An ultra-large format ultraviolet laser telecentric lens

Abstract

The present invention relates to an ultra-large-format ultraviolet laser telecentric lens, which includes a lens barrel and lenses installed in the lens barrel. The lenses are arranged in sequence from the object side to the image side along the optical axis as a first biconcave lens, a second meniscus lens, a third meniscus lens, a fourth biconvex lens, and a fifth plano-convex lens. The focal length f1 of the first biconcave lens and the total focal length f of the telecentric lens satisfy the relational expression: -1.8 < f1 / f < -2.0; the focal length f2 of the second meniscus lens and the total focal length f of the telecentric lens satisfy the relational expression: -2.0 < f2 / f < -3.0; the focal length f3 of the third meniscus lens and the total focal length f of the telecentric lens satisfy the relational expression: +1.6 < f3 / f < +2.2; the focal length f4 of the fourth biconvex lens and the total focal length f of the telecentric lens satisfy the relational expression: +3.1 < f4 / f < +3.3; the focal length f5 of the fifth plano-convex lens and the total focal length f of the telecentric lens satisfy the relational expression: +2.5 < f5 / f < +2.7. The present invention has a wavelength of 355 nm and a total focal length of 300 mm, and this telecentric lens can achieve the focusing of a laser beam perpendicular to the working surface.

Description

Technical Field

[0001] The present invention relates to the field of optical technologies, and particularly to an ultra-large format ultraviolet laser telecentric lens. Background Art

[0002] An ultra-large format ultraviolet laser telecentric lens scans an incident laser beam within a scanning angle range of ±θ around the optical axis of the lens in the object space, and vertically focuses it onto a flat imaging area in the image space. Within this scanning angle range, the spacing relationship between the focus of the laser beam in the imaging area and the optical axis follows a linear function with the incident scanning angle of the laser beam. That is, a laser beam scanned at a constant angular velocity generates a focus in the imaging area, and this focus moves at a constant speed. The size of the focus should be constant at each position in the imaging area. The size of the focus is determined depending on the processing purpose of the material (such as marking, peeling, or cutting).

[0003] Since the propagation of the laser beam in the lens depends on the refraction of the mirror surface for the specified wavelength beam, in order to achieve the incident of the light in the image space perpendicular to the working surface to improve the focus quality, the lens corrects the mirror surface shape for the wavelength of the processing laser beam used, that is, calculates the objective lens as follows: within the range of the predetermined imaging area, the normals of the imaging beams in the central area and the edge area are both perpendicular to the working surface. Under the conditions of a predetermined wavelength and a predetermined laser beam diameter, the objective lens has no or only very small optical imaging distortion (imaging distortion will cause a significant change in the size of the focus) within the imaging area of a predetermined size. When used in precision processing of laser materials, the lens has a large imaging area and a large total focal length. Summary of the Invention

[0004] The object of the present invention is to provide an ultra-large format ultraviolet laser telecentric lens with a wavelength of 355 nm and a total focal length of 300 mm, which can achieve the focusing of the laser beam perpendicular to the working surface.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] An ultra-large format ultraviolet laser telecentric lens, comprising a lens barrel and lenses installed inside the lens barrel. The lenses are arranged along the optical axis from the object side to the image side in sequence as a first biconcave lens, a second meniscus lens, a third meniscus lens, a fourth biconvex lens, and a fifth plano-convex lens. The focal length f1 of the first biconcave lens and the total focal length f of the telecentric lens satisfy the relation: -1.8 < f1 / f < -2.0. The focal length f2 of the second meniscus lens and the total focal length f of the telecentric lens satisfy the relation: -2.0 < f2 / f < -3.0. The focal length f3 of the third meniscus lens and the total focal length f of the telecentric lens satisfy the relation: +1.6 < f3 / f < +2.2. The focal length f4 of the fourth biconvex lens and the total focal length f of the telecentric lens satisfy the relation: +3.1 < f4 / f < +3.3. The focal length f5 of the fifth plano-convex lens and the total focal length f of the telecentric lens satisfy the relation: +2.5 < f5 / f < +2.7.

[0007] Further, the distance between the entrance pupil of the telecentric lens and the first biconcave lens is 30 mm.

[0008] Further, the lens barrel is a straight barrel with equal diameters at both ends, and contains parallel stepped positioning surfaces for positioning the lenses. The outer part of the lens barrel is a lens barrel housing and an adapter ring connected to the lens barrel housing from bottom to top.

[0009] Further, a protective sheet is provided inside the lens barrel. The protective sheet is a flat mirror and is located behind the fifth plano-convex lens.

[0010] Further, each lens is fixed inside the lens barrel by a corresponding lens holder and a retaining ring, and the coaxiality and parallelism of each lens and the corresponding lens holder are ensured through the cooperation adjustment of the lens holder and the retaining ring.

[0011] Further, the lens holder, the retaining ring, the lens barrel housing, and the adapter ring are all subjected to bead blasting and black anodizing treatment.

[0012] The ultra-large format ultraviolet laser telecentric lens of the present invention has an objective lens including five single lenses sharing the same optical axis. The five single lenses form a lens sequence of "negative-negative-positive-positive-positive". The first two single lenses have negative focal lengths, and the last three single lenses have positive focal lengths. It has a wavelength of 355 nm and a total focal length of 300 mm. This lens can achieve the focusing of a laser beam perpendicular to the working surface. Description of the Drawings

[0013] Figure 1 is a schematic diagram of the incident beams at each scanning angle along the image plane normal in an embodiment of the present invention;

[0014] Figure 2 is an optical-mechanical assembly drawing of the optical interval of the telecentric lens in an embodiment of the present invention;

[0015] Figure 3It is the actual image point diagram of the telecentric lens in an embodiment of the present invention;

[0016] In the figure: L1 is the first double concave lens, L2 is the second meniscus lens, L3 is the third meniscus lens, L4 is the fourth double convex lens, L5 is the fifth plano-convex lens, SG is the protective glass, 1 is the first retaining ring, 2 is the first lens mount, 3 is the second retaining ring, 4 is the second lens mount, 5 is the third retaining ring, 6 is the third lens mount, 7 is the fourth retaining ring, 8 is the fourth lens mount, 9 is the fifth retaining ring, 10 is the fifth lens mount, 11 is the protective glass lens mount, 12 is the protective glass retaining ring, 13 is the lens barrel housing, 14 is the lens barrel, 15 is the adapter ring. Detailed implementation manners

[0017] The technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0018] As Figure 1 , a super-large format ultraviolet laser telecentric lens of the present invention includes a lens barrel 14 and a first double concave lens L1, a second meniscus lens L2, a third meniscus lens L3, a fourth double convex lens L4, and a fifth plano-convex lens L5 arranged in sequence along the optical axis from the object side to the image side inside the lens barrel 14. Among them, the focal length f1 of the first double concave lens L1 and the total focal length f of the telecentric lens satisfy the relationship: -1.8 < f1 / f < -2.0, the focal length f2 of the second meniscus lens L2 and the total focal length f of the telecentric lens satisfy the relationship: -2.0 < f2 / f < -3.0, the focal length f3 of the third meniscus lens L3 and the total focal length f of the telecentric lens satisfy the relationship: +1.6 < f3 / f < +2.2, the focal length f4 of the fourth double convex lens L4 and the total focal length f of the telecentric lens satisfy the relationship: +3.1 < f4 / f < +3.3, and the focal length f5 of the fifth plano-convex lens L5 and the total focal length f of the telecentric lens satisfy the relationship: +2.5 < f5 / f < +2.7. The first double concave lens L1, the second meniscus lens L2, the third meniscus lens L3, the fourth double convex lens L4, and the fifth plano-convex lens L5 share the same optical axis and form a lens sequence of "negative-negative-positive-positive-positive". The first double concave lens L1 and the second meniscus lens L2 have negative focal lengths, and the third meniscus lens L3, the fourth double convex lens L4, and the fifth plano-convex lens L5 have positive focal lengths.

[0019] When there is only one scanning mirror in front of the telecentric lens, the EP position is the position of the mirror. When there are two scanning mirrors in front of the telecentric lens, the EP position is M1 / 2 + M2. Among them, M1 is the center distance between the two scanning mirrors, and M2 is the distance from the second scanning mirror to the telecentric lens.

[0020] In one embodiment, the entrance pupil EP of the telecentric lens of the present invention is located in front of the front vertex of the first biconcave lens L1 at a distance D1. The first biconcave lens L1 has a thickness TC1, its front surface has a radius r1 and its rear surface has a radius r2; the second meniscus lens L2 follows the first biconcave lens L1 with an air spacing D2. The second meniscus lens L2 has a thickness TC2, its front surface has a radius r3 and its rear surface has a radius r4; the third meniscus lens L3 follows the second meniscus lens L2 with an air gap D3. The third meniscus lens L3 has a thickness TC3, its front surface has a radius r5 and its rear surface has a radius r6; the fourth biconvex lens L4 follows the third meniscus lens L3 with an air gap D4. The fourth biconvex lens L4 has a thickness TC4, its front surface has a radius r7 and its rear surface has a radius r8; the fifth plano-convex lens L5 follows with an air gap D5. The fifth plano-convex lens L5 has a thickness TC5, its front surface has a radius r9 and its rear surface has a radius r10.

[0021] The protective sheet SG follows with an air isolation D6. The protective SG is a plane-parallel protective glass with a thickness of TC6. The imaging area BE is generated at a distance D7 relative to the protective sheet SG.

[0022] As the material, the first biconcave lens L1, the second meniscus lens L2, the third meniscus lens L3, the fourth biconvex lens L4, the fifth plano-convex lens L5 and the protective sheet SG are selected as fused silica glass with a refractive index of n.

[0023] Table 1: Radius, thickness and spacing values of the single lenses L1 to L5:

[0024]

[0025]

[0026] It is obtained from the arrangement of the lenses L1 to L5 in front of and behind each other and their air spacings D1 to D7. The total focal length f is 300 mm, and the telecentric lens is corrected for a wavelength of 355 nm.

[0027] Figure 3 This is the actual image point diagram of the ultra-large format ultraviolet laser telecentric lens. The geometric radius of the image point in the central field of view is 3.696 um, the geometric radius of the image point at half image height of 61.98 mm is 2.226 um, the geometric radius of the image point at half image height of 87.67 mm is 2.883 um, and the geometric radius of the image point at half image height of 124 mm in the edge field of view is 2.814 um. That is, from the center to the edge, the image point size of the entire working area is much smaller than 10 um, and the imaging distortion is extremely small.

[0028] In one embodiment, as Figure 2As shown in the figure, the lens barrel 14 is a straight barrel with equal diameters at both ends, and contains parallel stepped positioning surfaces for lens positioning. From the rear end to the front end of the lens barrel 14, a protective sheet lens holder 11, a protective sheet SG, a protective sheet retaining ring 12, a fifth lens holder 10, a fifth plano-convex lens L5, a fifth retaining ring 9; a fourth lens holder 8, a fourth biconvex lens L4, a fourth retaining ring 7; a third lens holder 6, a third meniscus lens L3, a third retaining ring 5; a second lens holder 4, a second meniscus lens L2, a second retaining ring 3; a first lens holder 2, a first biconcave lens L1, a first retaining ring 1 are provided in sequence. Grooves are provided on the protective sheet retaining ring 12, the first retaining ring 1, the second retaining ring 3, the third retaining ring 5, the fourth retaining ring 7, and the fifth retaining ring 9. The first retaining ring 1 and the inner wall of the first lens holder 2 are locked by fine-threaded screws to fix the first biconcave lens L1. The second retaining ring 3 and the inner wall of the second lens holder 4 are locked by fine-threaded screws to fix the second meniscus lens L2. The third retaining ring 5 and the inner wall of the third lens holder 6 are locked by fine-threaded screws to fix the third meniscus lens L3. The fourth retaining ring 7 and the inner wall of the fourth lens holder 8 are locked by fine-threaded screws to fix the fourth biconvex lens L4. The fifth retaining ring 9 and the inner wall of the fifth lens holder 10 are locked by fine-threaded screws to fix the fifth plano-convex lens L5. The protective sheet retaining ring 12 and the inner wall of the protective sheet lens holder 11 are locked by fine-threaded screws to fix the protective sheet SG; the outer diameters of the first lens holder 2, the second lens holder 4, the third lens 6 holder, and the fourth lens holder 8 are nested coaxially with the inner diameter of the lens barrel 14, and the assembly surfaces are installed in sequence and coincide. The inner diameter of the fifth lens holder 10 is nested coaxially with the outer diameter of the fourth lens holder 8, and the assembly surfaces are installed in sequence and coincide. The protective sheet lens holder 11 and the lens barrel 14 are locked by screw fit. Each lens is fixed in the lens barrel by the corresponding lens holder and retaining ring, and the coaxiality and balance of each lens and the corresponding lens holder are ensured through the cooperation adjustment of the lens holder and the retaining ring. Outside the lens barrel 14, there are a lens barrel housing 13 and an adapter ring 15 connected to the lens barrel housing 13 from bottom to top.

[0029] To eliminate stray light, the lens holders, retaining rings, lens barrel housing 13 and adapter ring 15 used in the present invention are all subjected to sandblasting and black anodizing treatment.

[0030] In the assembly process of the objective lens of the present invention, from bottom to top, the fifth plano-convex lens L5, the fourth biconvex lens L4, the third meniscus lens L3, the second meniscus lens L2, and the first biconcave lens L1 are fixed in sequence, and then the lens is inverted and the protective sheet SG is fixed. This installation method avoids the lens shape error that harms the lens quality during the installation process of the entire lens.

[0031] The above-mentioned specific implementation manners further elaborate on the purpose, technical solution and beneficial effects of the present invention. It should be understood that the above-mentioned is only the specific implementation manner of the present invention, and is not used to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A super-large-format ultraviolet laser telecentric lens, comprising a lens barrel and lenses installed inside the lens barrel, characterized in that: The lenses are arranged in sequence from the object side to the image side along the optical axis as the first biconcave lens, the second meniscus lens, the third meniscus lens, the fourth biconvex lens, and the fifth plano-convex lens. The focal length f1 of the first biconcave lens and the total focal length f of the telecentric lens satisfy the relationship: -1.8 < f1 / f < -2.

0. The focal length f2 of the second meniscus lens and the total focal length f of the telecentric lens satisfy the relationship: -2.0 < f2 / f < -3.

0. The focal length f3 of the third meniscus lens and the total focal length f of the telecentric lens satisfy the relationship: +1.6 < f3 / f < +2.

2. The focal length f4 of the fourth biconvex lens and the total focal length f of the telecentric lens satisfy the relationship: +3.1 < f4 / f < +3.

3. The focal length f5 of the fifth plano-convex lens and the total focal length f of the telecentric lens satisfy the relationship: +2.5 < f5 / f < +2.7; The lens barrel is a straight barrel with equal diameters at both ends, and contains parallel stepped positioning surfaces for lens positioning. From bottom to top on the outside of the lens barrel are a lens barrel housing and an adapter ring connected to the lens barrel housing; A protective sheet is provided inside the lens barrel. The protective sheet is a flat mirror and is located behind the fifth plano-convex lens; Each lens is fixed in the lens barrel by a corresponding lens holder and a retaining ring, and the coaxiality and parallelism of each lens and the corresponding lens holder are ensured through the cooperation adjustment of the lens holder and the retaining ring.

2. The ultra-large format ultraviolet laser telecentric lens according to claim 1, wherein: The distance between the entrance pupil of the telecentric lens and the first biconcave lens is 30 mm.

3. The ultra-large format ultraviolet laser telecentric lens according to claim 1, characterized in that: The lens holder, the retaining ring, the lens barrel housing, and the adapter ring are all subjected to bead blasting and black anodizing treatment.

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