Projection device and projection method based on cooperative scanning of optical fiber and galvanometer

Abstract

The invention discloses a projection device and a projection method based on cooperative scanning of an optical fiber and a galvanometer, and relates to the technical field of optical scanning and projection. Comprising a laser light source, a single-mode optical fiber used for conducting laser, an optical fiber driver used for driving the tail end of the single-mode optical fiber to vibrate, a two-dimensional galvanometer system used for reflecting laser emitted by the single-mode optical fiber, a galvanometer driver used for driving the two-dimensional galvanometer system and a synchronous control unit. The galvanometer only needs to perform low-frequency and large-step-length movement, and the mechanical bottleneck of high-speed large-angle deflection is avoided. And a high-frequency part is borne by inertia-free optical fiber vibration, so that high-frame-rate scanning is realized on the whole. The effective scanning range is expanded; the image brightness is improved; finally, dynamic distortion is reduced through slow movement of the galvanometer, nonlinear distortion is not prone to being generated through small-range scanning of the optical fiber, and the complexity of device correction is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical scanning and projection technology, and more particularly to a projection device and a projection method based on cooperative scanning of an optical fiber and a galvanometer. BACKGROUND

[0002] At present, the existing laser scanning projection system mostly uses a MEMS galvanometer or a galvanometer as a core scanning component. The basic principle is to form a two-dimensional scanning track on a projection surface by deflection of two galvanometers (corresponding to X and Y axes respectively) to reflect a laser beam.

[0003] However, such a system has the following technical bottlenecks: Contradiction between frame rate and scanning range: as a mechanical component, the deflection angle and speed of the galvanometer are limited by mechanical inertia. To obtain a large scanning range (large angle deflection), a longer stable time is needed, thereby resulting in a decrease in system frame rate. Conversely, under a high frame rate mode, the scanning range is necessarily limited.

[0004] Limitation of resolution and brightness: under a fixed frame rate and scanning range, if the image resolution is to be improved, more scanning points need to be added in unit time, which requires the galvanometer to vibrate at a higher frequency, which is difficult to design, and the single-point dwell time is shortened, resulting in a decrease in average brightness.

[0005] Nonlinearity and distortion: the scanning track of the galvanometer is usually grating or Lissajous, which is prone to nonlinear distortion in the edge area, and complex software algorithms are needed for correction.

[0006] Therefore, how to overcome the above bottlenecks is a problem that needs to be solved by those skilled in the art. SUMMARY

[0007] Therefore, the present application provides a projection device and a projection method based on cooperative scanning of an optical fiber and a galvanometer, aiming to overcome the inherent contradiction between frame rate, scanning range and brightness of the existing galvanometer scanning technology, and by cooperation of high-frequency micro-scan of the optical fiber and low-frequency macro-scan of the galvanometer, the scanning field of view of the system is effectively expanded, the equivalent frame rate and image brightness are improved, and the system structure is simplified without improving the performance limit of the galvanometer itself.

[0008] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions: A projection device based on cooperative scanning of an optical fiber and a galvanometer, comprising: a laser light source, a single-mode optical fiber for conducting laser light, an optical fiber driver for driving the end of the single-mode optical fiber to vibrate, a two-dimensional galvanometer system for reflecting the emitted laser light of the single-mode optical fiber, a galvanometer driver for driving the two-dimensional galvanometer system, and a synchronous control unit. The synchronization control unit is configured to perform the following operations: controlling the galvanometer driver to make the two-dimensional galvanometer system step to a series of macro scanning positions and keep stable; during the stable period of each macro scanning position, controlling the fiber driver to make the single-mode fiber end vibrate at a high frequency according to a preset rule to realize scanning of a local area, after completing the scanning of the current local area, driving the two-dimensional galvanometer system to step to the next macro scanning position, and repeating the above process until the projection of the entire frame image is completed.

[0009] Optionally, the final light spot coordinates (U, V) on the projection surface are obtained by vector superposition of the macro scanning position (U_g, V_g) and the local offset (u_f, v_f) generated by the high-frequency vibration of the fiber.

[0010] Optionally, the superposition is performed by the following formula: U=U_g+u_f V=V_g+v_f.

[0011] Optionally, the fiber driver is a piezoelectric ceramic driver.

[0012] Optionally, the synchronization control unit divides the scanning time of a frame of image into a plurality of macro frames corresponding to the macro scanning positions by time division, and each macro frame is further divided into a plurality of micro frames corresponding to complete local scanning of the fiber.

[0013] Optionally, the light spot position (U, V) and the galvanometer deflection angle (θ_x, θ_y) have a fixed mapping relationship, which is: U_g=k_x θ_x(t) V_g=k_y θ_y(t) wherein k_x and k_y are optical magnification coefficients; (U, V) is a two-dimensional coordinate system of the projection surface; and the deflection angle of the galvanometer system is (θ_x(t), θ_y(t)). Optionally, the synchronization control unit further includes coordinate synthesis, specifically, at any time t, the light spot coordinates (U(t), V(t)) on the projection surface are determined by the following formula: U(t)=k_x θ_x(t)+k_f _x(t) V(t)=k_y θ_y(t)+k_f _y(t) wherein k_f is an optical magnification coefficient of fiber scanning. Optionally, for the time t_{p,q} corresponding to the macro frame p and the micro frame q, the light spot position is: U(p,q)=U_g[p]+u_f[q] V(p,q) = V_g[p] + v_f[q] Where (u_f[q], v_f[q]) are the local coordinates of the optical fiber scanned in the q-th microframe, and |u_f[q]|≤ΔU_f / 2,|v_f[q]|≤ΔV_f / 2.

[0014] A projection method based on fiber optic and galvanometer co-scanning includes the following steps: 1) Determine the overall scanning parameters of the target image, including the macro-scan position sequence of the two-dimensional galvanometer system and the micro-scan sequence of the optical fiber at each macro-scan position; 2) Drive the two-dimensional galvanometer system to the current macro-scan position; 3) When the two-dimensional galvanometer system is in a stable state, drive the single-mode fiber to vibrate according to the current micro-scanning sequence, and at the same time modulate the intensity of the laser source to form a local image centered on the current macro-scanning position on the projection surface; 4) After completing the scanning of the current local image, drive the two-dimensional galvanometer system to step to the next macro-scan position and repeat the above process until the projection of the entire frame image is completed.

[0015] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a projection device and projection method based on optical fiber and galvanometer cooperative scanning, which has the following beneficial effects: Significantly improved equivalent frame rate: The galvanometer only needs to move at low frequency and with large step size, avoiding the mechanical bottleneck of high-speed, large-angle deflection. The high-frequency part is handled by the vibration of the non-inertial fiber, thus achieving high frame rate scanning as a whole.

[0016] Expanding the effective scanning range: The total scanning range of the system is determined by the maximum deflection angle of the galvanometer, while the resolution of the image is determined by the fine scanning capability of the optical fiber. This successfully decouples the coupling relationship between range and resolution / frame rate, achieving high-resolution projection over a large area.

[0017] Improved image brightness: Because the galvanometer remains stable at each positioning point, the optical fiber has enough time to scan the local area. The single-point dwell time is longer than that of a high-speed pure galvanometer system, resulting in higher average optical power and a brighter image.

[0018] Reduced image distortion: The slow movement of the galvanometer reduces dynamic distortion, while the small-range scanning of the fiber itself makes it less prone to nonlinear distortion, thus reducing the complexity of system correction. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the device structure provided by the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] This invention discloses a projection device based on fiber optic and galvanometer cooperative scanning, such as... Figure 1 As shown, it includes: a laser source, a single-mode fiber for transmitting laser light, a fiber driver for driving the end of the single-mode fiber to vibrate, a two-dimensional galvanometer system for reflecting the laser light emitted from the single-mode fiber, a galvanometer driver for driving the two-dimensional galvanometer system, and a synchronization control unit. The synchronization control unit is configured to perform the following operations: control the galvanometer driver to step the two-dimensional galvanometer system to a series of macro-scan positions and keep it stable; during the stabilization period of each macro-scan position, control the fiber driver to make the end of the single-mode fiber vibrate at a high frequency according to a preset pattern to achieve scanning of a local area; after completing the scanning of the current local area, drive the two-dimensional galvanometer system to step to the next macro-scan position and repeat the above process until the projection of the entire frame image is completed.

[0023] Specifically, the fiber optic driver can be a piezoelectric ceramic driver or a driving device based on other principles.

[0024] The vibration trajectory at the end of a single-mode fiber can be a liissajous pattern, a spiral, or a grating.

[0025] The core idea of ​​this invention is to expand a single galvanometer scanning point into a local high-resolution sub-region composed of fiber scanning. The fiber is responsible for high-speed, small-area fine scanning, while the galvanometer is responsible for low-speed, large-area coarse positioning. Through mathematical coordination, the two jointly determine the final position of the light spot on the projection surface.

[0026] Let the projection plane be a two-dimensional coordinate system (U,V).

[0027] The deflection angle of the galvanometer system is (θ_x(t), θ_y(t)). In a traditional system that does not consider cooperative scanning, the spot position (U, V) and the galvanometer deflection angle (θ_x, θ_y) have a fixed mapping relationship, which can be simplified as: U_g=k_x θ_x(t) V_g=k_y θ_y(t) Where k_x and k_y are optical magnification factors.

[0028] Fiber optic scanning deflects the emitted light rays by driving micromechanical vibrations at its end, which can be described as ( _x(t), _y(t)). This is a high-frequency (e.g., kHz level) small-angle scan.

[0029] The key improvement of this invention lies in the fact that the scanning center of the optical fiber is no longer fixed, but is modulated in real time by the position of the galvanometer. The coordinates of the final emitted light point are the vector superposition of the optical fiber scanning and the galvanometer scanning.

[0030] Let the total scanning time be T, and the target image consist of N x M pixels.

[0031] Time division: The total time T is divided into P macroframes, each macroframe corresponding to a stable position of the galvanometer. Each macroframe contains Q microframes, each microframe corresponding to a complete local scan of the optical fiber (such as a Lissajous pattern).

[0032] Coordinate composition: At any time t, the coordinates (U(t), V(t)) of the light point on the projection surface are determined by the following formula: U(t)=k_x θ_x(t)+k_f _x(t) V(t) = k_y θ_y(t)+k_f _y(t) Where k_f is the optical magnification factor for fiber scanning.

[0033] Collaborative control strategy: The motion of the galvanometer is slowly variable. Within a macroframe time ΔT_macro, θ_x and θ_y can be regarded as constants or slowly changing ramps, i.e., θ_x(t)≈Θ_x[p], θ_y(t)≈Θ_y[p], where p is the current macroframe index.

[0034] movement of optical fibers _x(t) and _y(t) is rapidly changing, with a frequency much higher than the update frequency of the galvanometer. They complete a preset local scanning pattern within a microframe.

[0035] The galvanometer's role is to point and position it to the center coordinates (U_g[p], V_g[p]) of the target sub-region (i.e., the region corresponding to the p-th macroframe).

[0036] The optical fiber's function is to scan all pixels within a local area centered at (U_g[p], V_g[p]) using high-frequency vibration. Its scanning range covers a rectangular or circular area of ​​size (ΔU_f, ΔV_f).

[0037] Therefore, the above coordinate synthesis formula can be concretized into a discrete form. For time t_{p,q} corresponding to macroframe p and microframe q, the position of the light spot is: U(p,q)=U_g[p]+u_f[q] V(p,q) = V_g[p] + v_f[q] Where (u_f[q], v_f[q]) are the local coordinates of the optical fiber scanned in the q-th microframe, and |u_f[q]|≤ΔU_f / 2,|v_f[q]|≤ΔV_f / 2.

[0038] In this way, the galvanometer only needs to move P positions to cover the entire field of view, and at each position, the optical fiber contributes Q pixels through its high frame rate local scanning. The total number of pixels in the system is NM≈PQ, but the equivalent frame rate is much higher than the frame rate of a pure galvanometer scanning of P points.

[0039] Specifically, the workflow is as follows: Step 1, Initialization: Set the target image resolution (e.g., 1000x1000), determine the number of galvanometer step points P (e.g., 50x50), and the number of fiber optic scanning points Q for each local region (e.g., 20x20). Q should be slightly larger than the total number of pixels to allow for overlapping scans.

[0040] Step 2, galvanometer positioning: The control unit calculates the p-th target position (Θ_x[p],Θ_y[p]) of the galvanometer and drives the galvanometer to this position and keeps it stable.

[0041] Step 3, Fiber Microscanning: During the period when the galvanometer is stable (macroframe), the fiber driver drives the fiber end with a high-frequency signal to move according to a preset pattern. _x(t) and The laser vibrates regularly, and its intensity is modulated according to the gray value of the target image at point (p,q). At this time, the trajectory of the light spot on the projection surface is a local scanning pattern centered at (U_g[p],V_g[p]).

[0042] Step 4, Synchronous Switching: When a macroframe ends, the control unit immediately commands the galvanometer to move to the next position (p+1), and the optical fiber begins scanning the next local area. This process requires precise synchronization between the galvanometer's settling time and the optical fiber's micro-scanning period.

[0043] Step 5: Repeat steps 2-4 until all P galvanometer positions have been traversed, thus completing the projection of a complete frame of image.

[0044] Example: Suppose that the galvanometer scans a 3x3 grid (P=9), and the optical fiber scans a 2x2 local region at each location (Q=4).

[0045] Galvanometer position: (U_g,V_g):(-1,-1),(0,-1),(1,-1),(-1,0),(0,0),(1,0),(-1,1),(0,1),(1,1) Local coordinates of the optical fiber (u_f, v_f): (-0.1, -0.1), (0.1, -0.1), (-0.1, 0.1), (0.1, 0.1) When the galvanometer is at position (0,0), the coordinates of the four points scanned by the optical fiber are: (0-0.1,0-0.1)=(-0.1,-0.1) (0+0.1,0-0.1)=(0.1,-0.1) (0-0.1,0+0.1)=(-0.1,0.1) (0+0.1,0+0.1)=(0.1,0.1) By combining the four fiber points at all nine galvanometer positions, a 6x6 high-resolution image can be obtained, while the galvanometer itself only moves nine times.

[0046] A projection method based on fiber optic and galvanometer co-scanning includes the following steps: 1) Determine the overall scanning parameters of the target image, including the macro-scan position sequence of the two-dimensional galvanometer system and the micro-scan sequence of the optical fiber at each macro-scan position; 2) Drive the two-dimensional galvanometer system to the current macro-scan position; 3) When the two-dimensional galvanometer system is in a stable state, drive the single-mode fiber to vibrate according to the current micro-scanning sequence, and at the same time modulate the intensity of the laser source to form a local image centered on the current macro-scanning position on the projection surface; 4) After completing the scanning of the current local image, drive the 2D galvanometer system to step to the next macro-scan position, and repeat the above process until the projection of the entire frame image is completed. Specifically, the macro-scan position sequence of the two-dimensional galvanometer system constitutes a coarse coverage of the projected field of view, while the micro-scan sequence of the optical fiber is responsible for pixel filling of each sub-region under the coarse coverage.

[0047] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0048] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A projection device based on fiber optic and galvanometer co-scanning, characterized in that, include: The system includes a laser source, a single-mode optical fiber for transmitting laser light, an optical fiber driver for driving the end of the single-mode optical fiber to vibrate, a two-dimensional galvanometer system for reflecting the laser light emitted from the single-mode optical fiber, a galvanometer driver for driving the two-dimensional galvanometer system, and a synchronization control unit. The synchronization control unit is configured to perform the following operations: control the galvanometer driver to step the two-dimensional galvanometer system to a series of macro-scan positions and maintain stability; during the stabilization period of each macro-scan position, control the fiber driver to cause the end of the single-mode fiber to vibrate at high frequency according to a preset pattern to achieve scanning of a local area; after completing the scanning of the current local area, drive the two-dimensional galvanometer system to step to the next macro-scan position and repeat the above process until the projection of the entire frame image is completed.

2. The projection device based on fiber optic and galvanometer co-scanning according to claim 1, characterized in that, It also includes the final light spot coordinates (U, V) on the projection surface, which are obtained by vector superposition of the macro-scan position (U_g, V_g) and the local offset (u_f, v_f) generated by the high-frequency vibration of the optical fiber.

3. A projection device based on fiber optic and galvanometer co-scanning according to claim 2, characterized in that, It is obtained by superimposing the following formulas: U = U_g + u_f V = V_g + v_f.

4. The projection device based on fiber optic and galvanometer cooperative scanning according to claim 1, characterized in that, The fiber optic driver is a piezoelectric ceramic driver.

5. A projection device based on fiber optic and galvanometer cooperative scanning according to claim 1, characterized in that, The synchronization control unit divides the scanning time of an image frame into multiple macroframes corresponding to macro-scanning positions by time division, and each macroframe is further divided into multiple microframes corresponding to complete local scanning of the optical fiber.

6. A projection device based on fiber optic and galvanometer cooperative scanning according to claim 1, characterized in that, The position of the light spot (U,V) and the deflection angle of the galvanometer (θ_x,θ_y) have a fixed mapping relationship as follows: U_g=k_x θ_x(t) V_g=k_y θ_y(t) Where k_x and k_y are optical magnification coefficients; (U, V) is the two-dimensional coordinate system of the projection plane; and the deflection angle of the galvanometer system is (θ_x(t), θ_y(t)).

7. A projection device based on fiber optic and galvanometer cooperative scanning according to claim 6, characterized in that, The synchronization control unit also includes coordinate synthesis, specifically, at any time t, the coordinates (U(t), V(t)) of the light spot on the projection surface are jointly determined by the following formula: U(t)=k_x θ_x(t)+k_f _x(t) V(t)=k_y θ_y(t)+k_f _y(t) Where k_f is the optical magnification factor for fiber scanning.

8. A projection device based on fiber optic and galvanometer cooperative scanning according to claim 5, characterized in that, For the times t_{p,q} corresponding to macroframe p and microframe q, the position of the light spot is: U(p,q)=U_g[p]+u_f[q] V(p,q) = V_g[p] + v_f[q] Where (u_f[q], v_f[q]) are the local coordinates of the optical fiber scanned in the q-th microframe, and |u_f[q]|≤ΔU_f / 2,|v_f[q]|≤ΔV_f / 2.

9. A projection method based on fiber optic and galvanometer co-scanning, applied to a projection device based on fiber optic and galvanometer co-scanning as described in any one of claims 1-8, comprising the following steps: 1) Determine the overall scanning parameters of the target image, including the macro-scan position sequence of the two-dimensional galvanometer system and the micro-scan sequence of the optical fiber at each macro-scan position; 2) Drive the two-dimensional galvanometer system to the current macro-scan position; 3) When the two-dimensional galvanometer system is in a stable state, drive the single-mode fiber to vibrate according to the current micro-scanning sequence, and at the same time modulate the intensity of the laser source to form a local image centered on the current macro-scanning position on the projection surface; 4) After completing the scanning of the current local image, drive the two-dimensional galvanometer system to step to the next macro-scan position and repeat the above process until the projection of the entire frame image is completed.

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