WO2019042339A1

WO2019042339A1 - F-theta lens suitable for use in laser processing

Info

Publication number: WO2019042339A1
Application number: PCT/CN2018/103136
Authority: WO
Inventors: 孙建超
Original assignee: 上海微电子装备（集团）股份有限公司
Priority date: 2017-08-30
Filing date: 2018-08-30
Publication date: 2019-03-07
Also published as: TWI664044B; CN109425962A; TW201912284A

Abstract

Disclosed is an F-theta lens suitable for use in laser processing. The F-theta lens comprises a first lens (1) with a positive optical power, a second lens (2) with a negative optical power, a third lens (3) with a positive optical power, a fourth lens (4) with a positive optical power, and a fifth lens (5) with a positive optical power. By means of optimizing the lens surface curvature of the lens, the F-theta lens has the characteristics of a large field of view, low telecentricity and small distortion, effectively reduces measurement errors of light spots in the horizontal direction during laser processing, and better inhibits deformation of laser spots in the range of a scanning field of view.

Description

An F-theta lens suitable for use in laser processing

Technical field

The invention belongs to the field of optical technology and relates to an F-theta lens for laser processing.

Background technique

The F-theta objective (F-theta objective) is often used for flat field and beam focusing to focus the incident laser beam into a planar image field that is sandwiched by an optical axis relative to the F-theta objective. The scan is in the region of the scan angle of ±θ, in which the ratio of the scan angle of the laser beam to the position of the laser beam incident point in the image field to the optical axis follows a linear function.

Due to the wavelength-dependent refraction of the laser beam, these F-theta objectives are calibrated to the wavelength of the laser beam in order to obtain a high focus quality in the image field as the laser beam passes through the F-theta objective lens, ie It is said that the objective lens is calculated such that it is for a predetermined laser beam wavelength and a preset laser beam diameter, within an allowable temperature tolerance range and in a pre-set image field. There is no or only a slight optical deviation, where optical deviation refers to a deviation that would result in a significant change in the focus size.

However, in applications where the laser beam is used to machine the material, the F-theta objective lens used with the laser beam is often required to have a large image field and a large total focal length.

The existing F-theta objective lens is prone to measurement error of the laser spot in the horizontal direction in the above application scenario, and the deformation of the laser spot is generated in the scanning field of view corresponding to the ±θ angle, which affects the quality of the laser beam processing process. The reason is that the F-theta lens in the prior art has problems of small field of view, large telecentricity, and large distortion.

Summary of the invention

It is an object of the present invention to provide an F-theta lens suitable for use in a laser processing process for improving the problems of small field of view, large telecentricity, and large distortion of the F-theta lens existing in the prior art.

In order to achieve the above object, the present invention provides an F-theta lens suitable for use in a laser processing process, the F-theta lens including, from the object side, along the optical axis to the image side, including: having positive power a first lens, a second lens having a negative power, a third lens having a positive power, a fourth lens having a positive power, and a fifth lens having a positive power;

The focal length of each lens satisfies the following relationship:

1.1<f ₁ /f<1.7;

-0.6<f ₂ /f<-0.3;

2.1<f ₃ /f<3.5;

0.9<f ₄ /f<1.6;

1.6<f ₅ /f<2.2;

Wherein, f ₁ is a focal length of the first lens; f ₂ is the focal length of the second lens; f is the focal length of the third _{lens. 3;} and where f is the focal length of the fourth _{lens. 4;} ₅ where f Is the focal length of the fifth lens; f is the total focal length of the F-theta lens.

Optionally, the first lens is a concave-convex lens; the second lens is a plano-concave lens; the third lens is a concave-convex lens; the fourth lens is a concave-convex lens; and the fifth lens is Concave-convex lens.

Optionally, a radius of curvature of the first lens near the object side mirror surface is r ₁ , and a radius of curvature of the first lens near the image side mirror surface is r ₂ , r ₁ >r ₂ .

Optionally, a radius of curvature of the third lens near the object side mirror surface is r ₅ , and a radius of curvature of the third lens near the image side mirror surface is r ₆ , r ₅ >r ₆ .

Optionally, a radius of curvature of the fourth lens near the object side mirror surface is r ₇ , and a radius of curvature of the fourth lens near the image side mirror surface is r ₈ , r ₇ >r ₈ .

Optionally, a radius of curvature of the mirror surface of the fifth lens near the object side is r ₉ , and a radius of curvature of the mirror surface of the fifth lens near the image side is r ₁₀ , r ₉ >r ₁₀ .

Optionally, the F-theta lens further includes a protection window, wherein the protection window is a planar lens and is disposed between the fifth lens and the image side.

Optionally, the aperture of the F-theta lens is 27 mm to 43 mm from the first lens.

Optionally, the lenses of the first lens, the second lens, the third lens, the fourth lens and the fifth lens are made of fused silica and/or synthetic resin.

Optionally, 200 mm ≤ f ≤ 400 mm, where f is the total focal length of the F-theta lens.

Optionally, the F-theta lens is suitable for an incident laser beam having a wavelength of 1070±5 nm.

Optionally, the F-theta lens is suitable for a laser beam incident angle of 0 to 20 degrees.

Compared with the prior art, the F-theta lens provided by the present invention suitable for use in a laser processing process has the following beneficial effects:

1. Large field of view, low telecentricity and small distortion;

2. Effectively reduce the measurement error of the spot in the horizontal direction during laser processing;

3. The laser spot deformation in the scanning field of view is better suppressed;

4, applied in the infrared high-energy laser related processing, can meet the needs of 200mm diameter two-dimensional scanning field of view.

DRAWINGS

1 is a schematic structural view of an F-theta lens according to a first embodiment of the present invention;

2 is a field curvature curve and a distortion curve diagram of an F-theta lens according to a first embodiment of the present invention;

3 is a view of a field-of-view diffraction pattern of an F-theta lens according to a first embodiment of the present invention;

4 is a schematic structural diagram of an F-theta lens according to a second embodiment of the present invention;

5 is a field curvature curve and a distortion curve diagram of an F-theta lens according to a second embodiment of the present invention;

FIG. 6 is a view of a field-of-view diffraction spot of an F-theta lens according to a second embodiment of the present invention.

Detailed ways

Specific embodiments of the present invention will be described in more detail below with reference to the drawings. Advantages and features of the present invention will be apparent from the description and appended claims. It should be noted that the drawings are in a very simplified form and both use non-precise proportions, and are only for convenience and clarity to assist the purpose of the embodiments of the present invention.

In order to solve the horizontal deviation of the spot appearing in the F-theta lens existing in the prior art and the spot deformation in the scanning field of view, the present invention provides an F-theta suitable for use in a laser processing process. Lens.

Embodiment 1

Please refer to FIG. 1. FIG. 1 is a schematic structural diagram of an F-theta lens according to a first embodiment of the present invention. The F-theta lens includes a first lens 1, a second lens 2, a third lens 3, and a fourth lens. 4, a fifth lens 5 and a protective window 6; wherein the first lens 1 has a positive power; the second lens 2 has a negative power; the third lens 3 has a positive power; and the fourth lens 4 has a positive power; The fifth lens 5 has positive refractive power; the protective window 6 is used to prevent the optical components inside the lens group from being affected by external dust and impurities, so the protective window 6 is a planar lens and does not have positive or negative power. .

Preferably, the focal length of each of the lenses and the total focal length f of the F-theta lens satisfy the following relationship:

f ₁ /f=1.55;

f ₂ /f=-0.45;

f ₃ /f=3.21;

f ₄ /f=1.1446;

f ₅ /f=1.86;

f=300;

Wherein f ₁ , f ₂ , f ₃ , f ₄ and f ₅ are the focal lengths of the first lens 1 to the fifth lens 5, respectively; the pupil of the F-theta lens is expressed within a range of 27 mm to 43 mm from the first lens Preferably, preferably, the aperture of the embodiment is disposed at 35.5 mm from the first lens, and the incident angle of the incident beam of the F-theta lens is 0 to 20 degrees.

Please refer to Table 1. Table 1 is a parameter of each lens of the F-theta provided by the first embodiment of the present invention, wherein "a" in the table represents a mirror surface of the lens near the object side, and "b" represents The mirror surface of the lens adjacent to the image side, the mirror surface of 1a represents the mirror surface of the first lens 1 on the side close to the object side, the mirror surface of 1b represents the mirror surface of the first lens 1 near the image side, and so on. 1a mirror has a radius of curvature r ₁ , 1b has a radius of curvature of r ₂ , 2a has a radius of curvature of r ₃ , 2b has a radius of curvature of r ₄ , 3a has a radius of curvature of r ₅ , and 3b has a radius of curvature of mirror The radius of curvature of the mirror surface of r ₆ , 4a is r ₇ , the radius of curvature of the mirror surface of 4b is r ₈ , the radius of curvature of the mirror surface of 5a is r ₉ , the radius of curvature of the mirror surface of 5b is r ₁₀ , and the radius of curvature of the mirror surface of 6a is r ₁₁ , 6b The radius of curvature of the mirror surface is r ₁₂ , and d ₁ , d ₃ , d ₅ , d ₇ , d ₉ and d ₁₁ respectively represent the thickness of each of the lenses, that is, on the optical axis between the front and rear surfaces of each of the lenses The intervals d ₂ , d ₄ , d ₆ , d ₈ and d ₁₀ respectively represent the air gap between the lenses, and the unit of curvature radius and thickness in the table is mm.

Table 1 is a parameter of each lens of the F-theta provided by the first embodiment of the present invention.

As can be seen from the above table, in the first lens 1, the radius of curvature of the mirror surface of 1a is larger than the radius of curvature of the mirror surface of 1b, and the mirror surface of 2b of the second lens 2 is a plane mirror. In the third lens 3, the radius of curvature of the mirror surface of 3a is larger than the radius of curvature of the mirror surface of 3b. The radius of curvature of the mirror surface of 4a in the fourth lens 4 is larger than the radius of curvature of the mirror surface of 4b, and the radius of curvature of the mirror surface of 5a in the fifth lens 5 is larger than the radius of curvature of the mirror surface of 5b.

Preferably, the lens is made of fused silica, and the fused silica has a good refractive index, which is very suitable for lens fabrication in the field of laser processing.

Please refer to FIG. 2. FIG. 2 is a field curve and a distortion curve diagram of the F-theta lens according to the first embodiment of the present invention. It can be seen from the figure that when the incident light diameter is 15 mm, the meridional field curvature curve T and the arc The sagittal curvature curve S is less than 110um, about 100um, and the distortion is less than 0.1%.

Please refer to FIG. 3. FIG. 3 is a perspective view of a F-theta lens field of view diffraction diffraction pattern according to a first embodiment of the present invention, wherein the ring in the figure is a diffraction limit, and the figure shows that the discrete phase point does not exceed the diffraction limit. Furthermore, it is explained that the F-theta lens provided by the embodiment has a small horizontal shift in the spot, and the spot distortion in the scanning field of view is small. The angle between the exit of the lens and the exit of the central field of view is less than 4 degrees.

Embodiment 2

Please refer to FIG. 4. FIG. 4 is a schematic structural diagram of an F-theta lens according to a second embodiment of the present invention. The F-theta lens includes: a first lens 1, a second lens 2, a third lens 3, and a fourth lens. 4, a fifth lens 5 and a protective window 6; wherein the first lens 1 has a positive power; the second lens 2 has a negative power; the third lens 3 has a positive power; and the fourth lens 4 has a positive power; The fifth lens 5 has positive refractive power; the protection window 6 is used to prevent the optical components inside the lens group from being affected by external dust and stray light, so the protection window 6 is a planar lens, and does not have positive power or negative optical focus. degree.

f ₁ /f=1.26;

f ₂ /f=-0.435;

f ₃ /f=2.25;

f ₄ /f=1.41;

f ₅ /f=2;

f=300

Wherein f ₁ , f ₂ , f ₃ , f ₄ and f ₅ are focal lengths of the first lens 1 to the fifth lens 5, respectively;

Referring to Table 2, Table 2 is a parameter of each lens of the F-theta according to the second embodiment of the present invention, wherein "a" in the table represents a mirror surface of the lens near the object side, and "b" represents The mirror surface of the lens near the image side, the radius of curvature of the mirror surface of 1a is r ₁ , the radius of curvature of the mirror surface of 1b is r ₂ , the radius of curvature of the mirror surface of 2a is r ₃ , and the radius of curvature of the mirror surface of 2b is r ₄ . The radius of curvature of the mirror surface of 3a is r ₅ , the radius of curvature of the mirror surface of 3b is r ₆ , the radius of curvature of the mirror surface of 4a is r ₇ , the radius of curvature of the mirror surface of 4b is r ₈ , the radius of curvature of the mirror surface of 5a is r ₉ , and the radius of curvature of the mirror surface of 5b The radius of curvature of the mirror surface of r ₁₀ , 6a is r ₁₁ , and the radius of curvature of the mirror surface of 6b is r ₁₂ , and d ₁ , d ₃ , d ₅ , d ₇ , d ₉ and d ₁₁ respectively represent the thickness of each of the lenses, that is, The spacing between the front and rear surfaces of the lens on the optical axis, d ₂ , d ₄ , d ₆ , d ₈ and d ₁₀ respectively represent the spatial separation between the lenses, and the unit of curvature radius and thickness in the table is Mm.

Table 2 is a parameter of each lens of the F-theta provided by the second embodiment of the present invention.

Please refer to FIG. 5. FIG. 5 is a field curvature curve and a distortion curve diagram of the F-theta lens according to the second embodiment of the present invention. It can be seen from the figure that when the incident light diameter is 15 mm, the meridional surface curvature curve T and the arc The sagittal curvature curve S is less than 110um, about 100um, and the distortion is less than 0.5%.

Please refer to FIG. 6. FIG. 6 is a view showing a diffraction pattern of a field of view of a F-theta lens according to a second embodiment of the present invention, wherein the ring in the figure is a diffraction limit, and the figure shows that the discrete phase point does not exceed the diffraction limit. Furthermore, it is explained that the F-theta lens provided by the embodiment has a small horizontal shift in the spot, and the spot distortion in the scanning field of view is small. The angle between the exit of the lens and the exit of the central field of view is less than 2.6°.

In summary, in the F-theta lens provided by the present invention for use in a laser processing process, the F-theta lens includes a first lens having positive power and a second lens having negative power, having a third lens of positive power, a fourth lens having positive power, and a fifth lens having positive power; by optimizing the mirror curvature of the lens, the F-theta lens has a large field of view, The characteristics of low telecentricity and small distortion effectively reduce the measurement error of the spot in the horizontal direction during laser processing, and better suppress the deformation of the laser spot in the scanning field of view.

The above is only a preferred embodiment of the present invention and does not impose any limitation on the present invention. Any changes in the technical solutions and technical contents disclosed in the present invention may be made by those skilled in the art without departing from the technical scope of the present invention. The content is still within the scope of protection of the present invention.

Claims

An F-theta lens suitable for use in a laser processing process, characterized in that the F-theta lens comprises, in order from the object side along the optical axis to the image side, a first lens having positive power, having a second lens of negative power, a third lens having positive power, a fourth lens having positive power, and a fifth lens having positive power;

The focal length of each lens satisfies the following relationship:

1.1<f 1 /f<1.7;

-0.6<f 2 /f<-0.3;

2.1<f 3 /f<3.5;

0.9<f 4 /f<1.6;

1.6<f 5 /f<2.2;

Wherein, f 1 is a focal length of the first lens; f 2 is the focal length of the second lens; f 3 is a focal length of the third lens; f 4 is the focal length of the fourth lens; f 5 is the The focal length of the fifth lens; f is the total focal length of the F-theta lens.
The F-theta lens suitable for use in a laser processing process according to claim 1, wherein the first lens is a concave-convex lens; and the second lens is a plano-concave lens; The lens is a concave-convex lens; the fourth lens is a concave-convex lens; and the fifth lens is a concave-convex lens.
The F-theta lens suitable for use in a laser processing process according to claim 2, wherein a radius of curvature of the mirror surface of the first lens adjacent to the object side is r 1 , the first lens The radius of curvature of the mirror surface near the image side is r 2 , r 1 > r 2 .
The F-theta lens suitable for use in a laser processing process according to claim 2, wherein a radius of curvature of the third lens near the object side mirror surface is r 5 , the third lens The radius of curvature of the mirror near the image side is r 6 , r 5 > r 6 .
The F-theta lens suitable for use in a laser processing process according to claim 2, wherein a radius of curvature of the mirror surface of the fourth lens adjacent to the object side is r 7 , the fourth lens The radius of curvature of the mirror near the image side is r 8 , r 7 > r 8 .
The F-theta lens suitable for use in a laser processing process according to claim 2, wherein a radius of curvature of the mirror surface of the fifth lens adjacent to the object side is r 9 , the fifth lens The radius of curvature of the mirror near the image side is r 10 , r 9 > r 10 .
An F-theta lens suitable for use in a laser processing process according to claim 1, further comprising a protective window, said protective window being a planar lens and disposed on said fifth lens and said Like the side between.
The F-theta lens suitable for use in a laser processing process according to claim 1, wherein the aperture of the F-theta lens is 27 mm to 43 mm from the first lens.
The F-theta lens suitable for use in a laser processing process according to claim 1, wherein said first lens, said second lens, said third lens, said fourth lens, and said The lens of the fifth lens is made of fused silica and/or synthetic resin.
The F-theta lens suitable for use in a laser processing process according to claim 1, wherein 200 mm ≤ f ≤ 400 mm, and f is the total focal length of the F-theta lens.
The F-theta lens suitable for use in a laser processing process according to claim 1, wherein the F-theta lens is suitable for an incident laser beam having a wavelength of 1070 ± 5 nm.
The F-theta lens suitable for use in a laser processing process according to claim 1, wherein the F-theta lens is suitable for a laser beam incident angle of 0 to 20 degrees.