A micro-projection scanning system

Abstract

The present application discloses a micro-projection scanning system, comprising: a first MEMS scanning mirror, a relay reflection device, a collimating lens, a second MEMS scanning mirror and a projection screen; wherein the laser beam is subjected to a one-dimensional scanning in a first scanning angle resonant motion in the horizontal direction by the first MEMS scanning mirror, and then is reflected multiple times by the relay reflection device to expand and fold the horizontal field of view of the first MEMS scanning mirror, and then the laser beam after multiple reflections is collimated by the collimating lens, and the size of the pixel point is controlled, and finally the laser beam is subjected to another dimensional scanning in a second scanning angle quasi-static motion in the vertical direction by the second MEMS scanning mirror to irradiate the projection screen; the maximum value of the first scanning angle is less than the maximum value of the second scanning angle. The above-mentioned micro-projection scanning system has a simple structure, and can not only realize two-dimensional image scanning, but also realize high-resolution and large field of view display.

Description

Technical Field

[0001] The present invention relates to the field of micro-projection technology, and in particular to a micro-projection scanning system. Background Art

[0002] Laser micro-projection is mainly used in head-up displays for smart car screens, wearable devices such as AR and VR, various consumer electronic products such as smart phones and digital cameras, artificial intelligence, and biomedicine.

[0003] Most of the existing micro-projectors on the market are area array spatial light modulation projection displays, such as liquid crystal display (LCD), digital light processing (DLP), and liquid crystal on silicon (LCoS). Their resolution and field of view are determined by the number of physical units of the spatial light modulator. To achieve a large field of view, the size, weight and power consumption of the projection equipment need to be increased, and the light utilization rate is not high. DLP technology is difficult to achieve in reducing the pixel pitch, and it is difficult to achieve high-resolution display on micro-projection. In addition, laser beam steering (LBS) is an emerging technology in the field of micro-projection and belongs to scanning light modulation.

[0004] At present, laser scanning mainly adopts multi-prism scanning mirrors and galvanometer technology based on the rotation or twisting of light reflectors. Traditional raster scanning projection often uses galvanometer-rotating mirror combination and galvanometer-galvanometer combination. The galvanometer-rotating mirror combination scanning system is large in size, low in scanning frequency, high in driving power consumption, high in cost, short in life, and it is difficult for the rotating mirror to maintain good stability during high-speed movement. In addition, there is also a scanning projection display based on a single dual-axis MEMS scanning mirror, that is, the scanning point performs simple harmonic motion in the x and y directions at the same time, directly realizing two-dimensional scanning. Although it has great advantages in device volume and aberration, the dual-axis MEMS scanning mirror structure is more complicated, and it is necessary to consider whether there is a problem of mechanical coupling between the torsion of the two axes. The isolation of the two signals must be considered in the path of the drive signal. During manufacturing, more than two process steps need to be added to achieve the isolation of the drive signal, which makes control more difficult and the scanning angle is limited.

[0005] The use of a galvanometer-galvanometer combined scanning system for line-by-line scanning makes it easy to infer and determine the image in terms of encoding and timing control, easy to make, and low cost. However, due to the optical path and the inherent scanning distortion of the galvanometer scanning method, pincushion distortion will appear in the x direction and barrel distortion will appear in the y direction. The resolution is related to the mechanical half-angle of the MEMS scanning mirror and the scanning frequency of the horizontal scanning galvanometer. To achieve high-resolution display, high-frequency horizontal scanning is required. When the MEMS scanning mirror vibrates at high frequency, it needs to work at the resonance point, otherwise it will produce high damping, resulting in a small scanning range, affecting the stability and response speed of the mechanical structure. The higher the inherent vibration angular frequency, the smaller the scanning angle when the MEMS scanning mirror works at the resonance point. Therefore, high-resolution display restricts the mechanical half-angle of the horizontal scanning galvanometer. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a micro-projection scanning system with a simple structure and capable of achieving high-resolution and large-viewing-angle display. The specific scheme is as follows:

[0007] A micro-projection scanning system, comprising:

[0008] A first MEMS scanning mirror is used to perform a one-dimensional scanning of the incident laser beam in a horizontal direction at a first scanning angle resonant motion;

[0009] A relay reflection device, used for multiple reflection of the laser beam scanned by the first MEMS scanning mirror, so as to expand and fold the horizontal field of view of the first MEMS scanning mirror;

[0010] A collimating lens, arranged on the reflected light path of the relay reflector, for collimating the laser beam after multiple reflections and controlling the size of the pixel points;

[0011] A second MEMS scanning mirror is used to perform another-dimensional scanning of the collimated laser beam at a second scanning angle in a quasi-static motion in a vertical direction; the maximum value of the first scanning angle is less than the maximum value of the second scanning angle;

[0012] The projection screen is used to receive the laser beam scanned by the second MEMS scanning mirror.

[0013] Preferably, in the above-mentioned micro-projection scanning system provided by an embodiment of the present invention, the scanning frequency of the first MEMS scanning mirror is greater than the scanning frequency of the second MEMS scanning mirror.

[0014] Preferably, in the micro-projection scanning system provided by an embodiment of the present invention, the relay reflection device comprises a first reflection mirror, a second reflection mirror, a third reflection mirror and a fourth reflection mirror arranged on the transmission optical path of the laser beam; wherein,

[0015] The first reflecting mirror is used to reflect the laser beam scanned by the first MEMS scanning mirror to the second reflecting mirror;

[0016] The second reflecting mirror is used to reflect the laser beam to the third reflecting mirror;

[0017] The first reflector and the second reflector are used to expand the horizontal field of view of the first MEMS scanning mirror;

[0018] The third reflecting mirror is used to reflect the laser beam to the fourth reflecting mirror;

[0019] The fourth reflecting mirror is used to reflect the laser beam to the collimating lens;

[0020] The third reflector and the fourth reflector are used to fold the horizontal field of view of the first MEMS scanning mirror so that the laser beam can be reflected by the second MEMS scanning mirror.

[0021] Preferably, in the micro-projection scanning system provided by the embodiment of the present invention, the first reflector and the second reflector are long strip-shaped plane reflectors.

[0022] Preferably, in the above-mentioned micro-projection scanning system provided by the embodiment of the present invention, the reflection surfaces of the third reflection mirror and the fourth reflection mirror are both spherical surfaces.

[0023] Preferably, in the above-mentioned micro-projection scanning system provided by the embodiment of the present invention, the third reflector and the fourth reflector are elongated spherical reflectors with different optical focal powers.

[0024] Preferably, in the above-mentioned micro-projection scanning system provided by the embodiment of the present invention, the sizes of the first MEMS scanning mirror and the second MEMS scanning mirror are both in the order of several millimeters.

[0025] It can be seen from the above technical scheme that a micro-projection scanning system provided by the present invention includes: a first MEMS scanning mirror, used to perform one-dimensional scanning of an incident laser beam in a horizontal direction at a first scanning angle resonant motion; a relay reflection device, used to reflect the laser beam scanned by the first MEMS scanning mirror for multiple times, and expand and fold the horizontal field of view of the first MEMS scanning mirror; a collimating lens, arranged on the reflection light path of the relay reflection device, used to collimate the laser beam after multiple reflections, and control the size of the pixel points; a second MEMS scanning mirror, used to perform another-dimensional scanning of the collimated laser beam in a vertical direction at a second scanning angle quasi-static motion; the maximum value of the first scanning angle is less than the maximum value of the second scanning angle; and a projection screen, used to receive the laser beam scanned by the second MEMS scanning mirror.

[0026] The laser projection scanning system provided by the present invention has a simple structure. Since the maximum value of the first scanning angle is smaller than the maximum value of the second scanning angle, that is, the first MEMS scanning mirror performs a small-angle scanning in the horizontal direction to ensure that the galvanometer achieves a higher resonant frequency and reliability, and the second MEMS scanning mirror performs a large-angle scanning in the vertical direction to ensure that the vertical field of view of the display is large enough, thereby not only realizing two-dimensional image scanning, but also realizing high-resolution and large field of view angle display. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0028] Figure 1 A main structural diagram of a micro-projection scanning system provided by an embodiment of the present invention;

[0029] Figure 2 A front view of a micro-projection scanning system provided by an embodiment of the present invention;

[0030] Figure 3 A top view of a micro-projection scanning system provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The present invention provides a micro-projection scanning system, such as Figures 1 to 3 As shown, it includes: a first MEMS scanning mirror (first micro-vibration mirror) 1, a relay reflection device (including a first reflection mirror 2, a second reflection mirror 3, a third reflection mirror 4 and a fourth reflection mirror 5), a collimating lens 6, a second MEMS scanning mirror (second micro-vibration mirror) 7 (or 9), and a projection screen 8; wherein,

[0033] A first MEMS scanning mirror 1 is used to perform a one-dimensional scanning of the incident laser beam in a horizontal direction at a first scanning angle (i.e., a scanning angle of the first MEMS scanning mirror); Figure 3 It shows two beam directions 12 and 13 of horizontal scanning of the first MEMS scanning mirror 1 in the resonant state;

[0034] A relay reflection device, used for multiple reflection of the laser beam scanned by the first MEMS scanning mirror, so as to expand and fold the horizontal field of view of the first MEMS scanning mirror;

[0035] The collimating lens 6 is arranged on the reflected light path of the relay reflector and is used to collimate the laser beam after multiple reflections and control the size of the pixel point;

[0036] The second MEMS scanning mirror 7 (or 9) is used to perform another-dimensional scanning of the collimated laser beam at a second scanning angle (i.e., the scanning angle of the second MEMS scanning mirror) in a quasi-static motion in a vertical direction; the maximum value of the first scanning angle is less than the maximum value of the second scanning angle; Figure 2 Two beam directions 10 and 11 are shown when the second MEMS scanning mirror is in a quasi-static motion and scans in a vertical direction; when the second MEMS scanning mirror is in position 7, the scanning beam propagates along direction 10; when the second MEMS scanning mirror is in position 9, the scanning beam propagates along direction 11;

[0037] The projection screen 8 is used to receive the laser beam scanned by the second MEMS scanning mirror 7 (or 9).

[0038] In the above-mentioned micro-projection scanning system provided by the embodiment of the present invention, it includes: a first MEMS scanning mirror, a relay reflection device, a collimating lens, a second MEMS scanning mirror and a projection screen; wherein, the laser beam is subjected to a first scanning angle resonant motion one-dimensional scanning in the horizontal direction by the first MEMS scanning mirror, and then is reflected multiple times by the relay reflection device to expand and fold the horizontal field of view of the first MEMS scanning mirror, and then the laser beam after multiple reflections is collimated by the collimating lens, and the size of the pixel point is controlled, and finally the laser beam is subjected to a second scanning angle quasi-static motion in the vertical direction by the second MEMS scanning mirror to be scanned in another dimension and irradiated onto the projection screen; the maximum value of the first scanning angle is less than the maximum value of the second scanning angle. The above-mentioned laser projection scanning system has a simple structure. Since the maximum value of the first scanning angle is less than the maximum value of the second scanning angle, that is, the first MEMS scanning mirror performs a small angle scanning in the horizontal direction to ensure that the galvanometer achieves a higher resonant frequency and reliability, and the second MEMS scanning mirror performs a large angle scanning in the vertical direction to ensure that the vertical field of view of the display is large enough, thereby realizing not only two-dimensional image scanning, but also high resolution and large field angle display.

[0039] In the specific implementation, in the micro-projection scanning system provided by the embodiment of the present invention, the scanning frequency of the first MEMS scanning mirror is greater than the scanning frequency of the second MEMS scanning mirror. The first MEMS scanning mirror is used as a fast scanning mirror, responsible for scanning at a small angle in the horizontal direction. The mechanical half angle of the small-angle horizontal scanning galvanometer is to ensure that the galvanometer achieves a higher resonant frequency and reliability; the second MEMS scanning mirror is used as a slow scanning mirror, responsible for scanning at a large angle in the vertical direction to ensure that the vertical field of view of the display is large enough.

[0040] In a specific implementation, in the micro-projection scanning system provided in the embodiment of the present invention, as Figure 1As shown, the relay reflection device includes a first reflection mirror 2, a second reflection mirror 3, a third reflection mirror 4 and a fourth reflection mirror 5 arranged on the transmission optical path of the laser beam; wherein,

[0041] A first reflecting mirror 2, used for reflecting the laser beam scanned by the first MEMS scanning mirror to a second reflecting mirror 3;

[0042] A second reflecting mirror 3, used for reflecting the laser beam to a third reflecting mirror 4;

[0043] The first reflector 2 and the second reflector 3 are used to expand the horizontal field of view of the first MEMS scanning mirror 1;

[0044] A third reflecting mirror 4, used for reflecting the laser beam to a fourth reflecting mirror 5;

[0045] a fourth reflector 5, used for reflecting the laser beam to the collimating lens 6;

[0046] The third reflecting mirror 4 and the fourth reflecting mirror 5 are used to fold the horizontal field of view of the first MEMS scanning mirror 1 so that the laser beam can be reflected by the second MEMS scanning mirror 7 .

[0047] It should be noted that the first reflector 2, the second reflector 3, the third reflector 4 and the fourth reflector 5 can be used as teleconverters, which not only enable the first MEMS scanning mirror 1 to achieve a field of view in the horizontal direction that is equivalent to the field of view in the vertical direction when scanning at a small angle to ensure that the displayed horizontal field of view is large enough, but also increase the distance between the two micro-vibration mirrors to reduce the degree of distortion of the scanning image distortion inherent in the galvanometer scanning method.

[0048] Furthermore, the third reflector 4 and the fourth reflector 5 fold the field of view of the first MEMS scanning mirror 1 so that the light beam can be reflected by the second MEMS scanning mirror 7; the first MEMS scanning mirror 1 and the second MEMS scanning mirror 7, two one-dimensional galvanometer mirrors, can cooperate with each other, and after completing a line of scanning and drawing an image in the horizontal direction, they move down one pixel and then start horizontal drawing again, so that the laser beam generated by the laser can cover all pixels under the reflection scanning of the two MEMS scanning mirrors.

[0049] In a specific implementation, in the micro-projection scanning system provided in the embodiment of the present invention, as Figure 1 As shown, the first reflector 2 and the second reflector 3 may be long strip-shaped plane reflectors.

[0050] In addition, in the specific implementation, in the above-mentioned micro-projection scanning system provided by the embodiment of the present invention, if Figure 1 As shown, the reflection surfaces of the third reflector 4 and the fourth reflector 5 are both spherical surfaces. Preferably, the third reflector 4 and the fourth reflector 5 can be long strip spherical reflectors with different optical focal powers.

[0051] In a specific implementation, in the above-mentioned micro-projection scanning system provided in an embodiment of the present invention, the range of the first scanning angle can be set to be less than ±10°. For example, when the first scanning angle (horizontal scanning angle) is less than ±5°, a horizontal field of view of 50° can be achieved; and the range of the second scanning angle can be set as needed according to the required projection area, which will not be elaborated here.

[0052] It should be noted that the main function of the collimating lens 6 is to collimate the light beam and control the size of the pixel. The field of view of the scanning light beam will be focused after being folded by the third reflector 4 and the fourth reflector 5, but the light beam itself will be deformed by being focused and then diverged by the concave mirror. At the same time, because it is off-axis reflection, the light beam will produce astigmatism. Therefore, a collimating lens can be used to collimate the light beam and control the size of the pixel.

[0053] In a specific implementation, in the above-mentioned micro-projection scanning system provided in an embodiment of the present invention, in order to ensure the scanning frequency and scanning angle of the MEMS scanning mirror and the micro-vibration mirror and to consider its cost and manufacturing difficulty, the sizes of the first MEMS scanning mirror and the second MEMS scanning mirror can be designed to be several millimeters.

[0054] In practical applications, the light source of the present invention can be a semiconductor laser, and the laser beam injected into the scanning system is a collimated thin beam. The driving mode is two one-dimensional galvanometers for two-dimensional scanning, and the laser beam passes through the first MEMS scanning mirror for horizontal scanning, and then passes through the first reflector, the second reflector, the third reflector, and the fourth reflector four relay reflectors in sequence to expand and fold the horizontal field of view, and then passes through the collimating lens for beam collimation, and finally passes through the second MEMS scanning mirror for vertical scanning and irradiation onto the projection screen, completing the image scanning of the entire system.

[0055] In summary, a micro-projection scanning system provided by an embodiment of the present invention includes: a first MEMS scanning mirror, used to perform one-dimensional scanning of an incident laser beam in a first scanning angle resonant motion in a horizontal direction; a relay reflection device, used to reflect the laser beam scanned by the first MEMS scanning mirror multiple times, and expand and fold the horizontal field of view of the first MEMS scanning mirror; a collimating lens, arranged on the reflection light path of the relay reflection device, used to collimate the laser beam after multiple reflections, and control the size of the pixel point; a second MEMS scanning mirror, used to perform another-dimensional scanning of the collimated laser beam in a second scanning angle quasi-static motion in a vertical direction; the maximum value of the first scanning angle is less than the maximum value of the second scanning angle; and a projection screen, used to receive the laser beam scanned by the second MEMS scanning mirror. The above-mentioned laser projection scanning system has a simple structure, the first MEMS scanning mirror performs a small angle scanning in the horizontal direction, ensuring that the galvanometer achieves a higher resonant frequency and reliability, and the second MEMS scanning mirror performs a large angle scanning in the vertical direction, which can ensure that the vertical field of view of the display is large enough, thereby not only realizing two-dimensional image scanning, but also realizing high resolution and large field of view display.

[0056] The micro-projection scanning system provided by the present invention can be mainly used in smart car head-up displays, wearable devices such as AR and VR, various consumer electronic products such as smart phones and digital cameras, artificial intelligence, biomedicine and other fields.

[0057] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0058] The micro-projection scanning system provided by the present invention is introduced in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A micro-projection scanning system, characterized in that: include: A first MEMS scanning mirror is used to perform a one-dimensional scanning of the incident laser beam in a horizontal direction at a first scanning angle resonant motion; A relay reflection device is used to reflect the laser beam scanned by the first MEMS scanning mirror for multiple times, so as to expand and fold the horizontal field of view of the first MEMS scanning mirror; the relay reflection device comprises a first reflection mirror, a second reflection mirror, a third reflection mirror and a fourth reflection mirror arranged on the transmission optical path of the laser beam; wherein, The first reflecting mirror is used to reflect the laser beam scanned by the first MEMS scanning mirror to the second reflecting mirror; The second reflecting mirror is used to reflect the laser beam to the third reflecting mirror; The first reflector and the second reflector are used to expand the horizontal field of view of the first MEMS scanning mirror; the first reflector and the second reflector are long strip-shaped plane reflectors; The third reflecting mirror is used to reflect the laser beam to the fourth reflecting mirror; The fourth reflector is used to reflect the laser beam to the collimating lens; The third reflector and the fourth reflector are used to fold the horizontal field of view of the first MEMS scanning mirror so that the laser beam can be reflected by the second MEMS scanning mirror; the third reflector and the fourth reflector are long spherical reflectors with different optical focal lengths; A collimating lens, arranged on the reflected light path of the relay reflector, for collimating the laser beam after multiple reflections and controlling the size of the pixel points; The second MEMS scanning mirror is used to perform another-dimensional scanning of the collimated laser beam in a second scanning angle quasi-static motion in the vertical direction; the maximum value of the first scanning angle is less than the maximum value of the second scanning angle; the first MEMS scanning mirror and the second MEMS scanning mirror cooperate with each other, and after completing a row of scanning and drawing an image in the horizontal direction, move down one pixel and then start horizontal drawing, so that the laser beam generated by the laser covers all pixels under the reflection scanning of the mirror surfaces of the first MEMS scanning mirror and the second MEMS scanning mirror; The projection screen is used to receive the laser beam scanned by the second MEMS scanning mirror.

2. The micro-projection scanning system according to claim 1, characterized in that: The scanning frequency of the first MEMS scanning mirror is greater than the scanning frequency of the second MEMS scanning mirror.

3. The micro-projection scanning system according to claim 2, characterized in that: The reflection surfaces of the third reflector and the fourth reflector are both spherical surfaces.

4. The micro-projection scanning system according to claim 1, characterized in that: The sizes of the first MEMS scanning mirror and the second MEMS scanning mirror are both in the order of several millimeters.

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