A facula shaping device and method based on partition modulation and customized polarization elements

Abstract

The application discloses a kind of spot shaping device and method based on partition modulation and custom polarized element, it is related to laser processing technical field, by 42.5 degree custom polarized beam splitter (PBS) random polarized light is divided into S / P light, makes both parallel to the partition silicon-based liquid crystal spatial light modulator (LCoS SLM) by total reflection surface, its A / B area liquid crystal orientation difference 90 degrees realizes independent modulation, again using P reflection polarized beam splitter (R-PBS) light beam and guarantee optical path consistent is combined.This method includes expansion, light splitting, partition modulation, light beam merging and secondary expansion focusing etc..The scheme realizes close to 100% energy utilization, it is applicable to more than 50W laser, the processing efficiency of annular light spot after shaping is higher than Gaussian beam 2 times or more, temperature gradient reduces, can be used for laser welding and metal 3D printing, solve the problem of energy waste, heat effect and insufficient precision.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser processing, in particular to a spot shaping device and method based on partition modulation and customized polarization elements. BACKGROUND

[0002] In the field of laser processing, Gaussian beams have significant limitations in material welding, metal 3D printing, and other scenarios due to their Gaussian distribution of energy, which is high in the center and low at the edges. The energy gradient can cause uneven temperature distribution during processing, easily causing thermal stress cracks. Moreover, the effective processing area is small, and the efficiency is low. Therefore, shaping Gaussian beams into non-Gaussian beams such as flat-top beams and ring-shaped beams has become a key to improving processing quality.

[0003] In the prior art, fiber lasers usually output random polarized light, while liquid crystal on silicon spatial light modulators (LCoSSLM) can only modulate linearly polarized light. The traditional scheme divides random polarized light into S / P polarized light through a polarizing beam splitter (PBS), and only the energy of one kind of polarized light can be utilized, resulting in a 50% waste of laser energy. In addition, the existing public documents (such as CN116909051B) have obvious defects: the distance between optical elements is too close, and under the irradiation of high-power laser above 50W, the reflective surface is easily deformed due to heat accumulation, affecting the precision of the spot, and water cooling cannot be added; the beam passes through the beam-splitting surface multiple times, with a light loss rate as high as 10-15%.

[0004] In view of this, the present application is proposed. SUMMARY

[0005] The purpose of the present application is to provide a spot shaping device and method based on partition modulation and customized polarization elements to solve the problems in the background art.

[0006] To solve the above technical problems, the present application provides a spot shaping device based on partition modulation and customized polarization elements, which comprises:

[0007] Fiber laser: for outputting random polarized light;

[0008] Beam expander: for expanding the random polarized light;

[0009] Customized polarizing beam splitter (PBS): the design angle of the beam-splitting surface is 42.5 degrees, and it is used to divide the random polarized light into S polarized light and P polarized light, wherein the S polarized light is reflected and the P polarized light is transmitted;

[0010] Full reflection surface: arranged in parallel with the beam-splitting surface of the customized PBS, used to reflect the transmitted P polarized light and make it parallel to the reflected S polarized light;

[0011] Silicon-based liquid crystal spatial light modulator (LCoS SLM): the effective area is divided into A and B areas, the liquid crystal orientation directions of the A and B areas are 90 degrees apart, used to respectively receive parallel S-polarized light and P-polarized light and perform phase modulation;

[0012] P-reflective polarization beam splitter (R-PBS): used to receive modulated S-polarized light and P-polarized light, wherein the R-PBS transmits S-polarized light and reflects P-polarized light, so that the two are combined into one light beam;

[0013] 4f optical module: used to expand or shrink the combined light beam;

[0014] Scanning galvanometer module and field lens: used to focus the light beam to the surface of the processing material.

[0015] Further, the splitting surface angle of the customized polarization beam splitter (customized PBS) is 40 to 50 degrees, and the reflection and transmission of S-polarized light and P-polarized light are realized by the interference film of the customized splitting surface.

[0016] Further, the incident angles of the S-polarized light and the P-polarized light to the silicon-based liquid crystal spatial light modulator (LCoS SLM) are each less than or equal to 5 degrees.

[0017] Further, the interference film of the P-reflective polarization beam splitter (R-PBS) is designed to reflect P-polarized light and transmit S-polarized light, and the optical paths of the S-polarized light and the P-polarized light at the P-reflective polarization beam splitter (R-PBS) are consistent.

[0018] Further, the A and B areas of the silicon-based liquid crystal spatial light modulator (LCoS SLM) do not overlap, and the A area corresponds to S-polarized light modulation and the B area corresponds to P-polarized light modulation.

[0019] A method for using a light spot shaping device based on partition modulation and customized polarization elements, comprising the following steps:

[0020] The fiber laser outputs random polarized light, which is expanded to 6-13 mm by a beam expander;

[0021] The random polarized light passes through a 42.5-degree customized polarization beam splitter (PBS), reflects S-polarized light, and transmits P-polarized light;

[0022] The transmitted P-polarized light is reflected by a total reflection surface and is parallel to the S-polarized light and is incident on the A and B areas of the silicon-based liquid crystal spatial light modulator (LCoS SLM), wherein the liquid crystal orientation directions of the A and B areas are 90 degrees apart;

[0023] The silicon-based liquid crystal spatial light modulator (LCoS SLM) performs phase modulation on the S / P-polarized light to form a non-Gaussian light beam;

[0024] The modulated light beam is directed to the R-PBS, the S light is transmitted, the P light is reflected and combined into a light beam;

[0025] The combined light beam is expanded by a 4f optical module, then focused to the material surface by a scanning galvanometer module and a field lens.

[0026] Further, the 4f optical module expands the light beam diameter from 8mm to 15mm.

[0027] Further, the optical paths of the S polarized light and the P polarized light are consistent, and the modulated non-Gaussian light beam includes but is not limited to a flat-top light beam and a ring light beam.

[0028] Further, the non-Gaussian light beam has a smaller energy gradient than a Gaussian light beam, which is suitable for laser welding and metal 3D printing.

[0029] Compared with the prior art, the beneficial effects of the present application are:

[0030] I. Energy utilization rate is significantly improved, breaking the bottleneck of 50% energy waste in traditional schemes:

[0031] 1. Dual-polarized light cooperative utilization: By customizing a 42.5-degree PBS and a full reflection surface, random polarized light is divided into S / P polarized light and modulated in the A / B area of the SLM respectively, and finally combined into a light beam by the R-PBS, achieving nearly 100% laser energy utilization rate (traditional scheme only 50%).

[0032] 2. Precise control of energy loss: The interference film design of the customized PBS can achieve full reflection of S light and full transmission of P light (reflectance / transmittance ≥ 99%), if a 45-degree PBS is used, the S light transmittance and P light reflectance are controlled within 5-10%, to minimize energy loss.

[0033] II. The light spot shaping precision and optical path consistency are significantly optimized:

[0034] 1. Partition modulation and optical path matching: The liquid crystal orientation directions of the A / B areas of the SLM are different by 90 degrees, respectively adapting to S / P polarized light modulation, and the optical path difference of S / P light after the full reflection surface and the R-PBS is ≤ λ / 5 (λ is the wavelength of the laser), avoiding light spot distortion caused by phase difference.

[0035] 2. Precise control of incident angle: the incident angle of S / P light to the SLM is ≤ 5 degrees, and the included angle between the outgoing light and the incident light is ≤ 10 degrees, reducing the modulation error caused by beam deviation and ensuring the phase loading precision.

[0036] III. Breakthrough the traditional limitations of high-power laser applicability:

[0037] 1. Optics thermal management optimization: Customized PBS spacing design between PBS and SLM avoids thermal accumulation caused by close proximity of elements in traditional solutions. Combined with the heat dissipation layout of the total reflection surface, it can withstand the power density of 50W or more continuous laser or nanosecond laser (such as 200W fiber laser), and the temperature rise of the reflective surface is ≤10℃, which does not affect the spot shaping effect.

[0038] 2. Compatible with industrial high-power processing: In metal 3D printing applications, using 500-2000W laser, the temperature gradient of the molten pool is reduced, avoiding splashing and cracking of materials due to sudden temperature changes, and improving the processing yield.

[0039] Four, dual improvement of processing efficiency and quality:

[0040] 1. Significant advantage of non-Gaussian beam: The energy gradient of the shaped flat-top beam or ring-shaped beam is small, and the temperature distribution is uniform during processing, which is more suitable for material welding and metal powder melting than Gaussian beam (high central energy). For example, the processing area of ring-shaped spot is increased by more than 2 times compared with Gaussian beam.

[0041] 2. Multi-functional processing adaptation: Different phase patterns can be loaded through SLM to flexibly generate flat-top light, ring-shaped light and other non-Gaussian beams.

[0042] Five, flexibility and compatibility of optical path design are enhanced

[0043] Customized PBS angle compatible with multiple scenarios: In addition to the optimal angle of 42.5 degrees, the interference film can be customized to adapt to the light splitting angles of 40 to 50 degrees, adapting to different laser polarization characteristics and optical path layout requirements, and improving flexibility.

[0044] SLM partition design adapts to polarization light modulation: A / B zones independently modulate S / P light, which can load the same or complementary phase patterns according to the processing requirements, such as simultaneously generating symmetrical ring-shaped beams, or further optimizing energy uniformity through complementary modulation. BRIEF DESCRIPTION OF DRAWINGS

[0045] Fig. 1 A flowchart of a method for using a spot shaping device based on partition modulation and customized polarization elements;

[0046] Fig. 2 A complete optical path of an existing fiber laser combined with SLM. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the present application will be clearly and completely described with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0048] Please refer to Figs. 1-2 The present application provides a technical solution: a light spot shaping device and method based on partition modulation and customized polarization elements, comprising:

[0049] I. Device construction and optical element installation

[0050] 1. Fiber laser installation

[0051] Fix the fiber laser on the optical path base, align the output end with the center of the beam expander, and ensure that the laser collimated beam axis is parallel to the base guide rail.

[0052] 2. Beam expander adjustment

[0053] Install the beam expander (the magnification is selected according to the requirements, such as 1:2), adjust the position of the beam expander, so that the laser spot diameter is 6-13mm (for example, from 4mm to 8mm) after expansion, and monitor the beam energy through the power meter.

[0054] 3. Customized polarization beam splitter (PBS) and total reflection surface installation

[0055] Fix the 42.5-degree angle customized PBS, and the light splitting surface of the PBS forms a 42.5-degree angle with the laser incident direction, to ensure that the random polarized light is incident to the PBS light splitting surface at an incident angle of 47.5 degrees (90-42.5 degrees).

[0056] Install a total reflection surface (such as a plane mirror) parallel to the PBS light splitting surface 4-13mm behind the PBS light splitting surface, and the spacing error between the reflection surface and the PBS light splitting surface is ≤0.1mm, to ensure that the transmitted P-polarized light is parallel to the reflected S-polarized light after reflection.

[0057] 4. LCoS SLM partition calibration

[0058] Install the LCoS SLM, and divide the effective area into A area and B area (physical partition or logical partition), and calibrate the liquid crystal orientation direction of A area and B area through a microscope camera: the liquid crystal orientation of A area is consistent with the vibration direction of S-polarized light (such as the vertical direction), the liquid crystal orientation of B area is consistent with the vibration direction of P-polarized light (such as the horizontal direction), and the included angle between the two is 90 degrees;

[0059] Adjust the position of the SLM, so that the S-polarized light is incident to the A area and the P-polarized light is incident to the B area, and the incident angle is ≤5 degrees (monitored by an angle meter).

[0060] 5. R-PBS installation and optical path adjustment

[0061] Install R-PBS on the SLM exit light path, and design the interference film to transmit S-polarized light and reflect P-polarized light;

[0062] Adjust the optical path of S light and P light through an optical path compensation sheet (such as a quartz glass sheet) to make the optical path difference of the two at the R-PBS ≤ λ / 10 (λ is the laser wavelength), ensuring consistent modulation effect.

[0063] 6. 4f optical module and scanning system installation

[0064] Install a 4f optical module (consisting of two lenses with the same focal length) to expand the beam diameter of the combined R-PBS to 15mm from 8mm;

[0065] Install the scanning galvanometer module and field lens in sequence, and select the field lens focal length according to the processing requirements (such as 160mm) to ensure that the focal point of the light beam coincides with the material surface.

[0066] II. Spot shaping method implementation process

[0067] 1. Laser output and beam expansion

[0068] Start the fiber laser, which can output random polarized light at a wavelength in the 1000-1100nm range (power can be set to 50-2000W);

[0069] Expand the random polarized light to a diameter of 6mm through the beam expander, and select the central region of the light beam through the diaphragm to reduce edge stray light.

[0070] 2. Polarized light splitting and parallelization

[0071] 2.1 The expanded random polarized light is incident to a 42.5-degree custom PBS:

[0072] S-polarized light is reflected by the PBS splitting surface at an angle of 95 degrees to the incident angle (due to a 47.5-degree incident angle);

[0073] P-polarized light transmits through the PBS splitting surface and is reflected by the total reflection surface;

[0074] 2.2 The total reflection surface reflects the P-polarized light to make its propagation direction parallel to that of the S-polarized light (the included angle between the two is ≤0.5 degrees), forming parallel S light and P light beams.

[0075] 3. Sub-area modulation and phase loading

[0076] 3.1 Parallel S light and P light are incident to the A and B areas of the SLM, respectively:

[0077] A zone liquid crystal loads phase modulation pattern (such as flat light phase distribution) on S light;

[0078] B zone liquid crystal loads the same or complementary phase modulation pattern (according to the shaping target adjustment) on P light;

[0079] 3.2 The modulated S light and P light exit from the SLM, maintaining parallel state, and the included angle between the exit light and the incident light is ≤10 degrees.

[0080] 4. Beam combination and optical path calibration

[0081] 4.1 The modulated S light and P light are incident to the R-PBS:

[0082] The S light transmits through the R-PBS beam splitter and changes the propagation direction after reflection by the total reflection surface;

[0083] The P light is reflected by the R-PBS beam splitter and combined with the S light in the same light path to form an S+P polarization mixed light beam;

[0084] 4.2 The phase consistency of the combined light beam is monitored by an interferometer, and if the optical path difference exceeds λ / 10, the position of the R-PBS or the total reflection surface is adjusted for compensation.

[0085] 5. Secondary beam expansion and focusing processing

[0086] 5.1 The combined light beam enters the 4f optical module, and the spot diameter is expanded from 8mm to 15mm by the lens group, improving the light beam coverage area;

[0087] 5.2 The expanded light beam is deflected by the scanning galvanometer module and focused to the surface of a metal material (such as a stainless steel powder bed) by a field lens, for laser welding or 3D printing:

[0088] The flat-top light beam is used for uniform heating of the material;

[0089] The annular light beam is used to expand the processing area, and the processing efficiency is improved by more than 2 times compared with the S light beam.

[0090] III. Key parameter debugging and error control

[0091] 1. PBS beam splitting efficiency verification

[0092] The S light and P light energy after passing through a 42.5 degree PBS is measured by a polarimeter:

[0093] Under ideal conditions, the S light reflectivity is ≥99%, and the P light transmittance is ≥99%;

[0094] If a 45 degree PBS is used, the S light transmittance and P light reflectivity are controlled within 5-10%.

[0095] 2. SLM partition incident angle calibration

[0096] The incident position of the light beam on the SLM is observed by an infrared CCD camera:

[0097] The deviation between the center of the light spot in area A and the incident point of S light is ≤0.1 mm;

[0098] The deviation between the center of the light spot in area B and the incident point of P light is ≤0.1 mm, ensuring that there is no overlap in partition modulation.

[0099] A method of a light spot shaping device based on partition modulation and a customized polarization element, when applied to machining 316L stainless steel powder, the temperature gradient of the molten pool is reduced, and the machining efficiency is improved.

Claims

1. A facuol shaping device based on zoned modulation and custom polarizing elements, characterized by: The application relates to a laser welding device, which comprises the following components: a fiber laser for outputting random polarization light; a beam expander for expanding the random polarization light; a customized polarization beam splitter with a splitting surface angle of 42.5 degrees for splitting the random polarization light into S-polarized light and P-polarized light, wherein the S-polarized light is reflected and the P-polarized light is transmitted; a total reflection surface arranged in parallel with the splitting surface of the customized polarization beam splitter for reflecting the transmitted P-polarized light and making it parallel to the reflected S-polarized light; a liquid crystal on silicon spatial light modulator, whose effective area is divided into an A area and a B area, and the liquid crystal orientation directions of the A area and the B area are 90 degrees different from each other, for receiving the parallel S-polarized light and P-polarized light respectively and performing phase modulation; a P-reflective polarization beam splitter for receiving the modulated S-polarized light and P-polarized light, wherein the P-reflective polarization beam splitter transmits the S-polarized light and reflects the P-polarized light, so that the two are combined into one light beam; a 4f optical module for expanding or shrinking the combined light beam; a scanning galvanometer module and a field lens for focusing the light beam onto the surface of a processing material.

2. A spot shaping device based on zone-plate modulation and custom polarizing elements as claimed in claim 1, characterized in that: The splitting surface angle of the customized polarization beam splitter also includes one of 40 to 50 degrees, and the reflection and transmission of the S-polarized light and P-polarized light are realized by customizing the interference film of the splitting surface.

3. A spot shaping device based on zone-plate modulation and custom polarizing elements as claimed in claim 1 characterized by: The incident angles of the S-polarized light and P-polarized light to the liquid crystal on silicon spatial light modulator are both less than or equal to 5 degrees.

4. A spot shaping device based on zone-plate modulation and custom polarizing elements as claimed in claim 1, characterized in that: The interference film of the P-reflective polarization beam splitter is designed to reflect the P-polarized light and transmit the S-polarized light, and the optical paths of the S-polarized light and P-polarized light at the P-reflective polarization beam splitter are consistent.

5. A spot shaping device based on zone-plate modulation and custom polarizing elements as claimed in claim 1, characterized in that: The A area and the B area of the liquid crystal on silicon spatial light modulator do not overlap, and the A area corresponds to S-polarized light modulation and the B area corresponds to P-polarized light modulation.

6. A method of using a facuiform shaping device based on a segmented modulator and custom polarizing element as claimed in any one of claims 1-5, characterized in that: The application also discloses a laser welding method, which comprises the following steps: a fiber laser outputs random polarization light, which is expanded to 6-13 mm by a beam expander; the random polarization light passes through a 42.5-degree customized polarization beam splitter, and the S-polarized light is reflected and the P-polarized light is transmitted; the transmitted P-polarized light is reflected by a total reflection surface and then is parallel to the S-polarized light and is incident on the A area and the B area of a liquid crystal on silicon spatial light modulator, wherein the liquid crystal orientation directions of the A area and the B area are 90 degrees different from each other; the liquid crystal on silicon spatial light modulator performs phase modulation on the S-polarized light and P-polarized light to form a non-Gaussian light beam; the modulated light beam is incident on a P-reflective polarization beam splitter, the S-polarized light is transmitted, the P-polarized light is reflected and combined into one light beam; the combined light beam is expanded by a 4f optical module, and then is focused onto the surface of a material by a scanning galvanometer module and a field lens.

7. A method of using a facuiform shaping device based on a segmented modulator and a custom polarizing element as defined in claim 6, characterized in that: The 4f optical module expands the diameter of the light beam from 8 mm to 15 mm.

8. A method of using a facuiform shaping device based on zoned modulation and custom polarizing elements as defined in claim 6, characterized in that: The optical paths of the S-polarized light and P-polarized light are consistent, and the modulated non-Gaussian light beam comprises a flat-top light beam or a ring-shaped light beam.

9. A method of using a facuiform shaping device based on zoned modulation and custom polarizing elements as defined in claim 6, characterized in that: The non-Gaussian light beam has a smaller energy gradient than a Gaussian light beam and can be used in laser welding and metal 3D printing.

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