CN100343715C - Optical lens for laser two-dimensional linear scanning - Google Patents

Abstract

The invention relates to an optical lens for realizing laser two-dimensional linear scanning, in particular to an f-theta lens which focuses a laser beam on a working plane and is suitable for laser marking and marking. The f-θ laser focusing optical lens is composed of three refracting lenses. According to the incident direction of the light, the focal power of the lens is negative, positive and positive in turn; the first two lenses are bent to the incident direction of the light, and the front surface of the third lens In the direction of the incident line; the glass materials of the three lenses are the same, and the range of the refractive index n is: 1.50≤n≤1.80. Its working area can reach φ710mm, and its focusing performance reaches the diffraction limit. It has the advantages of large working area, low processing cost, good marking quality, good focusing performance, simple and compact structure, etc., which provides the possibility to further expand the application range of laser marking. .

Description

Optical Lens for Laser 2D Linear Scanning

                      

The invention relates to an optical lens for realizing laser two-dimensional linear scanning, in particular to an f-theta lens which focuses a laser beam on a working plane and is suitable for laser marking and marking.

Background technique

Laser marking is a form of laser scanning. It is an important application of laser in the field of processing. Compared with traditional marking methods such as stamping, etching, and machine engraving, it has no pollution, high resolution, and It has the advantages of permanent contact and marking, and is widely used in the production of laser anti-counterfeiting marks, lettering and surface decoration.

Laser scanning technology includes high inertial scanning and low inertial scanning. Among them, high inertia scanning is a kind of mechanical scanning, which deflects the laser beam by rotating a prism, a plane mirror or a rotating polyhedron, but it realizes progressive scanning, and the scanning is unidirectional. Therefore, the scanning speed of the high inertia scanning method, Accuracy, etc. must be limited. Low inertia scanning is a kind of non-mechanical scanning, including acousto-optic scanning and galvanometer scanning. The galvanometer scanning process is that the laser beam passes through the reflecting surfaces of two scanning galvanometer X and scanning galvanometer Y whose rotation directions are perpendicular to each other. Focused by the f-theta lens to the working surface, it can realize pixel-addressed scanning.

Figure 1 is a schematic diagram of the working principle of a low-inertia galvanometer laser marking machine, see Figure 1, the laser beam [2] emitted by the laser [1] is expanded by the beam expander [3], and then passed through the X scanning galvanometer [ 4] and the Y scanning galvanometer [5] after reflection, incident to the f-θ lens [6], the laser beam is focused on the working surface [7]. Swing the X-scanning galvanometer and Y-scanning galvanometer around the rotation axis of the X-scanning galvanometer [8] and the Y-scanning galvanometer [9], and the laser focus spot performs a two-dimensional linear scan on the surface of the workpiece to mark the required graphics , text, symbols, etc.

No matter what kind of laser scanning system, the f-theta lens is the core component of the system, and the marking quality depends on the focusing performance of the f-theta lens. As the size of the working surface increases, the focused spot size will be greatly affected. At present, the working area of the laser marking machine generally does not exceed 300×300mm ² , and the f-θ lens used is made of glass of different materials, and the structure is complex, and the cost of the lens is high.

Contents of invention

The object of the present invention is to overcome the deficiencies in the prior art, and provide a f-θ optical focusing lens for low-inertia scanning with large working area, good focusing performance, simple structure and low cost.

The technical scheme adopted in the present invention is: provide an optical lens for laser two-dimensional linear scanning, which is a f-theta laser focusing optical lens, and the f-theta laser focusing optical lens consists of three refracting lenses Composition, along the incident direction of light, the focal powers of the three lenses are  ₆₁ ,  ₆₂ ,  ₆₃ in turn, and the value range when normalized relative to the focal length of the lens is: -3.5≤ ₆₁ ≤-3.0, 1.50≤  ₆₂ ≤ 2.0 and 1.50 ≤ _{ 63} ≤ 2.0; the first two lenses are bent towards the light incident direction, and the surface of the third lens close to the second lens is facing away from the light incident direction.

The three refracting lenses are all made of the same glass material, and the value range of the refractive index n is:

1.50≤n≤1.80.

Compared with the prior art, the present invention is characterized in that the f-θ laser focusing optical lens is only composed of three refracting lenses, the three lenses are made of the same common glass material, the lens structure is simple, and the processing cost is low; due to this The structure enables the working area to reach φ710mm, and the focusing performance of the laser beam on the working surface reaches the diffraction limit, and the marking quality is good, which provides the possibility to further expand the application range of laser marking.

Description of drawings

Figure 1 is a schematic diagram of the working principle of a low-inertia galvanometer laser marking machine;

Fig. 2 is a schematic structural view of an optical lens according to an embodiment of the present invention;

Fig. 3 is a ray tracing point diagram of an optical lens according to an embodiment of the present invention;

Fig. 4 is a distortion curve diagram of the optical lens described in one embodiment of the present invention;

Fig. 5 is a field curvature and astigmatism curve diagram of the optical lens described in an embodiment of the present invention;

Fig. 6 is a graph showing the relative irradiance distribution of the optical lens on the laser beam focusing plane according to an embodiment of the present invention;

Fig. 7 is a graph of energy concentration of the optical lens according to an embodiment of the present invention.

In Figure 1: [1], laser; [2], laser beam; [3], beam expander; [4], X scanning galvanometer; [5], Y scanning galvanometer; [6], f-θ Lens; [7], the laser beam focusing working surface; [8], the rotating shaft of the X scanning galvanometer; [9], the rotating shaft of the Y scanning galvanometer;

Among Fig. 2: [61], the first lens according to the incident direction of light; [62], the second lens according to the incident direction of light; [63], the third lens according to the incident direction of light; [631], The front surface of the third lens.

Detailed ways

The specific embodiments of the present invention will be further described below in conjunction with the accompanying drawings and examples.

Embodiment one:

The technical solution of this embodiment is to provide an f-θ optical lens for a low-inertia vibrating mirror laser marking machine. The laser marking machine uses a YAG laser with a working wavelength of 1.064 μm. The optical system works on this near-infrared monochromatic light. The aperture diaphragm is located outside the optical system, that is, the X-scanning mirror [4] shown in Figure 1.

Referring to accompanying drawing 2, it is the structural representation of optical lens described in the present embodiment, f-θ lens focal length f=680mm, F number F/NO=54, scanning angle θ=±30 °, X scans vibrating mirror to Y The distance d _{X of the scanning vibrating mirror, Y} =16mm, the distance d Y of the Y scanning vibrating mirror to the front surface of the first lens [61] according to the light incident direction _{, L1} =22mm, [62] is the second lens, [ 63] is the third lens, and [631] is the front surface of the third lens. The rest of the lens data is as follows: lens Radius of curvature (mm) Interval (mm) Air gap(mm) Material Refractive Index 61 -114 6.5 20.0 1.51 1905 62 -1092 12.5 10.0 1.51 -154 63 -2605 13.0 800.0 1.51 -224

The same colorless optical glass is used for the three lens materials, so there is no need to correct for chromatic aberration.

Embodiment two:

In the present embodiment, f-θ lens focal length f=680mm, F number F/NO=54.5, scan angle θ=±30°, distance from X scanning vibrating mirror to Y scanning vibrating mirror d _{X, Y} =16mm, The distance from the Y scanning galvanometer to the front surface of the first lens d _{Y, L1} = 16mm, the three lenses are made of the same colorless optical glass, and the rest of the data are as follows: lens Radius of curvature (mm) Lens Thickness(mm) Air gap(mm) Material Refractive Index 61 -113.5 6.8 20.5 1.53 1906 62 -1091 13.0 10.0 1.53 -154.5 63 -2610 13.0 803.0 1.53 -223

Referring to accompanying drawing 3, Fig. 3 is the ray tracing spot diagram that light passes through the optical system described in the present embodiment, namely the focusing situation of laser beam on workpiece surface, the circle at each field of view place in Fig. 3 represents Airy spot, by It can be seen that the spot diagrams of each field of view on the image plane fall within the Airy spot, indicating that the optical system has the focusing characteristics of the theoretical limit of diffraction.

The optical lens distortion curve figure described in the present embodiment is as shown in Figure 4, among the figure, the abscissa is the distortion value (unit %) relative to f-θ relation, and the ordinate represents the normalized field of view, as seen in Figure 4 , the relative domain change is less than 0.5%, which not only makes the image height and field of view meet the f-θ linear relationship, but also does not affect the marking quality and meets the marking requirements. Accompanying drawing 5 is the field curvature astigmatism curve of the lens, the abscissa represents the field curvature astigmatism value, and the ordinate is the normalized field of view, and the two curves S and T in the figure represent the sagittal and meridian planes respectively Field curvature, the difference between the two curves, that is, the astigmatism value is within the aberration tolerance range.

According to the working principle of the laser marking machine, in order to ensure the marking quality in a wide range, the irradiance of the laser beam on the surface of the workpiece is required to be evenly distributed and the energy concentrated. Referring to accompanying drawing 6, it is the relative irradiance distribution graph of the optical lens described in this embodiment on the laser marking machine working face, in Fig. 6, abscissa is marking range, and ordinate is the working face relative illuminance. It can be seen from Figure 6 that the irradiance distribution of the entire image plane is quite uniform, and although the edge has decreased, it still meets the requirements for use.

Referring to accompanying drawing 7, it is the energy concentration curve of the optical lens described in the present embodiment, as seen from Fig. 7, the energy of more than 80% is concentrated in the point in the Airy spot range.

Laser marking has been widely used because of its unique advantages. After strict aberration correction, the f-θ lens provided by the present invention as the optical focusing lens of the laser marking machine is composed of only three lenses, the length of the lens barrel is about 60mm, the working area reaches φ710mm, and the focusing performance reaches diffraction It has the advantages of large working area, low processing cost, good marking quality, good focusing performance, simple and compact structure, etc., which provides the possibility to further expand the application range of laser marking.

Claims (2)

1. an optical lens for laser two-dimensional linear scanning, it is a kind of f=theta laser focusing optical lens, it is characterized in that: described f=theta laser focusing optical lens consists of three refracting lenses (61), Composed of (62) and (63), along the incident direction of the light, the focal powers of the three lenses are  ₆₁ ,  ₆₂ ,  ₆₃ in turn, and the value range when normalized relative to the focal length of the lens is: -3.5≤ ₆₁ ≤ -3.0, 1.50 ≤  ₆₂ ≤ 2.0 and 1.50 ≤  ₆₃ ≤ 2.0; the first two lenses are bent towards the light incident direction, and the surface (631) of the third lens close to the second lens is facing away from the light incident direction. 2. A kind of optical lens for laser two-dimensional linear scanning according to claim 1, characterized in that: the three refracting lenses are all made of the same glass material, and the value range of the refractive index n is For: 1.50≤n≤1.80.

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