A Bessel laser processing head with double depth of focus

Abstract

A Bessel laser processing head with double focal depth includes a conical lens for converting an incident laser beam into a Bessel beam and a lens group for focusing the beam onto the processing surface, and a beam translation ring is arranged between the conical lens and the lens group; the conical lens is a liquid crystal flat conical lens, and the liquid crystal flat conical lens converts the incident laser beam into two divergent and convergent annular beams. The two annular beams enter the lens group after passing through the beam translation ring, so that the focal depth regions of the two annular beams are spliced together. The Bessel laser processing head with double focal depth provided in the invention can form a longer focal depth, up to twice the focal depth of an ordinary laser processing head under the condition of given the same laser characteristics through the cooperation of the liquid crystal flat conical lens and the beam translation ring, thereby realizing the synchronous improvement of the cutting processing efficiency and the processing quality.

Description

Technical Field

[0001] The present invention relates to the technical field of laser processing equipment, and particularly relates to a Bessel laser processing head with double focal depth. Background Art

[0002] Laser processing refers to a processing process in which a laser beam acts on the surface of an object to cause a change in the shape or properties of the object. In essence, the laser transfers energy to the processed material, causing physical or chemical changes in the processed material, so as to achieve the purpose of processing. Laser processing technologies mainly include application forms such as laser cutting, laser marking, laser welding, laser engraving, and laser drilling, and play an important role in industries such as machinery manufacturing, automobiles, aerospace, electronic chips, and construction.

[0003] In laser cutting equipment, the laser processing head is one of the most important core components. At present, the most commonly used laser processing head is the Bessel laser processing head. As Figure 1 shown, its principle is to convert the incident laser beam 1 into an annular beam through the refractive conical lens 2, generate a Bessel beam near the focus of the conical lens, and then focus the Bessel beam on the processing surface through the lens group 3 for cutting processing. The focal depth of a common Bessel laser processing head is relatively short. When cutting a product with a thickness greater than the focal depth, multiple scanning and cutting operations are required, resulting in low processing efficiency; and it is necessary to ensure the coincidence of the scanning paths during each cutting, which also poses high technical requirements for the operation accuracy.

[0004] In view of this, the present application aims to provide a Bessel laser processing head with a long focal depth, whose focal depth can reach twice that of a common laser processing head, improving the cutting efficiency and cutting quality. Summary of the Invention

[0005] The object of the present invention is to overcome the above-mentioned deficiencies of the prior art and provide a Bessel laser processing head with double focal depth. Under the same laser characteristics, the focal depth of this laser processing head is twice that of a common laser processing head, which can achieve the synchronous improvement of cutting processing efficiency and processing quality.

[0006] The technical solution of the present invention is: a Bessel laser processing head with double focal depth, including a conical lens for converting an incident laser beam into a Bessel beam and a lens group for focusing the beam on the processing surface. A beam translation ring is arranged between the conical lens and the lens group; the conical lens is a liquid crystal flat conical lens, and the liquid crystal flat conical lens converts the incident laser beam into two divergent and convergent annular beams. The two annular beams enter the lens group after passing through the beam translation ring, and finally the focal depth regions of the two annular beams are spliced together.

[0007] Further, the liquid crystal flat conical lens includes a substrate and a liquid crystal layer disposed between the two substrates.

[0008] Furthermore, the phase modulation of the incident light by the fast axis orientation of the liquid crystal molecules in the liquid crystal layer satisfies the following requirements:

[0009] a) When the incident light is right-handed circularly polarized light, after being modulated by the liquid crystal flat cone lens, the polarization state changes to left-handed circular polarization and carries a focusing conical phase. After focusing, a non-diffracting region is formed, and the generated light beam in this region has the characteristics of a Bessel beam. Continuing to propagate will form an annular beam;

[0010] b) When the incident light is left-handed circularly polarized light, after being modulated by the liquid crystal flat cone lens, the polarization state changes to right-handed circular polarization and carries a diverging conical phase. After diffraction, an annular beam is directly formed;

[0011] c) When the incident light is linearly polarized light, its left- and right-handed circular polarization components respectively obtain focusing and diverging conical phases after being modulated by the liquid crystal flat cone lens, and respectively focus and then diverge as well as directly diverge. The angles of divergence and convergence are equal;

[0012] d) When the incident light is elliptically polarized light, its left- and right-handed circular polarization components have different amplitudes. The diffraction process of the transmitted light is the same as when linearly polarized light is incident, but its intensity is related to the ellipticity;

[0013] e) When the incident light is unpolarized light, it is the superposition of all the above cases.

[0014] Furthermore, the beam translation ring is an annular flat glass with a conical through-hole in the center.

[0015] Furthermore, the side of the conical through-hole on the beam translation ring with a smaller diameter faces the liquid crystal flat cone lens.

[0016] Furthermore, the taper of the conical through-hole on the beam translation ring is associated with the divergence angle (deflection angle) of the light by the liquid crystal flat cone lens, so that the converging light beam generated by the conversion of the liquid crystal flat cone lens just completely passes through the conical through-hole in the center of the beam translation ring without being affected, and the diverging light beam generated by the conversion of the liquid crystal flat cone lens all passes through the ring body of the beam translation ring and is integrally translated, and is spliced with the converging light beam to form a whole. According to the grating diffraction formula, when the light beam is normally incident: ; where θ is the deflection angle, λ is the wavelength, p is the period along the radial direction, and the deflection angles corresponding to different periods are: .

[0017] Furthermore, when the beam translation ring works, its thickness and the light translation distance satisfy the following formula:

[0018] (1)

[0019] Where n is the refractive index of the material, α is the refraction angle, θ is the deflection angle of the liquid crystal flat panel conical lens, and l is the distance that the light beam is translated downward.

[0020] Furthermore, the installation position of the light beam translation ring is behind the focus of the liquid crystal flat panel conical lens, and the converging light beam passes through the focus and then passes through the light beam translation ring.

[0021] Furthermore, the lens group structure includes two lenses, and both lenses are convex lenses. Preferably, the two convex lenses form a 4f structure.

[0022] The beneficial effects of the present invention compared with the prior art: The present invention provides a Bessel laser processing head with double focal depth. Through the cooperation of the liquid crystal flat panel conical lens and the light beam translation ring, under the condition of the same laser characteristics, a longer focal depth can be formed, up to twice the focal depth of the ordinary laser processing head at most, so as to realize the synchronous improvement of the cutting processing efficiency and the processing quality. Description of the Drawings

[0023] Figure 1 is a schematic diagram of an existing Bessel laser processing head;

[0024] Figure 2 is a schematic diagram of the Bessel laser processing head in the present invention;

[0025] Figure 3 is a schematic diagram of the liquid crystal flat panel conical lens acting on right-handed circularly polarized light in Embodiment 1 of the present invention;

[0026] Figure 4 is a schematic diagram of the liquid crystal flat panel conical lens acting on left-handed circularly polarized light in Embodiment 1 of the present invention;

[0027] Figure 5 is a schematic diagram of the liquid crystal flat panel conical lens acting on linearly polarized light in Embodiment 1 of the present invention;

[0028] Figure 6 is a schematic diagram of the light beam translation ring in Embodiment 1 of the present invention;

[0029] Figure 7 is a schematic diagram of the working principle of the light beam translation ring in Embodiment 1 of the present invention;

[0030] In the figure: 1 - laser beam, 11 - divergent light beam, 12 - converging light beam, 2 - refractive conical lens, 3 - lens group, 4 - light beam translation ring, 5 - liquid crystal flat panel conical lens. Detailed Embodiments

[0031] The following will further describe the present invention in detail with specific embodiments. The methods or functional components not specifically described in the embodiments are all prior art.

[0032] Example 1

[0033] As shown in Figure 2-7 , this embodiment is a Bessel laser processing head with double depth of focus, including a liquid crystal flat conical lens 5 and a lens group 3. A beam translation ring 4 is arranged between the liquid crystal flat conical lens 5 and the lens group 3; the liquid crystal flat conical lens 5 can convert the incident laser beam 1 into two annular beams, namely a divergent beam 11 and a convergent beam 12. After passing through the beam translation ring 4, the two annular beams enter the lens group 3, so that the depth-of-focus regions of the two annular beams are spliced together.

[0034] In this embodiment, the liquid crystal flat conical lens 5 includes a substrate and a liquid crystal layer arranged between the two substrates. The phase modulation of the incident light by the liquid crystal layer based on the fast axis orientation of liquid crystal molecules satisfies the following requirements:

[0035] a) When the incident light is right-handed circularly polarized light, the polarization state is changed to left-handed circular polarization after being modulated by the liquid crystal flat conical lens 5, and it carries a focusing conical phase. After focusing, a non-diffracting region is formed, and the beam generated in this region has the characteristics of a Bessel beam and will form an annular beam when continuing to propagate; as shown in Figure 3 ;

[0036] b) When the incident light is left-handed circularly polarized light, the polarization state is changed to right-handed circular polarization after being modulated by the liquid crystal flat conical lens 5, and it carries a divergent conical phase and directly forms an annular beam after diffraction; as shown in Figure 4 ;

[0037] c) When the incident light is linearly polarized light, its left- and right-handed circular polarization components respectively obtain focusing and divergent conical phases after being modulated by the liquid crystal flat conical lens 5, and respectively diverge after focusing and directly diverge, and the divergence and convergence angles are equal; as shown in Figure 5 ;

[0038] d) When the incident light is elliptically polarized light, its left- and right-handed circular polarization components have different amplitudes, and the diffraction process of the transmitted light is the same as that when linearly polarized light is incident, but its intensity is related to the ellipticity;

[0039] e) When the incident light is unpolarized light, it is the superposition of all the above situations. It can be seen that the incident laser beam in this embodiment must be linearly polarized light.

[0040] In this embodiment, the beam translation ring 4 is an annular flat glass with a conical through hole in the center. The side with the smaller diameter of the conical through hole on the beam translation ring 4 faces the liquid crystal flat conical lens 5. According to the grating diffraction formula, when the beam is normally incident: ; where θ is the deflection angle, λ is the wavelength, and p is the period along the radial direction. The deflection angles corresponding to different periods are: .

[0041] In this embodiment, when the beam translation ring 4 is working, the translation distance of the light beam and its thickness satisfy the following formula:

[0042] ;

[0043] where n is the refractive index of the material of the beam translation ring 4, α is the refraction angle, θ is the deflection angle of the liquid crystal flat cone lens 5, and l is the distance by which the light beam is translated downward.

[0044] In this embodiment, the taper of the conical through hole on the beam translation ring 4 is associated with the light divergence angle (deflection angle) of the liquid crystal flat cone lens 5, so that the converging beam 12 generated by the conversion of the liquid crystal flat cone lens 5 just completely passes through the conical through hole at the center of the beam translation ring 4 without being affected, and the diverging beam 11 generated by the conversion of the liquid crystal flat cone lens 5 just completely passes through the beam translation ring 4 and is integrally translated, and is spliced with the converging beam 12 into one body. More specifically, the installation position of the beam translation ring 4 is behind the focal point of the liquid crystal flat cone lens 5, and the converging beam 12 passes through the focal point and then passes through the beam translation ring 4.

[0045] In this embodiment, the structure of the lens group 3 includes two lenses, and both lenses are convex lenses. The two convex lenses form a 4f structure. In some embodiments, the angle e and the angle C can be equal.

[0046] The above are only some embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have combinations and variations of the foregoing various technical features. Without departing from the spirit and scope of the present invention, improvements, variations, equivalent substitutions made by those skilled in the art, or the application of the structure or method of the present invention to other fields to achieve the same effect all fall within the protection scope of the present invention.

Claims

1. A Bessel laser processing head with double depth of focus, comprising a conical lens for converting an incident laser beam into a Bessel beam and a lens group for focusing the beam onto the processing surface, characterized in that: A beam translation ring is arranged between the conical lens and the lens group; the conical lens is a liquid crystal flat conical lens, and the liquid crystal flat conical lens converts the incident laser beam into two diverging and converging annular beams. The two annular beams enter the lens group after passing through the beam translation ring, so that the focal depth regions of the two annular beams are spliced together; The beam translation ring is an annular flat glass with a conical through hole in the center; The side with a smaller diameter of the conical through hole on the beam translation ring faces the liquid crystal flat conical lens; The taper of the conical through hole on the beam translation ring is associated with the divergence angle of the liquid crystal flat conical lens for light, so that the conical surface of the conical through hole is parallel to the light rays of the diverging beam generated by the liquid crystal flat conical lens; When the beam translation ring works, its thickness and the light ray translation distance satisfy the following formula: （1） Where n is the refractive index of the material, α is the refraction angle, θ is the deflection angle of the liquid crystal flat conical lens, and l is the distance of the beam translated up and down; The installation position of the beam translation ring is near the focal point of the liquid crystal flat conical lens, so that the converging beam generated by the conversion of the liquid crystal flat conical lens just passes through the conical through hole in the center of the beam translation ring without being affected, and the diverging beam generated by the conversion of the liquid crystal flat conical lens just passes through the beam translation ring and is integrally translated, and is spliced with the converging beam to form a whole.

2. The Bessel laser processing head according to claim 1, wherein : The liquid crystal flat conical lens includes a substrate and a liquid crystal layer arranged between the two substrates.

3. The Bessel laser processing head according to claim 2, wherein : The phase modulation of the incident light by the liquid crystal layer based on the fast axis orientation of the liquid crystal molecules meets the following requirements: a) When the incident light is right-handed circularly polarized light, the polarization state is changed to left-handed circularly polarized after being modulated by the liquid crystal flat conical lens, and carries a focusing conical phase. After focusing, a non-diffracting region is formed, and the beam generated in this region has the characteristics of a Bessel beam and will form an annular beam when continuing to transmit; b) When the incident light is left-handed circularly polarized light, the polarization state is changed to right-handed circularly polarized after being modulated by the liquid crystal flat conical lens, and carries a diverging conical phase, and directly forms an annular beam after diffraction; c) When the incident light is linearly polarized light, its left and right circularly polarized components obtain focusing and diverging conical phases respectively after being modulated by the liquid crystal flat conical lens, and are respectively focused and then diverged and directly diverged, and the divergence and convergence angles are equal; d) When the incident light is elliptically polarized light, its left and right circularly polarized components have different amplitudes, and the diffraction process of the transmitted light is the same as that when linearly polarized light is incident, but its intensity is related to the ellipticity; e) When the incident light is unpolarized light, it is the superposition of all the above situations.

4. The Bessel laser processing head according to claim 1, wherein : The lens group structure includes two convex lenses.

5. The Bessel laser processing head according to claim 4, characterized in that : The lens group structure selects a 4f structure.

Images