CN114077066B - Beam-expanding collimator - Google Patents
Beam-expanding collimator Download PDFInfo
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- CN114077066B CN114077066B CN202111194219.6A CN202111194219A CN114077066B CN 114077066 B CN114077066 B CN 114077066B CN 202111194219 A CN202111194219 A CN 202111194219A CN 114077066 B CN114077066 B CN 114077066B
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- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/09—Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
- G02B27/0927—Systems for changing the beam intensity distribution, e.g. Gaussian to top-hat
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/09—Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
- G02B27/0938—Using specific optical elements
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/09—Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
- G02B27/0938—Using specific optical elements
- G02B27/095—Refractive optical elements
- G02B27/0955—Lenses
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/28—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising
- G02B27/283—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising used for beam splitting or combining
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/28—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising
- G02B27/286—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising for controlling or changing the state of polarisation, e.g. transforming one polarisation state into another
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/30—Collimators
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Optical Couplings Of Light Guides (AREA)
- Lasers (AREA)
Abstract
The application is suitable for the technical field of laser beam shaping, and provides a beam expansion collimator which comprises an optical fiber, a spherical lens, a shaping crystal group, a biconcave lens and a plano-convex lens which are sequentially arranged; the shaping crystal group comprises a first birefringent crystal, a half-wave plate and a second birefringent crystal which are sequentially arranged, the first birefringent crystal is close to one end of the optical fiber, the first birefringent crystal is a birefringent crystal with an optical axis forward at 45 degrees, the half-wave plate is a half-wave plate with an optical axis rightward at 22.5 degrees, and the second birefringent crystal is a birefringent crystal with an optical axis rightward at 45 degrees; the application improves the problems of uneven energy distribution and low efficiency of the Gaussian distribution of the laser beam in the prior art, splits the laser beam into a plurality of laser beams with equal energy and equidistant arrangement, and achieves the effect of beam flattening, thereby ensuring that the energy distribution of the laser beams is even and improving the efficiency of laser processing.
Description
Technical Field
The application relates to the technical field of laser beam shaping, in particular to a beam expansion collimator.
Background
As an advanced processing tool, laser plays a significant role in industrial production, and with the development of global industry, the application field of laser processing technology is increasing, from material processing to automobile production, to 3D printing and other emerging industries. Such as in aero-engine manufacturing/automotive engine core device machining, power electromagnetic pole ear cutting, microelectronic/precision bearing/precision cutter and other high precision, micro device machining and manufacturing, metal surface rust cleaning, artwork micro-engraving, and the like.
The laser beam emitted by the laser is generally in Gaussian distribution, and the Gaussian distribution of laser energy has the defects of non-uniformity, low efficiency and the like in large-area application. For example, in laser cleaning applications, the gaussian distribution of energy concentrates in the middle and fades out in the surrounding energy during cleaning, resulting in problems of too deep a cleaning of the middle region of the beam and too shallow a cleaning of the surrounding. Therefore, converting the gaussian distribution of a laser beam into a beam having a uniform light intensity distribution is an urgent problem to be solved in the prior art.
Currently, a popular research scheme is the diffractive optical element (Diffractive optical elements, DOE) scheme, which uses an array of diffractive elements to change the phase of an input beam to obtain a desired intensity distribution. The scheme is an ideal selection scheme for shaping the laser beam, but the problems of high accuracy requirement and complex manufacture of the diffraction element array at present are that the scheme is too high in manufacture cost and inconvenient to popularize and apply.
Disclosure of Invention
Aiming at the situation, the application provides the beam expanding collimator, which effectively solves the problems of uneven laser beam Gaussian distribution energy and low efficiency in the prior art.
The embodiment of the application provides a beam expansion collimator, which comprises an optical fiber, a spherical lens, a shaping crystal group, a biconcave lens and a plano-convex lens which are sequentially arranged along the optical path direction of a laser beam emitted by the optical fiber;
the shaping crystal group comprises a first birefringent crystal, a half-wave plate and a second birefringent crystal which are sequentially arranged, the first birefringent crystal is close to one end of the optical fiber, the first birefringent crystal is a birefringent crystal with an optical axis forward at 45 degrees, the half-wave plate is a half-wave plate with an optical axis rightward at 22.5 degrees, and the second birefringent crystal is a birefringent crystal with an optical axis rightward at 45 degrees.
In one embodiment, the laser beam emitted by the optical fiber is separated by o after passing through the first birefringent crystal 1 Light sum e 1 Light two beams of light, o 1 Light and said e 1 The angular expression of the separation between light is:
where θ is the angle between the optical axis and the input light, n o And n e Refractive indices of the ordinary and extraordinary rays of the first birefringent crystal group, o 1 Light and said e 1 The light-separated pitch expression is:
wherein L is the thickness of the first birefringent crystal.
In an embodiment, the first birefringent crystal and the second birefringent crystal are made of a material having a difference between an ordinary refractive index and an extraordinary refractive index of greater than 0.15.
In one embodiment, the first birefringent crystal and the second birefringent crystal are yttrium vanadate crystals.
In an embodiment, the first and second birefringent crystals have an ordinary refractive index of 1.957159 and an extraordinary refractive index of 2.155721, and the first and second birefringent crystals have an optical axis angle of 45 °.
In one embodiment, when said o 1 Light and said e 1 The first birefringent crystal and the second birefringent crystal have a thickness of 1.87mm at a separation distance of 0.18mm between the light.
In one embodiment, the laser beam passing through the spherical lens is split into e after passing through the first birefringent crystal 1 Light sum o 1 Light, e 1 Light and o 1 The polarization direction of the light is vertical and horizontal respectively;
said e 1 Light and o 1 The polarization direction of the light after passing through the half-wave plate is rotated counterclockwise by 45 degrees and is called e 2 Light sum o 2 Light;
said e 2 Light passes through the firstAfter the birefringent crystal is divided into e 21 Light sum e 22 Light;
said o 2 The light is divided into o after passing through the second birefringent crystal 21 Light sum o 22 Light.
In one embodiment, the beam generated after passing through the plano-convex lens is a quasi-square flat-top beam with uniform spot energy distribution in the middle area.
In an embodiment, the focal points of the spherical lens, the first birefringent crystal, the half-wave plate, the second birefringent crystal, the biconcave lens, and the plano-convex lens are all located on the same horizontal line.
In an embodiment, the device further comprises a tail sleeve and a beam expanding lens barrel, wherein the tail sleeve is fixed at one end of the beam expanding lens barrel;
the tail sleeve is internally and sequentially fixed with a collimator outer seal and a crystal fixing seat, the crystal fixing seat is close to the beam expanding lens barrel, the spherical lens is fixed on the collimator outer seal, and the shaping crystal group is fixed on the crystal fixing seat;
beam expanding lens barrel: the beam expanding lens barrel is internally and sequentially fixed with a concave lens seat and a planoconvex lens, the concave lens seat is close to the tail sleeve, and the biconcave lens is fixed on the concave lens seat.
The application improves the problems of uneven laser beam Gaussian distribution energy and low efficiency in the prior art, and respectively expands, polarizes and re-expands the laser beam emitted by the optical fiber through the matching of the first birefringent crystal, the half-wave plate and the second birefringent crystal to finally obtain a square flat-top laser beam, namely, one laser beam is split into a plurality of laser beams with equal energy, thereby realizing the effect of laser beam flat-top, ensuring the energy distribution of the laser beams to be even and improving the efficiency of laser processing.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic cross-sectional view of a beam expanding collimator according to an embodiment of the present application.
Fig. 2 is a schematic structural diagram of the beam expanding collimator shown in fig. 1.
Fig. 3 is a schematic diagram of the laser light passing through the first birefringent crystal in the beam expansion collimator shown in fig. 1.
Fig. 4 is a schematic diagram of the laser light passing through the half-wave plate in the beam expanding collimator shown in fig. 1.
Fig. 5 is a schematic diagram of the laser light of the beam expanding collimator shown in fig. 1 passing through the second birefringent crystal.
Fig. 6 a-9 b are schematic views showing the effect of splitting one beam into four beams and gradually separating the four beams into different pitches by the beam expanding collimator shown in fig. 1.
Fig. 10 is a schematic view of a conventional laser beam gaussian distribution formed light spot.
Fig. 11 is a schematic view of a spot after shaping a laser beam by the beam expansion collimator shown in fig. 1.
The meaning of the labels in the figures is:
1. an optical fiber; 2. a spherical lens;
3. shaping the crystal group; 31. a first birefringent crystal; 32. a half-wave plate; 33. a second birefringent crystal;
4. biconcave lenses; 5. a plano-convex lens;
6. a housing; 61. a tail sleeve; 611. sealing the collimator; 612. a crystal fixing seat; 62. a beam expanding lens barrel; 621. a convex lens seat.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application will be further described in detail below with reference to the accompanying drawings, i.e., embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.
It will be understood that when an element is referred to as being "mounted" or "disposed" on another element, it can be directly or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly or indirectly connected to the other element. The terms "upper," "lower," "left," "right," and the like are used for convenience of description based on the orientation or positional relationship shown in the drawings, and do not denote or imply that the devices or elements in question must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be construed as limiting of the patent. The terms "first," "second," and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features. The meaning of "a plurality of" is two or more, unless specifically defined otherwise.
It should be further noted that, in the embodiments of the present application, the same reference numerals denote the same components or the same parts, and for the same parts in the embodiments of the present application, reference numerals may be given to only one of the parts or the parts in the drawings, and it should be understood that, for other same parts or parts, the reference numerals are equally applicable.
For the purpose of illustrating the technical aspects of the present application, reference is made to the drawings and examples.
Referring to fig. 1 and 2, an embodiment of the present application provides a beam expanding collimator, which is disposed at an output terminal of an optical fiber laser and is used for flattening a laser beam, so that energy of the laser beam is more uniform and efficiency is improved.
The beam expanding collimator comprises an optical fiber 1, a spherical lens 2, a shaping crystal group 3, a biconcave lens 4 and a plano-convex lens 5 which are sequentially arranged along the optical path direction of a laser beam emitted by the optical fiber 1, wherein the optical fiber 1 is a common optical fiber, the laser beam emitted by the output end of the optical fiber 1 is emitted into the beam expanding collimator, specifically, the laser beam transmitted by the optical fiber 1 outputs a Gaussian-distributed laser beam after passing through the spherical lens 2, and then the laser beam sequentially passes through the shaping crystal group 3, the biconcave lens 4 and the plano-convex lens 5 and finally emits a flattened laser beam.
A spherical lens 2, having a constant curvature from the center to the edge of the lens, is the first lens through which the laser beam passes after entering the beam expansion collimator, which is a common arrangement of beam expansion collimators in the prior art,
the shaping crystal group 3, the shaping crystal group 3 includes a first birefringent crystal 31, a half-wave plate 32 and a second birefringent crystal 33 sequentially arranged along the optical path direction of the laser beam, the first birefringent crystal 31 and the second birefringent crystal 33 are common birefringent crystals, the first birefringent crystal and the second birefringent crystal 33 refract an incident laser beam into two laser beams, the half-wave plate 32 is the common half-wave plate 32, and a phase difference occurs after the laser beams pass through the half-wave plate 32.
The first birefringent crystal 31 is close to one end of the optical fiber 1, the first birefringent crystal 31 is a birefringent crystal with an optical axis forward of 45 degrees, the half-wave plate 32 is a half-wave plate with an optical axis rightward of 22.5 degrees, the second birefringent crystal 33 is a birefringent crystal with an optical axis rightward of 45 degrees, the laser beam is divided into two beams after passing through the first birefringent crystal 31, and then the two beams deflect in the polarization direction after passing through the half-wave plate 32, and the two beams are divided into four beams after passing through the second birefringent crystal 33, and the four beams finally form a quasi-positive direction beam because the thicknesses of the first birefringent crystal 31 and the second birefringent crystal 33 are the same.
The biconcave lens 4 comprises concave surfaces which are oppositely arranged, and laser light enters from one concave surface of the biconcave lens 4 and exits from the other concave surface, so as to expand the beam of the incident laser light.
The plano-convex lens 5 comprises a flush surface and a convex surface which are oppositely arranged, the flush surface faces the biconcave lens 4, and laser is injected from the flush surface of the plano-convex lens 5 and is emitted from the convex surface, so that the injected point light source laser is converted into parallel beams.
In the embodiment, when the optical fiber is specifically used, the laser beam emitted from the optical fiber 1 passes through the spherical lens 2, the laser beam is focused and emitted into the shaping crystal group 3 under the action of the spherical lens 2, the laser beam is refracted by the first birefringent crystal 31 to obtain two beams, the two beams are changed in polarization direction by the half-wave plate 32, the two beams are emitted into four beams by the second birefringent crystal 33, and finally the four beams are converted into parallel beams by the plano-convex lens 5 to form a flat-top beam.
Referring to fig. 1 to 3, in one embodiment, the laser beam emitted from the optical fiber 1 is separated by o after passing through the first birefringent crystal 31 1 Light sum e 1 Light two beams o 1 The light is ordinary light, e 1 The light is the ordinary light, and after passing through the first birefringent crystal 31, the laser beam is divided into upper and lower beams of light, o 1 Light sum e 1 Light, and o 1 The polarization direction of the light is the horizontal direction, e 1 Polarization direction of light and o 1 Light is vertical, where o 1 Light sum e 1 The angular expression of the separation between light is:
where θ is the angle between the optical axis and the input light, n o And n e The refractive indices of the birefringent crystal ordinary and extraordinary rays, respectively.
The interval expression of the separation of the two light beams is as follows:
wherein L is the thickness of the first birefringent crystal 31, and the two light beams are o 1 Light sum e 1 O, which occurs after light is refracted by the first birefringent crystal 31 1 Light sum e 1 The light is two parallel beams of light, d is o 1 Light sum e 1 Distance between light.
Referring to FIG. 5, further, o 1 Light sum e 1 The spacing of the light after the second birefringent crystal 33 is also calculated according to the above formula.
Further, the first birefringent crystal 31 and the second birefringent crystal 33 are the same in thickness.
The present embodiment provides a method of calculating o 1 Light sum e 1 The method of separating the light into the space, the user can process and select the thickness of the first birefringent crystal 31 and the second birefringent crystal 33 according to the size requirement of the shaped light spot.
In an embodiment, the first birefringent crystal 31 and the second birefringent crystal 33 are yttrium vanadate crystals, the yttrium vanadate crystals have wide light transmission range, high transmittance and large birefringence, and the yttrium vanadate crystals are easy to process, so that the beam expansion effect can be better achieved as the first birefringent crystal 31 and the second birefringent crystal 33.
Referring to fig. 3, 4 and 5, further, the first and second birefringent crystals 31 and 33 have an ordinary refractive index of 1.957159 and an extraordinary refractive index of 2.155721, and the first and second birefringent crystals 31 and 33 have an optical axis angle of 45 °, and the laser light emitted from the optical fiber 1 is refracted into two parallel beams o after entering the first birefringent crystal 31 1 Light sum e 1 Light, after o 1 Light sum e 1 Light is incident on the second birefringent crystal 33 and is arranged to be parallel to each other o 21 Light, o 22 Light e 21 Light e 22 Four beams of light are emitted and form square flat-top light spots.
In an embodiment, the focal points of the spherical lens 2, the first birefringent crystal 31, the half-wave plate 32, the second birefringent crystal 33, the biconcave lens 4 and the plano-convex lens 5 are all positioned on the same horizontal line, and the axis of the optical fiber 1 passes through the focal points of the lenses at the same time, so that the laser beam can enter from the focal points when passing through the spherical lens 2, the first birefringent crystal 31, the half-wave plate 32, the second birefringent crystal 33, the biconcave lens 4 and the plano-convex lens 5, and the finally formed square flat-top light spot is ensured to be parallel to the optical fiber 1 and not to exit from one side.
Referring to fig. 1, in an embodiment, the beam expanding collimator further includes a tail sleeve 61 and a beam expanding lens barrel 62, the tail sleeve 61 is fixed at one end of the beam expanding lens barrel 62, the tail sleeve 61 and the beam expanding lens barrel 62 are hollow and transparent cylinder structures, the tail sleeve 61 is coaxially fixed at one end of the beam expanding lens barrel 62, the laser beam emitted from the optical fiber 1 is emitted into the beam expanding lens barrel 62 after passing through the tail sleeve 61 and finally emitted, and the tail sleeve 61 and the beam expanding lens barrel 62 are used for providing a fixed basis for the spherical lens 2, the first birefringent crystal 31, the half-wave plate 32, the second birefringent crystal 33, the biconcave lens 4 and the plano-convex lens 5.
The collimator outer seal 611 and the crystal fixing seat 612 are sequentially fixed in the tail sleeve 61, the collimator outer seal 611 is close to the optical fiber 1, the collimator outer seal 611 is of a hollow front-back transparent tubular structure, the collimator outer seal 611 and the tail sleeve 61 are coaxial, the spherical lens 2 is fixed in the collimator outer seal 611, and the spherical lens 2 and the collimator outer seal 611 are coaxial.
The crystal fixing seat 612 is a hollow front-back transparent cylindrical structure, the crystal fixing seat 612 and the tail sleeve 61 are coaxial, the shaping crystal set 3 is fixed in the crystal fixing seat 612, and the central points of the first birefringent crystal 31, the half-wave plate 32 and the second birefringent crystal 33 are all positioned on the axis of the crystal fixing seat 612.
The beam expanding lens barrel 62 is internally and sequentially fixed with a concave lens seat 621 and a plano-convex lens 5, the concave lens seat 621 is close to the tail sleeve 61, the concave lens seat 621 is of a hollow front-back transparent cylindrical structure, the biconcave lens 4 is fixed in the concave lens seat 621, the concave lens seat 621 and the beam expanding lens barrel 62 are coaxial, and the focal point of the biconcave lens 4 is positioned on the axis of the concave lens seat 621.
The plano-convex lens 5 is far from the biconcave lens 4, the distance between the focal points of the plano-convex lens 5 and the biconcave lens 4 determines the size of the square flat-top light spot finally formed, and a user can adjust the distance between the plano-convex lens 5 and the biconcave lens according to requirements.
Referring to fig. 6a to 9b, in an embodiment, there is provided an effect of gradually separating different pitches after splitting one laser beam into four laser beams, which are simulated by simulation software, and finally emitting the laser beam in a square flat top state after beam expansion refraction by the first and second birefringent crystals 31 and 33.
Wherein the horizontal plane in fig. 6a, 7a, 8a, 9a represents the spot diameter and the vertical axis represents the intensity of light; the horizontal axis in fig. 6b, 7b, 8b, and 9b represents the spot diameter, and the vertical axis represents the intensity of light.
Fig. 6a and 6b show the relationship between the laser intensity and the spot diameter in a beam of light, wherein fig. 6a is a three-dimensional simulation diagram, and fig. 6b is a schematic diagram showing the relationship between the spot diameter and the intensity of light, and is a cross-sectional view of a perspective view in fig. 6a, which corresponds to the laser intensity distribution in the laser emitted from the optical fiber 1 according to the present application, in which the laser energy is highly concentrated, the laser intensity is high near the central portion of the laser beam, and the intensity of light is rapidly attenuated as the laser diameter increases.
Fig. 7a and 7b, fig. 8a and 8b show the relationship between the laser intensity and the spot diameter when two beams of light are used, wherein fig. 7a and 8a are three-dimensional simulation diagrams, fig. 7b and 8b are schematic diagrams showing the relationship between the spot diameter and the light intensity, and are also respectively the cross-sectional views of the perspective views in fig. 7a and 8a, which correspond to the laser energy distribution situation of the laser beam after the beam is expanded by the first birefringent crystal in the present application, at the stage, the intensity of the central part of the laser beam is dispersed, the intensity of the light is attenuated by a small amplitude as the laser beam diameter increases, and rapid attenuation occurs when the laser beam diameter expands to be close to the edge of the laser beam, at the stage, the intensity of the laser beam has been primarily uniformly distributed, the high intensity area of the central part of the laser beam expands, but the energy distribution of the central part of the laser beam is not stable enough, and the distribution is irregular.
Fig. 9a and 9b show the relationship between the laser intensity and the spot diameter when four beams of light are used, wherein fig. 9a is a three-dimensional simulation diagram, fig. 9b is a schematic diagram of the relationship between the spot diameter and the light intensity, and is also a cross-sectional diagram of a perspective view in fig. 9a, which corresponds to the laser energy distribution situation after the laser beam is expanded by the second birefringent crystal in the present application, at this stage, the shaping and expanding of the laser beam are completed, forming a flat-top laser beam with a regular distribution, the laser beam has four points with high intensity around the central position, the laser beam central position between the four high-intensity points has smaller attenuation and higher intensity, and the energy attenuation between two adjacent high-intensity points is also smaller, compared with the curve in fig. 8b, the intensity attenuation of the light is further reduced with the change of the laser beam diameter until the laser beam intensity reaches the edge of the laser beam, at this stage, the laser beam intensity distribution is uniform, regular, and the high-intensity area is large.
Referring to fig. 10, the energy distribution of a conventional standard circular spot is shown in fig. 10, in which the energy in the center region of the spot is high and concentrated, and the energy in the spot away from the center is rapidly attenuated, and the energy distribution is uneven and concentrated in the center region.
Referring to fig. 11, fig. 11 shows that the square flat-top light spot after being shaped by the device has more uniform light spot energy distribution in the central area of the square flat-top light spot, and has larger area in the central high-energy area, smaller area in the energy reduction area around the light spot, namely more uniform light spot energy distribution in the square flat-top light spot compared with the traditional standard round light spot.
The above embodiments are only for illustrating the technical solution of the present application, and are not limiting; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present application, and are intended to be included in the scope of the present application.
Claims (9)
1. The beam expansion collimator is characterized by comprising an optical fiber (1), a spherical lens (2), a shaping crystal group (3), a biconcave lens (4) and a plano-convex lens (5) which are sequentially arranged;
the shaping crystal group (3) comprises a first birefringent crystal (31), a half-wave plate (32) and a second birefringent crystal (33) which are sequentially arranged along the optical path direction of the laser beam emitted by the optical fiber (1), the first birefringent crystal (31) is positioned at one end of the shaping crystal group (3) close to the optical fiber (1), the first birefringent crystal (31) is a birefringent crystal with an optical axis forward 45 degrees, the half-wave plate (32) is a half-wave plate with an optical axis rightward 22.5 degrees, and the second birefringent crystal (33) is a birefringent crystal with an optical axis rightward 45 degrees;
the laser beam emitted by the optical fiber (1) is separated o after passing through the first birefringent crystal (31) 1 Light sum e 1 Light two beams of light, o 1 Light and said e 1 The angular expression of the separation between light is:
where θ is the angle between the optical axis and the input light, n o And n e The first birefringent crystal (31) is searched forRefractive indices of ordinary and extraordinary rays, o 1 Light and said e 1 The light-separated pitch expression is:
wherein L is the thickness of the first birefringent crystal (31).
2. The beam expanding collimator according to claim 1, wherein the first birefringent crystal (31) and the second birefringent crystal (33) are made of a material having a difference between an ordinary refractive index and an extraordinary refractive index of more than 0.15.
3. The expanded beam collimator according to claim 2, characterized in that the first birefringent crystal (31) and the second birefringent crystal (33) are yttrium vanadate crystals.
4. A beam expanding collimator according to claim 3, characterized in that the first and second birefringent crystals (31, 33) have an ordinary refractive index of 1.957159 and an extraordinary refractive index of 2.155721, the first and second birefringent crystals (31, 33) having an optical axis angle of 45 °.
5. A beam expanding collimator according to claim 3, wherein when said o 1 Light and said e 1 The first birefringent crystal (31) and the second birefringent crystal (33) have a thickness of 1.87mm at a separation distance of 0.18mm between the lights.
6. The beam expanding collimator according to claim 1, characterized in that the laser beam passing through the spherical lens (2) is split into e after passing through the first birefringent crystal (31) 1 Light sum o 1 Light, e 1 Light and o 1 The polarization direction of the light is vertical and horizontal respectively;
said e 1 Light and o 1 The polarization direction of the light after passing through the half-wave plate (32) is rotated 45 degrees anticlockwise and becomes e 2 Light sum o 2 Light;
said e 2 The light is split into e after passing through the second birefringent crystal (33) 21 Light sum e 22 Light;
said o 2 The light is split into o after passing through the second birefringent crystal (33) 21 Light sum o 22 Light.
7. The beam expansion collimator according to claim 6, wherein the beam generated after passing through the plano-convex lens (5) is a square-like flat-top beam with uniform spot energy distribution in a middle area.
8. The beam expanding collimator according to claim 1, characterized in that the center points of the spherical lens (2), the first birefringent crystal (31), the half-wave plate (32), the second birefringent crystal (33), the biconcave lens (4) and the plano-convex lens (5) are all located on the same horizontal line.
9. The beam expanding collimator according to claim 1 or 8, further comprising a tail sleeve (61) and a beam expanding barrel (62), the tail sleeve (61) being fixed to one end of the beam expanding barrel (62);
a collimator outer seal (611) and a crystal fixing seat (612) are sequentially fixed in the tail sleeve (61), the crystal fixing seat (612) is close to the beam expanding lens barrel (62), the spherical lens (2) is fixed on the collimator outer seal (611), and the shaping crystal group (3) is fixed on the crystal fixing seat (612);
the beam expanding lens barrel (62) is internally and sequentially fixed with a concave lens seat (621) and a plano-convex lens (5), the concave lens seat (621) is close to the tail sleeve (61), and the biconcave lens (4) is fixed on the concave lens seat (621).
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