Multifunctional monitoring system, monitoring method and pointing method for laser processing

Abstract

The present invention relates to a multifunctional monitoring system, monitoring method and pointing method for laser processing, which solve the problems of slow data processing speed, high cost, large volume and high integration difficulty of existing laser processing methods. The system includes a spectroscopic module, a monitoring lens, an imaging component, a motion module and a signal processing module; the spectroscopic module is installed in the laser processing optical path, and the laser beam is divided into two paths through the spectroscopic module, one of which is deflected 90° by the spectroscopic module to enter the monitoring lens, and the other passes through the spectroscopic module to realize laser processing; the monitoring lens and the imaging component are arranged on the reflection optical path of the spectroscopic module; the motion module realizes the movement of the imaging component; the monitoring lens includes an optical system; the imaging component includes a detector and an imaging circuit board; the signal processing module is connected to the detector. At the same time, the present invention also provides a monitoring method based on the above system and a method for realizing the position pointing of the processing laser.

Description

Technical Field

[0001] The present invention relates to the field of laser processing technology, in particular to some laser processing fields with high requirements on laser power, energy distribution and beam pointing, and specifically to a multifunctional monitoring system, monitoring method and pointing method for laser processing. Background Art

[0002] Laser processing has the characteristics of high processing precision, good quality and flexibility, so it has been widely used in industrial fields such as steel, machinery, automobiles and semiconductors. For laser processing equipment, its reliability depends on the stability of the laser processing light path. The laser processing process is the result of the interaction between laser and material. The quality of processing is affected by process parameters such as laser power, energy distribution and beam pointing. Only by achieving effective process parameters can the best processing quality be guaranteed.

[0003] As laser processing technology becomes increasingly automated and intelligent, laser processing monitoring devices have become a hot topic in the field of laser technology at home and abroad. Introducing monitoring devices into laser processing equipment to monitor the processing beam power, energy distribution, and beam pointing during the operation of the equipment can effectively improve the controllability of laser processing and improve processing quality.

[0004] At present, in laser processing equipment, to measure process parameters such as laser power, energy distribution and beam pointing, at least three monitoring devices are required. This method leads to slow data processing speed and difficulty in integration. At the same time, the introduction of multiple monitoring devices brings problems such as high cost, large volume and high integration difficulty. In view of this, it is necessary to provide a monitoring device that can solve the above technical problems, which is used to monitor process parameters such as laser power, energy distribution and beam pointing. Summary of the invention

[0005] The purpose of the present invention is to solve the technical problems of slow data processing speed, high cost, large size and high integration difficulty of existing laser processing monitoring devices, and to provide a multifunctional monitoring system and monitoring method and pointing method for laser processing, which can realize multifunctional monitoring of process parameters such as laser power, energy distribution and beam pointing.

[0006] The technical solution of the present invention is:

[0007] A multifunctional monitoring system for laser processing includes a spectroscopic module, a monitoring lens, an imaging component, a motion module and a signal processing module; the spectroscopic module is installed in the laser processing optical path, and the laser beam is divided into two paths by the spectroscopic module, one of which is deflected 90 degrees by the spectroscopic module and enters the monitoring lens, and the other passes through the spectroscopic module to realize laser processing; the monitoring lens and the imaging component are arranged on the reflection optical path of the spectroscopic module; the motion module realizes the movement of the imaging component; the monitoring lens includes an optical system; the imaging component includes a detector and an imaging circuit board; the signal processing module is connected to the detector and is used to analyze the collected image, obtain process parameters such as laser power, energy distribution and beam pointing, and timely feed back to the numerical control system.

[0008] Furthermore, the optical system is a telecentric flat-field lens, comprising an aperture, a first positive lens, a first negative lens and a second positive lens, which are arranged in sequence from the object plane to the image plane.

[0009] Furthermore, the refractive index nd>1.75 and the dispersion coefficient vd<50 of the first positive lens; the refractive index nd<1.65 and the dispersion coefficient vd>30 of the first negative lens; the refractive index nd>1.75 and the dispersion coefficient vd<50 of the second positive lens.

[0010] Furthermore, the thickness of the first positive lens is 3.109mm, the radius of curvature of the light incident surface is 11.969mm, the semi-aperture is 5.03mm, the radius of curvature of the light exit surface is 19.639mm, and the semi-aperture is 4.47mm; the thickness of the first negative lens is 4mm, the radius of curvature of the light incident surface is -6.789mm, the semi-aperture is 2.73mm, the radius of curvature of the light exit surface is -13.119mm, and the semi-aperture is 3.28mm; the thickness of the second positive lens is 3.151mm, the radius of curvature of the light incident surface is 33.207mm, the semi-aperture is 3.35mm, the radius of curvature of the light exit surface is -35.899mm, and the semi-aperture is 3.24mm; the distance between the first positive lens and the first negative lens is 12.59mm, and the distance between the first negative lens and the second positive lens is 3.114mm; the distance between the second positive lens and the image plane is 12mm.

[0011] Furthermore, the spectroscopic module comprises a spectroscopic plate, and in order to strictly control the reflectivity and transmittance, an anti-reflection film and an anti-damage threshold film are plated on the surface of the spectroscopic plate.

[0012] Furthermore, in order to prevent stray light of other wavelengths from reaching the detector and affecting the measurement accuracy, a filter is provided between the monitoring lens and the imaging component. The filter is a narrow-band filter. In order to prevent strong light from damaging the detector, a baffle is provided between the monitoring lens and the imaging component.

[0013] Furthermore, the motion module includes a lead screw and a guide rail, and the imaging component is arranged on a nut of the lead screw to ensure the coaxiality requirement of the imaging component during movement.

[0014] At the same time, the present invention also provides a monitoring method based on the above-mentioned multifunctional monitoring system for laser processing, comprising the following steps:

[0015] 1) The laser beam is folded 90° to form an image through the beam splitting module;

[0016] 2) Read the gray value of each pixel according to the collected image, count the gray value of the entire spot, and calculate the illumination value E of the laser beam;

[0017]

[0018] Where, F: the reciprocal of the relative aperture of the optical system;

[0019] U: detector saturation voltage;

[0020] η: detector conversion factor;

[0021] QUOTE : optical system transmittance;

[0022] t: exposure time;

[0023] R: responsiveness;

[0024] DN: gray value;

[0025] 3) Integrate E to obtain energy I;

[0026]

[0027] Where S is the spot area.

[0028] In addition, the present invention also provides a method for realizing laser pointing by using the above system, comprising the following steps:

[0029] 1) Measure the off-axis amount;

[0030] The centroid coordinates of the light spot are captured at the focal plane, position 1 and position 2 parallel to the focal plane, respectively. The centroid coordinates of the focal plane are used to calibrate the optical axis and are recorded as (0, 0). The distance between position 1 and position 2 is D. The centroid coordinates of position 1 and position 2 are (x1, y1) and (x2, y2) respectively. In the off-axis case, x2 = x1, so the off-axis value is Where: f / is the focal length;

[0031] 2) Measure the tilt angle;

[0032] The centroid coordinates of the light spot are captured at the focal plane, position 1 and position 2 parallel to the focal plane. The centroid coordinates of the focal plane are used to calibrate the optical axis and are recorded as (x0, y0). The distance between the focal plane and position 2 is D2, the distance between position 1 and position 2 is D1, and the distance between position

[0033] The centroid coordinates of position 1 and position 2 are (x1, y1) and (x2, y2) respectively. In the case of tilt, x0 = x2 = x1, so the tilt angle is

[0034] .

[0035] Furthermore, step 1) also includes the following steps: performing multiple measurements to obtain multiple groups of off-axis values, and calculating the average value of the multiple groups of off-axis values; step 2) also includes the following steps: performing multiple measurements to obtain multiple groups of tilt angles, and calculating the average value of the multiple groups of tilt angles.

[0036] Compared with the prior art, the present invention has the following technical effects:

[0037] 1. The present invention can realize the measurement of multiple process parameters such as laser power, energy distribution and beam pointing through only one monitoring system, and has the advantages of low cost, small size, simple structure and easy integration.

[0038] 2. The present invention collects images through a monitoring system and can achieve multiple parameter measurements through signal processing.

[0039] 3. The present invention provides a multifunctional monitoring system for laser processing to realize a laser position pointing method. The method obtains the off-axis amount and tilt angle of the light beam according to the changes of the light spots at three positions, guides the installation of the processing laser head, and improves the laser processing accuracy.

[0040] 4. The aperture of the monitoring lens of the present invention is much larger than the current laser beam waist size, has strong versatility, and is compatible with most laser equipment. The monitoring lens belongs to a small aberration system with high imaging performance, and the optical transfer function is basically close to the diffraction limit, eliminating the influence of the optical system on the measurement results.

[0041] 5. The light splitting module of the present invention is a module with high transmittance, which ensures full utilization of energy in the processing light path and has no influence on the processing light path by monitoring unused light. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic diagram of the structure of the multifunctional monitoring system of the present invention;

[0043] Figure 2 This is a schematic diagram of the structure of the optical system of the monitoring lens of the present invention;

[0044] Figure 3The spot diagram of the monitoring lens of the present invention;

[0045] Figure 4 This is a schematic diagram of the off-axis measurement principle of the present invention;

[0046] Figure 5 This is a schematic diagram of the tilt angle measurement principle of the present invention.

[0047] Figure numerals: 1-spectrometer module, 2-monitoring lens, 3-filter, 4-baffle, 5-imaging component, 6-motion module, 7-signal processing module, 21-aperture, 22-first positive lens, 23-first negative lens, 24-second positive lens, 25-image plane. DETAILED DESCRIPTION

[0048] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0049] like Figure 1 The figure shows a multifunctional monitoring system for laser processing provided by the present invention, which has the function of monitoring process parameters such as laser power, energy distribution and beam pointing. The system includes a spectrometer module 1, a monitoring lens 2, a filter 3, a baffle 4, an imaging component 5, a motion module 6 and a signal processing module 7.

[0050] The spectrometer module 1 is installed in the laser processing optical path. The laser beam is divided into two paths through the spectrometer module 1. One path is deflected 90° by the spectrometer module 1 and enters the monitoring lens 2. The other path passes through the spectrometer module 1 and enters the processing head to realize laser processing. The spectrometer module 1 is equipped with a spectrometer plate. The surface of the spectrometer plate is coated with an anti-reflection film and an anti-damage threshold film to strictly control the reflectivity and transmittance. The monitoring lens 2, the filter 3, the baffle 4, and the imaging component 5 are arranged on the reflected light path of the spectrometer module 1. In actual installation, the monitoring lens 2, the imaging component 5, the motion module 6, and the signal processing module 7 are integrated into one and can be fixed on the spectrometer by screws.

[0051] On the optical module 1. The imaging component 5 includes a highly sensitive CCD or CMOS detector and an imaging circuit board. The motion module 6 realizes the movement of the imaging component 5, which includes a lead screw and a guide rail. The lead screw includes a screw and a nut. The imaging component 5 is fixedly set on the nut. The guide rail guides the translation of the nut to ensure the coaxiality requirement of the imaging component 5 during movement; the monitoring lens 2 includes an optical system and a mechanical structure of a fixed optical system. The mechanical structure adopts a lens-in-frame structure and a lens barrel with a glue injection hole. This installation method has good vibration resistance and dustproof advantages. The signal processing module 7 is connected to the detector to analyze the collected image, obtain process parameters such as laser power, energy distribution and beam pointing, and timely feedback to the CNC system.

[0052] like Figure 2The figure shows a schematic diagram of the optical system structure of the monitoring lens of the present invention. The optical system includes three lenses. The optical system includes an aperture 21, a first positive lens 22, a first negative lens 23 and a second positive lens 24 in sequence from the object plane to the image plane 25. The optical power is arranged in a positive, negative and positive form, without special glass, complex surface shape and cemented mirror, which is conducive to processing and assembly. The optical system has eight degrees of freedom. In addition to meeting the optical power requirements, it can also correct all primary aberrations. It belongs to a thin lens group separation structure, and uses positive and negative optical power separation to correct field curvature. It is a symmetrical objective lens. The optical system belongs to a new three-piece structure. The aperture of the traditional optical system is located behind the negative lens. The aperture is set behind the first positive lens, and the ability to correct the aperture aberration is limited. In order to achieve the image telecentricity of the monitoring lens 2, the aperture of the present invention is moved before the first positive lens 22.

[0053] The monitoring laser beam is deflected along the reflector to the detector direction, and the laser beam passes through the monitoring lens 2, filter 3, baffle 4 and detector in sequence. Among them, the monitoring lens 2 is used to image the light reflected by the laser beam at the detector, and it must adopt a telecentric design to ensure the accuracy of power measurement; the spectroscopic plate is placed above the processing focusing mirror in the processing light path, and the processing light is focused on the workpiece through the plate and the focusing mirror to make holes. The spectroscopic plate is used for beam deflection in the monitoring light path, and the plate coating must be strictly required to ensure the accurate correspondence between the reflected light and the transmitted light; the filter 3 is a narrow-band filter 3, corresponding to the laser wavelength and spectrum width, to prevent stray light of other wavelengths from reaching the detector and affecting the measurement accuracy; the baffle 4 is used to prevent strong light from damaging the detector during calibration; the detector is used to receive the light spot to analyze the characteristics of the beam.

[0054] The specific parameters and materials of each lens component of the optical system of the monitoring lens 2 in the embodiment of the present invention are shown in Table 1. Table 1 (Unit in the table: mm)

[0055]

[0056] The optical focal lengths of the three refractive mirror groups are Φ1, Φ2, and Φ3 respectively; the normalized values ​​are Φ1=0.36, Φ2=-1.2, and Φ3=1.

[0057] The system is implemented as follows: the laser beam is deflected 90° by the beam splitter plate, and then imaged on the detector through a telecentric flat-field lens. The focus is performed based on the image clarity, and the beam energy distribution and laser power are measured based on the grayscale value. The detector is then moved to two defocused positions, and the off-axis amount and tilt angle of the beam are obtained based on the changes in the light spots at the three positions to guide the assembly of the laser head.

[0058] The specific monitoring method provided by the present invention comprises the following steps:

[0059] 1) The laser beam is deflected 90° by the light splitting module 1 and imaged on the imaging component 5;

[0060] 2) If Figure 3 As shown, it is a spot diagram of the monitoring lens 2 provided by the present invention. The diffuse spot is much smaller than the detector pixel size, and the imaging quality basically reaches the diffraction limit. The optical system adopts a telecentric design, and the light emission degree of each field of view is less than 1°. The spot size is basically equal and maintains good roundness, which greatly reduces the energy distribution and energy measurement errors. The specific measurement method is: the gray value of each pixel can be directly read out according to the collected image, and the gray value of the entire spot is counted. The illumination value E (i.e., laser power) of the laser beam can be calculated by the following formula;

[0061]

[0062] Where, F: F number of the optical system, which is the reciprocal of the relative aperture of the optical system;

[0063] U: CCD saturation voltage;

[0064] η: CCD conversion factor;

[0065] QUOTE : optical system transmittance;

[0066] t: exposure time;

[0067] R: responsiveness;

[0068] DN: gray value.

[0069] 3) Integrate E to get energy I;

[0070]

[0071] Where S is the spot area.

[0072] In addition, the present invention also provides a method for realizing laser pointing by the above system, comprising the following steps:

[0073] 1) If Figure 4 As shown in the figure, the principle diagram of off-axis measurement provided by the present invention, the laser beam is focused on the detector through the optical lens, that is, the focal plane. The solid line represents the ideal light, and the dotted line represents the off-axis light. After the laser beam is off-axis, the line connecting the centroid of the focused light spot no longer coincides with the optical axis, which changes the taper of the converging light beam, and ultimately leads to a decrease in the quality of laser processing, such as uneven cutting end faces and reduced cylindricality of holes. The centroid coordinates of the light spot are captured at three positions, namely, the focal plane, position 1, and position 2. The centroid coordinates of the focal plane are used to calibrate the optical axis (reference axis) as a reference axis, denoted as (0, 0). Positions 1 and 2 are

[0074] Set the distance 2 to D, the centroid coordinates of position 1 and position 2 are (x1, y1) and (x2, y2) respectively. In the off-axis case, x2 = x1, so the off-axis value To measure the off-axis value more accurately, several positions can be selected and the average value can be calculated, where: f / is the focal length.

[0075] 2) If Figure 5 The figure shows the principle diagram of the tilt angle measurement provided by the present invention; the solid line represents the ideal light, and the dotted line represents the off-axis light. After the laser beam is tilted, the centroid line of the focused light spot no longer coincides with the optical axis, which changes the convergence position of the light beam, and ultimately leads to a decrease in the positioning accuracy and processing size accuracy of the laser processing. The centroid coordinates of the light spot are captured at the focal plane, position 1, and position 2, respectively. The centroid coordinates of the focal plane are used to calibrate the optical axis (reference axis) as a reference axis, denoted as (x0, y0). The distance between the focal plane and position 2 is D2, the distance between position 1 and position 2 is D1, and the centroid coordinates of position 1 and position 2 are respectively

[0076] is (x 1, y1) and (x2,y2), in the case of tilt, x0=x2=x1, so the tilt angle is

[0077] To measure the tilt angle more accurately, you can select several positions and calculate the average value.

[0078] The tilt angle and off-axis value obtained above are used to adjust the processing laser pointing and guide the installation of the processing laser head.

Claims

1. A multifunctional monitoring system for laser processing, characterized in that: It comprises a light splitting module (1), a monitoring lens (2), an imaging component (5), a motion module (6) and a signal processing module (7); The light splitting module (1) is installed in the laser processing optical path, and the laser beam is split into two paths through the light splitting module (1), one of which is deflected 90 degrees by the light splitting module (1) and enters the monitoring lens (2), and the other passes through the light splitting module (1) to achieve laser processing; the light splitting module (1) comprises a light splitting plate, and the surface of the light splitting plate is coated with an anti-reflection film and an anti-damage threshold film; The monitoring lens (2) and the imaging component (5) are arranged on the reflection light path of the light splitting module (1), and a filter (3) and a baffle (4) are also arranged between the monitoring lens (2) and the imaging component (5), and the filter (3) is a narrow-band filter; The motion module (6) realizes the movement of the imaging component (5); The monitoring lens (2) comprises an optical system; the imaging component (5) comprises a detector and an imaging circuit board; The signal processing module (7) is connected to the detector and is used to analyze the collected images; The optical system is a telecentric flat-field lens, comprising an aperture (21), a first positive lens (22), a first negative lens (23) and a second positive lens (24) which are arranged in sequence from the object plane to the image plane (25); The refractive index nd of the first positive lens (22) is greater than 1.75, and the dispersion coefficient vd is less than 50; the thickness of the first positive lens (22) is 3.109 mm, the radius of curvature of the light incident surface is 11.969 mm, the semi-aperture is 5.03 mm, and the radius of curvature of the light exit surface is 19.639 mm, and the semi-aperture is 4.47 mm; The refractive index nd of the first negative lens (23) is less than 1.65, and the dispersion coefficient vd is greater than 30; the thickness of the first negative lens (23) is 4 mm, the radius of curvature of the light incident surface is -6.789 mm, the semi-aperture is 2.73 mm, and the radius of curvature of the light exit surface is -13.119 mm, and the semi-aperture is 3.28 mm; The refractive index nd of the second positive lens (24) is greater than 1.75, and the dispersion coefficient vd is less than 50; the thickness of the second positive lens (24) is 3.151 mm, the radius of curvature of the light incident surface is 33.207 mm, the semi-aperture is 3.35 mm, the radius of curvature of the light exit surface is -35.899 mm, and the semi-aperture is 3.24 mm; The distance between the first positive lens (22) and the first negative lens (23) is 12.59 mm, the distance between the first negative lens (23) and the second positive lens (24) is 3.114 mm; and the distance between the second positive lens (24) and the image plane is 12 mm.

2. The multifunctional monitoring system for laser processing according to claim 1, characterized in that: The motion module (6) comprises a lead screw and a guide rail, and the imaging assembly (5) is arranged on a nut of the lead screw.

3. The monitoring method of the multifunctional monitoring system for laser processing according to claim 1 or 2, characterized in that: The following steps are involved: 1) The laser beam is folded 90° to form an image through the beam splitting module; 2) Read the gray value of each pixel according to the collected image, count the gray value of the entire spot, and calculate the illumination value E of the laser beam; ， Where, F: the reciprocal of the relative aperture of the optical system; U: detector saturation voltage; η: detector conversion factor; : optical system transmittance; t: exposure time; R: responsiveness; DN: gray value; 3) Integrate E to obtain energy I; ， Where S is the spot area.

4. A method for realizing laser pointing by using the multifunctional monitoring system for laser processing according to claim 1 or 2, characterized in that: The following steps are involved: 1) Measure the off-axis amount; The centroid coordinates of the light spot are captured at the focal plane, position 1 and position 2 parallel to the focal plane, respectively. The centroid coordinates of the focal plane are used to calibrate the optical axis and are recorded as (0, 0). The distance between position 1 and position 2 is D, and the centroid coordinates of position 1 and position 2 are (x1, y1) respectively. and (x2, y2), in the off-axis case x2 = x1, so the off-axis value Where: f′ is the focal length; 2) Measure the tilt angle; The centroid coordinates of the light spot are captured at the focal plane, position 1 and position 2 parallel to the focal plane, respectively. The centroid coordinates of the focal plane are used to calibrate the optical axis, recorded as (x0, y0). The distance between the focal plane and position 2 is D2, the distance between position 1 and position 2 is D1, and the centroid coordinates of position 1 and position 2 are (x1, y1) and (x2, y2), respectively. In the case of tilt, x0 = x2 = x1, so the tilt angle is: 。 5. The method for realizing laser pointing by the multifunctional monitoring system for laser processing according to claim 4 is characterized in that: Step 1) further includes the following steps: performing multiple measurements to obtain multiple groups of off-axis values, and calculating an average value of the multiple groups of off-axis values; Step 2) also includes the following steps: performing multiple measurements to obtain multiple groups of tilt angles, and calculating the average value of the multiple groups of tilt angles.

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