Laser scanning device

Abstract

The present application provides a laser scanning device, comprising: a laser for emitting divergent light; a collimating lens for receiving the divergent light emitted by the laser and for emitting a first parallel light; a scanning mirror for receiving the first parallel light and for changing the propagation direction of the first parallel light to emit a deflected light; a telecentric lens for receiving the deflected light emitted by the scanning mirror and for deflecting the deflected light incident from different directions into a second parallel light parallel to the optical axis of the telecentric lens; and a negative lens for receiving the second parallel light and for changing the propagation direction of the second parallel light to emit a scanning light.

Description

Technical Field

[0001] This application relates to a laser scanning device. Background Art

[0002] Existing laser scanning devices generally include a laser source, a collimating lens, and a scanning galvanometer. The collimating lens collimates the scanning light emitted by the laser source and then irradiates it onto the scanning galvanometer. The scanning galvanometer deflects to control the scanning light to exit at different angles. However, limited by high frequency and the structure of the galvanometer, the scanning range of the scanning device usually shrinks, and the scanning light at the edge position of the scanning range is affected by aberration, and the collimation and energy distribution of the laser will change. It is necessary to set a complex lens surface for the collimating lens for optimization, which increases the complexity of the optical system and also increases the design cost. Summary of the Invention

[0003] This application provides a laser scanning device in one aspect, including:

[0004] A laser for emitting divergent light;

[0005] A collimating lens for receiving the divergent light emitted by the laser and for emitting first parallel light;

[0006] A scanning mirror for receiving the first parallel light and for changing the propagation direction of the first parallel light to emit deflected light;

[0007] An afocal lens for receiving the deflected light emitted by the scanning mirror and for deflecting the deflected light incident from different directions into second parallel light parallel to the optical axis of the afocal lens; and

[0008] A negative lens for receiving the second parallel light and for changing the propagation direction of the second parallel light to emit scanning light.

[0009] The laser scanning device provided by the embodiment of this application, by setting an afocal lens, can change the first parallel light in different directions emitted from the scanning mirror into second parallel light parallel to the optical axis of the afocal lens. Then, in combination with a negative lens, the second parallel light can be diverged again into scanning light for emission, so as to obtain a larger scanning range. At the same time, when multiple beams of light emitted from the scanning mirror at different angles are incident on the negative lens, they are all parallel to the optical axis of the afocal lens. Therefore, the collimation and energy distribution of the laser at the edge position of the scanning range do not change significantly compared with the laser at the center position, and the scanning accuracy is improved with a simple combination.

[0010] In one embodiment, the collimating lens is a meta-lens, including a transparent substrate and a plurality of nanostructures disposed on the transparent substrate, and the plurality of nanostructures are used to deflect the propagation direction of the divergent light.

[0011] In one embodiment, the focal length of the collimating lens is less than 2 mm.

[0012] In one embodiment, the collimating lens is further configured to adjust the aberration of the first parallel light.

[0013] In one embodiment, the laser and the collimating lens are stacked and packaged in sequence.

[0014] In one embodiment, the focal length of the negative lens is less than the focal length of the telecentric lens.

[0015] In one embodiment, the scanning mirror includes a reflecting mirror and a deflecting device. The reflecting mirror is configured to reflect the first parallel light, and the deflecting device is configured to adjust the angle between the reflecting mirror and the first parallel light.

[0016] In one embodiment, the scanning mirror is stationary relative to the collimating lens. The scanning mirror includes a steering layer and a control device. The first parallel light passes through the steering layer, and the control device is configured to change the propagation direction of the first parallel light passing through the steering layer.

[0017] In one embodiment, the steering layer includes a plurality of liquid crystal molecules, and the control device is configured to control the deflection of the plurality of liquid crystal molecules.

[0018] In one embodiment, the laser, the collimating lens, and the scanning mirror are stacked and packaged in sequence. Description of the Drawings

[0019] Figure 1 It is a schematic structural diagram of a laser scanning device in an embodiment of the present application.

[0020] Figure 2 It is a schematic optical path diagram of a laser scanning device in an embodiment of the present application.

[0021] Figure 3 It is a schematic structural diagram of a collimating lens in an embodiment of the present application.

[0022] Figure 4 It is a schematic packaging structure diagram of a laser and a collimating lens in an embodiment of the present application.

[0023] Figure 5 It is a schematic structural diagram of a scanning mirror in an embodiment of the present application.

[0024] Description of the Main Element Symbols

[0025] Laser scanning device 100

[0026] Laser 10

[0027] Packaging structure 20

[0028] Encapsulation substrate 21

[0029] Encapsulation wall 22

[0030] Collimating lens 30

[0031] Transparent substrate 31

[0032] Nanostructure 33

[0033] Scanning mirror 50

[0034] Deflection layer 51

[0035] Control device 53

[0036] Telecentric lens 70

[0037] Negative lens 90

[0038] Divergent light L1

[0039] First parallel light L2

[0040] Deflected light Ld

[0041] Second parallel light L3

[0042] Scanning light L4

[0043] Optical axis O

[0044] Scanning plane P

[0045] Focal length f 0 、f i

[0046] Exit angle θ 0 、θ i

[0047] The following specific embodiments will further illustrate the present application in conjunction with the above drawings. Specific embodiments

[0048] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments.

[0049] Unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application.

[0050] To further elaborate on the technical means and effects adopted by this application to achieve the predetermined purpose, the following provides a detailed description of this application in conjunction with the accompanying drawings and preferred embodiments.

[0051] The embodiment of this application provides a laser scanning device, which can be applied to laser scanning projection systems with different distance, viewing angle, and resolution requirements, such as micro projectors, head-up displays, time-of-flight three-dimensional imaging devices (3D ToF). Please refer to Figure 1 , the laser scanning device 100 includes: a laser 10, a collimating lens 30, a scanning mirror 50, a telecentric lens 70, and a negative lens 90. Among them, the laser 10 is used to emit divergent light L1, the collimating lens 30 is used to receive the divergent light L1 emitted by the laser 10, and is used to emit the first parallel light L2. The scanning mirror 50 is used to receive the first parallel light L2, and is used to change the propagation direction of the first parallel light L2 and emit deflected light Ld. The telecentric lens 70 is used to receive the deflected light Ld emitted by the scanning mirror 50, and is used to deflect the deflected light Ld incident from different directions into the second parallel light L3 parallel to the optical axis O of the telecentric lens 70. The negative lens 90 is used to receive the second parallel light L3, and change the propagation direction of the second parallel light L3 to emit scanning light L4.

[0052] In this embodiment, please refer to Figure 1 and Figure 2 , the divergent light L1 emitted from the laser 10 becomes the first parallel light L2 parallel to the optical axis O of the collimating lens 30 after passing through the collimating lens 30. After the first parallel light L2 is incident on the scanning mirror 50, under the modulation of the scanning mirror 50, the deflected light Ld is emitted at an emission angle θ i , and the magnitude of the emission angle θ i depends on the deflection degree of the first parallel light L2 by the scanning mirror 50, that is, the scanning mirror 50 can emit the deflected light Ld at different magnitudes of the emission angle θ i respectively. After the deflected deflected light Ld is incident on the telecentric lens 70, it is deflected into the second parallel light L3 parallel to the optical axis O of the telecentric lens 70, that is, the deflected light Ld emitted from the scanning mirror 50 at different emission angles θ i are all deflected into the second parallel light L3 parallel to the optical axis O of the telecentric lens 70. The difference is that the deflected light Ld emitted from the scanning mirror 50 at different emission angles θ i has different distances from the optical axis O of the telecentric lens 70 when it exits the telecentric lens 70. When the emission angle θ i of the deflected light Ld is zero, the deflected light Ld coincides with the optical axis of the telecentric lens 70. When the emission angle θ i is larger, the distance between the second parallel light L3 emitted from the telecentric lens 70 and the optical axis of the telecentric lens 70 is larger. After the second parallel light L3 is incident on the negative lens 90, it is deflected by the negative lens 90 into scanning light L4, and is emitted at an emission angle θ0 Exit

[0053] In the embodiment of the present application, the laser scanning device 100 can deflect the first parallel light L2 into deflected lights Ld that are sequentially emitted at different emission angles θ by setting the scanning mirror 50. Then, by setting the telecentric lens 70, the deflected lights Ld emitted at different emission angles θ i can be converted into a second parallel light L3 parallel to the optical axis of the telecentric lens 70, so that the deflected lights Ld emitted at a larger emission angle θ i and the deflected lights Ld emitted at a smaller emission angle θ i have the same beam energy and cross-sectional size of the beam. Furthermore, when the converted second parallel light L3 is deflected by the negative lens 90 into the scanning light L4 and exits, the emission angle θ i of the scanning light L4 with a larger emission angle can be improved in beam quality. In addition, by setting the telecentric lens 70 in combination with the negative lens 90, the laser exits through the negative lens, which can bypass the structural limitations of the scanning mirror 50 itself, so that the emission angle θ 0 is greater than the emission angle θ 0 ,thereby further expanding the scanning range of the laser scanning device 100. i

[0054] In this embodiment, the laser 10 is a vertical-cavity surface-emitting laser (VCSEL). The divergent light L1 emitted from the laser 10 is approximately a point light source and is emitted outward at a certain divergence angle.

[0055] In this embodiment, please refer to Figure 3 ,the collimating lens 30 is a meta-lens, including a transparent substrate 31 and a plurality of nanostructures 33 disposed on the transparent substrate 31. The plurality of nanostructures 33 are used to change the propagation direction of the divergent light L1. Specifically, the nanostructures 33 are a plurality of densely arranged columnar structures at the nanoscale disposed on the transparent substrate 31. By setting the sizes and arrangement manners of the plurality of nanostructures 33, the light can be deflected to different degrees when passing through the combination of the transparent substrate 31 and the nanostructures 33, thereby achieving the focusing effect. The specific principle is that by setting nanostructures 33 with different sizes, the optical path differences of the light passing through different nanostructures 33 are different, so that the light has a different phase when exiting compared to when entering. By adjusting the wavefronts of the light exiting at different positions, the propagation direction of the light after exiting can be changed compared to the propagation direction of the light before exiting.

[0056] In this embodiment, a plurality of nanostructures 33 are arranged to deflect the divergent light L1 emitted by the laser 10 into a first parallel light L2 parallel to the optical axis of the collimating lens 30. In other embodiments, the arrangement of the plurality of nanostructures 33 can also be set as needed.

[0057] In this embodiment, the focal length of the collimating lens 30 is 2 mm. Specifically, since the collimating lens 30 is actually a metalens formed by the combination of the transparent substrate 31 and the nanostructures 33, the focal length of the collimating lens 30 depends on the size and arrangement of the plurality of nanostructures 33. Therefore, compared with existing lenses, it is easier for a metalens to achieve a shorter focal length, thereby making the optical path more compact and further improving the space utilization rate.

[0058] In this embodiment, the collimating lens 30 is also used to adjust the aberration of the first parallel light L2. Specifically, when collimating the divergent light L1, under the influence of off-axis aberrations (such as coma, astigmatism, and field curvature) of existing lenses, the energy distribution of the beam of the first parallel light L2 after collimation will be affected, thereby affecting the scanning effect. Therefore, existing lenses usually require optimization of the lens surface, resulting in an increase in cost and volume. By setting the collimating lens 30 as a metalens, the aberration of the first parallel light L2 can be adjusted by adjusting the arrangement of the plurality of nanostructures 33, thereby eliminating the influence of aberrations.

[0059] In this embodiment, please refer to Figure 4 , the laser 10 and the collimating lens 30 are stacked and packaged in sequence. Specifically, the laser 10 and the collimating lens 30 are fixed by a packaging structure 20. The packaging structure 20 includes a packaging substrate 21 and a packaging wall 22. The laser 10 is disposed on the packaging substrate 21, and the packaging wall 22 is a fixing structure formed by sequentially stacking on the packaging substrate 21 for fixing the collimating lens 30. By stacking and packaging the laser 10 and the collimating lens 30, a compact integrated structure can be formed between the laser 10 and the collimating lens 30, thereby improving the space utilization rate and reducing the difficulty of optical path setting.

[0060] In this embodiment, please refer to Figure 5, the scanning mirror 50 is stationary relative to the collimating lens 30. The scanning mirror 50 includes a steering layer 51 and a control device 53. The control device 53 is used to change the propagation direction of the first parallel light L2 incident on the steering layer 51. For example, the scanning mirror 50 is a liquid crystal module (Liquid Crystal Module, LCM). The steering layer 51 includes a plurality of liquid crystal molecules (not shown in the figure). After the first parallel light L2 passes through the steering layer 51, a deflected light Ld is emitted. The control device 53 is used to control the deflection of the plurality of liquid crystal molecules, so as to deflect the first parallel light L2 passing through the steering layer 51. Among them, the control device 53 includes control electrodes disposed on both sides of the steering layer 51 and corresponding control circuits. By controlling the magnitude of the voltage difference generated on both sides of the steering layer 51, the deflection degree of the liquid crystal molecules can be controlled, and further the deflection angle of the deflected light Ld can be changed.

[0061] In another embodiment, the scanning mirror 50 can also be a liquid crystal on silicon (Liquid Crystal On Silicon, LCOS) structure. The steering layer 51 is used to reflect the first parallel light L2, and the control device 53 is used to control the reflection angle of the steering layer 51 with respect to the first parallel light L2. In other embodiments, the scanning mirror 50 can also be other optical devices stationary relative to the collimating lens, and the present application does not limit this.

[0062] In this embodiment, the laser 10, the collimating lens 30, and the scanning mirror 50 are stacked and packaged in sequence. Specifically, since the scanning mirror 50 is stationary relative to the collimating lens 30, it can be stacked and packaged together with the laser 10 and the collimating lens 30, thereby further improving the space utilization rate, while reducing the difficulty of optical path setting, which is beneficial to reducing the manufacturing cost.

[0063] In other embodiments, the scanning mirror 50 includes a reflecting mirror and a deflection device (not shown in the figure). The reflecting mirror is used to reflect the first parallel light L2, and the deflection device is used to control the angle between the reflecting mirror and the first parallel light L2 to control the exit angle θ of the deflected light Ld when it exits from the scanning mirror 50. i . For example, the scanning mirror 50 can be a movable reflecting mirror composed of devices such as a microelectromechanical system (MicroelectroMechanical Systems, MEMS), a voice coil motor (Voice Coil Motor, VCM), or piezoelectric ceramics (piezoelectric ceramics, PZT).

[0064] In this embodiment, the telecentric lens 70 may include multiple lenses, which are combined to form a telecentric optical path. That is, the deflected light Ld incident at different incident angles will be deflected into the second parallel light L3 parallel to the optical axis of the telecentric lens 70. The multiple beams of the second parallel light L3 at different positions from the optical axis of the telecentric lens after deflection have the same energy distribution and the same size of the beam cross-section. Specifically, please continue to refer to Figure 2 , when the first parallel light L2 is deflected by the scanning mirror 50 and directly incident on the scanning plane P, the shape of the light spot formed on the scanning plane P will change with the exit angle θ i . If the shape of the light spot is circular when the exit angle θ i is zero, then as the exit angle θ i increases, the shape of the light spot will gradually elongate into an ellipse, and the major axis of the elliptical light spot will gradually increase, resulting in serious deformation of the light spot at the edge position and affecting the scanning effect. By setting the telecentric lens 70, the deflected light Ld corresponding to the edge position can be first converted into the second parallel light L3 with the same beam cross-section as the middle position, and then emitted through the negative lens 90. At this time, the shape of the light spot formed on the scanning plane P will not be affected by the exit angle θ i , thereby improving the scanning accuracy.

[0065] In this embodiment, the negative lens 90 is used to deflect the second parallel light L3 into the scanning light L4, so as to achieve scanning within a certain range. Specifically, please continue to refer to Figure 1 and Figure 2 , the negative lens 90 is coaxially arranged with the telecentric lens 70. The second parallel light L3 passing through the center of the negative lens 90 along the optical axis does not change its propagation direction, while the second parallel light L3 at a certain distance from the optical axis will be deflected by a certain amount and exit at an exit angle θ 0 .

[0066] In this embodiment, the focal length f 0 of the negative lens 90 is less than the focal length f i of the telecentric lens 70. Specifically, the exit angle θ 0 of the scanning light L4 is related to the exit angle θ i when the deflected light Ld exits from the scanning mirror 50, the focal length f 0 of the negative lens 90, and the focal length f i of the telecentric lens 70. The exit angle θ 0 can be expressed as:

[0067] θ 0 = arctan(f i * tanθ i / f 0 );

[0068] It can be seen that when the focal length f of the negative lens 900 less than the focal length f of the telecentric lens 70 i When this occurs, the exit angle θ of the scanning light L4 0 is greater than the exit angle θ when the deflected light Ld exits from the scanning mirror 50 i . That is, the scanning range of the scanning light L4 is greater than the deflection range of the scanning mirror 50 for the deflected light Ld. Thus, an expansion of the scanning range is achieved. In other embodiments, the focal length f of the negative lens 90 0 may also be equal to the focal length f of the telecentric lens 70 i , such that the range of the scanning light L4 is equal to the deflection range of the scanning mirror 50 for the deflected light Ld. At this time, the scanning light L4 exiting after passing through the telecentric lens 70 and the negative lens 90 can still optimize the light in the off-axis part with respect to the deflected light Ld.

[0069] In the embodiments of the present application, by providing the collimating lens 30, the telecentric lens 70, and the negative lens 90, the exit angle θ 0 of the scanning light L4 when it is relatively large can be optimized. By providing the collimating lens 30, it is beneficial to optimize the aberration of the first parallel light L2 after collimation, such that the beam energy distribution of the optimized first parallel light L2 is uniform. By providing the telecentric lens 70, it is beneficial to deflect the deflected light Ld exiting at different exit angles into the second parallel light L3 parallel to the optical axis of the telecentric lens 70, so that the multiple deflected second parallel lights L3 all have the same beam energy and beam cross-sectional size. Then, by providing the negative lens 90 to deflect the second parallel lights L3 at different positions and exit them as the scanning light L4, the scanning light L4 irradiated on the scanning plane P has the same spot shape and energy distribution, thereby improving the scanning accuracy.

[0070] In the embodiments of the present application, by providing the collimating lens 30 as a meta-lens and integrally packaging the laser 10 and the collimating lens 30, it is beneficial to improve the volume utilization rate, shorten the optical path, and reduce the difficulty of optical path design, thereby reducing costs.

[0071] Those of ordinary skill in the art of this technology should recognize that the above embodiments are merely used to illustrate the present application and are not intended to limit the present application. As long as appropriate changes and variations made to the above embodiments fall within the scope of the spirit of the present application, they fall within the scope of protection required by the present application.

Claims

1. A laser scanning device, characterized in that, it includes: a laser for emitting divergent light; a collimating lens for receiving the divergent light emitted by the laser and for emitting first parallel light; a scanning mirror for receiving the first parallel light and for changing the propagation direction of the first parallel light to emit deflected light; a telecentric lens for receiving the deflected light emitted by the scanning mirror and for deflecting the deflected light incident from different directions into second parallel light parallel to the optical axis of the telecentric lens; and a negative lens for receiving the second parallel light and for changing the propagation direction of the second parallel light to emit scanning light; wherein, the focal length of the negative lens is less than the focal length of the telecentric lens.

2. The laser scanning device according to claim 1, characterized in that, the collimating lens is a meta-lens, including a transparent substrate and a plurality of nanostructures disposed on the transparent substrate, and the plurality of nanostructures are used for deflecting the propagation direction of the divergent light.

3. The laser scanning device according to claim 2, characterized in that, the focal length of the collimating lens is less than 2 mm.

4. The laser scanning device according to claim 2, characterized in that, the collimating lens is further used for adjusting the aberration of the first parallel light.

5. The laser scanning device according to claim 2, characterized in that, the laser and the collimating lens are sequentially laminated and encapsulated.

6. The laser scanning device according to claim 1, characterized in that, the scanning mirror includes a reflecting mirror and a deflecting device, the reflecting mirror is used for reflecting the first parallel light, and the deflecting device is used for adjusting the included angle between the reflecting mirror and the first parallel light.

7. The laser scanning device according to claim 1, characterized in that, the scanning mirror is stationary relative to the collimating lens, and the scanning mirror includes a steering layer and a control device, and the control device is used for changing the propagation direction of the first parallel light incident on the steering layer.

8. The laser scanning device according to claim 7, characterized in that, the steering layer includes a plurality of liquid crystal molecules, the first parallel light passes through the steering layer, and the control device is used for controlling the deflection of the plurality of liquid crystal molecules.

9. The laser scanning device according to claim 7, characterized in that, the laser, the collimating lens and the scanning mirror are sequentially laminated and encapsulated.

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