F-theta Ultraviolet Field Lens Device with Large Aperture and Low Distortion

Abstract

The present invention provides an F-theta ultraviolet field lens device with a large aperture and low distortion, comprising: a first lens, a second lens, a third lens, a fourth lens, and a fifth lens; the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are arranged in sequence from the laser incident direction to the focusing plane; the first lens is a plano-concave lens or a convex-concave lens with a concave surface facing the laser incident direction; the second lens is a meniscus convex-concave lens with a convex surface facing the focusing plane; the third lens and the fourth lens are double-convex lenses; the fifth lens is a double-concave lens or a plano-concave lens. The large-aperture, low-distortion F-theta ultraviolet field lens provided by the present invention realizes large-field-of-view, low-distortion, and high-quality scanning on the premise of effectively ensuring the diameter of the incident light beam.

Description

Technical Field

[0001] The present invention relates to the field of laser processing such as laser marking and laser cutting. Specifically, it relates to an F-theta ultraviolet field lens device with a large aperture and low distortion. Background Art

[0002] In the existing F-theta ultraviolet field lens optical path, a (-+++) four-lens configuration is mostly adopted. Except for the first lens, the other lenses all play a role in converging light, which is essentially not conducive to expanding the scanning range of the field lens.

[0003] Patent document CN101236291 A discloses a telecentric F-theta optical lens and an optical system. The optical lens includes first, second, third, and fourth lenses arranged in sequence along the incident light direction. The first lens is a biconcave negative lens; the second lens is a meniscus positive lens with the curved surface facing the incident light side; the third lens is a plano-convex or biconvex positive lens; the fourth lens is a convex-plano or biconvex positive lens. In addition, the focal power of each lens and the system focal power of the optical lens preferably satisfy: -0.65 < f1 / fw < -0.55, 1.6 < f2 / fw < 2.5, 0.8 < f3 / fw < 1.2, 2.2 < f4 / fw < 2.5, where f1, f2, f3, and f4 are the focal powers of the first, second, third, and fourth lenses respectively, and fw is the system focal power of the optical lens. By arranging the four lenses into a "negative-positive-positive-positive" separated focal power system, the exit pupil of the F-theta optical lens is located at infinity, and the chief rays in the image space within the field of view are parallel to each other and perpendicular to the imaging plane. In addition, astigmatism and field curvature are well corrected, and the imaging is uniform across the entire field of view without vignetting. There is still room for improvement in the structure and technical effects of this patent. Summary of the Invention

[0004] Aiming at the defects in the prior art, the purpose of the present invention is to provide an F-theta ultraviolet field lens device with a large aperture and low distortion.

[0005] An F-theta ultraviolet field lens device with a large aperture and low distortion according to the present invention is characterized by including: a first lens, a second lens, a third lens, a fourth lens, and a fifth lens; the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are arranged in sequence from the laser incident direction to the focusing plane; the first lens is a plano-concave lens or a convex-concave lens with the concave side facing the laser incident direction; the second lens is a meniscus convex-concave lens with the convex side facing the focusing plane; the third lens and the fourth lens are biconvex lenses; the fifth lens is a biconcave lens or a plano-concave lens.

[0006] Preferably, the range of the ratio f1 / f of the focal length f1 of the first lens to the focal length f of the scanning field lens is as follows:

[0007] -0.35 ≤ f1 / f ≤ -0.55.

[0008] Preferably, the refractive index Nd1 and Abbe number Vd1 of the material of the first lens have the following ranges of values respectively:

[0009] 1.45 ≤ Nd1 ≤ 1.51, 54 ≤ Vd1 ≤ 70.

[0010] Preferably, the ratio f2 / f of the focal length f2 of the second lens to the focal length f of the scanning field lens has the following range of values:

[0011] 1.0 ≤ f2 / f ≤ 1.3.

[0012] Preferably, the refractive index Nd2 and Abbe number Vd2 of the material of the second lens have the following ranges of values respectively:

[0013] 1.45 ≤ Nd2 ≤ 1.53, 54 ≤ Vd2 ≤ 70.

[0014] Preferably, the ratio f3 / f of the focal length f3 of the third lens to the focal length f of the scanning field lens has the following range of values:

[0015] 0.5 ≤ f3 / f ≤ 0.85.

[0016] Preferably, the refractive index Nd3 and Abbe number Vd3 of the material of the third lens are as follows respectively:

[0017] 1.45 ≤ Nd3 ≤ 1.53, 54 ≤ Vd3 ≤ 70.

[0018] Preferably, the ratio f4 / f of the focal length f4 of the fourth lens to the focal length f of the scanning field lens, the refractive index Nd4, and the Abbe number Vd4 have the following ranges of values:

[0019] 0.65 ≤ f4 / f ≤ 0.9, 1.45 ≤ Nd4 ≤ 1.53, 54 ≤ Vd4 ≤ 70.

[0020] Preferably, the ratio f5 / f of the focal length f5 of the fifth lens to the focal length f of the scanning field lens, the refractive index Nd5, and the Abbe number Vd5 have the following ranges of values:

[0021] -1.1 ≤ f5 / f ≤ -0.8, 1.45 ≤ Nd5 ≤ 1.53, 54 ≤ Vd5 ≤ 70.

[0022] Preferably, the design wavelength of the large-aperture and low-distortion F-theta ultraviolet field lens device is 355 nm;

[0023] When the designed focal length of the large-aperture and low-distortion F-theta ultraviolet field lens device is 160 mm, the maximum allowable value of the incident beam diameter is not less than 12 mm, the scanning angle is not less than ±25 degrees, the scanning range is greater than 140 mm, and the distance between the incident aperture and the center of the first lens is 14 mm - 38 mm.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The large-aperture and low-distortion F-theta ultraviolet field lens provided by the present invention realizes large-field-of-view, low-distortion, and high-quality scanning while effectively ensuring the incident beam diameter.

[0026] 2. When the focal length of the present invention is 160 mm, the maximum allowable value of the incident beam diameter is not less than 12 mm, the scanning angle is not less than ±25 degrees, the scanning range is greater than 140 mm, the F-theta distortion is less than 0.1%, and the spot size is close to the diffraction limit.

[0027] 3. The structure of the present invention is reasonable and convenient to use, and can overcome the defects of the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Other features, objects, and advantages of the present invention will become more apparent by reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0029] Figure 1 It is a schematic structural diagram of the large-aperture and low-distortion F-theta ultraviolet field lens provided by the present invention.

[0030] Figure 2 It is a schematic diagram of the modulation transfer function of the large-aperture and low-distortion F-theta ultraviolet field lens provided by the present invention.

[0031] Figure 3 It is a schematic diagram of the simulated point array of the large-aperture and low-distortion F-theta ultraviolet field lens provided by the present invention.

[0032] Figure 4 It is a schematic diagram of the field curvature and F-theta distortion of the large-aperture and low-distortion F-theta ultraviolet field lens provided by the present invention.

[0033] As shown in the figure:

[0034] Incident aperture 1 Fourth lens 5

[0035] First lens 2 Fifth lens 6

[0036] Second lens 3 Focusing plane 7

[0037] Third lens 4 DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several changes and improvements can still be made. These all belong to the protection scope of the present invention.

[0039] A large-aperture, low-distortion F-theta ultraviolet field lens is as follows:

[0040] The large-aperture, low-distortion F-theta ultraviolet field lens is characterized in that the designed wavelength is 355 nm, the designed focal length is 160 mm, the designed value of the incident beam diameter is 12 mm, the designed scanning angle is ±25 degrees, and the distance from the position of the incident aperture galvanometer to the center of the first lens is 14 mm - 35 mm.

[0041] For the large-aperture, low-distortion F-theta ultraviolet field lens, the first lens 2 is a plano-concave lens or a convex-concave lens concave toward the laser incident direction, the second lens 3 is a meniscus convex-concave lens convex toward the focusing plane, the third lens 4 and the fourth lens are double-convex lenses, and the fifth lens 6 is a double-concave lens or a plano-concave lens.

[0042] For the large-aperture, low-distortion F-theta ultraviolet field lens, the ratio f1 / f of the focal length f1 of the first lens 2 to the focal length f of the scanning field lens, the material refractive index Nd1, and the Abbe number Vd1 are as follows:

[0043] -0.35 ≤ f1 / f ≤ -0.55, 1.45 ≤ Nd1 ≤ 1.51, 54 ≤ Vd1 ≤ 70;

[0044] For the second lens 3, the ratio f2 / f of the focal length f2 to the focal length f of the scanning field lens, the material refractive index Nd2, and the Abbe number Vd2 are as follows:

[0045] 1.0 ≤ f2 / f ≤ 1.3, 1.45 ≤ Nd2 ≤ 1.53, 54 ≤ Vd2 ≤ 70;

[0046] For the third lens 4, the ratio f3 / f of the focal length f3 to the focal length f of the scanning field lens, the material refractive index Nd3, and the Abbe number Vd3 are as follows:

[0047] 0.5 ≤ f3 / f ≤ 0.85, 1.45 ≤ Nd3 ≤ 1.53, 54 ≤ Vd3 ≤ 70;

[0048] For the fourth lens 5, the ratio f4 / f of the focal length f4 to the focal length f of the scanning field lens, the material refractive index Nd4, and the Abbe number Vd4 satisfy:

[0049] 0.65 ≤ f4 / f ≤ 0.9, 1.45 ≤ Nd4 ≤ 1.53, 54 ≤ Vd4 ≤ 70;

[0050] The ratio f5 / f of the focal length f5 of the fifth lens 6 to the focal length f of the scanning field lens, the refractive index Nd5 of the material, and the Abbe number Vd5 satisfy:

[0051] -1.1 ≤ f5 / f ≤ -0.8, 1.45 ≤ Nd5 ≤ 1.53, 54 ≤ Vd5 ≤ 70;

[0052] For each lens provided by the present invention, that is, the surface curvature radius R, thickness T, refractive index Nd of the material, and Abbe number Vd of each lens in the lens assembly are shown in the following table:

[0053]

[0054] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0055] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Without conflict, the embodiments of the present application and the features in the embodiments can be arbitrarily combined with each other.

Claims

1. An F-theta ultraviolet field lens device with a large aperture and low distortion, characterized in that, Including: A first lens, a second lens, a third lens, a fourth lens, and a fifth lens; The number of lenses is 5; The first lens, the second lens, the third lens, the fourth lens, and the fifth lens are arranged in sequence from the laser incident direction to the focal plane; The first lens is a plano-concave lens or a convex-concave lens concave toward the laser incident direction; The second lens is a meniscus convex-concave lens convex toward the focal plane; The third lens and the fourth lens are double-convex lenses; The fifth lens is a double-concave lens or a plano-concave lens; The range of the ratio f1 / f of the focal length f1 of the first lens to the focal length f of the field lens is as follows: -0.55 ≤ f1 / f ≤ -0.35; The range of the ratio f2 / f of the focal length f2 of the second lens to the focal length f of the field lens is as follows: 1.0 ≤ f2 / f ≤ 1.3; The range of the ratio f3 / f of the focal length f3 of the third lens to the focal length f of the field lens is as follows: 0.5 ≤ f3 / f ≤ 0.85; The range of the ratio f4 / f of the focal length f4 of the fourth lens to the focal length f of the field lens, the material refractive index Nd4, and the Abbe number Vd4 are as follows: 0.65 ≤ f4 / f ≤ 0.9, 1.45 ≤ Nd4 ≤ 1.53, 54 ≤ Vd4 ≤ 70; The range of the ratio f5 / f of the focal length f5 of the fifth lens to the focal length f of the field lens, the material refractive index Nd5, and the Abbe number Vd5 are as follows: -1.1 ≤ f5 / f ≤ -0.8, 1.45 ≤ Nd5 ≤ 1.53, 54 ≤ Vd5 ≤ 70.

2. The large-aperture and low-distortion F-theta ultraviolet field lens device according to claim 1, characterized in that, The ranges of the material refractive index Nd1 and the Abbe number Vd1 of the first lens are as follows: 1.45 ≤ Nd1 ≤ 1.51, 54 ≤ Vd1 ≤ 70.

3. The large-aperture and low-distortion F-theta ultraviolet field lens device according to claim 1, characterized in that, The ranges of the material refractive index Nd2 and the Abbe number Vd2 of the second lens are as follows: 1.45 ≤ Nd2 ≤ 1.53, 54 ≤ Vd2 ≤ 70.

4. The large-aperture and low-distortion F-theta ultraviolet field lens device according to claim 1, characterized in that, The material refractive index Nd3 and the Abbe number Vd3 of the third lens are as follows: 1.45 ≤ Nd3 ≤ 1.53, 54 ≤ Vd3 ≤ 70.

5. The large-aperture and low-distortion F-theta ultraviolet field lens device according to claim 1, characterized in that, The designed wavelength of the large-aperture and low-distortion F-theta ultraviolet field lens device is 355 nm; When the designed focal length of the large-aperture and low-distortion F-theta ultraviolet field lens device is 160 mm, the maximum allowable value of the incident beam diameter is not less than 12 mm, the scanning angle is not less than ±25 degrees, the scanning range is greater than 140 mm, and the distance from the incident aperture to the center of the first lens is 14 mm - 38 mm.

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