CN219016678U

CN219016678U - Near infrared flat field focusing lens

Info

Publication number: CN219016678U
Application number: CN202223172486.6U
Authority: CN
Inventors: 季轶群; 冯安伟
Original assignee: Suzhou University
Current assignee: Suzhou University
Priority date: 2022-11-29
Filing date: 2022-11-29
Publication date: 2023-05-12
Anticipated expiration: 2032-11-29

Abstract

The utility model relates to a near infrared flat field focusing lens. A concave-flat lens or a biconcave lens which is concavely arranged in the laser incidence direction, a meniscus lens which is concavely arranged in the laser incidence direction, a meniscus lens or a plano-convex lens which is convexly arranged in the focusing plane, and a biconvex lens are coaxially arranged in sequence along the laser incidence direction; by setting the shape and the relative position of each lens, clear images can be formed on near infrared light, and the geometric aberration of the lens can be effectively corrected, so that a clear flat image field can be obtained. The lens provided by the utility model is a near infrared flat field focusing lens with a large view field, a large aperture and a long working distance, is suitable for laser processing equipment such as laser marking, laser cutting and the like, can effectively improve the printing fineness and definition, has more true color restoration and is more convenient to operate. The utility model only uses four lenses, and the four lenses are all made of the same common glass material, thereby greatly reducing the production cost, saving the resources and having wide application prospect.

Description

Near infrared flat field focusing lens

Technical Field

The utility model particularly relates to a flat field focusing lens with near infrared, large aperture and large working face, which is suitable for the fields of laser processing equipment such as laser marking, laser cutting and the like.

Background

Flat field focusing mirrors, i.e. F-Theta focusing mirrors, are core elements of laser processing technology, often applied in the fields of laser marking, welding, engraving, etc., and function to focus laser energy on the surface of a workpiece being processed. Before the utility model is made, chinese patent No. 207181801U discloses a three-piece 355nm flat field lens which is in a negative-positive three-piece lens component configuration, and because only three pieces of lens components are used, the aberration is larger, and the configuration aberration and F-theta distortion are still difficult to be controlled ideally; and the diameter of the entrance pupil is only 10mm, the focal length is 160mm, and the scanning range is only 153' 153mm. Chinese patent No. CN212111952U discloses an F-theta scanning lens and optical lens assembly composed of four lenses and a piece of protective glass; the full field of view is only 40 degrees, the entrance pupil diameter is 30mm, the focal length is 256mm, and the scanning range is only 120' 120mm. The flat-field focusing lens provided by the prior art has the defects of small field of view, small aperture and small scanning range, and is difficult to meet the application requirements of the market.

Disclosure of Invention

Aiming at the defects of the prior art, the utility model provides the near infrared flat field focusing lens with large aperture, large working surface and good focusing effect.

In order to achieve the above object, the present utility model provides a near infrared flat field focusing lens, which has the following structure: a concave lens, a concave-convex lens, a single-sided convex lens and a biconvex lens are coaxially arranged in sequence along the transmission direction of an incident light beam; the concave lens is a concave flat lens or a biconcave lens concavely arranged in the laser incidence direction; the meniscus lens is a meniscus lens concavely arranged in the laser incidence direction; the single-sided convex lens is a concave-convex lens or a plano-convex lens which is arranged convexly to a focusing plane; the thickness of the concave lens is d in mm ₁ The curvature radius of the first surface and the second surface are respectively corresponding to R ₁ 、R ₂ Satisfies the condition 2 less than or equal to d ₁ ≤30，-500≤R ₁ <0，0<R ₂ Less than or equal to 2000; the thickness of the concave-convex lens is d ₂ The curvature radius of the first surface and the second surface are respectively corresponding to R ₃ 、R ₄ Satisfies the condition 2 less than or equal to d ₂ ≤30，-500≤R ₃ <0，-500≤R ₄ <0; the thickness of the single-sided convex lens is d ₃ A first surface and a second surfaceThe curvature radius corresponds to R ₅ 、R ₆ Satisfies the condition 2 less than or equal to d ₃ ≤30，R ₅ ≤-500，-500≤R ₆ <0; the thickness of the biconvex lens is d ₄ The curvature radius of the first surface and the second surface are respectively corresponding to R ₇ 、R ₈ Satisfies the condition 2 less than or equal to d ₄ ≤30，0<R ₇ ≤2000，-2000≤R ₈ <0。

The air interval of the concave lens, the concave-convex lens, the single-sided convex lens and the double-convex lens is L in sequence ₁ 、L ₂ And L ₃ Satisfies the condition 0.ltoreq.L ₁ ≤10， 0≤L ₂ ≤10，0≤L ₃ ≤10。

The working wavelength of the near infrared flat field focusing lens provided by the utility model is 1064nm; when the design focal length is 330mm, the maximum allowable value of the incident beam diameter is not less than 30mm, the scanning angle is not less than + -25 degrees, and the scanning range is not less than 200X 200mm.

The principle of the utility model is as follows: the near infrared flat field focusing lens adopts four lenses with different structures, and the first lens adopts a concave flat lens or a biconcave lens which is concave towards the incidence direction of laser; the second lens adopts a meniscus concave-convex lens concave towards the incidence direction of laser; the third lens adopts a concave-convex lens or a plano-convex lens protruding to a focusing plane; the fourth lens adopts a biconvex lens, and can form clear images for near infrared light by setting the shape and the relative position of the lens, so that the geometric aberration of the lens can be effectively corrected, and a clear flat image field is obtained; and the lens has a larger aperture, a larger field of view, and a longer working distance. The printing equipment adopting the lens has higher printing fineness and definition, more true color reproduction and more convenient operation due to long working distance of the lens.

Compared with the prior art, the utility model has the beneficial effects that:

1. the near infrared flat field focusing lens provided by the utility model realizes large-view-field and high-quality scanning under the condition of effectively ensuring the diameter of an incident light beam through reasonable light path configuration. The focusing light spot of the edge view field is more consistent with the focusing light spot of the center view field, and the processing precision is improved.

2. The near infrared flat field focusing lens provided by the utility model allows the maximum beam diameter to exceed 30mm when the focal length is 330mm, the scanning angle is +/-25 degrees, the scanning range is more than 200 multiplied by 200mm, the F-theta distortion is less than 1%, and the light spot size is close to the diffraction limit. The near infrared flat field focusing lens provided by the utility model has the advantages of large field of view, large aperture and long working distance.

3. The utility model only adopts one common glass material, only uses four lenses, has reasonable structure and convenient use, and can overcome the defects of the prior art.

Drawings

Fig. 1 is a schematic diagram of an optical path structure of a near infrared flat field focusing lens according to an embodiment of the present utility model;

FIG. 2 is a graph of an optical transfer function MTF provided by one embodiment of the present utility model;

FIG. 3 is a full field of view structured matrix dot column diagram provided by one embodiment of the present utility model;

FIG. 4 is a standard F-theta distortion plot provided by one embodiment of the present utility model.

In the figure, 1. A first lens concave lens; 2. a second lens meniscus lens; 3. a third lens single-sided convex lens; 4. a fourth lens lenticular lens; 5. a focal plane.

Detailed Description

The technical scheme of the utility model is further described below with reference to the accompanying drawings and examples.

Example 1

Referring to fig. 1, a schematic optical path structure of a near infrared flat field focusing lens according to this embodiment includes a first lens concave lens 1, a second lens meniscus lens 2, a third lens single-sided convex lens 3, a fourth lens biconvex lens 4, and a focusing plane 5 coaxially arranged in sequence along a transmission direction of an incident light beam.

The first lens adopts a concave flat lens or a biconcave lens which is concave towards the incidence direction of laser; the thickness of the concave lens is d in mm ₁ First, firstThe curvature radius of the surface and the second surface are respectively corresponding to R ₁ 、R ₂ Satisfies the condition 2 less than or equal to d ₁ ≤30，-500≤R ₁ <0，0<R ₂ ≤2000。

The second lens adopts a meniscus concave-convex lens concave towards the incidence direction of laser; the thickness of the concave-convex lens is d ₂ The curvature radius of the first surface and the second surface are respectively corresponding to R ₃ 、R ₄ Satisfies the condition 2 less than or equal to d ₂ ≤30，-500≤R ₃ <0，-500≤R ₄ <0。

The third single-sided convex lens adopts a concave-convex lens or a plano-convex lens protruding to a focusing plane; the thickness of the lens is d ₃ The curvature radius of the first surface and the second surface are respectively corresponding to R ₅ 、R ₆ Satisfies the condition 2 less than or equal to d ₃ ≤30，R ₅ ≤-500，-500≤R ₆ <0。

The fourth lens adopts a biconvex lens; the thickness of the biconvex lens is d ₄ The curvature radius of the first surface and the second surface are respectively corresponding to R ₇ 、R ₈ Satisfies the condition 2 less than or equal to d ₄ ≤30，0<R ₇ ≤2000，-2000≤R ₈ <0。

In this example, specific parameters of the curved surface radius, center thickness, material refractive index Nd, abbe coefficient Vd, and surface shape of each optical element (surface) of each lens member satisfy the conditions of table 1.

Table 1:

。

the optical characteristics of the near infrared flat field focusing lens provided in this example are shown in table 2.

Table 2:

。

as can be seen from the results of table 2, the lens can be seen in geometric optics as a large aperture, long working distance, large field of view.

Referring to fig. 2, a MTF graph of the optical transfer function of the near infrared flat field focusing lens is provided in this embodiment; the horizontal axis represents the number lp/mm of pairs per millimeter and the vertical axis represents the percentage. The optical transfer function MTF of the full view field is larger than 0.3 at 10lp/mm, and the curve is smooth and compact, which shows that the system has clear and uniform imaging and better imaging quality and resolution in the full view field.

Referring to fig. 3, a full-field structure matrix point column diagram of a near infrared flat field focusing lens is provided in this embodiment, wherein the marked meaning is a normalized field of view with an abscissa and an ordinate, and the angle of deflection of a galvanometer is controlled. The radial and sagittal light spots are uniform, the energy is concentrated, and the use requirement is met.

Referring to fig. 4, a standard F-theta distortion chart of a near infrared flat field focusing lens is provided in this embodiment, wherein the ordinate is the field of view, the abscissa is the F-theta distortion, and the F-theta distortion of the lens is less than 1% as can be seen in the chart.

The result proves that when the focal length of the near infrared flat field focusing lens is 330mm, the maximum beam diameter is allowed to exceed 30mm, the scanning angle is +/-25 degrees, the scanning range is larger than 200X 200mm, F-theta distortion is smaller than 1%, and the lens has a large field of view, a large aperture and a long working distance.

Claims

1. A near infrared flat field focusing lens, characterized by: a concave lens (1), a concave-convex lens (2), a single-sided convex lens (3) and a biconvex lens (4) are coaxially arranged in sequence along the transmission direction of an incident light beam; the concave lens (1) is a concave flat lens or a biconcave lens concavely arranged in the laser incidence direction; the concave-convex lens (2) is a meniscus concave-convex lens concavely arranged in the incidence direction of the laser; the single-sided convex lens (3) is a concave-convex lens or a plano-convex lens which is arranged convexly to a focusing plane; the concave lens (1) has a thickness d in mm ₁ The curvature radius of the first surface and the second surface are respectively corresponding to R ₁ 、R ₂ Satisfies the condition 2 less than or equal to d ₁ ≤30，-500≤R ₁ <0， 0<R ₂ Less than or equal to 2000; thickness of the meniscus lens (2)Is d ₂ The curvature radius of the first surface and the second surface are respectively corresponding to R ₃ 、R ₄ Satisfies the condition 2 less than or equal to d ₂ ≤30，-500≤R ₃ <0，-500≤R ₄ <0; the thickness of the single-sided convex lens (3) is d ₃ The curvature radius of the first surface and the second surface are respectively corresponding to R ₅ 、R ₆ Satisfies the condition 2 less than or equal to d ₃ ≤30，R ₅ ≤-500，-500≤R ₆ <0; the thickness of the biconvex lens (4) is d ₄ The curvature radius of the first surface and the second surface are respectively corresponding to R ₇ 、R ₈ Satisfies the condition 2 less than or equal to d ₄ ≤30，0<R ₇ ≤2000，-2000≤R ₈ <0。

2. The near infrared flat field focusing lens of claim 1, wherein: the concave lens (1), the concave-convex lens (2), the single-sided convex lens (3) and the biconvex lens (4) are arranged in mm as a unit, and the air interval of the concave lens (1), the concave-convex lens (2), the single-sided convex lens (3) and the biconvex lens (4) is L in sequence ₁ 、L ₂ And L ₃ Satisfies the condition 0.ltoreq.L ₁ ≤10， 0≤L ₂ ≤10，0≤L ₃ ≤10。