WO2023279662A1 - Laser rotary cutting system and rotary cutting method - Google Patents

Abstract

A laser rotary cutting system, comprising a laser device (1), a wedge lens group, a focusing lens (4) and an angle adjustment lens, wherein the wedge lens group is arranged downstream of the light path transmission of the laser device to achieve the translational motion of a light beam; the focusing lens is arranged downstream of the light path transmission of the focusing lens to focus the light beam; the angle adjustment lens is arranged on a light path between the wedge lens group and the laser device, or on a light path between the focusing lens and the wedge lens group; and the angle adjustment lens is used to adjust the flight angle of the light passing through the angle adjustment lens, and the angle adjustment lens and the wedge lens group rotate synchronously. The present invention further relates to a rotary cutting method using the rotary cutting system. The laser rotary cutting system has a simple structure, and is convenient to adjust.

Description

A kind of laser rotary cutting system and rotary cutting method technical field

The invention relates to the field of laser processing, in particular to a laser rotary cutting system and a rotary cutting method.

Background technique

Depending on the optical devices and working principles used inside the laser drilling device, the laser drilling can be divided into a galvanometer scanning drilling system, a three-wedge rotary scanning drilling system, and a Dove prism rotary scanning drilling system.

Among them, the galvanometer scanning drilling system is the most mature drilling system, with a large processing range and simple control. However, due to the limitation of mechanical resolution, it is difficult for the galvanometer scanning system to precisely process micro-holes with a diameter less than 0.2mm.

The three optical wedge rotary scanning drilling system needs to ensure the synchronous rotation of the three optical wedges, and also needs to accurately control the relative angle between the optical wedges. If the control accuracy is not good, it will affect the roundness and taper of the hole, which will affect the motor. The precision of the rotation control is extremely high, and the algorithm for controlling the radius and taper of the hole is very complicated, for example, the publication of the Chinese patent application publication number CN103056519A.

The manufacturing and installation errors of the Dove prism will have a great impact on the roundness and taper of the hole, so a complex compensation optical system is required to compensate the manufacturing and installation errors of the system. This not only greatly increases the volume and weight of the system, but also increases the manufacturing difficulty and production cost of the system. For example, the US Patent Publication No. is US7842901B2.

Contents of the invention

The technical problem to be solved by the present invention is to solve at least one of the above-mentioned problems.

The solution that the present invention solves its technical problem is:

A rotary cutting system, including a laser, a wedge mirror group, a focusing mirror, and an angle adjustment mirror; the wedge mirror group is arranged downstream of the optical path transmission of the laser, and the wedge mirror group is used to make the beam perform a translational movement; the The focusing mirror is arranged downstream of the optical path transmission of the focusing mirror, and the focusing mirror is used to focus the light beam; the angle adjustment mirror is arranged in the optical path between the wedge mirror group and the laser, or arranged in the In the optical path between the focusing mirror and the wedge mirror group; the angle adjustment mirror is used to adjust the flight angle of the light after passing through the angle adjustment mirror, and the angle adjustment mirror and the wedge mirror group rotate synchronously.

As a further improvement of the above technical solution, the angle adjustment mirror is a reflection mirror or a beam splitter.

As a further improvement of the above technical solution, the angle adjustment mirror is arranged between the wedge mirror group and the laser, and a quarter-wave plate is arranged between the angle adjustment mirror and the wedge mirror group, so A PBS beam-splitting prism is arranged between the quarter-wave plate and the wedge mirror group, the laser is arranged upstream of the PBS beam-splitting prism, and the optical path transmission is followed by the laser, the PBS beam-splitting prism, and the quarter-wave plate , Angle adjustment mirror, quarter wave plate, PBS beam splitting prism, wedge mirror group, focusing mirror.

As a further improvement of the above technical solution, the PBS dichroic prism includes two PBS triangular prisms, the cross section of the PBS triangular prisms is a right triangle, and the two PBS triangular prisms are spliced into a cuboid.

As a further improvement of the above technical solution, the angle adjustment mirror is arranged between the focus mirror and the wedge mirror group, the angle adjustment mirror is a beam splitter, and the beam splitter is used to reflect a part of the light to the focus mirror, The remaining light passes through the beam splitter, and a detector is arranged beside the beam splitter, and the detector is used to detect the position and angle of the light passing through the beam splitter.

As a further improvement of the above technical solution, the wedge mirror group includes the same two wedge mirrors, the two wedge mirrors are arranged symmetrically to each other, and the two wedge mirrors rotate synchronously with the angle adjustment mirror.

As a further improvement of the above technical solution, the distance between the two wedge mirrors is adjustable.

As a further improvement of the above technical solution, the laser is a pulsed laser.

The present invention also provides a rotary cutting method using the above rotary cutting system. Step 1, determine the processing cone angle and drilling radius of the rotary cutting hole, so that the focusing mirror is facing the position of the hole; step 2, adjust the wedge shape respectively. The mirror group and the angle adjustment mirror make the wedge mirror group and the angle adjustment mirror rotate synchronously, the angle adjustment mirror is a reflective mirror, and the wedge mirror group includes two mutually symmetrical wedge mirrors; step 3, turn on the laser.

As a further improvement of the above-mentioned technical solution, the hole radius is R, the R=f*tanβ1=f*tan2w, the f is the focal length of the focusing mirror, and the β1 is the exit angle after the light beam is reflected by the mirror, Described w is the angle of inclination of reflecting mirror; Described machining taper angle is θ, and described θ=arctan[(L1tanβ1+L2tanβ2+L3tanβ1+R)/f], wherein L1 is the distance between the nearest wedge mirrors of reflecting mirror Distance, L2 is the distance between the two wedge mirrors, the distance between the wedge mirror and the focus mirror, R is the hole radius, f is the focal length of the focus mirror; the angle between the wedge mirror exit light and the optical axis is β2 , the β2=arcsin[n2 sin[α-arcsin[sin(α+β1)/n2]]], wherein n2 is the refractive index of the wedge mirror, and α is the wedge angle of the wedge mirror.

The beneficial effect of the present invention is that the rotary cutting system of the present invention is different from the traditional technology in which multiple optical wedges are used to drive the laser to rotate, and the rotary cutting system of the present invention can drive the laser to rotate by rotating the angle adjustment mirror, effectively reducing The weight and volume of the rotating object are reduced, making the laser rotation speed faster and the processing accuracy higher.

The rotary cutting method in the present invention applies the above rotary cutting system, which is easy to operate, simple in structure, and convenient for users to adjust parameters.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly describe the drawings that need to be used in the description of the embodiments. Apparently, the described drawings are only some embodiments of the present invention, not all embodiments, and those skilled in the art can obtain other designs and drawings based on these drawings without creative work.

Fig. 1 is the schematic diagram that the angle adjustment mirror among the present invention is arranged in the optical path between described wedge mirror group and described laser;

Fig. 2 is the schematic diagram of the optical path in which the angle adjustment mirror is arranged between the focusing mirror and the wedge mirror in the present invention;

Fig. 3 is a schematic diagram of an embodiment of the present invention using both reflective mirrors and beam splitters.

In the accompanying drawings: 1-laser, 2-wedge mirror, 3-PBS beam splitting prism, 4-focusing mirror, 5-reflecting mirror, 6-beam splitting mirror, 7-detector.

detailed description

The idea, specific structure and technical effects of the present invention will be clearly and completely described below in conjunction with the embodiments and accompanying drawings, so as to fully understand the purpose, features and effects of the present invention. Apparently, the described embodiments are only some of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative efforts belong to The protection scope of the present invention. In addition, all the connection/connection relationships mentioned in this article do not refer to the direct connection of components, but mean that a better connection structure can be formed by adding or reducing connection accessories according to specific implementation conditions. The various technical features in the invention can be combined interactively on the premise of not contradicting each other.

In the present invention, in FIG. 1 , FIG. 2 and FIG. 3 , the line segment connecting the laser 1 represents the laser light.

As shown in Figure 1, a kind of rotary cutting system comprises laser 1, wedge-shaped mirror group, focusing mirror 4, angle adjustment mirror; Described wedge-shaped mirror group is arranged on the optical path transmission downstream of described laser 1, and described wedge-shaped mirror group uses To make the beam move in translation; the focusing mirror 4 is arranged downstream of the optical path transmission of the focusing mirror, and the focusing mirror 4 is used to focus the beam; the angle adjustment mirror is arranged between the wedge mirror group and the In the optical path between the lasers 1; the angle adjustment mirror is used to adjust the flight angle of light passing through the angle adjustment mirror, and the angle adjustment mirror and the wedge mirror group rotate synchronously.

In this embodiment, the laser light generated by the laser device 1 passes through the angle adjustment mirror, the wedge mirror group, and the focusing mirror 4 in turn. The user can adjust the angle adjustment mirror to adjust the angle at which the laser beam is emitted from the angle adjustment mirror, and then adjust the laser beam. The diameter of the hole, the user can also adjust the wedge-shaped mirror group to translate the path of the laser flight, which is very convenient to adjust. At the same time, the angle adjustment mirror and the wedge-shaped mirror group can be set as coaxial transmission, and the synchronization rate can be obtained. Guaranteed, the laser line can be rotated 360° to realize the function of rotary cutting.

During use, in order to adjust the exit angle of the light from the angle adjustment mirror, the user can tilt the angle adjustment mirror, and further, the scanning radius of the light beam on the processing surface can be changed. The high-speed rotation of the angle adjustment mirror and the wedge mirror group can realize the high-speed scanning of the beam on the processing surface.

Optionally, the angle adjustment mirror is a reflecting mirror 5 or a beam splitter 6 . Preferably, in this embodiment, the angle adjustment mirror is the reflection mirror 5 . The reflector 5 is light, and its angle of incidence and angle of reflection are relatively easy to adjust.

Preferably, the diameter of the reflector 5 is 15 mm, and the rotation speed of the reflector 5 and the wedge mirror group is 1000 to 48000 r/min.

Further, the angle adjustment mirror is a reflection mirror 5, and the angle adjustment mirror is arranged between the wedge mirror group and the laser 1, and a quarter is arranged between the angle adjustment mirror and the wedge mirror group. A wave plate, a PBS beamsplitter prism 3 is arranged between the quarter wave plate and the wedge mirror group, the laser 1 is arranged upstream of the PBS beamsplitter prism 3, and the optical path transmission is successively laser 1, PBS beam splitting prism 3, quarter wave plate, angle adjustment mirror, quarter wave plate, PBS beam splitting prism 3, wedge mirror group, focusing mirror 4.

The PBS beam splitter is adopted, so that the laser beam can be vertically incident on the angle adjustment mirror, so that the size of the selected angle adjustment mirror can be smaller, and then the quality and volume are smaller, and it is easier to achieve high-speed rotation.

If the PBS dichroic prism is not used, the angle between the laser incident on the angle adjustment mirror and the angle adjustment mirror is generally about 30° to 60°, so the area of the angle adjustment mirror is relatively larger, but this implementation For example, there is no need to use PBS beamsplitter prism and quarter wave plate, which reduces the loss of laser energy and saves equipment.

When in use, the quarter-wave plate can rotate the linearly polarized light. After the incident linearly polarized light passes through the quarter-wave plate, the phase difference between the outgoing light and the incident light produces a delay of π/2, one cycle is 2π. After the laser passes through the quarter-wave plate twice, its phase is retarded by π, so that the laser can finally completely pass through the PBS polarization beam splitter. The PBS polarization beam splitter can totally reflect the linearly polarized laser light emitted by the laser 1 onto the angle adjustment mirror. The angle adjustment mirror in this embodiment is preferably a reflection mirror 5, and the laser light passes through a quarter wave after being reflected by the reflection mirror 5. sheet, and finally completely pass through the PBS polarizing beam splitter to reach the wedge mirror group, so that the energy of the laser light generated by the laser 1 can be relatively completely preserved.

Of course, in actual use, instead of using the PBS dichroic prism 3 and the quarter-wave plate, it is also possible to direct the laser light to the reflector 5 through the laser 1 . In this embodiment, during rotary cutting, the normal of the reflector 5 is not collinear with the axis of rotation of the reflector.

In addition, the PBS polarization beam splitter and the quarter-wave plate are placed outside the angle adjustment mirror, which greatly reduces the weight of the driving components when the angle adjustment mirror moves, and improves the accuracy more effectively.

The PBS dichroic prism 3 includes two PBS triangular prisms. The cross section of the PBS triangular prisms is a right triangle, and the two PBS triangular prisms are spliced into a cuboid. The structure is simple and the setting is convenient. Preferably, the PBS dichroic prism 3 is a polarization dichroic prism, and its length, width and height are 10*10*10mm˜20*20*20mm. Optionally, the PBS dichroic prism 3 is made of quartz or ordinary glass.

As shown in Figure 2, as an alternative embodiment, the rotary cutting system includes a laser 1, a wedge mirror group, a focusing mirror, and an angle adjustment mirror; the wedge mirror group is arranged on the optical path of the laser 1 Downstream, the wedge mirror group is used to make the beam move in translation; the focusing mirror 4 is arranged on the optical path transmission downstream of the focusing mirror, and the focusing mirror 4 is used to focus the beam; the angle adjustment mirror is arranged on the In the optical path between the focusing mirror 4 and the wedge mirror group; the angle adjustment mirror is used to adjust the flight angle of the light after passing through the angle adjustment mirror, and the angle adjustment mirror and the wedge mirror group rotate synchronously.

In this embodiment, the angle adjustment mirror is arranged between the focusing mirror 4 and the wedge mirror 2, and there is a difference in position between the angle adjustment mirror and the above-mentioned embodiment where the angle adjustment mirror is arranged between the wedge mirror group and the laser 1, but both Both can adjust the tilt angle of the mirror by adjusting the angle, so as to adjust the radius of the rotary cutting hole.

In this embodiment, preferably, the angle adjustment mirror and the wedge mirror group are respectively driven by different motors, but preferably, the two motors rotate synchronously.

Optionally, the angle adjustment mirror is a reflecting mirror 5 or a beam splitter 6, preferably, the beam splitter 6 is used in this embodiment.

Further, the angle adjustment mirror is arranged between the focusing mirror 4 and the wedge mirror group, the angle adjustment mirror is a beam splitter 6, and the beam splitter 6 is used to reflect a part of the light to the focusing mirror 4, and the remaining The light passes through the beam splitter 6, and a detector 7 is arranged beside the beam splitter 6, and the detector 7 is used to detect the position and angle of the laser beam passing through the beam splitter 6. In this embodiment, the angle adjustment mirror adopts the beam splitter 6, so that the user can install the detector 7 from the back of the light-facing surface of the beam splitter 6, and the detector 7 can detect the position and posture of the incident laser beam into the beam splitter 6, thereby judging the light Whether the position of the rotary cutting machine is accurate, and then the accuracy of the rotary cutting can be judged by the result obtained by the detector 7. The user can form negative feedback through the setting of the detector 7, and adjust the position and posture of the angle adjustment mirror and the wedge mirror group accordingly through the result of the feedback, which can effectively improve the processing accuracy of the laser rotary cutting.

Furthermore, as shown in Figure 3, those skilled in the art can also adopt the following implementation mode, the angle adjustment mirror is arranged between the focusing mirror 4 and the wedge mirror 2, and is also arranged between the wedge mirror group and the laser mirror , in this case, the angle adjustment mirror between the wedge mirror group and the laser mirror adopts a reflector 5, which rotates synchronously with the wedge mirror group, and the reflector 5 is used to adjust the exit angle of the laser light emitted from the laser 1 , so that the radius of the rotary cutting hole can be adjusted, the angle adjustment mirror between the focusing mirror 4 and the wedge mirror 2 is a beam splitter 6, and the beam splitter 6 is a lens, and the beam splitter 6 is used for the wedge mirror group The outgoing beam is partially reflected, and the remaining part passes through the beam splitter 6.

Optionally, the beam splitter 6 can transmit 1%-10% of light, that is, 1%-10% of the laser light passes through the beam splitter 6, and the rest of the laser light is reflected to the focusing mirror.

The user can install a detector 7 on the backlight of the beam splitter 6, and the detector 7 is used to detect the pose of the light incident on the beam splitter 6, so as to ensure that the position of the laser transmission movement before the beam splitter 6 is accurate. The user can also monitor the laser in real time through the detector 7, so as to form negative feedback in time and ensure the processing accuracy.

In some embodiments, the focusing mirror 4 is made of quartz material or optical glass material, and optionally, its focal length is between 50 mm and 100 mm. In actual use, the longer the focal length of the focusing mirror 4 is, the larger the scanning radius of the laser beam on the processing surface is, and vice versa.

Optionally, the laser 1 is a pulsed laser 1, the pulse width generated by it can be nanoseconds, picoseconds or femtoseconds, and its wavelength can be between 300nm and 1100nm, preferably between 355nm and 1064nm. More preferably, the laser 1 generates a linearly polarized infrared laser with a wavelength of 1064nm, a pulse width of 300-350fs, and a diameter of 2-6mm.

In some embodiments, it can be any of the above implementations, the wedge mirror group includes the same two wedge mirrors 2, and the two wedge mirrors 2 are arranged symmetrically to each other, and the two wedge mirrors 2 and the The angle adjustment mirror rotates synchronously. The specifications and parameters of the two wedge mirrors 2 are the same, and the two wedge mirrors 2 are placed in opposite directions. The wedge mirror 2 downstream of the optical path is used to correct the change of the incident light angle by the wedge mirror 2 upstream of the optical path, so that the wedge mirror 2 downstream of the optical path emits light The angle of is the same as the angle of light reflected by reflector 5.

Preferably, the wedge mirror 2 is made of quartz material or optical glass material. Optionally, its outer diameter is 10mm to 30mm, its thickness is 3mm to 8mm, and its wedge angle is 6° to 12°. The user can adjust it according to the actual situation. The specifications of the wedge mirror 2 are selected.

In some embodiments, the distance between the two wedge mirrors 2 is adjustable. The taper of the circular hole can be changed by changing the relative distance between the two wedge mirrors 2 .

In some implementations, the relative positions between the reflector 5, the quarter-wave plate, the PBS polarization beam splitter and the relatively upstream wedge mirror 2 are fixed, and the user can install them in a movable On the platform, it can be translated left and right along the optical axis direction, and the relative position between the wedge mirror 2 of the upstream optical path and the wedge mirror 2 of the downstream optical path is changed by moving the platform, so that the beam is shifted along the optical axis direction to realize the taper of the hole Change.

In some embodiments, the laser 1 is a pulsed laser 1, and in addition, a beam expander mirror may be provided at the output end of the laser.

The present invention also provides a rotary cutting method using the rotary cutting system in any of the above embodiments, step 1, determine the processing cone angle and drilling radius of the rotary cutting hole, and make the focusing mirror 4 facing the position of the hole ; Step 2, adjust the wedge mirror group and the angle adjustment mirror respectively, so that the wedge mirror group and the angle adjustment mirror rotate synchronously; Step 3, turn on the laser 1 .

Optionally, the angle adjustment mirror is a reflecting mirror 5, and the wedge mirror group includes two wedge mirrors 2 that are symmetrical to each other.

The method can use the above-mentioned rotary cutting system, and the above-mentioned rotary cutting system has been described in words, and those skilled in the art should be able to understand it in conjunction with the accompanying drawings, so the description of the rotary cutting system will not be repeated here.

Further, the hole radius is R, the R=f*tanβ1=f*tan2w, the f is the focal length of the focusing mirror 4, the β1 is the exit angle after the light beam is reflected by the mirror, and the w is The angle of inclination of reflector 5; Described machining taper angle is θ, described θ=arctan[(L1tanβ1+L2tanβ2+L3tanβ1+R)/f], wherein L1 is the distance between reflector 5 and the nearest wedge mirror 2 , L2 is the distance between the two wedge mirrors 2, the distance between the wedge mirror 2 and the focusing mirror 4, R is the hole radius, f is the focal length of the focusing mirror 4; Angle is β2, described β2=arcsin[n2 sin[α-arcsin[sin(α+β1)/n2]]], wherein n2 is the refractive index of wedge mirror 2, and α is the wedge angle of wedge mirror 2.

Through this method, the user can adjust the exit angle of the reflector 55, the above-mentioned L1, and the above-mentioned L2 according to the parameters of the hole to be processed. In addition, for different hole specifications, the user can also change the focus lens 4 Thereby, the focal length of the focusing mirror 4 is adjusted, and the size of the wedge angle is adjusted by changing different wedge mirrors 2, which is very convenient for light adjustment.

It has been verified by experiments that in actual use, the invention has a large processing aperture and a taper range and high processing accuracy, and can realize aperture processing with a diameter of 0.01mm-5mm, and can realize tapered hole processing of ±7°. For example, to realize the processing of zero-taper holes, the principle is to use the outer side of the light focused by the focusing lens 4 to rotate and cut the inner wall of the hole along the depth direction of the hole, thereby forming a zero-taper hole.

The preferred embodiments of the present invention have been described in detail above, but the invention is not limited to the described embodiments, and those skilled in the art can also make various equivalent modifications or replacements without violating the spirit of the present invention. These equivalent modifications or replacements are all within the scope defined by the claims of the present application.

Claims (10)

1. A kind of rotary cutting system, comprises laser (1), is characterized in that, also comprises:

   A wedge-shaped mirror group, the wedge-shaped mirror group is arranged downstream of the optical path transmission of the laser (1), and the wedge-shaped mirror group is used to make the beam perform a translational movement;

   A focusing mirror (4), the focusing mirror (4) is arranged downstream of the optical path transmission of the focusing mirror, and the focusing mirror (4) is used to focus the light beam;

   An angle adjustment mirror, the angle adjustment mirror is arranged in the optical path between the wedge mirror group and the laser (1), or in the optical path between the focusing mirror (4) and the wedge mirror group; The angle adjustment mirror is used to adjust the flight angle of light passing through the angle adjustment mirror, and the angle adjustment mirror and the wedge mirror group rotate synchronously.
2. The rotary cutting system according to claim 1, characterized in that the angle adjustment mirror is a reflection mirror (5) or a beam splitter (6).
3. The rotary cutting system according to claim 1, wherein the angle adjustment mirror is a reflection mirror (5), and the angle adjustment mirror is arranged between the wedge mirror group and the laser (1), so A quarter-wave plate is provided between the angle adjustment mirror and the wedge mirror group, a PBS beamsplitter prism (3) is provided between the quarter-wave plate and the wedge mirror group, and the laser ( 1) It is arranged upstream of the PBS beam-splitting prism (3), and the optical path transmission is a laser (1), a PBS beam-splitting prism (3), a quarter-wave plate, an angle adjustment mirror, a quarter-wave plate, and a PBS Dichroic prism (3), wedge mirror group, focusing mirror (4).
4. The rotary cutting system according to claim 3, wherein the PBS dichroic prism (3) comprises two PBS triangular prisms, the cross section of the PBS triangular prism is a right triangle, and the two PBS triangular prisms are spliced into a cuboid .
5. The rotary cutting system according to claim 1, wherein the angle adjustment mirror is arranged between the focusing mirror (4) and the wedge mirror group, the angle adjustment mirror is a beam splitter (6), the The beam splitter (6) is used to reflect a part of the light to the focusing mirror (4), and the side of the beam splitter (6) is provided with a detector (7), and the detector (7) is used to detect the The position and angle of the light of the mirror (6).
6. The rotary cutting system according to claim 1, characterized in that, the wedge mirror group comprises two identical wedge mirrors (2), the two wedge mirrors (2) are arranged symmetrically to each other, and the two wedge mirrors (2) Rotate synchronously with the angle adjustment mirror.
7. The rotary cutting system according to claim 6, characterized in that the distance between the two wedge mirrors (2) is adjustable.
8. The rotary cutting system according to claim 1, characterized in that the laser (1) is a pulsed laser (1).
9. A rotary cutting method using the rotary cutting system according to claim 1, characterized in that, step 1, determining the processing cone angle and drilling radius of the rotary cutting drilling, so that the focusing mirror (4) is facing the hole of the drilling position; step 2, adjust the wedge-shaped mirror group and the angle adjustment mirror respectively, so that the wedge-shaped mirror group and the angle adjustment mirror rotate synchronously, and the angle adjustment mirror is a reflecting mirror (5), and the wedge-shaped mirror group includes two mutually symmetrical wedge mirror (2); step 3, turn on the laser (1).
10. The rotary cutting method according to claim 9, wherein the hole radius is R, the R=f*tanβ1=f*tan2w, the f is the focal length of the focusing mirror, and the β1 is a mirror The exit angle after the reflected light beam, the e is the inclination angle of the reflector; the processing cone angle is θ, the θ=arctan[(L1tanβ1+L2tanβ2+L3tanβ1+R)/f], where L1 is the reflector distance The distance between the nearest wedge mirrors, L2 is the distance between two wedge mirrors, the distance between the wedge mirror and the focusing mirror, R is the hole radius, f is the focal length of the focusing mirror; The included angle between is β2, described β2=arcsin[n2 sin[α-arcsin[sin(α+β1)/n2]]], wherein n2 is the refractive index of wedge mirror, and α is the wedge angle of wedge mirror.

Images