TWI664044B - F-theta lens suitable for use in laser processing - Google Patents

Abstract

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

Description

F-theta lens suitable for use in laser processing

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

F-theta objectives (F-theta objectives) are often used for flat field and beam focusing, focusing the incident laser beam into a flat image field, the laser beam is at an optical axis relative to the F-theta objective Scan within a scanning angle region with an included angle of ± θ. In this scanning angle region, the ratio of the scanning angle of the laser beam to the position of the laser beam incident point in the image field to the optical axis distance follows a linear function.

Due to the wavelength-dependent refraction of the laser beam, when the laser beam passes through the F-theta objective lens, in order to obtain a high focus quality in the image field, these F-theta objectives are calibrated to the wavelength of the laser beam In other words, the calculation of such an objective lens is such that: for a preset laser beam wavelength and a preset laser beam diameter, within an allowable temperature tolerance range, and in a preset size image field, this This kind of objective lens does not have or only has a slight optical deviation. Here, the optical deviation refers to a deviation that causes a significant change in the focal size.

However, in applications where laser beams are used to process materials, F-theta objectives used with laser beams often require a large image field and a large total focal length.

The existing F-theta objective lens is prone to the measurement error of the laser light point in the horizontal direction in the above-mentioned application scenario, and the laser light point is deformed within the scanning field of view corresponding to the ± θ angle, which affects the laser beam processing technology. The reason for this is that the F-theta lens in the prior art has the problems of small field of view, large telecentricity, and large distortion.

An object of the present invention is to provide an F-theta lens suitable for use in a laser processing process, which is used to improve the problems of a small F-theta lens field of view, large telecentricity, and large distortion 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 includes, from the object side, along the optical axis to the image side, including: The first lens, the second lens having a negative power, the third lens having a positive power, the fourth lens having a positive power, and the 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;

Where f ₁ is the focal length of the first lens; f ₂ is the focal length of the second lens; f ₃ is the focal length of the third lens; f ₄ is the focal length of the fourth lens; f _{5 is} described 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 meniscus lens; the second lens is a plano-concave lens; the third lens is a meniscus lens; the fourth lens is a meniscus lens; and the fifth lens is Concave-convex lenses.

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

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

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

Optionally, the curvature radius of the mirror surface of the fifth lens near the object side is r ₉ , and the curvature radius 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 protective window, and the protective window is a flat lens and is disposed between the fifth lens and the image side.

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

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

Optionally, the F-theta lens is suitable for a laser beam incident angle of 0-20 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 light spot in the horizontal direction during laser processing;

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

4. Applied in the processing of infrared high-energy lasers, it can meet the needs of 200mm diameter two-dimensional scanning field of view.

The specific embodiments of the present invention will be described in more detail below with reference to the schematic diagrams. The advantages and features of the present invention will become clearer from the following description and the scope of patent application. It should be noted that the drawings are in a very simplified form and all use inaccurate proportions, which are only used to facilitate and clearly assist the description of the embodiments of the present invention.

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

Example one

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; the fourth lens 4 has a positive power; The fifth lens 5 has a positive power; the protective window 6 is used to prevent the internal optical elements of the lens group from being affected by external dust and impurities. Therefore, the protective window 6 is a flat lens and does not have a positive power or a 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;

Among them, 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 behaves within a range of 27 mm to 43 mm from the first lens Good, preferably, the pupil of this embodiment is set at a distance of 35.5 mm from the first lens, and the design incident angle of the incident light beam of the F-theta lens is 0 to 20 degrees.

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

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

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

Please refer to FIG. 2. FIG. 2 is a field curve curve and distortion curve diagram of the F-theta lens provided by the first embodiment of the present invention. It can be seen from the figure that when the incident light aperture is 15 mm, the meridional field curve T and arc The sagittal field 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 diagram of a diffraction field point of an F-theta lens provided by a first embodiment of the present invention. The circle in the figure is a diffraction limit. As can be seen from the figure, the discrete phase point does not exceed the diffraction angle. The radiation limit further explains that the light spot appearing in the F-theta lens provided in this embodiment has a small horizontal displacement, and the light spot deformation within the scanning field of view is small. The angle between the light emitted from the edge of the lens field of view and the light emitted from the central field of view is less than 4 degrees.

Example two

Please refer to FIG. 4, which 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; the fourth lens 4 has a positive power; The fifth lens 5 has a positive power; the protective window 6 is used to prevent the internal optical elements of the lens group from being affected by external dust and stray light. Therefore, the protective window 6 is a flat lens and does not have a positive power or a negative power. degree.

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=1.26; f ₂ /f=-0.435; f ₃ /f=2.25; f ₄ / f = 1.41; f ₅ / f = 2; f = 300

Among them, f ₁ , f ₂ , f ₃ , f ₄ and f ₅ are focal lengths of the first lens 5 to the fifth lens 5, respectively.

Please refer to Table 2. Table 2 shows the parameters of each F-theta lens provided by the second embodiment of the present invention, where "a" in the table represents the mirror surface of the lens near the object side, and "b" represents In the lens, on the mirror surface near the image side, the curvature radius of the 1a mirror surface is r ₁ , the curvature radius of the 1b mirror surface is r ₂ , the curvature radius of the 2a mirror surface is r ₃ , and the curvature radius of the 2b mirror surface is r ₄ , The curvature radius of 3a mirror is r ₅ , the curvature radius of 3b mirror is r ₆ , the curvature radius of 4a mirror is r ₇ , the curvature radius of 4b mirror is r ₈ , the curvature radius of 5a mirror is r ₉ , and the curvature radius of 5b mirror Is r ₁₀ , the curvature radius of the 6a mirror surface is r ₁₁ , the curvature radius of the 6 b mirror surface is r ₁₂ , and d ₁ , d ₃ , d ₅ , d ₇ , d ₉ and d ₁₁ represent the thickness of each of the lenses, that is, each The distance 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 space interval between the lenses, and the unit of the radius of curvature and thickness in the table is mm. Table 2 shows the parameters of each F-theta lens provided by the second embodiment of the present invention.

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

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

Please refer to FIG. 5. FIG. 5 is a field curve curve and distortion curve chart of the F-theta lens provided by the second embodiment of the present invention. As can be seen from the figure, when the incident light aperture is 15 mm, the meridional field curve T and arc The sagittal field 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 diagram of diffraction field points of an F-theta lens provided by a second embodiment of the present invention. The circle in the figure is the diffraction limit. As can be seen from the figure, the discrete phase points do not exceed the winding. The radiation limit further explains that the light spot appearing in the F-theta lens provided in this embodiment has a small horizontal displacement, and the light spot deformation within the scanning field of view is small. The angle between the light emitted from the edge of the lens field of view and the light emitted from the central field of view is less than 2.6 °.

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

The above are only preferred embodiments of the present invention, and do not play any limiting role on the present invention. Any person skilled in the art, within the scope not departing from the technical solution of the present invention, make any equivalent replacement or modification to the technical solution and technical content disclosed in the present invention without departing from the technical solution of the present invention. The content still falls within the protection scope of the present invention.

1‧‧‧first lens

2‧‧‧Second lens

3‧‧‧ third lens

4‧‧‧ fourth lens

5‧‧‧ fifth lens

6‧‧‧ protection window

FIG. 1 is a schematic structural diagram of an F-theta lens provided by the first embodiment of the present invention; FIG. 2 is a field curvature curve and distortion curve diagram of the F-theta lens provided by the first embodiment of the present invention; F-theta lens field diffraction point diagram provided by the embodiment; FIG. 4 is a schematic structural diagram of the F-theta lens provided by the second embodiment of the present invention; FIG. 5 is a diagram of the F-theta lens provided by the second embodiment of the present invention Field curve curve and distortion curve diagram; FIG. 6 is a diagram of a field diffraction light spot of an F-theta lens provided by a second embodiment of the present invention.

Claims (12)

An F-theta lens suitable for use in a laser processing process is characterized in that the F-theta lens includes an optical lens having a positive optical power, The second lens with negative power, the third lens with positive power, the fourth lens with positive power, and the fifth lens with positive power; the focal length of each lens satisfies the following relationship: 1.1 <f1 / f <1.7; -0.6 <f2 / f <-0.3; 2.1 <f3 / f <3.5; 0.9 <f4 / f <1.6; 1.6 <f5 / f <2.2; wherein f ₁ is the focal length of the first lens; f ₂ is the focal length of the second lens; f ₃ is the focal length of the third lens; f ₄ is the focal length of the fourth lens; f ₅ is the focal length of the fifth lens; f is the F- The total focal length of 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; the second lens is a plano-concave lens; and the third lens is concave-convex The fourth lens is a meniscus lens; the fifth lens is a meniscus lens. The F-theta lens suitable for use in a laser processing process according to claim 2, wherein when the first lens is near the object-side mirror, the radius of curvature is r ₁ , and the first lens is near When the curvature radius of the mirror surface on 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 when the third lens is near the object-side mirror, the radius of curvature is r ₅ , and the third lens is near When the curvature radius of the mirror surface on 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 when the fourth lens is near the object-side mirror, the radius of curvature is r ₇ , and the fourth lens is near When the curvature radius of the mirror surface on 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 when the fifth lens is near the object-side mirror, the radius of curvature is r ₉ , and the fifth lens is near When the curvature radius of the mirror surface on the image side is r ₁₀ , r ₉ > r ₁₀ . The F-theta lens suitable for use in a laser processing process according to claim 1, further comprising a protective window, wherein the protective window is a flat lens and is disposed between the fifth lens and the image. Party. The F-theta lens suitable for use in a laser processing process according to claim 1, wherein a pupil 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 the first lens, the second lens, the third lens, the fourth lens, and the first lens The five-lens 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 200mm ≦ f ≦ 400mm, where 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 0-20 degrees.