1. An optical path changing device is characterized by comprising a driving motor, a turntable mechanism arranged on the driving motor, at least one reference arm arranged on the turntable mechanism, a first collimator arranged on one side of the turntable mechanism and a first reflector arranged below the first collimator;

the reference arm is fixedly arranged on the turntable mechanism and can rotate integrally with the turntable mechanism;

the reference arm comprises a triangular reflector for changing an optical path, and the triangular reflector comprises a first reflecting lens, a second reflecting lens and a third reflecting lens which are intersected in pairs;

when the triangular reflector is positioned on the light path of the first collimator and the first reflector, light emitted from the first collimator can be reflected to the first reflector through the first light reflecting lens, the second light reflecting lens and the third light reflecting lens in sequence, and the light reflected by the first reflector can be reflected to the first collimator through the third light reflecting lens, the second light reflecting lens and the first light reflecting lens in sequence.

2. The optical path changing device according to claim 1,

the emergent light reflected to the first reflector by the third reflector is perpendicular to the first reflector.

3. The optical path changing device according to claim 2,

the first reflector is perpendicular to the axis of the light hole of the first collimator;

the emergent light reflected to the first reflector by the third reflector is parallel to the axis of the light hole.

4. The optical path changing device according to any one of claims 1 to 3,

the first reflective lens, the second reflective lens and the third reflective lens are vertically intersected and connected in pairs;

the first reflector is positioned at the top of the second reflector and the third reflector;

in the radial direction along the turntable mechanism, the first reflector gradually inclines upwards from inside to outside, and the inner edge and the outer edge of the first reflector are respectively parallel to the reference plane of the turntable mechanism;

in the vertical direction, the light hole of the first collimator is higher than the inner edge of the first reflector and lower than the outer edge of the first reflector;

the third reflective lens is connected with the inner side edge of the first reflective lens;

the second mirror plate is connected with the rear end edge of the first mirror plate along the rotation direction of the turntable mechanism.

5. The optical path changing device according to any one of claims 1 to 3,

the first reflector is mounted on the support portion through a telescopic adjustment mechanism.

6. The optical path changing device according to any one of claims 1 to 3, wherein the turntable mechanism includes a disk and a mounting boss provided on a top surface of the disk;

the disc is connected with an output shaft of the driving motor, and the reference arm is installed on the side face of the installation boss.

7. The optical path changing device according to claim 6,

the reference arm further comprises a protection shell, the triangular reflector is installed in the protection shell, and the protection shell is connected with the installation boss through a fastener.

8. The optical path changing device according to claim 7,

the protective shell comprises a first plate, a second plate and a third plate which are intersected with each other in pairs;

the first reflector is bonded with the first plate, the second reflector is bonded with the second plate, and the third reflector is bonded with the third plate;

the side surface of the mounting boss is provided with a mounting inclined surface which is gradually inclined downwards from inside to outside in the radial direction of the disc;

the first plate and the second plate are respectively provided with a connecting lug, each connecting lug is connected with the mounting boss through the fastener, and the third plate is attached to the mounting inclined plane.

9. The optical path changing device according to any one of claims 1 to 3,

the turntable mechanism is uniformly distributed with a plurality of reference arms at intervals along the circumferential direction.

10. An optical interference system comprising a light source, a circulator, a detector, a coupler, a second collimator, a second mirror, and the optical path changing device according to any one of claims 1 to 9;

the light source, the circulator, the coupler, the second collimator and the second reflector are sequentially arranged at intervals;

the circulator, the coupler and the second collimator are sequentially connected through optical fibers;

the circulator and the coupler are respectively connected with the detector through optical fibers;

the coupler is connected with the first collimator through an optical fiber.

Background

The michelson interferometer is one of the most common optical interferometers. The principle of the michelson interferometer is that a beam of incident light is divided into two beams by a spectroscope and then reflected by corresponding plane mirrors, and the two beams of incident light have the same frequency, the same vibration direction and constant phase difference (that is, satisfy the interference condition), so that interference can occur. When the optical path difference of the two beams is within the range of the coherence length, interference occurs.

At present, the principle is applied to an optical biometric apparatus for measuring the axial length of an eye in ophthalmology, however, in order to take account of axial resolution, the optical biometric apparatus in ophthalmology generally adopts a broadband SLD light source with a bandwidth of 50nm of 3dB, and the coherence length of the optical biometric apparatus is only ten microns or more, so that the reference arm of the optical biometric apparatus is required to have the capability of continuously changing the optical path length so as to match the micron-sized coherence length of the light source.

At present, the optical path of the reference arm of the optical biological measuring instrument based on the method is changed in a linear sliding rail mode, the speed of changing the optical path is low, and the continuous change of the optical path is difficult to realize.

Disclosure of Invention

The invention aims to provide an optical path changing device and an optical interference system, which can conveniently change an optical path, and have high speed, high efficiency and large optical path changing amplitude.

The technical scheme of the invention provides an optical path changing device which comprises a driving motor, a turntable mechanism arranged on the driving motor, at least one reference arm arranged on the turntable mechanism, a first collimator arranged on one side of the turntable mechanism and a first reflector arranged below the first collimator;

the reference arm is fixedly arranged on the turntable mechanism and can rotate integrally with the turntable mechanism;

the reference arm comprises a triangular reflector for changing an optical path, and the triangular reflector comprises a first reflecting lens, a second reflecting lens and a third reflecting lens which are intersected in pairs;

when the triangular reflector is positioned on the light path of the first collimator and the first reflector, light emitted from the first collimator can be reflected to the first reflector through the first light reflecting lens, the second light reflecting lens and the third light reflecting lens in sequence, and the light reflected by the first reflector can be reflected to the first collimator through the third light reflecting lens, the second light reflecting lens and the first light reflecting lens in sequence.

In an optional technical solution, the outgoing light reflected by the third mirror to the first mirror is perpendicular to the first mirror.

In an alternative embodiment, the first mirror is perpendicular to an axis of the light hole of the first collimator;

the emergent light reflected to the first reflector by the third reflector is parallel to the axis of the light hole.

In one optional technical solution, the first reflective lens, the second reflective lens and the third reflective lens are perpendicularly intersected and connected in pairs;

the first reflector is positioned at the top of the second reflector and the third reflector;

in the radial direction along the turntable mechanism, the first reflector gradually inclines upwards from inside to outside, and the inner edge and the outer edge of the first reflector are respectively parallel to the reference plane of the turntable mechanism;

in the vertical direction, the light hole of the first collimator is higher than the inner edge of the first reflector and lower than the outer edge of the first reflector;

the third reflective lens is connected with the inner side edge of the first reflective lens;

the second mirror plate is connected with the rear end edge of the first mirror plate along the rotation direction of the turntable mechanism.

In one alternative, the first mirror is mounted on a support via a telescopic adjustment mechanism.

In one optional technical scheme, the turntable mechanism comprises a disc and a mounting boss arranged on the top surface of the disc;

the disc is connected with an output shaft of the driving motor, and the reference arm is installed on the side face of the installation boss.

In one optional technical scheme, the reference arm further comprises a protective shell, the triangular reflector is mounted in the protective shell, and the protective shell is connected with the mounting boss through a fastener.

In an optional technical scheme, the protective shell comprises a first plate, a second plate and a third plate which are intersected with each other in a pairwise manner;

the first reflector is bonded with the first plate, the second reflector is bonded with the second plate, and the third reflector is bonded with the third plate;

the side surface of the mounting boss is provided with a mounting inclined surface which is gradually inclined downwards from inside to outside in the radial direction of the disc;

the first plate and the second plate are respectively provided with a connecting lug, each connecting lug is connected with the mounting boss through the fastener, and the third plate is attached to the mounting inclined plane.

In an alternative embodiment, the turntable mechanism is provided with a plurality of reference arms distributed at intervals along a circumferential direction.

The technical scheme of the invention also provides an optical interference system which comprises a light source, a circulator, a detector, a coupler, a second collimator, a second reflector and the optical path changing device in any one technical scheme;

the light source, the circulator, the coupler, the second collimator and the second reflector are sequentially arranged at intervals;

the circulator, the coupler and the second collimator are sequentially connected through optical fibers;

the circulator and the coupler are respectively connected with the detector through optical fibers;

the coupler is connected with the first collimator through an optical fiber.

By adopting the technical scheme, the method has the following beneficial effects:

the optical path changing device and the optical interference system provided by the invention have the advantages that the turntable mechanism rotates under the driving of the driving motor, the turntable mechanism drives the reference arm to continuously and circularly rotate, collimated light of the first collimator firstly hits the first reflecting lens of the triangular reflector, the first reflecting lens reflects the light to the second reflecting lens, the second reflecting lens reflects the light to the third reflecting lens, finally the third reflecting lens reflects the light to the first reflector, and the light reflected by the first reflector can return to the first collimator along the original optical path, so that the optical path is increased. Light returning to the first collimator can enter the coupler to interfere with the first path of light, so that the left and right of the optical signal are enhanced, and the optical signal is easier to be monitored by the detector.

With the rotation of the driving motor, the optical path can be changed by more than 55mm every time the optical path passes through one set of triangular reflectors, and the change range of the optical path is large. The optical path change of one or more cycles can be completed by rotating the driving motor for one cycle, and the optical path change speed and the cycle period number can be arbitrarily increased by changing the rotating speed of the driving motor.

Drawings

Fig. 1 is a perspective view of an optical path changing device according to an embodiment of the present invention;

FIG. 2 is a top view of the reference arm mounted on the turntable mechanism;

FIG. 3 is a perspective view of the reference arm mounted on the turntable mechanism;

FIG. 4 is a perspective view of the turntable mechanism mounted on the drive motor;

FIG. 5 is a perspective view of a reference arm with a triangular mirror and a protective housing;

FIG. 6 is an exploded view of the triangular reflector and protective housing;

FIG. 7 is a schematic view of the first mirror mounted on the support via a telescoping adjustment mechanism;

FIG. 8 is a schematic diagram of an optical interference system according to an embodiment of the present invention.

Detailed Description

The following further describes embodiments of the present invention with reference to the accompanying drawings. In which like parts are designated by like reference numerals. It should be noted that the terms "front," "back," "left," "right," "upper" and "lower" used in the following description refer to directions in the drawings, and the terms "inner" and "outer" refer to directions toward and away from, respectively, the geometric center of a particular component.

As shown in fig. 1 to 3, an optical path changing apparatus according to an embodiment of the present invention includes a driving motor 1, a turntable mechanism 2 disposed on the driving motor 1, at least one reference arm 3 disposed on the turntable mechanism 2, a first collimator 4 disposed on one side of the turntable mechanism 2, and a first mirror 5 disposed below the first collimator 4.

The reference arm 3 is fixedly mounted on the turntable mechanism 2 and can rotate integrally with the turntable mechanism 2.

The reference arm 3 includes a triangular mirror 31 for changing an optical path, and the triangular mirror 31 includes a first mirror piece 311, a second mirror piece 312, and a third mirror piece 313 which intersect each other two by two.

When the triangular reflective mirror 31 is located on the light path between the first collimator 4 and the first reflective mirror 5, the light emitted from the first collimator 4 can be reflected to the first reflective mirror 5 through the first reflective mirror 311, the second reflective mirror 312, and the third reflective mirror 313 in sequence, and the light reflected by the first reflective mirror 5 can be reflected back to the first collimator 4 through the third reflective mirror 313, the second reflective mirror 312, and the first reflective mirror 311 in sequence.

The optical path changing device provided by the invention is used for continuously changing the optical path.

The optical path changing device comprises a drive motor 1, a turntable mechanism 2, at least one reference arm 3, a first collimator 4 and a first mirror 5.

The turntable mechanism 2 is installed on an output shaft of the driving motor 1, the driving motor 1 is a stepping motor, and the driving motor 1 can drive the turntable mechanism 2 to rotate.

The reference arm 3 is an optical structure that is used to change the optical path for subsequent interference. The reference arm 3 is fixedly mounted on the turntable mechanism 2, and can integrally rotate with the turntable mechanism 2.

The reference arm 3 includes a triangular mirror 31 for changing the optical path. The triangular reflective mirror 31 is composed of a first reflective mirror 311, a second reflective mirror 312, and a third reflective mirror 313 which intersect each other two by two.

A first collimator 4 is located outside the turntable mechanism 2 and is used for beam collimation.

The first reflector 5 is located below the first collimator 4 and is used for reflecting the outgoing light from the third reflective mirror 313.

As shown in fig. 1, when the triangular reflective mirror 31 rotates to the optical path between the first collimator 4 and the first reflective mirror 5, the light emitted from the first collimator 4 is emitted to the first reflective mirror 311 along the arrow a, then the first reflective mirror 311 reflects the light to the second reflective mirror 312 along the arrow b, then the second reflective mirror 312 reflects the light to the third reflective mirror 313 along the arrow c, and finally the third reflective mirror 313 reflects the light to the first reflective mirror 5 along the arrow d. The first mirror 5 in turn reflects light against arrow d to a third mirror 313, the third mirror 313 reflects light against arrow c to a second mirror 312, the second mirror 312 reflects light against arrow b to a first mirror 311, the first mirror 311 reflects light against arrow a to the first collimator 4.

The light is emitted from the first collimator 4 and reflected back to the first collimator 4 with a period of change of optical path length. Let L be the optical path length of light from the first collimator 4 to the first mirror 311₁The optical path of light from the first mirror 311 to the second mirror 312 is L₂The optical path of light from the second mirror 312 to the third mirror 313 is L₃The optical path of light from the third mirror 313 to the first mirror 5 is L₄In a period of changing the optical path length, the changed optical path length L is 2 (L)₁+L₂+L₃+L₄). The sizes and angles of the first reflective mirror 311, the second reflective mirror 312 and the third reflective mirror 313 can be set according to requirements, so that the optical path can be changed by more than 55mm after being reflected by one set of triangular reflective mirrors 32, the change range of the optical path is large, and a better interference effect can be provided.

The optical path change can be completed in one or more cycles every time the drive motor 1 rotates one cycle, and the optical path change speed and the cycle number can be arbitrarily increased by changing the rotation speed of the drive motor 1.

In one embodiment, as shown in fig. 1, the outgoing light beam reflected by the third reflective mirror 313 to the first reflective mirror 5 is perpendicular to the first reflective mirror 5, so that all the light beams emitted to the first reflective mirror 5 are reflected by the first reflective mirror 5 back to the third reflective mirror 313, and then reflected back to the first collimator 4 through the third reflective mirror 313, the second reflective mirror 312 and the first reflective mirror 311 in sequence.

The outgoing light ray reflected by the third reflecting mirror 313 to the first reflecting mirror 5 can be perpendicular to the first reflecting mirror 5 by adjusting the angle or position of the first reflecting mirror 5.

Whether the outgoing light beam reflected by the third mirror 313 to the first mirror 5 is perpendicular to the first mirror 5 can be determined by the detector 600 shown in fig. 8.

Light returning to the first collimator 4 enters the coupler 300 and interferes with the collection of light returning from the second collimator 400.

The interference signal in the coupler 300 is strongest when all light emitted by the first collimator 4 is reflected back to the first collimator 4.

When the detector 600 detects that the optical signal is strongest, it indicates that the emergent light reflected by the third mirror 313 to the first mirror 5 is perpendicular to the first mirror 5.

In one embodiment, as shown in fig. 1, the first reflector 5 is perpendicular to the axis of the light hole 41 of the first collimator 4, and the outgoing light beam reflected by the third reflector 313 to the first reflector 5 is parallel to the axis of the light hole 41, so as to ensure that the incoming light beam of the first collimator 4 to the first reflector 311 is parallel to the outgoing light beam of the third reflector 313 to the first reflector 5, and each of the incoming light beams is parallel to the first reflector 5, so that all the light beams are reflected by the first reflector 5.

The outgoing light beam reflected by the third reflecting mirror 313 to the first reflecting mirror 5 can be parallel to the axis of the light aperture 41 by adjusting the inclination angle of the triangular reflecting mirror 31 on the turntable mechanism 2.

In one embodiment, as shown in fig. 1-3, the first mirror plate 311, the second mirror plate 312, and the third mirror plate 313 are connected in a vertical intersection of two.

The first mirror plate 311 is on top of the second mirror plate 312 and the third mirror plate 313.

In the radial direction along the turntable mechanism 2, the first reflective mirror 311 gradually inclines upwards from the inside to the outside, and the inner edge and the outer edge of the first reflective mirror 311 are respectively parallel to the reference plane of the turntable mechanism 2.

In the vertical direction, the light hole 41 of the first collimator 4 is higher than the inner edge of the first mirror piece 311 and lower than the outer edge of the first mirror piece 311.

The third mirror plate 313 is connected to the inner edge of the first mirror plate 311.

The second mirror plate 312 is connected to the rear end edge of the first mirror plate 311 in the direction along the rotation of the turntable mechanism 2.

In this embodiment, the included angle of the triangular reflective mirror 31 is a right angle, that is, the first reflective mirror 311, the second reflective mirror 312 and the third reflective mirror 313 are connected in a perpendicular intersecting manner.

When installed, the first mirror plate 311 is positioned above the second mirror plate 312 and the third mirror plate 313. The third mirror plate 313 is located at the inner edge of the first mirror plate 311. In the rotation direction of the turntable mechanism 2, one end of the first mirror piece 311 and the second mirror piece 312 passing through the first collimator 4 first is referred to as a front end, and one end of the first mirror piece passing through the first collimator 4 later is referred to as a rear end. The second mirror plate 312 is connected to the rear end edges of the first mirror plate 311 and the second mirror plate 312.

In order to direct the light exiting from the first collimator 4 towards the first mirror plate 311, the first mirror plate 311 is arranged obliquely, specifically: in a radial direction along the turntable mechanism 2, the first mirror plate 311 is inclined upward gradually from the inside to the outside, and the inner edge and the outer edge of the first mirror plate 311 are parallel to the reference plane of the turntable mechanism 2, respectively. That is, the inner edge of the first mirror plate 311 is lower than the outer edge thereof, and the first mirror plate 311 is not tilted in the rotation direction along the turntable mechanism 2. The reference plane of the turntable mechanism 2 may be the top surface or the ground surface of the disk 21, which means that the front and rear end edges of the first mirror plate 311 have the same height.

The second mirror plate 312 is held perpendicular to the reference plane of the turntable mechanism 2, and the light reflecting surface of the third mirror plate 313 is inclined upward toward the outside.

The light hole 41 of the first collimator 4 is between the inner edge and the outer edge of the first mirror 311 in the vertical direction, so that the light emitted from the first collimator 4 can be directed to the first mirror 311, then reflected by the second mirror 312 and the third mirror 313 in sequence, and directed to the first mirror 5.

In one embodiment, as shown in fig. 7, the first mirror 5 is mounted on the support 6 by a telescopic adjustment mechanism 7.

The telescopic adjusting mechanism 7 can be a screw rod, an air cylinder or an oil cylinder and other telescopic mechanisms. The telescopic end 71 of the adjusting mechanism 7 is connected with the first reflector 5 to drive the first reflector 5 to move.

Specifically, the base of the first mirror 5 is connected to the telescopic end 71.

According to the needs, the base of the first reflector 5 is connected with two adjusting mechanisms 7, the telescopic ends 71 of the two adjusting mechanisms 7 are connected on the opposite corners of the base of the first reflector 5, and when the telescopic amounts of the two telescopic ends 71 are different, the angle of the first reflector 5 can be adjusted.

The telescopic end 71 is connected to the base of the first reflector 5 by a ball pin, and the first reflector 5 is swingable with respect to the telescopic end 71.

In one embodiment, as shown in fig. 2-4, the turntable mechanism 2 includes a disk 21 and a mounting boss 22 disposed on a top surface of the disk 21.

The disc 21 is connected to the output shaft of the drive motor 1, and the reference arm 3 is mounted on the side of the mounting boss 22.

In this embodiment, the turntable mechanism 2 includes a disk 21 and a mounting boss 22, the mounting boss 22 is connected to the top surface of the disk 21, the mounting boss 22 is located at the middle portion of the disk 21, and the reference arm 3 is mounted on the side surface of the mounting boss 22 by a fastener 23 (e.g., a bolt).

In one embodiment, as shown in fig. 1-6, the reference arm 3 further includes a protective housing 32, the triangular mirror 31 is mounted in the protective housing 32, and the protective housing 32 is connected to the mounting boss 22 by a fastener 23.

In this embodiment, the protective case 32 is attached to the outer side of the triangular mirror 31, thereby protecting the triangular mirror 31. When installed, the protective housing 32 is connected to the mounting boss 22 by fasteners 23.

In one embodiment, as shown in fig. 1-6, protective housing 32 includes a first plate 321, a second plate 322, and a third plate 323 intersecting two by two.

The first mirror plate 311 is bonded to the first plate 321, the second mirror plate 312 is bonded to the second plate 322, and the third mirror plate 313 is bonded to the third plate 323.

The side surface of the mounting boss 22 has a mounting inclined surface 221, and the mounting inclined surface 221 is gradually inclined downward from the inside to the outside in a radial direction along the disk 21.

The first plate member 321 and the second plate member 322 are respectively provided with a connecting lug 324, each connecting lug 324 is respectively connected with the mounting boss 22 through a fastener 23, and the third plate member 323 is attached to the mounting inclined surface 221.

In this embodiment, the protective housing 32 is formed by connecting two of the first plate 321, the second plate 322, and the third plate 323. The first mirror plate 311 is adhered to the bottom surface of the first plate 321, the second mirror plate 312 is adhered to the inner side surface of the second plate 322, and the third mirror plate 313 is adhered to the inner side surface of the third plate 323. In order to facilitate the assembly of the protective case 32 with the mounting boss 22, the side surface of the mounting boss 22 is provided with a mounting inclined surface 221, and the top of the mounting boss 22 is narrow and the lower part is wide, so that the mounting inclined surface 221 is gradually inclined downward in the radial direction along the disk 21. Mounting holes 222 are respectively formed in one corner of the bottom and one corner of the top of the mounting inclined surface 221, connecting lugs 324 are respectively arranged on the first plate member 321 and the second plate member 322, each connecting lug 324 is respectively connected with the mounting boss 22 through a fastener 23, and the end of the fastener 23 is fastened in the mounting hole 222. After installation, the third plate 323 abuts the installation ramp 221.

In one embodiment, as shown in fig. 1-3, a plurality of reference arms 3 are uniformly distributed on the turntable mechanism 2 at intervals along the circumferential direction.

The plurality of reference arms 3 are uniformly distributed along the circumferential direction of the turntable mechanism 2, and each reference arm 3 can change the optical path once when the driving motor 1 drives the turntable mechanism 2 to rotate for a circle, so that the efficiency of changing the optical path is improved, and the optical path can be continuously changed.

As shown in fig. 8, an optical interference system according to an embodiment of the present invention includes a light source 100, a circulator 200, a detector 600, a coupler 300, a second collimator 400, a second mirror 500, and an optical path changing device according to any of the foregoing embodiments.

The light source 100, the circulator 200, the coupler 300, the second collimator 400, and the second mirror 500 are sequentially disposed at intervals.

The circulator 200, the coupler 300, and the second collimator 400 are connected in sequence by optical fibers.

The circulator 200 and the coupler 300 are connected to the probe 600 through optical fibers, respectively.

The coupler 300 is connected to the first collimator 4 through an optical fiber.

The optical interference system provided by the embodiment can be used in medical equipment.

The optical interference system includes a light source 100, a circulator 200, a detector 600, a coupler 300, a second collimator 400, a second mirror 500, and an optical path changing device.

For the structure, structure and operation principle of the optical path changing device, please refer to the description part of the optical path changing device, which is not repeated herein.

The light source 100 is an SLD light source, belonging to a broadband light source, for providing an interference light source.

The circulator 200 is used to protect the light source 100 from the reflected light causing damage to the light source 100.

The coupler 300 is used for splitting and combining light, and the splitting ratio can be arbitrarily set as required.

The second collimator 400 is used to collimate the beam.

The second mirror 500 is used to reflect the light emitted from the second collimator 400 back to the second collimator 400.

The detector 600 is used to monitor the optical signal.

Light from the light source 100 passes through the circulator 200 and enters the coupler 300. The coupler 300 splits the light beam into two paths, the first path of light beam propagating through the second collimator 400 and the second path of light beam propagating through the first collimator 4. Wherein the first light beam is used for actual detection or inspection, such as inspection of the length of the eye axis, etc., and the second light beam is used for changing the optical path to interfere with the returned first light beam in the coupler 300, and then the detector 600 can monitor the stronger optical signal for subsequent precise operation.

After the first light beam and the second light beam interfere at the coupler 300, one light beam directly passes to the detector 600. The other light beam is transmitted to the circulator 200 and then transmitted to the detector 600, no reflected light is irradiated to the light source 100, and therefore, the circulator 200 can prevent the reflected light from damaging the light source 100.

According to the needs, the above technical schemes can be combined to achieve the best technical effect.

The foregoing is considered as illustrative only of the principles and preferred embodiments of the invention. It should be noted that, for those skilled in the art, several other modifications can be made on the basis of the principle of the present invention, and the protection scope of the present invention should be regarded.