laser, and the focal length of the equivalent lens is f. 2 The focal length of the focusing lens is f, and the distance between the equivalent lens and the focusing lens is s; Calculate the focal length f of the equivalent lens according to the desired equivalent focal length and the equivalent focal length of the lens combination 2 ; According to the focal length f of the equivalent lens 2 the desired phase distribution of the laser array is obtained; Applying the expected array distribution to the array laser to change the position where the array laser is focused on the workpiece.

2. The optical phased array axial focus regulation method according to claim 1, Characterized in that, The focal length f of the equivalent lens 2 is determined by the following formula:

3. The optical phased array axial focus regulation method according to claim 2, Characterized in that, The expected laser array phase distribution is: Where x and y respectively represent the spatial coordinates of the laser distribution in the x direction and the y direction, k = 2π / λ is the wave number, and λ is the wavelength of the array laser.

4. Optical phased array axial focus regulation system, Characterized in that, Comprising: Array laser coherent combination optical path, used to realize the coherent combination and output of multiple unit beams; High reflector, arranged on the output path of the array laser coherent combination optical path, most of the laser output by the array laser coherent combination optical path is reflected by the high reflector, and a small part is transmitted through the high reflector; Focusing lens: The array laser reflected from the high reflector is focused on the workpiece to be processed after passing through the focusing lens. The distance between the focal point and the focusing lens is f. Assume that the axial step distance of the focal point each time is dz. Then the expected equivalent focal length corresponding to the nth step is f equ = f + n·dz, n = 0, 1, 2…; Signal acquisition module, used to acquire the optical signal transmitted through the high reflector and convert it into an electrical signal; The data processing module compensates for the phase difference and phase noise between the unit beams in the array laser based on the electrical signals output by the signal acquisition module, so as to control the phases of the unit beams to be consistent; after the phases of the unit beams are controlled to be consistent, it determines the focal depth of the array laser on the workpiece to be processed; according to the expected equivalent focal length, it calculates the expected array distribution of the array laser, including: regarding the array laser and the focusing lens as a lens combination composed of two lenses, the phase of the equivalent lens in the lens combination corresponds to the phase of the array laser, and the focal length of the equivalent lens is f 2 , the focal length of the focusing lens is f, and the distance between the equivalent lens and the focusing lens is s; according to the expected equivalent focal length and the equivalent focal length of the lens combination, it calculates the focal length f of the equivalent lens 2 ; according to the focal length f of the equivalent lens 2 it obtains the expected laser array phase distribution; applies the expected array distribution to the array laser to change the position where the array laser is focused on the workpiece to be processed.

5. The optical phased array axial focus regulation system according to claim 4, Characterized in that, The array laser coherent combination optical path includes a seed laser, a 1×N beam splitter, N phase modulators, N fiber amplifiers and a laser beam combining device; The laser output by the seed laser is divided into N unit beams by the 1×N beam splitter, and each unit beam is phase modulated and amplified by the corresponding phase modulator and fiber amplifier, and the N unit beams after phase modulation and amplification are combined and output by the laser beam combining device.

6. The optical phased array axial focus regulation system according to claim 5, Characterized in that, The data processing module is connected to the phase modulators of each unit beam for control.

7. The optical phased array axial focus regulation system according to claim 4 or 5 or 6, Characterized in that, The focal length f of the equivalent lens 2 is determined by the following formula: The expected laser array phase distribution is: Where x and y respectively represent the spatial coordinates of the laser distribution in the x direction and the y direction, k = 2π / λ is the wave number, and λ is the wavelength of the array laser.

Images