CN112276370B - A three-dimensional code laser marking method and system based on spatial light modulator - Google Patents

Abstract

The invention discloses a three-dimensional code laser marking method and system based on a spatial light modulator, belonging to the field of laser processing. The spatial light modulator is superimposed with a phase shift Fresnel lens, a spatial grating and a Bessel shaping lens. Including: extracting the contour information of each color block in the three-dimensional code color image to generate the corresponding contour image; respectively using the preset phase corresponding to each contour image as the initial value of the holographic algorithm light field model to perform iterative calculation to obtain the corresponding contour image. Target phase; input each target phase to the spatial light modulator in turn to phase-modulate the incident laser beam and output a Bessel beam, thereby marking each contour image on the target material in turn. Using the spatial light modulator to carry out 3D code laser marking, multi-focus marking can be realized under the condition of unchanged optical path, and the marking rate can be improved, and the Bessel beam can improve marking uniformity and resolution.

Description

A three-dimensional code laser marking method and system based on spatial light modulator

technical field

The invention belongs to the field of laser processing, and more particularly, relates to a three-dimensional code laser marking method and system based on a spatial light modulator.

Background technique

A QR code is a square code consisting of black and white squares. With the development and popularization of the computer and network industries, due to the open-source nature of the QR code, its storage capacity is insufficient, the stored data structure is single, the confidentiality is insufficient, and the weak anti-counterfeiting and anti-copying capabilities limit the existence of the QR code in the physical world. The next step in the Internet era. Random three-dimensional code adds random color information on the basis of two-dimensional code, and is processed on a special multi-layer anti-counterfeiting material, which has the characteristics of three-dimensional, unique and non-reproducible. It overcomes the disadvantage that ordinary two-dimensional codes are easy to be copied, and can be widely used in products that require strict anti-counterfeiting labels.

At present, in the field of two-dimensional code and three-dimensional code laser marking, a high-speed positioning and marking system combined with a laser galvanometer is usually used. The system uses vector scanning and moving the galvanometer to quickly mark the target area. Depending on the beam quality of the laser output by the laser galvanometer, the main way to adjust the output is to adjust the duty cycle of the galvanometer laser output to change the laser power, and the scanning is slow when marking a series of two-dimensional codes on a large scale. At the same time, the control of the galvanometer is mostly limited to small amplitude swings of the galvanometer in all directions. When multi-focus marking is required, multiple galvanometers or single galvanometers are required for multiple markings.

SUMMARY OF THE INVENTION

Aiming at the defects and improvement requirements of the prior art, the present invention provides a method and system for laser marking of three-dimensional codes based on spatial light modulators, the purpose of which is to use spatial light modulators for laser marking of three-dimensional codes without changing the optical path. In the case of multi-focus marking, the marking rate is improved, and the spatial light modulator modulates the output Bessel beam to improve marking uniformity and resolution, and has the advantages of high speed, high efficiency, low loss and low cost.

In order to achieve the above object, according to one aspect of the present invention, a three-dimensional code laser marking method based on a spatial light modulator is provided, wherein the spatial light modulator is superimposed with a phase shift Fresnel lens, a spatial grating and a Bessel. and the method includes: S1, randomly converting a target two-dimensional code or a target two-dimensional dot matrix into a color image of a three-dimensional code, and extracting the contour information of each color block in the color image of the three-dimensional code, so as to generate a corresponding color block for each color block. S2, use the preset phase corresponding to each described outline image as the initial value of the holographic algorithm light field model to perform iterative calculation to obtain the target phase corresponding to each described outline image; S3, use each described target phase The phases are sequentially input to the spatial light modulator, so that the spatial light modulator performs phase modulation on the incident laser beam according to the received target phase and then outputs a Bessel beam, so as to mark the target material in turn. Outline image.

Further, the S1 includes: generating the target two-dimensional code or the target two-dimensional lattice according to the initial information; dividing the target two-dimensional code or the target two-dimensional lattice into a plurality of minimum marking units, and adding random color blocks to generate the color image of the three-dimensional code; using an erosion algorithm to diffuse the color image of the three-dimensional code to extract the contour information of the color blocks.

Further, the holographic algorithm light field model is generated based on the simulated annealing algorithm and the intensity transfer equation, and the generated holographic algorithm light field model is:

为引入振幅自由度后第

次迭代输出的光场幅值，

为迭代次数，

为信号场影响因子，

为信号区域的目标光强，

为第

次迭代后噪声区域的输出，

为第

次迭代后的复相位，

为虚数单位。in,

After the introduction of the amplitude degree of freedom,

The magnitude of the light field output by the next iteration,

is the number of iterations,

is the signal field influence factor,

is the target light intensity in the signal area,

for the first

the output of the noise region after one iteration,

for the first

the complex phase after one iteration,

is an imaginary unit.

Further, the iterative equation of the phase in the light field model of the holographic algorithm is:

、

、

表示入射面，

为第

次迭代的相位分布，

为迭代次数，

为第

次迭代的相位分布，

为梯度收敛参数，

为迭代收敛方向。in,

,

,

represents the incident surface,

for the first

The phase distribution of the next iteration,

is the number of iterations,

for the first

The phase distribution of the next iteration,

is the gradient convergence parameter,

is the iterative convergence direction.

Further, in the step S2, using the preset phase corresponding to each contour image as the initial value of the holographic algorithm light field model to perform iterative calculation includes: setting the amplitude value of each contour image as the target amplitude value, and Read the corresponding preset phase in the preset configuration file according to each of the target amplitudes; take the preset phase corresponding to each of the contour images as the initial value of the light field model of the holographic algorithm, and use the The target amplitude corresponding to the contour image is used as the target value of the light field model of the holographic algorithm to perform iterative calculation to obtain each target phase.

Further, before outputting the Bessel beam in S3, the method further includes: outputting the Bessel beam after shielding the zero aurora in the Bessel beam.

Further, before outputting the Bessel beam in S3, the method further includes: retaining the zero aurora in the Bessel beam and outputting the Bessel beam, so as to mark each beam on the target material in turn. the outline image.

Further, in S3, the horizontal position and the axial focus of the Bessel beam are adjusted by adjusting the phase-shifting Fresnel lens and/or the space grating.

Further, before the S1, the method further includes: increasing the light damage threshold of the spatial light modulator to 40W/cm ² -150W/cm ² by means of physical cooling.

According to another aspect of the present invention, a three-dimensional code laser marking system based on a spatial light modulator is provided, wherein the spatial light modulator is superimposed with a phase-shifting Fresnel lens, a spatial grating and a Bessel shaping lens, The system includes: a conversion and extraction module for randomly converting a target two-dimensional code or a target two-dimensional dot matrix into a color image of a three-dimensional code, and extracting the outline information of each color block in the color image of the three-dimensional code to generate the color block a corresponding contour image; a calculation module for performing iterative calculation with the preset phase corresponding to each of the contour images as the initial value of the light field model of the holographic algorithm, so as to obtain the target phase corresponding to each of the contour images; a superposition module, for stacking phase-shifted Fresnel lenses, spatial gratings and Bessel shaping lenses in the spatial light modulator; a modulation and marking module for sequentially inputting each of the target phases to the spatial light modulator , so that the spatial light modulator phase-modulates the incident laser beam according to the received target phase and then outputs a Bessel beam, so as to mark the contour images on the target material in sequence.

In general, through the above technical solutions conceived by the present invention, the following beneficial effects can be achieved:

(1) Add 3D code information on the basis of black and white QR code and dot matrix, which improves the anti-counterfeiting, randomness and storage capacity of QR code; obtains the corresponding 3D contour information, and converts the three holograms corresponding to the 3D contour information. The phase map is sequentially loaded into the spatial light modulator for 3D code laser marking, and multi-focus marking is realized under the condition of the same optical path, which improves the marking rate;

(2) A phase-shifting Fresnel lens, a spatial grating and a Bessel shaping lens are superimposed in the spatial light modulator to shape the incident laser beam into a Bessel beam, which improves marking uniformity and resolution under the same laser power. rate, and marking at different positions and focal points can be achieved without changing the laser beam;

(3) Increase the iterative step size when iteratively calculate the modulation phase, and design the energy uniformity of the 3D code optical field as an iterative condition to optimize the marking resolution and marking speed at the same time;

(4) The marking resolution is further improved by separating and shielding the zero aurora in the Bessel beam.

Description of drawings

1 is a flowchart of a method for laser marking of three-dimensional codes based on a spatial light modulator proposed by an embodiment of the present invention;

2 is a schematic structural diagram of a three-dimensional code marking device formed based on a spatial light modulator;

3 is a schematic diagram of a marking process of a three-dimensional code laser marking method based on a spatial light modulator proposed by an embodiment of the present invention;

FIG. 4 is a block diagram of a three-dimensional code laser marking system based on a spatial light modulator according to an embodiment of the present invention.

Throughout the drawings, the same reference numbers are used to refer to the same elements or structures, wherein:

1 is the laser, 2 is the half-wave plate beam splitter combination, 3 is the mirror, 4 is the beam expander, 5 is the spatial light modulator, 6 is the upper computer, 7 is the diaphragm, 8 is the focusing system, and 9 is the focusing noodle.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as there is no conflict with each other.

In the present invention, the terms "first", "second" and the like (if any) in the present invention and the accompanying drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

FIG. 1 is a flowchart of a three-dimensional code laser marking method based on a spatial light modulator according to an embodiment of the present invention. Referring to FIG. 1 , in conjunction with FIGS. 2 to 3 , the method for marking a three-dimensional code laser based on a spatial light modulator in this embodiment will be described in detail. The method includes operations S1 to S3 .

In operation S1, the target two-dimensional code or the target two-dimensional dot matrix is randomly converted into a color image of the three-dimensional code, and the contour information of each color block in the color image of the three-dimensional code is extracted to generate a contour image corresponding to each color block.

According to the embodiment of the present invention, operation S1 includes sub-operation S11-sub-operation S13.

In sub-operation S11, the target two-dimensional code or the target two-dimensional lattice is generated according to the initial information. The initial information refers to the data information to be encoded.

In sub-operation S12, the target two-dimensional code or the target two-dimensional dot matrix is divided into a plurality of minimum marking units, and random color blocks are added to generate a color image of the three-dimensional code. The smallest marking unit refers to the smallest black and white squares that form a two-dimensional code or two-dimensional lattice. In this embodiment, color information is randomly generated with the smallest graphic unit as the unit, and the color complexity is ensured, and a 3D code with higher randomness is obtained directly by using color seeds to grow, and the obtained 3D code color image is composed of three different colors. block composition. Due to the randomness of the added color blocks, the randomness of the color image of the three-dimensional code is guaranteed, which makes it difficult to copy the three-dimensional code and improves the anti-counterfeiting ability. The color image of the three-dimensional code generated in operation S12 is shown in the leftmost figure in FIG. 3 .

In sub-operation S13, the 3D code color image is diffused using an erosion algorithm to extract contour information of each color block. Further, a color block of the same color is extracted to form a contour image corresponding to the color block, thereby three contour images can be generated, corresponding to three color blocks of different colors respectively. The resulting contour image is shown in the second column from the left of Figure 3.

In operation S2, the preset phase corresponding to each contour image is used as the initial value of the light field model of the holographic algorithm to perform iterative calculation, so as to obtain the target phase corresponding to each contour image.

According to the embodiment of the present invention, the light field model of the holographic algorithm is generated based on the simulated annealing algorithm and the Transport of Intensity Equation (TIE), and the generated light field model of the holographic algorithm is:

为引入振幅自由度后第

次迭代输出的光场幅值，

为迭代次数，

为信号场影响因子，

为信号区域的目标光强，

为第

次迭代后噪声区域的输出，

为第

次迭代后的复相位，

为虚数单位。该光场模型中以光场能量均匀度和点阵情况均匀度参数作为迭代条件进行计算，提高了三维码标刻的分辨率。全息算法光场模型中相位的迭代方程为：in,

After the introduction of the amplitude degree of freedom,

The magnitude of the light field output by the next iteration,

is the number of iterations,

is the signal field influence factor,

is the target light intensity in the signal area,

for the first

the output of the noise region after one iteration,

for the first

the complex phase after one iteration,

is an imaginary unit. In the light field model, the energy uniformity of the light field and the uniformity of the lattice situation are used as the iterative conditions for calculation, which improves the resolution of the 3D code marking. The iterative equation of the phase in the light field model of the holographic algorithm is:

、

、

表示入射面，

为第

次迭代的相位分布，

为迭代次数，

为第

次迭代的相位分布，

为梯度收敛参数，

为迭代收敛方向。与传统迭代方程相比，该迭代方程中的迭代步长由1、2、3、4……变为2⁰、2¹、2²、2³……，具有更大的迭代步长，提高了三维码在线标刻的速度。可以理解的是，基于其他算法生成的全息算法光场模型也可实现操作S2，本实施例中提供的基于模拟退火算法和强度传输方程生成的全息算法光场模型具有更优的标刻分辨率和标刻速度。in,

,

,

represents the incident surface,

for the first

The phase distribution of the next iteration,

is the number of iterations,

for the first

The phase distribution of the next iteration,

is the gradient convergence parameter,

is the iterative convergence direction. Compared with the traditional iterative equation, the iterative step size in this iterative equation is changed from 1, 2, 3, 4... to 2 ⁰ , 2 ¹ , 2 ² , 2 ³ ... It improves the speed of online marking of 3D codes. It can be understood that the light field model of the holographic algorithm generated based on other algorithms can also realize the operation S2, and the light field model of the holographic algorithm generated based on the simulated annealing algorithm and the intensity transfer equation provided in this embodiment has better marking resolution. and marking speed.

According to the embodiment of the present invention, operation S2 includes sub-operation S21 and sub-operation S22.

In sub-operation S21, the amplitude of each contour image is set as the target amplitude, and the corresponding preset phase is read in the preset configuration file according to each target amplitude.

For the three contour images generated in operation S1, the amplitudes of the three contour images are calculated respectively, and the amplitudes are the target amplitudes for laser marking. The preset configuration file stores information related to conventional three-dimensional code marking modulation, for example, includes a preset phase, and the preset phase is used as the initial phase for calculating the hologram.

In sub-operation S22, the preset phase corresponding to each contour image is used as the initial value of the light field model, and the target amplitude corresponding to each contour image is used as the target value of the light field model to perform iterative calculation, so as to obtain each target phase.

For any contour image, the initial phase corresponding to the contour image is substituted into the light field model of the holographic algorithm for iterative calculation, and the corresponding iterative phase and the light field amplitude corresponding to the iterative phase are obtained. If the amplitude of the light field is equal to the target amplitude corresponding to the contour image, the iterative calculation is stopped, and the iterative phase obtained by this iterative calculation is set as the target phase, so as to obtain the holographic phase map corresponding to each contour image, as shown on the left side of Figure 3 shown in the third column.

In the embodiment of the present invention, a phase shift Fresnel lens, a spatial grating and a Bessel shaping lens are superimposed in the spatial light modulator.

Spatial light modulator refers to a device that can modulate a certain parameter of the light field through liquid crystal molecules under active control, thereby writing certain information into the light wave to achieve the purpose of light wave modulation, such as modulating the amplitude, phase, and polarization state of the light wave. Wait. The modulation effect of the spatial light modulator can be customized. In this embodiment, the spatial light modulator is controlled to realize the phase modulation effect of the phase-shifted Fresnel lens, the spatial grating and the Bessel shaping lens.

By loading the phase of the Bessel shaping lens, the incident laser beam can be modulated and shaped into a Bessel beam from a Gaussian beam. Compared with an ordinary Gaussian beam, the edge light intensity distribution is more uniform when stamping a dot matrix. By loading a space grating and a phase-shifting Fresnel lens, the horizontal position and axial focus position of the 3D code marking can be adjusted without moving the stage.

In operation S3, each target phase is sequentially input to the spatial light modulator, so that the spatial light modulator performs phase modulation on the incident laser beam according to the received target phase, and then outputs a Bessel beam, so as to sequentially mark each target material on the target material. Outline image.

In the embodiment of the present invention, the marking device used for marking the three-dimensional code is shown in FIG. 2 . Referring to Figure 2, the marking device includes a laser 1, a half-wave plate beam splitter combination 2, a mirror 3, a beam expander 4, a spatial light modulator 5, a host computer 6, a diaphragm 7, a focusing system 8 and a focusing surface 9. The three-dimensional code laser marking method based on the spatial light modulator is, for example, executed in the host computer 6, which is, for example, a computer.

The laser 1 is, for example, a fiber laser, with a power range of 10W-20W, a wavelength of, for example, 1064 nm, and a pulse width of, for example, 20 ns. The half-wave plate beam splitter combination 2 is used to control the energy of the laser beam output by the laser 1 to prevent the output power of the laser beam from exceeding the damage threshold of the spatial light modulator 5 . The beam expander 4 is used to ensure that the diameter of the laser beam is slightly larger than the liquid crystal surface of the spatial light modulator 5, so that the limited pixels of the spatial light modulator 5 can be fully utilized and the uniformity of the light intensity of the entire modulation surface can be improved. The polarization direction of the laser beam at the beam expander 4 should be consistent with the orientation of the liquid crystal molecules on the liquid crystal surface to ensure that the modulation process is pure phase modulation. The spatial light modulator 5 is connected to the upper computer 6 , and performs phase modulation on the laser beam by loading the composite phase map output from the upper computer 6 and outputs a Bessel beam. When the light beam output by the spatial light modulator 5 has multiple diffraction orders, when performing high-precision marking, the modulated light of +1 order is passed through the diaphragm 7, and other lights are blocked outside the diaphragm 7. The focusing system 8 is used to focus the modulated Bessel beam onto the marking plane, and the marking plane is located at the focusing plane 9 . The target material is located at the focal plane 9 .

The laser beam generated by the laser 1 passes through the half-wave plate beam splitter combination 2, the mirror 3, and the beam expander 4 in turn, and then reaches the spatial light modulator 5. The spatial light modulator 5 phase-phases the laser beam under the control of the host computer 6. The Bessel beam is modulated to output the Bessel beam, and the Bessel beam passes through the diaphragm 7 and the focusing system 8 in sequence and then reaches the focusing surface 9 to mark the target material at the focusing surface 9 .

Further, in order to improve marking accuracy and marking pattern uniformity, the spatial light modulator 5 first loads a Bessel shaping lens to modulate the laser beam into a Bessel beam before performing phase modulation on the laser beam; The target phase corresponding to the contour image is added, and the phase-shift Fresnel lens and space grating are added to adjust the horizontal position and axial focus of the Bessel beam by adjusting the phase-shift Fresnel lens and/or space grating to achieve different colors. The purpose of marking the regions with different focal lengths. After the laser beam passes through the spatial light modulator 5, the three-dimensional code parts corresponding to different color information are marked at different focal lengths near the marking plane, and finally a pattern of anti-counterfeiting three-dimensional code with uneven surface is formed, as shown in the far right of Figure 3 .

In an embodiment of the present invention, in operation S3, the spatial light modulator 5 is controlled to shield the zero aurora in the Bessel beam and output the Bessel beam, so as to mark each contour image on the target material in sequence. Thereby effectively improving the marking resolution.

In another embodiment of the present invention, in operation S3, the spatial light modulator 5 is controlled to retain the zero aurora in the Bessel beam and output the Bessel beam, so as to mark each contour image on the target material in sequence. Thus, the light utilization rate is enhanced under the condition of ensuring the marking resolution.

According to the embodiment of the present invention, before the operation S1 is performed, the light damage threshold of the spatial light modulator needs to be increased to 40W/cm ² -150W/cm ² by means of physical cooling to meet the marking requirements. Physical cooling methods are, for example, water cooling, air cooling, and the like.

FIG. 4 is a structural block diagram of a three-dimensional code laser marking system based on a spatial light modulator according to an embodiment of the present invention. Referring to FIG. 4 , the three-dimensional code laser marking system 400 based on the spatial light modulator includes a conversion and extraction module 410 , a calculation module 420 and a modulation and marking module 430 . A phase-shifting Fresnel lens, a spatial grating and a Bessel shaping lens are superimposed in the spatial light modulator.

The extraction module 410, for example, performs operation S1 for randomly converting the target two-dimensional code or the target two-dimensional dot matrix into a color image of the three-dimensional code, and extracts the contour information of each color block in the color image of the three-dimensional code, so as to generate a contour image corresponding to each color block. .

The calculation module 420, for example, performs operation S2, for performing iterative calculation using the preset phase corresponding to each contour image as the initial value of the light field model of the holographic algorithm, so as to obtain the target phase corresponding to each contour image.

The modulation and marking module 430, for example, performs operation S3 for sequentially inputting each target phase to the spatial light modulator, so that the spatial light modulator performs phase modulation on the incident laser beam according to the received target phase and outputs a Bessel beam, Each contour image is marked on the target material in sequence.

The three-dimensional code laser marking system 400 based on the spatial light modulator is used to execute the three-dimensional code laser marking method based on the spatial light modulator in the above-mentioned embodiments shown in FIG. 1 to FIG. 3 . For details not exhausted in this embodiment, please refer to the three-dimensional code laser marking method based on the spatial light modulator in the embodiments shown in the foregoing FIG. 1 to FIG. 3 , which will not be repeated here.

Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (8)

1. A three-dimensional code laser marking method based on a spatial light modulator is characterized in that a phase shift Fresnel lens, a spatial grating and a Bessel shaping lens are superposed in the spatial light modulator, and the method comprises the following steps:

s1, randomly converting the target two-dimensional code or the target two-dimensional lattice into a three-dimensional code color image, and extracting contour information of each color block in the three-dimensional code color image to generate a contour image corresponding to each color block;

s2, respectively taking the preset phase corresponding to each contour image as an initial value of a holographic algorithm light field model to carry out iterative computation so as to obtain a target phase corresponding to each contour image;

the holographic algorithm light field model is generated based on a simulated annealing algorithm and an intensity transmission equation, and the generated holographic algorithm light field model is as follows:

wherein G is⁽ⁿ⁾For introducing amplitude selfThe light field amplitude output by the nth iteration after degree, n is the iteration number, m is the signal field influence factor, I_0|SRIs the target light intensity of the signal region,

for the output of the noise region after the nth iteration,

complex phase after nth iteration, i is an imaginary number unit;

the iterative equation of the phase in the holographic algorithm light field model is as follows:

wherein x is_j、y_jAnd j represents an incident surface of the light source,

is the phase distribution of the (n + 1) th iteration, n is the number of iterations,

phase distribution for the nth iteration, a_nAs gradient convergence parameter, h_nIs the iterative convergence direction;

and S3, sequentially inputting each target phase to the spatial light modulator, so that the spatial light modulator outputs Bessel beams after performing phase modulation on incident laser beams according to the received target phase, and sequentially marking each contour image on a target material.

2. The spatial light modulator-based three-dimensional code laser marking method according to claim 1, wherein the S1 comprises:

generating the target two-dimensional code or the target two-dimensional lattice according to the initial information;

dividing the target two-dimensional code or the target two-dimensional lattice into a plurality of minimum marking units, and adding random color blocks to generate the three-dimensional code color image;

and diffusing the three-dimensional code color image by using a corrosion algorithm to extract the outline information of each color block.

3. The method for laser marking of the three-dimensional code based on the spatial light modulator as claimed in claim 1 or 2, wherein the step of S2 performing the iterative computation by using the preset phase corresponding to each of the contour images as the initial value of the light field model of the holographic algorithm comprises:

setting the amplitude of each contour image as a target amplitude, and reading a corresponding preset phase in a preset configuration file according to each target amplitude;

and respectively taking the preset phase corresponding to each contour image as an initial value of the holographic algorithm light field model, and taking the target amplitude corresponding to each contour image as a target value of the holographic algorithm light field model for iterative computation to obtain each target phase.

4. The method for laser marking three-dimensional code based on spatial light modulator according to claim 1, wherein before outputting the bessel beam in S3, further comprising: and shielding zero polar light in the Bessel light beam and then outputting the Bessel light beam.

5. The method for laser marking three-dimensional code based on spatial light modulator according to claim 1, wherein before outputting the bessel beam in S3, further comprising: preserving zero-pole light in the Bessel beam and outputting the Bessel beam.

6. The method for laser marking three-dimensional code based on spatial light modulator according to claim 1, wherein the horizontal position and the axial focus of the bessel beam are adjusted by adjusting the phase shift fresnel lens and/or the spatial grating in S3.

7. The spatial light modulator-based three-dimensional code laser marking method according to claim 1, wherein before the S1, the method further comprises: increasing the light damage threshold of the spatial light modulator to 40W/cm by physical cooling²-150W/cm²。

8. The three-dimensional code laser marking system based on the spatial light modulator is characterized in that a phase shift Fresnel lens, a spatial grating and a Bessel shaping lens are superposed in the spatial light modulator, and the system comprises:

the conversion and extraction module is used for randomly converting the target two-dimensional code or the target two-dimensional lattice into a three-dimensional code color image and extracting contour information of each color block in the three-dimensional code color image so as to generate a contour image corresponding to each color block;

the calculation module is used for respectively taking the preset phase corresponding to each contour image as an initial value of a holographic algorithm light field model to carry out iterative calculation so as to obtain a target phase corresponding to each contour image;

the holographic algorithm light field model is generated based on a simulated annealing algorithm and an intensity transmission equation, and the generated holographic algorithm light field model is as follows:

wherein G is⁽ⁿ⁾The optical field amplitude value output for the nth iteration after the introduction of the amplitude freedom degree is obtained, wherein n is the iteration number, m is a signal field influence factor, I_0|SRIs the target light intensity of the signal region,

for the output of the noise region after the nth iteration,

complex phase after nth iteration, i is an imaginary number unit;

the iterative equation of the phase in the holographic algorithm light field model is as follows:

wherein x is_j、y_jAnd j represents an incident surface of the light source,

is the phase distribution of the (n + 1) th iteration, n is the number of iterations,

phase distribution for the nth iteration, a_nAs gradient convergence parameter, h_nIs the iterative convergence direction;

and the modulation and marking module is used for sequentially inputting each target phase to the spatial light modulator, so that the spatial light modulator outputs Bessel beams after performing phase modulation on incident laser beams according to the received target phases, and the contour images are sequentially marked on a target material.

Images