Large-aperture continuous zooming transmission-type laser beam expanding system

Abstract

The invention belongs to the technical field of laser beam expanding systems, and particularly relates to a large-aperture continuous zooming transmission-type laser beam expanding system, which comprises an incident end, a laser beam expanding system and a laser beam expanding system, the incident end is used for receiving 532.1 nm wave band laser; the zoom lens group module is of a double-lens-group linkage structure formed by a negative lens group and a positive lens group; according to the output end, the dynamic adjustment range of the caliber of the output end is 60-300 mm, and the beam expanding multiple can be continuously adjusted to be 2X-10X. The total number of the optical lenses is less than or equal to 6 and comprises at least two high-order aspheric mirrors; and the parallelism error of the emergent beam is less than or equal to 10 arc seconds. According to the invention, high-efficiency laser application can be realized through shape control that the beam diameter is increased and the divergence angle is reduced, power density is reduced and energy control that the far-field energy concentration degree is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser beam expansion systems, and in particular relates to a large-aperture continuous zoom transmission laser beam expansion system. Background Art

[0002] Traditional laser beam expanders are all small-aperture laser beam expander lenses. Currently, commercial laser beam expander lenses on the market are basically within the diameter of φ100mm. Large-aperture laser beam expanders have not yet been commercialized due to factors such as material limitations and difficulty in development. Only in some projects of scientific research institutes are there large-aperture laser beam expander systems involved, and most of them are reflective structures, which are easier to implement than transmissive structures. Large-aperture laser beam expanders with dynamic magnification are relatively rare. This type of system requires a transmissive system to implement, so it has greater technical challenges as a whole. To this end, the present invention designs a large-aperture dynamic magnification laser beam expander lens. Summary of the Invention

[0003] The purpose of the present invention is to provide a large-aperture continuous zoom transmission laser beam expansion system, which can realize high-efficiency laser applications through shape control such as increasing the beam diameter and reducing the divergence angle, and energy control such as reducing the power density and improving the far-field energy concentration.

[0004] The technical solutions adopted by the present invention are as follows:

[0005] Large-aperture continuous zoom transmissive laser beam expansion system, including:

[0006] Incident end: The incident end has a fixed aperture of Φ30mm; the incident end receives 532.1nm band laser;

[0007] Zoom lens module: The zoom lens module is composed of a negative lens group and a positive lens group to form a double lens group linkage structure;

[0008] Output port: The output port diameter has a dynamic adjustment range of 60mm-300mm, and the beam expansion ratio is continuously adjustable from 2X to 10X; the total number of optical lenses is ≤ 6, including at least 2 high-order aspheric lenses;

[0009] The parallelism error of the output beam is ≤10 arc seconds.

[0010] Preferably, the zoom lens module drives the lens spacing through a precision guide rail, and the beam expansion ratio M is:

[0011]

[0012] Among them, k is the spacing compensation coefficient, f1 is the focal length of the negative lens group in the front group, f1=50mm; f2 is the focal length of the positive lens group in the rear group, f2=100-500mm; the wavefront distortion control target is less than λ / 10; where λ represents the laser wavelength, λ=532.1nm; λ / 10 requires the wavefront distortion, i.e., the optical path difference, to be less than one tenth of the wavelength.

[0013] Preferably, the negative lens group is made of CaF2 fused quartz composite material with a thermal expansion coefficient of less than 0.8×10 -6 / K; the surface of the positive lens group is coated with a multilayer dielectric film, and the laser damage threshold is greater than 10J / cm 2 .

[0014] Preferably, the laser beam expansion system includes a double-cemented achromatic mirror group and an aspheric mirror curvature design. In a 532.1nm single-wavelength laser system, dispersion is the difference in refractive index of light of different wavelengths; dispersion can cause secondary spectral aberrations, affecting beam quality. The double-cemented mirror group is made of two different optical materials, crown glass and flint glass, and suppresses the secondary spectrum through the complementary material dispersion. Mathematically, its achromatic condition is:

[0015]

[0016] Where Δn is the material dispersion coefficient and d is the lens thickness. This ensures that the beam wavefront distortion is less than λ / 10 in the 532.1nm band, improving energy distribution uniformity.

[0017] Traditional spherical mirrors introduce spherical aberration and coma in the beam expansion system, which is especially significant at a large aperture of Φ300mm. Aspherical mirrors use high-order surface equations, such as the conic constant + k coefficient, to accurately correct aberrations. The surface formula is:

[0018]

[0019] Where c is the inverse of the curvature radius and h is the cone constant. This optimizes the beam wavefront uniformity and reduces energy loss.

[0020] In the present invention, the double-cemented mirror group reduces the secondary spectrum by 90% and improves the energy density distribution uniformity to 95%.

[0021] In the present invention, the aspheric mirror compresses the spherical aberration to λ / 15 when the beam is expanded 10 times, ensuring that the parallelism of the light output is better than 10".

[0022] The present invention is the first to integrate a double-cemented achromatic + aspheric combination in a transmissive large-aperture beam expansion system, with a total number of lenses ≤ 6.

[0023] Preferably, the mechanical support structure adopts a silicon carbide lens barrel with an integrated active vibration reduction platform. The lens barrel adopts a honeycomb lightweight design, which reduces weight by 40% and increases stiffness by 30%. The support points adopt a three-point positioning system, and each point integrates a piezoelectric ceramic actuator to achieve nanometer-level position adjustment.

[0024] Advantages of silicon carbide lens barrel: Silicon carbide (SiC) has a diameter of less than 0.8×10 -6 The ultra-low thermal expansion coefficient of 100 / K and high stiffness with an elastic modulus greater than 400GPa are suitable for large-aperture systems (Φ300mm). Under temperature fluctuations of ±5°C, the lens barrel deformation is less than 1μm, preventing optical path deviation. The necessity of an active vibration reduction platform: External vibrations such as those caused by equipment operation or environmental disturbances can cause micro-displacement of the lens, affecting parallelism. The active vibration reduction platform uses piezoelectric sensors + feedback control to isolate vibrations with frequencies greater than 100Hz, ensuring displacement errors of less than 0.1μm.

[0025] In the present invention, the silicon carbide lens barrel + active vibration reduction combination solves the thermal deformation and vibration problems of large-aperture systems and provides a stable foundation for dynamic magnification; traditional reflective systems cannot achieve this.

[0026] Preferably, the adjustment and calibration system includes a laser interferometer and a micro-radian tilt adjustment mechanism; the laser interferometer uses the interference fringes of a 532.1 nm laser to monitor the wavefront error in real time; the principle is based on the Mach-Zehnder interferometer:

[0027]

[0028] Where ΔL is the optical path difference; when the error is greater than λ / 20, the system automatically triggers correction;

[0029] During dynamic zooming, lens tilt deviation can cause off-axis aberrations such as coma. Micro-radian adjustment ensures that the lens tilt error is less than 0.5 micro-radians (1 micro-radian = 0.206 arc seconds), maintaining light parallelism ≤ 10".

[0030] At 10x beam expansion, the wavefront error is controlled within λ / 15. The measured calibration system in this invention reduces assembly time by 70%, whereas traditional manual calibration takes several hours, and achieves stable parallelism better than 10".

[0031] The technical effects achieved by the present invention are:

[0032] This invention compresses the beam divergence angle and improves energy concentration: Laser beams naturally diverge during transmission, resulting in rapid energy decay as distance increases. The beam expansion system reduces the output beam divergence angle by a factor of M by increasing the beam diameter (expansion ratio M = f2 / f1). For example, a 10x expansion ratio reduces the divergence angle by a factor of 10, thereby enhancing far-field energy concentration and making it suitable for long-distance transmission scenarios.

[0033] This invention reduces the risk of optical component damage: The localized energy density of high-power lasers can easily cause ablation of lens coatings or thermal distortion. The beam expansion system increases the cross-sectional area of ​​the beam, reducing the optical power density per unit area, protecting optical components from damage and extending system life.

[0034] This invention expands long-distance transmission and detection capabilities: In applications such as lidar and space communications, the beam expansion system suppresses beam spread, significantly increasing the effective range. For example, in detection or communication systems, it ensures that the beam remains focused over long distances, improving signal strength and accuracy.

[0035] This invention optimizes beam quality and energy distribution: Combining aberration correction technology with a beam expansion system improves the laser's wavefront uniformity, ensuring a more uniform beam energy distribution. This enhances the laser's focusing ability and overall performance, making it suitable for precision machining or measurement applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is the optical path diagram of the present invention in the 10-fold beam expansion state;

[0037] Figure 2 This is the optical path diagram of the present invention in the 7-fold beam expansion state;

[0038] Figure 3 This is the optical path diagram of the present invention in the 6-fold beam expansion state;

[0039] Figure 4 This is the optical path diagram of the present invention in the 2x beam expansion state. DETAILED DESCRIPTION

[0040] In order to make the purpose and advantages of the present invention more clearly understood, the present invention is described in detail below with reference to the following examples. It should be understood that the following text is only used to describe one or more specific embodiments of the present invention and does not strictly limit the scope of protection of the present invention.

[0041] like Figure 1-Figure 4 As shown, the large-aperture continuous zoom transmission laser beam expansion system includes:

[0042] Incident end: The incident end has a fixed aperture of Φ30mm; the incident end receives 532.1nm band laser;

[0043] Zoom lens module: The zoom lens module is composed of a negative lens group and a positive lens group to form a double lens group linkage structure;

[0044] Output port: The output port diameter has a dynamic adjustment range of 60mm-300mm, and the beam expansion ratio is continuously adjustable from 2X to 10X; the total number of optical lenses is ≤ 6, including at least 2 high-order aspheric lenses;

[0045] The parallelism error of the output beam is ≤10 arc seconds.

[0046] Preferably, the zoom lens module drives the lens spacing through a precision guide rail, and the beam expansion ratio M is:

[0047]

[0048] Among them, k is the spacing compensation coefficient, f1 is the focal length of the negative lens group in the front group, f1=50mm; f2 is the focal length of the positive lens group in the rear group, f2=100-500mm; the wavefront distortion control target is less than λ / 10; where λ represents the laser wavelength, λ=532.1nm; λ / 10 requires the wavefront distortion, i.e., the optical path difference, to be less than one tenth of the wavelength.

[0049] Preferably, the negative lens group is made of CaF2 fused quartz composite material with a thermal expansion coefficient of less than 0.8×10 -6 / K; the surface of the positive lens group is coated with a multilayer dielectric film, and the laser damage threshold is greater than 10J / cm 2 .

[0050] Preferably, the laser beam expansion system includes a double-cemented achromatic mirror group and an aspheric mirror curvature design. In a 532.1nm single-wavelength laser system, dispersion is the difference in refractive index of light of different wavelengths; dispersion can cause secondary spectral aberrations, affecting beam quality. The double-cemented mirror group is made of two different optical materials, crown glass and flint glass, and suppresses the secondary spectrum through the complementary material dispersion. Mathematically, its achromatic condition is:

[0051]

[0052] Where Δn is the material dispersion coefficient and d is the lens thickness. This ensures that the beam wavefront distortion is less than λ / 10 in the 532.1nm band, improving energy distribution uniformity.

[0053] Traditional spherical mirrors introduce spherical aberration and coma in the beam expansion system, which is especially significant at a large aperture of Φ300mm. Aspherical mirrors use high-order surface equations, such as the conic constant + k coefficient, to accurately correct aberrations. The surface formula is:

[0054]

[0055] Where c is the inverse of the curvature radius and h is the cone constant. This optimizes the beam wavefront uniformity and reduces energy loss.

[0056] In the present invention, the double-cemented mirror group reduces the secondary spectrum by 90% and improves the energy density distribution uniformity to 95%.

[0057] In the present invention, the aspheric mirror compresses the spherical aberration to λ / 15 when the beam is expanded 10 times, ensuring that the parallelism of the light output is better than 10".

[0058] The present invention is the first to integrate a double-cemented achromatic + aspheric combination in a transmissive large-aperture beam expansion system, with a total number of lenses ≤ 6.

[0059] Preferably, the mechanical support structure adopts a silicon carbide lens barrel with an integrated active vibration reduction platform. The lens barrel adopts a honeycomb lightweight design, which reduces weight by 40% and increases stiffness by 30%. The support points adopt a three-point positioning system, and each point integrates a piezoelectric ceramic actuator to achieve nanometer-level position adjustment.

[0060] Advantages of silicon carbide lens barrel: Silicon carbide (SiC) has a diameter of less than 0.8×10 -6 The ultra-low thermal expansion coefficient of 100 / K and high stiffness with an elastic modulus greater than 400GPa are suitable for large-aperture systems (Φ300mm). Under temperature fluctuations of ±5°C, the lens barrel deformation is less than 1μm, preventing optical path deviation. The necessity of an active vibration reduction platform: External vibrations such as those caused by equipment operation or environmental disturbances can cause micro-displacement of the lens, affecting parallelism. The active vibration reduction platform uses piezoelectric sensors + feedback control to isolate vibrations with frequencies greater than 100Hz, ensuring displacement errors of less than 0.1μm.

[0061] In the present invention, the silicon carbide lens barrel + active vibration reduction combination solves the thermal deformation and vibration problems of large-aperture systems and provides a stable foundation for dynamic magnification; traditional reflective systems cannot achieve this.

[0062] Preferably, the adjustment and calibration system includes a laser interferometer and a micro-radian tilt adjustment mechanism; the laser interferometer uses the interference fringes of a 532.1 nm laser to monitor the wavefront error in real time; the principle is based on the Mach-Zehnder interferometer:

[0063]

[0064] Where ΔL is the optical path difference; when the error is greater than λ / 20, the system automatically triggers correction;

[0065] During dynamic zooming, lens tilt deviation can cause off-axis aberrations such as coma. Micro-radian adjustment ensures that the lens tilt error is less than 0.5 micro-radians (1 micro-radian = 0.206 arc seconds), maintaining light parallelism ≤ 10".

[0066] At 10x beam expansion, the wavefront error is controlled within λ / 15. The measured calibration system in this invention reduces assembly time by 70%, whereas traditional manual calibration takes several hours, and achieves stable parallelism better than 10".

[0067] In this invention, the laser beam expansion system is a core optical component in laser technology. By changing the spatial distribution characteristics of the beam, it significantly improves the efficiency of laser applications. Its main functions can be summarized as follows:

[0068] 1. Compress the beam divergence angle and improve energy concentration.

[0069] The natural divergence of a laser beam causes its energy to decay rapidly as the transmission distance increases. The beam expansion system reduces the divergence angle of the output beam by a factor of M by increasing the beam diameter.

[0070] 2. Reduce the risk of damage to optical components

[0071] The local energy density of high-power lasers can easily cause lens coating ablation or thermal distortion. The beam expansion system reduces the optical power density per unit area by increasing the beam cross-sectional area.

[0072] 3. Expand long-distance transmission and detection capabilities

[0073] In the fields of lidar, space communications, etc., the beam expansion system greatly increases the effective range by suppressing the diffusion of the light beam.

[0074] 4. Optimize beam quality and energy distribution

[0075] The beam expansion system combined with aberration correction technology can improve the wavefront uniformity of the laser.

[0076] The core value of the laser beam expansion system lies in "shape control" and "energy control":

[0077] Shape control: reshape the spatial characteristics of the beam through geometric optics (diameter ↑, divergence angle ↓);

[0078] Energy control: Reduce power density to protect the system while improving far-field energy concentration.

[0079] Its technological evolution is moving towards tunability (dynamic magnification), intelligence (adaptive correction) and adaptability to extreme environments (space / vacuum).

[0080] In the present invention, the technical indicators are: light input aperture: φ30mm; light output aperture: φ60mm---φ300mm; beam expansion ratio: 2X---10X; laser band: 532.1nm; number of lenses: ≤6 pieces; light output parallelism: better than 10".

[0081] The foregoing is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained herein shall, unless otherwise specified or limited, be implemented in accordance with conventional means in the art.

Claims

1. Large-aperture continuous zoom transmission laser beam expansion system, characterized by: include Incident end: The incident end has a fixed aperture of Φ30mm; the incident end receives 532.1nm band laser; Zoom lens module: The zoom lens module is composed of a negative lens group and a positive lens group to form a double lens group linkage structure; Output port: The output port diameter has a dynamic adjustment range of 60mm-300mm, and the beam expansion ratio is continuously adjustable from 2X to 10X; the total number of optical lenses is ≤ 6, including at least 2 high-order aspheric lenses; The parallelism error of the output beam is ≤10 arc seconds.

2. The large-aperture continuous zoom transmission laser beam expansion system according to claim 1, characterized in that: The zoom lens module drives the lens spacing through a precision guide rail, and the beam expansion ratio M is: Among them, k is the spacing compensation coefficient, f1 is the focal length of the negative lens group in the front group, f1=50mm; f2 is the focal length of the positive lens group in the rear group, f2=100-500mm; the wavefront distortion control target is less than λ / 10; where λ represents the laser wavelength, λ=532.1nm; λ / 10 requires the wavefront distortion, i.e., the optical path difference, to be less than one tenth of the wavelength.

3. The large-aperture continuous zoom transmission laser beam expansion system according to claim 2, characterized in that: The negative lens group is made of CaF2 fused quartz composite material, and the thermal expansion coefficient is less than 0.8×10 -6 / K; the surface of the positive lens group is coated with a multilayer dielectric film, and the laser damage threshold is greater than 10J / cm 2 .

4. The large-aperture continuous zoom transmission laser beam expansion system according to claim 3, characterized in that: The laser beam expansion system includes a double-cemented achromatic mirror set and an aspheric mirror curvature design. In a 532.1nm single-wavelength laser system, dispersion refers to the difference in refractive index of light of different wavelengths. Dispersion can cause secondary spectral aberrations, affecting beam quality. The double-cemented mirror set is made of two different optical materials, crown glass and flint glass, and suppresses the secondary spectrum through the complementary dispersion of the materials. Mathematically, its achromatic condition is: Where Δn is the material dispersion coefficient and d is the lens thickness. This ensures that the beam wavefront distortion is less than λ / 10 in the 532.1nm band, improving energy distribution uniformity. Traditional spherical mirrors introduce spherical aberration and coma in the beam expansion system, which is more significant at a large aperture of Φ300mm. Aspherical mirrors use high-order surface equations to accurately correct aberrations. The surface formula is: Where c is the inverse of the radius of curvature and h is the cone constant.

5. The large-aperture continuous zoom transmission laser beam expansion system according to claim 4, characterized in that: The mechanical support structure uses a silicon carbide lens barrel with an integrated active vibration reduction platform. The lens barrel adopts a honeycomb lightweight design, which reduces weight by 40% and increases rigidity by 30%. The support points use a three-point positioning system, and each point integrates a piezoelectric ceramic actuator to achieve nanometer-level position adjustment. Advantages of a silicon carbide lens barrel: Under temperature fluctuations of ±5°C, the lens barrel deformation is less than 1μm, preventing optical path deviation. The necessity of an active vibration reduction platform: External vibrations such as those from equipment operation or environmental disturbances can cause micro-displacement of the lens, affecting parallelism. The active vibration reduction platform uses piezoelectric sensors and feedback control to isolate vibrations with frequencies greater than 100Hz, ensuring displacement errors of less than 0.1μm.

6. The large-aperture continuous zoom transmission laser beam expansion system according to claim 5, characterized in that: The calibration system includes a laser interferometer and a micro-radian tilt adjustment mechanism. The laser interferometer uses the interference fringes of a 532.1nm laser to monitor wavefront errors in real time. The principle is based on the Mach-Zehnder interferometer. Where ΔL is the optical path difference; when the error is greater than λ / 20, the system automatically triggers correction; During dynamic zooming, lens tilt deviation can cause off-axis aberrations. Micro-radian adjustment ensures that the lens tilt error is less than 0.5 micro-radians (1 micro-radian = 0.206 arc seconds), maintaining light parallelism ≤ 10".

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